Inhibition of Glycogen Synthase Kinase 3 Reduces Cystogenesis and Fluid Secretion by Renal Epithelial Cells
Pankaj Pandey and Reena Rao
Kidney Institute, University of Kansas Medical Center, Kansas City, Kansas, 66160
AIM: Large fluid filled cysts are a hallmark of polycystic kidney disease. Development and growth of cysts require proliferation of cells and luminal secretion of fluid. Increased intracellular concentrations of cAMP are known to be important for proliferation as well as chloride ion secretion by epithelial cells in the context of polycystic kidney disease. In previous studies, we found that inhibition of Glycogen synthase kinase 3 (GSK3), a serine/threonine protein kinase, can reduce renal cAMP generation. Hence, in the present study we examined if inhibition of GSK3 can reduce cyst development and progression by renal epithelial cells.
METHODS: In vitro cystogenesis assays were carried out on a collagen I matrix using renal tubular epithelial cells, MDCK1 and M1 cells. For secretion studies, polarized cells were grown on transwell- snapwells and channel-specific short circuit currents were measured in an Ussing chamber. Forskolin, an adenylate cyclase agonist was used to increase cAMP levels and induce cystogenesis. GSK3 inhibitors LiCl (10mM), SB 216763 (10μM) and TDZD-8 (10μM) were used.
OBSERVATIONS: Inhibition of GSK3 effectively retarded forskolin-induced cystogenesis and cysts growth in MDCK cells as demonstrated by reduced cyst number and time dependent cyst expansion. GSK3 inhibitor treatment also reduced cell proliferation and forskolin induced and chloride channel specific short circuit current compared to control cells.
CONCLUSION: Our studies demonstrate that GSK3 inhibition is a new and effective approach to reduce cystogenesis in polycystic kidney disease.