Sleep deprivation induces pathological changes in rat masticatory muscles: Role of Toll like signaling pathway and atrophy

The aim of this study was to evaluate the Toll like signaling pathway and atrophy after sleep deprivation (SD) in rat masticatory muscles: masseter and temporal. A total of 24 animals was distributed into three groups: Control group (CTL, n=8), subjected to SD for 96h (SD96, n=8) and subjected to SD for 96h more 96h of sleep recovery (SD96+R, n=8). Histopathological analysis revealed the presence of acute inflammatory cells, congested vessels, fibrosis, and high cellularity in the skeletal muscle fibers from masseter and temporal submitted to SD. These morphological alterations were not observed in the control group since neither inflammatory cells nor congested vessels were observed to this group. In the group SD96+R, the absence of inflammation was noticed to the masseter only. In this group, COX-2 and TNF-alpha downregulation were detected when comparing to control group. MyD88 and pIKK decreased in SD96 and SD96+R groups being pNFKBp50 downregulatated in SD96+R. MyD88 expression increased in rats submitted to SD96 and SD96+R in temporal when compared to control group. On the other hand, pIKK decreased the protein expression in groups SD96 and SD96+R while pNFKBp50 showed a decreased protein expression in group SD96 only. The activation of atrophy by means of MAFbx upregulation was detected in temporal muscle in SD96 and SD96+R when compared to control. In summary, our results show that SD is able to induce morphological alterations in rat masticatory muscles. Toll like signaling pathway and atrophy play important roles in ethiopathogenesis induced by SD, being dependent of skeletal muscle type.