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

Update in postinfectious bronchiolitis obliterans

Postinfectious bronchiolitis obliterans (PiBO) is a rare and severe form of chronic obstructive lung disease caused by an infectious injury to the lower respiratory tract. The most commonly recognized inciting stimuli leading to PiBO are airway pathogens, such as adenovirus and Mycoplasma. PiBO is characterized by persistent and nonreversible airway obstruction, with functional and radiological evidence of small airway involvement. The literature has limited information on the aetiology, clinical profile, treatment, and outcome of PiBO.

The Devastating Health Consequences of the Ohio Derailment: A Closer Look at the Effects of Vinyl Chloride Spill

On 3 February 2023, a train derailed in the village of East Palestine, Ohio, home to approximately 4700 residents [...].

Electrospun-Based Membranes as a Key Tool to Prevent Respiratory Infections

The use of electrospun meshes has been proposed as highly efficient protective equipment to prevent respiratory infections. Those infections can result from the activity of micro-organisms and other small dust particles, such as those resulting from air pollution, that impair the respiratory tract, induce cellular damage and compromise breathing capacity. Therefore, electrospun meshes can contribute to promoting air-breathing quality and controlling the spread of such epidemic-disrupting agents due to their intrinsic characteristics, namely, low pore size, and high porosity and surface area. In this review, the mechanisms behind the pathogenesis of several stressors of the respiratory system are covered as well as the strategies adopted to inhibit their action. The main goal is to discuss the performance of antimicrobial electrospun nanofibers by comparing the results already reported in the literature. Further, the main aspects of the certification of filtering systems are highlighted, and the expected technology developments in the industry are also discussed.

Ammonia exposure by intratracheal instillation causes severe and deteriorating lung injury and vascular effects in mice

OBJECTIVE

Ammonia (NH₃) is a corrosive alkaline gas that can cause life-threatening injuries by inhalation. The aim was to establish a disease model for NH₃-induced injuries similar to acute lung injury (ALI) described in exposed humans and investigate the progression of lung damage, respiratory dysfunction and evaluate biomarkers for ALI and inflammation over time.

METHODS

Female BALB/c mice were exposed to an NH₃ dose of 91.0 mg/kg·bw using intratracheal instillation and the pathological changes were followed for up to 7 days.

RESULTS

NH₃ instillation resulted in the loss of body weight along with a significant increase in pro-inflammatory mediators in both bronchoalveolar lavage fluid (e.g. IL-1β, IL-6, KC, MMP-9, SP-D) and blood (e.g. IL-6, Fibrinogen, PAI-1, PF4/CXCL4, SP-D), neutrophilic lung inflammation, alveolar damage, increased peripheral airway resistance and methacholine-induced airway hyperresponsiveness compared to controls at 20 h. On day 7 after exposure, deteriorating pathological changes such as increased macrophage lung infiltration, heart weights, lung hemorrhages and coagulation abnormalities (elevated plasma levels of PAI-1, fibrinogen, endothelin and thrombomodulin) were observed but no increase in lung collagen. Some of the analyzed blood biomarkers (e.g. RAGE, IL-1β) were unaffected despite severe ALI and may not be significant for NH₃-induced damages.

CONCLUSIONS

NH₃ induces severe acute lung injuries that deteriorate over time and biomarkers in lungs and blood that are similar to those found in humans. Therefore, this model has potential use for developing diagnostic tools for NH₃-induced ALI and for finding new therapeutic treatments, since no specific antidote has been identified yet.

