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Occupational and environmental exposures to bitumen fumes during road paving or roofing activities represent a safety issue since this complex mixture of volatile compounds and particles contains carcinogenic polycyclic aromatic hydrocarbons (PAH). However, epidemiological and experimental animal studies failed to draw unambiguous conclusions concerning bitumen fumes toxicity. In order to gain better insights on their genotoxic potential, we used an experimental device able to generate bitumen fumes at 170 degrees C (upper range used during road paving operations) with a total particulate matter of 112 +/- 13 mg/m(3) and a mass median aerodynamic diameter of 4.6 mu m. The nose-only exposure of Big Blue(R) transgenic rats was performed 6 h/day for 5 consecutive days. Biological exposure to this aerosol was monitored by measuring the rat urinary levels of 1-hydroxypyrene and lungs were collected at various time-points after the end of treatment for further analysis. As determined by the 32P post-labeling method, no DNA bulky adduct was found in control animal lungs, while one was detected in exposed rats 3 and 30 days after the end of treatment, suggesting that this genetic alteration was rather stable. However, there was no correlation between the amount of DNA adduct and the level of urinary of 1-hydroxypyrene. The pulmonary mutagenic properties of bitumen fumes were determined by analyzing the mutation frequency and spectrum of the neutral reporter gene cII inserted into the transgenic rodent genome. Thirty days after exposure, the cII mutant frequency was similar in control and exposed rat lungs. However, a modification of the mutation spectrum was noticeable in treated animals. The most striking difference was an increase of G:C to T:A and A:T to C:G transversions in exposed rodents. In addition, the increased occurrence of G:C to T:A transversions at CpG dinucleotides in treated animals was consistent with DNA adduction by PAH. Even though these data failed to demonstrate a clear pulmonary mutagenic potential of bitumen fumes in our experimental conditions, the analysis of the mutational spectrum provides a sensitive measure of a quantitative increase of specific mutations which may be associated with DNA adduct formation. The weak mutagenic response might also be related to the small inhalable fraction of bitumen fume particles reaching the deep lung. In conclusion, these results could give insights on the mechanism of action of bitumen fumes and provide additional information concerning human risk assessment associated with bitumen exposure. [ABSTRACT FROM AUTHOR]

Synthetic amorphous silica nanomaterials (SAS) are extensively used in food and tire industries. In many industrial processes, SAS may become aerosolized and lead to occupational exposure of workers through inhalation in particular. However, little is known about the in vivo genotoxicity of these particulate materials. To gain insight into the toxicological properties of four SAS (NM-200, NM-201, NM-202, and NM-203), rats are treated with three consecutive intratracheal instillations of 3, 6, or 12 mg/kg of SAS at 48, 24, and 3 hrs prior to tissue collection (cumulative doses of 9, 18, and 36 mg/kg). Deoxyribonucleic acid (DNA) damage was assessed using erythrocyte micronucleus test and the standard and Fpg-modified comet assays on cells from bronchoalveolar lavage fluid (BALF), lung, blood, spleen, liver, bone marrow, and kidney. Although all of the SAS caused increased dose-dependent changes in lung inflammation as demonstrated by BALF neutrophilia, they did not induce any significant DNA damage. As the amount of SAS reaching the blood stream and subsequently the internal organs is probably to be low following intratracheal instillation, an additional experiment was performed with NM-203. Rats received three consecutive intravenous injections of 5, 10, or 20 mg/kg of SAS at 48, 24, and 3 hrs prior to tissue collection. Despite the hepatotoxicity, thrombocytopenia, and even animal death induced by this nanomaterial, no significant increase in DNA damage or micronucleus frequency was observed in SAS-exposed animals. It was concluded that under experimental conditions, SAS induced obvious toxic effects but did cause any genotoxicity following intratracheal instillation and intravenous injection., (© 2014 Wiley Periodicals, Inc.)

