Polyzyklische aromatische Kohlenwasserstoffe (PAH) im Innenraum

In recent years, the use of tar-containing parquet glue led to intensive discussion because of the health effects associated with indoor pollution caused by polycyclic aromatic hydrocarbons (PAH) contained in these materials. In addition to environmental tobacco smoke, fossil and organic fuels in stoves, cookers, firesides and other combustion processes contribute to the build up of PAH in the indoor environment. However, food remains to be the greatest source of PAH exposure to man; >90% of the daily PAH intake is food related. In the present review, an attempt will be made to throw light on the question of whether PAH exposure from indoor air sources may cause health effects.

Use of human-derived liver cell lines for the detection of environmental and dietary genotoxicants; current state of knowledge

This article gives an overview of the results of genotoxicity tests, which have been conducted within the last 5 years with the human liver cell line HepG2. It is an update of an earlier review from 1998 (by Knasmüller et al.). In addition, a number of publications are discussed which are relevant for the use of human derived liver cell lines in genetic toxicology. They concern the establishment of new endpoints, the development of new cell lines and possible pitfalls and problems. HepG2 cells have been used to test a wide variety of compounds over the last years. The most interesting observations are that the cells are highly sensitive toward polycyclic aromatic hydrocarbons and that genotoxic effects are seen with a number of carcinogenic mycotoxins, that give negative results in other in vitro assays. Carcinogenic metals such as As and Cd caused positive results as well, whereas only marginal or negative results were seen with nitrosamines. The low sensitivity toward these latter carcinogens is probably due to a lack of cytochrome P4502E1 which catalyses their activation. Also, a number of structurally different synthetic pesticides as well as bioactive plant constituents ("natural pesticides") have been tested and with some of them genotoxic effects were found. In most experiments, the formation of micronuclei was used as an endpoint; however also the single cell gel electrophoresis assay is increasingly used. Several transfectant lines of HepG2 have been constructed which express increased levels of phase I enzymes (such as CYP1A1, CYP1A2, CYP2E1 etc.); furthermore, cell lines became available which express human glutathione-S-transferases. These new clones might be particularly useful for the investigation of specific classes of genotoxicants and also for mechanistic studies. Apart from HepG2 cells, a number of other human derived liver cell lines have been isolated, but so far no data from genotoxicity experiments are available, except for Hep3B cells, which were compared with HepG2 and found to be less sensitive in general. Studies with HepG2 clones of a different origin indicate that the cells differ in regard to their sensitivity toward genotoxicants; also medium effects and the cultivation time might affect the outcome of genotoxicity studies. Overall, the results support the assumption that HepG2 cells are a suitable tool for genotoxicity testing.

Protective effects of Brussels sprouts towards B[a]P-induced DNA damage: a model study with the single-cell gel electrophoresis (SCGE)/Hep G2 assay

The aim of this study was to investigate the chemoprotective effects of Brussels sprouts juice towards benzo[a]pyrene (B(a)P)-induced DNA damage in the single-cell gel electrophoresis (SCGE)/Hep G2 test system. This assay combines the advantages of the SCGE assay with that of the use of human-derived cells possessing inducible phase I and phase II enzymes. Co-treatment of Hep G2 cells with small amounts of Brussels sprouts juice (0.25-2.0 microl/ml) and B(a)P reduced the genotoxic effect of the latter in a dose-dependent manner. Contrary to the results with the crude juice, unexpected synergistic effects were observed with allyl isothiocyanate (AITC, 1.0-6.0 microM), a breakdown product of sinigrin, which is the most abundant glucosinolate in Brussels sprouts. Although these concentrations of AITC did not cause DNA damage per se, at higher concentrations (> or =25 microM), the compound caused a pronounced dose-dependent DNA damage by itself. Mechanistic studies showed that Brussels sprouts juice causes induction of activities of ethoxyresorufin O-deethylase (EROD) and glutathione S-transferase (GST) at dose levels which were protective towards B(a)P. In combined treatment experiments with (+/-)-anti-benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE, 5.0 microM), the main genotoxic metabolite of B(a)P, and Brussels sprouts juice, only weak protection was found indicating that the mechanism of chemoprotection of Brussels sprouts is not mediated through inactivation of this metabolite. In conclusion, our findings show that Brussels sprouts are highly protective against B(a)P-induced DNA damage in human-derived cells.

Studies on the in vivo and in vitro mutagenicity and the lipid peroxidation of chlorinated surface (drinking) water in rats and metabolically competent human cells

In the present study, DNA damaging and mutagenic effects of chlorinated drinking water (CDW) extracts obtained from polluted raw water resources were examined in metabolically competent human Hep G2 hepatoma cells using the in vitro micronucleus assay and the single cell gel electrophoresis (SCGE, comet assay). Additionally, the in vivo induction of micronuclei (MN) was studied in polychromatic erythrocytes (PCEs) derived from bone marrow of CDW-treated Wistar rats. Furthermore, we examined the influence of CDW on the lipid peroxidation (LpO) in blood, liver, kidney and testicle of rats. The results demonstrated significant increases of micronucleated PCEs in the bone marrow of rats fed with relatively low CDW doses (33.3ml/kg body weight per day). Similar effects, i.e. increases of MN frequencies, were found in Hep G2 hepatoma cells after CDW treatment (41 MN/1000 binucleated cells (BNCs) for 167ml CDW) in comparison to the vehicle control (24 MN/1000 BNC). Additionally, DNA damages caused by CDW were observed in the comet assay. As a product of LpO, the levels of malondialdehyde (MDA) were significantly enhanced almost in all animals and organs tested after CDW treatment. In livers and serum of rats dose-dependent increases of MDA were observed. The data indicated that extracts from CDW obtained from polluted raw water were able to cause oxidative damages and to induce various biological effects in mammalian cells in vivo and in vitro, i.e. clastogenicity and/or aneugenicity, DNA strand breaks and/or alkali-labile damages. The consistency of the results among the various biological systems and endpoints led to the conclusion that the consumption of chlorinated drinking water obtained from polluted raw water may enhance the body burden with mutagenic and/or carcinogenic substances and therefore, means a potential genetic hazard for human health.

