review article mitochondria-targeted antioxidants: future...

Review ArticleMitochondria-Targeted Antioxidants Future Perspectives inKidney Ischemia Reperfusion Injury

Aleksandra Kezic12 Ivan Spasojevic3 Visnja Lezaic12 and Milica Bajcetic45

1School of Medicine University of Belgrade Dr Subotica 8 11000 Belgrade Serbia2Clinic for Nephrology Clinical Center of Serbia Pasterova 2 11000 Belgrade Serbia3Department of Life Sciences Institute for Multidisciplinary Research University of Belgrade Kneza Vieslava 1 11000 Belgrade Serbia4Department of Pharmacology Clinical Pharmacology and Toxicology School of Medicine University of BelgradePO Box 38 11000 Belgrade Serbia5Clinical Pharmacology Unit University Childrenrsquos Hospital 11000 Belgrade Serbia

Correspondence should be addressed to Aleksandra Kezic aleksandrakezicyahoocomand Milica Bajcetic mbajceticdoctorcom

Received 19 February 2016 Accepted 28 April 2016

Academic Editor Jacek Zielonka

Copyright copy 2016 Aleksandra Kezic et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Kidney ischemiareperfusion injury emerges in various clinical settings as a great problem complicating the course and outcomeIschemiareperfusion injury is still an unsolved puzzle with a great diversity of investigational approaches putting the focus onoxidative stress andmitochondriaMitochondria are both sources and targets of ROSThey participate in initiation and progressionof kidney ischemiareperfusion injury linking oxidative stress inflammation and cell death The dependence of kidney proximaltubule cells on oxidative mitochondrial metabolism makes them particularly prone to harmful effects of mitochondrial damageThe administration of antioxidants has been used as a way to prevent and treat kidney ischemiareperfusion injury for a longtime Recently a new method based on mitochondria-targeted antioxidants has become the focus of interest Here we review thecurrent status of results achieved in numerous studies investigating these novel compounds in ischemiareperfusion injury whichspecifically targetmitochondria such asMitoQ Szeto-Schiller (SS) peptides (Bendavia) SkQ1 and SkQR1 and superoxide dismutasemimics Based on the favorable results obtained in the studies that have examinedmyocardial ischemiareperfusion injury ongoingclinical trials investigate the efficacy of some novel therapeutics in preventing myocardial infarctThis also implies future strategiesin preventing kidney ischemiareperfusion injury

1 Introduction

Ischemiareperfusion injury (IRI) is a major cause of acutekidney injury (AKI) formerly known as acute renal failure[1] The incidence of AKI in hospitalized patients has beenreported to be between 2 and 7 and even greater than10 in intensive care unit (ICU) patients contributing toincreased mortality rate [2] Kidney IRI is of great impor-tance occurring in various clinical settings including shockvascular and cardiac surgery sepsis and kidney transplan-tation During kidney transplantation IRI causes delayedgraft function (DGF) that has been associated with morefrequent episodes of acute rejection and progression to

chronic allograft nephropathy [2ndash4] Complex interplay ofpathophysiological processes linking inflammation abnor-mal repair and fibrosis makes AKI an important risk factorfor progression of chronic kidney disease [5ndash7] Basicallyreperfusion phenomena consist of events which ldquoparadox-icallyrdquo continue to damage tissue in spite of establishedcirculation and oxygen supply to the tissue that previouslywas under ischemia Pathogenesis of IRI is rather complexand involves hypoxic injury production of reactive oxygenspecies (ROS) inflammation apoptosis and necrosis [8]Reactive oxygen species (ROS) include oxygen radicals suchas superoxide radical anion (O

2

∙minus) and hydroxyl radical(HO∙) and certain nonradicals that either are oxidizing agents

Hindawi Publishing CorporationOxidative Medicine and Cellular LongevityVolume 2016 Article ID 2950503 12 pageshttpdxdoiorg10115520162950503

2 Oxidative Medicine and Cellular Longevity

or are easily converted into radicals such as hydrogen perox-ide (H

2O2) and hypochlorous acid (HOCl) ROS generation

represents a cascade of reactions starting with the productionof O2

∙minus that can be further converted to H2O2via superoxide

dismutases (SOD) manganese (MnSOD) in mitochondriaand copper-zinc (CuZnSOD) in the cytosol The main sinksfor H

2O2are catalase (CAT) and glutathione peroxidase

(GPx) The latter uses glutathione (GSH) which is oxidizedto GSSG and recycled by glutathione reductase There areother enzymes that can remove H

2O2 such as perox-

iredoxinthioredoxinthioredoxin reductase (PrxTrxTrxR)system However CAT activity is about three orders ofmagnitude higher compared to PrxTrxTrxR system [9]which is essential under physiological settings for keeping lowlevels of mitochondrial H

2O2emission and for normal redox

signaling via regulation of thiol redox switches on differentproteins [10]

H2O2can also react with transition metals such as iron

or copper to produce HO∙ the most reactive species in livingsystems [11] The main reactive nitrogen species (RNS) arenitric oxide (NO∙) and peroxynitrite (ONOOminus) ONOOminusis formed via reaction between NO and O

2

∙minus and can befurther protonated and decomposed to nitrogen dioxideradical (NO

2

∙) and HO∙ [12 13] These radicals are ldquocagedrdquo(ie generated close to each other) so they can recombinequickly and much of ONOOminus undergoes isomerisation tonitrate Some amount of ONOOminus in vivo reacts with CO

2to

form nitrosoperoxycarbonate (ONOOCO2

minus) About 35 ofONOOCO

2

minus is decomposed to NO2

∙ and carbonate radical(CO3

∙minus) [14] The latter is highly oxidizing species targetingNADPH and proteins [15 16]

Mitochondria are the major site of ROS production dueto inevitable leakage of electrons from electron transportchain (ETC) onto oxygen [17] Other major intracellular sitesof ROS generation are enzymes such as NADPH oxidase(NOX) and xanthine oxidase (XO)

Initially in ischemic phase kidney tubular epithelial andendothelial cells are main producers of ROS and are lateraccompanied by activated leucocytes that is oxidative burstrelated to inflammation These events reveal the role of ROSin exerting detrimental effects on cellular structure linkingoxidative stress inflammation and cell death ROS throughinteractions with small metabolites as well as proteins lipidsand nucleic acids might irreversibly destroy or alter the func-tion of these target molecules and belonging organelles andcells ROS can also serve as homeostatic signaling moleculeswhich primarily depends on magnitude and duration ofprovoking stimuli for ROS production

In recent years it has become clear thatmitochondria havecritical role in initiation and progression of renal IRI Theyare early responders to the anoxia and then reoxygenationinitiating responses that lead to changed metabolic andbioenergetic status autophagy inflammation and inductionof cell death pathways Several approaches mainly in exper-imental studies with a few human trials have been usedin investigating the options for preventing and treatment ofIRI with special emphasis on modulation of inflammatoryresponse inhibition of apoptosis and amelioration of oxida-tive stress but currently there is no effective pharmacological

treatment to address the main mechanisms of ischemic AKI[18ndash20] Recently novel therapeutic approach called ischemicpreconditioning has become translated from animal modelsto humans [20 21] It is based on the observations thatepisodes of nonlethal ischemia can precondition the kidneyto be protected in subsequent prolonged ischemia

Nevertheless oxidative stress is crucial for the cascadeof processes participating in the pathogenesis of IRI Sincemitochondria as both sources and targets of ROS are initia-tors of complex mechanisms in IRI it seems reasonable fromtherapeutic perspective to develop pharmacological methodaiming to decrease mitochondrial oxidative damage

In this review we will summarize the mechanisms ofmitochondrial ROS production and some options for poten-tial treatment strategies

2 The Role of Mitochondria inthe Pathogenesis of IRI

By impairing electron transport and energy metabolism andby altering cellular redox potential via ROS productionmitochondria trigger events leading to apoptosis a hall-mark of IRI Electron transport along ETC to O

2is tightly

coupled to oxidative phosphorylation for ATP synthesis Innormal for instance nonischemic cells the main source ofROS is ETC [22 23] Most oxygen consumed is reducedto water through 4 steps of single electron reduction bycytochrome c oxidase Electrons generated from reducednicotinamide adenine dinucleotide (NADH) are acceptedby NADH dehydrogenase (Complex I) and those fromsuccinate are accepted by succinate dehydrogenase (ComplexII) Electrons are then passed to cytochrome bc1 (ComplexIII) through coenzymeQ (CoQ) and to cytochrome c oxidase(Complex IV) using cytochrome c as a carrier The laststep is transfer of electron from cytochrome c oxidase toO2to form water (Figure 1) Electron flow mediated by

the respiratory chain enzyme complex drives proton (H+)translocation from the matrix side at the level of complexesI III and IV to the intermembrane space side therebyestablishing an electrochemical potential gradient or protonmotive force across the inner membrane [23] Since theinner mitochondrial membrane is almost impermeable thiselectrochemical gradient is used to reintroduce protons backthrough the proton channel of complex V (ATP synthase)ATP synthesis from ADP and inorganic phosphate is thencatalyzed by F

