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.

Activation of sonic hedgehog signaling pathway in olfactory neuroblastoma.

OBJECTIVES: Sonic hedgehog (Shh) signaling pathway is associated with tumor development; however, the role of Shh signaling in the development of olfactory neuroblastoma (ONB) is unknown. This study aimed to investigate the relationship between the regulation of Shh signaling and the pathogenesis of ONB. METHODS: The expression of Shh signaling components was characterized by immunohistochemistry in human non-tumor olfactory epithelium and ONB specimens, and by RT-PCR and immunoblotting in human ONB cell lines. The impact of the treatment with cyclopamine (a selective inhibitor of the Shh pathway) and/or exogenous Shh on ONB cell proliferation, cycle and apoptosis was examined by MTT, soft agar colony formation and flow cytometry assays, respectively. The influence of Shh signaling on the expression of Shh signaling components and cell cycle-related regulators was determined by immunoblotting and quantitative RT-PCR, respectively. RESULTS: The expression of Pacthed1, Gli1 and Gli2 was detected in 70, 70, and 65% of human ONB specimens, respectively, and in proportion of ONB cell lines, but not in non-tumor olfactory epithelium. Treatment with cyclopamine inhibited the proliferation and colony formation of ONB cells, induced ONB cell cycle arrest and apoptosis, and down-regulated the expression of Pacthed1, Gli1 and cyclin D1, but up-regulated p21 expression in vitro. These regulatory effects of cyclopamine were partially or completely erased by exogenous Shh. CONCLUSION: These data suggest that the Shh signaling pathway is crucial for the growth of ONB.

A critical role of Sonic Hedgehog signaling in maintaining the tumorigenicity of neuroblastoma cells.

Accumulated evidence suggests a major role for the activation of the Sonic Hedgehog (SHH) signaling pathway in the development of neural crest stem cells that give rise to the sympathetic nervous system. We therefore investigated the involvement of SHH signaling in the pathogenesis of neuroblastoma, a common childhood malignant tumor of the sympathetic nervous system. Human neuroblastoma cell lines and a majority of primary neuroblastoma specimens showed high-level expression of the pathway targets and components, indicating persistent activation of the SHH pathway. All of the neuroblastoma cell lines we examined expressed significant levels of SHH ligand, suggesting an autocrine, ligand-dependent activation of the SHH pathway in neuroblastoma cells. Inhibition of SHH signaling by cyclopamine induced apoptosis and blocked proliferation in all major types of neuroblastoma cells, and abrogated the tumorigenicity of neuroblastoma cells. Moreover, the knockdown of GLI2 in neuroblastoma BE (2)-C and SK-N-DZ cell lines resulted in the inhibition of colony formation. Our study has revealed a molecular mechanism for the persistent activation of the SHH pathway which promotes the development of neuroblastoma, and suggests a new approach for the treatment of this childhood malignant tumor. (Cancer Sci 2009; 100: 1848-1855).

[Suppression of nicotinic ACh receptors-mediated currents by activation of Eph/Ephrin-B1 signaling involves Src tyrosine kinase and mitogen-activated protein kinase in ciliary ganglion neurons].

Recent studies showed that Eph/Ephrin tyrosine kinase family plays an important role in the development and functional maintenance of the nervous system, but its function in the sympathetic nervous system is still obscure. In the present study, we examined the effect of Eph/Ephrin-B1 signaling on the whole-cell currents mediated by either alpha7 or alpha3-nicotinic acetylcholine receptors (nAChRs) in acutly dissociated ciliary ganglion (CG) neurons. Firstly, we detected the effect of Ephrin-B1 on nAChRs currents. The neurons were randomly divided into control group, Ephrin-B1Fc-treated group that was stimulated by recombinant Ephrin-B1Fc, IgG-treated group, and Ephrin-B1-treated group. Secondly, we studied the regulatory mechanism of Ephrin-B1Fc on nAChRs currents. The neurons were randomly divided into control group, Ephrin-B1Fc-treated group, PP2 (inhibitor of Src tyrosine kinase) or PD98095 (antagonist of mitogen-activated protein kinase)-treated group, Ephrin-B1Fc + PP2 or PD98095-treated group. The results showed that there was no significant difference between the currents in control group, IgG-treated group and Ephrin-B1-treated group, but Ephrin-B1Fc significantly suppressed both alpha3-nAChRs and alpha7-nAChRs-mediated currents (P=0.002, P=0.003). Pretreatment with PP2 or PD98095 could partially rescue the Ephrin-B1Fc-induced suppression of currents mediated by alpha3-nAChRs or alpha7-nAChRs respectively. These results suggest that the Eph/Ephrin-B1 signaling may inhibit alpha3-nAChRs and alpha7-nAChRs-mediated currents on CG neurons, involving Src tyrosine kinase and mitogen-activated protein kinase signaling in the regulation of sympathetic nervous system.