A study of enzymatic activity in cell cultures via the analysis of volatile biomarkers.

Aldehyde dehydrogenase (ALDH) enzymes are responsible for the metabolism of aldehydes, including acetaldehyde (AA), and are linked to disease. We describe a method to study ALDH activity in cell cultures involving the measurement of AA concentrations in the gas/vapour phase. This has been achieved using selected ion flow tube mass spectrometry (SIFT-MS), developed for the rapid quantification of trace gases in humid media. Human cells of the hepG2 hepatocellular carcinoma cell line and primary bone marrow-derived mesenchymal stem cells (hMSCs) depleted AA from the culture media, but the application of ALDH inhibitors diethylaminobenzaldehyde (DEAB) and disulfiram (DSF), suppressed this depletion or in some cases resulted in elevated AA concentrations. Further, the cells were shown to reduce the dimethyl sulphoxide (DMSO) to dimethyl sulphide, which is mediated by methionine sulfoxide reductase A (MsrA) enzymes. Interestingly, this process was also inhibited by DEAB and DSF. The results of this study indicate that SIFT-MS gas phase analysis could be applied to the study of volatile metabolites of intracellular enzyme reactions, this having potential utility in disease research and drug discovery.