Therapeutic value of melatonin in an experimental model of liver injury and regeneration

Melatonin has marked antioxidant properties. The aim of the present study was to evaluate the therapeutic effect of melatonin on acute liver injury induced in rats by carbon tetrachloride (CCl4), allyl alcohol (AA) and their combination. A total of 108 male Wistar rats were divided into 12 experimental groups according to their treatment regimen (n = 5-10 rats in each group). Melatonin (100 mg/kg body weight, BW) was administered 6 hr (a) after a single dose of CCl4 (intragastrically 0. 66 mL/kg BW diluted 1:1 v/v with corn oil); (b) a single dose of AA (intraperitonealy, 0.62 mmol/kg BW 1:50 v/v in 0.9% saline solution); and (c) a combination of the above substances. Rats were sacrificed at 24 and 48 hr post-toxin administration and the therapeutic effect of melatonin was investigated by assessment of histopathological changes and lipid peroxidation alterations determined by measuring tissue malondialdehyde plus 4-hydroxy-nonenal (MDA + 4-HNE), plasma MDA and plasma levels of liver enzymes. The levels of a key antioxidant, glutathione (GSH), were measured in liver tissue homogenates. Hepatic necrosis was significantly reduced in the melatonin-treated rats 48 hr after administration of CCl4, AA and CCl4 + AA. The levels of hepatic enzymes in plasma were found to be significantly reduced at 24 and 48 hr in the CCl4 + AA treated rats after melatonin administration. Additionally, MDA and MDA + 4-HNE concentrations were significantly reduced at 24 and 48 hr time-points in all groups that received melatonin. GSH levels were decreased in liver after the toxic substances administration, whereas melatonin reversed this effect. In conclusion, a single dose of melatonin decreased hepatic injury induced by CCl4, AA and CCl4 + AA. The inhibition of the oxidative stress and therefore lipid peroxidation by melatonin in CCl4 and AA administered animals, may constitute the protective mechanism of melatonin against acute liver injury.     

A dual effect of N-acetylcysteine on acute ethanol-induced liver damage in mice.

Reactive oxygen species (ROS) have been associated with acute ethanol-induced liver damage. N-acetylcysteine (NAC) is a glutathione (GSH) precursor and direct antioxidant. In this study, we investigated the effects of NAC on acute ethanol-induced liver damage. Female ICR mice were administered by gavage with a single dose of ethanol (6g/kg). NAC was administered in two different modes. In mode A, mice were injected with different doses of NAC at 30min before ethanol. In mode B, mice were injected with different doses of NAC at 4h after ethanol. Acute ethanol-induced liver damage was estimated by measuring serum alanine aminotransferase (ALT) activity and histopathological changes. Result showed that a single dose of ethanol (6g/kg) caused a significant increase in serum ALT activity, followed by microvesicular steatosis and necrosis in mouse liver. Pretreatment with NAC significantly protected against acute ethanol-induced liver damage in a dose-independent manner. Correspondingly, pretreatment with NAC significantly attenuated acute ethanol-induced lipid peroxidation and GSH depletion and inhibited hepatic TNF-alpha mRNA expression. By contrast, post-treatment with NAC aggravated ethanol-induced hepatic lipid peroxidation and worsened acute ethanol-induced liver damage in a dose-dependent manner. Taken together, NAC has a dual effect on acute ethanol-induced liver damage. Pretreatment with NAC prevent from acute ethanol-induced liver damage via counteracting ethanol-induced oxidative stress. When administered after ethanol, NAC might behave as a pro-oxidant and aggravate acute ethanol-induced liver damage.     

不同剂量还原型谷胱甘肽对大鼠急性肝损伤的修复作用

目的探讨不同剂量的还原型谷胱甘肽对大鼠急性肝损伤的修复作用。方法用四氯化碳诱导大鼠急性肝损伤,给予不同剂量还原型谷胱甘肽腹腔注射,7天后处死大鼠,观察血清转氨酶AST、ALT及HE染色观察肝脏病理形态。结果肝损伤模型组与对照组相比血清转氨酶明显升高,肝细胞广泛脂肪变性。还原型谷胱甘肽组的转氨酶高于模型组,肝脏细胞肿胀、脂肪变性程度均明显低于模型组,但还原型谷胱甘肽小剂量组与加倍剂量组之间无显著差异。结论还原型谷胱甘肽对大鼠急性肝损伤有修复作用,但增加药物剂量并不能增强其对肝损伤的修复作用。     

