YAP Regulates Microglial Anti-Inflammatory Responses and Alleviates Cognitive Impairment Through the IL-33/ST2 Pathway after Traumatic Brain Injury

Traumatic brain injury (TBI) is a neurological disease that seriously endangers human life and has a poor prognosis. In particular, neuroinflammation during secondary injury after TBI affects the course of TBI, and interleukin-33 (IL-33) plays an important regulatory role in neuroinflammation after TBI. Meanwhile, the Yes-associated protein (YAP) can influence the prognosis after TBI. In this study, we explored whether the upregulation of YAP in astrocytes can enhance the protective effect of IL-33 against neuroinflammation after TBI. In the current study, the markers of microglial proinflammatory/anti-inflammatory responses both in vivo and in vitro were assessed after the administration of exogenous IL-33. Adeno-associated virus targeting astrocytes in vivo and lentivirus transfecting astrocytes in vitro were used to overexpress YAP, and the expression and localization of proteins were evaluated by Western blotting and immunofluorescence staining. Chromatin immunoprecipitation-quantitative Polymerase Chain Reaction (qPCR) assays were performed to confirm that YAP transcriptionally regulates the IL33 gene by binding directly to its promoter region. Astegolimab was administered to block Growth Stimulation Express Gene 2 Protein (ST2) receptors in vivo and in vitro. Morris water maze and Y-maze tests were employed to assess cognitive function after TBI. The results demonstrated that the expression levels of both YAP and IL-33 were significantly decreased during the early phase of TBI. Concurrently, the anti-inflammatory marker CD206 in microglia was also markedly reduced in the acute stage post-TBI. Importantly, YAP was found to enhance IL-33 secretion by binding to its gene promoter, thereby activating the IL-33/ST2 signaling pathway. This activation promoted anti-inflammatory responses in microglia, which were mediated through the NF-κB signaling pathway, and ultimately led to improved cognitive function. These beneficial effects were effectively reversed by the administration of astegolimab, confirming the specificity of the YAP/IL-33/ST2 mechanism. Above all, we found that YAP produced by astrocytes regulates microglial anti-inflammatory responses through the IL-33/ST2 pathway, thereby improving cognitive function after TBI.