Therapeutic benefits of recombinant alpha1-antitrypsin IgG1 Fc-fusion protein in experimental emphysema

BACKGROUND

Alpha-1 antitrypsin (AAT) is a major serine protease inhibitor. AAT deficiency (AATD) is a genetic disorder characterized by early-onset severe emphysema. In well-selected AATD patients, therapy with plasma-derived AAT (pAAT), "augmentation therapy", provides modest clinical improvement but is perceived as cumbersome with weekly intravenous infusions. Using mouse models of emphysema, we compared the effects of a recombinant AAT-IgG1 Fc-fusion protein (AAT-Fc), which is expected to have a longer half-life following infusion, to those of pAAT.

METHODS

In an elastase model of emphysema, mice received a single intratracheal instillation of porcine pancreatic elastase (PPE) or human leucocyte elastase (hLE). AAT-Fc, pAAT, or vehicle was administered intraperitoneally 1 day prior to or 3 weeks following elastase instillation. Lung function and histology assessments were performed at 7 and 32 days after elastase instillation. In a cigarette smoke (CS) model of emphysema, mice were exposed to CS daily, 5 days a week, for 6 months and AAT-Fc, pAAT, or vehicle were administered every 10 days during the last 3 months of CS exposure. Assessments were performed 3 days after the last CS exposure. Immune responses to lung elastin peptide (EP) and the effects of AAT-Fc or pAAT treatment on dendritic cell (DC) function were determined ex vivo.

RESULTS

Both elastase instillation and CS exposure triggered emphysema-like alveolar enlargement, increased lung compliance, and increased markers of inflammation compared to controls. Administration of AAT-Fc either prior to or following elastase instillation or during CS exposure provided greater protection than pAAT against alveolar enlargement, lung dysfunction, and airway inflammation. When challenged ex vivo with EP, spleen mononuclear cells from elastase-exposed mice exhibited dose-dependent production of IFNγ and IL-17, suggesting immune reactivity. In co-culture experiments with splenic CD4+ T cells isolated from elastase-exposed mice, AAT-Fc treatment prior to EP-priming of bone marrow-derived dendritic cells inhibited the production of IFNγ and IL-17.

CONCLUSIONS

Compared to pAAT, AAT-Fc more effectively prevented or attenuated elastase- and CS-induced models of emphysema. These effects were associated with immunomodulatory effects on DC activity. AAT-Fc may provide a therapeutic option to individuals with AATD- and CS-induced emphysema.

High-resolution image-guided WEB aneurysm embolization by high-frequency optical coherence tomography

BACKGROUND

High-frequency optical coherence tomography (HF-OCT) is an intra-vascular imaging technique capable of assessing device-vessel interactions at spatial resolution approaching 10 µm. We tested the hypothesis that adequately deployed Woven EndoBridge (WEB) devices as visualized by HF-OCT lead to higher aneurysm occlusion rates.

METHODS

In a leporine model, elastase-induced aneurysms (n=24) were treated with the WEB device. HF-OCT and digital subtraction angiography (DSA) were performed following WEB deployment and repeated at 4, 8, and 12 weeks. Protrusion (0-present, 1-absent) and malapposition (0-malapposed, 1-neck apposition >50%) were binary coded. A device was considered 'adequately deployed' by HF-OCT and DSA if apposed and non-protruding. Aneurysm healing on DSA was reported using the 4-point WEB occlusion score: A or B grades were considered positive outcome. Neointimal coverage was quantified on HF-OCT images at 12 weeks and compared with scanning electron microscopy (SEM).

RESULTS

Adequate deployment on HF-OCT correlated with positive outcome (P=0.007), but no statistically significant relationship was found between good outcome and adequate deployment on DSA (P=0.289). Absence of protrusion on HF-OCT correlated with a positive outcome (P=0.006); however, malapposition alone had no significant relationship (P=0.19). HF-OCT showed a strong correlation with SEM for the assessment of areas of neointimal tissue (R²=0.96; P<0.001). More neointimal coverage of 78%±32% was found on 'adequate deployment' cases versus 31%±24% for the 'inadequate deployment' cases (P=0.001).

CONCLUSION

HF-OCT visualizes features that can determine adequate device deployment to prognosticate early aneurysm occlusion following WEB implantation and can be used to longitudinally monitor aneurysm healing progression.

Ellagic Acid Ameliorates Lung Inflammation and Heart Oxidative Stress in Elastase-Induced Emphysema Model in Rat

Chronic obstructive pulmonary disease (COPD) is one of the most important factors in the progress of cardiovascular disease (CVD) which is associated with limited airflow and alveolar demolition. The aim of this study is to investigate the possible protective effect of ellagic acid (EA), as a natural anti-oxidant, against pulmonary arterial hypertension (PAH) and development of lung and heart injuries induced by elastase. Sixty healthy male Sprague-Dawley rats (150-180 g) were divided into six groups: control (saline 0.9%, 1 ml/kg, by gavage), porcine pancreatic elastase (PPE) (25 UI/kg, intratracheal), EA (10, 15, and 30 mg/kg, gavage), PPE + EA (30 mg/kg, by gavage). Lead II electrocardiogram was used to evaluate the inotropic and chronotropic parameters of rat heart using Bio-Amp device and the LabChart software. The anti-oxidant levels (superoxide dismutase, catalase, and glutathione) and malondialdehyde were measured by appropriate kits, and right ventricular systolic pressure (RVSP) was recorded by the PowerLab system and measured by the LabChart software (ADInstruments). Elastase administration caused an increase in RVSP which was in line with elevated inflammatory cells and cytokines, as well as lipid peroxidation, and decreased anti-oxidant levels. Also, electrocardiogram parameters significantly changed in elastase group compared with control rats. Co-treatment with EA not only restored elastase-depleted anti-oxidant levels and prevented pulmonary arterial hypertension but also improved cardiac chronotropic and inotropic properties. Our results documented that elastase administration leads to pulmonary arterial hypertension and EA, as an anti-inflammatory and anti-oxidant factor, can protect development of lung and heart injuries induced by elastase.

WEB Device Shape Changes in Elastase-Induced Aneurysms in Rabbits

BACKGROUND AND PURPOSE

While WEB devices have been shown to be safe and effective for aneurysm treatment, WEB-shape modification compression has been associated with incomplete aneurysm occlusion. We explored the relationship between occlusion rates and WEB-shape modification in different WEB device types in an experimental aneurysm model.

MATERIALS AND METHODS

Elastase-induced aneurysms were created in rabbits and treated with dual-layer (n = 12), single-layer (n = 12), or single-layer sphere (n = 12) WEB devices. Aneurysms were followed up either at 3 or 12 months. Angiographic occlusion was graded using the WEB Occlusion Scale: grade I, complete; grade II, complete but recess filling; grade III, residual neck; or grade IV, residual aneurysm. WEB-shape modification and histologic features were also analyzed.

RESULTS

Grade I or II occlusion was seen in 16 (44%) aneurysms, and grade I, II, or III ("adequate") occlusion was observed in 22 (61.1%) aneurysms at follow-up. WEB-shape modification was observed in 22 (61.1%) aneurysms. WEB-shape modification was higher in single-layer (9/12) and dual-layer (10/12) devices compared with single-layer sphere devices (3/12). Aneurysms with WEB-shape modification had a higher level of thrombus organization in the dome compared with those without WEB-shape modification (68% [15/22] versus 50% [7/14]). WEB-shape modification was not correlated with angiographic or histologic outcomes but was significantly correlated with levels of fibrosis and smooth muscle cells in the aneurysm.

CONCLUSIONS

WEB-shape modification is not associated with incomplete aneurysm occlusion of WEB devices in the rabbit model but may be related to connective tissue formation and the healing response to WEB device implantation.

Nanoparticle-based targeted delivery of pentagalloyl glucose reverses elastase-induced abdominal aortic aneurysm and restores aorta to the healthy state in mice

AIM

Abdominal aortic aneurysms (AAA) is a life-threatening weakening and expansion of the abdominal aorta due to inflammatory cell infiltration and gradual degeneration of extracellular matrix (ECM). There are no pharmacological therapies to treat AAA. We tested the hypothesis that nanoparticle (NP) therapy that targets degraded elastin and delivers anti-inflammatory, anti-oxidative, and ECM stabilizing agent, pentagalloyl glucose (PGG) will reverse advance stage aneurysm in an elastase-induced mouse model of AAA.