The cytogenetic alterations in leukocytes and the increased risk for leukemia, lymphoma, or all lymphohematopoietic cancer observed in workers occupationally exposed to styrene have been associated with its hepatic metabolisation into styrene-7,8-oxide, an epoxide which can induce DNA damages. However, it has been observed that styrene-7,8-oxide was also found in the atmosphere of reinforced plastic industries where large amounts of styrene are used. Since the main route of exposure to these compounds is inhalation, in order to gain new insights regarding their systemic genotoxicity, Fisher 344 male rats were exposed in full-body inhalation chambers, 6 h/day, 5 days/week for 4 weeks to styrene-7,8-oxide (25, 50, and 75 ppm) or styrene (75, 300, and 1000 ppm). Then, the induction of micronuclei in circulating reticulocytes and DNA strand breaks in leukocytes using the comet assay was studied at the end of the 3rd and 20th days of exposure. Our results showed that neither styrene nor styrene-7,8-oxide induced a significant increase of the micronucleus frequency in reticulocytes or DNA strand breaks in white blood cells. However, in the presence of the formamidopyridine DNA glycosylase, an enzyme able to recognize and excise DNA at the level of some oxidized DNA bases, a significant increase of DNA damages was observed at the end of the 3rd day of treatment in leukocytes from rats exposed to styrene but not to styrene-7,8-oxide. This experimental design helped to gather new information regarding the systemic genotoxicity of these two chemicals and may be valuable for the risk assessment associated with an occupational exposure to these molecules., (Copyright © 2012 Elsevier Ireland Ltd. All rights reserved.)

Asbestos-induced mutagenicity in the lung may involve reactive oxygen/nitrogen species (ROS/RNS) released by alveolar macrophages. With the aim of proposing an alternative in vitro mutagenesis test, a coculture system of rat alveolar macrophages (NR8383) and transgenic Big Blue Rat2 embryonic fibroblasts was developed and tested with a crocidolite sample. Crocidolite exposure induced no detectable increase in ROS production from NR8383, contrasting with the oxidative burst that occurred following a brief exposure (1 hour) to zymosan, a known macrophage activator. In separated cocultures, crocidolite and zymosan induced different changes in the gene expressions involved in cellular inflammation in NR8383 and Big Blue. In particular, both particles induced up-regulation of iNOS expression in Big Blue, suggesting the formation of potentially genotoxic nitrogen species. However, crocidolite exposure in separated or mixed cocultures induced no mutagenic effects whereas an increase in Big Blue mutants was detected after exposure to zymosan in mixed cocultures. NR8383 activation by crocidolite is probably insufficient to induce in vitro mutagenic events. The mutagenesis assay based on the coculture of NR8383 and Big Blue cannot be used as an alternative in vitro method to assess the mutagenic properties of asbestos fibres.

At present, there is controversy over the neurotoxic potential of styrene. Several epidemiological and clinical studies have shown that styrene exposure causes alterations of central nervous system functions in humans. Neurotransmitters have been implicated in the pathogenesis of styrene neurotoxicity in rodents. Several studies carried out on postmortem brain tissue suggest that styrene may alter dopaminergic neurotransmission in rabbit or rat brain. Moreover, in vitro studies suggest that both styrene and styrene oxide inhibit the uptake of dopamine (DA) in purified synaptic vesicles prepared from rat brain striata. To date, biochemical studies on animals have explored global tissue levels of neurotransmitters with sub-acute exposures to styrene. However, extracellular levels of neurotransmitters are more closely related to behaviour than are global tissue levels. The present study determined changes in the extracellular concentrations of DA, serotonin (5-HT) and their acid metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), in striatal dialysates from freely moving adult male rats after exposure to 750 and 1,000 ppm styrene, 6 h per day, 5 days per week for 4 weeks. We also determined the concentrations of DA, 5-HT and their acid metabolites in striatum, nucleus accumbens and prefrontal cortex obtained postmortem from similarly exposed rats. Exposure to 1,000 ppm of styrene caused a significant decrease in extracellular acid metabolite concentrations. Tissue levels of acid metabolites were also decreased to a lesser extent. The effects were observed 72 h after discontinuing exposure but had vanished 17 days later. There was no change in DA or 5-HT concentrations either in the dialysates or tissues. Exposure to 750 ppm styrene caused no changes in the concentrations of DA, 5-HT and their acid metabolites either in the dialysates or tissues. The possibility that the effect of styrene is mediated by monoamine oxidase (MAO) inhibition is discussed.

