HIF1α调控线粒体融合分裂与自噬对抗糖尿病心肌缺血再灌注损伤的机制研究

The incidence of perioperative complications in diabetic patients was five times higher than that in non-diabetic patients. Sevoflurane postconditioning (SPostC) has an effect on stablizing mitochondrial fusion/fission balance, rescuing mitophagy flux; its myocardial protection against ischemia reperfusion injury (IRI) is widely recognized. However, we found that this effect was weaken in diabetic myocardium due to impaired HIF1α leading to excessive mitochondrial fission, and lack of mitophagic clearance. It’s confirmed that hypoxia sensitive genes (SKN-1 / Nrf and STL-1 / SLP-2, BNIP3) act as downstream target genes of HIF1α directly related to mitochondrial fusion and mitophagy. Hereby, we suggest that: up-regulation and stabilization of HIF1α-induced hypoxia sensitive genes is the key of maintaining mitochondrial fusion/fission balance, rescuing mitophagy, which is also the central of restoring SPostC protective effect. Therefore in this study, we focus on the vulnerability of diabetic myocardium, in order to restore the ability of diabetic myocardium against IRI, as well as reversing SPostC protective effect in diabetic myocardium, based on maintaining the balance of mitochondrial fusion/fission by activating the downstream key hypoxia sensitive genes of HIF1α.

糖尿病患者围术期并发症的发生率较非糖尿病患者高5倍以上。正常心肌发生缺血再灌注损伤（IRI）时，七氟醚后处理（SPostC）通过稳定线粒体融合分裂平衡、挽救自噬流所发挥的对抗IRI的心肌保护作用被广泛认可。然而我们发现糖尿病心肌中该作用被弱化，关键在于HIF1α受损致线粒体分裂过度，自噬清除不足。文献证实HIF1α下游低氧敏感基因中关键靶基因（SKN-1/Nrf与STL-1/SLP-2，BNIP3）与线粒体融合分裂及自噬极为相关，由此我们提出维持线粒体融合分裂与自噬的平衡、稳定线粒体形态与功能的关键在于上调并稳定HIF1α诱导低氧敏感基因，这也是逆转SPostC保护作用的核心所在。因此，本研究以糖尿病心肌易损性为着眼点，以激活HIF1α下游低氧敏感基因中关键靶基因为要素，以调控线粒体融合分裂平衡为目的，旨在恢复糖尿病心肌抵抗IRI的能力，由此逆转SPostC对糖尿病心肌的保护作用。

糖尿病患者围术期并发症的发生率较非糖尿病患者高5倍以上。正常心肌发生缺血再灌注损伤（IRI）时，七氟醚后处理（SPostC）通过稳定线粒体融合分裂平衡、挽救自噬流所发挥的对抗IRI的心肌保护作用被广泛认可。然而我们发现糖尿病心肌中该作用被弱化，关键在于HIF1-α受损致线粒体分裂过度，自噬清除不足。文献证实HIF1-α下游低氧敏感基因中关键靶基因（SKN-1/Nrf与STL-1/SLP-2，BNIP3）与线粒体融合分裂及自噬极为相关，由此我们提出维持线粒体融合分裂与自噬的平衡、稳定线粒体形态与功能的关键在于上调并稳定HIF1-α诱导低氧敏感基因，这也是逆转SPostC保护作用的核心所在。因此，本研究以糖尿病心肌易损性为着眼点，以激活HIF1-α下游低氧敏感基因中关键靶基因为要素，以调控线粒体融合分裂平衡为目的，旨在恢复糖尿病心肌抵抗IRI的能力，由此逆转SPostC对糖尿病心肌的保护作用。本研究在细胞水平研究表明，高糖通过影响乳鼠心肌细胞及H9C2 细胞系线粒体的形态，降低其连接度及拉长度，使其由网状向点块状改变，并降低其膜电位水平，从而导致心肌细胞能量代谢紊乱；在细胞水平及动物在体水平表明，H9C2心肌细胞发生H/R后，HIF-1α/MIF/AMPK信号通路可能是SPostC对抗H/R损伤的关键环节。在高糖状态下，SPostC可以通过上调HIF-1α和MIF的表达来恢复其心肌保护作用；通过药理学干预即DFO联合SPostC通过恢复受损的HIF-1α进而促进HIF-1α/BNIP3介导的线粒体自噬减轻糖尿病GK大鼠心肌缺血再灌注损伤；并且发现SpostC能够激活PI3K/AKT信号通路，通过增加AKT的磷酸化水平，促进HIF-1α调控线粒体裂解和融合，维持线粒体动力学平衡，从而减轻心肌缺血再灌注损伤。这是从探讨分子学机制向临床干预的转化，对保护围术期糖尿病心肌有重要意义。