title: Capabilities of HPLC with APEX-Q nebulisation ICP-MS and ESI MS/MS to compare selenium uptake and speciation of non-malignant with different B cell lymphoma lines.
abstract: The formation of intracellular dimethylselenide (DMSe) as a product of exposure of non-malignant (PBMCs) and lymphoma (RL and DHL-4) cell lines to methylseleninic acid (MSA) at clinical levels is suggested here for the first time. This was achieved by analysis of cell lysates by HPLC coupled to ICP-MS via APEX-Q nebulisation, enabling limits of detection for target methyl-Se species which are up to 12-fold lower than those obtained with conventional nebulisation. Methyl-Se-glutathione (CH₃Se-SG), although detected in lysates of cells exposed to MSA, was found to be a reaction product of MSA with glutathione. This was confirmed by HPLC-ESI MS (MS) analysis of lysates of control cells (unexposed to Se) spiked with MSA. The MS/MS data obtained by collision-induced dissociation fragmentation of the ion m/z 402 (for [M+H](+) ⁸⁰Se) were consistent with the presence of CH₃Se-SG. Formation of DMSe was not detected by HPLC-ICP-MS in these spiked lysates, and it was found to require live cells in cell media containing MSA. Interestingly, the ratio of DMSe to CH₃Se-SG was significantly higher in lymphoma cells exposed to MSA in comparison to non-malignant cells. Moreover, maximum Se uptake levels in lymphoma cell lines seemed to be reached much earlier (after 10 min of MSA exposure) than in non-malignant cells. Finally, the GC-TOF-MS speciation data obtained for cell headspace suggested that the major Se species (dimethyldiselenide) appeared to be present in lymphoma cell headspace at significantly higher concentrations than in non-malignant cell headspace after only 10 min of exposure to MSA. Evidence for the presence of dimethylselenidesulfide in lymphoma cell headspace is also provided for the first time.
authors.affiliation: LGC Limited, Queens Road, Teddington, Middlesex TW11 OLY, UK. Heidi.Goenaga-Infante@lgc.co.uk
authors.forename: Heidi
authors.initials: H
authors.lastname: Goenaga-Infante
authors.forename: Shireen
authors.initials: S
authors.lastname: Kassam
authors.forename: Emma
authors.initials: E
authors.lastname: Stokes
authors.forename: Christopher
authors.initials: C
authors.lastname: Hopley
authors.forename: Simon P
authors.initials: SP
authors.lastname: Joel
mesh_terms: D002460:Cell Line; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D016393:Lymphoma, B-Cell / Q000737:chemistry* / Q000378:metabolism; D013058:Mass Spectrometry; D016566:Organoselenium Compounds / Q000378:metabolism / Q000494:pharmacology; D012643:Selenium / Q000032:analysis* / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D016566:Organoselenium Compounds; C008493:methylselenic acid; D012643:Selenium; C013503:dimethylselenide