Peripheral Sympathectomy Alters Neuroinflammatory and Microglial Responses to Sleep Fragmentation in Female Mice

Sleep loss, either induced by obstructive sleep apnea or other forms of sleep dysfunction, induces an inflammatory response, as commonly measured by increased circulating levels of pro-inflammatory cytokines. Increased catecholamines from sympathetic nervous system (SNS) activation regulates this peripheral inflammation. However, the role that catecholamines play in mediating neuroinflammation from sleep perturbations is undescribed. The aims of this study were to determine (i) the effect of peripheral SNS inhibition upon neuroinflammatory responses to sleep fragmentation (SF) and (ii) whether homeostasis can be restored after 1 week of recovery sleep. We measured gene expression levels of pro- and anti-inflammatory cytokines and microglial activity in brain (prefrontal cortex, hippocampus and hypothalamus) of female mice that were subjected to acute SF for 24 hours, chronic SF for 8 weeks, or 7 days of recovery after chronic SF. In each experiment, SF and control mice were peripherally sympathectomized with 6-hydroxydopamine (6-OHDA) or injected with vehicle. SF elevated cytokine mRNA expression in brain and increased microglial density and cell area in some regions. In addition, chronic SF promoted hyper-ramification in resting microglia upon exposure to chronic, but not acute, SF. Effects of chronic SF were more pronounced than acute SF, and 1 week of recovery was not sufficient to alleviate neuroinflammation. Importantly, 6-OHDA treatment significantly alleviated SF-induced inflammation and microglial responses. This study provides evidence of SNS regulation of neural inflammation from SF, suggesting a potential role for therapeutics that could mitigate neuroinflammatory responses to sleep dysfunction.