Abstract: Abstract: Objective To study the inhibitory effect of panax notoginseng saponins (PNS) on 3-nitrotyrosine (3-NT) formation in brain induced by heme/NO2 －/H2O2 or ONOO － pathways in vitro. Methods According to the two major pathways of 3-NT formation in vivo, the models of protein nitration induced by heme/NaNO2/H2O2 or ONOO － system were established, respectively, in vitro. Bovine serum albumin (BSA)/rat plasma protein or rat brain homogenate protein were utilized as reactive substrates in both systems. Samples were divided into blank-control group, 3-NT group and PNS group(including low-, medium- and high-concentration subgroups). In 3-NT group, samples were exposed to heme /NaNO2 /H2O2 or ONOO－ system, respectively, at 37 ℃ for 30 min, whereas in PNS group, samples were pre-incubated with PNS (at final concentrations of 50 mg/L, 100 mg/L, and 200 mg/L) at 37 ℃ for 5 min before the nitrating system exposure. The 3-NT level in each group was detected by Western blot assy. Results Compared with the blank-control group, both heme/NaNO2/H2O2 and ONOO－ system can induce significant 3-NT generation in BSA/ rat plasma protein or rat brain homogenate protein (P＜0.05). Compared with model group, PNS pre-treatment markedly inhibited 3-NT expression in BSA/rat plasma protein in a dose-dependent manner (P＜0.05), the inhibitory effect of low intervention on the level of 3-NT in rat brain homogenate protein was not significant (P＞0.05). Medium- and high-concentrations of PNS pre-treatment markedly inhibited 3-NT accumulation, with maximum effect at the concentration of 200 mg/L (P＜0.05). Conclusion Medium- and highconcentrations of PNS can inhibit 3-NT formation in brain tissue mediated by either heme/NO2－/H2O2 or ONOO－ pathways,implying that potential neuroprotective action against 3- NT involves pathological conditions, like trauma, stroke, and neurodegenerative diseases.

Key words: brain injuries, chemotherapy, adjuvant, in vitro, panax notoginseng saponins(PNS), 3-nitrotyrosine(3-NT), heme, peroxynitrite anion