DNA and inflammatory mediators in bronchoalveolar lavage fluid from children with acute inhalational injuries

Vesicular and extravesicular protein analyses from the airspaces of ozone-exposed mice revealed signatures associated with mucoinflammatory lung disease

Lung epithelial lining fluid (ELF) harbors a variety of proteins that influence homeostatic and stress responses in the airspaces. Exosomes, nano-sized extracellular vesicles, contain many proteins that vary in abundance and composition based on the prevailing conditions. Ozone causes inflammatory responses in the airspaces of experimental animals and humans. However, the exosomal protein signatures contained within the ELF from ozone-exposed lung airspaces remain poorly characterized. To explore this, we hypothesized that ozone triggers the release of exosome-bound inflammatory proteins from various cells that reflect mucoobstructive lung disease. Accordingly, we repetitively exposed adult male and female C57BL/6 mice to HEPA-filtered air (air) or 0.8 ppm ozone (4 h per day) for 14 days (five consecutive days of exposure, 2 days of rest, five consecutive days of exposure, 2 days of rest, four consecutive days of exposure). Exosome-bound proteomic signatures, as well as the levels of soluble inflammatory mediators in the bronchoalveolar lavage fluid (BALF), were determined 12-16 h after the last exposure. Principal component analyses of the exosome-bound proteome revealed a clear distinction between air-exposed and ozone-exposed mice, as well as between ozone-exposed males and ozone-exposed females. In addition to 575 proteins that were enriched in both sexes upon ozone exposure, 243 and 326 proteins were enriched uniquely in ozone-exposed males and females, respectively. Ingenuity pathway analyses on enriched proteins between ozone- and air-exposed mice revealed enrichment of pro-inflammatory pathways. More specifically, macrophage activation-related proteins were enriched in exosomes from ozone-exposed mice. Cytokine analyses on the BALF revealed elevated levels of G-CSF, KC, IP-10, IL-6, and IL-5 in ozone-exposed mice. Finally, the histopathological assessment revealed significantly enhanced intracellular localization of mucoinflammatory proteins including MUC5B and FIZZ1 in ozone-exposed mice in a cell-specific manner indicating the cellular sources of the proteins that are ferried in the exosomes upon ozone-induced lung injury. Collectively, this study identified exosomal, secretory, and cell-specific proteins and biological pathways following repetitive exposure of mice to ozone.

Postnatal Ozone Exposure Disrupts Alveolar Development, Exaggerates Mucoinflammatory Responses, and Suppresses Bacterial Clearance in Developing Scnn1b-Tg+ Mice Lungs

Increased levels of ambient ozone, one of the six criteria air pollutants, result in respiratory tract injury and worsening of ongoing lung diseases. However, the effect of ozone exposure on the respiratory tract undergoing active lung development and simultaneously experiencing mucoinflammatory lung diseases, such as cystic fibrosis, remains unclear. To address these questions, we exposed Scnn1b transgenic (Scnn1b-Tg⁺) mice, a mouse model of cystic fibrosis-like lung disease, and littermate wild-type (WT) mice to ozone from postnatal days (PND) 3-20 and examined the lung phenotypes at PND21. As compared with filtered air (FA)-exposed WT mice, the ozone-exposed WT mice exhibited marked alveolar space enlargement, in addition to significant eosinophilic infiltration, type 2 inflammation, and mucous cell metaplasia. Ozone-exposed Scnn1b-Tg⁺ mice also exhibited significantly increased alveolar space enlargement, which was also accompanied by exaggerated granulocytic infiltration, type 2 inflammation, and a greater degree of mucus obstruction. The alveolar space enlargement in ozone-exposed WT, FA-exposed Scnn1b-Tg⁺, and ozone-exposed Scnn1b-Tg⁺ mice was accompanied by elevated levels of MMP12 protein in macrophages and Mmp12 mRNA in the lung homogenates. Finally, although bacterial burden was largely resolved by PND21 in FA-exposed Scnn1b-Tg⁺ mice, ozone-exposed Scnn1b-Tg⁺ mice exhibited compromised bacterial clearance, which was also associated with increased levels of IL-10, an immunosuppressive cytokine, and marked mucus obstruction. Taken together, our data show that ozone exposure results in alveolar space remodeling during active phases of lung development and markedly exaggerates the mucoinflammatory outcomes of pediatric-onset lung disease, including bacterial infections, granulocytic inflammation, mucus obstruction, and alveolar space enlargement.

Inhalation Injury: Unmet Clinical Needs and Future Research

Pulmonary and systemic insults from inhalation injury can complicate the care of burn patients and contribute to significant morbidity and mortality. However, recent progress in diagnosis and treatment of inhalation injury has not kept pace with the care of cutaneous thermal injury. There are many challenges unique to inhalation injury that have slowed advancement, including deficiencies in our understanding of its pathophysiology, the relative difficulty and subjectivity of bronchoscopic diagnosis, the lack of diagnostic biomarkers, the necessarily urgent manner in which decisions are made about intubation, and the lack of universal recommendations for the application of mucolytics, anticoagulants, bronchodilators, modified ventilator strategies, and other measures. This review represents a summary of critical shortcomings in our understanding and management of inhalation injury identified by the American Burn Association's working group on Cutaneous Thermal Injury and Inhalation Injury in 2018. It addresses our current understanding of the diagnosis, pathophysiology, and treatment of inhalation injury and highlights topics in need of additional research, including 1) airway repair mechanisms; 2) the airway microbiome in health and after injury; and 3) candidate biomarkers of inhalation injury.

Inhalation Injury: State of the Science 2016

This article summarizes research conducted over the last decade in the field of inhalation injury in thermally injured patients. This includes brief summaries of the findings of the 2006 State of the Science meeting with regard to inhalation injury, and of the subsequent 2007 Inhalation Injury Consensus Conference. The reviewed studies are categorized in to five general areas: diagnosis and grading; mechanical ventilation; systemic and inhalation therapy; mechanistic alterations; and outcomes.

Need for Mechanical Ventilation in Pediatric Scald Burns: Why it Happens and Why it Matters

Scald burns are the most common thermal injury among children. A small subset of pediatric scald burns are complicated by the need for mechanical ventilation (MV). Studies suggest that 4 to 5% of pediatric scald burns will require MV, and these patients tend to be younger with larger burns. Identifying why pediatric patients with scald burns require MV has remained unclear, and few studies have sought to elucidate possible mechanisms. After institutional review board approval, a retrospective review of all pediatric patients with scald burns admitted to the Burn Center between 2010 and 2013 was conducted. Variables collected included age, sex, weight, height, race, ethnicity, socioeconomic status or type of insurance, hospital length of stay, burn size and location, Department of Child and Family Services (DCFS) involvement, time to intubation from admission, reason for intubation, need for MV, duration of MV, need for operative intervention, 24-hour and 48-hour total fluid intake and urine output, glucose levels, infectious complications, comorbidities, and mortality. Patients who required MV were then compared with those who did not require MV to identify statistically significant differences between groups. The MV patients (n = 6) and nonventilated patients (n = 339) did not show significant differences in regards to gender, body mass index, ethnicity, and type of insurance; however, MV patients were younger and had larger burns. The mean age of MV patients was 8.2 + 5.0 months compared with 40.7 + 45.2 months for non-MV (P = .002). The mean percentage of TBSA burn in MV patients was 17.3 + 9.0% compared with 4.5 + 3.9% for non-MV (P < .001). Burn location was significant, and 66.6% of MV patients had burns on the face or neck compared with 23.6% of non-MV (P = .015). MV patients were more likely to have been victims of child abuse, as DCFS was involved in 67% of MV patients vs. 28% of non-MV patients (P = .036). Fifty percent of patients requiring MV had either a preceding upper respiratory infection, diagnosis of asthma, or congenital defects, compared with 6% of non-MV patients (P = .004). MV patients received more fluids for 48 hours compared with non-MV patients (2275.7 vs. 1332.3 ml, P = .013) and had a higher 48-hour urine output (2.34 vs. 1.34 ml/kg/hr, P = .013). Pediatric scald burns that require MV have an increased mortality risk and length of stay. MV patients were younger with larger burns. They received more fluids than non-MV patients, and child abuse, asthma, and stress hyperglycemia within the first 72 hours of injury were common among MV patients. Importantly, burn size and previous history of asthma were found to be independent predictors of the need for MV.

Risk factors for the development of heterotopic ossification in seriously burned adults: A National Institute on Disability, Independent Living and Rehabilitation Research burn model system database analysis

BACKGROUND

Heterotopic ossification (HO) is a debilitating complication of burn injury; however, incidence and risk factors are poorly understood. In this study, we use a multicenter database of adults with burn injuries to identify and analyze clinical factors that predict HO formation.

METHODS

Data from six high-volume burn centers, in the Burn Injury Model System Database, were analyzed. Univariate logistic regression models were used for model selection. Cluster-adjusted multivariate logistic regression was then used to evaluate the relationship between clinical and demographic data and the development of HO.

RESULTS

Of 2,979 patients in the database with information on HO that addressed risk factors for development of HO, 98 (3.5%) developed HO. Of these 98 patients, 97 had arm burns, and 96 had arm grafts. When controlling for age and sex in a multivariate model, patients with greater than 30% total body surface area burn had 11.5 times higher odds of developing HO (p < 0.001), and those with arm burns that required skin grafting had 96.4 times higher odds of developing HO (p = 0.04). For each additional time a patient went to the operating room, odds of HO increased by 30% (odds ratio, 1.32; p < 0.001), and each additional ventilator day increased odds by 3.5% (odds ratio, 1.035; p < 0.001). Joint contracture, inhalation injury, and bone exposure did not significantly increase odds of HO.

