© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Induction of nitric oxide synthase in human vascular smooth muscle: interactions between proinflammatory cytokines
aDepartment of Cardiothoracic Surgery, Imperial College of Science, Technology and Medicine, National Heart and Lung Institute, Heart Science Centre, Harefield Hospital, Harefield, Middlesex UB9 6JH, UK
bDepartment of Histochemistry, Royal Postgraduate Medical School, Du Cane Road, London W12 0NN, UK
cUnit of Critical Care, Royal Brompton Hospital, Sydney Street, London SW3 6NP, UK
* Corresponding author. Tel.: +44 (1895) 828893; Fax: +44 (1895) 828900.
Objective: We have attempted to demonstrate the induction of inducible nitric oxide synthase in human vascular tissue and define the capacity of different cytokines to induce this enzyme. Methods: Segments of human arteries were stimulated with lipopolysaccharide (10 µg/ml), interleukin-1β (5 U/ml), tumor necrosis factor-
(10 U/ml), and interferon-
(200 U/ml). Cytokines were either used alone or in certain combinations, as well as in the presence of L-NG-monomethyl-arginine (100 µmol/l) or cycloheximide (1 µmol/l). Induction was assessed by measurement of mRNA expression, immunocytochemical localisation of the expressed protein, nitric oxide synthase activity and levels of nitrite, a product of nitric oxide formation. Results: PCR analysis showed the presence of mRNA for iNOS in stimulated samples which could be inhibited by cycloheximide. There was positive staining with an antibody against human iNOS in the media of stimulated vessel segments. Stimulated segments were also shown to contain Ca2+-independent nitric oxide synthase activity. The cytokines and lipopolysaccharide together gave a significant rise in levels of nitrite in the medium after 36 and 48 h, which was inhibited by L-NG-monomethyl-arginine and cycloheximide. Only interferon-
incubated alone was capable of increasing nitrite levels. This effect was enhanced by co-incubation with either interleukin-1β, tumor necrosis factor-
or lipopolysaccharide. Conclusion: We have shown that increased production of nitrite by human vascular tissue in response to cytokines is associated with induction of iNOS as shown at the molecular and protein levels, and further supported by the presence of increased Ca2+-independent nitric oxide synthase activity following cytokine stimulation.
KEYWORDS Nitric oxide; Septic shock; Atherosclerosis; Cytokines; Human