Significance of tumor necrosis factor (TNF) and interleukin-1 (IL-1) in the pathogenesis of fulminant hepatitis: possible involvement of serine protease in TNF-mediated liver injury

Granulocyte colony-stimulating factor and interleukin-1β are important cytokines in repair of the cirrhotic liver after bone marrow cell infusion: comparison of humans and model mice

We previously described the effectiveness of autologous bone marrow cell infusion (ABMi) therapy for patients with liver cirrhosis (LC). We analyzed chronological changes in 19 serum cytokines as well as levels of specific cytokines in patients after ABMi therapy and in a mouse model of cirrhosis generated using green fluorescent protein (GFP)/carbon tetrachloride (CCl4). We measured expression profiles of cytokines in serum samples collected from 13 patients before and at 1 day and 1 week after ABMi. Child-Pugh scores significantly improved in all of these patients. To analyze the meaning of early cytokine change, we infused GFP-positive bone marrow cells (BMCs) into mice with CCl4-induced LC and obtained serum and tissue samples at 1 day and as well as at 1, 2, 3, and 4 weeks later. We compared chronological changes in serum cytokine expression in humans and in the model mice at 1 day and 1 week after BMC infusion. Among 19 cytokine, both granulocyte colony-stimulating factor (G-CSF) and interleukin-1β(IL-1β) in serum was found to show the same chronological change pattern between human and mice model. Next, we examined changes in cytokine expression in cirrhosis liver before and at 1, 2, 3, and 4 weeks after BMC infusion. Both G-CSF and IL-1β were undetectable in the liver tissues before and at 1 week after BMC infusion but increased at 2 weeks and continued until 4 weeks after infusion. The infused BMCs induced an early decrease of both G-CSF and IL-1β in serum and an increase in the model mice with LC. These dynamic cytokine changes might be important to repair liver cirrhosis after BMC infusion.

Lack of therapeutic effects of gabexate mesilate on the hepatic encephalopathy in rats with acute and chronic hepatic failure

BACKGROUND AND AIM

Inflammation plays a pivotal role in liver injury. Gabexate mesilate (GM, a protease inhibitor) inhibits inflammation by blocking various serine proteases. This study examined the effects of GM on hepatic encephalopathy in rats with acute and chronic liver failure.

METHODS

Acute and chronic liver failure (cirrhosis) were induced by intraperitoneal TAA administration (350 mg/kg/day for 3 days) and common bile duct ligation, respectively, in male Sprague-Dawley rats. Rats were randomized to receive either GM (50 mg/10 mL/kg) or saline intraperitoneally for 5 days. Severity of encephalopathy was assessed by the Opto-Varimex animal activity meter and hemodynamic parameters, mean arterial pressure and portal pressure, were measured (only in chronic liver failure rats). Plasma levels of liver biochemistry, ammonia, nitrate/nitrite, interleukins (IL) and tumor necrosis factor (TNF)-alpha were determined.

RESULTS

In rats with acute liver failure, GM treatment significantly decreased the plasma levels of alanine aminotransferase (P = 0.02), but no significant difference of motor activity, plasma levels of ammonia, IL-1beta, IL-6, IL-10 and TNF-alpha or survival was found. In chronic liver failure rats, GM significantly lowered the plasma TNF-alpha levels (P = 0.04). However, there was no significant difference of motor activity, other biochemical tests or survival found. GM-treated chronic liver failure rats had higher portal pressure (P = 0.04) but similar mean arterial pressure in comparison with saline-treated rats.

CONCLUSIONS

Chronic GM treatment does not have a major effect on hepatic encephalopathy in rats with TAA-induced acute liver failure and rats with chronic liver failure induced by common bile duct ligation.

