No abstract

Direct infusion mass spectrometry (DIMS) is growing in popularity as an effective method for the screening of biological samples in clinical metabolomics. Being quick to execute, DIMS generally requires special skills when interpreting the results of measurements. By inspecting the similarities between two-dimensional electrospray ionization with quadrupole time-of-flight (ESI-QTOF) and matrix-assisted laser desorption/ionization (MALDI) mass spectra, the pipeline for processing QTOF mass spectra using open-source packages (MALDIquant, MSnbase and MetaboAnalystR) was tested. Previously, all algorithmic workflows have relied on the application of software either provided by a vendor or privately developed by enthusiasts. Here, we computationally examined two ways of interpreting the DIMS results of human blood metabolomic profiling. The studied spectra were acquired using ESI-QTOF maXis Impact II (Bruker Daltonics, Billerica, MA, USA), then pre-processed using COMPASS/DataAnalysis commercial software and mapped onto the metabolites using in-lab-developed MatLab scripts. Alternatively, in this work we used the open-source packages MALDIquant, for spectrum pre-processing, and MetaboAnalystR, for data interpretation, instead of the low-availability commercial and home-made tools. Using a set of 100 plasma samples (20 from volunteers with normal body mass index and 80 from patients at different stages of obesity), we observed a high degree of concordance in annotated metabolic pathways between the proprietary DataAnalysis/MatLab pipeline and our freely available solution.

There is no direct evidence supporting that SDS is a carcinogen, so to investigate this fact, we used HaCaT keratinocytes as a model of human epidermal cells. To reveal the candidate proteins and/or pathways characterizing the SDS impact on HaCaT, we proposed comparative proteoinformatics pipeline. For protein extraction, the performance of two sample preparation protocols was assessed: 0.2% SDS-based solubilization combined with the 1DE-gel concentration (Protocol 1) and osmotic shock (Protocol 2). As a result, in SDS-exposed HaCaT cells, Protocol 1 revealed 54 differentially expressed proteins (DEPs) involved in the disease of cellular proliferation (DOID:14566), whereas Protocol 2 found 45 DEPs of the same disease ID. The ‘skin cancer’ term was a single significant COSMIC term for Protocol 1 DEPs, including those involved in double-strand break repair pathway (BIR, GO:0000727). Considerable upregulation of BIR-associated proteins MCM3, MCM6, and MCM7 was detected. The eightfold increase in MCM6 level was verified by reverse transcription qPCR. Thus, Protocol 1 demonstrated high effectiveness in terms of the total number and sensitivity of MS identifications in HaCaT cell line proteomic analysis. The utility of Protocol 1 was confirmed by the revealed upregulation of cancer-associated MCM6 in HaCaT keratinocytes induced by non-toxic concentration of SDS. Data are available via ProteomeXchange with identifier PXD035202.

Using tandem mass spectrometry with electrospray ionization, a comparative analysis of HaCaT keratinocyte proteins was carried out before and after exposure of cells to sodium dodecyl sulfate (25 mg/ml) for 48 hours; proteins encoded by human chromosome 18 genes were chosen as the comparison proteins. A total of 2418 proteins were detected in the HaCaT immortalized human keratinocytes, 70% of these proteins were identified by two or more unique peptides. Panoramic mass spectrometry analysis identified 38 proteins encoded by chromosome 18 genes, 27 proteins were common to control HaCaT cells and HaCaT cells exposed to SDS. Using the Metascape database (https://metascape.org), an enrichment analysis of GO terms of the Biological Process category of chromosome 18 gene encoded proteins of HaCaT keratinocytes was performed before and after the SDS exposure. The SDS exposure resulted in a slight enrichment of the GO term "response to stimulus" (GO:0050896) and the related GO term "negative regulation of biological process" (GO:0048519). We found decreased expression levels of membrane proteins encoded by chromosome 18 genes related to cell-cell adhesion (GO:0098609), such as DSC1, DSC3, and DSG1. A decrease in the expression level of desmosomal cadherins is characteristic of malignant neoplasms developing from epithelial tissue cells of various internal organs, mucous membranes, and skin. The method of preparation of HaCaT keratinocyte samples used in this work increased the sensitivity of proteomic analysis of cell culture and made it possible to identify twice as many proteins in one gel strip as compared to the number of proteins (1284) in HaCaT samples subjected to osmotic shock and cleavage by trypsin in solution.