Reduced light exposure mitigates streptozotocin-induced vascular changes and gliosis in diabetic retina by an anti-inflammatory effect and increased retinal cholesterol turnover.

Diabetic retinopathy is not cured efficiently and changes of lifestyle measures may delay early retinal injury in diabetes. The aim of our study was to investigate the effects of reduced daily light exposure on retinal vascular changes in streptozotocin (STZ)-induced model of DM with emphasis on inflammation, Aqp4 expression, visual cycle and cholesterol metabolism-related gene expression in rat retina and RPE. Male Wistar rats were divided into the following groups: 1. control; 2. diabetic group (DM) treated with streptozotocin (100 mg/kg); 3. group exposed to light/dark cycle 6/18 h (6/18); 4. diabetic group exposed to light/dark cycle 6/18 h (DM+6/18). Retinal vascular abnormalities were estimated based on lectin staining, while the expression of genes involved in the visual cycle, cholesterol metabolism, and inflammation was determined by qRT-PCR. Reduced light exposure alleviated vasculopathy, gliosis and the expression of IL-1 and TNF-α in the retina with increased perivascular Aqp4 expression. The expression of genes involved in visual cycle and cholesterol metabolism was significantly up-regulated in RPE in DM+6/18 vs. DM group. In the retina only the expression of APOE was significantly higher in DM+6/18 vs. DM group. Reduced light exposure mitigates vascular changes and gliosis in DM via its anti-inflammatory effect, increased retinal cholesterol turnover and perivascular Aqp4 expression.

The interplay between metabolic dysregulations and non-alcoholic fatty liver disease in women after menopause.

The hypoestrogenic period after menopause and associated metabolic imbalance might facilitate the onset of non-alcoholic fatty liver disease (NAFLD) and its progression. The prevalence of NAFLD increases in patients experiencing premature ovarian insufficiency, as well as surgical or natural menopause. The postmenopausal period is characterized by dyslipidemia and insulin resistance associated with an increased influx of free fatty acids to the liver with consequent steatosis and further progression of NAFLD. More than half of postmenopausal women with diabetes mellitus type 2 suffer from NAFLD. It is suggested that estrogens slow the progression of chronic liver diseases by suppression of inflammation, improvement of mitochondrial function, alleviation of oxidative stress, insulin resistance, and fibrogenesis. The hyperandrogenic state of polycystic ovary syndrome (PCOS) is associated with the development of NAFLD in women of reproductive age, but it is difficult to extend these findings to menopause due to inappropriate diagnosis of PCOS after menopause. Lifestyle intervention, including physical activity and dietary regimens, remains the first-line preventive and therapeutic option for NAFLD. There are contradictory reports on the use of menopausal hormonal therapy (MHT) and NAFLD. It is necessary to investigate the potential effects of estradiol dose, progesterone type, selective estrogen receptor modulators and tissue-selective estrogen complex compounds on NAFLD development and progression in postmenopausal women. The present review aims to explore the pathophysiological and clinical aspects of liver metabolic disturbances in women after menopause, focusing on the possible preventive and therapeutic strategies in NAFLD, including the potential role of MHT.

The Role of MIF in Hepatic Function, Oxidative Stress, and Inflammation in Thioacetamide-induced Liver Injury in Mice: Protective Effects of Betaine.

BACKGROUND: Macrophage migration inhibitory factor (MIF) is a multipotent cytokine that contributes to the inflammatory response to chemical liver injury. This cytokine exhibits pro- and anti-inflammatory effects depending on the etiology and stage of liver disease. OBJECTIVE: Our study aimed to investigate the role of MIF in oxidative stress and inflammation in the liver, and modulatory effects of betaine on MIF in thioacetamide (TAA)-induced chronic hepatic damage in mice. METHODS: The experiment was performed on wild type and knockout MIF-/- C57BL/6 mice. They were divided into the following groups: control; Bet-group that received betaine (2% wt/v dissolved in drinking water); MIF-/- mice group; MIF-/-+Bet; TAA-group that received TAA (200 mg/kg b.w.), intraperitoneally, 3x/week/8 weeks); TAA+Bet; MIF-/-+TAA, and MIF-/-+TAA+Bet. In TAA- and Bet-treated groups, animals received the same doses. After eight weeks of treatment, blood samples were collected for biochemical analysis, and liver specimens were prepared for the assessment of parameters of oxidative stress and inflammation. RESULTS: In MIF-/-mice, TAA reduced transaminases, γ-glutamyltranspeptidase, bilirubin, malondialdehyde (MDA), oxidative protein products (AOPP), total oxidant status (TOS), C-reactive protein (CRP), IL-6, IFN-γ, and increased thiols and total antioxidant status (TAS). Betaine attenuated the mechanism of MIF and mediated effects in TAA-induced liver injury, reducing transaminases, γ-glutamyltranspeptidase, bilirubin, MDA, AOPP, TOS, CRP, IL-6, IFN-g, and increasing thiols. CONCLUSION: MIF is a mediator in hepatotoxic, pro-oxidative, and proinflammatoryeffects of TAA-induced liver injury. MIF-targeted therapy can potentially mitigate oxidative stress and inflammation in the liver, but the exact mechanism of its action requires further investigation. Betaine increases anti-oxidative defense and attenuates hepatotoxic effects of MIF, suggesting that betaine can be used for the prevention and treatment of liver damage.

