Mutsumi Kongo

Therapeutic effect of melatonin on carbon tetrachloride-induced acute liver injury in rats

The therapeutic effect of melatonin on acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). Melatonin (10, 50, or 100 mg/kg body weight [BW]) was intraperitoneally administered to male Wistar rats 6 hr after intraperitoneal injection of CCl4 (1.6 g/kg BW) at which time an apparent liver injury occurred. This post‐melatonin administration dose dependently prevented the progression of liver injury at 24 hr after CCl4 injection, judging from the levels of serum transaminases, indices of liver cell damage. Rats injected with CCl4 alone showed an increase in liver lipid peroxide (LPO) content and a decrease in liver reduced glutathione content at 6 and 24 hr after the injection. The post‐melatonin administration dose dependently ameliorated both changes found at 24 hr after CCl4 injection. Rats injected with CCl4 alone showed an increase in liver triglyceride (TG) content and decreases in serum TG concentration and liver tryptophan 2,3‐dioxygenase (TDO) activity, a marker of the inhibition of liver protein synthesis by CCl4, at 6 and 24 hr after the injection, and also a decrease in serum albumin concentration at 24 hr. The changes in serum TG, albumin concentration, liver TG content, and TDO activity found at 24 hr after CCl4 injection were not ameliorated by the post‐administration of melatonin. The same administration of melatonin dose dependently reduced liver LPO content in CCl4‐untreated rats. These results indicate that melatonin exerts a therapeutic effect on CCl4‐induced acute liver injury in rats, possibly through its antioxidant action.

Melatonin exerts a therapeutic effect on cholestatic liver injury in rats with bile duct ligation.

Abstract: We examined whether melatonin exerts a therapeutic effect on cholestatic liver injury in rats treated with bile duct ligation (BDL). Cholestatic liver injury was induced in male Wistar rats aged 4 wk by ligating the bile duct. Cholestatic liver injury developed 5 days after BDL and continued to 13 days, judging from the levels of serum hepatobiliary injury markers. The serum concentration of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, and the hepatic level of TBARS and the activity of hepatic myeloperoxidase, an index of tissue neutrophil infiltration, increased 5 days after BDL, and these increases were enhanced at 13 days. A similar increase in the serum total cholesterol concentration occurred 5 and 13 days after BDL, while the hepatic cholesterol concentration tended to increase at 13 days. When melatonin [10 or 100 mg/kg body weight (BW)] was orally administered to BDL‐treated rats everyday for 8 days, starting 5 days after BDL, the indoleamine attenuated cholestatic liver injury observed at 13 days after BDL was more effective at the higher dose than at the lower dose. The administered melatonin (10 or 100 mg/kg BW) reduced the increases in serum and hepatic TBARS concentrations and hepatic myeloperoxidase activity observed at 13 days after BDL and the higher dose of indoleamine was more effective than the lower dose. Neither dose of melatonin affected the increased serum total cholesterol concentration or the hepatic cholesterol concentration observed at 13 days after BDL. These results indicate that orally administered melatonin at pharmacological doses exerts a therapeutic effect on cholestatic liver injury in rats with BDL possibly through its antioxidant and anti‐inflammatory actions.

Preventive effect of melatonin on the progression of α-naphthylisothiocyanate-induced acute liver injury in rats

Abstract: The preventive effect of melatonin on the progression of α‐naphthylisothiocyanate (ANIT)‐induced acute liver injury with cholestasis was examined in rats treated once with the hepatotoxin [75 mg/kg body weight (BW), i.p.]. In rats treated with ANIT alone, liver injury with cholestasis occurred 24 hr after treatment and progressed at 48 hr, judging from the serum levels of hepatobiliary marker enzymes and components. Melatonin (10 or 100 mg/kg BW) was orally administered to the ANIT‐treated rats, 24 hr after the hepatotoxin treatment at which time hepatic injury had already developed. The administered indoleamine prevented the progression of liver cell damage rather than biliary cell damage more effectively at the higher dose than at the lower dose. In rats treated with ANIT alone, the serum and hepatic concentrations of thiobarbituric acid reactive substances, an index of lipid peroxidation, and the hepatic activity of myeloperoxidase, an index of tissue neutrophil infiltration, increased 24 hr after treatment and further increased at 48 hr. In the liver of rats treated with ANIT alone, Cu,Zn‐superoxide dismutase activity decreased 24 hr after treatment and was further reduced at 48 hr, although there was no change in Mn‐superoxide dismutase activity. Catalase and Se‐glutathione peroxidase activities also decreased at 48 hr, while reduced glutathione concentrations remained increased at 24 and 48 hr. The melatonin administered to the ANIT‐treated rats attenuated the increases in serum and hepatic concentrations of thiobarbituric acid reactive substances and the decreases in hepatic activities of Cu,Zn‐superoxide dismutase, catalase, and Se‐glutathione peroxidase found at 48 hr after the hepatotoxin treatment more effectively at the higher dose than at the lower dose; on the other hand, melatonin treatment had no effect on the increases in hepatic myeloperoxidase activity and reduced glutathione concentration found at 48 h. These results indicate that orally administered melatonin at pharmacological doses prevents the progression of ANIT‐induced acute liver injury, mainly liver cell damage, in rats, and suggest that the administered melatonin exerts these preventive effects through its direct and indirect antioxidant actions.

