Bronchiolar Damage Research Articles

NLRP3/GSDMD mediated pyroptosis induces lung inflammation susceptibility in diesel exhaust exposed mouse strains

BackgroundGenetic diversity among species influences the disease severity outcomes linked to air pollution. However, the mechanism responsible for this variability remain elusive and needs further investigation. ObjectiveTo investigate the genetic factors and pathways linked with differential susceptibility in mouse strains associated with diesel exhaust exposure. MethodsC57BL/6 and Balb/c mice were exposed to diesel exhaust (DE) for 5 days/week for 30 min/day for 8 weeks. Body weight of mice was recorded every week and airway hyperresponsiveness towards DE exposure was recorded after 24 h of last exposure. Mice were euthanised to collect BALF, blood, lung tissues for immunobiochemical assays, structural integrity and genetic studies. ResultsC57BL/6 mice showed significantly decreased body weight in comparison to Balb/c mice (p < 0.05). Both mouse strains showed lung resistance and damage to elastance upon DE exposure compared to respective controls (p < 0.05) with more pronounced effects in C57BL/6 mice. Lung histology showed increase in bronchiolar infiltration and damage to the wall in C57BL/6 mice (p < 0.05). DE exposure upregulated pro-inflammatory and Th2 cytokine levels in C57BL/6 in comparison to Balb/c mice. C57BL/6 mice showed increase in Caspase-1 and ASC expression confirming activation of downstream pathway. This showed significant activation of inflammasome pathway in C57BL/6 mice with ∼2-fold increase in NLRP3 and elevated IL-1β expression. Gasdermin-D levels were increased in C57BL/6 mice demonstrating induction of pyroptosis that corroborated with IL-1β secretion (p < 0.05). Genetic variability among both species was confirmed with sanger’s sequencing suggesting presence of SNPs in 3’UTRs of IL-1β gene influencing expression between mouse strains. ConclusionsC57BL/6 mice exhibited increased susceptibility to diesel exhaust in contrast to Balb/c mice via activation of NLRP3-related pyroptosis. Differential susceptibility between strains may be attributed via SNPs in the 3'UTRs of the IL-1β gene.

Diesel exhaust exposure impairs recovery of lung epithelial and cellular damage in murine model

Studies have investigated the relationship between diesel exhaust (DE) exposure and lung health, highlighting the potential for DE to induce pulmonary inflammation and oxidative stress. However, the resolution of inflammation upon withdrawal of DE exposure needs further investigation. Therefore, resolution of diesel exhaust-induced lung damage was studied in the murine model. Mice (6 weeks) were divided into three groups. Group 1 (control) mice were exposed to filtered air, Group 2 (DE) mice were exposed to DE (5.1 ± 0.7 mg/m3) & Group 3 (DE-FA) mice were exposed to DE followed by filtered air exposure. Airway hyper-responsiveness was recorded after 24 h of the last exposure. BALF and lung samples were collected for cytokine estimation, immunobiological assays, and western blot analysis. DE exposure showed an increase in lung resistance thereby causing alteration in lung function parameters (p < 0.05) which was restored in the DE-FA group. BALF analysis showed a significant increase in total cell count and protein content in DE with no resolution in DE-FA groups (p < 0.05). Lung histology showed no reduction in the bronchiolar thickness and damage in the DE-FA group suggesting irreversible lung damage (p < 0.05). The significant increase in inflammatory cytokine levels, and collagen deposition showed persistent inflammatory phase and lung damage in the DE-FA group(p < 0.05). ZO-1 was significantly decreased in both test groups indicating disintegrated lung epithelium where in claudin-5 expression showed increased lung permeability. A significant increase in neutrophil elastase activity and decreased expression of, Elafin, resulted in lung epithelial damage in the DE-FA group. Lung injury marker alpha1-antitrypsin was increased in DE-FA groups indicating an immune defense mechanism against neutrophil elastase. The study showed that DE exposure causes persistent lung damage via neutrophil elastase-associated disruption of the epithelial barrier integrity and membrane dysfunction.