Effect of Betaine Supplementation on Liver Tissue and Ultrastructural Changes in Methionine-Choline-Deficient Diet-Induced NAFLD.

Nonalcoholic fatty liver disease (NAFLD) represents a hepatic manifestation of metabolic syndrome. The aim of this study was to examine the effect of betaine on ultrastructural changes in the mouse liver with methionine- and choline-deficient (MCD) diet-induced NAFLD. Male C57BL/6 mice were divided into groups: Control-fed with standard chow, BET-standard chow supplemented with betaine (1.5% w/v drinking water), MCD-fed with MCD diet, and MCD + BET-MCD diet with betaine supplementation for 6 weeks. Liver samples were taken for pathohistology and transmission electron microscopy. The MCD diet-induced steatosis, inflammation, and balloon-altered hepatocytes were alleviated by betaine. MCD diet induced an increase in mitochondrial size versus the control group (p < 0.01), which was decreased in the betaine-treated group. In the MCD diet-fed group, the total mitochondrial count decreased versus the control group (p < 0.01), while it increased in the MCD + BET group versus MCD (p < 0.01). Electron microscopy showed an increase in the number of autophagosomes in the MCD and MCD + BET group versus control, and a significant difference in autophagosomes number was detected in the MCD + BET group by comparison with the MCD diet-treated group (p < 0.05). Betaine decreases the number of enlarged mitochondria, alleviates steatosis, and increases the number of autophagosomes in the liver of mice with NAFLD.

Prenatal Androgenization Induces Anxiety-Like Behavior in Female Rats, Associated with Reduction of Inhibitory Interneurons and Increased BDNF in Hippocampus and Cortex.

Anxiety is one of the most frequent psychiatric disorders. Despite the fact that most studies describe an anxiolytic effect of testosterone, hyperandrogenemia in mothers is assumed to be related to an increased risk of mood disorders in their offspring. An increasing body of scientific evidence suggests that an altered expression of interneuronal markers of the hippocampus may be the cause of anxiety. The aim of this study was to examine the influence of maternal hyperandrogenemia on behavioral parameters of anxiety-like behavior, neuropeptide Y (NPY) and parvalbumin (PV) expression in the hippocampus, and the level of the brain-derived neurotrophic factor (BDNF) in the hippocampus and cerebral cortex. Pregnant female Wistar albino rats were treated with testosterone undecanoate on the 20th day of gestation. Anxiety-like behavior in adult female offspring was evaluated by the elevated plus maze test and the open field. The number of PV and NPY immunoreactive cells in the hippocampus was determined immunohistochemically. The level of BDNF expression in the hippocampus and cerebral cortex was analyzed with the Western blot test. Prenatal hyperandrogenization increased anxiety-like behavior in female offspring and decreased expression of NPY+ and PV+ in the CA1 region of the hippocampus as compared to the control group. BDNF expression in the hippocampus and cerebral cortex of prenatally androgenized female offspring was significantly increased in comparison with the controls. Prenatal hyperandrogenization may be the cause of anxiety-like behavior in female offspring. Decrease in NPY and PV expression in the hippocampus may explain the possible mechanism of hyperandrogenization induced anxiety.

The effects of dietary methionine restriction on the function and metabolic reprogramming in the liver and brain - implications for longevity.

