Li Wei, Yang Xueqi, Ding Mao, Shi Wenjuan, Huang Yuyou, An Qi, Qi Zhifeng, Zhao Yongmei
Institute of Cerebrovascular Diseases Research, Xuanwu Hospital of Capital Medical University, Beijing, China.
Beijing Geriatric Medical Research Center, Beijing, China.
Front Cell Neurosci. 2023 Mar 8;17:1065873. doi: 10.3389/fncel.2023.1065873. eCollection 2023.
Intracellular zinc accumulation has been shown to be associated with neuronal death after cerebral ischemia. However, the mechanism of zinc accumulation leading to neuronal death in ischemia/reperfusion (I/R) is still unclear. Intracellular zinc signals are required for the production of proinflammatory cytokines. The present study investigated whether intracellular accumulated zinc aggravates I/R injury through inflammatory response, and inflammation-mediated neuronal apoptosis. Male Sprague-Dawley rats were treated with vehicle or zinc chelator TPEN 15 mg/kg before a 90-min middle cerebral artery occlusion (MCAO). The expressions of proinflammatory cytokines TNF-α, IL-6, NF-κB p65, and NF-κB inhibitory protein IκB-α, as well as anti-inflammatory cytokine IL-10 were assessed at 6 or 24 h after reperfusion. Our results demonstrated that the expression of TNF-α, IL-6, and NF-κB p65 increased after reperfusion, while the expression of IκB-α and IL-10 decreased, suggesting that cerebral ischemia triggers inflammatory response. Furthermore, TNF-α, NF-κB p65, and IL-10 were all colocalized with the neuron-specific nuclear protein (NeuN), suggesting that the ischemia-induced inflammatory response occurs in neurons. Moreover, TNF-α was also colocalized with the zinc-specific dyes Newport Green (NG), suggesting that intracellular accumulated zinc might be associated with neuronal inflammation following cerebral I/R. Chelating zinc with TPEN reversed the expression of TNF-α, NF-κB p65, IκB-α, IL-6, and IL-10 in ischemic rats. Besides, IL-6-positive cells were colocalized with TUNEL-positive cells in the ischemic penumbra of MCAO rats at 24 h after reperfusion, indicating that zinc accumulation following I/R might induce inflammation and inflammation-associated neuronal apoptosis. Taken together, this study demonstrates that excessive zinc activates inflammation and that the brain injury caused by zinc accumulation is at least partially due to specific neuronal apoptosis induced by inflammation, which may provide an important mechanism of cerebral I/R injury.
细胞内锌蓄积已被证明与脑缺血后的神经元死亡有关。然而，缺血/再灌注（I/R）中导致神经元死亡的锌蓄积机制仍不清楚。促炎细胞因子的产生需要细胞内锌信号。本研究调查了细胞内蓄积的锌是否通过炎症反应和炎症介导的神经元凋亡加重I/R损伤。雄性Sprague-Dawley大鼠在大脑中动脉闭塞（MCAO）90分钟前用溶剂或锌螯合剂TPEN 15mg/kg进行处理。在再灌注后6或24小时评估促炎细胞因子TNF-α、IL-6、NF-κB p65和NF-κB抑制蛋白IκB-α以及抗炎细胞因子IL-10的表达。我们的结果表明，再灌注后TNF-α、IL-6和NF-κB p65的表达增加，而IκB-α和IL-10的表达降低，提示脑缺血引发炎症反应。此外，TNF-α、NF-κB p65和IL-10均与神经元特异性核蛋白（NeuN）共定位，提示缺血诱导的炎症反应发生在神经元中。此外，TNF-α也与锌特异性染料纽波特绿（NG）共定位，提示细胞内蓄积的锌可能与脑I/R后的神经元炎症有关。用TPEN螯合锌可逆转缺血大鼠中TNF-α、NF-κB p65、IκB-α、IL-6和IL-10的表达。此外，再灌注后24小时，MCAO大鼠缺血半暗带中IL-6阳性细胞与TUNEL阳性细胞共定位，表明I/R后锌蓄积可能诱导炎症和炎症相关的神经元凋亡。综上所述，本研究表明过量锌激活炎症，锌蓄积导致的脑损伤至少部分是由于炎症诱导的特异性神经元凋亡，这可能为脑I/R损伤提供一个重要机制。
