hypothesis the generation of pro-oxidants secondary to abnormal placental perfusion interacts with...

HypothesisHypothesis

The generation of pro-oxidants secondary to abnormal placental perfusion interacts with maternal constitutional factors to generate oxidative stress.

QuestionsQuestions

Is there evidence of oxidative stress?

What is the source of oxidative stress?

Are antioxidants reduced?

Evidence of oxidative Evidence of oxidative stress in preeclampsiastress in preeclampsia

Increased circulating markersLipids (MDA, isoprostanes)Activated blood cellsAntibodies to ox-LDL

Tissue changesIncreased nitrotyrosine (NO + O) in placenta and maternal vessels

Ascorbate consumption

QuestionsQuestions

Is there evidence of oxidative stress?

What is the source of oxidative stress?

Are antioxidants reduced?

The placenta as a source The placenta as a source of oxidative stressof oxidative stress

Speculation:Uterine blood flow is reduced with uterine contractions.In addition uterine blood flow is not privileged and is decreased with posture and activity.With abnormal implantation might these physiological changes result in a hypoxia reperfusion scenario?

QuestionsQuestions

Is there evidence of oxidative stress?

What is the source of oxidative stress?

Are antioxidants reduced?

Xanthine Xanthine Oxidase/DehydrogenaseOxidase/Dehydrogenase

Xanthine Xanthine dehydrogenase (XOD)

NADH + Uric Acid

Xanthine Xanthine oxidase (XO)O + Uric Acid.

2

XOD + hypoxia XOD XO

Cytokines

XOD XO

Cytokeratin XOD

Normal 7 wks

Normal 18 wks

Normal 34 wks

Preeclampsia 28 wks

The definitive questionThe definitive question

Can preventing oxidative stress prevent endothelial activation and Stage 2 of preeclampsia?

A (small) randomized A (small) randomized controlled trial of antioxidant controlled trial of antioxidant

therapy to prevent therapy to prevent preeclampsiapreeclampsia

Chappell LC, Seed PT, Briley AL, Kelly FJ, Lee R, Hunt BJ, Parmar K, Bewley Chappell LC, Seed PT, Briley AL, Kelly FJ, Lee R, Hunt BJ, Parmar K, Bewley SJ, Shennan AH, Steer PJ, Poston L. Lancet 1999;354:810-816SJ, Shennan AH, Steer PJ, Poston L. Lancet 1999;354:810-816

High risk women identified by: doppler of uterine artery (20 and 24

weeks gestation)preeclampsia in previous pregnancychronic hypertensionprevious early onset preeclampsia

DesignDesign

positive screened women randomized at 20 weeks to 1 gm ascorbic acid and 400 IU vitamin E (n = 141) or placebo (n = 142)

If doppler not positive at 24 weeks Rx stopped

intent to treat analysisprimary outcome 30% reduction in

evidence of endothelial activation (PAI-1/PAI-2)

ResultsResults

PAI-1/PAI-2 20% with Rx (p < 0.015)

Preeclampsia (p = 0.02)Placebo 24/142Rx 11/141

Stage 2: Maternal Syndrome

Oxidative Stress

Stage 1: Reduced Placental perfusion abnormal

implantation

Maternal Constitution:

Genetic, Behavioral,

Environment

Future approachesFuture approaches

Identify women with predispositions and treat appropriately (e.g.thrombophillia, dyslipidemia)

Antioxidants?

Antioxidants for Antioxidants for preeclampsiapreeclampsia

Will they work?

Are they safe?

Antioxidant TrialAntioxidant Trial(in preparation)(in preparation)

NICHD/NHLBI/?Canada/?WHO

DesignDesign

RCT of vitamin C (1000 mg.) and Vitamin E (400 iU) vs. placebo

Prospective collection of data and biological materials

Primary outcome• severe growth restriction < 3d

centile• Infant death after 20 weeks

gestationPower analysis

p < 0.05 and power = 0.8 to detect 30% reduction in primary outcome

DesignDesign

Subjects• Nulliparous low risk women

(9000)• ? High risk women (3600)• ? Women from low C and E

intake areas (WHO)

NICHD Antioxidant NICHD Antioxidant TrialsTrials

Does it satisfy the Does it satisfy the “requirements“?“requirements“?

