摘要：

Polycystic kidney disease (PKD) is a lethal disorder characterized by progressive expansion of renal cysts. Genetic mutations associated with PKD are thought to disrupt intracellular Caregulation, leading to abnormal proliferation of tubule epithelial cells. cAMP stimulates the B-Raf/MEK/extracellular signal-regulated kinase (B-Raf/MEK/ERK) pathway and accelerates the proliferation of cells that are cultured from PKD cysts. By contrast, cAMP inhibits the proliferation of cells from normal human kidneys (NHK) and M-1 mouse collecting duct cells. Previously, it was found that a sustained reduction of intracellular Calevels in NHK and M-1 cells that were treated with Caentry blockers allowed cAMP activation of the B-Raf/MEK/ERK pathway, switching the cells to a cAMP-growth stimulated phenotype. In this study, primary cultures of cyst epithelial cells from autosomal dominant (ADPKD) and recessive (ARPKD) PKD kidneys were used to determine whether controlled addition of Cacould reverse the aberrant mitogenic response to cAMP. Steady-state intracellular Calevels were found to be 20 nM lower in cyst-derived ADPKD cells (57 ± 2 nM) compared with NHK cells (77 ± 2 nM). Treatment of ADPKD cells or ARPKD cells with either Bay K8644, a Cachannel activator, or A23187, a Caionophore, caused sustained increases in intracellular Calevels and completely reversed the mitogenic response to cAMP. Elevation of intracellular Calevels in ADPKD cells increased Akt activity and blocked cAMP-dependent B-Raf and ERK activation. Thus, increases in [Ca]are able to restore the normal anti-mitogenic response to cAMP in cells that are derived from two genetically distinct forms of PKD.

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