Effects of resveratrol-mediated inhibition of NOD-like receptor protein 3 inflammasomevia activating silent information regulator 1 on the injury of intestinal mucosal barrier function after sepsis

Abstract

To explore whether resveratrol (RSV) could activate silent information regulator 1 (SIRT1) to regulate the activation of NOD-like receptor protein 3 (NLRP3) inflammasome in sepsis induced intestinal injury model, and then reduce intestinal inflammation and cell apoptosis, so as to play a protective role in intestinal barrier function. (1) In vitro experiment: human Colorectal adenocarcinoma cells (Caco-2) were cultured, which were divided into normal group (normal culture on complete medium for 48 hours), lipopolysaccharide (LPS) group (normal culture on complete medium for 24 hours, then LPS containing 2 mg/L complete medium intervention for 6 hours), RSV low, medium and high concentration groups and SIRT1 inhibitor (EX-527) group (complete medium normal culture for 24 hours, LPS containing 2 mg/L complete medium intervention for 6 hours, followed by RSV 10, 20, 40 μmol/L or EX-527 10 μmol/L intervention for 6 hours, respectively). The levels of tumor necrosis factor-α (TNF-α) and interleukins (IL-6, IL-18, IL-1β) in the cell supernatant were determined by enzyme linked immunosorbent assay (ELISA). The apoptosis level of the cells was detected by flow cytometry. Western blotting was used to detect the protein levels of NLRP3, SIRT1, caspase-1 and apoptosis-related point-like protein (ASC). (2) In vivo experiment: according to random number table method, 24 male Wistar rats were divided into sham operation group (Sham group), cecal ligation and perforation (CLP) 6 hours group (CLP 6 h group), CLP 24 h group and RSV intervention group [RSV (20 mg/kg) was intraperitoneally injected 6 hours and 12 hours after CLP], with 6 rats in each group. The levels of NLRP3, caspase-1 and ASC in the intestine of rats were detected by immunohistochemistry. (1) Compared with the normal group, the levels of inflammatory factors in the cell supernatant of the LPS group were increased and the expression of SIRT1 protein was decreased, while the protein expressions of NLRP3, caspase-1 and ASC were increased. Compared with LPS group, different concentrations of RSV reduced the level of inflammatory factors, increased the activity of SIRT1, inhibited the expression of NLRP3 inflammasome and its downstream products caspase-1 and ASC, and the effect of high concentration of RSV (40 μmol/L) was the most significant [TNF-α (ng/L): 8.77±0.43 vs. 12.66±0.81, IL-6 (ng/L): 1.35±0.20 vs. 1.93±0.09, IL-1β (ng/L): 1.05±0.04 vs. 1.31±0.07, IL-18 (ng/L): 519.50±11.16 vs. 622.70±30.69, SIRT1/β-actin: 0.80±0.05 vs. 0.58±0.02, caspase-1/β-actin: 0.55±0.06 vs. 0.78±0.06, ASC/β-actin: 0.78±0.08 vs. 1.04±0.15, all P < 0.05], while SIRT1 inhibitor EX-527 had the opposite effects. There was no significant difference in the apoptosis rate among normal group, LPS group, and low, medium and high concentration RSV groups, as well as EX-527 group [(7.03±0.57)%, (9.67±0.55)%, (9.57±0.70)%, (9.30±2.15)%, (9.87±0.97)%, (9.07±0.93)%, F = 2.590, P = 0.082]. (2) Immunohistochemical results showed that compared with the Sham group, the expressions of NLRP3 inflammasomes and downstream products caspase-1 and ASC in the intestinal epithelial cells in CLP 6 h group, CLP 24 h group and RSV intervention group were significantly increased. The percentage of ASC-positive area in intestinal epithelium of RSV intervention group was significantly lower than that of CLP 6 h group [(15.22±2.73)% vs. (19.88±2.67)%, P < 0.05], and the expressions of NLRP3 and caspase-1 were significantly lower than those of CLP 24 h group [(9.31±1.37)% vs. (13.19±1.92)%, (19.57±3.92)% vs. (27.28±6.33)%, both P < 0.05]. After sepsis, high concentration of RSV could inhibit the activation of NLRP3 inflammasome by activating SIRT1, thereby reduce the expression of caspase-1 and ASC, and inhibit the secretion of inflammatory factors to reduce the inflammatory response.