The Important Role Of Connexin 43 In Subarachnoid Hemorrhage-induced Cerebral Vasospasm

Objective:Delayed cerebral ischemia(DCI)is a late phase of consequences of subarachnoid hemorrhage(SAH)that causes poor outcome or death in up to 30% of patients with SAH.As it has become the focus of current research,DCI is thought to be caused by the combined effects of angiographic vasospasm,a reduction in cerebral blood flow(CBF)and microvascular constriction and thrombosis.To better understand the pathological mechanism underlying DCI,several experimental rat models employing a double cisterna magna injection have been developed and proposed,but high mortality from DCI still remains.Gap junctions are involved in the development of cerebral vasospasm(CVS)and subsequent DCI after SAH.However,the specific roles and regulatory functions of related connexin isoforms remain unknown.The aim of this study was to investigate the importance of connexin 43(Cx43)in CVS and determine whether Cx43 alterations are modulated via the protein kinase C(PKC)signaling transduction pathway.Materials and methods:In this study,we described a simple and efficient SAH rat model with a tiny incision,few surgical complications and low mortality.At 7 days post-SAH induction,the diameter and luminal cross-sectional area(CSA)of the basilar artery(BA)were measured,and in vivo fluorescence microscopy and magnetic resonance perfusion-weighted imaging(MRPWI)were used to evaluate the occurrence of DCI.Normal and sham-operated groups served as references.Meanwhile,we investigated the temporal changes that occurred in Cx43 in both in vitro and in vivo CVS models and found that an increase in Cx43 mediated the development of SAH-induced CVS.Enhanced gap junction-mediated intercellular communication(GJIC)was observed in vitro,and this effect was reversed by preincubation with specific PKC inhibitors(chelerythrine or GF 109203X).Results:Compared to the sham group,in the SAH group,the diameter and CSA of the BA were decreased,and the CBF in the SAH group was also reduced to barely half of the level in the sham group.Moreover,delayed cerebral ischemia(DCI)was observed in vivo by perfusion-weighted imaging(PWI)and intravital fluorescence microscopy on day 7 after SAH.Both the proportion and severity of microarterial constrictions were increased significantly in the SAH group when compared to those in the sham group.Nevertheless,our SAH model only suffered a 6.6% death rate.However,DCI was attenuated by pretreatment with Cx43 siRNA or PKC inhibitors,and the increase in Cx43 expression was reversed by PKC inhibitors.These data provide strong evidence that Cx43 plays an important role in CVS and indicate that changes in Cx43 expression may be mediated by the PKC pathway.Conclusion:The current study demonstrates that our SAH model was successfully established and may serve to help identify a novel target for the treatment of DCI after SAH.These data also provided strong evidence that Cx43 plays an important role in CVS and indicate that changes in Cx43 expression may be mediated by the PKC pathway.The current findings suggest that Cx43 and the PKC pathway are novel targets for developing treatments for SAH?induced CVS.