Musk ketone enhances benzo(a)pyrene induced mutagenicity in human derived Hep G2 cells

Musk ketone is a widely used artificial fragrance which has been identified in human fatty tissue and milk. The mutagenic and comutagenic effects of this compound were studied in micronucleus tests with a human derived hepatoma cell line (Hep G2). Exposure of the cells to MK alone in the range between 5 and 5000 ng/ml did not cause induction of MN. When the cells were treated simultaneously with MK (5-5000 ng/ml) and 0.2 microg/ml benzo(a)pyrene, no synergistic effects were detected; benzo(a)pyrene (B(a)P) itself caused an 1.5-fold increase of MN over the spontaneous background frequency (60 versus 39 MN/1000 binucleated cells). In a third experimental series, the cells were pretreated with MK for 28h and subsequently exposed to 0.2 microg/ml B(a)P. In this case, a pronounced comutagenic effect was observed: The LOAEL for MK was 0.05 microg/ml. With higher doses (0.5, 1.0 and 5.0 microg MK/ml), a significant increase of B(a)P induced MN frequencies was measured, the induction rates being 50, 66, and 88%, respectively. Additional measurements of 7-ethoxyresorufin deethylase indicated that MK induces cytochrome P450 isoenzymes (1A1) which play a key role in the activation of B(a)P. The results of the present study show that MK amplifies the genotoxic effects of B(a)P in human derived cells and indicate that exposure of humans to MK might increase their susceptibility to the health hazards of B(a)P and other polycyclic aromatic hydrocarbons.

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.

Biodegradability of some antibiotics, elimination of the genotoxicity and affection of wastewater bacteria in a simple test

Most antibiotics and their metabolites are excreted by humans after administration and therefore reach the municipal sewage with the excretions. Only little is known about their biodegradability in aquatic environments. It was recognised that genotoxic substances may represent a health hazard to humans but also may affect organisms in the environment. Therefore, the biodegradability of some clinically important antibiotic drugs (ciprofloxacin, ofloxacin, metronidazole) and hereby the elimination of their genotoxicity was investigated as the first step of an environmental risk assessment using the Closed Bottle test (CBT) (OECD 301 D) and the SOS chromotest. Additionally, to assess toxicity of the antibiotics tested against aquatic bacteria (i) a growth inhibition test (GIT) with Pseudomonas putida was conducted, (ii) a toxicity control was used in the CBT and (iii) the colony forming units (CFUs) were monitored in the test vessels. Worst case concentrations of the antibiotics in hospital effluents were estimated and compared with minimum inhibitory concentrations for susceptible pathogenic bacteria and with the genotoxic potency in the SOS chromotest. Both the concentrations calculated for hospital effluents and the adverse effects in bacteria were in the same order of magnitude. None of the test compounds were biodegraded. The genotoxicity was not eliminated.

SOS chromotest and mutagenicity in Salmonella: evidence for mechanistic differences

An examination of the relationship of the experimental results obtained with chemicals tested in the SOS chromotest and for mutagenicity in Salmonella indicates that the two assays respond to different genotoxic stimuli. Furthermore, the relationship between results obtained in these assays and in rodents carcinogenicity bioassays suggests that the short-term assays respond to a different spectrum of carcinogens. The same conclusions were reached based upon an analysis of the structural features associated with these three phenomena. With respect to using these short-term assays to predict carcinogens, the present results suggest that they are not equivalent, but complement one another.

SOS induction of selected naturally occurring substances in Escherichia coli (SOS chromotest)

Naturally occurring substances were tested for genotoxicity using a modified laboratory protocol of the Escherichia coli PQ37 genotoxicity assay (SOS chromotest) in the presence and in the absence of an exogenous metabolizing system from rat liver S9-mix. Aristolochic acid I, II, the plant extract aristolochic acid and psoralene were genotoxic; cycasine, emodine, monocrotaline and retrorsine were classified as marginal genotoxic in the SOS chromotest in the absence of S9-mix. In the presence of an exogenous metabolizing system from rat liver S9-mix aristolochic acid I, the plant extract, beta-asarone, cycasin, monocrotaline, psoralen and retrorsine showed genotoxic effects; aristolochic acid II marginal genotoxic effects. Arecoline, benzyl acetate, coumarin, isatidine dihydrate, reserpine, safrole, sanguinarine chloride, senecionine, senkirkine, tannin and thiourea revealed no genotoxicity in the SOS chromotest either in the presence or in the absence of an exogenous metabolizing system from rat liver S9-mix. For 17 of 20 compounds, the results obtained in the SOS chromotest could be compared to those obtained in the Ames test. It was found that 12 (70.6%) of these compounds give similar responses in both tests (6 positive and 6 negative responses). The present investigation and those reported earlier, the SOS chromotest, using E. coli PQ37, was able to detect correctly most of the Salmonella mutagens and non-mutagens.

Use of metabolically competent human hepatoma cells for the detection of mutagens and antimutagens

The human hepatoma line (Hep G2) has retained the activities of various phase I and phase II enzymes which play a crucial role in the activation/detoxification of genotoxic procarcinogens and reflect the metabolism of such compounds in vivo better than experimental models with metabolically incompetent cells and exogenous activation mixtures. In the last years, methodologies have been developed which enable the detection of genotoxic effects in Hep G2 cells. Appropriate endpoints are the induction of 6-TGr mutants, of micronuclei and of comets (single cell gel electrophoresis assay). It has been demonstrated that various classes of environmental carcinogens such as nitrosamines, aflatoxins, aromatic and heterocyclic amines and polycyclic aromatic hydrocarbons can be detected in genotoxicity assays with Hep G2 cells. Furthermore, it has been shown that these assays can distinguish between structurally related carcinogens and non-carcinogens, and positive results have been obtained with rodent carcinogens (such as safrole and hexamethylphosphoramide) which give false negative results in conventional in vitro assays with rat liver homogenates. Hep G2 cells have also been used in antimutagenicity studies and can identify mechanisms not detected in conventional in vitro systems such as induction of detoxifying enzymes, inactivation of endogenously formed DNA-reactive metabolites and intracellular inhibition of activating enzymes.

