The Effect Of Chemerin On The Inflammatory Microenvironment Of Inflammatory Bowel Disease (IBD) And Hepatocellular Carcinoma

Inflammatory bowel disease (IBD) is a group of diseases characterized by chronically recurrent episodes of intestinal inflammation, and includes ulcerative colitis (UC) and Crohn’s disease (CD). IBD is fairly commn in western countries,the prevalence rate is 100-200/100000.In the past 10 years,the incidence of IBD has an increase of about 10-20 times in China. Given the serious harm and higher malignant transformation probability in IBD,extensive attention has been paid to explore the pathogenesis of IBD.The exact pathogenesis of IBD is poorly understood until now.The etiology of IBD is complex, and includes genetic susceptibility, environmental factors,and abnormal mucosal immune responses to antigenic material in the gut, such as the symbiotic bacteria.Most of the current therapies for IBD involve treatment with glucocorticosteroids and 5-aminosalicylic acid;however,they display limited beneficial action. Immunosuppressive drugs have also been used to control severe illness, regardless of the more serious complications and toxic side effects associated with them. So it is important for studies on immune-pathogenesis of IBD. Although the etiology of IBD remains unknown, there is circumstantial evidence to link IBD to the mucosal immune system’s failure to attenuate immunity to luminal antigens.In antigen-induced inflammatory,lymphocyte hyper-reactivity was considered to play a major role in the development of the disease. In antigen-induced colitis,lymphocytes activated and differentiated to effector cells in the lamina propria or in mesenteric lymph nodes.The signaling lymphocyte activation molecule family of receptors and their associated signaling adaptors play a pivotal role in the regulation of cellular immunity. Dysfunction of lymphocyte-related molecules resulted in immunodeficiency, breakdown of tolerance, abnormal lymphocyte development and leading to inflammation.Chemerin is present in various inflammatory sites and closely involved in tissue inflammation. Recent studies have demonstrated that chemerin treatment could cause either anti-inflammatory or pro-inflammatory effects according to the disease model investigated. Elevated circulating chemerin was recently found in patients with inflammatory bowel disease (IBD), however, the role of chemerin in intestinal inflammation remains unknown. In this study we demonstrated that the administration of exogenous chemerin (aa17-156) aggravated the severity of dextran sulphate sodium (DSS)-induced colitis, which was characterized by higher clinical scores, extensive mucosal damage and significantly increased local and systemic production of pro-inflammatory cytokines including IL-6, TNF-a and IFN-y. Interestingly, chemerin appeared not to influence the magnitudes of inflammatory infiltrates in the colons, but resulted in significantly decreased colonic expression of M2 macrophage-associated genes including Arginase 1 (Arg-1), Yml, FIZZ1 and IL-10 following DSS exposure, suggesting an impaired M2 macrophage skewing in vivo. Furthermore, the in vitro experiment showed that the addition of chemerin directly suppressed M2 macrophage-associated gene expression and STAT6 phosphorylation in IL-4-stimulated macrophages. Significantly elevated chemerin levels were found in the colons from DSS-exposed mice and UC patients, and appeared to positively correlate with disease severity. Moreover, in vivo administration of neutralizing anti-chemerin antibody significantly improved intestinal inflammation following DSS exposure. Taken together, our findings reveal a pro-inflammatory role of chemerin in DSS-induced colitis and the ability of chemerin to suppress anti-inflammatory M2 macrophage response. Our study also suggests that up-regulated chemerin in inflamed colons may contribute to the pathogenesis of IBD.Cancer is still a major public health problem in most parts of the world, although tremendous progress on cancer molecular biology and treatment has achieved. Hepatocellular carcinoma (HCC, also called malignant hepatoma) is is one of the most prevalent human malignant tumors worldwide. HCC is the fifth most common malignancy and the third leading cause of cancer-related death worldwide. China is a high incidence region of liver cancer. Half the newly diagnosed HCC patients are in China, especially the down-country.Thus exploration of the underlying mechanisms of HCC carcinogenesis and development is needed to provide theoretical basis for future clinical applications.HCC is usually hard to be observed at the early stage. However, when obvious symptoms show up, the prognosis is generally poor due to tumor progression.Although the surgery and liver transplantation provided valid approaches for HCC, the 5-years recurrence rate are always up to 54.1-61.5%,of which 62.4-77.8% occurred in the first two years after resections and it will lead to the poorer prognosis because of tumor invasiveness,frequent intrahepatic spread and