A novel small molecule CFTR inhibitor attenuates HCO₃⁻ secretion and duodenal ulcer formation in rats

Abstract

Ϫ ) secretion (DBS). Although impaired DBS is observed in CF mutant mice and in CF patients, which would predict increased ulcer susceptibility, duodenal injury is rarely observed in CF patients and is reduced in CF mutant mice. To explain this apparent paradox, we hypothesized that CFTR dysfunction increases cellular [HCO 3 Ϫ ] and buffering power. To further test this hypothesis, we examined the effect of a novel, potent, and highly selective CFTR inhibitor, CFTR inh-172, on DBS and duodenal ulceration in rats. DBS was measured in situ using a standard loop perfusion model with a pH stat under isoflurane anesthesia. Duodenal ulcers were induced in rats by cysteamine with or without CFTR inh-172 pretreatment 1 h before cysteamine. Superfusion of CFTR inh-172 (0.1-10 M) over the duodenal mucosa had no effect on basal DBS but at 10 M inhibited acid-induced DBS, suggesting that its effect was limited to CFTR activation. Acid-induced DBS was abolished at 1 and 3 h and was reduced 24 h after treatment with CFTRinh-172, although basal DBS was increased at 24 h. CFTR inh-172 treatment had no effect on gastric acid or HCO 3 Ϫ secretion. Duodenal ulcers were observed 24 h after cysteamine treatment but were reduced in CFTR inh-172-pretreated rats. CFTRinh-172 acutely produces CFTR dysfunction in rodents for up to 24 h. CFTR inhibition reduces acid-induced DBS but also prevents duodenal ulcer formation, supporting our hypothesis that intracellular HCO 3 Ϫ may be an important protective mechanism for duodenal epithelial cells.

Discovery of α-Aminoazaheterocycle-Methylglyoxal Adducts as a New Class of High-Affinity Inhibitors of Cystic Fibrosis Transmembrane Conductance Regulator Chloride Channels

“…‫,ءءء‬ P Ͻ 0.001. jpet.aspetjournals.org teamine treatment, i.p. injection of CFTR inh -172 (at 1 mg/ kg) 1 h before cysteamine treatment reduced duodenal ulceration (Akiba et al, 2005). Finally, CFTR inhibitors, such as CFTR inh -172, glibenclamide, and 5-nitro-2-(3-phenylpropylamino)-benzoic acid, by inhibiting transepithelial ion transport, retard renal cyst growth using MDCK cells as a model , suggesting that such molecules could contribute to the pharmacological treatment of autosomal-dominant polycystic kidney disease.…”

Guanylin peptides regulate electrolyte and fluid transport in the Gulf toadfish (Opsanus beta) posterior intestine

“…Bafilomycin (Enzo Life Sciences) was used to inhibit the apical VHA and prepared in DMSO at 1.0 mmol/l for application in a final concentration of 2 mol/l and 0.1% DMSO, which has been previously used in the Gulf toadfish (27,31). CFTRinh-172 (Sigma) was used to inhibit a putative apical CFTR channel (1,6,7,48) and prepared in DMSO at 1.0 mmol/l for application in a final concentration of 10 mol/l and 0.1% DMSO, which is in the mid-range solubility limit for this blocker (1).…”

Endogenous Luminal Surface Adenosine Signaling Regulates Duodenal Bicarbonate Secretion in Rats

“…Unlike ATP, which activates P2Y G q/11 receptors followed by the increase of cellular Ca 2ϩ , ADO activates P1 G i receptors (A 1 and A 3 ) or G s receptors (A 2A and A 2B ). The latter receptors increase adenylate cyclase activity, which elevates cellular cAMP, directly activating the cystic fibrosis transmembrane regulator (CFTR), an important component of active DBS (Hogan et al, 1997;Seidler et al, 1997;Hirokawa et al, 2004;Akiba et al, 2005). There is, however, no published study addressing the effect of luminal ADO on bicarbonate secretion.…”