Recombinant neuroglobin ameliorates early brain injury after subarachnoid hemorrhage via inhibiting the activation of mitochondria apoptotic pathway

Abstract Neuroglobin (Ngb) overexpression is considered as an intrinsic neuroprotective response. Therefore, exogenous Ngb increased in brain tissues has become a promising therapeutic strategy for neurological diseases. Previous studies demonstrated that transactivator of transcription (TAT) protein transduction domain was able to mediate synthetic Ngb entrance into neurons, and then protected brain from hypoxia-ischemic injury. However, the role of recombinant Ngb on early brain injury following subarachnoid hemorrhage (SAH) has not been elucidated. The objectives of this study were to investigate the expression of endogenous Ngb in brain using a rabbit model of SAH, and to verify whether TAT-Ngb fusion protein could be delivered into brain parenchyma, as well as to explore the neuroprotective effect of Ngb and its possible mechanisms. We found that Ngb expressions were up regulated in the transcript and protein levels in a similar time dependent manner after SAH as compared to the sham group. Moreover, TAT-Ngb fusion protein was successfully generated and transferred into brain neurons. Compared with the saline- and Ngb-treated group, neuronal viabilities and neurological outcomes were significantly improved 72 h post-SAH in the TAT-Ngb-treated group. Likewise, anti-apoptotic Bcl-2 protein was also elevated obviously. Conversely, pro-apoptotic factors including caspase 3, caspase 9 and Bax were greatly decreased after TAT-Ngb treatment. Our results suggest that Ngb plays a neuroprotective effect in rabbits suffering from SAH possibly through inhibiting the SAH-induced activation of mitochondria apoptotic pathway. Furthermore, TAT-mediated Ngb delivery into brain may be a promising therapeutic approach.