基于TLR4信号通路的中药抗肝脏疾病作用研究进展

肝脏疾病是发生在肝脏的所有疾病的总称。近年来中药在治疗肝脏疾病中有一定优势,其实验研究作用显著或临床应用疗效较好,不良反应较少,呈现了广阔的前景。Toll样受体4(TLR4)信号通路与肝脏疾病息息相关,其抑制机制是通过TLR4介导的信号通路活化核转录因子-κB(NF-κB),抑制白细胞介素-1β(IL-1β),白细胞介素-6(IL-6)和肿瘤坏死因子-α(TNF-α)等炎症因子的分泌,抑制肝细胞的炎症损伤,进一步抑制了IL-1β,IL-6,TNF-α等对肝星状细胞(HSC)等细胞的激活,其阻断TRL4通路的方式为①抑制TLR4的表达;②抑制TLR4二聚体化;③阻断胞内信号转导,通过作用于衔接蛋白,作用于激酶IL-1受体相关激酶(IRAKs),作用于去泛素化酶锌指蛋白A20(TLRAFst)。通过这几个方面阻断TRL4通路,抑制炎症反应发生,达到抗肝脏疾病的作用。因此,抑制或增强TLR4信号通路或针对TLR4信号通路中某些环节进行干预成为肝病治疗的新策略。目前TLR4信号通路成为中药抗肝脏疾病的靶点之一。本文对近年中药抗TLR4信号通路活化,通过中药单体及有效部位、中药提取物、中药复方等发挥抗肝脏疾病作用的文献进行整理,为下一步中西医治疗肝脏疾病提供重要的指导意义和方向。

Adiponectin,a key adipokine in obesity related liver diseases

Non-alcoholic fatty liver disease (NAFLD) comprising hepatic steatosis,non-alcoholic steatohepatitis (NASH),and progressive liver fibrosis is considered the most common liver disease in western countries.Fatty liver is more prevalent in overweight than normal-weight people and liver fat positively correlates with hepatic insulin resistance.Hepatic steatosis is regarded as a benign stage of NAFLD but may progress to NASH in a subgroup of patients.Besides liver biopsy no diagnostic tools to identify patients with NASH are available,and no effective treatment has been established.Visceral obesity is a main risk factor for NAFLD and inappropriate storage of triglycerides in adipocytes and higher concentrations of free fatty acids may add to increased hepatic lipid storage,insulin resistance,and progressive liver damage.Most of the adipose tissue-derived proteins are elevated in obesity and may contribute to systemic inflammation and liver damage.Adiponectin is highly abundant in human serum but its levels are reduced in obesity and are even lower in patients with hepatic steatosis or NASH.Adiponectin antagonizes excess lipid storage in the liver and protects from inflammation and fibrosis.This review aims to give a short survey on NAFLD and the hepatoprotective effects of adiponectin.

New perspectives in occult hepatitis C virus infection

Occult hepatitis C virus (HCV) infection, defined as the presence of HCV RNA in liver and in peripheral blood mononuclear cells (PBMCs) in the absence of detectable viral RNA in serum by standard assays, can be found in anti-HCV positive patients with normal serum levels of liver enzymes and in anti-HCV negative patients with persistently elevated liver enzymes of unknown etiology. Occult HCV infection is distributed worldwide and all HCV genotypes seem to be involved in this infection. Occult hepatitis C has been found not only in anti-HCV positive subjects with normal values of liver enzymes or in chronic hepatitis of unknown origin but also in several groups at risk for HCV infection such as hemodialysis patients or family members of patients with occult HCV. This occult infection has been reported also in healthy populations without evidence of liver disease. Occult HCV infection seems to be less aggressive than chronic hepatitis C although patients affected by occult HCV may develop liver cirrhosis and even hepatocellular carcinoma. Thus, anti-HCV negative patients with occult HCV may benefit from antiviral therapy with pegylated-interferon plus ribavirin. The persistence of very low levels of HCV RNA in serum and in PBMCs, along with the maintenance of specific T-cell responses against HCV-antigens observed during a long-term follow-up of patients with occult hepatitis C, indicate that occult HCV is a persistent infection that is not spontaneously eradicated. This is an updated report on diagnosis, epidemiology and clinical implications of occult HCV with special emphasis on anti-HCV negative cases.

Role for mycobacterial infection in pathogenesis of primary biliary cirrhosis?

Primary biliary cirrhosis （PBC） is a progressive cho- lestatic liver disease characterized by the immune- mediated destruction of biliary epithelial cells in small intrahepatic bile ducts. The disease is characterized by circulating antimitochondrial antibodies （AMAs） as well as disease-specific antinuclear antibodies, cholestatic liver function tests, and characteristic histological fea- tures, including granulomas. A variety of organisms are involved in granuloma formation, of which mycobacte- ria are the most commonly associated. This has led to the hypothesis that mnycobacteria may be involved in the pathogenesis of PBC, along with other infectious agents. Additionally, AMAs are found in a subgroup of patients with rnycobacterial infections, such as lep- rosy and pulmonary tuberculosis. Antibodies against species-specific mycobacterial proteins have been re- ported in patients with PBC, but it is not clear whether these antibodies are specific for the disease. In addi- tion, data in support of the involvement of the role of molecular mimicry between rnycobacterial and human mitochondrial antigens as triggers of cross-reactive im- mune responses leading to the loss of immunological tolerance, and the induction of pathological features have been published. Thus, antibodies against myco- bacterial heat shock protein appear to cross-recognize AMA-specific autoantigens, but it is not clear whether these autoantibodies are mycobacterium-species-spe- cific, and whether they are pathogenic or incidental. The view that mycobacteria are infectious triggers of PBC is intriguing, but the data provided so far are not conclusive.

