PG Classroom - Seminar - Oxidative Stress







What is Oxidative stress? (O.S.)


– Oxidative stress is a general term used to describe the steady state level of oxidative damage a cell, tissue or organ, caused by the reactive oxygen species (R.O.S.).

– In a healthy body, R.O.S. and antioxidants remain in balance. When the balance is disrupts towards an overabundance of R.O.S., O.S. occurs.

– O.S. influences the entire reproductive lifespan of a woman and even-thereafter - menopause.

– O.S. results from an imbalance between prooxidants (FREE RADICALS) & body scavenging ability (antioxidants).

– The level of oxidative stress is determined by the balance between the rate at which oxidative damage is induced (INPUT) & the rate at which it is efficiently repaired and removed.

What Are Free Radicals ? (FRs)

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.

Therefore if two FRs react, they neutralize each other.

However, if the FRs react with stable molecules, there is generation of more free radicals.

What are free Radicals ? (FRs)

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.

Reactive Oxygen Species (R.O.S.): -

– 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 R.O.S..

– E.g.- H2O2, HOCL, NO.

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+

Body cells-

– Endothelium (NO3 – Nitric Oxide, NO2 – Nitrous Oxide),

– Macrophages (NO2)

– Neurons (ONOOH – Peroxy nitrite).


Phagocytosis or biogenetics

Oxidation of foods and endogenous compounds.

Transportation of substances for energy production.

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

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.

– 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

Actions of FRs

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

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.

– Mutation of cells.

How body protect against Free-radicals?


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’

Moreover we can as well supplement these from outside `in vitro Antioxidants.`

In VIVO Antioxidants:

1) Enzymes

Name Acts against Present in

SOD (Superoxide desmutase) Superoxide Cytosol, mitochondria

CATALASE H2O2 Blood, bone marrow,

Mucus membrane kidney;


GOP (Glutathion peroxidase) H2O2 lipid peroxidation. Membranes of lipids,

Hemoglobin and erythrocytes.

2) Preventive AOs

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

3) Scavenger AOs

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

In Vivo Antioxidants : Source

In the form of Medicines

– Vitamin A, C & E.

– Cystene, Glutathion, Methionine,

– Bioflavines, Se, Zn.

Food Sources:

– Green & yellow vegetables.

– Herbs : Turmeric, Garlic, Grape, Tea, Berries, Carrot, Spinach

– Red Meat, kidney, liver & Lipoic Acid.

Conditions in Obstetrics and Gynecology

Oxidative stress has been implicated in the etiology of various pathological conditions.

– Pregnancy related

• Preeclampsia

• Maternal diabetes

• Spontaneous abortions

– Gynecological conditions

• Endometriosis

• Malignancies

• Infertility

– Other conditions

• Myocardial infarction

• Cataract

• Rheumatoid arthritis.


Effect on embryo

Successful implantation and development of fertilized egg requires low superoxide environment and optimal NO concentration.

Can be studied by observing effect of O.S. on ART as there is increase in R.O.S. and lipid peroxidation product MDA (malondialdehyde) in peritoneal fluid of infertile patient, there may be defect in oocyte DNA, cumulus cell mass plus as there are multiple sources of R.O.S. generation in ART.


Embryo two cell stage is thought to be most vulnerable stage to R.O.S. during which it is protected by antioxidant in fallopian tube.

Reactive Oxygen Species (R.O.S.) – both endogenous and exogenous cause alterations in lipids, proteins, DNA, mitochondria, decrease in ATP, apoptosis and fragmentation.

In natural implantation, embryo is protected by various oxygen scavengers in fallopian tube and follicular fluid,metal binding proteins like transferrin,vitamin A, ascorbate, pyruvate, taurine, hypotaurine, cystamine are non enzymatic compounds important in embryo protection against O.S..SOD, catalase and GTX are enzymatic compounds.


Several defense mechanism against R.O.S. are present both in embryos and their surroundings.

In vivo embryos are protected against oxidative stress by oxygen scavengers present in follicular and oviductal fluids.

