Neurite outgrowth induced by stimulation of angiotensin II AT2 receptors in SH-SY5Y neuroblastoma cells involves c-Src activation.

Neuroblastoma, the most common extracranial solid tumor occurring in childhood, originates from the aberrant proliferation of neural crest cells. Accordingly, the mechanism underling neuronal differentiation could provide new strategies for neuroblastoma treatment. It is well known that neurite outgrowth could be induced by Angiotensin II (Ang II) AT2 receptors; however, the signaling mechanism and its possible interaction with NGF (neural growth factor) receptors remain unclear. Here, we show that Ang II and CGP42112A (AT2 receptor agonist) promote neuronal differentiation by inducing neurite outgrowth and ßIII-tubulin expression in SH-SY5Y neuroblastoma cells. In addition, we demonstrate that treatment with PD123319 (AT2 receptor antagonist) reverts Ang II or CGP42112A-induced differentiation. By using specific pharmacological inhibitors we established that neurite outgrowth induced by CGP42112A requires the activation of MEK (mitogen-activated protein kinase kinase), SphK (sphingosine kinase) and c-Src but not PI3K (phosphatidylinositol 3-kinase). Certainly, CGP42112A stimulated a rapid and transient (30 s, 1 min) phosphorylation of c-Src at residue Y416 (indicative of activation), following by a Src deactivation as indicated by phosphorylation of Y527. Moreover, inhibition of the NGF receptor tyrosine kinase A (TrkA) reduced neurite outgrowth induced by Ang II and CGP42112A. In summary, we demonstrated that AT2 receptor-stimulated neurite outgrowth in SH-SY5Y cells involves the induction of MEK, SphK and c-Src and suggests a possible transactivation of TrkA. In that regard, AT2 signaling pathway is a key player in neuronal differentiation and might be a potential target for therapeutic treatments.

IgA response by oral infection with an attenuated Yersinia enterocolitica mutant: implications for its use as oral carrier vaccine.

Yersinia enterocolitica (Ye) mutant strain (sycH-) is unable to secrete the virulence protein YopH. Mucosal vaccination is often required to induce protection, but stimulating strong IgA response is frequently difficult. Here, we addressed whether Ye sycH- might induce IgA response, and investigated its attenuation in TNFRp55-/-, IL-12p40-/- and IL-4-/- mice. We found that Ye sycH- colonizes Peyer's patches, and induces higher Yersinia-specific IgA levels in feces and in serum compared with Ye wild type. The Ye sycH-mutant proved to be attenuated and induced IgA in both wild-type and immunodeficient mice. These lines of evidence show the attenuation of Ye sycH- and its ability to stimulate an IgA response. This mutant might be useful as an oral vaccine carrier.