free radical

44
Free Radicals and Antioxidants Dep.of Biochemistry Faculty of Medicine.Hasanuddin Univ. Rosdiana Natzir.,MD.,Ph.D.,Prof.Sp.Biok. SYSTEM GERIATRIC

Upload: ahmadyanio

Post on 11-Dec-2015

20 views

Category:

Documents


1 download

DESCRIPTION

Kuliah Biokimia Geriatri

TRANSCRIPT

Page 1: Free Radical

Free Radicals and Antioxidants

Dep.of BiochemistryFaculty of Medicine.Hasanuddin Univ.

Rosdiana Natzir.,MD.,Ph.D.,Prof.Sp.Biok.

•SYSTEM GERIATRIC

Page 2: Free Radical

TOPICS

• THE FREE RADICAL THEORY. • MITOCHONDRIA AND AGING. • THE GLYCATION THEORY. • PROTEINS DAMAGE AND MAINTENANCE IN AGING. • DNA DAMAGE AND DNA REPAIR. • TELOMERES THEORY.

Page 3: Free Radical

30/08/2002 3

Introduction  There was an era when people were worried about the disease processes and its treatment.

But off late, tremendous efforts are being made to find out the ways of prevention of important diseases.

The important research studies are rightly to be repeated with other populations, but nevertheless give an opportunity to consider the integrated actions of the known reducing (Antioxidant) systems.

Inadequacy of certain internally produced reducing systems has been postulated as being at the core of some disease processes.

Page 4: Free Radical

30/08/2002 4

It is believed that life has originated from basic chemicals.

By free radical reaction, largely initialled by ionising radiation from sun.

Paradoxically the same reactions creating life may also be responsible for many diseases, ageing and death.

Page 5: Free Radical

30/08/2002 5

Free Radicals

• These are highly reactive chemical entities that have a single unpaired electron in their outer most orbit.

• Under certain conditions can be highly toxic to the cells.

• Generally unstable and try to become stable, either by accepting or donating an electron.

Page 6: Free Radical

• Therefore if two FRs react, they neutralise each other.• However, if the FRs react with stable molecules, there

is generation of more free radicals.

• This characteristic enables the FRs to participate in auto catalytic chain reactions,

– Molecules with which they react are themselves converted to free radicals to propagate the chain of damages.

30/08/2002 6

Page 7: Free Radical

30/08/2002 7

Reactive Oxygen Species (ROS): -

These are free radicals derived initially from oxygen. But as they do not contain unpaired electrons in their outermost orbit, they do not qualify as free radicals and so are referred to separately as ROS.

Eg. - H2O2, HOCL, NO.

Free radicals are formed in side our body by both PHYSIOLOGICAL (Natural) and PATHOLOGICAL stimuli : -

Page 8: Free Radical

They are two conditions of stimuli to form FRs :

1.Physiological stimuli.2.Pathological stimuli.

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 8

Page 9: Free Radical

30/08/2002 9

Physiological Stimuli that Form FRs

• Normal respiration –

– O2 – Superoxide, – H2O2 – Hydrogen Peroxide– HOCL – Hypochlorous acid– NO – Nitric Oxide

• Transition metals present inside our body when are in free form behave as free radicals. Fe2+, Cu+

Page 10: Free Radical

• Body cells-

– Endothelium (NO3 – Nitric Oxide, NO2 – Nitrous Oxide), – Macrophages (NO2) – Neurones (ONOOH – Peroxy nitrite).

• Ageing

• Phagocytosis or biogenetics

• Oxidation of foods and endogenous compounds. • Transportation of substances for energy production.

30/08/2002 10

Page 11: Free Radical

30/08/2002 11

Pathological Stimuli that Form FRs

• Radiation Breaks the water inside our body: H2O =H+ + OH-

• Metabolism of drugs CCl3• Transition Metals Cu+, Fe2+• Ultraviolet rays• Emotional stress

Page 12: Free Radical

30/08/2002 12

Actions of FRs

Mechanism of Action: • They act on the cell membranes and

membranes of different organelles of cells and cause cell injury and death by oxidative reactions.

• So FRs are also called OXIDANTS.