Therapeutic effects of cytokine modulator Y-40138 in the rat alcoholic liver disease model

Background and Aim: Inflammatory cytokines, such as tumor necrosis factor‐α (TNF‐α) and interferon‐gamma (IFN‐γ), induce liver injury in the rat alcoholic liver disease (ALD) model. Y‐40138 is known to suppress the pro‐inflammatory cytokines and augment the anti‐inflammatory cytokines. We investigated whether or not Y‐40138 may be effective as a novel immunotherapy in the rat ALD model. Methods: Male Wistar rats were fed Lieber‐DeCarli ethanol liquid diet. The effects of Y‐40138 treatment in the ALD models were assessed by analyzing the serum and the liver tissues. Results: The serum levels of alanine aminotransferase (ALT), TNF‐α, and IFN‐γ, and the liver levels of TNF‐α and IFN‐γ were significantly higher in the ethanol‐fed group than in the pair‐fed group. The immunohistochemistry of the liver TNF‐α and 4‐hydroxynonenal (4HNE), and the expressions of TNF‐α and IFN‐γ mRNA were increased, too. The gene expressions of interleukin‐10 (IL‐10) in the ethanol‐fed group were suppressed as compared with the pair‐fed group. The serum triglyceride (TG) and liver TG were increased, and Oil Red O and α‐smooth muscle actin (α‐SMA) staining showed greater expression by ethanol‐fed feeding. After administration of Y‐40138, enzyme linked immunosorbent assay and real‐time polymerase chain reaction of the liver showed that the increased TNF‐α and IFN‐γ were suppressed, and that IL‐10 was augmented. Moreover, ethanol‐induced lipid accumulation in the liver was suppressed by administering Y‐40138. Conclusions: Y‐40138 decreased the inflammation, fibrosis, oxidative stress, and lipid synthesis, and augmented the anti‐inflammatory cytokines of the liver. These results indicate that the multiple cytokine production modulator, Y‐40138, is a promising novel therapy for ALD.     

Protection by bicyclol derivatives against acetaminophen‐induced acute liver failure in mice and its active mechanism

Background/Aims: To find a novel drug against acute liver failure, a methionine derivative of bicyclol (WLP‐S‐10) was studied in acetaminophen‐injected mice. Methods: At first, 10 derivatives of bicyclol were tested in male KunMing strain mice injected with CCl₄, acetaminophen or d ‐galactosamine plus lipopolysaccharide (LPS), serum alanine aminotransferase (ALT) and mortality rate were determined. Among the 10 derivatives, a methionine derivative of bicyclol (WLP‐S‐10) was shown to be the most effective. A single dose of WLP‐S‐10 200 mg/kg was intraperitoneally injected 1 h before administration of a lethal dose of acetaminophen; the mortality rate, liver lesions, serum ALT, aspartate aminotransferase (AST) and liver glutathione (GSH) were determined. Mitochondrial GSH and adenosine triphosphate (ATP) levels, cytochrome C and apoptosis‐inducing factor (AIF) leakage, mitochondrial swelling and membrane potential were determined. Results: As a result, WLP‐S‐10 200 mg/kg significantly reduced liver injury induced by CCl₄ and decreased the mortality rate of mice because of acute liver failure caused by lethal dosage of acetaminophen or d ‐galactosamine plus LPS. WLP‐S‐10 200 mg/kg markedly reduced liver necrosis, serum ALT and AST elevation and GSH depletion after injection of acetaminophen. WLP‐S‐10 inhibited mitochondrial swelling, breakdown of membrane potential and depletion of mitochondrial ATP, and also reduced release of cytochrome C and AIF from mitochondria induced by acetaminophen. Conclusions: The results indicate that WLP‐S‐10 is a novel potential compound against acetaminophen‐induced acute liver failure in mice, and its active mechanism is mainly related to protection against necrosis and apoptosis of hepatocytes through inhibition of mitochondrial energy (ATP) depletion and AIF and cytochrome C release.     

