Connexin 43 stabilizes astrocytes in a stroke-like milieu to facilitate neuronal recovery

Aim： Connexin 43 （Cx43） is a member of connexin family mainly expressed in astrocytes, which forms gap junctions and hemichannels and maintains the normal shape and function of astrocytes. In this study we investigated the role of Cx43 in astrocytes in facilitating neuronal recovery during ischemic stroke. Methods： Primary culture of astrocytes or a mixed culture of astrocytes and cortical neurons was subjected to oxygen glucose deprivation and reperfusion （OGD/R）. The expression of Cx43 and Ephrin-A4 in astrocytes was detected using immunocytochemical staining and Western blot assays. Intercellular Ca2~ concentration was determined with Fluo-4 AM fluorescent staining. Middle cerebral artery occlusion （MCAO） model rats were used for in vivo studies. Results： OGD/R treatment of cultured astrocytes caused a decrement of Cx43 expression and translocation of Cx43 from cell membrane to cytoplasm, accompanied by cell retraction. Furthermore, OGD/R increased intracellular Ca2~ concentration, activated CaMKII/CREB pathways and upregulated expression of Ephrin-A4 in the astrocytes. All these changes in OGD/R-treated astrocytes were alleviated by overexpression of Cx43. In the cortical neurons cultured with astrocytes, OGD/R inhibited the neurite growth, whereas overexpression of Cx43 or knockdown of Ephrin-A4 in astrocytes restored the neurite growth. In MCAO model rats, neuronal recovery was found to be correlated with the recuperation of Cx43 and Ephrin-A4 in astrocytes. Conclusion： Cx43 can stabilize astrocytes and facilitate the resistance to the deleterious effects of a stroke-like milieu and promote neuronal recovery.