Inhalational Constrictive Bronchiolitis: The Evolution of our Understanding of this Disease

The case definition of inhalational constrictive bronchiolitis (CB) has changed over the generations. We identify changes in the description of this illness over time associated with different exposures and present the natural history of CB in a case attributed to military burn pit exposure. The initial descriptions of this disease began with nitric acid spills and silage exposures. In these events, there was an acute exposure, typically a short-term resolution of the adverse respiratory events, and then a progression, leading to disability or a respiratory death. The life-saving role of corticosteroid therapy in this situation was recognized. War gas exposures of World War I and then Saddam Hussein's use of sulfur mustard gas in the Iran-Iraq War followed. More recently the findings associated with diacetyl exposure in commercial popcorn workers remained consistent with previously described presentations, but then the clinical presentation in troops returning from deployment to Southwest Asia was very different, yet with the same histologic findings. We recognize unreconciled disparities in the clinical, physiologic, and imaging presentation in those with inhalational bronchiolitis and acknowledge this as perhaps one of the difficult diagnoses in respiratory medicine.

Occupational Bronchiolitis: An Update

Occupational bronchiolitis is characterized by inflammation of the small airways, and represents a heterogeneous set of lung conditions that can occur following a range of inhalation exposures related to work. The most common clinical presentation includes insidious onset of exertional dyspnea and cough. Multiple reports in recent years have drawn attention to previously unrecognized risk factors for occupational bronchiolitis following exposures in several settings. Both current and past occupational exposures, including prior military deployment-related exposures, should be considered in patients undergoing evaluation for unexplained dyspnea. Diagnostic testing for potential bronchiolitis should include a thorough assessment of the small airways.

Chemical Characterization of Electronic Cigarette (e-cigs) Refill Liquids Prior to EU Tobacco Product Directive Adoption: Evaluation of BTEX Contamination by HS-SPME-GC-MS and Identification of Flavoring Additives by GC-MS-O

The present study focused on the determination of benzene, toluene, ethylbenzene and xylenes (BTEX) concentration levels in 97 refill liquids for e-cigs selected by the Italian National Institute of Health as representative of the EU market between 2013 and 2015 prior to the implementation of the European Union (EU) Tobacco Product Directive (TPD). Most of the e-liquids investigated (85/97) were affected by BTEX contamination, with few exceptions observed (levels below the limit of quantification (LOQ) of headspace-solid phase micro extraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) methodology). Across brands, concentration levels ranged from 2.7 to 30,200.0 µg/L for benzene, from 1.9 to 447.8 µg/L for ethylbenzene, from 1.9 to 1,648.4 µg/L for toluene and from 1.7 to 574.2 µg/L for m,p,o-xylenes. The variability observed in BTEX levels is likely to be related to the variability in contamination level of both propylene glycol and glycerol and flavoring additives included. No correlation was found with nicotine content. Moreover, on a limited number of e-liquids, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) analysis was performed, allowing the identification of key flavoring additives responsible of specific flavor notes. Among them, diacetyl is a flavoring additive of concern for potential toxicity when directly inhaled into human airways. The data reported are eligible to be included in the pre-TPD database and may represent a reference for the ongoing evaluation on e-liquids safety and quality under the current EU Legislation.

Identification of Cytotoxic Flavor Chemicals in Top-Selling Electronic Cigarette Refill Fluids

We identified the most popular electronic cigarette (EC) refill fluids using an Internet survey and local and online sales information, quantified their flavor chemicals, and evaluated cytotoxicities of the fluids and flavor chemicals. "Berries/Fruits/Citrus" was the most popular EC refill fluid flavor category. Twenty popular EC refill fluids were purchased from local shops, and the ingredient flavor chemicals were identified and quantified by gas chromatography-mass spectrometry. Total flavor chemical concentrations ranged from 0.6 to 27.9 mg/ml, and in 95% of the fluids, total flavor concentration was greater than nicotine concentration. The 20 most popular refill fluids contained 99 quantifiable flavor chemicals; each refill fluid contained 22 to 47 flavor chemicals, most being esters. Some chemicals were found frequently, and several were present in most products. At a 1% concentration, 80% of the refill fluids were cytotoxic in the MTT assay. Six pure standards of the flavor chemicals found at the highest concentrations in the two most cytotoxic refill fluids were effective in the MTT assay, and ethyl maltol, which was in over 50% of the products, was the most cytotoxic. These data show that the cytotoxicity of some popular refill fluids can be attributed to their high concentrations of flavor chemicals.