METHOD AND RESULTS

Porcine pancreatic elastase (PPE) was applied periadventitially to the infrarenal aorta in mice and AAA was allowed to develop for 14 days. Nanoparticles loaded with PGG (EL-PGG-NPs) were then delivered via IV route at 14-day and 21-day (10 mg/kg of body weight). A control group of mice received no therapy. The targeting of NPs to the AAA site was confirmed with fluorescent dye marked NPs and gold NPs. Animals were sacrificed at 28-d. We found that targeted PGG therapy reversed the AAA by decreasing matrix metalloproteinases MMP-9 and MMP-2, and the infiltration of macrophages in the medial layer. The increase in diameter of the aorta was reversed to healthy controls. Moreover, PGG treatment restored degraded elastic lamina and increased the circumferential strain of aneurysmal aorta to the healthy levels.

CONCLUSION

Our results support that site-specific delivery of PGG with targeted nanoparticles can be used to treat already developed AAA. Such therapy can reverse inflammatory markers and restore arterial homeostasis.

IL (Interleukin)-33 Suppresses Abdominal Aortic Aneurysm by Enhancing Regulatory T-Cell Expansion and Activity

Objective- Inflammation occurs during the progression of abdominal aortic aneurysm (AAA). IL (interleukin)-33 is a pleiotropic cytokine with multiple immunomodulatory effects, yet its role in AAA remains unknown. Approach and Results- Immunoblot, immunohistochemistry, and immunofluorescent staining revealed increased IL-33 expression in adventitia fibroblasts from mouse AAA lesions. Daily intraperitoneal administration of recombinant IL-33 or transgenic IL-33 expression ameliorated periaorta CaPO4 injury- and aortic elastase exposure-induced AAA in mice, as demonstrated by blunted aortic expansion, reduced aortic wall elastica fragmentation, enhanced AAA lesion collagen deposition, attenuated T-cell and macrophage infiltration, reduced inflammatory cytokine production, skewed M2 macrophage polarization, and reduced lesion MMP (matrix metalloproteinase) expression and cell apoptosis. Flow cytometry analysis, immunostaining, and immunoblot analysis showed that exogenous IL-33 increased CD4+Foxp3+ regulatory T cells in spleens, blood, and aortas in periaorta CaPO4-treated mice. Yet, ST2 deficiency muted these IL-33 activities. Regulatory T cells from IL-33-treated mice also showed significantly stronger activities in suppressing smooth muscle cell inflammatory cytokine and chemokine expression, macrophage MMP expression, and in increasing M2 macrophage polarization than those from vehicle-treated mice. In contrast, IL-33 failed to prevent AAA and lost its beneficial activities in CaPO4-treated mice after selective depletion of regulatory T cells. Conclusions- Together, this study established a role of IL-33 in protecting mice from AAA formation by enhancing ST2-dependent aortic and systemic regulatory T-cell expansion and their immunosuppressive activities.

Endothelial Progenitor Cells and Notch-1 Signaling as Markers of Alveolar Endothelium Regeneration in Pulmonary Emphysema

We studied the effects of elastase, cigarette smoke extract, D-galactosamine hydrochloride, and tyrosine kinase inhibitor SU5416 on endothelial progenitor cells and angiogenesis precursors, as well as on Notch-1 expression by immature endothelial cells. Simultaneously with pulmonary emphysema, different damaging factors with diverse mechanisms of action caused pathological changes in the microvascular network of the lungs and destroyed the alveolar endothelium in female C57Bl/6 mice. D-galactosamine hydrochloride disturbed mobilization of endothelial progenitor cells expressing VEGFR (CD45-CD309+) and angiogenesis progenitors (CD45-CD309+CD117+) and their migration into emphysema expanded lungs. Elastase inhibited VEGFR-expressing endothelial progenitor cells, while cigarette smoke extract inhibited cells with CD45-CD31+CD34+ phenotype. In pulmonary emphysema provoked by elastase or D-galactosamine hydrochloride, angiogenesis was provided by endothelial cells with CD45-CD31+CD34+ phenotype, whereas in emphysema modeled with SU5416 or cigarette smoke extract, it was provided by the endothelial VEGFR-expressing cells and mature CD31+ endothelial cells, respectively. Replenishment of immature endothelial cells damaged by elastase and SU5416 involved Notch-1+ angiogenesis precursors and Notch-1+ endothelial progenitor cells with VEGFR.

The role of FGF-2 in smoke-induced emphysema and the therapeutic potential of recombinant FGF-2 in patients with COPD

Although the positive effects of recombinant fibroblast growth factor-2 (rFGF-2) in chronic obstructive pulmonary disease (COPD) have been implicated in previous studies, knowledge of its role in COPD remains limited. The mechanism of FGF2 in a COPD mouse model and the therapeutic potential of rFGF-2 were investigated in COPD. The mechanism and protective effects of rFGF-2 were evaluated in cigarette smoke-exposed or elastase-induced COPD animal models. Inflammation was assessed in alveolar cells and lung tissues from mice. FGF-2 was decreased in the lungs of cigarette smoke-exposed mice. Intranasal use of rFGF-2 significantly reduced macrophage-dominant inflammation and alveolar destruction in the lungs. In the elastase-induced emphysema model, rFGF-2 improved regeneration of the lungs. In humans, plasma FGF-2 was decreased significantly in COPD compared with normal subjects (10 subjects, P = 0.037). The safety and efficacy of inhaled rFGF-2 use was examined in COPD patients, along with changes in respiratory symptoms and pulmonary function. A 2-week treatment with inhaled rFGF-2 in COPD (n = 6) resulted in significantly improved respiratory symptoms compared with baseline levels (P < 0.05); however, the results were not significant compared with the placebo. The pulmonary function test results of COPD improved numerically compared with those in the placebo, but the difference was not statistically significant. No serious adverse events occurred during treatment with inhaled rFGF-2. The loss of FGF-2 production is an important mechanism in the development of COPD. Inhaling rFGF-2 may be a new therapeutic option for patients with COPD because rFGF-2 decreases inflammation in lungs exposed to cigarette smoke.

IL-17 Plays a Role in Respiratory Syncytial Virus-induced Lung Inflammation and Emphysema in Elastase and LPS-injured Mice

Respiratory syncytial virus (RSV) is associated with enhanced progression of chronic obstructive pulmonary disease (COPD) and COPD exacerbations. However, little is known about the role of IL-17 in RSV-induced lung injury. We first investigated the role of RSV infection in enhancing mucous cell hyperplasia (MCH) and airspace enlargement in the lungs of mice injured with elastase and LPS (E/LPS). Mice injured with E/LPS had an enhanced and prolonged neutrophilic response to RSV that was associated with decreased levels of type I IFN and increased levels of IL-17, IL-23, CXCL-1, granulocyte colony stimulating factor (GCSF), CXCL-5, and matrix metalloproteinase (MMP)-9. In addition, extent of MCH and mean weighted alveolar space were increased significantly in the lungs of E/LPS-injured mice infected with RSV compared with E/LPS-only or RSV-only controls. Interestingly, immunodepletion of IL-17 before viral infection diminished the RSV-driven MCH and airspace enlargement in the E/LPS-injured animals, suggesting that IL-17 may be a therapeutic target for MCH and airspace enlargement when enhanced by RSV infection.

Activation of p70S6 Kinase-1 in Mesenchymal Stem Cells Is Essential to Lung Tissue Repair

All‐trans retinoic acid (ATRA) or mesenchymal stem cells (MSCs) have been shown to promote lung tissue regeneration in animal models of emphysema. However, the reparative effects of the combination of the two and the role of p70S6 kinase‐1 (p70S6k1) activation in the repair process have not been defined. Twenty‐one days after intratracheal instillation of porcine pancreatic elastase (PPE), MSC and/or 10 days of ATRA treatment was initiated. Thirty‐two days later, static lung compliance (Cst), mean linear intercepts (MLIs), and alveolar surface area (S) were measured. After PPE, mice demonstrated increased values of Cst and MLI, and decreased S values. Both ATRA and MSC transfer were individually effective in improving these outcomes while the combination of ATRA and MSCs was even more effective. The combination of p70S6k1^−/− MSCs transfer followed by ATRA demonstrated only modest effects, and rapamycin treatment of recipients with wild‐type (WT) MSCs and ATRA failed to show any effect. However, transfer of p70S6k1 over‐expressing‐MSCs together with ATRA resulted in further improvements over those seen following WT MSCs together with ATRA. ATRA activated p70S6k1 in MSCs in vitro, which was completely inhibited by rapamycin. Tracking of transferred MSCs following ATRA revealed enhanced accumulation and extended survival of MSCs in recipient lungs following PPE but not vehicle instillation. These data suggest that in MSCs, p70S6k1 activation plays a critical role in ATRA‐enhanced lung tissue repair, mediated in part by prolonged survival of transferred MSCs. p70S6k1‐activated MSCs may represent a novel therapeutic approach to reverse the lung damage seen in emphysema. stemcellstranslationalmedicine2018;7:551–558

