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Haggie PM, Phuan PW, Tan JA, Zlock L, Finkbeiner WE, Verkman AS. Inhibitors of pendrin anion exchange identified in a small molecule screen increase airway surface liquid volume in cystic fibrosis. FASEB J 2016; 30:2187-97. [PMID: 26932931 DOI: 10.1096/fj.201600223r] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 02/06/2016] [Indexed: 12/31/2022]
Abstract
Pendrin (SLC26A4) is a Cl(-)/anion exchanger expressed in the epithelium of inflamed airways where it is thought to facilitate Cl(-) absorption and HCO3 (-) secretion. Studies using pendrin knockout mice and airway epithelial cells from hearing-impaired subjects with pendrin loss of function suggest involvement of pendrin in inflammatory lung diseases, including cystic fibrosis (CF), perhaps by regulation of airway surface liquid (ASL) volume. Here we identified small-molecule pendrin inhibitors and demonstrated their efficacy in increasing ASL volume. A cell-based, functional high-throughput screen of ∼36,000 synthetic small molecules produced 3 chemical classes of inhibitors of human pendrin. After structure-activity studies, tetrahydropyrazolopyridine and pyrazolothiophenesulfonamide compounds reversibly inhibited pendrin-facilitated Cl(-) exchange with SCN(-), I(-), NO3 (-), and HCO3 (-) with drug concentration causing 50% inhibition down to ∼2.5 μM. In well-differentiated primary cultures of human airway epithelial cells from non-CF and CF subjects, treatment with IL-13, which causes inflammation with strong pendrin up-regulation, strongly increased Cl(-)/HCO3 (-) exchange and the increase was blocked by pendrin inhibition. Pendrin inhibition significantly increased ASL depth (by ∼8 μm) in IL-13-treated non-CF and CF cells but not in untreated cells. These studies implicate the involvement of pendrin-facilitated Cl(-)/HCO3 (-) in the regulation of ASL volume and suggest the utility of pendrin inhibitors in inflammatory lung diseases, including CF.-Haggie, P. M., Phuan, P.-W., Tan, J.-A., Zlock, L., Finkbeiner, W. E., Verkman, A. S. Inhibitors of pendrin anion exchange identified in a small molecule screen increase airway surface liquid volume in cystic fibrosis.
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Affiliation(s)
- Peter M Haggie
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA; Department of Physiology, University of California, San Francisco, San Francisco, California, USA; and
| | - Puay-Wah Phuan
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA; Department of Physiology, University of California, San Francisco, San Francisco, California, USA; and
| | - Joseph-Anthony Tan
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA; Department of Physiology, University of California, San Francisco, San Francisco, California, USA; and
| | - Lorna Zlock
- Department of Pathology, University of California, San Francisco, San Francisco, California, USA
| | - Walter E Finkbeiner
- Department of Pathology, University of California, San Francisco, San Francisco, California, USA
| | - A S Verkman
- Department of Medicine, University of California, San Francisco, San Francisco, California, USA; Department of Physiology, University of California, San Francisco, San Francisco, California, USA; and
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Abstract
Acid-base homeostasis and pH regulation are critical for both normal physiology and cell metabolism and function. The importance of this regulation is evidenced by a variety of physiologic derangements that occur when plasma pH is either high or low. The kidneys have the predominant role in regulating the systemic bicarbonate concentration and hence, the metabolic component of acid-base balance. This function of the kidneys has two components: reabsorption of virtually all of the filtered HCO3(-) and production of new bicarbonate to replace that consumed by normal or pathologic acids. This production or generation of new HCO3(-) is done by net acid excretion. Under normal conditions, approximately one-third to one-half of net acid excretion by the kidneys is in the form of titratable acid. The other one-half to two-thirds is the excretion of ammonium. The capacity to excrete ammonium under conditions of acid loads is quantitatively much greater than the capacity to increase titratable acid. Multiple, often redundant pathways and processes exist to regulate these renal functions. Derangements in acid-base homeostasis, however, are common in clinical medicine and can often be related to the systems involved in acid-base transport in the kidneys.
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Affiliation(s)
- L Lee Hamm
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
| | - Nazih Nakhoul
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
| | - Kathleen S Hering-Smith
- Department of Medicine, Section of Nephrology, Tulane Hypertension and Renal Center of Excellence, Tulane University School of Medicine, New Orleans, Louisiana; and Medicine Service, Southeast Louisiana Veterans Health Care System, New Orleans, Louisiana
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