Testing of SOS induction of artificial polycyclic musk fragrances in E. coli PQ37 (SOS chromotest)

Synthetic fragrances are widespread in the environment. Residues were found in animals, human tissues and breast milk. Therefore, six artificial polycyclic musk fragrances--Galaxolide, Tonalide, Celestolide, Phantolide, Cashmeran and Traseolide--were tested for SOS induction using the Escherichia coli PQ37 genotoxicity assay (SOS chromotest) in the presence (+S9) and absence (-S9) of an exogenous metabolizing system. All compounds tested exhibited no SOS inducing potency with the SOS chromotest. These results could be rated as one indicator of the biological inactivity of this group of compounds with respect to genotoxicity.

Salmonella mutagenicity of musk ambrette depends on both microsomal and bacterial enzyme activity

Former studies revealed musk ambrette as a mutagen in Salmonella typhimurium TA 100 in the presence (+S9) but not in the absence (-S9) of an exogenous metabolizing system. To clarify the role of bacterial nitroreductases (NR) in the toxification of musk ambrette to mutagenic metabolites the compound was examined with the Salmonella/mammalian microsome assay using the NR deficient strain S.typhimurium TA 100 NR in the presence and absence of S9. Musk ambrette showed mutagenicity in Salmonella typhimurium TA 100 (+S9) but no mutagenicity in the NR deficient strain TA 100 NR (+S9). Additionally, no mutagenicity was detected in both TA 100 (-S9) and TA 100 NR (-S9). These results indicate the need for both mammalian microsomal enzymes and bacterial nitroreductases to cause the mutagenicity of musk ambrette.

Genotoxicity of polycyclic musk fragrances in the sister-chromatid exchange test

The synthetic polycyclic musk fragrance compounds Galaxolide (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethyl-cyclo-penta-(g)-2-++ +benzopyrane, Tonalide (7-acetyl-1,1,3,4,4,6-hexamerthyltetraline), Celestolide (4-acetyl-1,1-dimethyl-6-tert, butylindane), Phantolide (6-acetyl-1,1,2,3,3,5-hexamethylindane), Cashmeran (6,7-dihydro-1,1,2,3,3-pentamethyl-4-(5H) indanone) and Traseolide (5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane) are widely used as fragrance ingredients in perfumes, lotions and detergents; as food additives in cigarettes and fish baits. Several studies identified polycyclic musk fragrances in aquatic environment samples, human milk and human adipose tissue as highly lipophil with human lymphocytes.

In vitro genotoxicity of polycyclic musk fragrances in the micronucleus test

The synthetic polycyclic musk fragrance compounds galaxolide (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(g)-2-b enzopyrane), tonalide (7-acetyl-1,1,3,4,4,6-hexamerthyltetraline), celestolide (4-acetyl-1,1-dimethyl-6-tert-butylindane), phantolide (6-acetyl-1,1,2,3,3,5-hexamethylindane), cashmeran (6,7-dihydro-1,1,2,3,3-pentamethyl-4-(5H) indanone) and traseolide (5-acetyl-1,1,2,6-tetramethyl-3-isopropylindane) were examined for their genotoxicity in the micronucleus test (MNT) with human lymphocytes in vitro in the presence and absence of an exogenous metabolizing system containing rat liver S9 and the metabolically competent human hepatoma cell line Hep G2. Compound concentrations were employed up to cytotoxic doses. Galaxolide, tonalide, celestolide, phantolide, cashmeran and traseolide revealed no genotoxicity in the micronucleus test with human lymphocytes and with the human hepatoma cell line Hep G2.

Genotoxic effects of three Fusarium mycotoxins, fumonisin B1, moniliformin and vomitoxin in bacteria and in primary cultures of rat hepatocytes

The genotoxic effects of three widespread Fusarium toxins, vomitoxin (VOM), moniliformin (MON) and fumonisin B1 (FB1) were investigated in bacterial tests and in micronucleus (MN) and chromosomal aberration (CA) assays with primary rat hepatocytes. All three toxins were devoid of activity in gene mutation assays with Salmonella typhimurium strains TA98 and TA100 and in SOS chromotests with E. coli strain PQ37 in the presence and absence of metabolic activation. FB1 and VOM gave negative results in differential DNA repair assays with E. coli K-12 strains (343/753, uvrB/recA and 343/765, uvr+/rec+); with MON, a marginal effect was seen in the absence of metabolic activation mix at relatively high concentrations (> or = 55 micrograms/ml). In metabolically competent rat hepatocytes stimulated to proliferate with EGF and subphysiological Ca2+ concentrations, a decrease of cell division was observed with all three toxins at concentrations > or = 10 micrograms/ml, VOM was strongly cytotoxic at 100 micrograms/ml. All three mycotoxins caused moderate increases of the MN frequencies at low concentrations (< or = 1 microgram/ml), but no clear dose-response effects were seen and at higher exposure levels the MN frequencies declined. In the CA experiments with hepatocytes, pronounced dose-dependent effects were observed with all three toxins. MON caused a 9-fold increase over the spontaneous background level after exposure of the cells to 1 microgram/ml for 3 h, with FB1 and VOM, the increases were 6- to 7-fold under identical experimental conditions. This is the first report on clastogenic effects of VOM and FB1 in mammalian cells, with MON induction of CAs in V-79 cells has been described earlier. Since all three mycotoxins caused CAs at very low concentration levels in liver cells in vitro, it is possible that such effects may also occur in humans and mammals upon consumption of Fusarium-infected cereals.