Mechanisms of protection by melatonin against acetaminophen-induced liver injury in mice

The present study was performed to determine whether melatonin protects mouse liver against severe damage induced by acetaminophen (APAP) administration and where melatonin primarily functions in the metabolic pathway of APAP to protect mouse liver against APAP-induced injury. Treatment of mice with melatonin (50 or 100 mg/kg, p.o.) 8 or 4 hr before APAP administration (750 mg/kg, p.o.) suppressed the increase in plasma alanine aminotransferase and aspartate aminotransferase activities in a dose- and a time-dependent manner. Melatonin treatment (100 mg/kg, p.o.) 4 hr before APAP administration remarkably inhibited centrilobular hepatic necrosis with inflammatory cell infiltration and increases in hepatic lipid peroxidation and myeloperoxidase activity, an index of tissue neutrophil infiltration, as well as release of nitric oxide and interleukin-6 into blood circulation at 9 hr after APAP administration. However, melatonin neither affected hepatic reduced glutathione (GSH) content nor spared hepatic GSH consumption by APAP treatment. Moreover, pretreatment with melatonin 4 hr before APAP administration did not influence the induction of hepatic heat shock protein 70 (HSP70) by APAP and melatonin alone did not induce HSP70 in mouse liver. These results indicate that exogenously administered melatonin exhibits a potent hepatoprotective effect against APAP-induced hepatic damage probably downstream of the activity of cytochrome P450 2E1, which works upstream of GSH conjugation in the pathway of APAP metabolism, via its anti-nitrosative and anti-inflammatory activities in addition to its antioxidant activity.     

Neutrophil depletion protects against murine acetaminophen hepatotoxicity

We previously reported that liver natural killer (NK) and NKT cells play a critical role in mouse model of acetaminophen (APAP)-induced liver injury by producing interferon gamma (IFN-gamma) and modulating chemokine production and subsequent recruitment of neutrophils into the liver. In this report, we examined the role of neutrophils in the progression of APAP hepatotoxicity. C57BL/6 mice were given an intraperitoneal toxic dose of APAP (500 mg/kg), which caused severe acute liver injury characterized by significant elevation of serum ALT, centrilobular hepatic necrosis, and increased hepatic inflammatory cell accumulation. Flow cytometric analysis of isolated hepatic leukocytes demonstrated that the major fraction of increased hepatic leukocytes at 6 and 24 hours after APAP was neutrophils (Mac-1+ Gr-1+). Depletion of neutrophils by in vivo treatment with anti-Gr-1 antibody (RB6-8C5) significantly protected mice against APAP-induced liver injury, as evidenced by markedly reduced serum ALT levels, centrilobular hepatic necrosis, and improved mouse survival. The protection was associated with decreased FasL-expressing cells, cytotoxicity against hepatocytes, and respiratory burst in hepatic leukocytes. In intracellular adhesion molecule (ICAM)-1-deficient mice, APAP caused markedly reduced liver injury when compared with wild-type mice. The marked protection in ICAM-1-deficient mice was associated with decreased accumulation of neutrophils in the liver. Hepatic GSH depletion and APAP-adducts showed no differences among the antibody-treated, ICAM-1-deficient, and normal mice. In conclusion, accumulated neutrophils in the liver contribute to the progression and severity of APAP-induced liver injury.     

The type of dietary fat modulates intestinal tight junction integrity, gut permeability, and hepatic toll-like receptor expression in a mouse model of alcoholic liver disease