PARP-1 inhibition ameliorates elastase induced lung inflammation and emphysema in mice

COPD is associated with high morbidity and mortality and no effective treatment is available till date. We have previously reported that PARP-1 plays an important role in the establishment of airway inflammation associated with asthma and ALI. In the present work, we have evaluated the beneficial effects of PARP-1 inhibition on COPD pathogenesis utilizing elastase induced mouse model of the disease. Our data show that PARP-1 inhibition by olaparib significantly reduced the elastase-induced recruitment of inflammatory cells particularly neutrophils in the lungs of mice when administered at a dose of 5 mg/kg b.wt (i.p.). Reduction in the lung inflammation was associated with suppressed myeloperoxidase activity. Further, the drug restored the redox status in the lung tissues towards normal as reflected by the levels of ROS, GSH and MDA. Olaparib administration prior to elastase instillation blunted the phosphorylation of P65-NF-κB at Ser 536 without altering phosphorylation of its inhibitor IκBα in the lungs. Furthermore, olaparib down regulated the elastase-induced expression of NF-κB dependent pro-inflammatory cytokines (TNF-A, IL-6), chemokine (MIP-2) and growth factor (GCSF) severely both at the mRNA and protein levels. Additionally, PARP-1 heterozygosity suppressed the recruitment of inflammatory cells and production of TNF-A, IL-6, MIP-2 and GCSF in the BALF to the similar extent as exhibited by olaparib administration. Finally, PARP-1 inhibition by olaparib or gene deletion protected against elastase-induced emphysema markedly. Overall, our data strongly suggest that PARP-1 plays a critical role in elastase induced lung inflammation and emphysema, and thus may be a new drug target candidate in COPD.

Synergistic Effect of Hydrogen Peroxide and Elastase on Elastic Fiber Injury In Vitro

This laboratory has previously shown that hyperoxia enhances airspace enlargement in a hamster model of elastase-induced emphysema. To further understand the mechanism responsible for this finding, the effect of oxidants on elastase activity was studied in vitro, using a radiolabeled elastic fiber matrix derived from rat pleural mesothelial cells. Matrix samples were treated with either 0.1%, 1%, 3%, or 10% hydrogen peroxide (H2O2) for 1 hr, then incubated with 1.0 μg/ml porcine pancreatic elastase for 2 hrs. Radioactivity released from the matrix was used as a measure of elastolysis. Results indicate that sequential exposure to H2O2 and elastase markedly enhanced elastolysis compared to enzyme treatment alone. A 22% increase in elastolysis was seen with 0.1% H2O2 (325 vs. 396 cpm; P < 0.05), whereas samples pretreated with 1%, 3%, and 10% H2O2 showed increases of 53% (274 vs. 420 cpm; P < 0.05), 71% (381 vs. 653 cpm; P < 0.01), and 38% (322 vs. 443 cpm; P < 0.01), respectively. Exposure to various concentrations of H2O2 alone (0.1% to 10%) produced only minimal elastolysis (<20 cpm). However, 1% H2O2 was capable of degrading peptide-free desmosine and isodesmosine, suggesting that exposure to this oxidant may reduce the stability of the elastic fiber matrix. With regard to lung diseases such as emphysema, H2O2 and other oxidants derived from inflammatory cells or the environment could possibly act as priming agents for elastase-mediated breakdown of elastic fibers, resulting in amplification of lung injury.

From bench to bedside: utility of the rabbit elastase aneurysm model in preclinical studies of intracranial aneurysm treatment

Preclinical studies are important in helping practitioners and device developers improve techniques and tools for endovascular treatment of intracranial aneurysms. Thus an understanding of the major animal models used in such studies is important. The New Zealand rabbit elastase induced arterial aneurysm of the common carotid artery is one of the most commonly used models in testing the safety and efficacy of new endovascular devices. In this review we discuss: (1) the various techniques used to create the aneurysm, (2) complications of aneurysm creation, (3) natural history of the arterial aneurysm, (4) histopathologic and hemodynamic features of the aneurysm, (5) devices tested using this model, and (6) weaknesses of the model. We demonstrate how preclinical studies using this model are applied in the treatment of intracranial aneurysms in humans. The model has similar hemodynamic, morphological, and histologic characteristics to human aneurysms, and demonstrates similar healing responses to coiling as human aneurysms. Despite these strengths, however, the model does have many weaknesses, including the fact that the model does not emulate the complex inflammatory processes affecting growing and ruptured aneurysms. Furthermore, the extracranial location of the model affects its ability to be used in preclinical safety assessments of new devices. We conclude that the rabbit elastase model has characteristics that make it a simple and effective model for preclinical studies on the endovascular treatment of intracranial aneurysms, but further work is needed to develop aneurysm models that simulate the histopathologic and morphologic characteristics of growing and ruptured aneurysms.

Matricellular protein CCN3 mitigates abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a major cause of morbidity and mortality; however, the mechanisms that are involved in disease initiation and progression are incompletely understood. Extracellular matrix proteins play an integral role in modulating vascular homeostasis in health and disease. Here, we determined that the expression of the matricellular protein CCN3 is strongly reduced in rodent AAA models, including angiotensin II-induced AAA and elastase perfusion-stimulated AAA. CCN3 levels were also reduced in human AAA biopsies compared with those in controls. In murine models of induced AAA, germline deletion of Ccn3 resulted in severe phenotypes characterized by elastin fragmentation, vessel dilation, vascular inflammation, dissection, heightened ROS generation, and smooth muscle cell loss. Conversely, overexpression of CCN3 mitigated both elastase- and angiotensin II-induced AAA formation in mice. BM transplantation experiments suggested that the AAA phenotype of CCN3-deficient mice is intrinsic to the vasculature, as AAA was not exacerbated in WT animals that received CCN3-deficient BM and WT BM did not reduce AAA severity in CCN3-deficient mice. Genetic and pharmacological approaches implicated the ERK1/2 pathway as a critical regulator of CCN3-dependent AAA development. Together, these results demonstrate that CCN3 is a nodal regulator in AAA biology and identify CCN3 as a potential therapeutic target for vascular disease.

Preclinical Testing of a Novel Thin Film Nitinol Flow-Diversion Stent in a Rabbit Elastase Aneurysm Model

BACKGROUND AND PURPOSE

Thin film nitinol can be processed to produce a thin microporous sheet with a low percentage of metal coverage (<20%) and high pore attenuation (∼70 pores/mm(2)) for flow diversion. We present in vivo results from the treatment of experimental rabbit aneurysms by using a thin film nitinol-based flow-diversion device.

MATERIALS AND METHODS

Nineteen aneurysms in the rabbit elastase aneurysm model were treated with a single thin film nitinol flow diverter. Devices were also placed over 17 lumbar arteries to model perianeurysmal branch arteries of the intracranial circulation. Angiography was performed at 2 weeks (n = 7), 1 month (n = 8), and 3 months (n = 4) immediately before sacrifice. Aneurysm occlusion was graded on a 3-point scale (grade I, complete occlusion; grade II, near-complete occlusion; grade III, incomplete occlusion). Toluidine blue staining was used for histologic evaluation. En face CD31 immunofluorescent staining was performed to quantify neck endothelialization.

RESULTS

Markedly reduced intra-aneurysmal flow was observed on angiography immediately after device placement in all aneurysms. Grade I or II occlusion was noted in 4 (57%) aneurysms at 2-week, in 6 (75%) aneurysms at 4-week, and in 3 (75%) aneurysms at 12-week follow-up. All 17 lumbar arteries were patent. CD31 staining showed that 75% ± 16% of the aneurysm neck region was endothelialized. Histopathology demonstrated incorporation of the thin film nitinol flow diverter into the vessel wall and no evidence of excessive neointimal hyperplasia.

CONCLUSIONS

In this rabbit model, the thin film nitinol flow diverter achieved high rates of aneurysm occlusion and promoted tissue in-growth and aneurysm neck healing, even early after implantation.

Complications of elastase-induced arterial saccular aneurysm in rabbits: case reports and literature review

Endoluminal infusion and incubation of elastase with or without collagenase into the rabbit common carotid artery is an established model of arterial saccular aneurysm. The model mimics naturally occurring human cerebral aneurysms in many ways, including histologic and morphologic characteristics, hemodynamic pressures, and shear stresses. However, complications have been associated with the model. Here, we report 2 complications: 1) the first known case of iatrogenic laryngeal hemiplegia in a rabbit; and 2) histopathologically confirmed iatrogenic hippocampal and cerebellar infarcts (stroke). Finally, we present and review data from current literature on the morbidity and mortality associated with this model.