0F1ATPase Every decrease in the rate of mito-

chondrial phosphorylation increases electron leakage fromthe ETC and consequently increases the production of O

2

∙minusMitochondria have defense mechanism to neutralize ROSSuperoxide radical anion is converted to H

2O2by MnSOD

and H2O2is further degraded to H

2O In mitochondria

about 70ndash80 of H2O2removal has been attributed to

GPx [9] ROS may induce mild mitochondrial oxidativestress or diffuse to the cytosol playing an important role incellular homeostasis mitosis and differentiation and servingas signaling molecules in different physiological responses[24 25] This constant production of small amounts of ROSis necessary to maintain the appropriate ldquoredox staterdquo of cell

Oxidative Medicine and Cellular Longevity 3

I

III

II

CoQ

ee

eIV

SOD

GPxFADH2 FADHNADH

Cyt c

O2∙minus

2H+

NAD+

H2OH2O12O2

H+

H+

H+

H2O2

O2

Figure 1 Formation of various reactive oxygen species from electron transport chain in mitochondria O2

∙minus superoxide anion SODsuperoxide dismutase GPx glutathione peroxidase CoQ coenzyme Q Cyt c cytochrome c

which is crucial for the activation of several genes and thefunction of numerous enzymes On the other hand H

2O2

that escapes mitochondria is removed by CAT GPx andother H

2O2removing systems but an excess can activate

potentially detrimental cascades for example via NF-120581BWhat happens to the mitochondria in ischemia The

effect depends on the duration of ischemia Ischemia causesalterations to the mitochondrial ETC complexes If ischemicepisodes are of short duration the electronegativity of theETC complexes and leakage of electrons is increased withconsequently increased ROS formation ROS can triggersignaling events that lead to the synthesis of proteins includ-ing MnSOD and thereby providing beneficial role that isthe part of ischemic preconditioning phenomena [26] Aprolonged period of ischemia results in decreased activityof the complexes I and IV of ETC and subsequent electronleak of that reduce O

2to form superoxide radicals when

O2is reintroduced following reperfusion [24 27] Also

impaired ETC results in decreased ATP production followingreperfusion During prolonged ischemiamore of detrimentalradicals are produced Superoxidemainly attacks Fe-S centersin ETC proteins to provoke the reduction of Fe3+ andliberation of Fe2+ leaving aconitase and other transporters ofelectrons dysfunctional [28]These Fe2+ ions are important inFenton chemical reaction whereby H

2O2can be converted to

the highly reactive HO∙ which is more detrimental for cellstructure proteins and membrane lipids It is important tonote that HO∙ has a drastically shorter diffusion radius inphysiological milieu compared to H

2O2 and it is too reactive

to pass membranes In short HO∙ is more dangerous fortargets that are nearby the site of production H

2O2generated

in mitochondria can affect other organelles nucleus andsurrounding cells [29]The prolonged ischemia decreases theactivity of antioxidant enzymes such as MnSOD and causesGSH depletion [30 31]

The involvementinterference of ROS in signaling cas-cades might have both detrimental and beneficial effectsCellular hypoxia appears to be the key signal for activation ofHIF-1120572 nuclear factor-120581B (NF-120581B) activator protein 1 (AP-1)and mitogen activated protein kinases (MAPK) In additionROS have been directly implicated in programmed cell death[2 32 33] Under hypoxia transcriptional cell activity isdirected to synthesis of proinflammatory and cytoprotectivemolecules [34] So far the available data have implied aproinflammatory action of NF-120581B as one of the key playersin pathogenesis of IRI [35ndash38] Besides chemokines andcytokines NF-120581B is implicated in the production of bothROSand HIF-1 that is there is a positive feedback loop serving asan amplification mechanism [35 39]

Massive production of ROS during reperfusion is sec-ondary to electron leak mostly at complexes I and III[40] The overproduction of O

2

∙minus may lead to formationof ONOOminus which is a highly reactive molecule and leadsto nitration of proteins including complexes I and III andfurther tissue injury [40 41] Renal content of 3-nitrotyrosine(the footprint of peroxynitrite) increases during ischemiaPertinent to this ∙NO that is formed via activity of inducibleNO synthase (iNOS) is also increased [42ndash44] iNOS isinduced in kidney IRI [45ndash48] Studies using inhibition ofexpression and activity of iNOS or even absence of iNOSshowed amelioration of kidney IRI suggesting that NOgenerated by iNOS had detrimental role and contributed tokidney IRI [45 47 49] This by oxidant-induced disruptionof protein complexes I and III potentiates electron leakand further O

2

∙minus generation The whole process is drivenby ROS-induced ROS release and may become a viciouscycle that induces mitochondrial permeability transitionpore (mPTP) opening [50] Because of mitochondrial GSHdepletion during ischemia conversion of H

2O2to water is

insufficient in reperfusion favoring formation of HO∙ via


Fenton reaction [24 31] As a consequence membrane per-meability is affected ldquoRedox staterdquo is altered by the oxidationof pyridines and thiols with consequent modification ofNADHNAD+ and GSHGSSG ratio [44] Excessive ROSformation recovery of pH and calciumoverload facilitate theopening of mPTP with consequent loss of cytochrome c andpyridine nucleotides favoring further ROS generation andtriggering cell death [50ndash52] The opening of mPTP resultsin redistribution of NADH and calcium to the cytosol andan influx of water to mitochondria causing mitochondrialmatrix swelling and outer mitochondrial membrane rupturewith release of proapoptotic factors leading to cell deathReleased calcium to cytosol activates proteases nucleasesand phospholipases which trigger apoptosis [52]

Additionally mitochondria has other componentsbesides ETC that contribute to ROS production includingNOX4 monoamine oxidase and growth factor adaptorprotein Shc (p66Shc) but this contribution is rather lowcompared with the generation of ROS from ETC [22]

3 Mode of the Action of Mitochondria-Targeted Drugs

According to previously mentioned data it seems reasonableto develop pharmacological method that decreases mito-chondrial oxidative damage in order to decrease kidneyIRI The relatively unsatisfactory efficacy of conventionalantioxidants may be the consequence of their low penetranceto themitochondria interior whichnot only is themain site ofROS production but also suffers fromoxidative stress as othercellular compartments The inner mitochondrial membraneis highly impermeable and rich in cardiolipin andmaintains astrong negative internal potential of minus180mV that is requiredfor the function of electron transport chain

To overcome these limitations mitochondria-targetedantioxidants have been developed to provide their deliv-ery to the mitochondrion interior Mitochondria-targetedantioxidants are usually chimeric molecules of a cation triph-enylphosphonium (TPP) conjugated with an antioxidantmoiety such as coenzyme Q

10or plastoquinone [53 54] The

proton motive force in the inner mitochondrial membranemaintaining the large mitochondrial membrane potentialand the positive charge of lipophilic cation drive a transportof these cationic antioxidants intomitochondriaThe result ofthis mitochondrial uptake is a chimeric drug concentration10000 times higher in the mitochondrial matrix than in thecytosol [55] Apart from the TPP rhodamine 123 is anothersuitable lipophilic cation to be conjugated to mitochondria-selective molecules [56] However lipophilic cations have adisadvantage Since the charge accumulation into the matrixleads to mitochondrial membrane depolarization at con-centrations greater than 10 120583M toxicity has been observed[56]

Recently use of short peptide sequences with specificphysicochemical properties for delivery of compoundsto inner mitochondria has emerged [57] The Szeto-Schiller SS peptides have exhibited marked antioxidantproperties by scavenging ROS and inhibiting linoleic acid

oxidation [58 59] They feature a common structuralmotif of alternating aromatic (Phe Tyr and Dmt (2101584061015840-dimethyltyrosine)) and basic (Arg Lys) residues SS peptidesfreely penetrate membranes in a potential-independentmanner due to their aromatic-cationic amino acid sequenceTyr or Dmt residues are likely responsible for the ROSscavenging abilities of these peptides [60] Another optionaloligopeptide is conjugated to manganese metalloporphyrinand belongs to novel class of mitochondria-targeted SODmimics named Mn-porphyrin-oligopeptide conjugates[61]

N-acetyl-L-cysteine (NAC) has been known for theefficiency in protecting cells against oxidants [62] Inorder to deliver the tripeptide glutathione (L-120574-glutamyl-L-cysteinylglycine or GSH) and its analog NAC into mito-chondria choline esters (MitoGSH andMitoNAC) have beenutilized [63] Experiments with MitoNAC were performedusing cultured cells However in vivo data are missing

Among the other mitochondria-targeted compoundswith different mode of penetrance and action that are worthmentioning is diazoxide the opener of mitochondrial KATPchannels The precise mechanisms how active mitochondrialKATP channels lead to decreased ROS production when oxy-gen is delivered during reperfusion are still unclear althoughthey are in some ways similar to events elicited by ischemicpreconditioning [64] Opened K channels result in a loweredmitochondrial membrane potential and lowered redox stateof NAD system leading to decreased ROS production byrespiratory chain Complex I [65]