Oxidative stress can be avoided by preventing against R.O.S. formation, interception by antioxidants and repair.

Metal chelation is major means of controlling lipid peroxidation and DNA fragmentation, and metal binding proteins such as transferrin are important in potential radical- generating reactions.

Numerous non enzymatic compounds such as vitamin A, ascorbate and pyruvate have antioxidant function. Other sulphur compounds such as GSH, taurine, hypoturine and cysteamine are equally important in protecting embryo against R.O.S..

Enzymatic defence mechanism protecting oocytes and embryos include SOD, catalase or GPX.


Both embryos and spermatozoa possess repair mechanisms to counteract toxic effects of R.O.S..

Newly fertilized eggs are capable of repairing the damages DNA of spermatozoa.

Both in vitro and in vivo repair of damaged spermatozoa or inject DNA is known to occur in oocytes.

In addition, the pronuclei of the oxidatively damaged embryos can be rescued by transferring into normal cytoplasm.

However, the ability of mitochondrial DNA to auto repair leads to a progressive decline in mitochondrial function.

DNA damage beyond the capacity to repair results in apoptosis and fragmentation of the early embryo or morbidity in later life.


Numerous endogenous and exogenous conditions can induce oxidative stress on the embryos.

Various metabolic pathways and enzymes can produce endogenous R.O.S. including oxidative phosphorylation, B. Nicotinamide adenine dinudeotide phosphate reduced (B – NADPH) oxidase and xanthine oxidase.

Embryo 2-cell block is associated with R.O.S. at this stage.

Angiogenesis is a pathophysiological process involving formation of blood vessels.

It is necessary for follicular development, endometrial growth, embryo development, growth of embryo development growth of placenta vessel and repair.

A complex cytokine influence at the maternal fetal interface creates condition on that are necessary to implant embryo in the endometrium.

Any imbalance between cytokines and angiogenic factors, could result in implantation failure and pregnancy loss.

DNA damage and pregnancy outcome

For a favourable pregnancy outcome, sperm DNA needs to be normal.

Sperm DNA damage can occur as a result of defective sperm chromatin packaging, apoptosis and oxidative stress.

Greater miscarriage rates in ICSI can be due to damage to DNA; while zygotes resulting from IUF have a higher blastocyst development rate over ICSI.

Also, sperm from infertile men with more DNA abnormalties tend to have abnormal blastocyst development, failed implantations and spontaneous miscarriages.

The deleterious consequences of fragmented paternal DNA become evident when embryonic genome is activated.

Sperm chromatin structure assay can detect DNA fragmentation, so that counseling of couples before ICSI & IVF is possible

DNA fragmentation, more than 30% and high DNA stainability are at a greater risk of failure to initiate ongoing pregnancy.



– An endogenous No system exists in the fallopian tubes. NO has a relaxing effect on smooth muscles and it has similar effects on tabular contractility.

– Deficiency of NO may lead to tubal motility dysfunction, resulting in retention of the ovum, delayed sperm transport and infertility.

– NO levels in the fallopian tubes are cytotoxic to the invading microbes and also may be toxic to spermatozoa.

– The presence of NO synthase enzymes, both the constitutive and inducible forms was delineated by immunohistochemistry and the presence of NADPH diaphorase activity in human tubal cells.

– The presence of NO was demonstrated by positive NADPH diaphorase activity in the human fallopian tube.

Umbilical cord

Umbilical cord lipid peroxide concentrations reflect the extent of cell membrane damage by R.O.S.

Persistent intrauterine asphyxia may result in ischemia to the organs, leading to permanent damage, especially to the brain.

Oxygen free radicals activity in the neonate at birth and its relationship to umbilical cord acid-base status has been investigated in singleton deliveries.

Lipoperoxide levels, cord blood pH and base excess were significantly related with singleton deliveries.

In cases of uncomplicated labor followed by spontaneous vaginal delivery, significantly higher lipid peroxide concentrations were seen compared with those delivered following elective.

Caesarean section. Especially noted was an increase in the levels of malondialdehyde (MDA), while the hydroperoxide increase of 27% and base excess increase of 78% were seen.

