SLC26A3 inhibitor identified in small molecule screen blocks colonic fluid absorption and reduces constipation.

Abstract

SLC26A3 (downregulated in adenoma; DRA) is a Cl-/anion exchanger expressed in the luminal membrane of intestinal epithelial cells, where it facilitates electroneutral NaCl absorption. SLC26A3 loss of function in humans or mice causes chloride-losing diarrhea. Here, we identified slc26a3 inhibitors in a screen of 50,000 synthetic small molecules done in Fischer rat thyroid (FRT) cells coexpressing slc26a3 and a genetically encoded halide sensor. Structure-activity relationship studies were done on the most potent inhibitor classes identified in the screen: 4,8-dimethylcoumarins and acetamide-thioimidazoles. The dimethylcoumarin DRAinh-A250 fully and reversibly inhibited slc26a3-mediated Cl- exchange with HCO3-, I-, and thiocyanate (SCN-), with an IC50 of ~0.2 μM. DRAinh-A250 did not inhibit the homologous anion exchangers slc26a4 (pendrin) or slc26a6 (PAT-1), nor did it alter activity of other related proteins or intestinal ion channels. In mice, intraluminal DRAinh-A250 blocked fluid absorption in closed colonic loops but not in jejunal loops, while the NHE3 (SLC9A3) inhibitor tenapanor blocked absorption only in the jejunum. Oral DRAinh-A250 and tenapanor comparably reduced signs of constipation in loperamide-treated mice, with additive effects found on coadministration. DRAinh-A250 was also effective in loperamide-treated cystic fibrosis mice. These studies support a major role of slc26a3 in colonic fluid absorption and suggest the therapeutic utility of SLC26A3 inhibition in constipation.

• Authors: Peter M Haggie, Onur Cil, Sujin Lee, Joseph-Anthony Tan, Amber A Rivera, Puay-Wah Phuan, Alan S Verkman
• Journal: JCI insight (JCI Insight) Vol. 3 Issue 14 (07 26 2018) ISSN: 2379-3708 [Electronic] United States
• PMID: 30046015 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)

Chemical References

• Antiporters
• Chloride-Bicarbonate Antiporters
• Chlorides
• Slc26A4 protein, rat
• Slc26a3 protein, mouse
• Slc9a3 protein, rat
• Sodium-Hydrogen Exchanger 3
• Sulfate Transporters
• Loperamide

Topics

• Animals
• Antiporters (antagonists & inhibitors, chemistry, genetics, metabolism, pharmacology)
• Chloride-Bicarbonate Antiporters (pharmacology)
• Chlorides (metabolism)
• Constipation (drug therapy)
• Cystic Fibrosis
• Disease Models, Animal
• Drug Evaluation, Preclinical
• Epithelial Cells (drug effects, metabolism)
• HEK293 Cells
• High-Throughput Screening Assays
• Humans
• Ion Transport
• Loperamide (pharmacology)
• Mice
• Rats
• Rats, Inbred F344
• Sodium-Hydrogen Exchanger 3 (pharmacology)
• Sulfate Transporters (antagonists & inhibitors, genetics, metabolism, pharmacology)