Kupffer cells are responsible for liver cirrhosis induced by carbon tetrachloride

Inhibition of Kupffer cells could disrupt the sequence of events leading to organ injury by damping down the fibrogenic stimulus. To elucidate the role of Kupffer cells in liver fibrosis and cirrhosis, rats were treated with gadolinium chloride (GdCl(3)) and cirrhosis was induced by subchronic carbon tetrachoride (CCl(4)) administration. Carbon tetrachloride was administered three times per week for 8 weeks to male Wistar rats treated simultaneously with GdCl(3) (20 mg kg(-1), i.p. daily); appropriate controls were performed. Serum enzyme activities of alkaline phosphatase (ALP), gamma-glutamyl transpeptidase (gamma-GTP) and alanine aminotransferase (ALT) and bilirubin concentration increased significantly by CCl(4), whereas GdCl(3) prevented completely the increase in gamma-GTP and partially prevented the increase in ALP, ALT and bilirubins (P < 0.05). Liver glycogen was depleted by CCl(4), an effect that GdCl(3) was not capable of preventing. Moreover, gadolinium by itself depleted it. Lipid peroxidation increased about 2.5-fold by administration with CCl(4), whereas GdCl(3) preserved lipid peroxidation within normal values. Hepatic collagen increased threefold after subchronic intoxication with CCl(4) (P < 0.05) whereas GdCl(3) prevented partially (P < 0.05) the increase in collagen content, as evidenced by the liver hydroxyproline content and by the histopathological analysis. The present results suggest that Kupffer cells are needed for the production of CCl(4)-induced cirrhosis, because their inactivation with GdCl(3) prevents the disease.     

Protective role of Kupffer cells in acetaminophen-induced hepatic injury in mice

Hepatic injury induced by various toxic agents, including acetaminophen (APAP), has been attributed, in part, to the production of proinflammatory cytokines and other mediators by resident Kupffer cells within the liver. However, recent evidence from our laboratory has demonstrated that hepato-protective factors, such as interleukin (IL)-10 and cyclooxygenase-derived mediators, are also upregulated in response to hepatic damage to help protect against exacerbated injury, and Kupffer cells have been suggested to be a source of these modulatory factors. In other models, Kupffer cells also serve important regulatory functions in pathophysiological states of the liver. Therefore, we reevaluated the role of Kupffer cells in a murine model of APAP-induced liver injury using liposome-entrapped clodronate (liposome/clodronate) as an effective Kupffer cell-depleting agent. We show that in contrast to pretreatment of mice with a widely used macrophage inhibitor, gadolinium chloride, which did not deplete Kupffer cells but moderately protected against APAP-induced hepatotoxicity as reported previously, the intravenous injection of liposome/clodronate caused nearly complete elimination of Kupffer cells and significantly increased susceptibility to APAP-induced liver injury as compared with mice pretreated with empty liposomes. This increased susceptibility was apparently unrelated to the metabolism of APAP since liposome/clodronate pretreatment did not alter APAP-protein adduct levels. Instead, Kupffer cell depletion by liposome/clodronate led to significant decreases in the levels of hepatic mRNA expression of several hepato-regulatory cytokines and mediators, including IL-6, IL-10, IL-18 binding protein and complement 1q, suggesting that Kupffer cells are a significant source for production of these mediators in this model. Our findings indicate that, in addition to their protoxicant activities, Kupffer cells can also have an important protective function in the liver through the production of a variety of modulatory factors which may counteract inflammatory responses and/or stimulate liver regeneration.     

Restoration of hepatic mitochondria during recovery from carbon tetrachloride intoxication

During CCl₄ intoxication in rats, a disruption of hepatic mitochondrial structure and function occurs, which is characterized by a loss of respiratory activity, loss of phosphorylation coupled to respiration, and mitochondrial swelling, attended by loss of cristae structure. Within 15–25 hr, after full development of the mitochondrial lesion, the function and structure of the mitochondria are largely restored. Studies of the turnover of mitochondrial DNA and the rates of synthesis of mitochondrial DNA and protein indicated that the CCl₄-insulted hepatocyte is repairing the mitochondrial damage by the insertion of specific elements into the damaged organelle, rather than by proliferation of undamaged mitochondria for replacement. The failure of ethidium bromide, oxytetracycline and chloramphenicol, specific inhibitors of mitochondrial protein, and/or nucleic acid synthesis, to block this restoration substantiates the postulated repair process, and also indicates the non-critical nature of the respective mitochondrial functions during the repair process. Cytochrome measurements made during the period of acute damage revealed normal levels of cytochrome c, c₁ and aa₃. The observed elevation of cytochrome b is attributed to contamination of the preparation by hemoglobin.     

