A murine model of elastase- and cigarette smoke-induced emphysema

Alpha-7 Nicotinic Receptor Agonist Protects Mice Against Pulmonary Emphysema Induced by Elastase

Pulmonary emphysema is a primary component of chronic obstructive pulmonary disease (COPD), a life-threatening disorder characterized by lung inflammation and restricted airflow, primarily resulting from the destruction of small airways and alveolar walls. Cumulative evidence suggests that nicotinic receptors, especially the α7 subtype (α7nAChR), is required for anti-inflammatory cholinergic responses. We postulated that the stimulation of α7nAChR could offer therapeutic benefits in the context of pulmonary emphysema. To investigate this, we assessed the potential protective effects of PNU-282987, a selective α7nAChR agonist, using an experimental emphysema model. Male mice (C57BL/6) were submitted to a nasal instillation of porcine pancreatic elastase (PPE) (50 µl, 0.667 IU) to induce emphysema. Treatment with PNU-282987 (2.0 mg/kg, ip) was performed pre and post-emphysema induction by measuring anti-inflammatory effects (inflammatory cells, cytokines) as well as anti-remodeling and anti-oxidant effects. Elastase-induced emphysema led to an increase in the number of α7nAChR-positive cells in the lungs. Notably, both groups treated with PNU-282987 (prior to and following emphysema induction) exhibited a significant decrease in the number of α7nAChR-positive cells. Furthermore, both groups treated with PNU-282987 demonstrated decreased levels of macrophages, IL-6, IL-1β, collagen, and elastic fiber deposition. Additionally, both groups exhibited reduced STAT3 phosphorylation and lower levels of SOCS3. Of particular note, in the post-treated group, PNU-282987 successfully attenuated alveolar enlargement, decreased IL-17 and TNF-α levels, and reduced the recruitment of polymorphonuclear cells to the lung parenchyma. Significantly, it is worth noting that MLA, an antagonist of α7nAChR, counteracted the protective effects of PNU-282987 in relation to certain crucial inflammatory parameters. In summary, these findings unequivocally demonstrate the protective abilities of α7nAChR against elastase-induced emphysema, strongly supporting α7nAChR as a pivotal therapeutic target for ameliorating pulmonary emphysema.

An innate contribution of human nicotinic receptor polymorphisms to COPD-like lesions

Chronic Obstructive Pulmonary Disease is a generally smoking-linked major cause of morbidity and mortality. Genome-wide Association Studies identified a locus including a non-synonymous single nucleotide polymorphism in CHRNA5, rs16969968, encoding the nicotinic acetylcholine receptor α5 subunit, predisposing to both smoking and Chronic Obstructive Pulmonary Disease. Here we report that nasal polyps from rs16969968 non-smoking carriers exhibit airway epithelium remodeling and inflammation. These hallmarks of Chronic Obstructive Pulmonary Disease occur spontaneously in mice expressing human rs16969968. They are significantly amplified after exposure to porcine pancreatic elastase, an emphysema model, and to oxidative stress with a polymorphism-dependent alteration of lung function. Targeted rs16969968 expression in epithelial cells leads to airway remodeling in vivo, increased proliferation and production of pro-inflammatory cytokines through decreased calcium entry and increased adenylyl-cyclase activity. We show that rs16969968 directly contributes to Chronic Obstructive Pulmonary Disease-like lesions, sensitizing the lung to the action of oxidative stress and injury, and represents a therapeutic target.

Human polymorphisms in nicotinic acetylcholine receptor genes have been linked to both smoking and lung diseases like Chronic Obstructive Pulmonary Disease (COPD) or lung cancer. Here the authors identify a direct role for a human coding polymorphism in COPD-like lesions independent of smoke or nicotine exposure.

