Comparison of toxic effects of nitric oxide and peroxynitrite on Uronema marinum (Ciliata: Scuticociliatida).
To discover the effects of nitric oxide (NO) and peroxynitrite on Uronema marinum (a ciliate responsible for systemic scuticociliatosis in cultured olive flounder Paralichthys olivaceus), the dose-dependent inhibitory effect of NO donors, S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholinosydnonimine (SIN-1) on the proliferation and survival of U. marinum was investigated. The inhibitory effects of exogenous superoxide dismutase (SOD) and catalase on the toxicity of SIN-1 were also investigated. After 24 h of incubation in the presence of 0.2 mM SNAP, the number of ciliates was not statistically different from that of the controls, whereas incubation in the presence of 0.5 mM SNAP reduced the number of parasites significantly to 59.1% of controls. Concentrations of SNAP higher than 0.5 mM resulted in greater reductions in the number of ciliates, but levels of generated NO far exceeded physiological ranges. The number of viable ciliates incubated for 24 h with 0.2 mM SIN-1 was reduced significantly to 25.0%, and all ciliates were killed by incubation in concentrations above 0.5 mM SIN-1. Although SOD decreased the toxic effect of SIN-1 on U. marinum, protection was not complete and did not improve after increasing the SOD concentration from 50 to 400 U ml(-1). Addition of catalase ranging from 500 to 10000 U ml(-1) completely protected U. marinum from SIN-1 toxicity. Ciliates exposed to catalase alone or catalase plus SIN-1 showed significantly higher and dose-dependent proliferation rates compared to controls. Addition of haemoglobin, ranging from 0.5 to 2.0 mg ml(-1), also protected U. marinum from SIN-1 toxicity, and increased the proliferation rate dose-dependently. In conclusion, resistance of U. marinum to oxidative and nitrative stress may allow this pathogen to withstand the NO- and oxygen-radical-dependent killing mechanisms of phagocytic cells.
Lee
Eun Hye
EH
Department of Aquatic Life Medicine, Pukyong National University, Pusan 608-737, Korea.
Kim
Sung Mi
SM
Kwon
Se Ryun
SR
Kim
Sung Koo
SK
Nam
Yoon Kwon
YK
Kim
Ki Hong
KH
D000818:Animals; D002374:Catalase / Q000378:metabolism; D016798:Ciliophora / Q000187:drug effects* / Q000254:growth & development*; D004305:Dose-Response Relationship, Drug; D006454:Hemoglobins / Q000378:metabolism; D008981:Molsidomine / Q000031:analogs & derivatives / Q000633:toxicity*; D020030:Nitric Oxide Donors / Q000633:toxicity*; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000633:toxicity*; D013482:Superoxide Dismutase / Q000378:metabolism
D006454:Hemoglobins; D020030:Nitric Oxide Donors; C110881:S-nitro-N-acetylpenicillamine; C002385:linsidomine; D008981:Molsidomine; D002374:Catalase; D013482:Superoxide Dismutase; D010396:Penicillamine