Indian Journal Of Pharmacology
This study aimed to evaluate the antidiarrheal efficacy and pharmacological properties of ethyl 2-(4-oxo-3-o-tolyl-3,4-dihydroquinazolin-2-ylthio)acetate (DQA) as an inhibitor of cystic fibrosis transmembrane conductance regulator protein (CFTR) both in vitro and in vivo. The effects of DQA on CFTR function and cell viability were investigated in Fisher rat thyroid (FRT) cells expressing human CFTR and human intestinal epithelial T84 cells by short-circuit current measurements and MTT assays, respectively. In vivo antidiarrheal efficacy of DQA was evaluated in a closed loop model of cholera in mice. In permeabilized FRT cells, apical chloride current induced by CFTR agonists (10 M forskolin, 100 M CPT-cAMP, and 20 M apigenin) was inhibited by DQA with IC(50) ~ 20 M and complete inhibition at 200 M. The inhibitory effect was reversible and not associated with cytotoxicity to FRT cells (5-500 M DQA for 24 h). Likewise, DQA effectively inhibited both forskolin and cholera toxin-induced transepithelial chloride secretion in T84 cells. In mice, intraluminal injection of 100 M DQA reduced cholera toxin (1 g/closed loop)-induced intestinal fluid secretion by 85% without affecting intestinal fluid absorption. DQA represents a new class of small molecule CFTR inhibitor with potential application in treatment of cholera.