Haemoglobin binding of a musk xylene metabolite in man

Analysis of elimination half-lives in MamTKDB 1.0 related to bioaccumulation: Requirement of repeated administration and blood plasma values underrepresent tissues

When building the novel public mammalian toxicokinetic database (MamTKDB) we collected and included 3927 elimination half-lives (^elimt_1/2) for 1407 xenobiotics in various species (rat, human, mouse, dog, monkey, rabbit, cattle, pig, sheep, guinea pig, hamster, horse and goat) with specification of compartment (whole body, organ/tissue, cell type, medium) studied. Here we describe and analyse the collected data in MamTKDB 1.0. Most ^elimt_1/2 are for humans and rats and their data differ in some ways: whereas the rat data are mainly for pesticides, the human data are mainly for pharmaceuticals and environmental contaminants. There are also differences in types of compartments studied and in metabolites followed: human ^elimt_1/2 are mainly whole body based (i.e. based on blood plasma or excretion), animal data are additionally for various organs/tissues, cells or media. Contrary to human studies, animal studies regularly administrate radiolabeled (e.g. ¹⁴C) substances and distribution of both parent and eventual metabolites are followed, measuring the radioactivity. In rats, substances had been given through single, preconditioning or repeated administration. Single administration studies dominated, but repeated studies generally had longer ^elimt_1/2 than single or preconditioning studies for which ^elimt_1/2 were similar. Repeated administration studies should better ascertain steady state conditions throughout the body, a process involving time-dependent tissue loading, and the data show that for most substances, repeated studies are required to address bioaccumulation potential. About 65% of the substances in MamTKDB 1.0 fulfilled the octanol-water and octanol-air partitioning-based screening criteria (log K_ow > 2 and log K_oa > 5) for further bioaccumulation assessment and/or testing, and most of the substances with long ^elimt_1/2 in both humans and rats fulfill these criteria. Of note, however, there are also many chemicals with log K_ow > 2 with intermediate or short ^elimt_1/2. Per- and polyfluoroalkyl substances (PFAS) stand out in that they often have log K_oa < 5. Rats are poor toxicokinetic test models for perfluoroalkyl acids (PFAAs) for which pigs (and possibly mice) ^elimt_1/2 data resemble those of humans better. Perfluorinated carboxylic acids (PFCAs) and perfluorinated sulfonic acids (PFSAs) of similar molecular weight had similar ^elimt_1/2 in the species tested. For polychlorinated biphenyls (PCBs), ^elimt_1/2 increases with the degree of chlorination in humans. In relation to other compartments, blood plasma/serum had among the shortest ^elimt_1/2 in rats and often underrepresent ^elimt_1/2 in tissues. Rat data were divided into 38 compartment (tissue or media) types out of which 20 had sufficient data for correlational tests. In general, there was a strong degree of correlation of rat ^elimt_1/2 in-between most compartments, but there were also exceptions. Surprisingly, the correlation between brain and white fat was relatively weak. Interestingly, several substances or their metabolites bound to haemoglobin in red blood cells. MamTKDB 1.0 allows investigation on how certain chemical characteristics influence ^elimt_1/2 and is a promising database for assessment of bioaccumulation potential.

Synthetic Musk Compounds in Human Biological Matrices: Analytical Methods and Occurrence-A Review

Extensive use of synthetic musk compounds (SMs) in numerous consumer and personal care products has resulted in direct human exposures via dermal absorption, inhalation of contaminated dust and volatilized fragrances, and oral ingestion of contaminated foods and liquids. SMs and their metabolites are lipophilic, hence commonly detected in various biological matrices such as blood, breast milk, and adipose tissue. Appropriate analytical techniques are needed to detect and quantify SMs in biological matrices to assess their potential effects on human health. Different methods to process and analyze SMs in biological matrices, including sample-pretreatment, solvent extraction, cleanup, and instrumental analysis, are presented in this review. The concentration levels of selected musk compounds in biological samples from different countries/regions are summarized. Finally, research gaps and questions pertaining to the analysis of SMs are identified and suggestions made for future research studies.