Review of Inhalation Health Risks Involving Chloromethylisothiazolinone (CMIT) and Methylisothiazolinone (MIT) Used as Disinfectants in Household Humidifiers

The association between lung injury and exposure to humidifier disinfectant (HD) containing a mixture of chloromethylisothiazolinone (CMIT) and methylisothiazolinone (MIT) has been controversial in South Korea. This study conducts a literature review in order to evaluate the likelihood of CMIT/MIT reaching the lower part of the respiratory tract and causing lung injury. A literature review focused on the inhalation risk of HD containing a mixture of CMIT and MIT. The major contents included the physicochemical properties of CMIT and MIT contained in HDs and methodological reviews on substance analysis, toxicity tests and clinical cases. HD products marketed in South Korea have been reported to contain approximately 1-2% CMIT and 0.2-0.6% MIT along with magnesium nitrate (20-25%), magnesium chloride (0.2-1.0%), and water (70-75%). The types of CMIT and MIT dispersed into the air and deposited in the respiratory tract are assumed to be either gaseous substances or nanoparticles mixed with magnesium salts. The result of the literature review including clinical cases of lung injury among CMIT/MIT HD product users, demonstrated that these chemicals likely reach the lower respiratory tract and accordingly cause lung injury. A number of humidifier disinfectant-associated lung injury cases with clinical evidence should be prioritized in risk assessment of HD containing CMIT and MIT, even though there might be insufficient evidence in all related areas, including inhalation exposure assessment studies, animal testing, and epidemiological studies.

The Heat Shock Protein 90 Inhibitor, AT13387, Protects the Alveolo-Capillary Barrier and Prevents HCl-Induced Chronic Lung Injury and Pulmonary Fibrosis

Hydrochloric acid (HCl) exposure causes asthma-like conditions, reactive airways dysfunction syndrome, and pulmonary fibrosis. Heat Shock Protein 90 (HSP90) is a molecular chaperone that regulates multiple cellular processes. HSP90 inhibitors are undergoing clinical trials for cancer and are also being studied in various pre-clinical settings for their anti-inflammatory and anti-fibrotic effects. Here we investigated the ability of the heat shock protein 90 (HSP90) inhibitor AT13387 to prevent chronic lung injury induced by exposure to HCl in vivo and its protective role in the endothelial barrier in vitro. We instilled C57Bl/6J mice with 0.1N HCl (2 µL/g body weight, intratracheally) and after 24 h began treatment with vehicle or AT13387 (10 or 15 mg/kg, SC), administered 3×/week; we analyzed histological, functional, and molecular markers 30 days after HCl. In addition, we monitored transendothelial electrical resistance (TER) and protein expression in a monolayer of human lung microvascular endothelial cells (HLMVEC) exposed to HCl (0.02 N) and treated with vehicle or AT13387 (2 µM). HCl provoked persistent alveolar inflammation; activation of profibrotic pathways (MAPK/ERK, HSP90); increased deposition of collagen, fibronectin and elastin; histological evidence of fibrosis; and a decline in lung function reflected in a downward shift in pressure–volume curves, increased respiratory system resistance (Rrs), elastance (Ers), tissue damping (G), and hyperresponsiveness to methacholine. Treatment with 15 mg/kg AT13387reduced alveolar inflammation, fibrosis, and NLRP3 staining; blocked activation of ERK and HSP90; and attenuated the deposition of collagen and the development of chronic lung injury and airway hyperreactivity. In vitro, AT13387 prevented HCl-induced loss of barrier function and AKT, ERK, and ROCK1 activation, and restored HSP70 and cofilin expression. The HSP90 inhibitor, AT13387, represents a promising drug candidate for chronic lung injury that can be administered subcutaneously in the field, and at low, non-toxic doses.

High concentrations of ammonia induced cytotoxicity and bronchoconstriction in a precision-cut lung slices rat model

Exposure to high concentrations of ammonia (NH3) can cause life-threatening lung damages. The objective of this study was to establish a translational in vitro model for NH3-induced lung injury. Precision-cut lung slices (PCLS) from rats were exposed to NH3 and toxicological responses and cell viability were quantified by analysis of LDH, WST-1, inflammatory mediators (IL-1β, IL-6, CINC-1, MMP-9, RAGE and IL-18), and by microscopic evaluation of bronchoconstriction induced by electric-field-stimulation (EFS) or methacholine (MCh). Different treatment strategies were assessed to prevent or reverse the damages caused by NH3 using anti-inflammatory, anti-oxidant or neurologically active drugs. Exposure to NH3 caused a concentration-dependent increase in cytotoxicity (LDH/WST-1) and IL-1β release in PCLS medium. None of the treatments reduced cytotoxicity. Deposition of NH3 (24-59 mM) on untreated PCLS elicited an immediate concentration-dependent bronchoconstriction. Unlike MCh, the EFS method did not constrict the airways in PCLS at 5 h after NH3-exposure (47-59 mM). Atropine and TRP-channel antagonists blocked EFS-induced bronchoconstriction but these inhibitors could not block the immediate NH3-induced bronchoconstriction. In conclusion, NH3 exposure caused cytotoxic effects and lung damages in a concentration-dependent manner and this PCLS method offers a way to identify and test new concepts of medical treatments and biomarkers that may be of prognostic value.

