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Furathiocarb is a carbamate insecticide found in marine ecosystems as well as river water and sediments. The aim of this study was to characterize species differences in the in vitro metabolism of furathiocarb in seven mammalian species (human, monkey, minipig, rat, mouse, dog, rabbit) analyzed by LC-TOF-MS/MS, in order to provide qualitative and quantitative chemical-specific data to enhance toxicological risk assessment. Furathiocarb was mainly biotransformed to carbofuran metabolic pathway via (N-S) bond-cleavage. Two hydroxylated and sulfoxidated metabolites of furathiocarb were also detected (oxidation pathway). No unique human metabolites were detected. The carbofuran metabolic pathway was more predominant than the furathiocarb oxidation pathway in all species studied; differences based on hepatic clearance rates (CLH), were up to 9.4-fold in monkey and 7-fold in rats, while it was 4.3-fold in human. Animal to human differences in the carbofuran pathway are within the default toxicokinetic uncertainty factor, except for mouse (3.9-fold). Our findings on metabolic profiling and in vitro-in vivo extrapolations are helpful for the interpretation of toxicological findings and chemical risk assessment of furathiocarb.

Furathiocarb is a carbamate insecticide detected in ecosystems. Its main metabolite carbofuran has been alluded to affect birth outcomes and disturb hormone levels in humans. The metabolism of furathiocarb in humans has not been characterized. The metabolism studies were performed using hepatic microsomes from ten donors and fifteen human cDNA-expressed CYPs. The initial screening and identification of the metabolites were performed by LC-TOF. Quantifications and fragmentations were performed by LC/MS-MS. Furathiocarb was metabolized to eight phase I metabolites via two general pathways, carbofuran metabolic pathway and furathiocarb oxidation pathway. Six metabolites in the carbofuran metabolic pathway (carbofuran, 3-hydroxycarbofuran, 3-ketocarbofuran, 3-keto-7-phenolcarbofuran, 3-hydroxy-7-phenolcarbofuran, and 7-phenolcarbofuran) were identified with the help of authentic standards. The two unidentified metabolites in the furathiocarb oxidation pathway are probably hydroxylated and sulfoxidated derivatives of furathiocarb. The carbofuran metabolic pathway was more predominant than the furathiocarb oxidation pathway, ratios ranged from 24- to 115-fold in a 10-donor panel of hepatic microsomes. On the basis of recombinant CYP studies, the carbofuran pathway was dominated by CYP3A4 (95.9%); contributions by CYP1A2 (1.3%) and CYP2B6 (2.0%) were minor. The minor furathiocarb oxidation pathway was catalyzed by CYP2C19 and CYP2D6 (hydroxylated/sulfoxidated metabolite A) and by CYP3A5, CYP3A4 and CYP2A6 (metabolite B). High and significant correlation between carbofuran metabolic pathway and CYP3A4 marker activities (midazolam-1’-hydroxylation and omeprazole-sulfoxidation) were observed. Ketoconazole, a CYP3A4-inhibitor, inhibited the carbofuran pathway by 32–86% and hydroxylated/sulfoxidated metabolite-B formations by 41–62%. The data suggest that in humans, the carbofuran metabolic pathway is dominant, and CYP3A4 is the major enzyme involved. These results provide useful scientific information for furathiocarb risk assessment in humans.

On the basis of official Finnish Medicines Authority (Fimea)-approved drug monographs, less than half of the approved small-molecule drugs between 2007 and 2016 were substrates, inhibitors or inducers of CYP enzymes, predominantly of CYP3A4. No significant unexpected, life-threatening, CYP-associated drug-drug interactions (CYP-DDIs) of newly approved drug entities have been observed in the last 10–15 years. The present analysis seems to suggest that tools to study and predict potentially significant CYP-DDIs are working and efficient.