4 Mitochondria-Targeted Antioxidants inRenal IRI

Mitochondria-targeted antioxidants have already been usedin other experimental pathology models and one of themMitoQ has been used in two Phase II trials in humans regard-ing treatment of Parkinson disease and chronic hepatitis Cshowing long term safety and tolerance [66 67] Because ofa positively charged lipophilic cation MitoQ is accumulatedin the negatively charged interior of mitochondria Theantioxidant component of MitoQ is the ubiquinone that isalso found in coenzyme Q

10(Figure 2) [53] By the action

of the enzyme Complex II in the mitochondrial respiratorychain ubiquinone part of MitoQ is rapidly activated to theactive ubiquinol antioxidant [68] After detoxifying ROS theubiquinol part of MitoQ is converted to ubiquinone which isagain subjected to Complex II to be recycled back to activeantioxidant ubiquinol [68] This process makes MitoQ aneffective mitochondria-targeted antioxidant

The reason for the use of MitoQ in kidney IRI came fromthe studies usingMitoQ to decrease heart and hepatic IRI andto prevent kidney damage during cold storage [69ndash71] Usingthismodel it was demonstrated that administration ofMitoQprior to the onset of ischemia reduced oxidative damageand severity of renal IRI thereby providing functionalprotection to the kidney [72] The group of Skulachev et alsynthesized plastoquinonyl-decyl-triphenylphosphoniumIn this compound named SkQ1 ubiquinone was replaced


O

O

O

OMitoQuinone

OH

OH

O

O

MitoQuinol

OH

OH

O

O

SkQ1

NOHN

O

OHO

OH

SkQR1

H+

P+

P+

P+

Figure 2 Mitochondria-targeted antioxidants with ubiquinone or plastoquinone antioxidant moiety that are used in kidneyischemiareperfusion injury

by plastoquinone (Figure 2) [54 73] The effect of SkQ1 onkidney IRI using a culture of kidney epithelial cells has beenstudied Preincubation with SkQ1 increased survival of thesecells and diminished mitochondrial fission induced by theanoxiareoxygenation procedure [74 75] In experimentalmodel of a single-kidney ischemia (90min) followed byreoxygenation injection of SkQ1 to rats a day before kidneyischemia significantly improved survival compared to theexperimental animals subjected to kidney IRI without anyprevious treatment [74]

In another experimental study the authors used amitochondria-targeted compound containing a charged rho-damine molecule conjugated with plastoquinone namedSkQR1 (Figure 2) [76] An intraperitoneal injection of SkQR1to rats exposed to kidney IRI normalized the ROS level andlipid peroxidized products in kidney mitochondria signif-icantly decreased BUN and blood creatinine and loweredmortality compared to animals that were subjected to kidneyIRI without any given drug [76] Additionally SkQR1 wasfound to provide the kidney with elements of ischemictolerance signaling mechanisms Administration of SkQR1induced erythropoietin (EPO) and the phosphorylated form

of GSK-3120573 in rat kidney [76] EPO is known to afford someprotection against ischemic damage [77 78] In a pilot clinicaltrial investigating the efficacy of EPO to prevent AKI aftercoronary artery bypass grafting (CABG) it was shown thatEPO administration resulted in an incidence of AKI of 8compared with an incidence of 29 in the placebo group[79] Phosphorylated form of GSK-3120573 correlates with activityof prosurvival genes Via inhibition of GSK-3120573 protectivesignaling pathways act on the end effector mPTP that isthey prevent the induction of themitochondrial permeabilitytransition restore mitochondrial membrane potential anddecrease ROS production [80ndash82] The authors concludedthat treatment with SkQR1 provided linked synergy betweenantioxidative effects and ischemic tolerance signaling mech-anisms due to the targeted delivery of this compound tomitochondria [76] Beside the kidney IRI MitoQ and SkR1have been shown to have the role in amelioration of AKIinduced by cisplatin and gentamycin [83 84]

A number of reports demonstrate that open mitochon-drial KATP channels which are redox sensitive effectivelyblock the generation and release of ROS [85 86] Interest-ingly agents opening the ATP-sensitive K channel (KATP)


O

HN

NH

HN

O

OH

NH

O

HN

O

OH

SS-31

H2N

NH2

NH2

Figure 3 Chemical structure of SS-31

including diazoxide were effective in ameliorating cardiacand neural IRI [87 88] but ineffective and even injuriousin kidney IRI [89] In a report of Sun et al a large doseof diazoxide given before kidney ischemia prevented ROSaccumulation in mitochondria thereby reducing oxidativestress consequent tubular cell apoptosis and increase inserum creatinine [90] Considering this effect dependenceon widespread opening of the mitochondrial KATP channelsa large dose of diazoxide is needed but this phenomenonraises the question of the role of mitochondrial K channelsor associated respiratory chain components in the ROSproduction depending on specific tissue

mPTP as another potential target for pharmacologicalintervention in IRI was supported by preclinical and clinicalstudies [91 92] The substances that block opening of mPTPprotect mitochondrial structure and respiration during earlyreperfusion and accelerate recovery of ATP CypD is a com-ponent ofmPTP Animals with CypD gene ablation or treatedwith cyclosporin A (CsA) a CypD inhibitor were protectedfrom renal IRI [93ndash95] These promising results were nottranslated into clinical nephrology compared to extensiveinvestigation in cardiology since the nephrotoxic profile ofCsAmakes this drug unsuitable for clinical application in thetreatment of renal IRI [96 97]

A growing number of publications speak in favor ofcompound Szeto-Schiller- (SS-) 31 peptide also known asBendavia (Figure 3) Besides scavenging of ROS Bendaviaalso inhibits mPTP and thereby prevents mitochondrialrelease of cytochrome c and consequently apoptosis [98]However recent study of Brown et al did not confirmthe role of Bendavia in direct inhibition of mPTP butrather emphasized its role in decreased ROS production andindirectly decreased mPTP opening Bendavia may optimizethe mitochondrial phospholipid cardiolipin microdomainsresulting in reduced electron leak from the inner membrane[99]

SS-31 peptide that is Bendavia demonstrated efficacyin several animal models of different pathologic conditionsby reducing oxidative stress [100ndash102] Regarding IRI theefficacy of Bendavia was mostly investigated in experimental

models of myocardial ischemia If Bendavia was given toanimals in minutes prior to reperfusion or in the first 10minutes of reperfusion then the effect of reduced infarc-tion and the extent of coronary no-reflow were achieved[103 104] These encouraging experimental results needconfirmation in ongoing clinical trials for acute coronarysyndromes [105] Also in experimental model of kidneyIRI Bendavia reduced oxidative stress prevented tubularapoptosis and necrosis and reduced inflammation [106]Because of the rapidATP recovery after Bendavia administra-tion microvascular endothelial cells are protected leading toreducedmicrovascular congestion that provides better reflowto the medulla [106] The effect of Bendavia was exploredin experimental model of percutaneous transluminal renalangioplasty (PTRA) a condition that may be associatedwith impairment of renal function Infusion of Bendaviaat the time of percutaneous transluminal renal angioplastydecreases oxidative stress apoptosis and inflammation andimproves renal function in animal experimental model ofrenal artery stenosis [107]

Since oxidative stress is dependent on both ROS pro-duction and removal by antioxidant enzymes and takinginto consideration that IRI significantly reduces Mn SODand CuZn SOD mRNA expression the use of antioxidativeenzymes might alleviate kidney IRI MnSOD knockout (KO)mice that exhibit low expression and activity of MnSODin distal nephron after ischemiareperfusion show similarlevels of injury to the proximal tubule and distal nephron andequally altered renal functionwhen compared with wild-typemice [108] Additionally these KO mice exhibit increasedproliferating cell nuclear antigen- (PCNA-) positive nuclei inthe distal nephrons autophagy andmitochondrial biogenesisindicating that chronic oxidative stress stimulates multiplesurvival signaling pathways to protect kidney against acuteoxidative stress following ischemiareperfusion [108] Thelimitation of this study is that proximal tubule especially itsS3 fragment damaged in IRI the most in this specific mousestrain was not affected by lack of MnSOD and thereforefailed to assess the role of abolished MnSOD activity withinproximal tubules in IRI


N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+

Figure 4 Chemical structures of Mn porphyrins investigated inexperimental models of kidney ischemiareperfusion injury

There are several reports showing protective role ofSOD mimics in experimental models of kidney IRI [109ndash113] SOD mimics are a group of substances which catalyzethe oxidation and reduction of O

2

∙minus They include cationicmetalloporphyrins with Mn porphyrins (MnP) Mn(III)salens Mn(II) cyclic polyamines metal oxides Mn(III)biliverdins and metallocorroles (MCs) [114] MnSOD mim-ics are stoichiometric scavengers of O

