Astrocytic YAP prevents the glutamate neurotoxicity by upregulation of EAAT2 expression and promotes the gain of stemness in astrocytes in ischemic stroke mice

The excessive glutamate-mediated excitotoxicity is a major cause of the neuron death in ischemic stroke (IS). Astrocytic glutamate transporter protein-1 (GLT-1, also named excitatory Amino acid Transporter 2, EAAT2) is essential for maintaining low extracellular glutamate and preventing glutamate neurotoxicity, while its expression is regulated by Yes-associated protein (YAP) signaling reported by our previous study. Recent studies have shown that ischemic injury of the brain induces the gain of stemness in astrocytes dependent on the de novo DNA Methyltransferase DNMT3A, and YAP signaling contributes to DNA methylation remodeling upon mouse embryonic stem cell differentiation. However, it remains unknown the roles of astrocytic YAP signaling in IS and whether it regulates the glutamate-mediated excitotoxicity and the gain of stemness in astrocytes induced by IS. In this study, we found that IS was aggravated in YAP^GFAP-CKO mice with inhibition of the functional behavioral recovery, larger injury area, more apoptotic neurons and more inflammatory infiltration. Furthermore, YAP deletion in astrocytes impaired the formation of glial scars due to the reduction of astrocytic proliferation, and inhibition of activation and gain of stemness in astrocytes induced by IS. Additionally, the expression of EAAT2 was significantly decreased in the cortical astrocytes of YAP^GFAP-CKO mice after IS through downregulating β-catenin signaling. Activation of EAAT2 by LDN-212320 partially restored the deficits such as neuronal death and behavioral recovery impairment in YAP^GFAP-CKO mice after IS. Furthermore, activation of astrocytic YAP signaling by XMU-MP-1 upregulated the EAAT2 expression, and inhibited the loss of neurons, and promoted the gain of stemness in astrocytes and functional recovery of mice in IS. These results identify that astrocytic YAP signaling prevents the glutamate neurotoxicity by upregulating EAAT2 expression and promotes the gain of stemness in astrocytes in IS, which provides a novel drug target for IS treatment.