Background: Interactions between the gut, immune system, and the liver, as well as the type of fat in the diet, are critical components of alcoholic liver disease (ALD). The goal of the present study was to determine the effects of saturated fat (SF) and unsaturated fat (USF) on ethanol (EtOH)‐induced gut‐liver interactions in a mouse model of ALD. Methods: C57BL/6N mice were fed Lieber–DeCarli liquid diets containing EtOH and enriched in USF (corn oil) or SF (medium chain triglycerides:beef tallow). Control mice were pair‐fed on an isocaloric basis. Liver injury and steatosis, blood endotoxin levels, intestinal permeability, and tight junction (TJ) integrity, as well as hepatic Toll‐like receptor (TLR) gene expression, were evaluated. Results: After 8 weeks of EtOH feeding, liver injury and steatosis were observed in USF + EtOH group compared with control and SF + EtOH. Significantly increased intestinal permeability in conjunction with elevated blood endotoxin levels were observed in the ileal segments of the mice fed USF + EtOH. USF diet alone resulted in down‐regulation of intestinal TJ protein mRNA expression compared with SF. Importantly, alcohol further suppressed TJ proteins in USF + EtOH, but did not affect intestinal TJ in SF + EtOH group. The type of fat in the diet alone did not affect hepatic TLR expression. Compared with control animals, hepatic TLR (TLR 1, 2, 3, 4, 7, 8, 9) mRNA expression was significantly (p < 0.05) increased in USF + EtOH, but not in SF + EtOH group. Notably, TLR5 was the only up‐regulated TLR in both SF + EtOH and USF + EtOH groups. Conclusions: Dietary fat is an important cofactor in alcohol‐associated liver injury. We demonstrate that USF (corn oil/linoleic acid) by itself results in dysregulation of intestinal TJ integrity leading to increased gut permeability, and alcohol further exacerbates these alterations. We postulate that elevated blood endotoxin levels in response to USF and alcohol in conjunction with up‐regulation of hepatic TLRs combine to cause hepatic injury in ALD.     

Inhibitory effect of melatonin on lung oxidative stress induced by respiratory syncytial virus infection in mice

Abstract: Previous research has shown that antioxidant (butylated hydroxyanisole) treatment ameliorates respiratory syncytial virus (RSV)‐induced disease and lung inflammation. Melatonin has been reported to exhibit a wide varieties of biological effects, including antioxidant and anti‐inflammation, and has no evident toxicity and side effect. But it is not known whether melatonin would modify RSV‐induced lung disease and oxidative stress. The present study was to establish the involvement of oxidative stress in the pathogenesis of RSV‐induced lung inflammation, and to investigate the protective effect of administration of melatonin in mice with RSV‐induced oxidative pulmonary injury for 4 days. Malondialdehyde (MDA), an end product of lipid peroxidation, and glutathione (GSH) and superoxide dismutase (SOD) and nitric oxide (NO) levels were evaluated in lung tissue homogenates by spectrophotometry. Hydroxyl radical (˙OH), one of the indicators of free radical formation, was also detected in lung homogenates by Fenton reaction. Tumor necrosis factor‐a (TNF‐a) concentrations in mouse serum were measured with ELISA assay. The results demonstrated that the mice intranasally inoculated with RSV resulted in oxidative stress changes by increasing NO, MDA and ˙OH levels, and decreasing GSH and SOD activities, whereas administration of melatonin significantly reversed all these effects. Furthermore, melatonin inhibited production of proinflammatory cytokines such as TNF‐a in serum of RSV‐infected mice. These results suggest that melatonin ameliorates RSV‐induced lung inflammatory injury in mice via inhibition of oxidative stress and proinflammatory cytokine production and may be as a novel therapeutic agent in virus‐induced pulmonary infection.     

Hepatic fibrosis in biliary-obstructed rats is prevented by Ginkgo biloba treatment

AIM: To assess the antioxidant and antifibrotic effects of long-term Ginkgo biloba administration on liver fibrosis induced by biliary obstruction in rats. METHODS: Liver fibrosis was induced in male Wistar albino rats by bile duct ligation and scission (BDL). Ginkgo biloba extract (EGb 761, 50 mg/kg·per d) or saline was administered for 28 d. At the end of the treatment period, all rats were killed. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) levels were determined to assess liver functions and tissue damage, respectively. Tumor necrosis factorα (TNF-α) was also assayed in serum samples. Liver tissues were taken for determination of the hepatic malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Production of reactive oxidants was monitored by chemiluminescence (CL) assay. Serum AST, ALT, LDH, and TNF-α levels were elevated in the BDL group as compared to control group and were significantly decreased by EGb treatment. RESULTS: Hepatic GSH level, depressed by BDL, was elevated back to control level in EGb-treated BDL group. Increase in tissue MDA level, MPO activity and collagen content due to BDL were also attenuated by EGb treatment. Furthermore, luminol and lucigenin CL values in BDL group increased dramatically compared to control and reduced by EGb treatment. CONCLUSION: Our results suggest that Ginkgo biloba protects the liver from oxidative damage following BDL in rats. This effect possibly involves the inhibition of neutrophil infiltration and lipid peroxidation; thus, restoration of oxidant and antioxidant status in the tissue.     

