Comparative study of bronchoalveolar lavage fluid: effect of species, age, and method of lavage

Regenerative and progressing lesions in lungs and lung-associated lymph nodes from fourteen 90-day inhalation studies with chemically different particulate materials

Rat lungs and lung-associated lymph nodes from 14 inhalation studies with chemically different particulate materials were histopathologically re-evaluated, and the bronchoalveolar lavage fluid (BALF) data and lung burden analyses were compared. All investigated substances caused similar lesions. For most substances, 1 mg/m3 of respirable particulate matter was established as the borderline for adverse morphological changes after the 90-day exposure period, confirmed by the increase in polymorphonuclear neutrophils in BALF. Possible reversibility was demonstrated when recovery groups are included in the study especially allowing the differentiation between regeneration or progressing of inflammatory changes during the recovery period. It was concluded, that the major driver of toxicity is not an intrinsic chemical property of the particle but a particle effect. Concerning classification for specific target organ toxicant (STOT) repeated exposure (RE), this paper highlights that merely comparing the lowest concentration, at which adverse effects were observed, with the Classification Labelling and Packaging (CLP) regulation (EC) no. 1272/2008 guidance values is inappropriate and might lead to a STOT classification under CLP for a large part of the substances discussed in this paper, on the basis of typically mild to moderate findings in rat lung and lung-associated lymph nodes on day 1 after exposure. An in-depth evaluation of the pathologic findings is required and an expert judgement has to be included in the decision on classification and labeling, evaluating the type and severity of effects and comparing these with the classification criteria.

PLATOX: Integrated In Vitro/In Vivo Approach for Screening of Adverse Lung Effects of Graphene-Related 2D Nanomaterials

Graphene-related two-dimensional nanomaterials possess very technically promising characteristics, but gaps exist regarding their potential adverse health effects. Based on their nano-thickness and lateral micron dimensions, nanoplates exhibit particular aerodynamic properties, including respirability. To develop a lung-focused, in vitro/in vivo screening approach for toxicological hazard assessment, various graphene-related nanoplates, i.e., single-layer graphene (SLG), graphene nanoplatelets (GNP), carboxyl graphene, graphene oxide, graphite oxide and Printex 90® (particle reference) were used. Material characterization preceded in vitro (geno)toxicity screening (membrane integrity, metabolic activity, proliferation, DNA damage) with primary rat alveolar macrophages (AM), MRC-5 lung fibroblasts, NR8383 and RAW 264.7 cells. Submerse cell exposure and material-adapted methods indicated material-, cell type-, concentration-, and time-specific effects. SLG and GNP were finally chosen as in vitro biologically active or more inert graphene showed eosinophils in lavage fluid for SLG but not GNP. The subsequent 28-day inhalation study (OECD 412) confirmed a toxic, genotoxic and pro-inflammatory potential for SLG at 3.2 mg/m3 with an in vivo-ranking of lung toxicity: SLG > GNP > Printex 90®. The in vivo ranking finally pointed to AM (lactate dehydrogenase release, DNA damage) as the most predictive in vitro model for the (geno)toxicity screening of graphene nanoplates.

Research-Relevant Clinical Pathology Resources: Emphasis on Mice, Rats, Rabbits, Dogs, Minipigs, and Non-Human Primates

Clinical pathology testing for investigative or biomedical research and for preclinical toxicity and safety assessment in laboratory animals is a distinct specialty requiring an understanding of species specific and other influential variables on results and interpretation. This review of clinical pathology principles and testing recommendations in laboratory animal species aims to provide a useful resource for researchers, veterinary specialists, toxicologists, and clinical or anatomic pathologists.

Assessment of cellular and molecular metrics for dose selection in an in vivo comet assay: A case study with MDI

The in vivo comet assay can evaluate the genotoxic potential of a chemical in theoretically any tissue that can be processed to a single cell suspension. This flexibility enables evaluation of point-of-contact tissues using a relevant route of test material administration; however, assessing cytotoxicity is essential for the interpretation of comet results. Histopathological evaluation is routinely utilized to assess cytotoxicity, but temporal- and cell-specific considerations may compromise applicability to the comet assay. In the present study, 1,1'-methylenebis(4-isocyanatobenzene) (4,4'-MDI) was administered to rats for 6 h by nose-only inhalation, and the comet assay was conducted to evaluate genotoxicity in the site-of-contact tissue (bronchoalveolar lavage cells) and distal tissues (liver and glandular stomach). Given the reactive nature of MDI, cellular and molecular metrics at the site-of-contact- including inflammation, macrophage activation, apoptosis/necrosis, and oxidative stress- were used to set appropriate exposure concentrations, in addition to the standard systemic measures of toxicity. In the range-finding study, a concentration of 4 mg/m³ was considered the maximum noninflammatory concentration; hence target concentrations of 2, 5, and 11 mg/m³ were selected for the comet study. In the lung lavage, MDI exposure substantially increased total protein and β-glucuronidase, along with cellular apoptosis. Although MDI did not increase the comet assay response (% tail DNA) in any of the tissues examined, the positive control (ethyl methanesulfonate, EMS) significantly increased % tail DNA in all tissues. In total, these data indicate that appropriate cellular and molecular measurements may facilitate dose selection to discern cellular status in the comet assay.

