Diltiazem Inhibits Coronary Spasm via Inhibition of Cav1.2Phosphorylation and Protein Kinase C Activation in a Mouse Model of Coronary Spastic Angina.

Calcium antagonists are used for coronary spastic angina (CSA) treatment. We previously identified a phospholipase C (PLC) -δ1 gene variant that results in enhanced PLC activity in patients with CSA and developed a CSA animal model by generating vascular smooth muscle cell-specific human variant PLC-δ1 overexpression (PLC-TG) mice. In this study, we investigated the molecular mechanism of CSA using the PLC-TG mice and the inhibitory effect of a calcium antagonist, diltiazem hydrochloride (DL).We treated the PLC-TG and wild-type (WT) mice with oral DL or trichlormethiazide (TM) (control) for 2 weeks. Ergometrine injection-induced coronary spasm was observed on the electrocardiogram in all 5 PLC-TG mice treated with TM, but only in 1 of 5 PLC-TG mice treated with DL. Voltage-dependent calcium channel (Cav1.2) phosphorylation and protein kinase C (PKC) activity were enhanced in the aortas of PLC-TG mice treated with TM. DL treatment significantly inhibited Cav1.2 phosphorylation and PKC activity. Although total Cav1.2 expression was similar between WT and PLC-TG mice treated with TM, DL treatment significantly increased its expression in PLC-TG mice. Furthermore, its expression remained high after DL discontinuation. DL and PKC inhibitor suppressed intracellular calcium response to acetylcholine in cultured rat aortic smooth muscle cells transfected with variant PLC-δ1.These results indicate that enhanced PLC activity causes coronary spasm, presumably via enhanced Cav1.2 phosphorylation and PKC activity, both of which were inhibited by DL. Enhanced total Cav1.2 expression after DL discontinuation and high PKC activity may be an important mechanism underlying the calcium antagonist withdrawal syndrome.

Folic acid improves acetylcholine-induced vasoconstriction of coronary vessels isolated from hyperhomocysteinemic mice: an implication to coronary vasospasm.

Human atherosclerotic coronary vessels elicited vasoconstriction to acetylcholine (Ach) and revealed a phenomenon of vasospasm. Homocysteine (Hcy) levels are elevated in the atherosclerotic plaque tissue, suggesting its pathological role in endothelial damage in atherosclerotic diseases. Accordingly, we examined the role hyperhomocysteinemia in coronary endothelial dysfunction, vessel wall thickness, lumen narrowing, leading to acute/chronic coronary vasospasm. The therapeutic potential and mechanisms of folic acid (FA) using hyperhomocysteinemic cystathionine beta synthase heterozygote (CBS-/+) and wild type (CBS+/+) mice were addressed. The CBS-/+ and CBS+/+ mice were treated with or without a Hcy lowering agent FA in drinking water (0.03 g/L) for 4 weeks. The isolated mouse septum coronary artery was cannulated and pressurized at 60 mmHg. The wall thickness and lumen diameters were measured by Ion-Optic. The vessels were treated with Ach (10(-8) -10(-5) M) and, for comparison, with non-endothelial vasodilator sodium nitroprusside (10(-5) M). The endothelium-impaired arteries from CBC-/+ mice constricted in response to Ach and this vasoconstriction was mitigated with FA supplementation. The level of endothelial nitric oxide synthase (eNOS) was lower in coronary artery in CBS-/+ than of CBS+/+ mice. Treatment with FA increased the levels of Ach-induced NO generation in the coronary artery of CBS-/+ mice. The results suggest that Ach induced coronary vasoconstriction in CBS-/+ mice and this vasoconstriction was ameliorated by FA treatment. The mechanisms for the impairment of vascular function and therapeutic effects of FA may be related to the regulation of eNOS expression, NO availability and tissue homocysteine.

[Inhibitory effect and acting mechanism of Tongxinluo on IL-1beta-mediated coronary intimal hyperplasia and 5-hydroxytryptamine-induced coronary vasospasm in small swine].

OBJECTIVE: To observe the inhibitory effect of Tongxinluo (TXL) on coronary vaso spasm in small swine in vivo, and to investigate its possible acting mechanism. METHODS: The model of coronary atherosclerosis in 16 male small swines was established by left thoracotomy after anesthesia, isolated the sections of left anterio-descending branch and proximal end of rotator branch with similar outer diameter, and encapsulated them with paper-towel holding 2.5 microg interleukin-1beta. Two weeks later, the condition of coronary vasospasm induced by catheter intra-coronary injection of 5-hydroxytryptamine (5-HT, 10 microg/kg) was observed through coronary artery contrast examination. The 12 swines with successfully formed coronary vaso spasm were randomly divided into 2 groups, the TXL group and the control group. They were fed with special diet, but TXL 1 g/(kg d) was administered additionally to the TXL group for 4 weeks. The observation on coronary vasospasm was repeated 1 week after discontinuation of TXL treatment, then the animals were sacrificed, their vascular sections enclosed with IL-1beta was taken to conduct the pathologic examination and to detect the expressions of Rho kinase mRNA and its substrate myosin- binding subunit phosphorylation (MBS-P) by RT-PCR and Western blot method. RESULTS: Coronary artery contrast showed that local coronary stenosis occurred in the 12 model swines to different extents (20% - 30%, and vascular spasm on them could be induced by 5-HT. At the time of repeating examination, 11 vascular sections in the control group still maintain their positive spasm reaction to 5-HT, but only 2 in the TXL group did so, the reaction turned to negative in 1 and 10 in the two groups respectively. Pathological examination showed that different degrees of macrophage aggregation could be found in both groups. The degree of lumen stricture and endometrial hyperplasia in the TXL group was obviously attenuated than those in the control group. The expressions of Rho kinase mRNA and MBS-P in the control group were up-regulated obviously. As compared with those in the control group, they were inhibited significantly in the TXL group, as (71.5 +/- 2.4) vs (98.2 +/- 7.7)% and 16,633 +/- 1,390 vs 25,818 +/- 4,745, respectively (all P < 0.05). CONCLUSION: TXL could obviously inhibit the coronary intimal hyperplasia mediated by IL-1beta and coronary vasospasm induced by 5-HT, one of its mechanisms is possibly the inhibition on the intracellular Rho kinase mRNA expression in the IL-1beta enclosed vascular section to decrease the level of MBS-P.

Calcium channel blockers for the treatment of coronary artery spasm: rationale, effects, and nursing responsibilities.

Coronary artery spasm is recognized as a cause of ischemic heart disease, producing a syndrome of the variant form of angina that occurs at rest. Spasm also may play a role in other types of rest angina (unstable angina) and exertional angina. Calcium is essential for the basic tonus of vascular smooth muscle. The accentuated contraction that occurs in coronary artery spasm is the result of an increase in intracellular calcium ions. Current therapy is aimed at blocking the slow calcium currents that are responsible for electrical activation and contraction of smooth muscle cells. A marked coronary vasodilatation is produced with calcium channel blockers, thus demonstrating effective therapy for coronary artery spasm. A similar effect is achieved by nitrates, and these agents will continue to have a role in the therapy of spasm. Calcium channel blockers produce beneficial effects on myocardial oxygen supply and demand and, therefore, are also useful in the prevention of classic exertional angina caused by fixed obstruction. Verapamil and diltiazem possess electrophysiologic effects and have, in addition, proved useful in the treatment of supraventricular dysrhythmias.