Abstract 12530: Altered Expression and Phosphorylation Levels of L-type Calcium Channel Play a Critical Role in the Mouse Model of Coronary Spastic Angina
We recently showed that coronary spasm is induced in transgenic mice with enhanced phospholipase C-delta 1 activity (PLC-TG) (Circulation 2012). Calcium antagonist treatment is commonly accepted as a therapy for coronary spastic angina, but its precise mechanism remains unclear. We studied the efficacy of calcium antagonist, diltiazem (DL), and investigated alteration in calcium signaling-related proteins of the mouse aorta.
Ten homozygous PLC-TG mice at mean age of 24 weeks were divided into DL (60 mg/kg/day) group and control group which was treated with trichlormethiazide (1 mg/kg/day)(each n=5). Each drug was added to drinking water for 14 days. There were no differences in blood pressure and heart rate between the two groups before and after drug administration. Intravenous ergometrine maleate at 50 mg/kg induced ST-segment elevation in all 5 control mice, but in only one in DL group (p≤0.01), indicating an inhibitory effect of DL on coronary spasm in the PLC-TG mice.
Western blot analysis of the mouse aorta showed that L-type calcium channel (Cav1.2) expression in PLC-TG mice was significantly decreased to 40±20% of wild type (WT) mice (p≤0.05, n=6). Although the expression level of phosphorylated serine-1928 Cav1.2 (p-Cav1.2), which is related to Cav1.2 activation, was not different between PLC-TG and WT mice, the ratio of p-Cav1.2 to total Cav1.2 was significantly increased in PLC-TG mice by 3.3±1.3 times compared with WT (p≤0.01). Expression levels of calcium influx regulating proteins, inositol 1,4,5-triphosphate receptor-1 and A-kinase anchoring protein, did not differ between PLC-TG and WT.
After DL administration, Cav1.2 expression in PLC-TG mice was significantly increased by 2.3±1.2 times compared with PLC-TG mice without DL administration (p≤0.05). Most notably, the expression level of p-Cav1.2 was markedly decreased, indicating a lower level of Cav1.2 activity in PLC-TG mice after DL.
In conclusion, alterations in protein expression and phosphorylation levels of Cav1.2 were suggested to be implicated in the pathogenesis of coronary spasm. DL exhibits an inhibitory effect on coronary spasm, at least in part through suppression of phosphorylation of Cav1.2.
- © 2013 by American Heart Association, Inc.