Conclusion
SIK2 may promote autophagy through the mTOR/ULK1 signaling pathway, and inhibiting SIK2 can reduce abnormal autophagy and alleviate myocardial IR injury in rats. 目的: 探究盐诱导激酶2（SIK2）对大鼠心脏缺血再灌注损伤的影响及机制。 方法: 建立大鼠心肌缺血再灌注损伤模型，随机分为假手术组、缺血再灌注组、SIK2抑制剂组，5只/组（造模前24 h左股静脉注射博舒替尼10 mg/kg）。超声检测大鼠心功能，HE染色观察大鼠心肌组织病理变化，透射电镜观察心肌细胞自噬情况，蛋白免疫印迹法检测各组大鼠心肌组织中SIK2和LC3B、Beclin-1、p62等自噬相关蛋白以及p-mTOR、mTOR、p-ULK1、ULK1相关通路蛋白含量。 结果: 与假手术组比较，缺血再灌注组心肌组织病理损伤严重，自噬小体数量增加（P < 0.05），同时SIK2蛋白表达增多（P < 0.01）；与缺血再灌注组相比，SIK2抑制剂组SIK2蛋白表达减少（P < 0.01），心肌组织病理损伤较轻，自噬小体数量减少（P < 0.05）。与假手术组相比，缺血再灌注组LVEF、FS值降低（79.33±3.40 vs 38.67±2.49，59.33±5.25 vs 19.33±1.25，P < 0.001）；与缺血再灌注组相比，SIK2抑制剂组LVEF、FS值升高（38.67±2.49 vs 59.33±3.40，19.33±1.25 vs 30.67±3.40，P < 0.05），3组IVSDd、LVPWDd无明显差别（P > 0.05）。与假手术组相比，缺血再灌注组LC3-Ⅱ/LC3-Ⅰ、Beclin-1蛋白表达增多，p62蛋白表达减少（P < 0.01）；与缺血再灌注组相比，SIK2抑制剂组LC3-Ⅱ/LC3-Ⅰ、Beclin-1蛋白表达减少，p62蛋白表达增多（P < 0.05）。与假手术组相比，缺血再灌注组p-ULK1（Ser757）蛋白表达增多（P < 0.01），p-mTOR蛋白表达减少（P < 0.0001）；与缺血再灌注组相比，SIK2抑制剂组p-ULK1（Ser757）蛋白表达减少（P < 0.01），p-mTOR蛋白表达增多（P < 0.05）；各组mTOR、ULK1无明显差异（P > 0.05）。 结论: SIK2可能通过mTOR/ULK1信号通路促进细胞自噬，对SIK2进行抑制，可以减少异常自噬，缓解心肌缺血再灌注损伤。
Methods
Fifteen male SD rats were randomized equally into sham operation group, myocardial IR model group, and SIK2 inhibitor group (in which the rats were treated with intravenous injection of 10 mg/kg bosutinib via the left femoral vein 24 h before modeling). Ultrasound was used to detect the cardiac function of the rats, and myocardial pathologies were observed with HE staining. Transmission electron microscopy was used to observe autophagy of myocardial cells, and Western blotting was performed to detect the contents of the autophagy-related proteins SIK2, LC3B, Beclin-1, p62 and the expressions of p-mTOR, mTOR, p-ULK1, and ULK1 in myocardial tissue.
Objective
To explore the role of salt-inducible kinase 2 (SIK2) in myocardial ischemia-reperfusion (IR) injury in rats.
Results
Myocardial IR injury significantly increased the number of autophagosomes (P < 0.05) and the expression of SIK2 protein (P < 0.01) in the myocardial tissues. Treatment with bosutinib before modeling obviously lowered the expression of SIK2 protein (P < 0.01), alleviated myocardial pathologies, and reduced the number of autophagosomes (P < 0.05) in the myocardial tissue. The rats with myocardial IR injury showed obviously lowered LVEF and FS values (P < 0.001), which were significantly improved by bosutinib treatment (P < 0.05); no significant difference was detected in IVSDd or LVPWDd among the 3 groups (P > 0.05). Myocardial IR injury obviously increased the expressions of LC3-II/LC3-I and Beclin-1 proteins and lowered the expression of p62 protein (P < 0.01), and these changes were significantly rescued by bosutinib treatment (P < 0.05). The rat models of myocardial IR injury showed significantly increased expression of p-ULK1 (Ser757) (P < 0.01) and lowered expression of p-mTOR protein (P < 0.0001) in the myocardium, and these changes were obviously reversed by bosutinib (P < 0.01 or 0.05); there was no significant difference in mTOR and ULK1 expressions among the 3 groups (P > 0.05).