Zhou Xiaoyang, Fan Guo-Chang, Ren Xiaoping, Waggoner Jason R, Gregory Kimberly N, Chen Guoli, Jones W Keith, Kranias Evangelia G
Department of Pharmacology and Cell Biophysics, University of Cincinnati College of Medicine, Cincinnati, OH 45267-0575, USA.
Cardiovasc Res. 2007 Aug 1;75(3):487-97. doi: 10.1016/j.cardiores.2007.04.005. Epub 2007 Apr 19.
The histidine-rich Ca-binding protein (HRC) is a Ca-storage protein in cardiac sarcoplasmic reticulum. Recent transgenic studies revealed that this protein inhibits the maximal rates of sarcoplasmic reticulum Ca-transport, leading to cardiac dysfunction. In view of the role of sarcoplasmic reticulum Ca-cycling in myocardial ischemia/reperfusion injury, we designed this study to gain further insight into the role of HRC during ischemia/reperfusion.
The transgenic mouse model with cardiac-specific overexpression of HRC was utilized and cardiac contractile parameters were assessed before and after ischemia/reperfusion injury by Langendorff perfusion. After a 20-min stabilization period, the hearts were subjected to 40 min of global ischemia, followed by 60 min of reperfusion. We found that although transgenic (TG) hearts showed depressed cardiac function (25%) compared to wild types (WTs) at baseline, they exhibited better recovery of left ventricular developed pressure (86.6+/-2.6% in TGs vs. 58.3+/-4.0% in WTs of pre-ischemic values, P<0.05) and higher rates of contraction and relaxation after ischemia/reperfusion than WTs. This improvement was accompanied by smaller infarcts (23.1+/-1.7% in TGs vs. 41.1+/-2.5% in WTs of infarct region-to-risk region ratio, P<0.05) and lower creatine kinase release. Notably, the extent of apoptotic cell death was significantly attenuated, as evidenced by decreased DNA fragmentation, upregulation of the antiapoptotic protein Bcl-2, and downregulation of the active caspases (3, 9 and 12) following ischemia/reperfusion in TG hearts, compared with WTs. Extension of these studies to an in vivo model of 30-min myocardial ischemia, via coronary artery occlusion, followed by 24-h reperfusion, showed that the infarct region-to-risk region ratio was 9+/-0.9% in TGs, compared with 20.4+/-2.9% in WTs (P<0.05).
Our findings suggest that increased cardiac HRC expression protects against ischemia/reperfusion injury in the heart, resulting in improved recovery of function and reduced infarction.
富含组氨酸的钙结合蛋白（HRC）是心脏肌浆网中的一种钙储存蛋白。最近的转基因研究表明，这种蛋白会抑制肌浆网钙转运的最大速率，从而导致心脏功能障碍。鉴于肌浆网钙循环在心肌缺血/再灌注损伤中的作用，我们设计了本研究，以进一步深入了解HRC在缺血/再灌注过程中的作用。
利用心脏特异性过表达HRC的转基因小鼠模型，通过Langendorff灌注评估缺血/再灌注损伤前后的心脏收缩参数。在20分钟的稳定期后，心脏进行40分钟的全心缺血，随后进行60分钟的再灌注。我们发现，虽然转基因（TG）心脏在基线时与野生型（WT）相比心脏功能降低（25%），但在缺血/再灌注后，它们的左心室舒张末压恢复更好（TG组为缺血前值的86.6±2.6%，WT组为58.3±4.0%，P<0.05），且收缩和舒张速率高于WT。这种改善伴随着较小的梗死面积（TG组梗死区域与危险区域比值为23.1±1.7%，WT组为41.1±2.5%，P<0.05）和较低的肌酸激酶释放。值得注意的是，凋亡细胞死亡程度显著减轻，与WT相比，TG心脏在缺血/再灌注后DNA片段化减少、抗凋亡蛋白Bcl-2上调以及活性半胱天冬酶（3、9和12）下调证明了这一点。将这些研究扩展到通过冠状动脉闭塞进行30分钟心肌缺血、随后进行24小时再灌注的体内模型，结果显示TG组梗死区域与危险区域比值为9±0.9%，WT组为20.4±2.9%（P<0.05）。
我们的研究结果表明，心脏HRC表达增加可保护心脏免受缺血/再灌注损伤，从而改善功能恢复并减少梗死。