Exposure to bitumen fumes during paving and roofing activities may represent an occupational health risk. To date, most of the studies performed on the biological effect of asphalt fumes have been done with regard to their content in carcinogenic polycyclic aromatic hydrocarbons (PAH). In order to gain an additional insight into the mechanisms of action of bitumen fumes, we studied their pulmonary effects in rodents following inhalation using the microarray technology. Fisher 344 rats were exposed for 5 days, 6 h/day to bitumen fumes generated at road paving temperature (170 degrees C) using a nose-only exposition device. With the intention of studying the early transcriptional events induced by asphalt fumes, lung tissues were collected immediately following exposure and gene expression profiles in control and exposed rats were determined by using oligonucleotide microarrays. Data analysis revealed that genes involved in lung inflammatory response as well as genes associated with PAH metabolization and detoxification were highly expressed in bitumen-exposed animals. In addition, the expression of genes related to elastase activity and its inhibition which are associated with emphysema was also modulated. More interestingly genes coding for monoamine oxidases A and B involved in the metabolism of neurotransmitters and xenobiotics were downregulated in exposed rats. Altogether, these data give additional information concerning the bitumen fumes biological effects and would allow to better review the health effects of occupational asphalt fumes exposure.

Road paving workers are exposed to bitumen fumes (CAS No. 8052-42-4), a complex mixture of volatile compounds and particles containing carcinogenic and non-carcinogenic polycyclic aromatic hydrocarbons. However, epidemiological and experimental animal studies failed to draw unambiguous conclusions concerning their toxicity. In order to gain better insights on their genotoxic potential, we used an experimental design able to generate bitumen fumes at road paving temperature (temperature: 170 degrees C, total particulate matter: 100mg/m3) and perform a nose-only exposure of Big Blue transgenic rodents 6h/day for five consecutive days. The mutagenic properties of bitumen fumes were determined by analyzing the mutation frequency and spectrum of the neutral reporter gene cII inserted into the rodent genome. We previously observed in mouse lung, that bitumen fumes did not induce an increase of cII mutants, a modification of the mutation spectrum, nor the formation of DNA adducts. Since DNA adducts were found in the lungs of rats exposed to asphalt fumes in similar conditions, we decided to carry out an analogous experiment with Big Blue rats. A DNA adduct was detected 3 and 30 days after the end of treatment suggesting that these genetic alterations were quite steady. Thirty days after exposure, the cII mutant frequency was similar in control and exposed rats. In addition, a slight but not significant modification of the mutation spectrum associated with an increase of G:C to T:A and A:T to C:G transversions was noticeable in the treated animals. Then, these data failed to demonstrate a pulmonary mutagenic potential for bitumen fumes generated at road paving temperature in our experimental conditions despite the presence of a DNA adduct. These results may provide information concerning the pulmonary mechanism of action of this aerosol and may contribute to the occupational health hazard assessment.

Triadimefon has been shown to inhibit monoamine uptake, bind to the dopamine (DA) transporter, and stimulate dopamine efflux in rat brain tissue, in vitro. To determine whether these changes also occur in the intact animal and to study the reversibility of the effects observed, we used in vivo microdialysis to determine changes in the concentrations of DA, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA) in the striatal dialysates from free moving adult rats after exposure to triadimefon 50, 100 and 200mg/kg, i.p. Triadimefon induced a gradual dose- and time-dependent accumulation of extracellular DA accompanied by a small increase in the HVA and 5-HIAA concentrations. These changes were still present 24h after treatment in the group treated with 200mg/kg and had vanished 48 h after treatment. In contrast to the DA efflux induced by S(+)-amphetamine (2mg/kg, i.p.), that induced by triadimefon was totally inhibited by the infusion of 10(-5)M tetrodotoxin (TTX), a voltage-gated Na(+) channel blocker, thus showing that the increase in extracellular DA induced by triadimefon was an action potential-dependent mechanism. GBR 12909 (10mg/kg, i.p.), a dopamine uptake inhibitor, induced a gradual increase in striatal dopamine similar to that induced by triadimefon, whereas the effects on the acid metabolites were not exactly the same. The present results indicate that triadimefon acts in vivo as a DA transporter inhibitor and could also act on the serotoninergic system.

