title: Role of the nitric oxide synthase pathway in inhibition of growth of interferon-sensitive and interferon-resistant Rickettsia prowazekii strains in L929 cells treated with tumor necrosis factor alpha and gamma interferon.
abstract: The ability of tumor necrosis factor alpha (TNF-alpha) alone and in combination with gamma interferon (IFN-gamma) to inhibit the growth of interferon-sensitive and -resistant Rickettsia prowazekii strains in mouse L929 cells was examined, and the possible role of the nitric oxide synthase pathway in the suppression of rickettsial growth induced by TNF-alpha, IFN-gamma, or both cytokines was evaluated. TNF-alpha inhibited the growth of strains Madrid E (IFN-gamma sensitive and alpha/beta interferon [IFN-alpha/beta] sensitive) and Breinl (IFN-gamma sensitive and IFN-alpha/beta resistant), but not that of strain 83-2P (IFN-gamma resistant and IFN-alpha/beta resistant), in L929 cells. Inhibition of the growth of the Madrid E strain in L929 cells treated with TNF-alpha and IFN-gamma in combination was greater than that observed with either TNF-alpha or IFN-gamma alone. Similarly, inhibition of the growth of the Breinl strain in L929 cells treated with both cytokines was greater than that observed with TNF-alpha alone; however, it did not differ significantly from the inhibition observed with IFN-gamma alone. Although strain 83-2P was resistant to TNF-alpha or IFN-gamma alone, its growth was inhibited in L929 cells treated with TNF-alpha and IFN-gamma in combination. Nitrite production was measured in mock-infected and infected L929 cell cultures, and the nitric oxide synthase inhibitors NG-methyl-L-arginine (NGMA) and aminoguanidine were used to evaluate the role of the nitric oxide synthase pathway in cytokine-induced inhibition of rickettsial growth. Nitrite production was induced in mock-infected or R. prowazekii-infected L929 cell cultures treated with IFN-gamma plus TNF-alpha, but not in mock-infected cultures that were untreated or treated with IFN-gamma or TNF-alpha alone. Nitrite production was also not induced in untreated, R. prowazekii-infected cultures; however, in some instances, it was induced in infected cultures treated with IFN-gamma or TNF-alpha alone. Nitrite production was blocked by NGMA or aminoguanidine, and these compounds markedly relieved the synergistic inhibitory effect of IFN-gamma plus TNF-alpha on the growth of strain 83-2P in L929 cells. In contrast, NGMA did not alleviate the inhibition of the growth of the Madrid E strain in L929 cells treated with IFN-gamma or TNF-alpha alone; however, it slightly and variably relieved the inhibition of the growth of the Madrid E strain in L929 cells treated with IFN-gamma and TNF-alpha in combination.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile 36688-0002.
authors.forename: J
authors.initials: J
authors.lastname: Turco
authors.forename: H H
authors.initials: HH
authors.lastname: Winkler
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000502:physiology*; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D066298:In Vitro Techniques; D007370:Interferon Type I / Q000494:pharmacology*; D007371:Interferon-gamma / Q000494:pharmacology*; D007739:L Cells; D051379:Mice; D019001:Nitric Oxide Synthase; D009573:Nitrites / Q000378:metabolism; D011994:Recombinant Proteins; D012283:Rickettsia prowazekii / Q000254:growth & development*; D014364:Tryptophan / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D019323:omega-N-Methylarginine
chemical_list: D007370:Interferon Type I; D009573:Nitrites; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; D019323:omega-N-Methylarginine; D007371:Interferon-gamma; D014364:Tryptophan; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases