Down-regulation of galectin-3 in the pathogenesis of intestinal Behçet’s disease : implication of proteomics and functional studies

Abstract

Background: Although intestinal Behçet’s disease (BD) has an unpredictable disease course with exacerbations and remission like inflammatory bowel disease (IBD), data concerning diagnosis, treatment, and prognosis are yet to be determined and the pathogenesis of intestinal BD are poorly understood. Therefore, we aimed to discover biomarkers by investigating the differentially expressed proteins in the intestinal tissues from patients with intestinal BD using proteomics analysis and validate the markers associated with disease pathogenesis by functional studies. Methods: Intestinal tissue samples were obtained from intestinal BD patients who underwent surgery due to disease exacerbation for the screening study. Two-dimensional electrophoresis (2-DE) was performed to characterize the total proteins of intestinal BD patients. Candidate protein spots were identified using matrix-assisted laser desorption/ionization tandem time-of-flight (MALDI-TOF/TOF) and bioinformatics analysis. Various in vitro and in vivo functional validation studies were applied to validate the results of 2-DE and MS. Results: Proteomic profiles of tissue samples were compared, and approximately 550 protein spots were observed in each of the gels. Mass spectrometric analysis identified seven differentially expressed proteins in intestinal BD patients, of which 4 proteins were up-regulated including heat shock protein 27, transgelin, manganese superoxide dismutase, and calprotectin, and 3 were down-regulated including heat shock protein 60, selenium binding protein, and galectin-3. In the inflamed mucosa of intestinal BD patients, galectin-3 expressions were reduced compared with controls, which was consistent with the proteomic results. The mRNA expressions of anti-inflammatory cytokines, such as TGFB and IL10, were markedly decreased in shGal-3 cell lines. Moreover, caspase-1 activation and IL-1β production were significantly increased in galectin-3-/- BMDMs compared with WT BMDMs upon S.typhimurium infection which facilitates the activation of NLRC4 inflammasome. In addition, epithelial cell death rate was increased in shGal-3 cell lines, along with that XBP1s are decreased and GRP78 was increased in shGal-3 HT-29 cells compared with control cells. Conclusions: A distinct proteomic profile of the intestinal tissues in intestinal BD patients was found that 4 up-regulated and 3 down-regulated proteins were identified and galectin-3 expressions were decreased in the inflamed mucosa of intestinal BD patients. Anti-inflammatory cytokine productions were decreased and NLRC4 inflammasomes were activated by down-regulating galectin-3. In addition, galectin-3 was associated with autophagy-induced cell death. Our data indicate that galectin-3 might play a protective role in the pathogenesis of intestinal BD.