Cyclic AMP inhibits production of interleukin-6 and migration in human vascular smooth muscle cells.
BACKGROUND
Gene expression induced by tumor necrosis factor-alpha (TNF-alpha) is involved in the regulation of vascular smooth muscle cell (VSMC) proliferation and migration, two events critical to formation of stenotic vascular lesions. In some systems, elevating adenosine 3',5'-cyclic monophosphate (cyclic AMP) inhibits TNF-alpha induced gene transcription. We recently demonstrated that interleukin-6 (IL-6) was chemotactic to VSMC. Therefore, we tested the hypothesis that elevating cyclic AMP would inhibit TNF-alpha-mediated IL-6 expression and VSMC migration.


METHODS
VSMC were cultured from saphenous vein remaining after coronary artery bypass grafting. Migration of VSMC through a porous membrane was determined. Intracellular cyclic AMP was elevated by exposing the cells to forskolin or 8-Br-cyclic AMP and was measured by radioimmunoassay. IL-6 was measured by enzyme-linked immunosorbent assay.


RESULTS
TNF-alpha induced migration of VSMC in a concentration-dependent manner. Incubation of cells with forskolin significantly increased cyclic AMP. Co-incubation of cells with TNF-alpha in combination with 8-Br-cyclic AMP or forskolin inhibited migration by approximately 25 and 70%, respectively. Incubation with TNF-alpha increased release of IL-6 from VSMC 18-fold over basal. This stimulated release was inhibited by either 8-Br-cyclic AMP or forskolin. In cells stimulated with TNF-alpha, addition of an antibody to IL-6 reduced migration by 25%.


CONCLUSIONS
These data show that IL-6 produced by VSMC contributes to cell migration induced by TNF-alpha. Further, elevating cyclic AMP inhibited TNF-alpha-induced release of IL-6, and migration of VSMC. These results are consistent with the notion that mechanisms that increase intracellular cyclic AMP, such as activation of beta-adrenergic receptors on VSMC, act as a brake on cell migration.
Newman
Walter H
WH
Department of Surgery, Mercer University School of Medicine, Medical Center of Central Georgia, Macon, Georgia 31210, USA. newman_wh@mercer.edu
Castresana
Manuel R
MR
Webb
Jerry G
JG
Wang
Zhongbiao
Z
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000906:Antibodies / Q000494:pharmacology; D002465:Cell Movement / Q000187:drug effects*; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000276:immunology; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism*; D012501:Saphenous Vein; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D000906:Antibodies; D015850:Interleukin-6; D014409:Tumor Necrosis Factor-alpha; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D000242:Cyclic AMP