Potential Protective Effects of Naringin on Oculo-Pulmonary Injury Induced by PM10 (Wood Smoke) Exposure by Modulation of Oxidative Damage and Acetylcholine Esterase Activity in a Rat Model

BACKGROUND

Millions of households in the world depend on wood and biomass for cooking and heating. This dependence leads to undesirable toxic effects, such as ocular and pulmonary toxicity.

OBJECTIVES

The present study examined the potential oculoprotective and pulmonary protective activity of naringin (NRG), a naturally occurring flavonoid, against wood smoke (WS)-induced toxicity in a rat model.

METHODS

Forty-eight adult male albino rats were randomly distributed into six (n=8) groups. All rats were fed, given water, and observed for 21 days, Group I (control) received only distilled water and no WS exposure, Group II was exposed to WS, Group III was exposed to WS and given 50 mg/kg/d α-tocopherol (vitamin E), Group IV was exposed to WS and given 80 mg/kg/day NRG, Group V was administered only 80 mg/kg/d NRG only, and Group VI was administered only 50 mg/kg/d vitamin E. WS exposure was for 20 min/d. The effect of NRG treatment on acetylcholinesterase activity, nitric oxide radical production, malondialdehyde level, and antioxidant enzymes (ie, superoxide dismustase and catalase) in WS-exposed rats was examined.

RESULTS

Subchronic (21 day) exposure to WS induced ocular and pulmonary toxicity manifested by the infiltration of parenchyma, atrophy, and inflammation of the cells, which was correlated with alterations in antioxidant enzyme concentrations. Cell damage was associated with an increase in acetylcholinesterase activity and nitric oxide radical concentrations. The toxicity triggered by WS was modulated by the coadministration of NRG.

CONCLUSION

These results suggest that NRG treatment may be useful to reduce WS-induced oxidative stress and related ocular and pulmonary damage in rats. (Curr Ther Res Clin Exp. 2012; 73:XXX-XXX).

Evaluation of diacetyl mediated pulmonary effects in physiologically relevant air-liquid interface models of human primary bronchial epithelial cells

Diacetyl is an artificial flavouring agent, known to cause bronchiolitis obliterans. Diacetyl-induced pulmonary effects were assessed in human primary bronchial epithelial cells (PBEC) cultured at air-liquid interface (ALI). The PBEC-ALI models were exposed to clean air (sham) and diacetyl vapour (1, 3, 10 and 30 ppm) for 30 min. At 6 and 24 h post-exposure, cell medium was sampled for assessment of cytotoxicity measurement, and CXCL8, MMP9 secretion by ELISA. Pro-inflammatory, oxidative stress, tissue injury/repair, anti-protease and beta-defensin markers were assessed using qRT-PCR. Additionally, epidermal growth factor receptor ligands (amphiregulin) and anti-protease (SLPI) were analysed at 6 h, 8 h and 24 h post exposure to 1 and 10 ppm diacetyl. No significant cytotoxicity was observed at any exposure level. MMP9 was significantly increased in both apical and basal media at 24 h. Both SLPI and amphiregulin secretion were significantly increased following exposure to 10 ppm diacetyl. Exposure of PBEC-ALI model to diacetyl vapour resulted in significantly altered transcript expression of pro-inflammatory, oxidative stress, anti-protease, tissue injury/repair markers. Changes in transcript expression of significantly altered markers were more prominent 24 h post-exposure compared to 6 h. This study warrants further mechanistic investigations to elucidate the pulmonary effects of inhaled diacetyl vapour using physiologically relevant in vitro models.

