Endothelial alpha-1-antitrypsin attenuates cigarette smoke induced apoptosis in vitro

Proteolysis and Deficiency of α1-Proteinase Inhibitor in SARS-CoV-2 Infection

The SARS-CoV-2 pandemic had stimulated the emergence of numerous publications on the α1-proteinase inhibitor (α1-PI, α1-antitrypsin), especially when it was found that the regions of high mortality corresponded to the regions with deficient α1-PI alleles. By analogy with the data obtained in the last century, when the first cause of the genetic deficiency of α1-antitrypsin leading to elastase activation in pulmonary emphysema was proven, it can be supposed that proteolysis hyperactivation in COVID-19 may be associated with the impaired functions of α1-PI. The purpose of this review was to systematize the scientific data and critical directions for translational studies on the role of α1-PI in SARS-CoV-2-induced proteolysis hyperactivation as a diagnostic marker and a therapeutic target. This review describes the proteinase-dependent stages of viral infection: the reception and penetration of the virus into a cell and the imbalance of the plasma aldosterone-angiotensin-renin, kinin, and blood clotting systems. The role of ACE2, TMPRSS, ADAM17, furin, cathepsins, trypsin- and elastase-like serine proteinases in the virus tropism, the activation of proteolytic cascades in blood, and the COVID-19-dependent complications is considered. The scientific reports on α1-PI involvement in the SARS-CoV-2-induced inflammation, the relationship with the severity of infection and comorbidities were analyzed. Particular attention is paid to the acquired α1-PI deficiency in assessing the state of patients with proteolysis overactivation and chronic non-inflammatory diseases, which are accompanied by the risk factors for comorbidity progression and the long-term consequences of COVID-19. Essential data on the search and application of protease inhibitor drugs in the therapy for bronchopulmonary and cardiovascular pathologies were analyzed. The evidence of antiviral, anti-inflammatory, anticoagulant, and anti-apoptotic effects of α1-PI, as well as the prominent data and prospects for its application as a targeted drug in the SARS-CoV-2 acquired pneumonia and related disorders, are presented.

[Proteolysis and deficiency of α1-proteinase inhibitor in SARS-CoV-2 infection]

The SARS-CoV-2 pandemia had stimulated the numerous publications emergence on the α1-proteinase inhibitor (α1-PI, α1-antitrypsin), primarily when it was found that high mortality in some regions corresponded to the regions with deficient α1-PI alleles. By analogy with the last century's data, when the root cause of the α1-antitrypsin, genetic deficiency leading to the elastase activation in pulmonary emphysema, was proven. It is evident that proteolysis hyperactivation in COVID-19 may be associated with α1-PI impaired functions. The purpose of this review is to systematize scientific data, critical directions for translational studies on the role of α1-PI in SARS-CoV-2-induced proteolysis hyperactivation as a diagnostic marker and a target in therapy. This review describes the proteinase-dependent stages of a viral infection: the reception and virus penetration into the cell, the plasma aldosterone-angiotensin-renin, kinins, blood clotting systems imbalance. The ACE2, TMPRSS, ADAM17, furin, cathepsins, trypsin- and elastase-like serine proteinases role in the virus tropism, proteolytic cascades activation in blood, and the COVID-19-dependent complications is presented. The analysis of scientific reports on the α1-PI implementation in the SARS-CoV-2-induced inflammation, the links with the infection severity, and comorbidities were carried out. Particular attention is paid to the acquired α1-PI deficiency in assessing the patients with the proteolysis overactivation and chronic non-inflammatory diseases that are accompanied by the risk factors for the comorbidities progression, and the long-term consequences of COVID-19 initiation. Analyzed data on the search and proteases inhibitory drugs usage in the bronchopulmonary cardiovascular pathologies therapy are essential. It becomes evident the antiviral, anti-inflammatory, anticoagulant, anti-apoptotic effect of α1-PI. The prominent data and prospects for its application as a targeted drug in the SARS-CoV-2 acquired pneumonia and related disorders are presented.

