Plasma Thiol Research Articles

Selective Thiol Detection in Authentic Biological Samples with the Use of Screen-printed Electrodes.

A selective voltammetric determination of homocysteine and glutathione was applied to cell tissue culture media and human plasma via a single two-step method. The two-step method relies on the 1,4-Michael addition reaction between electro-oxidized catechol and the target thiol. Furthermore, the procedure relies on the differing reaction kinetics of the ortho-quinone with various thiol species giving different responses as a function of the scan rate. At faster scan rates homocysteine is only detected, while at slower scan rates the adduct signal reflects both homocysteine and glutathione. As a result, the quantification of both homocysteine and glutathione can be determined with a combination of both sets of data. The previous proof-of-concept (P. T. Lee, D. Lowinsohn, and R. G. Compton, Sensors, 2014, 14, 10395), is applied to the quantification of thiols in both tissue culture media and human plasma alone. Analytical parameters were determined for both homocysteine and glutathione in the respective media and the linear range. The sensitivities in tissue culture media are ca. 3 nA μM(-1) and ca. 1 nA μM(-1) and the limits of detections are ca. 2 μM and ca. 1 μM for homocysteine and glutathione, respectively. In human plasma, the sensitivities were determined to be 94 and 39 nA μM(-1), and the limit of detections are ca. 0.8 μM and ca. 0.8 μM for homocysteine and glutathione, respectively.

Decreased plasma thiol antioxidant barrier and selenoproteins as potential biomarkers for ongoing methylmercury intoxication and an individual protective capacity.

Manifestation of methylmercury (MeHg) toxicity depends on individual susceptibility to MeHg, as well as MeHg burden level. Therefore, biomarkers that reflect the protective capacity against MeHg are needed. The critical role of oxidative stress in the pathogenesis of MeHg cytotoxicity has been demonstrated. Because MeHg has high affinity for selenohydryl groups, sulfhydryl groups, and selenides, and causes posttranscriptional defects in selenoenzymes, proteins with selenohydryl and sulfhydryl groups should play a critical role in mediating MeHg-induced oxidative stress. Here, plasma oxidative stress markers and selenoproteins were investigated in MeHg-intoxicated rats showing neuropathological changes after 4 weeks of MeHg exposure. The thiol antioxidant barrier (-SHp) level significantly decreased 2 weeks after MeHg exposure, which is an early stage at which no systemic oxidative stress, histopathological changes, or clinical signs were detected. Diacron reactive oxidant metabolite (d-ROM) levels significantly increased 3 weeks after MeHg exposure, indicating the occurrence of systemic oxidative stress. Rats treated with lead acetate or cadmium chloride showed no changes in levels of -SHp and d-ROM. Selenoprotein P1 abundance significantly decreased in MeHg-treated rats, whereas it significantly increased in rats treated with Pb or Cd. Plasma selenium-dependent glutathione peroxidase (GPx3) activity also significantly decreased after MeHg exposure, whereas plasma non-selenoenzyme glutathione reductase activity significantly increased in MeHg-treated rats. The results suggest that decreased capacity of -SHp and selenoproteins (GPx3 and selenoprotein P) can be useful biomarkers of ongoing MeHg cytotoxicity and the individual protective capacity against the MeHg body burden.

Advanced oxidation protein products, total thiol levels and total oxidant/antioxidant status in patients with nash.