Page 13: Free Radical

30/08/2002 13

Actions of FRs

• FRs cause lipid peroxidation.– The PUFA of cell membrane are more vulnerable

for this injury. By lipid peroxidation FR increases the permeability of cells, leading to calcium influx and altered PH of the cell.

• FRs alter the enzyme and receptor proteins.– FRs cause – cross-linking of proteins and

fragmentation of protein strands, oxidation of amino acids like cysteine, Methionine.

– These alterations in the enzymes and receptors inside the cell lead to abnormal cell behaviour.

Page 14: Free Radical

30/08/2002 14

Actions of FRs

• FRs cause fracturing on the cell nucleus resulting in single strand DNA damage.

• This oxidative injury may be.– Lethal – Leading to cell death and ultimately

removed by phagocytosis.– Sub lethal - which may result in

• Increased cell permeability.• Toxicity.• Mutation of cells.

Page 15: Free Radical

30/08/2002 15

FRs Induce Chain Reaction

• During the process of oxidant damage resulting in tissue destruction & degeneration, some electrons may escape oxidation and become FRs

• This chain reaction may produce diseases like: -– Carcinogenesis.– Myocardial reperfusion injury.– Shock related injury.– Arteriosclerosis.– Rheumatoid arthritis.– Adult respiratory diseases.– Diabetes.– Obesity.– Lipid abnormality. Etc.

Page 16: Free Radical

30/08/2002 16

Antioxidants (AOs)

• These are substances, which protect us against potentially harmful free radicals derived from oxygen.

• To combat the injurious effects of FRs our body has its own system of ‘in vivo’ Antioxidants’.

• In normal healthy state a balance is maintained between FRs & AOs

• The ‘AO’ activity of serum is measured as - % inhibition of lipid peroxidation in a standardised brain homogenate.

• Moreover we can as well supplement these from outside (in vitro Antioxidants).

Page 17: Free Radical

30/08/2002 17

In Vivo Antioxidants: -

I.EnzymesI.Enzymes

Name Acts against Present in

SOD (Superoxide dismutase)

Super oxide cytosol mitochondria.

CATALASE H2 O2 Blood, bone marrow, Mucus membrane Kidney; Liver.

GOP (Glutathion peroxidase)

H2 O2, lipid

peroxidation

membranes of lipids, Haemoglobin and erythrocytes

Page 18: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 18

In Vivo Antioxidants: -

These are binding proteins. They keep the free ions of plasma in a binding form, so prevent oxidation injury. Eg.-Transferin for Fe, Ceruloplasmin for Cu

II. II. Preventive AOPreventive AOss

III. III. Scavenger AOScavenger AOss

Also called chain breaking enzymes, they break the catalytic chain propagated by FRs.

Page 19: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 19

In Vivo Antioxidants: - Source

Vitamin A, C & E,

Cystine, Glutathion, Melthionine,

Bioflavines, Se, Zn.

I. In the form of Medicines:

II. Food sources:

Green & yellow vegetables

Herbs: -Turmeric/kunyit, Garlic, Grape, Tea, Berries, Carrot, Spinach, Broccoli,

Red Meat, Kidney, Liver & Lipoic Acid

Page 20: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 20

Oxidative Stress: -

• Under normal conditions body maintains an equilibrium between its own FR’s and Antioxidants.

• When this equilibrium breaks, a state called oxidation stress arises with in, due to FR formation or AO system.

Page 21: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 21

Example:

AO Status in Normal Pregnancy: -

• There is increased need for AOs as there is increased production of FRs due to

– Pregnancy being a stressful condition. – Because of the rapidly growing foetus there is increased

cellular activity.

Page 22: Free Radical

• Thus AO activity during normal pregnancy progressively increases as demonstrated by

Serum tocopherol. Activity of GOP. Serum ceruloplasmin & transferring level.

• However, there is no evidence to suggest the need for administration of ‘AOs’ during normal pregnancy but drugs that lead to ‘FR’ formation must be avoided.

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 22

Page 23: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 23

AOs & Diabetic Embryopathy: -

• Oxidative stress has been suggested to contribute to the increased risk of foetal malformations in poorly controlled diabetics. – There are reports of lipid peroxidation in cell

membranes in diabetic pregnancies – Periods of maternal hyperglycaemia & hypoglycemia may

cause marked changes in the availability of glucose to the foetus.

