Mechanistic Study of the Role of IL-22 in Hepatocyte’s Survival of Pakistani Patients with End Stage Liver Disease

Abstract

Hepatitis is a menace that has now spread its terror in all parts of the world due to rapidly increasing mortality rates. Major etiological agents of Hepatitis include infection with Hepatitis B/C Virus, excessive alcohol intake, Non-Alcoholic Steatohepatitis (NASH) and others. Hepatitis is the principle cause of end stage liver disease (hepatocellular carcinoma, decompensated cirrhosis). The most prevalent type of cancer in the liver is hepatocellular carcinoma. Hepatocellular carcinoma (HCC) is one of the leading causes of deaths around the world. The current treatment regimen has so far proven to be unsuccessful in countering the effects of this life threatening disease. The present study was designed to investigate the role of Interleukin-22 (IL-22) in the survival of hepatocytes (liver cells) during end stage liver disease (cirrhosis and HCC). In the current study, resected/explanted liver tissue samples of the patients with ESLD were obtained from Hepato-Pancreato-Biliary Liver Transplant Unit of Sheikh Zayd Hospital, Lahore. Evaluation of the qualitative expression of IL-22, its negative feedback regulator Supressor of cytokine signaling 3 (SOCS3) and IL-22 induced anti-apoptotic protein B-cell lymphoma extra-large (Bcl xL) was done by Immunohistochemical analysis (IHC). High expression levels of IL-22, Bcl-xL and SOCS3 within patients with ESLD were observed. Furthermore, significant relationship was established between the expression of the IL-22 and Bcl-xL and different underlying etiologies. The observed results reveal that the expression of IL 22 and its downstream signaling molecule varies with the type of etiological agent responsible for the development of ESLD. It was also observed that as the disease progresses the immune xvii response generated also varies as suggested by the difference in expression of proteins under study with the different histological grades of infected liver tissues i.e. chronic hepatitis, cirrhosis and HCC. The study indicated that IL-22 plays a vital role in driving the response of hepatocytes to the increasingly harsh environment of the liver during the course of liver disease. In order to validate the results of wet lab analysis (by IHC), In silico analysis of the pathway regulating the action of IL-22 within liver was performed by using a qualitative modeling software (GenoTech). The biological regulatory network designed by GenoTech not only indicated the states of the network in which expression of IL-22 is in homeostasis, it also showed the state of network at which the expression of IL-22 is well regulated in the presence of an etiological agent (HBV, HCV, Excessive Alcohol intake, NASH and others leading to ESLD) that concurs with findings of Immunohistochemical analysis. IL-22 mediates the survival of hepatocytes by increasing the production of pro-survival proteins such as Bcl-xL. This pro-survival role of IL-22 may lead to the destruction of livers own cells therefore, transforming the pro-survival role of IL-22 into pro-cancer. From this study, it can be constituted IL-22 plays a vital role in cellular survival by increasing the production of Bcl-xL (a cellular survival protein) during end stage liver disease .