2

∙minus and accumulate inmitochondria depending on positive charge and lipophilicity[115] MnPs are among the most potent MnSOD mimicsdesigned and optimized to mimic the action of the enzymecatalytic site and to increase mitochondrial accumulation[115] Manganese (III) tetrakis(1-methyl-4 pyridyl) porphyrin(MnTMPyP) one of the MnPs acts as SOD mimic andperoxynitrite scavenger (Figure 4) MnTMPyP decreasedlipid peroxidation nitrotyrosine content in the proximaltubular region caspase-3 activation and tubular epithelialcell damage following ischemiareperfusion [109] In addi-tionMnTMPyP decreased the expression of the proapoptoticgenes Bax and FasL At first the effects of SOD mimics

were almost exclusively assigned to the removal of O2

∙minus andONOOminus but recent data suggest the direct H

2O2-driven

oxidation of signaling proteins such as NF-120581B [114 116]This was implied in experimental work of Dorairsquos groupwho used Mn(III) meso-tetrakis(N-n-hexylpyridinium-2-yl)porphyrin (MnTnHex-2-PyP5+) (Figure 4) [113] Theyshowed that giving of renoprotective cocktail containingMnTnHex-2-PyP5+ to rats 24 h before at the beginning and24 h after kidney IRI ameliorated AKI and induced adaptiveresponse via mild prooxidative stress [113] The improve-ment of renoprotective cocktail was achieved by adding N-acetylcysteine that couples with MnTnHex-2-PyP5+ As aresult oxidative stress was enhanced via production of H

2O2

[112 116] The prooxidative action of MnPs is manifested byoxidation of Cys-62 of p50 subunit of NF-120581B thereby pre-ventingNF-120581B activation [116 117] It has been proposed thatupon oxidation of cysteines of Kelch-like ECH-associatedprotein 1 (KEAP1) that is nuclear factor-E2-related factor(Nrf2) inhibitor porphyrin-based SODmimicsMn(II) cyclicpolyamines and nitroxides activate Nrf2 Activation of Nrf2results in upregulation of endogenous antioxidative defenses[117]

There are several other investigatedMnSODmimics suchas MnSalens mangafodipir (Mn complex with dipyridoxyldiphosphate) substances named tempone and oxazolidine-5-doxylstearate belonging to nitroxides andMitoSOD consist-ing of TTP cation conjugated with a O

2

∙minus-selective pentaazamacrocyclic Mn(II) SOD mimic but the data on the useof these compounds in vivo kidney ischemiareperfusionmodels are still missing [115] Mito-CP is a five-memberednitroxide CP conjugated to a TTP cation It has preventedcisplatin-induced renal dysfunction renal cell inflammationand tubular cell apoptosis [83] Favorable effects in thismodel of AKI are promising for investigating the role ofMito-CP in renal IRI Other potential compounds to beinvestigated in the prevention of kidney IRI include vitaminE [118] lipoic acid [119] and Ebselen [120] conjugated tothe TPP cation and targeted to mitochondria Although 4-hydroxy-2266-tetramethylpiperidin-1-oxyl (Tempol) is notSOD mimic it is a free radical scavenger and has been usedin experimental model of kidney IRI Tempol significantlyreduced the increase in creatinine after kidney IRI inductionin rats [121 122] Also Tempol significantly reduced kidneyMDA level and nitrotyrosine staining

Overall these findings support the potential use someof SOD mimics and previously mentioned mitochondria-targeted antioxidants as therapeutic agents in renal IRI(Table 1)

5 Conclusion

Mitochondrial ROS generation participates in deleteriouscascade of events provoked by ischemiareperfusion leadingto tubular cell death and AKI So far investigated treatmentby antioxidants has not been successfully translated into clin-ical practice Mitochondria-targeted antioxidants represent anovel approach especially in clinical settings in which kidneyIRI could be prevented or ameliorated Experimental data


Table 1 Mitochondria-targeted antioxidants in kidney ischemiareperfusion injury

Drug Antioxidant moiety ReferenceMitoQ Ubiquinone [72]SkQ1 SkQR1 Plastoquinone [74ndash76]SS-31 (Bendavia) Tyr or Dmt (2101584061015840-dimethyltyrosine) residues [106 107]SOD mimic

(i) MnTMPyP Manganese metalloporphyrin [109ndash113](ii) MnTnHex-2-PyP5+

are encouraging despite the fact that most of the data comefrom the studies exploring myocardial IRI Those resultsjustify development of this preventative strategy in kidneyIRI for clinical use as some of them such as MitoQ and (SS)-31 are already being evaluated in humans for prevention ofmyocardial IRI

Competing Interests

The authors declare that they have no competing interests

References

[1] R W Schrier W Wang B Poole and A Mitra ldquoAcute renalfailure definitions diagnosis pathogenesis and therapyrdquo TheJournal of Clinical Investigation vol 114 no 1 pp 5ndash14 2004

[2] G M Chertow E Burdick M Honour J V Bonventre andD W Bates ldquoAcute kidney injury mortality length of stay andcosts in hospitalized patientsrdquo Journal of the American Societyof Nephrology vol 16 no 11 pp 3365ndash3370 2005

[3] N Perico D CattaneoMH Sayegh andG Remuzzi ldquoDelayedgraft function in kidney transplantationrdquo The Lancet vol 364no 9447 pp 1814ndash1827 2004

[4] J Boletis A Balitsari V Filiopoulos et al ldquoDelayed renal graftfunction the influence of immunosuppressionrdquo Transplanta-tion Proceedings vol 37 no 5 pp 2054ndash2059 2005

[5] D P Basile ldquoThe endothelial cell in ischemic acute kidneyinjury implications for acute and chronic functionrdquo KidneyInternational vol 72 no 2 pp 151ndash156 2007

[6] J V Bonventre and L Yang ldquoCellular pathophysiology ofischemic acute kidney injuryrdquoThe Journal of Clinical Investiga-tion vol 121 no 11 pp 4210ndash4221 2011

[7] M A Venkatachalam K A Griffin R Lan H Geng PSaikumar andA K Bidani ldquoAcute kidney injury a springboardfor progression in chronic kidney diseaserdquo American Journal ofPhysiologymdashRenal Physiology vol 298 no 5 pp F1078ndashF10942010

[8] P Devarajan ldquoUpdate onmechanisms of ischemic acute kidneyinjuryrdquo Journal of the American Society of Nephrology vol 17 no6 pp 1503ndash1520 2006

[9] A J Ristic D Savic D Sokic et al ldquoHippocampal antioxidativesystem in mesial temporal lobe epilepsyrdquo Epilepsia vol 56 no5 pp 789ndash799 2015

[10] A Bindoli and M P Rigobello ldquoPrinciples in redox signalingfrom chemistry to functional significancerdquo Antioxidants ampRedox Signaling vol 18 no 13 pp 1557ndash1593 2013

[11] M E Andrades AMorina S Spasic and I Spasojevic ldquoBench-to-bedside review sepsismdashfrom the redox point of viewrdquoCritical Care vol 15 no 5 article 230 2011

[12] S J Klebanoff ldquoOxygen metabolism and the toxic properties ofphagocytesrdquoAnnals of Internal Medicine vol 93 no 3 pp 480ndash489 1980

[13] V J Thannickal and B L Fanburg ldquoReactive oxygen species incell signalingrdquo American Journal of PhysiologymdashLung CellularandMolecular Physiology vol 279 no 6 pp L1005ndashL1028 2000

[14] G Ferrer-Sueta and R Radi ldquoChemical biology of peroxyni-trite kinetics diffusion and radicalsrdquo ACS Chemical Biologyvol 4 no 3 pp 161ndash177 2009

[15] S Goldstein and G Czapski ldquoReactivity of ONOO-versussimultaneous generation of ∙NO and O

2

∙minus toward NADHrdquoChemical Research in Toxicology vol 13 no 8 pp 736ndash7412000

[16] A MMichelson and J Maral ldquoCarbonate anions effects on theoxidation of luminol oxidative hemolysis 120574-irradiation and thereaction of activated oxygen species with enzymes containingvarious active centresrdquoBiochimie vol 65 no 2 pp 95ndash104 1983

[17] Q Chen S Moghaddas C L Hoppel and E J LesnefskyldquoIschemic defects in the electron transport chain increase theproduction of reactive oxygen species from isolated rat heartmitochondriardquo American Journal of PhysiologymdashCell Physiol-ogy vol 294 no 2 pp C460ndashC466 2008

[18] A Bajwa G R Kinsey andMDOkusa ldquoImmunemechanismsand novel pharmacological therapies of acute kidney injuryrdquoCurrent Drug Targets vol 10 no 12 pp 1196ndash1204 2009

[19] S A Silver H Cardinal K Colwell D Burger and J G Dick-hout ldquoAcute kidney injury preclinical innovations challengesand opportunities for translationrdquo Canadian Journal of KidneyHealth and Disease vol 2 no 1 article 30 pp 1ndash11 2015

[20] S Faubel L S Chawla G M Chertow S L Goldstein B LJaber and K D Liu ldquoOngoing clinical trials in AKIrdquo ClinicalJournal of the American Society of Nephrology vol 7 no 5 pp861ndash873 2012

