Effects of subchronic exposure to styrene on the extracellular and tissue levels of dopamine, serotonin and their metabolites in rat brain.

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.

Immune Signature of Malignant Pleural Mesothelioma as Assessed by Transcriptome Analysis.

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.

Man-made mineral fiber hazardous properties assessment using transgenic rodents: example of glass fiber testing.

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.

Role of tachykinins and neutral endopeptidase in toluene diisocyanate-induced bronchial hyperresponsiveness in guinea pigs.

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.

Bronchial responsiveness and inflammation in guinea-pigs exposed to toluene diisocyanate: a study on single and repeated exposure.

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.

Toluene diisocyanate-induced airway hyperresponsiveness to intravenous acetylcholine: a study on single and repeated exposure in guinea-pigs.

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.

Guinea pig pulmonary response to sensitization by five preformed monoisocyanate-ovalbumin conjugates.

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)

Quantitative evaluation of sensory irritating and neurobehavioural properties of aliphatic ketones in mice.

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.

Sensory irritation caused by various industrial airborne chemicals.

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.