In this study we aim to evaluate the relationship of advanced oxidation protein products (AOPP), total thiol, total antioxidant status (TAS), total oxidant status (TOS) levels and oxidative stress index (OSI) in patients with nonalcoholic steatohepatitis (NASH). A total of 28 patients with NASH and 19 age-and-gender-matched healthy subjects were enrolled in the study as control group. Plasma AOPP and thiol levels were determined by spectrophotometric methods. Plasma TAS and TOS levels were measured using commercially available kits and OSI was calculated. Plasma AOPP (256.7 vs. 125.8 μmol/L) and TOS levels (8.9 vs. 5.9 μmol H2O2 equiv/L) were higher in patients with NASH than the controls (p<0.019 and p<0.041 respectively). Plasma total thiol levels (235.0 vs. 291.6 μmol/L) were lower in patients with NASH than the controls (p<0.001). TAS levels (1.14 vs. 1.14 mmol Trolox equiv/L) were not significantly different in patients with NASH than the controls (p>0.900). OSI values (8.0 vs. 5.5) were higher in patients with NASH than the controls (p<0.039). Our findings indicate that oxidative stress increases in patients with NASH as shown by increases in TOS level. We think effective antioxidant therapy to inhibit protein oxidation and also to increase of TAS and total thiol levels may be a therapeutic option in patients with NASH who have under increased oxidative stress.

OP-030 The Association between Plasma Thiols Levels and Left Ventricular Diastolic Dysfunction in Patient with Hypertension

OP-030 The Association between Plasma Thiols Levels and Left Ventricular Diastolic Dysfunction in Patient with Hypertension

PP-090 Relationship between Plasma Thiol Levels with Left Ventricle Geometric Patterns and Left Ventricle Diastolic Functions in Patients with Newly Diagnosed Essential Hypertension

PP-090 Relationship between Plasma Thiol Levels with Left Ventricle Geometric Patterns and Left Ventricle Diastolic Functions in Patients with Newly Diagnosed Essential Hypertension

Plasma thiols levels in Alzheimer's disease mice under diet-induced hyperhomocysteinemia: effect of S-adenosylmethionine and superoxide-dismutase supplementation.

Widely confirmed reports were published on association between hyperhomocysteinemia, B vitamin deficiency, oxidative stress, and amyloid-β in Alzheimer's disease (AD). Homocysteine, cysteine, cysteinylglycine and glutathione are metabolically interrelated thiols that may be potential indicators of health status and disease risk; they all participate in the metabolic pathway of homocysteine. Previous data obtained in one of our laboratories showed that B vitamin deficiency induced exacerbation of AD-like features in TgCRND8 AD mice; these effects were counteracted by S-adenosylmethionine (SAM) supplementation, through the modulation of DNA methylation and antioxidant pathways. Since the cellular response to oxidative stress typically involves alteration in thiols content, a rapid and sensitive HPLC method with fluorescence detection was here used to evaluate the effect of SAM and superoxide-dismutase (SOD) supplementation on thiols level in plasma, in TgCRND8 mice. The quantitative data obtained from HPLC analysis of mice plasma samples showed significant decrease of thiols level when the B vitamin deficient diet was supplemented with SAM + SOD and SOD alone, the latter showing the greatest effect. All these considerations point out the measurement of plasma thiols concentration as a powerful tool of relevance for all clinical purposes involving the evaluation of oxidative stress. The coupling of HPLC with fluorimetric detection, here used, provided a strong method sensitivity allowing thiols determination at very low levels.

Simultaneous determination of albumin and low-molecular-mass thiols in plasma by HPLC with UV detection.

In this paper, we describe a simple and robust HPLC based method for determination of total low- and high-molecular-mass thiols, protein S-linked thiols and reduced albumin in plasma. The method is based on derivatization of analytes with 2-chloro-1-methylquinolinium tetrafluoroborate, separation and quantification by reversed-phase liquid chromatography followed by UV detection. Disulfides were converted to their thiol counterparts by reductive cleavage with tris(2-carboxyethyl)phosphine. Linearity in detector response for total thiols was observed over the range of 1-40 μmol L(-1) for Hcy and glutathione (GSH), 5-100 μmol L(-1) for Cys-Gly, 20-300 μmol L(-1) for Cys and 3.1-37.5 μmol L(-1) (0.2-2.4gL(-1)) for human serum albumin (HSA). For the protein S-bound forms these values were as follows: 0.5-30 μmol L(-1) for Hcy and GSH, 2.5-60 μmol L(-1) for Cys-Gly and 5-200 μmol L(-1) for Cys. The LOQs for total HSA, Cys, Hcy, Cys-Gly and GSH were 0.5, 0.2, 0.4, 0.3 and 0.4 μmol L(-1), respectively. The estimated validation parameters for all analytes are more than sufficient to allow the analytical method to be used for monitoring of the total and protein bound thiols as well as redox status of HSA in plasma.

