Inhibition of release of tumor necrosis factor-alpha from human vascular tissue and smooth muscle cells by glucocorticoids

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Abstract
Objectives Based on our previous study that bacterial lipopolysaccharide stimulates release of tumor necrosis factor (TNF)-alpha from human vascular tissue and smooth muscle cells, we tested the hypothesis that release of TNF could be inhibited by pretreatment with glucocorticoids. Design Prospective, repeated-measures analysis of concentration-response relationships. Setting Academic anesthesiology research laboratory. Subjects Segments of internal mammary artery and saphenous vein were obtained during coronary artery bypass surgery. Interventions None. Measurements and Main Results Confluent human smooth muscle cells, cultured from saphenous vein and internal mammary artery, were exposed to 20 micro g/mL of bacterial lipopolysaccharide following pretreatment for 18 hrs with either 0.1, 1.0, or 10.0 micro M of dexamethasone. At 1, 3, 6, 18, and 24 hrs, the culture medium was removed and analyzed for biologically active TNF-alpha using the L929 cell cytotoxicity assay. Smooth muscle cells exposed to bacterial lipopolysaccharide but not treated with dexamethasone served as controls. In control internal mammary cells, bacterial lipopolysaccharide stimulated TNF-alpha release in a time-dependent manner to a peak of 36 +/- 2.3 U/mg of cell protein at 6 hrs, compared with 0.7 +/- 0.3 U/mg of cell protein in cells not exposed to lipopolysaccharide. Dexamethasone inhibited bacterial lipopolysaccharide-stimulated release at all time points in a concentration-dependent manner. For instance, at 6 hrs, TNF-alpha was 12 +/- 2.2, 6.9 +/- 1.7, and 2.3 +/- 0.9 U/mg of cell protein for cells pretreated with 0.1, 1.0, and 10.0 micro M of dexamethasone, respectively (p < .05 vs. control). In separate experiments, segments of internal mammary artery and saphenous vein were obtained from five patients who received 1 g of methylprednisolone intravenously during induction of anesthesia, and from seven patients who did not receive methylprednisolone. Bacterial lipopolysaccharide induced rele6ase of TNF-alpha from vascular tissues of untreated patients in a time-dependent manner (e.g., 733 +/- 44 U/g of tissue at 6 hrs in saphenous vein). In contrast, in patients treated with methylprednisolone, bacterial lipopolysaccharide did not stimulate release from vascular tissues incubated for up to 24 hrs. Conclusions These results indicate that human vascular tissue, particularly the smooth muscle cell, may be a source of TNF-alpha and that glucocorticoids inhibit release stimulated by bacterial lipopolysaccharide. (Crit Care Med 1997; 25:519-522)