Abstract Background Expression of the antiapoptotic molecule, MCL1 has been detected in fibrotic intestine of both ileum of Crohńs disease patients1 and murine chronic colitis2. We analyse here the effects of blocking mcl1 on inflammation and fibrosis in murine acute and chronic colitis, on the intestinal expression of autophagy markers and on the leukocyte adhesion to the endothelium Methods C57Bl/6 mice underwent 1 DSS cycle (17 days) or 2DSS cycles (34 days) and in both cases, they were administered with vehicle or S63845 (25 mg/kg, i.p. 5days/week), during the whole protocol. RNA was isolated and gene expression of pro-inflammatory cytokines, and profibrotic markers was quantified by qPCR. A sample from the colon was paraffin embedded for the analysis of collagen deposition, quantified by the QuPath® software in Syrius Red stained slides. Protein expression of autophagy markers (p62 and LC3II/I Ratio) and apoptosis (BAX) were analyzed by Western Blot and quantified by Image J®. The effects of a single dose of S63845 (25 mg/kg, ip; 4 h before TNFα) on leukocyte adhesion to the endothelium induced by TNFα (500ng/mouse, i.p) were analysed in vivo in the mouse cremaster muscle via intravital microscopy and the expression of cd11b and cd18 were determined by flow cytometry. Results The mRNA expression of inflammatory cytokines (il1b, tnfα), chemokines (cxcl1, cxcl3) and tgfβ increased in the colon of DSS- compared with non-DSS-treated mice (naïve), and it was significantly higher in samples obtained from 2DSS cycles than in those with 1 DSS cycle (Table 1). In DSS-treated mice, the administration of S63845 compared with Vh: a) reduced the expression of inflammatory cytokines and chemokines in mice underwent 1 and 2 DSS cycles (Table 1); b) it did not alter the thickness of submucosa collagen layer (27.8 (24.6-28.7) vs 25.8 (22.2-35.4) at day 17, but it significantly did at day 34 (19.6 ± 1.7 vs 42.4 ± 3.2*); and c) diminished the protein expression of p62 and LC3II/I Ratio (0.3 (0.3-0.5) vs 0.8 (0.4-1.0)# and 0.7 ± 0.1 vs 0.9±0.05, P = 0.053), respectively, and BAX (0.6 (0.4-0.9 vs 1 (0.7-1.3), P = 0,0553) at day 34. In mice treated with TNFα, a single dose of S63845 significantly prevented the adhesion of leukocytes to the endothelium compared with Vh (1.8±0.8 and 13.5±3.8 leukocytes, respectively, P = 0.0223) and it significantly reduced the expression of cd11b (93302.7±4920 u.a vs 75235.5± 3867 u.a, P = 0.0203* respectively) while not that of cd18 in neutrophils (Ly6G+ cells). Conclusion The systemic administration of the MCL1 inhibitor, S63845 decreased the adhesion of neutrophils to the endothelium and exerts an anti-inflammatory effect in murine colitis which is associated with the prevention of both the inhibition of autophagy and intestinal fibrosis. References: 1. Seco-Cervera M et al Biochim Biophys Acta Mol Basis Dis. 2024 Feb;1870(2):166966BBA 2. Jarén, A et al UEG 2025 poster communication *t-test; #Mann-Whitnney; Conflict of interest: Jarén, Ana: Nothing to disclouse Macias Ceja, Dulce Carolina: No Burgos, Rebeca: No conflict of interest Lidón-Aguilella, Isabel: No conflict of interest Patel, Jalpa: No conflict of interest Cejudo-Garcés, Andrea: Nothing to disclosure Cosín-Roger, Jesús: No conflict of interest Prof. Dr. Ortiz-Masiá, Dolores: No conflict of interest
Jarén et al. (Thu,) studied this question.