Ethanol-induced Hepatotoxicity Research Articles

Protective effect of Nigella sativa oil against binge ethanol-induced oxidative stress and liver injury in rats

AimNigella sativa L. (Ranunculaceae) is considered as a therapeutic plant-based medicine for liver damage. In this study, the aim was to study the effect of Nigella sativa oil (NSO) pretreatment on ethanol-induced hepatotoxicity in rats. MethodRats were given Nigella sativa oil at doses of 2.5 and 5.0 mL·kg−1, orally for 3 weeks, followed by oral ethanol (EtOH) administration (5 g·kg−1) every 12 h three times (binge model). ResultsBinge ethanol application caused significant increases in plasma transaminase activities and hepatic triglyceride and malondialdehyde (MDA) levels. It decreased hepatic glutathione (GSH) levels, but did not change vitamins E and vitamin C levels and antioxidant enzyme activities. NSO (5.0 mL·kg−1) pretreatment significantly decreased plasma transaminase activities, hepatic MDA, and triglyceride levels together with amelioration in hepatic histopathological findings. ConclusionNSO pretreatment may be effective in protecting oxidative stress-induced hepatotoxicity after ethanol administration

Prevention of ethanol-induced hepatotoxicity by fermented Curcuma longa L. in C57BL/6 mice

The protective effect of fermented Curcuma longa L. (FC) was investigated in male C57BL/6 mice under ethanol-induced oxidative stress. Ethanol markedly elevated levels of serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in mice. However, mice receiving FC prior to ethanol treatment did not display hepatotoxicity as evidenced by the significant reductions of AST and ALT activities. When compared to the ethanol-alone treated group, FC group exhibited a significant decrease in cytochrome P-450 2E1 (CYP2E1) activity, an enzyme associated with oxidative stress. Indicators of the hepatic antioxidant defense system, such as levels of superoxide dismutase, catalase, glutathione reductase and glutathione were also increased in FC-pretreated mice. The amelioration of malondialdehyde was indicative of the protective effect of FC against liver damage mediated by ethanol. These results suggest that FC could be a candidate used for the prevention against alcoholic liver diseases by the alleviation of oxidative stress via suppressing CYP2E1.

Quercetin attenuates chronic ethanol hepatotoxicity: Implication of “free” iron uptake and release

Emerging evidence has displayed that oxygen free radicals especially ones promoted by “free” iron play an important role in the development of alcoholic liver disease (ALD). Naturally-occurring quercetin has been reported to prevent ALD and iron overload-induced damage aside from the “free” iron. The purpose was to explore the potential mechanisms by which quercetin arrests alcohol-induced “free” iron disorder. Chronic alcohol (30% of total calories) or iron (0.2%)-fed adult male C57BL/J mice for 15weeks resulted in significantly elevated levels of hepatic iron, labile iron pool-Fe and serum non-transferrin bound iron, accompanied with sustained oxidative damage. The hepatotoxicity was further exacerbated by ethanol and iron. Quercetin (100mg/kg. body weight) alleviated the detrimental effects induced by ethanol and/or iron. The expressions of divalent metal transporter 1, zinc transporter member 14, mucolipin 1, transferrin receptor 1 (TfR1) and ferritin were up-regulated by ethanol and/or iron, which were partially normalized by quercetin. Quercetin prevented ethanol-induced hepatotoxicity, which may be partially attributed to the alleviated disorder of bound iron and “free” iron. The significant suppression of ethanol-stimulated molecules for “free” iron uptake and release may contribute to the hepatoprotective effect of quercetin, although TfR1-mediated physiological pathway of iron uptake also played a role.

An Evaluation of the Preventive Effect of the Methanol Extract of Thai Basil (Ocimum basilicum L.) on Ethanol-induced Hepatotoxicity in Rats

