Cytokine-induced venodilatation in humans in vivo: eNOS masquerading as iNOS.
- Publication Type:
- Journal Article
- Citation:
- Cardiovasc Res, 1999, 41 (3), pp. 754 - 764
- Issue Date:
- 1999-03
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OBJECTIVE: Venodilatation is a feature of endotoxaemia and sepsis. We have tested directly the hypothesis that three cytokines (IL-1 beta, TNF alpha and IL-6) generated during endotoxaemia affect venous tone in humans in vivo by increasing NO generation and explored whether the NO comes from the iNOS or eNOS isoform. DESIGN AND INTERVENTION: Cytokines were given into a superficial vein in very low doses sufficient only to produce changes in the study vessel. The effects of cytokines on the response to noradrenaline were examined. RESULTS: IL-1 beta increased basal NO-induced dilatation in the study vein, and this was sufficient to attenuate the constrictor response to exogenous noradrenaline or sympathetic stimulation. The effects were maximal at 6 h and both NG-monomethyl-L-arginine and aminoguanidine caused significant reversal of the IL-1 beta effects. However, no induction of iNOS mRNA was detected in the tissue samples. Instead, mRNA encoding eNOS and GTP cyclohydrolase-1 was detected in all vessels. CONCLUSION: The simplest explanation of these results is that IL-1 beta induces expression of GTP cyclohydrolase-1 which leads to increased generation of BH4 and activation of eNOS. This study identifies IL-1 beta as a key cytokine causing physiologically significant venodilatation in humans by increasing NO generation and suggests that this can occur even in the absence of iNOS expression.
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