Dynamics of Lead Bioavailability and Speciation in Indoor Dust and X-ray Spectroscopic Investigation of the Link between Ingestion and Inhalation Pathways

Lead (Pb) exposure from household dust is a major childhood health concern because of its adverse impact on cognitive development. This study investigated the absorption kinetics of Pb from indoor dust following a single dose instillation into C57BL/6 mice. Blood Pb concentration (PbB) was assessed over 24 h, and the dynamics of particles in the lung and gastro-intestinal (GI) tract were visualized using X-ray fluorescence (XRF) microscopy. The influence of mineralogy on Pb absorption and particle retention was investigated using X-ray absorption near-edge structure spectroscopy. A rapid rise in PbB was observed between 0.25 and 4 h after instillation, peaking at 8 h and slowly declining during a period of 24 h. Following clearance from the lungs, Pb particles were detected in the stomach and small intestine at 4 and 8 h, respectively. Analysis of Pb mineralogy in the residual particles in tissues at 8 h showed that mineral-sorbed Pb and Pb-phosphates dominated the lung, while organic-bound Pb and galena were the main phases in the small intestines. This is the first study to visualize Pb dynamics in the lung and GI tract using XRF microscopy and link the inhalation and ingestion pathways for metal exposure assessment from dust.

Cerium oxide and barium sulfate nanoparticle inhalation affects gene expression in alveolar epithelial cells type II

BACKGROUND

Understanding the molecular mechanisms of nanomaterial interacting with cellular systems is important for appropriate risk assessment. The identification of early biomarkers for potential (sub-)chronic effects of nanoparticles provides a promising approach towards cost-intensive and animal consuming long-term studies. As part of a 90-day inhalation toxicity study with CeO₂ NM-212 and BaSO₄ NM-220 the present investigations on gene expression and immunohistochemistry should reveal details on underlying mechanisms of pulmonary effects. The role of alveolar epithelial cells type II (AEII cells) is focused since its contribution to defense against inhaled particles and potentially resulting adverse effects is assumed. Low dose levels should help to specify particle-related events, including inflammation and oxidative stress.

RESULTS

Rats were exposed to clean air, 0.1, 0.3, 1.0, and 3.0 mg/m³ CeO₂ NM-212 or 50.0 mg/m³ BaSO₄ NM-220 and the expression of 391 genes was analyzed in AEII cells after one, 28 and 90 days exposure. A total number of 34 genes was regulated, most of them related to inflammatory mediators. Marked changes in gene expression were measured for Ccl2, Ccl7, Ccl17, Ccl22, Ccl3, Ccl4, Il-1α, Il-1ß, and Il-1rn (inflammation), Lpo and Noxo1 (oxidative stress), and Mmp12 (inflammation/lung cancer). Genes related to genotoxicity and apoptosis did not display marked regulation. Although gene expression was less affected by BaSO₄ compared to CeO₂ the gene pattern showed great overlap. Gene expression was further analyzed in liver and kidney tissue showing inflammatory responses in both organs and marked downregulation of oxidative stress related genes in the kidney. Increases in the amount of Ce were measured in liver but not in kidney tissue. Investigation of selected genes on protein level revealed increased Ccl2 in bronchoalveolar lavage of exposed animals and increased Lpo and Mmp12 in the alveolar epithelia.

CONCLUSION

AEII cells contribute to CeO₂ nanoparticle caused inflammatory and oxidative stress reactions in the respiratory tract by the release of related mediators. Effects of BaSO₄ exposure are low. However, overlap between both substances were detected and support identification of potential early biomarkers for nanoparticle effects on the respiratory system. Signs for long-term effects need to be further evaluated by comparison to a respective exposure setting.

