Inhaled crocidolite mutagenicity in lung DNA.

We used transgenic mice carrying the lacI reporter gene to study the mutagenesis potential of asbestos crocidolite. The animals were exposed by nose-only inhalation to an aerosol containing 5.75 mg/m(3) crocidolite dust for 6 hr/day and 5 consecutive days. After 1, 4, and 12 weeks, we examined four end points: the cytology of bronchoalveolar lavage, the lung load of crocidolite, the hydrophobic DNA adducts, and the mutations in the lacI reporter gene. Twelve weeks after exposure, nearly 10% of the inhaled fibers remained in the lung (227 +/- 103 ng/mg lung). There was evidence of a typical inflammatory response consisting of multinucleate macrophages at weeks 4 and 12, whereas immediately after the exposure, we observed numerous polymorphonuclear neutrophils. The mutant frequency significatively increased during the fourth week after the exposure: 13.5 [time] 10(-5) in the exposed group versus 6. 9 10(-5) in the control group. The induction factor, defined by the ratio of checked mutants of exposed mice to checked mutants of control mice, was 1.96. The mutation spectrum of control lung DNA and exposed lung DNA was similar, suggesting the possible involvement of a DNA repair decrease in crocidolite-treated animals. We used the (32)P-postlabeling method and did not detect any increase of either 5 mC or bulky adduct in treated mice. This is the first study that demonstrates asbestos mutagenicity in vivo after a nose-only inhalation.

Genotoxicity of 3-methylcholanthrene in liver of transgenic big Blue mice.

Transgenic mice provide a unique tool for studying the tissue specificity and mutagenic potential of chemicals. Because 3-methylcholanthrene (3MC) was found mutagenic in bacteria, clastogenic in bone marrow, and induces DNA adducts in animals, we were interested to determinine whether this xenobiotic provokes (1) cell proliferation, (2) transcriptional activity changes, (3) DNA adducts, and (4) hepatic mutations in transgenic Big Blue mice carrying the lambdaLIZ phage shuttle vector. Big Blue C57/Bl male mice were treated with a single intraperitoneal dose of 80 mg/kg 3MC for 1, 3, 6, 14, or 30 days. Cell proliferation was checked by 5-bromo-2-deoxyuridine labeling and immunohistochemical detection. The maximal increase of the mitotic index was evidenced after 3 days (2.9 times the control value; P < 0.01). The relative nucleus area, reflecting the transcriptional activity, was also the highest in the treated group after 3 days: 1.86 times the control value, on average (P < 0.01). Four major DNA adducts, determined according to the [(32)P]-postlabeling method, were evidenced in liver DNA of treated mice, 6 days after the treatment: the spot intensities increased in a time-dependent manner. The mutant frequency of liver DNA was the highest after 14 days: 20.3 +/- 2.9 x 10(-5) in the treated vs. 7.6 +/- 2.7 x 10(-5) in the control mice (P < 0.01). Sequencing of the lambda lacI mutant plaques showed mainly G:C --> T:A and C:G --> A:T transversions. In conclusion, 3MC at first induced nuclear enlargement and a slight increase of cell proliferation in liver, followed by parallel formation of DNA adducts and mutations. This study shows how transgenic models allow in vivo evaluation of mechanistically simultaneous endpoints.

Short-term crocidolite inhalation studies in mice: validation of an inhalation chamber.

A nose-only inhalation chamber is described: this chamber being computer automated has been particularly designed for mice on which it was validated using a crocidolite aerosol at a nominal concentration of 13.6 mg/m3, 6 h/day during 5 days. A month later the mice showed typical inflammatory bronchoalveolar liquids with many polynucleated or activated macrophages and asbestos bodies. The burden of crocidolite fibers ranged from 345,000 to 1,300,000 fibers per mg of dried lung. This study demonstrates that during the month that followed a short-term mice exposure to crocidolite fibers, the inflammatory response was still persistent. These toxicological endpoints validate the nose-only inhalation chamber to be useful for common or transgenic mice.

Interdependence of polymorphonuclear neutrophils and macrophages stained for N-acetyl-beta-glucosaminidase in lavage effluents from toluene diisocyanate-exposed rat lungs.