Bronchopneumonia with interstitial pneumonia in beef feedlot cattle: Characterization and laboratory investigation.

Bronchopneumonia with interstitial pneumonia (BIP) has been considered a variant of acute interstitial pneumonia (AIP) rather than a distinct disease. This study compared 18 BIP, 24 bronchopneumonia (BP), and 13 AIP cases in feedlot beef cattle. Grossly, BIP cases typically had cranioventral lung lesions of similar morphology and extent as BP cases, but the caudodorsal lung appeared overinflated, bulged on section, and had interlobular edema and emphysema. Gross diagnosis of BIP had 83% sensitivity and 73% specificity relative to histopathology. Histologic lesions of BIP in cranioventral areas were of chronic BP, while caudodorsal lesions included alveolar and bronchiolar damage and inflammation, interstitial hypercellularity, and multifocal hemorrhages. In BIP cases, cranioventral lung lesions were more chronic than caudodorsal lesions. Histologic scores and microbiology data were comparable in cranioventral lung of BIP versus BP cases and caudodorsal lung of BIP versus AIP cases, with differences reflecting a more chronic disease involving less virulent bacteria in BIP versus BP. Mycoplasma bovis infection was similarly frequent among groups, and a viral cause of BIP was not identified. Lesion morphology and similar blood cytokine concentrations among groups argued against sepsis as a cause of lung injury. Surfactant dysfunction was identified in BIP and BP, and was only partially the result of protein exudation. These and other findings establish BIP as a distinct condition in which chronic cranioventral BP precedes acute caudodorsal interstitial lung disease, supporting a role of chronic inflammation in heightened sensitivity to 3-methylindole or another lung toxicant.

Adipose triglyceride lipase-mediated lipid catabolism is essential for bronchiolar regeneration.

The lung airways are constantly exposed to inhaled toxic substances, resulting in cellular damage that is repaired by local expansion of resident bronchiolar epithelial club cells. Disturbed bronchiolar epithelial damage repair lies at the core of many prevalent lung diseases, including chronic obstructive pulmonary disease, asthma, pulmonary fibrosis, and lung cancer. However, it is still not known how bronchiolar club cell energy metabolism contributes to this process. Here, we show that adipose triglyceride lipase (ATGL), the rate-limiting enzyme for intracellular lipolysis, is critical for normal club cell function in mice. Deletion of the gene encoding ATGL, Pnpla2 (also known as Atgl), induced substantial triglyceride accumulation, decreased mitochondrial numbers, and decreased mitochondrial respiration in club cells. This defect manifested as bronchiolar epithelial thickening and increased airway resistance under baseline conditions. After naphthalene‑induced epithelial denudation, a regenerative defect was apparent. Mechanistically, dysfunctional PPARα lipid-signaling underlies this phenotype because (a) ATGL was needed for PPARα lipid-signaling in regenerating bronchioles and (b) administration of the specific PPARα agonist WY14643 restored normal bronchiolar club cell ultrastructure and regenerative potential. Our data emphasize the importance of the cellular energy metabolism for lung epithelial regeneration and highlight the significance of ATGL-mediated lipid catabolism for lung health.

Blocking Toll-like receptor 9 attenuates bleomycin-induced pulmonary injury.

BackgroundAcute respiratory distress syndrome (ARDS) is one of the most common complications in coronavirus disease 2019 patients suffering from acute lung injury (ALI). In ARDS, marked distortion of pulmonary architecture has been reported. The pulmonary lesions in ARDS include hemodynamic derangements (such as alveolar edema and hemorrhage), vascular and bronchiolar damage, interstitial inflammatory cellular aggregations, and eventually fibrosis. Bleomycin induces ARDS-representative pulmonary damage in mice and rats; therefore, we used bleomycin model mice in our study. Recently, Toll-like receptor 9 (TLR9) was implicated in the development of ARDS and ALI.MethodsIn this study, we evaluated the efficiency of a TLR9 blocker (ODN2088) on bleomycin-induced pulmonary damage. We measured the apoptosis rate, inflammatory reaction, and fibroplasia in bleomycin- and bleomycin + ODN2088-treated mice.ResultsOur results showed a significant amelioration in bleomycin-induced damage to pulmonary architecture following ODN2088 treatment. A marked decrease in pulmonary epithelial and endothelial apoptosis rate as measured by cleaved caspase-3 expression, inflammatory reaction as indicated by tumor necrosis factor α expression, and pulmonary fibrosis as demonstrated by Van Gieson staining and α-smooth muscle actin immunohistochemistry were observed following ODN2088 treatment.ConclusionsAll these findings indicate that blocking downstream TLR9 signaling could be beneficial in prevention or mitigation of ARDS through hemodynamic derangements, inflammation, apoptosis, and fibrosis.

