Quantification of relevant metabolites in apoptotic bodies from HK-2 cells by targeted metabolomics based on liquid chromatography-tandem mass spectrometry

Background: Apoptotic bodies play an important role in the cellular communication as a consequence of the great variety of biomolecules they harbor. There is evidence that 1st generation apoptotic bodies from HK-2 cells induced by cisplatin or UV light trigger apoptosis in na & iuml;ve HK-2 cells whereas 2nd generation apoptotic bodies activate cell proliferation showing an opposite effect. Thus, the development of new analytical strategies to quantify the changes in the involved metabolites is imperative to shed light on the biological mechanisms which trigger apoptosis and cell proliferation. Results: A LC-(Q-Orbitrap)MS method has been developed to quantify the metabolites unequivocally identified in the apoptotic body fluid from HK-2 cells in our previous works based on untargeted metabolomics. Thus, two different columns and gradients were tested and the HILIC column was selected taking into account the retention times and chromatographic separation. Also, different normal collision energies were tested for each metabolite and the parallel reaction monitoring was chosen to carry out the quantitative analysis. Once the method was optimized, it was evaluated in terms of linearity, limits of detection and quantification, matrix effects, accuracy, and precision, for each metabolite. Limits of detection ranged from 0.02 to 1.4 ng mL-1.-1 . A total of 9 relevant metabolites proposed as potential biomarkers to reveal metabolic differences among apoptotic bodies from HK-2 cells were quantified and some insights about the biological relevance were discussed. Significance: The first targeted metabolomics methodology enabling the quantification of relevant metabolites in apoptotic bodies from HK-2 cells was developed using LC-(Q-Orbitrap)MS. Pyridoxine, kynurenine, and creatine concentrations were determined in apoptotic bodies from HK-2 cells treated with cisplatin and UV light. Phe- nylacetylglycine, hippuric acid, butyrylcarnitine, acetylcarnitine, carnitine, and phenylalanine were determined in 1st and 2nd generation apoptotic bodies from HK-2 cells treated with cisplatin. Concentrations determined were useful to establish their biological role in the metabolism.