RESUMO
PFASs are defined as substances that contain at least one fully fluorinated methyl (CF3-) or methylene (-CF2-) carbon atom. The excellent technical properties of members of the PFAS group have led to their use in a wide range of applications. The substance group comprises more than 10,000 individual compounds. A variety of adverse effects has been described for single substances. For the majority of the PFASs, neither toxicokinetic data nor effect data is available. Hence, because of the small number of PFASs for which a full toxicological profile is available, grouping based on the existing data is not feasible. A critical problem of PFASs and their degradation products is the very high persistence, which clearly fulfils the criterion for the substance property Very Persistent (vP) according to Annex XIII of the REACH Regulation. Because of this property the European Commission is planning to take action. Defining suitable subgroups appears to be a scientifically based approach. However, to reach this goal, large data gaps would have to be closed which would take up to centuries, a time-frame, which is not defendable with respect to potential irreversible harm. Because of the time pressure resulting from the potential irreversible harm, the precautionary principle has been selected as an appropriate tool to handle PFASs and in the restriction proposal PFASs are treated as one group. This approach is justified in the view of the advisory committee of the German Society for Toxicology. ECHA's proposal received a lot of attention in the public. However, communication so far has obviously led to the misunderstanding of a proven health hazard for all PFASs. Communication should explain the justification of the broad inclusion of substances as being based on the precautionary principle. Data gaps versus current knowledge need to be clearly communicated; communication should also include the possibility for derogation of essential use. It should address the issue of suitable substitutes to avoid unintended health consequences; and it should mention that existing persistent environmental contamination calls for developing innovation in remediation techniques.
Assuntos
Fluorocarbonos , Poluentes Químicos da Água , Fluorocarbonos/toxicidade , Poluição AmbientalRESUMO
Amiodarone is an antiarrhythmic agent inducing adverse effects on the nervous system, among others. We applied physiologically based pharmacokinetic (PBPK) modeling combined with benchmark dose modeling to predict, based on published in vitro data, the in vivo dose of amiodarone which may lead to adverse neurological effects in patients. We performed in vitro-in vivo extrapolation (IVIVE) from concentrations measured in the cell lysate of a rat brain 3D cell model using a validated human PBPK model. Among the observed in vitro effects, inhibition of choline acetyl transferase (ChAT) was selected as a marker for neurotoxicity. By reverse dosimetry, we transformed the in vitro concentration-effect relationship into in vivo effective human doses, using the calculated in vitro area under the curve (AUC) of amiodarone as the pharmacokinetic metric. The upper benchmark dose (BMDU) was calculated and compared with clinical doses eliciting neurological adverse effects in patients. The AUCs in the in vitro brain cell culture after 14-day repeated dosing of nominal concentration equal to 1.25 and 2.5 µM amiodarone were 1.00 and 1.99 µg*h/mL, respectively. The BMDU was 385.4 mg for intravenous converted to 593 mg for oral application using the bioavailability factor of 0.65 as reported in the literature. The predicted dose compares well with neurotoxic doses in patients supporting the hypothesis that impaired ChAT activity may be related to the molecular/cellular mechanisms of amiodarone neurotoxicity. Our study shows that predicting effects from in vitro data together with IVIVE can be used at the initial stage for the evaluation of potential adverse drug reactions and safety assessment in humans.
