Nanomolar Naloxone Attenuates Neurotoxicity Induced by Oxidative Stress and Survival Motor Neuron Protein Deficiency

Oxidative stress and survival motor neuron (Smn) protein deficiency are the major causes of motor neuronal death. Naloxone exhibits neuroprotection against ischemic stroke and anti-inflammation. In this study, we determined whether nanomolar naloxone provides neuroprotection under oxidative stress (H₂O₂) and Smn deficiency in a motor neuron-like cell line, NSC34. In H₂O₂-treated NSC34 cells, naloxone (1–10 nM) increased cell survival and mitochondria membrane potential. In addition, naloxone decreased NADPH oxidase (NOX) 2 activation, reactive oxygen species production and oxygen consumption rate. Moreover, naloxone increased anti-apoptotic Bcl-2 expression, attenuated apoptotic protein (Bax, cytochrome c, and caspase) expression and decreased apoptotic death. Furthermore, naloxone also increased Smn mRNA and protein expression. In Smn knockdown NSC34 cells, Smn deficiency significantly increased H₂O₂ cytotoxicity. Naloxone exhibited neuroprotection at higher concentrations in Smn knockdown NSC34 cells than in control cells. In conclusion, naloxone attenuated neurotoxicity induced by H₂O₂ and Smn deficiency. Our findings also revealed the involvement of Smn protein in naloxone protection and oxidative stress-related neurotoxicity.