Effects of two oral antidiabetics, pioglitazone and repaglinide, on aconitase inactivation, inflammation and oxidative/nitrosative stress in tissues under alloxan-induced hyperglycemia

Pathological changes identified in different tissues in hyperglycemic state are undoubtedly connected with increased oxidative/nitrosative stress and inflammation. In our study myeloperoxidase (MPO), nitrotyrosine and lipid peroxidation were enhanced in the heart and lung of alloxan-treated hyperglycemic animals. Additionally, pulmonary aconitase was inhibited. In the testis the changes occurred as an increase of MPO and lipid peroxidation, and as a decrease of aconitase. The effects of two different antidiabetics, the peroxisome proliferator activated receptor gamma (PPARγ) agonist, pioglitazone, and a short acting insulin secretagogue, repaglinide, on the mentioned parameters, were investigated and compared. The insulin deficient alloxan-induced hyperglycemic animals were used to differentiate a direct anti-oxidative effect of the drugs from secondary effects mediated via increased insulin sensitivity or secretion. Pioglitazone acted by normalization of pulmonary and testicular aconitase, normalization of pulmonary and cardiac nitrotyrosine, reduction of pulmonary and testicular MPO, and by reduction of lipid peroxidation in all tissues examined. Repaglinide prevented oxidative changes by normalization of aconitase activity in the lung and testis, and by reduction of lipid peroxidation and nitrotyrosine in the heart and lung. At the same time, no effect of this drug on MPO was observed. Finally, principal component analysis was performed to explore and visualize similarities and differences of the results obtained for the both drugs.     

Effects of carvedilol on oxidative stress in human endothelial cells and healthy volunteers

Objective Carvedilol is a nonselective - and ₁-receptor antagonist with additional antioxidant properties in vitro. In this study, we assessed the antioxidative potential of carvedilol in cell culture and in antihypertensive doses in healthy men.Methods In vitro, human cultured endothelial cells were treated with native low-density lipoprotein (LDL), oxidized LDL or tumor necrosis factor (TNF) in the absence and in the presence of carvedilol (40 µM); 8-iso-prostaglandin (PG)F₂, as parameter of oxidative stress, was determined in the supernatants. In a double-blind, randomized, cross-over study, 17 healthy men received 25 mg carvedilol b.i.d., 100 mg metoprolol b.i.d. or placebo for 6 days. After each treatment, systemic oxidative stress was assessed by measuring urinary excretion of 8-iso-PGF₂ and 2,3-dinor-5,6-dihydro-8-iso-PGF₂, and the plasma concentration of 3-nitrotyrosine by means of gas chromatography-tandem mass spectrometry. In addition, thiobarbituric acid-reactive substances (TBARS) in plasma were assessed using spectrophotometry.Results Native LDL and oxidized LDL induced 8-iso-PGF₂ production in endothelial cells. Carvedilol significantly reduced this effect (e.g., for oxidized LDL: 2.66±0.22 pg vs 1.46±0.14 pg 8-iso-PGF₂ per µg protein, P<0.05). In healthy volunteers, carvedilol and metoprolol markedly decreased blood pressure and heart rate, but had no statistically significant effect on any indicator of oxidative stress measured. Remarkably, a trend toward reduction of urinary isoprostanes and 3-nitrotyrosine in plasma by both active treatments was observed, suggesting a non-specific antioxidative effect by blockade.Conclusions In vitro, the antioxidative potential of carvedilol was confirmed. In healthy men, antihypertensive doses of carvedilol exert no specific inhibition of oxidative stress.     