Methionine is an essential sulphur-containing amino acid involved in protein synthesis, regulation of protein function and methylation reactions. Dietary methionine restriction (0.12-0.17% methionine in food) extends the life span of various animal species and delays the onset of aging-associated diseases and cancers. In the liver, methionine restriction attenuates steatosis and delays the development of non-alcoholic steatohepatitis due to antioxidative action and metabolic reprogramming. The limited intake of methionine stimulates the fatty acid oxidation in the liver and the export of lipoproteins as well as inhibits de novo lipogenesis. These effects are mediated by various signaling pathways and effector molecules, including sirtuins, growth hormone/insulin-like growth factor-1 axis, sterol regulatory element binding proteins, adenosine monophosphate-dependent kinase and general control nonderepressible 2 pathway. Additionally, methionine restriction stimulates the synthesis of fibroblast growth factor-21 in the liver, which increases the insulin sensitivity of peripheral tissues. In the brain, methionine restriction delays the onset of neurodegenerative diseases and increases the resistance to various forms of stress through antioxidative effects and alterations in lipid composition. This review aimed to summarize the morphological, functional and molecular changes in the liver and brain caused by the methionine restriction, with possible implications in the prolongation of maximal life span.

Betaine modulates oxidative stress, inflammation, apoptosis, autophagy, and Akt/mTOR signaling in methionine-choline deficiency-induced fatty liver disease.

We examined the effects of betaine, an endogenous and dietary methyl donor essential for the methionine-homocysteine cycle, on oxidative stress, inflammation, apoptosis, and autophagy in methionine-choline deficient diet (MCD)-induced non-alcoholic fatty liver disease (NAFLD). Male C57BL/6 mice received standard chow (control), standard chow and betaine (1.5% w/v in drinking water), MCD, or MCD and betaine. After six weeks, serum and liver samples were collected for analysis. Betaine reduced MCD-induced increase in liver transaminases and inflammatory infiltration, as well as hepatosteatosis and serum levels of low-density lipoprotein, while it increased that of high-density lipoprotein. MCD-induced hepatic production of reactive oxygen and nitrogen species was significantly reduced by betaine, which also improved liver antioxidative defense by increasing glutathione content and superoxide-dismutase, catalase, glutathione peroxidase, and paraoxonase activity. Betaine reduced the liver expression of proinflammatory cytokines tumor necrosis factor and interleukin-6, as well as that of proapoptotic mediator Bax, while increasing the levels of anti-inflammatory cytokine interleukin-10 and antiapoptotic Bcl-2 in MCD-fed mice. In addition, betaine increased the expression of autophagy activators beclin 1, autophagy-related (Atg)4 and Atg5, as well as the presence of autophagic vesicles and degradation of autophagic target sequestosome 1/p62 in the liver of NAFLD mice. The observed effects of betaine coincided with the increase in the hepatic phosphorylation of mammalian target of rapamycin (mTOR) and its activator Akt. In conclusion, the beneficial effect of betaine in MCD-induced NAFLD is associated with the reduction of liver oxidative stress, inflammation, and apoptosis, and the increase in cytoprotective Akt/mTOR signaling and autophagy.

The Effects of Betaine on the Nuclear Fractal Dimension, Chromatin Texture, and Proliferative Activity in Hepatocytes in Mouse Model of Nonalcoholic Fatty Liver Disease.

The effects of betaine on hepatocytes chromatin architecture changes were examined by using fractal and gray-level co-occurrence matrix (GLCM) analysis in methionine/choline-deficient (MCD) diet-induced, nonalcoholic fatty liver disease (NAFLD). Male C57BL/6 mice were divided into groups: (1) Control: standard diet; (2) BET: standard diet and betaine supplementation through drinking water (solution 1.5%); (3) MCD group: MCD diet for 6 weeks; (4) MCD+BET: fed with MCD diet + betaine for 6 weeks. Liver tissue was collected for histopathology, immunohistochemistry, and determination of fractal dimension and GLCM parameters. MCD diet induced diffuse micro- and macrovesicular steatosis accompanied with increased Ki67-positive hepatocyte nuclei. Steatosis and Ki67 immunopositivity were less prominent in the MCD+BET group compared with the MCD group. Angular second moment (ASM) and inverse difference moment (IDM) (textural homogeneity markers) were significantly increased in the MCD+BET group versus the MCD group (p<0.001), even though no difference between the MCD and the control group was evident. Heterogeneity parameters, contrast, and correlation were significantly increased in the MCD group versus the control (p<0.001). On the other hand, betaine treatment significantly reduced correlation, contrast, and entropy compared with the MCD group (p<0.001). Betaine attenuated MCD diet-induced NAFLD by reducing fat accumulation and inhibiting hepatocyte proliferation. Betaine supplementation increased nuclear homogeneity and chromatin complexity with reduction of entropy, contrast, and correlation.