A Novel Cellular Therapy to Treat Pancreatic Pain in Experimental Chronic Pancreatitis Using Human Alpha-1 Antitrypsin Overexpressing Mesenchymal Stromal Cells

Chronic pancreatitis (CP) is characterized by pancreatic inflammation, fibrosis, and abdominal pain that is challenging to treat. Mesenchymal stromal cells (MSCs) overexpressing human alpha-1 antitrypsin (hAAT-MSCs) showed improved mobility and protective functions over native MSCs in nonobese diabetic mice. We investigated whether hAAT-MSCs could mitigate CP and its associated pain using trinitrobenzene sulfonic acid (TNBS)-induced CP mouse models. CP mice were given native human MSCs or hAAT-MSCs (0.5 × 10⁶ cells/mouse, i.v., n = 6–8/group). The index of visceral pain was measured by graduated von Frey filaments. Pancreatic morphology and pancreatic mast cell count were analyzed by morphological stains. Nociceptor transient receptor potential vanilloid 1 (TRPV1) expression in dorsal root ganglia (DRG) was determined by immunohistochemistry. hAAT-MSC-treated CP mice best preserved pancreatic morphology and histology. MSC or hAAT-MSC infusion reduced abdominal pain sensitivities. hAAT-MSC therapy also suppressed TRPV1 expression in DRG and reduced pancreatic mast cell density induced by TNBS. Overall, hAAT-MSCs reduced pain and mitigated pancreatic inflammation in CP equal to MSCs with a trend toward a higher pancreatic weight and better pain relief in the hAAT-MSC group compared to the MSC group. Both MSCs and hAAT-MSCs might be used as a novel therapeutic tool for CP-related pain.

Alpha-1 Antitrypsin and Hepatocellular Carcinoma in Liver Cirrhosis: SERPINA1 MZ or MS Genotype Carriage Decreases the Risk

Heterozygotes for Z or S alleles of alpha-1-antrypsin (AAT) have low serum AAT levels. Our aim was to compare the risk of hepatocellular carcinoma (HCC) in patients with liver cirrhosis carrying the SERPINA1 MM, MZ and MS genotypes. The study groups consisted of 1119 patients with liver cirrhosis of various aetiologies, and 3240 healthy individuals served as population controls. The MZ genotype was significantly more frequent in the study group (55/1119 vs. 87/3240, p < 0.0001). The MS genotype frequency was comparable in controls (32/119 vs. 101/3240, p = 0.84). MZ and MS heterozygotes had lower serum AAT level than MM homozygotes (medians: 0.90 g/L; 1.40 g/L and 1.67 g/L; p < 0.001 for both). There were significantly fewer patients with HCC in the cirrhosis group among MZ and MS heterozygotes than in MM homozygotes (5/55 and 1/32 respectively, vs. 243/1022, p < 0.01 for both). The risk of HCC was lower in MZ and MS heterozygotes than in MM homozygotes (OR 0.3202; 95% CI 0.1361–0.7719 and OR 0.1522; 95% CI 0.02941–0.7882, respectively). Multivariate analysis of HCC risk factors identified MZ or MS genotype carriage as a protective factor, whereas age, male sex, BMI and viral aetiology of cirrhosis increased HCC risk.

Overexpression of alpha-1 antitrypsin in mesenchymal stromal cells improves their intrinsic biological properties and therapeutic effects in nonobese diabetic mice

Islet/β cell dysfunction and death caused by autoimmune-mediated injuries are major features of type 1 diabetes (T1D). Mesenchymal stromal cells (MSCs) have been used for the treatment of T1D in animal models and clinical trials. Based on the anti-inflammatory effects of alpha-1 antitrypsin (AAT), we generated human AAT engineered MSCs (hAAT-MSCs) by infecting human bone marrow-derived MSCs with the pHAGE CMV-a1aT-UBC-GFP-W lentiviral vector. We compared the colony forming, differentiation, and migration capacity of empty virus-treated MSCs (hMSC) and hAAT-MSCs and tested their protective effects in the prevention of onset of T1D in nonobese diabetic (NOD) mice. hAAT-MSCs showed increased self-renewal, better migration and multilineage differentiation abilities compared to hMSCs. In addition, polymerase chain reaction array for 84 MSC-related genes showed that 23 genes were upregulated, and 3 genes were downregulated in hAAT-MSCs compared to hMSCs. Upregulated genes include those critical for the stemness (ie, Wnt family member 3A [WNT3A], kinase insert domain receptor [KDR]), migration (intercellular adhesion molecule 1 [ICAM-1], vascular cell adhesion protein 1 [VICAM-1], matrix metalloproteinase-2 [MMP2]), and survival (insulin-like growth factor 1 [IGF-1]) of MSCs. Pathway analysis showed that changed genes were related to growth factor activity, positive regulation of cell migration, and positive regulation of transcription. In vivo, a single intravenous infusion of hAAT-MSCs significantly limited inflammatory infiltration into islets and delayed diabetes onset in the NOD mice compared with those receiving vehicle or hMSCs. Taken together, overexpression of hAAT in MSCs improved intrinsic biological properties of MSCs needed for cellular therapy for the treatment of T1D.