肥胖者吸烟对动脉僵硬度与氧化应激的影响

目的观察肥胖者吸烟对动脉僵硬度及氧化应激的影响。方法选取大学在校男生85人,按照BMI或腰围大小分为2组,对照组41人,实验组44人,实验组进行吸烟干预25d,对照组无任何干预,测定对照组及实验组吸烟前、后每位受试者动脉僵硬度、血浆谷胱甘肽、丙二醛、尿酸含量并进行对比。结果实验组吸烟前与对照组比较,动脉僵硬度（1．78±0．26VS1．97±0．38,P〈0．05）及血浆丙二醛[（3．88±1．13）μmol／LVS（4．32±1．56）μmol／L,P〈0．05]、尿酸含量[（295±43）μmol／LVS（361±57）μmol／L,P〈0．05]显著增高;实验组吸烟后与对照组及实验组吸烟前比较,动脉顺应性显著下降[（1．54±0．32）ml／mmHgVS（1．97±0．38）ml／mmHg,P〈0．01;（1．54±0．32）ml／mmHgVS（1．78±0．26）ml／mmHg,P〈0．05],与对照组比较,实验组吸烟前后丙二醛尿酸含量则显著上升[丙二醛：（4．32±1．56）vs（3．88±1．13）,（4．77±1．07）vs（3．88±1．13）;尿酸：（361±57）VS（295±43）,（472±39）μmol／L vs（295±43）μmol／L,P〈0．01或P〈0．05]。结论氧化应激反应产物丙二醛、尿酸含量的增高,说明机体氧化．抗氧化机制失衡有助于动脉僵硬度和动脉顺应性发生改变,增加心血管疾病的患病风险,而肥胖者吸烟更具有患病的高危性。     

Efficacy of subantimicrobial-dose doxycycline against nitrosative stress in chronic periodontitis

Aim:

To evaluate the effectiveness of subantimicrobial-dose doxycycline (SDD) as an adjunct to scaling and root planing (SRP) treatment against the nitrosative stress of moderate to advanced chronic periodontitis.

Methods:

Adults with untreated chronic periodontitis (n=174) were randomly administered SRP+SDD (n=87) (20 mg of doxycycline twice daily) or SRP+placebo (n=87) treatment for 3 months. At baseline and after 3 months, the probing depths (PD), bleeding on probing (BOP) and clinical attachment level (CAL) were measured, and a gingivomucosal biopsy was collected to assay the induction of nitric oxide synthase (iNOS) and 3-nitrotyrosine (3NT), and blood was collected to assay for total nitrites and nitrates (NO_x) and 3NT.

Results:

Compared to baseline, at the completion of treatment, significant decreases in the levels of tissue iNOS and 3NT and serum NO_x and 3NT were observed in both groups. SRP+SDD yielded a greater reduction in the gingivomucosal and serum nitrosative stress markers than did SRP+placebo. PD, BOP, and CAL reduction were correlated with the nitrosative stress parameters.

Conclusion:

On a short-term basis, SDD therapy may be used as an adjunct to SRP treatment against nitrosative stress in moderate to advanced chronic periodontitis.     

Inhibitory effects of sildenafil and tadalafil on inflammation,oxidative stress and nitrosative stress in animal model of bronchial asthma

BackgroundCyclic neucleotides are involved in many cellular functions including smooth muscle relaxation, inflammation, and signal transduction. Sildenafil and tadalafil are phosphodiesterase-5 (PDE-5) inhibitors which prevent the degradation of cyclic neucleotide i.e. guanosine 3′,5′ cyclic monophosphate (cGMP) and increase the levels of cGMP. In this study sildenafil and tadalafil were evaluated for their anti-inflammatory, anti-oxidative and anti-nitrosative stress potential in animal model of bronchial asthma.MethodsWistar rats were sensitized with 10 mg intraperitoneal (ip) ovalbumin adsorbed to 10 μg of aluminum hydroxide on day 0. Animals were given sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) from day 1 to day 14. Also, on day 14 animals were challenged with ovalbumin (1 mg ip). After 24 h, samples were collected to analyze interleukin-4 (IL-4) and tumour necrosis factor-α (TNF-α), in serum and bronchoalveolar lavage fluid (BALF). The oxidative stress markers malondialdehyde (MDA), reduced glutathione (GSH) and nitric oxide metabolites (NO_x) were also measured in serum.ResultsPre-treatment with sildenafil (1 and 3 mg/kg ip) and tadalafil (1 and 3 mg/kg ip) significantly reduced the levels of pro-inflammatory cytokines IL-4 and TNF-α in rat serum and BALF. In addition, pre-treatment with both the drugs decreased the levels of MDA and NO_x and increased the levels of GSH in serum.ConclusionsSildenafil and tadalafil decreased pro-inflammatory cytokines in serum and BALF. Both drugs inhibit oxidative and nitrosative stress in animal model of bronchial asthma and could have a therapeutic potential in bronchial asthma.     

