Janus kinases (JAK) and signal transducers and activator of transcription (STAT) proteins are activated in response to many cytokines and growth factors and are well studied in the immune system. This study was conducted to examine the role of the JAK/STAT pathway in neurons in response to tumor necrosis factor-␣ (TNF␣) and insulin-like growth factor-1 (IGF-1), which play a major role during neurodegeneration, and to study their effect on expression of suppressors of cytokine signaling 3 (SOCS-3), belonging to the novel family of feedback regulators of cytokine and growth factor activities. In this report, we showed that TNF␣ is inhibitory to the survival of primary cortical neurons at higher doses and that IGF-1 can rescue TNF␣-stimulated cell death. We showed that the JAK/ STAT pathway is involved in this rescue as tyrphostin AG490, a specific inhibitor of JAK/STAT, completely inhibits cell survival in response to IGF-1. STAT3 gets tyrosine-phosphorylated and translocated to the nucleus in response to IGF-1. Northern blot, semi-quantitative reverse transcription-PCR, and real time PCR experiments demonstrated that the JAK/STAT pathway also up-regulated SOCS-3 mainly in response to IGF-1. SOCS-3 associated with the IGF receptor and blocked further STAT3 activation. To our knowledge, this is the first report that demonstrated the importance of the JAK/STAT pathway and the role of SOCS-3 in the survival of neurons in response to IGF-1. We have subsequently shown that SOCS-3 overexpression, on one hand, leads to neuroblastoma cell death and on the other hand leads to primary cell differentiation, indicating the involvement of SOCS-3 in cell survival and differentiation.

Novel trinuclear complexes C23H31N6O6CuSn2Cl5 [1], C23H31N6O6CuZr2Cl5 [2], C23H31N6O6ZnSn2Cl5 [3], and C23H31N6O6ZnZr2Cl5 [4] were synthesized and characterized by spectroscopic (IR, 1H, 13C, 2D COSY, and 119Sn NMR, EPR, UV-vis, ESI-MS) and analytical methods. In complexes 1-4, the geometry of copper and zinc metal ions were described as square-based pyramidal with l-tryptophan coordinated to copper/zinc via carboxylate group while Sn/Zr was present in the hexacoordinate environment. The interaction of 1 and 2 with calf thymus DNA in Tris buffer was studied by electronic absorption titration, luminescence titration, cyclic voltammetry, circular dichroism, and viscometric measurements. The emission quenching of these complexes by [Fe(CN)6]4- depressed greatly when bound to DNA. Observed changes in the circular dichoric spectra of DNA in presence of 1 and 2 support the strong binding of complexes with DNA. The relative specific viscosity of DNA bound to 1 and 2 decreased, indicating that the complexes bind to DNA via covalent binding. The results reveal that the extent of DNA binding of 1 was greater than that of 2. To evaluate the mechanistic pathway of DNA inhibition, counting experiments and MTT assay were employed to assess the induction of apoptosis by 1. Western blot analysis of whole cell lysates and mitochondrial fractions with Bcl-2 and p-53 family proteins and caspase-3 colorimetry assay were also carried out on a human neuroblastoma cell line SY5Y.

The findings suggest that ethanol-induced apoptosis of insulin-stimulated neuronal cells can be reduced by activating PI3 K and inhibiting pro-apoptosis gene expression and intracellular signaling through non-insulin-dependent pathways.