Assuntos
Amiodarona/toxicidade , Antiarrítmicos/toxicidade , Modelos Biológicos , Síndromes Neurotóxicas/etiologia , Amiodarona/administração & dosagem , Amiodarona/farmacocinética , Animais , Antiarrítmicos/administração & dosagem , Antiarrítmicos/farmacocinética , Área Sob a Curva , Disponibilidade Biológica , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Relação Dose-Resposta a Droga , Humanos , Técnicas In Vitro , Síndromes Neurotóxicas/fisiopatologia , Ratos , Distribuição Tecidual , Testes de ToxicidadeRESUMO
Lead (Pb) exposure of consumers and the environment has been reduced over the past decades. Despite all measures taken, immission of Pb onto agricultural soils still occurs, with fertilizer application, lead shot from hunting activities, and Pb from air deposition representing major sources. Little is known about the intermediate and long-term consequences of these emissions. To gain more insight, we established a mathematical model that considers input from fertilizer, ammunition, deposition from air, uptake of Pb by crops, and wash-out to simulate the resulting Pb concentrations in soil over extended periods. In a further step, human oral exposure by crop-based food was simulated and blood concentrations were derived to estimate the margin of exposure to Pb-induced toxic effects. Simulating current farming scenarios, a new equilibrium concentration of Pb in soil would be established after several centuries. Developmental neurotoxicity represents the most critical toxicological effect of Pb for humans. According to our model, a Pb concentration of ~ 5 mg/kg in agricultural soil leads to an intake of approximately 10 µg Pb per person per day by the consumption of agricultural products, the dose corresponding to the tolerable daily intake (TDI). Therefore, 5 mg Pb/kg represents a critical concentration in soil that should not be exceeded. Starting with a soil concentration of 0.1 mg/kg, the current control level for crop fields, our simulation predicts periods of ~ 50 and ~ 175 years for two Pb immission scenarios for mass of Pb per area and year [scenario 1: ~ 400 g Pb/(ha × a); scenario 2: ~ 175 g Pb/(ha × a)], until the critical concentration of ~ 5 mg/kg Pb in soil would be reached. The two scenarios, which differ in their Pb input via fertilizer, represent relatively high but not unrealistic Pb immissions. From these scenarios, we calculated that the annual deposition of Pb onto soil should remain below ~ 100 g/(ha × a) in order not to exceed the critical soil level of 5 mg/kg. We propose as efficient measures to reduce Pb input into agricultural soil to lower the Pb content of compost and to use alternatives to Pb ammunition for hunting.
Assuntos
Produtos Agrícolas/metabolismo , Fertilizantes/efeitos adversos , Contaminação de Alimentos , Intoxicação por Chumbo/etiologia , Chumbo/efeitos adversos , Modelos Teóricos , Solo/química , Qualidade de Produtos para o Consumidor , Produção Agrícola , Produtos Agrícolas/crescimento & desenvolvimento , Monitoramento Ambiental , Fazendas , Fertilizantes/análise , Abastecimento de Alimentos , Humanos , Chumbo/análise , Chumbo/sangue , Intoxicação por Chumbo/sangue , Intoxicação por Chumbo/diagnóstico , Medição de Risco , Fatores de Risco , Fatores de TempoRESUMO
In vitro studies are increasingly proposed to replace in vivo toxicity testing of substances. We set out to apply physiologically based pharmacokinetic (PBPK) modeling to predict the in vivo dose of amiodarone that leads to the same concentration-time profile in the supernatant and the cell lysate of cultured primary human hepatic cells (PHH). A PBPK human model was constructed based on the structure and tissue distribution of amiodarone in a rat model and using physiological human parameters. The predicted concentration-time profile in plasma was in agreement with human experimental data with the unbound fraction of amiodarone in plasma crucially affecting the goodness-of-fit. Using the validated kinetic model, we subsequently described the in vitro concentration-time data of amiodarone in PHH culture. However, this could be only appropriately modeled under conditions of zero protein binding and the very low clearance of the in vitro system in PHH culture. However, these represent unphysiological conditions and, thus, the main difference between the in vivo and the in vitro systems. Our results reveal that, for meaningful quantitative extrapolation from in vitro to in vivo conditions in PBPK studies, it is essential to avoid non-intended differences between these conditions. Specifically, clearance and protein binding, as demonstrated in our analysis of amiodarone modeling, are important parameters to consider.