– Also conc. of lipids, notably the ketone bodies and branched chain amino acids in the maternal circulation contribute to altered nutrition for the embryo

Leading to FR conc. & foetal malformation in embryo.

Page 24: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 24

AOs & Diabetic Embryopathy: -

• During later part of pregnancy

load of glucose in the mitochondria may accelerate the flow of electrons through respiratory chain including mitochondrial leakage of free radicals.

– This leads to production of FR in embryonic tissues to cause congenital malformations.

Page 25: Free Radical

• Thus maintenance of normal concentration of metabolites of all nutrient class may be important for prevention of adverse foetal outcome.

• But the question is “ will dietary supplements alone hold the key to the future in diabetic embryopathy”?

• However, maintenance of blood glucose level at euglycemic level is always important for prevention of Diabetic embryopathy .

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 25

Page 26: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 26

AOs & Down Syndrome: -

• Free radicals being the hallmark of aging, are greatly increased with maternal age.

• So FRs play a role in pathogenesis of Down’s syndrome.

• Administration of AOs may help in preventing this disease.

Page 27: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 27

FRs & AOs in PIH : -

• Increased activity of free radicals promote maternal uterine vascular malformations.

– FRs are promoters of maternal vasoconstriction.

• O2 , H2 O2 & NO2 in combinations

– Inactivate the NO (a vasorelaxant) – Causes PG synthatase activity.– Produce peroxynitrate, a potent oxidant

PIH –pituitary inhibiting hormone

Page 28: Free Radical

• leading to the subsequent development of PIH • Evidence-.

– Lipid peroxide in pre-eclamptic placenta is about 1.8 times higher in comparison to normal placenta.

– Vit. E is less in serum of PIH patients.

– Severity of hypertension has been found to be inversely proportional to concentration of Vit. E.

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 28

Page 29: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 29

FRs & AOs in Preterm Delivery: -

• Sub clinical chorioamnionitis leads to liberation of bacterial antitoxins (polysaccharide in nature) and inflammatory cytokines.

• These cause stimulation of inflammatory cells and cells of CX. which in turn produce NO2.

• Evidence: There is N2O in vaginal samples of females having preterm delivery.

• So antioxidants may play a part in the treatment of preterm delivery.

Page 30: Free Radical

30/08/2002 30

FRs & AOs in New Born Babies: -

• In recent years experimental and clinical data have provided compelling evidences for involvement of oxygen derived ‘FRs’ in disorders of prematurity.– Chronic lung disease– Retinopathy– Intra ventricular haemorrhages.– Necrotising Enterocolitis: - FRs cause

microvascular injury and cell permeability leading to necrotising enterocolitis.

Page 31: Free Radical

30/08/2002 31

FRs & AOs in New Born Babies: -

• PDA: - Hypoxanthine radical in NBB leads to formation

of PGE2 and causes PDA.•  Kwashiorkor: -

– Studies suggest that kwashiorkor babies have FRs in their body .

‘AO’ in Kwashiorkor babies are due to deficiency of Vit. A, E, C, Inositol & Selinium.

• Ideally the future treatment of Neonates with all these disease should include AO therapy.

Page 32: Free Radical

30/08/2002 32

Carcinogenesis: -

• Basics of cancer formation: -– A normal cell can undergo malignant

transformation in presence of procarcinogens and carcinogens.

– However, in early stages, it can revert back to normal cell when detected and corrected by our body immune system.

– Without immune system detection a normal cell is converted to malignant cell in stages –

• Initiation Promotion Progression

Page 33: Free Radical

30/08/2002 33

FRs in Carcinogenesis: -

• Free radicals are formed from stimulants like – Radiation - Xenobiotics - Inflammatory cells - Respiration etc, which act on cellular targets to cause oxidant

DNA damage in form of mutagenesis & clostogenesis,

Page 34: Free Radical

- which cause: - initiation of carcinogenesis by-

• Activation of protooncogens.• Inactivation or loss of tumour suppresser genes.• Normal cell becomes initiated cell.

