GCH-1在Nrf2/HO-1通路激活防治糖尿病心肌病中的作用与机制

Diabetic cardiomyopathy increases the risk of heart failure and death. At present, there are no effective approaches to preventing the development of diabetic cardiomyopathy in the clinic. The search for new therapeutic targets and pharmacological agents for protection of the heart against diabetic cardiomyopathy is of primary importance. Recent studies have identified GTP cyclohydrolase 1 (GCH-1) and its product tetrahydrobiopterin as potent regulators of nitric oxide production and oxidative/nitrosative stress that are implicated in the pathogenesis of diabetic cardiomyopathy. The objective of this project is to test whether moderate dosage of antioxidant NAC can activate cardiac GTP cycl-ohydrolase 1 (GCH-1) through Nrf2 activation. It may serve as a potential therapeutic target for diabetic cardiomyopathy when the upstream Nrf2 is injured. Recently, we have found that streptozotocin-induced type 1 diabetes resulted in cardiac GCH-1 degradation and diabetic cardiomyopathy in C57BL/6 mice, concomitant with decreases in nitric oxide. Especially interestingly, these detrimental effects of diabetes on mouse hearts were abrogated by cardiomyocyte-specific overexpression of GCH1 by gene transfer. Furthermore, we found that NAC anti-diabetic effect was delivered by the Nrf2 upregulation of NO, and GCH-1 knockdown cancelled NAC cardioprotection but didn’t affect Nrf2 expression. Thus, we speculated that NAC could conferred cardioprotection through the activation of Nrf2/GCH-1/NO signaling. We will incorporate the uses of Nrf2 and GCH-1 transgenic mice and the uses of adenovirus overexpression and siRNA knockdown as well as specific protein inhibition to explore the role of Nrf2/GCH-1/NO in NAC cardioprotection. Successful completion of these innovative studies will elucidate the molecular mechanisms in the pathogenesis of diabetic cardiomyopathy. The findings from these studies will lay the foundation for developing the novel strategies that can be implemented to treat diabetic cardiomyopathy.

糖尿病心肌病（DCM）增加心衰和死亡风险，临床上尚无有效方法阻止其发展。高糖诱导活性氧（ROS）大量增加导致心肌细胞氧化/氮化应激加重是DCM发展的关键但大剂量抗氧化剂治疗存在争议，因此阐明抗氧化治疗的机制及最终作用分子，避免大剂量抗氧化剂治疗的副作用十分关键。我们前期研究发现 DCM 的发生与GTP环式水解酶(GCH-1)降解密切相关，而高表达GCH-1能够升高保护性一氧化氮（NO）和减轻DCM，同时抗氧化剂（NAC）通过激活Nrf2来升高NO达到保护心肌的作用，且抑制GCH-1之后DCM心肌保护作用消失但不影响Nrf2。我们推测NAC主要通过升高Nrf2来激活GCH-1诱导的NO含量增加达到抗氧化及保护DCM心肌, 进而假设GCH-1在Nrf2防治DCM中起重要作用。本课题旨在在Nrf2表达下降的情况下，从多途径激活NO，达到保护心肌的作用，为研究DCM的机制、开发新药物提供理论依据。

糖尿病心肌病（DCM）增加心衰和死亡风险，临床上尚无有效方法阻止其发展。DCM进展中，高糖诱导活性氧（ROS）大量增加导致心肌细胞氧化/氮化应激加重是DCM发展的关键，FoxO1蛋白是不良血管重建的关键。但大剂量抗氧化剂治疗存在争议，本实验着力于寻找合适的抗氧化治疗方式并研究其机制及最终作用分子，避免大剂量抗氧化剂治疗的副作用，研究发现，糖尿病导致野生型小鼠心脏GTP环化水解酶1 (GCH1)蛋白的降解，心肌细胞特异性过表达GTP环化水解酶1可保护糖尿病小鼠的神经元型一氧化氮合成酶 (nNOS),升高保护性一氧化氮（NO），还可改善糖尿病损伤的细胞内Ca2+信号，保护肌浆网Ca2+操作子的表达，从而减少心脏纤维化和细胞凋亡，改善糖尿病引起的心脏重塑和功能障碍。 此外，IPo 和脂联素 (APN) 的组合增加了核和/或线粒体 STAT3 的激活，并且用抗氧化剂异氟醚进行心脏预处理与血管内皮生长因子 (VEGF) 调节 eNOS 磷酸化和 NO 产生有关。上述以不同方式缓解心脏氧化应激，激活NO的产生，以保护心肌，研究DCM的机制，为治疗DCM提供理论依据。