Protective effect of melatonin against α-naphthylisothiocyanate-induced liver injury in rats

The protective effect of melatonin against α‐naphthylisothiocyanate (ANIT)‐induced liver injury with cholestasis was examined in rats injected once with the toxicant (75 mg/kg body weight (BW)). In rats injected with ANIT alone, liver injury with cholestasis did not occur 12 hr after the injection but appeared at 24 hr, judging from the serum levels of marker enzymes and components. When melatonin (10 or 100 mg/kg BW) was orally administered to the ANIT‐injected rats at 12 hr after the injection, the administered indoleamine dose‐dependently prevented the formation of liver injury with cholestasis. In rats injected with ANIT alone, serum lipid peroxide (LPO) concentration increased 24 hr after the injection, while liver LPO concentration increased 12 hr after the injection and further increased at 24 hr. Myeloperoxidase (MPO) activity, an index of tissue neutrophil infiltration, in the liver of the ANIT‐injected rats increased 12 hr after the injection and further increased at 24 hr. The oral administration of melatonin (10 or 100 mg/kg BW) to the ANIT‐injected rats attenuated the increases in serum and liver LPO concentrations and liver MPO activity found at 24 hr after the injection in a dose‐dependent manner. These results indicate that orally administered melatonin at pharmacological doses protects against ANIT‐induced liver injury with cholestasis in rats, and suggest that this protective effect of melatonin could be due to its antioxidant action and its inhibitory action against neutrophil infiltration in the liver of ANIT‐injected rats.

An association between lipid peroxidation and α-naphthylisothiocyanate-induced liver injury in rats

An association between lipid peroxidation and alpha-naphthylisothiocyanate (ANIT)-induced liver injury was examined in rats injected once with the toxicant (75 mg/kg body weight). The severity of liver injury was estimated 12, 24, 48, and 72 h after ANIT injection. Liver injury appeared 24 h after ANIT injection, progressed at 48 h, and recovered at 72 h, judging from the serum levels of marker enzymes and components. Serum lipid peroxide (LPO) concentration increased 24 h after ANIT injection and further increased at 48 h, but this increase was attenuated at 72 h. In contrast, liver LPO content increased 12 h after ANIT injection and further increased 24 and 48 h, but this increase was attenuated at 72 h. Similarly, myeloperoxidase (MPO) activity, an index of neutrophil infiltration, in the liver tissue increased 12 h after ANIT injection and further increased at 24 and 48 h, but this increase was attenuated at 72 h. Either serum LPO concentration or liver LPO content was significantly correlated with liver MPO activity (r = 0.661 for serum LPO concentration; r = 0.585 for liver LPO content). These results suggest that lipid peroxidation might be associated with ANIT-induced liver injury in rats and that this lipid peroxidation might occur via oxygen radicals derived from neutrophils infiltrated into the liver tissue of ANIT-intoxicated rats.

Effect of melatonin on changes in hepatic antioxidant enzyme activities in rats treated with alpha-naphthylisothiocyanate

We have reported that melatonin protects against α‐naphthylisothiocyanate (ANIT)‐induced acute liver injury in rats by preventing enhanced lipid peroxidation. Herein, we examine the effect of melatonin on hepatic antioxidant enzyme activities in rats with a single i.p. injection of ANIT (75 mg/kg body weight) in order to clarify the protective mechanism of the indoleamine against ANIT‐induced acute liver injury. Rats received a single oral administration of melatonin (10 or 100 mg/kg body weight) at 12 hr after ANIT treatment. Hepatic Cu,Zn‐superoxide dismutase (Cu,Zn‐SOD), Mn‐superoxide dismutase (Mn‐SOD), catalase (CAT), Se‐glutathione peroxidase (Se‐GSH‐Px), glutathione reductase (GSSG‐R), and glucose‐6‐phosphate dehydrogenase (G‐6‐PDH) activities and reduced glutathione (GSH) concentration were determined 12 and 24 hr after ANIT treatment. ANIT‐treated rats showed decreases in hepatic Cu,Zn‐SOD and GSSG‐R activities at 24 hr after treatment, transient increases in hepatic CAT and Se‐GSH‐Px activities at 12 hr, and no changes in hepatic Mn‐SOD and G‐6‐PDH activities at 12 or 24 hr. Only the high dose of melatonin attenuated the decrease in hepatic Cu,Zn‐SOD activity, while both doses of the indoleamine almost completely attenuated the decrease in hepatic GSSG‐R activity. Neither dose of melatonin affected hepatic CAT, Se‐GSH‐Px, and G‐6‐PDH activities. ANIT‐treated rats showed an increase in hepatic GSH concentration at 24 hr after treatment. Neither dose of melatonin affected the increase in hepatic GSH concentration. These results indicate that orally administered melatonin prevents decreases in Cu,Zn‐SOD and GSSG‐R activities in the liver of ANIT‐treated rats, and suggest that the indoleamine may protect against ANIT‐induced acute liver injury by attenuating the disruption of hepatic antioxidant defense systems.

