OPTIMAL TIME AND DOSAGE OF PHENYL N-TERT-BUTYL NITRONE (PBN) FOR THE INHIBITION OF NITRIC-OXIDE SYNTHASE INDUCTION IN MICE

We have previously reported that phenyl N-tert-butyl nitrone (PEN) inh ibits the induction of inducible nitric oxide synthase (iNOS) and, thu s, prevents the overproduction of nitric oxide (NO), resulting in the reduction of endotoxin-mediated death in mice. In this study, to exami ne the effect of PEN in detail, we investigated the dose- and administ ration-timing dependence of PEN on endotoxin-induced NO generation in mice. NO generation was monitored in the mouse liver after administrat ion of lipopolysaccharide (LPS) by the in vivo NO-spin trapping method using the iron complex of N-methyl-D-glucamine dithiocarbamate (MGD) as a spin trap, followed by ex vivo EPR measurement of the liver tissu e. PEN was effective in reducing liver NO generation monitored 6 h aft er endotoxin injection when it was administered shortly before or afte r LPS injection. The maximum inhibition of liver NO was obtained when PEN was administered 30 min before LPS injection. ID50 for the inhibit ion was estimated to be approximately 200 mg/kg when the LPS dose of 5 0 mg/kg was used. Expression of mRNA for iNOS in the liver as estimate d by reverse transcription polymerase chain reaction was decreased whe n PEN was given 30 min before LPS injection, indicating that the reduc tion of expression of iNOS protein by PEN, which has been shown previo usly, is at least in part caused by a decrease in mRNA expression. Cop yright (C) 1996 Elsevier Science Inc.