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Down‐regulation of Intermediate Conductance Calcium‐activated Potassium Channel (IKCa) Inhibits Human Coronary Smooth Muscle Cell (HCSMC) Proliferation
Author(s) -
Miura Hiroto,
Toyama Kazuyoshi,
Hatoum Ossama A,
Saito Takashi,
Gutterman David D
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.5.a1176
Subject(s) - small interfering rna , platelet derived growth factor receptor , cell cycle , cell growth , microbiology and biotechnology , chemistry , endocrinology , biology , growth factor , medicine , cell , receptor , transfection , biochemistry , gene
We previously reported in HCSMCs that platelet‐derived growth factor‐BB (PDGF)‐induced proliferation is associated with IKCa up‐regulation and is inhibited by pharmacological blockade of IKCa activity. We hypothesized that IKCa down‐regulation inhibits SMC proliferation. Methods PDGF (20ng/ml)‐induced IKCa mRNA expression, DNA synthesis, changes in [Ca 2+ ]i, expression of early gene, transcriptional factors and cyclins, and cell cycle progression were determined in HCSMCs treated with or without 1‐ethyl‐2‐benzimidazolinone, which down‐regulates IKCa (EBIO, 300μM), or small interfering RNA (siRNA) specific to IKCa. Results EBIO and siRNA strongly inhibited PDGF–induced up‐regulation of IKCa mRNA expression. PDGF‐induced DNA synthesis was reduced (EBIO; 1.5±0.1‐fold of control, p<0.05 vs PDGF alone 2.6±0.2, n=38, and siRNA; 2.3±0.2, p<0.05 vs PDGF alone 3.4±0.3, n=24). IKCa down‐regulation inhibited PDGF‐induced rise in [Ca 2+ ]i, [Ca 2+ ]i‐dependent phosphorylation of cAMP response element binding protein, and expression of c‐fos and cyclins. Fetal bovine serum‐induced cell cycle progression was delayed by EBIO (G0/G1 phase; 74±1%, p<0.05 vs FBS alone 68±2, n=10) and by siRNA (76±3%, p<0.05 vs FBS alone 70±3, n=8). In conclusion IKCa up‐regulation is necessary for SMC proliferation via regulating mitogen‐induced, [Ca 2+ ]i‐dependent stimulation of signaling pathways and cell cycle progression from G 0 /G 1 to S phase. IKCa might be a new therapeutic target to retard restenosis and atherosclerosis.