Pulmonary lesions induced by SARS-CoV-2 infection in domestic cats.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 2019, which ranges from fatal disease in some to mild or subclinical in most affected individuals. Many recovered human patients report persistent respiratory signs; however, lung disease in post-acute infection is poorly understood. Our objective was to describe histologic lung lesions and viral loads following experimental SARS-CoV-2 infection in 11 cats. Microscopic evaluation at 3, 6, 10, or 28 days postinoculation (DPI) identified mild to moderate patchy interstitial pneumonia, bronchiolar epithelial damage, and occlusive histiocytic bronchiolitis. Based on immunohistochemistry, alveolar septal thickening was due to CD204-positive macrophages, fewer B and T lymphocytes, type II pneumocytes, and capillary proliferation with a relative dearth of fibrosis. In blood vessel endothelium, there was reactive hypertrophy or vacuolar degeneration and increased MHC II expression at all time points. Unexpectedly, one cat from the 28 DPI group had severe subacute regionally extensive lymphohistiocytic pneumonia with multifocal consolidation, vasculitis, and alveolar fibrin. Reverse transcriptase-quantitative polymerase chain reaction identified SARS-CoV-2 RNA within the lung at 3 and 6 DPI, and viral RNA was below the limit of detection at 10 and 28 DPI, suggesting that pulmonary lesions persist beyond detection of viral RNA. These findings clarify our comparative understanding of disease induced by SARS-CoV-2 and suggest that cats can serve as an informative model to study post-acute pulmonary sequelae.

Bronchioalveolar stem cells are a main source for regeneration of distal lung epithelia in vivo.

Bronchioalveolar stem cells (BASCs) are a potential source for lung regeneration, but direct invivo evidence for a multipotential lineage contribution during homeostasis and disease is critically missing, since specific genetic labeling of BASCs has not been possible. We developed a novel cell tracing approach based on intein-mediated assembly of newly engineered split-effectors, allowing selective targeting of dual-marker expressing BASCs in the mouse lung. RNA sequencing of isolated BASCs demonstrates that BASCs show a distinct transcriptional profile, characterized by co-expression of bronchiolar and alveolar epithelial genes. We found that BASCs generate the majority of distal lung airway cells after bronchiolar damage but only moderately contribute to cellular turnover under homeostatic conditions. Importantly, DTA-mediated ablation of BASCs compromised proper regeneration of distal airways. The study defines BASCs as crucial components of the lung repair machinery and provides a paradigmatic example for the detection and manipulation of stem cells that cannot be recognized by a single marker alone.