Rimonabant Improves Oxidative/Nitrosative Stress in Mice with Nonalcoholic Fatty Liver Disease.

The present study deals with the effects of rimonabant on oxidative/nitrosative stress in high diet- (HFD-) induced experimental nonalcoholic fatty liver disease (NAFLD). Male mice C57BL/6 were divided into the following groups: control group fed with control diet for 20 weeks (C; n = 6); group fed with HFD for 20 weeks (HF; n = 6); group fed with standard diet and treated with rimonabant after 18 weeks (R; n = 9); group fed with HFD and treated with rimonabant after 18 weeks (HFR; n = 10). Daily dose of rimonabant (10 mg/kg) was administered to HFR and R group by oral gavage for two weeks. Treatment induced a decrease in hepatic malondialdehyde concentration in HFR group compared to HF group (P < 0.01). The concentration of nitrites + nitrates in liver was decreased in HFR group compared to HF group (P < 0.01). Liver content of reduced glutathione was higher in HFR group compared to HF group (P < 0.01). Total liver superoxide dismutase activity in HFR group was decreased in comparison with HF group (P < 0.01). It was found that rimonabant may influence hepatic iron, zinc, copper, and manganese status. Our study indicates potential usefulness of cannabinoid receptor type 1 blockade in the treatment of HFD-induced NAFLD.

Alpha-lipoic acid affects the oxidative stress in various brain structures in mice with methionine and choline deficiency.

Deficiency in methionine or choline can induce oxidative stress in various organs such as liver, kidney, heart, and brain. This study was to examine the effects of alpha-lipoic acid (LA) on oxidative stress induced by methionine and choline deficiency (MCD) in several brain structures. Male mice C57BL/6 (n = 28) were divided into four groups: (1) control - continuously fed with standard chow; (2) LA - fed with standard chow and receiving LA; (3) MCD2 - fed with MCD diet for two weeks, and (4) MCD2+LA - fed with MCD diet for two weeks and receiving LA (100 mg/kg/day intraperitonealy [i.p.]). Brain tissue (cortex, hypothalamus, striatum and hippocampus) was taken for determination of oxidative stress parameters. MCD diet induced a significant increase in malondialdehyde and NOx concentration in all brain regions, while LA restored their content to normal values. Similar to this, in MCD2 group, activity of total SOD, MnSOD, and Cu/ZnSOD was reduced by MCD diet, while LA treatment improved their activities in all brain structures. Besides, in MCD2 group a decrease in catalase activity in cortex and GSH content in hypothalamus was evident, while LA treatment induced an increase in catalase activity in cortex and striatum and GSH content in hypothalamus. LA treatment can significantly reduce lipid peroxidation and nitrosative stress, caused by MCD diet, in all brain regions by restoring antioxidant enzymes activities, predominantly total SOD, MnSOD, and Cu/ZnSOD, and to a lesser extent by modulating catalase activity and GSH content. LA supplementation may be used in order to prevent brain oxidative injury induced by methionine and choline deficiency.

The relationship between atherosclerosis and pulmonary emphysema.

INTRODUCTION: The etiopathogenesis of atherosclerosis and subsequent pulmonary emphysema has not been fully elucidated. EXPERIMENTAL STUDIES: Foam cells are of great importance in the development of these diseases. It is known that local cytokine secretion and modification of native lipoprotein particles, which are internalized by the vascular and alveolar macrophages via the scavenger receptors on the surfaces of these cells, lead to the formation of foam cells. Thus, the exacerbation of local inflammatory process in the vascular and lung tissue ensues due to a generation of reactive oxygen species, resulting in further lipoprotein modification and cytokine production. Accumulating evidence suggests that oxidants may facilitate the inflammatory response by impairing antiprotease function, directly attacking vascular and lung matrix proteins and by inactivating enzymes involved in elastin synthesis and vascular and lung repair. CLINICAL STUDIES: Cigarette smoke is recognized as a rich source of oxidants. Nearly 90% of all patients with chronic obstructive pulmonary disease are smokers. The process of atherogenesis is also influenced by tobacco smoke. CONCLUSION: The role of vascular and alveolar macrophages has become increasingly important in understanding the development of atherosclerosis and resulting pulmonary emphysema.

