No abstract

Endogenous adenylyl cyclase agonists promote cell proliferation and electrolyte secretion of human ADPKD and ARPKD cells in vitro. We suggest that increased levels of cAMP may accelerate cyst growth and overall renal enlargement in patients with PKD.

Reif GA, Yamaguchi T, Nivens E, Fujiki H, Pinto CS, Wallace DP. Tolvaptan inhibits ERK-dependent cell proliferation, Cl Ϫ secretion, and in vitro cyst growth of human ADPKD cells stimulated by vasopressin. Am J Physiol Renal Physiol 301: F1005-F1013, 2011. First published August 3, 2011 doi:10.1152/ajprenal.00243.2011In autosomal dominant polycystic kidney disease (ADPKD), arginine vasopressin (AVP) accelerates cyst growth by stimulating cAMP-dependent ERK activity and epithelial cell proliferation and by promoting Cl Ϫ -dependent fluid secretion. Tolvaptan, a V2 receptor antagonist, inhibits the renal effects of AVP and slows cyst growth in PKD animals. Here, we determined the effect of graded concentrations of tolvaptan on intracellular cAMP, ERK activity, cell proliferation, and transcellular Cl Ϫ secretion using human ADPKD cyst epithelial cells. Incubation of ADPKD cells with 10 Ϫ9 M AVP increased intracellular cAMP and stimulated ERK and cell proliferation. Tolvaptan caused a concentration-dependent inhibition of AVP-induced cAMP production with an apparent IC50 of ϳ10 Ϫ10 M. Correspondingly, tolvaptan inhibited AVP-induced ERK signaling and cell proliferation. Basolateral application of AVP to ADPKD cell monolayers grown on permeable supports caused a sustained increase in short-circuit current that was completely blocked by the Cl Ϫ channel blocker CFTRinh-172, consistent with AVP-induced transepithelial Cl Ϫ secretion. Tolvaptan inhibited AVP-induced Cl Ϫ secretion and decreased in vitro cyst growth of ADPKD cells cultured within a three-dimensional collagen matrix. These data demonstrate that relatively low concentrations of tolvaptan inhibit AVP-stimulated cell proliferation and Cl Ϫ -dependent fluid secretion by human ADPKD cystic cells.

Progressive renal enlargement due to the growth of innumerable fluid-filled cysts is a central pathophysiological feature of autosomal dominant polycystic kidney disease (ADPKD). These epithelial neoplasms enlarge slowly and damage noncystic parenchyma by mechanisms that have not been clearly defined. In a microarray analysis of cultured human ADPKD cyst epithelial cells, periostin mRNA was overexpressed 15-fold compared with normal human kidney (NHK) cells. Periostin, initially identified in osteoblasts, is not expressed in normal adult kidneys but is expressed transiently during renal development. We found periostin in cyst-lining cells in situ in the extracellular matrix adjacent to the cysts and within cyst fluid. ADPKD cells secreted periostin across luminal and basolateral plasma membranes. Periostin increased proliferation of cyst epithelial cells 27.9 ± 3.1% ( P < 0.001) above baseline and augmented in vitro cyst growth but did not affect proliferation of normal renal cells. Expression of αV-integrin, a periostin receptor, was ninefold higher in ADPKD cells compared with NHK cells, and antibodies that block αV-integrin inhibited periostin-induced cell proliferation. We conclude that periostin is a novel autocrine mitogen secreted by mural epithelial cells with the potential to accelerate cyst growth and promote interstitial remodeling in ADPKD.