Decrease of binding sites for phalloidin on the surface of liver cells during carbon tetrachloride intoxication

Summary Isolated hepatocytes prepared from rats poisoned with carbon tetrachloride bind lower amounts of phalloidin than normal liver cells. This behaviour corresponds to the decreased toxicity of phalloidin during CCl₄ poisoning as described by Floersheim (1966).This work was supported by the Deutsche Forschungsgemeinschaft.     

Hepatoprotective effects of polymethoxyflavones against acute and chronic carbon tetrachloride intoxication

In the present study, we explore the protective effects of Citrus aurantium L. extract (CAE) against acute and chronic CCl₄-induced hepatotoxicity. The quantitative analysis of CAE was performed using HPLC-UV to determine the nobiletin content was approximately 27%. For the acute model, the male ICR mice were orally treated with water, silymarin (positive control, 200 mg/kg) and CAE (50 and 200 mg/kg) for 3 days prior to CCl₄ (1 mL/kg, 50% v/v in olive oil) IP injection. For the chronic model (n = 6/group), the mice were treated with each treatment for 28 consecutive days and CCl₄ (1 mL/kg, 20%) was injected twice a week. In both the acute and chronic models, the CCl₄ alone treated group showed histopathologic alterations with a significantly increase in serum hepatic enzyme levels together with a disrupted anti-oxidative status. In contrast, the CAE treatments restored pathologic alterations and recovered the oxidative status by enhancing antioxidant enzymes and reducing lipid peroxidation levels. Furthermore, CAE enhanced nuclear factor E2-related factor 2 (Nrf2) and its related cytoprotective signals, including NAD(P)H quinone oxidoreductase 1, UDP-glucuronosyltransferase, and γ-glutamylcysteine synthetase. Taken together, the present study demonstrates that CAE exerts a protective effect against CCl₄-induced hepatotoxicity with its anti-oxidant, anti-inflammatory, and anti-apoptotic activity.     

Metformin protects against carbon tetrachloride hepatotoxicity in mice

In the present study, the hepatoprotective effect of metformin (Met), a dimethylbiguanide anti-hyperglycemic, was examined in a mouse model of liver damage induced by chronic repeated administration of carbon tetrachloride (CCl(4)) (5 microl/kg, twice a week for 12 weeks). Met, when given orally in drinking water at an estimated daily dose of 25 or 50 mg/kg for 10 weeks starting 2 weeks after CCl(4) challenge, protected against CCl(4) hepatotoxicity. The results indicate that the hepatoprotection afforded by Met treatment at a dose of 25 mg/kg against CCl(4) toxicity may at least in part be mediated by the enhancement of mitochondrial glutathione redox status.     

The protective action of thymol against carbon tetrachloride hepatotoxicity in mice.

The protective action of thymol (paramethyl-isopropyl-phenol) was investigated against carbon tetrachloride (CCl(4))-induced hepatotoxicity in male Swiss albino mice. The CCl(4)at a dose of 20 microl kg(-1)produced damage to liver cells and was followed by the significant increase (P<0.001) in serum alanine aminotransferase (ALT) activity and hepatic lipid peroxidation after 24 h. The hepatocellular necrosis was further confirmed by histopathological examination of liver section. Oral administration of thymol in a single dose (300 mg kg(-1)) resulted in significant (P<0.05) amelioration of CCl(4)-induced hepatotoxicity. Thymol also inhibited lipid peroxidation induced by CCl(4)in vivo. The protection offered by thymol was also evident from histopathology photomicrograph. In a separate in vitro assay, thymol inhibited the non-enzymatic lipid peroxidation of normal mice liver homogenate induced by Fe(3+)-ascorbate. The present study suggests that thymol protects the liver against CCl(4)-induced toxicity and the protection may be mediated through its ability to inhibit lipid peroxidation. However, other interactions between thymol and CCl(4)remains to be elucidated. 1999 Academic Press.     

Tolerogenic role of Kupffer cells in allergic reactions

Drug-induced allergic reactions (DIARs), including allergic hepatitis, cutaneous reactions, and blood dyscrasias, are unpredictable and can be life threatening. Although current studies suggest that DIARs are caused by immunogenic drug-protein adducts, it remains unclear what factors determine the susceptibility to DIARs. We hypothesized that most individuals may be resistant to DIARs in part because they become immunologically tolerant to drug-protein adducts in the liver, an organ with tolerogenic properties. Because animal models of DIARs are elusive, we tested this hypothesis using a murine model of 2,4-dinitrochlorobenzene (DNCB)-induced delayed type hypersensitivity reaction that is mediated by immunogenic 2,4-dinitrophenylated (DNP)-protein adducts. Intravenous pretreatment of mice with DNP-BSA led to its accumulation in hepatic Kupffer cells (KC) and induced immunological tolerance to subsequent DNCB sensitization. Tolerance could be abrogated by prior depletion of KC or induced in na?ve mice by transferring a T cell-depleted, KC-enriched fraction of liver nonparenchymal cells from mice tolerized 1 month earlier by DNP-BSA pretreatment. These findings implicate KC as a primary and sustained inducer of tolerance against DNP-protein adducts and suggest a similar role in modulating allergic reactions against drug-protein adducts. Perhaps genetic and/or environmental factors affecting the activities of these cells may play a role in determining individual susceptibility to DIARs.     