Aim: The present study was investigated the preventive effect of methanol extract of Ocimum bacilicum (MOEB) on ethanol induced hepatotoxicity in rats. Study Design: Male Wistar rats weighing 200–250 g were divided into six groups of six rats each as follows: the normal control rats we read ministered with distilled water(NC), the ethanol control was administered with ethanol (5 g/kg)(EC), extract treated group given only the extract (120 mg/ kg body)(ET) and experimental groups EX1 to EX3 were fed with ethanol (5 g/kg) plus MOEB in graded doses of 80 mg, 120 mg and 160 mg/kg body for 30 days. Place and Duration of Study: This study was conducted at the Department of Biological Sciences (DBS) of University of Botswana between July 2009-June 2010. Methodology: At the end of the experiment, rats were sacrificed; blood and liver tissue were collected to conduct the bioassays. From the blood collected, thiobarbituric acidreactive substances (TBARS), reduced glutathione (GSH), catalase (CAT) and superoxide dismutase (SOD) were estimated together with the liver markers such as alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP). From the liver tissue collected, about 10 small pieces were fixed in 10% formalin for histological preparations and the rest was used for bioassays such as TBARS, GSH, CAT and SOD. Original Research Article European Journal of Medicinal Plants, 4(2): 158-170, 2014 159 Results: The results indicated that there were significant difference between the experimental rats (EX-groups) when compared with alcohol control (EC-group) in all the parameters checked and they were not significantly different from the normal control (NCgroup). Again, the groups, treated with extracts only, did not show any negative effect, which clearly indicated that the extract had no toxic effects. A significant reduction in the levels of TBARS, ALT, and AST and a significant increase in the levels of GSH, CAT and SOD were noticed in EX groups when compared with the EC groups. Thus the results indicated a significant protection by these extracts against ethanol-induced hepatotoxicity (P ≤0.05). Conclusion: The present study showed that MEOB is a potent antioxidant agent in preventing and controlling the hepatotoxicity induced by ethanol and induce a protective effect by decreasing the oxidative stress and increasing the antioxidant status.

Asiatic acid from Potentilla chinensis attenuate ethanol-induced hepatic injury via suppression of oxidative stress and Kupffer cell activation.

This study examined the effect of Asiatic acid from Potentilla chinensis (AAPC) on chronic ethanol-induced hepatic injury. Rats underwent intragastric administration of ethanol (5.0–9.0 g/kg) once a day for 12 weeks. A subset of rats were also intragastrically treated with AAPC (2, 4 or 8 mg/kg) once a day. In the end, AAPC treatment significantly protected against ethanol-induced liver injury, as evidenced by the decrease in serum alanine and aspartate aminotransferases levels and the attenuation of histopathological changes in rats. Additionally, AAPC significantly decreased blood alcohol and acetaldehyde concentrations by enhancing alcohol dehydrogenase and aldehyde dehydrogenase activities. Mechanistically, studies showed that AAPC remarkably alleviated the formations of malondialdehyde and myeloperoxidase, restored impaired antioxidants, including superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase, and inhibited cytochrome P450 (CYP)2E1 activity. Moreover, the over-expression of cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), the elevated plasma endotoxin level and the up-regulated Toll-like receptor 4 (TLR4), CD14 and myeloid differentiation factor 88 (MyD88) as well as nuclear factor-κB were also suppressed by AAPC in ethanol-intoxicated rats. In conclusion, the protective effect of AAPC on ethanol-induced hepatotoxicity was mainly due to its ability to attenuate oxidative stress and inhibit Kupffer cell activation by decreasing the level of plasma endotoxin and the expression of TLR4, CD14 and MyD88.

Deletion of circadian gene Per1 alleviates acute ethanol-induced hepatotoxicity in mice

The severity of ethanol-induced liver injury is associated with oxidative stress and lipid accumulation in the liver. Core circadian clock is known to mediate antioxidative enzyme activity and lipid metabolism. However, the link between circadian clock and ethanol-induced hepatotoxicity remains unclear. Here we showed that extents of acute ethanol-induced liver injury and steatosis in mice exhibit circadian variations consistent with hepatic expression of Period (Per) genes. Mice lacking clock gene Per1 displayed less susceptible to ethanol-induced liver injury, as evidenced by lower serum transaminase activity and less severe histopathological changes. Ethanol-induced lipid peroxidation was alleviated in Per1−/− mice. However, Per1 deletion had no effect on antioxidants depletion caused by ethanol administration. Ethanol-induced triglycerides (TG) accumulation in the serum and liver was significantly decreased in Per1−/− mice compared with that in wild-type (WT) mice. Analysis of gene expression in the liver revealed peroxisome proliferators activated receptor-gamma (PPARγ) and its target genes related to TG synthesis are remarkably down-regulated in Per1−/− mice. HepG2 cells were treated with ethanol at 150mM for 3 days. Per1 overexpression augmented lipid accumulation after treatment with ethanol in HepG2 cells, but had no effect on ethanol-induced oxidative stress. Expression of genes related to lipogenesis, including PPARγ and its target genes, was up-regulated in cells overexpressing Per1. In conclusion, these results indicated that circadian rhythms of ethanol-induced hepatotoxicity are controlled by clock gene Per1, and deletion of Per1 protected mice from ethanol-induced liver injury by decreasing hepatic lipid accumulation.