Plasma levels of homocysteine and cysteine increased in pediatric NAFLD and strongly correlated with severity of liver damage.

Non-alcoholic fatty liver disease (NAFLD) is a spectrum of metabolic abnormalities ranging from simple triglyceride accumulation in the hepatocytes to hepatic steatosis with inflammation, ballooning and fibrosis. It has been demonstrated that the pathogenesis of NAFLD involves increased oxidative stress, with consumption of the major cellular antioxidant, glutathione (GSH). Liver has a fundamental role in sulfur compound metabolism, although the data reported on plasma thiols status in NAFLD are conflicting. We recruited 63 NAFLD patients, and we analyzed all plasma thiols, such as homocysteine (Hcy), cysteine (Cys), cysteinylglycine (CysGly) and GSH, by high-performance liquid chromatography (HPLC) with fluorescence detection. Hcy, Cys and CysGly plasma levels increased in NAFLD patients (p < 0.0001); whereas GSH levels were decreased in NAFLD patients when compared to controls (p < 0.0001). On the contrary, patients with steatohepatitis exhibited lower levels of Hcy and Cys than subjects without. Furthermore, a positive correlation was found between Hcy and Cys and the presence of fibrosis in children with NAFLD. Taken together, these data demonstrated a defective hepatic sulfur metabolism in children with NAFLD, and that high levels of Hcy and Cys probably correlates with a pattern of more severe histological liver damage, due to mechanisms that require further studies.

Role of cytochrome P450-mediated metabolism and identification of novel thiol-conjugated metabolites in mice with phenytoin-induced liver injury

Phenytoin, 5,5-diphenylhydantoin (DPH), is widely used as an anticonvulsant agent. Severe hepatic injury rarely occurs in patients who received DPH. The development of liver injury is thought to be caused by reactive metabolites; however, the metabolites suggested to contribute to hepatotoxicity have not yet been detected in vivo and their effect on developing the liver injury is largely unknown. We recently demonstrated that DPH treatment decreased hepatic glutathione (GSH) contents, and GSH-depleted condition exacerbated DPH-induced liver injury in mice. The aim of the present study was to identify the reactive metabolite and to investigate the role of P450-mediated metabolisms in DPH-induced liver injury. We identified a novel GSH-conjugated (GS)-DPH, a conjugate of putative electrophilic arene oxide intermediate with GSH, in the bile of mice with DPH-induced liver injury. In plasma, cysteine- or N-acetylcysteine-conjugated DPH was detected, and these thiol conjugates levels were correlated with the plasma alanine aminotransferase (ALT) levels. These changes were significantly reduced by pretreatment with P450 inhibitor. Furthermore, the increases of hepatic P450 activities were in parallel with elevation of plasma thiol conjugates levels. These findings suggest that the arene oxide intermediate, which can be converted to thiol conjugates, is involved in DPH-induced liver injury.

Erythrocyte Membrane Stability to Hydrogen Peroxide is Decreased in Alzheimer Disease