Hemoglobin Adducts and Urinary Metabolites of Arylamines and Nitroarenes

Arylamines and nitroarenes are intermediates in the production of pharmaceuticals, dyes, pesticides, and plastics and are important environmental and occupational pollutants. N-Hydroxyarylamines are the toxic common intermediates of arylamines and nitroarenes. N-Hydroxyarylamines and their derivatives can form adducts with hemoglobin (Hb-adducts), albumin, DNA, and tissue proteins in a dose-dependent manner. Most of the arylamine Hb-adducts are labile and undergo hydrolysis in vitro, by mild acid or base, to form the arylamines. According to current knowledge of arylamine adduct-formation, the hydrolyzable fraction is derived from the reaction products of the arylnitroso derivatives that yield arylsulfinamide adducts with cysteine. Hb-adducts are markers for the bioavailability of N-hydroxyarylamines. Hb-adducts of arylamines and nitroarenes have been used for many biomonitoring studies for over 30 years. Hb-adducts reflect the exposure history of the last four months. Biomonitoring of urinary metabolites is a less invasive process than biomonitoring blood protein adducts, and urinary metabolites have served as short-lived biomarkers of exposure to these hazardous chemicals. However, in case of intermittent exposure, urinary metabolites may not be detected, and subjects may be misclassified as nonexposed. Arylamines and nitroarenes and/or their metabolites have been measured in urine, especially to monitor the exposure of workers. This review summarizes the results of human biomonitoring studies involving urinary metabolites and Hb-adducts of arylamines and nitroarenes. In addition, studies about the relationship between Hb-adducts and diseases are summarized.

Human exposure to nitro musks and the evaluation of their potential toxicity: an overview

Synthetic nitro musks are fragrant chemicals found in household and personal care products. The use of these products leads to direct exposures via dermal absorption, as well as inhalation of contaminated dust and volatilized fragrances. Evidence also suggests that humans are exposed to low doses of these chemicals through oral absorption of contaminated liquids and foods. As these compounds are lipophilic, they and their metabolites, have been found not only in blood, but also breast milk and adipose tissue. After personal use, these environmentally persistent pollutants then pass through sewage treatment plants through their effluent into the environment.Little is known about the biological effects in humans after such a prolonged low dose exposure to these chemicals. While epidemiologic studies evaluating the effects of nitro musk exposures are lacking, there is limited evidence that suggest blood levels of nitro musks are inversely related to luteal hormone levels. This is supported by animal models and laboratory studies that have shown that nitro musks are weakly estrogenic. Nitro musks exposure has been associated with an increased risk of tumor formation in mice. The evidence suggests that while nitro musks by themselves are not genotoxic, they may increase the genotoxicity of other chemicals. However, animal models for nitro musk exposure have proven to be problematic since certain outcomes are species specific. This may explain why evidence for developmental effects in animals is conflicting and inconclusive. Given that animal models and cell-line experiments are suggestive of adverse outcomes, further epidemiologic studies are warranted.

Reaction of nitroso derivatives of dinitropyrenes with sulfhydryl groups of peptides and hemoglobinin vitroand in rats

