Increased intracellular cyclic adenosine 3',5'-monophosphate inhibits release of tumor necrosis factor-α from human vascular tissue and cultured smooth muscle cells

Li Ming Zhang, Manuel R. Castresana, Issam J. Shaker, Martin L. Dalton, Sandra K. Leeper-Woodford, Walter H. Newman

Research output: Contribution to journalArticle

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Abstract

Objectives: We recently reported that bacterial lipopolysaccharide stimulates release of tumor necrosis factor (TNF)-α from both human vascular tissue and cultured smooth muscle cells. In the current study, we tested the hypothesis that increased intracellular cyclic adenosine 3',5'-monophosphate (cAMP) could inhibit TNF-α release. Design: Prospective, repeated-measures analysis. Setting: Academic research laboratory. Subjects: Segments of internal mammary artery and saphenous vein from patients undergoing coronary artery bypass surgery. Measurements and Main Results: Segments of saphenous vein and internal mammary artery and confluent smooth muscle cells cultured from these vessels were incubated in the presence of 20 μg/mL bacterial lipopolysaccharide, alone or with the addition of forskolin or 8-Br-cAMP. At 0, 1, 3, 6, 18, and 24 hrs, the incubation medium was removed from vessel segments or cells and was analyzed for biologically active TNF-α, using the L929 cell cytotoxicity assay. cAMP was extracted from tissue and cells with 0.1N HCl and was analyzed by radioimmunoassay. Bacterial lipopolysaccharide stimulated the release of TNF-α from internal mammary smooth muscle cells at all time points. For example, at 6 hrs, TNF-α concentration in the medium from lipopolysaccharide-stimulated cells was 20 ± 1.6 U/mg of cell protein, compared with 0.9 ± 0.5 U/mg of cell protein in control cell medium (p < .05). Forskolin-inhibited bacterial lipopolysaccharide stimulated TNF-α release. In the presence of lipopolysaccharide and forskolin, TNF-α release at 6 hrs was 8.6 ± 1.5 U/mg of cell protein (p < .05 vs. in the presence of bacterial lipopolysaccharide alone). Bacterial lipopolysaccharide, alone, bad no effect on intracellular cAMP. Forskolin increased intracellular cAMP levels to 74.0 ± 12 pmol/mg of cell protein at 6 hrs from a control level of 7.7 ± 0.4 pmol/mg (p < .05). The 8-Br-cAMP, an agent that mimics the action of intracellular cAMP, also inhibited TNF-α release stimulated by lipopolysaccharide. Similar inhibition by forskolin and 8-Br-cAMP on TNF-α release was obtained with smooth muscle cells from saphenous vein. Finally, in tissue segments from either internal mammary artery or saphenous vein, both forskolin and 8-Br-cAMP inhibited lipopolysaccharide-stimulated TNF-α release. Conclusions: These results are consistent with the conclusion that vascular tissue, particularly the smooth muscle cell, is a source of TNF-α. Further, bacterial lipopolysaccharide-stimulated tumor TNF-α release can be inhibited by increased intracellular cAMP.

Original languageEnglish (US)
Pages (from-to)1855-1861
Number of pages7
JournalCritical care medicine
Volume25
Issue number11
DOIs
Publication statusPublished - Nov 22 1997
Externally publishedYes

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Keywords

  • Bacterial lipopolysaccharide
  • Blood vessels
  • Cyclic AMP
  • Smooth muscle cells
  • Tumor necrosis factor-α

ASJC Scopus subject areas

  • Critical Care and Intensive Care Medicine

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