Morphological elucidation of short-chain fatty acid receptor GPR41-positive enteric sensory neurons in the colon of mice with dextran sulfate sodium-induced colitis

Although the etiology of inflammatory bowel disease (IBD) remains unclear, it has generally been accepted that abnormalities in the intestinal immune system and dysbiosis of the gut microbiota are involved in the pathology of IBD. Recently, short-chain fatty acids (SCFAs) produced by gut microbiota were reported to maintain intestinal homeostasis through their receptors, such as GPR41. However, there are contradictory reports about the role of GPR41 in intestinal inflammation. Consequently, the roles of GPR41 in dysbiosis induced by intestinal inflammation remain unclear. Thus, we investigated the distribution of GPR41 in the colonic mucosa of mice with dextran sulfate sodium (DSS)-induced colitis. GPR41-immunoreactive fibrous structures were observed in the colonic lamina propria and muscularis layer of normal mice. In addition, GPR41-immunoreactive fibrous structures partly colocalized with calcitonin gene-related peptide (CGRP; a neurotransmitter of cholinergic enteric sensory neurons)-immunoreactive nerve fibers in the colonic lamina propria, indicating that GPR41 is expressed in cholinergic intrinsic sensory neurons. Furthermore, both GPR41-immunoreactivities and CGRP-immunoreactivities were significantly increased in the lamina propria of the colon in mice with DSS-induced colitis. Interestingly, GPR41-immunoreactivities were often found in close proximity to F4/80(+) macrophages in the colonic mucosa of normal mice, and their frequency was elevated in the colonic mucosa of mice with DSS-induced colitis. Therefore, the crosstalk between SCFA-sensing intrinsic sensory neurons and macrophages might be involved in the pathology of acute colitis.