Our recent study revealed that photobiomodulation (PBM) inhibits delayed neuronal death by preserving mitochondrial dynamics and function following global cerebral ischemia (GCI). In the current study, we clarified whether PBM exerts effective roles in endogenous neurogenesis and long-lasting neurological recovery after GCI. Adult male rats were treated with 808 nm PBM at 20 mW/cm2 irradiance for 2 min on cerebral cortex surface (irradiance ∼7.0 mW/cm2, fluence ∼0.8 J/cm2 on the hippocampus) beginning 3 days after GCI for five consecutive days. Cognitive function was evaluated using the Morris water maze. Neural stem cell (NSC) proliferation, immature neurons, and mature neurons were examined using bromodeoxyuridine (BrdU)-, doublecortin (DCX)-, and NeuN-staining, respectively. Protein expression, such as NLRP3, cleaved IL1β, GFAP, and Iba1 was detected using immunofluorescence staining, and ultrastructure of astrocyte and microglia was observed by transmission electron microscopy. The results revealed that PBM exerted a markedly neuroprotective role and improved spatial learning and memory ability at 58 days of ischemia/reperfusion (I/R) but not at 7 days of reperfusion. Mechanistic studies revealed that PBM suppressed reactive astrocytes and maintained astrocyte regeneration at 7 days of reperfusion, as well as elevated neurogenesis at 58 days of reperfusion, as evidenced by a significant decrease in the fluorescence intensity of GFAP (astrocyte marker) but unchanged the number of BrdU-GFAP colabeled cells at the early timepoint, and a robust elevation in the number of DCX-NeuN colabeled cells at the later timepoint in the PBM-treated group compared to the GCI group. Notably, PBM treatment protected the ultrastructure of astrocyte and microglia cells at 58 days but not 7 days of reperfusion in the hippocampal CA1 region. Furthermore, PBM treatment significantly attenuated the GCI-induced immunofluorescence intensity of NLRP3 (an inflammasome component), cleaved IL1β (reflecting inflammasome activation) and Iba1, as well as the colocalization of NLRP3/GFAP or cleaved IL-1β/GFAP, especially in animals subjected to I/R at 58 days. Taken together, PBM treatment performed postischemia exerted a long-lasting protective effect on astrocytes and promoted endogenous neurogenesis in the hippocampal CA1 region, which might contribute to neurological recovery after GCI.

中文翻译：

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光生物调节促进海马 CA1 NSC 向神经元分化并促进认知功能恢复，包括全球脑缺血后 NLRP3 炎症小体的缓解。

我们最近的研究表明，光生物调节 (PBM) 通过保护全脑缺血 (GCI) 后的线粒体动力学和功能来抑制延迟的神经元死亡。在目前的研究中，我们阐明了 PBM 是否在内源性神经发生和 GCI 后的持久神经恢复中发挥有效作用。从 GCI 后 3 天开始，用 808 nm PBM 在大脑皮层表面以 20 mW/cm2 辐照度处理 2 分钟（辐照度为 7.0 mW/cm2，海马上的通量为 0.8 J/cm2），连续 5 天。使用莫里斯水迷宫评估认知功能。分别使用溴脱氧尿苷 (BrdU)、双皮质素 (DCX) 和 NeuN 染色检查神经干细胞 (NSC) 增殖、未成熟神经元和成熟神经元。蛋白质表达，如 NLRP3、切割的 IL1β、GFAP、免疫荧光染色检测Iba1，透射电镜观察星形胶质细胞和小胶质细胞超微结构。结果表明，PBM 在缺血/再灌注 (I/R) 58 天但在再灌注 7 天时发挥显着的神经保护作用并改善空间学习和记忆能力。机制研究表明，PBM 在再灌注 7 天时抑制反应性星形胶质细胞并维持星形胶质细胞再生，并在再灌注 58 天时促进神经发生，GFAP（星形胶质细胞标记物）的荧光强度显着降低，但未改变与 GCI 组相比，PBM 处理组在早期时间点 BrdU-GFAP 共标记细胞，以及在较晚时间点 DCX-NeuN 共标记细胞数量显着增加。值得注意的是，PBM 处理在海马 CA1 区域再灌注 58 天而不是 7 天时保护了星形胶质细胞和小胶质细胞的超微结构。此外，PBM 处理显着减弱了 GCI 诱导的 NLRP3（炎症小体成分）、裂解的 IL1β（反映炎症小体激活）和 Iba1 的免疫荧光强度，以及 NLRP3/GFAP 或裂解的 IL-1β/GFAP 的共定位，尤其是在动物中在第 58 天进行 I/R。总之，在缺血后进行的 PBM 治疗对星形胶质细胞发挥了持久的保护作用，并促进了海马 CA1 区的内源性神经发生，这可能有助于 GCI 后的神经功能恢复。此外，PBM 处理显着减弱了 GCI 诱导的 NLRP3（炎症小体成分）、裂解的 IL1β（反映炎症小体激活）和 Iba1 的免疫荧光强度，以及 NLRP3/GFAP 或裂解的 IL-1β/GFAP 的共定位，尤其是在动物中在第 58 天进行 I/R。总之，在缺血后进行的 PBM 治疗对星形胶质细胞发挥了持久的保护作用，并促进了海马 CA1 区的内源性神经发生，这可能有助于 GCI 后的神经功能恢复。此外，PBM 处理显着减弱了 GCI 诱导的 NLRP3（炎症小体成分）、裂解的 IL1β（反映炎症小体激活）和 Iba1 的免疫荧光强度，以及 NLRP3/GFAP 或裂解的 IL-1β/GFAP 的共定位，尤其是在动物中在第 58 天进行 I/R。总之，在缺血后进行的 PBM 治疗对星形胶质细胞发挥了持久的保护作用，并促进了海马 CA1 区的内源性神经发生，这可能有助于 GCI 后的神经功能恢复。