Issues determining direct airways hyperresponsiveness in mice

Cullin5 drives experimental asthma exacerbations by modulating alveolar macrophage antiviral immunity

Asthma exacerbations caused by respiratory viral infections are a serious global health problem. Impaired antiviral immunity is thought to contribute to the pathogenesis, but the underlying mechanisms remain understudied. Here using mouse models we find that Cullin5 (CUL5), a key component of Cullin-RING E3 ubiquitin ligase 5, is upregulated and associated with increased neutrophil count and influenza-induced exacerbations of house dust mite-induced asthma. By contrast, CUL5 deficiency mitigates neutrophilic lung inflammation and asthma exacerbations by augmenting IFN-β production. Mechanistically, following thymic stromal lymphopoietin stimulation, CUL5 interacts with O-GlcNAc transferase (OGT) and induces Lys48-linked polyubiquitination of OGT, blocking the effect of OGT on mitochondrial antiviral-signaling protein O-GlcNAcylation and RIG-I signaling activation. Our results thus suggest that, in mouse models, pre-existing allergic injury induces CUL5 expression, impairing antiviral immunity and promoting neutrophilic inflammation for asthma exacerbations. Targeting of the CUL5/IFN-β signaling axis may thereby serve as a possible therapy for treating asthma exacerbations.

Ziziphus mauritiana Lam attenuates inflammation via downregulating NFκB pathway in LPS-stimulated RAW 264.7 macrophages & OVA-induced airway inflammation in mice models

ETHNOPHARMACOLOGICAL RELEVANCE

Ziziphus mauritiana Lam leaves were utilized in treating asthma, diabetes, inflammation, and hepatic diseases in Indian traditional medicine. The leaves were used as an edible vegetables in rural parts of India.

AIM OF THE STUDY

The aim is to prove the anti-inflammatory activity of Ziziphus mauritiana Lam leaves against LPS-stimulated RAW 264.7 macrophages and OVA-induced airway inflammation in mice through its attenuation mechanism in the NFκB signalling pathway.

MATERIALS AND METHODS

Terpenoids present in MEZ were quantified using U(H)PLC analysis. MEZ at 50 and 100 μg/mL were tested against LPS stimulated RAW 264.7 macrophages. The concentration of NO, ROS, and cytokines was quantified from the cell culture supernatants. OVA-induced asthma in mice was adopted for screening airway inflammation. MEZ at 250 and 500 mg/kg was tested for airway hyperresponsiveness, leukocyte counting, pro-inflammatory cytokines (IL-4, IL-5, IL-13 and TNF-α), lung histopathology, and various inflammatory gene expressions in lungs for NFκB signalling pathway in asthma.

RESULTS

Terpenoids like betulin, betulinic acid, oleanolic acid, and ursolic acid were quantified from U(H)PLC analysis. MEZ at higher doses reduced the NO, ROS, and pro-inflammatory cytokines in LPS stimulated RAW 264.7 macrophages. MEZ at 500 mg/kg significantly reduced AHR and also decreased total and differential leukocytes. MEZ also reduced the expressions of ICAM, VCAM, and Muc5C genes. Histopathological analysis revealed MEZ significantly reduced the leukocyte infiltration and mucus hypersecretion in the lungs. MEZ suppressed lung inflammation by inhibition of p65 mediated IκB-α translocation in the NFκB signalling pathway.

CONCLUSION

From these findings, MEZ significantly reduced airway inflammation by inhibiting NFκB mediated inflammatory pathway. Hence, this study proved that Ziziphus mauritiana Lam has anti-asthmatic potential in Indian traditional medicine.

Oscillometry of the respiratory system: a translational opportunity not to be missed

Airway oscillometry has become the de facto standard for quality assessment of lung physiology in laboratory animals and has demonstrated its usefulness in understanding diseases of small airways. Nowadays, it is seeing extensive use in daily clinical practice and research; however, a question that remains unanswered is how well physiological findings in animals and humans correlate? Methodological and device differences are obvious between animal and human studies. However, all devices deliver an oscillated airflow test signal and output respiratory impedance. In addition, despite analysis differences, there are ways to interpret animal and human oscillometry data to allow suitable comparisons. The potential with oscillometry is its ability to reveal universal features of the respiratory system across species, making translational extrapolation likely to be predictive. This means that oscillometry can thus help determine if an animal model displays the same physiological characteristics as the human disease. Perhaps more importantly, it can also be useful to determine whether an intervention is effective as well as to understand if it affects the desired region of the respiratory system, e.g., the periphery of the lung. Finally, findings in humans can also inform preclinical scientists and give indications as to what type of physiological changes should be observed in animal models to make them relevant as models of human disease. The present article will attempt to demonstrate the potential of oscillometry in respiratory research, an area where the development of novel therapies is plagued with a failure rate higher than in other disease areas.

