Nitric oxide regulates monocyte chemotactic protein-1.
BACKGROUND
Monocyte chemotactic protein-1 (MCP-1) is a 76-amino-acid chemokine thought to be the major chemotactic factor for monocytes. We and others have demonstrated that NO inhibits monocyte-endothelial cell interactions and atherogenesis. We hypothesize that the antiatherogenic effect of NO may be due in part to its inhibition of MCP-1 expression.


RESULTS
Smooth muscle cells (SMCs) were isolated from normal rabbit aortas by the explant method. Cells were then exposed to LPS (10 microg/mL), native LDL, or oxidized LDL (30 microg/mL) for 6 hours. The expression of MCP-1 in SMCs and chemotactic activity in the conditioned medium were induced by lipopolysaccharide (LPS) or by oxidized LDL but not native LDL. The induction of MCP-1 by cytokines or oxidized lipoproteins was associated with an increased generation of superoxide anion by the SMCs and increased activity of the transcriptional protein nuclear factor-kappaB (NFkappaB). The induced expression of MCP-1 and activation of NFkappaB were reduced by previous exposure of the SMCs to the NO donor DETA-NONOate (100 micromol/L) (P<.05). To determine whether NO exerted its effect at a transcriptional level, SMCs and COS cells were transfected with a 400-bp fragment of the MCP-1 promoter. Promoter activity was enhanced by oxidized LDL, and LPS was inhibited by DETA-NO. Nuclear run-on assays confirmed that the effect of NO occurred at a transcriptional level. To investigate the role of endogenous NO in the regulation of MCP-1 in vivo, New Zealand White rabbits were fed normal chow, normal chow plus nitro-L-arginine (LNA), high-cholesterol diet (Chol), or high-cholesterol diet supplemented with L-arginine (Arg). After 2 weeks, thoracic aortas were harvested and total RNA was isolated. Northern analysis using full-length MCP-1 cDNA demonstrated increased expression in Chol and LNA aortas; this expression was decreased in aortas from Arg animals.


CONCLUSIONS
These studies indicate that the antiatherogenic effect of NO may be mediated in part by its inhibition of MCP-1 expression.
Tsao
P S
PS
Division of Cardiovascular Medicine, Stanford University School of Medicine, Calif 94305-5246, USA.
Wang
B
B
Buitrago
R
R
Shyy
J Y
JY
Cooke
J P
JP
D000818:Animals; D019556:COS Cells; D018932:Chemokine CCL2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D011817:Rabbits; D013481:Superoxides / Q000378:metabolism; D014226:Triazenes / Q000494:pharmacology
C105351:1-hydroxy-2-oxo-3,3-bis(2-aminoethyl)-1-triazene; D018932:Chemokine CCL2; D014226:Triazenes; D013481:Superoxides; D009569:Nitric Oxide