Radiofrequency therapy improves exercise capacity of mice with emphysema

Emphysema is a common phenotype of chronic obstructive pulmonary disease (COPD). Although resection of emphysematous tissue can improve lung mechanics, it is invasive and fraught with adverse effects. Meanwhile, radiofrequency (RF) treatment is an extracorporeal method that leads to tissue destruction and remodeling, resulting in “volume reduction” and overall improvement in lung compliance of emphysematous lungs. Whether these changes lead to improved exercise tolerance is unknown. Here, we investigated the effectiveness of RF treatment to improve the exercise capacity of mice with emphysema. Fifty-two mice (7 weeks of age) were used in this experiment. A bilateral emphysema model was created by intratracheally instilling porcine pancreatic elastase (PPE) (1.5U/100 g body weight). RF treatment (0.5 W/ g body weight) was administered extracorporeally 14 days later and mice were sacrificed after another 21 days. The exercise capacity of mice was measured using a treadmill. Treadmill runs were performed just before PPE instillation (baseline), before RF treatment and before sacrifice. Following sacrifice, lung compliance and mean linear intercept (Lm) were measured and fibrosis was assessed using a modified Ashcroft score. There were 3 experimental groups: controls (instilled with saline, n = 12), emphysema (instilled with porcine pancreatic elastase, PPE, n = 11) and emphysema + treatment (instilled with PPE and given RF, n = 9). At endpoint, the maximum velocity of the emphysema + treatment group was significantly higher than that of the emphysema group, indicating improved exercise tolerance (86.29% of baseline vs 61.69% of baseline, p = 0.01). Histological analysis revealed a significant reduction in emphysema as denoted by Lm between the two groups (median 29.60 µm vs 35.68 µm, p = 0.03). The emphysema + treatment group also demonstrated a higher prevalence of lung fibrosis (≧Grade 3) compared with the emphysema group (11.7% vs 5.4%, p < 0.01). No severe adverse events from RF were observed. RF treatment improved the exercise capacity of mice with emphysema. These data highlight the therapeutic potential of RF treatment in improving the functional status of patients with COPD.

Mesenchymal stromal cells-based therapy in a murine model of elastase-induced emphysema: Simvastatin as a potential adjuvant in cellular homing

Chronic Obstructive Pulmonary Disease - COPD is characterized by the destruction of alveolar walls associated to a chronic inflammatory response of the airways. There is no clinical therapy for COPD. In this context, cell-based therapies represent a promising therapeutic approach for chronic lung disease. The goal of this work was to evaluate the effect of simvastatin on cell-based therapy in a mice emphysema model. Female FVB mice received intranasal instillation of elastase (three consecutive doses of 50 μL) in order to promote pulmonary emphysema. After 21 days of the first instillation, the animals were treated with Adipose-Derived Mesenchymal Stromal Cells (AD-MSC, 2.6 × 10⁶) via retro-orbital infusion associated or not with simvastatin administrated daily via oral gavage (15 mg/kg/15d). Before and after these treatments, the histological and morphometrical analyses of the lung tissue, as so as lung function (whole body plethysmography) were evaluated. PAI-1 gene expression, an upregulated factor by ischemia that indicate a low survival of transplanted MSC, was also evaluated. The result regarding morphological and functional aspects of both lungs, presented no significant difference among the groups (AD-MSC or AD-MSC + Simvastatin). However, significant anatomical difference was observed in the right lung of the both groups of mice. The results shown a higher deposition of cells in the right lung, with might to be explained by anatomical differences (slightly higher right bronchi). Decreased levels of PAI-1 were observed in the simvastatin treated groups. The pulmonary ventilation was similar between the groups with only a tendency to a lower in the elastase treated animals due to a low respiratory frequency. In conclusion, the results suggest that both AD-MSC and simvastatin treatments could promote an improvement of morphological recovery of pulmonary emphysema, that it was more pronounced in the right lung.

