Phosphoinositol 3-kinase Inhibitor Research Articles

Insulin-like Growth Factor-1-mediated Neuroprotection against Oxidative Stress Is Associated with Activation of Nuclear Factor κB

The role of insulin-like growth factor 1 (IGF-1) for the treatment of neurodegenerative disorders, such as Alzheimer's disease, has recently gained attention. The present study demonstrates that IGF-1 promotes the survival of rat primary cerebellar neurons and of immortalized hypothalamic rat GT1-7 cells after challenge with oxidative stress induced by hydrogen peroxide (H2O2). Neuroprotective concentrations of IGF-1 specifically induce the transcriptional activity and the DNA binding activity of nuclear factor kappaB (NF-kappaB), a transcription factor that has been suggested to play a neuroprotective role. This induction is associated with increased nuclear translocation of the p65 subunit of NF-kappaB and with degradation of the NF-kappaB inhibitory protein IkappaBalpha. IGF-1-mediated protection of GT1-7 cells against oxidative challenges was mimicked by overexpression of the NF-kappaB subunit c-Rel. Partial inhibition of NF-kappaB baseline activity by overexpression of a dominant-negative IkappaBalpha mutant enhanced the toxicity of H2O2 in GT1-7 cells. The pathway by which IGF-1 promotes neuronal survival and activation of NF-kappaB involves the phosphoinositol (PI) 3-kinase, because both effects of IGF-1 are blocked by LY294002 and wortmannin, two specific PI 3-kinase inhibitors. Taken together, our results provide evidence for a novel molecular link between IGF-1-mediated neuroprotection and induction of NF-kappaB that is dependent on the PI 3-kinase pathway.

Gene regulation after Fc epsilon RI stimulation in the murine mast cell line CPII.

Mast cells produce a number of lymphokines and chemokines upon Fc epsilonRI stimulation. However, signal cascades and transcription factors involved in the induction of the corresponding genes are still poorly understood. We addressed this issue using transient transfections of a TNF alpha promoter-driven reporter gene and corresponding 5' successive deletions, the two phosphoinositol-3 kinase inhibitors demethoxyviridin and wortmannin, ELISAs and Western and Southwestern blots. Nuclear factor of activated T cells (NF-AT) and AP1 transcription factors together mediate the activation of TNF alpha transcription in mast cells upon IgE plus antigen stimulation which, in contrast to the degranulation reaction and leukotriene synthesis, is independent of phosphoinositol-3-kinase. TNF alpha regulation in mast cells provides an experimental system for direct comparison of the regulation of this cytokine in T cells. In the context of our recent findings on IL-5 gene regulation in mast cells, a picture emerges in which NF-AT, dependent on the cytokine and not on cell type, interacts with a specific cofactor (AP1 for TNF alpha, GATA for IL-5). Multiple NF-AT family members found to be expressed in mast cells provide the structural basis for these different interactions with cofactors. The insensitivity of TNF alpha gene activation and release to inhibitors of phosphoinositol-3 kinase demonstrates that the activation of NF-AT and/or AP1 transcription factors in mast cells is not triggered along this signaling cascade.