Male Sprague-Dawley rats were exposed to toluene diisocyanate (TDI) concentrations between 0.082 and 1.087 ppm for 4 h, and pulmonary lavage was carried out 24 h after initiation of the exposure. Cells recovered from the lavage effluents of TDI-exposed rat lungs were identified and counted, then pulmonary macrophages (PMs) resulting from cytocentrifuged preparations were examined for N-acetyl-beta-glucosaminidase (NAG) cytochemical staining. Exposure to TDI led to a parallel and concentration-dependent increase in the number of polymorphonuclear neutrophils (PMNs) and the proportion of PMs stained for NAG, suggesting that the same primary event initiates the two cell responses.

Testing natural indigo for genotoxicity.

The genotoxicity of indigo has been assessed by two short-term tests. The mutagenicity of natural indigo was compared with that of synthetic indigo. Both chemicals were tested using the standard procedure of the Salmonella/microsome mutagenicity test as described by Ames. The substance exhibits mutagenicity towards strains TA1538 and TA98 when S9 preparations of rat liver induced with Aroclor 1254 were present in the medium. The clastogenic potential was evaluated by the micronucleus test in the bone marrow of male mice. The test compound was administered twice with an interval of 24 h, the animals were killed 30 h and 54 h after the first treatment. When the test compound was given by oral gavage as two equal dosages of 0.1, 1 and 1.2 g/kg body weight, no statistically significant increase in the percentage of polychromatic erythrocytes with micronuclei was observed for any group treated with natural indigo.

Evaluation of non-radioactive labelling and detection of deoxyribonucleic acids. Part Two: Colorigenic methods and comparison with chemiluminescent methods.

The diagnosis of genetic infections and cancerous diseases is carried out more and more often at a molecular level using Southern's technique which is based on the use of 32P-labelled DNA. In order to circumvent the risks and rapid decrease in radioactivity associated with these latter techniques, new colorigenic methods have been developed. In this work, we describe the use of dTTP analogues (digoxigenin-dUTP and biotin-dUTP) for the labelling of probes and detection of target DNA. Using digoxigenin-11-dUTP, 0.1 aM of a 561 bp target DNA was detected by using a modified Southern procedure. The reliability and the high sensitivity of such methods make them a good tool for DNA investigation in research as well as in testing laboratories.

Evaluation of non-radioactive labelling and detection of deoxyribonucleic acids. Part One: Chemiluminescent methods.

The growth of analytical methods for the detection of nucleic acid from various biological samples reflects recent advances in biotechnology development especially in the areas of genetic, infections and cancer diagnosis. The target DNA is detected by hybridization techniques derived from Southern's blotting. However such assays, based on the use of 32P labelled DNA probes, bring with them the associated problems of handling radioactive materials. In order to overcome these difficulties, a number of chemiluminescent detection methods have recently been developed. These new, alternative probe labelling procedures and chemiluminescent detection methods are easy to use in routine assays performed in research laboratories as well as for medical applications, and can reach the level of sensitivity found in classical radiolabelling techniques. The techniques investigated include peroxydase, biotin 16-dUTP or digoxigenin 11-dUTP probe labelling. The target DNAs are transferred onto nitrocellulose or nylon membranes and further fixed by heat or UV crosslinking. Specific hybridization on the target DNA is finally revealed by the use of chemiluminescent substrates. For all these techniques the detection limit is 10 aM (attomol) of a 561 bp target DNA. However for the probes labelled with peroxydase and with digoxigenin the detection limit drops to 1.0 aM of the target DNA. In the present paper we shall compare several of these DNA labelling and detection procedures and show that the detection threshold can vary by as much as a factor of 20 from method to method. This is the first time that various chemiluminescent methods for label and detection of DNA are compared and evaluated in order to determine the best protocol.

Cytotoxicity assessment of heparin nanoparticles in NR8383 macrophages.

The bioavailability of low molecular weight heparin (LMWH) has been increased by encapsulation in nanoparticles. As a complement to these results, the cytotoxicity and apoptosis induced by LMWH nanoparticles prepared by two methods [nanoprecipitation (NP) and double emulsion (DE)] using Eudragit RS (RS) and poly-epsilon-caprolactone (PCL) have been analysed. Particle sizes varied from 54 to 400nm with zeta potential values between -65 and +63mV. Our results showed that the method of nanoparticle preparation affects their properties, especially in terms of drug incorporation and cell tolerance. Cell viability ranged from 6% to 100% depending on the preparation method and physicochemical properties of the particles and the type of toxicity assay. Particle diameter and zeta potential seemed to be the most valuable cytotoxicity markers when cell viability was measured by Trypan blue exclusion and MTT respectively. Nanoparticles prepared by DE were better tolerated than those of NP. LMWH encapsulation into the cationic nanoparticles reduces remarkably their toxicity. Apoptosis evaluation showed activated caspases in exposed cells. However, no nuclear fragmentation was detected in NR8383 cells whatever the tested nanoparticles. DE nanoparticles of RS and PCL can be proposed as a good LMWH delivery system due to their low toxicity (IC(50) approximately 2.33 and 0.96mg/mL, respectively).

