title: [Ca2+]i reduction increases cellular proliferation and apoptosis in vascular smooth muscle cells: relevance to the ADPKD phenotype.
abstract: Cardiovascular complications are the leading cause of morbidity and mortality in autosomal dominant polycystic kidney disease. Pkd2+/- vascular smooth muscle cells (VSMCs) have an abnormal phenotype and defective intracellular Ca2+ ([Ca2+]i) regulation. We examined cAMP content in vascular smooth muscles from Pkd2+/- mice because cAMP is elevated in cystic renal epithelial cells. We found cAMP concentration was significantly increased in Pkd2+/- vessels compared with wild-type vessels. Furthermore, reducing the wild-type VSMC [Ca2+]i by Verapamil or BAPTA-AM significantly increased cellular cAMP concentration (mainly by phosphodiesterase [PDE] inhibition), the rate of VSMC proliferation (determined by direct cell counting, 3H-incorporation, FACS analysis of cells entering S phase, and quantitative Western PCNA and ERK1/2 analyses), and the rate of apoptosis (by Hoechst staining, FACS analysis of the Annexin-V positive cells, and quantitative Western Bax, cytochrome c, and activated caspase 9 and 3 analyses). The low [Ca2+]i induced VSMC proliferation was independent of cAMP/B-Raf signaling, while that of apoptosis was promoted by cAMP. In summary, Pkd2+/- VSMCs have elevated cAMP levels. This elevation can also be induced by reducing [Ca2+]i in wild-type VSMCs. The [Ca2+]i reduction and cAMP accumulation can cause an increase in both cellular proliferation and apoptosis, resembling Pkd mutant phenotype.
authors.affiliation: Division of Nephrology and Hypertension, Mayo Clinic College of Medicine, Rochester, Minn 55905, USA.
authors.forename: Sertac N
authors.initials: SN
authors.lastname: Kip
authors.forename: Larry W
authors.initials: LW
authors.lastname: Hunter
authors.forename: Qun
authors.initials: Q
authors.lastname: Ren
authors.forename: Peter C
authors.initials: PC
authors.lastname: Harris
authors.forename: Stefan
authors.initials: S
authors.lastname: Somlo
authors.forename: Vicente E
authors.initials: VE
authors.lastname: Torres
authors.forename: Gary C
authors.initials: GC
authors.lastname: Sieck
authors.forename: Qi
authors.initials: Q
authors.lastname: Qian
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000235:genetics; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D049109:Cell Proliferation; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000032:analysis; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D017346:Protein Serine-Threonine Kinases / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000502:physiology; D048493:Proto-Oncogene Proteins B-raf / Q000032:analysis; D051057:Proto-Oncogene Proteins c-akt; D050396:TRPP Cation Channels
chemical_list: D015105:3',5'-Cyclic-AMP Phosphodiesterases; D002118:Calcium; D000242:Cyclic AMP; D054703:Cyclic Nucleotide Phosphodiesterases, Type 4; D008565:Membrane Proteins; D019950:Mitogen-Activated Protein Kinase 1; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D050396:TRPP Cation Channels; C482120:Braf protein, mouse