[21] N Gassanov A M Nia E Caglayan and F Er ldquoRemoteischemic preconditioning and renoprotection from myth to anovel therapeutic optionrdquo Journal of the American Society ofNephrology vol 25 no 2 pp 216ndash224 2014

[22] T Kalogeris Y Bao and R J Korthuis ldquoMitochondrial reactiveoxygen species a double edged sword in ischemiareperfusionvs preconditioningrdquo Redox Biology vol 2 no 1 pp 702ndash7142014

[23] Y-R Chen and J L Zweier ldquoCardiacmitochondria and reactiveoxygen species generationrdquo Circulation Research vol 114 no 3pp 524ndash537 2014

[24] T P Dalton H G Shertzer and A Puga ldquoRegulation of geneexpression by reactive oxygenrdquoAnnual Review of Pharmacologyand Toxicology vol 39 pp 67ndash101 1999

[25] K Irani Y Xia J L Zweier et al ldquoMitogenic signalingmediatedby oxidants in ras-transformed fibroblastsrdquo Science vol 275 no5306 pp 1649ndash1652 1997


[26] R Bolli ldquoThe late phase of preconditioningrdquo CirculationResearch vol 87 no 11 pp 972ndash983 2000

[27] W Rouslin ldquoMitochondrial complexes I II III IV and Vin myocardial ischemia and autolysisrdquo American Journal ofPhysiologymdashHeart and Circulatory Physiology vol 13 no 6 ppH743ndashH748 1983

[28] J E Baker and B Kalyanaraman ldquoIschemia-induced changes inmyocardial paramagneticmetabolites implications for intracel-lular oxy-radical generationrdquo FEBS Letters vol 244 no 2 pp311ndash314 1989

[29] MMojia J B Pristov D Maksimovic-Ivanic et al ldquoExtracellu-lar iron diminishes anticancer effects of vitamin C an in vitrostudyrdquo Scientific Reports vol 4 article 5955 2014

[30] A Arduini A Mezzetti E Porreca et al ldquoEffect of ischemiaand reperfusion on antioxidant enzymes and mitochondrialinner membrane proteins in perfused rat heartrdquo Biochimica etBiophysica Acta (BBA)mdashMolecular Cell Research vol 970 no 2pp 113ndash121 1988

[31] W Jassem C Ciarimboli P N Cerioni V Saba S J Nortonand G Principato ldquoGlyoxalase II and glutathione levels in ratliver mitochondria during cold storage in Euro-Collins andUniversity of Wisconsin solutionsrdquo Transplantation vol 61 no9 pp 1416ndash1420 1996

[32] A J Whitmarsh and R J Davis ldquoTranscription factor AP-1 reg-ulation bymitogen-activated protein kinase signal transductionpathwaysrdquo Journal of Molecular Medicine vol 74 no 10 pp589ndash607 1996

[33] A J McGowan M C Ruiz-Ruiz A M Gorman A Lopez-Rivas andTG Cotter ldquoReactive oxygen intermediate(s) (ROI)common mediator(s) of poly(ADP-ribose)polymerase (PARP)cleavage and apoptosisrdquo FEBS Letters vol 392 no 3 pp 299ndash303 1996

[34] C A Latanich and L H Toledo-Pereyra ldquoSearching for NF-120581B-based treatments of ischemia reperfusion injuryrdquo Journal ofInvestigative Surgery vol 22 no 4 pp 301ndash315 2009

[35] T C Nichols ldquoNF-120581B and reperfusion injuryrdquo Drug News andPerspectives vol 17 no 2 pp 99ndash104 2004

[36] C C Cao X Q Ding Z L Ou et al ldquoIn vivo transfec-tion of NF-120581B decoy oligodeoxynucleotides attenuate renalischemiareperfusion injury in ratsrdquo Kidney International vol65 no 3 pp 834ndash845 2004

[37] A Kezic J U Becker and F Thaiss ldquoThe effect of mTOR-inhibition on NF-120581B activity in kidney ischemia-reperfusioninjury in micerdquo Transplantation Proceedings vol 45 no 5 pp1708ndash1714 2013

[38] X Wan L Fan B Hu et al ldquoSmall interfering RNA targetingIKK120573 prevents renal ischemia-reperfusion injury in ratsrdquoAmer-ican Journal of Physiology Renal Physiology vol 300 no 4 ppF857ndashF863 2011

[39] J Rius M Guma C Schachtrup et al ldquoNF-120581B links innateimmunity to the hypoxic response through transcriptionalregulation of HIF-1120572rdquo Nature vol 453 no 7196 pp 807ndash8112008

[40] H-L Lee C-L Chen S T Yeh J L Zweier and Y-R ChenldquoBiphasic modulation of the mitochondrial electron transportchain in myocardial ischemia and reperfusionrdquo American Jour-nal of PhysiologymdashHeart and Circulatory Physiology vol 302no 7 pp H1410ndashH1422 2012

[41] P Wang and J L Zweier ldquoMeasurement of nitric oxide andperoxynitrite generation in the postischemic heart evidence forperoxynitrite-mediated reperfusion injuryrdquo Journal of BiologicalChemistry vol 271 no 46 pp 29223ndash29230 1996

[42] M Saito and IMiyagawa ldquoReal-timemonitoring of nitric oxidein ischemia-reperfusion rat kidneyrdquoUrological Research vol 28no 2 pp 141ndash146 2000

[43] M G Salom B Arregui L F Carbonell F Ruiz J L Gonzalez-Mora and F J Fenoy ldquoRenal ischemia induces an increasein nitric oxide levels from tissue storesrdquo American Journal ofPhysiologymdashRegulatory Integrative and Comparative Physiologyvol 289 no 5 pp R1459ndashR1466 2005

[44] L MWalker J L York S Z Imam S F Ali K L Muldrew andP R Mayeux ldquoOxidative stress and reactive nitrogen speciesgeneration during renal ischemiardquo Toxicological Sciences vol63 no 1 pp 143ndash148 2001

[45] E Noiri T Peresleni F Miller and M S Goligorsky ldquoIn vivotargeting of inducible NO synthase with oligodeoxynucleotidesprotects rat kidney against ischemiardquo The Journal of ClinicalInvestigation vol 97 no 10 pp 2377ndash2383 1996

[46] H Chiao Y Kohda P McLeroy L Craig S Linas and R AStar ldquo120572-Melanocyte-stimulating hormone inhibits renal injuryin the absence of neutrophilsrdquo Kidney International vol 54 no3 pp 765ndash774 1998

[47] P K Chatterjee N S A Patel E O Kvale et alldquoInhibition of inducible nitric oxide synthase reduces renalischemiareperfusion injuryrdquo Kidney International vol 61 no3 pp 862ndash871 2002

[48] A Kezic F Thaiss J U Becker T Y Tsui and M BajceticldquoEffects of everolimus on oxidative stress in kidney model ofischemiareperfusion injuryrdquo American Journal of Nephrologyvol 37 no 4 pp 291ndash301 2013

[49] H Ling P E Gengaro C L Edelstein et al ldquoEffect ofhypoxia on proximal tubules isolated fromnitric oxide synthaseknockout micerdquo Kidney International vol 53 no 6 pp 1642ndash1646 1998

[50] D B Zorov M Juhaszova and S J Sollott ldquoMitochondrialROS-induced ROS release an update and reviewrdquo Biochimicaet Biophysica Acta (BBA)mdashBioenergetics vol 1757 no 5-6 pp509ndash517 2006

[51] A P Halestrap P M Kerr S Javadov and K-Y WoodfieldldquoElucidating the molecular mechanism of the permeabilitytransition pore and its role in reperfusion injury of the heartrdquoBiochimica et Biophysica ActamdashBioenergetics vol 1366 no 1-2pp 79ndash94 1998

[52] M Crompton ldquoThemitochondrial permeability transition poreand its role in cell deathrdquoThe Biochemical Journal vol 341 part2 pp 233ndash249 1999

[53] G F Kelso C M Porteous C V Coulter et al ldquoSelectivetargeting of a redox-active ubiquinone to mitochondria withincells antioxidant and antiapoptotic propertiesrdquo The Journal ofBiological Chemistry vol 276 no 7 pp 4588ndash4596 2001

[54] V P Skulachev V N Anisimov Y N Antonenko et al ldquoAnattempt to prevent senescence a mitochondrial approachrdquoBiochimica et Biophysica ActamdashBioenergetics vol 1787 no 5 pp437ndash461 2009

[55] H M Cocheme G F Kelso A M James et al ldquoMitochondrialtargeting of quinones therapeutic implicationsrdquo Mitochon-drion vol 7 pp S94ndashS102 2007

[56] M P Murphy ldquoSelective targeting of bioactive compounds tomitochondriardquo Trends in Biotechnology vol 15 no 8 pp 326ndash330 1997

[57] L F Yousif K M Stewart and S O Kelley ldquoTargetingmitochondria with organelle-specific compounds strategiesand applicationsrdquo ChemBioChem vol 10 no 12 pp 1939ndash19502009


[58] H H Szeto ldquoMitochondria-targeted peptide antioxidantsnovel neuroprotective agentsrdquo The AAPS Journal vol 8 no 3pp E521ndashE531 2006

