National Key Laboratory of Frigid Zone Cardiovascular Diseases, Department of Pharmacology (State-Province Key Laboratories of Biomedicine-Pharmaceutics of China, Key Laboratory of Cardiovascular Research, Ministry of Education, International Cooperation Base for Major Cardiovascular Diseases in Cold Regions, China) College of Pharmacy (D.L., Changzhu Li, Z.Z., K.G., H.B., J.Y., K.S., L. Zhang, J.L., Chenhong Li, J.S., L. Zhao, Y.P., L.X., Y.Z., Y. Lu, B.Y., Z.P.), First Affiliated Hospital, Harbin Medical University, China.
National Key Laboratory of Frigid Zone Cardiovascular Diseases, Department of Cardiology (Y. Liu, D.Y., X.Z., Z.-R.Z., Y. Li, Z.P.), First Affiliated Hospital, Harbin Medical University, China.
Circulation. 2024 Jul 9;150(2):111-127. doi: 10.1161/CIRCULATIONAHA.123.067517. Epub 2024 May 10.
G protein-coupled receptors play a critical role in atrial fibrillation (AF). Spexin is a novel ligand of galanin receptors (GALRs). In this study, we investigated the regulation of spexin and GALRs on AF and the underlying mechanisms.
Global spexin knockout (SPX-KO) and cardiomyocyte-specific GALRs knockout (GALR-cKO) mice underwent burst pacing electrical stimulation. Optical mapping was used to determine atrial conduction velocity and action potential duration. Atrial myocyte action potential duration and inward rectifying K current () were recorded using whole-cell patch clamps. Isolated cardiomyocytes were stained with Fluo-3/AM dye, and intracellular Ca handling was examined by CCD camera. A mouse model of AF was established by Ang-II (angiotensin II) infusion.
Spexin plasma levels in patients with AF were lower than those in subjects without AF, and knockout of spexin increased AF susceptibility in mice. In the atrium of SPX-KO mice, potassium inwardly rectifying channel subfamily J member 2 () and sarcolipin () were upregulated; meanwhile, current was increased and Ca handling was impaired in isolated atrial myocytes of SPX-KO mice. GALR2-cKO mice, but not GALR1-cKO and GALR3-cKO mice, had a higher incidence of AF, which was associated with higher current and intracellular Ca overload. The phosphorylation level of CREB (cyclic AMP responsive element binding protein 1) was upregulated in atrial tissues of SPX-KO and GALR2-cKO mice. Chromatin immunoprecipitation confirmed the recruitment of p-CREB to the proximal promoter regions of and . Finally, spexin treatment suppressed CREB signaling, decreased current and decreased intracellular Ca overload, which thus reduced the inducibility of AF in Ang-II-infused mice.
Spexin reduces atrial fibrillation susceptibility by inhibiting CREB phosphorylation and thus downregulating and transcription by GALR2 receptor. The spexin/GALR2/CREB signaling pathway represents a novel therapeutic avenue in the development of agents against atrial fibrillation.
G 蛋白偶联受体在心房颤动（AF）中起着关键作用。 Spexin 是甘丙肽受体（GALRs）的新型配体。在这项研究中，我们研究了 Spexin 和 GALRs 对 AF 的调节及其潜在机制。
全身性 Spexin 敲除（SPX-KO）和心肌细胞特异性 GALRs 敲除（GALR-cKO）小鼠接受爆发性起搏电刺激。光学映射用于确定心房传导速度和动作电位持续时间。使用全细胞膜片钳记录心房肌细胞动作电位持续时间和内向整流钾电流（I K1 ）。用 Fluo-3/AM 染料染色分离的心肌细胞，并通过 CCD 相机检查细胞内 Ca 处理。通过 Ang-II（血管紧张素 II）输注建立 AF 小鼠模型。
AF 患者的 Spexin 血浆水平低于无 AF 患者，Spexin 敲除增加了小鼠的 AF 易感性。在 SPX-KO 小鼠的心房中，钾内向整流通道亚家族 J 成员 2（KCNJ2）和肌浆球蛋白（SARC）上调；同时，SPX-KO 小鼠的分离心房肌细胞中 I K1 增加，Ca 处理受损。GALR2-cKO 小鼠而非 GALR1-cKO 和 GALR3-cKO 小鼠的 AF 发生率更高，这与更高的 I K1 和细胞内 Ca 过载有关。SPX-KO 和 GALR2-cKO 小鼠的心房组织中 CREB（环磷酸腺苷反应元件结合蛋白 1）的磷酸化水平升高。染色质免疫沉淀证实了 p-CREB 募集到 KCNJ2 和 SARC 的近端启动子区域。最后，Spexin 处理抑制了 CREB 信号传导，降低了 I K1 和细胞内 Ca 过载，从而减少了 Ang-II 输注小鼠的 AF 易感性。
Spexin 通过抑制 CREB 磷酸化来降低心房颤动的易感性，从而通过 GALR2 受体下调 KCNJ2 和 SARC 的转录。Spexin/GALR2/CREB 信号通路代表了开发针对心房颤动的新型治疗药物的新途径。
