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.
Zembowicz
A
A
William Harvey Research Institute, St. Bartholomew's Hospital Medical College, London, England.
Vane
J R
JR
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