Nitro musks are cogenotoxicants by inducing toxifying enzymes in the rat

In the present study, musk xylene (MX) and musk ketone (MK) were examined for their potency to induce toxifying enzymes in the liver of Sprague-Dawley rats, using an in vivo/in vitro model. After i.p. application of 10, 20 and 40 mg/day MX and MK over a period of 5 days, 9000 x g liver fractions (S9M) were used to study the toxification of a number of well-known pregenotoxicants in the SOS chromotest, i.e., benzo[a]pyrene (B[a]P), 2-aminoanthracene (2-AA), and aflatoxin B1 (AFB1). The genotoxic potencies of B[a]P, 2-AA and AFB1 in the presence of S9M were compared to those obtained in the presence of S9 fractions of untreated animals (S9O, negative control). S9M fractions derived from MK-treated rats showed an increased potency to toxify B[a]P, 2-AA and AFB1 in comparison to S9O fractions (for instance: TIP[toxifying induction potency] = 70 per nmol AFB1 using 10 mg MK treatment). In comparison, S9M fractions from MX-pretreated rats exhibited an increased genotoxicity only when using 2-AA (TIP = 0.04) and AFB1 (TIP = 61) as pregenotoxicants, but not when using B[a]P. To summarize the results, both MX and MK were strong inducers of toxifying liver enzymes. Therefore, these compounds seem to be cogenotoxicants for a number of well-known pregenotoxicants. Synergistic effects were found when using inducers of toxifying enzymes and pregenotoxicants in the in vivo/in vitro induction model.

[Co-genotoxic potential of PCB mixtures from pediatric fatty tissue]

In the present study a mixture containing the 11 PCB major components identified in fatty tissues of children was examined for its potency to enhance the toxification of pregenotoxicants (cogenotoxicity) in the liver. As a basis for the study GC/MS PCB analyses of 207 fatty tissue samples of children were used. The PCB mixture was produced on this basis. As a model for the identification of the cogenotoxic potency of the PCB mixtures an in vivo/in vitro enzyme induction assay was developed. The goal of the study was to clarify the question, whether the in vivo pretreatment of rats with a complex PCB pattern derived from children led to a synergism of cogenotoxicants and pregenotoxicants with regard to the enhancement of the in vitro toxification of benzo[a]pyrene (B[a]P) and 2-aminoanthracene (2-AA) to DNA reactive metabolites. Using the SOS-Chromotest as the in vitro part of the induction assay, all liver enzyme fractions of PCB pretreated rats (S9PCB) showed an increase of the toxification of the pregenotoxicants B[a]P and 2-AA in comparison to enzyme factions of untreated animals (S9(0)). With regard to the reactivity pattern it may be supposed that the PCB mixture probably induced cytochrome P450-dependent oxigenases of the subclasses CYP1A1 and CYP1A2. Additionally, it seems to be of interest that the use of S9(0) fractions did not lead to any or only to weak toxification of B[a]P and 2-AA. Thus, a synergism of cogenotoxicants and pregenotoxicants could be confirmed. PCB could be identified in fatty tissues of children in amounts up to 1 mg/kg. Additionally, pregenotoxicants like polycyclic aromates, mycotoxins and/or aminocontaining compounds, are available in almost all environmental sources. Therefore, from the present point of view, a genetic risk caused by PCB in humans (children) cannot be excluded.

A comparative study of five nitro musk compounds for genotoxicity in the SOS chromotest and Salmonella mutagenicity

Five nitro musk compounds widely used in cosmetics and detergents were examined for DNA-damaging and mutation-inducing properties. For this purpose two short-time assays were used, the SOS chromotest and the Salmonella/mammalian microsome test. Musk ambrette showed mutagenicity in Salmonella typhimurium TA 100 requiring metabolic activation by rat liver postmitochondrial supernatant (S9) but it lacked mutagenicity in the absence of S9 and genotoxicity in the SOS chromotest. Musk xylene, musk ketone, musk moskene and musk tibetene showed neither mutagenicity nor genotoxicity in the presence and absence of S9.

Chemical structure and genotoxicity: studies of the SOS chromotest

Analyses of a data base consisting of 461 chemicals tested in the SOS chromotest with MULTICASE resulted in the development of an SAR model that displayed a highly significant concordance (87.3%) between experimental and predicted results of chemicals not included in the model. An analysis of the nature of the biophores and their modulators revealed that electrophilicity and structural features affecting: (a) accessibility of the electrophile to the nucleophilic site on the DNA; and (b) the bulkiness of the DNA adduct were factors determining the probability that a chemical would induce DNA error prone repair and if so the extent of this activity. Additional analyses indicated that there were significant mechanistic similarities between the SOS chromotest and mutations in Salmonella as determined in the standard ('Ames') assay.

[Mutagenicity, genotoxicity and cogenotoxicity of environmentally relevant nitro musk compounds]