Diesel engine emissions have been classified as a potential human carcinogen and may cause a variety of other health effects. Human exposure to diesel engine emissions is highly variable within the population. Therefore, specific methods for the biomonitoring of human exposure to diesel engine emissions are required for exposure assessment within epidemiological studies. Haemoglobin adducts of dinitropyrenes may serve as biomarkers for human exposures to diesel engine emissions.To characterize structures of dinitropyrene reaction products with sulfhydryl groups, glutathione was used to trap electrophilic nitroso intermediates formed from dinitropyrenes and glutathione S-conjugates were identified and characterized by Qtrap techniques using (HPLC-MS/MS) high-performance liquid chromatography coupled to triple quadrupole mass spectrometry. Nitrosonitropyrene-derived sulfinamides, sulfenamides and glutathione thioethers bound to carbon atoms in the aromatic ring, presumably formed by a rearrangement of intermediate sulfenamide cations, were formed in low yields. In haemoglobin from rats orally administered dinitropyrenes, mild alkaline hydrolysis of haemoglobin released aminonitropyrenes, which were identified by HPLC-MS/MS. The results demonstrate that dinitropyrenes undergo nitroreduction in rats and that the intermediate nitrosonitropyrenes bind to heamoglobin. The haemoglobin adducts formed from dinitropyrenes seem, in contrast to previous studies, to be hydrolysable and thus represent sulfen- and sulfinamides derived from the intermediate nitrosonitropyrenes. The developed Qtrap methods to detect and characterize glutathione S-conjugates rapidly may have wide applications in attempts to characterize reactive intermediates formed in complex mixtures in low concentrations.

Enhanced sensitivity for the determination of ambiphilic polyaromatic amines by LC–MS/MS after acetylation

A new method for the analysis of aminonitropyrenes and diaminopyrenes was developed for urine and hemoglobin samples using LC-MS/MS. A good separation by LC was only achieved after derivatization of the amino group, which also increased sensitivity to a limit of detection (LOD) of 0.1 pg (on column) for diaminopyrene and 5 pg for aminonitropyrene using electrospray ionization (ESI). Compared to a derivatization with pentafluorobenzoyl chloride yielding only one sensitive MS/MS transition, acetylation offers the advantages of a higher selectivity with two sensitive MS/MS transitions and the possibility of a direct detection of acetylated aminonitropyrenes and diaminopyrenes formed metabolically in vivo. Acetylated diaminopyrene was detected in urine and after hydrolysis of the corresponding hemoglobin adducts followed by acetylation in blood samples of rats after administration of dinitropyrene but not in controls. A method based on GC-MS with negative chemical ionization of the electrophore labelled metabolites was non-selective since only one major ion [M - HF]- was formed and some isobaric peaks were observed preventing unequivocal analyte identification at concentrations close to the LOD.

Formation of nitro musk adducts of rainbow trout hemoglobin for potential use as biomarkers of exposure

The high use of nitro musk xylene (MX) and musk ketone (MK) as fragrances, and their persistence and bioaccumulation potential make them ubiquitous environmental contaminants. The 4-amino-MX (AMX) and 2-amino-MK (AMK) metabolites have been detected in trout fish hemoglobin (Hb) samples by gas chromatography-ion trap-mass spectrometry (GC-MS). Twelve Hb samples prepared from rainbow trout that were exposed to MX and MK, over a period of 24 and 72 h, were analyzed. Amino metabolites were liberated by basic hydrolysis and extracted from the fish Hb into n-hexane. The extract was concentrated, analyzed, and spiked with a standard solution (80 pg/microl) of AMX or AMK and reanalyzed. Concentrations of AMX from 10 to 25 ng/g were detected in Hb from fish taken 24 and 72 h after MX exposure. At 24 and 72 h after MK exposure, the concentration of AMK was found to be 25-51 ng/g and 9.5-25 ng/g, respectively. Concentrations of AMK in Hb from two of the three trout were substantially lower after 72 h compared with 24 h exposure. The AMX and AMK metabolites were not detected in four control samples. Average recoveries exceeding 89 and 86% could be achieved for AMX and AMK, respectively, with a coefficient of variation (CV) around 5%.

