In vitro genotoxicity of carcinogenic asarone isomers.

The present study focused on genotoxic properties of the carcinogenic phenylpropanoids α-asarone and ß-asarone, which are found in several herbs and spices, such as Acorus calamus or Acorus gramineus. Cytotoxic and genotoxic effects were determined in human liver carinoma HepG2 cells, in hamster lung fibroblast V79 cells and in human cytochrome P450 1A2 and human sulfotransferase 1C2 transfected V79 cells (tV79). The Alamar blue assay was used to measure cytotoxicity of both isomers prior to the identification of DNA damaging properties by single cell gel electrophoresis (comet assay). Furthermore, the phosphorylation status of the histone H2AX, as a response of DNA double strand breaks, was investigated in HepG2 cells by Western blot analysis and visualized by immunofluorescence microscopy. After 24 h of incubation a significant reduction of cell viability was found. Moreover, both asarone isomers induced DNA strand breaks in V79 cells after 1 h of incubation. In tV79 cells even more pronounced DNA damaging properties were exhibited, whereas in HepG2 cells the compounds were found to be less effective. Furthermore, in tV79 cells a significant increase of formamidopyrimidine-DNA-glycosylase-sensitive sites was observed. DNA strand breaks, induced by aA, were to some extent characterized as DNA double strand breaks. In summary, asarone-induced cytotoxicity and genotoxicity is strongly influenced by the cellular metabolic enzyme status and therefore, a contribution of their respective metabolites to in vitro toxicity can be suggested.

[Lipoid Pneumonia Associated with Lipid-Containing Nasal Sprays and Nose Drops]. / Lipidpneumonie durch Lipid-haltige Nasensprays und -tropfen.

BACKGROUND: Regularly updating the German pharmacopoeia on contemporary preparations DAC/NRF, chapter "Nasal Applications" and the recommendations on "Nasal Oils" as well as "Nasal Ointments and Emulsions", the issue of the risk of lipoid pneumonia associated with the use of plant oils and when compared to mineral oils arose. MATERIAL AND METHODS: We searched different databases: the "Grosse Deutsche Arzneimittelspezialitäten-Taxe" containing all products available in German pharmacies, the Cochrane Library, the pharmacovigilance-database of the BfArM, and Medline to evaluate the benefit/risk-ratio of plant oils in nasal drops and sprays. RESULTS: In German pharmacies, a number of both, mineral oil-containing drugs for nasal application and plant oil-containing medical devices are available. The risk of lipoid pneumonia described for mineral oil-containing nasal products can not entirely be transferred to plant oil-containing products. However, evidence from the literature suggests a risk for lipoid pneumonia, which needs to be considered given the non-proven efficacy of such medical devices in the majority of proposed indications. To minimize risks, recommendations are made for patient groups that should not use lipid-containing nasal products. CONCLUSIONS: Acknowledging the potential lethal outcome of lipoid pneumonia, a demanding diagnosis, and absence of a specific therapy, lipid-containing nasal products should be used only with great caution. Based on the current knowledge, the statements regarding the risk of lipoid pneumonia for lipid-containing nasal products in the DAC/NRF should not be modified.

Detection of pyrrolizidine alkaloids in German licensed herbal medicinal teas.