In the present study a new in vivo/in vitro animal model was used to study the ability and potency of musk ketone and musk xylene to induce liver specific oxygenases (in vivo) which are necessary of toxify different premutagens, pregenotoxicants and/or precarcinogens to the ultimate DNA damaging agents. Therefore, rats were pretreated with 10, 20 and 40 mg/d nitro musk (NMV) for 5 days by intraperitoneal (i.p.) injection. Then the postmitochondrial fractions of the hepatocytes (S9M) were used to examine the metabolic potency for toxification of the pregenotoxicants benzo[a]pyrene (B[a]P) and 2-aminoanthracene (2-AA) using the SOS chromotest (in vitro). Furthermore, musk xylene, musk ketone, musk ambrette, musk moskene and musk tibetene were examined for their mutagenicity in the Salmonella/microsome assay using S. typhimurium TA97, TA98, TA100 and TA102 and for their genotoxicity in the SOS chromotest using Escherichia coli PQ37 (sfiA::lacZ) in the presence and absence of an exogenous metabolizing system (S9 of PCB induced rats = S9A). Both musk ketone and musk xylene were identified als inducers of toxifying enzymes (oxygenases) in rat liver. Using the in vivo/in vitro model these isoenzyme inductions led to a metabolisation (toxification) of the pregenotoxicants benzo[a]pyrene (B[a]P) and/or 2-aminoanthracene (2-AA) (cogenotoxicity). Using S9M fractions of rats which were i.p.-pretreated with 5 x 40 mg musk ketone the induction factor in the SOS chromotest was IFmax = 4.0 by using 1 nmole B[a]P and IFmax > 4.0 by using 20 nmole 2-AA. Thus, musk ketone seems to be a Cytochrome P450 1A1 and 1A2 isoenzyme inducer in mammals. On the other hand the S9M fractions of musk xylene pretreated rats showed only a toxification of 2-AA (IFmax = 3.0). Therefore, a synergistic effect of enzyme inducers, i.e. musk xylene and musk ketone, and pregenotoxicants, i.e. B[a]P and 2-AA, regarding DNS damaging effects was identified. Musk ambrette showed high mutagenicity in S. typhimurium TA100 (500 His(-)-revertants per mumole, +S9A). Unexpectedly, these DNA damaging effects were not caused by bacterial nitroreductases but by rat S9A metabolisation (!). SOS inducing DNA damages in E. coli PQ37 were not produced (IFmax < 1.5). On the basis of the results presented and under consideration of the concentrations of NMV, other cogenotoxicants and pregenotoxicants such as B[a]P and 2-AA in environmental samples and human tissues, a genotoxic risk for humans has to be assumed.

[Antimicrobial oligopeptides--an important factor in non-specific defense against infection]

For survival of plants, animals as well as main in a nature full of aggressive microbes, endogenous antibiotics play an essential role, which is not yet fully appreciated in medicine and science. For example in the granules of polymorphonuclear granulocytes and macrophages or even of specialized epithelial cells such as Paneth cells in the crypts of the intestinal mucosa, oligopeptides are produced with a wide range of antimicrobial activity. According to their chemical structures and modes of action they can be grouped into various different families. The physiological role of these agents on the surface of skin and mucosa or within host tissue is only incompletely understood.

SOS induction in Escherichia coli and Salmonella mutagenicity: a comparison using 330 compounds

To examine the concordance of two microbial genotoxicity short-term assays, 330 experimental results for the SOS chromotest using tester strain Escherichia coli PQ37 were compared with the results of the Salmonella/mammalian microsome mutagenicity assay with Salmonella typhimurium TA97, TA98, TA100, TA102, TA104, TA1535, TA1537 and/or TA1538. With respect to qualitative features, the concordance between SOS chromotest and Salmonella mutagenicity test results was 86.4% (sensitivity, 78.6%; specificity, 100%; chi 2 = 188.6). None of the non-mutagens (N = 120) were able to induce the SOS system. Additionally, 45 of the 210 S.typhimurium mutagens (21.5%) did not induce the SOS repair system. On closer examination, the majority of these 45 compounds (84%) were mutagens with activities between 0.001 and 10 rev/nmol. Even though the experimental protocols of both systems were not standardized, the correlation coefficient for the experimental results of the two test systems was 0.7 for the 330 chemicals. Except for aliphatic epoxides (r = 0.47), the mutagenicity/SOS induction correlations for congeneric data sets (polycyclic aromatic hydrocarbons, nitroarenes, nitroarenofurans, mycotins) were even better (r = 0.72-0.95). Additionally, computer automated structure evaluation (CASE) analyses of the nature of the structural determinants associated with each endpoint indicate extensive homologies. The data can be taken to indicate that the two phenomena reflect common mechanisms of action.

The structural basis of the genotoxicity of nitroarenofurans and related compounds

The CASE (Computer-Automated Structure Evaluation) methodology has been applied to an investigation of the basis of the genotoxicity (sfiA induction) of 79 nitroarenofurans and related molecules examined with the E. coli PQ37 genotoxicity assay (SOS chromotest). CASE identified 9 major activating structural fragments (biophores) responsible for the probability of genotoxicity (SAR). With respect to quantitative features, CASE identified 8 major molecular subunits related to the genotoxic potency (QSAR). Both the SAR as well as the QSAR analysis indicate that a nitro group on position 2 of the furan ring is important for activity provided one or more aromatic rings are attached to the furan ring, i.e. 2-nitrobenzofuran, 2-nitronaphthofuran, 2-nitroanthrafuran and 8-nitropyrenofuran. Additionally, a small substituent at position 3 of the furan ring, i.e. the methyl group of R7371, the ethyl group of R7427 and the butyl group of R7429, enhance the activity of 2-nitronaphtho[2,1-b]furan (R6597), whereas longer aliphatic chains decrease activity. Moreover, the activity of the nitro group at position 2 of the furan ring was increased by substitution of a methoxy group at position 7 of the R6597 structure. Additionally the n-octanol/water partition coefficient (log P) was found to be an important descriptor for the genotoxic potency in E. coli PQ37. Using the identified descriptors CASE correctly predicted the probability of genotoxicity of all of the genotoxicants and non-genotoxicants in the data base. The calculated genotoxic potency was equally good: 94% of all predicted results were within plus/minus one order of magnitude of the experimental result. Using CASE in the predictive mode, the program correctly predicted the probability of sfiA induction in E. coli of 95.8% of 24 "unknown" nitroarenofurans which were not part of the learning set (QSAR with r = 0.88-0.97).