Effects of Diacetyl Flavoring Exposure in Mice Metabolism

Diacetyl is a flavoring that imparts a buttery flavor to foods, but the use or exposure to diacetyl has been related to some diseases. We investigated the effect of oral intake of diacetyl in male and female C57/Bl mice. We performed a target metabolomics assay using ultraperformance liquid chromatography paired with triple quadrupole mass spectrometry (UPLC-MS/MS) for the determination and quantification of plasmatic metabolites. We observed alterations in metabolites present in the urea and tricarboxylic acid (TCA) cycles. Peroxynitrite plasmatic levels were evaluated by a colorimetric method, final activity of superoxide dismutase (SOD) was evaluated by an enzymatic method, and mouse behavior was evaluated. Majority of the assay showed differences between control and treatment groups, as well as between genders. This may indicate the involvement of sex hormones in the regulation of a normal metabolic profile, and the implication of sex differences in metabolite disease response.

Increased chemical acetylation of peptides and proteins in rats after daily ingestion of diacetyl analyzed by Nano-LC-MS/MS

Background

Acetylation alters several protein properties including molecular weight, stability, enzymatic activity, protein-protein interactions, and other biological functions. Our previous findings demonstrating that diacetyl/peroxynitrite can acetylate L-lysine, L-histidine, and albumin in vitro led us to investigate whether diacetyl-treated rats suffer protein acetylation as well.

Methods

Wistar rats were administered diacetyl daily for four weeks, after which they were sacrificed, and their lung proteins were extracted to be analysed by Nano-LC-MS/MS (Q-TOF). A C18 reversed-phase column and gradient elution with formic acid/acetonitrile solutions from 2 to 50% over 150 min were used to separate the proteins. Protein detection was performed using a microTOF-Q II (QTOF) equipped with captive source and an electrospray-ionization source. The data from mass spectrometry were processed using a Compass 1.7 and analyzed using Protein Scape, software that uses Mascot algorithms to perform protein searches.

Results

A set of 3,162 acetylated peptides derived from 351 acetylated proteins in the diacetyl-treated group was identified. Among them, 23 targeted proteins were significantly more acetylated in the diacetyl-treated group than in the PBS control. Protein acetylation of the group treated with 540 mg/kg/day of diacetyl was corroborated by Western blotting analysis.

Conclusions

These data support our hypothesis that diacetyl exposure in animals may lead to the generation of acetyl radicals, compounds that attach to proteins, affecting their functions and triggering adverse health problems.

Effects by inhalation of abundant fragrances in indoor air - An overview

Odorous compounds (odors) like fragrances may cause adverse health effects. To assess their importance by inhalation, we have reviewed how the four major abundant and common airborne fragrances (α-pinene (APN), limonene (LIM), linalool (LIL), and eugenol (EUG)) impact the perceived indoor air quality as odor annoyance, sensory irritation and sensitization in the airways. Breathing and cardiovascular effects, and work performance, and the impact in the airways of ozone-initiated gas- and particle phase reactions products have also been assessed. Measured maximum indoor concentrations for APN, LIM and LIL are close to or above their odor thresholds, but far below their thresholds for sensory irritation in the eyes and upper airways; no information could be traced for EUG. Likewise, reported risk values for long-term effects are far above reported indoor concentrations. Human exposure studies with mixtures of APN and LIM and supported by animal inhalation models do not support sensitization of the airways at indoor levels by inhalation that include other selected fragrances. Human exposure studies, in general, indicate that reported lung function effects are likely due to the perception rather than toxic effects of the fragrances. In general, effects on the breathing rate and mood by exposure to the fragrances are inconclusive. The fragrances may increase the high-frequency heart rate variability, but aerosol exposure during cleaning activities may result in a reduction. Distractive effects influencing the work performance by fragrance/odor exposure are consistently reported, but their persistence over time is unknown. Mice inhalation studies indicate that LIM or its reaction mixture may possess anti-inflammatory properties. There is insufficient information that ozone-initiated reactions with APN or LIM at typical indoor levels cause airway effects in humans. Limited experimental information is available on long-term effects of ozone-initiated reaction products of APN and LIM at typical indoor levels.

Basic science of electronic cigarettes: assessment in cell culture and in vivo models

Electronic cigarettes (e-cigarettes, ECIGs) were introduced into the market a decade ago as an alternative to tobacco smoking. Whether ECIGs are safe and whether they qualify as smoking cessation tool is currently unknown. Their use has markedly expanded in that period, despite the fact that potential toxic effects of the vapour created by the e-cigarette and the nicotine-containing cartridge fluid have been incompletely studied. Marketing targets diverse groups including older smokers but also young people. Whereas the adverse health effects of nicotine inhaled by users of ECIGs has been well documented, less is known about the other components. An increasing number of in vitro and in vivo studies demonstrate a range of adverse effects of both the vapour created by ECIGs as well as the nicotine-containing fluid. Importantly, these studies demonstrate that toxicity from ECIGs, although this may be less than that caused by tobacco products, not only arises from its nicotine content. Furthermore, there are no data on the long-term consequences of ECIG use. The wide range of ECIG products available to consumers and the lack of standardisation of toxicological approaches towards ECIG evaluation complicates the assessment of adverse health effects of their use. Here we review the current data on preclinical studies on ECIGs describing their effects in cell culture and animal models.

