endothelin-1 and 3-3--4-5--tetrahydroxystilbene

Although few epidemiological studies have demonstrated that C-reactive protein (CRP) is related to insulin resistance, no study to date has examined the molecular mechanism. Here, we show that recombinant CRP attenuates insulin signaling through the regulation of spleen tyrosine kinase (Syk) on small G-protein RhoA, jun N-terminal kinase (JNK) MAPK, insulin receptor substrate-1 (IRS-1), and endothelial nitric oxide synthase in vascular endothelial cells. Recombinant CRP suppressed insulin-induced NO production, inhibited the phosphorylation of Akt and endothelial nitric oxide synthase, and stimulated the phosphorylation of IRS-1 at the Ser307 site in a dose-dependent manner. These events were blocked by treatment with an inhibitor of RhoA-dependent kinase Y27632, or an inhibitor of JNK SP600125, or the transfection of dominant negative RhoA cDNA. Next, anti-CD64 Fcgamma phagocytic receptor I (FcgammaRI), but not anti-CD16 (FcgammaRIIIa) or anti-CD32 (FcgammaRII) antibody, partially blocked the recombinant CRP-induced phosphorylation of JNK and IRS-1 and restored, to a certain extent, the insulin-stimulated phosphorylation of Akt. Furthermore, we identified that recombinant CRP modulates the phosphorylation of Syk tyrosine kinase in endothelial cells. Piceatannol, an inhibitor of Syk tyrosine kinase, or infection of Syk small interference RNA blocked the recombinant CRP-induced RhoA activity and the phosphorylation of JNK and IRS-1. In addition, piceatannol also restrained CRP-induced endothelin-1 production. We conclude that recombinant CRP induces endothelial insulin resistance and dysfunction, and propose a new mechanism by which recombinant CRP induces the phosphorylation of JNK and IRS-1 at the Ser307 site through a Syk tyrosine kinase and RhoA-activation signaling pathway.

Topics: Animals; C-Reactive Protein; Cattle; Cells, Cultured; Endothelial Cells; Endothelin-1; Endothelium, Vascular; Insulin; Insulin Receptor Substrate Proteins; Insulin Resistance; Intracellular Signaling Peptides and Proteins; MAP Kinase Kinase 4; MAP Kinase Signaling System; Mice; Nitric Oxide; Nitric Oxide Synthase Type III; Oncogene Protein v-akt; Phosphoproteins; Phosphorylation; Protein-Tyrosine Kinases; Receptors, IgG; Recombinant Proteins; rhoA GTP-Binding Protein; Signal Transduction; Stilbenes; Syk Kinase

Although spleen tyrosine kinase (Syk) has crucial roles in various cells, its function on vascular smooth muscle contraction has not been determined. In the present study, we performed experiments to determine if Syk contributes to the endothelin-1 (ET-1)-mediated contraction in rat aortic smooth muscle. ET-1-induced contraction of aortic strips was inhibited by piceatannol, PD98059, and SB203580, inhibitors of Syk, extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 mitogen-activated protein kinase (MAPK), respectively. Piceatannol also attenuated high K(+)-induced contraction. ET-1 dose-dependently enhanced the activity of Syk and this was inhibited by piceatannol in both rat aortic strip and rat aortic smooth muscle cells. The phosphorylation of p38 MAPK and heat shock protein 27 (HSP27), but not that of ERK1/2, in response to ET-1 was inhibited by both piceatannol and SB203580. These results suggest that Syk may play an important role in the regulation of aortic smooth muscle contraction induced by ET-1, which may be mediated by the p38 MAPK/HSP27 signaling pathway.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Aorta; Calcium-Calmodulin-Dependent Protein Kinases; Cells, Cultured; Dose-Response Relationship, Drug; Endothelin-1; Enzyme Inhibitors; Flavonoids; Imidazoles; Immunoblotting; Immunoprecipitation; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Male; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Protein-Tyrosine Kinases; Pyridines; Rats; Rats, Sprague-Dawley; Stilbenes; Syk Kinase; Vasoconstriction