The genotoxicity of unsubstituted and nitrated polycyclic aromatic hydrocarbons

To determine the DNA damaging properties of unsubstituted and substituted polycyclic hydrocarbons, 61 aromatic and heterocyclic compounds were examined for the induction of the SOS system in E. coli PQ37. PAH such as benzo[ghi]fluoranthene, benzo[j]fluoranthene, benzo[c]phenanthrene, benzo[a]pyrene, chrysene, dibenzo[a,1]pyrene, fluoranthene and triphenylene showed relatively high genotoxicity. With respect to the nitroarenes, the highest genotoxic potencies were exhibited by the dinitropyrenes. The SOS-inducing potency of nitroarenes increased from the bicyclic to the tetracyclic ring system. Additionally, it was seen that any increase in the extent of nitration is paralleled by an increase of genotoxicity. Whereas PAH required metabolic activation by hepatic cytochrome P-450 enzymes, nPAH were direct-acting genotoxicants.

[Ecology and causality--on the reliability of environmental medicine knowledge]

In principle, environmental medicine has two responsibilities. On the one hand this special field is required to provide a practicable and enlightening medicine for people seeking help. On the other hand environmental medicine as an ecological medicine" is required to analyse the truth content in science and the reliability of scientific knowledge with regard to environmental processes. For not only direct-acting toxicities of environmental chemicals but also the imbalance in ecological systems possess pathogenic potencies. Do these ecological processes in systems actually have the demanded obvious causality?

The influence of culture conditions on the susceptibility of Salmonella typhimurium in the Salmonella mutagenicity test

To determine the variability of tester strain susceptibility in the Salmonella mutagenicity assay and to optimize the culturing procedure we examined the influences of the overnight culture period (12-16 h), the use of an additional short-term culturing procedure (1-4 h) and the Salmonella density (cfu/plate) on the rate of revertants per plate. As tester strains we used Salmonella typhimurium TA97, TA98, TA100 and TA102. As shown previously for other microbial genotoxicity short-term tests (i.e. with Escherichia coli PQ37), we observed the highest susceptibility of the Salmonella strains, i.e. the highest amounts of revertants per plate, when using a 12 h overnight culture followed by a 2 h short-term culturing procedure. We calibrated the bacterial count to 100 x 10(6) cfu per assay by photometric measurement (600 nm). Initially, we used 0-1 nmole 2,4,7-trinitro-9-fluorenone with S. typhimurium TA97, 0-15 nmole daunomycin with strain TA98, 0-25 nmole sodium azide with strain TA100 and 0-15 nmole methylmethanesulfonate with strain TA102 as reference compounds in the standard plate incorporation test. Subsequently, to evaluate the results of the culturing procedure variations we examined 22 well-known mutagenic and direct-acting (-S9-mix) compounds out of different chemical classes using both the standard and a modified culturing procedure. The comparison of these results showed a 64% (for 4-nitroquinoline-N-oxide) to 421% (for sodium azide) increased amount of revertants for the modified test protocol.

Influence of S9 mix composition on the SOS response in Escherichia coli PQ37 by polycyclic aromatic hydrocarbons

To investigate the variability in test results obtained with the SOS chromotest (Escherichia coli PQ37 genotoxicity assay) when varying the composition of the exogenous metabolizing system (S9 mix), we examined the influence of different S9 and NADP concentrations, of buffer pH value, of SDS concentrations, the effects of E. coli PQ37 density and centrifugation steps on the expression of beta-galactosidase (beta g) and alkaline phosphatase (ap) activity, the calculated induction factors (IFs) and SOS-inducing potencies (SOSIPs). Additionally we examined the metabolic potency (stability) of S9 mix when stored at 37 degrees C before use. Initially, we used 0-5000 ng (= 0-20 nmole) benzo[a]pyrene (B[a]P) as a reference compound for the test procedure in the presence of standard S9 mix. Subsequently, to evaluate the results of S9 mix variations we examined several polycyclic aromatic hydrocarbons (PAHs) using both the standard and a modified S9 mix composition and test protocol. We observed the highest beta g and ap activities and/or IFs using only 11-27 microliters 9000 x g liver supernatant (S9) from Aroclor 1254-induced rats per assay (20-50% of standard amount) and calibrating the S9 mix Tris buffer to pH 7.8-8.0. 60-300 micrograms NADP/assay (10-50% of standard) was sufficient for optimum activation of PAHs. In contrast to previous investigations about the variability of the SOS chromotest in the absence of a metabolizing system, higher induction factors were obtained when using higher bacterial densities (12-18 x 10(6) cfu/assay). Centrifugation steps as recommended by other investigators were not necessary when using optimum S9 amounts. The metabolic activity of S9 mix remained nearly constant approximately 20 min after preparation, but decreased to 80% of its activity in about 1 h.

Structural basis of the genotoxicity of polycyclic aromatic hydrocarbons

The Computer Automated Structure Evaluation (CASE) system has been applied to investigate the structural basis of the genotoxicity of 37 polycyclic aromatic hydrocarbons examined with the Escherichia coli PQ37 genotoxicity assay (SOS chromotest). CASE identified eight activating and one inactivating structural fragments responsible, for the probability and three activating and one inactivating fragment responsible for the potency of the activity (P less than or equal to 0.15). The present analysis indicate that the main activating fragments identified by CASE were similar to the descriptor for the bay (or modified bay) and K region of PAHs. Using these fragments the computer correctly predicted the probability of genotoxicity of 93.6% of the known genotoxicants and nongenotoxicants in the database. Moreover, the concordance between prediction and experimental results for molecules not in the learning set is greater than 78%.

