How long do the systemic and ventilatory responses to toluene diisocyanate persist in dermally sensitized mice?

BACKGROUND: Years after removal from exposure, workers with occupational asthma still show respiratory symptoms and airway hyperresponsiveness on re-exposure to the offending agent. OBJECTIVE: We investigated the persistence of the respiratory responsiveness to toluene diisocyanate (TDI) in a mouse model. METHODS: BALB/C mice received dermal applications of TDI on days 1 and 8, and a single intranasal instillation of TDI on day 10, 15, 20, 25, 30, 40, 50, 60, or 90. After instillation, early (1 hour) changes in ventilatory function and methacholine responsiveness (22 hours) were assessed. Cell counts and macrophage inflammatory protein 2 were measured in bronchoalveolar lavage. Total serum IgE, IgG(1), and IgG(2a) were quantified. Lymphocyte subpopulations were assessed in auricular and cervical lymph nodes, and release of IL-4 and IFN-gamma by these lymph node cells was measured. RESULTS: Toluene diisocyanate-treated mice showed immediate ventilatory changes, increased methacholine reactivity, and an influx of neutrophils and macrophage inflammatory protein 2 in bronchoalveolar lavage as long as 50 days after initial treatment. These mice also showed a relative increase in CD19(+) cells and a decrease in CD4(+) and CD8(+) cells in auricular lymph nodes. Increased release of IL-4 and IFN-gamma in auricular lymph node cells was observed only until 20 days after sensitization. Total serum IgE, IgG(1), and IgG(2a) remained significantly elevated in TDI-sensitized mice until 90 days after dermal sensitization. CONCLUSION: Ventilatory and lung inflammatory responses decrease with increasing delay between sensitization and challenge, despite persistent humoral signs of sensitization.

N-acetyl cysteine pre-treatment attenuates inflammatory changes in the warm ischemic murine lung.

BACKGROUND: The warm ischemic period in non-heart-beating donor lungs may contribute to a higher degree of ischemia-reperfusion injury after lung transplantation. We investigated the impact and timing of administration of N-acetyl cysteine (NAC) on inflammatory parameters. METHODS: Ischemia (I) was induced by clamping the hilum of the left lung for 90 minutes, and some protocols were followed by reperfusion (R) for 4 hours. Mice were divided into nine groups (n = 6/group): three control groups ([sham] (thoracotomy only), [I] and [I+R]); two groups with saline instillation only ([saline+I] and [saline+I+R]); and four experimental groups with NAC (50 mg/kg), administered by instillation ([NAC+I], [NAC+I+R] and [I+NAC+R]) or by aerosol ([NACaero+I+R]). Cell counts and protein levels in bronchoalveolar lavage (BAL) were determined. RESULTS: NAC administered prior to hilar clamping led to a significant decrease in macrophages and lymphocytes and interleukin (IL)-1 beta levels after ischemia. NAC also resulted in significantly fewer macrophages, lymphocytes and neutrophils as well as IL-1 beta, keratinocyte cytokine (KC), monocyte chemoattractant protein (MCP)-1 and IL-6 levels in BAL taken after reperfusion. CONCLUSIONS: NAC treatment prior to warm ischemia attenuates inflammatory changes after both the ischemic and reperfusion periods.

Strain-dependent acute lung injury after intra-tracheal administration of a 'refined' aniline-denatured rapeseed oil: a murine model of the toxic oil syndrome?

Most attempts to reproduce the toxic oil syndrome in animals, either with case-related oils or with refined rapeseed oils, have been unsuccessful. An aniline-denatured rapeseed oil that was subsequently refined according to a protocol yielding relevant markers of "toxic oil" (oil RSO160401) had led to possibly relevant lesions following oral administration in mice. Therefore, in the present study, RSO160401 was subjected to a more extended in vivo testing. To try and maximize the response, BALB/c, DBA/2, A/J, and C57BL/6 mice were administered RSO160401 oil by a single intra-tracheal instillation (1ml/kg), with sacrifice 2 or 7 days post-exposure. Intra-tracheal administration led to a strain-dependent acute response: acute pulmonary damage in DBA/2 and A/J mice, and increases in blood eosinophilia in DBA/2 mice (6.5% vs 3.1% in controls). The pulmonary lesions regressed with time after exposure, being more complete in A/J than in DBA/2 mice. The observation of strain-dependent effects suggests that genetic susceptibility is an important factor in disease induction by the RSO160401 oil.

Immunological determinants of ventilatory changes induced in mice by dermal sensitization and respiratory challenge with toluene diisocyanate.

The objective of the study was to characterize better the immunologic mechanisms underlying a previously developed animal model of chemical-induced asthma. BALB/c and severe combined immunodeficiency disease (SCID) mice received toluene diisocyanate (TDI) or vehicle on each ear on day 1 and/or day 7. On day 10, they were intranasally challenged with TDI or vehicle. Ventilatory function was monitored by whole body plethysmography for 40 min after challenge. Reactivity to methacholine was measured 23 h later: enhanced pause and actual resistance measurements. Pulmonary inflammation was assessed 1, 6, and 24 h after challenge by bronchoalveolar lavage (BAL). Tumor necrosis factor-alpha and macrophage inflammatory protein (MIP)-2 levels were measured in BAL. Immunological parameters included total IgE, IgG1, and IgG2a in serum, lymphocyte populations in auricular and cervical lymph nodes, and IL-4 and IFN-gamma levels in supernatants of lymph node cells, cultured with or without concanavalin A. Ventilatory changes suggestive of airway obstruction and increased methacholine reactivity were observed in all TDI-sensitized and TDI intranasally instilled mice, except in SCID mice. A neutrophil influx, accompanied by an increase in MIP-2 levels, was found in BAL of all responding groups 6 and 24 h after intranasal challenge. In BALB/c mice an increased level of CD19+ B cells was found in the auricular lymph nodes. IL-4 and IFN-gamma levels were increased in supernatants of concanavalin A-stimulated auricular lymph node cells from BALB/c mice completely treated with TDI. These results indicate that our model is dependent on the presence of lymphocytes, but it is not characterized by a preferential stimulation of Th1 or Th2 lymphocytes.

Validation of a mouse model of chemical-induced asthma using trimellitic anhydride, a respiratory sensitizer, and dinitrochlorobenzene, a dermal sensitizer.

BACKGROUND: Occupational asthma can be caused by chemicals. Previously, we established a murine model of immunologically mediated chemical-induced asthma using toluene diisocyanate. OBJECTIVE: We sought to verify this model using trimellitic anhydride (TMA), a respiratory sensitizer, and 1-chloro-2,4-dinitrobenzene (DNCB), a dermal sensitizer. METHODS: BALB/c mice received dermal applications (vehicle or chemical) on days 1 and 7. On day 10, they received an intranasal instillation (vehicle or chemical). Whole-body plethysmography (enhanced pause) was used to monitor changes in ventilatory function and methacholine reactivity. Pulmonary inflammation was assessed by using bronchoalveolar lavage (cells, TNF-alpha levels, and macrophage inflammatory protein 2 levels). Immunologic parameters included total serum IgE levels, lymphocyte distribution in auricular and cervical lymph nodes, and IL-4 and IFN-gamma levels in supernatants of lymph node cells incubated with or without concanavalin A. RESULTS: Mice dermally treated and intranasally challenged with TMA experienced markedly increased enhanced pause immediately after intranasal challenge and increased methacholine reactivity (24 hours later). Mice similarly treated with DNCB did not show any ventilatory changes. Neutrophil influx and increased macrophage inflammatory protein 2 and TNF-alpha levels were found in bronchoalveolar lavage fluid in both TMA- and DNCB-treated mice. The proportion of CD19+ B cells was increased in auricular and cervical lymph nodes of TMA-treated mice. IL-4 and IFN-gamma levels were increased in supernatants of concanavalin A-stimulated auricular and cervical lymph node cells of TMA- or DNCB-treated mice; however, the relative proportions of IL-4 and IFN-gamma levels differed between TMA- and DNCB-treated mice. Serum total IgE levels were increased in TMA-treated mice only. CONCLUSION: Both compounds induce a mixed T(H)1-T(H)2 response, but only TMA induced ventilatory changes. CLINICAL IMPLICATIONS: In the workplace avoiding skin contact with chemical sensitizers might be advised to prevent chemical-induced asthma.

Pulmonary toxicity of polyvinyl chloride particles after a single intratracheal instillation in rats. Time course and comparison with silica.