Keratinocyte growth factor protects against elastase-induced pulmonary emphysema in mice

Pulmonary emphysema is characterized by persistent inflammation and progressive alveolar destruction. The keratinocyte growth factor (KGF) favorably influences alveolar maintenance and repair and possesses anti-inflammatory properties. We aimed to determine whether exogenous KGF prevented or corrected elastase-induced pulmonary emphysema in vivo. Treatment with 5 mg x kg(-1) x day(-1) KGF before elastase instillation prevented pulmonary emphysema. This effect was associated with 1) a sharp reduction in bronchoalveolar lavage fluid total protein and inflammatory cell recruitment, 2) a reduction in the pulmonary expression of the chemokines CCL2 (or monocyte chemoattractant protein-1) and CXCL2 (or macrophage inflammatory protein-2alpha) and of the adhesion molecules ICAM-1 and VCAM-1, 3) a reduction in matrix metalloproteinase (MMP)-2 and MMP-9 activity at day 3, and 4) a major reduction in DNA damage detected by terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling (TUNEL) in alveolar cells at day 7. Treatment with KGF after elastase instillation had no effect on elastase-induced emphysema despite the conserved expression of the KGF receptor in the lungs of elastase-instilled animals as determined by immunohistochemistry. In vitro, KGF abolished the elastase-induced increase in CCL2, CXCL2, and ICAM-1 mRNA in the MLE-12 murine alveolar epithelial cell line. We conclude that KGF pretreatment protected against elastase-induced pulmonary inflammation, activation of MMPs, alveolar cell DNA damage, and subsequent emphysema in mice.

IkappaB kinase-2-independent and -dependent inflammation in airway disease models: relevance of IKK-2 inhibition to the clinic

Nuclear factor kappaB (NF-kappaB) is a transcription factor believed to be central in the expression of numerous inflammatory genes and the pathogenesis of many respiratory diseases. We have previously demonstrated increased NF-kappaB pathway activation in a steroid-sensitive animal model of lipopolysaccharide (LPS)-driven airway inflammation. It is noteworthy that this phenomenon was not observed in a steroid-insensitive model of elastase-induced inflammation in the rat. The aim of this study was to gather further evidence to suggest that these similar profiles of neutrophilic inflammation can be NF-kappaB-dependent or -independent by determining the impact of an IkappaB kinase-2 (IKK-2) inhibitor, 2-[(aminocarbonyl)amino]-5-(4-fluorophenyl)-3-thiophenecarboxamide (TPCA-1). In the LPS model, TPCA-1 blocked the increase in NF-kappaB DNA binding, a marker of NF-kappaB pathway activation. This inhibition was associated with a reduction in inflammatory mediator release [tumor necrosis factor alpha (TNFalpha)/interleukin-1beta (IL-1beta)/matrix metalloproteinase-9 (MMP-9)] and lung inflammatory cell burden (neutrophilia/eosinophilia). These data were paralleled with a steroid and in human cell based assays. In the elastase-driven inflammation model, in which our group has previously failed to measure an increase in NF-kappaB DNA binding, neither TPCA-1 nor the steroid, affected mediator release (IL-1beta/MMP-9) or cellular burden (neutrophilia/lymphomononuclear cells). This is the first study to examine the effect of an IKK-2 inhibitor in well validated models that mimic aspects of the inflammatory lesion evident in diseases such as COPD. In conclusion, we have demonstrated that animal models with similar profiles of airway inflammation can be IKK-2 inhibitor/steroid-sensitive or -insensitive. If both profiles of inflammation exist in the clinic, then this finding is extremely exciting and may lead to greater understanding of disease pathology and the discovery of novel anti-inflammatory targets.

Transcription factor Nrf2 plays a pivotal role in protection against elastase-induced pulmonary inflammation and emphysema

Emphysema is one of the major pathological abnormalities associated with chronic obstructive pulmonary disease. The protease/antiprotease imbalance and inflammation resulting from oxidative stress have been attributed to the pathogenesis of emphysema. Nrf2 is believed to protect against oxidative tissue damage through the transcriptional activation of a battery of antioxidant enzymes. In this study, we investigated the protective role of Nrf2 in the development of emphysema using elastase-induced emphysema as our model system. We found that elastase-provoked emphysema was markedly exacerbated in Nrf2-knockout (KO) mice compared with wild-type mice. The severity of emphysema in Nrf2-KO mice correlated intimately with the degree of lung inflammation in the initial stage of elastase treatment. The highly inducible expression of antioxidant and antiprotease genes observed in wild-type alveolar macrophages was significantly attenuated in the lungs of Nrf2-KO mice. Interestingly, transplantation of wild-type bone marrow cells into Nrf2-KO mice retarded the development of initial lung inflammation and subsequent emphysema, and this improvement correlated well with the appearance of macrophages expressing Nrf2-regulated antiprotease and antioxidant genes. Thus, Nrf2 appears to exert its protective effects through the transcriptional activation of antiprotease and antioxidant genes in alveolar macrophages.

Superoxide dismutase expression attenuates cigarette smoke- or elastase-generated emphysema in mice

RATIONALE

Oxidants are believed to play a major role in the development of emphysema.

OBJECTIVES

This study aimed to determine if the expression of human copper-zinc superoxide dismutase (CuZnSOD) within the lungs of mice protects against the development of emphysema.

METHODS

Transgenic CuZnSOD and littermate mice were exposed to cigarette smoke (6 h/d, 5 d/wk, for 1 yr) and compared with nonexposed mice. A second group was treated with intratracheal elastase to induce emphysema.

MEASUREMENTS

Lung inflammation was measured by cell counts and myeloperoxidase levels. Oxidative damage was assessed by immunofluorescence for 3-nitrotyrosine and 8-hydroxydeoxyguanosine and lipid peroxidation levels. The development of emphysema was determined by measuring the mean linear intercept (Lm).

MAIN RESULTS

Smoke exposure caused a fourfold increase in neutrophilic inflammation and doubled lung myeloperoxidase activity. This inflammatory response did not occur in the smoke-exposed CuZnSOD mice. Similarly, CuZnSOD expression prevented the 58% increase in lung lipid peroxidation products that occurred after smoke exposure. Most important, CuZnSOD prevented the onset of emphysema in both the smoke-induced model (Lm, 68 exposed control vs. 58 exposed transgenic; p < 0.04) and elastase-generated model (Lm, 80 exposed control vs. 63 exposed transgenic; p < 0.03). These results demonstrate for the first time that antioxidants can prevent smoke-induced inflammation and can counteract the proteolytic cascade that leads to emphysema formation in two separate animal models of the disease.

CONCLUSIONS

These findings indicate that strategies aimed at enhancing or supplementing lung antioxidants could be effective for the prevention and treatment of this disease.

Amelioration of pulmonary emphysema by in vivo gene transfection with hepatocyte growth factor in rats

BACKGROUND

Hepatocyte growth factor (HGF) is an important mitogen and morphogen that contributes to the repair process after lung injury. The goal of the present study was to characterize its role in pulmonary emphysema, which may lead to the development of new treatment strategies with HGF.

METHODS AND RESULTS

HGF mRNA and protein levels in lung tissue and plasma from elastase-induced emphysema rats transiently increased, then declined significantly to below the basal level in a time-dependent manner (P<0.01). Furthermore, changes in HGF were correlated with histologically progressive emphysematous changes and deterioration in pulmonary physiology. Use of the HVJ (hemagglutinating virus of Japan) envelope method resulted in successful transfection of cDNA encoding human HGF, as demonstrated by an efficient expression of HGF in alveolar endothelial and epithelial cells. Transfection of HGF resulted in a more extensive pulmonary vasculature and inhibition of alveolar wall cell apoptosis, and those effects led to improved exercise tolerance and gas exchange (P<0.05), which persisted for more than 1 month.

CONCLUSIONS

Decreased HGF expression due to a failure in sustained endogenous production after injury was associated with emphysema-related histopathologic and physiological changes in the present rat model. In addition, induction of HGF expression by a gene-transfection method resulted in improved pulmonary function via inhibition of alveolar cell apoptosis, enhancement of alveolar regeneration, and promotion of angiogenesis.

Comparison of cell-type-specific vs transmural aortic gene expression in experimental aneurysms

OBJECTIVE

Abdominal aortic aneurysm (AAA) progression and disease resistance are related to mural cellularity; adventitial macrophages and neocapillaries predominate in larger, advanced aneurysms, whereas smaller AAAs have fewer macrophages and retain more medial smooth muscle cells (SMCs). Expression analysis of mRNA derived from the entire aorta may mask the role that specific cell types play in modulating disease progression. We used laser capture microdissection (LCM) to isolate SMC and macrophage-predominant mural cell populations for gene expression analysis in variable-flow AAA.