Pulmonary transplantation of alpha-1 antitrypsin (AAT)-transgenic macrophages provides a source of functional human AAT in vivo

Inherited deficiency of the antiprotease alpha-1 antitrypsin (AAT) is associated with liver failure and early-onset emphysema. In mice, in vivo lentiviral transduction of alveolar macrophages (AMs) has been described to yield protective pulmonary AAT levels and ameliorate emphysema development. We here investigated the pulmonary transplantation of macrophages (PMT) transgenic for AAT as a potential therapy for AAT deficiency-associated lung pathology. Employing third-generation SIN-lentiviral vectors expressing the human AAT cDNA from the CAG or Cbx-EF1α promoter, we obtained high-level AAT secretion in a murine AM cell line as well as murine bone marrow-derived macrophages differentiated in vitro (AAT MΦ). Secreted AAT demonstrated a physiologic glycosylation pattern as well as elastase-inhibitory and anti-apoptotic properties. AAT MΦ preserved normal morphology, surface phenotype, and functionality. Furthermore, in vitro generated murine AAT MΦ successfully engrafted in AM-deficient Csf2rb^-/- mice and converted into a CD11c⁺/Siglec-F⁺ AM phenotype as detected in bronchoalveolar lavage fluid and homogenized lung tissue 2 months after PMT. Moreover, human AAT was detected in the lung epithelial lining fluid of transplanted animals. Efficient AAT expression and secretion were also demonstrated for human AAT MΦ, confirming the applicability of our vectors in human cells.

The Role of Macrophages in the Development of Acute and Chronic Inflammatory Lung Diseases

Macrophages play an important role in the innate and adaptive immune responses of organ systems, including the lungs, to particles and pathogens. Cumulative results show that macrophages contribute to the development and progression of acute or chronic inflammatory responses through the secretion of inflammatory cytokines/chemokines and the activation of transcription factors in the pathogenesis of inflammatory lung diseases, such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), ARDS related to COVID-19 (coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)), allergic asthma, chronic obstructive pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). This review summarizes the functions of macrophages and their associated underlying mechanisms in the development of ALI, ARDS, COVID-19-related ARDS, allergic asthma, COPD, and IPF and briefly introduces the acute and chronic experimental animal models. Thus, this review suggests an effective therapeutic approach that focuses on the regulation of macrophage function in the context of inflammatory lung diseases.

Alpha-1 antitrypsin deficiency and recombinant protein sources with focus on plant sources: Updates, challenges and perspectives

Alpha-1 antitrypsin deficiency (A1ATD) is an autosomal recessive disease characterized by low plasma levels of A1AT, a serine protease inhibitor representing the most abundant circulating antiprotease normally present at plasma levels of 1-2 g/L. The dominant clinical manifestations include predispositions to early onset emphysema due to protease/antiprotease imbalance in distal lung parenchyma and liver disease largely due to unsecreted polymerized accumulations of misfolded mutant A1AT within the endoplasmic reticulum of hepatocytes. Since 1987, the only FDA licensed specific therapy for the emphysema component has been infusions of A1AT purified from pooled human plasma at the 2020 cost of up to US $200,000/year with the risk of intermittent shortages. In the past three decades various, potentially less expensive, recombinant forms of human A1AT have reached early stages of development, one of which is just reaching the stage of human clinical trials. The focus of this review is to update strategies for the treatment of the pulmonary component of A1ATD with some focus on perspectives for therapeutic production and regulatory approval of a recombinant product from plants. We review other competitive technologies for treating the lung disease manifestations of A1ATD, highlight strategies for the generation of data potentially helpful for securing FDA Investigational New Drug (IND) approval and present challenges in the selection of clinical trial strategies required for FDA licensing of a New Drug Approval (NDA) for this disease.

Ma R, Fang Q. Rcn3 Suppression Was Responsible for Partial Relief of Emphysema as Shown by Specific Type II Alveolar Epithelial Cell Rcn3 CKO Mouse Model

BACKGROUND

Chronic obstructive pulmonary disease (COPD), characterized by irreversible airflow limitation, is a highly prevalent lung disease worldwide and imposes increasing disease burdens globally. Emphysema is one of the primary pathological features contributing to the irreversible decline of pulmonary function in COPD patients, but the pathogenetic mechanisms remain unclear. Reticulocalbin 3 (Rcn3) is an endoplasmic reticulum (ER) lumen protein localized in the secretory pathway of living cells. Rcn3 in type II alveolar epithelial cell (AECIIs) has been reported to play a critical role in regulating perinatal lung development and bleomycin-induced lung injury-repair processes. We hypothesized that Rcn3 deficiency is associated with the development of emphysema during COPD, which is associated with the dysfunction of injury-repair modulated by alveolar epithelial cells.