Inflammatory stress and idiosyncratic hepatotoxicity: hints from animal models

Adverse drug reactions (ADRs) present a serious human health problem. They are major contributors to hospitalization and mortality throughout the world (Lazarou et al., 1998; Pirmohamed et al., 2004). A small fraction (less than 5%) of ADRs can be classified as "idiosyncratic." Idiosyncratic ADRs (IADRs) are caused by drugs with diverse pharmacological effects and occur at various times during drug therapy. Although IADRs affect a number of organs, liver toxicity occurs frequently and is the primary focus of this review. Because of the inconsistency of clinical data and the lack of experimental animal models, how IADRs arise is largely undefined. Generation of toxic drug metabolites and induction of specific immunity are frequently cited as causes of IADRs, but definitive evidence supporting either mechanism is lacking for most drugs. Among the more recent hypotheses for causation of IADRs is that inflammatory stress induced by exogenous or endogenous inflammagens is a susceptibility factor. In this review, we give a brief overview of idiosyncratic hepatotoxicity and the inflammatory response induced by bacterial lipopolysaccharide. We discuss the inflammatory stress hypothesis and use as examples two drugs that have caused IADRs in human patients: ranitidine and diclofenac. The review focuses on experimental animal models that support the inflammatory stress hypothesis and on the mechanisms of hepatotoxic response in these models. The need for design of epidemiological studies and the potential for implementation of inflammation interaction studies in preclinical toxicity screening are also discussed briefly.

Effect of JIANPI HUOXUE decoction on inflammatory cytokine secretion pathway in rat liver with lipopolysaccharide challenge

AIM: To evaluate the effect of Chinese traditional medicinal prescription, JIANPI HUOXUE decoction (JHD) on cytokine secretion pathway in rat liver induced by lipopolysaccharide (LPS).

METHODS: Twenty-four male SD rats were divided into normal group (n = 4), model group (n = 10) and JHD group (n = 10) randomly. Rats in model group and JHD group were administrated with normal saline or JHD via gastrogavage respectively twice a day for 3 d. One hour after the last administration, rats were injected with LPS via tail vein, 50 &mgr;g/kg. Simultaneously, rats in normal group were injected with equivalent normal saline. After LPS stimulation for 1.5 h, serum and liver tissue were collected. Pathological change of liver tissues was observed through hematoxylin-eosin (H.E.) staining. Tumor necrosis factor alpha (TNF-α) in serum were assayed by enzyme linked immunosorbent assay (ELISA). The protein expression of TNF-α, phosphorylated inhibit-κB (p-IκB) and CD68 in liver were assayed by Western blot. The distribution of CD68 protein in liver was observed through immunohistochemical staining. The mRNA expression of TNF-α, interleukin-6 (IL-6), CD14, toll-like receptor 2 (TLR2) and TLR4 in liver were assayed by real-time RT-PCR.

RESULTS: Predominant microvesicular change, hepatocyte tumefaction and cytoplasm dilution were observed in liver tissues after LPS administration as well as obvious CD68 positive staining in hepatic sinusoidal. After LPS stimulation, serum TNF-α (31.35 ± 6.06 vs 12 225.40 ± 9007.03, P < 0.05), protein expression of CD68 (1.13 ± 0.49 vs 3.36 ± 1.69, P < 0.05), p-IκB (0.01 ± 0.01 vs 2.07 ± 0.83, P < 0.01) and TNF-α (0.27 ± 0.13 vs 1.29 ± 0.37, P < 0.01) in liver and mRNA expression of TNF-α (1.96 ± 2.23 vs 21.45 ± 6.00, P < 0.01), IL-6 (4.80 ± 6.42 vs 193.50 ± 36.36, P < 0.01) and TLR2 (1.44 ± 0.62 vs 4.16 ± 0.08, P < 0.01) in liver were also increased significantly. These pathological changes were all improved in JHD group. On the other hand, TLR4 mRNA (1.22 ± 0.30 vs 0.50 ± 0.15, P < 0.05) was down-regulated and CD14 mRNA increased but not significantly after LPS stimulation.

CONCLUSION: JHD can inhibit cytokine secretion pathway induced by LPS in rat liver, which is probably associated with its regulation on CD68, p-IκB and endotoxin receptor TLR2.

Granulocyte colony-stimulating factor impairs liver regeneration in mice through the up-regulation of interleukin-1beta

BACKGROUND/AIMS

Stem cell induction via granulocyte colony-stimulating factor (G-CSF) administration is utilized in the treatment of various diseases. Therefore, we examined the effect of G-CSF administration to a liver fibrosis model induced by dimethylnitrosamine (DMN).

