Abstract
Background & aims:
Proliferation, differentiation, and morphogenesis of the intestinal epithelium are tightly regulated by a number of molecular pathways. Coordinated action of intestine is achieved by gastrointestinal hormones, most of which exert these actions through G-protein-coupled receptors. We herein investigated the role of Gαq/11-mediated signaling in intestinal homeostasis.
Methods:
Intestinal tissues from control (Gnaqflox/floxGna11+/+ ), Int-Gq knock-out (KO) (VilCre+/-Gnaqflox/floxGna11+/+ ), G11 KO (Gnaqflox/floxGna11-/- ), and Int-Gq/G11 double knock-out (DKO) (VilCre+/-Gnaqflox/floxGna11-/- ) mice were examined by microscopy, transmission electron microscopy, and immunohistochemistry. The effect of Gαq/11-mediated signaling was studied in the cell lineage, proliferation, and apoptosis. Dextran sodium sulfate (DSS) colitis was induced to study the role of Gαq/11 in colon.
Results:
Paneth cells were enlarged, increased in number, and mislocalized in Int-Gq/G11 DKO small intestine. Paneth cells also reacted with PAS and Muc2 antibody, indicating an intermediate character of Paneth and goblet cells. The nuclear β-catenin, T-cell factor 1, and Sox9 expression were reduced severely in the crypt base of Int-Gq/G11 DKO intestine. Proliferation was activated in the crypt base and apoptosis was enhanced along the crypt. Int-Gq/G11 DKO mice were susceptible to DSS colitis. Proliferation was inhibited in the crypt of unaffected and regenerative areas. Cystic crypts, periodic acid-Schiff-positive cells, and Muc2-positive cells were unusually observed in the ulcerative region.
Conclusions:
The Gαq/11-mediated pathway plays a pivotal role in the preservation of intestinal homeostasis, especially in Paneth cell maturation and positioning. Wnt/β-catenin signaling was reduced significantly in the crypt base in Gαq/G11-deficient mice, resulting in the defective maturation of Paneth cells, induction of differentiation toward goblet cells, and susceptibility to DSS colitis.
Keywords:
Atoh1, atonal homolog 1; BrdU, bromodeoxyuridine; DSS, dextran sodium sulfate; Defa1, defensin α1; Dll1, delta-like 1; FGF, fibroblast growth factor; Fzd, frizzled; Gna11; Gnaq; Hes, hairy/enhancer of split; IEC, intestinal epithelial cell; Ihh, Indian hedgehog; Intermediate Cell; NICD, Notch intracellular cytoplasmic domain; PAS, periodic acid–Schiff; PCR, polymerase chain reaction; PKC, protein kinase C; Paneth Cell; TEM, transmission electron micrograph; TUNEL, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling; Tcf, T-cell factor; Wnt; mRNA, messenger RNA; qPCR, quantitative real-time polymerase chain reaction.