Pulmonary Endothelial Cell Apoptosis in Emphysema and Acute Lung Injury

Apoptosis plays an essential role in homeostasis and pathogenesis of a variety of human diseases. Endothelial cells are exposed to various environmental and internal stress and endothelial apoptosis is a pathophysiological consequence of these stimuli. Pulmonary endothelial cell apoptosis initiates or contributes to progression of a number of lung diseases. This chapter will focus on the current understanding of the role of pulmonary endothelial cell apoptosis in the development of emphysema and acute lung injury (ALI) and the factors controlling pulmonary endothelial life and death.

Alpha-1 Antitrypsin Investigations Using Animal Models of Emphysema

Animal models of disease help accelerate the translation of basic science discoveries to the bedside, because they permit experimental interrogation of mechanisms at relatively high throughput, while accounting for the complexity of an intact organism. From the groundbreaking observation of emphysema-like alveolar destruction after direct instillation of elastase in the lungs to the more clinically relevant model of airspace enlargement induced by chronic exposure to cigarette smoke, animal models have advanced our understanding of alpha-1 antitrypsin (AAT) function. Experimental in vivo models that, at least in part, replicate clinical human phenotypes facilitate the translation of mechanistic findings into individuals with chronic obstructive pulmonary disease and with AAT deficiency. In addition, unexpected findings of alveolar enlargement in various transgenic mice have led to novel hypotheses of emphysema development. Previous challenges in manipulating the AAT genes in mice can now be overcome with new transgenic approaches that will likely advance our understanding of functions of this essential, lung-protective serine protease inhibitor (serpin).

Effects of cigarette smoke on pulmonary endothelial cells

Cigarette smoking is the leading cause of preventable disease and death in the United States. Cardiovascular comorbidities associated with both active and secondhand cigarette smoking indicate the vascular toxicity of smoke exposure. Growing evidence supports the injurious effect of cigarette smoke on pulmonary endothelial cells and the roles of endothelial cell injury in development of acute respiratory distress syndrome (ARDS), emphysema, and pulmonary hypertension. This review summarizes results from studies of humans, preclinical animal models, and cultured endothelial cells that document toxicities of cigarette smoke exposure on pulmonary endothelial cell functions, including barrier dysfunction, endothelial activation and inflammation, apoptosis, and vasoactive mediator production. The discussion is focused on effects of cigarette smoke-induced endothelial injury in the development of ARDS, emphysema, and vascular remodeling in chronic obstructive pulmonary disease.

Native matrix-based human lung alveolar tissue model in vitro: studies of the reparatory actions of mesenchymal stem cells

Studies of lung diseases in vitro often rely on flat, plastic-based monocultures, due to short lifespan of primary cells, complicated anatomy, lack of explants, etc. We hereby present a native 3D model with cues for repopulating epithelial cells. Abilities of mesenchymal stem cells (MSC) to modulate bacterial lipopolysaccharide (LPS) and cigarette smoke-induced injury to pulmonary epithelium were tested in our model. Post-mortem human lung tissue was sliced, cut and decellularized. Resulting matrix pads were reseeded with pulmonary epithelium (A549 line). Markers of the layer integrity and certain secreted proteins in the presence of cigarette smoke extract (CSE) and LPS were assessed via Western blot, ELISA and RT-PCR assays. In parallel, the effects of MSC paracrine factors on exposed epithelial cells were also investigated at gene and protein levels. When cultured on native 3D matrix, A549 cells obtain dual, type I- and II-like morphology. Exposure to CSE and LPS leads to downregulation of several epithelial proteins and suppressed proliferation rate. MSC medium added to the model restores proliferation rate and some of the epithelial proteins, i.e. e-cadherin and beta-catenin. CSE also increases secretion of pro-inflammatory cytokines by epithelial cells and upregulates transcription factor NFκB. Some of these effects might be counteracted by MSC in our model. We introduce repopulated decellularized lung matrix that highly resembles in vivo situation and is convenient for studies of disease pathogenesis, cytotoxicology and for exploring therapeutic strategies in the human lung context in vitro. MSC paracrine products have produced protecting effects in our model.

