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We investigated acute and delayed respiratory changes after inhalation exposure to chlorine (Cl-2) with the aim to understand the pathogenesis of the long-term sequelae of Cl-2-induced lung-injury. In a rat model of nose-only exposure we analyzed changes in airway hyperresponsiveness (AHR), inflammatory responses in airways, expression of pro-inflammatory markers and development of lung fibrosis during a time course from 5 h up to 90 days after a single inhalation of Cl-2. A single dose of dexamethasone (10 mg/Kg) was administered 1 h following Cl-2-exposure. A 15-min inhalation of 200 ppm Cl-2 was non-lethal in Sprague-Dawley rats. At 24 h post exposure, Cl-2-exposed rats displayed elevated numbers of leukocytes with an increase of neutrophils and eosinophils in bronchoalveolar lavage (BAL) and edema was shown both in lung tissue and the heart At 24 h, the inflammasome-associated cytokines IL-1 beta and IL-18 were detected in BAL Concomitant with the acute inflammation a significant AHR was detected. At the later time-points, a delayed inflammatory response was observed together with signs of lung fibrosis as indicated by increased pulmonary macrophages, elevated TGF-beta expression in BAL and collagen deposition around airways. Dexamethasone reduced the numbers of neutrophils in BAL at 24 h but did not influence the AHR. Inhalation of Cl-2 in rats leads to acute respiratory and cardiac changes as well as pulmonary inflammation involving induction of TGF-beta 1. The acute inflammatory response was followed by sustained macrophage response and lack of tissue repair. It was also found that pathways apart from the acute inflammatory response contribute to the Cl(2-)induced respiratory dysfunction.

Context: Titanium dioxide (TiO2) nanoparticles (NPs) are regarded as relatively non-toxic in concentrations occurring in occupational environments. Nevertheless, it is conceivable that adverse health effects may develop in sensitive populations such as individuals with respiratory diseases. Objective: We investigated whether single or repeated exposure to TiO2 could aggravate inflammatory responses in naive mice and mice with ovalbumin (OVA)-induced airway inflammation. Methods: Exposure to aerosolized TiO2 was performed during OVA sensitization, before, or during the OVA challenge period. The effects on respiratory physiology, inflammatory cells in bronchoalveolar lavage (BAL) and inflammatory mediators in BAL and serum were assessed 24 h after the last OVA challenge or TiO2 exposure. Results: A single exposure of TiO2 had a marked effect on responses in peripheral airways and increasing infiltration of neutrophils in airways of naive animals. Marked aggravation of airway responses was also observed in animals with allergic disease provided that the single dose TiO2 was given before allergen challenge. Repeated exposures to TiO2 during sensitization diminished the OVA-induced airway eosinophilia and airway hyperresponsiveness but concomitant exposure to TiO2 during the OVA challenge period resulted in neutrophilic airway inflammation and a decline in general health condition as indicated by the loss of body weight. Conclusion: We conclude that inhalation of TiO2 may aggravate respiratory diseases and that the adverse health effects are highly dependent on dose and timing of exposure. Our data imply that inhalation of NPs may increase the risk for individuals with allergic airway disease to develop symptoms of severe asthma., Forskningsfinansiär: Swedish Ministry of Defence

BACKGROUND: Volatile monoisocyanates are formed through thermal degradation when products containing polyurethane are heated. Repeated exposure to diisocyanates, such as toluene diisocyanate (TDI) are a well-known cause of occupational asthma. However, although monoisocyanates are abundant in occupational settings, there are few data concerning their ability to provoke immune reactions and asthma. We compared immune reactivity and respiratory disease following single or repeated inhalation exposures to the monoisocyanates methyl isocyanate (MIC) and isocyanic acid (ICA) with the effects of TDI. METHODS: Isocyanates were administrated either as single vapor exposures or as repeated intranasal instillations in rats. Adverse health effects were monitored by analyzing airway inflammation, respiratory function and weight gain. Immune reactivity caused by repeated exposures was studied by analysis of isocyanate-specific antibodies and airway infiltration of immune competent cells. RESULTS: Repeated exposures to TDI induced airway infiltration of neutrophils and lymphocytes, while neither MIC nor ICA provoked a detectable inflammatory response. Antibodies against isocyanate-albumin conjugates were detected in serum after both exposures to TDI and MIC, but not to ICA. TDI-exposed rats also displayed IgG antibodies against MIC-albumin conjugates. Even though MIC did not induce airway inflammation, single exposure provoked an increase in airway resistance and repeated exposures caused weight loss similar to that of TDI. CONCLUSIONS: Airway exposure to TDI produces an antibody response not only against TDI but also against MIC-protein conjugates. This indicates that immune reactivity against abundant monoisocyanates in occupational environments can occur in individuals pre-sensitized with low abundance but highly sensitizing diisocyanates.

Substance P is a tachykinin and a biologically active neuropeptide. The peptide produces salivation, neuronal excitation, vasodilatation, increased vascular permeability and contraction of smooth muscles in the respiratory tract. The study was designed to evaluate the acute effects in guinea pigs of inhaled aerosolized Substance P (SP). Apart from the acute toxic effect of the peptide, the distribution in different organs was also investigated. The acute inhalation toxicity of SP (LC50, 15 min) when co-administrated with the neutral endopeptidase inhibitor thiorphan was 368 microg m(-3). The peptide caused an increase in respiratory rate proceeding a decrease in tidal volume. As the exposure proceeded, a decrease in both respiratory rate and further decreases in tidal volume were observed until either the animal died or the exposure was terminated. The decreases in respiratory rate and tidal volume were probably due to bronchoconstriction caused by SP. Eighteen per cent of the inhaled amount of radioactive SP was retained in the body, and the highest concentrations of radioactivity were found in the kidney, lung and liver. Substance P in combination with thiorphan administered as an aerosol is extremely toxic and highly potent. Exposure to the substance at extremely low air concentrations may result in incapacitation in humans.

Context: Exposure to toxic alkylating mustard agents causes both acute and long-term effects to the lungs as indicated by increased number of inflammatory cells in airways, lung edema and lung tissue fibrosis. We have previously demonstrated that treatment with the corticosteroid dexamethasone 1 hr after lung exposure to the alkylating mustard melphalan, protect mice from acute and sub-acute inflammatory responses, as well as from lung fibrosis. Objective: In order to address the importance of early anti-inflammatory treatment, we investigated the therapeutic effect of dexamethasone administered 1, 2 or 6 hrs following exposure to melphalan. Methods: Female C57BL/6 mice were via intratracheal instillation exposed to the nitrogen mustard analogue melphalan and treated i.p. with dexamethasone 1, 2 or 6 hours after exposure. Twenty hours or 14 days post exposure mice were subjected to analysis of respiratory mechanics where the effects of incremental doses of methacholine on central and peripheral lung components were measured. We also determined the amount of neutrophils and lymphocytes in the bronchoalveolar lavage fluid and measured the amount of collagen content in the lungs. Results: Melphalan exposure exerted a significant effect on both central and peripheral respiratory function. Dexamethasone given one hour post exposure protected the lung against the damaging effects of melphalan. Collagen deposition 14 days after exposure was decreased with dexamethasone treatment. Conclusion: Early dexamethasone treatment (within one hour after exposure) is important in order to reduce the airway reactivity and inflammation caused by toxic alkylating mustards such as melphalan.