Mechanisms of Coronary Arteriolar Dysfunction in Type 2 Diabetes

描述(申请人提供)：冠状动脉小动脉功能高度依赖于内皮细胞(EC)和血管平滑肌细胞(VSMC)的完整性。2型糖尿病与缺血性心脏病的发病率增加有关，缺血性心脏病通常与糖尿病患者的发病率和死亡率增加有关的冠状动脉疾病有关。表皮生长因子受体(EGFR)酪氨酸激酶是参与细胞生长和迁移的众多因子之一，已被证明在微血管肌源性张力的发展中起关键作用，表现为微血管对压力增加的收缩反应。我们的研究表明，2型糖尿病小鼠(缺乏瘦素受体基因的db-/db小鼠)冠状动脉小动脉EGFR酪氨酸激酶磷酸化加剧，与冠状动脉小动脉功能障碍相关，特征是内皮依赖性松弛减少和肌源性张力增强。有趣的是，在db-/db-小鼠体内抑制EGFR酪氨酸激酶显著改善冠状动脉小动脉功能。因此，糖尿病中增强的EGFR酪氨酸激酶可能是一个关键的上游信号，导致无数下游信号，包括氧化应激、NFkB和PARP-1。更重要的是，氧化应激、核因子kappaβ(NFkB转录和核因子)和多聚腺苷二磷酸核糖聚合酶(PARP-1核因子)与2型糖尿病的发生和发展密切相关，可能在糖尿病冠状动脉小动脉功能障碍中起关键作用。我们的初步数据表明，db-/db-小鼠冠状动脉小动脉的氧化应激(超氧化物；O2.-)、p65-NFkB活性和PARP-1活性增加。尽管有这些联系，但尚未确定糖尿病的冠状小动脉病变与EGFR酪氨酸激酶、氧化应激、NFkB和PARP-1途径之间的联系。因此，我们的中心假设是，EGFR酪氨酸激酶磷酸化加剧导致ROS、NFkB和PARP活性增加，这反过来又导致2型糖尿病患者冠状动脉小动脉功能障碍。我们将确定：目的1.抑制EGFR酪氨酸激酶降低db-/db-小鼠的O2.-，p65-NFkB和PARP活性，并改善冠脉小动脉功能；目的2.抑制O2.-产生或清除O2。-在db-/db-小鼠改善冠状动脉小动脉EC和VSMC功能障碍；目的3.增加p65-NFkB和PARP-1活性在db-/db-小鼠冠状动脉小动脉功能障碍中起关键作用。该项目的成功完成将确定EGFR酪氨酸激酶的恶化如何导致氧化应激、NFkB和PARP-1活性增加的机制，这反过来又是导致冠状动脉小动脉功能障碍的原因，并将为糖尿病的血管病变机制提供新的见解。

DESCRIPTION (provided by applicant): Coronary arteriolar function is highly dependent on the integrity of endothelial cells (EC) and vascular smooth muscle cells (VSMC). Type 2 diabetes is associated with increased prevalence of ischemic heart disease, generally related to coronary artery disease that is associated with increased morbidity and death in diabetic patients. Epidermal growth factor receptor (EGFR) tyrosine kinase, of the many factors involved in cell growth and migration has been shown to be critical in the development of microvascular myogenic tone expressed as microvascular constriction in response to pressure increases. Our studies show an exacerbation of EGFR tyrosine kinase phosphorylation in coronary arteriolar from type 2 diabetic mice (db-/db- mice lacking leptin receptor gene) associated with coronary arteriolar dysfunction characterized by a reduced endothelial-dependent relaxation and potentiation of myogenic tone. Interestingly, in vivo inhibition of EGFR tyrosine kinase in db-/db- mice significantly improves coronary arteriolar function. Thus, enhanced EGFR tyrosine kinase in diabetes could be a critical up stream signal leading to a myriad of downstream signaling including oxidative stress, NFkB and PARP-1. More importantly, oxidative stress, nuclear factor kappa Beta (NFkB-transcriptional and nuclear factor) and poly(ADP-ribose)polymerase (PARP-1 nuclear factor), which are highly implicated in the etiology and progression of type 2 diabetes, could be critical in coronary arteriolar dysfunction in diabetes. Our preliminary data indicate an increase in oxidative stress (superoxide; O2.-), p65- NFkB activity and PARP-1 activity in coronary arterioles from db-/db- mice. Despite these connections, there has been no link determined between the coronary arteriolar pathology of diabetes with EGFR tyrosine kinase, oxidative stress, NFkB and PARP-1 pathway. Therefore, our central hypothesis is that exacerbation of EGFR tyrosine kinase phosphorylation leads to the increased ROS, NFkB and PARP activity, which in turn are responsible for coronary arteriolar dysfunction in type 2 diabetes. We will determine that: Aim 1. EGFR tyrosine kinase inhibition reduces O2.-, p65-NFkB and PARP activity, and improves coronary arteriolar function in db-/db- mice; Aim 2. Inhibition of O2.- production or scavenging of O2.- in db-/db- mice improves coronary arteriolar EC and VSMC dysfunction; Aim 3. Increased p65-NFkB and PARP-1 activities are critical in coronary arteriolar dysfunction in db-/db- mice. The successful completion of this project will determine the mechanisms how exacerbation of EGFR tyrosine kinase leads to the increased oxidative stress, NFkB and PARP-1 activity, which in turn are responsible for coronary arteriolar dysfunction, and will provide new insight into the vasculopathy mechanisms in diabetes.