S1P2 Reduces Mast Cell Activation and Colonic Inflammation of L-Arginine-Induced Acute Pancreatitis.

backgroundAcute pancreatitis (AP) is a serious pancreatic disorder and colonic inflammation is involved in the progression of AP. However, the role of mast cells in the regulation of colonic inflammation in AP has been less studied; thus, we explored the role of mast cells in the regulation of colonic inflammation.

methodsAn AP model was established by intraperitoneal injection of L-arginine or caerulein. Colonic inflammation in AP was tested using H&E staining. The mRNA levels were quantified using qRT-PCR. The protein level of sphingosine-1-phosphate receptor 2 (S1P2) was quantified using western blotting or immunohistochemistry. The gut microbiota was analyzed using 16S rRNA sequencing.

resultsThe Western blot analysis revealed that S1P2 expression was decreased by 0.63-fold in L-arginine-AP-induced colonic inflammation. Ketotifen, a second-generation H1-antihistamine and mast cell stabilizer, increased the survival rate (90%) in the L-arginine-AP model and increased the mRNA level of S1P2 by 1.33-fold and protein expression by 1.47-fold, suggesting that ketotifen inhibited mast cell activation through the S1P2 pathway. Similarly, treatment with the S1P2 agonist CYM-5520 in the L-arginine-AP model did not result in death and decreased the proportion of mast cells in the spleen by 1.58-fold. Moreover, gut microbiome analysis revealed that the abundance of proteobacteria decreased in L-arginine-AP mice pretreated with CYM-5520. In vitro experiments revealed a 2.1-fold decrease in S1P2 expression following mast cell stimulation, and the absence of S1P2 promoted mast cell degranulation.

conclusionThis study provides evidence that S1P2 can ameliorate colonic inflammation in an L-arginine-induced AP mouse model by inhibiting mast cell activation.