결명자 추출물의 난알부민 감작으로 천식이 유발된 마우스에서의 개선 효과

Objectives : In this study, we investigated the effect of Cassia obtusifolia Linne (Cassiae Semen; CS) extract on ovalbumin (OVA)-induced allergic asthma in mice. Methods : CR was extracted with 70% ethanol. For in vitro study, HMC-1, human mast cells were treated with CS extract at 0.2 and <TEX>$0.5mg/m{\ell}$</TEX> for 1 h, and then stimulated with compound (C) 48/80 for 30 min. Primary spleenocytes were isolated from the spleen of mice, treated with CS extract for 1 h, and then stimulated with ConA for 24 h. For in vivo study, mice were sensitized at day 0, 7 and 14 with 0.2% OVA and then airway challenged using neublizer at day 21, 23, 25, and 27 to induced allergic asthma. CS extract at doses of 100 and 300 mg/kg body weight was orally administered during OVA challenge once per a day. The levels of allergic mediators such as histamine, OVA-specific IgE, IL-4, and <TEX>$IFN-{\gamma}$</TEX> were measured in the sera of mice or culture supernatants by EIA and ELISA, respectively. The expression of IL-4 and <TEX>$IFN-{\gamma}$</TEX> gene was determined by RT-PCR. The histopathological change of lung tissues was observed with hematoxylin and eosin (H&E) and Periodic acid Schiff (PAS) staining. Results : The treatment of CS extract in HMC-1 cells significantly inhibited C48/80-induced degranulation, and histamine release. The treatment of CS extract in spleenocytes suppressed the expression of IL-4 and <TEX>$IFN-{\gamma}$</TEX> mRNA. The administration of CS extract in OVA-induced asthmatic mice significantly decreased the levels of OVA-specific IgE, and IL-4 in a dose-dependent manner with OVA-control group. In addition, CS extract inhibited the infiltration of inflammatory cells and bronchiolar damage with epithelial thickening in lung tissues of OVA-induced asthma mice, and also mucin accumulation. Conclusions : These results indicate that CS extract prevents asthmatic damage through regulating the allergic immune response.

Pathology, toxicology, and latency of irritant gases known to cause bronchiolitis obliterans disease: Does diacetyl fit the pattern?

Bronchiolitis obliterans (BO) is a rare disease involving concentric bronchiolar fibrosis that develops rapidly following inhalation of certain irritant gases at sufficiently high acute doses. While there are many potential causes of bronchiolar lesions involved in a variety of chronic lung diseases, failure to clearly define the clinical features and pathological characteristics can lead to ambiguous diagnoses. Irritant gases known to cause BO follow a similar pathologic process and time course of disease onset in humans. Studies of inhaled irritant gases known to cause BO (e.g., chlorine, hydrochloric acid, ammonia, nitrogen oxides, sulfur oxides, sulfur or nitrogen mustards, and phosgene) indicate that the time course between causal chemical exposures and development of clinically significant BO disease is typically limited to a few months. The mechanism of toxic action exerted by these irritant gases generally involves widespread and severe injury of the epithelial lining of the bronchioles that leads to acute respiratory symptoms which can include lung edema within days. Repeated exposures to inhaled irritant gases at concentrations insufficient to cause marked respiratory distress or edema may lead to adaptive responses that can reduce or prevent severe bronchiolar fibrotic changes. Risk of BO from irritant gases is driven substantially by toxicokinetics affecting concentrations occurring at the bronchiolar epithelium. Highly soluble irritant gases that cause BO like ammonia generally follow a threshold-dependent cytotoxic mechanism of action that at sufficiently high doses results in severe inflammation of the upper respiratory tract and the bronchiolar epithelium concurrently. This is followed by acute respiratory distress, pulmonary edema, and post inflammatory concentric fibrosis that become clinically obvious within a few months. In contrast, irritant gases with lower solubility like phosgene also follow a threshold-dependent mechanism of cytotoxicity action but can exhibit more insidious and isolated bronchiolar tissue damage with a similar latency to fibrosis. To date, animal and human studies on the highly soluble gas, diacetyl, have not identified a coherent pattern of pathology and latency that would be expected based on studies of other known causes of bronchiolitis obliterans disease.