[59] K Zhao G-M Zhao D Wu et al ldquoCell-permeable peptideantioxidants targeted to inner mitochondrial membrane inhibitmitochondrial swelling oxidative cell death and reperfusioninjuryrdquo Journal of Biological Chemistry vol 279 no 33 pp34682ndash34690 2004

[60] C C Winterbourn H N Parsons-Mair S Gebicki J MGebicki and M J Davies ldquoRequirements for superoxide-dependent tyrosine hydroperoxide formation in peptidesrdquo Bio-chemical Journal vol 381 no 1 pp 241ndash248 2004

[61] S Asayama E Kawamura S Nagaoka and H KawakamildquoDesign of manganese porphyrin modified with mitochondrialsignal peptide for a new antioxidantrdquoMolecular Pharmaceuticsvol 3 no 4 pp 468ndash470 2006

[62] L N Hanly N Chen K Aleksa et al ldquoN-acetylcysteine as anovel prophylactic treatment for ifosfamide-induced nephro-toxicity in children translational pharmacokineticsrdquo Journal ofClinical Pharmacology vol 52 no 1 pp 55ndash64 2012

[63] S-S Sheu D Nauduri and M W Anders ldquoTargeting antioxi-dants tomitochondria a new therapeutic directionrdquoBiochimicaet Biophysica ActamdashMolecular Basis of Disease vol 1762 no 2pp 256ndash265 2006

[64] G J Gross and J A Auchampach ldquoBlockade of ATP-sensitivepotassium channels prevents myocardial preconditioning indogsrdquo Circulation Research vol 70 no 2 pp 223ndash233 1990

[65] A Szewczyk W Jarmuszkiewicz and W S Kunz ldquoMitochon-drial potassium channelsrdquo IUBMB Life vol 61 no 2 pp 134ndash143 2009

[66] B J Snow F L Rolfe M M Lockhart et al ldquoA double-blind placebo-controlled study to assess the mitochondria-targeted antioxidant MitoQ as a disease-modifying therapy inParkinsonrsquos diseaserdquo Movement Disorders vol 25 no 11 pp1670ndash1674 2010

[67] E J Gane F Weilert D W Orr et al ldquoThe mitochondria-targeted anti-oxidant mitoquinone decreases liver damage in aphase II study of hepatitis C patientsrdquo Liver International vol30 no 7 pp 1019ndash1026 2010

[68] A M James H M Cocheme R A J Smith and M P Mur-phy ldquoInteractions of mitochondria-targeted and untargetedubiquinones with the mitochondrial respiratory chain andreactive oxygen species implications for the use of exogenousubiquinones as therapies and experimental toolsrdquo The Journalof Biological Chemistry vol 280 no 22 pp 21295ndash21312 2005

[69] P Mukhopadhyay B Horvath Z Zsengeller et al ldquoMitochon-drial reactive oxygen species generation triggers inflammatoryresponse and tissue injury associated with hepatic ischemiandashreperfusion therapeutic potential of mitochondrially targetedantioxidantsrdquo Free Radical Biology and Medicine vol 53 no 5pp 1123ndash1138 2012

[70] V J Adlam J C Harrison C M Porteous et al ldquoTargetingan antioxidant to mitochondria decreases cardiac ischemia-reperfusion injuryrdquoThe FASEB Journal vol 19 no 9 pp 1088ndash1095 2005

[71] T Mitchell D Rotaru H Saba R A J Smith M P Mur-phy and L A MacMillan-Crow ldquoThe mitochondria-targetedantioxidant mitoquinone protects against cold storage injury ofrenal tubular cells and rat kidneysrdquo Journal of Pharmacology andExperimental Therapeutics vol 336 no 3 pp 682ndash692 2011

[72] A J Dare E A Bolton G J Pettigrew J A Bradley K Saeb-Parsy and M P Murphy ldquoProtection against renal ischemia-reperfusion injury in vivo by the mitochondria targeted antiox-idant MitoQrdquo Redox Biology vol 5 pp 163ndash168 2015

[73] Y N Antonenko A V Avetisyan L E Bakeeva et alldquoMitochondria-targeted plastoquinone derivatives as tools tointerrupt execution of the aging program 1 Cationic plasto-quinone derivatives synthesis and in vitro studiesrdquo Biochem-istry vol 73 no 12 pp 1273ndash1287 2008

[74] L E Bakeeva I V Barskov M V Egorov et al ldquoMitochondria-targeted plastoquinone derivatives as tools to interrupt execu-tion of the aging program 2 Treatment of some ROS- and age-related diseases (heart arrhythmia heart infarctions kidneyischemia and stroke)rdquo Biochemistry vol 73 no 12 pp 1288ndash1299 2008

[75] E Y Plotnikov A K Vasileva A A Arkhangelskaya IB Pevzner V P Skulachev and D B Zorov ldquoInterrela-tions of mitochondrial fragmentation and cell death underischemiareoxygenation and UV-irradiation protective effectsof SkQ1 lithium ions and insulinrdquo FEBS Letters vol 582 no20 pp 3117ndash3124 2008

[76] E Y Plotnikov A A Chupyrkina S S Jankauskas et al ldquoMech-anisms of nephroprotective effect of mitochondria-targetedantioxidants under rhabdomyolysis and ischemiareperfusionrdquoBiochimica et Biophysica Acta (BBA)mdashMolecular Basis of Dis-ease vol 1812 no 1 pp 77ndash86 2011

[77] E J Sharples andMM Yaqoob ldquoErythropoietin in experimen-tal acute renal failurerdquo Nephron Experimental Nephrology vol104 no 3 pp e83ndashe88 2006

[78] E J Sharples N Patel P Brown et al ldquoErythropoietin pro-tects the kidney against the injury and dysfunction causedby ischemia-reperfusionrdquo Journal of the American Society ofNephrology vol 15 no 8 pp 2115ndash2124 2004

[79] Y R Song T Lee S J You et al ldquoPrevention of acute kidneyinjury by erythropoietin in patients undergoing coronary arterybypass grafting a pilot studyrdquo American Journal of Nephrologyvol 30 no 3 pp 253ndash260 2009

[80] M Juhaszova D B Zorov S H Kim et al ldquoGlycogen synthasekinase- 3beta mediates convergence of protection signaling toinhibit the mitochondrial permeability transition porerdquo Journalof Clinical Investigation vol 113 no 11 pp 1535ndash1549 2004

[81] Z Wang Y Ge H Bao L Dworkin A Peng and R GongldquoRedox-sensitive glycogen synthase kinase 3120573-directed controlof mitochondrial permeability transition rheostatic regulationof acute kidney injuryrdquo Free Radical Biology and Medicine vol65 pp 849ndash858 2013

[82] E Y Plotnikov A V Kazachenko M Y Vyssokikh et al ldquoTherole of mitochondria in oxidative and nitrosative stress duringischemiareperfusion in the rat kidneyrdquo Kidney Internationalvol 72 no 12 pp 1493ndash1502 2007

[83] P Mukhopadhyay B Horvath Z Zsengeller et alldquoMitochondrial-targeted antioxidants represent a promisingapproach for prevention of cisplatin-induced nephropathyrdquoFree Radical Biology and Medicine vol 52 no 2 pp 497ndash5062012

[84] S S Jankauskas E Y Plotnikov M A Morosanova etal ldquoMitochondria-targeted antioxidant SkQR1 amelioratesgentamycin-induced renal failure and hearing lossrdquo Biochem-istry vol 77 no 6 pp 666ndash670 2012

[85] H T F Facundo J G de Paula and A J Kowaltowski ldquoMito-chondrial ATP-sensitive K+ channels prevent oxidative stress


permeability transition and cell deathrdquo Journal of Bioenergeticsand Biomembranes vol 37 no 2 pp 75ndash82 2005

[86] H T F Facundo J G de Paula and A J KowaltowskildquoMitochondrial ATP-sensitive K+ channels are redox-sensitivepathways that control reactive oxygen species productionrdquo FreeRadical Biology andMedicine vol 42 no 7 pp 1039ndash1048 2007

[87] F Domoki F Bari K Nagy D W Busija and L Siklos ldquoDia-zoxide prevents mitochondrial swelling and Ca2+ accumulationin CA1 pyramidal cells after cerebral ischemia in newborn pigsrdquoBrain Research vol 1019 no 1-2 pp 97ndash104 2004

[88] M Ichinose H Yonemochi T Sato and T Saikawa ldquoDia-zoxide triggers cardioprotection against apoptosis induced byoxidative stressrdquo American Journal of PhysiologymdashHeart andCirculatory Physiology vol 284 no 6 pp H2235ndashH2241 2003

[89] W B Reeves and S V Shah ldquoActivation of potassium channelscontributes to hypoxic injury in proximal tubulesrdquoThe Journalof Clinical Investigation vol 94 no 6 pp 2289ndash2294 1994