The brain and erythrocytes have similar susceptibility toward free radicals. Therefore, erythrocyte abnormalities might indicate the progression of the oxidative damage in Alzheimer disease (AD). The aim of this study was to investigate erythrocyte membrane stability and plasma antioxidant status in AD. Fasting blood samples (from 17 patients with AD and 14 healthy controls) were obtained and erythrocyte membrane stability against hydrogen peroxide and 2,2'-azobis-(2-amidinopropane) dihydrochloride (AAPH), serum Trolox equivalent antioxidant capacity (TEAC), residual antioxidant activity or gap (GAP), erythrocyte catalase activity (CAT), erythrocyte superoxide dismutase (SOD) activity, erythrocyte nonproteic thiols, and total plasma thiols were determined. A significant decrease in erythrocyte membrane stability to hydrogen peroxide was found in AD patients when compared with controls (P<0.05). On the contrary, CAT activity (P<0.0001) and total plasma thiols (P<0.05) were increased in patients with AD compared with controls. Our results indicate that the most satisfactory measurement of the oxidative stress level in the blood of patients with AD is the erythrocyte membrane stability to hydrogen peroxide. Reduced erythrocyte membrane stability may be further evaluated as a potential peripheral marker for oxidative damage in AD.

Personalized metabolomics for predicting glucose tolerance changes in sedentary women after high-intensity interval training.

High-intensity interval training (HIIT) offers a practical approach for enhancing cardiorespiratory fitness, however its role in improving glucose regulation among sedentary yet normoglycemic women remains unclear. Herein, multi-segment injection capillary electrophoresis-mass spectrometry is used as a high-throughput platform in metabolomics to assess dynamic responses of overweight/obese women (BMI > 25, n = 11) to standardized oral glucose tolerance tests (OGTTs) performed before and after a 6-week HIIT intervention. Various statistical methods were used to classify plasma metabolic signatures associated with post-prandial glucose and/or training status when using a repeated measures/cross-over study design. Branched-chain/aromatic amino acids and other intermediates of urea cycle and carnitine metabolism decreased over time in plasma after oral glucose loading. Adaptive exercise-induced changes to plasma thiol redox and orthinine status were measured for trained subjects while at rest in a fasting state. A multi-linear regression model was developed to predict changes in glucose tolerance based on a panel of plasma metabolites measured for naïve subjects in their untrained state. Since treatment outcomes to physical activity are variable between-subjects, prognostic markers offer a novel approach to screen for potential negative responders while designing lifestyle modifications that maximize the salutary benefits of exercise for diabetes prevention on an individual level.

High plasma thiocyanate levels are associated with enhanced myeloperoxidase-induced thiol oxidation and long-term survival in subjects following a first myocardial infarction

Elevated levels of myeloperoxidase (MPO) are associated with poor cardiovascular outcomes. MPO uses H2O2 to generate oxidants including HOCl and HOSCN, from chloride and thiocyanate (SCN−) ions, respectively. SCN− is the preferred substrate. Elevation of this anion decreases HOCl generation and increases HOSCN formation, a thiol-specific oxidant. Such changes are of potential relevance to people with elevated SCN− levels, such as smokers. In this retrospective study, we examined whether elevated plasma MPO and SCN− levels increased thiol oxidation as a result of increased HOSCN formation, and impacted on long-term survival in 176 subjects (74 non-smokers, 46 smokers, and 56 previous smokers) hospitalized after a first myocardial infarction. Plasma thiols were not significantly altered in smokers compared to non-smokers or past smokers. However, significant positive correlations were detected between SCN− levels and MPO-induced thiol loss in the total population (r = 0.19, P = 0.020) and smokers alone (r = 0.58, P < 0.0001). Twelve-year all-cause mortality data indicate that above median MPO is significantly associated with higher mortality, but below-median MPO and above-median SCN− results in increased survival, compared to below-median SCN−. Cox proportional hazard analysis showed a significant decrease in mortality for each 1 μM increase in SCN− (0.991; P = 0.040). Subject age was, as expected, a strong predictor of subject survival. Overall these data suggest that subjects with below-median MPO and above-median SCN− have better long-term survival, and that elevated plasma levels of SCN− might be protective in at least some populations.

DNA damage and antioxidant status in medical residents occupationally exposed to waste anesthetic gases.

