The Laboratory of Emergency Medicine, School of Second Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu, 221002, China; Department of Emergency Medicine, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, 221002, China.
The Laboratory of Emergency Medicine, School of Second Clinical Medicine, Xuzhou Medical University, Xuzhou, Jiangsu, 221002, China; Department of Nuclear Medicine, Luoyang Central Hospital Affiliated to Zhengzhou University, Luoyang, Henan, 471000, China.
Nitric Oxide. 2024 Dec 1;153:26-40. doi: 10.1016/j.niox.2024.10.004. Epub 2024 Oct 5.
Ischemic stroke is a major cause of death and disability. The activation of neuronal nitric oxide synthase (nNOS) and the resulting production of nitric oxide (NO) via NMDA receptor-mediated calcium influx play an exacerbating role in cerebral ischemia reperfusion injury. The NO rapidly reacts with superoxide (O) to form peroxynitrite (ONOO), a toxic molecule may modify proteins through tyrosine residue nitration, ultimately worsening neuronal damage. SIRT6 has been proven to be crucial in regulating cell proliferation, death, and aging in various pathological settings. We have previous reported that human SIRT6 tyrosine nitration decreased its intrinsic catalytic activity in vitro. However, the exact role of SIRT6 function in the process of cerebral ischemia reperfusion injury is not yet fully elucidated. Herein, we demonstrated that an increase in the nitration of SIRT6 led to reduce its enzymatic activity and aggravated hippocampal neuronal damage in a rat model of four-artery cerebral ischemia reperfusion. In addition, reducing SIRT6 nitration resulted in increase the activity of SIRT6, alleviating hippocampal neuronal damage. Moreover, SIRT6 nitration affected its downstream molecule activity such as PARP1 and GCN5, promoting the process of neuronal ischemic injury in rat hippocampus. Additionally, treatment with NMDA receptor antagonist MK801, or nNOS inhibitor 7-NI, and resveratrol (an antioxidant) diminished SIRT6 nitration and the catalytic activity of downstream molecules like PARP1 and GCN5, thereby reducing neuronal damage. Finally, in the biochemical regulation of SIRT6 activity, tyrosine 257 was essential for its activity and susceptibility to nitration. Replacing tyrosine 257 with phenylalanine in rat SIRT6 attenuated the death of SH-SY5Y neurocytes under oxygen-glucose deprivation (OGD) conditions. These results may offer further understanding of SIRT6 function in the pathogenesis of cerebral ischemic diseases.
缺血性脑卒中是死亡和残疾的主要原因。神经元型一氧化氮合酶（nNOS）的激活以及通过 NMDA 受体介导的钙内流产生的一氧化氮（NO）在脑缺血再灌注损伤中起加重作用。NO 迅速与超氧化物（O）反应形成过氧亚硝酸盐（ONOO），一种有毒分子可能通过酪氨酸残基硝化修饰蛋白质，最终加重神经元损伤。SIRT6 已被证明在各种病理情况下对细胞增殖、死亡和衰老的调节至关重要。我们之前报道过，人 SIRT6 酪氨酸硝化会降低其内在的催化活性。然而，SIRT6 功能在脑缺血再灌注损伤过程中的确切作用尚未完全阐明。在此，我们证明 SIRT6 的硝化增加导致其酶活性降低，并加重四血管脑缺血再灌注大鼠模型中海马神经元损伤。此外，减少 SIRT6 硝化导致 SIRT6 活性增加，减轻海马神经元损伤。此外，SIRT6 硝化会影响其下游分子如 PARP1 和 GCN5 的活性，促进大鼠海马神经元缺血性损伤过程。此外，NMDA 受体拮抗剂 MK801 或 nNOS 抑制剂 7-NI 和白藜芦醇（一种抗氧化剂）的治疗可减少 SIRT6 硝化和下游分子如 PARP1 和 GCN5 的催化活性，从而减少神经元损伤。最后，在 SIRT6 活性的生化调节中，酪氨酸 257 对其活性和硝化敏感性至关重要。在大鼠 SIRT6 中用苯丙氨酸取代酪氨酸 257 可减轻氧葡萄糖剥夺（OGD）条件下 SH-SY5Y 神经细胞的死亡。这些结果可能为进一步了解 SIRT6 在缺血性脑疾病发病机制中的功能提供依据。
