Behavioral Neuroscience Program, Department of Psychology, Michigan State University, 766, Service Road, East Lansing, MI, 48824, USA.
Neuroscience Program, Michigan State University, East Lansing, MI, 48824, USA.
Cell Mol Neurobiol. 2023 Apr;43(3):1369-1384. doi: 10.1007/s10571-022-01256-x. Epub 2022 Jul 21.
Seasonal changes in peripheral inflammation are well documented in both humans and animal models, but seasonal changes in neuroinflammation, especially the impact of seasonal lighting environment on neuroinflammation remain unclear. To address this question, the present study examined the effects of environmental lighting conditions on neuroinflammation in a diurnal rodent model, Nile grass rats (Arvicanthis niloticus). Male and female grass rats were housed in either bright (brLD) or dim (dimLD) light during the day to simulate a summer or winter light condition, respectively. After 4 weeks, microglia markers Iba-1 and CD11b, as well as pro-inflammatory cytokines TNF-α and IL-6, were examined in the anterior cingulate cortex (ACC), basolateral amygdala (BLA), and dorsal hippocampus (dHipp). The results revealed that winter-like dim light during the day leads to indicators of increased neuroinflammation in a brain site- and sex-specific manner. Specifically, relatively few changes in the neuroinflammatory markers were observed in the ACC, while numerous changes were found in the BLA and dHipp. In the BLA, winter-like dimLD resulted in hyper-ramified microglia morphology and increased expression of the pro-inflammatory cytokine IL-6, but only in males. In the dHipp, dimLD led to a higher number and hyper-ramified morphology of microglia as well as increased expression of CD11b and TNF-α, but only in females. Neuroinflammatory state is thus influenced by environmental light, differently in males and females, and could play a role in sex differences in the prevalence and symptoms of psychiatric or neurological disorders that are influenced by season or other environmental light conditions. Diurnal Nile grass rats were housed under bright or dim light during the day for 4 weeks, simulating seasonal fluctuations in daytime lighting environment. Dim light housing resulted in hyper-ramified morphology of microglia (scale bar, 15 μm) and altered expression of pro-inflammatory cytokines (TNF-α) in a sex- and brain region-specific manner.
季节性外周炎症变化在人类和动物模型中均有详细记录，但神经炎症的季节性变化，特别是季节性光照环境对神经炎症的影响尚不清楚。为了解决这个问题，本研究检查了环境光照条件对昼夜节律性啮齿动物模型（尼罗河草鼠）神经炎症的影响。雄性和雌性草鼠白天分别被安置在明亮（brLD）或昏暗（dimLD）的光照环境中，以分别模拟夏季或冬季光照条件。4 周后，在额前皮质（ACC）、基底外侧杏仁核（BLA）和背侧海马（dHipp）中检测小胶质细胞标志物 Iba-1 和 CD11b 以及促炎细胞因子 TNF-α和 IL-6。结果表明，白天类似冬季的昏暗光照会以特定于脑区和性别的方式导致神经炎症的增加。具体而言，在 ACC 中观察到的神经炎症标志物变化相对较少，而在 BLA 和 dHipp 中则发现了大量变化。在 BLA 中，类似冬季的昏暗光照导致小胶质细胞形态的超分支化和促炎细胞因子 IL-6 的表达增加，但仅在雄性中。在 dHipp 中，昏暗光照导致小胶质细胞数量增加、形态超分支化以及 CD11b 和 TNF-α的表达增加，但仅在雌性中。因此，神经炎症状态受环境光照的影响，在男性和女性中存在差异，并且可能在受季节或其他环境光照条件影响的精神或神经障碍的患病率和症状的性别差异中发挥作用。昼夜节律性尼罗河草鼠白天被安置在明亮或昏暗的光照环境中 4 周，模拟日间光照环境的季节性波动。昏暗光照导致小胶质细胞形态的超分支化（标尺，15μm）和促炎细胞因子（TNF-α）表达的改变，具有性别和脑区特异性。