[Pathophysiological mechanisms of angiogenesis in atherogenesis].

INTRODUCTION: Atherosclerosis is a progressive, multifactorial, diffuse, multisystemic, chronic, inflammatory disease, which is manifested by disorders of vascular, immune and metabolic system. Pathogenesis of this disease is not fully understood. Accordingly, angiogenesis represents a special field of research due to its role in atherogenesis. STEPS OF ANGIOGENESIS: Angiogenesis is a complex biological process, which requires the precise coordination of its four steps (vasodilatation and permeability, vessel destabilization and matrix degradation, endothelial cell proliferation and migration, and lumen formation and vessel stabilization). MEDIATORS OF ANGIOGENIC PROCESS: The process of forming new blood vessels is regulated by a delicate balance between proangiogenic and antiangiogenic molecules. Numerous soluble growth factors and inhibitors, cytokines, proteases, extracellular matrix proteins and adhesion molecules, as well as hypoxia, inflammatory process, shear stress, hypertension and interaction between cells and extracellular matrix strictly control the angiogenic process. Neovascularization is halted due to the downregulation of angiogenic factors or the increase of inhibitors of this process. TUMOR VASCULARIZATION: In the asymptomatic phase of cancerogenesis, cancer rarely exceeds the diameter of 1-2 millimeters. However, when the metabolic demand increases, it leads to tumor vascularization. In this way, tumor switches to an angiogenic phenotype. The molecular basis of angiogenic switch refers to increased production of angiogenic factors and/or loss of angiogenic inhibitors. CONCLUSION: The contribution of angiogenic process has become increasingly meaningful in understanding the pathogenesis ofatherosclerosis.

The effect of calorie restriction on acute ethanol-induced oxidative and nitrosative liver injury in rats.

The aim of our study was to examine the effect of calorie restriction (CR) on oxidative and nitrosative liver injury in rats, induced by acute ethanol intoxication. Male Wistar rats were divided into groups: (1) control; (2) calorie-restricted groups with intake of 60-70% (CR60-70) and 40-50% of daily energy needs (CR40-50); (3) ethanol-treated group (E); (4) calorie-restricted, ethanol-treated groups (E+CR60-70 and E+CR40-50). Ethanol was administered in 5 doses of 2g/kg every 12h, and duration of CR was 5 weeks before ethanol treatment. Malondialdehyde and nitrite and nitrate level were significantly lower in E+CR60-70 and higher in E+CR40-50 vs. E group. Liver reduced glutathione content and activity of both superoxide dismutase izoenzymes were significantly higher in E+CR60-70 and lower in E+CR40-50 vs. E group. Oxidative stress may be a potential mechanism of hormetic effects of CR on acute ethanol-induced liver injury.

Alcoholic liver disease/nonalcoholic fatty liver disease index: distinguishing alcoholic from nonalcoholic fatty liver disease.

OBJECTIVE: The alcoholic liver disease (ALD)/nonalcoholic fatty liver disease (NAFLD) (ANI) scoring system was constructed as a response to a clinical need for avoiding the risks of liver biopsy in diagnosing the etiology of fatty liver disease. The aim of this study was to test the reliability of ANI as a noninvasive method to distinguish ALD from NAFLD. MATERIALS AND METHODS: One hundred and thirty-five patients were classified into two groups, ALD and NAFLD, according to the pathohistological results. Parameters for ANI are aspartate aminotransferase, alanine aminotransferase, mean corpuscular volume, BMI, and sex. ANI was calculated using an online calculator, official site of Mayo Clinic. RESULTS: ANI was significantly higher in patients with ALD than NAFLD (P<0.01). The cutoff point of ANI is -0.66. ANI greater than -0.66 indicates ALD, whereas ANI less than -0.66 yields a higher probability of NAFLD with high specificity (96.7%) and sensitivity (84.1%). The mean corpuscular volume and aspartate aminotransferase/alanine aminotransferase ratio were higher, whereas BMI was lower in patients with ALD than in NAFLD (P<0.01). CONCLUSION: The ANI scoring system may be used for the estimation of alcoholic origin of steatosis/steatohepatitis and may help in triaging patients for liver biopsy. ANI less than -0.66 indicates NAFLD, whereas ANI greater than -0.66 confirms the alcoholic etiology, but does not exclude the contribution of associated factors toward the development of fatty liver in a Serbian population.