Organosilane-Based Coating of Quartz Species from the Traditional Ceramics Industry: Evidence of Hazard Reduction Using In Vitro and In Vivo Tests

The exposure to respirable crystalline silica (RCS), e.g. quartz, in industrial settings can induce silicosis and may cause tumours in chronic periods. Consequently, RCS in the form of quartz and cristobalite has been classified as human lung carcinogen category 1 by the International Agency for Research on Cancer in 1997, acknowledging differences in hazardous potential depending on source as well as chemical, thermal, and mechanical history. The physico-chemical determinants of quartz toxicity are well understood and are linked to density and abundance of surface silanol groups/radicals. Hence, poly-2-vinylpyridine-N-oxide and aluminium lactate, which effectively block highly reactive silanol groups at the quartz surface, have formerly been introduced as therapeutic approaches in the occupational field. In the traditional ceramics industry, quartz-containing raw materials are indispensable for the manufacturing process, and workers are potentially at risk of developing quartz-related lung diseases. Therefore, in the present study, two organosilanes, i.e. Dynasylan® PTMO and Dynasylan® SIVO 160, were tested as preventive, covalent quartz-coating agents to render ceramics production safer without loss in product quality. Coating effectiveness and coating stability (up to 1 week) in artificial alveolar and lysosomal fluids were first analysed in vitro, using the industrially relevant quartz Q1 as RCS model, quartz DQ12 as a positive control, primary rat alveolar macrophages as cellular model system (75 µg cm⁻²; 4 h of incubation ± aluminium lactate to verify quartz-related effects), and lactate dehydrogenase release and DNA strand break induction (alkaline comet assay) as biological endpoints. In vitro results with coated quartz were confirmed in a 90-day intratracheal instillation study in rats with inflammatory parameters as most relevant readouts. The results of the present study indicate that in particular Dynasylan® SIVO 160 (0.2% w/w of quartz) was able to effectively and stably block toxicity of biologically active quartz species without interfering with technical process quality of certain ceramic products. In conclusion, covalent organosilane coatings of quartz might represent a promising strategy to increase workers’ safety in the traditional ceramics industry.

Effects from a 90-day inhalation toxicity study with cerium oxide and barium sulfate nanoparticles in rats

Background

Nanomaterials like cerium oxide and barium sulfate are frequently processed in industrial and consumer products and exposure of humans and other organisms is likely. Generally less information is given on health effects and toxicity, especially regarding long-term exposure to low nanoparticle doses. Since inhalation is still the major route of uptake the present study focused on pulmonary effects of CeO₂NM-212 (0.1, 0.3, 1.0, 3.0 mg/m³) and BaSO₄NM-220 nanoparticles (50.0 mg/m³) in a 90-day exposure setup. To define particle-related effects and potential mechanisms of action, observations in histopathology, bronchoalveolar lavage and immunohistochemistry were linked to pulmonary deposition and clearance rates. This further allows evaluation of potential overload related effects.

Results

Lung burden values increased with increasing nanoparticle dose levels and ongoing exposure. At higher doses, cerium clearance was impaired, suggesting lung overload. Barium elimination was extremely rapid and without any signs of overload. Bronchoalveolar lavage fluid analysis and histopathology revealed lung tissue inflammation with increasing severity and post-exposure persistency for CeO₂. Also, marker levels for genotoxicity and cell proliferation were significantly increased. BaSO₄ showed less inflammation or persistency of effects and particularly affected the nasal cavity.

Conclusion

CeO₂ nanoparticles penetrate the alveolar space and affect the respiratory tract after inhalation mainly in terms of inflammation. Effects at low dose levels and post-exposure persistency suggest potential long-term effects and a notable relevance for human health. The generated data might be useful to improve nanoparticle risk assessment and threshold value generation. Mechanistic investigations at conditions of non-overload and absent inflammation should be further investigated in future studies.

Change in agglomeration status and toxicokinetic fate of various nanoparticles in vivo following lung exposure in rats

The deposition characteristics in lungs following inhalation, the potential toxic effects induced and the toxicokinetic fate including a possible translocation to other sites of the body are predominantly determined by the agglomeration status of nanoscaled primary particles. Systemic particle effects, i.e. effects on remote organs besides the respiratory tract are considered to be of relevant impact only for de-agglomerated particles with a nanoscaled aspect. Rats were exposed to various types of nanoscaled particles, i.e. titanium dioxide, carbon black and constantan. These were dispersed in physiologically compatible media, e.g. phosphate buffer, sometimes including auxiliaries. Rats were treated with aqueous nanoparticle dispersions by intratracheal instillation or were exposed to well-characterized nanoparticle aerosols. Subsequently, alterations in the particle size distribution were studied using transmission electron microscopy (TEM) as well as the bronchoalveolar lavage (BAL) technique. Based on the results in various approaches, a tendency of nanoscaled particles to form larger size agglomerates following deposition and interaction with cells or the respiratory tract is predominant. The contrary trend, i.e. the increase of particle number due to a disintegration of agglomerates seems not to be of high relevance.