[90] Z Sun X Zhang K Ito et al ldquoAmelioration of oxidativemitochondrial DNA damage and deletion after renal ischemicinjury by the KATP channel opener diazoxiderdquo AmericanJournal of PhysiologymdashRenal Physiology vol 294 no 3 ppF491ndashF498 2008

[91] S Javadov M Karmazyn and N Escobales ldquoMitochondrialpermeability transition pore opening as a promising therapeutictarget in cardiac diseasesrdquo Journal of Pharmacology and Exper-imental Therapeutics vol 330 no 3 pp 670ndash678 2009

[92] D Morin R Assaly S Paradis and A Berdeaux ldquoInhibitionof mitochondrial membrane permeability as a putative phar-macological target for cardioprotectionrdquo Current MedicinalChemistry vol 16 no 33 pp 4382ndash4398 2009

[93] K Devalaraja-Narashimha A M Diener and B J PadanilamldquoCyclophilin D gene ablation protects mice from ischemic renalinjuryrdquo American Journal of PhysiologymdashRenal Physiology vol297 no 3 pp F749ndashF759 2009

[94] C W Yang H J Ahn H J Han et al ldquoPharmacologicalpreconditioning with low-dose cyclosporine or FK506 reducessubsequent ischemiareperfusion injury in rat kidneyrdquo Trans-plantation vol 72 no 11 pp 1753ndash1759 2001

[95] D Singh V Chander and K Chopra ldquoCyclosporine protectsagainst ischemiareperfusion injury in rat kidneysrdquo Toxicologyvol 207 no 3 pp 339ndash347 2005

[96] D K Ysebaert K E De Greef E J Nouwen G A VerpootenE J Eyskens and M E De Broe ldquoInfluence of cyclosporinA on the damage and regeneration of the kidney after severeischemiareperfusion injuryrdquo Transplantation Proceedings vol29 no 5 pp 2348ndash2351 1997

[97] G M Goncalves M A Cenedeze C Q Feitoza et al ldquoThe roleof immunosuppressive drugs in aggravating renal ischemia andreperfusion injuryrdquo Transplantation Proceedings vol 39 no 2pp 417ndash420 2007

[98] K Zhao G-M Zhao D Wu et al ldquoCell-permeable peptideantioxidants targeted to inner mitochondrial membrane inhibitmitochondrial swelling oxidative cell death and reperfusioninjuryrdquoThe Journal of Biological Chemistry vol 279 no 33 pp34682ndash34690 2004

[99] D A Brown H N Sabbah and S R Shaikh ldquoMitochondrialinner membrane lipids and proteins as targets for decreasingcardiac ischemiareperfusion injuryrdquo Pharmacology andThera-peutics vol 140 no 3 pp 258ndash266 2013

[100] D-F Dai T Chen H Szeto et al ldquoMitochondrial targetedantioxidant peptide ameliorates hypertensive cardiomyopathyrdquo

Journal of the American College of Cardiology vol 58 no 1 pp73ndash82 2011

[101] L Yang K Zhao N Y Calingasan G Luo H H Szetoand M F Beal ldquoMitochondria targeted peptides protectagainst 1-methyl-4-phenyl-1236-tetrahydropyridine neuro-toxicityrdquoAntioxidantsampRedox Signaling vol 11 no 9 pp 2095ndash2104 2009

[102] S Cho H H Szeto E Kim H Kim A T Tolhurst and JT Pinto ldquoA novel cell-permeable antioxidant peptide SS31attenuates ischemic brain injury by down-regulating CD36rdquoJournal of Biological Chemistry vol 282 no 7 pp 4634ndash46422007

[103] R A Kloner S L Hale W Dai et al ldquoReduction ofischemiareperfusion injury with bendavia a mitochondria-targeting cytoprotective peptiderdquo Journal of the American HeartAssociation vol 1 no 3 pp e001644ndashe001644 2012

[104] D A Brown S L Hale C P Baines et al ldquoReductionof early reperfusion injury with the mitochondria-targetingpeptide bendaviardquo Journal of Cardiovascular Pharmacology andTherapeutics vol 19 no 1 pp 121ndash132 2014

[105] A K Chakrabarti K Feeney C Abueg et al ldquoRationale anddesign of the EMBRACESTEMI Study a phase 2a randomizeddouble-blind placebo-controlled trial to evaluate the safetytolerability and efficacy of intravenous Bendavia on reperfusioninjury in patients treated with standard therapy includingprimary percutaneous coronary intervention and stenting forST-segment elevation myocardial infarctionrdquo American HeartJournal vol 165 no 4 pp 509ndash514e7 2013

[106] H H Szeto S Liu Y Soong et al ldquoMitochondria-targetedpeptide accelerates ATP recovery and reduces ischemic kidneyinjuryrdquo Journal of the American Society of Nephrology vol 22no 6 pp 1041ndash1052 2011

[107] A Eirin Z Li X Zhang et al ldquoA mitochondrial permeabil-ity transition pore inhibitor improves renal outcomes afterrevascularization in experimental atherosclerotic renal arterystenosisrdquo Hypertension vol 60 no 5 pp 1242ndash1249 2012

[108] N Parajuli and L A MacMillan-Crow ldquoRole of reduced man-ganese superoxide dismutase in ischemia-reperfusion injury apossible trigger for autophagy and mitochondrial biogenesisrdquoAmerican Journal of PhysiologymdashRenal Physiology vol 304 no3 pp F257ndashF267 2013

[109] H L Liang G Hilton J Mortensen K Regner C P Johnsonand V Nilakantan ldquoMnTMPyP a cell-permeant SOD mimeticreduces oxidative stress and apoptosis following renal ischemia-reperfusionrdquoAmerican Journal of PhysiologymdashRenal Physiologyvol 296 no 2 pp F266ndashF276 2009

[110] KDobashi BGhosh J KOrak I Singh andAK Singh ldquoKid-ney ischemia-reperfusion modulation of antioxidant defensesrdquoMolecular and Cellular Biochemistry vol 205 no 1-2 pp 1ndash112000

[111] H Saba I Batinic-Haberle S Munusamy et al ldquoManganeseporphyrin reduces renal injury andmitochondrial damage dur-ing ischemiareperfusionrdquo Free Radical Biology and Medicinevol 42 no 10 pp 1571ndash1578 2007

[112] J Cohen T Dorai C Ding I Batinic-Haberle and M GrassoldquoThe administration of renoprotective agents extends warmischemia in a rat modelrdquo Journal of Endourology vol 27 no 3pp 343ndash348 2013

[113] T Dorai A I Fishman C Ding I Batinic-Haberle D SGoldfarb and M Grasso ldquoAmelioration of renal ischemia-reperfusion injury with a novel protective cocktailrdquo Journal ofUrology vol 186 no 6 pp 2448ndash2454 2011


[114] I Batinic-Haberle A Tovmasyan E R H Roberts ZVujaskovic K W Leong and I Spasojevic ldquoSOD therapeu-tics latest insights into their structure-activity relationshipsand impact on the cellular redox-based signaling pathwaysrdquoAntioxidants amp Redox Signaling vol 20 no 15 pp 2372ndash24152014

[115] S Miriyala I Spasojevic A Tovmasyan et al ldquoManganesesuperoxide dismutase MnSOD and its mimicsrdquo Biochimica etBiophysica Acta vol 1822 no 5 pp 794ndash814 2012

[116] I Batinic-Haberle I Spasojevic H M Tse et al ldquoDesign of Mnporphyrins for treating oxidative stress injuries and their redox-based regulation of cellular transcriptional activitiesrdquo AminoAcids vol 42 no 1 pp 95ndash113 2012

[117] I Batinic-Haberle A Tovmasyan and I Spasojevic ldquoAn educa-tional overview of the chemistry biochemistry and therapeuticaspects of Mn porphyrinsmdashfrom superoxide dismutation toH2O2-driven pathwaysrdquo Redox Biology vol 5 pp 43ndash65 2015

[118] R A J Smith C M Porteous C V Coulter and M P MurphyldquoSelective targeting of an antioxidant to mitochondriardquo Euro-pean Journal of Biochemistry vol 263 no 3 pp 709ndash716 1999

[119] S E Brown M F Ross A Sanjuan-Pla A-R B ManasR A J Smith and M P Murphy ldquoTargeting lipoicacid to mitochondria synthesis and characterization of atriphenylphosphonium-conjugated 120572-lipoyl derivativerdquo FreeRadical Biology and Medicine vol 42 no 12 pp 1766ndash17802007

[120] A Filipovska G F Kelso S E Brown S M Beer R AJ Smith and M P Murphy ldquoSynthesis and characterizationof a triphenylphosphonium-conjugated peroxidase mimeticinsights into the interaction of ebselen with mitochondriardquoTheJournal of Biological Chemistry vol 280 no 25 pp 24113ndash241262005

[121] P K Chatterjee S Cuzzocrea P A J Brown et al ldquoTempola membrane-permeable radical scavenger reduces oxidantstress-mediated renal dysfunction and injury in the ratrdquoKidneyInternational vol 58 no 2 pp 658ndash673 2000