To investigate the effects of occupational exposure to waste anesthetic gases on genetic material and antioxidant status in professionals during their medical residency. The study group consisted of 15 medical residents from Anesthesiology and Surgery areas, of both genders, mainly exposed to isoflurane and to a lesser degree to sevoflurane and nitrous oxide; the control group consisted of 15 young adults not exposed to anesthetics. Blood samples were drawn from professionals during medical residency (eight, 16 and 22 months of exposure to waste anesthetic gases). DNA damage was evaluated by comet assay, and antioxidant defense was assessed by total thiols and the enzymes glutathione peroxidase (GPX), superoxide dismutase (SOD) and catalase (CAT). When comparing the two groups, DNA damage was significantly increased at all time points evaluated in the exposed group; plasma thiols increased at 22 months of exposure and GPX was higher at 16 and 22 months of exposure. Young professionals exposed to waste anesthetic gases in operating rooms without adequate scavenging system have increased DNA damage and changes in redox status during medical residency. There is a need to minimize exposure to inhalation anesthetics and to provide better work conditions.

Largazole Pharmacokinetics in Rats by LC-MS/MS

A highly sensitive and specific LC-MS/MS method for the quantitation of largazole thiol, the active species of the marine-derived preclinical histone deacetylase inhibitor, largazole (prodrug), was developed and validated. Largazole thiol was extracted with ethyl acetate from human or rat plasma along with the internal standard, harmine. Samples were separated on an Onyx Monolithic C18 column by a stepwise gradient elution with 0.1% formic acid in methanol and 0.1% aqueous formic acid employing multiple reaction monitoring (MRM) detection. Linear calibration curves were obtained in the range of 12.5–400 ng/mL with 200 µL of human plasma. The overall intra-day precision was from 3.87% to 12.6%, and the inter-day precision was from 7.12% to 9.8%. The accuracy at low, medium and high concentrations ranged from 101.55% to 105.84%. Plasma protein bindings of largazole thiol in human and rat plasma as determined by an ultrafiltration method were 90.13% and 77.14%, respectively. Plasma drug concentrations were measured by this LC-MS/MS method. The pharmacokinetics of largazole thiol in rats was studied following i.v. administration at 10 mg/kg and found to follow a two-compartment model. Largazole thiol was rapidly eliminated from systemic circulation within 2 h. The established LC-MS/MS method is suitable for the analysis of largazole thiol in human plasma, as well.

Evaluation of oxidative stress and DNA damage in cement and tannery workers in Egypt

In Egypt, workers have potentially high exposure levels to chromium (VI) in the cement production and construction industry and to chromium (III) in the leather tanning industry. This study aimed to evaluate the effect of chromium exposure on lipoperoxidation, thiol antioxidants and DNA in cement and tannery workers. This study was conducted on 65 adult male volunteers. These subjects were divided into three groups: Group I (control group); 23 normal healthy volunteers, Group II; 22 cement workers and Group III; 20 tannery workers. All participants were subjected to thorough history, clinical examination and laboratory determination of total blood and urinary chromium, plasma malondialdehyde and total thiol in plasma and assessment of oxidative DNA damage through p53 overexpression. About one third of cement and tannery workers had severe skin and chest manifestations and severe nasal manifestations were observed in 22.7% and 20% of cement and tannery workers, respectively. The blood and urinary Cr and plasma malondialdehyde levels of cement and tannery were significantly higher than control group. Additionally, there was a significant increase of total thiol in control group compared to exposed groups. About half of cement and one third of tannery groups expressed high grade of p53 expression. The blood chromium revealed significant negative correlation with thiol, but, positive correlation with malondialdehyde and p53 expression. Cement and tannery workers should be subjected to frequent clinical examination and blood or urine chromium analysis level to keep guard against its toxic consequences.