Biomarkers in risk assessment of asbestos exposure

Developments in the field of molecular epidemiology and toxicology have given valuable tools for early detection of impending disease or toxic condition. Morbidity due to respiratory distress, which may be due to environmental and occupational exposure, has drawn attention of researchers worldwide. Among the occupational exposure to respiratory distress factors, fibers and particles have been found to be main culprits in causing diseases like asbestosis, pleural plaques, mesotheliomas and bronchogenic carcinomas. An early detection of the magnitude of exposure or its' effect using molecular end points is of growing importance. The early inflammatory responses like release of the inflammatory cells collected by non-invasive methods give an indication of the unwanted exposure and susceptibility to further complications. Since free radicals like O2-, OH, OOH, NO, NOO, etc. are involved in the progression of asbestos-related diseases and lead to cytogenetic changes, an evaluation of antioxidant states reducing equivalents like GSH and ROS generation can be a good biomarker. The cytogenetic end points like chromosomal aberration, micronucleus formation and sister chromatid exchange give indication of genetic damage, hence they are used as effective biomarkers. New techniques like fluorimetric analysis of DNA unwinding, alkaline elution test, fluorescent in situ hybridization and comet assay are powerful tools for early detection of initiation of disease process and may help in planning strategies for minimizing morbidity related to asbestos fiber exposure. The present review article covers in detail possible biomarkers for risk assessment of morbidity due to fibers/particles in exposed population.

In vivo inhibition of inducible nitric oxide synthase decreases lung injury induced by Toxocara canis in experimentally infected rats

The direct effect of nitric oxide (NO) on the viability of Toxocara canis larvae was studied. We observed that the nitric oxide donors, SIN-1 and SNOG, exert no cytotoxic effect on the in vitro viability of T. canis larvae. In addition, we developed a model in rats to elucidate the role of NO during T. canis infection. We evaluated different indicators in four experimental groups: morphological parameters, the total number cells and cell types recovered, nitrite and protein concentration, lactate dehydrogenase and alkaline phosphatase enzymatic activity in the bronchoalveolar lavage fluid, lung index and detection of anti-T. canis specific antibodies. We observed significant differences between non-infected and infected groups. The infected animals treated with the inducible nitric oxide synthase (iNOS) inhibitor aminoguanidine were less damaged than infected, non-treated animals. Our results suggest that the in vivo inhibition of the synthesis of NO triggered by iNOS diminishes the deleterious effects of the parasite upon the host, especially the vascular alterations in the lungs. We could show that in vivo production of NO induced by infection with T. canis results in direct host damage. Thus, this induction may constitute an evasion/adaptation mechanism of the parasite.

Pulmonary inflammation in rats after intratracheal instillation of quartz, amorphous SiO2, carbon black, and coal dust and the influence of poly-2-vinylpyridine-N-oxide (PVNO)

