High glucose and insulin inhibit VSMC MKP-1 expression by blocking iNOS via p38 MAPK activation.
Our laboratory has recently demonstrated a role for the phosphatidylinositol 3-kinase-mediated inducible NO synthase (iNOS) signaling pathway in acute regulation of insulin-induced mitogen-activated protein phosphatase-1 (MKP-1) expression in primary cultures of rat aortic vascular smooth muscle cells (VSMCs) (N. Begum, L. Ragolia, M. McCarthy, and N. Duddy. J. Biol. Chem. 273: 25164-25170, 1998). We now show that prolonged treatment of VSMCs with 100 nM insulin and high glucose (25 mM) for 12-24 h, to mimic hyperinsulinemia and hyperglycemia, completely blocked MKP-1 mRNA and protein expression in response to subsequent acute insulin treatment. To understand the mechanism of insulin resistance induced by high glucose and insulin, we studied the regulation of iNOS protein induction in these cells. Both high glucose and chronic insulin treatment caused a marked impairment of iNOS induction in response to acute insulin. Blocking of signaling via the p38 mitogen-activated protein kinase (MAPK) pathway by prior treatment for 1 h with SB-203580, a synthetic p38 MAPK inhibitor, completely prevented the inhibition of iNOS induced by high glucose and insulin and restored MKP-1 induction to levels observed with acute insulin treatment. In contrast, PD-98059, a MEK inhibitor, had no effect. Furthermore, high glucose and chronic insulin treatment caused sustained p38 MAPK activation. We conclude 1) that chronic insulin and high glucose-induced insulin resistance is accompanied by marked reductions in both iNOS and MKP-1 inductions due to p38 MAPK activation that leads to excessive cell growth and 2) that p38 MAPK/extracellular signal-regulated kinase pathways regulate iNOS induction, thereby controlling MKP-1 expression, which in turn inactivates MAPKs as a feedback mechanism and inhibits cell growth.
Begum
N
N
Diabetes Research Laboratory, Winthrop University Hospital, Mineola, New York 11501, USA. nbegum@winthrop.org
Ragolia
L
L
D000818:Animals; D001011:Aorta / Q000166:cytology; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D054638:Dual Specificity Phosphatase 1; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology*; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D017874:Immediate-Early Proteins / Q000235:genetics*; D007328:Insulin / Q000494:pharmacology*; D007333:Insulin Resistance / Q000502:physiology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D017027:Protein Tyrosine Phosphatases / Q000235:genetics*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011921:Rats, Inbred WKY; D048051:p38 Mitogen-Activated Protein Kinases
D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007004:Hypoglycemic Agents; D007093:Imidazoles; D017874:Immediate-Early Proteins; D007328:Insulin; D011725:Pyridines; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D019869:Phosphatidylinositol 3-Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; D054638:Dual Specificity Phosphatase 1; C517021:Dusp1 protein, rat; D017027:Protein Tyrosine Phosphatases; D005947:Glucose; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one