Assuntos
Amiodarona/toxicidade , Testes de Toxicidade/métodos , Vasodilatadores/toxicidade , Animais , Simulação por Computador , Hepatócitos , Humanos , Técnicas In Vitro , Cinética , Fígado , Modelos Biológicos , Ligação Proteica , Ratos , Distribuição TecidualRESUMO
The antihistaminic drug methapyrilene was withdrawn from the market in 1979 because of hepatocarcinogenicity in rats. Since then, the drug has been used as a model hepatotoxin especially for transcriptomic analyses using material from in vivo studies. Much less transcriptomics data are available from in vitro studies, and no studies have investigated proteomic effects of methapyrilene in vitro. Thus, the present study was aimed to characterize the proteomic response of primary rat hepatocytes to methapyrilene, to broaden our knowledge on the molecular mechanisms of methapyrilene toxicity, and to compare the results of collagen sandwich-cultured hepatocytes to in vivo data. In vitro methapyrilene concentrations (0.39 µM, 6.25 µM, and 100 µM) were chosen to cover an in vivo-relevant range. Based on published pharmacokinetic data they correspond to concentrations in portal vein blood for previously in vivo-tested doses of methapyrilene, up to a concentration showing slight cytotoxicity. Analysis of proteomic alterations by two-dimensional gel electrophoresis and mass-spectrometric protein identification demonstrated consistent and concentration-dependent effects of methapyrilene, in particular on mitochondrial proteins. Data suggest substantial deregulation of amino acid and ammonia metabolism and effects on mitochondrial energy supply pathways. The effects identified in vitro concur well with into previous in vivo observations. Several effects, for example, the influence of methapyrilene on S-adenosylmethionine metabolism, have not been described previously. The data suggest that already non-toxic concentrations of methapyrilene alter components of the intermediary metabolism, such as branched-chain amino acid metabolism, as well as urea and tricarboxylic cycle enzymes. In summary, data substantially add to our knowledge on molecular mechanisms of methapyrilene hepatotoxicity at the protein level.
Assuntos
Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Metapirileno/toxicidade , Proteínas/metabolismo , Animais , Técnicas de Cultura de Células/métodos , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Biologia Computacional , Perfilação da Expressão Gênica , Antagonistas dos Receptores Histamínicos H1/toxicidade , Masculino , Espectrometria de Massas , Proteínas/genética , Proteômica/métodos , Ratos Wistar , Testes de Toxicidade/métodosRESUMO
Drug-induced liver injury (DILI) cannot be accurately predicted by animal models. In addition, currently available in vitro methods do not allow for the estimation of hepatotoxic doses or the determination of an acceptable daily intake (ADI). To overcome this limitation, an in vitro/in silico method was established that predicts the risk of human DILI in relation to oral doses and blood concentrations. This method can be used to estimate DILI risk if the maximal blood concentration (Cmax) of the test compound is known. Moreover, an ADI can be estimated even for compounds without information on blood concentrations. To systematically optimize the in vitro system, two novel test performance metrics were introduced, the toxicity separation index (TSI) which quantifies how well a test differentiates between hepatotoxic and non-hepatotoxic compounds, and the toxicity estimation index (TEI) which measures how well hepatotoxic blood concentrations in vivo can be estimated. In vitro test performance was optimized for a training set of 28 compounds, based on TSI and TEI, demonstrating that (1) concentrations where cytotoxicity first becomes evident in vitro (EC10) yielded better metrics than higher toxicity thresholds (EC50); (2) compound incubation for 48 h was better than 24 h, with no further improvement of TSI after 7 days incubation; (3) metrics were moderately improved by adding gene expression to the test battery; (4) evaluation of pharmacokinetic parameters demonstrated that total blood compound concentrations and the 95%-population-based percentile of Cmax were best suited to estimate human toxicity. With a support vector machine-based classifier, using EC10 and Cmax as variables, the cross-validated sensitivity, specificity and accuracy for hepatotoxicity prediction were 100, 88 and 93%, respectively. Concentrations in the culture medium allowed extrapolation to blood concentrations in vivo that are associated with a specific probability of hepatotoxicity and the corresponding oral doses were obtained by reverse modeling. Application of this in vitro/in silico method to the rat hepatotoxicant pulegone resulted in an ADI that was similar to values previously established based on animal experiments. In conclusion, the proposed method links oral doses and blood concentrations of test compounds to the probability of hepatotoxicity.
