Abstract
BACKGROUND: Chromogranin-A produced by epithelial enterochromaffin cells is implicated in the development of ulcerative colitis (UC). In an animal model of UC, the lack of CHGA regulates the plasticity of macrophages and p/53 caspase activation in colitis. Over the last years, progresses have been done in understanding the implications of multiple chromogranin-A derived peptides in several pathologies. In UC and macrophages, the transcription factor X-linked binding protein (XBP1) is a key component of the endoplasmic reticulum (ER) stress response, which induces intestinal mucosal injury and epithelial apoptosis. Intestinal epithelial apoptosis is mediated by p53-apoptotic pathway through the activation of p53-upregulated modulator of apoptosis (PUMA), Bcl-2 associated-X protein (BAX), Bcl-2 associated death promoter (BAD) and Bcl-2 antagonist/killer-1 (BAK1) proteins. Previously, we showed that chromofungin (CHGA47-66; CHR) protects against acute colitis by regulating macrophage-cytokines production. However, the effects of CHR on ER stress/p53-dependent apoptosis in colitis are still unknown. AIMS: We aimed to investigate whether CHR suppress inflammation-induced epithelial apoptosis through ER stress/p53-apoptosis in colitis METHODS: UC-related colitis was induced in C57BL/6 mice (7 weeks) by administering DSS (5%, 5 days). Preventive CHR (2.5 mg/kg/day) or vehicle (Saline) treatments started 1-day before colitis induction and lasted for 5-days. Disease activity index, histologic scores, XBP1, and modulator of apoptosis, PUMA, BAD, BAX, BAK1were quantified using whole colonic sections and q-RT-PCR. Naive peritoneal macrophages were exposed to CHR (200 ng/ml, 2h) or PBS and then to LPS (100 ng/ml, 6h) to promote classically activated macrophages (M1) and the same markers were studied. RESULTS: In colitic conditions, CHR treatment ameliorated the onset and severity of colitis, which was associated with a significant reduction in ER stress/p53-dependent apoptosis as reflected by a significant decrease of Xbp1, Puma, Bad, Bax and Bak1. In vitro, compared to untreated group, LPS-stimulated macrophages treated with CHR demonstrated a significant decrease of Xbp1, Puma, Bad, Bax and Bak1 when compared to LPS PBS-treated macrophages. CONCLUSIONS: CHR decreases the severity of colitis and the inflammatory process via the suppression of mucosal and pro-inflammatory macrophages-related ER stress and p53-dependent apoptosis. Functional analysis of CHGA may lead to a novel therapy for IBD. FUNDING AGENCIES: CCC