Effects of poly-2-vinylpyridine-N-oxide (PVNO) were investigated in numerous in vivo and in vitro studies published in the nineteen sixties and seventies. These studies showed that PVNO inhibited development of fibrosis from quartz dust and improved lung clearance of quartz after inhalation exposure. Ameliorating effects of PVNO were observed also for pulmonary damage from colloidal SiO2 and organic substances, and the fibrogenic inflammation caused by carrageenan. Although it is not proven that silicosis is a precondition for quartz-induced lung tumours, we investigated the hypothesis that PVNO could reduce the lung tumour risk from quartz in rats. A carcinogenicity study was therefore started in rats with the main focus on the quantitative relationships among pulmonary inflammation, fibrosis and neoplasia caused by intratracheal instillation of 3 mg quartz DQ 12 with or without additional subcutaneous PVNO treatment. Other study groups were treated with multiple dust instillations, i.e. 30 instillations of 0.5 mg amorphous SiO2 at intervals of 2 weeks, 10 instillations of 0.5 mg of ultrafine carbon black or 1 mg coal at weekly intervals. The analyses of the bronchoalveolar lavage fluid (BALF) 9 months after start of the life-time study showed that the aim of producing similar levels of increased enzyme concentrations in the four groups treated with quartz/PVNO, amorphous SiO2, carbon black and coal was achieved. A 2.5- to 7.7-fold increase for lactate dehydrogenase (LDH), total protein, alkaline phosphatase and gamma-glutamyl transferase (gamma-GT) was found in these groups as compared to the control. In contrast, quartz treatment without PVNO increased the LDH level up to 24-fold and of total protein to 13-fold. However, the cell counts in the BALF were not so much different in all five groups, i.e. quartz without PVNO (leukocytes: 480.000, PMN: 190.000), quartz with PVNO (leukocytes: 300.000, PMN: 100.000), amorphous SiO2 (leukocytes: 570.000, PMN: 315.000), carbon black (leukocytes: 390.000, PMN: 150.000) and coal (leukocytes: 200.000, PMN: 65.000). Histopathological investigations after four weeks and three months revealed that the used PVNO sample was active in the quartz and amorphous SiO2 groups and markedly reduced the incidences or severity of several pulmonary changes such as macrophage accumulation, inflammatory cell infiltration, interstitial fibrosis, bronchiolo-alveolar hyperplasia, alveolar lipoproteinosis and amorphous SiO2 -induced granulomatous alveolitis/interstitial fibrotic granulomas. Also in the lung-associated lymph nodes (LALN), PVNO treatment significantly reduced the incidence and severity of inflammation in both quartz and amorphous SiO2 groups as evidenced by the presence of well-circumscribed aggregates of intact particle-laden macrophages without signs of degeneration and accompanying granulocytic infiltration and fibrosis. Immunological investigations at the 9 months timepoint on the in vitro production of reactive nitrogen (RNI) or oxygen (ROI) intermediates and tumour necrosis factor (TNF-alpha) from BALF-derived cells indicated a diminished responsiveness to LPS in all particle treatment groups. A diminished production of ROI was also found in the quartz, carbon black, and coal dust groups, respectively, as compared to the values seen in the quartz/PVNO- and amorphous SiO2 treated groups. Treatment with quartz plus PVNO restored the capability of the cells to respond to LPS as compared to the treatment with quartz alone. TNF-alpha production was diminished in the groups treated with quartz, carbon black, and coal dust alone whereas in the quartz/PVNO- and amorphous SiO2-treated groups an elevated TNF-alpha production was seen. These results led to the conclusion that only amorphous SiO2 did not affect the "normal" ability of the cells to respond to LPS and that PVNO protected the cells from a toxic effect of the quartz particles.

Acute changes in lung histopathology and bronchoalveolar lavage parameters in mice exposed to the choking agent gas phosgene

Phosgene (CG) is a highly irritant gas widely used industrially as a chemical intermediate for the production of dyes, pesticides, and plastics, and can cause life-threatening pulmonary edema within 24 hours of exposure. This study was designed to investigate acute changes in lung tissue histopathology and selected bronchoalveolar lavage fluid (BALF) factors over time to determine early diagnostic indicators of exposure. Three groups of 40 male mice each were exposed to 32 mg/m3 (8 ppm) CG for 20 minutes, and 3 groups of 40 control male mice were exposed to filtered room air for 20 minutes, both exposures were followed by room air washout for 5 minutes. At 1, 4.8, 12, 24, 48, and 72 hours after exposure each group of mice was euthanized and processed for histopathology, bronchoalveolar lavage or gravimetric measurements, respectively. Over time, the histopathological lesions were characterized by acute changes consisting of alveolar and interstitial edema, fibrin and hemorrhage, followed by significant alveolar and interstitial flooding with inflammatory cell infiltrates and scattered bronchiolar and terminal airway epithelial degeneration and necrosis. From 48 to 72 hours, there was partial resolution of the edema and degenerative changes, followed by epithelial and fibroblastic regeneration centered on the terminal bronchiolar areas. Bronchoalveolar lavage was processed for cell differential counts, LDH, and protein determination. Comparative analysis revealed significant increases in both postexposure lung wet/dry weight ratios, and early elevations of BALF LDH and protein, and later elevations in leukocytes. This article describes the use of histopathology to chronicle the temporal pulmonary changes subsequent to whole body exposure to phosgene, and correlate these changes with BALF ingredients and postexposure lung wet weights in an effort to characterize toxic gas-induced acute lung injury and identify early markers of phosgene exposure.