METHODS

Rat AAAs were created via porcine pancreatic elastase (PPE) infusion. Aortic flow was increased via femoral arteriovenous fistula creation (HF-AAA) or reduced via unilateral iliac ligation (LF-AAA) in selected cohorts. SMC and macrophage-predominant cell populations were isolated via LCM and analyzed for expression of pro-inflammatory transcription factors and chemokines, cytokines, and proteolytic enzymes via real-time polymerase chain reaction.

RESULTS

Aortic PPE infusion precipitated endothelial cell (EC) denudation, SMC apoptosis, and elastic lamellar degeneration. Increased aortic flow (HF > NF > LF) stimulated restorative EC and SMC proliferation (45.8 +/- 6.6 > 30.5 +/- 2.1 > 21 +/- 3.6 and 212.2 +/- 9.8 > 136.5 +/- 8.9 > 110 +/- 13.5, respectively, for both cell types; P < .05) at 5 days after PPE infusion, while simultaneously reducing medial SMC apoptosis and transmural macrophage infiltration. Expression of nuclear factor kappa B (NF-kappab), granulocyte macrophage-colony stimulating factor (GM-CSF), macrophage migration inhibitory (MIF), heparin-binding EGF-like factor (HB-EGF) and inducible nitric oxide synthase (iNOS) varied between cell types and flow conditions at all time points examined. Gelatinolytic protease expression varied by cell type in response to flow loading (eg, increased in SMCs, decreased in macrophages), consistent with observed patterns of elastolysis and SMC proliferation reported in prior experiments.

CONCLUSIONS

Flow differentially regulates cell-specific AAA gene expression. Whole-organ analysis of AAA tissue lysates obscures important cellular responses to inflammation and flow, and may explain previous seemingly contradictory observations regarding proteolysis and cell proliferation. Cell-type specific expression and functional analyses may substantially clarify the pathophysiology of AAA disease.

CLINICAL RELEVANCE

Understanding aneurysmal aortic degeneration at the most fundamental level is a critical precursor to the development of next-generation therapies such as drug-eluting endografts and/or medical therapies to limit expansion of preclinical AAA in high-risk or elderly patients. Although animal modeling is necessary to gain insight into the early initiating events of AAA disease, the methods used in such analyses have critical bearing on the conclusions drawn regarding pathogenesis and potential therapeutic derivations. By analyzing cell-type-specific gene expression rather than whole-organ tissue lysates, the precise roles of important mediators such as metalloproteinases can be placed in the appropriate context. Further refinement of these techniques may allow cell-specific therapies to be applied at defined time points in disease progression with improved patient outcome and reduced procedural morbidity.

A novel coating biomaterial for intracranial aneurysms: Effects and safety in extra- and intracranial carotid artery

Methyl-2-cyanoacrylate, a widely used material for coating cerebral aneurysm, was recently withdrawn. The aim of the present study was to develop an alternative coating material for cerebral aneurysm, which is safe, effective and stable within the brain. In the first experiment, an aneurysm model of the common carotid artery was produced in a rabbit by the local application of elastase. The aneurysm produced was covered by no material (Group A), a cellulose cotton sheet and conventional methyl-2-cyanoacrylate (Group B), a newly produced polyglycolic acid felt and fibrin glue (Group C), or a cellulose cotton sheet and fibrin glue (Group D). Histological examination showed that the materials resulted in the formation of tight connective tissue around the artery, and that the material was completely replaced by the connective tissue after 12 weeks. This change was found exclusively in Group C, but not in Group A or the other materials, although a temporary thickening of the intima was also observed at the site of the elastase application in Group C. In Group D, a long-term, marked thickening of the intima was observed. In the second experiment, using an intracranial internal carotid artery from a beagle, the applied polyglycolic acid felt and fibrin glue to the intracranial artery induced the formation of connective tissue around the artery that was completely absorbed 16 weeks after surgery. There were no signs of intimal thickening or of adverse reactions in nervous tissue. The present results suggest that polyglycolic acid felt and fibrin glue is a possible candidate for a safe, effective biomaterial to wrap or coat cerebral aneurysm.

Adenovirus-Mediated Transfer and Overexpression of Heme Oxygenase 1 cDNA in Lungs Attenuates Elastase-Induced Pulmonary Emphysema in Mice

Heme oxygenase 1 (HO-1) is an inducible enzyme that catalyzes heme to generate bilirubin, ferritin, and carbon monoxide. Because enhanced expression of HO-1 provides an anti-inflammatory effect and confers cytoprotection, we examined whether HO-1 overexpression induced by inoculation of mice with an adenovirus encoding HO-1 (Ad.HO-1) in the lung would prevent pulmonary emphysema induced by porcine pancreatic elastase (PPE). Pretreatment with Ad.HO-1, which upregulated production of HO-1 in the lung, attenuated the PPE-induced increase of neutrophils in bronchoalveolar lavage fluid (BALF) and enlargement of alveoli. It also reduced PPE-induced elevated levels of tumor necrosis factor alpha, interleukin (IL)-6, and keratinocyte-derived chemokine, and increased the level of anti-inflammatory cytokine IL-10 in BALF. These results suggest that Ad.HO-1-induced HO-1 overexpression suppressed PPE-induced emphysema by attenuating neutrophilic inflammation via modulating cytokine and chemokine profiles in mouse lungs.

Hepatocyte growth factor induces angiogenesis in injured lungs through mobilizing endothelial progenitor cells

Circulating endothelial progenitor cells (EPCs) play a pivotal role in angiogenesis. Hepatocyte growth factor (HGF) is known to induce proliferation and motility in endothelial cells, and to play a role in mitogenic and morphogenic actions. However, the role of HGF in EPC mobilization has not been clearly described yet. We investigated the effect of HGF on mobilizing EPCs and on angiogenesis in elastase-induced lung injury. HGF significantly increased the triple-positive (Sca-1(+), Flk-1(+), and c-kit(+)) fraction in peripheral mononuclear cells in mice. The bone marrow-derived cells were recruited into the injured lungs, where they differentiated to capillary endothelial cells. HGF induced proliferation of both bone marrow-derived and resident endothelial cells in the alveolar wall. In conclusion, the present study suggests that HGF induces EPC mobilization from the bone marrow and enhances the proliferation of endothelial cells in vivo. These complex effects induced by HGF orchestrate pulmonary regeneration in emphysematous lung parenchyma.

Hemodynamic forces regulate mural macrophage infiltration in experimental aortic aneurysms

Blood flow (BF) and wall shear stress (WSS) influence reactive oxygen species production and oxidative stress in abdominal aortic aneurysm (AAA) disease. To gain further insight into the mechanisms of hemodynamic influences on AAA inflammation, we examined aneurysm macrophage density, chemotaxis and survival under varying aortic flow conditions. Rat AAAs were created via porcine pancreatic elastase (PPE) infusion. In selected cohorts, AAA flow was increased via left common femoral arteriovenous fistula (AVF) creation (HF-AAA) or decreased by left common iliac ligation (LF-AAA). WSS was highest in HF-AAA (10.4 +/- 2.3 dyn/cm(2) vs. 2.4 +/- 0.4 and 0.5 +/- 0.2 for NF- and LF-AAA, respectively, P < 0.001) 7 days after PPE infusion, with reduced medial macrophage density and increased apoptosis. Adventitial macrophage density was not significantly influenced by flow. Monocyte chemoattractant protein-1 (MCP-1) and granulocyte-macrophage colony-stimulating factor (GM-CSF) gene expression correlated with observed macrophage densities in the media and adventitia. Luminal flow conditions regulate AAA inflammation in part via influences on medial macrophage density. Hemodynamic forces may modulate AAA inflammation and diameter enlargement via direct regulation of intimal macrophage adhesion, transmural migration or survival.

Retinoic acid fails to reverse emphysema in adult mouse models

BACKGROUND

Previous work has shown that all-trans-retinoic acid reverses elastase induced emphysema in rats. Since there is currently no effective treatment for pulmonary emphysema, the effect of retinoic acid should be further investigated in other adult species. A study was undertaken using two murine models of emphysema to evaluate the effect of retinoic acid.

METHODS

The models used were an elastase induced emphysema model for acute alveolar destruction and a tumour necrosis factor (TNF)-alpha transgenic mouse which exhibits chronic air space enlargement, loss of elastic recoil, increased lung volume, and pulmonary hypertension comparable to human pulmonary emphysema. All-trans-retinoic acid (2 mg/kg) was injected for 12 successive days after the establishment of emphysema. The effects of treatment were evaluated using physiological and morphometric analyses.

