Lipid mediators of inflammation are a group of signaling molecules produced by various cells under physiological conditions and modulate the inflammatory process during various pathologic conditions. Although eicosanoids and F2-isoprostanes are recognized lipid mediators of inflammation, there is no consensus yet on the extraction and mass spectrometry (MS) method for their analysis in individual human tear samples. Thus, the aim of this study was to develop an optimal method for extraction of lipid mediators of inflammation in the tear film and evaluate MS techniques for their analysis.
Basal tears were collected from each eye of 19 subjects using glass microcapillaries. Lipid extraction was performed using either varying concentrations of acidified methanol, a modified Folch method, or solid-phase extraction. Initially, an untargeted analysis of the extracts was performed using SCIEX TripleTOF 5600 mass spectrometer to identify any lipid mediators of inflammation (eicosanoids) and later a targeted analysis was performed using the SCIEX 6500 Qtrap to identify and quantify prostaglandins and isoprostanes. Mass spectra and chromatograms were analyzed using Peakview, XCMS, and Multiquant software.
Prostaglandins and isoprostanes were observed and quantified using the Qtrap mass spectrometer under multiple reaction monitoring (MRM) mode after solid-phase extraction. Extraction with acidified methanol along with the Folch method produced cleaner spectra during MS with the Triple time of flight (TOF) mass spectrometer. Lipid mediators of inflammation were not observed in any of the tear samples using the Triple TOF mass spectrometer.
Solid-phase extraction may be the method of choice for extraction of prostaglandins and isoprostanes in low volumes of tears. The SCIEX Qtrap 6500 in MRM mode may be suitable to identify and quantify similar lipid mediators of inflammation.
Department of Optometry and Vision Science (S.P., J.C., J.J.N.), School of Optometry, University of Alabama at Birmingham, Birmingham, AL; Targeted Metabolomics and Proteomics Laboratory (L.W.), School of Medicine, University of Alabama at Birmingham, Birmingham, AL.
Address correspondence to Shyam Panthi, Ph.D., School of Optometry University of Alabama at Birmingham VH 341, 1670 University Blvd, Birmingham, AL 35294-0019; e-mail: firstname.lastname@example.org, email@example.com
The authors have no funding or conflicts of interest to disclose.
Supported in part by the UAB Vision Science Research Center Core Grant NIH P30 EY003039.
Presented in part at the Association for Research in Vision and Ophthalmology Annual Meeting, Seattle, Washington, May 1 to 5, 2016.
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Accepted August 12, 2018