Ethics, morality, and conflicting interests: how questionable professional integrity in some scientists supports global corporate influence in public health

Clinical and public health research, education, and medical practice are vulnerable to influence by corporate interests driven by the for-profit motive. Developments over the last 10 years have shown that transparency and self-reporting of corporate ties do not always mitigate bias. In this article, we provide examples of how sound scientific reasoning and evidence-gathering are undermined through compromised scientific enquiry resulting in misleading science, decision-making, and policy intervention. Various medical disciplines provide reference literature essential for informing public, environmental, and occupational health policy. Published literature impacts clinical and laboratory methods, the validity of respective clinical guidelines, and the development and implementation of public health regulations. Said literature is also used in expert testimony related to resolving tort actions on work-related illnesses and environmental risks. We call for increased sensitivity, full transparency, and the implementation of effective ethical and professional praxis rules at all relevant regulatory levels to rout out inappropriate corporate influence in science. This is needed because influencing the integrity of scientists who engage in such activities cannot be depended upon.

Occupational causes of constrictive bronchiolitis

PURPOSE OF REVIEW

New literature from 2009 to 2012 regarding occupational constrictive bronchiolitis challenges textbook descriptions of this disease, formerly thought to be limited to fixed airflow limitation arising in the wake of accidental overexposure to noxious chemicals. Indolent evolution of dyspnea without a recognized hazardous exposure is a more common presentation.

RECENT FINDINGS

Biopsy-confirmed case series of constrictive bronchiolitis from US soldiers, Iranian survivors of sulfur mustard gassing, hospital-based studies, and flavoring-related cases document that indolent constrictive bronchiolitis cases can have normal spirometry or either restrictive or obstructive abnormalities. High-resolution computerized tomography studies can be normal or reflect air-trapping and mosaic attenuation on expiratory films. Thus, in the absence of noninvasive abnormalities, the diagnosis in dyspneic patients may require thoracoscopic biopsy in settings in which exposure risk has not been recognized. Many workers with occupational constrictive bronchiolitis stabilize with cessation of exposures causing bronchiolar epithelial necrosis.

SUMMARY

Clinicians need a high index of suspicion for constrictive bronchiolitis in young patients with rapidly progressing exertional dyspnea, regardless of spirometric and radiologic findings. Identification of novel causes and exposure-response relations for known causes are needed to provide guidance for protecting workers at risk for this largely irreversible lung disease.

Popcorn flavoring effects on reactivity of rat airways in vivo and in vitro

"Popcorn workers' lung" is an obstructive pulmonary disease produced by inhalation of volatile artificial butter flavorings. In rats, inhalation of diacetyl, a major component of butter flavoring, and inhalation of a diacetyl substitute, 2,3-pentanedione, produce similar damage to airway epithelium. The effects of diacetyl and 2,3-pentanedione and mixtures of diacetyl, acetic acid, and acetoin, all components of butter flavoring, on pulmonary function and airway reactivity to methacholine (MCh) were investigated. Lung resistance (RL) and dynamic compliance (Cdyn) were negligibly changed 18 h after a 6-h inhalation exposure to diacetyl or 2,3-pentanedione (100-360 ppm). Reactivity to MCh was not markedly changed after diacetyl, but was modestly decreased after 2,3-pentanedione inhalation. Inhaled diacetyl exerted essentially no effect on reactivity to mucosally applied MCh, but 2,3-pentanedione (320 and 360 ppm) increased reactivity to MCh in the isolated, perfused trachea preparation (IPT). In IPT, diacetyl and 2,3-pentanedione (≥3 mM) applied to the serosal and mucosal surfaces of intact and epithelium-denuded tracheas initiated transient contractions followed by relaxations. Inhaled acetoin (150 ppm) exerted no effect on pulmonary function and airway reactivity in vivo; acetic acid (27 ppm) produced hyperreactivity to MCh; and exposure to diacetyl + acetoin + acetic acid (250 + 150 + 27 ppm) led to a diacetyl-like reduction in reactivity. Data suggest that the effects of 2,3-pentanedione on airway reactivity are greater than those of diacetyl, and that flavorings are airway smooth muscle relaxants and constrictors, thus indicating a complex mechanism.