High levels of free oxygen radical activity in the fetus are a function of the labor process as are the changes in acid-base balance.

Follicles and follicular fluid

Several defence mechanisms against R.O.S. are present both in embryos and their surroundings.

In VIVO embryos are protected against oxidative stress by oxygen scavengers present in follicular and oviduct fluid blocks DNA damage and support cytoplasmic maturation in paracrine oocytes Vit. C deficiency characteristically with follicular atresia and premature resumption of meiosis.

Ascorbic acid can be depleted both by oxidant scavenging as well as by cellular secretion.

In the pre-ovulatory follicles, ascorbic acid is depleted by the presence of luteinizing hormone transferrin suppresses R.O.S. generation and is important for the successful development of follicles.

In the follicular fluid, transferring levels have been found for follicle maturation.

Amniotic fluid

Presence of R.O.S. is detected in amniotic fluid is second and third trimester

Antioxidant capacity is reported to correlate with gestational age and estimate fetal weights.

Cystamine present in follicular fluid is a precursor of hypotaurine, maintains redox status in oocytes maintains GSH content. Increases synchronous pronuclei formation. Improves normal embryo development.

Taurine & hypotaurine present in the follicular fluid is a chelating agent, neutralization of cytotoxic aldehydes improves embryo development, neutralizes hydrotyle radicals.

In IVF patients follicular fluid R.O.S. and lipid peroxidation levels might be potential markers for predicting success in IVF patients.

Oxidative stress in fetal membranes

The production of R.O.S., prostaglandins, proinflammatory cytokines and proteases has been implicated in the pathogenesis of term and preterm labor.

PPROM results initially from R.O.S. damage to collagen in the chorio-amnion, leading to tear/rupture in the membrane as demonstrated by epidemiological and by invitro studies.


OVER 20% of the women of reproductive age in Europe and the USA regularly smoke cigarettes, Tobacco is a major source of exogenous pro-oxidants, R.O.S. and free radical generators are present in both its gas and partyiculate phase.

Active smoking affects the pro-oxidant/antioxidant balance inside the Graffian follicle in women undergoing ovulation induction for IVF.

Cigarette smoking is associated with increased intensity of lipid peroxidation inside the mature ovarian follicle, which is accompanied by the depletion of local antioxidant scavengers. There is a depletion of both enzymatic and non-enzymatic antioxidants in the follicular fluid of smokers.

The decreased antioxidant capacity of follicular fluid in the smokers is, most likely, a secondary phenomenon caused by the utilization of antioxidants in defense reactions neutralizing R.O.S. originating from, or induced by, the tobacco smoke constituents.

A relatively high diploidy has been reported in unfertilized oocytes originating from smoking IVF-embryo transfer patients, suggesting a smoking related meiotic immaturity of the oocytes.

An increased risk of trisomy has been observed in the off-spring of mothers who smoke cigarettes.

A shift of the pro-oxidant/antioxidant balance inside the ovarian follicle towards oxidative stress may provide another possible explanation of impaired folliculogenesis in female smokers undergoing IVF-embryo transfer.

How are O.S. and pregnancy related?

Higher levels of antioxidants are found in pregnancy as there is increase in free radicals because

Pregnancy being a stressful condition

Increased cellular activity

Increased lipid peroxidation

increased antioxidants demonstrated by -

– Increased S. Tocopherol.

– Increased Glutathion peroxidase.

– Increased Ceruloplasmin & transferrin.

Normal pregnancy has well balanced ratio of free radicals and antioxidants.

Increased spontaneous auto oxidation of lipids leads to increased lipid peroxides.

NO has controversial role.

It is found to be at lower levels in preterm labor patients and also, at term – the level decreased – this establishes NO as uterine relaxant. While some evidence suggest increased NO in amniotic fluid intrapartum.

Reperfusion injury occurring intrapartum also causes oxidative stress. So, there occurs decline in vitamin C level which scavenges R.O.S. in aqueous phase.

