No abstract

The potent vasoconstrictor peptide endothelin-1 (ET-1) has been implicated in the pathophysiology of atherosclerosis and its complications. Since inflammation of the vessel wall is a hallmark of atherosclerosis, the purpose of the present study was to investigate the influence of ET-1 on cytokine production in human vascular smooth muscle cells (SMC) as a marker of inflammatory cell activation. ET-1 (100 pM - 1 microM) stimulated interleukin-6 (IL-6) secretion from human vascular SMC in a concentration-dependent manner. The ET-A-receptor antagonist BQ-123 (10 microM), but not the ET-B-receptor antagonist BQ-788, inhibited IL-6 release. ET-1 also transiently increased IL-6 mRNA compatible with regulation of IL-6 release at the pretranslational level. Electrophoretic mobility shift assays demonstrated time- and concentration-dependent activation of the proinflammatory transcription factor nuclear factor-kappaB (NF-kappaB) in ET-1-stimulated human vascular SMC. A decoy oligodeoxynucleotide bearing the NF-kappaB binding site inhibited ET-1-stimulated IL-6 release to a great extent suggesting that this transcription factor plays a key role for cytokine production elicited by ET-1. Moreover, the antioxidant pyrrolidine dithiocarbamate (10 microM) inhibited ET-1-induced IL-6 release indicating involvement of reactive oxygen species in ET-1 signaling. ET-1-stimulated IL-6 secretion was also suppressed by diphenylene iodonium (40 microM), an inhibitor of flavon-containing enzymes such as NADH/NADPH oxidase. The results demonstrate the ability of ET-1 to induce an inflammatory response in human vascular SMC. These observations may contribute to a better understanding of the role of ET-1 in inflammatory activation of the vessel wall during atherogenesis.

The renin-angiotensin system contributes to atherogenesis. Matrix metalloproteinases (MMP) are thought to participate in plaque destabilization through degradation of extracellular matrix. This study tested whether angiotensin II (ANG II) induces MMP in human vascular smooth muscle cells (SMC). ANG II induced expression of MMP-1, -3, and -9, but not of MMP-2 in SMC. The expression of MMP-1, a key enzyme for collagen degradation, was studied in detail. SMC stimulated with ANG II concentration-dependently released enzymatically active MMP-1. The ANG II type 1 receptor antagonists losartan and candesartan blocked ANG-II-induced MMP-1 release. Inhibition experiments with actinomycin D suggest ANG-II-induced MMP-1 mRNA regulation at the transcriptional level. Decoy oligodeoxynucleotides against nuclear factor-ĸB and activator protein 1 inhibited MMP-1 secretion, demonstrating participation of these transcription factors in MMP-1 transcription. Stimulation of MMP-1 by ANG II depended on cyclooxygenase 2. The antioxidants pyrrolidine dithiocarbamate and N-acetylcysteine, the flavin protein inhibitor diphenylene iodonium, and the NADP(H) oxidase inhibitor apocynin blocked MMP-1 release, suggesting a redox-sensitive mechanism involving NADP(H) oxidase. The reactive oxygen species (ROS) donor 2,3-dimethoxy-1,4-naphthoquinone induced MMP-1 secretion and enhanced ANG-II-stimulated MMP-1 expression. These findings indicate that ROS may increase their own production by activation of NADP(H) oxidase. The capability of ANG II to induce functionally active MMP in human SMC may contribute to the altered plaque composition seen in complicated stages of atherosclerosis.