Bioavailability of fine dispersed platinum as emitted from automotive catalytic converters: a model study

Automobile exhaust catalytic converters emit fine dispersed elemental platinum, Pt (0), in the nanometer range coated on larger aluminium oxide carrier particles. A pre-requisite for a potential systemic toxic effect of the emitted platinum is its bioavailability which was investigated using laboratory animals. To this end, a model substance was synthesised which consisted of aluminium oxide particles < or = 5 microns onto which platinum particles > or = 4 nm were deposited by a calcination process. These particles closely resemble those emitted from automobile exhaust converters. This model substance was applied to female Lewis rats in two doses by intratracheal instillation; the animals were killed after 1, 7, 28 and 90 days. In addition, the model substance was also applied during a 90-day inhalation study. After microwave digestion of the tissues, the platinum was determined in all organs and body fluids by inductively coupled plasma/mass spectrometry (ICP/MS). Platinum was found in the blood, urine and faeces and all important organs (liver, spleen, kidneys, adrenals, stomach, femur). Based on the platinum content determined in the body fluids and all organs (except the lung and the faeces) it was calculated that up to 16% of the platinum was retained in the lung 1 day after intratracheal instillation and up to 30% of the fine dispersed platinum deposited on an average during 90 days inhalation in the lung was bioavailable. Using size exclusion chromatography (SEC) in combination with ICP/MS, it was shown that > or = 90% of the bioavailable platinum was bound to high molecular weight compounds (approximately 80-800 kDa), most likely proteins.

Kinetics of protein depletion in rat bronchoalveolar lavage fluid following in vitro exposure to nitrogen dioxide

Upon inhalation, nitrogen dioxide (NO(2)), a strong oxidizing agent, first comes into contact and reacts with the fluids lining the airways of the respiratory tract. These respiratory tract lining fluids (RTLF) form a barrier between the inhaled toxic pollutant and the epithelium which protects the underlying tissue from inflammation. Proteins, mainly albumin, and antioxidants are the major components of the RTLF. Many studies have utilized human blood plasma to study the interaction of an extracellular fluid with ozone. In this study, we used bronchoalveolar lavage fluids (BALF) as a more specific surrogate for rat RTLF, and we utilized the native fluorescence as a marker to investigate the depletion kinetics of naturally-occurring protein following exposure to NO(2) in a controlled flow reactor system. We also studied the depletion kinetics of albumin in a buffered salt solution. The results indicated that: (1) the decay in fluorescence was linearly dependent on the concentration of NO(2), indicating that protein oxidation was first order with respect to NO(2) concentration in both BALF and in buffered albumin solution; (2) the depletion kinetics of protein in BALF was non-linear with respect to substrate concentration; (3) the rate of protein depletion was much slower in BALF than in a buffered solution of albumin, suggesting that the presence of antioxidants in BALF protected proteins from being oxidized by NO(2); and (4) whereas the addition of ascorbic acid to buffered albumin solution significantly attenuated albumin depletion, the addition of glutathione had no effect. This suggested that the reaction rate constant of ascorbic acid was considerably higher than that of glutathione.

BN 52021 (a platelet activating factor-receptor antagonist) decreases alveolar macrophage-mediated lung injury in experimental extrinsic allergic alveolitis

Several lines of research indirectly suggest that platelet activating factor (PAF) may intervene in the pathogenesis of extrinsic allergic alveolitis (EAA). The specific aim of our study was to evaluate the participation of PAF on macrophage activation during the acute phase of EAA in an experimental model of this disease developed in guinea pigs. Initially we measured the concentration of PAF in bronchoalvedar lavage fluid, blood and lung tissue. In a second phase we evaluate the participation of PAF on alveolar macrophage activation and parenchymal lung injury. The effect of PAF on parenchymal lung injury was evaluated by measuring several lung parenchymatous lesion indices (lung index, bronchoalvedar lavage fluid (BALF) lactic hydrogenase activity and BALF alkaline phosphatase activity) and parameters of systemic response to the challenge (acute phase reagents). We observed that induction of the experimental EAA gave rise to an increase in the concentration of PAF in blood and in lung tissue. The use of the PAF-receptor antagonist BN52021 decreases the release of lysosomal enzymes (beta-glucuronidase and tartrate-sensitive acid phosphatase) to the extracellular environment both in vivo and in vitro. Furthermore, antagonism of the PAF receptors notably decreases pulmonary parenchymatous lesion. These data suggest that lung lesions from acute EAA are partly mediated by local production of PAF.

