Yunjing Luo

Production of polycyclic aromatic hydrocarbon metabolites from a peroxynitrite/iron(III) porphyrin biomimetic model and their mutagenicities

Some polycyclic aromatic hydrocarbons (PAHs) are typical promutagens that require metabolic activation to exhibit their mutagenicities and carcinogenicities. The metabolites of three PAHs, pyrene (PY), fluoranthene (FLU), and benzo[a]pyrene (BaP), produced from the peroxynitrite/T(p-Cl)PPFeCl(peroxynitrite/(chloride)iron(III)tetrakis(p-chlorophenyl)porphyrin) system, have been identified with high-performance liquid chromatography coupled with electron spray ionization tandem mass spectrometry. The results demonstrated that three major metabolites were the quinone group, OH group, and nitro group. In the Ames test, all three PAH metabolites became mutagenic without using the enzymatic activating system, whereas their parents did not show positive results. Cell transformation assay indicated that 1,3-nitro-BaP and BaP metabolites produced from this biomimetic system have more serious effects in inducing cancer than the BaP parent.

Metabolism of benzo[a]pyrene in peroxynitrite/Fe(III) porphyrin system

The peroxynitrite/porphyrin biomimetic system was established to investigate the effects of peroxynitrite on benzo[a]pyrene (B[a]P) metabolism. Three model systems consisting of different iron porphyrins were compared, and the results showed that the peroxynitrite/T(p-Cl)PPFeCl system was the highest catalytic efficiency in the metabolism of B[a]P. We analyzed the B[a]P metabolites produced from this system by RP-HPLC method and firstly identified the formation of nitrobenzo[a]pyrenes which are the special metabolites of B[a]P induced by peroxynitrite.

Identification of Nitration Sites by Peroxynitrite on p16 Protein

Injury of p16 has been implicated in some cancers. In this paper, we focus on the need for identification of peroxynitrite-dependent nitration sites on p16 with HPLC–MS/MS method. Two mono-nitrated residues Tyr129 and Tyr44 were detected in the course of p16 modification induced by peroxynitrite at relative low doses. As suggested by peptide mapping sequence analysis, Tyr44 was more liable to be nitrated by ONOO−. Study on the chemical environment of two Tyr residues reveals that steric hindrance may be the structural determinant for the nitration sequence. Through technique of SDS-PAGE, ONOO− could induce p16 nitration, even strongly damage the combination of p16 with CDK4, which further influence p16’s activity.

Theoretical Study on the Mechanisms of the Reaction of Peroxynitrous Acid and Phenol

Abstract The mechanisms of the reactions of the radicals (·OH and ·NO2) derived from peroxynitrous acid with phenol have been studied using density functional theory (DFT) at the B3LYP/6-311++G(d, p)//B3LYP/6-311G(d, p) level. The geometries of all the molecules were optimized, and the harmonic vibration frequencies and the energies were calculated as well. The calculation results show that the primary products of the reaction of peroxynitrous acid and phenol are o-hydroxyphenol and p-hydroxyphenol, due to their relatively lower activation barriers. This conclusion is in agreement with the corresponding experimental data. In addition, the effects of solvents on these reactions were also investigated. The results suggest that polar solvents can reduce the activation energy and hence facilitate the occurrence of reactions.

Effect of Inhibition of Water-Soluble Propolis Extracts (WSPE) on biomolecules Damage Induced by Peroxynitrte

Peroxynitrite (ONOO-) is a cytotoxicant with strong oxidizing and nitrating properties toward various biomolecules, including amino acids, DNA, lipids and proteins, thus can cause cell death, carcinogenesis or aging. The aim of this study was to investigate whether water-soluble propolis extracts (WSPE) could scavenge peroxynitre and further inhibit peroxynitrite-mediated tyrosine nitration, DNA strand breaks and low density lipoprotein (LDL) oxidation. The results show that WSPE have a strong ability to scavenge ONOO-, and its inhibition on ONOO- exhibited a concentration-dependent manner. It is suggested that propolis extracts might be developed as an effective peroxynitrite inhibitor for the prevention of ONOO- involved diseases.

