Regulation of Mitogen-activated Protein Kinase Phosphatase-1 Induction by Insulin in Vascular Smooth Muscle Cells
EVALUATION OF THE ROLE OF THE NITRIC OXIDE SIGNALING PATHWAY AND POTENTIAL DEFECTS IN HYPERTENSION*
- From the Diabetes Research Laboratory, Winthrop University Hospital, Mineola, New York 11501 and the School of Medicine, State University of New York, Stony Brook, New York 11794
Abstract
In this study, we examined the regulation of mitogen-activated protein kinase phosphatase (MKP-1) expression by insulin in primary vascular smooth muscle cell cultures. Insulin caused a rapid time- and dose-dependent induction of MKP-1 mRNA and protein expression. Blockade of nitric-oxide synthase (NOS) withN G-monomethyl-l-arginine acetate, and cGMP with RpcGMP, completely inhibited MKP-1 expression. Insulin-mediated MKP-1 expression was preceded by inducible NOS (iNOS) induction and cGMP production. Blockade of phosphatidylinositol 3-kinase (PI3-kinase) signaling with wortmannin inhibited insulin-mediated iNOS protein induction, cGMP production, and MKP-1 expression. To evaluate potential interactions between NOS and the mitogen-activated protein kinase (MAPK) signaling pathways, we employed PD98059 and SB203580, two specific inhibitors of ERKs and p38 MAPK. These inhibitors abolished the effect of insulin on MKP-1 expression. Only PD98059 inhibited insulin-mediated iNOS protein induction. Vascular smooth muscle cells from spontaneous hypertensive rats exhibited a marked decrease in MKP-1 induction due to defects in insulin-induced iNOS expression because of reductions in PI3-kinase activity. Treatment with sodium nitroprusside and 8-bromo-cGMP restored MKP-1 mRNA expression to levels comparable with controls. We conclude that insulin-induced MKP-1 expression is mediated by PI3-kinase-initiated signals, leading to the induction of iNOS and elevated cGMP levels that stimulates MKP-1 expression.
Footnotes
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↵* This work was supported in part by a grant-in-aid from the American Heart Association, New York State Affiliate, and the medical education funds from Winthrop University Hospital.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵‡ To whom correspondence should be addressed: the Diabetes Research Laboratory, Winthrop University Hospital, 259 First St., Mineola, NY 11501. Tel.: 516-663-3915; Fax: 516-663-4780.
- Abbreviations:
- MAPK
-
mitogen-activated protein kinase
- MKP-1
-
mitogen-activated protein kinase phosphatase
- VSMC
-
vascular smooth muscle cell(s)
- NOS
-
nitric-oxide synthase
- iNOS
-
inducible NOS
- PI3-kinase
-
phosphatidylinositol 3-kinase
- l-NMMA
-
N G-monomethyl-l-arginine acetate
- RpcGMP
-
Rp-8 CPT-cyclic guanosine monophosphate
- IGF-1
-
insulin growth factor-1
- FBS
-
fetal bovine serum
- SHR
-
spontaneous hypertensive rats
- SNP
-
sodium nitroprusside
- WKY
-
Wistar Kyoto rats. ERK, extracellular regulated kinase
- JNK
-
c- jun amino-terrminal kinase
- SAPK
-
stress-activated protein kinase.
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- Received April 24, 1998.
- Revision received June 25, 1998.
- The American Society for Biochemistry and Molecular Biology, Inc.