叔丁基痉基茴香醚对小鼠醋氨酚中毒性肝损伤的操作作用

目的：采用小鼠醋氨酚中毒性肝损伤模型探讨２（３）－叔丁基－４－羟基茴香醚（ＢＨＡ）对肝脏的保护作用。方法：通过腹腔注射醋氨酚制备小鼠肝损伤模型,测定小鼠血清丙氨酸转氨酶（ＡＬＴ）活笥和肝匀浆液中的丙二醛（ＭＤＡ）含量、超氧化的岐化酶（ＳＯＤ）活性及谷胱甘肽（ＧＳＨ）含量。结果：０．２％及０．５％的ＢＨＡ都能显著对抗醋氨酚所致小鼠肝损伤的血清ＡＬＴ活性升高,肝组织ＭＤＡ含量升高、ＳＯＤ活性降低及还原     

Piperine,an active ingredient of black pepper attenuates acetaminophen–induced hepatotoxicity in mice

ObjectiveTo explore the hepatoprotective and antioxidant effects of piperine against acetaminophen-induced hepatotoxicity in mice.MethodsIn mice, hepatotoxicity was induced by a single dose of acetaminophen (900 mg/kg b.w. i.p.). Piperine (25 mg/kg b.w. i.p.) and standard drug silymarin (25 mg/kg b.w. i.p.) were given to mice, 30 min after the single injection of acetaminophen. After 4 h, the mice were decapitated. Activities of liver marker enzymes [(aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP)] and inflammatory mediator tumour necrosis factor-alpha (TNF-α) were estimated in serum, while lipid peroxidation and antioxidant status (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glutathione-s-transferase and glutathione) were determined in liver homogenate of control and experimental mice.ResultsAcetaminophen induction (900 mg/kg b.w. i.p.) significantly increased the levels of liver marker enzymes, TNF-α, and lipid peroxidation, and caused the depletion of antioxidant status. Piperine and silymarin treatment to acetaminophen challenged mice resulted in decreased liver marker enzymes activity, TNF-α and lipid peroxidation levels with increase in antioxidant status.ConclusionsThe results clearly demonstrate that piperine shows promising hepatoprotective effect as comparable to standard drug silymarin.     

2-Mercaptoethane sulfonate (MESNA) protects against biliary obstruction-induced oxidative damage in rats.

The aim of this study was to assess the antioxidant and antifibrotic effects of chronic administration of 2-mercaptoethane sulfonate (MESNA) on oxidative liver damage and fibrosis induced by biliary obstruction in rats. Liver fibrosis was induced in male Wistar albino rats by bile duct ligation and scission (BDL). MESNA (150mg/kg, i.p.) or saline was administered for 28 days. At the end of the experiment, rats were killed by decapitation. Serum aspartate aminotransferase (AST), and alanine aminotransferase (ALT) levels were determined to assess liver function. Tumor necrosis factor-alpha (TNF-alpha) and lactate dehidrogenase (LDH) were also assayed in serum samples. Liver tissues were taken for determination of the free radicals, hepatic malondialdehyde (MDA) levels, an end product of lipid peroxidation; glutathione (GSH) levels, a key antioxidant; myeloperoxidase (MPO) activity, as an indirect index of neutrophil infiltration. Hepatic collagen content, as a fibrosis marker was also determined. Serum AST, ALT, LDH and TNF-alpha levels were elevated in the BDL group as compared to control group, while this increase was significantly decreased by MESNA treatment. BDL caused a significant (p<0.05-0.001) decrease in GSH levels while MDA levels and MPO activity were increased in the liver tissue. These changes were reversed by MESNA treatment. Collagen contents of the liver tissue was increased by BDL (p<0.001), and reversed back to the control levels with MESNA. Since MESNA administration alleviated the BDL-induced oxidative injury of the liver and improved the hepatic functions, it seems likely that MESNA with its antioxidant and antifibrotic properties, may be of potential therapeutic value in protecting the liver fibrosis and oxidative injury due to biliary obstruction.     