Berberine exerts nephroprotective effect against cisplatin-induced kidney damage through inhibition of oxidative/nitrosative stress,inflammation, autophagy and apoptosis

The aim of this study was to investigate the therapeutic activity of isoquinoline alkaloid berberine against cisplatin (CP)-induced nephrotoxicity in mice. Berberine was administered at daily doses of 1, 2 and 3 mg/kg by gavage for two successive days, 48 h after intraperitoneal CP injection (13 mg/kg). Mice were sacrificed 24 h after the last dose of berberine. Histopathological changes and the increase in serum creatinine and blood urea nitrogen (BUN) induced by CP were significantly ameliorated by berberine in a dose-dependent manner. Additionally, oxidative/nitrosative stress, evidenced by the increase in renal 4-hydroxynonenal (4-HNE), 3-nitrotyrosine (3-NT), cytochrome P450 E1 (CYP2E1) and heme oxygenase (HO-1) expression, was significantly reduced. The expression of nuclear factor-kappaB (NF-κB), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) was markedly suppressed by berberine, indicating the inhibition of inflammatory response. Treatment of CP-intoxicated animals with berberine also significantly reduced the expression of p53, active caspase-3 as well as autophagy marker light chain 3B (LC3B) in the kidneys. The results of the current study showed the nephroprotective activity of berberine against CP-induced renal injury, which could be attributed to the inhibition of oxidative/nitrosative stress, inflammation, autophagy and apoptosis.     

Differences in reasons for smoking between younger and older smokers

The reasons why older people smoke have not been examined in the literature. This paper attempted to examine the differences in motivation and maintenance factors of elderly and young smokers using the Horn-Waingrow Why do you smoke questionnaire. One hundred and thirteen clinical patients and 112 non-patient controls were used in this study. The clinical group was divided into an elderly group (n = 58) and a younger group (n = 55). The results of a discriminant analysis showed that patients significantly differed from non-patients on 'automatic habit and stimulation', and 'crutch/tension reduction' factors. Elderly patients were found to be significantly differentiated from both younger patients and the control group on the 'pleasurable relaxation' factor. These findings offer support for the US Surgeon Generals' report that elderly smokers do have different motivating factors for their smoking behaviours from younger smokers.     

Maternal exposure to environmental tobacco smoke, GSTM1/T1 polymorphisms and oxidative stress

Environmental tobacco smoking (ETS) is known to be associated with adverse pregnancy outcomes. The purpose of this study was to investigate the relationship between maternal exposure to ETS and oxidative stress for neonates, as well as the effect of maternal genetic polymorphisms, glutathione-S-transferase M1 (GSTM1) and GSTT1, on this relationship. We used the radioimmunoassay to measure the urinary concentration of cotinine in 266 pregnant women who denied smoking cigarettes during pregnancy and in their singleton babies. In addition, the urinary concentration of malondialdehyde (MDA) and 8-hydroxy-2-deoxyguanosine (8-OH-dG) were assessed using high-performance liquid chromatography and enzyme-linked immunosorbent assay, respectively. We also extracted DNA from whole blood obtained from the mothers and then conducted polymerase chain reaction on the samples to determine the GSTM1 and GSTT1 genotypes. The maternal cotinine concentration was found to be significantly associated with the fetal cotinine concentration, particularly for mothers whose urine cotinine concentrations were above 120 microg/gcr (p<0.01). The fetal urine cotinine concentration was also found to be significantly associated with the fetal urine MDA concentration (p<0.01). When the null type maternal GSTM1 or the wild type GSTT1 was present, the maternal oxidative stress level increased significantly as the maternal continine concentration increased (MDA: p<0.01; 8-OH-dG: p<0.01). No significant relationships were found between maternal cotinine and fetal oxidative stress markers, however, the fetal MDA levels increased significantly as fetal cotinine levels increased. These results suggest that the maternal exposure to ETS affects the fetal urine cotinine concentration and induces production of maternal oxidative stress. In addition, maternal genetic polymorphisms of GSTM1 and GSTT1 may modify the oxidative stress by maternal exposure to ETS.     