Oxidative stress in pregnancy results in –

Abortion (defective genetics and implantation)


Vesicular mole (DNA damage)


Preterm labour :

Sub-clinical chorioamnionitis


Bacterial toxins


Inflammatory cells


NO2 release


Oxidative stress occurs when there is imbalance between prooxidants and antioxidants which famous oxidation. Deficient levels of Vit. E and C can lead to oxidative stress.

Both Vit. E and Vit. C are non enzymatic antioxidants.

Vitamin E:

– Present in ovary and follicular fluid.

– It is a major chain breaking antioxidants in membranes, directly neutralizes superoxide anion hydrogen peroxide and hydroxyl radical.

– Increases number of embryos developing to expanded blastocysts and also increases viability of embryos exposed to heat shock.

Vitamin C:

– Present in ovary

It is also a chain breaking antioxidant.

Competitively protects the lipoproteins from peroxyl radicals and recycles vitamin E.

Reduces presence of sulfahydryls.

Supplementation reduces the risk of ovulating aneuploid and diploid oocytes.

Multivitamin supplementation during pregnancy may prevent DNA damage.

Lower dietary intake of Vit. C and E is associated with higher incidence of pre-term labors. Oxidative stress leads to focal collagen damage in the fetal membranes and results in pre-term labor.

Oxidative stress in Spontaneous abortions

Miscarriage (early pregnancy failure) is a pregnancy-related disease, the pathophysiology of which is still not completely understood. Lipid peroxidation and alterations in antioxidant enzyme activites may be of importance in the pathogenesis of this disorder.

Glutathione peroxidase (GSH-Px) and Catalase (CAT) activities is significantly increased while Total superoxide desmutase and non-enzymatic superoxide radical scavenger activities is decreased in patient with pregnancy failure.

Oxidative stress in placental tissues of early pregnancy failure, as the oxidative processes seem to be counteracted by the physiologic activation of antioxidant enzymes such as CAT and GSH-Px. Moreover, a compensatory mechanism might be developed against possible oxidative damage in patients with miscarriage.



– Endometriosis is a common gynecologic disorder that affects 8 to 10% of all reproductive age women, and is found in up to 50% of asymptomatic women undergoing laparoscopic tubal ligation.

R.O.S. is involved in the endometrial associated infertility and may play a role in the regulation of the expression of genes encoding immunoregulators, cytokines, and cell adhesions molecules implicated in the pathogenesis of endometriosis. Increased production of Hydroxyl radical and other free radicals in endometriosis is due to the activation of the immune system, and the various antigens in endometrial cells are excessively expressed.

Activated peritoneal macrophages promote disease by secretion of growth factors and cytokines that stimulate proliferation of ectopic endometrium and inhibit antioxidant activity.

Retrograde menstruation is likely to carry highly prooxidants factors, such as heme and iron, into the peritoneal cavity, as well as apoptotic endometrial cells, which are well known inducers of oxidative stress.

Nitric oxide (NO)

Levels of NO were demonstrated in peritoneal fluid of patents with endometriosis.

Peritoneal macrophages express higher levels of NOS, have higher NOS enzyme activity, and produce more no in response to immune-stimulation in vitro.

High levels of NO adversely affect sperm embryos, implantation and oviductal function. Thus reduction in peritoneal fluid NO production or blocking NO effects may improve fertility in women with endometriosis.

Expression of NOS is elevated in patients with endometriosis, and a common polymorphism of exon 7 at nucleotide 894 in the endothelial NOS gene may be associated with endometriosis. Hence variations in the expression of the eNOS gone may be involved in endometrial angiogenesis and thus modulate the process of endometriosis.

Glutathione peroxidase

Phase-dependent changes of GPX expression are seen in the surface and glandular epithelia in the eutopic endometrium during the menstrual cycle in the fertile control. However, this is lost in the eutopic endometrium in endometriosis.

The aberrant expression of GPX in the eutopic endometrium throughout the cycle suggests a pathological role in endometriosis and adenomyosis.

In endometriosis, expression of SOD is pronounced in the endometrium throughout the menstrual cycle, suggesting that superoxide plays a key role in infertility in endometriosis.