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.

Mutagenicity of 4,4'-methylene-bis-(2-chloroaniline) "MOCA" and its N-acetyl derivatives in S. typhimurium.

4,4'-methylene-bis-(2-chloroaniline) ("MOCA") and two identified urinary N-acetyl and N,N'-diacetyl derivatives were tested in a Salmonella/mammalian microsome assay. No mutagenic activity was observed without rat liver S9 mix activation. In the presence of rat liver S9 mix, the chemicals were mutagens, but the mutagenicity of N-acetyl derivatives to strain TA100 was reduced when compared to that of "MOCA", and a greater amount of S9 was required to exhibit the mutagenicity of the N,N'-diacetyl-"MOCA". These data suggest that N-acetylation does not account for the mutagenic effectiveness of "MOCA".

Use of non-radioactive methods for the determination of the expression, the sequence and the copy-number of transgene in mice.

Marshall's observation that "toxicology goes molecular", is turning out to be more true than ever; namely as it is observed that toxicological endpoints are the point of interaction between proteins and genes following the administration of toxicants. Transgenic mice represent a valuable tool for studying the adverse effects of chemicals in genetically engineered animals such as p53 deficient mice, or mice carrying the v-Ha-ras oncogene. The latter were used in our laboratory for such toxicological assessments of chemicals. In order to verify that the transgene was expressed in normal, as well as in tumor cells, the transgene was detected in different tissues fixed with various solutions using in situ hybridization. It was also specifically retrotranscribed from paraffin-embedded tissues and consequently sequenced using a Taq polymerase reaction. We found that the transgene was expressed in various organs. It carries a specific mutation of codon 12 leading to the activation of its encoded product (transducin: p21v-Ha-ras). Moreover using a laser scanning densitometer, it has been demonstrated that 2 to 3 copies of the transgene were present per genome-equivalent in some tissues. All experiments were realized using non-radioactive labelling and detection (chemiluminescent or colorigenic) methods. Indeed, the screening of such animals was realized in a easier and a safer manner using the methods described in this paper than the usual methods based on the use of radiolabelled precursors.

From ancient remedies to modern therapeutics: pine bark uses in skin disorders revisited.

The effect of French maritime pine bark extract (PBE) on the gene expression profile of HaCaT human keratinocytes was studied using high density filter arrays. The expression profile of both control and PBE-treated cells was determined. Interestingly, PBE was shown to downregulate both calgranulin A and B genes which are known to be upregulated in psoriasis and various dermatoses. Thus, PBE could be considered in human dermatoses.

Determination of amplification level of the c-erbB-2 proto-oncogene in human breast carcinomas: a comparative study between non-radioactive and radioactive labelling.

A quantitative method of polymerase chain reaction (PCR) using both digoxigenin and radioactive labelled probes has been used for the detection of the c-erbB-2 proto-oncogene amplification in breast carcinomas with formalin-fixed paraffin-embedded tissue sections. c-erbB-2 proto-oncogene amplification has been demonstrated in 14 infiltrating ductal carcinomas. The technique consisted of the co-amplification of c-erbB-2 and IFN-gamma (interferon-gamma) genes. The latter was considered as a single copy gene per genome-equivalent. The aim of this study was to compare two quantitative PCR techniques based on the incorporation of either digoxigenin-11-dUTP or 32P-dCTP, during amplification. For the colorigenic method, using the Dig system, after electrophoresis and transfer, the specific bands were revealed with a chromogenic substrate of phosphatase. Their intensity estimated by scanning photometry following blot transparisation. After electrophoresis, the radioactive gel was submitted to radioautography and the band intensities evaluated by scanning spectrophotometry. For the 14 samples, a good agreement between both methods was noted. The colorigenic method is a valuable alternative to radiolabelling due to: i) time saving, ii) reagent conservation, iii) safe manipulation and iv) sensitivity of the same order for both methods.

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.