CYP enzyme induction is a sensitive biomarker for phenotypic metabolic competence of in vitro test systems; it is a key event associated with thyroid disruption, and a biomarker for toxicologically relevant nuclear receptor-mediated pathways. This paper summarises the results of a multi-laboratory validation study of two in vitro methods that assess the potential of chemicals to induce cytochrome P450 (CYP) enzyme activity, in particular CYP1A2, CYP2B6, and CYP3A4. The methods are based on the use of cryopreserved primary human hepatocytes (PHH) and human HepaRG cells. The validation study was coordinated by the European Union Reference Laboratory for Alternatives to Animal Testing of the European Commission’s Joint Research Centre and involved a ring trial among six laboratories. The reproducibility was assessed within and between laboratories using a validation set of 13 selected chemicals (known human inducers and non-inducers) tested under blind conditions. The ability of the two methods to predict human CYP induction potential was assessed. Chemical space analysis confirmed that the selected chemicals are broadly representative of a diverse range of chemicals. The two methods were found to be reliable and relevant in vitro tools for the assessment of human CYP induction, with the HepaRG method being better suited for routine testing. Recommendations for the practical application of the two methods are proposed.

Pregnane X receptor (PXR), constitutive androstane receptor (CAR), aryl hydrocarbon receptor (AHR) and peroxisome proliferator‐activated receptor α (PPARα) are ligand‐activated transcription factors that regulate expression of many xenobiotic‐metabolizing enzymes including several cytochrome P450 (CYP) enzymes. Many xenobiotics induce CYP enzymes through these intracellular receptors and consequently affect toxicokinetics and possible metabolic activation of the receptor ligands and other xenobiotics utilizing similar metabolic pathways. However, it is now apparent that the xenobiotic receptors regulate also many endogenous functions and signalling pathways, and xenobiotic exposure thus may dysregulate an array of fundamental cell functions. This MiniReview surveys and discusses the multifaceted roles of xenobiotic receptors, for which CYP induction may serve as the first alert and possibly a biomarker for exposure to xenobiotics. With the current emergence of the adverse outcome pathway (AOP) concept, these receptors are being and will be assigned as molecular initiating events or key events in numerous discrete toxicity pathways.

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The aim of this study was to analyze angiographic findings and the presence and topography of cerebral ischemic and/or hemorrhagic lesions in cerebral CT or MRI, and to assess the long-term clinical outcome of a series of 136 consecutive cervicocephalic artery dissection (CCAD) patients. Pulsatile tinnitus was evaluated as a symptom of CCAD. Medical records and films were reviewed retrospectively. Irregular stenosis was found in angiography in 50% and occlusion in 33% of the dissected cervicocephalic arteries. Irregular stenosis normalized in 81% and occlusion recanalized in 34%. Other findings, such as pseudoaneurysms, intimal flaps, double lumens, and irregular dilatations were rare and often remained unchanged in follow-up. Pulsatile tinnitus was a presenting symptom in 12% of the CCAD patients, but the majority of patients had concomitant head or neck pain, ischemic brain symptoms, Horner’s syndrome, or cranial neuropathies. Of the 131 patients who underwent brain imaging, 73 (56%) had signs of infarction in cerebral CT or MRI. Occlusion of the dissected vessel was accompanied by infarction in 76%, irregular stenosis in 40%, and other findings only rarely. Of the anterior circulation infarctions, 95% (39/41) were territorial, subcortical, or territorial infarctions with fragmentation and could thus be considered embolic. Subarachnoid hemorrhage was found in CT in 5 of the 22 patients (23%) with intracranial dissection. The patient’s long-term clinical outcome was assessed using two methods: a classification into categories based on neurological symptoms and defects and the modified Rankin Scale (mRS). Of the 136 CCAD patients, 60% recovered with no or mild disability and 79% scored 0–2 on mRS. In the case of dissection of one or more cervicocephalic arteries without occlusion, the figures were 75% and 89%. In the case of occlusive dissection of one or more arteries, only about 35% of the patients recovered well, having no or mild disability, and 61% scored 0–2 on mRS. No significant differences were seen in recovery after intra- and extracranial dissections. In conclusion: irregular stenosis, which is the most common angiographic finding in CCAD, is associated with brain infarction less frequently than occlusion, and the long-term clinical outcome is good in most cases. Occlusion of the dissected vessel causes more brain infarctions, and only about 35% of the patients recover well, having no or mild disability. More than 10% of CCAD patients have pulsatile tinnitus as a presenting, and sometimes the only symptom.

