Satonori Higuchi

Involvement of immune-related factors in diclofenac-induced acute liver injury in mice.

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical drug therapy. However, the underlying mechanism of DILI is little known. It is difficult to predict DILI in humans due to the lack of experimental animal models. Diclofenac, a non-steroidal anti-inflammatory drug rarely causes severe liver injury in human, but there is some evidence for immunoallergic idiosyncratic reactions. In this study, the mechanism of diclofenac-induced liver injury in mice was investigated. First, we established the dosing condition for liver injury in normal mice. Plasma ALT and AST levels were significantly increased in diclofenac-administered (80 mg/kg, i.p.) mice in a dose- and time-dependent manner. Among several interleukins (ILs) and chemokines, mRNA expression of helper T (Th) 17 cell-mediated factors, such as retinoid orphan receptor (ROR)-γt, and signal transducers and activators of transcription factor (STAT) 3 in the liver, and the plasma IL-17 level were significantly increased. Neutralization of IL-17 tended to suppress the hepatotoxicity of diclofenac, suggesting that IL-17 was partly involved. Gadolinium chloride (GdCl₃) administration demonstrated that Kupffer cells are not likely to be involved in diclofenac hepatotoxicity. Hepatic expressions of IL-1β mRNA and plasma IL-1β were significantly increased soon after the diclofenac administration. Then, the results of an in vivo neutralization study of IL-1β suggested that IL-1β was involved early in the time of pathogenesis of the diclofenac-induced liver injury. In conclusion, we firstly developed a diclofenac-induced acute liver injury model in normal mice, and the involvement of IL-17 and IL-1β was clarified.

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.

IL-4 mediates dicloxacillin-induced liver injury in mice

Drug-induced liver injury (DILI) is a major problem in drug development and clinical drug therapy. In most cases, the mechanisms are still unknown. It is difficult to predict DILI in humans due to the lack of experimental animal models. Dicloxacillin, penicillinase-sensitive penicillin, rarely causes cholestatic or mixed liver injury, and there is some evidence for immunoallergic idiosyncratic reaction in human. In this study, we investigated the mechanisms of dicloxacillin-induced liver injury. Plasma ALT and total-bilirubin (T-Bil) levels were significantly increased in dicloxacillin-administered (600 mg/kg, i.p.) mice. Dicloxacillin administration induced Th2 (helper T cells)-mediated factors and increased the plasma interleukin (IL)-4 level. Neutralization of IL-4 suppressed the hepatotoxicity of dicloxacillin, and recombinant mouse IL-4 administration (0.5 or 2.0 μg/mouse, i.p.) exacerbated it. Chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTh2) is a cognate receptor for prostaglandin (PG) D(2), and is suggested to be involved in Th2-dependent allergic inflammation. We investigated the effect of 13,14-Dihydro-15-keto-PGD(2) (DK-PGD(2); 10 μg/mouse, i.p.) administration on dicloxacillin-induced liver injury. DK-PGD(2)/dicloxacillin coadministration resulted in a significant increase of alanine aminotransferases and a remarkable increase of macrophage inflammatory protein 2 expression. In conclusion, to the best of our knowledge, this is the first report to demonstrate that dicloxacillin-induced liver injury is mediated by a Th2-type immune reaction and exacerbated by DK-PGD(2).

Interleukin-17 is involved in α-naphthylisothiocyanate-induced liver injury in mice

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical drug therapy. The pathogenesis of DILI usually involves the participation of the parent drug or metabolites that either directly affect the cell biochemistry or elicit an immune response. However, in most cases the mechanisms are unknown. Alpha-naphthylisothiocyanate (ANIT) is known as a hepatotoxicant that causes biliary cell and hepatocyte damage and induces intense neutrophil infiltration in the liver. To investigate whether an immune-mediated mechanism is involved in ANIT-induced liver injury, we examined the plasma AST, ALT and T-Bil levels, hepatic expression of transcriptional factors, cytokines and CXC chemokine genes, plasma IL-17 level and histopathological changes in liver after ANIT administration in mice. Hepatic mRNA expression of retinoid related orphan receptor gamma t (ROR gamma t) and macrophage inflammatory protein (MIP-2) and plasma IL-17 level was significantly increased in ANIT-administered mice as well as the plasma AST, ALT and T-Bil. Neutralization of IL-17 using anti-IL-17 antibody (100 microg/mouse, single i.p.) suppressed the hepatotoxic effect of ANIT. Co-administration of recombinant IL-17 (1 microg/mouse, single i.p.) to ANIT-administered mice resulted in a remarkable increase of the plasma AST, ALT and T-Bil levels. In conclusion, it was firstly demonstrated that IL-17 is involved in the ANIT-induced liver injury in mice.

