Establishment of a mouse model for amiodarone-induced liver injury and analyses of its hepatotoxic mechanism.

Drug-induced liver injury (DILI) is the most frequent cause of post-marketing warnings and withdrawals. Amiodarone (AMD), an antiarrhythmic, presents a risk of liver injury in humans, and its metabolites, formed by cytochrome P450 3A4, are likely more toxic to hepatocytes than AMD is. However, it remains to be clarified whether the metabolic activation of AMD is involved in liver injury in vivo. In this study, to elucidate the underlying mechanisms of AMD-induced liver injury, mice were administered AMD [1000 mg kg(-1), per os (p.o.)] after pretreatment with dexamethasone [DEX, 60 mg kg(-1), intraperitoneal (i.p.)], which induces P450 expression, once daily for 3 days. The plasma alanine aminotransferase (ALT) levels were significantly increased by AMD administration in the DEX-pretreated mice, and the liver concentrations of desethylamiodarone (DEA), a major metabolite of AMD, were correlated with the changes in the plasma ALT levels. Cytochrome c release into the hepatic cytosol and triglyceride levels in the plasma were increased in DEX plus AMD-administered mice. Furthermore, the ratio of reduced glutathione to oxidized glutathione disulfide in the liver significantly decreased in the DEX plus AMD-administered mice. The increase of ALT levels was suppressed by treatment with gadolinium chloride (GdCl3 ), which is an inhibitor of Kupffer cell function. From these results, it is suggested that AMD and/or DEA contribute to the pathogenesis of AMD-induced liver injury by producing mitochondrial and oxidative stress and Kupffer cell activation. This study proposes the mechanisms of AMD-induced liver injury using an in vivo mouse model.

Involvement of immune- and inflammatory-related factors in flucloxacillin-induced liver injury in mice.

Drug-induced liver injury (DILI) is a serious problem in pre-clinical stages of drug development and clinical pharmacotherapy, but the pathogenesis of DILI has not been elucidated. Flucloxacillin (FLX), which is a ß-lactam antibiotic of the penicillin class that is used widely in Europe and Australia, rarely causes DILI. Clinical features suggest that FLX-induced liver injury is caused by immune- and inflammatory-related factors, but the mechanism of FLX-induced liver injury is unknown. The purpose of this study was to elucidate the mechanisms of FLX-induced liver injury in vivo. Plasma alanine aminotransferase, aspartate aminotransferase and total-bilirubin levels were significantly elevated in FLX-administered mice [1000 mg kg(-1) , intraperitoneally (i.p.)]. Toll-like receptor 4 (TLR4) ligands, such as high-mobility group box 1 (HMGB1) and S100A8/A9, were significantly increased in FLX-administered mice, and inflammatory factors, such as interleukin (IL)-1ß, tumor necrosis factor-alpha (TNF-α), macrophage inflammatory protein (MIP)-2, CXC chemokine-ligand-1 (CXCL1) and monocyte chemoattractant protein (MCP)-1, were also significantly elevated. IL-17-related transcriptional factors and cytokines were increased, and the administration of recombinant IL-17 (2 mg per body weight, i.p.) resulted in an exacerbation of the FLX-induced liver injury. TLR4-associated-signal transduction may be involved in FLX-induced liver injury, and IL-17 is an exacerbating factor.

Involvement of oxidative stress and immune- and inflammation-related factors in azathioprine-induced liver injury.

Drug-induced liver injury (DILI) is a growing concern in the fields of drug development and clinical drug therapy because numerous drugs have been linked to hepatotoxicity. However, it is difficult to predict DILI in humans due to the lack of experimental animal models. Although azathioprine (AZA), which is a widely used immunosuppressive drug, is generally well tolerated, a small number of patients prescribed AZA develop severe hepatitis. However, the mechanism underlying this process has not yet been elucidated. In this study, we developed a mouse model of AZA-induced liver injury and investigated the mechanisms responsible for the hepatotoxicity of AZA. Female BALB/c mice were orally administered AZA. After AZA administration, the plasma levels of alanine aminotransferase and aspartate aminotransferase were increased, and liver damage was confirmed through a histological evaluation. In addition, the hepatic glutathione levels and superoxide dismutase activity were significantly decreased. The plasma levels of reactive oxygen species were significantly increased during the early phase of AZA-induced liver injury, and the hepatic mRNA levels of immune- and inflammation-related factors were also significantly changed. In conclusion, oxidative stress and the subsequently activated immune- and inflammation-related factors are involved in AZA-induced liver injury.

Metabolic activation and inflammation reactions involved in carbamazepine-induced liver injury.

Drug-induced liver injury is a major safety concern in drug development and clinical pharmacotherapy; however, advances in the understanding of the mechanisms of drug-induced liver injury are hampered by the lack of animal models. Carbamazepine (CBZ) is a widely used antiepileptic agent. Although the drug is generally well tolerated, only a small number of patients prescribed CBZ develop severe hepatitis. In the present study, we developed a mouse model of CBZ-induced liver injury and elucidated the mechanisms accounting for the hepatotoxicity of CBZ. Male BALB/c mice were orally administered CBZ for 5 days. The plasma levels of alanine aminotransferase and aspartate aminotransferase were prominently increased, and severe liver damage was observed via histological evaluation. The analysis of the plasma concentration of CBZ and its metabolites demonstrated that 3-hydroxy CBZ may be relevant in CBZ-induced liver injury. The hepatic glutathione levels were significantly decreased, and oxidative stress markers were significantly altered. Mechanistic investigations found that hepatic mRNA levels of toll-like receptor 4, receptor for advanced glycation end products, and their ligands were significantly increased. Moreover, the plasma concentrations of proinflammatory cytokines were also increased. Prostaglandin E(1) administration ameliorated the hepatic injury caused by CBZ. In conclusion, metabolic activation followed by the stimulation of immune responses was demonstrated to be involved in CBZ-induced liver injury in mice.