Aminoguanidine potentiates the hepatoprotective effect of silymarin in CCL4 treated rats

This study examined the possible hepatoprotective effect of aminoguanidine in comparison with silymarin and investigated the possible beneficial effects of the combination of aminoguanidine and silymarin on CCL4-induced liver fibrosis. Male Wister albino rats were randomly divided into five groups (10 rats/group). Group I included control rats injected only with liquid paraffin and saline; group II represents CCL(4) control (injected with CCL(4) 3 times a week for 6 weeks in a dose of 25μl/100gm.b.w i.p, diluted 1:6 with liquid paraffin); group III treated with aminoguanidine (100 mg/kg); group IV was given silymarin (100 mg/kg); group V was given aminoguanidine (100 mg/kg) and silymarin (100 mg/kg). Fibrosis was depicted histologically and biochemically. CCL4 increased serum liver enzymes (ALT, AST, and ALP), lactate dehydrogenase (LDH), level of nitric oxide (NO), tumor necrosis factor alpha (TNFα) and liver malondialdehyde content (MDA), collagen fiber percent and decreased liver reduced glutathione (GSH) content as endogenous antioxidant. Histopathological changes induced by CCL4 include regenerative nodules, deteriorated parenchyma; the lobules were infiltrated with fat and structurally altered. Aminoguanidine, silymarin and their combination reduced these changes and attenuated the pathological effects of CCL(4) induced liver injury. The combination of both drugs was better than each drug alone. It is concluded that aminoguanidine has protective effect against CCL(4) induced hepatoxicity via its iNOS inhibition and antioxidant effects. In addition, the combination of AG with silymarin has more potent hepatoprotective effect than each drug alone.     

Beraprost sodium, a prostacyclin (PGI) analogue, ameliorates concanavalin A-induced liver injury in mice.

BACKGROUND/AIMS: Prostacyclin (PGI(2)) is a potent mediator in the inflammatory and coagulation processes. The aim of this study was to test whether beraprost sodium, a PGI(2) analogue, could prevent experimental hepatic injury induced by concanavalin A (Con A), which is a model of fulminant hepatic failure. METHODS: Beraprost (100 microg/kg) was administered intraperitoneally simultaneously with Con A (40 mg/kg) in C57B6J mice. Blood circulation in the liver was determined by laser-Doppler flowmetry. Plasma levels of alanine aminotransferase (ALT), tumor necrosis factor (TNF)-alpha, interferon (IFN)-gamma, and interleukin (IL)-6 were determined. Levels of TNF-alpha and IFN-gamma in culture supernatant of splenocytes were also determined. RESULTS: Beraprost administration reduced the incidence of death following hepatic failure (76.5% vs. 29.4%, P<0.05). Plasma levels of ALT were significantly lower in the beraprost-treated group than in the control group, and in the former, there was concomitant suppression of the histological features of injury. Beraprost significantly increased hepatic blood flow volume in Con A-treated mice. Plasma levels of TNF-alpha and IFN-gamma were significantly reduced at 6 and 12 h after Con A injection, respectively, but the levels of IL-6 were increased at 6 h. In vitro, beraprost also suppressed Con A-induced TNF-alpha production in splenocytes, while it stimulated IFN-gamma production. CONCLUSION: These findings imply that beraprost suppresses Con A-induced liver injury. These data also suggest that beraprost, which is clinically effective in treating pulmonary hypertension, may have therapeutic potential for preventing hepatic injury.     

国产还原型谷胱甘肽治疗酒精性肝病疗效观察

目的 通过多中心随机对照研究,评价国产四类新药还原型谷胱甘肽（ＧＳＨ）针剂对酒精性肝病的疗效和安全性。方法 以意大利Ｆｏｓｃａｍａ生化公司生产还原型谷胱甘肽（ＴＡＤ）为对照药,治疗１１０例酒精性肝病进行疗效观察。选择病例均有明确饮酒史五年以上,每日饮酒量超过８０～１２０ｇ,按随机表分组,ＧＳＨ治疗组,ＴＡＤ对照组各５５例,用药剂量、途径、疗程两组相同。主要观察指标,肝 油三脂、胆固醇及胃肠道症状。