Role of Guanylate‐binding Protein 5 in Colonic Inflammation

Abstract

Background & Aim： Guanylate-binding protein 5 (GBP5) is an essential component of cell-autonomous immune responses against microbial infection. Here we investigated the potential roles for GBP5 in the pathogenesis of inflammatory bowel diseases (IBD) including Crohn's disease (CD) and ulcerative colitis (UC). Method Colon tissues were collected from IBD patients at the Sixth Affiliated Hospital of Sun Yat-sen University, Guangzhou, China. Colitis mice were obtained by feeding male C57BL/6 mice with 2.5% dextran sulfate sodium (DSS) water for 7days. Global gene expression profiles in the colonic mucosa of CD and UC were examined with our microarray dataset GSE16879. Individual gene and protein expression were analyzed by quantitative real-time PCR (qPCR) and Western blot, respectively. Gene enrichment analysis was performed with WEB-based Gene Set Analysis Toolkit (WebGestalt). Immunohistochemistry and three-color immunofluorescence were performed to examine the tissue and cellular localization of GBP5. Three GBP5 specific siRNA were used to transfect THP-1 and Jurkart T cells to investigate the cellular function of GBP5. Result Both immunohistochemistry and immunofluorescence analyses indicated that GBP5 was only expressed in immune cells including T lymphocytes, B lymphocytes and macrophages, in the mucosa and the germinal center of the intestine, More GPB5 positive cells were observed in areas with more severe inflammation from the same patient. Consistently, highly elevated GBP5 expression was observed in the colonic mucosa of IBD patients and DSS induced colitis mice, In addition, the expression level of GBP5 returned to normal levels in the responders after infliximab treatment, but remained elevated in the non-responders (Figure 1). From our transcriptome dataset, genes correlated with GBP5 were identified, and these genes were enriched in myeloid leukocyte activation and immune effector process, In line with this, GBP5 knockdown with siRNA in THP-1 and Jukart T cell line led to the decreased expressions of TNFα, IFNG, IL-8, IL-18, CASP2, NLRP1 and NLRP4 (Figure 2). Discussion Our observations demonstrated that GBP5 participated in IBD pathogenesis, The role of GBP5 in IBD may involve the regulation of immune cells and cytokines, Since GBP5 is a microbial sensor, our study may supply a novel link between the host and gut microbiota in the pathogenesis of IBD. Future effort will use the intestinal gbp5-/- conditional knockout mouse model to define the exact role of GBP5 in IBD.