Thiazolidinone CFTR inhibitor identified by high-throughput screening blocks cholera toxin–induced intestinal fluid secretion

TLDR

Secretory diarrhea, a leading cause of infant mortality in developing countries and significant adult morbidity, depends on CFTR‑mediated chloride transport, whose dysfunction underlies cystic fibrosis. The authors performed a high‑throughput screen of 50,000 diverse compounds to identify inhibitors of cAMP‑stimulated chloride transport in CFTR‑expressing epithelial cells. They discovered six thiazolidinone CFTR inhibitors, with CFTR(inh)-172 exhibiting nanomolar, reversible, voltage‑independent inhibition, no toxicity, high selectivity, and reducing cholera toxin–induced intestinal fluid secretion by over 90% in mice, indicating therapeutic potential for secretory diarrhoea.

Abstract

Secretory diarrhea is the leading cause of infant death in developing countries and a major cause of morbidity in adults. The cystic fibrosis transmembrane conductance regulator (CFTR) protein is required for fluid secretion in the intestine and airways and, when defective, causes the lethal genetic disease cystic fibrosis. We screened 50,000 chemically diverse compounds for inhibition of cAMP/flavone-stimulated Cl(-) transport in epithelial cells expressing CFTR. Six CFTR inhibitors of the 2-thioxo-4-thiazolidinone chemical class were identified. The most potent compound discovered by screening of structural analogs, CFTR(inh)-172, reversibly inhibited CFTR short-circuit current in less than 2 minutes in a voltage-independent manner with K(I) approximately 300 nM. CFTR(inh)-172 was nontoxic at high concentrations in cell culture and mouse models. At concentrations fully inhibiting CFTR, CFTR(inh)-172 did not prevent elevation of cellular cAMP or inhibit non-CFTR Cl(-) channels, multidrug resistance protein-1 (MDR-1), ATP-sensitive K(+) channels, or a series of other transporters. A single intraperitoneal injection of CFTR(inh)-172 (250 micro g/kg) in mice reduced by more than 90% cholera toxin-induced fluid secretion in the small intestine over 6 hours. Thiazolidinone CFTR inhibitors may be useful in developing large-animal models of cystic fibrosis and in reducing intestinal fluid loss in cholera and other secretory diarrheas.