Involvement of Th2 cytokines in the mouse model of flutamide-induced acute liver injury

Drug‐induced liver injury is a growing concern for pharmaceutical companies and patients because numerous drugs have been linked to hepatotoxicity and it is the most common reason for a drug to be withdrawn. Flutamide rarely causes liver dysfunction in humans, and immune allergic reactions have been suggested in some cases. In this study, we investigated the mechanisms of flutamide‐induced liver injury in BALB/c mice. Plasma alanine aminotransferase and aspartate aminotransferase levels were significantly increased 3, 6 and 9 h after flutamide (1500 mg kg−1, p.o.) administration. The biomarker for oxidative stress was not changed, but Th2‐dominant immune‐related factors, such as interleukin (IL)‐4, IL‐5, STAT6 and GATA‐binding protein (GATA)‐3, were induced in flutamide‐administered mice. The pre‐administration of monoclonal‐IL‐4 antibody suppressed the hepatotoxicity of flutamide. In addition, we investigated the effect of 13,14‐dihydro‐15‐keto‐PGD2 (DK‐PGD2; 10 µg per mouse, i.p.) administration on flutamide‐induced acute liver injury. Coadministration of DK‐PGD2 and flutamide resulted in a significant increase in alanine aminotransferase and a remarkable increase of macrophage inflammatory protein‐2. In conclusion, we demonstrated that flutamide‐induced acute liver injury is mediated by Th2‐dominant immune responses in mice. Copyright

Th2 cytokine‐mediated methimazole‐induced acute liver injury in mice

Drug‐induced liver injury (DILI) is a major safety concern in drug development and clinical practice. The pathogenesis of DILI usually involves the participation of the parent drug or metabolites that either affect cellular function or elicit an immune response. However, the mechanisms leading to DILI are unknown in most cases. Methimazole (MTZ) is used as an antithyroid drug and is well known to have induced liver injuries such as cholestatic hepatitis in a small number of human cases. Immune‐mediated reactions were also suggested to play a role in MTZ‐induced acute liver injury, but the mechanism underlying this process has not been elucidated. To address this issue, we measured plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, hepatic glutathione levels, hepatic expression of CD4+ Th cell‐related transcriptional factors, cytokines and chemokines, plasma interleukin (IL)‐4 levels and histopathological changes in the liver following MTZ (450 mg kg−1, p.o.) administration in mice. The hepatic expression of mRNA for Th2 cell‐related factors, such as GATA‐binding protein, macrophage inflammatory protein‐2 (MIP‐2) and plasma IL‐4 levels, as well as plasma AST and ALT levels, was significantly increased in mice treated with MTZ. These changes were markedly enhanced by pre‐treatment with L‐buthionine sulfoximine (3 mmol kg−1, i.p.) and MTZ (15 mg kg−1, p.o.). Neutralization of IL‐4 using a monoclonal anti‐mouse IL‐4 antibody (100 µg/mouse, single i.p.) suppressed the hepatotoxic effect of MTZ. In conclusion, this report is the first to demonstrate that Th2 cytokine‐mediated immune responses are involved in MTZ‐induced acute liver injury in mice. Copyright

Mechanisms of the hepatoprotective effects of tamoxifen against drug-induced and chemical-induced acute liver injuries

Although estrogen receptor (ER)α agonists, such as estradiol and ethinylestradiol (EE2), cause cholestasis in mice, they also reduce the degree of liver injury caused by hepatotoxicants as well as ischemia-reperfusion. The functional mechanisms of ERα have yet to be elucidated in drug-induced or chemical-induced liver injury. The present study investigated the effects of an ERα agonist, selective ER modulators (SERMs) and an ER antagonist on drug-induced and chemical-induced liver injuries caused by acetaminophen, bromobenzene, diclofenac, and thioacetamide (TA). We observed hepatoprotective effects of EE2, tamoxifen (TAM) and raloxifene pretreatment in female mice that were exposed to a variety of hepatotoxic compounds. In contrast, the ER antagonist did not show any hepatoprotective effects. DNA microarray analyses suggested that monocyte to macrophage differentiation-associated 2 (Mmd2) protein, which has an unknown function, is commonly increased by TAM and RAL pretreatment, but not by pretreatment with the ER antagonist. In ERα-knockout mice, the hepatoprotective effects of TAM and the increased expression of Mmd2 mRNA were not observed in TA-induced liver injury. To investigate the function of Mmd2, the expression level of Mmd2 mRNA was significantly knocked down to approximately 30% in mice by injection of siRNA for Mmd2 (siMmd2). Mmd2 knockdown resulted in a reduction of the protective effects of TAM on TA-induced liver injury in mice. This is the first report of the involvement of ERα in drug-induced or chemical-induced liver injury. Upregulation of Mmd2 protein in the liver was suggested as the mechanism of the hepatoprotective effects of EE2 and SERMs.

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 β‐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)‐1β, 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. Copyright

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.