Assuntos
Doença Hepática Induzida por Substâncias e Drogas/diagnóstico , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/diagnóstico , Administração Oral , Algoritmos , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Simulação por Computador , Expressão Gênica/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Humanos , Técnicas In Vitro , Dose Máxima Tolerável , Preparações Farmacêuticas/administração & dosagem , Preparações Farmacêuticas/sangue , Farmacocinética , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Máquina de Vetores de SuporteRESUMO
PURPOSE: The pivotal trials for stroke prevention in non-valvular atrial fibrillation (NVAF) compared rivaroxaban, dabigatran, and apixaban with warfarin, as did most claims-based studies. Comparisons with phenprocoumon, the most frequently used vitamin K antagonist (VKA) in Germany, are scarce. METHODS: Risk of bleeding, ischemic stroke, and all-cause mortality in patients with NVAF were analyzed using data for 2010 to 2014 from a large German claims database. New users of oral anticoagulants from January 2012 to December 2013 were included and observed over 1 year. Baseline characteristics were adjusted using propensity score matching and logistic regression. Several sensitivity analyses were carried out. RESULTS: Fifty-nine thousand four hundred forty-nine rivaroxaban, 23,654 dabigatran, 4894 apixaban, and 87,997 matched phenprocoumon users were included. Adjusted hazard ratios (95% confidence intervals) compared with phenprocoumon were as follows: hospitalized bleedings: rivaroxaban 1.04 (0.97; 1.11), dabigatran 0.87 (0.77; 0.98), and apixaban 0.65 (0.50; 0.86); ischemic stroke: rivaroxaban 1.05 (0.94; 1.17), dabigatran 1.14 (0.96; 1.35), and apixaban 1.84 (1.20; 2.84); all-cause mortality: rivaroxaban 1.17 (1.11; 1.22), dabigatran 1.04 (0.95; 1.13), and apixaban 1.14 (0.97; 1.34). CONCLUSIONS: With rivaroxaban, no significant differences were observed compared to phenprocoumon with regard to hospitalized bleedings or ischemic strokes. Dabigatran was associated with fewer bleedings and a similar risk of ischemic strokes compared to phenprocoumon. Apixaban was also associated with fewer bleedings but was unexpectedly associated with more ischemic strokes, possibly reflecting selective prescribing. The association of rivaroxaban with higher all-cause mortality unrelated to bleedings or strokes has been described previously but remains to be explained.
Assuntos
Anticoagulantes/uso terapêutico , Fibrilação Atrial/tratamento farmacológico , Femprocumona/uso terapêutico , Acidente Vascular Cerebral/prevenção & controle , Administração Oral , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticoagulantes/efeitos adversos , Fibrilação Atrial/complicações , Fibrilação Atrial/mortalidade , Isquemia Encefálica/epidemiologia , Isquemia Encefálica/prevenção & controle , Bases de Dados Factuais , Feminino , Seguimentos , Alemanha , Hemorragia/induzido quimicamente , Hemorragia/epidemiologia , Humanos , Masculino , Pessoa de Meia-Idade , Femprocumona/efeitos adversos , Acidente Vascular Cerebral/epidemiologia , Vitamina K/antagonistas & inibidores , Adulto JovemRESUMO
Adverse drug reactions (ADRs) are a common problem in daily clinical practice and they may in part result from medication errors. According to the extended interpretation in the new European pharmacovigilance guideline, medication error-related reactions are classified as ADRs. Therefore, the pharmacovigilance system needs to be adjusted to record medication errors. As a partner in the German pharmacovigilance system, the Drug Commission of the German Medical Association (DCGMA) has set up a project for developing a subsystem for the recording and assessment of medication errors within the existing spontaneous reporting system for ADRs. The aim of the project was to evaluate the feasibility of recording and assessing medication errors within the existing structures and to investigate whether it is possible to deduce risk-reducing strategies from the information obtained by the case reports. In the present narrative review, the experience of the DCGMA with the recording and assessment of medication errors is described. The conclusions and recommendations from the analysis of the reports of medication errors show how they can be used to improve medication safety. The project has closed a gap in pharmacovigilance.