The lung as a source and a target organ for T- and B-lymphocytes

In lung transplantation, a substantial number of donor leukocytes are transferred from the donor to the recipient by the graft. Using a rat model, it was analyzed in this study to what extent leukocytes leave the lung, to which phenotype they belong, and to which organs they migrate. The model used was the orthotopic transplantation of the left lung of LEW.7B(RT7b) rats into LEW(RT7a) recipients. Lung allografts are not rejected in this strain combination, which differs only in the RT7 system, a genetic polymorphism of CD45. Using the RT7b marker (monoclonal antibody His41), the distribution of donor leukocytes passively transferred with the graft was studied by immunohistology 2 wk after transplantation. At this time, 2.9 +/- 0.1% (n = 6) of the peripheral blood leukocytes in the recipients were derived from the donor lung. The donor cell population detected in the blood consisted of T cells (59 +/- 4%), B cells (5.1 +/- 0.2%) and a surprisingly high fraction of natural killer (NK) cells (36 +/- 3%). No monocytes or granulocytes were found. In lymph nodes, spleen and thymus donor-derived T- and B-cells could be shown in typical T- and B-areas, respectively. Donor-derived leukocytes were found in the liver and the skin. In the tissue and the bronchoalveolar lavage (BAL) of the host lung, predominantly T cells were found. Furthermore, in the donor tissue and BAL more than 70% of T- and B-cells were host type, demonstrating that the donor lung had been repopulated to a great extent by host lymphocytes. This supports the relevance of BAL as a diagnostic tool in lung diseases. Thus, the lung is an immunologically important site, releasing lymphocytes which migrate to other organs and also attracting many lymphocytes from the circulation.

Rapid, high performance liquid chromatography-based, periodate-coupled thiobarbituric acid method for the determination of sialic acid in bronchoalveolar lavage fluid

A simple, rapid high performance liquid chromatographic adaptation of the periodate-coupled thiobarbituric acid (TBA) method was developed for the quantification of sialic acid (SIAC) in supernatants from bronchoalveolar lavage fluids (BALF). Malondialdehyde released from BALF samples in various amounts did not interfere with the accurate quantification of SIAC.

Role of lysosomal enzymes released by alveolar macrophages in the pathogenesis of the acute phase of hypersensitivity pneumonitis

Hydrolytic enzymes are the major constituents of alveolar macrophages (AM) and have been shown to be involved in many aspects of the inflammatory pulmonary response. The aim of this study was to evaluate the role of lysosomal enzymes in the acute phase of hypersensitivity pneumonitis (HPs). An experimental study on AM lysosomal enzymes of an HP-guinea-pig model was performed. The results obtained both in vivo and in vitro suggest that intracellular enzymatic activity decrease is, at least partly, due to release of lysosomal enzymes into the medium. A positive but slight correlation was found between extracellular lysosomal activity and four parameters of lung lesion (lung index, bronchoalveolar fluid total (BALF) protein concentration, BALF LDH and BALF alkaline phosphatase activities). All the above findings suggest that the AM release of lysosomal enzymes during HP is a factor involved, although possibly not the only one, in the pulmonary lesions appearing in this disease.

Comparison of the pulmonary surfactant content in alveolar macrophages of newborn, young, and adult rats

The phospholipid composition of the 150-g pellet containing macrophages from neonatal lung lavages resembles that of surfactant. To study whether this composition reflects the surfactant content of the macrophage, we isolated the alveolar phospholipids and macrophages from the lavage fluids of fetal, newborn, young, and adult Wistar rats. The alveolar surfactant phospholipids increased from fetal levels of 2.8 nmol/mg dry lung weight (DLW) to 39 nmol/mg DLW at day 1, decreased sharply within the first week, and stabilized at a level of 2-4 nmol/mg DLW after day 15. The number of alveolar macrophages increased significantly during the first postnatal day from approximately 750 to more than 5000 (per mg DLW), decreased during the next 4 days, and varied strongly at older ages. We estimated the surfactant content in the macrophages semiquantitatively by polarization microscopy. Birefringence augmented significantly during the first 1.5 days after birth and decreased after that concurrently with the amount of alveolar surfactant. However, only cells without birefringent inclusions sedimented at 150g, whereas the phospholipid composition of the pellets falsely suggested that large amounts of intracellular surfactant were present in its cells. At least two populations of macrophages (surfactant-rich and surfactant-poor) are present in the growing animal. We suggest that differences in function of these various types of macrophages also might depend on surfactant congestion.

Cellular and biochemical indices of bronchoalveolar lavage for detection of lung injury following insult by airborne toxicants

Cellular and biochemical profiles of bronchoalveolar lavage (BAL) material after inhalation or intratracheal exposure to various airborne toxicants clearly reflect that BAL has the potential of being a useful tool for the rapid screening of lung injury. The cellular and biochemical responses not only predict inflammation, extent of tissue damage and toxic nature of the substances, but could also help in understanding the molecular mechanisms of pathogenicity. Depending upon the changes of BAL in animals acutely exposed to a pulmonary toxicant, future in-depth studies along with complete histopathological evaluations could be made. Also, the assessment of macromolecules of pharmacological importance in the lavage, especially the secretory products of alveolar macrophages and other lung cell types, could be very useful in predicting the toxic potential of various airborne substances and could also serve as important indicators of developing chronic lung diseases and, therefore, necessitate further studies.