BACKGROUND: Because of the hepatotoxic, mutagenic, and cancerogenic effects of pyrrolizidine alkaloids (PAs) the German Federal Institute for Risk Assessment (BfR) recommends not to exceed a daily PA intake of 0.007 µg/kg body weight (0.42 µg/60 kg adult). In a recent study conducted by the BfR, up to 5647 µg PA/kg dried herbal material were detected in tea products marketed as food. PURPOSE: The present study aimed at elucidating whether medicinal teas licensed or registered as medicinal products contain PAs as well. STUDY DESIGN: One hundred sixty-nine different commercially available medicinal teas, i.e. 19 nettle (Urtica dioica L.), 12 fennel (Foeniculum vulgare Mill.), 14 chamomile (Matricaria recutita L.), 11 melissa (Melissa officinalis L.) and 4 peppermint (Mentha piperita L.) teas as well as 109 tea mixtures were analyzed for the presence of 23 commercially available PAs. METHOD: LC/MS was used for the determination of the PAs RESULTS: In general, the total PA contents ranging 0-5668 µg/kg. Thirty percent of the tested single-ingredient tea products and 56.9% of the tested medicinal tea mixtures were found to contain PA concentrations above the limit of quantification (LOQ) of 10 µg/kg. In 11 medicinal teas PA contents >300 µg/kg dry herb were determined thus exceeding the recommended limit for PA intake by BfR. In addition three products of the investigated tea mixtures revealed extremely high PA contents of 4227, 5137, and 5668 µg/kg. Generally, single-ingredient tea products contained much less or even no detectable amounts of PAs when compared to the tea mixtures. PAs in the range between 13 and 1080 µg/kg were also detected in five analyzed aqueous herbal infusions of the medicinal tea mixture products with the highest PA content. Two out of the five investigated herbal infusions exceeded the recommended BfR limit for PA intake. CONCLUSION: This study demonstrates clearly that also medicinal teas licensed as medicinal products may partly contain high amounts of PAs exceeding current recommendations. For that reason manufacturers are advised to carry out more rigorous quality control tests devoted to the detection of PAs. This is very important to minimize PAs in medicinal teas accounting for possible additional exposure of the consumer to PAs from other food sources (e.g. honey).

Feasibility study of nonclinical safety assessments on homeopathic preparations using the example of protoanemonin in Pulsatilla pratensis L.

Homeopathy is a world-wide available form of complementary therapy, which has a tradition of 200years. Due to the long history of clinical use, i.e. reflected by the first edition of the Homeopathic Pharmacopoeia of the US of 1914, the conduct of toxicological studies is not required if the safety has been otherwise substantiated. The aim of this article is to establish a risk assessment procedure without full toxicological examination, using homeopathic preparations from Pulsatilla pratensis L. as an example. The literature review shows that protoanemonin is the most relevant constituent of these plants regarding potential toxicity. Based on structural alerts protoanemonin is classified as a Cramer class III compound with the threshold of toxicological concern (TTC) of 180µg/day in adults. Neither computer aided toxicology methods (Toxtree and Derek Nexus®) nor a literature search revealed any evidence of genotoxic, carcinogenic or teratogenic potential of protoanemonin. The protoanemonin exposure from a maximum daily dose of a typical homeopathic preparation of P. pratensis L. does not exceed the TTC. The presented method is transparent, reproducible and applicable to other homeopathic substances as a use-case scenario for computational toxicology in order to evaluate an approach for safety assessment of homeopathic medicinal products.

Limettin and furocoumarins in beverages containing citrus juices or extracts.

Phototoxic and photo-genotoxic furocoumarins occur, e.g., in citrus species, parsnip, parsley, celery, and figs. They exhibit phototoxic and photo-genotoxic properties in combination with UV radiation, while less is known about the phototoxicity of the coumarin derivative limettin mainly found in limes and lemons. Risk assessment of dietary furocoumarins is based on a threshold approach and on estimates of 1.2-1.45 mg for the average daily exposure for adults via the diet in several countries. In these estimates, the major contribution to overall daily exposure has been attributed to citrus-flavored non-alcoholic beverages, in spite of a lack of analytical data for those products. Therefore, we analyzed a number of furocoumarins in a variety of citrus-containing beverages and included limettin in the pattern of analyzed constituents. Our findings provide strong evidence that grapefruit juice and not citrus-flavored non-alcoholic beverages is the major source of furocoumarin exposure in a Western diet. Based on these findings it can be assumed that the average dietary exposure to furocoumarins is about 3-fold lower than previously estimated, i.e. in the range of 548 and 2237 microg/day for the average and high consumer, respectively. The coumarin derivative limettin was mainly found in lime products.

Toxicity of green tea extracts and their constituents in rat hepatocytes in primary culture.