There is an exaggerated expression of Cu, Zn-SOD and Mn-SOD in eutopic endometrium in endometriosis and adenomyosis.

Oxidatively modified lipids

Evidence of oxidative stress in the peritoneal fluid of women with endometriosis and presence of oxidatively modified lipids in the peritoneal fluid has been demonstrated.

Oxidation specific epitopes and macro phages are present in the endometrium and in endometriosis.

Lipid peroxides interact with proteins, resulting in oxidatively modified proteins that are antigenic .

Auto antibodies to oxidatively modified proteins have been detected in subjects of coronary artery disease, pre-eclamptic pregnancy and other vascular disease.

The detection of increased anti-oxidized modified low density lipoproteins auto-antibody titer is thought to represent a biologic marker of enhanced low-density lipoprotein oxidation in vivo.

Macrophages through scavenger receptor play an important role in the uptake and removal of modified proteins, which can be formed as a result of inflammatory processes scavenger receptors also known as oxidized low density lipoprotein receptors do not recognize native low density lipoprotein. Oxidatively modified lipid proteins constitute legends for scavenger receptor.

The presence of macrophages expressing scavenger receptor in the peritoneal cavity of women with endometriosis may indicate oxidative damage to cellular or acellular components of the peritoneum.

Staining with antibodies to oxidatively modified lipid proteins HNE-2 and MDA-2 in both endometrium and endometriosis tissues containing stromal cells, strongly indicate the occurrence of oxidatively stress in endometriotic tissue.


Neutrophil activation

Hypothesis Decidual and placental ischaemia

Chronic inflammation with cytokines

And ROS increased in endothelin



Increased in Neutrophil activation



E selection damage to vessel walls by proteases and

(Adhesion Molecules) (endothelium)

Increased permeability and



and hypertension

There is increase in CD 11b and CD 18 in women with preeclampsia, these two serve as indices of neutrophil activation in vivo.

Increased myeloperoxidase is also a marker.

Increased F2 isoprostane are suggestive of increased lipid peroxidation level of F2 / isoprostane correlates with CD11b & CD18 expression. So, role of oxidative stress in PIH is strengthened.

CD11b also correlates with S. uric acid level. So, correlation with disease severity is under evaluation.


Nitric oxide is a potent vasodilator synthesized from L-arginine by endothelial cells.

In human, it maintains the normal low pressure vasodilated state characteristic of fetoplacental perfusion

NO is increased in women with preeclampsia as a compensatory mechanism for increased Synthesis and release of vasoconstrictors and platelet aggregating agents.

Besides causing direct inactivation of NO as a vasodilator Xanthine oxidase (XO) derived O2- reacts with NO to form a potent peroxynitrite ONOO- which has been detected both within the vasculature and in vessel walls of placenta after preeclampsia.

Increased endothelial NO synthesis, decreased SOD and increased nitro-tyrosine staining in maternal vasculature of women with preeclampsia have also been reported, indicating increased peroxynitrite formation.

Endothelial Cell Dysfunction in Pre-eclampsia

Preeclampsia is a multisystem disorder and endothelial dysfunction is one of the main pathogenic features of preeclampsia.

The markers of endothelial dysfunction such as tissue plasminogen activator, von Willebrand factor, sE-selectine and fibronectin are elevated in patients with preeclampsia.

Although the exact mechanism of vascular endothelial damage in preeclampsia are unclear, increased lipid peroxidation may lead to endothelial cell dysfunction.

Endothelial Cell Dysfunction in Pre-eclampsia

TNF-α, tissue factor of placental origin, endothelial nitric oxide synthase (eNOS) and excessive activity of the enzyme polymerase may contribute to endothelial dysfunction.

Compared with normotensive pregnant women, women with preeclampsia have reduced expression of endothelial mRNA and protein for eNOS. Reduced expression of constitutive NOS in the vascular system leads to reduced production of NO. NOS. inhibition lead to increased endothelial permeability and an abnormal response of the endothelial cells to the stress challenge of the preeclampsia.

endothelial dysfunction may also result from increased shedding of syncytiotrophoblast membrane micro-vesicular particles into the maternal circulation.