난알부민으로 유도된 천식 마우스에서 상백피 추출물의 면역조절효능 연구

Objectives : The root bark of Morus alba L. (Mori Cortex Radidus; MCR) has been traditionally used to reduce heat from the lungs, soothe asthma, and edema and to promote urination. In this study, we investigated the effect of MCR ethanol extract on ovalbumin (OVA)-induced allergic asthma in mice. Methods : Mice were sensitized at day 0, 7 and 14 with 0.2% OVA and then airway challenged at day 21, 23, 25, 27 and 29 to induce allergic asthma. MCR extracts at doses of 50 and 100 mg/kg body weight (bw) were orally administered during OVA challenge once per a day. The levels of allergic mediators such as histamine, OVA-specific IgE, IFN-<TEX>${\gamma}$</TEX> and IL-4 were measured in the sera of mice by ELISA. The histopathological change of lung tissues was observed with hematoxylin and eosin (H&E) staining. Results : MCR extract significantly decreased not only the serum levels of histamine, OVA-specific IgE, and IL-4 compared with those of OVA control group, but significantly increased the serum level of IFN-<TEX>${\gamma}$</TEX>. In H&E staining, MCR extract inhibited the infiltration of inflammatory cells and bronchiolar damage with epithelial thickening in lung tissues of OVA-induced asthma mice. Conclusions : These results indicate that MCR extract inhibits lung damage by asthma through regulating the allergic immune response, suggesting that MCR may be used as a useful agent for the treatment of allergic asthma.

Cytokine release, small airway injury, and parenchymal damage during mechanical ventilation in normal open-chest rats

Lung morpho-functional alterations and inflammatory response to various types of mechanical ventilation (MV) have been assessed in normal, anesthetized, open-chest rats. Measurements were taken during protective MV [tidal volume (Vt) = 8 ml/kg; positive end-expiratory pressure (PEEP) = 2.6 cmH(2)O] before and after a 2- to 2.5-h period of ventilation on PEEP (control group), zero EEP without (ZEEP group) or with administration of dioctylsodiumsulfosuccinate (ZEEP-DOSS group), on negative EEP (NEEP group), or with large Vt (26 ml/kg) on PEEP (Hi-Vt group). No change in lung mechanics occurred in the Control group. Relative to the initial period of MV on PEEP, airway resistance increased by 33 +/- 4, 49 +/- 9, 573 +/- 84, and 13 +/- 4%, and quasi-static elastance by 19 +/- 3, 35 +/- 7, 248 +/- 12, and 20 +/- 3% in the ZEEP, NEEP, ZEEP-DOSS, and Hi-Vt groups. Relative to Control, all groups ventilated from low lung volumes exhibited histologic signs of bronchiolar injury, more marked in the NEEP and ZEEP-DOSS groups. Parenchymal and vascular injury occurred in the ZEEP-DOSS and Hi-Vt groups. Pro-inflammatory cytokine concentration in the bronchoalveolar lavage fluid (BALF) was similar in the Control and ZEEP group, but increased in all other groups, and higher in the ZEEP-DOSS and Hi-Vt groups. Interrupter resistance was correlated with indexes of bronchiolar damage, and cytokine levels with vascular-alveolar damage, as indexed by lung wet-to-dry ratio. Hence, protective MV from resting lung volume causes mechanical alterations and small airway injury, but no cytokine release, which seems mainly related to stress-related damage of endothelial-alveolar cells. Enhanced small airway epithelial damage with induced surfactant dysfunction or MV on NEEP can, however, contribute to cytokine production.

Adaptive Processes in the Respiratory System and Adrenals in Concomitant Brain Injury

Objective: to study the nature and time of development of pulmonary and adrenal structural changes in early concomitant brain injury. Materials and methods. The lungs and adrenals from 120 persons who had died from severe concomitant brain injury were morphologically studied. Pulmonary and adrenal specimens were embedded in paraffin. Histological sections were stained in hematoxylin-eosin, by using the procedures developed by Weigert, van Gieson, and Mallory. The Schick test and other histochemical methods were used. Morphometric studies were also employed. Statistical processing used Student’s t-test. Results. In injury, the early pulmonary structural changes were ascertained to be circulatory disorders, bronchial and bronchiolar mucosal damage, and the development of atelectases and focal emphysema. The morphological criteria for increased adrenal cortical functional activity are focal delipidization, diminished cortical transparency, the «spotty» appearance of the cortex, boundary-spanning between the cortical and reticular zones, multiple cytolysis, and iron plethora. Conclusion. Severe concomitant brain injury is followed by pulmonary structural changes underlying acute respiratory failure. Adrenal structural and functional changes play an important role in the pathogenesis of lung injury. Key words: severe concomitant brain injury, lung injury, adrenals.