Recent reports on sporadic cases of liver disorders (acute hepatitis, icterus, hepatocellular necrosis) after ingestion of dietary supplements based on hydro-alcoholic extracts from green tea leaves led to restrictions of the marketing of such products in certain countries of the EU. Since green tea is considered to exert a number of beneficial health effects, and, therefore, green tea products are widely used as dietary supplements, we were interested in the possible mechanism of hepatotoxicity of green tea extracts and in the components involved in such effects. Seven hours after seeding on collagen, rat hepatocytes in primary culture were treated with various hydro-alcoholic green tea extracts (two different native 80% ethanolic dry extracts and an 80% ethanolic dry extract cleared from lipophilic compounds). Cells were washed, and reduction of resazurin, used as a viability parameter monitoring intact mitochondrial function, was determined. It was found that all seven green tea extracts examined enhanced resazurin reduction significantly at a concentration range of 100-500 microg/ml medium, while a significant decrease was observed at 1-3mg/ml medium. Decreased levels were concomitant with abundant necrosis as observed by microscopic inspection of the cultures and with increased leakage of lactate dehydrogenase activity from the cells. In a separate series of experiments, the green tea constituents (-)-epicatechin, (-)-epigallocatechin-3-gallate, caffeine and theanine were tested at concentrations reflecting their levels in a typical green tea extract. Synthetic (+)-epigallocatechin (200 microM) was used for comparison. Cytotoxicity was found with (-)-epigallocatechin-3-gallate only. The concomitant addition of 0.25 mM ascorbate/0.05 mM alpha-tocopherol had no influence on cytotoxicity. In conclusion, our results suggest that high concentrations of green tea extract can exert acute toxicity in rat liver cells. (-)-Epigallocatechin-3-gallate seems to be a key constituent responsible for this effect. The relatively low bioavailability of catechins reported after oral exposure to green tea argues, however, against a causal role of these constituents in the reported liver disorders.

Evaluation of a vincristine resistant Caco-2 cell line for use in a calcein AM extrusion screening assay for P-glycoprotein interaction.

AIM: To develop a fast fluorometric screening assay based on vincristine resistant Caco-2 cells (Caco-2VCR) in order to elucidate potential P-glycoprotein (Pgp) interactions of compounds, and to characterise Caco-2VCR cells with regard to their expression of the efflux transporters Pgp, MRP1 and MRP2. METHODS: We applied the Caco-2VCR cells to a 96-well plate-based calcein AM extrusion assay. The Caco-2VCR cells were cultured as monolayers and incubated with calcein AM with/without addition of Pgp modulators. Fourteen known Pgp modulators were tested in the assay (chloropromazine, cyclosporin A, domperidone, digoxin, ivermectin, ketoconazole, loperamide, metoprolol, propranolol, progesterone, quinidine, quinine, verapamil and vincristine). For each compound an EC50 value was calculated. Protein and mRNA levels of the efflux transporters were analysed by Western blot and polymerase chain reaction techniques. RESULTS: All compounds with the exception of digoxin displayed increased calcein levels. Protein and mRNA analysis showed increased levels of Pgp after vincristine exposure, while expression of the efflux transporters MRP1 and MRP2 remained unchanged. CONCLUSIONS: The calcein AM extrusion assay applied to Caco-2VCR cells can be a valuable tool as a screening assay for new compounds and their potential interaction with P-glycoprotein.

Benzene metabolism in rodent hepatocytes: role of sulphate conjugation.

1. Hepatocytes isolated from the adult male NMRI mouse or Wistar rat were incubated for 1 h with 0.5 mM 14C-benzene, the supernatant was separated from the cells, and analysed for benzene metabolites. Separately, formation of sulphate conjugates during benzene metabolism was studied in hepatocytes in the presence of 35S-sulphate. In addition sulphate conjugation of the benzene metabolites hydroquinone and 1,2,4-trihydroxybenzene was investigated in mouse liver cytosol supplemented with 3'-phosphoadenosine-5'-phospho-35S-sulphate. 2. Two novel metabolites, not detectable in rat hepatocyte incubations, were found in mouse hepatocytes, and were identified as 1,2,4-trihydroxybenzene sulphate and hydroquinone sulphate. Formation of the 35S-labelled conjugates could be demonstrated in incubations of mouse liver cytosol with hydroquinone or 1,2,4-trihydroxybenzene supplemented with 3'-phosphoadenosine-5'-phospho-35S-sulphate, and in mouse hepatocytes incubated with benzene and 35S-sulphate. 3. In comparison with hepatocytes from the Wistar rat, hepatocytes from the NMRI mouse were almost three times more effective in metabolizing benzene. The higher formation of hydroquinone, and the formation of trihydroxybenzene sulphate and hydroquinone sulphate, mainly contributed to the higher rate of benzene metabolism. 4. In conclusion, qualitative and quantitative differences in benzene metabolism may contribute to the higher susceptibility of mouse towards the myelotoxic and leucaemogenic action of benzene.