MATERIALS AND METHODS

We examined Rcn3 expression in lung specimens from COPD patients and non-COPD control patients undergoing lung lobectomy or pneumonectomy. Two mouse models of emphysema were established by cigarette smoke (CS) exposure and intratracheal instillation of porcine pancreatic elastase (PPE). Rcn3 expression was detected in the lung tissues from these mice. Furthermore, conditional knockout (CKO) mice with Rcn3 deletion specific to AECIIs were used to explore the role of Rcn3 in PPE-induced emphysema progression. Rcn3 protein expression in lung tissues was evaluated by Western blot and immunohistochemistry. Rcn3 mRNA expression in lung tissues was detected by qPCR.

RESULTS

Rcn3 expression was significantly increased in the lung specimens from COPD patients versus non-COPD patients and the level of Rcn3 increase was associated with the degree of emphysema. Rcn3 expression were also significantly up-regulated in both CS-induced and PPE-induced emphysematous mouse lungs. Moreover, the selective ablation of Rcn3 in AECIIs significantly alleviated severity of the mouse emphysema in response to intratracheal installation of PPE.

CONCLUSION

Our data, for the first time, indicated that suppression of Rcn3 expression in AECIIs has a beneficial effect on PPE-induced emphysema.

Extracellular matrix remodelling in COPD

The extracellular matrix (ECM) of the lung plays several important roles in lung function, as it offers a low resistant pathway that allows the exchange of gases, provides compressive strength and elasticity that supports the fragile alveolar-capillary intersection, controls the binding of cells with growth factors and cell surface receptors and acts as a buffer against retention of water.COPD is a chronic inflammatory respiratory condition, characterised by various conditions that result in progressive airflow limitation. At any stage in the course of the disease, acute exacerbations of COPD may occur and lead to accelerated deterioration of pulmonary function. A key factor of COPD is airway remodelling, which refers to the serious alterations of the ECM affecting airway wall thickness, resistance and elasticity. Various studies have shown that serum biomarkers of ECM turnover are significantly associated with disease severity in patients with COPD and may serve as potential targets to control airway inflammation and remodelling in COPD. Unravelling the complete molecular composition of the ECM in the diseased lungs will help to identify novel biomarkers for disease progression and therapy.

The impact of periodontitis in the course of chronic obstructive pulmonary disease: Pulmonary and systemic effects

AIMS

The aim of this study was to verify the impact of periodontitis in the course of chronic obstructive pulmonary disease (COPD) in C57Bl/6J mice.

MAIN METHODS

The animals were randomly divided into four groups (n = 8): Basal, Periodontitis (P), COPD and COPD+P. COPD was induced by orotracheal instillation of 30 μl of cigarette extract 3 times/week for 7 weeks. Periodontitis was induced by ligation technique for 22 days. Euthanasia was performed on 51st day. The analyzes were total/differential cells and cytokines recovered from bronchoalveolar lavage (BAL), total/differential blood cell count, platelets, total marrow cell count, airway collagen deposition, alveolar enlargement analyzed by mean linear intercept (Lm), mucus and bone crest reabsorption. One-way ANOVA followed by the Student-Newman-Keuls was used.

KEY FINDINGS

The association COPD+P decreased macrophages (p = 0,0351), TNF-α (p = 0,0071) and INF-γ (p = 0,0004) in BAL, when compared to the COPD group maintaining emphysema levels by alveolar enlargement (p < .05) reorganization of collagen fibers (p = .001) and also mean linear intercept (lm) (p = .001) and mucus (p = .0001). The periodontitis group caused TNF-α increase (p = 0, 0001) in BAL.

