Department of Anesthesia, Critical Care, and Pain Medicine, Massachusetts General Hospital, 149 13th Street, Charlestown, MA 02129, USA.
Basic Res Cardiol. 2011 Jun;106(4):635-43. doi: 10.1007/s00395-011-0167-y. Epub 2011 Mar 11.
Nitric oxide (NO)-dependent soluble guanylate cyclase (sGC) activation is an important component of cardiac signal transduction pathways, including the cardioprotective signaling cascade induced by ischemic preconditioning (IPC). The sGCα subunit, which binds to the common sGCβ1 subunit, exists in two different isoforms, sGCα1 and sGCα2, but their relative physiological roles remain unknown. In the present study, we studied Langendorff-perfused isolated hearts of genetically engineered mice lacking functional sGCα1 (sGCα1KO mice), which is the predominant isoform in the heart. Our results show that the loss of sGCα1 has a positive inotropic and lusitropic effect on basal cardiac function, indicating an important role for sGCα1 in regulating basal myocardial contractility. Surprisingly, IPC led to a similar 35-40% reduction in infarct size and concomitant protein kinase Cε (PKCε) phosphorylation in both wild-type (WT) and sGCα1KO hearts subjected to 40 min of global ischemia and reperfusion. Inhibition of the activation of all sGC isoforms by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ, 10 μmol/L) completely abolished the protection by IPC in WT and sGCα1KO hearts. NO-stimulated cGMP production was severely attenuated in sGCα1KO hearts compared to WT hearts, indicating that the sGCα2 isoform only produces minute amounts of cGMP after NO stimulation. Taken together, our results indicate that although sGCα1 importantly regulates cardiac contractility, it is not required for cardioprotection by IPC. Instead, our results suggest that possibly only minimal sGC activity, which in sGCα1KO hearts is provided by the sGCα2 isoform, is sufficient to transduce the cardioprotective signal induced by IPC via phosphorylation of PKCε.
一氧化氮（NO）依赖性可溶性鸟苷酸环化酶（sGC）的激活是心脏信号转导途径的重要组成部分，包括缺血预处理（IPC）诱导的心脏保护信号级联反应。sGCα 亚基与常见的 sGCβ1 亚基结合，存在两种不同的同工型，sGCα1 和 sGCα2，但它们的相对生理作用仍不清楚。在本研究中，我们研究了缺乏功能性 sGCα1（sGCα1KO 小鼠）的基因工程小鼠的 Langendorff 灌注分离心脏，sGCα1 是心脏中的主要同工型。我们的结果表明，sGCα1 的缺失对基础心功能具有正性变力和变时作用，表明 sGCα1 在调节基础心肌收缩力方面具有重要作用。令人惊讶的是，IPC 导致 40 分钟的整体缺血和再灌注后，WT 和 sGCα1KO 心脏的梗塞面积减少 35-40%，同时蛋白激酶 Cε（PKCε）磷酸化。用 1H-[1,2,4]恶二唑[4,3-a]喹喔啉-1-酮（ODQ，10 μmol/L）抑制所有 sGC 同工型的激活完全消除了 WT 和 sGCα1KO 心脏中 IPC 的保护作用。与 WT 心脏相比，sGCα1KO 心脏中的 NO 刺激的 cGMP 产生严重减弱，表明 sGCα2 同工型在 NO 刺激后仅产生少量的 cGMP。总之，我们的结果表明，尽管 sGCα1 重要地调节心脏收缩力，但它不是 IPC 保护所必需的。相反，我们的结果表明，可能只有最小量的 sGC 活性，在 sGCα1KO 心脏中由 sGCα2 同工型提供，足以通过 PKCε 的磷酸化转导 IPC 诱导的心脏保护信号。