Malignant pleural mesothelioma (MPM) is a highly malignant tumor arising in patients previously exposed to asbestos fibers. Its increasing incidence and its social, financial and human impact have become a frequent problem in many industrialized countries. The unresponsiveness of malignant mesothelioma to conventional therapies has led clinicians to develop new treatments. As immunotherapy has been shown to offer promising and targeted treatment of MPM patients, the knowledge of the immunoresistance level of MPM may be a valuable tool for "à la carte" therapy. In a previous work, we profiled the gene expression of two MPM tissues compared to healthy mesothelial cells using a 10K cDNA microarray. Subsequent clustering analysis identified several clusters of differentially-expressed genes among those that are functionally-related to the immune system. In this report, we focus on genes with expression changes that may facilitate tumor escape from immune-mediated rejection. We also analyzed the immune reaction by staining the immunocompetent cells surrounding the tumor. Interestingly, the tumor with the strongest escape response, as shown by the expression of numerous immunoresistance-associated genes, displayed the strongest T cell infiltrate. The main genes conferring immunoresistance are CD74, HLADOA, HLADMB, PTGS1, IGFBP7 and TGFB3, by favoring immune tolerance, and CFLAR, DFFA, TNFRSF6, BNIP3L by impairing apoptosis. These observations have fundamental consequences in the understanding of immunological properties of MPM, and offer a new insight into the mechanisms whereby MPM may circumvent host-mediated immune activities and promotes its own development. For an immunomodulation strategy to cure mesothelioma, it is crucial to characterize the MPM "immune signature" to design adapted immunotherapies., (Copyright© 2005 International Institute of Anticaner Research (Dr. John G. Delinassios), All rights reserved.)

Transgenic BigBlue rats were exposed to CM 44 glass fibers (6.3 mg/m3) by nose only, 6 h/day for 5 days. Two endpoints were examined 1, 3, 14, 28, and 90 days following exposure: fiber biopersistence and mutations in lung DNA. The half-time of the fibers >20 microm was 12.8 days, and mutant frequencies of control and exposed rats were similar across all time points. The mutation spectra of both series were similar after 28 days of fixation time. These results showed that a glass fiber with a high clearance in the lung seems to not present any significant effect on mutagenesis on lung DNA and are in marked contrast to results for asbestos, which caused a twofold mutant frequency increase as described in a previous study.

During hot application of bitumen containing materials, e.g. in hot paving or roofing, fumes are emitted that contain polycyclic aromatic compounds. Previous studies with rodents exposed to bitumen and coal-tar fume condensates showed formation of DNA adducts. In order to clarify the genotoxicity of bitumen fumes, we designed a study by using mice carrying a reporter gene for mutagenesis analysis and exposed by nose-only to a constant and reproducible aerosol of bitumen fumes. We analyzed the genotoxic activity of inhaled bitumen fumes generated under those controlled conditions through the induction of mutation and DNA adducts in Big Blue mice. Mice were exposed to bitumen fumes (100 mg/m(3) total particulate matter) 6 h per day during 5 days by nose-only in an inhalation chamber designed in our laboratory. Following a 30-day fixation period, the experiment was terminated and lung DNA was extracted for mutant frequency and adduct determinations. The mutant frequency was determined using the cII and the lacI mutant analysis systems. In, addition, 61 and 54 mutants were sequenced in control and exposed groups, respectively. The study did not show any mutation or adduct induction in the exposed group compared to the control group: cII mutant frequencies were 11.0+/-4.5x10(-5) and 11.0+/-4.8x10(-5) in control and exposed lungs, respectively. Identically, using the lacI mutation detection system, the mutant frequencies were 6.4+/-3.1x10(-5) and 5.8+/-2.0x10(-5). The mutation spectra of both series were quite similar with regard to transition and transversion frequencies. The absence of genotoxicity in the group exposed to 100 mg/m(3) bitumen is discussed with regard to dosage of inhaled polycyclic aromatic compounds and species.

