Nicotine-enhanced oxidation of low-density lipoprotein and its components by myeloperoxidase/H2O2/Cl- system

In this study, the effect of nicotine on the LDL oxidation by the MPO/H₂O₂/Cl^- system and the effect of HOCl on LDL and some of its components, such as methyl linoleate, vitamin E and the amino acid tryptophan were explored. Nicotine, in micromolar concentrations, enhanced the tryptophan oxidation, either present in LDL or free, in solution. Nicotine also decreased the formation of conjugated dienes and oxygen consumption in a methyl linoleate / HOCl system, and there was evidence to suggest an increase in chlorohydrin formation. Acceleration of the vitamin E oxidation by HOCl was also observed in the presence of nicotine. These data show that the interaction of nicotine and HOCl can promote significant biochemical modifications in LDL particle and some of its components involved in the pathogenesis of cardiovascular and other diseases.

nicotine; myeloperoxidase; hypochlorous acid; low-density lipoprotein; methyl linoleate; vitamin E; tryptophan

Authorship

Olga M.M.F. Oliveira

Instituto de Química, UNESP, Departamento de Bioquímica e Tecnologia Química, Rua Prof. Francisco Degni, 55, Jardim Quitandinha, 14800-900 Araraquara, SP, BrasilUNESPBrasilAraraquara, SP, BrasilInstituto de Química, UNESP, Departamento de Bioquímica e Tecnologia Química, Rua Prof. Francisco Degni, 55, Jardim Quitandinha, 14800-900 Araraquara, SP, Brasil

Iguatemy L. Brunetti

Faculdade de Ciências Farmacêuticas de Araraquara, UNESP, Rodovia Araraquara-Jaú, Km 01, 14801-902 Araraquara, SP, BrasilUNESPBrasilAraraquara, SP, BrasilFaculdade de Ciências Farmacêuticas de Araraquara, UNESP, Rodovia Araraquara-Jaú, Km 01, 14801-902 Araraquara, SP, Brasil

Najeh M. Khalil

Departamento de Farmácia, UNICENTRO, Rua Simeão Camargo Varela de Sá, 03, Vila Carli, 85040-080 Guarapuava, PR, BrasilUNICENTROBrasilGuarapuava, PR, BrasilDepartamento de Farmácia, UNICENTRO, Rua Simeão Camargo Varela de Sá, 03, Vila Carli, 85040-080 Guarapuava, PR, Brasil

Correspondence to: Najeh Maissar Khalil E-mail: najeh@unicentro.br

SCIMAGO INSTITUTIONS RANKINGS

Figures

Figures (4)

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Figure 1 -
A) Effect of nicotine on the rate of free tryptophan oxidation by the MPO/H2O2/Clsystem. Tryptophan (0.1 mM) was incubated with MPO (1.0 nM) in 50 mM sodium acetate buffer (pH 5.5), containing 0.14 M NaCl, at 30 °C. The reaction initiated adding 0.25 mM H2O2, in the absence or presence of various concentrations of nicotine (Mean ± SD; n=5) . (B) Rates of tryptophan oxidation in the LDL particle. LDL (80 µg protein/mL) was incubated with MPO (1.0 nM) in absence or presence of various concentrations of nicotine, in 50 mM sodium phosphate buffer (pH 7.4) containing 0.14 M NaCl, at 25 °C. The reaction initiated adding 0.5 mM H2O2 (Mean ± SD; n=6). * Significantly different from control (p < 0.05).

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Figure 2 -
A) Effect of nicotine on the ML oxidation by HOCl. 1.3 mM ML, 1.0 mM HOCl and 0 (¦), 0.1 (?), 0.5 (?) or 1.0 (?) µM nicotine in 50 mM sodium phosphate buffer, (pH 7.4), with 50 mM SDS at 37 °C. The arrow shows the initial absorbance, before addition of HOCl. B) Effect of nicotine on the TMB oxidation by HOCl in the presence of ML. Nicotine (NIC, µM) and ML (1.3 mM ) were incubated for 1 min and 0.5 mM HOCl was added, in a medium containing 50 mM SDS in phosphate buffer (pH 7.4). After 5 min, the remaining HOCl was estimated by adding 2.8 mM TMB and monitoring absorbance at 652 nm (Mean ± SD; n=5). * Significantly different from control (the sum of % inhibition of TMB oxidation by the systems ML/HOCl and nicotine/ HOCl), with p<0.05.