– Procarcinogens are metabolically activated by FRs, which cause promotion and progression of these initiated cells to cancer

– Ultimately carcinogenesis sets in

30/08/2002 34

Page 35: Free Radical

30/08/2002 35

FRs & AOs in Carcinogenesis: -Normal cell

Repair by AOsInitiation

Initiated Cell

Premalignant Cell

Malignant Cell

Repair by AOs

Repair by AOs

FRs Activation of procarcinogens & Carcinogens Genetic Damage

Promotion

Progression

FRs

- Tumour promoters

- Spontaneous

FRs

- Dysregulation

- Greater Cell autonomy

- Reduced Growth Factor dependence

CLINICAL CANCERCLINICAL CANCER

Page 36: Free Radical

30/08/2002 36

AOs in Cancer Prevention: -

• DEFENCE: - enzymes with antioxidant property cause first line of defence by: -– Protecting the lipids and enzymes against oxidation

Retarding the generation of free radicals Creating a balance of ‘AOs’ against FRs in the body  PREVENTS : -

• Cell pathology.• Metabolic disturbances.• Changes in cell permeability.• Eormation of toxic products.

Prevention of initiation of Carcinogenesis

Page 37: Free Radical

30/08/2002 37

AOs in Cancer Prevention: -

• INTERVENTION at promotion & progression stages: – Local deactivation of genotoxins responsible for

further nuclear mutations– Inactivation of tumour promoters eg.- activation of

granulocytes. – Simulate oxygen.– Maintenance of proper function of gap junction

communication.– Maintenance of physical stability of membrane &

also within cells.

Page 38: Free Radical

30/08/2002 38

AOs in Cancer Prevention: -

• Majority of epidemiological data suggest supplementation with antioxidants

- Vit.- A, E, C; - beta carotene & selenium, decreases the

incidence of various cancers.

Page 39: Free Radical

30/08/2002 39

RECOMMENDED FOR CARCINOMA PREVENTION(Federation of Obstetric & Gynaecological Societies of India)

AOs in Cancer Prevention: -

Antioxidant RDA Recommended Dose

Possible Toxicity Level

Features Causing Req.

Vitamin ‘A’ 5000 IU 12,500 IU Chronic intake of 125,000 IU

Smoking

Vitamin ‘E’ 10-20 IU 200-800 IU >1,200 IU High PUFA intake, Smoking

Vitamin ‘C’ 60 mg 1000 mg Negligible / 1-2Gms

Stress, OCP,Smoking

Selenium None 50-200 mg >200mg Aging, High PUFA intake, Smoking, Heavy metals

Page 40: Free Radical

30/08/2002 40

FRs & AOs in Infertility - Male

• Various studies have suggested Conc. of Malon –di-Aldehyde (MDA) is inversely proportional to fertility in case of males.

• In asthenospermic and oligoasthenospermic males there is increased serum concentration of MDA.

• Even in normospermic males if there is concentration of MDA there is reduced fertility.

• Addition of vitamin E causes decreased concentration of MDA and improves fertility.

Page 41: Free Radical

30/08/2002 41

FRs & AOs in Infertility - Female

• FRs cause -– Short luteal phase and LPDS.– In IVF arrest the cell growth (div) at 2, 4, 8 cell

stages– Hamper the regulation of corpus luteum.

•  Addition of ‘AOs’ improves the results.

Page 42: Free Radical

30/08/2002 42

CONCLUSION

Oxidant generation is a part of human life.

Every O2 atom we breath in ,is converted to water

inside our body by addition of four electrons

sequentially.

When four electrons are added three ‘FRs’- O2,

H2 O2 & OH are formed along with water.

So where there is life there are oxidants.

Page 43: Free Radical

30/08/2002 43

CONCLUSION

But when produced in excess, they can cause

any disease.

So our concern should be to FRs in systemic

circulation.

However, careful use of ‘AOs’ and newer and

more accurate methods to measure oxidant

generation in humans , will go a long way to find

out the exact contribution of oxidants in disease

processes and the role of ‘AOs’ to prevent it.

Page 44: Free Radical

30/08/2002 Antioxidants in Obstetrics and Gynaecology - Prof.S.N.Panda & Dr.Sasmita Das 44

THANK YOUTHANK YOU