Insulin resistance in polycystic ovary syndrome (PCOS) results from a postbinding defect in signaling. Insulin receptor and insulin receptor substrate (IRS)-1 serine hyperphosphorylation by an unidentified kinase(s) contributes to this defect. We investigated whether insulin resistance is selective, affecting metabolic but not mitogenic pathways, in skeletal muscle as it is in cultured skin fibroblasts in PCOS. Extracellular signal-regulated kinase (ERK)1/2 activation was increased in skeletal muscle tissue and in cultured myotubes basally and in response to insulin in women with PCOS compared with control women. Mitogen-activated/extracellular signal-regulated kinase kinase (MEK)1/2 was also activated in PCOS, whereas p38 mitogen-activated protein kinase phosphorylation and signaling from the insulin receptor to Grb2 was similar in both groups. The activity of p21Ras was decreased and Raf-1 abundance increased in PCOS, suggesting that altered mitogenic signaling began at this level. MEK1/2 inhibition reduced IRS-1 Ser 312 phosphorylation and increased IRS-1 association with the p85 subunit of phosphatidylinositol 3-kinase in both groups. We conclude that in PCOS skeletal muscle, 1) mitogenic signaling is enhanced in vivo and in culture, 2) ERK1/2 activation inhibits association of IRS-1 with p85 via IRS-1 Ser 312 phosphorylation, and 3) ERK1/2 activation may play a role in normal feedback of insulin signaling and contribute to resistance to insulin's metabolic actions in PCOS. Diabetes 55: [751][752][753][754][755][756][757][758][759] 2006

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Progression of cancer leads to hypoxic solid tumors that mount specific cell signaling responses to low oxygen conditions. An important objective of anti-cancer therapy is the development of new drugs that suppress hypoxic responses in solid tumors. Apigenin is a natural flavone that has been shown to have chemopreventive and/or anti-cancer properties against a number of tumor types. However, the mechanisms underlying apigenin's chemopreventive properties are not yet completely understood. In this study, we have investigated the effects of apigenin on expression of hypoxia-inducible factor-1 (HIF-1) in human metastatic prostate PC3-M cancer cells. We found that hypoxia induced a time-dependent increase in the level of HIF-1alpha subunit protein in PC3-M cells, and treatment with apigenin markedly decreased HIF-1alpha expression under both normoxic and hypoxic conditions. Further, apigenin prevented the activation of the HIF-1 downstream target gene vascular endothelial growth factor (VEGF). We then showed that apigenin inhibited expression of HIF-1alpha by reducing stability of the protein as well as by reducing the level of HIF-1alpha mRNA. We also found that apigenin inhibited Akt and GSK-3beta phosphorylation in PC3-M cells. Further experiments demonstrated that constitutively active Akt blunted the effect of apigenin on HIF-1alpha expression. Taken together, our results identify apigenin as a bioflavonoid that inhibits hypoxia-activated pathways linked to cancer progression in human prostate cancer, in particular the PI3K/Akt/GSK-3 pathway. Further studies on the mechanism of action of apigenin will likely provide new insight into its applicability for pharmacologic targeting of HIF-1alpha for cancer therapeutic or chemopreventive purposes.

Excessive glial activation, with overproduction of cytokines and oxidative stress products, is detrimental and a hallmark of neurodegenerative disease pathology. Suppression of glial activation is a potential therapeutic approach, and protein kinases are targets of some antiinflammatory drugs. To address an unmet need for selective inhibitors of glial activation, we developed a novel 3-amino-6-phenylpyridazine derivative that selectively blocks increased IL-1 beta, iNOS, and NO production by activated glia, without inhibition of potentially beneficial glial functions.

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