The role of tachykinins in toluene diisocyanate (TDI)-induced non-specific bronchial hyperreactivity (NSBH) in guinea pigs was investigated, and it was determined whether or not the activity of airway neutral endopeptidase (NEP) was inhibited in conditions where a bronchial hyperreactivity to acetylcholine (ACh) was observed. Exposures to 3 ppm TDI for 1 h, or to 0.029 ppm for 8 weeks caused a significant bronchial hyperreactivity to ACh. The depletion of tachykinins by a pretreatment with capsaicin (140 mg/kg) eliminated the TDI-induced airway hyperresponsiveness in both patterns of exposure to TDI. Capsaicin treatment had no effect on the response to ACh in guinea-pigs exposed to air (controls). Bronchial NEP activity determined by histoenzymology was significantly less 4 and 24 h after the end of a 1-h exposure to 3 ppm TDI than after exposure to air. Bronchial NEP activity evaluated 24 h after the end of a 48-h exposure to 0.116 ppm TDI, or a 1-week exposure to 0.050 ppm TDI was not significantly different from those of controls exposed to air, whereas in the same conditions of exposure a NSBH is observed in guinea-pigs. These data suggest that tachykinins released from C-fibers upon acute or repeated exposures to high or low concentrations of TDI, respectively, play an essential role in the observed bronchial hyperreactivity, and that the inhibition of NEP by TDI cannot completely account for the observed airway hyperreactivity.

The question of whether or not toluene diisocyanate (TDI)-induced airway hyperresponsiveness in the guinea-pig is accompanied by neutrophil influx into bronchoalveolar lavage fluid (BALF) was addressed. Two modes of exposure were studied; (1) acute exposures where animals were exposed to 3 ppm TDI for 1 h and experiments were carried out 30 min, 4 h, 24 h, 48 h and 1 week after the TDI exposures; (2) subacute exposures where animals were exposed to 0.080 and 0.046 ppm TDI for 48 h 1 week, respectively, and experiments were carried out 24 h after the TDI exposures. The changes in airway responsiveness to increasing doses of intravenous acetylcholine (ACh) in anaesthetized and tracheotomized spontaneously breathing guinea-pigs were examined. In order to elucidate the possible relationships of airway responsiveness to cellular infiltration, bronchoalveolar lavage was performed in additional group of guinea-pigs exposed to the same conditions. After acute exposure to 3 ppm TDI, increased bronchial responsiveness was evident within 30 min, lasted 48 h, but had vanished 1 week after the exposure. An influx of neutrophils occurred into the BALF within 1 h after exposure. The influx of neutrophil into BALF lasted 48 h and vanished 1 week after the end of exposure. After 48 h of exposure to TDI at 0.080 ppm, or 0.046 ppm for 1 week, increased bronchial responsiveness was evident 24 h after the end of the both modes of exposure, but no influx of neutrophils was observed into the BALF. It was concluded that even though the neutrophil influx and hyperresponsiveness evolve in the same way after acute exposure to a high concentration of TDI (3 ppm), this is not the case after subchronic exposure to low concentrations of TDI, where a bronchial hyperresponsiveness is observed without detectable neutrophil influx.

