Abstract 16586: The Intermediate-Conductance Ca2+-activated K+ Channel KCa3.1 Regulates Proliferation of Human Coronary Smooth Muscle Cells
Introduction: Vascular smooth muscle cell (VSMC) proliferation is a pathological process occurring in vascular remodeling. We have previously demonstrated that the intermediate-conductance Ca2+-activated K+ channel KCa3.1 is upregulated in proliferating VSMCs, and the blockade, knockdown and deficiency of KCa3.1 suppress VSMC proliferation. Here we further explored the mechanism by which KCa3.1 regulates VSMC proliferation.
Methods and Results: Platelet-derived growth factor-BB (PDGF, 20 ng/ml)-induced proliferation (using a BrdU incorporation assay) of human coronary artery VSMCs was attenuated by lowering intracellular Ca2+ concentration ([Ca2+]i) with BAPTA (30 μ M, an intracellular Ca2+ chelator) and was enhanced by a forced rise in [Ca2+]i with A23187 (0.1 to 1 nM, a Ca2+ ionophore). KCa3.1 blockade with TRAM-34 (100 nM, a specific blocker of KCa3.1) or siRNA knockdown reduced proliferation by inhibiting the rise in [Ca2+]i, as assessed in fluorescence microscopy with Fluo-4 (a Ca2+-sensitive dye), and by attenuating the expression of phosphorylated CREB (cAMP response element binding protein), c-fos and NOR-1 (neuron-derived orphan receptor-1), while the anti-proliferative effect was suppressed by a forced rise in [Ca2+]i with A23187. In contrast, KCa3.1 stimulation with EBIO-1 (100 to 300 μ M, a KCa3.1 opener) unexpectedly suppressed proliferation by inhibiting the rise in [Ca2+]i and by abolishing the expression of KCa3.1 and PDGF β-receptors, concomitantly with attenuating phosphorylated CREB, c-fos and cyclins levels, and inhibiting cell cycle progression. Furthermore, KCa3.1 blockade did not affect the characteristic round shape of VSMCs expressing high l-caldesmon and low calponin-1 (a dedifferentiation state), whereas KCa3.1 stimulation induced a spindle-shape appearance with low l-caldesmon and high calponin-1. On the other hand, KCa3.1 overexpression initiated VSMC proliferation and potentiated PDGF-induced proliferation by inducing CREB phosphorylation, c-fos and NOR-1.
Conclusions: KCa3.1 plays an important role in VSMC proliferation via controlling Ca2+-dependent signaling pathways and therefore constitutes a new therapeutic target for vascular remodeling such as atherosclerosis and restenosis.
- © 2012 by American Heart Association, Inc.