The toxicities of polycyclic aromatic hydrocarbons (PAHs) have been extensively explored due to their carcinogenic and mutagenic potency; however, little is known about the metabolic responses to chronic environmental PAH exposure among the general population. In the present study, 566 healthy volunteers were dichotomized into exposed and control groups to investigate PAH-induced perturbations in the metabolic profiles. Nine urine PAH metabolites were measured by a sensitive LC–MS/MS method to comprehensively evaluate the PAH exposure level of each individual, and the metabolic profiles were characterized via a LC–MS-based metabolomic approach. PAH exposure was correlated to its metabolic outcomes by linear and logistic regression analyses. Metabolites related to amino acid, purine, lipid, and glucuronic acid metabolism were significantly changed in the exposed group. 1-Hydroxyphenanthrene and dodecadienylcarnitine have potential as sensitive and reliable biomarkers for PAH exposure and its metabolic outcomes, respectively, in the general population. These findings generally support the hypothesis that environmental PAH exposure causes oxidative stress-related effects in humans. The current study provides new insight into the early molecular events induced by PAH exposure in the actual environment.Keywords: environmental health; Metabolomics; molecular epidemiology; oxidative stress; PAH exposure;

Gliomas are the most common and lethal primary malignant brain tumors. Recent studies implicate an important role for a rare population of glioma stem cells (GSCs) in glioma maintenance and recurrence. New therapeutic strategies are desperately needed requiring insights into the biological and molecular mechanisms underlying the self-renewal and differentiation of GSCs. We now investigate the metabolic signatures of three glioma cell lines with different stemness using a liquid chromatography-mass spectrometry (LC-MS)-based metabolomics approach. Cellular metabolites differentially expressed in U87MG stem-like cells (SLCs) relative to U87 malignant glioma cells (GCs) and U87MG stem-like cell differentiation cells (SLCDCs) were identified. The specific and significant alterations including nucleotide metabolism, glycerophospholipid metabolism, glutathione metabolism, carnitine metabolism and tryptophan metabolism were characterized. Cell function assays were further used to evaluate the self-renewal ability of SLCs treated with differential metabolites, indicating that these metabolites are involved in the maintenance of stemness. The results provide valuable information on the association of the significantly altered metabolites and metabolic pathways with SLC self-renewal and differentiation.

An integrated approach combining data acquisition using MSE and multi-period product ion scan (mpMS/MS), with high-resolution characteristic extracted ion chromatograms (hcXIC) as a data mining method, was developed for in vivo drug metabolites screening and identification. This approach is illustrated by analyzing metabolites of a potential anticancer agent, 3,6,7-trimethoxyphenanthroindolizidine (CAT) in rat urine based on rapid resolution liquid chromatography combined with tandem mass spectrometry (RRLC–MS/MS). Untargeted full-scan MSE enabled the high-throughput acquisition of potential metabolites, and targeted mpMS/MS contributed to the sensitivity and specificity of the acquisition of molecules of interest. The data processing method hcXIC, based on the structure of CAT, was shown to be highly effective for the metabolite discovery. Through the double-filtering effect of the characteristic ion and accurate mass, conventional extracted ion chromatograms that contained a substantial number of false-positive peaks were simplified into chromatograms essentially free of endogenous interferences. As a result, 21 metabolites were detected in rat urine after oral administration of CAT. Based on the characteristic fragmentation patterns of the phenanthroindolizidine alkaloid, the structures of 9 metabolites were identified. Furthermore, the interpretation of the MS/MS spectra of these metabolites enabled the determination of demethylation position as well as the differentiation between N-oxidized and hydroxylated metabolites.Graphical abstractHighlights► A RRLC–MS/MS approach was developed for metabolite analysis. ► MSE and mpMS/MS were integrated to improve throughput and sensitivity. ► The metabolites of a potential anticancer agent CAT were detected in rat urine. ► Demethylated, N-oxidized and hydroxylated metabolites were identified.

A rapid, sensitive, specific and accurate analytical method of ultra-fast liquid chromatography combined with tandem mass spectrometry (UFLC–MS/MS) was established for simultaneous quantitative analysis of 16 distinct endogenous estrogens and their metabolites (EMs) in postmenopausal female urine. The quantitative method utilized a hydrolysis/extraction/derivatization step and a UFLC system to achieve separation in 16 min. The lower limit of quantitation for each estrogen metabolite was 2 pg mL−1 with the percent recovery of a known added amount of estrogen at 93.2–109.3%. The intra-batch accuracy and precision for all analytes were 87.5–107.7% and 0.6–11.7%, respectively, while inter-batch accuracy and precision were 87.0–105.8% and 1.2–10.2%, respectively. Using this developed and validated method, the comprehensive metabolic profiling of 16 EMs in urine samples of 86 postmenopausal female breast cancer patients and 36 healthy controls was investigated by systematic statistical analysis. As a result, the circulating levels of 6 EMs were found to be different by a comparison of patients and healthy controls. The parent estrogens, estrone (E1) and 17β-estradiol (E2), as well as 2-hydroxyestradiol (2-OHE2) and 4-hydroxyestradiol (4-OHE2) were produced in higher abundance, whereas 16α-hydroxyestrone (16α-OHE1) and 2-methoxyestradiol (2-MeOE2) were decreased in the breast cancer group. 2-OHE2 and 4-OHE2 in particular showed significant elevation in patients, which are consistent with the carcinogenic mechanism hypothesis that catechol estrogens can react with DNA via quinones, resulting in mutations to induce breast cancer. Thus, 2,4-hydroxylation may be the dominant metabolic pathway for parent estrogens rather than 16α-hydroxylation. The lower level of 2-MeOE2 in the breast cancer group was believed to correlate with its protective effect against tumor formation. This study could provide valuable information on the association of the EM metabolic pathway with carcinogenesis as well as identify potential biomarkers for estrogen-induced breast cancer risk.