橙皮素对糖尿病大鼠冠状动脉平滑肌电位门控钾通道的影响

Hyperglycemia, a metabolic condition which is an important characteristic of diabetes, is known to down-regulate expression of voltage-gated potassium channels (Kv), depress Kv currents and disorder myogenic response in coronary arterial (CA) vascular smooth muscle (VSMC). Diabetic patients have a higher incidence of coronary heart disease (CHD). Kv is crucial for regulating CA resistance. We recently for the first time demonstrated that hesperetin (HSP) augments Kv currents, depresses Ca2+ inward currents, reduces intracellular Ca2+ levels and induces relaxation in CA VSMCs isolated from normal rats. However, it remains unknown whether HSP might protect against impairing effect of hyperglycemia on CA VSMC Kv, and if so, what might be the underlying mechanism. The aim of this proposal is to investigate effects of HSP on diabetes-induced disorders in coronary myogenic response, Kv currents and Kv expression by using myograph, patch clamp, RT-PCR and Western blot, respectively. To explore the responsible molecular mechanism, we will further study role of protein kinase A and C in protection of HSP against the effects of hyperglycemia on CA VSMC by observing effect of HSP on expression of the protein kinases and effects of inhibiting the protein kinases on protection of HSP. The results of this project are expected to formulate a theoretical basis for using HSP clinically in prevention and treatment of diabetes-related coronary complications.

糖尿病使冠状动脉（CA）血管平滑肌（VSMC）电位门控钾通道（Kv）表达下调，Kv电流减小，CA肌原性反应障碍，易导致冠状动脉性心脏病（CHD）。CA VSMC Kv是调节CA血管阻力的关键因素。我们最近证实橙皮素（HSP）增加正常大鼠CA VSMC Kv电流，在国内外首次提出，HSP降低CA VSMC细胞内Ca2+水平并舒张CA与促进Kv电流有关。HSP对糖尿病CA VSMC肌原性反应和Kv有何作用至今未见报道。基于设想HSP可保护CA免受糖尿病危害，我们拟分别通过离体血管、膜片钳和基因蛋白表达实验，研究HSP对糖尿病和高浓度葡萄糖所致的CA肌原性反应障碍、Kv功能受抑和Kv表达下调的影响。本项目还将通过观察HSP对蛋白激酶A和蛋白激酶C表达的影响，及蛋白激酶抑制剂对HSP增加Kv电流的影响，进一步探讨HSP作用的分子机制。本项目将为临床使用HSP有效防治糖尿病CHD提供基础理论依据。

糖尿病使冠状动脉（CA）血管平滑肌（VSMC）电位门控钾通道（Kv）功能和表达降低，CA肌原性反应障碍，易导致冠状动脉性心脏病（CHD）。改善CA肌原性反应是防治糖尿病CHD的关键。CA VSMC Kv是调节CA血管阻力的关键因素。橙皮素（HSP）对心血管系统具有多种有益作用，包括血管舒张、抑制细胞增生、抑制血管形成等作用，但其具体作用机制尚不清楚。本课题通过离体血管环、膜片钳、基因蛋白表达等实验，研究HSP对糖尿病和高浓度葡萄糖所致的大鼠CA肌原性反应障碍、Kv功能受抑和Kv表达下调的影响。通过预孵蛋白激酶A（PKA）抑制剂和蛋白激酶C（PKC）抑制剂，研究蛋白激酶对HSP舒张作用的影响，进一步探讨HSP作用的机制。慢性动物实验结果表明，HSP通过增加Kv1.2表达而改善Kv功能进一步减轻糖尿病所引起的CA肌原性反应障碍，而对Kv1.5通道的表达没有明显影响。急性实验结果显示，HSP可对抗高糖所致的正常大鼠CA舒缩功能障碍、VSMC Kv电流减小和Kv1.2通道表达下调；抑制剂实验显示PKA参与了HSP的舒张作用。本研究揭示了HSP上调血管平滑肌Kv的功能和表达而发挥对糖尿病大鼠CA的保护作用，为临床使用HSP防治糖尿病CHD提供基础理论依据。