Assuntos
Sistemas de Notificação de Reações Adversas a Medicamentos , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Notificação de Abuso , Erros de Medicação , Alemanha , Humanos , FarmacovigilânciaRESUMO
OBJECTIVE: Flupirtine is a nonopioid analgesic with regulatory approval in a number of European countries. Because of the risk of serious liver injury, its use is now limited to short-term pain management. We aimed to identify genetic risk factors for flupirtine-related drug-induced liver injury (DILI) as these are unknown. MATERIALS AND METHODS: Six flupirtine-related DILI patients from Germany were included in a genome-wide association study (GWAS) involving a further 614 European cases of DILI because of other drugs and 10,588 population controls. DILI was diagnosed by causality assessment and expert review. Human leucocyte antigen (HLA) and single nucleotide polymorphism genotypes were imputed from the GWAS data, with direct HLA typing performed on selected cases to validate HLA predictions. Four replication cases that were unavailable for the GWAS were genotyped by direct HLA typing, yielding an overall total of 10 flupirtine DILI cases. RESULTS: In the six flupirtine DILI cases included in the GWAS, we found a significant enrichment of the DRB1*16:01-DQB1*05:02 haplotype compared with the controls (minor allele frequency cases 0.25 and minor allele frequency controls 0.013; P=1.4 × 10(-5)). We estimated an odds ratio for haplotype carriers of 18.7 (95% confidence interval 2.5-140.5, P=0.002) using population-specific HLA control data. The result was replicated in four additional cases, also with a haplotype frequency of 0.25. In the combined cohort (six GWAS plus four replication cases), the haplotype was also significant (odds ratio 18.7, 95% confidence interval 4.31-81.42, P=6.7 × 10(-5)). CONCLUSION: We identified a novel HLA class II association for DILI, confirming the important contribution of HLA genotype towards the risk of DILI generally.
Assuntos
Aminopiridinas/efeitos adversos , Doença Hepática Induzida por Substâncias e Drogas/genética , Cadeias beta de HLA-DQ/genética , Cadeias HLA-DRB1/genética , Adulto , Idoso , Doença Hepática Induzida por Substâncias e Drogas/etiologia , Feminino , Estudo de Associação Genômica Ampla , Humanos , Masculino , Pessoa de Meia-Idade , Polimorfismo de Nucleotídeo ÚnicoRESUMO
PURPOSE: In 1986, the risk of agranulocytosis prompted German authorities to restrict the indications for metamizole use. After an initial decline, prescriptions increased from <20 million defined daily doses in 1990 to >140 million in 2012. Concurrently, spontaneous reports of agranulocytosis increased from about 10 in 1990 to >50 in 2012. In this study, reports were analyzed to identify targets for risk minimization measures. METHODS: Reports of suspected metamizole-induced agranulocytosis (neutrophils < 0.5 × 10(9) cells/l) between 1990 and 2012 were identified in the German spontaneous reporting database. Cases for which original reporting documents were available were eligible for analysis. Patient characteristics, indication, clinical course, and outcome were assessed. RESULTS: One hundred sixty-one reports were analyzed. The mean age of the patients was 56.8 years (11-93) and 64.6 % were female. Off-label use was identified in about 25 % of cases. Neutrophils fell below 100/µl in 63 and intercurrent infections developed in 109 cases. Thirty-eight patients (23.6 %) died. In two thirds of the cases, agranulocytosis occurred within 6 weeks of permanent or intermittent metamizole treatment, in 30.5 % within 7 days, including 18 cases of immediate onset after the first or second administration. CONCLUSION: The reported cases show severe clinical courses and are, to some extent, a result of off-label use. Due to the absence of individual risk factors and presence of variable onset patterns, risk minimization measures should focus on restricting use to defined clinical situations and providing concise risk information for patients and healthcare professionals.
Assuntos
Sistemas de Notificação de Reações Adversas a Medicamentos , Agranulocitose/induzido quimicamente , Dipirona/efeitos adversos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Anti-Inflamatórios não Esteroides/efeitos adversos , Criança , Uso de Medicamentos/tendências , Feminino , Alemanha , Humanos , Masculino , Pessoa de Meia-Idade , Uso Off-Label/estatística & dados numéricos , Adulto JovemAssuntos
Fluorocarbonos , Animais , Feminino , Humanos , Fígado , Masculino , Proteômica , Ratos , Medição de Risco , Caracteres SexuaisRESUMO
The TTC concept uses toxicological data from animal testing to derive generic human exposure threshold values (TTC values), below which the risk of adverse effects on human health is considered to be low. It uses distributions of no-observed-adverse-effect levels (NOAELs) for substances. The 5th percentile value is divided by an uncertainty factor (100) to give a TTC value. As the toxicological data underpinning the TTC concept are from tests with oral exposure, the exposure is to be understood as an external oral exposure. For risk assessment of substances with a low absorption (by the oral route, or through skin), the internal exposure is more relevant than the external exposure. European legislation allows that tests might not be necessary for substances with negligible absorption with low internal exposure. The aim of this work is to derive internal TTC values to allow the TTC concept to be applied to situations of low internal exposure. The external NOAEL of each chemical of three databases (Munro, ELINCS, Food Contact Materials) was multiplied by the bioavailability of the individual chemical. Oral bioavailability was predicted using an in silico prediction tool (ACD Percepta). After applying a reduced uncertainty factor of 25, we derived internal TTC values. For Cramer class I, the internal TTC values are 6.9 µg/kg bw/d (90 % confidence interval: 3.8-11.5 mg/kg bw/d); for Cramer class II/III 0.1 µg/kg bw/d (90 % confidence interval: 0.08-0.14 µg/kg bw/d).
