MS-DIAL (v.4.70) was used for feature annotation. Peak picking was performed with a minimum peak height of 200 and a mass slice width of 0.1. Peaks were aligned across all chromatograms with a 0.1 min retention time tolerance and a 0.01 m/z MS1 tolerance.
Features from polar metabolomics were first matched against an in-house database comprising values of retention time (RT) and accurate mass (AM). A total of 122 compounds were annotated at level 1. Additional annotations in the dataset were performed at levels 3 and 4, on features exhibiting a high intensity and signal-to-noise ratio, with accurate mass (MS1) and fragmentation pattern (MS2) matches against HMDB-indexed compounds using MS-FINDER (v.3.52 ) (Tsugawa et al., 2016).
"],"repository":["MetaboLights"],"study_status":["Public"],"ptm_modification":[""],"instrument_platform":["Liquid Chromatography MS - negative - hilic"],"chromatography_protocol":["Analytical measurements were performed on a Vanquish Horizon UHPLC system (Thermo Fisher Scientific).
Polar metabolites were separated on a Premier BEH zHilic (2.1 x 100 mm, 1.7 μm, Waters Corp.) column protected with a 5 mm guard column. Solvent A was 20 mM ammonium acetate in water (100%) with pH adjusted to 9.2 with 0.1 % ammonium hydroxide solution (25%, Fisher Scientific). Solvent B was 100% acetonitrile. The elution of polar metabolites was obtained by increasing percentage of solvent A from 10 to 60 % from 0.3 to 12.3 min). The column was washed at 100 % A for 4.7 column volumes and reconditioned at 10 % A for 9.2 column volumes for a total run time of 21 min. The flow rate at elution was 0.4 mL/min, the column temperature was 30°C and the injection volume was 4 μL.
"],"publication":["Neurotoxicity of Propylene Glycol Butyl Ether: Multiomic Evidence from Human BrainSpheres. 10.1101/2025.05.22.655411."],"submitter_affiliation":["University of Geneva"],"submitter_name":["Isabel Meister","Mathieu GALMICHE"],"organism_part":["hiPSC cell","mixture","Growth Medium"],"technology_type":["mass spectrometry assay"],"disease":[""],"extraction_protocol":["Brain Spheres in 1.5 mL Eppendorfs were first washed in 1 mL ammonium acetate (150 mM in water) to remove traces of culture medium. The wash solution was removed after gravity sedimentation of Brain Spheres and 1 mL methanol / water (8:2, v/v) containing 1 μM CHES (Sigma-Aldrich) as technical internal standard was added for polar metabolomics extraction. After a few seconds vortexing (Vortex Genie-2, Scientific Industries), spheres were disrupted in an ice bath by 10 consecutive cycles of ultrasonication of 10 seconds each separated by 30 second breaks to reduce heat production (Vibra-Cell VCX500, Sonics & Materials Inc.). Sonication intensity was set at 30 % amplitude. After extraction, samples were incubated at -20°C for 1 h to promote protein precipitation and centrifuged at 14000 g for 15 minutes at 4°C (5430R, Eppendorf SE). The supernatant containing polar metabolites was collected and evaporated to dryness on low temperature setting (Savant SC210A concentrator, 61 Thermo Fisher Scientific Inc.).
On the day of analysis, dry extracts were reconstituted for metabolomics in 150 μL acetonitrile / water (7:3, v/v) containing 2 μM HEPES (Sigma-Aldrich) as technical internal standard. Recovery was enhanced by vortexing samples for 10 seconds and shaking them at 1200 rpm and 4°C for 15 minutes. Samples were then placed in the freezer overnight to trigger the precipitation of potential particles. After centrifugation (14000 g, 4°C, 15 min), 40 μL of each sample was pooled for constituting QC samples. Polar metabolomics extracts were transferred into MaxQuant PP vials (Waters Corp.).