METHODS

ICR mice were subcutaneously injected with either G-CSF (150microg/kg) or saline at days 0, 3, 7 and 10. Subacute liver injury was established by intraperitoneal injection of DMN (10mg/kg) on three consecutive days of each week.

RESULTS

G-CSF administration significantly decreased the survival rate of mice treated with DMN. There was no difference in the degree of liver injury or fibrosis between either group of mice. However, assessment by proliferating cell nuclear antigen (PCNA) revealed that the G-CSF-treated mice experienced a greater degree of inhibition of liver cell proliferation than the control mice. Interleukin-1beta (IL-1beta) mRNA expression increased in the livers of G-CSF-treated mice. PCNA staining and analysis of cell cycle-related proteins also revealed that passive immunization with anti-IL-1beta-neutralizing antibody improved the impaired hepatocellular regeneration and resulted in an improved survival rate of mice treated with G-CSF and DMN.

CONCLUSIONS

G-CSF administration suppressed liver cell proliferation through the up-regulation of IL-1beta expression in DMN-induced liver injury.

The Role of Tumor Necrosis Factor Alpha in Lipopolysaccharide/Ranitidine-Induced Inflammatory Liver Injury

Exposure to a nontoxic dose of bacterial lipopolysaccharide (LPS) increases the hepatotoxicity of the histamine-2 (H2) receptor antagonist, ranitidine (RAN). Because some of the pathophysiologic effects associated with LPS are mediated through the expression and release of inflammatory mediators such as tumor necrosis factor alpha (TNF), this study was designed to gain insights into the role of TNF in LPS/RAN hepatotoxicity. To determine whether RAN affects LPS-induced TNF release at a time near the onset of liver injury, male Sprague-Dawley rats were treated with 2.5 x 10(6) endotoxin units (EU)/kg LPS or its saline vehicle (iv) and 2 h later with either 30 mg/kg RAN or sterile phosphate-buffered saline vehicle (iv). LPS administration caused an increase in circulating TNF concentration. RAN cotreatment enhanced the LPS-induced TNF increase before the onset of hepatocellular injury, an effect that was not produced by famotidine, a H2-receptor antagonist without idiosyncrasy liability. Similar effects were observed for serum interleukin (IL)-1beta, IL-6, and IL-10. To determine if TNF plays a causal role in LPS/RAN-induced hepatotoxicity, rats were given either pentoxifylline (PTX; 100 mg/kg, iv) to inhibit the synthesis of TNF or etanercept (Etan; 8 mg/kg, sc) to impede the ability of TNF to reach cellular receptors, and then they were treated with LPS and RAN. Hepatocellular injury, the release of inflammatory mediators, hepatic neutrophil (PMN) accumulation, and biomarkers of coagulation and fibrinolysis were assessed. Pretreatment with either PTX or Etan resulted in the attenuation of liver injury and diminished circulating concentrations of TNF, IL-1beta, IL-6, macrophage inflammatory protein-2, and coagulation/fibrinolysis biomarkers in LPS/RAN-cotreated animals. Neither PTX nor Etan pretreatments altered hepatic PMN accumulation. These results suggest that TNF contributes to LPS/RAN-induced liver injury by enhancing inflammatory cytokine production and hemostasis.

Effect of leflunomide on immunological liver injury in mice

AIM: To study the effect of leflunomide on immunological liver injury (ILI) in mice.

METHODS: ILI was induced by tail vein injection of 2.5 mg Bacillus Calmette-Guerin (BCG), and 10 d later with 10 mg lipopolysaccharide (LPS) in 0.2 mL saline (BCG + LPS). The alanine aminotransferase (ALT), aspartate aminotransferase (AST), nitric oxide (NO) level in plasma and molondiadehyde (MDA), glutathione peroxidase (GSHpx) in liver homogenate were assayed by spectroscopy. The serum content of tumor necrosis factors-α (TNF-α) was determined by ELISA. Interleukin-1 (IL-1), interleukin-2 (IL-2) and Concanavalin A (ConA)-induced splenocyte proliferation response were determined by methods of ³H-infiltrated cell proliferation.