Structural requirements for the induction of the SOS repair in bacteria by nitrated polycyclic aromatic hydrocarbons and related chemicals

The CASE (computer-automated structure evaluation) methodology was used to investigate the structural basis of the SOS-inducing activity of 56 nitrated polycyclic aromatic hydrocarbons (nitroarenes, nPAH) and the unsubstituted parent PAH molecules. Based upon the presence and/or absence of structural features, CASE identified 5 activating (biophores) and 4 inactivating (biophobes) fragments responsible for the SOS-inducing activity. Based upon these fragments, CASE correctly calculated the genotoxicity of 94.6% of the molecules in the training set (sensitivity = 0.85, specificity = 1.0). Disregarding the questionable experimental results of the unexpected very weak direct-acting activity of the unsubstituted benzo[a]pyrene, dibenzo[a,h]anthracene and 7,12-dimethylbenz[a]anthracene, the concordance of the prediction was 100%, i.e., sensitivity = 1.0, specificity = 1.0. Additionally, the quantitative analysis of the SOS-inducing potency showed a good correlation between the experimental and predicted results. The present analyses indicate an identity in the structural determinants responsible for SOS induction in E. coli PQ37 (SOS chromotest) and mutagenicity in Salmonella typhimurium.

Genotoxicity of polycyclic aromatic hydrocarbons in escherichia coli PQ37

In the present investigation, 32 polycyclic aromatic hydrocarbons (PAHs) were tested for genotoxicity in E. coli PQ37 using the standard tube assay of the SOS chromotest. PAHs such as benzo[ghi]fluoranthene, benzo[j]fluoranthene, benzo[a]pyrene, chrysene, dibenzo[a,l]pyrene, fluoranthene and triphenylene exhibited high genotoxicity when incubated in the presence of an exogenous metabolic activation mixture. The results were compared to those obtained with the Salmonella/microsome test.

[Methods and knowledge--the necessity for a system-oriented environmental medicine]

Despite the marked signs that human interventions and manipulations of the natural environment are dangerous to human health, physicians are not very interested in correlations between diseases and changes of the global environment. Physicians and scientists of the medical faculties of the universities as well as residents and general practitioners mostly ignore ecological effects on human life. The reason for this is not only insufficient education, but in particular a wrong theoretical basis with regard to the explanations of global biological and ecological processes. The present paper is supposed to point to the major problems of environmental medicine and the necessity of broader and more detailed scientific knowledge to recognise the multidimensional nature of kinetic and evolutionary systems.

Sources of variability of the Escherichia coli PQ37 genotoxicity assay (SOS chromotest)

To determine the variability in test results obtained with the Escherichia coli PQ37 genotoxicity assay (SOS chromotest) when varying the test protocol, we examined the influences of sodium dodecylsulfate (SDS) concentrations, of buffer pH and composition on the enzyme assays, the effects of E. coli PQ37 density and culture conditions on the expression and/or determination of alkaline phosphatase (ap) and beta-galactosidase (beta-g) activities, the calculated induction factors (IF) and the SOS-inducing potentials (SOSIP). Initially, we used 0-190 ng (0-1 nmole) 4-nitroquinoline-1-oxide (4-NQO) as a reference compound for the standard procedure in the absence of metabolic activation. Subsequently, to evaluate the results of protocol variations we examined several mutagenic compounds of differing chemical classes using both the standard and a modified assay procedure. We observed the highest enzyme activities using 1 mg SDS per tube and calibrating the ap buffer to pH 8.05 and the beta-g buffer to pH 7.75. The longer the incubation period, the higher the enzyme activities. However, with respect to IF and SOSIP there is no reason to incubate in excess of 90 min. We found no significant differences in the IF and SOSIP values when varying substrate conversion times. There was, however, a definite decrease in beta-g activity when extended substrate incubation times were used. Higher enzyme activities are obtained when the bacterial count is increased. Using lower bacterial counts the enzyme activities decreased, but the sensitivity of E. coli towards genotoxic compounds increased.

The SOS-Chromo-spottest: evaluation of a short-term test for the determination of genotoxic compounds in contaminated environmental samples

To evaluate the sensitivity of the SOS-Chromo-spottest towards genotoxic compounds 5 reference chemicals (4-nitroquinoline-1-oxide (4-NQO), methylmethansulfonate (MMS), 2,4,7-trinitro-9-fluorenone (TNF), sodium azide (SA) and daunomycin (DM) were tested by 3 different agar plate media (STA-plates: synthetic media containing Xgal, B-plates: synthetic media containing 1% lactose and bromocresolpurple, C-plates: 1% lactose bromocresolpurple media containing complex nutrients). Even 1 ng of 4-NQO showed genotoxic effects by using STA-plates. The threshold value for MMS was 80 nl, for TNF 160 ng and for DM 80 ng. Similarly the spottest with B-plates are positive results, but the sensitivity of this test procedure was 80 to 250 times lower than the STA-plate test. The C-plate test only reacted with high amounts of 4-NQO (1000 ng). Therefore, the SOS-chromo-spottest with STA-media described by Quillardet and Hofnung seems to be a sufficient procedure to detect genotoxic compounds in contaminated environmental samples directly without previous extraction procedures. The simpler B-plates can be used to examine the genotoxicity of certain compounds like industrial or household chemicals where the genotoxicants can be expected to be present in high doses.

[The mutagenicity of organic microcontamination in the environment. II. The mutagenicity of volatile organic halogens in the Salmonella microsome test (Ames Test) with regard to the contamination of groundwater and drinking water]

To determine the sensitivity and specificity of microbial shortterm-tests for the registration of the mutagenic potency of halogenated hydrocarbons (OHV) 18 pure substances out of the groups of halomethanes, -ethanes and -ethylenes were examined with different laboratory methods (classical Ames-Test, Spot-Testing, Preincubation-Procedure) of the Salmonella-Microsome-Test (Ames-Test). The Salmonella typhimurium- strains TA97, TA98, TA100 und TA102 were used with and without metabolic activation of Arochlor 1254 induced rat-liver microsomes. Mutagenicity with one or several procedures shows 1,1,2,2-tetrachloroethane, hexachloroethane, trichloroethylene, bromdichloromethane and bromoform without metabolic activation and dichloromethane, tetrachloromethane, 1,1,2,2-tetrachloroethane, hexachloroethane, 1,1-dichloroethylene, trans-1,2-dichloroethylene, tetrachloroethylene and bromdichloromethane with metabolic activation. The range of sensitivity amounted from microgram to nanogram values of OHV's per plate, so that the Ames-test can be a sensitive screening method sufficient for detection of mutagenic effects by several OHV's in high contaminated environmental samples even without extraction procedures.