Biochemical mechanisms in drug-induced liver injury:Certainties and doubts

Drug-induced liver injury is a significant and still unresolved clinical problem. Limitations to knowledge about the mechanisms of toxicity render incomplete the detection of hepatotoxic potential during preclinical development. Several xenobiotics are lipophilic substances and their transformation into hydrophilic compounds by the cytochrome P-450 system results in production of toxic metabolites. Aging, preexisting liver disease, enzyme induction or inhibition, genetic variances, local 02 supply and, above all, the intrinsic molecular properties of the drug may affect this process. Necrotic death follows antioxidant consumption and oxidation of intracellular proteins, which determine increased permeability of mitochondrial membranes, loss of potential, decreased ATP synthesis, inhibition of Ca^2＋-dependent ATPase, reduced capability to sequester Ca^2＋ within mitochondria, and membrane bleb formation. Conversely, activation of nucleases and energetic participation of mitochondria are the main intracellular mechanisms that lead to apoptosis. Non-parenchymal hepatic cells are inducers of hepatocellular injury and targets for damage. Activation of the immune system promotes idiosyncratic reactions that result in hepatic necrosis or cholestasis, in which different HLA genotypes might play a major role. This review focuses on current knowledge of the mechanisms of drug-induced liver injury and recent advances on newly discovered mechanisms of liver damage. Future perspectives including new frontiers for research are discussed.

Anti-lipid peroxidation and protection of liver mitochondria against injuries by picroside Ⅱ

AIM: To investigate the anti-lipid peroxidation and protection of liver mitochondria against injuries in mice with liver damage by picroside Ⅱ. METHODS: Three animal models of liver damage induced by carbon tetrachloride (CCl4: 0.1 mL/10 g, ip), D-galactasamine (D-GaIN: 500 mg/kg, ip) and acetaminophen (AP: 0.15 g/kg, ip) were respectively treated with various concentrations of picroside Ⅱ (5, 10, 20 mg/kg, ig). Then we chose the continuously monitoring method (recommended by International Clinical Chemistry League) to analyze serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) values, Marland method to detect the activity of manganese-superoxide dismutase (SOD) in liver mitochondria, TBA colorimetry to determine the content of malonicdialdehyde (MDA) in liver tissue, DTNB method to evaluate the activity of glutathioneperoxidase (GSH-Px) and Lowry method to detect protein level in liver tissue. Meanwhile, effects of picroside Ⅱ on the activity of ATPase and swelling extent of mitochondria in hepatocytes damaged by AP were also evaluated. RESULTS: Picroside Ⅱ could significantly prevent liver toxicity in the three models of liver damage. It decreased the high levels of ALT and AST in serum induced by the administration of CCl4, D-GaIN and AP, reduced the cellular damage of liver markedly, and appeared to be even more potent than the positive control drug of biphenyl dimethyl dicarboxylate pilules (DDB). In groups treated with different doses of picroside Ⅱ, compared to the model group, the content of MDA in serum decreased evidently, whereas the content of SOD and GSH-Px increased in a dose dependent manner, and the difference was statistically significant. Further, in the study of AP model, picroside Ⅱ inhibited AP-induced liver toxicity in mice, enhanced the activity of ATPase, improved the swelling extent of mitochondria and helped to maintain a normal balance of energy metabolism. CONCLUSION: Picroside II can evidently relieve hepatocyte injuries induced by CCI4, D-GaIN and AP, help scavenge free radicals, protect normal constructions of mitochondria membrane and enhance the activity of ATPase in mitochondria, thereby modulating the balance of liver energy metabolism, which might be part of the mechanisms of hepatoprotective effects of picroside Ⅱ.

Reduced antioxidant level and increased oxidative damage in intact liver lobes during ischaemia-reperfusion

AIM： To determine whether increased blood flow of the liver can cause oxidative stress and hepatocyte damage, and to elaborate methods suitable for measuring the antioxidant defence during hepatic surgery on rat model.METHODS： In nembutal narcosis, the left lateral and the medial lobes of the liver were clipped for 45 rain to make the total blood supply flow through the other lobes. Total antioxidant status, glutathione peroxidase and superoxide dysmutase activity, as well as the concentrations of diene conjugates and free sulphydril groups, H-donating ability and reducing power of the liver samples were determined. Chemiluminescent intensity of the liver was also measured. Metal ions （Al, Ca, Cu, Fe, Mg, Mn, Zn） and P and S concentrations of the liver were determined with an inductively coupled plasma optical emission spectrometer and Se content was measured by cathodic stripping voltammetry.RESULTS： Glutathione peroxidase and superoxide dysmutase activities of the liver decreased significantly in the hyperemia group compared to those observed in the sham operated group. The level of total antioxidant status was also significantly lower in the hyperemia group. H-donating ability, reducing power and free sulphydril group concentration showed the same tendency. A significant correlation （P〈0.05） was found between the changes in non-specific antioxidant activities. This pointed to simultaneous activity of the antioxidant defence system. Al, Cu, Mn, Zn, and S were lower in the hyperemia group than in the sham operated group when the levels of Ca, Fe, Mg, Se and P ions were higher during hyperemia.CONCLUSION： Oxidative stress is one of the main factors for the injury of intact liver lobes during ischaemia-reperfusion.

Role of autoimmunity in primary biliary cirrhosis

Primary biliary cirrhosis(PBC) is an autoimmune liver disease characterized by the presence of serum autoantibodies and chronic nonsuppurative destructive cholangitis.The pathogenesis of PBC involves environmental factors,genetic predisposition and loss of immune tolerance.In recent years,it has become univocally accepted that an inappropriately activated immune response is one of the most important factors in PBC.In this study,the role of autoimmunity in PBC is summarized and a feasible research orientation is recommended.