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.

钙拮抗剂用于冠状动脉痉挛性心绞痛 (CSA) 治疗。我们之前确定了一种磷脂酶 C (PLC) -δ1 基因变异，该变异导致 CSA 患者的 PLC 活性增强，并通过生成血管平滑肌细胞特异性人类变异 PLC-δ1 过表达 (PLC-TG) 小鼠开发了 CSA 动物模型。在这项研究中，我们使用 PLC-TG 小鼠研究了 CSA 的分子机制和钙拮抗剂盐酸地尔硫卓 (DL) 的抑制作用。

我们用口服 DL 或三氯噻嗪 (TM)（对照）治疗 PLC-TG 和野生型 (WT) 小鼠 2 周。在用 TM 治疗的所有 5 只 PLC-TG 小鼠的心电图上观察到麦角新碱注射诱导的冠状动脉痉挛，但仅在用 DL 治疗的 5 只 PLC-TG 小鼠中的 1 只中观察到。电压依赖性钙通道 (Cav1.2) 磷酸化和蛋白激酶 C (PKC) 活性在用 TM 处理的 PLC-TG 小鼠的主动脉中得到增强。DL 处理显着抑制 Cav1.2 磷酸化和 PKC 活性。尽管总 Cav1.2 表达在用 TM 处理的 WT 和 PLC-TG 小鼠之间相似，但 DL 处理显着增加了其在 PLC-TG 小鼠中的表达。此外，在 DL 中断后，其表达仍然很高。

这些结果表明增强的 PLC 活性导致冠状动脉痉挛，可能是通过增强的 Cav1.2 磷酸化和 PKC 活性，这两者都被 DL 抑制。DL 中断后总 Cav1.2 表达增强和高 PKC 活性可能是钙拮抗剂戒断综合征的重要机制。