[Environment, knowledge and preventive medicine. 1. The ecotoxicologic system model]

Especially in the area of public health organisations are many questions about the medical valuation of environmental pollutions. Now the complicated coherences between environment and health contains great problems on scientific investigations. With the aid of an ecological model of environmental systems it is possible to estimate effects of anthropogene pollutions. The aim is the development of a sufficient health protection program.

[The mutagenicity of organic microcontaminants in the environment. I. The mutagenicity of selected herbicides and insecticides in the Salmonella microsome test (Ames test) with regard to the pathogenic potency of contaminated ground and drinking water]

For determination of the mutagenicity of herbicides and insecticides in working and environmental relevant concentrations we examined 26 pure substances of the chemical groups of polychlorinated alicyclic hydrocarbons, phenoxy fatty acids and and triazines with the Salmonella-microsome-test (S. typhimurium strains TA 97, TA 98, TA 100 and TA 102 with and without metabolic activation with Aroclor 1254 induced rat liver microsome fraction). Only one substance--Chlorthiamide--showed mutagenicity in concentrations of 0.001 microgram/plate. In all the other substances examined we found numbers of revertants near the spontaneous mutagenic rates. However a human carcinogenic potential can't be excluded, because several toxicological studies with mammalians showed a carcinogenic activity of organohalogenic insecticides without mutagenic activity in biological short term tests.

[The mutagenicity of surface water, waste water and drinking water in the Rhine-Neckar region in the Salmonella microsome test (Ames Test)]

We have shown recently that the quality of surface water in urban and industrialized regions is of dubious hygienic. Therefore, in further studies we examined 46 water samples between October and November 1986 from the Rhine-river and its tributaries between km 400 and 440 using the Salmonella mutagenicity test (Ames-test). Additionally, we examined 8 samples from the waterworks of Mannheim and 4 samples from a lake in the Mannheim area. Each of our 464 samples was examined using Salmonella strains TA 97, TA 98, TA 100 and TA 102 with and without Aroclor-1254-induced S9-fraction from rat liver. 9.7% of the water samples showed mutagenic effects in the Ames test, the majority (70%) with low activity. High mutagenic effects were found in the waste water of the purification plants of Mannheim and Ludwigshafen and of some small but very highly contaminated brooks (Kraichbach, Leimbach). Two out of 8 untreated water samples of the waterworks of Mannheim showed mutagenic effects in the undiluted water following metabolic activation. We never found mutagenic effects in all samples taken from the same site. The Ames-test is a useful screening procedure for the determination of mutagenic or cancerogenic effects of environmental contaminants. It allows an evaluation of mixtures of anthropogenically polluted environmental samples for potentially genotoxic effects. Our results show that our water resources pose ecological hazards. This should be prevented by a better control of the industrial and communal waste water before it is allowed to flow into the river.

[Bacteriologic quality of water from the Rhine and its tributaries in the Rhine-Neckar region. II. Salmonellas--public health significance and health risks]

Salmonella-infections, the epidemiology and the spread of these germs into the environment are a serious hygienic problem even today. Probably one of the most important reservoirs of germs is the water of rivers and lakes. Its relevance for the infective chain in the overcrowded region Rhein-Neckar was examined very insufficiently until now. Even though, the municipal, two-stepped purification-plants are widely improved, the pollution of the pre-floating compartments with Salmonellae seems to be always a problem. In 1982, 1983 and 1986 164 water-specimens were collected at 34 sites along the river Rhine and its affluxes in the Rhine-Neckar-Region and tested for the occurrence of Salmonellae. 35 serotypes could be isolated 156 fold in a 200-ml-specimen. Along the collecting-sites with a higher concentration of waste-water they could be found even in smaller volumes of water (2.5 ml, 12 isolates). Especially those species could be identified, which had been reported at the public-health-departments in Mannheim, Ludwigshafen and Heidelberg as the cause of gastroenteritis during the test-period. Some divergences were observed due to the different resistance of the serotypes. The negligent deal with quite often high-contaminated surface-water (in agriculture, for private purposes) and the high environmental stability of many Salmonella-serotypes results in many infect-chains in the tested Rhine-Neckar-Region. This is one of several explanations for the still high incidence of gastroenteritis.

[Bacteriologic quality of water from the Rhine and its tributaries in the Rhine-Neckar region. I. Bacterial count and Enterobacteriaceae of the current status of pollution]

During the period of May 1982 to January 1983 and March 1986 to May 1986, 164 water-specimens had been collected along the river Rhine and its affluxes in the overcrowded Rhine-Neckar-Region from 34 collecting-sites on 8 different days. The specimens were tested for the total-germ-count and the titers of different Enterobacteriaceae-species. The total-germ-count examined concentrations of several hundreds up to 1.8 million germ in 1 ml river-water. Extremely high concentrations were found along the waste-water-influxes (purification-plants) and the overloaded Rhine-affluences (Leimbach, Kraichbach, Speyerbach, Rehbach, Neckar). The waste-water-samples from the central flow of the Rhine-river showed germ-concentrations of less than 10.000/ml, due to the mix-up of the waste water with the Rhine-water. Enterobacteriaceae--549 isolates together--could be found mainly in specimens from all collected sites in low titers. E. coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia liquefaciens and Citrobacter freundii had been the highest recovery rate. The isolation of Salmonellae was examined because of specific methods in a separate study (2. Communication). Based on these data, it has to be concluded, that the water of the Rhine-river and its affluxes in the Rhine-Neckar-Region is an uncontrolled germ-reservoir. The use of this water for bathing, unprocessed drinking-water or for agriculture purpose has to be refused from the hygienic point of view.