Morphine Induced Neuroprotection in Ischemic Stroke by Activating Autophagy Via mTOR-Independent Activation of the JNK1/2 Pathway.

Abstract

Morphine (Mor) has exhibited efficacy in safeguarding neurons against ischemic injuries by simulating ischemic/hypoxic preconditioning (I/HPC). Concurrently, autophagy plays a pivotal role in neuronal survival during IPC against ischemic stroke. However, the involvement of autophagy in Mor-induced neuroprotection and the potential mechanisms remain elusive. Our experiments further confirmed the effect of Mor in cellular and animal models of ischemic stroke and explored its potential mechanism. The findings revealed that Mor enhanced cell viability in a dose-dependent manner by augmenting autophagy levels and autophagic flux in neurons subjected to oxygen-glucose deprivation/reoxygenation (OGD/R). Pretreatment of Mor improved neurological outcome and reduced infarct size in mice with middle cerebral artery occlusion/reperfusion (MCAO/R) at 1, 7 and 14 days. Moreover, the use of autophagy inhibitors nullified the protective effects of Mor, leading to reactive oxygen species (ROS) accumulation, increased loss of mitochondrial membrane potential (MMP) and neuronal apoptosis in OGD/R neurons. Results further demonstrated that Mor-induced autophagy activation was regulated by mTOR-independent activation of the c-Jun NH2- terminal kinase (JNK)1/2 Pathway, both in vitro and in vivo. Overall, these findings suggested Mor-induced neuroprotection by activating autophagy, which were regulated by JNK1/2 pathway in ischemic stroke.