Effect of inactivated Streptococcus pneumoniae as non-pathogenic particles on the severity of pneumonia caused by respiratory syncytial virus infection in mice

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We made inactivated Streptococcus pneumoniae (ISP) as non-pathogenic particles.

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We evaluated effects of ISP on development of pneumonia by RSV infection in mice.

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ISP didn’t show histopathological effects on lungs of RSV-infected mice.

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ISP reduced virus titer and infiltration of lymphocyte in the lungs.

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The inherent activity of ISP as particles in RSV infection is discussed.

The severity of pneumonia in respiratory syncytial virus (RSV) infection is strongly related to host immune response and external factors such as bacteria and environmental chemicals. We investigated the effect of inactivated Streptococcus pneumoniae (ISP) as non-pathogenic particles on the severity of pneumonia in RSV-infected mice. Mice were intranasally exposed to ISP before RSV infection. On day 5 post-infection, we examined tissues, virus titer, and infiltrated cells in the lungs. The ISP did not cause significant histopathological effects in the lungs of RSV infected mice, but reduced virus titer. It also reduced the ratio of lymphocyte infiltration into the lungs and consequently the ratio of macrophage increased. In addition, we found that ISP increased RANTES level in bronchoalveolar lavage fluid from RSV-infected mice on day 1 post-infection, but reduced type I interferon levels. Thus, ISP did not exacerbate pneumonia in RSV infection, rather, it might mildly reduce the severity. We characterize and discuss the inherent activity of ISP as non-pathogenic particles inducing the role of RANTES on the pneumonia in RSV infection.

Comparisons of acute inflammatory responses of nose-only inhalation and intratracheal instillation of ammonia in rats

Objective: To establish a rat model with respiratory and pulmonary responses caused by inhalation exposure to non-lethal concentrations of ammonia (NH₃) that can be used for evaluation of new medical countermeasure strategies for NH₃-induced acute lung injury (ALI). This is of great value since no specific antidotes of NH₃-induced injuries exist and medical management relies on supportive and symptomatically relieving efforts. Methods: Female Sprague-Dawley rats (8-9 weeks old, 213g ± 2g) were exposed to NH₃ using two different exposure regimens; nose-only inhalation or intratracheal instillation. The experiment was terminated 5 h, 24 h, 14 and 28 days post-exposure. Results: Nose-only inhalation of NH₃ (9000-15 000 ppm) resulted in increased salivation and labored breathing directly post-exposure. Exposure did not increase inflammatory cells in bronchoalveolar lavage fluid but exposure to 12 000 ppm NH₃ during 15 min reduced body weight and induced coagulation abnormalities by increasing serum fibrinogen levels. All animals were relatively recovered by 24 h. Intratracheal instillation of NH₃ (1%) caused early symptoms of ALI including airway hyperresponsiveness, neutrophilic lung inflammation and altered levels of coagulation factors (increased fibrinogen and PAI-1) and early biomarkers of ALI (IL-18, MMP-9, TGFβ) which was followed by increased deposition of newly produced collagen 14 days later. Histopathology analysis at 5 h revealed epithelial desquamation and that most lesions were healed after 14 days. Conclusions: This study demonstrates that intratracheal instillation can reproduce several early hallmarks of ALI. Our findings therefore support that the intratracheal instillation exposure regimen can be used for new medical countermeasure strategies for NH₃-induced ALI.

Post-infectious bronchiolitis obliterans

Bronchiolitis obliterans is a rare and severe chronic lung disease resulting from a lower respiratory tract lesion. It may occur after a bone marrow or lung transplantation, infectious diseases, or less frequently after inhaling toxic substances or after connective tissue diseases. Pathology, pathogenesis, and molecular biology, as well as the best treatment of bronchiolitis obliterans, remain the subject of ongoing research. This review discusses our current knowledge of different areas of bronchiolitis obliterans associated with infectious lesions.