Dexmedetomidine, an Alpha 2a Adrenergic Receptor Agonist, Mitigates Experimental Autoimmune Encephalomyelitis by Desensitization of CXCR7 in Microglia

The autoimmune disease multiple sclerosis (MS) and its animal model, experimental autoimmune encephalomyelitis (EAE), is characterized by an ascending paralysis that is characterized by extensive infiltration of the central nervous system by inflammatory cells. Although several studies to some extent uncover the cellular mechanisms of microglia that govern EAE pathogenesis, the molecular mechanisms that orchestrate the movement of microglia remain unknown, and potential novel therapeutic strategies are still required. In this study, we report that dexmedetomidine, an alpha 2a adrenergic receptor agonist, attenuates the clinical severity of EAE with less infiltration of microglia. During EAE, dexmedetomidine inhibits SDF-1- and I-TAC-induced chemotaxis of microglia mediated by CXCR7 but not CXCR4 or CXCR3. Most importantly, the alpha 2a adrenergic receptor is essential in dexmedetomidine-induced CXCR7 desensitization in microglia. Further experiments confirmed that CXCR7 desensitization required atypical protein kinase C ζ activation, while conventional and novel protein kinase C isoforms were not involved. Altogether, our data elucidate the mechanism of dexmedetomidine-induced CXCR7 desensitization in microglia and amelioration in EAE, which might lead to a better understanding of the therapeutic effects of dexmedetomidine as well as its implications for CXCR7 desensitization in autoimmune disease.