The ability of 5 dissimilar monoisocyanates conjugated to ovalbumin (OA) as a carrier protein to induce pulmonary hypersensitivity towards the hapten specific component was assessed by using a previously described method based on the determination of a respiratory index (RI) in the guinea pig. The test chemicals included the commercially available p-tolyl and hexyl monoisocyanates (TMI and HMI), with 4-isocyanoto-4'-diphenylmethane (IDM), 4-isocyanoato-4'-methyldiphenylmethane (IMDM) and 1-isocyanato-methyl-1,3,3-trimethylcyclohexane (IMTC) as synthetized monoisocyanates. Guinea pigs were exposed daily to an aerosol of the OA conjugate of each monoisocyanate up to day 15. Increases in respiratory rate and/or respiratory collapse occurred in the guinea pigs exposed to TMI-OA and HMI-OA conjugates by days 9 and 15, with RI values of 155 and 177, respectively, being recorded. The greatest mean RI values in guinea pigs exposed to IDM-OA, IMDM-OA and IMTC-OA conjugates up to day 15 were 20, 25 and 22, respectively, and were not indicative of any pulmonary reaction. Guinea pigs exposed in parallel to each test conjugate did not exhibit any pulmonary reaction when they were exposed to OA on the challenge days. All these findings evidence pulmonary hypersensitivity as the result of exposure to TMI-OA and HMI-OA conjugates and suggest a high degree of conjugation and strong linkage of all the monoisocyanates with OA.(ABSTRACT TRUNCATED AT 250 WORDS)

A short inhalation experiment was performed on mice using 22 industrial airborne irritants. The parameter chosen as an index of sensory irritation was the reflex decrease in respiratory rate. For each compound, systematic determination of the concentration associated with a 50% decrease in the respiratory rate (RD50) permitted, on the basis of the same end point, a comparison of their relative potencies. The possibility of using the obtained data as initial guidelines to establish acceptable Threshold Limit Values (TLVs) in the workplace was examined.

A decrease in respiratory rate resulting from irritation of upper airways and a decrease in duration of immobility in a 'behavioural despair' swimming test occurred in mice during and following short-term inhalation exposures to some commonly used aliphatic ketones. Linear concentration-effect relationships were obtained that allowed two different median active levels (MALs) to be calculated. MALs that produced a 50% decrease in respiratory rate (RD50) were calculated as indicators of the sensory irritation potency of diisobutyl ketone, mesityl oxide, methyl amyl ketone, methyl isoamyl ketone and methyl propyl ketone. MALs that produced a 50% decrease in immobility (ID50) were determined for acetone, isophorone, mesityl oxide, methyl amyl ketone, methyl isoamyl ketone, methyl isobutyl ketone and methyl propyl ketone. The systematic determination of MALs permits classification of ketones in terms of their relative potencies for eliciting a given effect. The lowest MAL indicates the primary manifestation of toxicity, against which protection should be taken. MALs associated with such critical responses may be useful in the establishment of safe levels of occupational exposure to ketones, a conclusion supported by the linear relationship that was found to exist between MALs and occupational standards.

We examined the changes in airway responsiveness to increasing doses of intravenous acetylcholine (ACh), in groups of 10 anaesthetized and tracheotomized spontaneously breathing guinea-pigs, 20 h after inhalation exposure to toluene diisocyanate (TDI). TDI exposure consisted of a single 4-h exposure to 1.2 ppm, intermittent exposures to 1.078 and 0.126 ppm for 4 h daily for 2 consecutive days, and continuous exposures to 0.118 ppm for 48 h or to 0.045 and 0.023 ppm for 1 week. Airway resistance (Raw) of the corresponding control groups, which inhaled clean filtered air, was used as baseline, and was similar for air and TDI groups. All the patterns of exposure, except exposure to 0.126 ppm TDI for 4 h daily for 2 consecutive days, significantly reduced by 28-60% the dose of ACh calculated to cause a 200% increase in Raw (ED200). The results indicate that TDI-induced airway hyperresponsiveness to ACh in guinea-pigs can occur at a level of exposure as low as 0.023 ppm for 1 week, and is consistent with the hypothesis of a cumulative effect.