14-Deoxyandrographolide targets adenylate cyclase and prevents ethanol-induced liver injury through constitutive NOS dependent reduced redox signaling in rats

Chronic alcoholism is one of the most common causes of liver diseases worldwide. Nitric oxide (NO) has been proposed to have potential for clinical application against chronic hepatocellular injuries. However, mechanisms underlying hepatoprotective functions of NO in ethanol-induced apoptosis are largely unknown. Sprauge-Dawley rats were exposed to ethanol for 8 weeks. Half of the ethanol-fed animals received 14-deoxyandrographolide (14-DAG) treatment for the last 4 weeks of study. Preventive effect of 14-DAG against ethanol-induced hepatotoxicity involved constitutive nitric oxide synthase (cNOS) activation followed by up-regulation of γ-glutamylcysteine synthetase activity and reduced oxidative stress. Enhanced interaction of cNOS with caveolin-1 caused down-regulation of enzyme activity and led to depletion of NO in the hepatocytes of ethanol-fed animals. 14-DAG acted as activator of adenylate cyclase and modulated cyclic AMP (cAMP) mediated expression of caveolin-1 and calmodulin. This eventually favored activation of cNOS through inhibition of cNOS-caveolin-1 interaction. Our results suggest that, protective effect of 14-DAG against ethanol-induced hepatic injury is based on its ability to reduce oxidative stress through cNOS dependent improvement of redox status. 14-DAG mediated activation of adenylate cyclase-cAMP signaling leading to up-regulation of cNOS may provide a promising approach in the prevention of liver diseases during chronic alcoholism.

Endogenous A1 adenosine receptor protects mice from acute ethanol-induced hepatotoxicity

Previous studies have indicated a critical role of adenosine and its receptors in the pathogenesis of liver diseases. The aim of this study was to determine the contribution of A1 adenosine receptor (A1AR) to acute ethanol-induced hepatotoxicity. Wild-type (WT) and A1AR−/− mice were intragastrically administered with ethanol (5g/kg), and hepatic injury was evaluated 6h thereafter. Mice lacking A1AR were more susceptible to ethanol-induced liver damage than WT mice, as evidenced by higher serum transaminase levels and increased extent of histopathological changes. Ethanol induced triglycerides accumulation in the serum and liver, and this accumulation was augmented in A1AR−/− mice. Analysis of gene expression in the liver revealed up-regulated mRNA levels of genes related to lipogenesis (including: FAS, SCD1, ACC1, DGAT2, and PPARγ) in A1AR−/− mice after ethanol treatment. In addition, lack of A1AR aggravated lipid peroxidation and superoxide dismutase depletion caused by acute ethanol exposure. A subsequent study revealed that, pretreatment with A1AR antagonist DPCPX increases the sensitivity of mice to ethanol-induced liver injury. In conclusion, these results indicated that endogenous A1AR activation protects mice against acute ethanol-induced liver injury by reducing oxidative stress and decreasing lipid accumulation.

Autophagy in the liver

Autophagy in the liver

Diosmin protects against ethanol-induced hepatic injury via alleviation of inflammation and regulation of TNF-α and NF-κB activation

The present investigation was designed to evaluate the efficacy of diosmin against ethanol-induced hepatotoxicity in rats by modulating various mechanisms including ethanol metabolizing enzymes, generation of free radicals, imbalance in oxidant–antioxidant status, oxidative damage to membrane lipids, activation of transcription factors and elevation in inflammatory markers involved in ethanol-induced hepatic damage. Diosmin is a flavone glycoside, having anti-inflammatory and anti-cancer properties. Thirty female Wistar rats segregated in five groups, each with six animals. Group I as control followed by Group II, III and IV were treated with ethanol for 28 days. While groups III and IV were administered with diosmin at 10 mg/kg b wt (D1) and 20 mg/kg b wt (D2) respectively prior to ethanol administration. Group V was given only higher dose of diosmin. In ethanol-treated group, ethanol metabolizing enzymes viz., CYP 450 2E1 and alcohol dehydrogenase (ADH) significantly increased by 77.82% and 32.32% in liver tissues respectively as compared with control group and this enhancement is significantly normalized with diosmin administration. Diosmin administration (D1 & D2) significantly (p < 0.001) attenuates oxidative stress markers i.e., LPO, GSH, GPx, GR and XO by 90.77 & 137.55%, 17.18 & 25%, 37.3 & 49.86%, 21.63 & 44.9% and 56.14 &77.19% respectively. Serum ALT, AST and LDH significantly increased by 102.03, 116.91 and 45.20% in ethanol-treated group as compared with control group. Group III and IV animals showed significant reduction in the serum toxicity markers. Diosmin further alleviated ethanol-induced NF-κB activation, enhanced expression of TNF-α, COX-2 and iNOS. Findings from the present study permit us to conclude that diosmin alleviates alcoholic liver injury via modulating ethanol metabolizing pathway, inhibition of oxidative stress markers and suppression of inflammatory markers. This may represent a novel protective strategy against ethanol-induced liver diseases.

