The role of circadian rhythm proteins Rev-Erbα and β in the development of neuronal injury after traumatic brain injury.

Background/aim: Circadian rhythm proteins (CRPs) play critical roles in both physiological and pathophysiological conditions, including neurodegenerative disorders. As members of CRPs, the nuclear receptors Rev-Erbα/β regulate circadian rhythm particularly by inhibiting Bmal1 protein and are involved in the neuroinflammation and cell death processes. However, their roles in the development of neuronal injury after traumatic brain injury (TBI) were largely unexplored, and so were investigated in the present study. Materials and methods: For the induction of TBI, animals were subjected to the cryogenic model of TBI, which is a commonly used animal model and shares essential similarities with cerebral ischemia in terms of pathophysiological cascades. To assess the impact of Rev-Erb proteins on TBI, both Rev-Erbα and Rev-Erbβ proteins were activated or deactivated, and their expression profiles were determined by western blot analyses. Infarct volume and brain swelling were analyzed by cresyl violet staining. Blood-brain barrier (BBB) permeability was analyzed by immunoglobulin G extravasation. Neuronal survival was analyzed by NeuN immunohistochemistry. Results: Our observations indicate that Rev-Erbβ significantly reduced brain injury after TBI, which was reversed by inhibiting this protein. Not activation but the inhibition of both Rev-Erb proteins increased brain swelling significantly. In addition, both Rev-Erbα and Rev-Erbβ improved BBB permeability and neuronal survival significantly, which were reversed by their inhibitions. Conclusion: Our results show that Rev-Erbα and particularly Rev-Erbβ play significant roles in the development of neuronal injury after TBI. Our findings suggest that Rev-Erb proteins would be a potential therapeutic target for the treatment of neurodegenerative diseases.