Studies On The Role Of Nitric Oxide (NO), Tumor Necrosis Factor (TNF) In Liver Damage And The Mechanisms Of Protective Action Of New Anti-Hepatitis Drugs (Sy-801 And Sy-640) On Liver Damage In Mice

The therapy of viral hepatitis is still a big difficulty, although various kinds of drugs have been used in the clinic. In the past decades, the investigation of anti-hepatitis drugs was based on the protection against chemical-induced liver injury. It is well known that chemical-induced liver injury by certain chemicals differs far from human hepatitis in the aspect of pathogenesis. Some drugs are effective in chemical-induced liver injury but showed no remarkable effects in human hepatitis. In order to explore a new therapeutic path and new method for study the mechanism underlying the liver injury and the mechanism of protective action of drugs against liver damage, we have established an immunological liver injury model by injection of micro lipopolysaccha-ride(LPS) into BCG(bacilli Calmette Guérin)-primed mice. The pathogenesis of BCG+LPS induced hepatitis was reported to be closely related to the infiltration of inflammatory cells into the liver.Nitric oxide(NO) and tumor necrosis factor(TNF) are two main inflammatory mediators released from phagocytes. The role of NO in liver injury induced by BCG+LPS has not been studied both domestically and aborad. The present studies were to evaluate the role of NO and TNF in liver damage in order to lay a base for exploring a new approach for searching hepato- prectants.Sy-801, the second generation of DDB, and Sy-640 are two new hepatoprectants developed by our institute. Both Sy-801 and Sy-640 showed significantly protective action against chemical-induced liver injury. The potency of the two hepatoprectants are greater than DDB. The present paper reports the role of NO and TNF in immunological liver injury induced by BCG+LPS in mice as well as the mechanisms of protective action of both Sy-801 and Sy-640 on this immunological liver injury model. The results are described as follows:Remarkable plasma NO elevation and severe liver necrosis were induced by i. v. injection of LPS into BCG-primed mice. The inhibition of NO synthesis by N~G- monomethyl-L-arginine, an inhibitor of NO synthase, resulted in exacerbation of liver injury. However, promotion of NO synthesis induced alleviation of liver damage.TNF was also involved in liver damage induced by BCG plus LPS. Splenectomy neither showed influence on BCG+LPS induced increases of plasma NO and TNF levels, nor alter the degree of liver necrosis.Activation of Kupffer cells by large doses of retinol induced further increase of plasma NO and TNF levels, and was associated with increment of liver necrosis induced by BCG+LPS. In contrast, suppression of Kupffer cells by silica or carbon resulted in reduction of plasma NO and TNF levels, and was related to the alleviation of liver necrosis.Pretreatment of mice with Sy-801 and Sy-640, the two new anti-hepatitis drugs, induced further increase of plasma NO level and reduction of TNF level induced by BCG+LPS, and amelioration of the liver damage.Sy-801 and Sy-640 exhibited significant inhibiting effect on TNF and NO production by BCG-elicited murine macrophages when stimulated with LPS.Sy-801 and Sy-640 significantly inhibited BCG+LPS induced elevation of TNF mRNA level in murine peritoneal macrophages.Marked increases of NO and citrulline levels and damage of hepatocyte surface architecture were noticed when the mouse hepatocytes were cocultured with BCG- primed murine peritoneal macrophages in case of challenge with LPS. Sy-801 and Sy-640 significantly inhibited the production of NO and citrulline and ameliorated of the damage of the hepatocyte surface membrane.It may be deduced from the above results that NO plays a dual action on liver damage, i. e. damaging and protective. TNF released by macrophages is also one of the key factors leading to the damage of liver cells. Kupffer cells were involved in the pathogenesis of BCG+LPS induced liver injury by releasing NO and TNF. The spleen plays a minimal role in BCG+LPS induced liver injury in mice. The mechanism(s) by which Sy-801 and Sy-640 protect BCG+LPS induced damage may be the results of stimulating NO production by certain cells and inhibition of TNF expression by macrophages.