CONCLUSION

Risk factors for HO development include greater than 30% total body surface area burn, arm burns, arm grafts, ventilator days, and number of trips to the operating room. Future studies can use these results to identify highest-risk patients to guide deployment of prophylactic and experimental treatments.

LEVEL OF EVIDENCE

Prognostic study, level III.

A Multidisciplinary Children's Airway Center: Impact on the Care of Patients With Tracheostomy

BACKGROUND

Children with complex airway problems see multiple specialists. To improve outcomes and coordinate care, we developed a multidisciplinary Children's Airway Center. For children with tracheostomies, aspects of care targeted for improvement included optimizing initial hospital discharge, promoting effective communication between providers and caregivers, and avoiding tracheostomy complications.

METHODS

The population includes children up to 21 years old with tracheostomies. The airway center team includes providers from pediatric pulmonology, pediatric otolaryngology/head and neck surgery, and pediatric gastroenterology. Improvement initiatives included enhanced educational strategies, weekly care conferences, institutional consensus guidelines and care plans, personalized clinic schedules, and standardized intervals between airway examinations. A patient database allowed for tracking outcomes over time.

RESULTS

We initially identified 173 airway center patients including 123 with tracheostomies. The median number of new patients evaluated by the center team each year was 172. Median hospitalization after tracheostomy decreased from 37 days to 26 days for new tracheostomy patients <1 year old discharged from the hospital. A median of 24 care plans was evaluated at weekly conferences. Consensus protocol adherence increased likelihood of successful decannulation from 68% to 86% of attempts. The median interval of 8 months between airway examinations aligned with published recommendations.

CONCLUSIONS

For children with tracheostomies, our Children's Airway Center met and sustained goals of optimizing hospitalization, promoting communication, and avoiding tracheostomy complications by initiating targeted improvements in a multidisciplinary team setting. A multidisciplinary approach to management of these patients can yield measurable improvements in important outcomes.

CFTR-regulated MAPK/NF-κB signaling in pulmonary inflammation in thermal inhalation injury

The mechanism underlying pulmonary inflammation in thermal inhalation injury remains elusive. Cystic fibrosis, also hallmarked with pulmonary inflammation, is caused by mutations in CFTR, the expression of which is temperature-sensitive. We investigated whether CFTR is involved in heat-induced pulmonary inflammation. We applied heat-treatment in 16HBE14o- cells with CFTR knockdown or overexpression and heat-inhalation in rats in vivo. Heat-treatment caused significant reduction in CFTR and, reciprocally, increase in COX-2 at early stages both in vitro and in vivo. Activation of ERK/JNK, NF-κB and COX-2/PGE2 were detected in heat-treated cells, which were mimicked by knockdown, and reversed by overexpression of CFTR or VX-809, a reported CFTR mutation corrector. JNK/ERK inhibition reversed heat-/CFTR-knockdown-induced NF-κB activation, whereas NF-κB inhibitor showed no effect on JNK/ERK. IL-8 was augmented by heat-treatment or CFTR-knockdown, which was abolished by inhibition of NF-κB, JNK/ERK or COX-2. Moreover, in vitro or in vivo treatment with curcumin, a natural phenolic compound, significantly enhanced CFTR expression and reversed the heat-induced increases in COX-2/PGE2/IL-8, neutrophil infiltration and tissue damage in the airway. These results have revealed a CFTR-regulated MAPK/NF-κB pathway leading to COX-2/PGE2/IL-8 activation in thermal inhalation injury, and demonstrated therapeutic potential of curcumin for alleviating heat-induced pulmonary inflammation.

Pathophysiology and biomarkers of acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is defined as an acute-onset, progressive, hypoxic condition with radiographic bilateral lung infiltration, which develops after several diseases or injuries, and is not derived from hydrostatic pulmonary edema. One specific pathological finding of ARDS is diffuse alveolar damage. In 2012, in an effort to increase diagnostic specificity, a revised definition of ARDS was published in JAMA. However, no new parameters or biomarkers were adopted by the revised definition. Discriminating between ARDS and other similar diseases is critically important; however, only a few biomarkers are currently available for diagnostic purposes. Furthermore, predicting the severity, response to therapy, or outcome of the illness is also important for developing treatment strategies for each patient. However, the PaO₂/FIO₂ ratio is currently the sole clinical parameter used for this purpose. In parallel with progress in understanding the pathophysiology of ARDS, various humoral factors induced by inflammation and molecules derived from activated cells or injured tissues have been shown as potential biomarkers that may be applied in clinical practice. In this review, the current understanding of the basic pathophysiology of ARDS and associated candidate biomarkers will be discussed.

Curbing inflammation in burn patients

Patients who suffer from severe burns develop metabolic imbalances and systemic inflammatory response syndrome (SIRS) which can result in multiple organ failure and death. Research aimed at reducing the inflammatory process has yielded new insight into burn injury therapies. In this review, we discuss strategies used to curb inflammation in burn injuries and note that further studies with high quality evidence are necessary.