We previously revealed that long-term treatment with nicotine suppresses microglial activation, resulting in a protective effect against thrombin-induced shrinkage of the striatal tissue in organotypic slice cultures. Here, the effect of nicotine on impaired M1 and protective M2 microglial polarization was investigated using the BV-2 microglial cell line in the presence or absence of thrombin. Following nicotine treatment, α7 nicotinic acetylcholine receptor expression transiently increased and then gradually decreased until 14 days. Treatment with nicotine for 14 days slightly polarized M0 microglia to M2b and d subtypes. Co-exposure of thrombin and low concentration of interferon-γ recruited inducible NO synthase (iNOS)- and interleukin-1β-double-positive M1 microglia in a thrombin-concentration-dependent manner. Treatment with nicotine for 14 days significantly decreased the thrombin-induced increase of iNOS mRNA levels and conversely showed a tendency to increase arginase1 mRNA levels. Moreover, treatment with nicotine for 14 days suppressed thrombin-induced phosphorylation of p38 MAPK through the α7 receptor. Repeated intraperitoneal administration of α7 agonist PNU-282987 for 14 days selectively evoked the apoptosis of iNOS-positive M1 microglia at the perihematomal area and showed a neuroprotective effect in an in vivo intracerebral hemorrhage model. These findings revealed that long-term stimulation of α7 receptor causes suppression of thrombin-induced activation of p38 MAPK followed by apoptosis in neuropathic M1 microglia.

Graphical Abstract

中文翻译：

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长期刺激 α7 烟碱乙酰胆碱受体通过 M1 小胶质细胞凋亡挽救出血性神经元损失

我们之前发现，长期尼古丁治疗会抑制小胶质细胞活化，从而对器官切片培养物中凝血酶诱导的纹状体组织收缩产生保护作用。在这里，使用 BV-2 小胶质细胞系在存在或不存在凝血酶的情况下研究尼古丁对受损的 M1 和保护性 M2 小胶质细胞极化的影响。尼古丁治疗后，α7烟碱乙酰胆碱受体表达短暂增加，然后逐渐下降，直至14天。用尼古丁治疗 14 天，M0 小胶质细胞轻微极化为 M2b 和 d 亚型。凝血酶和低浓度干扰素-γ 的共同暴露以凝血酶浓度依赖性方式招募诱导型 NO 合酶 (iNOS) 和白细胞介素 1β-双阳性 M1 小胶质细胞。尼古丁治疗 14 天显着降低了凝血酶诱导的 iNOS mRNA 水平的增加，相反显示出精氨酸酶 1 mRNA 水平增加的趋势。此外，尼古丁治疗 14 天可抑制凝血酶通过 α7 受体诱导的 p38 MAPK 磷酸化。连续 14 天重复腹腔注射 α7 激动剂 PNU-282987 可选择性诱发血肿周围区域 iNOS 阳性 M1 小胶质细胞凋亡，并在体内脑出血模型中显示出神经保护作用。这些发现表明，长期刺激 α7 受体会抑制凝血酶诱导的 p38 MAPK 激活，进而导致神经病性 M1 小胶质细胞凋亡。

图形概要