SIGNIFICANCE

Periodontitis, per se, does not alter any of the parameters analyzed, except for increased TNF-α in BAL. However, its association with COPD caused macrophages TNF-α and INF-γ alterations, when compared to the COPD group maintaining emphysema levels by alveolar enlargement and reorganization of collagen fibers. It seems that periodontitis is influencing the course of Th1 profile cell, and cytokines and pulmonary alterations. Further studies are needed to clarify the regulatory process underlying these two diseases.

Risk Assessment for Use of a Porcine Circovirus-Contaminated Reagent in a Barrier Maintained Rodent Colony

A proposal for the use of porcine pancreatic elastase (PPE) to develop a mouse model of pulmonary emphysema raised concerns about introducing contaminating porcine viruses into our barrier facility. Porcine Circovirus (PCV) is a known contaminant of vaccines and cell cultures that have been exposed to porcine-derived reagents. Endemic infection of PCV3 in laboratory mice has been reported, and some evidence supports natural PCV infection in wild mice. PPE samples from 2 different vendors tested positive for DNA from both PCV2 and 3. To allow model development with these reagents to proceed, we developed a protocol that would meet scientific objectives, minimize exposure of mice, and provide information on the potential for the virus to spread. Five d after BALB/c mice received intralaryngeal administration of PPE, lungs were harvested and analyzed for evidence of disease. Tissues from other major organs were submitted to test for disseminated PCV2 and 3 DNA. Similarly, tissues (including lungs) from direct contact nude sentinel mice were analyzed for the presence of the virus. To evaluate the possibility of endemic PCV2/3 infection, we also surveyed non-porcine reagent exposed mice on other studies. PCV2 and 3 was not detected in any of the tissues submitted. Although this study provided no evidence of infection and transmission of PCV2/3 from the contaminated PPE sample over the 5 d study, further work is needed to understand the risks and impact of introducing PCV contaminated cells or reagents into barrier maintained rodent colonies.

LJ-529, a partial peroxisome proliferator-activated receptor gamma (PPARγ) agonist and adenosine A3 receptor agonist, ameliorates elastase-induced pulmonary emphysema in mice

Chronic obstructive pulmonary disease (COPD) is the leading cause of human death worldwide. Currently available therapies for COPD mainly relieve symptoms and preserve lung function, suggesting the need to develop novel therapeutic or preventive regimens. Because chronic inflammation is a mechanism of emphysematous lesion formation and because adenosine A₃ receptor signaling and peroxisome proliferator-activated receptor gamma (PPARγ) regulate inflammation, we investigated the effect of LJ-529, a selective adenosine A₃ receptor agonist and partial PPARγ agonist, on inflammation in vitro and elastase-induced pulmonary emphysema in vivo. LJ-529 markedly ameliorated elastase-induced emphysematous lesion formation in the lungs in vivo, as indicated by the restoration of pulmonary function, suppression of airspace enlargement, and downregulation of elastase-induced matrix metalloproteinase activity and apoptotic cell death in the lungs. LJ-529 induced the expression of PPARγ target genes, the activity of PPARγ and several cytokines involved in inhibiting inflammation and inducing anti-inflammatory M2-like phenotypes. Moreover, LJ-529 did not exhibit significant cytotoxicity in normal cell lines derived from various organs in vitro and induced minimal changes in body weight in vivo, suggesting no overt toxicity of LJ-529 in vitro or in vivo. These results indicate the potential of LJ-529 as a novel therapeutic/preventive agent for emphysema with limited toxicity.

Chronic exposure to diesel particles worsened emphysema and increased M2-like phenotype macrophages in a PPE-induced model