The computational approach is one of the newest and fastest developing techniques in pharmacokinetics, ADME (absorption, distribution, metabolism, excretion) evaluation, drug discovery and toxicity. However, to date, the software packages devoted to ADME prediction, especially of metabolism, have not yet been adequately validated and still require improvements to be effective. Most are 'open' systems, under constant evolution and able to incorporate rapidly, and often easily, new information from user or developer databases. Quantitative in silico predictions are now possible for several pharmacokinetic (PK) parameters, particularly absorption and distribution. The emerging consensus is that the predictions are no worse than those made using in vitro tests, with the decisive advantage that much less investment in technology, resources and time is needed. In addition, and of critical importance, it is possible to screen virtual compounds. Some packages are able to handle thousands of molecules in a few hours. However, common experience shows that, in part at least for essentially irrational reasons, there is currently a lack of confidence in these approaches. An effort should be made by the software producers towards more transparency, in order to improve the confidence of their consumers. It seems highly probable that in silico approaches will evolve rapidly, as did in vitro methods during the last decade. Past experience with the latter should be helpful in avoiding repetition of similar errors and in taking the necessary steps to ensure effective implementation. A general concern is the lack of access to the large amounts of data on compounds no longer in development, but still kept secret by the pharmaceutical industry. Controlled access to these data could be particularly helpful in validating new in silico approaches. © 2002 Elsevier Science B.V. All rights reserved.

The purpose of this review is to describe the present state of knowledge regarding host susceptibility factors that may determine the occurrence, development and severity of interstitial lung disease (ILD) caused by exogenous agents. First, host susceptibility may pertain to differences in the delivery and/or persistence of the noxious agent in the lung. The deposition and clearance of inhaled particles or fibres may vary depending on innate anatomical or physiological characteristics, and on acquired changes, such as nasal disease or smoking-induced alterations. Genetically- or environmentally-induced interindividual differences in the expression of pulmonary biotransformation enzymes may form the basis for, or contribute to the risk of, drug-induced interstitial lung disease. Secondly, there are genetic and acquired variations in various enzymatic and nonenzymatic defence systems that protect cells and tissues against oxidative stress, which is often involved in the pathogenesis of interstitial lung disease caused by particles, fibres, metals, organic agents and drugs. Thirdly, the occurrence of immunological sensitization is dependent on both genetic and environmental factors. This has been demonstrated in chronic beryllium lung disease and in hypersensitivity pneumonitis. Fourthly, the propensity of individuals to develop particular types of inflammation, such as granulomas, is probably under genetic control. The regulation and resolution of inflammation and fibrogenesis caused by dust particles are also partly determined by genetic factors, involving cytokine networks and growth factors. In conclusion, although the issue of genetics pervades the entire discussion of host susceptibility, genes are not the only determinants of health and disease. Environmental factors may be equally important in shaping host susceptibility. Therefore, research must be focused on both the genetic bases and the environmental determinants of interstitial lung disease, in order to provide mechanism-based prevention strategies, early detection of, and improved therapy for these conditions.

The maintenance of the major hepatic cytochrome P450 (CYP) enzymes has been studied in precision-cut human liver slices cultured for up to 72 h in supplemented RPMI 1640 medium. The relative apoprotein levels of 11 CYP enzymes were determined using a panel of antipeptide antibodes. In addition, 7-ethoxyresorufin O-deethylase, tolbutamide methylhydroxylase, debrisoquine 4-hydroxylase, and testosterone 6β-hydroxylase activities were determined as enzymatic markers for CYP1A2, CYP2C9, CYP2D6, and CYP3A4, respectively. There was a large variation in the rate of decline of different CYP levels with time in culture. Based on the rate of decrease, CYP enzymes could be separated into two groups, with CYP2C9, CYP2D6, CYP3A4, and CYP4A11 being relatively stable (half-lives between 70 and 104 h), compared with CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C19, CYP2E1, and CYP3A5, which were relatively unstable (half-lives between 23 and 36 h). Enzyme activities decreased at rates similar to those of their corresponding apoproteins. There was also a large difference in the stability of individual CYP enzymes from different liver donors, particularly for the most rapidly declining CYP enzymes. Similar losses of CYP enzymes were found when human river slices were cultured in supplemented Williams' medium E for 72 h, except that CYP2E1 apoprotein levels were better maintained. Because of the variable decreases of CYP enzymes, xenobiotic metabolism studies are best performed with freshly cut rather than cultured human liver slices. Chemicals/CAS: Culture Media; Cytochrome P-450 Enzyme System, 9035-51-2; Isoenzymes