The Role Of Pyruvate Kinase M2 In Intestinal Epithelial Cells During The Development Of Inflammatory Bowel Diseases

Inflammatory bowel diseases(IBD)are chronic relapsing inflammatory disorders that affect the entire gastrointestinal tract.Due to its unclarified pathogenic mechanisms,IBD cannot be cured entirely,and may cause colitis-related tumors.In the early years,IBD mainly occurred in developed countries.Nowadays,the incidence rate in China has increased rapidly,becoming one of the most imminent challenges.In the face of this critical issue,researchers need to explore the pathogenic factors behind IBD in extenso to improve the diagnosis,treatment and prognosis of IBD.Pyruvate kinase(PK)is a key rate-limiting enzyme in glycolysis.It is mainly responsible for converting enolpyruvate to pyruvate,boosting energy production.Pyruvate kinase exists in multiple isoforms,among which the most important one is PKM(1 and 2).Many studies have shown that PKM2 is involved in cell proliferation,survival and drug resistance as well as other related aspects: PKM2 possess two molecular configurations,a dimeric form of low pyruvate kinase activity and a tetrameric form of high pyruvate kinase activity,and PKM2's differentiated function from PKM1 is mainly endowed by its dimer.Due to the presence of PKM2 dimers,PKM2 has different new biological functions.Recently,enhanced levels of PKM2 were found in the feces and sera from patients with active IBD and the detection of this cell-free PKM2 was correlated with the severity of intestinal inflammation..The suppression of PKM2 in intestinal macrophages can protect the occurrence of colitis.Howerver,the role of PKM2 in intestinal epithelial cells during the development of inflammatory bowel diseases remains unclear.Thus,this paper aims to reveal the mechanisms of PKM2 in intestinal epithelial cells in IBD and to further illustrate the biological significance of PKM2's high-expression presence in intestinal epithelial cells.When researching PKM2's role in intestinal epithelial cells,we found that the expression of PKM2 protein was largely deficient in intestinal epithelial cells in a mouse colitis model and in those of patient tissues.We further discovered that 2-DG and Shikonin can advance disease development on mouse colitis model.The Cre-Loxp system was subsequently used to construct the intestinal epithelial-specific Knockout of PKM2 mice.The experiment on DSS-induced colitis model showed that the structure of intestinal barrier in Pkm2 knockout mice was significantly impaired and its cell proliferation were inhibited.RANseq result showed that the Wnt/?-catenin signaling pathway was substantively curbed in Pkm2-specific knockout mice.Based on the above-mentioned findings,we utilized the rat intestinal epithelial cells IEC-6for a series of in vitro experiments,and through co-immunoprecipitation experiment,we discovered that PKM2 interacts directly with ?-catenin,which indicates that PKM2 may exert effects on the response mechanism of intestinal epithelial cells by interacting with ?-catenin.Our study further indicates that cell proliferation and repairment were to a large extend suppressed as a result of PKM2 inhibition performed by RNAi technology.The use of overexpression plasmid can enhance the process of cell proliferation and repairment,while Pkm2 overexpression plasmid lost its promoting effect on cell proliferation after introducing ?-catenin.After using the polyethylenimine(PEI)to transfer the Pkm2 plasmid into the mouse colon,PKM2's protective role in the DSS-induced colitis model was then discovered.To summarize,PKM2's high expression in intestinal epithelial cells can contribute to the protection of intestinal tract through interacting with ?-catenin,and a decrease in PKM2 level may lead to colitis.Our results reveal and demonstrate the crucial functions of PKM2 in the development of colitis and shed light on a brand-new strategy for IBD treatment and prevention.