Our previous in vitro studies indicated that emulsion polyvinyl chloride (PVC) particles (PVC-E3), with a mean diameter of 2 microm, exhibited a moderate toxicity in different pulmonary cell cultures. The in vitro cytotoxicity and pro-inflammatory potential of PVC-E3 particles were reduced when the additives had been "washed off" (PVC-W3), indicating that PVC-particle associated toxicity is probably related to the residual additives. In the present study, male Wistar rats (230 +/- 18 g) received a single intratracheal instillation of vehicle, crystalline silica particles [Min-U-Sil, 10 mg/kg body weight (BW)], PVC-E3 (10 or 50 mg/kg BW), or PVC-W3 (10 or 50 mg/kg BW). After 2, 7, 28, or 90 days, the rats were sacrificed (n = 6) and pulmonary injury and inflammation were determined by measuring lung weight, lactate dehydrogenase (LDH) activity and protein concentrations in bronchoalveolar lavage fluid (BALF), differential BALF cell count, and histopathology. Silica exposure resulted in pulmonary inflammation and damage at all time points with a progressive deterioration. Exposure to high concentrations of PVC particles caused pulmonary inflammation and damage, which were similar to the silica-exposed group at 2 days, but at 90 days, most parameters had returned to the control level, except for minor histopathological lesions. PVC-E3 did not induce more damage than PVC-W3. Two days after exposure, PVC-W3 caused less neutrophil but more eosinophil influx than PVC-E3. Although the pulmonary toxicity of both PVC-E3 and PVC-W3 appeared limited, this in vivo study has not confirmed the conclusion from the in vitro toxicity tests that removal of residual additives reduces the toxicity of PVC-E3 particles.

Pulmonary toxicity of polyvinyl chloride particles after repeated intratracheal instillations in rats. Elevated CD4/CD8 lymphocyte ratio in bronchoalveolar lavage.

Occupational exposure to polyvinyl chloride (PVC) particles has been associated with interstitial lung disease. Our previous study showed that a single intratracheal instillation of emulsion PVC particles, with or without residual additives, induces acute but transient alveolitis in a dose-dependent manner in rats. The aim of the present study was to investigate the pulmonary response after the administration of the same PVC particles (PVC-E3 and PVC-W3) given in the same cumulative doses (10 and 50 mg/kg BW), but fractionated as seven intratracheal instillations (7 x 1.4 and 7 x 7.1 mg/kg BW) in the course of 3 weeks (day 0 to day 21). Pulmonary response was characterized by analysis of lung weight, bronchoalveolar lavage (BAL) fluid for lactate dehydrogenase (LDH), total protein, and cell cytology, and a microscopic evaluation of lung tissue. BAL T lymphocyte phenotypes (CD3 + CD4 +, CD3 + CD8+) were analyzed by flow cytometry. On day 28, lung weights, BAL-LDH, cell numbers in BAL, and CD4/CD8 ratios in BAL T lymphocytes were higher in rats that had received the high dose of PVC-E3 or PVC-W3 than in rats that had received the low dose of PVC particles and control rats. On day 90, the pulmonary response had partially regressed towards control values, but there were still microscopically evident lesions in the lungs and greater CD4/CD8 ratio in the high dose groups. There were significant positive correlations between the CD4/CD8 ratio and a histopathology score of the lung (r = 0.36, P = 0.038 on day 28, and r = 0.46, P = 0.006 on day 90). In conclusion, repeated intratracheal instillations of PVC particles yielded similar results as single instillations. The examined PVC particles have the potential of inducing a limited and transient acute inflammatory reaction in the lung, and possibly a more persistent alteration of pulmonary T lymphocyte subsets towards a high CD4/CD8 ratio.

Validity of methods to predict the respiratory sensitizing potential of chemicals: A study with a piperidinyl chlorotriazine derivative that caused an outbreak of occupational asthma.

A piperidinyl chlorotriazine (PCT) derivative, used as a plastic UV-stabilizer, caused an outbreak of occupational asthma. We verified, in BALB/c mice, the sensitizing potential of PCT in comparison to a known respiratory sensitizer (toluene diisocyanate [TDI]) and a known dermal sensitizer (oxazolone), using three different methods in order to evaluate the validity of current models of sensitization. These included the local lymph node assay (LLNA) and the mouse IgE test. In addition, respiratory hyper-reactivity was assessed following a novel protocol involving dermal sensitization (20 microl of a 3% solution on each ear for three days) and intranasal challenge (0.1% or 1%, 10 microl per nostril on day 10), followed, after 24 h, by a methacholine challenge (using whole-body plethysmography), bronchoalveolar lavage, and histology. PCT was also used for structure-activity relationship (SAR) models for (respiratory) sensitization. High concentrations of PCT (10 and 20%) resulted in significant responses in the local lymph node assay (LLNA; stimulation indices (SI) of 2.7 +/- 0.9 and 3.2 +/- 0.6, respectively). The mouse IgE test was positive with 20% PCT only. Methacholine responsiveness was increased only in previously sensitized mice receiving a challenge with TDI or PCT. However, there was no evidence for pulmonary inflammation. The SAR studies indicated that PCT could be a respiratory sensitizer. Based on an approved test protocol such as the LLNA and the mouse IgE test, PCT proved to be a weak sensitizer when compared to TDI and oxazolone. However, in a protocol involving an intranasal challenge, PCT appeared to be a respiratory sensitizer of similar potency to TDI.