Focus

Focus

Hepatoprotective effect of peptic hydrolysate from salmon pectoral fin protein byproducts on ethanol-induced oxidative stress in Sprague–Dawley rats

Bioactive peptides were generated by pepsin hydrolysis from salmon pectoral fin protein byproduct, and the hepatoprotective effect of the peptic hydrolysate (PH) on ethanol-induced oxidative stress was investigated in Sprague–Dawley rats. Administration of ethanol for 4weeks significantly (p<0.05) increased serum markers of liver damage, such as alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, and lactate dehydrogenase; however, these activities decreased significantly (p<0.05) after PH administration. Elevated thiobarbituric acid reactive substance levels in liver tissue and serum decreased significantly (p<0.05) following administration of PH. Ethanol exposure significantly (p<0.05) decreased glutathione contents in liver and serum, and hepatic antioxidant enzyme activities such as superoxide dismutase and glutathione peroxidase, while the PH treatment significantly (p<0.05) increased these altered parameters. These results indicate that the PH had a protective effect against ethanol-induced hepatotoxicity that was comparable to that of silymarin, which was supported by evaluating liver histopathology in the rats.

Effect of Vimliv on lipid profile and histopathology in ethanol-induced hepatotoxicity in albino Wistar rats

Background: Liver disease is considered to be a serious health problem, as the liver is an important organ for the detoxification and deposition of endogenous and exogenous substances. Objective: The present study is carried out to investigate the effect of Vimliv in ethanol-induced hepatotoxicity. Materials and Methods: Ethanol (3 g/kg) was dissolved in water and injected intragastrically, for a period of 35 days. Vimliv was dissolved in carboxy methyl cellulose and administered to rats at doses of 25 and 50 mg/kg for a period of 35 days as coadministration. Results: Administration of Vimliv resulted in significant reduction of blood glucose, serum urea, creatinine, lipid profile and increase in albumin. Administration of Vimliv also shows better pathological effects on liver and kidney. Conclusion: Therefore, this study suggests that Vimliv has the hepatoprotective effect and consequently may alleviate liver and renal damage associated with ethanol-induced hepatotoxicity in rats.

Additive effect of alpha-tocopherol and ascorbic acid in combating ethanol-induced hepatic fibrosis

ObjectiveTo investigate the efficacy of combined administration of alpha-tocopherol (AT) and ascorbic acid (AA) in reducing ethanol-induced hepatotoxicity.MethodsRats were maintained for 90 days and grouped as follows: I – control rats, II – ethanol, III – alpha-tocopherol, IV – ethanol + alpha-tocopherol, V – AA, VI – ethanol + ascorbic acid, VII – alpha-tocopherol + ascorbic acid, VIII – ethanol + alpha-tocopherol + ascorbic acid. At the end of the experimental period, markers of hepatic function, oxidative stress, and the expression of markers of inflammation and fibrosis were assayed.ResultsThe markers of hepatic function, lipid peroxidation products, protein carbonyls, and the expression of nuclear factor kappa B, tumor necrosis factor alpha, transforming growth factor beta 1, cytochrome P4502E1, and collagen Type I were elevated after ethanol administration. All these parameters were reduced in the ethanol group administered AT and AA in combination. The activities of antioxidant enzymes which were reduced by ethanol administration were enhanced on combined administration of AT and AA. The reduction in hepatic fibrosis was almost 20% more in AT and AA co-administered group compared with AT and AA alone treated groups.DiscussionCombined administration of fat soluble AT and water soluble AA was beneficial against ethanol-induced hepatotoxicity. This may be due to their different subcellular localizations.