"],"organism":["blank","reference compound","Homo sapiens"],"full_dataset_link":["https://www.ebi.ac.uk/metabolights/MTBLS12771"],"author":["Mathieu Galmiche. University of Geneva. Institute of Pharmaceutical Sciences of Western Switzerland (ISPSO), Rue Michel-Servet 1, 1211 Geneva 4, Switzerland. mathieu.galmiche@unige.ch. +41223796894.","Isabel Meister. University of Geneva. Institute of Pharmaceutical Sciences of Western Switzerland (ISPSO), Rue Michel-Servet 1, 1211 Geneva 4, Switzerland. isabel.meister@unige.ch.","Serge Rudaz. University of Geneva. Institute of Pharmaceutical Sciences of Western Switzerland (ISPSO). Serge.Rudaz@unige.ch. +41223796572."],"data_transformation_protocol":["The instrumental drift was corrected with an R-based LOESS regression algorithm . After drift correction, features displaying a CV higher than 20% on pooled QCs and/or a D-ratio higher than 40 were excluded from the dataset. Additionally, features with more than 33% missingness (defined as peak area below the limit of detection, i.e. 3 times the peak area measured in the blank) in samples, and/or more than 10% of missingness in pooled QCs, were also excluded. Finally, to account for differences in total cellular material in the samples, Probabilistic Quotient Normalization (PQN) was performed on both metabolomics and lipidomics using an in-house platform.
"],"study_factor":["Exposure solvent","Exposure dose","Exposure time"],"submitter_email":["mathieu.galmiche@ki.se","isabel.meister@unige.ch"],"sample_collection_protocol":["Neural progenitor cells (NPCs) were generated through embryoid body formation from induced pluripotent stem cells (iPSCs), themselves derived from human CCD-1079Sk fibroblasts (ATCC® CRL-2097) using Epstein–Barr virus-based vectors, as previously described (Wen et al., 2014). NPCs were then grown and amplified in cell culture flasks coated with Geltrex® in Neural Expansion Medium. Cell passages were performed at 90% confluency. BSs were then prepared from the NPCs as previously described (Pamies et al., 2017). At 95 % of NPCs confluency, cells were washed with Dulbecco's Phosphate Buffered Saline (DPBS) and detached from the flasks using StemPro Accutase Cell Dissociation Reagent (GIBCO) for 2-3 min. 2x106 cells per well were plated in 2 mL of NEM in non-treated six-well plates. The plates were placed in an incubator at 37ºC and 5% CO2 under constant gyratory shaking (Kuhner orbital plate shaker, 88 rpm) allowing cell aggregation. After two days, cell medium was changed to differentiation medium consisting of Neurobasal Electro Medium, 1% Glutamax (Gibco), 2% B27/Neurobasal Electro, 0.01 μg/mL BDNF (PeproTech), 0.01 μg/mL GDNF (PeproTech) and 1% Penicillin-Streptomycin (10,000 U/mL). Medium changes with NDM were effectuated three times a week and cultures were kept until 8 weeks.
BSs were exposed to propylene glycol butyl ether (PGBE, CAS 5131-66-8), to its metabolite 2-butoxypropionic acid (2BPA, CAS 14620-87-2), or to cuprizone (CUP, CAS 370-81-0). Seven-week-old BSs were exposed either one time and collected after 24h or 48h (24/48h) (acute exposure) or exposed repeatedly at each medium change, i.e., three times, during one week (1W) and collected at the end of the week, to 5, 10 or 20 mM of PGBE and 2BPA. Untreated BSs were used as controls.
"],"omics_type":["Metabolomics"],"study_design":["ultra-performance liquid chromatography-mass spectrometry","propylene glycol butyl ether","iPSC derived cell line","untargeted metabolites"],"curator_keywords":["ultra-performance liquid chromatography-mass spectrometry","propylene glycol butyl ether","iPSC derived cell line","untargeted metabolites"],"mass_spectrometry_protocol":["The MS instrument was an Exploris 120 Mass Spectrometer (Thermo Fisher Scientific Inc.) equipped with a heated electrospray (HESI) source.