Bovine serum albumin‐confined silver nanoclusters as fluorometric probe for detection of biothiols

Fluorescent bovine serum albumin-confined silver nanoclusters (BSA-AgNCs) were demonstrated to be a novel and environmentally friendly probe for the rapid detection of biothiols such as cysteine (Cys), homocysteine (Hcy) and glutathione (GSH). The sensing was ascribed to the strong affinity between the mercapto group of the biothiols and the silver nanoclusters. The fluorescence intensity of BSA-AgNCs was quenched efficiently on increasing the concentration of biothiol, corresponding with a red-shift in emission wavelength. However, the fluorescence of the silver nanoclusters was almost unchanged in the presence of other α-amino acids at 10-fold higher concentrations. By virtue of this specific response, a new, simple and rapid fluorescent method for detecting biothiols has been developed. The linear ranges for Cys, Hcy and GSH were 2.0 × 10(-6) to 9.0 × 10(-5) M (R(2) = 0.994), 2.0 × 10(-6) to 1.2 × 10(-4) M (R(2) = 0.996) and 1.0 × 10(-5) to 8.0 × 10(-5) M (R(2) = 0.980), respectively. The detection limits were 8.1 × 10(-7) M for Cys, 1.0 × 10(-6) M for Hcy and 1.1 × 10(-6) M for GSH. Our proposed method was successfully applied to the determination of thiols in human plasma and the recovery was 94.83-105.24%. It is potentially applicable to protein-stabilized silver nanoclusters in a chemical or biochemical sensing system.

Lack of Association between Nuclear Factor Erythroid-Derived 2-Like 2 Promoter Gene Polymorphisms and Oxidative Stress Biomarkers in Amyotrophic Lateral Sclerosis Patients

Oxidative stress involvement has been strongly hypothesized among the possible pathogenic mechanisms of motor neuron degeneration in amyotrophic lateral sclerosis (ALS). The intracellular redox balance is finely modulated by numerous complex mechanisms critical for cellular functions, among which the nuclear factor erythroid-derived 2-like 2 (NFE2L2/Nrf2) pathways. We genotyped, in a cohort of ALS patients (n = 145) and healthy controls (n = 168), three SNPs in Nrf2 gene promoter: −653 A/G, −651 G/A, and −617 C/A and evaluated, in a subset (n = 73) of patients, advanced oxidation protein products (AOPP), iron-reducing ability of plasma (FRAP), and plasma thiols (-SH) as oxidative damage peripheral biomarkers. Nrf2 polymorphisms were not different among patients and controls. Increased levels of AOPP (P < 0.05) and decreased levels of FRAP (P < 0.001) have been observed in ALS patients compared with controls, but no difference in -SH values was found. Furthermore, no association was found between biochemical markers of redox balance and Nrf2 polymorphisms. These data confirm an altered redox balance in ALS and indicate that, while being abnormally modified compared to controls, the oxidative stress biomarkers assessed in this study are independent from the −653 A/G, −651 G/A, and −617 C/A Nrf2 SNPs in ALS patients.

HPLC separation of human serum albumin isoforms based on their isoelectric points

Human serum albumin (HSA) is the most abundant protein in plasma. Cys34, the only free Cys residue, is the predominant plasma thiol and a relevant sacrificial antioxidant. Both in vivo circulating HSA and pharmaceutical preparations are heterogeneous with respect to the oxidation state of Cys34. In this work, we developed an external pH gradient chromatofocusing procedure that allows the analysis of the oxidation status of HSA in human plasma and biopharmaceutical products based on the different apparent isoelectric points and chemical properties of the redox isoforms. Specifically, reduced-mercury blocked HSA (HSA-SHg(+)), HSA with Cys34 oxidized to sulfenic acid (HSA-SOH) and HSA oxidized to sulfinate anion (HSA-SO2(-)) can be separated with resolutions of 1.4 and 3.1 (first and last pair) and hence quantified and purified. In addition, an N-terminally degraded isoform (HSA3-585) in different redox states can be resolved as well. Confirmation of the identity of the chromatofocusing isolated isoforms was achieved by high resolution whole protein MS. It is proposed that the chromatofocusing procedure can be used to produce more exact and complete descriptions of the redox status of HSA in vivo and in vitro. Finally, the scalability capabilities of the chromatofocusing procedure allow for the preparation of highly pure standards of several redox isoforms of HSA.