Antioxidant and hepatoprotective effect of Garcinia indica fruit rind in ethanolinduced hepatic damage in rodents

The protective effects of aqueous extracts of the fruit rind of Garcinia indica (GIE) on ethanol-induced hepatotoxicity and the probable mechanisms involved in this protection were investigated in rats. Liver damage was induced in rats by administering ethanol (5 g/kg, 20% w/v p.o.) once daily for 21 days. GIE at 400 mg/kg and 800 mg/kg and the reference drug silymarin (200 mg/kg) were administered orally for 28 days to ethanol treated rats, this treatment beginning 7 days prior to the commencement of ethanol administration. Levels of marker enzymes (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP)), triglyceride (sTG), albumin (Alb) and total protein (TP) were evaluated in serum. Antioxidant parameters (reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione reductase (GR)), hepatic triglycerides (hTG) and the lipid peroxidation marker malondialdehyde (MDA) were determined in liver. GIE and silymarin elicited significant hepatoprotective activity by attenuating the ethanol–elevated levels of AST, ALT, ALP, sTG, hTG and MDA and restored the ethanol-depleted levels of GSH, SOD, CAT, GPx, GR, Alb and TP. GIE 800 mg/kg demonstrated greater hepatoprotection than GIE 400 mg/kg. The present findings indicate that hepatoprotective effects of GIE in ethanol-induced oxidative damage may be due to an augmentation of the endogenous antioxidants and inhibition of lipid peroxidation in liver.

Identification of N-Acetyltaurine as a Novel Metabolite of Ethanol through Metabolomics-guided Biochemical Analysis

The influence of ethanol on the small molecule metabolome and the role of CYP2E1 in ethanol-induced hepatotoxicity were investigated using liquid chromatography-mass spectrometry (LC-MS)-based metabolomics platform and Cyp2e1-null mouse model. Histological and biochemical examinations of ethanol-exposed mice indicated that the Cyp2e1-null mice were more resistant to ethanol-induced hepatic steatosis and transaminase leakage than the wild-type mice, suggesting CYP2E1 contributes to ethanol-induced toxicity. Metabolomic analysis of urinary metabolites revealed time- and dose-dependent changes in the chemical composition of urine. Along with ethyl glucuronide and ethyl sulfate, N-acetyltaurine (NAT) was identified as a urinary metabolite that is highly responsive to ethanol exposure and is correlated with the presence of CYP2E1. Subsequent stable isotope labeling analysis using deuterated ethanol determined that NAT is a novel metabolite of ethanol. Among three possible substrates of NAT biosynthesis (taurine, acetyl-CoA, and acetate), the level of taurine was significantly reduced, whereas the levels of acetyl-CoA and acetate were dramatically increased after ethanol exposure. In vitro incubation assays suggested that acetate is the main precursor of NAT, which was further confirmed by the stable isotope labeling analysis using deuterated acetate. The incubations of tissues and cellular fractions with taurine and acetate indicated that the kidney has the highest NAT synthase activity among the tested organs, whereas the cytosol is the main site of NAT biosynthesis inside the cell. Overall, the combination of biochemical and metabolomic analysis revealed NAT is a novel metabolite of ethanol and a potential biomarker of hyperacetatemia.

Dietary agents in the prevention of alcohol-induced hepatotoxicty: preclinical observations

Long term alcohol consumption is one of the important causes for liver failure and death. To complicate the existing problem there are no dependable hepatoprotective drugs and a large number of patients prefer using complementary and alternative medicines for treating and managing hepatic complications. Almost 25 centuries ago, Hippocrates, the father of medicine, proclaimed "Let food be thy medicine and medicine be thy food." Exploring the association between diet and health continues even today. Preclinical studies carried out in the recent past have shown that the commonly used dietary agents like Allium sativum (garlic), Camellia sinensis (tea), Curcuma longa (turmeric), Emblica officinalis (Indian gooseberry), Ferula asafoetida (asafoetida), Garcinia cambogia (Malabar tamarind), Glycine max (soyabean), Murraya koenigii (curry leaves), Piper betle (beetle leaf), Prunus armeniaca (apricot), Ocimum gratissimum (wild basil), Theobroma cacao (cocoa), Trigonella foenum-graecum (fenugreek) and Vitis vinifera (grapes) protect against ethanol-induced hepatotoxicity. Mechanistic studies have shown that the beneficial effects of these phytochemicals in preventing the ethanol-induced hepatotoxicity are mediated by the antioxidant, free radical scavenging, anti-inflammatory and anti-fibrotic effects. The present review for the first time collates the hepatoprotective effects of these agents and also emphasizes on aspects that need future research to establish their utility in humans.