Toxicity assessment of environmental pollutant phenanthrene in clam Venerupis philippinarum using oxidative stress biomarkers

The objective of this study was to assess potential toxic effects of phenanthrene (PHE) on tissues of clam Venerupis philippinarum using parameters of antioxidant defenses and oxidative stress. Antioxidant biomarkers including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), superoxide dismutase (SOD), and glutathione (GSH), as well as DNA damage and lipid peroxidation (LPO) in gills and digestive glands of V. philippinarum, were analyzed after a 1-, 3-, 6-, 10- and 15-day exposure to seawater containing PHE at concentrations of 2, 10, 50 μg/L. The results showed that the activity of most antioxidant enzymes was induced throughout the exposure period, and different trends were detected with time of exposure. The oxidative stress could be obviously caused in the gills and digestive glands under the experimental conditions. Overall, our results show that digestive glands are more sensitive to marine environmental stressors than gills, and GSH is proposed as potential useful biomarker as it showed good correlation with the target contaminant. This could provide useful information for toxic risk assessment of environmental pollutant PHE.     

Effect of exposure to fluoride and acetaminophen on oxidative/nitrosative status of liver and kidney in male and female rats

BackgroundThis study was undertaken to investigate, the effect of 6 weeks treatment with acetaminophen (AAP) and fluoride (F), administered either separately or together, on nitric oxide generation, lipid and protein peroxidation, total antioxidant status and level of reduced glutathione in the liver and kidney of male and female Wistar Han rats. Also, the influence of AAP on F excretion in urine was determined.MethodsThirty adult male and female rats were divided into five equal groups of six each: (I) controls drinking tap water; (II) controls drinking tap water and receiving 1 ml of tap water intragastrically; (III) animals receiving 12 mg F/L in drinking water; (IV) animals receiving 150 mg AAP/kg b.w./day; (V) animals receiving 12 mg F/L in drinking water and 150 mg AAP/kg b.w./day.ResultsF and AAP given separately and both together enhanced oxidative and nitrosative stress in investigated tissues. No gender differences were observed in oxidative/nitrosative stress parameters during treatment with F and/or AAP. Interestingly, the combined exposure to F and AAP resulted in an enhancement of oxidative/nitrosative stress in kidney of male and female rats compared to the group treated separately with F and AAP. No additive effect in the measured parameters in the liver during co-exposure to both xenobiotics was noticed.ConclusionsAs expected, the urinary F excretion increased in an exposure time-dependent manner in rats receiving F or a combination of F and AAP. The study also showed that AAP significantly decreased urinary F.     

Textile industrial effluent induces mutagenicity and oxidative DNA damage and exploits oxidative stress biomarkers in rats

Exposure to complex mixtures like textile effluent poses risks to animal and human health such as mutations, genotoxicity and oxidative damage. Aim of the present study was to quantify metals in industrial effluent and to determine its mutagenic, genotoxic and cytotoxic potential and effects on oxidative stress biomarkers in effluent exposed rats. Metal analysis revealed presence of high amounts of zinc, copper, chromium, iron, arsenic and mercury in industrial effluent. Ames test with/without enzyme activation and MTT assay showed strong association of industrial effluent with mutagenicity and cytotoxicity respectively. In-vitro comet assay revealed evidence of high oxidative DNA damage. When Wistar rats were exposed to industrial effluent in different dilutions for 60 days, then activities of total superoxide dismutase and catalase and hydrogen peroxide concentration were found to be significantly lower in kidney, liver and blood/plasma of effluent exposed rats than control. Vitamin C in a dose of 50 mg/kg/day significantly reduced oxidative effects of effluent in rats. On the basis of this study it is concluded that industrial effluent may cause mutagenicity, in-vitro oxidative stress-related DNA damage and cytotoxicity and may be associated with oxidative stress in rats. Vitamin C may have ameliorating effect when exposed to effluent.     

内质网应激与氧化应激:恶性循环还是双刃剑?

目的综述内质网应激与氧化应激之间相互作用关系的研究进展。探讨氧化应激与内质网应激相互作用诱发相关疾病的机制。方法阅读国内外文献数据库中相关文献,尤其是近年来关于氧化应激与内质网之间关系的文献,结合临床,从疾病诱发机制等方面对文献进行整理和综述。结果根据疾病背景,促进细胞存活的治疗策略主要在于加强保护未折叠蛋白反应(UPR)信号响应,衰减内质网应激水平,或者灭活UPR促凋亡化合物;而从氧化应激出发,控制氧化应激水平,减弱内质网应激是控制疾病发作的重要方法。结论本文对两种应激关系的研究近况进行整理总结,为相关疾病发病机制的深入研究和临床应用提供理论依据。     

