Abstract 17285: Disruption of A-kinase Anchoring Protein 150 Causes Coronary Spasm Through Enhanced Calcium Sensitization: A Potential Role of Microrna-30b
Introduction: We previously reported that human variant form of phospholipase C (PLC)-δ1, an amino acid replacement of arginine 257 to histidine (R257H), shows an enhanced PLC activity, leading to the increased intracellular calcium concentration ([Ca2+]i) (Circulation 2002). Furthermore, we generated mice overexpressing variant PLC-δ1 specifically in the vascular smooth muscle cells (VSMCs)(PLC-TG) and demonstrated that PLC-TG mice can be an animal model of coronary spastic angina (Circulation 2012). The A-kinase anchoring protein (AKAP) 150 regulates the activity of L-type calcium channel and [Ca2+]i. We showed that disruption of AKAP150 in mice (AKAP-KO) unexpectedly causes ST elevation and coronary spasm by ergometrine injection (30 mg/kg)(AHA 2015). In the present study, we investigated a potential mechanism focusing on calcium sensitization and its regulation.
Methods and Results: We crossed AKAP-KO with PLC-TG to generate AKAP-PLC mice, and compared calcium response among the four genotypes (wild type (WT), PLC-TG, AKAP-KO, and AKAP-PLC mice). VSMCs were isolated from the mouse aorta of each genotype. Being consistent with our previous report, change in [Ca2+]i response to acetylcholine (ACh, 10-5 M), measured by fura-2, was greater in PLC-TG (163±38 nmol/L) than in WT VSMCs (132±46). Importantly, it was not enhanced in AKAP-KO (114±20) and AKAP-PLC VSMCs (102±28) and was similar to that in WT VSMCs, suggesting that increase in [Ca2+]i may not be involved in coronary spasm induced in AKAP-KO and AKAP-PLC mice. The gene and protein expression of CaMKII, a key molecule for calcium sensitization, was increased by 1.9±0.3-fold and 1.7±0.1-fold, respectively, in AKAP-KO compared with WT VSMCs (both p<0.05). The CaMKII activity was higher by 2.5-fold in AKAP-KO than in WT mice. MicroRNA (miR)-30b was shown to inhibit gene expression of CaMKII. The miRNA assay showed that its expression in AKAP-KO aorta was decreased to 0.3±0.2-fold of that in WT aorta (p=0.08, n=3).
Conclusion: Coronary spasm was unexpectedly induced in AKAP-KO mice without enhanced influx of Ca2+, but with enhanced calcium sensitization. Downregulation of miR-30b may be involved in its mechanism.
Author Disclosures: K. Nishizaki: None. H. Tomita: None. M. Senoo: None. N. Narita: None. M. Narita: None. M. Yonekura: None. H. Ichikawa: None. Y. Kimura: None. M. Tanaka: None. T. Osanai: None. K. Okumura: None.
- © 2016 by American Heart Association, Inc.