Morphology of Adaptive Processes in the Respiratory System in Acute Period of Multiple Injury

Morphological studies were studied to examine the lungs of the persons who had died due to severe mechanical trauma unaccompanied by head injury (и=85). The purpose of the investigation was to study the pattern and timing of pulmonary structural changes in the early period of mechanical trauma. It has been found that the early pulmonary structural changes in trauma are circulatory disorders, bronchial and bronchiolar mucosal damage, and the development of acute emphysema and focal atelectases and dystelectases. In subsequent hours, pulmonary structural changes significantly progress. Pulmonary edema and signs of a systemic inflammatory reaction develop just in the first hours after trauma.

Pulmonary Bronchiolar Cytotoxicity and Formation of Dichloroacetyl Lysine Protein Adducts in Mice Treated with Trichloroethylene

This study was undertaken to test the hypothesis that bronchiolar damage induced by trichloroethylene (TCE) is associated with bioactivation within the Clara cells with the involvement of CYP2E1 and CYP2F2. Histopathology confirmed dose-dependent Clara cell injury and disintegration of the bronchiolar epithelium in CD-1 mice treated with TCE doses of 500 to 1000 mg/kg i.p. Immunohistochemical studies, using an antibody that recognizes dichloroacetyl lysine adducts, revealed dose-dependent formation of adducts in the bronchiolar epithelium. Localization of dichloroacetyl adducts in the Clara cells coincided with damage to this cell type in TCE-treated mice. Pretreatment of CD-1 mice with diallyl sulfone, an inhibitor of CYP2E1 and CYP2F2, abrogated the formation of the dichloroacetyl adducts and protected against TCE-induced bronchiolar cytotoxicity. Treatment of wild-type and CYP2E1-null mice with TCE (750 mg/kg i.p.) also elicited bronchiolar damage that correlated with the formation of adducts in the Clara cells. Immunoblotting, using lung microsomes from TCE-treated CD-1 mice, showed dose-dependent production of dichloroacetyl adducts that comigrated with CYP2E1 and CYP2F2. However, TCE treatment resulted in a loss of immunoreactive CYP2E1 and CYP2F2 proteins and p-nitrophenol hydroxylation, a catalytic activity associated with both cytochrome P450 enzymes. The TCE metabolite, chloral hydrate, was formed in incubations of TCE with lung microsomes from CD-1, wild-type, and CYP2E1-null mice. The levels were higher in CD-1 than in either wild-type or CYP2E1-null mice, although levels were higher in CYP2E1-null than in wild-type mice. These findings supported the contention that TCE bioactivation within the Clara cells, predominantly involving CYP2F2, correlated with bronchiolar cytotoxicity in mice.

Identification of Bronchioalveolar Stem Cells in Normal Lung and Lung Cancer

Injury models have suggested that the lung contains anatomically and functionally distinct epithelial stem cell populations. We have isolated such a regional pulmonary stem cell population, termed bronchioalveolar stem cells (BASCs). Identified at the bronchioalveolar duct junction, BASCs were resistant to bronchiolar and alveolar damage and proliferated during epithelial cell renewal in vivo. BASCs exhibited self-renewal and were multipotent in clonal assays, highlighting their stem cell properties. Furthermore, BASCs expanded in response to oncogenic K-ras in culture and in precursors of lung tumors in vivo. These data support the hypothesis that BASCs are a stem cell population that maintains the bronchiolar Clara cells and alveolar cells of the distal lung and that their transformed counterparts give rise to adenocarcinoma. Although bronchiolar cells and alveolar cells are proposed to be the precursor cells of adenocarcinoma, this work points to BASCs as the putative cells of origin for this subtype of lung cancer.

