Expression of an endothelial-type nitric oxide synthase isoform in human neutrophils: Modification by tumor necrosis factor-alpha and during acute myocardial infarction

OBJECTIVES The purpose of this study was to determine whether human neutrop hils express an endothelial-type nitric oxide synthase (eNOS), and to study the: effect of tumor necrosis factor-alpha (TNF-alpha) on its expression. BACKGROUND Several studies have demonstrated the presence of a constitutive ly expressed nitric oxide synthase (NOS) in neutrophils. Cardiovascular dis ease is characterized by increased levels of plasma TNF-alpha, a cytokine t hat has demonstrated eNOS messenger ribonucleic acid (mRNA) destabilization in cultured endothelial cells. METHODS Neutrophils were obtained from healthy volunteers and from patients with acute myocardial infarction (AMI). RESULTS Human neutrophils express eNOS mRNA and eNOS protein. Stimulation o f neutrophils with TNF-alpha decreased eNOS protein expression by reducing eNOS mRNA stabilization. In the present study, we also show that the cytoso l of human neutrophils contains proteins that bind to a specific region wit hin the 3'-untranslated region (3'-UTR) of eNOS mRNA. Tumor necrosis factor -alpha increased the binding of the cytosolic proteins to the 3'-UTR of eNO S mRNA. Simvastatin reduced the TNF-alpha-related binding activity of neutr ophil cytosolic proteins to eNOS mRNA, which was associated with its protec tive effect on eNOS protein expression. The in vivo reproduction of the in vitro findings was performed in neutrophils obtained from patients with AMI and showed a diminished expression of eNOS protein, which was associated w ith increased binding of the cytosolic proteins. CONCLUSIONS These observations demonstrate that human neutrophils express e NOS, which is downregulated by TNF-alpha and during AMI. This effect is ass ociated with increased binding of neutrophil cytosolic proteins to the 3'-U TR of eNOS mRNA. (J Am Coil Cardiol 2001;37: 800-7) (C) 2001 by the America n College of Cardiology.