Oxidative and nitrosative stress in trichloroethene-mediated autoimmune response

Reactive oxygen and nitrogen species (RONS) are implicated in the pathogenesis of several autoimmune diseases. Also, increased lipid peroxidation and protein nitration are reported in systemic autoimmune diseases. Lipid peroxidation-derived aldehydes (LPDAs) such as malondialdehyde (MDA) and 4-hydroxynonenal (HNE) are highly reactive and bind proteins covalently, but their potential to elicit an autoimmune response and contribution to disease pathogenesis remain unclear. Similarly, nitration of protein could also contribute to disease pathogenesis. To assess the status of lipid peroxidation and/or RONS, autoimmune-prone female MRL+/+ mice (5-week old) were treated with trichloroethene (TCE), an environmental contaminant known to induce autoimmune response, for 48 weeks (0.5mg/ml via drinking water), and formation of antibodies to LPDA-protein adducts was followed in the sera of control and TCE-treated mice. TCE treatment led to greater formation of both anti-MDA- and -HNE-protein adduct antibodies and higher serum iNOS and nitrotyrosine levels. The increase in TCE-induced oxidative stress was associated with increases in anti-nuclear-, anti-ssDNA- and anti-dsDNA-antibodies. These findings suggest that TCE exposure not only leads to oxidative/nitrosative stress, but is also associated with induction/exacerbation of autoimmune response in MRL+/+ mice. Further interventional studies are needed to establish a causal role of RONS in TCE-mediated autoimmunity.     

The radioprotective effect of Nigella sativa on nitrosative stress in lens tissue in radiation-induced cataract in rat

Objective: The aim of this study was to investigate the antioxidant and radioprotective effects of Nigella sativa oil (NSO) and thymoquinone (TQ) against ionizing radiation-induced cataracts in lens after total cranium irradiation (IR) of rats with a single dose of 5 gray (Gy).

Materials and methods: Seventy-four Sprague-Dawley rats were used for the experiment. The rats were randomly divided into six groups. Group A received total cranium IR plus NSO (1?g?kg^–1?d^–1) orally through an orogastric tube. Group B received total cranium IR plus TQ (50?mgkg^–1?d^–1) daily by intraperitoneal injection. Group C received 5?Gy of gamma IR as a single dose to total cranium plus 1?ml saline. Group D₁ just received 1?ml saline. Group D₂ just received dimethyl sulfoxide. Group D₃ did not receive anything.

Results: At the end of the 10th d, cataract developed in 80% of the rats in IR group only. After IR, cataract rate dropped to 20% and 50% in groups which were treated with NSO and TQ, respectively, and was limited at grades 1 and 2. Nitric oxide synthase activity, nitric oxide and peroxynitrite levels in the radiotherapy group were higher than those of all other groups.

Conclusions: The results implicate a major role for NSO and TQ in preventing cataractogenesis in ionizing radiation-induced cataracts in the lenses of rats, wherein NSO were found to be more potent.     

The anti-inflammatory prostaglandin 15d-PGJ<Subscript>2</Subscript> decreases oxidative/nitrosative mediators in brain after acute stress in rats

Rationale Immobilisation stress is followed by accumulation of oxidative/nitrosative mediators in brain after the release of tumour necrosis factor-alpha (TNF) and other cytokines, nuclear factor kappa B (NFB) activation, nitric oxide synthase-2 (NOS-2) and cyclooxygenase-2 (COX-2) expression in the brain.Objectives This study was conducted to assess if some of the anti-inflammatory products of COX can modify the accumulation of oxidative/nitrosative species seen in brain after stress and to study the mechanisms by which this effect is achieved.Methods Young-adult male Wistar rats were subjected to a single session of immobilisation during 6 h.Results In stressed animals, brain levels of the anti-inflammatory 15d-PGJ₂ increases concomitantly with COX-2 expression. Inhibition of COX-2 with NS-398 prevents stress-induced 15d-PGJ₂ increase. Injection of supraphysiological doses of 15d-PGJ₂ (80–120 g/kg) decreases stress-induced increase in NOS-2 activity as well as the stress-induced increase in NO metabolites. On the other hand, 15d-PGJ₂ decreases stress-induced malondialdehyde (an indicator of lipid peroxidation) accumulation in cortex and prevents oxidation of the main anti-oxidant glutathione. The mechanisms involved in the anti-oxidative properties of 15d-PGJ₂ in stress involve NFB blockade (by preventing stress-induced IB decrease) as well as inhibition of TNF release in stressed animals. At the doses tested, 15d-PGJ₂ decreases COX-2 expression and PGE₂ release during stress, suggesting an alternative mechanism for this endogenous compound.Conclusions These findings demonstrate a role for this anti-inflammatory pathway in the brain response to stress and open the possibility for preventing accumulation of oxidative/nitrosative species and subsequent brain damage.     