Repeated exposure to low levels of sulfur dioxide (SO 2) enhances the development of ovalbumin-induced asthmatic reactions in guinea pigs

Sulfur dioxide (SO2) is one of the major air pollutants. It is known to aggravate asthma symptoms in human beings, but few studies have focused on the effects of SO2 upon the development of bronchial asthma in animal models. This study was undertaken to evaluate the role of SO2 upon the development of ovalbumin (OA)-induced asthmatic reactions in guinea pigs. Guinea pigs were divided into four groups: (1) OA- and SO2-exposed group (n = 12), (2) SO2-exposed group (n = 12), (3) OA-exposed group (n = 11), and (4) saline-exposed group (n = 7). Guinea pigs of the first and second groups were exposed to 0.1 ppm SO2 for 5 hours a day on 5 consecutive days. Guinea pigs in the first and third groups inhaled 0.1% OA aerosols for 45 minutes a day on days 3, 4, and 5. One week after the sensitization procedure, all the guinea pigs underwent bronchial challenge with 1.0% OA aerosols, using unrestricted whole-body plethysmography. Bronchoalveolar lavage and histopathologic examination were performed 24 hours after the bronchial challenge. Increases in enhanced pause (Penh), as an index of airway obstruction, after the bronchial challenge was significantly higher in OA- and SO2-exposed group (group 1) than the other groups (P < .05, respectively). Eosinophil counts in bronchoalveolar lavage fluids were also significantly higher in group 1 than in the other groups (P < .05, respectively). Histopathologic findings of bronchial and lung tissue in the group 1 showed an infiltration of inflammatory cells, bronchiolar epithelial damage, and mucus and cell plug in the lumen, but no significant abnormalities were observed in the other groups. These results indicate that repeated exposure to low levels of sulfur dioxide may enhance the development of ovalbumin-induced asthmatic reactions in guinea pigs.

NK1-receptor activation prevents hydrocarbon-induced lung injury in mice.

Recent evidence suggests that neurokinin (NK)-receptor activation may have a protective role in maintaining lung integrity when challenged by airborne toxicants such as sulfur dioxide, ozone, acrolein, or hydrocarbons. To investigate the effect of NK1-receptor activation on hydrocarbon-induced lung injury, B6.A.D. (Ahr d/Nats) mice received subchronic exposures to JP-8 jet fuel (JP-8). Lung injury was assessed by the analysis of pulmonary physiology, bronchoalveolar lavage fluid, and morphology. Hydrocarbon exposure to target JP-8 concentrations of 50 mg/m3, with saline treatment, was characterized by enhanced respiratory permeability to 99mTc-labeled diethylenetriaminepentaacetic acid, alveolar macrophage toxicity, and bronchiolar epithelial damage. Mice administered [Sar9,Met(O2)11]substance P, an NK1-receptor agonist, after each JP-8 exposure had the appearance of normal pulmonary values and tissue morphology. In contrast, endogenous NK1-receptor antagonism by CP-96345 administration exacerbated JP-8-enhanced permeability, alveolar macrophage toxicity, and bronchiolar epithelial injury. These data indicate that NK1-receptor activation may have a protective role in preventing the development of hydrocarbon-induced lung injury, possibly through the modulation of bronchiolar epithelial function.

1-Nitronaphthalene Toxicity in Rat Lung and Liver: Effects of Inhibiting and Inducing Cytochrome P450 Activity

In rats, 1-nitronaphthalene (1-NN) causes both pulmonary and hepatic toxicity. Pulmonary toxicity is evident as bronchiolar damage, with necrosis of Clara cells and ciliated cells, whereas hepatic injury involves vacuolation of centrilobular hepatocytes. Pretreatment with O, O, S-trimethylphosphorodithioate [OOS-MeP(S)] or p-xylene gave three- to fourfold protection against 1-NN toxicity. These pretreatments also prevented both the increase in lung weight and the rise in γ-glutamyltranspeptidase and alkaline phosphatase activity in bronchoalveolar lavage fluid normally associated with 1-NN toxicity. Pretreatment with Aroclor 1254 or β-naphthoflavone (β-NF) did not alter the LD50 of 1-NN. Aroclor or β-NF pretreatment did, however, prevent morphological signs of lung injury and any increase in either lung weight or enzyme activity in bronchoalveolar lavage fluid. Liver damage was not prevented by these treatments; indeed, injury was exacerbated and was transferred from centrilobular to periportal areas. In control rats the covalent binding of [1 14C]NN to liver microsomes was eight times greater than to lung microsomes. Pretreatment with OOS-MeP(S) decreased covalent binding to lung microsomes, without affecting binding to liver microsomes. Conversely, both Aroclor and β-NF slightly increased covalent binding in lung, but increased liver binding by 250-300%. Phenobarbitone also increased binding to liver microsomes by 250-300%, but failed to increase, or alter, the distribution of liver damage. The reported effects of these pretreatments indicate that the toxicity of 1-NN is probably activated by isoenzyme CYP2B1 in lung, but by isoenzymes CYP1A1 or CYP1A2 in the liver.

