Nitric oxide decreases cytokine-induced endothelial activation. Nitric oxide selectively reduces endothelial expression of adhesion molecules and proinflammatory cytokines.

TLDR

NO represses VCAM‑1 transcription by inhibiting NF‑κB, potentially limiting endothelial activation and monocyte adhesion, which may underlie its anti‑atherogenic and anti‑inflammatory effects. The study tested whether nitric oxide limits endothelial activation by treating cytokine‑stimulated human saphenous vein endothelial cells with NO donors and measuring VCAM‑1 expression. Using NO donors on cytokine‑stimulated endothelial cells, the authors assessed VCAM‑1 surface expression and employed nuclear run‑on, promoter reporter, and EMSA assays to show transcriptional repression via NF‑κB inhibition. NO reduced IL‑1α‑induced VCAM‑1 expression by 35–55 %, lowered monocyte adhesion, decreased other adhesion molecules and pro‑inflammatory cytokines, and this effect was independent of cGMP and replicated across multiple cytokines and LPS, while inhibition of endogenous NO increased VCAM‑1 but did not enhance cytokine‑induced expression.

Abstract

To test the hypothesis that nitric oxide (NO) limits endothelial activation, we treated cytokine-stimulated human saphenous vein endothelial cells with several NO donors and assessed their effects on the inducible expression of vascular cell adhesion molecule-1 (VCAM-1). In a concentration-dependent manner, NO inhibited interleukin (IL)-1 alpha-stimulated VCAM-1 expression by 35-55% as determined by cell surface enzyme immunoassays and flow cytometry. This inhibition was paralleled by reduced monocyte adhesion to endothelial monolayers in nonstatic assays, was unaffected by cGMP analogues, and was quantitatively similar after stimulation by either IL-1 alpha, IL-1 beta, IL-4, tumor necrosis factor (TNF alpha), or bacterial lipopolysaccharide. NO also decreased the endothelial expression of other leukocyte adhesion molecules (E-selectin and to a lesser extent, intercellular adhesion molecule-1) and secretable cytokines (IL-6 and IL-8). Inhibition of endogenous NO production by L-N-monomethyl-arginine also induced the expression of VCAM-1, but did not augment cytokine-induced VCAM-1 expression. Nuclear run-on assays, transfection studies using various VCAM-1 promoter reporter gene constructs, and electrophoretic mobility shift assays indicated that NO represses VCAM-1 gene transcription, in part, by inhibiting NF-kappa B. We propose that NO's ability to limit endothelial activation and inhibit monocyte adhesion may contribute to some of its antiatherogenic and antiinflammatory properties within the vessel wall.