Plasma homocysteine levels in HIV-infected men with and without lipodystrophy

ObjectiveLipodystrophy syndrome is an unexpected clinical manifestation in patients infected with HIV and might be a clinical marker of increased risk for cardiovascular diseases (CVDs). Because hyperhomocysteinemia has been associated with CVD, the goal of the present study was to investigate homocysteine (Hcy) levels and their association with the factors of lipodystrophy syndrome in men with HIV. MethodsHcy metabolism-related molecules were determined in 13 men infected with HIV with lipodystrophy (HIV+LIP), 10 men with HIV without lipodystrophy (HIV), and 10 healthy controls (C). ResultsSignificant (P < 0.05) increased Hcy plasma levels were found in HIV (20.5%) and in HIV+LIP (35.2%) compared with the control group. Plasma levels of vitamin B12 (HIV, 26.5%; HIV+LIP, 28.8%) and folate (HIV, 39.1% and HIV+LIP, 49.4%) were significantly (P < 0.05) lower in the two groups of HIV patients compared with control. HIV+LIP men presented raised plasma total sulfur-containing amino acids (20.1%) and lower total plasma thiol (11.3%) than controls. The same was not observed in the HIV group. Spearman's correlation test revealed significant (P < 0.05) association between plasma Hcy and duration of highly active antiretroviral therapy (HAART) and plasma insulin, as well as plasma adiponectin levels. ConclusionOur results demonstrated that HIV+LIP men were more susceptible to disturbances in Hcy metabolism compared with men infected with HIV without lipodystrophy characteristics. Duration of HAART treatment, elevated plasma insulin, and low levels of adiponectin seem to be relevant for the appearance of these Hcy metabolic disorders.

Antioxidant Effect of Grape Seed Proanthocyanidin Extract against Potassium Dichromate Induced Oxidative DNA Damage in Small Intestine of Adult Male Albino Rats

Background: Chromium usage is increasing worldwide. Oral exposure to hexavalent chromium Cr (VI) in animals and humans causes various health hazards. Cr (VI) compounds are classified as class I human carcinogens. Antioxidants were reported to inhibit chemical carcinogenesis. Grape seed proanthocyanidin extract (GSPE), naturally occurring compounds, have antioxidant, anti-inflammatory, anti-allergic and anti-tumor activities. Objectives: Accordingly, this work was conducted to investigate the antioxidant effect of GSPE against oxidative DNA damage induced by potassium dichromate on small intestine of adult male albino rats through biochemical and microscopic study. Study design: Forty adult male albino rats were included in this study and divided into four equal groups. Group I served as control group. Group II received 100mg/kg/day GSPE. Group III was treated with 15mg/kg/day potassium dichromate. Group IV received both K dichromate and GSPE in their previous doses. All animals were treated orally by syringe feeding method for two months. Body weight, plasma and tissue malondialdehyde (MDA) and total thiol (T-SH) of all studied groups were measured. In addition, light microscopic examination of small intestine using hematoxylin and eosin stains and immunostaining for detection of p53 positive cells as well as scanning electron microscopic examination were carried out. Results: The current study showed that adult male albino rats treated orally with potassium dichromate showed decrease in body weight, significant increase in plasma and intestinal tissue MDA and significant decrease in plasma and intestinal tissue thiol level. All these changes were associated with severe histological alterations in the wall of the small intestine especially the duodenum with significant increase of p53 positive cells. GSPE were found to counteract the toxic effect of potassium dichromate by attenuating oxidative stress and DNA damage. Conclusion: It is concluded that GSPE is promising as an agent that can potentially reduce K dichromate induced toxic effects in small intestine through its antioxidant effect.