Carbon tetrachloride (1 ml/kg body weight as a 1:1 mixture of CCl(4) and mineral oil) was orally administered to rats. After 12 h, the activity of plasma ALT (alanine aminotransferase) was significantly higher than that of the control group, and plasma ALT and AST (aspartate aminotransferase) activities significantly increased 24 h after CCl(4) administration. These results indicated that the necrotic process had initiated at about 12 h and developed thereafter. After 6-24 h of CCl(4) administration, the hepatic level of vitamin C, the most sensitive indicator of oxidative stress, decreased significantly, indicating that oxidative stress was significantly enhanced 6 h after CCl(4) intoxication and thereafter. Oral administration of vitamin E (1 ml/kg body weight as a 1:1 mixture of alpha-tocopherol and mineral oil) 12 h before CCl(4) administration caused a significant elevation of liver vitamin E level and ameliorated liver necrosis 24 h after CCl(4) intoxication based on plasma AST and ALT. Vitamin E also significantly restored the hepatic vitamin C concentration 12 and 24 h after CCl(4) intoxication, demonstrating that vitamin E functioned as an antioxidant. The liver vitamin E concentration was not changed by vitamin E supplementation to rats that did not receive CCl(4). This result indicated that vitamin E accumulated in the damaged liver. The activation of JNK, ERK1/2 and p38 MAPK took place 1.5 h after CCl(4) administration. Co-administration of alpha-tocopherol with CCl(4) did not affect these early changes in MAPKs.

Summary D -Galactosamine ( D -Galn: 300 mg/kg) was intraperitoneally administered to rats. After 6 h the activity of plasma GOT and GPT was significantly higher than that of the control group and plasma GOT and GPT activities increased thereafter. These results indicated that the necrotic process was initiated at about 6 h and developed thereafter. With coadministration of DMSO (1 h before administration of D -Galn: 2.5 mL/kg, oral), plasma GOT and GPT were significantly lower, showing that DMSO inhibited the necrotic action of DGaln. After 6-24 h of D -Galn administration, the hepatic level of vitamin C, the most sensitive indicator of oxidative stress, decreased significantly, indicating that oxidative stress was significantly enhanced 6 h after D -Galn intoxication and thereafter. DMSO significantly restored the liver vitamin C level 24 h after D -Galn injection, demonstrating that DMSO effectively ameliorated the oxidative stress caused by D -Galn, resulting in the prevention of necrosis of the liver. Phosphorylated JNK and phospho-ERK were significantly increased transiently 6-12 h after treatment with D -Galn. These results indicated that oxidative stress and the activation of JNK took place almost simultaneously. Phosphorylated p38 MAPK was not changed and DMSO treatment did not affect the change of these MAPKs by D -Galn. Key Words DMSO, galactosamine, MAPK, oxidative stress, vitamin C Hepatoprotection remains one of the major challenges in nutritional and clinical therapy to limit liver injuries such as chronic hepatitis and fulminant hepatic failure. To study this issue more effectively, experimental methods are necessary to cause effective hepatic failure. Chemical toxins such as D -galactosamine ( D -Galn) ( 1 ), thioacetamide ( 2 ), and carbon tetrachloride ( 3 ) have been used for this purpose. D -Galn is known as a toxin causing necrosis of the liver by UTP depletion and inhibition of protein synthesis ( 4 ). Recently, we reported that radical reactions were caused by D -Galn in the early stage based on a decrease in vitamin C ( 1 ), resulting in necrosis. In chemically induced hepatitis ( 1-3 ), liver vitamin C was firstly consumed by oxidative stress, indicating that vitamin C was the most sensitive indicator of oxidative stress ( 5 ).Antioxidants in foods are therefore expected to protect the liver from oxidative stress caused by these chemicals. To survey the antioxidative effect of food factors, it is necessary to investigate effects of a known antioxidant on the liver. Only limited studies are available and DMSO is reported to function as an antioxidant in cultured hepatocytes ( 6 ) as well as in the rat liver under thioacetamide intoxication (6)(7)(8). In this report, we have attempted to investigate whether DMSO functions in vivo as an antioxidant and protects against necrosis of the liver caused by D -Galn even in a pharmacological dose. For this purpose we evaluated oxidative stress using hepatic vitamin C level and activation profiles of the three major subclasses of the MAPK (mitogen a...

CCl 4 (0.5 ml/kg as CCl 4 ) was orally administered to rats. Twelve hours after administration of CCl 4 , plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, indicators of liver necrosis, were significantly higher than those in the control group showing that active liver necrosis took place. At the same time the level of liver vitamin C was decreased significantly compared to that in the control group. Oral administration of 100 mg/kg each of celecoxib 3 and 8 h after CCl 4 treatment did not change plasma ALT and AST and liver vitamin C levels 12 h after CCl 4 treatment, but 24 h after CCl 4 treatment, significantly decreased plasma ALT and AST levels and elevated liver vitamin C level. These finding suggested that celecoxib effectively ameliorated the necrotic action and the oxidative stress induced by CCl 4 in the second phase. Although the plasma levels of all ceramide species were significantly increased 24 h after CCl 4 intoxication, treatment with celecoxib significantly reduced the total ceramide concentration in plasma. These results indicated that celecoxib significantly ameliorated the toxicity of CCl 4 in the second phase.

Ceramide mediates apoptosis and is upregulated by oxidative stress. To reveal the causative agent of diabetes-induced complications, we examined the changes in ceramide metabolism during diabetes. Two and 8 weeks after intraperitoneal injection of streptozotocin (STZ: 40 mg kg À1 body weight) to rats, tissue ceramide levels were analyzed by liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS). Blood glucose was significantly increased 2 weeks after STZ administration. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and blood urea nitrogen (BUN) levels were also increased in the diabetic rats, suggesting that hepatic and renal damage was induced by STZ administration. Vitamin C, an indicator of oxidative stress, was significantly decreased in the plasma, liver, and kidney of rats 2 weeks after STZ administration. Although no differences in hepatic ceramide levels were observed between the control and diabetic rats, plasma and renal ceramide levels were significantly increased 8 weeks after STZ administration. In the liver and kidney, acid and neutral sphingomyelinase (SMase) activities were not increased, while secretory sphingomyelinase (sSMase) activity was increased in the plasma of diabetic rats after STZ administration. These data indicated that STZ administration induced the increase in plasma ceramide levels via the increase in sSMase activity. It was suggested that increased plasma ceramide levels were involved in the renal damage induced by STZ in diabetic rats accompanied with the enhancement of oxidative stress.

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