TNF-α, a circulating cytokine has also been implicated as causing endothelial dysfunction in preeclampsia.

Blood cultured from patient with preeclampsia showed higher TNF-α release from the leukocytes in patients with preeclampsia compared with normotensive pregnant women. Significantly higher tissue level of TNF- α where demonstrated in the placenta from with preeclampsia.


Pregnancy is characterized by increased generation of pro-oxidants from the placenta.

Poor antioxidant reserves can also tilt the balance in favour of peroxidation.

Lipid peroxidation results in primary lipid peroxidation products such as lipid hydroperoxides and secondary products such as malondialdehyde and lipid peroxides.

Lipid hydroperoxides are formed and bound to lipoproteins. They are then carried to distant sites where the hydroperoxides can cause ongoing lipid peroxidation and result in systemic oxidative stress.

Increased generation of R.O.S. leads to increased. Lipid peroxides.

Normal pregnancy is associated with physiological hyperlipidomia Pre-eclampsia is characterized by further elevation of serum triglycerides and serum free fatty acid.

Placenta may be site of generation of lipid peroxides in pre-eclamptic patient.

Both enhanced lipid peroxidation and alternation of immune responses are involved in endothelial cell dysfunction in pre-eclampsia.

Enhanced lipid peroxidation may result from excessive production of reactive oxygen species by neutrophil activation in pre-eclampsia.

The increase in antioxidants is probably of a compensatory nature responding to increased peroxide load in pre-eclampsia load in pro-eclampsia and may reflect the severity of diseases.


Increased activity of free radical promote maternal uterine vascular malformations.

FRs are promoters of maternal vasoconstriction.

O2, H2O2, & NO2 in combination. Which inactivate the NO (vasorelaxant)

Increased PG synthatase activity

Produce peroxynitrite, a potent oxidant.

Sources : In vivo anti-oxidants.

In The form of medicines

Vit. A, C & E.

Cystene, Glutathione, Methionine

Bioflavines, Se, Zn

Food sources:

– Green and yellow vegetables.

– Herbs : Turmeric, garlic, grape, tea, berries, carrot, spinach

– Red meat, kidney, liver & Lipoic acid.


– Deficient levels of vitamin E & C can lead to oxidative stress.

– Vit. E lipid peroxidation chain breaking antioxidant that inhibits NADPH oxidase in the placental tissues.

– Dietary intake of vitamin C & E is important because these are not synthesized endogenously vitamin C (1000 mg/ day) & Vitamin E (400 IU) day should be given

– Both directly intake of antioxidants and the status of oxidative stress in the mother may influence IUGR.

Evidence of Pre - eclampsia

Lipid peroxide concentration 1.8 time commoner in placenta of pre-eclamptic patient.

Vitamin E level is decreased in serum of PIH patients.

Concentration of Vitamin E level has been found inversely proportional to the severity of pre-eclampsia.

Concentration of serum uric acid level is directly proportional to the severity of pre-eclampsia.


Alteration in Prostaglandin Metabolism

– Diabetes induced alteration of several metabolites such as Arachidonic acid and prostaglandins, specifically PGE2 have teratogenic capacity.

– Developmental disturbances due to inhibition of COX are similar to those found in embryos exposed to high glucose concentrations.

– Decreased cycloxygenase (Cox)-2 activity results in diminished PGE2 production.

– Decreased in PGE2 causes rise in atherothrombotic tendency resulting in thrombosis and embryopathy.

– Activity of catalase – an antioxidant enzyme and m-RNA levels of antioxidant enzyme is more in malformation resistant strain of rat.

– While less R.O.S. defence found in malformation prone strain.

– Hyperglycemia in diabetes induced down regulation of embryonic COX-2 gene expression may be a primary event in diabetic embryopathy.


Oxidative stress has been suggested to contribute to increased risk of fetal malformations in poorly controlled diabetics.

There are reports of increased lipid peroxidation in cell membranes in diabetic pregnancies as LDL from pregnant diabetic mother is more susceptible to oxidation.

