Rho-kinase: a potential link between hypercholesterolemia and abnormal vascular smooth muscle contraction

Testosterone and cholesterol vasodilation of rat aorta involves L-type calcium channel inhibition

Testosterone has rapid nongenomic vasodilator effects which could be involved in protective cardiovascular actions. Several authors suggested specific mechanisms to explain this effect, but this matter was not clarified yet. We studied the actions of testosterone and cholesterol on endothelium-denuded rat aorta and their effects on the L-type Ca²⁺ current (I_Ca,L) and potassium current (I_K). Testosterone (1–100 μM) totally relaxed, in a rapid and concentration-dependent way, the aortic rings contracted by KCl or by (−)-Bay K8644 (BAY). Cholesterol also fully relaxed the contractions induced by KCl. None of the potassium channel antagonists tested (glibenclamide, tetraethylammonium and 4-aminopyridine) modified significantly the relaxant effect of testosterone. The antagonist of classic testosterone receptors, flutamide, did not modify the vasorelaxant effect of testosterone. Furthermore, testosterone and cholesterol inhibited either basal and BAY-stimulated I_Ca,L in A7r5 cells and they have no effects on I_K. In summary, our results demonstrate that cholesterol and testosterone relax rat aorta by inhibiting LTCC. This effect of testosterone is not mediated by the classic hormone receptor or by potassium channel activation. These results suggest that the vasodilator mechanism of cholesterol and testosterone is the same.

Comparison of effects of rosuvastatin (10 mg) versus atorvastatin (40 mg) on rho kinase activity in caucasian men with a previous atherosclerotic event

In addition to inhibiting cholesterol biosynthesis, statins also inhibit the formation of isoprenoid intermediates, which are required for the activation of the Rho/Rho kinase (ROCK) pathway. Increased ROCK activity has been implicated in causing endothelial dysfunction and atherosclerosis. However, it is not known whether statins, at doses used to lower cholesterol levels, inhibit ROCK activity in humans with atherosclerosis. Furthermore, it is not known whether lipophilic and hydrophilic statins differ in their ability to inhibit ROCK activity. Accordingly, we enrolled 30 men with stable atherosclerosis (low-density lipoprotein [LDL] > or =100 mg/dL) in a randomized, double-blind study comparing equivalent LDL-lowering doses of a hydrophilic statin (rosuvastatin 10 mg once a day) with a lipophilic statin (atorvastatin 40 mg once a day) for 28 days. We assessed the change in lipids, ROCK activity, and flow-mediated dilation (FMD) of the brachial artery before and after statin therapy. Both treatment groups exhibited comparable 30% to 32% and 42% to 45% reductions in total and LDL cholesterol, respectively. Only atorvastatin reduced triglycerides, and neither statin altered high-density lipoprotein cholesterol. Whereas both statins inhibited ROCK activity (p <0.0001), the extent of inhibition was greater with rosuvastatin (18 +/- 2% vs 8 +/- 2%, p = 0.0006). Statins also improved FMD from 7.4 +/- 0.6 to 9.3 +/- 0.4 (p = 0.003) with rosuvastatin being slightly better than atorvastatin. The inhibition of ROCK activity by statins did not correlate with reductions in LDL (p = 0.57) but was associated with improvement in FMD. In conclusion, these findings provide direct clinical evidence that statins, at clinically relevant doses, could differentially inhibit ROCK activity and improve endothelial function by cholesterol-independent mechanism.