FERMENTED SEA TANGLE (LAMINARIA JAPONICA) ATTENUATES ETHANOL-INDUCED OXIDATIVE STRESS IN SPRAGUE-DAWLEY RATS

ABSTRACT In this study, we fermented sea tangle (FST) using Lactobacillus brevis BJ20, and its protective effect against the ethanol-induced hepatotoxicity in Sprague-Dawley rats was evaluated. Administration of ethanol to rats for 3 weeks induced liver damage with significant increase in hepatic malondialdehyde level and decrease in glutathione and antioxidant enzyme activities including catalase, superoxide dismutase and glutathione peroxidase. However, pretreatment of rats with FST inhibited the ethanol-induced oxidative stress in liver by suppressing the lipid peroxidation, and maintained the levels of antioxidant enzymes as well as glutathione. Further, FST markedly decreased the lipid peroxidation in many vital organs such as kidney, heart, microsome, mitochondria, testis and spleen of rats. The biochemical changes were consistent with histopathological observations indicating marked hepatoprotective effect of FST. Hence, these results suggested that the FST exhibit potent hepatoprotection against the ethanol-induced oxidative stress in rats. PRACTICAL APPLICATIONS In this study, hepatoprotective effects of fermented sea tangle (FST) against the ethanol-induced hepatic damage in rats were evaluated. The FST significantly attenuated oxidative stress by induced ethanol by increasing antioxidant enzyme activities including catalase, superoxide dismutase and glutathione peroxidase, and in addition inhibited the lipid peroxidation in many vital organs. These results suggested that the FST can be used as potential ingredient for functional food and/or beverage.

Most cited articles: ethanol-induced hepatotoxicity, anticarcinogenic effects of polyphenolic compounds in tea, dose–response modeling, novel roles of epoxide hydrolases and arsenic-induced suicidal erythrocyte death

Every year, the editors of the Archives of Toxicology review the most cited articles from the previous 2 years (Table 1). This year, topping the most cited list (51 citations) is a comprehensive review by Arthur I. Cederbaum on the mechanisms of ethanol-induced liver injury, describing the contributions of oxidative stress and CYP2E1. The second most cited article also focuses on oxidative stress, but from a different perspective. Chung S. Yang describes how polyphenolic compounds in tea act as anticarcinogens. Besides their antioxidant properties, polyphenolic compounds prevent DNA damage and modulate carcinogen metabolism. Metabolic detoxification of carcinogens is also catalyzed by epoxide hydrolases. Martina Decker and colleagues contributed a comprehensive review, in which they describe that epoxide hydrolases play a role not only in detoxification but also in signaling processes by metabolizing lipids, thereby influencing blood pressure and inflammation. Edward J. Calabrese critically discusses why the hormesis model became marginalized in dose–response modeling. Finally, the most frequently cited original article was published by Hasan Mahmud and colleagues. They show that arsenic induces suicidal death of erythrocytes by increasing cytosolic Ca concentrations, which may explain why environmental arsenic exposure causes anemia. Table 1 provides highlights of the most cited articles of 2009 and 2010. References

Heme oxygenase-1 mediates the protective role of quercetin against ethanol-induced rat hepatocytes oxidative damage

Quercetin, one of the most widely distributed flavonoids in plants, possesses strong free radical scavenging ability and potent hepatoprotective effects. However, the protective effect and mechanism of quercetin on ethanol-induced oxidative damage in hepatocytes remain unclear. In this study, primary rat hepatocytes were incubated with ethanol and quercetin in the presence or absence of ZnPP 9, an antagonist of HO-1 induction. The ethanol-induced hepatotoxicity was found to be greatly diminished by pre-treatment of quercetin and this hepatoprotective effect could be partly blocked by ZnPP 9. This study also showed that quercetin significantly stimulated HO-1 expression at both mRNA and protein levels, then subsequently induced HO-1 activity. To further study the signaling pathways underlying quercetin-induced HO-1 up-regulation, HO-1 expression and activity in cytosolic microsomal fractions and Nrf2 expression in nuclear fractions were analyzed following quercetin or/and MAPK inhibitor(s) as well as PI3K inhibitor incubation for primary rat hepatocytes. These results indicated that ERK was required to induce HO-1 expression in rat hepatocytes. In summary, these data suggested that quercetin attenuates ethanol-induced oxidative stress through a pathway which involves ERK activation and HO-1 upregulation.