Biomonitoring of exposure to aromatic amines: haemoglobin adducts in humans

Haemoglobin (Hb) adducts from aromatic amines (AAs) are well established biomarkers of exposure. Tobacco smoking and occupational exposure are major sources of AA Hb adducts. The origin of background levels in non-smokers and non-occupationally exposed humans are largely unknown. Here we examine the determination of AA Hb adducts, focussing on the analytical strategies for Hb isolation, removal of unbound AAs from Hb solutions, hydrolysis of the Hb bound AAs, extraction, preconcentration, clean-up and derivatisation of the free amines for determination by gas chromatography-mass spectrometry. Finally, a detailed summary of available results on the determination of AA Hb adducts is given.

Biomonitoring of arylamines and nitroarenes

Arylamines and nitroarenes are very important intermediates in the industrial manufacture of dyes, pesticides and plastics, and are significant environmental pollutants. The metabolic steps of N-oxidation and nitroreduction to yield N-hydroxyarylamines are crucial for the toxic properties of arylamines and nitroarenes. Nitroarenes are reduced by microorganisms in the gut or by nitroreductases and aldehyde dehydrogenase in hepatocytes to nitrosoarenes and N-hydroxyarylamines. N-Hydroxyarylamines can be further metabolized to N-sulphonyloxyarylamines, N-acetoxyarylamines or N-hydroxyarylamine N-glucuronide. These highly reactive intermediates are responsible for the genotoxic and cytotoxic effects of this class of compounds. N-Hydroxyarylamines can form adducts with DNA, tissue proteins, and the blood proteins albumin and haemoglobin in a dose-dependent manner. DNA and protein adducts have been used to biomonitor humans exposed to such compounds. All these steps are dependent on enzymes, which are present in polymorphic forms. This article reviews the metabolism of arylamines and nitroarenes and the biomonitoring studies performed in animals and humans exposed to these substances.

Evaluation of health risks caused by musk ketone

Among the nitro musks, musk ketone (MK) as a synthetic compound with a typical musk odor is widely used in cosmetics. In the European Community the total amount used in fragrances has been reported to be 110 tons/a. Additionally, relevant amounts of MK are used in Indian joss sticks. As a result of its inherently low biodegradability MK has been detected in the aquatic environment (surface water, sediments, edible fish). Moreover, it has been shown that MK concentrates in human fatty tissue and breast milk, indicating that humans are constantly exposed. Several studies provided convincing evidence of lack of a genotoxic potential for MK. However, MK was identified as a strong inducer of phase I enzymes in rodents and a cogenotoxicant in vitro in human derived cells in rather low doses, suggesting that exposure to MK might increase the susceptibility to health hazards caused by carcinogens in humans.

Musk xylene and musk ketone amino metabolites in the aquatic environment

The monoamino metabolites of the nitro musk fragrances musk xylene (MX) and musk ketone (MK) were analysed simultaneously with their parent compounds by GC/ECD, GC/PND and GC/EI/MS in the various compartments of the aquatic environment. In this review the data of the metabolites 4-NH2-MX, 2-NH2-MX, and 2-NH2-MK in five river water and seven sewage samples, six sediment samples and in a total of 33 biota samples are summarized and discussed. In the effluents of two municipal sewage plants low nitro musk concentrations and comparatively high levels of the amino metabolites (maximum concentrations: 34 ng 4-NH2-MX/L, 250 ng 2-NH2-MK/L) were analysed indicating that besides adsorption to the sludge the metabolization pathway plays an important role in the sewage plant. In water samples from the river Elbe the transformation products were the dominant compounds as well. In general, in water samples the concentrations of 2-NH2-MK exceeded those of the main MX metabolite 4-NH2-MX significantly. In biota samples 4-NH2-MX seems to be the main metabolite, very often its contents were higher than those of the parent compound. Maximum concentrations of 4-NH2-MX were found in tenches from a sewage pond (3600 microg/kg lipid), a species dependent bioaccumulation was discussed. The bioconcentration of 2-NH2-MK in biota samples is relatively low. There are only few toxicological studies on the mixed amino nitroaromatics, whose data indicate the relevance of the monoamino metabolites in environmental analysis and toxicology and the urgent need of further investigations.