Periods of maternal hyperglycemia and hypoglycemia may cause marked changes in availability of glucose to the fetus.

Also increased concentration of lipids, notably the ketone bodies and branched chain amino acids in the maternal circulation contribute to altered nutrition for the embryo leading to increase FR concentration and fetal malformation in embryo.

During later part of pregnancy increased load of glucose in mitochondria may accelerate flow of electrons through respiratory chain including mitochondrial leakage of free radicals.

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

FRS being the hall mark of aging, are greatly increased with increased maternal age.

Reactive oxygen species and hyperglycemia

Embryos cultured under hyperglycemic conditions show increased formation of R.O.S. and depletion of GSH contents as well as reduced synthesis of GSH. The addition of free radical scavenging enzymes (e.g. SOD, catalase, GPX and N-acetylcysteine, butylated hydrosytolouene) to culture media reduced the incidence of embryonic malformation after hyperglycemia.

Hyperglycemia-induced embryonic malformations may be due to increased R.O.S. formation and depletion of intracellular GSH in embryonic tissues. GSH depletion and impaired responsiveness of GSH synthesizing enzyme to oxidative stress during organogenesis may have important roles in the development of embryonic malformation in diabetes.

Pregnancy complicated by poor control of diabetes is associated with a high risk of embryopathies, spontaneous abortions and perinatal mortality attributed to excessive oxidative stress. Both lipid peroxidation and scavenging enzyme activities may be valuable, sensitive indices of fetal/neonatal threat in diabetic pregnancy in humans. Adequate measurements at the time of birth would significantly contributed to clarifying the fetal/neonatal status in a medical and legal context, and may be even of value in altering therapy in newborn infants.

Reactive oxygen species and hyperglycemia

Dysmorphogenesis caused by maternal diabetes is correlated with R.O.S. induced inhibition of glyceraldehydes-3-phosphate dehydrogenase (GAPDH) in embryos indicating that inhibition of GAPDH plays, a causal role in diabetic embryopathy.

The offspring of women with diabetes mellitus are at increased risk for congenital defects. The incidence and severity of the defects are related to glycemia within the first weeks of pregnancy, during which organogenesis is initiated.

Maternal diabetes also inhibits the expression of PAX-3, an embryonic gene required for neural tube closure caused by increased levels of oxidative stress. Alpha-tocopherol blocks these defects.

Antioxidants in Diabetes

Oxidative stress has been suggested to contribute to the increased risk of fetal malformation in poorly controlled diabetes.

Maintenance of blood glucose level to euglycemic level is always important for prevention of diabetic embryopathy.

Antioxidants such as vitamin E and butylated hydroxytoluene, Vit. C, GS4 precursor, N acetyl cystene or transgenic over expression of copper / zinc superoxide desmutase.

In vitro, embryonic dysmorphogenesis has been shown to be significantly diminished, either by restricting the influx of oxidative substrates such as pyruvates to the embryonic mitochondria or by improving the embryonic capacity to scavenge free oxygen radicals.

Elevated levels of copper zinc SOD, catalase, GPX & SOD elicit a protective effect against diabetes associated embryopathy.


O.S. is implicated in cervical cancer, endometrial cancer, ovarian cancer, vaginal cancer, vulval cancer.

The burst of R.O.S. has carcinogenic,teratogenic and genotoxic effects and is correlated with DNA damage.

Oxidative modification of nucleic acids by R.O.S. could result in transformation of normal cells to malignant cells.

R.O.S. induced lipid peroxidation has been implicated in malignant transformation indicate the extent of lipid peroxidation in general and serve as markers of cellular damage due to FRs

Over expression of NOS is seen in chronic inflammation which leads to genotoxicity.

NO may mediate DNA damage through formation of carcinogenic nitrosamines, generation of R.O.S. and inhibition of DNA damage repair mechanism.

It can thus be implicated as tumour initiating agent.

Biochemical estimation of lipid peroxidation products,reduced Glutathione, SOD, catalase, NO can be helpful in evaluation of O.S. in gynec malignancies and their modification after therapy.



Click here to view other articles in this section