Proinflammatory mediators chronically downregulate the formation of the endothelium-derived hyperpolarizing factor in arteries via a nitric oxide/cyclic GMP-dependent mechanism.
BACKGROUND
Endothelium-dependent dilator responses mediated by NO and endothelium-derived hyperpolarizing factor (EDHF) are altered in arteriosclerosis and sepsis. The possibility that proinflammatory mediators that stimulate the expression of inducible NO synthase (NOS II) affect the generation of EDHF was examined in isolated arteries.


RESULTS
Under combined blockade of NOS and cyclooxygenase, EDHF-mediated relaxation elicited by several agonists was significantly attenuated in rabbit carotid and porcine coronary arteries exposed to cytokines and lipopolysaccharide. The blunted relaxation was coincident with NOS II expression and was prevented by inhibition of NOS II as well as of global protein synthesis. The NO donor CAS 1609 and 8-bromo-cGMP mimicked the proinflammatory mediator effect. In contrast, long-term blockade of endothelial NO generation increased the relaxation in carotid but not in coronary arteries. Proinflammatory mediators reduced the synthesis of EDHF assessed as hyperpolarization of vascular smooth muscle cells elicited by the effluent from bradykinin-stimulated coronary arteries. Proinflammatory mediators induced NOS II expression in cultured endothelial cells and decreased the expression of cytochrome P450 enzymes, which are the most probable candidates for the synthesis of EDHF.


CONCLUSIONS
Proinflammatory mediators inhibit the formation of EDHF in isolated arteries. This impairment is coincident with NOS II expression in the arterial wall and seems to be mediated through the induced generation of NO, which downregulates the putative EDHF-forming enzyme. Thus, a decreased formation of EDHF may contribute to the endothelial dysfunction in arteriosclerosis and sepsis.
Kessler
P
P
Institut für Kardiovaskuläre Physiologie und Institut für Anaesthesiologie, Klinikum der J.W.G.-Universität, Frankfurt/Main, Germany.
Popp
R
R
Busse
R
R
Schini-Kerth
V B
VB
D000818:Animals; D001158:Arteries / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D001685:Biological Factors / Q000096:biosynthesis*; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000502:physiology*; D065607:Cytochrome P-450 Enzyme Inhibitors; D004730:Endothelium, Vascular / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D018836:Inflammation Mediators / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D013552:Swine; D014664:Vasodilation / Q000502:physiology
D001685:Biological Factors; D065607:Cytochrome P-450 Enzyme Inhibitors; D018836:Inflammation Mediators; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide; D006152:Cyclic GMP