Sonic hedgehog protects cortical neurons against oxidative stress

Oxidative stress is one of the most important pathological mechanisms in neurodegenerative diseases and ischemia. Recent studies have indicated that the sonic hedgehog (SHH) signaling pathway is involved in these diseases, but the underlying mechanisms remains elusive. Here we report that the SHH pathway was activated in primary cultured cortical neurons after exposure to hydrogen peroxide (H₂O₂). H₂O₂ treatment decreased the cell viability of neurons, and inhibition of endogenous SHH signaling exacerbated its neurotoxicity. Activation of SHH signaling protected neurons from H₂O₂-induced apoptosis and increased the cell viability while those effects were partially reversed by blocking SHH signals. Exogenous SHH increased the activities of Superoxide dismutase (SOD) and Glutathione peroxidase (GSH-PX) in H₂O₂-treated neurons and decreased production of Malondialdehyde (MDA). It also promoted expression of the anti-apoptotic gene Bcl-2 and inhibited expression of pro-apoptotic gene Bax. Activation of SHH signals upregulated both Neurotrophic factors vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF). Pretreatment with SHH inhibited the activation of ERK (extracellular signal-regulated kinases) signals induced by H₂O₂. Our findings demonstrate that activation of SHH signaling protects cortical neurons against oxidative stress and suggest a potential role of SHH for the clinic treatments of brain ischemia and neurodegenerative disorders.