Abstract
Background. NLRP3 inflammasome is a multiprotein complex involved both in maintaining intestinal homeostasis and shaping immune responses during bowel inflammation. In particular, NLRP3 recruits and activates caspase-1, leading to interleukin-(IL)-1beta release, a key cytokine involved in the pathophysiology of intestinal inflammation. Drugs able to block NLRP3 signaling could represent an innovative strategy to treat bowel inflammation. This study examined how the direct blockade of NLRP3 with a selective irreversible inhibitor, compares, in term of efficacy, with drugs acting downstream to NLRP3 signaling (i.e. caspase-1 inhibitor and IL-1beta receptor antagonist).
Methods. The effects of INF39 (selective NLRP3 inhibitor), Ac-YVAD-cmk (YVAD, caspase-1 inhibitor), anakinra (IL-1beta receptor antagonist) and dexamethasone (DEX, used as a standard comparator) were tested in male rats (n=6 for group), with colitis induced by intrarectal administration of 2,4-dinitrobenzenesulfonic acid (DNBS, 15 mg/rat), to assess systemic (body and spleen weight) and tissue inflammatory parameters (macroscopic and microscopic damage, tumor necrosis factor [TNF], IL-1beta and myeloperoxidase [MPO] levels). Animals received YVAD or anakinra intraperitoneally, while INF39 or DEX were given orally, starting on the same day of colitis induction.
Results. Colitis was associated with a decrease in body weight and an increase in spleen weight. The macroscopic and microscopic damage scores, as well as tissue TNF, IL-1beta and MPO levels were increased. Treatment with NLRP3 signalling inhibitors, but not DEX, improved body weight. INF39 and DEX counteracted the increase in spleen weight and ameliorated the macroscopic and microscopic damage scores, more effectively than YVAD and anakinra. The increased colonic MPO levels were counteracted by all test drugs, although YVAD and anakinra were less effective. Only INF39 and DEX reduced the increased colonic TNF levels, and they elicited a greater reduction of IL-1beta release than anakinra and YVAD. Data regarding the effects of test drugs are displayed in the table.
Conclusions. Selective and direct NLRP3 blockade is more effective than caspase-1 inhibition and IL-1beta receptor blockade in reducing systemic and intestinal inflammatory alterations. These findings suggest that the direct inhibition of NLRP3 may represent a better therapeutic strategy for treatment of bowel inflammatory disorders than drugs acting downstream on the NLRP3 pathway.