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Figure 3 -
Effect of nicotine on ML oxidation: (1) ML (1.3 mM) and (2) immediately after addition of HOCl (1 mM), as they develop at 10-second intervals, in the directions indicated by the arrows. A, nicotine absence and B, with 1.0 µM nicotine. The reaction medium was 50 mM sodium phosphate buffer (pH 7.4), with 50 mM SDS at 37 °C. C) Oxygen depletion during oxidation of ML by HOCl. 10 mM ML was prepared in 50 mM sodium phosphate buffer (pH 7.4) with 50 mM SDS. Reaction initiated adding 1.0 mM HOCl, at 37 °C, in the absence or presence of nicotine. a) ML and nicotine absent; b) ML, HOCl and 2.0 µM nicotine; c) ML, HOCl and 1.0 µM nicotine; d) ML, HOCl and 0.2 µM nicotine; e) ML and HOCl.

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Figure 4 -
Effect of nicotine on the oxidation of vitamin E (5 mM) by HOCl (0.05 mM) in 50 mM sodium phosphate buffer (pH 7.4) with 50 mM SDS at 37 °C. (A) Reaction time-course: without nicotine (¦); with 0.1 (?), 1.0(?) or 5.0 (?) µM nicotine. Spectral variation during reaction at 1 second intervals (arrows show increasing time) in the absence (B) or presence (C) of 1 µM nicotine, the number 1 shown the vitamin E spectrum in the reaction mixture before the HOCl.

Figure 1 - A) Effect of nicotine on the rate of free tryptophan oxidation by the MPO/H2O2/Clsystem. Tryptophan (0.1 mM) was incubated with MPO (1.0 nM) in 50 mM sodium acetate buffer (pH 5.5), containing 0.14 M NaCl, at 30 °C. The reaction initiated adding 0.25 mM H2O2, in the absence or presence of various concentrations of nicotine (Mean ± SD; n=5) . (B) Rates of tryptophan oxidation in the LDL particle. LDL (80 µg protein/mL) was incubated with MPO (1.0 nM) in absence or presence of various concentrations of nicotine, in 50 mM sodium phosphate buffer (pH 7.4) containing 0.14 M NaCl, at 25 °C. The reaction initiated adding 0.5 mM H2O2 (Mean ± SD; n=6). * Significantly different from control (p < 0.05).

Figure 2 - A) Effect of nicotine on the ML oxidation by HOCl. 1.3 mM ML, 1.0 mM HOCl and 0 (¦), 0.1 (?), 0.5 (?) or 1.0 (?) µM nicotine in 50 mM sodium phosphate buffer, (pH 7.4), with 50 mM SDS at 37 °C. The arrow shows the initial absorbance, before addition of HOCl. B) Effect of nicotine on the TMB oxidation by HOCl in the presence of ML. Nicotine (NIC, µM) and ML (1.3 mM ) were incubated for 1 min and 0.5 mM HOCl was added, in a medium containing 50 mM SDS in phosphate buffer (pH 7.4). After 5 min, the remaining HOCl was estimated by adding 2.8 mM TMB and monitoring absorbance at 652 nm (Mean ± SD; n=5). * Significantly different from control (the sum of % inhibition of TMB oxidation by the systems ML/HOCl and nicotine/ HOCl), with p<0.05.

Figure 3 - Effect of nicotine on ML oxidation: (1) ML (1.3 mM) and (2) immediately after addition of HOCl (1 mM), as they develop at 10-second intervals, in the directions indicated by the arrows. A, nicotine absence and B, with 1.0 µM nicotine. The reaction medium was 50 mM sodium phosphate buffer (pH 7.4), with 50 mM SDS at 37 °C. C) Oxygen depletion during oxidation of ML by HOCl. 10 mM ML was prepared in 50 mM sodium phosphate buffer (pH 7.4) with 50 mM SDS. Reaction initiated adding 1.0 mM HOCl, at 37 °C, in the absence or presence of nicotine. a) ML and nicotine absent; b) ML, HOCl and 2.0 µM nicotine; c) ML, HOCl and 1.0 µM nicotine; d) ML, HOCl and 0.2 µM nicotine; e) ML and HOCl.

Figure 4 - Effect of nicotine on the oxidation of vitamin E (5 mM) by HOCl (0.05 mM) in 50 mM sodium phosphate buffer (pH 7.4) with 50 mM SDS at 37 °C. (A) Reaction time-course: without nicotine (¦); with 0.1 (?), 1.0(?) or 5.0 (?) µM nicotine. Spectral variation during reaction at 1 second intervals (arrows show increasing time) in the absence (B) or presence (C) of 1 µM nicotine, the number 1 shown the vitamin E spectrum in the reaction mixture before the HOCl.

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Nicotine-enhanced oxidation of low-density lipoprotein and its components by myeloperoxidase/H2O2/Cl- system

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[1] Correspondence to: Najeh Maissar Khalil E-mail: najeh@unicentro.br