The influence of environmental and genetic factors on CYP2D6, CYP1A2 and UDP-glucuronosyltransferases in man using sparteine, caffeine, and paracetamol as probes.

The impact of gender, use of oral contraceptive steroids (OCS), coffee consumption and of smoking on the metabolism of sparteine, caffeine, and paracetamol was studied in 194 randomly selected subjects (98 male and 95 female). Thirty-eight of the male volunteers were cigarette smokers, 40 of the female subjects were smokers and/or users of OCS. The metabolic ratio of sparteine oxidation (MRs) showed a trimodal distribution. 7.7% of the subjects had a MRs > 20 and thus were poor metabolizers (PMs). Within the extensive metabolizer (EM) subjects, a distinct subgroup accounting for 11% was observed with 20 > MRs > 1.2. Six of the 15 phenotypical PMs were heterozygous EMs by genotyping. This indicates the existence of one or several CYP2D6 mutations which cannot be identified by the currently employed genotyping methods. In each subgroup, i.e. smokers/OCS and non-smokers/non-OCS, the cumulative frequency distribution of the heterozygous (wt/B) phenotype caused a shift to higher MRs compared with the wild-type homozygotes (wt/wt). Thus, for the in vivo activity of CYP2D6, genetic determinants prevail over environmental factors. Smoking, use of oral contraceptive steroids, caffeine consumption, or gender had no influence on sparteine metabolism. The distribution of the paracetamol glucuronide/paracetamol metabolic ratio appeared to be unimodal although skewed. Glucuronidation capacity was clearly affected by gender, OCS use and smoking. It was higher in male than in female subjects. Male smokers had the highest, and female non-smokers/non-OCS users the lowest metabolic ratio. CYP1A2 activity, as determined by a caffeine metabolic ratio ((AFMU + 1X + 1U)/1, 7U), was multimodally distributed and was clearly increased in smokers. It was significantly correlated to paracetamol glucoronidation in male heavy smokers (r=0.85), suggesting an element of co-regulation of CYP1A2 and of paracetamol conjugating UDP-glucuronosyltransferase isozymes, including UGTI.6.

Drug-metabolizing enzyme activities in freshly isolated oval cells and in an established oval cell line from carcinogen-fed rats.

The activities of several different phase I and phase II drug-metabolizing enzymes were measured in freshly isolated oval cells from rats fed a choline-deficient/DL-ethionine-supplemented diet for 6 weeks and also in vitro in the established oval cell line OC/CDE 6. No cytochrome P450 was spectrophotometrically measurable in both preparations and two cytochrome P450-dependent monoxygenase activities, aminopyrine N-demethylase and ethoxyresorufin O-deethylase, could not be detected in the oval cells of both sources. However, cytosolic glutathione transferase, microsomal epoxide hydrolase and UDP-glucuronosyltransferase activities were clearly measurable in oval cells. Similar enzyme activities were found in freshly isolated and cultured oval cells. The highest activities of these three enzymes were detected during the exponential growth phase of the cultured cells; thereafter the activities decreased until the cells reached confluency. Changes in phenol UDP-glucuronosyltransferase (UGT1A1) mRNA levels paralleled the variations in UDP-glucuronosyltransferase activity, i.e. they were high in exponentially growing oval cells and low in confluent cell cultures. Taking into account that oval cells are able to proliferate in the livers of rats continuously fed a choline-deficient/DL-ethionine-supplemented diet and that none of the analyzed drug metabolizing enzymes are involved in the activation or detoxication of DL-ethionine, the described pattern might be part of a more general, nonspecific, protection mechanism enabling these cells to overcome the cytotoxic effects of a variety of carcinogens and to proliferate even in their presence. Furthermore, the expression of microsomal epoxide hydrolase, cytosolic glutathione transferase and UDP-glucuronosyltransferase appears to depend on the proliferative status of the cells.