Induction of nitric oxide synthase activity by toxic shock syndrome toxin 1 in a macrophage-monocyte cell line.
Toxic shock syndrome toxin 1 (TSST-1) is a Mr 22,000 protein produced by Staphylococcus aureus. It is thought to be the cause of toxic shock syndrome. We investigated the hypothesis that TSST-1 induces nitric oxide (NO) synthase and that the NO formed may be involved in the pathogenesis of toxic shock syndrome. We used the murine monocyte-macrophage cell line J744.2 that responds to TSST-1 and also expresses NO synthase activity upon immunological stimulation. J774.2 macrophages stimulated with TSST-1 (10-100 nM) generated nitrite, a breakdown product of NO, and induced concentration-dependent elevations of cGMP in the pig kidney epithelial cell line (LLC-PK1). This latter effect was due to the generation of L-arginine-derived NO for it was (i) abolished by oxyhemoglobin (10 microM), a scavenger of NO, or by methylene blue (10 microM), an inhibitor of NO-activated guanylate cyclase; (ii) potentiated by superoxide dismutase (100 units/ml), which prolongs the life of NO; (iii) inhibited by NG-monomethyl-L-arginine (0.3 mM), an inhibitor of NO synthase; (iv) significantly decreased when L-arginine (0.4 mM) in the medium was replaced by D-arginine (0.4 mM). Moreover, TSST-1 (100 nM) enhanced the activity of cytosolic NO synthase in J774.2 cells. Hydrocortisone (1 microM) but not indomethacin (5 micrograms/ml) or salicylic acid (5 micrograms/ml) prevented the generation of NO2- and the increases in cGMP levels in LLC-PK1 cells induced by J774.2 cells stimulated with TSST-1. The effects of hydrocortisone were partially reversed by coincubation with RU 486 (1 microM), an antagonist of glucocorticoid receptors. Thus, TSST-1 and perhaps other exotoxins produced by Gram-positive bacteria induce NO synthase and the increased NO formation may contribute to toxic shock syndrome and possibly to changes in the immune responses that accompany infection.
William Harvey Research Institute, St. Bartholomew's Hospital Medical College, London, England.
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Zembowicz
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Vane
D000594:Amino Acid Oxidoreductases / Q000096:biosynthesis*; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001427:Bacterial Toxins; D002460:Cell Line; D003600:Cytosol / Q000201:enzymology; D004768:Enterotoxins / Q000494:pharmacology*; D004790:Enzyme Induction; D006854:Hydrocortisone / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D008264:Macrophages; D008751:Methylene Blue / Q000494:pharmacology; D009000:Monocytes; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase; D010108:Oxyhemoglobins / Q000494:pharmacology; D012459:Salicylates / Q000494:pharmacology; D020156:Salicylic Acid; D013211:Staphylococcus aureus; D013237:Stereoisomerism; D018089:Superantigens; D013482:Superoxide Dismutase / Q000494:pharmacology; D019323:omega-N-Methylarginine
D001427:Bacterial Toxins; D004768:Enterotoxins; D010108:Oxyhemoglobins; D012459:Salicylates; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D013482:Superoxide Dismutase; D000594:Amino Acid Oxidoreductases; D020156:Salicylic Acid; D008751:Methylene Blue; D006854:Hydrocortisone; D007213:Indomethacin