The relationship between cell proliferation, Cl- secretion, and renal cyst growth: a study using CFTR inhibitors.
BACKGROUND
In autosomal-dominant polycystic kidney disease (ADPKD), cAMP-stimulated cell proliferation and Cl- secretion via the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel drive the enlargement of fluid-filled epithelial cysts. To investigate how CFTR blockers inhibit cyst growth, we studied cAMP-dependent Cl- secretion, cell proliferation, and cyst growth using type I Madin Darby canine kidney (MDCK) cells as a model of renal cyst development and growth.


METHODS
We grew MDCK cysts in collagen gels in the presence of the cAMP agonist forskolin, measured Cl- secretion with the Ussing chamber technique, and assayed cell proliferation using nonpolarized and polarized MDCK cells. To inhibit CFTR, we used glibenclamide, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), genistein, and the specific CFTR inhibitor CFTRinh-172. As controls, we tested the effects of blockers of other types of apical membrane Cl- channels and inhibitors of basolateral membrane ion channels and transporters.


RESULTS
In the absence of inhibitors of transepithelial ion transport, forskolin stimulated dramatic cyst growth. CFTR blockers and inhibitors of basolateral membrane ion channels and transporters retarded cyst growth. In contrast, blockers of other types of apical membrane Cl- channels, which were without effect on CFTR, failed to inhibit cyst growth. Inhibition of cyst growth by CFTR blockers was correlated with inhibition of cAMP-stimulated Cl- current (correlation coefficient = 0.81; P < 0.05), but not cell proliferation (correlation coefficient = 0.50; P > 0.05).


CONCLUSIONS
Our data suggest that CFTR blockers might retard cyst growth predominantly by inhibiting fluid accumulation within the cyst lumen.
Li
Hongyu
H
Department of Physiology, University of Bristol, School of Medical Sciences, University Walk, Bristol, United Kingdom.
Findlay
Iain A
IA
Sheppard
David N
DN
D000818:Animals; D001565:Benzoates / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors; D004285:Dogs; D004553:Electric Conductivity; D004848:Epithelium / Q000378:metabolism; D019833:Genistein / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects; D052177:Kidney Diseases, Cystic / Q000378:metabolism* / Q000473:pathology* / Q000517:prevention & control; D009579:Nitrobenzoates / Q000494:pharmacology; D013844:Thiazoles / Q000494:pharmacology; D053778:Thiazolidines
C482900:3-((3-trifluoromethyl)phenyl)-5-((3-carboxyphenyl)methylene)-2-thioxo-4-thiazolidinone; D001565:Benzoates; D018118:Chloride Channels; D002712:Chlorides; D009579:Nitrobenzoates; D013844:Thiazoles; D053778:Thiazolidines; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D005576:Colforsin; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D019833:Genistein; D000242:Cyclic AMP; D005905:Glyburide