Chronic exposure to ambient levels of air pollution induces respiratory illness exacerbation by increasing inflammatory responses and apoptotic cells in pulmonary tissues. The ineffective phagocytosis of these apoptotic cells (efferocytosis) by macrophages has been considered an important factor in these pathological mechanisms. Depending on microenvironmental stimuli, macrophages can assume different phenotypes with different functional actions. M1 macrophages are recognized by their proinflammatory activity, whereas M2 macrophages play pivotal roles in responding to microorganisms and in efferocytosis to avoid the progression of inflammatory conditions. To verify how exposure to air pollutants interferes with macrophage polarization in emphysema development, we evaluated the different macrophage phenotypes in a PPE- induced model with the exposure to diesel exhaust particles. C57BL/6 mice received intranasal instillation of porcine pancreatic elastase (PPE) to induce emphysema, and the control groups received saline. Both groups were exposed to diesel exhaust particles or filtered air for 60 days according to the groups. We observed that both the diesel and PPE groups had an increase in alveolar enlargement, collagen and elastic fibers in the parenchyma and the number of macrophages, lymphocytes and epithelial cells in BAL, and these responses were exacerbated in animals that received PPE instillation prior to exposure to diesel exhaust particles. The same response pattern was found inCaspase-3 positive cell analysis, attesting to an increase in cell apoptosis, which is in agreement with the increase in M2 phenotype markers, measured by RT-PCR and flow cytometry analysis. We did not verify differences among the groups for the M1 phenotype. In conclusion, our results showed that both chronic exposure to diesel exhaust particles and PPE instillation induced inflammatory conditions, cell apoptosis and emphysema development, as well as an increase in M2 phenotype macrophages, and the combination of these two factors exacerbated these responses. The predominance of the M2-like phenotype likely occurred due to the increased demand for efferocytosis. However, M2 macrophage activity was ineffective, resulting in emphysema development and worsening of symptoms.

Extracellular Matrix Component Remodeling in Respiratory Diseases: What Has Been Found in Clinical and Experimental Studies?

Changes in extracellular matrix (ECM) components in the lungs are associated with the progression of respiratory diseases, such as asthma, chronic obstructive pulmonary disease (COPD), and acute respiratory distress syndrome (ARDS). Experimental and clinical studies have revealed that structural changes in ECM components occur under chronic inflammatory conditions, and these changes are associated with impaired lung function. In bronchial asthma, elastic and collagen fiber remodeling, mostly in the airway walls, is associated with an increase in mucus secretion, leading to airway hyperreactivity. In COPD, changes in collagen subtypes I and III and elastin, interfere with the mechanical properties of the lungs, and are believed to play a pivotal role in decreased lung elasticity, during emphysema progression. In ARDS, interstitial edema is often accompanied by excessive deposition of fibronectin and collagen subtypes I and III, which can lead to respiratory failure in the intensive care unit. This review uses experimental models and human studies to describe how inflammatory conditions and ECM remodeling contribute to the loss of lung function in these respiratory diseases.

Atorvastatin dose-dependently promotes mouse lung repair after emphysema induced by elastase

Emphysema results in a proteinase - antiproteinase imbalance, inflammation and oxidative stress. Our objective was to investigate whether atorvastatin could repair mouse lungs after elastase-induced emphysema. Vehicle (50 μL) or porcine pancreatic elastase (PPE) was administered on day 1, 3, 5 and 7 at 0.6 U intranasally. Male mice were divided into a control group (sham), PPE 32d (sacrificed 24 h after 32 days), PPE 64d (sacrificed 24 h after 64 days), and atorvastatin 1, 5 and 20 mg treated from day 33 until day 64 and sacrificed 24 h later (A1 mg, A5 mg and A20 mg, respectively). Treatment with atorvastatin was performed via inhalation for 10 min once a day. We observed that emphysema at day 32 was similar to emphysema at day 64. The mean airspace chord length (Lm) indicated a recovery of pulmonary morphology in groups A5 mg and A20 mg, as well as recovery of collagen and elastic fibers in comparison to the PPE group. Bronchoalveolar lavage fluid (BALF) leukocytes were reduced in all atorvastatin-treated groups. However, tissue macrophages were reduced only in the A20 mg group compared with the PPE group, while tissue neutrophils were reduced in the A5 mg and A20 mg groups. The redox balance was restored mainly in the A20 mg group compared with the PPE group. Finally, atorvastatin at doses of 5 and 20 mg reduced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and matrix metalloproteinase-12 (MMP-12) compared with the PPE group. In conclusion, atorvastatin was able to induce lung tissue repair in emphysematous mice.