Taurine chloramine inhibits the synthesis of nitric oxide and the release of tumor necrosis factor in activated RAW 264.7 cells.

Taurine is present in high concentrations in most mammalian tissues, including those that prodigiously produce oxidants. Taurine protects against bronchiolar damage induced by NO2, ozone, bleomycin, and amiodarone. Taurine is chlorinated to form taurine chloramine (Tau-Cl) by the halide-dependent myeloperoxidase system and, under physiological conditions, reduces HOCl toxicity. Although NO and its metabolites, NO2- and NO3-, are thought to be major mediators of tissue damage resulting from oxidant exposure, cytokines, including tumor necrosis factor (TNF), are also involved. We examined the effects of Tau-Cl on NO production and TNF release by using RAW 264.7 cells activated with recombinant interferon-gamma (rIFN-gamma; 50 U/ml) and lipopolysaccharide (LPS; 10 micrograms/ml). NO was measured spectrophotometrically as NO2- after reaction with Griess reagent and TNF was measured by ELISA. Tau-Cl (0.5 mM) inhibits NO and TNF released into the medium by 47% and 43%, respectively. Tau-Cl is actively transported into RAW 264.7 cells by an uptake system that is energy, temperature, and Na+ dependent. Competition experiments demonstrate that the uptake system for Tau-Cl is distinct from that for taurine. In addition, the NO synthase activity of cytosolic preparations from activated RAW 264.7 cells is irreversibly inhibited by pretreatment with Tau-Cl. We demonstrate that Tau-Cl inhibits production of NO and TNF by activated macrophages and suggest a mechanism through which taurine supplementation may protect against oxidant-induced tissue damage.

Experimental Polyacrylamide-induced Acute Injury in Rat Lung

We recently reported the first case of accidental aspiration of polyacrylamide occurring in a 26-year-old man. The patient developed severe airway obstruction and parenchymal lung damage and died. Autopsy revealed numerous polyacrylamide particles in his lungs, as well as extensive bronchiolar and alveolar damage. Gas chromatographic and mass spectrometric assessment of the lung tissue failed to reveal polyacrylamide activity, although assessment of the suspending solvent of the polyacrylamide showed a pattern characteristic of an aliphatic hydrocarbon mixture with a prominent dodecane peak. This experimental study was performed to determine the nature and extent of damage to rat bronchial and alveolar epithelia following endotracheal instillation of polyacrylamide, hydrocarbon mixture (petroleum distillate), dodecane (C12H26), or normal saline. The rat lungs were examined grossly and microscopically 10 min and 24, 72, and 96 h after endotracheal instillation, following inflation and fixation with 10 percent buffered formaldehyde. Gross examination revealed congested, mottled visceral pleural surfaces in the rats treated with polyacrylamide and dodecane. There were no pleural exudates or effusions. Microscopically, vascular engorgement, bronchiolitis, and focal pneumonia were observed. Vascular engorgement was most pronounced at 72 to 96 h in rat lungs treated with polyacrylamide and dodecane and was moderate at 24 h in rats treated with petroleum distillate. Focal organizing pneumonia was marked at 96 h in rats treated with petroleum distillate, at 72 h in those treated with polyacrylamide, and at 24 h in those treated with dodecane. The saline-treated control animals showed no change. Our findings suggest that polyacrylamide, dodecane, and petroleum distillate are strong irritants to the airways. However, a direct obstructive/mechanical effect of the polyacrylamide upon the airway has not been excluded. Airway exposure to polyacrylamide may result in lung injury secondary to the polyacrylamide itself, its suspending agents, or both.