Assuntos
Bases de Dados Factuais , Níveis Máximos Permitidos , Testes de Toxicidade/métodos , Xenobióticos/toxicidade , Administração Oral , Disponibilidade Biológica , Europa (Continente) , Regulamentação Governamental , Nível de Efeito Adverso não Observado , Valores de Referência , Medição de Risco , Testes de Toxicidade/normas , Xenobióticos/classificação , Xenobióticos/farmacocinéticaRESUMO
Arsenic is a human carcinogen that occurs ubiquitously in soil and water. Based on epidemiological studies, a benchmark dose (lower/higher bound estimate) between 0.3 and 8 µg/kg bw/day was estimated to cause a 1 % increased risk of lung, skin and bladder cancer. A recently published study by EFSA on dietary exposure to inorganic arsenic in the European population reported 95th percentiles (lower bound min to upper bound max) for different age groups in the same range as the benchmark dose. For toddlers, a highly exposed group, the highest values ranged between 0.61 and 2.09 µg arsenic/kg bw/day. For all other age classes, the margin of exposure is also small. This scenario calls for regulatory action to reduce arsenic exposure. One priority measure should be to reduce arsenic in food categories that contribute most to exposure. In the EFSA study the food categories 'milk and dairy products,' 'drinking water' and 'food for infants' represent major sources of inorganic arsenic for infants and also rice is an important source. Long-term strategies are required to reduce inorganic arsenic in these food groups. The reduced consumption of rice and rice products which has been recommended may be helpful for a minority of individuals consuming unusually high amounts of rice. However, it is only of limited value for the general European population, because the food categories 'grain-based processed products (non rice-based)' or 'milk and dairy products' contribute more to the exposure with inorganic arsenic than the food category 'rice.' A balanced regulatory activity focusing on the most relevant food categories is required. In conclusion, exposure to inorganic arsenic represents a risk to the health of the European population, particularly to young children. Regulatory measures to reduce exposure are urgently required.
Assuntos
Arsênio/análise , Contaminação de Alimentos/análise , Comportamento de Redução do Risco , Adolescente , Fatores Etários , Arsênio/toxicidade , Criança , Pré-Escolar , Laticínios/análise , Água Potável/análise , Água Potável/química , Exposição Ambiental/efeitos adversos , Exposição Ambiental/prevenção & controle , Contaminação de Alimentos/prevenção & controle , Humanos , Lactente , Oryza/químicaRESUMO
In general, xenobiotic metabolizing enzymes (XMEs) are expressed in lower levels in the extrahepatic tissues than in the liver, making the former less relevant for the clearance of xenobiotics. Local metabolism, however, may lead to tissue-specific adverse responses, e.g. organ toxicities, allergies or cancer. This review summarizes the knowledge on the expression of phase I and phase II XMEs and transporters in extrahepatic tissues at the body's internal-external interfaces. In the lung, CYPs of families 1, 2, 3 and 4 and epoxide hydrolases are important phase I enzymes, while conjugation is less relevant. In skin, phase I-related enzymatic reactions are considered less relevant. Predominant skin XMEs are phase II enzymes, whereby glucuronosyltransferases (UGT) 1, glutathione-S-transferase (GST) and N-acetyltransferase (NAT) 1 are important for detoxification. The intestinal epithelium expresses many transporters and phase I XME with high levels of CYP3A4 and CYP3A5 and phase II metabolism is mainly related to UGT, NAT and Sulfotransferases (SULT). In the kidney, conjugation reactions and transporters play a major role for excretion processes. In the bladder, CYPs are relevant and among the phase II enzymes, NAT1 is involved in the activation of bladder carcinogens. Expression of XMEs is regulated by several mechanisms (nuclear receptors, epigenetic mechanisms, microRNAs). However, the understanding why XMEs are differently expressed in the various tissues is fragmentary. In contrast to the liver - where for most XMEs lower expression is demonstrated in early life - the XME ontogeny in the extrahepatic tissues remains to be investigated.
