β-Adrenoceptor Blockade Moderates Neuroinflammation in Male and Female EAE Rats and Abrogates Sexual Dimorphisms in...

Our previous studies showed more severe experimental autoimmune encephalomyelitis (EAE) in male compared with female adult rats, and moderating effect of propranolol-induced β-adrenoceptor blockade on EAE in females, the effect associated with transcriptional stimulation of Nrf2/HO-1 axis in spinal cord microglia. This study examined putative sexual dimorphism in propranolol action on EAE severity. Propranolol treatment beginning from the onset of clinical EAE mitigated EAE severity in rats of both sexes, but to a greater extent in males exhibiting higher noradrenaline levels and myeloid cell β₂-adrenoceptor expression in spinal cord. This correlated with more prominent stimulatory effects of propranolol not only on CX3CL1/CX3CR1/Nrf2/HO-1 cascade, but also on Stat3/Socs3 signaling axis in spinal cord microglia/myeloid cells (mirrored in the decreased Stat3 and the increased Socs3 expression) from male rats compared with their female counterparts. Propranolol diminished the frequency of activated cells among microglia, increased their phagocyting/endocyting capacity, and shifted cytokine secretory profile of microglia/blood-borne myeloid cells towards an anti-inflammatory/neuroprotective phenotype. Additionally, it downregulated the expression of chemokines (CCL2, CCL19/21) driving T-cell/monocyte trafficking into spinal cord. Consequently, in propranolol-treated rats fewer activated CD4+ T cells and IL-17+ T cells, including CD4+IL17+ cells coexpressing IFN-γ/GM-CSF, were recovered from spinal cord of propranolol-treated rats compared with sex-matched saline-injected controls. All the effects of propranolol were more prominent in males. The study as a whole disclosed that sexual dimorphism in multiple molecular mechanisms implicated in EAE development may be responsible for greater severity of EAE in male rats and sexually dimorphic action of substances affecting them. Propranolol moderated EAE severity more effectively in male rats, exhibiting greater spinal cord noradrenaline (NA) levels and myeloid cell β₂-adrenoceptor (β₂-AR) expression than females. Propranolol affected CX3CR1/Nrf2/HO-1 and Stat3/Socs3 signaling axes in myeloid cells, favored their anti-inflammatory/neuroprotective phenotype and, consequently, reduced Th cell reactivation and differentiation into highly pathogenic IL-17/IFN-γ/GM-CSF-producing cells.