Inhibition of Endothelial Vascular Cell Adhesion Molecule-1 Expression by Nitric Oxide Involves the Induction and Nuclear Translocation of IκBα*
- From the Vascular Medicine and Atherosclerosis Unit, Cardiovascular Division, Brigham & Women’s Hospital and Harvard Medical School, Boston, Massachusetts 02115
Abstract
The induction of vascular cell adhesion molecule-1 (VCAM-1) expression by tumor necrosis factor (TNF)-α requires the activation of nuclear factor-κB (NF-κB) via a process involving the phosphorylation and degradation of its cytoplasmic inhibitor, IκBα. We have shown that nitric oxide (NO) decreases VCAM-1 expression via inhibition of NF-κB activation. To determine how NO inhibits NF-κB, we studied the fate of IκBα following TNF-α stimulation in the presence of NO donorsS-nitrosoglutathione and sodium nitroprusside. Activation of NF-κB by TNF-α occurred within 15 min and coincided with rapid degradation of IκBα. Co-treatment with NO donors did not prevent IκBα phosphorylation or degradation. However, after 2 h of TNF-α stimulation, NO donors inhibited NF-κB activation and augmented IκBα resynthesis and nuclear translocation by 2.5- and 3-fold, respectively. This correlated with a 75% reduction in TNF-α-induced VCAM-1 expression. In a time-dependent manner, NO donors alone caused the nuclear translocation of IκBα. To confirm that NO donors have similar effects as endogenously derived NO, murine macrophage-like cells, RAW264.7, were co-cultured with endothelial cells. Induction of RAW264.7-derived NO inhibited lipopolysaccharide-induced endothelial VCAM-1 expression, which was reversed by the NO synthase inhibitorN ω-monomethyl-l-arginine. These findings indicate that NO inhibits NF-κB activation and VCAM-1 expression by increasing the expression and nuclear translocation of IκBα.
Footnotes
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↵* This work was supported by Grants HL-52233 and HL-09650 from the National Institutes of Health.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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↵‡ Recipient of the Feodor Lynen Fellowship (Alexander von Humboldt Stiftung).
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↵§ Established Investigator of the American Heart Association. To whom correspondence should be sent: Cardiovascular Division, Dept. of Medicine, 221 Longwood Ave., LMRC-316, Boston, MA 02115. Tel.: 617-732-6538; Fax: 617-264-6336; E-mail: jkliao{at}bics.bwh.harvard.edu.
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↵1 The abbreviations used are: VCAM-1, vascular cell adhesion molecule-1; TNF-α, tumor necrosis factor-α; IFN-γ, interferon-γ; mIFN-γ, murine interferon-γ; GSNO,S-nitrosoglutathione; IκBα, inhibitor κBα; LPS, bacterial lipopolysaccharide; LNMA,N ω-monomethyl-l-arginine; NF-κB, nuclear factor-κB; PBS, phosphate-buffered saline; NO, nitric oxide.
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- Received July 16, 1997.
- Revision received September 26, 1997.