Oxidative stress and oxidative damage in chemical carcinogenesis

Reactive oxygen species (ROS) are induced through a variety of endogenous and exogenous sources. Overwhelming of antioxidant and DNA repair mechanisms in the cell by ROS may result in oxidative stress and oxidative damage to the cell. This resulting oxidative stress can damage critical cellular macromolecules and/or modulate gene expression pathways. Cancer induction by chemical and physical agents involves a multi-step process. This process includes multiple molecular and cellular events to transform a normal cell to a malignant neoplastic cell. Oxidative damage resulting from ROS generation can participate in all stages of the cancer process. An association of ROS generation and human cancer induction has been shown. It appears that oxidative stress may both cause as well as modify the cancer process. Recently association between polymorphisms in oxidative DNA repair genes and antioxidant genes (single nucleotide polymorphisms) and human cancer susceptibility has been shown.     

Markers of oxidative‐nitrosative stress induced by artesunate are followed by clastogenic and aneugenic effects and apoptosis in human lymphocytes

Artesunate (ARS) is a semi‐synthetic derivative of artemisinin, used as an outstanding antimalarial drug, which also displays antitumor, anti‐inflammatory and immunosuppressive effects. In spite of the numerous reports showing the antitumor activity of ARS, the particular mechanisms associated with its cytotoxicity and genotoxicity in non‐neoplastic human cells remain unclear. Here we aimed to verify the specific chromosome damages and the changes in markers of oxidative‐nitrosative stress and apoptosis triggered by ARS exposure in human peripheral blood lymphocytes. Cultures were incubated in the presence of ARS and the number of binucleated cells was determined. To discriminate between micronuclei (MN) containing a whole chromosome or an acentric chromosome, the MN test was employed in combination with the fluorescence in situ hybridization assay. Alterations in the levels of superoxide anion (O₂^?) and nitric oxide (NO) were measured by the nitroblue tetrazolium and Griess assay, respectively. Changes in the expression of the apoptotic markers were assessed by immunocytochemistry. We found that ARS induced a significant formation of both centromere‐positive MN (C⁺ MN) and centromere‐negative MN (C^– MN). These alterations were accompanied by an increase in both cellular levels of O₂^? and total NO production, and a remarkable enhancement in the expression of the apoptotic markers cytochrome c and caspases 8 and 9. Together these findings reveal that ARS induces changes in the oxidative‐nitrosative status of human lymphocytes, which are followed by apoptosis and clastogenic and aneugenic effects.     

Nicotine enantiomers and oxidative stress

Nicotine affects a variety of cellular processes ranging from induction of gene expression to secretion of hormones and modulation of enzymatic activities. The objective of this study was to characterize the toxicity of nicotine enantiomers as well as their ability to induce oxidative stress in an in vitro model using Chinese hamster ovary (CHO) cells. Colony formation assay has demonstrated that (−)-nicotine is the more toxic of the enantiomers. At 6 mM concentrations, (−)-nicotine was found to be ≈28- and 19-fold more potent than (+)-, and (±)-nicotine (racemic), respectively. Results also indicated that the toxicity of (±)-nicotine is higher than that of (+)-nicotine. (−)-Nicotine at a 10 mM concentration substantially decreased glutathione (GSH) levels (46% decrease). In addition, a 3-fold increase in malondialdehyde (MDA) level was evident in cells after exposure to 10 mM (−)-nicotine. Increased lactate dehydrogenase (LDH) activities in the media demonstrated that cellular membrane integrity was disturbed in nicotine treated cells. In the presence of superoxide dismutase (SOD) and catalase (CAT), the LDH activities returned to control value in 24 h with all concentrations of (−)-, (+)-, and (±)-nicotine. The decreases in LDH activities in the presence of the radical scavenging enzymes SOD and CAT suggest that membrane damage may be due to free radical generation.