• Should have as primary outcome an endpoint relevant to neonatal well-being.– IUGR and death

• Must be large enough to detect adverse fetal/neonatal outcome.– At least 4500 women in each arm

NICHD Antioxidant NICHD Antioxidant TrialsTrials

Does it satisfy the Does it satisfy the “requirements“?“requirements“?• Should have as primary outcome an

endpoint relevant to neonatal well-being.– IUGR and death

• Must be large enough to detect adverse fetal/neonatal outcome.– At least 4500 women in each arm

Admits our knowledge is limited and collects mechanistic data

Preventing Preventing PreeclampsiaPreeclampsiathe “bottom line“the “bottom line“

Any future clinical trial must be guided by well established pathophysiological information

We must understand a disease before we can prevent it!

SummarySummary

Calcium and aspirin in large clinical trials did not reduce the frequency of preeclampsia

“Hints” from the aspirin trials indicate that the strategy of early treatment may be effective

Increasing data supports diverse maternal factors contributing to the pathogenesis of preeclampsia

Oxidative stress may be the convergence point

Keep your fingers crossed!

Aspirin for Aspirin for PreeclampsiaPreeclampsiaPrevention trialsPrevention trials

PreeclampsiaASA Placebo RR (95% CI)

SmallTrials

10/3193%

50/28418%

0.2 (0.1, 0.4)

Largetrials

949/139286.8%

1032/137657.5%

0.9 (0.8, 1.0)

Alltrials

959/142476.7%

1082/140497.7%

0.9 (0.8, 1.0)

After Carits et al NEJM 338:701; 1998

Aspirin for Aspirin for PreeclampsiaPreeclampsiaPrevention trialsPrevention trials

IncidenceASA Placebo RR (95% CI)

PretermDelivery

2404/1372917.5%

2540/1364518.6%

0.9 (0.9, 1.0)

PerinatalDeath

418/144072.9%

450/142533.2%

0.9 (0.8, 1.0)

After Carits et al NEJM 338:701; 1998

Why the Discrepancies?Why the Discrepancies?ASA Trial SpecificASA Trial Specific

%Preec.

%SGA

BirthWeight

“ASA” “ASA” “ASA”n + - + - + -

* *Intent to Rx 604 1.7 5.6 5.6 6.3 3249 3169

* * *Compliance 558 1.9 5.7 2.9 7.0 3314 3122

The impact of compliance

Why the Discrepancies?Why the Discrepancies?ASA Trial SpecificASA Trial Specific

Wrong dose of ASA?

Wrong timing?(*time of day and time of pregnancy)

Poor compliance?

SummarySummary

Trials of preeclampsia prevention (early treatment) have not demonstrated clinically relevant effects.

In single center trial with compliance monitoring ASA was minimally effective.

Future studies should identify a relevant target before more trials.

There may be different targets in different subsets of preeclamptic women.

Chlamydia pneumoniaeChlamydia pneumoniaeassociation with vascular diseaseassociation with vascular disease

Seropositivity is more commonCoronary artery diseaseCerebrovascular diseaseHypertension

OrganismsPresent in diseased coronariesPresent in atherosclerotic tissueTropism for vascular tissue (smooth muscle and endothelium)

Chlamydia pneumoniaeChlamydia pneumoniaeassociation with preeclampsiaassociation with preeclampsia

Adjusted(age)

%IgG

OR CI OR CI

Preeclampsia 68% 3.1 1.2,7.9

3.3 1.2,9.5

Normal 41%

No difference in I gM or I gA

Aspirin for Aspirin for PreeclampsiaPreeclampsia

The NIH High Risk StudyThe NIH High Risk Study

Incidence ofPreeclampsia %

Risk Group n ASA PlaceboPregestationalDiabetes

462 18 22

Hypertension 763 26 25Multifetalgestation

678 12 16

Previouspreeclampsia

600 17 19

All groups 2503 18 20

Oxidative stress in Oxidative stress in preeclampsiapreeclampsia

linkage of placenta and systemiclinkage of placenta and systemic

Stable products of lipid peroxidation

Activated neutrophils/monocytes

Microvillus fragments