RESULTS: Leflunomide (4, 12, 36 mg·kg^-1) was found to significantly decrease the serum transaminase (ALT, AST) activity and MDA content in liver homogenate, and improve reduced GSHpx level of liver homogenate. Leflunomide (4, 12, 36 mg·kg^-1) significantly lowered TNF-α and NO level in serum, and IL-1 produced by intraperitoneal macrophages (PMF). Moreover, the decreased IL-2 production and ConA-induced splenocyte proliferation response were further inhibited.

CONCLUSION: These findings suggested that leflunomide had significant protective action on ILI in mice.

Effect of age and carbon tetrachloride on cytokine concentrations in rat liver

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) concentrations were measured in livers of young-adult and old rats administered carbon tetrachloride or vehicle. IL-1beta levels were higher and IL-6 levels were lower in old rats than in young-adult rats. Carbon tetrachloride treatment increased IL-1beta and decreased TNF-alpha and IL-6. The elevation in IL-1beta was diminished by aging. These results indicate that the increase in carbon tetrachloride hepatotoxicity that occurs in old age could be related to a dysregulation of inflammatory cytokines.

Serum and liver concentrations of tumor necrosis factor alpha and interleukin-1beta following administration of carbon tetrachloride to male rats

Inflammatory cytokines are recognized as early mediators of tissue damage and repair. The purpose of this study was to determine the effects of carbon tetrachloride administration on tumor necrosis factor-alpha (TNF-alpha) and interleukin 1beta (IL-1beta) concentrations in serum and liver of rats. Administration of 0.2 ml/kg, i.p., of CCl4 to male Fischer 344 rats caused modest increases in serum levels of both cytokines; elevations of TNF-alpha were statistically significant at 4 and 12 h, and elevations of IL-1beta were statistically significant at 24 h. Although CCl4 produced substantial increases in liver IL-1beta concentrations (more than 3-fold), levels of TNF-alpha were not affected. Treatment with 0.1, 0.32 or 1.0 ml/kg of CCl4 produced dose-dependent increases in serum alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) activities, but serum cytokine concentrations were not dose-dependent and did correspond with serum ALT and SDH activities. The results suggest that IL-1beta production in rat liver is stimulated by hepatotoxic doses of CCl4. Production of TNF-alpha may also be induced, but the source of TNF-alpha in serum could be a tissue or organ other than liver.

Regulation of cell cycle-related genes in rat hepatocytes by transforming growth factor beta1

Transforming growth factor beta (TGF-beta) is a potent inhibitor of the proliferation of many cell types. We investigated the effects of TGF-beta1 on cyclin D1, cyclin A, p21, p27, and p53 mRNA expressions in primary cultured rat hepatocytes by the reverse-transcription polymerase chain reaction (RT-PCR) method. TGF-beta1 decreased the level of cyclin A mRNA in a dose-dependent manner, while it had little effect on the level of cyclin D1 mRNA. p21 mRNA expression was greatly induced by TGF-beta1 in a p53-independent mechanism, while p27 mRNA expression was not affected by TGF-beta1. These results suggest that TGF-beta1 may inhibit liver cell proliferation by regulating p21 and cyclin A mRNAs.

Ethanol and cytokine secretion

Cytokines are regulatory polypeptides secreted during the generation of an immune or inflammatory response by lymphocytes, cells of the monocyte/macrophage series, and a variety of other cell types. Alterations in the production, site of action, or metabolism of cytokines by exogenous factors, such as ethanol (EtOH), may have deleterious effects on the immune system as a whole. EtOH has been implicated in the onset of a variety of immune defects in vivo including effects on the production of cytokines critically involved in inflammatory responses (tumor necrosis factor, interleukin 1 and interleukin 6). In this review, we examine current knowledge regarding the effects of EtOH on the release of cytokines in humans and in animal models, in vitro and in vivo, which may help to elucidate the adverse actions of EtOH on mammalian immune systems.