Assuntos
Transporte Biológico/fisiologia , Xenobióticos/metabolismo , Animais , Sistema Enzimático do Citocromo P-450/metabolismo , Humanos , Proteínas de Membrana Transportadoras/metabolismoRESUMO
There is a need of guidance on how local irritancy data should be incorporated into risk assessment procedures, particularly with respect to the derivation of occupational exposure limits (OELs). Therefore, a board of experts from German committees in charge of the derivation of OELs discussed the major challenges of this particular end point for regulatory toxicology. As a result, this overview deals with the question of integrating results of local toxicity at the eyes and the upper respiratory tract (URT). Part 1 describes the morphology and physiology of the relevant target sites, i.e., the outer eye, nasal cavity, and larynx/pharynx in humans. Special emphasis is placed on sensory innervation, species differences between humans and rodents, and possible effects of obnoxious odor in humans. Based on this physiological basis, Part 2 describes a conceptual model for the causation of adverse health effects at these targets that is composed of two pathways. The first, "sensory irritation" pathway is initiated by the interaction of local irritants with receptors of the nervous system (e.g., trigeminal nerve endings) and a downstream cascade of reflexes and defense mechanisms (e.g., eyeblinks, coughing). While the first stages of this pathway are thought to be completely reversible, high or prolonged exposure can lead to neurogenic inflammation and subsequently tissue damage. The second, "tissue irritation" pathway starts with the interaction of the local irritant with the epithelial cell layers of the eyes and the URT. Adaptive changes are the first response on that pathway followed by inflammation and irreversible damages. Regardless of these initial steps, at high concentrations and prolonged exposures, the two pathways converge to the adverse effect of morphologically and biochemically ascertainable changes. Experimental exposure studies with human volunteers provide the empirical basis for effects along the sensory irritation pathway and thus, "sensory NOAEChuman" can be derived. In contrast, inhalation studies with rodents investigate the second pathway that yields an "irritative NOAECanimal." Usually the data for both pathways is not available and extrapolation across species is necessary. Part 3 comprises an empirical approach for the derivation of a default factor for interspecies differences. Therefore, from those substances under discussion in German scientific and regulatory bodies, 19 substances were identified known to be human irritants with available human and animal data. The evaluation started with three substances: ethyl acrylate, formaldehyde, and methyl methacrylate. For these substances, appropriate chronic animal and a controlled human exposure studies were available. The comparison of the sensory NOAEChuman with the irritative NOAECanimal (chronic) resulted in an interspecies extrapolation factor (iEF) of 3 for extrapolating animal data concerning local sensory irritating effects. The adequacy of this iEF was confirmed by its application to additional substances with lower data density (acetaldehyde, ammonia, n-butyl acetate, hydrogen sulfide, and 2-ethylhexanol). Thus, extrapolating from animal studies, an iEF of 3 should be applied for local sensory irritants without reliable human data, unless individual data argue for a substance-specific approach.
Assuntos
Poluentes Ocupacionais do Ar/toxicidade , Irritantes/toxicidade , Exposição Ocupacional/análise , Poluentes Ocupacionais do Ar/química , Poluentes Ocupacionais do Ar/farmacocinética , Olho/efeitos dos fármacos , Humanos , Irritantes/química , Irritantes/farmacocinética , Nível de Efeito Adverso não Observado , Exposição Ocupacional/efeitos adversos , Sistema Respiratório/efeitos dos fármacos , Medição de Risco , Limiar Sensorial , Solubilidade , Níveis Máximos PermitidosRESUMO
Information on toxicokinetics is critical for animal-free human risk assessment. Human external exposure must be translated into human tissue doses and compared with in vitro actual cell exposure associated to effects (in vitro-in vivo comparison). Data on absorption, distribution, metabolism and excretion in humans (ADME) could be generated using in vitro and QSAR tools. Physiologically-based toxicokinetic (PBTK) computer modelling could serve to integrate disparate in vitro and in silico findings. However, there are only few freely-available PBTK platforms currently available. And although some ADME parameters can be reasonably estimated in vitro or in silico, important gaps exist. Examples include unknown or limited applicability domains and lack of (high-throughput) tools to measure penetration of barriers, partitioning between blood and tissues and metabolic clearance. This paper is based on a joint EPAA--EURL ECVAM expert meeting. It provides a state-of-the-art overview of the availability of PBTK platforms as well as the in vitro and in silico methods to parameterise basic (Tier 1) PBTK models. Five high-priority issues are presented that provide the prerequisites for wider use of non-animal based PBTK modelling for animal-free chemical risk assessment.