RESULTS

In contrast to the rat, administration of all-trans-retinoic acid in these murine models did not improve the emphysema. Moreover, worsening of emphysema was observed in TNF-alpha transgenic mice treated with all-trans-retinoic acid. The level of keratinocyte chemoattractant (KC), a CXC chemokine, in bronchoalveolar lavage fluid was increased in TNF-alpha transgenic mice following retinoic acid treatment. These data raise the possibility that retinoic acid causes deterioration of emphysema by promoting inflammation in this model.

CONCLUSIONS

In these models, retinoic acid did not show positive effects on emphysema. The effect of retinoic acid in the treatment of pulmonary emphysema remains controversial, and further studies are required to determine its physiological effects under a variety of experimental conditions.

Bone marrow-derived cells contribute to lung regeneration after elastase-induced pulmonary emphysema

All-trans retinoic acid (ATRA) is known to reverse the anatomic and physiologic signs of pulmonary emphysema. However, the origin of the progenitor cells involved in this lung regeneration remains unclear. Recently, it was shown that bone marrow could be the source of progenitor cells for several cell types. Mice with elastase-induced emphysema were treated with ATRA, granulocyte colony-stimulating factor (G-CSF), or a combination of both. ATRA or G-CSF promoted lung regeneration and increased bone marrow-derived cell (BMC) numbers in alveoli. Combined treatment of both had an additive effect, which indicated that BMC mobilization might be important in lung regeneration.

Mouse Models of Abdominal Aortic Aneurysms

Many mouse models of abdominal aortic aneurysms have been developed that use a diverse array of methods for producing the disease, including genetic manipulation and chemical induction. These models could provide insight into potential mechanisms in the development of this disease. Although experimental studies on abdominal aortic aneurysms (AAAs) have used a variety of mammalian and avian approaches, there is an increasing reliance on the use of mice. The models recapitulate some facets of the human disease including medial degeneration, inflammation, thrombus formation, and rupture. Most of the mouse models of AAA are evoked either by genetically defined approaches or by chemical means. The genetic approaches are spontaneous and engineered mutations. These include defects in extracellular matrix maturation, increased degradation of elastin and collagen, aberrant cholesterol homeostasis, and enhanced production of angiotensin peptides. The chemical approaches include the intraluminal infusion of elastase, periaortic incubations of calcium chloride, and subcutaneous infusion of AngII. A common feature of these models is the reduction of AAA incidence and severity by the prophylactic administration of matrix metalloproteinase (MMP) inhibitors or genetically engineered deficiencies of specific members of this proteolytic protein family. The validation of mouse models of AAAs will provide insight into the mechanisms of progression of the human disease.

Elastase-induced changes in lung function: relationship to morphometry and effect of drugs

Intratracheal administration of porcine pancreatic elastase (PPE) produced a dose related decline in lung function, as assessed by changes in dynamic lung compliance (C(dyn)) in New Zealand White rabbits. This occurred within 24 h of administration and persisted for 56 days (n=6). These lung function changes were accompanied by histological evidence of emphysema in the lungs and were not mimicked by intratracheal administration of the proteolytic enzyme trypsin. Neither the lung function nor the histological changes induced by elastase could be prevented or reversed by either the glucocorticosteroid, dexamethasone, or all trans retinoic acid (ATRA).Our data suggest that local administration of elastase to the lungs of rabbits may provide a convenient way to assess the effects of drugs on the changes induced by elastase in airways.

Coordinate expression of fibulin-5/DANCE and elastin during lung injury repair

Fibulin-5, previously known as DANCE and EVEC, is a secreted extracellular matrix protein that functions as a scaffold for elastin fiber assembly and as a ligand for integrins alphavbeta3, alphavbeta5, and alpha9beta1. Fibulin-5 is developmentally regulated in the lung, and lung air space enlargement develops in mice deficient in fibulin-5. Fibulin-5 is also induced in adult lung following lung injury by hyperoxia. To further examine the role of fibulin-5 during repair of lung injury, we assessed fibulin-5 expression during elastase-induced emphysema in C57/b mice. Mice were treated with either saline or elastase via the trachea, and the lung was examined 20 days after treatment. Fibulin-5 mRNA was induced almost fourfold, whereas elastin mRNA was minimally elevated. Immunohistochemistry studies showed that fibulin-5 was induced in cells within the alveolar wall following elastase treatment. Western analysis demonstrates that fibulin-5 was strongly expressed in isolated primary lung interstitial fibroblasts. Fibulin-5 protein was localized to the fibroblast cell layer in culture, and brief elastase treatment degraded the protein. Intact fibulin-5 did not accumulate in the culture media. Treatment of fibroblasts with the proinflammatory cytokine interleukin-1beta abolished fibulin-5 mRNA expression. Our results indicate that fibulin-5 is coordinately expressed and regulated with elastin in lung fibroblasts and may serve a key role during lung injury and repair.

Transcriptional regulation of pulmonary elastin gene expression in elastase-induced injury

Previously we have shown that treatment of confluent, pulmonary fibroblast cultures with elastase results in upregulation of elastin mRNA and protein levels. In the present study we focused on determining the level at which elastin expression is upregulated after elastase exposure. We examined as models for this investigation elastin gene expression in primary pulmonary fibroblast cells during the transition from subconfluent to confluent cultures and in confluent, matrix-laden cultures treated briefly with elastase. In addition, we extended our studies to mice that were given an intratracheal dose of elastase; the effects on lung elastin mRNA and elastin promoter activity levels were measured and compared with results from in vitro cell models. The results demonstrate that upregulation of elastin gene expression during the transition of subconfluent to confluent cultures and after elastase injury is associated with an increase in the level of transcription both in vitro and in vivo. Furthermore, intratracheal administration of elastase to transgenic mice illustrates that the increased levels of elastin mRNA are accompanied by increased activity of the elastin gene promoter in cells spatially positioned near major sites of tissue injury.

The effect of lysozyme on elastase-mediated injury

Previous studies by this laboratory demonstrated that lysozyme is increased in human pulmonary emphysema, and that it preferentially binds to elastic fibers, which undergo degradation in this disease. In the current investigation, the relationship between lysozyme and elastic fiber injury was further examined, both in vitro and in vivo. The effect of exogenously administered egg-white lysozyme on pancreatic elastase-induced injury was determined using a biosynthetically radiolabeled extracellular matrix preparation mainly composed of elastic fibers. Although matrix treated with lysozyme showed attachment of the protein to elastic fibers, there was no significant increase in elastolysis compared with untreated controls following exposure to either 1 microg/ml or 100 ng/ml of pancreatic elastase. However, lysozyme did impair the ability of hyaluronan (HA) to prevent elastase injury to elastic fibers. Matrix samples sequentially treated with lysozyme and HA, then incubated with 1 microg/ml or 100 ng/ml of pancreatic elastase, showed significantly increased elastolysis compared with those treated with HA alone. Since HA is closely associated with elastic fibers in vivo, the ability of lysozyme to enhance elastolysis was further tested in an animal model of emphysema induced by intratracheal administration of porcine pancreatic elastase. Animals exposed to aerosolized lysozyme prior to elastase administration showed significantly increased airspace enlargement. The mean linear intercept of the lysozyme-treated animals was 123 microm compared with 75 microm for controls receiving aerosolized water (P < 0.0001). These findings suggest that lysozyme may not be an innocuous component of the inflammatory response associated with pulmonary emphysema, but may actually play a role in the pathogenesis of the disease.

Severity of elastase-induced emphysema is decreased in tumor necrosis factor-alpha and interleukin-1beta receptor-deficient mice

A single intratracheal dose of porcine pancreatic elastase, which is cleared from the lung by 24 hours, was administered to wild-type, IL-1beta type 1 receptor-deficient, double TNF-alpha (type 1 and type 2) receptor-deficient, and combined TNF-alpha (type 1 receptor) plus IL-1beta receptor-deficient mice. The mean linear intercept (Lm) of saline-treated mice was 32(3) microm [mean(SE)]. For wild-type elastase-treated mice, Lm was 81(6) microm at 21 days versus 52(5) microm at 5 days after treatment, indicating that alveolar wall remodeling occurs long after the elastase injury. At 21 days, Lm values were 67(10), 62(3), and 39(5) microm in elastase-treated mice deficient in the IL-1beta receptor, double TNF-alpha receptors, and combined receptors, respectively. The level of apoptosis assessed by a terminal deoxynucleotidyl transferase-catalyzed in situ nick end-labeling assay was increased at 5 days after elastase treatment and was markedly and similarly attenuated in the IL-1beta, the double TNF-alpha, and the combined receptor-deficient mice. Our results indicate that inflammatory mediators exacerbate elastase-induced emphysema. We estimate that in the combined TNF-alpha + IL-1beta receptor-deficient mice, inflammation accounts for about 80% of the emphysema that develops after elastase treatment; decreased apoptosis of lung cells likely contributes to decreased severity of emphysema.

