Urinary Amino-PAHs in relation to diesel engine emissions and urinary mutagenicity.

Diesel exhaust has long been of health concern due to established toxicity including carcinogenicity in humans. However, the precise components of diesel engine emissions that drive carcinogenesis are still unclear. Limited work has suggested that nitrated polycyclic aromatic hydrocarbons (NPAHs) such as 1-nitropyrene and 2-nitrofluorene may be more abundant in diesel exhaust. The present study aimed to examine whether urinary amino metabolites of these NPAHs were associated with high levels of diesel engine emissions and urinary mutagenicity in a group of highly exposed workers including both smokers and nonsmokers. Spot urine samples were collected immediately following a standard work shift from each of the 54 diesel engine testers and 55 non-tester controls for the analysis of five amino metabolites of NPAHs, and cotinine (a biomarker of tobacco smoke exposure) using liquid chromatography-mass spectrometry. An overnight urine sample was collected in a subgroup of non-smoking participants for mutagenicity analysis using strain YG1041 in the Salmonella (Ames) mutagenicity assay. Personal exposure to fine particles (PM2.5) and more-diesel-specific constituents (elemental carbon and soot) was assessed for the engine testers by measuring breathing-zone concentrations repeatedly over several full work shifts. Results showed that it was 12.8 times more likely to detect 1-aminopyrene and 2.9 times more likely to detect 2-aminofluorene in the engine testers than in unexposed controls. Urinary concentrations of 1-aminopyrene were significantly higher in engine testers (p < 0.001), and strongly correlated with soot and elemental carbon exposure as well as mutagenicity tested in strain YG1041 with metabolic activation (p < 0.001). Smoking did not affect 1-aminopyrene concentrations and 1-aminopyrene relationships with diesel exposure. In contrast, both engine emissions and smoking affected 2-aminofluorene concentrations. The results confirm that urinary 1-aminopyrene may serve as an exposure biomarker for diesel engine emissions and associated mutagenicity.

The associations of nitrated polycyclic aromatic hydrocarbon exposures with plasma glucose and amino acids.

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) have been widely studied for their mutagenic and carcinogenic effects. This study aims to investigate whether exposure to nitro-PAHs is associated with biomarkers of carbohydrate metabolism, an underlying risk factor for metabolic disorder. Early morning urine and blood samples were longitudinally collected two times with a four-week interval from 43 healthy adults. Five urinary amino-PAHs (1-aminonaphthalene, 2-aminonaphthalene, 9-aminophenanthrene, 2-aminofluorene, and 1-aminopyrene) were measured as biomarkers of nitro-PAH exposures. We measured plasma concentrations of glucose and six amino acids that can regulate insulin secretion, including aspartate (Asp), glutamate (Glu), glutamine (Gln), alanine (Ala), Arginine (Arg), and ornithine (Orn). We found that increasing concentrations of 9-aminophenanthrene were significantly associated with increasing glucose levels and with decreasing Asp, Glu, Ala, and Orn levels. We estimated that 26.4 %-43.8 % of the 9-aminophenanthrene-associated increase in glucose level was mediated by Asp, Glu, and Orn. These results suggest that exposure to certain nitro-PAHs affects glucose homeostasis, partly resulting from the depletion of insulin-stimulating amino acids (Asp, Glu, and Orn).

Nitrated Polycyclic Aromatic Hydrocarbons and Arachidonic Acid Metabolisms Relevant to Cardiovascular Pathophysiology: Findings from a Panel Study in Healthy Adults.

Concerns on nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in the environment have mainly arisen from their mutagenic and carcinogenic effects. The objective of this study is to investigate whether nitro-PAH exposures are associated with biomarkers of cardiovascular pathophysiology. In a panel study design, urines and blood samples were collected up to four times with a 2-week interval from 89 healthy adults. We measured 1-naphthylamine, 2-naphthylamine, 9-aminophenanthrene, 2-aminofluorene, and 1-aminopyrene as biomarkers of nitro-PAH exposures. We measured three urinary metabolites of arachidonic acid (AA) including 20-hydroxyeicosatetraenoic acid (20-HETE) from the cytochrome P450 (CYP) pathway, 8-isoprostane from the nonenzymatic pathway, and 11-dehydro-thromboxane B2 (11-dhTXB2) from the cyclooxygenase (COX) pathway. Urinary malondialdehyde, 8-hydroxy-2'-deoxyguanosine (8-OHdG), and 6-sulfatoxymelatonin (aMT6s) were measured to reflect systemic oxidative stress. Plasma concentrations of the soluble P-selectin and von Willebrand factor (vWF) were measured as biomarkers of platelet activation and endothelial dysfunction. We found that increased urinary concentrations of amino-PAHs were significantly associated with increased 20-HETE, 11-dhTXB2, and 8-OHdG and with decreased 8-isoprostane and aMT6s. Increased amino-PAHs were positively associated with P-selectin and vWF, respectively. These results suggest that exposure to nitro-PAHs increases systemic oxidative stress and alters AA metabolism toward CYP and COX pathways, leading to an increased cardiovascular disease risk.