Metabolic Transformation of Indeno[1,2,3-cd]pyrene and Toxicities of Its Metabolites

A porphyrin/peroxynitrite biomimetic system was used to study the metabolism of indeno[1,2,3-cd]pyrene (IND) induced by peroxynitrite. The metabolites were identified using high-performance liquid chromatography coupled with electro-spray ionization tandem mass spectrometry as OH-IND, IND-quinone and 2NO2-IND. By stopping the reaction at different stages, we discovered that IND was first transformed to IND-quinone and 2NO2-IND, which were then transformed to OH-IND. Mutation assays including Ames tests and cell transformation experiments showed enhancement of the mutagenicity after the activation by the peroxynitrite/Fe(III)porphyrin system. The results also showed that 2NO2-IND and IND-quinone played key roles in the mutagenicity of PAHs after metabolic activation.

Spectrometric study on the interaction between peroxynitrite and Bovine Serum Albumin

Bovine Serum Albumin (BSA) was used as a target protein to study the structure change through tyrosine nitration by peroxynitrite. The correlation between BSA nitration and the structure change was established. The results show that the nitration of BSA by simulating the situation in vivo (continuous infusion of ONOO−) is two times efficiency than infusion ONOO− at one time. The nitration by peroxynitrite lead to α-helix structure reduced and β-sheet structure increased, which make significant changes of BSA backbone.

Analyses of PAis Metabolites Using a Peroxynitrite/Fe(III) porphyrin Biomimetic System by HPLC

The peroxynitrite/Fe(III)porphyrin chemical system was established firstly to investigate the effects of peroxynitrite on the metabolism of polycyclic aromatic hydrocarbons(PAHs). By comparing the conversion ratio of benzo[a]pyrene (B[a]P) in four model systems consisting of different iron porphyrins, we found that the peroxynitrite/T(p-Cl)PPFeCl system showed the highest catalytic efficiency, which conversion ratio of B[a]P reached 20.71%. We also analyzed the metabolites of B[a]P and pyrene (PN) produced from this system by HPLC and MS methods, and successfully identified the formation of nitrobenzo [a] pyrene and nitropyrene which are the special metabolites induced by peroxynitrite.

The Kinetics Sudies of Peroxynitrite Decomposition Catalyzed by 5, 10, 15, 20 - Tetrakis [4-(3-Piridiniumproxy) Phenyl]-PorphyrinCobalt(II)

Peroxynitrite is a toxic biological oxidant which has been implicated in many pathophysiological conditions. Metalloporphyrins can catalyze it decomposition to protect the cells. A cobalt water-soluble porphyrin Co(II)TPP-OC3Py was synthesized and its ability to catalyze peroxynitrite decomposition was studied by stopped-flow spectrophotometer. The catalytic activity of Co(II)T-PPOC3Py is comparable to iron and manganese porphyrins which have been investigated before. The catalytic mechanism is related to the intermediate formed from the reaction of Co(II)TPPOC3Py and peroxynitrite, and the catalytic ability depends on whether the intermediate is reduced easily.

Studies on Kinetics of Reaction Between Peroxynitrite and Tryptophan

Peroxynitrite (ONOO-) is a potent cytotoxin, and it can damage tryptophan, tyrosine and other biomolecules. The kinetics of tryptophan damaged by peroxynitrite was studied by stopped-flow spectrophotometer at 25degC. When peroxynitrite is present in excess, there are many products formed including nitrotryptophan, hydroxytryptohan, N-formylkinurenine or dihydroxytryptophan, oxindole, and hydropyrroloindole. The kinetics of tryptophan loss can represent the kinetics of peroxynitrite damaging tryptophan as a whole. The kinetics of this reaction was studied by monitoring the decrease of fluorescence of tryptophan, and the apparrent second order rate, 2.85 x 104 Mmiddot1 smiddot1, and the apparent activation energy, 39.4 kJ-molmiddot1 are derived.