[Induction of arthritis in healthy knee joints after intra-articular injection of the proteolytic enzyme elastase - An experimental investigation in the rabbit]

AIM

Humoral aspects are being discussed in the initiation of arthritis. Therefore, the effects of the proteolytic enzyme elastase on the cartilage of knee joints in rabbits have been investigated. The enzyme was evaluated using activities comparable to those in post-traumatic knee joint hemarthrosis in humans.

METHOD

Polymorphonuclear leukocyte elastase was injected into one of the knee joints of 10 rabbits. In 5 animals (first study group), joints were then immobilized with a cast for 6 weeks. In the other 5 (second study group), no immobilization was applied. In the first zero group (2 animals), 0.9 % NaCl was injected intra-articularly without immobilization, whereas in the second zero group (2 anmals) knees were immobilized for 6 weeks without prior injection. Thus, the effect of immobilization could be evaluated additionally. Joint specimens were then examined histologically and electron microscopically.

RESULTS

There was clear evidence of elastase having severe destructive effects on cartilage regardless of additional joint-immobilization. In neither zero group was there prearthritic damage to the cartilage.

CONCLUSION

To prevent the initiation of cartilage damage by humoral factors, early elimination of the pathological intra-articular effusion is necessary.

Hemorrhagic activity and muscle damaging effect of Pseudomonas aeruginosa metalloproteinase (elastase)

Pseudomonas aeruginosa elastase, a Bacillus subtilis thermolysin-like zinc-proteinase was examined for hemorrhagic activity and its effect on muscle and endothelial cells. Subcutaneous and intramuscular injections of elastase into mice caused severe hemorrhage with an acute increase of creatine phosphokinase activity in serum. The elastase also possessed fibrinogenolytic and fibrinolytic activities. The Aalpha and Bbeta chains of fibrinogen were completely hydrolyzed as demonstrated by their electrophoretic disappearance on SDS polyacrylamide gels. The pathological study indicates that elastase induces changes in the structure of the vascular wall and causes leakage of the plasma component and red and white blood cells into the extravascular tissue. This is further supported by results showing injury to cultured endothelial cells and macrophages. These data indicate that P. aeruginosa elastase directly affects endothelial cells and destroys the basement membrane of blood vessels to cause hemorrhage. Since fibrinogenolytic activity is an additional component of this elastase and this activity induces the hemorrhagic tendency, the damage in tissues could become increasingly severe.

Morphologic changes in the aorta during elastase infusion in the rat aneurysm model

BACKGROUND

The morphologic changes in the aorta during elastase infusion, which have not previously been investigated, were examined in the rat abdominal aortic aneurysm model.

MATERIALS AND METHODS

A total of 80 Wistar rats were divided into five groups. A 1.0-cm segment of infra-renal abdominal aorta was infused with 25 U of elastase in 1 mL saline for 10 (n = 14), 20 (n = 14), 30 (n = 14), 60 (n = 19), or 120 min (n = 19). In the 120-min group, transparency and aortic diameter were recorded every 10 min. In each group, 7 rats were killed immediately after infusion. The aortas were excised for histologic examination. The aortic diameters were measured 7 days after infusion in the remaining rats.

RESULTS

The infused aorta became transparent within 50 min of elastase infusion. The aortic diameter increased rapidly for the first 30 min of infusion. Histologically, the elastic tissue was completely absent after 60 min of infusion. The aortic diameters in the 60- and 120-min groups were not significantly different 7 days after infusion.

CONCLUSIONS

Morphologic changes in the infused aorta are complete after 60 min of elastase infusion. It may be possible to shorten the elastase infusion time from 120 to 60 min in this model.

Factors influencing mortality in the rat elastase-induced-aneurysm model

BACKGROUND

Intraarterial infusion of elastase has been used to create an experimental model of aortic aneurysm in rats. Unfortunately, the utility of this model is limited by a high mortality rate among experimental animals. This study examined the factors influencing mortality to help refine this model.

MATERIALS AND METHODS

A total of 126 Wistar rats were divided into six groups. A 1.0-cm segment of infra-renal abdominal aorta was clamped (n = 21), clamped and cannulated via the femoral artery (n = 21), infused with saline (n = 21), or infused with solution containing 25 U of elastase from three different lots (each group, n = 21). Clamping or infusion was performed for 30 (n = 7), 60 (n = 7), and 120 min (n = 7). The mortality rates were calculated at 7 days.

RESULTS

There were no deaths in the clamp group, but 29% of the rats that underwent cannulation with clamping or saline infusion for 2 h died. The mortality rate for a 30-min elastase infusion ranged from 0 to 71%. Mortality for a 60-min infusion ranged from 14 to 100%. Mortality for a 2-h infusion ranged from 43 to 100%. The mortality rate was dependent on the treatment time and the elastase lot number.

CONCLUSIONS

Aortic cannulation, elastase infusion, and prolonged infusion times all increase the mortality rate in the elastase-induced rat aortic aneurysm model. Mortality is also dependent on the elastase lot number.

The pulmonary matrix, glycosaminoglycans and pulmonary emphysema

This paper reviews recent evidence of the effect of intratracheal hyaluronan (HA) to limit the induction of experimental emphysema in hamsters. Experimental emphysema was induced by both neutrophil and pancreatic elastase instilled intratracheally. Emphysema was quantified anatomically by measurement of alveolar mean linear intercept. Hyaluronidase, instilled intratracheally, enhanced the induction of experimental emphysema. Air-space size measured one week after intratracheal instillation of elastase showed that administration of 1 mg HA immediately following elastase administration resulted in a marked reduction in air-space enlargement (82 microM vs 122 microM, p < 0.01). Similarly, animals given either 1 or 2 mg HA 2 h before elastase or 2mg HA 1 h after elastase showed a significant decrease in air-space enlargement compared to controls (96 microM, 88 microM vs 120 microM and 66 microM vs 104 microM, respectively; p < 0.05. Experimental emphysema induced by neutrophil elastase was also limited by the administration of 1 or 4 mg of HA, administered 2 h prior to elastase (57 and 59 microM, respectively vs 64 for controls, p < 0.05). Characterization of administered HA showed a mean molecular weight of 104,800 Da, less than 5% protein and a uronic acid/hexosamine ratio of 1, which is characteristic of HA. Studies using fluorescein-labeled hyaluronan (HA) showed fluorescence associated with interstitial, pleural and vascular elastic fibers. The mechanism of attachment of the administered HA to elastin remains unknown. Fluorescein labeling of elastin was visible for at least 4 h post-instillation. These studies indicate a protective effect of hyaluronan against elastase degradation of pulmonary elastin in vivo by both pancreatic and neutrophil elastases. The anatomical studies further suggest a mechanism of protective coating of hyaluronan which may limit access to pulmonary elastin from neutrophils and alveolar macrophages. Results also suggest that a reduction in pulmonary hyaluronan content increases the susceptibility of elastin to degradation by elastases. These studies provide evidence for an antielastase effect of hyaluronan which is not dependent upon enzyme inhibition but on anatomical protection of pulmonary elastin by other mechanisms.

[Changes of plasma nitric oxide and tumor necrosis factor-alpha in lung elastase injury induced inflammatory response of hamster]

OBJECTIVE

To investigate the role of the NO and TNF-alpha in lung elastase injury induced inflammatory response of hamster.

METHODS

Lung elastase injury induced inflammatory hamster model was established. NOS activity in airway epithelial cells and lung monocytes/macrophage, as well as the serum content of NO and TNF-alpha were measured respectively.

RESULTS

The results indicated that iNOS activity in epithelium and monocytes/macrophages were significantly enhanced. In the early period of inflammation the NO and TNF-alpha content in serum increased obviously and maintained in a high level (P < 0.001).

CONCLUSIONS

This Study suggested that both NO and TNF-alpha are important mediators participating in the lung elastase injury-induced inflammatory response. Our data suggested NO might play a regulatory role in the release of TNF-alpha.