Comparing lung oscillometry with a novel, portable flow interrupter device to measure lung mechanics

In the community setting, assessing spirometry in school-aged children is often limited by the unavailability of respirology technicians at the point-of-care. We developed a new technique called the Rapid Expiratory Occlusion Method (REOM) that measures respiratory resistance during normal breathing, without specialized training. The aim was to examine the concordance between respiratory resistance measured with the REOM and respiratory resistance measured by oscillometry on the tremoflo. Children aged 6-17 yr, with or without asthma, received respiratory resistance testing on the tremoflo, then on the REOM. Three to five replicates with a coefficient of variation ≤15% were obtained on each instrument; the primary outcome was the concordance between the average respiratory resistance on the REOM and that measured at 5 Hz (R₅) on the tremoflo. Thirty-two children (11 girls; 21 boys) were enrolled with a mean age of 11.2 (range 6-17) yr; after excluding two children not meeting reproducibility criteria, 9 healthy controls, 15 controlled asthmatics, and 6 poorly controlled asthmatics were included. Resistance measured on the REOM showed a strong correlation with R₅ measured on the tremoflo (P < 0.0001) with no significant differences on the Bland-Altman analyses. Children and their parents found the REOM easy to use and would consider for home use if recommended by their doctor. With the high concordance between resistance values measured on the REOM and that on the tremoflo combined with perceived ease of use, the REOM appears as a promising means for measuring lung function, thus supporting further testing of other psychometric properties.NEW & NOTEWORTHY We have developed a novel version of the interrupter technique to measure respiratory resistance. The Rapid Expiratory Occlusion Method (REOM) is a small handheld device that measures respiratory resistance and demonstrates excellent correlation with airway oscillometry. With its ease of use, REOM may be promising for use in community practice, patient's homes, and, if paired with a telemedicine application, could enable the healthcare provider to monitor patients in their homes.

Mechanical consequences of allergic induced remodeling on mice airway resistance and compressibility

The effect of remodeling on airway function is uncertain. It may affect airway compressibility during forced expirations differently than airflow resistance, providing a tool for its assessment. The aim of the current study was to compare the effects of acute and chronic antigen challenge on methacholine-induced bronchoconstriction assessed from resistance and maximal tidal expiratory flow. Balb/C mice were sensitized with ovalbumin (OVA) and challenged either daily for three days with intra-nasal OVA or daily for 5 days and three times a week for 5 subsequent weeks. Acute and chronic allergen challenge induced airway hyperresponsiveness (AHR) to methacholine. However the relationship between maximal tidal expiratory flow and resistance during methacholine challenge was different between the two conditions, suggesting that the determinants of AHR are not identical following acute and chronic allergen exposure. We conclude that the contrast of changes in maximal tidal expiratory flow and respiratory resistance during methacholine-induced bronchoconstriction may allow the detection of the mechanical consequences of airway remodeling.

Prenatal acetaminophen induces liver toxicity in dams, reduces fetal liver stem cells, and increases airway inflammation in adult offspring

BACKGROUND & AIMS

During pregnancy, acetaminophen is one of the very few medications recommended by physicians to treat fever or pain. Recent insights from epidemiological studies suggest an association between prenatal acetaminophen medication and an increased risk for development of asthma in children later in life. The underlying pathogenesis of such association is still unknown.

METHODS

We aimed to develop a mouse model to provide insights into the effect of prenatal acetaminophen on maternal, fetal and adult offspring's health. The toxic effect of acetaminophen was studied in mice on 1) maternal liver; mirrored by biomarkers of liver injury, centrilobular necrosis, and infiltration of granulocytes; 2) fetal liver; reflected by the frequency of hematopoietic stem cells, and 3) postnatal health; evaluated by the severity of allergic airway inflammation among offspring.

RESULTS

We observed an increased susceptibility towards acetaminophen-induced liver damage in pregnant mice compared to virgins. Moreover, hematopoietic stem cell frequency in fetal liver declined in response to acetaminophen. Furthermore, a greater severity of airway inflammation was observed in offspring of dams upon prenatal acetaminophen treatment, identified lung infiltration by leukocytes and eosinophil infiltration into the airways.

