Department of Neurology, General Hospital of Shenyang Military Area Command, Shenyang, Liaoning 110016, P.R. China.
Department of Neurology, The General Hospital of Tianjin Medical University, Tianjin 300020, P.R. China.
Mol Med Rep. 2019 Mar;19(3):1443-1452. doi: 10.3892/mmr.2019.9827. Epub 2019 Jan 7.
The present study aimed to investigate the effects of low‑dose lipopolysaccharide (LPS) on ischemia/reperfusion (I/R)‑induced brain injury, and to explore the mechanism of phosphoinositide 3‑kinase (PI3K)/Akt/forkhead box protein (Fox)O1 signaling pathway. Male Sprague‑Dawley rats were divided into control group (control), ischemia/reperfusion surgery group (I/R) and low‑dose LPS treatment group (LPS). An I/R model was established and the hemodynamic parameters were recorded at the end of I/R injury. The brain tissues were observed by hematoxylin and eosin staining, immunohistochemistry and terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labeling staining. Microglia were treated with LPS following hypoxia/reoxygenation. The cellular viability was detected by 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide assay. The apoptotic rate of microglia was detected using AnnexinV/propidium iodide staining. The expression of B‑cell lymphoma (Bcl)‑2, Bcl‑2‑associated X (Bax), and caspase‑3 were detected by western blot analysis and reverse transcription‑quantitative polymerase chain reaction. Akt, phosphorylated (p)‑Akt, FoxO1 and p‑FoxO1 expression were detected by western blotting. It was previously reported that, following I/R injury, neuronal cells were disorderly and brain injury markers (neuron‑specific enolase and S100 β), inflammatory cytokines [interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α] levels were significantly upregulated. In the present study, the expression levels of Bax, caspase‑3 Akt and p‑Akt were significantly higher, while that of Bcl‑2, FoxO1 and p‑FoxO1 were significantly lower in the I/R group. LPS treatment significantly increased the viability of neuronal cells and decreased the rate of neuronal cell apoptosis. Following the addition of PI3K signaling pathway inhibitor LY294002 to microglia, LPS reduced the levels of activated Akt, increased the downstream regulatory gene phosphorylation of FoxO1 and reduced microglia apoptosis. It was concluded that LPS can alleviate I/R‑induced brain injury, inhibit neuronal cells apoptosis and protect neuronal cells via the PI3K/Akt/FoxO1 signaling pathway.
本研究旨在探讨低剂量脂多糖（LPS）对缺血再灌注（I/R）诱导的脑损伤的影响，并探讨磷脂酰肌醇 3-激酶（PI3K）/Akt/叉头框蛋白（Fox）O1 信号通路的机制。雄性 Sprague-Dawley 大鼠分为对照组（对照）、缺血再灌注手术组（I/R）和低剂量 LPS 治疗组（LPS）。建立 I/R 模型，在 I/R 损伤结束时记录血流动力学参数。苏木精和伊红染色、免疫组织化学和末端脱氧核苷酸转移酶介导的 dUTP 缺口末端标记染色观察脑组织。用 LPS 处理缺氧/复氧后的小胶质细胞。通过 3-（4,5-二甲基噻唑-2-基）-2,5-二苯基四唑溴盐测定法检测细胞活力。用 AnnexinV/碘化丙啶染色检测小胶质细胞的凋亡率。用 Western blot 分析和逆转录-定量聚合酶链反应检测 B 细胞淋巴瘤（Bcl）-2、Bcl-2 相关 X（Bax）和半胱天冬酶-3 的表达。用 Western blot 检测 Akt、磷酸化（p）-Akt、FoxO1 和 p-FoxO1 的表达。据报道，在 I/R 损伤后，神经元细胞排列紊乱，脑损伤标志物（神经元特异性烯醇化酶和 S100β）、炎症细胞因子[白细胞介素（IL）-1β、IL-6 和肿瘤坏死因子-α]水平显著上调。在本研究中，I/R 组 Bax、半胱天冬酶-3、Akt 和 p-Akt 的表达水平显著升高，而 Bcl-2、FoxO1 和 p-FoxO1 的表达水平显著降低。LPS 治疗显著增加神经元细胞活力，降低神经元细胞凋亡率。向小胶质细胞中加入 PI3K 信号通路抑制剂 LY294002 后，LPS 降低了激活 Akt 的水平，增加了 FoxO1 的下游调节基因磷酸化，减少了小胶质细胞凋亡。综上所述，LPS 可通过 PI3K/Akt/FoxO1 信号通路减轻 I/R 诱导的脑损伤，抑制神经元细胞凋亡，保护神经元细胞。
