BLT1 in dendritic cells promotes Th1/Th17 differentiation and its deficiency ameliorates TNBS-induced colitis

Leukotriene B4(LTB4)synthesis is enhanced in the colonic mucosa in patients with inflammatory bowel disease(IBD).BLT1,a highaffinity receptor for LTB4,exhibits no effect on the progression of dextran sodium sulfate(DSS)-induced colitis,which mostly relies on innate immunity.Here,we reported that BLT1 regulates trinitrobenzene sulfonic acid(TNBS)-induced colitis,which reflects CD4+T-cell-dependent adaptive immune mechanisms of IBD.We found that BLT1 signaling enhanced the progression of colitis through controlling the production of proinflammatory cytokines by dendritic cells(DCs)and modulating the differentiation of Th1 and Th17.BLT1−/−mice displayed an alleviated severity of TNBS-induced colitis with reduced body weight loss and infiltrating cells in the lamina propria.BLT1 deficiency in DCs led to reduced production of proinflammatory cytokines,including IL-6,TNF-α,and IL-12,and these results were further confirmed via treatment with a BLT1 antagonist.The impaired cytokine production by BLT1−/−DCs subsequently led to reduced Th1 and Th17 differentiation both in vitro and in vivo.We further performed a conditional DC reconstitution experiment to assess whether BLT1 in DCs plays a major role in regulating the pathogenesis of TNBS-induced colitis,and the results indicate that BLT1 deficiency in DCs also significantly reduces disease severity.The mechanistic study demonstrated that BLT1-regulated proinflammatory cytokine production through the Gαiβγsubunit-phospholipase Cβ(PLCβ)-PKC pathway.Notably,we found that treatment with the BLT1 antagonist also reduced the production of proinflammatory cytokines by human peripheral blood DCs.Our findings reveal the critical role of BLT1 in regulating adaptive immunity and TNBS-induced colitis,which further supports BLT1 as a potential drug target for adaptive immunity-mediated IBD.

Deficiency of the G protein Gαq ameliorates experimental autoimmune encephalomyelitis with impaired DC-derived IL-6 production and Th17 differentiation

Many G protein-coupled receptors （GPCRs） are reported to be involved in the pathogenesis of multiple sclerosis （MS）, and -40% of all identified GPCRs rely on the Gaq/11 G protein family to stimulate inositol lipid signaling. However, the function of Ga subunits in MS pathogenesis is still unknown. In this study, we attempted to determine the role of Gaq in the pathogenesis of experimental autoimmune encephalomyelitis （EAE）, a well-known mouse model of MS. We discovered that compared with wild-type mice, Gaq-knockout mice exhibited less severe EAE symptoms, with lower clinical scores, reduced leukocyte infiltration and less extensive demyelination. Moreover, a significantly lower percentage of Th17 cells, one of the key players in MS pathogenesis, was observed in Gaq-knockout EAE mice. Studies in vitro demonstrated that deficiency of Gaq in CD4＋ T cells directly impaired Th17 differentiation. In addition, deficiency of Gaq significantly impaired DC-derived IL-6 production, thus inhibiting Th17 differentiation and the Gaq-PLCβ-PKC and Gaq-MAPKs signaling pathways involved in the reduced IL-6 production by DCs. In summary, our data highlighted the critical role of Gaq in regulating Th17 differentiation and MS oathogenesis.