Associations of ozone exposure with urinary metabolites of arachidonic acid.

BACKGROUND: Ozone (O3) exposure has been associated with biomarkers of platelet activation and oxidative stress. The metabolism of arachidonic acid (AA) plays an important role in platelet activation and oxidative stress. However, AA metabolic pathways have not been examined in relation to O3 and other air pollutants. METHODS: Early morning urine and fasting blood were longitudinally collected up to four times from 89 healthy adults (22-52 years old, 25 women) in Changsha City, China. We measured three urinary AA metabolites, namely 11-dehydro-Thromboxane B2 (11-dhTXB2) produced from the arachidonic cyclooxygenase pathway, 20-hydroxyeicosatetraenoic acid (20-HETE) from the CYPs pathway, and 8-isoprostane from the non-enzymatic pathway. Urinary malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured as indicators of oxidative damage to lipids and DNA, respectively. We measured soluble P-selectin (sCD62p) concentrations in plasma as an indicator of platelet activation. Indoor and outdoor air pollutants were measured and combined with participants' time-activity pattern to calculate personal exposure to O3, PM2.5, NO2, and SO2 averaged over 12-hour, 24-hour, 1-week, and 2-week periods prior to biospecimen collection, respectively. Linear mixed-effects models were used to examine the relationships of AA metabolites with air pollutant exposures, plasma sCD62p, and urinary MDA & 8-OHdG. RESULTS: We found that a 10% increase in 12 h and 24 h O3 exposure were associated with increases in urinary11-dhTXB2 by 1.4% (95%, 0.1% to 2.6%) and 1.3% (0.05% to 2.5%), respectively. These associations remained robust after adjusting for co-pollutant exposures. No significant associations were observed between 11-dhTXB2 and other pollutants or between O3 exposures and other AA metabolites. All the three AA metabolites were significantly and positively associated with urinary MDA and 8-OHdG, whereas only urinary 11-dhTXB2 was significantly and positively associated with plasma sCD62p. CONCLUSIONS: A metabolite of AA from the cyclooxygenase pathway was positively associated with short-term O3 exposure, and with a plasma marker of platelet activation and two urinary markers of oxidative stress. The results suggest that O3 exposure may contribute to increased platelet activation and oxidative damages via altering the metabolism of AA.

Simultaneous quantification of urinary 6­sulfatoxymelatonin and 8­hydroxy­2'­deoxyguanosine using liquid chromatography-tandem mass spectrometry.

Oxidative stress is involved in the pathophysiology of many diseases and natural aging. Urinary 8­hydroxy­2'­deoxyguanosine (8­OHdG), a stable product of DNA oxidative damage, has been widely used as an oxidative stress biomarker. However, only reporting 8­OHdG level, as commonly done previously, does not take into account of damaged DNA molecules that have not been repaired and excreted in urine. Melatonin is known to help with DNA repairs and hence can modify 8­OHdG levels. 6­sulfatoxymelatonin (aMT6s) is a major metabolite of melatonin excreted in urine. Hence it is useful to measure both urinary 8­OHdG and aMT6s together. Here we describe a newly developed and validated method to simultaneously measure these two compounds using high-performance liquid chromatography-tandem mass spectrometry. Using a liquid-liquid extraction (20% methanol) at a pH ~ 7, as opposed to a solid-phase extraction used previously, substantially expedited the sample pretreatment process. The calibration curves showed a linear range from 0.5 to 100 ng/mL for aMT6s with a R2 of 0.9999 and from 1.5 to 100 ng/mL for 8­OHdG with R2 of 0.9985. The recovery for 8­OHdG and aMT6s was 102 ±â€¯2% and 88 ±â€¯4%, respectively. The limits of detection were 0.1 ng/mL for aMT6s and 0.5 ng/mL for 8­OHdG, while the lower limits of quantification were 0.3 ng/mL for aMT6s and 1.0 ng/mL for 8­OHdG. For both compounds, the retention time standard deviation was 0.03 min, and inter-day and intra-day variability, expressed as relative standard deviation (RSD), ranged from 4.5%-15.8%. The new method was successfully applied to analyze both compounds in the first morning and midday urine voids from five volunteers. The results support that this method is capable of rapidly and accurately measuring urinary 8­OHdG and aMT6s simultaneously. This new method is expected to have important applications in biomedical and environmental health studies involving the oxidative stress pathophysiological pathway.