extrahepatic metastasis.The vast majority of previous studies focused solely on malignant cells themselves, regarding tumors just as masses of autonomous cells and aiming at identifying the molecular and genetic changes associated with this malignant transformation. Reeently,accumulating evidences indicated that tumor cells loeated in a complex microenvironment consisted of immune cells,matrix cells,vascular endothelial cells,cytokines and chemokines which were called "tumor microenvironment". A malignant cycle of inflammation and renovation promotes oncogenesis.With regard to HCC,most lesions develop in a milieu of chronic inflammation produced by hepatitis B or C viruses as well as dysregulated cellular proliferation due to cirrhosis. As an important part of tumor microenvironment, immune microenvironment plays a critical role in carcinogenesis, metastatic invasion and dissemination.The inflammatory microenvironment of hepatocellular carcinoma is mainly consist of immune cells,strmal cells and a variety of inflammatory molecules.In the process of the occurrence and development of liver cancer,multiple immunosuppressive factors play an important role.Among of these factors, the recruiting, activation and amplification of immunosuppressive cells are the important facors that promote tumor progression.Immunosuppressive cells including regulatory T cells and a variety of myeloid-derived cells.The most important two types of myeloid-derived cells that inhibit immunoreaction are tumor-associated macrophage (TAM) and myeloid-derived suppressor cells (MDSC).MDSC can be divided into two classes:one is neutrophils-like MDSC (PMN-MDSC) and the other is monocyte-like MDSC (M-MDSC).TAM has the largest number of myeloid-derived cells in tumor microenvironment and has the phenotype of M2.The tumor microenvironment has high level expression of various inflammatory mediators,they could induce the MDSC and TAM activation,and play an important role in the process of MDSC and TAM migrating to the tumor tissue.Chemerin is a kind of newly discovered chemokines in recent years,also called Tazarotene-induced gene 2 (TIG2) or Retinoic acid receptor responder 2 (RARRES2). Chemerin plays an important role in inflammation and metabolism.Although Chemerin is firstly isolated from the ascite of ovarian cancer or hepatoma patients,the research reports of its role in the tumor genesis and development is still very little so far. Pachynski R et al report that Chemerin could inhibit melonoma growth by promoting the infiltration of NK cells into tumors tissue.The role of Chemerin in hepatocellular carcinoma and its mechanism has not been reported so far, our study has explored the role of Chemerin in the occurrence and development of hepatocellular carcinoma and its possible mechanisms.In the first section of this study, we collected cancer tissues and adjacent tissues from hepatocellular carcinoma patients,and then detected the expression changes of Chemerin in tumor tissues by immunohistochemistry.We found that the expression of Chemerin is remarkable reduced in tumor tissue compared with the tissue adjacent to carcinoma. We use tissue microarray combined with clinical follow-up data to confirm that the expression of Chemerin is negatively correlated with the malignant degree of hepatocellular carcinoma and positively related with prognosis.By testing the expression level of Chemerin in different hepatoma cell lines with various invasive ability as well as liver cancer tissue cells and adjacent tissues cells,we found that the expression levels are decreased along with increasing ability of cell metastasis, suggesting that Chemerin is negatively correlated with metastasis.In the second section of this study, We used two kinds of mouse hepatoma cell lines that stable transfected with Chemerin gene to establish two kinds of hepatocellular carcinoma modle,the one modle is subcutaneous transplanted tumor modle of mouse hepatocellular carcinoma,the other is orthotopic transplated tumor model of mouse hepatocellular carcinoma. We found that overexpression of Chemerin could significantly inhibit the occurrence and development of tumor in either of the two kinds of hepatocellular carcinoma modle.In the thirdly section of this study,we found that overexpression of Chemerin does not affect the proliferation, apoptosis, cell cycle and recruitment of Hepal-6. We have tested the proportion of immune cells that infiltrated into tumor tissue. We found that overexpression Chemerin could increase the infiltration of CD45+ leukocytes, CD4+ T cells and CD8+ T cells and could reduce the proportion of macrophages,M2 cells and PMN-MDSCs,but has no effect on NK cells.In the fourth section of this study, we found that overexpression of Chemerin does not affect the proliferation and recruitment of monocyte-like MDSC but inhibit monocyte-like MDSC differentiate into neutrophile-like MDSC.More detailed mechanisms of the inhibition role of Chemerin exert on hepatocellular carcinoma occurrence and development is still need a lot of work to further study.