Different sensitivity of various brain structures to thioacetamide-induced lipid peroxidation.

Thioacetamide (TAA) exerts hepatotoxic, neurotoxic and carcinogenic effects. The aim of our study was to investigate the effects of TAA on lipid peroxidation and catalase activity in various rat brain regions. Male Wistar rats were divided into following groups: 1. control, saline-treated; 2. thioacetamide-treated groups, TAA300 (300 mg/kg), TAA600 (600 mg/kg) and TAA900 (900 mg/kg). Daily dose of TAA (300 mg/kg) was administered intraperitoneally once (TAA300), twice (TAA600) and three times (TAA900) in consecutive days. Brain samples were collected 24 h after the last dose of TAA and malondialdehyde (MDA) level and catalase activity were determined in cortex, brainstem and hippocampus. MDA level was significantly increased while catalase activity was significantly lower in all brain regions in TAA900 group in comparison with control group. In TAA600 MDA level was increased in the brainstem and cortex when compared to control (p < 0.01). The same dose of TAA 600 mg/kg induced a significant decline in catalase activity in the brainstem and cortex and an increase in its activity in the hippocampus when compared to control (p < 0.01). In TAA300 an increase in MDA level was evident only in the brainstem. Catalase activity was significantly higher in the cortex and hippocampus in TAA300 group in comparison with control (p < 0.01). Based on these results, it may be concluded that various rat brain regions have different sensitivity to TAA-induced lipid peroxidation with hippocampus being less sensitive than cerebral cortex and brainstem.

[The role of oxidative/nitrosative stress in pathogenesis of paracetamol-induced toxic hepatitis].

INTRODUCTION: Paracetamol is an effective analgesic/antipyretic drug when used at therapeutic doses. However, the overdose of paracetamol can cause severe liver injury and liver necrosis. The mechanism of paracetamol-induced liver injury is still not completely understood. Reactive metabolite formation, depletion of glutathione and alkylation of proteins are the triggers of inhibition of mitochondrial respiration, adenosine triphosphate depletion and mitochondrial oxidant stress leading to hepatocellular necrosis. ROLE OF OXIDATIVE STRESS IN PARACETAMOL-INDUCED LIVER INJURY: The importance of oxidative stress in paracetamol hepatotoxicity is controversial. Paracetamol-induced liver injury cause the formation of reactive oxygen species. The potent sources of reactive oxygen are mitochondria, neutrophils. Kupffer cells and the enzyme xatnine oxidase. Free radicals lead to lipid peroxidation, enzymatic inactivation and protein oxidation. ROLE OF MITOCHONDRIA IN PARACETAMOL-INDUCED OXIDATIVE STRESS: The production of mitochondrial reactive oxygen species is increased, and the glutathione content is decreased in paracetamol overdose. Oxidative stress in mitochondria leads to mitochondrial dysfunction with adenosine triphosphate depletion, increase mitochondrial permeability transition, deoxyribonucleic acid fragmentation which contribute to the development of hepatocellular necrosis in the liver after paracetamol overdose. ROLE OF KUPFFER CELLS IN PARACETAMOL-INDUCED LIVER INJURY: Paracetamol activates Kupffer cells, which then release numerous cytokines and signalling molecules, including nitric oxide and superoxide. Kupffer cells are important in peroxynitrite formation. On the other hand, the activated Kupffer cells release anti-inflammatory cytokines. ROLE OF NEUTROPHILS IN PARACETAMOL-INDUCED LIVER INJURY: Paracetamol-induced liver injury leads to the accumulation of neutrophils, which release lysosomal enzymes and generate superoxide anion radicals through the enzyme nicotinamide adenine dinucleotide phosphate oxidase. Hydrogen peroxide, which is influenced by the neutrophil-derived enzyme myeloperoxidase, generates hypochlorus acid as a potent oxidant. ROLE OF PEROXYNITRITE IN PARACETAMOL-INDUCED OXIDATIVE STRESS: Superoxide can react with nitric oxide to form peroxynitrite, as a potent oxidant. Nitrotyrosine is formed by the reaction of tyrosine with peroxynitrite in paracetamol hepatotoxicity. CONCLUSION: Overdose of paracetamol may produce severe liver injury with hepatocellular necrosis. The most important mechanisms of cell injury are metabolic activation of paracetamol, glutathione depletion, alkylation of proteins, especially mitochondrial proteins, and formation of reactive oxygen/nitrogen species.