Proceedings of The Physiological Society
University of Edinburgh (2011) Proc Physiol Soc 25, PC23
The vascular smooth muscle T-type calcium channel: an anti-proliferative target for heme oxygenase-1?
H. Duckles1, H. E. Boycott1, J. L. Scragg1, J. P. Boyle1, K. E. Porter1, C. Peers1
1. Division of Cardiovascular and Neuronal Remodelling, University of Leeds, Leeds, United Kingdom.
Excess proliferation of vascular smooth muscle cells (VSMC) is a central feature of vascular disorders such as hypertension, restenosis and atherosclerosis (1). T-type calcium channels provide an important route for calcium entry in disease-associated VSMC proliferation, and under these conditions VSMC also increase expression of heme oxygenase-1 (HO-1) (1) (2). HO-1 catabolises free heme to produce biliverdin, iron, and carbon monoxide (CO), and exhibits anti-proliferative effects, possibly through the production of CO (2). We aimed to investigate the effects and possible interactions of HO-1, CO, and T-type calcium channel inhibition on VSMC proliferation. VSMC were explanted from fragments of saphenous vein (SV) of patients undergoing coronary bypass and propagated in primary culture. Proliferation assays were performed over 4 days in the absence or presence of the T-type channel inhibitor mibefradil, an inducer of HO-1, CoPPIX, or the CO donor compound, CORM-3. Viable cells were counted using trypan blue and a hemocytometer. Statistical analysis was performed using two-tailed paired T-test and one-way ANOVA with Bonferroni’s multiple comparison test, as appropriate. Proliferation was reduced by 39.7 ±8.8%, p<0.05, n=3, in the presence of 3μM mibefradil, and by 37.7 ±2.8%, p<0.05, n=3, following HO-1 induction by 3μM CoPPIX (induction verified by western blotting, n=2). CORM-3 application (3-30μM) produced a dose dependent decrease in proliferation, a reduction of 36.0 ±4.4%, P<0.01, n=3, was observed in the presence of 3μM CORM-3. The application of 3μM mibefradil and 3μM CoPPIX simultaneously reduced proliferation by 57.7 ±8.1%, P<0.05, n=3. These preliminary data support the idea that CO is antiproliferative through inhibition of VSMC T-type calcium channels. This signalling pathway may therefore be a novel target for pharmacological intervention in vascular disorders involving excess SMC proliferation.
Where applicable, experiments conform with Society ethical requirements