cAMP直接激活的交换蛋白（EPAC）对窦房结功能障碍的矫正作用研究

窦房结功能障碍（SND）是由窦房结和（或）临近组织病变引起的窦房结起搏和（或）传导功能障碍，发病率高且疗效差。起搏细胞是窦房结中能够自发产生动作电位和节律的细胞，现有的起搏机制是膜钟与钙钟在cAMP-PKA及其下游通路调控下产生，详细机制不清。申请人前期预实验发现，激活cAMP的另一效应因子，环磷酸腺苷直接激活的交换蛋白（EPAC），能够改变钙震荡特性，提高起搏细胞自发节律。据此本项目提出，cAMP-EPAC是参与调控起搏细胞自发节律的另一重要通路，EPAC1过表达能提高起搏细胞自律性并改善窦房结功能障碍。本项目拟采用无损窦房结组织共聚焦钙成像、膜片钳和局部在体病毒转染等技术，结合RyR2R420Q小鼠模型，证明cAMP-EPAC1介导肾上腺素受体β-AR级联激活下游通路参与起搏作用的电生理细节和生物学功能，探究EPAC1过表达对窦房结功能障碍的矫正作用，为窦房结相关疾病的防治提供新思路。

Sinus node dysfunction (SND) is sinus node impulse generating and (or) propagating dysfunction caused by pathological changes in sinus node and (or) adjacent tissue, with high incidence and poor treatment effect. Pacemaker cells are the cells in the sinus node that can spontaneously generate action potentials and rhythms. The current pacemaking mechanism is that it’s produced by membrane clock and calcium clock under the regulation of cAMP-PKA and its downstream pathway. The detailed mechanism is unclear. The applicant’s preliminary experiments discovered that activation of another effector of cAMP, the exchange protein directly activated by cyclic AMP (EPAC), can change calcium transient properties and enhance the automaticity of pacemaker cells. Thus, this project proposes that cAMP-EPAC is another important signaling pathway involved in regulating pacemaker cells’ spontaneous rhythm. EPAC1 overexpression can potentiate the pacemaker cells’ automaticity and improve sinus node dysfunction. This project intends to use intact sinoatrial node tissue calcium imaging with confocal microscope, patch clamp and local in vivo virus transfection techniques, combined with the RyR2R420Q mouse model. We aim to prove the electrophysiological details and biological function of cAMP-EPAC1 mediating adrenergic receptor β-AR cascade and activating downstream pathway, and to explore the corrective effect of EPAC1 overexpression on sinus node dysfunction, which provides new ideas for prevention and treatment of the sinus node related diseases.