Change in hepatic antioxidant defense system with liver injury development in rats with a single α-naphthylisothiocyanate intoxication

The change in hepatic antioxidant defense system with the development of alpha-naphthylisothiocyanate (ANIT)-induced liver injury was examined in rats injected once with the toxicant (75 mg/kg body weight). Liver injury with cholestasis did not occur 12 h after ANIT injection, but appeared at 24 h, progressed at 48 h, and recovered at 72 h, judging from the serum levels of marker enzymes and components. Liver lipid peroxide content increased 12 h after ANIT injection and further increased 24 and 48 h, but this increase was attenuated at 72 h. Liver superoxide dismutase and catalase activities decreased 24 and 48 h, respectively, after ANIT injection, although the catalase activity increased at 12 h, but these decreases were attenuated at 72 h. Liver Se-glutathione peroxidase activity remained unchanged 24, 48, and 72 h after ANIT injection, although the activity increased at 12 h. Liver reduced glutathione content increased 24 h after ANIT injection, but the increase was reduced time dependently thereafter. Liver ascorbic acid content increased 12 h after ANIT injection and further increased at 24 h, but the increase was reduced time dependently thereafter. These results indicate that the change in hepatic antioxidant defense system occurs before and with the development of ANIT-induced liver injury in rats, and suggest that the reduction of hepatic antioxidant defense system mediated by SOD and catalase could contribute to the liver injury development through an enhancement of hepatic lipid peroxidation.

Inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract on hepatic triglyceride accumulation with the progression of carbon tetrachloride-induced acute liver injury in rats

The inhibitory effect of Oren-gedoku-to (Huanglian-Jie-Du-Tang) extract (TJ-15) on hepatic triglyceride (TG) accumulation with the progression of acute liver injury was examined in rats intoxicated with carbon tetrachloride (CCl4). TJ-15 at a dose of 100, 250 or 500 mg/kg body weight (BW) was orally administered to male Wistar rats aged 7 weeks, 6 h after the intraperitoneal injection of CCl4 (1.0 ml/kg BW) at which time apparent liver injury and hepatic TG accumulation occurred. TJ-15 significantly prevented not only the progression of liver injury but also inhibited hepatic TG accumulation with the progression of the injury in a dose-dependent manner when these effects were examined 24 h after CCl4 injection. In CCl4-untreated rats with oral administration of TJ-15 at a dose of 100, 250 or 500 mg/kg BW, liver and serum TG concentrations decreased depending on the dose of the herbal medicine. These results indicate that in rats intoxicated once with CCl4, orally administered TJ-15 can inhibit hepatic TG accumulation with the progression of acute liver injury by its decreasing action on serum and liver TG levels, leading to a prevention of the progression of the liver injury.

Contribution of the antilipid peroxidative action of Dai-saiko-to extract to its preventive effect on carbon tetrachloride-induced acute liver injury in rats

Post‐oral administration of Dai‐saiko‐to extract (TJ‐8), a traditional herbal medicine, ameliorated acute liver injury in rats intoxicated with carbon tetrachloride (CCl4). This TJ‐8 administration inhibited an increase in lipid peroxide contents in the liver homogenate and microsomal fraction and a decrease in glucose‐6‐phosphatase activity in the liver microsomal fraction, an index of lipid peroxidation‐mediated damage in liver microsomes, during the progression and recovery of the liver injury. These results indicate that the antilipid peroxidative action of TJ‐8 contributes to its preventive effect on CCl4‐induced acute liver injury in rats.

Therapeutic Effect of Melatonin on Cholestatic Liver Injury in Rats with Bile Duct Ligation

We examined the therapeutic effect of melatonin (MT) on cholestatic liver injury in rats with bile duct ligation (BDL). Cholestatic liver injury occurred 5 days after BDL and proceeded at 13 days, judging from the levels of serum hepatobiliary injury markers. Increases in the hepatic levels of thiobarbituric acid reactive substances (TBARS), an index of lipid peroxidation, and reduced glutathione (GSH) and the hepatic activity of myeloperoxidase (MPO), an index of tissue neutrophil infiltration, were observed 5 and 13 days after BDL. When MT at a dose of 10 or 100 mg/kg body weight was orally administered to rats with BDL everyday for one week, starting 6 days after BDL, a high dose of the indoleamine significantly attenuated cholestatic liver injury at 13 days after BDL. The daily administration of a high dose of MT significantly attenuated the increases in hepatic TBARS and GSH levels and MPO activity observed 13 days after BDL. These results indicate that MT administered orally at pharmacological doses exerts a therapeutic effect on cholestatic liver injury in rats with BDL possibly through its antioxidant and anti-inflammatory actions.