Article

Naloxone attenuates ischemic brain injury in rats through suppressing the NIK/IKKα/NF-κB and neuronal apoptotic pathways

Authors: Xuan Wang1, Zu-jun Sun2, Jun-lu Wu2, Wen-qiang Quan2, Wei-dong Xiao3, Helen Chew3, Cui-min Jiang1, Dong Li2
1 Department of Pharmacy, Putuo People’s Hospital, Shanghai 200060, China
2 Department of Clinical Laboratory, Shanghai Tongji Hospital, Tongji University School of Medicine, Shanghai 200065, China
3 Sol Sherry Thrombosis Research Center, Temple University, Philadelphia, PA 19140, USA
Correspondence to: Cui-min Jiang: 1098618044@qq.com, Dong Li: lidong@tongji.edu.cn,
DOI: 10.1038/s41401-018-0053-3
Received: 28 January 2018
Accepted: 22 May 2018
Advance online: 14 June 2018

Abstract

Although naloxone has been documented to exert neuroprotection in animal model of cerebral ischemia, the mechanism is not well understood. In this present study we investigated whether naloxone affected the mitochondrial apoptotic pathway in ischemic brain injury of rats. SD rats were subjected to a permanent middle cerebral artery occlusion surgery, and received naloxone (0.5, 1, 2 mg/kg, i.v.) immediately after ischemia. Neurological deficits were evaluated 24 h after ischemia using the McGraw Stroke Index, and then the rats were killed, and the brains were collected for further analyses. We show that naloxone treatment dose-dependently decreased the infarction volume and morphological injury, improved motor behavioral function, and markedly curtailed brain edema. Furthermore, naloxone administration significantly inhibited the nuclear translocation of NF-κB p65 and decreased the levels of nuclear NF-κB p65 in the ischemic penumbra. Naloxone administration also dose-dependently increased the NF-κB inhibitory protein (IκBα) levels and attenuated phosphorylated NIK and IKKα levels in the ischemic penumbra. In addition, naloxone administration dose-dependently increased Bcl-2 levels, decreased Bax levels, stabilized the mitochondrial transmembrane potential, and inhibited cytochrome c release and caspase 3 and caspase 9 activation. These results indicate that the neuroprotective effects of naloxone against ischemic brain injury involve the inhibition of NF-κB activation via the suppression of the NIK/IKKα/IκBα pathway and the obstruction of the mitochondrial apoptotic pathway in neurons.
Keywords: cerebral ischemia; naloxone; NF-κB; mitochondrial apoptotic pathway; neuroprotection

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