Malondialdehyde (MDA) is a reactive aldehyde generated from endogenous peroxidation of polyunsaturated fatty acids. Malondialdehyde-induced damages of cellular DNA and proteins are associated with several pathological conditions and diseases. Breast cancer patients are known with elevated lipid peroxidation/oxidative stress. Post-translational modifications of blood hemoglobin have been used as biomarkers of exposure to chemicals.<br/>Two types of malondialdehyde-induced modification, namely the Schiff base and the dihydropyridine (DHP), were identified at various sites in the peptide digest of human hemoglobin by the high-resolution mass spectrometry. The relative extents of the dose-responsive modifications were simultaneously quantified in globin isolated from the blood of breast cancer patients and the control subjects by the nanoflow liquid chromatography nanoelectrospay ionization tandem mass spectrometry under selected reaction monitoring (nanoLC-nESI-MS/MS-SRM). The results showed that 14 Schiff base- and 9 DHP- types of MDA-induced modifications in human hemoglobin were identified. The Schiff base and the DHP types of modification led to the mass increase of 54 and 134 amu, respectively, at mainly the lysine and histidine residues. The degrees of modification increase dose-dependently in ten of the Schiff base- and four of the DHP-sites. Thus, the relative extents of these 14 dose-responsive modifications were simultaneously quantified by nanoLC-nESI-MS/MS-SRM. The results indicated that DHP formation at b-Lys-59 is significantly higher in hemoglobin isolated from the blood of breast cancer patients than that in healthy female subjects (p &lt; 0.05). Starting from one drop of blood, measuring DHP formation at b-Lys-59 in hemoglobin might represent useful biomarkers for MDA-induced protein damage in breast cancer.

Malondialdehyde induces post-translational modifications in hemoglobin of breast cancer patients

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