Activation of the PERK/MANF/STAT3 Pathway in Astrocytes Promotes Synaptic Remodeling and Neurological Recovery in the Acute Phase After Stroke in Mice

Astrocytes play a crucial role in ensuring neuronal survival and function. In stroke, astrocytes trigger the unfolded protein response (UPR) to restore endoplasmic reticulum homeostasis. Mesencephalic astrocyte-derived neurotrophic factor (MANF), a newly identified endoplasmic reticulum stress-induced neurotrophic factor, attenuates cerebral ischemic injury by reducing inflammatory responses. The mechanisms by which astrocytes regulate MANF expression and the role of MANF in modulating inflammation remain to be elucidated. In this study, we constructed middle cerebral artery occlusion (MCAO)/reperfusion model in C57BL/6J mice and an oxygen glucose deprivation/reoxygenation model in a neuronal and astrocyte coculture system. The present study utilized an intraventricular injection of adeno-associated virus (AAV) to effectively block the PERK pathway in astrocytes. Moreover, MANF-siRNA was employed to suppress endogenous MANF expression, while rhMANF was used as an exogenous supplement. 2,3,5-Triphenyltetrazolium chloride (TTC), modified neurological severity score (mNSS), adhesive removal test, Golgi staining, hematoxylin-eosin (HE) staining, western blot, and enzyme-linked immunosorbent assay (ELISA) were applied to evaluate the protective effects of PERK pathway and the expression of MANF in astrocytes. In vitro experiments, ELISA, cell counting kit-8 (CCK-8), and western blot were used to detect the mechanisms by which MANF regulates neuroinflammation. The results showed that blocking the astrocytic PERK pathway decreased MANF expression, aggravated synaptic loss, and exacerbated infarct volume and neurological outcomes. Conversely, cellular experiments showed that activation of PERK increased MANF expression, promoted synaptic protein expression, and increased neuronal cell viability. Additionally, increasing exogenous MANF inhibited STAT3 phosphorylation, reduced the release of inflammatory factors, and improved neuronal cell viability. In conclusion, our study demonstrates that after stroke, astrocytes activate PERK and upregulate MANF expression, which inhibits STAT3 phosphorylation, reduces proinflammatory cytokine release, rescues neuronal synapse loss, and promotes the recovery of neurological function in mice.