Benidipine, a Calcium Channel Blocker, Regulates Proliferation and Phenotype of Vascular Smooth Muscle Cells

Regulation of smooth muscle cells in development and vascular disease: current therapeutic strategies

Vascular smooth muscle cells (SMCs) exhibit extensive phenotypic diversity and rapid growth during embryonic development, but maintain a quiescent, differentiated state in adult. The pathogenesis of vascular proliferative diseases involves the proliferation and migration of medial vascular SMCs into the vessel intima, possibly reinstating their embryonic gene expression programs. Multiple mitogenic stimuli induce vascular SMC proliferation through cell cycle progression. Therapeutic strategies targeting cell cycle progression and mitogenic stimuli have been developed and evaluated in animal models of atherosclerosis and vascular injury, and several clinical studies. Recent discoveries on the recruitment of vascular progenitor cells to the sites of vascular injury suggest new therapeutic potentials of progenitor cell-based therapies to accelerate re-endothelialization and prevent engraftment of SMC-lineage progenitor cells. Owing to the complex and multifactorial nature of SMC regulation, combinatorial antiproliferative approaches are likely to be used in the future in order to achieve maximal efficacy and reduce toxicity.

Relaxation of rat thoracic aorta by fibrate drugs correlates with their potency to disturb intracellular calcium of VSMCs

Phenotypic modifications of vascular smooth muscle cells (VSMCs) contribute to pathological changes in atherosclerosis where modulation of intracellular calcium plays an important role. In this study, three fibrate drugs, namely gemfibrozil (Gem), fenofibric acid (Fa) and bezafibrate (Beza), were revealed to relax thoracic aorta associated with their potency to reduce intracellular calcium ([Ca²⁺]i) in cultured VSMCs. Relaxation effect of Gem, Fa and Beza was assayed on precontracted rat aortic rings. [Ca²⁺]i level in VSMCs following addition of these fibrates was measured by laser scanning confocal microscopy or flow cytometry. Resultantly, three fibrates showed activity for vasodilation with potency order of Gem>Fa>Beza. Sustained potent reduction of [Ca²⁺]i was observed with Gem 50mg/L and mild reduction with Fa 400-600mg/L, while no effect had been detected for Beza under our current system. Thus, the potency of these fibrates to relax aortic rings correlate well with their effect on [Ca²⁺]i reduction, strongly implicating an underlying causal relationship. Considering that Gem potently reduces [Ca²⁺]i in its clinical concentration range, this study suggests an insight to in situ pharmacological effects of anti-atherosclerosis and clinical toxicity risk.

Connexin 43 hemichannel regulates H9c2 cell proliferation by modulating intracellular ATP and [Ca2+]

Connexin 43 (Cx43), known to be the main protein building blocks of gap junctions and hemichannels in mammalian heart, plays an important role in cardiocytes proliferation. Gap junctional intercellular communication has been suggested to be necessary for cellular proliferation and differentiation. However, the effect of Cx43 hemichannel on cardiocytes proliferation and the mechanism remain unclear. In this study, rat heart cell line H9c2 was used. The Cx43 location, the proliferation rate and hemichannel activity of H9c2 cells and Wnt-3a(+)-H9c2 cells were investigated and the changes of intracellular ATP and [Ca(2+)] were determined. Results showed that the inhibited hemichannel induced by 18beta-glycyrrhetinic acid (GA) evoked intracellular ATP and [Ca(2+)] increase and enhanced H9c2 cell proliferation. Wnt-3a(+)-H9c2 cells displayed enhanced hemichannel activity and proliferation rate. Inhibited hemichannel of Wnt-3a(+)-H9c2 cells induced by 18beta-GA decreased intracellular ATP, increased [Ca(2+)], and enhanced the proliferation of H9c2 cells. This study validated the role of hemichannel in H9c2 cell proliferation regulation, and showed a mechanism involved in the regulation of H9c2 cell proliferation. The proliferation could be enhanced by Cx43 hemichannel-mediated ATP release accompanying intracellular [Ca(2+)] change. However, different changes of ATP were observed in Wnt-3a(+)-H9c2 cells. These findings provided new insights into the molecular mechanisms of proliferation regulation in H9c2 cells and the effect of Wnt-3a on intracellular ATP.