CONCLUSION

Our newly developed mouse model on prenatal use of acetaminophen reflects findings from epidemiological studies in humans. The availability of this model will allow improvement in our understanding of how acetaminophen-related hepatotoxicity is operational in pregnant individuals and how an increased risk for allergic diseases in response to prenatal acetaminophen is mediated. Such insights, once available, may change the recommendations for prenatal acetaminophen use.

Delivered dose estimate to standardize airway hyperresponsiveness assessment in mice

Airway hyperresponsiveness often constitutes a primary outcome in respiratory studies in mice. The procedure commonly employs aerosolized challenges, and results are typically reported in terms of bronchoconstrictor concentrations loaded into the nebulizer. Yet, because protocols frequently differ across studies, especially in terms of aerosol generation and delivery, direct study comparisons are difficult. We hypothesized that protocol variations could lead to differences in aerosol delivery efficiency and, consequently, in the dose delivered to the subject, as well as in the response. Thirteen nebulization patterns containing common protocol variations (nebulization time, duty cycle, particle size spectrum, air humidity, and/or ventilation profile) and using increasing concentrations of methacholine and broadband forced oscillations (flexiVent, SCIREQ, Montreal, Qc, Canada) were created, characterized, and studied in anesthetized naïve A/J mice. A delivered dose estimate calculated from nebulizer-, ventilator-, and subject-specific characteristics was introduced and used to account for protocol variations. Results showed that nebulization protocol variations significantly affected the fraction of aerosol reaching the subject site and the delivered dose, as well as methacholine reactivity and sensitivity in mice. From the protocol variants studied, addition of a slow deep ventilation profile during nebulization was identified as a key factor for optimization of the technique. The study also highlighted sensitivity differences within the lung, as well as the possibility that airway responses could be selectively enhanced by adequate control of nebulizer and ventilator settings. Reporting results in terms of delivered doses represents an important standardizing element for assessment of airway hyperresponsiveness in mice.

Ozone-induced injury and oxidative stress in bronchiolar epithelium are associated with altered pulmonary mechanics

In these studies, we analyzed the effects of ozone on bronchiolar epithelium. Exposure of rats to ozone (2 ppm, 3 h) resulted in rapid (within 3 h) and persistent (up to 72 h) histological changes in the bronchiolar epithelium, including hypercellularity, loss of cilia, and necrotizing bronchiolitis. Perivascular edema and vascular congestion were also evident, along with a decrease in Clara cell secretory protein in bronchoalveolar lavage, which was maximal 24 h post-exposure. Ozone also induced the appearance of 8-hydroxy-2'-deoxyguanosine, Ym1, and heme oxygenase-1 in the bronchiolar epithelium. This was associated with increased expression of cleaved caspase-9 and beclin-1, indicating initiation of apoptosis and autophagy. A rapid and persistent increase in galectin-3, a regulator of epithelial cell apoptosis, was also observed. Following ozone exposure (3-24 h), increased expression of cyclooxygenase-2, inducible nitric oxide synthase, and arginase-1 was noted in bronchiolar epithelium. Ozone-induced injury and oxidative stress in bronchiolar epithelium were linked to methacholine-induced alterations in pulmonary mechanics. Thus, significant increases in lung resistance and elastance, along with decreases in lung compliance and end tidal volume, were observed at higher doses of methacholine. This indicates that ozone causes an increase in effective stiffness of the lung as a consequence of changes in the conducting airways. Collectively, these studies demonstrate that bronchiolar epithelium is highly susceptible to injury and oxidative stress induced by acute exposure to ozone; moreover, this is accompanied by altered lung functioning.

Assessment of murine lung mechanics outcome measures: alignment with those made in asthmatics

Although asthma is characterized as an inflammatory disease, recent reports highlight the importance of pulmonary physiology outcome measures to the clinical assessment of asthma control and risk of asthma exacerbation. Murine models of allergic inflammatory airway disease have been widely used to gain mechanistic insight into the pathogenesis of asthma; however, several aspects of murine models could benefit from improvement. This review focuses on aligning lung mechanics measures made in mice with those made in humans, with an eye toward improving the translational utility of these measures. A brief description of techniques available to measure murine lung mechanics is provided along with a methodological consideration of their utilization. How murine lung mechanics outcome measures relate to pulmonary physiology measures conducted in humans is discussed and we recommend that, like human studies, outcome measures be standardized for murine models of asthma.