Role of mammalian target of rapamycin in hypoxic or ischemic brain injury: potential neuroprotection and limitations

Hypoxic or ischemic stress causes serious brain injury via various pathologic mechanisms including suppressed protein synthesis, neuronal apoptosis, and the release of neurotoxic substances. Many neuroprotective treatments of hypoxic or ischemic brain injury rely on these pathologic mechanisms. The mammalian target of rapamycin (mTOR), an atypical Ser/Thr protein kinase, could be a novel therapeutic target. mTOR plays a critical role in regulating many activities such as protein synthesis, cell growth, and cell death. Furthermore, mTOR could promote angiogenesis, neuronal regeneration, and synaptic plasticity, reduce neuronal apoptosis, and remove neurotoxic substances, which are all closely associated with the repair and survival mechanisms of hypoxic or ischemic brain injury. Although there is currently controversy with regard to regulating the activation of mTOR, the effective neuroprotective functions resulting from mTOR activation have been confirmed by various studies. Considering the potential capability for mTOR in regulating the repair and survival mechanisms of hypoxic or ischemic brain injury, mTOR may be a novel target for neuroprotective treatment.