MS acquisition was done in negative mode, with spray voltage set at -2.3 kV, the transfer tube temperature at 320°C, the sheath gas flow at 50 AU, the auxiliary gas flow at 10 AU, the sweep gas flow at 2 AU. Full scan MS1 centroid spectra were acquired with 60k resolution at 200 m/z and AGC 100%, in a mass range from 80 to 600 m/z and the MS2 data-dependent spectra with the Top4 approach. The intensity threshold was set at 1e5 for precursor fragmentation and there was a 3 second dynamic exclusion of previously fragmented precursor ions within a 10-ppm tolerance. The isolation window was set at 0.9 m/z, the collision energy at 15 eV, and the resolution was 15k at 200 m/z. An exclusion list was prepared using a solvent blank injection to remove contaminants from the MS1 ions to be fragmented.
"],"metabolite_name":["Taurine","Methylimidazoleacetic acid","D-Fructose","GTP","N-Acetyl-asparagine","C6H12O5","Glucose","Ketoglutaramic acid","Folic acid","Dimethylguanosine","CDP","Erythritol","gamma-Glutamyl-cysteine","C6H10N2O4","GDP","Methylaconitate isomer 2","Methylaconitate isomer 3","Methylaconitate isomer 4","b-citryl-glutamic acid","Pantothenol","C6H11NO3","4-hydroxy-2-oxo-glutaric acid","N-Formyl-phenylalanine","Threonine","CMP","Methionine","C10H13N2O6","C5H4N4O","Citrulline","GMP","C5H9NO3","N2-Methylguanosine","Glutathione (GSH)","Valeric acid","C7H12O4","Glycerophosphorylethanolamine","C5H9NO4","Lysine","Citra/Gluta/Ita-conic acid 1","UDP-glucose","4-Hydroxyphenyllactic acid","cis-Urocanic acid","N-(1-deoxy-1-fructosyl)threonine","Imidazoleacetic acid riboside","4-Hydroxyproline","Glutamic acid","Suberic acid","C9H10O3","cAMP","D-Mannose","Guanine","C4H6O3","Glycerol-3-phosphate","Arginine","N1-Methylguanosine","Glutaric acid","Pyroglutamic acid","3-Amino(iso)butanoic acid","N-Acetyl-aspartic acid","N5-Acetyl-ornithine","D-Galactose","Creatinine","Alanine","Fructose-6-phosphate","N-Acetylhistidine","Phenylalanine","C5H8O2","Deoxyuridine","N2-Acetyl-lysine","C5H8O4","UDP-glucuronic acid","C5H8O3","Tryptophan","C5H8O5","Pseudouridine","Xanthine","Methylaconitate isomer 1","N-Acetyl-glutamine","Glucose-6-phosphate","Glycero-galacto-octulose","5,6-dihydrouridine","C5H10O6 - Arabinonic acid ?","7-Methylguanine","N-Formyl-methionine","Valine","N5-Methylglutamine","Asparagine","Nitrotyrosine","ATP","Uracil","N-Acetylneuraminic acid","Pantothenic acid","C3H7NO3 - Isoserine ?","C4H6O4 - diacid","C11H18N3O6 - Ophthalmic acid ?","C5H8N2O5","Phosphodimethylethanolamine","Guanosine","Creatine","N-Acetyl-valine","Hydroxybutyric acid isomer 3","ADP","Sulfinoalanine","C7H11NO6","C6H10O5","Hydroxybutyric acid isomer 1","C6H10O6","Hydroxybutyric acid isomer 2","UTP","Orotic acid","C10H11NO4","C10H19NO3","C4H7NO3","C4H7NO4","C14H17N5O8 (N6-succinyladenosine ?)","Tyrosine","UDP","C5H5O3","C9H13N3O4 - Deoxycytidine ?","AMP","N-Acetyl-threonine","2-Hydroxy-3-methylbutyric acid","Cytidine","C10H11N4O6 - Xanthosine","C7H10O5","C7H14O6","Fructose-1,6-diphosphate","Uridine","Succinic acid","UMP","Hypoxanthine","N-Acetylaspartylglutamic acid","2-Aminoadipic acid","N-Acetyl-methionine","D-Glucose","CDP-choline","Hippuric acid","C10H11N2O8 - Orotidine","Serine","C8H16N2O4","N-Acetyl-serine","Proline","N2-Succinyl-glutamic acid","Methyl/Methoxy-catechol sulfate","Leucine","CHES","Phosphoethanolamine","Azelaic acid","Sucrose or C12H22O11 isomer","C4H8O5","Ribose","4-Aminobutanoic acid (GABA)","Aspartic acid","N-Acetylglucosamine phosphate","cis-Aconitic acid","N-Acetyl-glutamic acid","Isoleucine","Adenosine","C8H14O5","C9H18N2O3","C5H10O5","C8H11NOS - Dopamine-4-O-sulfate ?","C6H8O6","C10H18O5","C5H10O3","N-methylhydantoin","Adenine","Uric acid","3-Methylglutaconic acid","Phosphocreatine","C8H7NO3","Galactitol / Mannitol / Sorbitol","Xylitol","Acetylneuraminic acid isomer 2","C5H7NO3","N-Acetyl-taurine","Acetylneuraminic acid isomer 1","Fumaric acid","HEPES","TMP","Inosine","2-O-Methylinosine","Phosphoglyceric acid","C9H9NO4","Galactose","N-Acetyl-cysteine","CTP","Glutamine"],"additional_accession":[]},"is_claimable":false,"name":"Neurotoxicity of Propylene Glycol Butyl Ether: Multiomic Evidence from Human BrainSpheres","description":"Exposure to solvents may contribute to the development of neurodevelopmental and neurodegenerative diseases. Glycol ethers consist in a widely used class of organic solvents leading to workers and consumers exposure via many different applications. Ethylene glycol ethers are gradually being replaced by propylene glycol ethers thought to be less toxic. However, their neurotoxicity is not systematically assessed prior to placing them on the market. Therefore, this study investigated the potential neurotoxicity of propylene glycol butyl ether (PGBE) for which no official occupational limit has been established. To this aim, new approach methodologies have been used. Human induced pluripotent stem cells-derived BrainSpheres model was exposed to PGBE and to its main metabolite, 2-butoxypropanoic acid (2BPA). An integrative multiomic approach (transcriptomics, proteomics, metabolomics and lipidomics) was adopted to assess molecular alterations, derive benchmark concentrations and define potential mechanisms of action. PGBE was neurotoxic at occupationally relevant exposure concentrations. This was shown for the first time in human cells. And, although PGBE was more cytotoxic than 2BPA, both compounds showed very similar neurotoxicity. PGBE and 2BPA strongly affected the cell cycle, induced oxidative stress and perturbed energy and lipid metabolism. They also targeted specific nervous system processes, such as axon guidance and synapse organization. Finally, 2BPA may trigger ferroptosis by increased iron uptake. Our results show an urgent need for public health authorities to carefully assess the risk glycol ethers pose to humans, to properly protect the workers as well as individuals in the general population unknowingly exposed from indoor air contaminations.
","dates":{"publication":"2026-08-25","submission":"2025-07-24"},"accession":"MTBLS12771","cross_references":{"KEGG":["Creatinine","CHES","Cytidine","Creatine","Citrulline","CDP-choline","CMP","CDP","CTP","C6H12O5","C5H8O3","C9H10O3","C8H7NO3","C10H11NO4","C5H10O3","C10H19NO3","C7H14O6","C5H4N4O","C9H18N2O3","C10H18O5","C6H10O6","C4H7NO3","C5H5O3","C5H8O4","C5H9NO4","C8H16N2O4","C10H13N2O6","C3H7NO3 - Isoserine ?","C9H13N3O4 - Deoxycytidine ?","C6H10N2O4","C10H11N2O8 - Orotidine","C4H7NO4","C5H10O5","C4H6O3","C6H10O5","C10H11N4O6 - Xanthosine","C8H11NOS - Dopamine-4-O-sulfate ?","C8H14O5","C7H12O4","C4H8O5","C5H10O6 - Arabinonic acid ?","C7H10O5","C9H9NO4","C5H8O2","C6H8O6","C7H11NO6","C6H11NO3","C5H9NO3","C14H17N5O8 (N6-succinyladenosine ?)","C4H6O4 - diacid","Citra/Gluta/Ita-conic acid 1","C5H8O5","C11H18N3O6 - Ophthalmic acid ?","C5H8N2O5","C5H7NO3"]}}