Multiple oxidative and advanced oxidative modifications of hemoglobin in gastric cancer patients measured by nanoflow LC-MS/MS

Multiple oxidative modifications on hemoglobin are elevated in breast cancer patients as measured by nanoflow liquid chromatography-tandem mass spectrometry

Breast cancer is strongly connected with elevated oxidative stress. Oxidative modifications of hemoglobin can serve as biomarkers for monitoring oxidative stress status in vivo. The structure of hemoglobin modifications derived from malondialdehyde (MDA) in human blood hemoglobin exists as N-propenal and dihydropyridine (DHP). This study reports the simultaneous quantification of eleven modified peptides in hemoglobin derived from MDA and advanced histidine oxidation in 16 breast cancer patients and 16 healthy women using nanoflow liquid chromatography nanoelectrospray ionization tandem mass spectrometry. The results reveal statistically significant increases in the formation of MDA-derived N-propenal and DHP of lysine and advanced oxidation of histidine in hemoglobin of breast cancer patients with the Mann-Whitney U-test p values < 0.0001 and the AUC of ROC between 0.9277 and 1.0. Furthermore, the elevation in modified peptides is significant in patients with early stages of breast cancer. By measuring these oxidative modifications in hemoglobin from a drop of blood, the role of lipid peroxidation and oxidative stress in breast cancer can be assessed using this sensitive assay.

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

Acrolein is a major component in cigarette smoke and a product of endogenous lipid peroxidation. It is difficult to distinguish human exposure to acrolein from exogenous sources versus endogenous causes, as components in cigarette smoke can stimulate lipid peroxidation in vivo. Therefore, analysis of acrolein-induced DNA and protein adducts by the highly accurate, sensitive, and specific mass spectrometry-based methods is vital to estimate the degree of damage by this IARC Group 2A carcinogen. This Perspective reviews the analyses of acrolein-induced DNA and protein adducts in humans by mass spectrometry focusing on samples accessible for biomonitoring, including DNA from leukocytes and oral cells and abundant proteins from blood, i.e., hemoglobin and serum albumin.

Characterization and Quantification of Acrolein-Induced Modifications in Hemoglobin by Mass Spectrometry─Effect of Cigarette Smoking

Exposure to acrolein, the smallest α, β-unsaturated aldehyde, in humans originates from cigarette smoking and other environmental sources, food cooking, and endogenous lipid peroxidation and metabolism. The protein modification caused by acrolein is associated with various diseases, including cancer, cardiovascular, and neurodegenerative diseases. In this study, acrolein-modified human hemoglobin was reduced by sodium borohydride. Thus, three types of modifications, that is, Schiff base, Michael addition, and formyl-dehydropiperidion adducts, were converted to the corresponding stable adducts, leading to mass increases of 40.0313, 58.0419, and 96.0575 Da, respectively. These stable acrolein-modified hemoglobin peptides were identified by nanoflow liquid chromatography coupled to a high-resolution nanoelectrospray ionization tandem mass spectrometry. Among the 26 different types and sites of modifications, 15 of them showed a dose-dependent increase with increasing concentrations of acrolein. To investigate the role of acrolein-induced modifications in smoking and oral cancer, the 15 dose-responsive acrolein-modified peptides, together with three ethylated peptides previously identified, were quantified in oral cancer patients, healthy smokers, and healthy nonsmokers. The results reveal that the relative extents of the Michael-type adduct at α-Lys-16, α-His-50, and β-Lys-59 are significantly higher in smokers (oral cancer and healthy) than in nonsmokers. Areas under the receiver operating characteristic curve of these peptides range from 0.7500 to 0.9375, indicating the ability to discriminate smokers from nonsmokers. Additionally, these acrolein-modified peptides correlate with three ethylated peptides at the N-termini of α- and β-globin, as well as β-His-77, and with the number of cigarettes smoked per day. Therefore, measuring the reduced Michael adducts at α-Lys-16, α-His-50, and β-Lys-59 of hemoglobin from one drop of blood by this sensitive and specific method may reflect the increase of acrolein exposure due to cigarette smoking.

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

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 high-resolution 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 N-propenal-type at α-Lys-11, α-Lys-16, α-Lys-61, β-Lys-8, and β-Lys-17, 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.

Identification of crucial salivary proteins/genes and pathways involved in pathogenesis of temporomandibular disorders

Temporomandibular disorder (TMD) is a collective term for a group of conditions that lead to impairment of the function of the temporomandibular joint. The proteins/genes and signaling pathways associated with TMD are still poorly understood. The aim of this study was to identify key differentially expressed salivary proteins/genes (DEGs) associated with TMD progression using LC-MS/MS coupled with a bioinformatics approach. The protein–protein interaction network was obtained from the STRING database and the hub genes were identified using Cytoscape including cytoHubba and MCODE plug-ins. In addition, enrichment of gene ontology functions and the Reactome signaling pathway was performed. A total of 140 proteins/genes were differentially expressed. From cluster analysis, a set of 20 hub genes were significantly modulated: ALB, APOA1, B2M, C3, CAT, CLU, CTSD, ENO1, GSN, HBB, HP, HSPA8, LTF, LYZ, MMP9, S100A9, SERPINA1, TF, TPI1, and TXN. Two enriched signaling pathways, glycolysis and gluconeogenesis, and tryptophan signaling pathway involving the hub genes CAT, ENO1, and TPI1 have been identified. The rest of the hub genes were mainly enriched in the innate immune system and antimicrobial peptides signaling pathways. In summary, hub DEGs and the signaling pathways identified here have elucidated the molecular mechanisms of TMD pathogenesis.

Changing Perspectives from Oxidative Stress to Redox Signaling-Extracellular Redox Control in Translational Medicine

Extensive research has changed the understanding of oxidative stress that has been linked to every major disease. Today we distinguish oxidative eu- and distress, acknowledging that redox modifications are crucial for signal transduction in the form of specific thiol switches. Long underestimated, reactive species and redox proteins of the Thioredoxin (Trx) family are indeed essential for physiological processes. Moreover, extracellular redox proteins, low molecular weight thiols and thiol switches affect signal transduction and cell–cell communication. Here, we highlight the impact of extracellular redox regulation for health, intermediate pathophenotypes and disease. Of note, recent advances allow the analysis of redox changes in body fluids without using invasive and expensive techniques. With this new knowledge in redox biochemistry, translational strategies can lead to innovative new preventive and diagnostic tools and treatments in life sciences and medicine.