IL-17A Mediated Enhanced Pmn Transmigration Under Inflammatory Conditions.Role Of MiR-150-targeting C-myb In Colonic Epithelial Disruption During Murine And Human Ulcerative Colitis

My doctoral work includes two projects:"IL-17A mediated enhanced PMN transmigration under inflammatory conditions" and "Role of miR-150-targeting c-Myb in colonic epithelial disruption during murine and human ulcerative colitis"Neutrophil (polymorphonuclear leukocyte PMN) plays a central role in inflammation and is a major cause of tissue damage. The mechanisms that control PMN response and regulate their infiltration involve multiple cell types and various inflammatory factors, studies in this area are still inadequate. In our study, we first developed multiple murine inflammatory diseases such as DSS-induced colitis, STZ-induced diabetes, LPS-induced lung inflammation and complete adjuvant-induced chronic inflammation. After all the mice developed inflammatory diseases, we induced peritonitis on these mice already under inflammatory conditions and assay the transmigration of PMN during peritonitis. We show in this study that PMN response and infiltration were significantly enhanced in mice experiencing various types of systemic inflammation, including colitis and diabetes. Adoptive transfer of leukocytes from mice with inflammation into healthy recipients or from healthy into inflammatory recipients followed by inducing peritonitis demonstrated that both circulating PMN and tissue macrophages were altered under inflammatory conditions and that they collectively contributed to enhanced PMN infiltration. Detailed analyses of DSS-induced colitis revealed that enhancement of PMN infiltration and macrophage function only occurred at the later stage of inflammation and was associated with markedly increase IL-17A in blood serum. In vitro and ex vivo treatment of isolated PMN and macrophage confirmed that IL-17A directly modulates these cells and significantly enhances their inflammatory responses. Neutralization of IL-17A eliminated the enhancement of PMN infiltration and IL-6production and also prevented severe tissue damage in DSS-treated mice. Thus, IL-17A produced at the chronic stage of colitis serves as an essential feedback signal that enhances PMN infiltration and promotes inflammation.In the last study we demonstrated that IL-17A mediated enhanced PMN infiltration and caused severe tissue damage at the late stage of colitis. However, the mechanisms of the pathophysiology of ulcerative colitis are still incompletely understood. Ulcerative colitis, as one kind of inflammatory bowel diseases, is induced by inflammatory dysfunction in the gastrointestinal tract. This process includes the gene, environment factors and disruption of intestinal mucosal barrier function, which associated with the regulation of the immune and tissue repairing-related gene expression. MicroRNAs are a class of non-coding RNAs consisting of approximately22nucleotides in length. They have recently emerged as a new regulator of gene expression and are reported to play an important role in the pathology of different diseases. In our study, we surveyed the expression profile of apoptosis-related microRNA by real-time quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) in DSS induced murine colitis. We found that miR-150was strongly elevated, whereas c-Myb, a transcription factor and a target gene of miR-150, was significantly reduced in colon tissue after DSS treatment. Interestingly, elevation of miR-150and down regulation of c-Myb was also observed in human colon with active ulcerative colitis compared to the normal colon. Supporting the observation of DSS treatment inducing colonic cell apoptosis, Bcl-2, an anti-apoptotic protein known to be regulated by c-Myb, was reduced in colon tissue of DSS-treated mice. Furthermore, forced expression of pre-miR-150in colonic epithelial HT-29cells strongly elevated miR-150levels and decreased c-Myb and Bcl-2levels, thus enhancing cell apoptosis induced by serum deprivation. Together, the present study presents the first evidence that miR-150and its targeting of c-Myb may serve as a new mechanism underlying the colonic epithelial disruption in DSS-induced murine experimental colitis and in active human ulcerative colitis.