Inhalation toxicity of methyl isocyanate: biochemical and cytological profile of bronchoalveolar lavage fluid in rats

Acute pulmonary injury in rats following a single inhalation exposure to methyl isocyanate (3.2 mg l-1) was reflected by alterations in the biochemical and cytological constituents of bronchoalveolar lavage fluid (BALF) over a period of 30 days. Total protein, sialic acid and lactic acid contents of BALF were increased followed by a gradual decline to normalcy between day 3 and day 30 post-exposure. The activity of lactic dehydrogenase also increased progressively with time. The cellularity of BALF was increased significantly and primarily comprised of polymorphonuclear neutrophils at 8 days. The adherence of macrophages was unchanged but their viability was lowered at 30 days post-exposure. The results indicate the significance of bronchoalveolar lavage analysis in monitoring pulmonary toxicity by methyl isocyanate, which is characterized by the hypoxic condition and reduced cellular defence. Some toxic manifestations are potentially reversible with time after cessation of exposure.

Functional, biochemical, and histopathological evidence of airway obstruction in rats following a four-hour acute inhalation exposure to n-butyl isocyanate

Pulmonary function, arterial blood gases, acid-base status, and bronchoalveolar lavage fluid (BALF) composition were assessed in male Wistar rats after a single 4-h exposure to 0, 7.6, 23.5 or 55.2 mg n-butyl isocyanate (n-BIC)/m3 air. No significant changes other than transient clinical signs were observed in the rats exposed to 7.6 mg/m3 air. Four weeks after exposure the animals of the 55.2 mg/m3 group showed significant effects: those were pronounced histopathological changes of airways and parenchyma, and elevated relative lung weight. The neutrophils, LDH, and protein in BALF were elevated. Quasi-static lung compliance, peak expiratory flow rate, mean mid expiratory flow rate were decreased whereas lung resistance, residual volume, and single breath CO-diffusing capacity were increased. Blood gas measurements revealed an elevation in hemoglobin, pH, arterio-alveolar oxygen difference, and venous admixture. Arterial pO2 and pCO2 were decreased. In animals exposed to 23.5 mg/m3 only marginal effects were detectable.

Interspecies comparisons of lung responses to inhaled particles and gases

Two important challenges for inhalation toxicologists involve the elucidation of mechanisms of lung toxicity caused by inhalation of chemicals or particulate materials, as well as the extrapolation of animal data to humans. Because risk estimates of toxicity generally are dependent upon experimental data for which a variety of species are utilized, a fundamental knowledge of species similarities and differences in lung anatomy, physiology, biochemistry, cell biology, and corresponding disease processes is essential. In the present review, the known mechanisms of particle deposition and clearance among various species have been highlighted and related to structure/function relationships and pathogenetic responses to some selected inhaled toxicants. In the aggregate, there is remarkable homogeneity in form and function among the species. Morphologic aspects of the respiratory tract and lung defense mechanisms are qualitatively similar among species. On the other hand, quantitative differences between humans and experimental animals are known to exist with respect to deposition and mucociliary clearance of inhaled particulates, and these factors are likely to influence the dose that is delivered to specific target sites in the lung. It is interesting to consider that pathologic cellular events following asbestos, ozone, and nitrogen dioxide exposure are likely to occur at similar sites in humans, nonhuman primates, and rodents. In this respect, it has been demonstrated that the early lesions of asbestos-induced lung disease in both rats and humans are initiated at similar anatomical sites, i.e., the junctions of terminal airways and alveolar regions. PMs and complement-mediated mechanisms have been implicated in the development of asbestosis in rats; however, it remains to be determined whether complement activation plays an important role in human asbestosis, although pulmonary and interstitial macrophages clearly are associated with the fibrogenic process associated with this restrictive lung disease. The toxic pulmonary effects following ozone exposure have been well studied in rodents and nonhuman primates. It has been established that distal airway and alveolar epithelial cells are principal targets of oxidant pollutants, and this is well supported by dosimetry considerations, morphologic observations, and morphometric analyses. Chronic ozone exposure in rats and monkeys causes epithelial injury at the level of the terminal bronchiole and proximal alveolar regions of the lung.(ABSTRACT TRUNCATED AT 400 WORDS)