Elastase in intestinal mucus enhances the cytotoxicity of Shiga toxin type 2d

Shiga toxin variant type 2d (Stx2d) produced by some strains of Shiga toxin-producing Escherichia coli is composed of an enzymatically active A subunit and a B (binding) pentamer. The cytotoxicity of Stx2d is increased (activated) 10-1000-fold for Vero cells when the toxin is incubated with mucus obtained from the small intestine of mice. In this study we isolated an Stx2d activator and identified it as a mouse elastase with strong homology to human elastase IIIB. Moreover, commercially available porcine pancreatic elastase preparations also activated Stx2d cytotoxicity although with a lower specific activity than isolated mouse elastase. Elastase directly nicked the Stx2d A subunit to A(1) and A(2), an event that did not correlate with activation. However, elastase also reduced the size and changed the isoelectric point of the A(2) peptide, as determined by SDS-polyacrylamide gel electrophoresis and two-dimensional electrophoresis followed by Western immunoblot analysis. This elastase-mediated size and charge shift in the A(2) peptide of Stx2d occurred concurrently with activation of the toxin. Both the reduction in size of the Stx2d A(2) peptide by incubation with elastase as well as the associated activation of Stx2d cytotoxicity were fully inhibited by elastatinal, an elastase-specific inhibitor.

A rabbit model of abdominal aortic aneurysm associated with intimal thickening

A model of abdominal aortic aneurysm with intimal thickening was developed in the rabbit. A segment of the abdominal aorta just proximal to the bifurcation (1 or 2 cm in length) was dissected and isolated with clamps. This segment was perfused by injecting physiologic saline or 100 U/ml of hog pancreatic elastase from the lumen. Perfusion was performed manually for 5 min and the peak pressure in the segment was between 300 and 400 mm Hg in order to cause aortic wall injury. After 4 weeks, animals that had received perfusion with elastase had aneurysms in the perfused segment on arteriography. None of the other animals developed aortic aneurysms. Histologically, the segments of aorta perfused with saline exhibited intimal hyperplasia. In addition to the intimal hyperplasia, the segments of aorta perfused with elastase solution showed lysis of the elastic lamellae in the media that resulted in aneurysm formation.

The kinetics of elastolysis: elastin catabolism during experimentally induced fibrosis

Lung injury and matrix destruction result in the release into the circulation of desmosine, a product of elastin catabolism. To determine whether measurements of desmosine concentrations in the urine can provide important information about the severity of lung injury, we measured the kinetics of lung elastin catabolism following elastase-induced and fibrotic lung injury in mice. Pancreatic elastase instillation in the lung caused immediate elastin destruction, removing as much as 25% of the lung elastin within the first few hours. Peak concentrations of desmosine peptides appeared in the blood within 1-2 hours, and soluble elastin peptides in the lung and urine followed a similar course with peak levels occurring early and then declining rapidly, approaching control levels by 24 hours. More than half of the desmosine peptides removed from the lung following elastase injury were sequestered by the kidney and then slowly released over a period of several days. Lung histology and morphological measurements indicated that bleomycin, TiO2, and SiO2 instillation resulted in severely fibrotic lungs. However, the lung injuries sustained from these agents resulted in minimal elastin damage, representing less than 0.1% of the total lung elastin catabolized as estimated by desmosine analysis. The rapid accumulation of desmosine in renal tissue and its slow release into the urine keep urine concentrations low and minimize the power of urine desmosine assays for quantifying low level tissue destruction.

Pulmonary vagal reflexes and breathing pattern are not altered in elastase-induced emphysema in rats

The role of nonmyelinated and myelinated vagal afferents in pulmonary reflexes and breathing pattern was examined in elastase-treated emphysemic rats. Fourteen to 17 days after intratracheal instillation of 1 IU/gm of porcine pancreatic elastase or 0.5 mL of saline, elastase-treated rats had a decreased alveolar surface area to volume of parenchyma (Sv) (42.44 +/- 1.7 vs. 31.51 +/- 1.1 mm2/mm3), increased quasistatic compliance (QSC) (1.05 +/- 0.06 vs. 1.25 +/- 0.09 mL/cm H2O), functional residual capacity (FRC) (4.31 +/- 0.10 vs. 5.88 +/- 0.37 mL), residual volume (RV) (3.02 +/- 0.14 vs. 4.27 +/- 0.31 mL), and total lung capacity (TLC) (14.04 +/- 0.28 vs. 15.58 +/- 0.54 mL). There were no changes in the strength of the pulmonary chemoreflex, the strength of the Hering-Breuer inflation reflex, or breathing pattern before or after vagal perineural capsaicin treatment (VPCT) or vagotomy. There were, however, significant negative correlations between Sv and TLC, FRC and RV, and a near significant (p < .09) negative correlation between Sv and QSC, but no significant correlations between Sv and indices of either the pulmonary chemoreflex or Hering-Breuer inflation reflex. The results indicate that pulmonary vagal nonmyelinated and myelinated reflex activity and breathing pattern are not affected by elastase-induced emphysema in rats.

Potency of truncated secretory leukoprotease inhibitor assessed in acute lung injury models in hamsters

We evaluated the potency of truncated secretory leukoprotease inhibitor (truncated SLPI) in a human sputum elastase (HSE)-induced lung injury model and in a specific neutrophil-mediated acute lung injury model in hamsters. Intratracheal administration of HSE induced acute lung hemorrhage that could be measured by determination of the hemoglobin content in the bronchoalveolar lavage fluid. Intratracheal administration of truncated SLPI 1 hr before HSE administration inhibited acute lung hemorrhage in a dose-dependent manner (ED50 = 46.8 microg/kg), as did i.v. injection of the inhibitor given 2 min before HSE administration (ED50 = 14.7 mg/kg). Intratracheal administration of endotoxin (lipopolysaccharide) induced pulmonary neutrophilia. Twenty-four hours after lipopolysaccharide administration, the addition of formyl-methionyl-leucyl-phenylalanine resulted in a neutrophil-dependent acute lung injury that expressed an increase in hemoglobin content and in elastase-like activity in bronchoalveolar lavage fluids. In this model, lung injury was significantly attenuated by i.v. and intratracheal administration of truncated SLPI. These results suggest that truncated SLPI appears to be a good candidate inhibitor for the treatment of destructive lung diseases due to neutrophils.

Further investigation of the use of intratracheally administered hyaluronic acid to ameliorate elastase-induced emphysema

Previously, this laboratory has shown that intratracheally administered hyaluronic acid (HA) significantly reduces air-space enlargement in a hamster model of emphysema induced with pancreatic elastase. Whereas HA was given immediately following elastase in those initial studies, the current investigation determined the effect of instilling HA up to 2 h before or after intratracheal administration of elastase to hamsters. Both 1 and 2 mg HA, given 2 h before pancreatic elastase, significantly decreased (p < .05) air-space enlargement compared to controls (as measured by the mean linear intercept). Instillment of 2 mg HA, 1 h after pancreatic elastase, had a similar effect (p < .05). In contrast, 1 mg HA, given 1 or 2 h after pancreatic elastase, did not significantly affect the mean linear intercept. Against human neutrophil elastase, HA exhibited the same protective effect. While neutrophil elastase induced less air-space enlargement than pancreatic elastase, both 1 and 4 mg of HA, given 2 h prior to the enzyme, still produced a significant reduction (p < .05) in the mean linear intercept. HA exerted this effect despite the fact that it initiates a transient influx of neutrophils into the lung. Since HA does not slow the clearance of intratracheally instilled [14C] albumin from the lung, its mechanism of action may not involve physical interference with the movement of elastase through the lung, but may instead depend on interaction with elastic fibers. Evidence for an association between these two matrix constituents was provided by studies using fluorescein-labeled HA. Overall, these results further suggest that HA may be useful in preventing lung injury by elastases.

Effect of salmeterol on Pseudomonas aeruginosa infection of respiratory mucosa

We have studied the effect of salmeterol on both P. aeruginosa interactions with the mucosa of nasal turbinate organ cultures and on pyocyanin-induced (20 microg/ml) and elastase-induced (100 microg/ml) damage to nasal epithelial cells. Organ cultures were exposed to salmeterol either by preincubation with 4 x 10(-7) M salmeterol for 30 min or by pipetting 20 microl of 4 x 10(-7) M salmeterol onto the organ culture surface immediately prior to bacterial inoculation. Infected organ cultures (8 h) had significantly (p < or = 0.01) increased epithelial damage, and P. aeruginosa was predominantly associated with damaged epithelium and mucus. Salmeterol significantly (p < or = 0.02) reduced epithelial damage caused by infection and the total number of adherent bacteria (p < or = 0.05), but bacterial distribution on the mucosa was unchanged. Nasal epithelial cells incubated with pyocyanin (20 microg/ml) or elastase (100 microg/ml) for 3 h had significantly (p < or = 0.05) increased cytoplasmic blebbing and mitochondrial damage versus control values. Elastase also significantly (p < or = 0.05) increased cell projection and reduced the level of ciliation. Cells preincubated with salmeterol (2 x 10(-7) M) showed a significant reduction in some features of cell damage caused by both toxins, which was inhibited by the beta2-adrenoceptor antagonist propranolol. Our results indicate that salmeterol reduces P. aeruginosa-induced damage to both organ culture and nasal epithelium.