[122] U Aksu B Ergin R Bezemer et al ldquoScavenging reactiveoxygen species using tempol in the acute phase of renalischemiareperfusion and its effects on kidney oxygenation andnitric oxide levelsrdquo Intensive CareMedicine Experimental vol 3article 21 2015

Submit your manuscripts athttpwwwhindawicom

Stem CellsInternational

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014


MEDIATORSINFLAMMATION

of


Behavioural Neurology

EndocrinologyInternational Journal of



Disease Markers


BioMed Research International

OncologyJournal of



Oxidative Medicine and Cellular Longevity


PPAR Research

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Immunology ResearchHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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OphthalmologyJournal of


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Parkinsonrsquos Disease

Evidence-Based Complementary and Alternative Medicine

Volume 2014Hindawi Publishing Corporationhttpwwwhindawicom


or are easily converted into radicals such as hydrogen perox-ide (H

2O2) and hypochlorous acid (HOCl) ROS generation

represents a cascade of reactions starting with the productionof O2

∙minus that can be further converted to H2O2via superoxide

dismutases (SOD) manganese (MnSOD) in mitochondriaand copper-zinc (CuZnSOD) in the cytosol The main sinksfor H

2O2are catalase (CAT) and glutathione peroxidase

(GPx) The latter uses glutathione (GSH) which is oxidizedto GSSG and recycled by glutathione reductase There areother enzymes that can remove H

2O2 such as perox-

iredoxinthioredoxinthioredoxin reductase (PrxTrxTrxR)system However CAT activity is about three orders ofmagnitude higher compared to PrxTrxTrxR system [9]which is essential under physiological settings for keeping lowlevels of mitochondrial H

2O2emission and for normal redox

signaling via regulation of thiol redox switches on differentproteins [10]

H2O2can also react with transition metals such as iron

or copper to produce HO∙ the most reactive species in livingsystems [11] The main reactive nitrogen species (RNS) arenitric oxide (NO∙) and peroxynitrite (ONOOminus) ONOOminusis formed via reaction between NO and O

2

∙minus and can befurther protonated and decomposed to nitrogen dioxideradical (NO

2

∙) and HO∙ [12 13] These radicals are ldquocagedrdquo(ie generated close to each other) so they can recombinequickly and much of ONOOminus undergoes isomerisation tonitrate Some amount of ONOOminus in vivo reacts with CO

2to

form nitrosoperoxycarbonate (ONOOCO2

minus) About 35 ofONOOCO

2

minus is decomposed to NO2

∙ and carbonate radical(CO3

∙minus) [14] The latter is highly oxidizing species targetingNADPH and proteins [15 16]

Mitochondria are the major site of ROS production dueto inevitable leakage of electrons from electron transportchain (ETC) onto oxygen [17] Other major intracellular sitesof ROS generation are enzymes such as NADPH oxidase(NOX) and xanthine oxidase (XO)

Initially in ischemic phase kidney tubular epithelial andendothelial cells are main producers of ROS and are lateraccompanied by activated leucocytes that is oxidative burstrelated to inflammation These events reveal the role of ROSin exerting detrimental effects on cellular structure linkingoxidative stress inflammation and cell death ROS throughinteractions with small metabolites as well as proteins lipidsand nucleic acids might irreversibly destroy or alter the func-tion of these target molecules and belonging organelles andcells ROS can also serve as homeostatic signaling moleculeswhich primarily depends on magnitude and duration ofprovoking stimuli for ROS production

In recent years it has become clear thatmitochondria havecritical role in initiation and progression of renal IRI Theyare early responders to the anoxia and then reoxygenationinitiating responses that lead to changed metabolic andbioenergetic status autophagy inflammation and inductionof cell death pathways Several approaches mainly in exper-imental studies with a few human trials have been usedin investigating the options for preventing and treatment ofIRI with special emphasis on modulation of inflammatoryresponse inhibition of apoptosis and amelioration of oxida-tive stress but currently there is no effective pharmacological

treatment to address the main mechanisms of ischemic AKI[18ndash20] Recently novel therapeutic approach called ischemicpreconditioning has become translated from animal modelsto humans [20 21] It is based on the observations thatepisodes of nonlethal ischemia can precondition the kidneyto be protected in subsequent prolonged ischemia

Nevertheless oxidative stress is crucial for the cascadeof processes participating in the pathogenesis of IRI Sincemitochondria as both sources and targets of ROS are initia-tors of complex mechanisms in IRI it seems reasonable fromtherapeutic perspective to develop pharmacological methodaiming to decrease mitochondrial oxidative damage

In this review we will summarize the mechanisms ofmitochondrial ROS production and some options for poten-tial treatment strategies

2 The Role of Mitochondria inthe Pathogenesis of IRI

By impairing electron transport and energy metabolism andby altering cellular redox potential via ROS productionmitochondria trigger events leading to apoptosis a hall-mark of IRI Electron transport along ETC to O

2is tightly

coupled to oxidative phosphorylation for ATP synthesis Innormal for instance nonischemic cells the main source ofROS is ETC [22 23] Most oxygen consumed is reducedto water through 4 steps of single electron reduction bycytochrome c oxidase Electrons generated from reducednicotinamide adenine dinucleotide (NADH) are acceptedby NADH dehydrogenase (Complex I) and those fromsuccinate are accepted by succinate dehydrogenase (ComplexII) Electrons are then passed to cytochrome bc1 (ComplexIII) through coenzymeQ (CoQ) and to cytochrome c oxidase(Complex IV) using cytochrome c as a carrier The laststep is transfer of electron from cytochrome c oxidase toO2to form water (Figure 1) Electron flow mediated by

the respiratory chain enzyme complex drives proton (H+)translocation from the matrix side at the level of complexesI III and IV to the intermembrane space side therebyestablishing an electrochemical potential gradient or protonmotive force across the inner membrane [23] Since theinner mitochondrial membrane is almost impermeable thiselectrochemical gradient is used to reintroduce protons backthrough the proton channel of complex V (ATP synthase)ATP synthesis from ADP and inorganic phosphate is thencatalyzed by F

0F1ATPase Every decrease in the rate of mito-

chondrial phosphorylation increases electron leakage fromthe ETC and consequently increases the production of O

2

∙minusMitochondria have defense mechanism to neutralize ROSSuperoxide radical anion is converted to H

2O2by MnSOD

and H2O2is further degraded to H

2O In mitochondria

about 70ndash80 of H2O2removal has been attributed to

GPx [9] ROS may induce mild mitochondrial oxidativestress or diffuse to the cytosol playing an important role incellular homeostasis mitosis and differentiation and servingas signaling molecules in different physiological responses[24 25] This constant production of small amounts of ROSis necessary to maintain the appropriate ldquoredox staterdquo of cell


I

III

II

CoQ

ee

eIV

SOD

GPxFADH2 FADHNADH

Cyt c

O2∙minus

2H+

NAD+

H2OH2O12O2

H+

H+

H+

H2O2

O2




2O2












2O2generated




2


2


2O2to water is




















O

O

O

OMitoQuinone

OH

OH

O

O

MitoQuinol

OH

OH

O

O

SkQ1

NOHN

O

OHO

OH

SkQR1

H+

P+

P+

P+







O

HN

NH

HN

O

OH

NH

O

HN

O

OH

SS-31

H2N

NH2

NH2









N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+



2


2




2O2-driven


2O2



2



5 Conclusion







Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















I

III

II

CoQ

ee

eIV

SOD

GPxFADH2 FADHNADH

Cyt c

O2∙minus

2H+

NAD+

H2OH2O12O2

H+

H+

H+

H2O2

O2




2O2












2O2generated




2


2


2O2to water is




















O

O

O

OMitoQuinone

OH

OH

O

O

MitoQuinol

OH

OH

O

O

SkQ1

NOHN

O

OHO

OH

SkQR1

H+

P+

P+

P+







O

HN

NH

HN

O

OH

NH

O

HN

O

OH

SS-31

H2N

NH2

NH2









N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+



2


2




2O2-driven


2O2



2



5 Conclusion







Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of


































O

O

O

OMitoQuinone

OH

OH

O

O

MitoQuinol

OH

OH

O

O

SkQ1

NOHN

O

OHO

OH

SkQR1

H+

P+

P+

P+







O

HN

NH

HN

O

OH

NH

O

HN

O

OH

SS-31

H2N

NH2

NH2









N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+



2


2




2O2-driven


2O2



2



5 Conclusion







Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















O

HN

NH

HN

O

OH

NH

O

HN

O

OH

SS-31

H2N

NH2

NH2









N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+



2


2




2O2-driven


2O2



2



5 Conclusion







Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of

















N

N

N

N

MnTMPyP

N

N

N

N

N+

N+

N+

N+ N+

N+N+

N+

Mn+

Mn+ 5Clminus

MnTnHex-2-PyP5+



2


2




2O2-driven


2O2



2



5 Conclusion







Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of





















Competing Interests


References
















2
























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of




























































































































of






Disease Markers



OncologyJournal of





PPAR Research



Journal of

ObesityJournal of
















review article mitochondria-targeted antioxidants: future...

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