Slco2a1 deficiency exacerbates experimental colitis via inflammasome activation in macrophages: a possible mechanism of chronic enteropathy associated with SLCO2A1 gene

Rieko Nakata,Koji Otani,Shuhei Hosomi,Yoshinobu Nakamura,Toshio Watanabe,Yasuaki Nagami,Yasuhiro Fujiwara,Yu Nishida,Fumio Tanaka,Shigehiro Itani,Hiroaki Okuda,Yuji Nadatani,Noriko Kamata,Tetsuya Tanigawa,Hirokazu Yamagami,Naoko Sugita,Takeo Nakanishi,Koichi Taira

doi:10.1038/s41598-020-61775-9

Abstract

Loss-of-function mutations in the solute carrier organic anion transporter family, member 2a1 gene (SLCO2A1), which encodes a prostaglandin (PG) transporter, have been identified as causes of chronic nonspecific multiple ulcers in the small intestine; however, the underlying mechanisms have not been revealed. We, therefore, evaluated the effects of systemic knockout of Slco2a1 (Slco2a1−/−) and conditional knockout in intestinal epithelial cells (Slco2a1ΔIEC) and macrophages (Slco2a1ΔMP) in mice with dextran sodium sulphate (DSS)-induced acute colitis. Slco2a−/− mice were more susceptible to DSS-induced colitis than wild-type (WT) mice, but did not spontaneously develop enteritis or colitis. The nucleotide-binding domain, leucine-rich repeats containing family, pyrin domain-containing-3 (NLRP3) inflammasome was more strongly upregulated in colon tissues of Slco2a−/− mice administered DSS and in macrophages isolated from Slco2a1−/− mice than in the WT counterparts. Slco2a1ΔMP, but not Slco2a1ΔIEC mice, were more susceptible to DSS-induced colitis than WT mice, partly phenocopying Slco2a−/− mice. Concentrations of PGE2 in colon tissues and macrophages from Slco2a1−/− mice were significantly higher than those of WT mice. Blockade of inflammasome activation suppressed the exacerbation of colitis. These results indicated that Slco2a1-deficiency increases the PGE2 concentration, resulting in NLRP3 inflammasome activation in macrophages, thus exacerbating intestinal inflammation.

Highlights

Loss-of-function mutations in the solute carrier organic anion transporter family, member 2a1 gene (SLCO2A1), which encodes a prostaglandin (PG) transporter, have been identified as causes of chronic nonspecific multiple ulcers in the small intestine; the underlying mechanisms have not been revealed
These results demonstrated that Slco2a1 deficiency per se does not induce intestinal inflammation
We focused on the role of the NLRP3 inflammasome in the exacerbated colitis in Slco2a1−/− mice. mRNA expression of pro-inflammatory cytokines in colon tissues as assessed by RT-qPCR was increased in Slco2a1−/− compared to WT mice on days 3 and 7 of dextran sodium sulphate (DSS) treatment (Fig. 3a)., Casp[1] mRNA expression was decreased (Fig. 3b), protein levels of pro- and cleaved IL-1β, cleaved caspase-1 (CASP1), and NLRP3 were significantly elevated in Slco2a1−/− compared to WT mice with colitis (Fig. 3c, Supplementary Fig. S3)