Assuntos
Poluentes Ambientais/farmacocinética , Poluentes Ambientais/toxicidade , Modelos Biológicos , Alternativas aos Testes com Animais , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Exposição Ambiental/efeitos adversos , Humanos , Farmacocinética , Medição de RiscoRESUMO
The EFSA Panel on Food Additive and Flavourings (FAF Panel) provides a scientific opinion on the safety of soy leghemoglobin from genetically modified Komagataella phaffii as a food additive in accordance with Regulation (EC) No 1331/2008. The proposed food additive, LegH Prep, is intended to be used as a colour in meat analogue products. The yeast Komagataella phaffii strain MXY0541 has been genetically modified to produce soy leghemoglobin; the safety of the genetic modification is under assessment by the EFSA GMO Panel (EFSA-GMO-NL-2019-162). The amount of haem iron provided by soy leghemoglobin from its proposed uses in meat analogue products is comparable to that provided by similar amounts of different types of meat. The exposure to iron from the proposed food additive, both at the mean and 95th percentile exposure, will be below the 'safe levels of intake' established by the NDA Panel for all population groups. Considering that the components of the proposed food additive will be digested to small peptide, amino acids and haem B; the recipient (non GM) strain qualifies for qualified presumption of safety status; no genotoxicity concern has been identified and no adverse effects have been identified at the highest dose tested in the available toxicological studies, the Panel concluded that there was no need to set a numerical acceptable daily intake (ADI) and that the food additive does not raise a safety concern at the proposed use in food category 12.9 and maximum use level. The Panel concluded that the use of soy leghemoglobin from genetically modified Komagataella phaffii MXY0541 as a new food additive does not raise a safety concern at the proposed use and use level. This safety evaluation of the proposed food additive remains provisional subject to the ongoing safety assessment of the genetic modification of the production strain by the GMO Panel (EFSA-GMO-NL-2019-162).
RESUMO
The EFSA Panel on Food Additives and Flavourings was requested to evaluate 14 flavouring substances assigned to the Flavouring Group Evaluation 80 (FGE.80), using the Procedure as outlined in the Commission Regulation (EC) No 1565/2000. Thirteen substances have already been considered in FGE.80 and its revision and in FGE.96 [FL-no: 10.005, 10.024, 10.025, 10.050, 10.061, 10.069, 10.070, 10.072, 10.169, 13.009, 13.012, 13.161 and 16.055]. The remaining flavouring substance 3a,4,5,7a-tetrahydro-3,6-dimethylbenzofuran-2(3H)-one [FL-no: 10.057] has been cleared with respect to genotoxicity in FGE.217Rev3 and it is considered in this revision 2 of FGE.80. The substance [FL-no: 10.057] was evaluated through a stepwise approach that integrates information on the structure-activity relationships, intake from current uses, threshold of toxicological concern (TTC) and available data on metabolism and toxicity. The Panel concluded that [FL-no: 10.057] does not give rise to safety concerns at its levels of dietary intake, when estimated on the basis of the 'Maximised Survey-derived Daily Intake' (MSDI) approach. Besides the safety assessment of the flavouring substance, the specifications for the material of commerce have also been considered and the information provided was complete for [FL-no: 10.057]. However, for the flavouring substance [FL-no: 10.057] in the present revision and for eight substances evaluated in previous revisions, the 'modified Theoretical Added Maximum Daily Intakes' (mTAMDIs) values are above the TTC for their structural class (III). For four substances previously evaluated in FGE.80Rev1 and in FGE.96, use levels are still needed to calculate the mTAMDI estimates. Therefore, in total for 13 flavouring substances, data on uses and use levels should be provided to finalise their safety evaluations. For [FL-no: 10.050, 10.069 and 13.161], information on the composition of stereoisomeric mixtures is needed.