Enzymes involved in glutathione metabolism in rat liver and blood after carbon tetrachloride intoxication

Some glutathione-metabolizing enzymes in rat liver cytosol, blood plasma and urine of rats administered carbon tetrachloride (CCl₄) were investigated.After CCl₄ at different doses (0.3, 1.2, 2.5 ml/kg at 24, 12 and 3 or 6 h, respectively) liver glutathione reductase (GR), glyoxalase 1 (GLY-I) and glutathione S-transferases (GST) significantly decreased, while thioltransferase and glutathione peroxidase (GPX) did not change their activity.At the times under investigation the glutathione level significantly increased in the liver and the above-mentioned enzymes in plasma, thus evidencing a liver injury.The GR, GPX and GST assayed in urine within 72 h after CCl₄ administration showed a maximum of activity at 35–48 h.     

肝脏巨噬细胞在组织稳态和肝脏疾病中的功能探讨

巨噬细胞在肝脏中扮演关键角色,对于维持组织稳态和确保机体对肝损伤的迅速应答至关重要。对肝脏巨噬细胞的异质亚群划分,有利于更加全面深入地理解其功能。库普弗细胞是一种驻留在肝脏中的、可自我维持的巨噬细胞群体,区别于单核细胞衍生的巨噬细胞,后者仅在损伤发生时迅速聚集至肝脏。特定的环境信号决定肝脏巨噬细胞的进一步极化表型和功能。不同亚群的肝脏巨噬细胞既可以促进肝脏在损伤或感染后组织完整性的恢复,也会导致如肝炎、纤维化、癌症等疾病病程的加剧。重点介绍近年来有关肝脏巨噬细胞的起源、分类和功能的新发现,并探讨它们在肝脏生理和病理状态下的不同功能,以期为肝脏巨噬细胞的深入研究提供理论基础。

     

Enhanced liver injury in acatalasemic mice following exposure to carbon tetrachloride

The hypothtical involvement of hydrogen peroxide (H₂O₂) in carbon tetrachloride (CCl₄)-induced acute liver injury and the potential preventive effect of catalase on hepatotoxicity have been studied in acatalasemic (C3H/AnLC_s ^bC₂ ^b) mice and compared with normal (C3H/AnLC_s ^aC_s ^a) mice. A single intraperitoneal injection of CCl₄ (20% in olive oil/g body weight) caused increases in serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in both mouse groups, but the extents of increases did not show significant differences between the two mouse groups until 12 h. The variation in increases of serum AST and ALT levels in acatalasemic and normal mice turned to be distinctly different from 12 h. At 18 h (peak point for ALT) and 24 h (peak point for AST), the serum enzyme levels in acatalasemic mice were nearly two-fold higher than those in normal ones, the difference being statistically significant (p <0.01). The liver malondialdehyde (MDA) level in acatalasemic mice was also higher than that in normals at 18 h (p <0.05). The extent of the centrilobular necrosis was histologically more severe in acatalasemic mice. The catalase activity in livers of acatalasemic mice was one-third to one-fifth those of normal mice (p <0.05) before and after treatment. The decreased catalase activity in acatalasemic mice might increase tissue or cellular levels of H₂O₂ during the later phase of the acute liver injury. From these findings, we conclude that H₂O₂ breakdown in liver would account for the difference in the later stages of the acute liver damage between the two groups of mice, and catalase is important in inhibiting hepatotoxicity of CCl₄ in the later stage.     

Tolerogenic role of Kupffer cells in immune-mediated adverse drug reactions

Immune-mediated adverse drug reactions (IADR) account for approximately 6-10% of all adverse drug reactions. Although IADR are often referred to as rare (afflicting 1/100 to 1/100,000 patients), their unpredictable and serious nature makes them a significant economic burden and safety concern to the health care community and the pharmaceutical industry. Current studies suggest that IADR are caused by immunogenic drug-protein adducts; however, it remains unclear why only a small percentage of patients are susceptible to developing these reactions. We hypothesized that most individuals may be resistant to IADR because they develop immunological tolerance to drug-protein adducts in the liver, an organ with tolerogenic properties. We tested this hypothesis using a murine model of T-cell-mediated reaction against a hapten, 2,4-dinitrochlorobenzene (DNCB). We showed that pre-treatment of mice with a protein adduct of DNCB led to its accumulation in Kupffer cells (KC) of the liver and induced tolerance to subsequent DNCB sensitization. KC depletion and adoptive transfer experiments further supported that KC may act as a primary inducer of immunological tolerance against protein adducts of haptens or drugs. Functional activities of KC, which are regulated by genetic and/or environmental factors, may play an important role in determining individual susceptibility to IADR.