Targeting Connexin43 provides anti-inflammatory effects after intracerebral hemorrhage injury by regulating YAP signaling

Abstract

Background: In the central nervous system(CNS),Connexin43 (Cx43) is mainly expressed in astrocytes and regulates astrocytic network homeostasis. Like Cx43 overexpression,abnormal excessive opening of Cx43 hemichannels (Cx43Hcs) on reactive astrocytes aggravates the inflammatory response and cell death in CNS pathologies.However, the role of excessive Cx43Hc opening in intracerebral hemorrhage (ICH) injury is not clear.Methods: Hemin stimulation in primary cells and collagenase IV injection in C57BL/6J (B6) mice were used as ICH modals in vitro and vivo.Cx43 mimetic peptide Gap19 was treated after ICH injury. Ethidium bromide (EtBr) uptake assays was used to measure the opening of Hcs. Western blot and immunofluorescence were used to measure the expression of protein. qRT-PCR and ELISA were used to determine the level of cytokines. Co-immunoprecipitation(Co-IP) and Duolink in situ proximity ligation assay (PLA) were applied to measure the association between proteins.Results: In this study,Cx43 expression was upregulated, and excessive Cx43Hc opening was observed in mice after ICH injury. Delayed treatment with Gap19significantly alleviated hematoma volume and neurological deficits after ICH injury. In addition,Gap19 decreased inflammatory cytokine levels in the tissue surrounding the hematoma and decreased reactive astrogliosis after ICH injury in vitro and in vivo, as determined by GFAP staining. Intriguingly, Cx43 transcriptional activity and expression in astrocytes were significantly increased after hemin stimulation in culture.However,Gap19 treatment downregulated astrocytic Cx43 expression through the ubiquitin-proteasome pathway without affecting Cx43 transcription. Additionally, our data showed that Gap19 increased YAP nuclear translocation, which upregulated SOCS1 and SOCS3 expression, and then inhibited the TLR4-NFκB and JAK2-STAT3 pathways in hemin-stimulated astrocytes. Finally, the YAP inhibitor verteporfin (VP) reversed the anti-inflammatory effect of Gap19 in vitro and almost completely blocked its protective effects in vivo after ICH injury.Conclusions: This study provides new insight into potential treatment strategies for ICH injury involving astroglial Cx43 and Cx43Hcs.Suppression of abnormal astroglial Cx43 expression and Cx43Hc opening by Gap19 plays anti-inflammatory and neuroprotective roles after ICH injury.