Malondialdehyde-Induced Post-translational Modifications in Hemoglobin of Smokers by NanoLC–NSI/MS/MS Analysis

Abstract

Malondialdehyde (MDA) is the most abundant α,β-unsaturated aldehyde generated from endogenous peroxidation of polyunsaturated fatty acids and is present in cigarette smoke. Post-translational modifications of blood hemoglobin can serve as biomarkers for exposure to chemicals. In this study, two types of MDA-induced modifications, the N-propenal and the dihydropyridine (DHP), were identified at multiple sites in human hemoglobin digest by the highresolution mass spectrometry. The N-propenal and the DHP types of modification led to the increase of 54.0106 and 134.0368 amu, respectively, at the N-terminal and lysine residues. Among the 21 MDA-modified peptides, 14 with dose−response to MDA concentrations were simultaneously quantified in study subjects by the nanoflow liquid chromatography nanoelectrospray ionization tandem mass spectrometry under selected reaction monitoring (nanoLC−NSI-MS/MS-SRM) without prior enrichment. The results showed that the modifications of the Npropenal-type at α- , as well as the DHP-type at the α-N-terminal valine, are significantly higher in hemoglobin isolated from the blood of smokers than in nonsmoking individuals. This is the first report to identify and quantify multiple sites of MDA-induced modifications in human hemoglobin from peripheral blood. Our results suggest that the MDA-derived modifications on hemoglobin might represent valuable biomarkers for MDA-induced protein damage.

Mass Spectrometry Analysis of DNA and Protein Adducts as Biomarkers in Human Exposure to Cigarette Smoking: Acrolein as an Example

“…We have employed this NPR approach to various adducts (glutathionylation, nitration, nitrosylation, chlorination, oxidation, methylation, ethylation, carboxymethylation, and carboxyethylation, malondialdehyde, etc.) in human Hb to observe their relationship with smoking, oxidative stress, and diseases (diabetes and cancer). − The strategy is straightforward, without derivatization or enrichment by antibodies or affinity probes. The high sensitivity is attributed to the nanoflow LC and the fast scan rate of the ion trap mass spectrometer, albeit with the sacrifice of resolution .…”

Malondialdehyde-Induced Post-Translational Modification of Human Hemoglobin

“…Translation of observations obtained by using such high MDA concentrations to physiology or pathology are expected to be limited. A limitation of the study by Chen et al are the Hb-MDA molar ratios used, i.e., 1:1 to 1:5. Considering an erythrocytic Hb concentration of 8 mM, the MDA concentrations to be used in order to achieve Hb-MDA molar ratios of 1:1 to 1:5 would be 8 mM to 40 mM and consequently irrational.…”

Response to “Malondialdehyde-Induced Post-Translational Modification of Human Hemoglobin”

“…Our bottom-up proteomic strategy employs enzyme hydrolysis of Hb into MDA-modified peptides and unmodified peptides under mild conditions (37 °C, pH 8.0), followed by the analysis of the peptides using LC-MS/MS with a linear ion trap mass spectrometer. 4 The identity of the modified peptides is confirmed by (1) the collision-induced dissociation spectrum, (2) coelution in LC at multiple SRM transitions with different fragment ions, and (3) the difference in retention time (ΔRT) between the modified peptide and the reference peptide. The digestion efficiency was calculated by comparing it with the synthetic peptide standards.…”

“…27 In our study of MDA-Hb, we used the native reference peptide method for the relative quantification of 21 N-propenal and dihydropyridine (DHP) adducted peptides. 4 Among them, the levels of six modified peptides, including α-Lys-11 and β-Lys-17, are higher in smokers than in nonsmokers. To synthesize the N-propenal lysine at α-Lys-11 and β-Lys-17 of these two peptides, one would need to start from peptides with N-and C-terminal amino groups protected before reaction with MDA and perform deprotection after adduct formation.…”

“…Figure D and E show the nanoLC-MS/MS chromatograms of the trypsin digest of Hb (100 μM) incubated with MDA (0.25 mM) at 37 °C for 12 h, measuring both M+72 and M+54, respectively. In Figure E, the peak eluted at 37.73 min is the N -propenal adduct (+54) of the peptide containing α-Lys-11 . There are three peaks, a, b, and c, in MDA-treated Hb eluting about 27 min at the SRM channel of +72, Figure B–D.…”