Altered expression of inflammasomes in Hirschsprung's disease.

AIM OF THE STUDY: The pathogenesis of Hirschsprung's disease-associated enterocolitis (HAEC) is poorly understood. Inflammasomes are a large family of multiprotein complexes that act to mediate host immune responses to microbial infection and have a regulatory or conditioning influence on the composition of the microbiota. Inflammasomes and the apoptosis-associated speck-like protein (ASC) lead to caspase-1 activation. The activated caspase-1 promotes secretion of pro-inflammatory cytokines (IL-1β and IL-18) from their precursors (pro-IL-1β and pro-IL-18). Inflammasomes have been implicated in a host of inflammatory disorders. Among the inflammasomes, NLRP3, NLRP12 and NLRC4 are the most widely investigated. Knock-out mice models of inflammasomes NLRP3, NLRP12, NLRC4, caspase-1 and ASC are reported to have higher susceptibility to experimental colitis. The purpose of this study was to investigate the expression of NLRP3, NLRP12, NLRC4, caspase-1, ASC, pro-IL-1β and pro-IL-18 in the bowel specimens from patients with HSCR and controls.

METHODS: Pulled-through colonic specimens were collected from HSCR patients (n = 6) and healthy controls from the proximal colostomy of children with anorectal malformations (n = 6). The gene expression of NLRP3, NLRP12, NLRC4, caspase-1, ASC, pro-IL-1β and pro-IL-18 was assessed using qPCR. The protein distribution was assessed using immunofluorescence and confocal microscopy.

MAIN RESULTS: qRT-PCR analysis revealed that NLRP3, NLRP12, NLRC4, ASC and pro-IL-1β gene expressions was significantly downregulated in the aganglionic and ganglionic colon of patients with HSCR compared to controls. Confocal microscopy revealed a markedly decreased expression of NLRP3, NLRP12, NLRC4 and ASC protein in the colonic epithelium of aganglionic and ganglionic bowel of patients with HSCR compared to controls.

CONCLUSIONS: To our knowledge, this is the first study analyzing NLRP3, NLRP12, NLRC4, ASC and pro-IL-1β gene expressions in patients with HSCR. Decreased expression of NLRP3, NLRP12, NLRC4, ASC and pro-IL-1β in the aganglionic and ganglionic bowel may increase susceptibility of HSCR patients to develop HAEC.