Alpha-1 Antitrypsin and Lung Cell Apoptosis

Discovery of alpha-1 antitrypsin (A1AT) as the principal circulating inhibitor of neutrophil elastase was critical to the appreciation of protease/antiprotease imbalance involvement in the pathogenesis of emphysema. Additional targets of A1AT have been uncovered, along with their contribution to alveolar wall destruction induced by cigarette smoke exposure. We highlight in this report mechanisms of A1AT antiapoptotic effects on structural lung endothelial cells. This function was largely dependent on uptake of the protein from the circulation via clathrin- and, in part, caveolae-mediated endocytosis and on specific interactions with cysteine proteases such as capsase-3, -6, and -7. Exposures to cigarette smoke diminished A1AT intracellular uptake and its anticaspase action, suggesting that even in A1AT-suficient individuals, cigarette smoke may weaken the serpin's endothelial prosurvival effect. In addition, cigarette smoke exposure or genetic mutations known to induce posttranslational modifications such as oxidation or polymerization may alter A1AT bidirectional intracellular traffic in endothelial cells and thus determine its functional bioavailability in certain lung compartments. Uncovering and harnessing the A1AT canonical and noncanonical mechanisms will advance our understanding of the pathogenesis of emphysema and may provide means to improve the effectiveness of therapies in both A1AT-sufficient and A1AT-deficient individuals.

The Association Between α1-Antitrypsin and Coronary Artery Ectasia

Coronary artery ectasia (CAE) is associated with coronary artery disease (CAD). The underlying pathophysiology of CAE is not fully understood. α₁-antitrypsin (A1AT) plays a role in the tissue protease system, and AAT-1 deficiency (A1ATD) has been shown to be related to CAD. We compared A1AT serum levels in patients with and without CAE to determine the association between A1AT levels and the extent of ectasia using the Markis score. We included 50 patients (38 males) with isolated CAE and 46 patients (28 males) with normal coronary arteries after coronary angiography. The levels of A1AT were measured by nephelometry. The median A1AT levels were lower in patients with isolated CAE than in the control group (1.27 ng/mL [range: 1.07-1.37 ng/mL] vs 1.43 ng/mL [range: 1.27-1.59 ng/mL]; P < .001). According to the Markis classification, the extent of CAE was not correlated with A1AT levels ( P = .41). Our results demonstrate an inverse relationship between serum A1AT levels and CAE. α₁-antitrypsin is fundamental for the stability and integrity of the arterial wall. Lack of elastase inhibition in cases of A1ATD may contribute to ectasia formation by facilitating proteolysis and weakening the arterial wall.

Alpha-1 Antitrypsin as a Therapeutic Agent for Conditions not Associated with Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin is a positive acute phase reactant whose serum level rises in response to inflammatory stress, presumably to balance pro-inflammatory processes. In addition to its serine protease inhibitory action, alpha-1 antitrypsin exhibits broader anti-inflammatory and immunomodulatory activity, and increasing its serum concentration by the administration of exogenous alpha-1 antitrypsin to above-normal levels potentially could be therapeutic in conditions other than alpha-1 antitrypsin deficiency. In vitro observations, studies in animal models and in some instances early human trials suggest that intravenous or inhaled alpha-1 antitrypsin has beneficial effects in type 1 diabetes, viral infections, graft-versus-host disease, cystic fibrosis, and alpha-1 antitrypsin-replete chronic obstructive pulmonary disease among others. While the results of pivotal clinical trials have not been reported to date, new indications for alpha-1 antitrypsin therapy are likely to emerge in the future based on currently available scientific data.

Tumor necrosis factor-α driven inflammation in alpha-1 antitrypsin deficiency: a new model of pathogenesis and treatment

Alpha-1 antitrypsin (AAT) deficiency (AATD) has traditionally been thought of as a genetic disorder characterized by lung destruction and early emphysema in a low AAT, and high neutrophil elastase (NE) environment in the lungs of affected individuals. Recently, a growing body of evidence has emerged to support the hypothesis that tumor necrosis factor alpha (TNF-α) is essential in the pathogenesis of both genetic AATD and non-genetic chronic obstructive pulmonary disease (COPD). Reports have highlighted the importance of TNF-α driven immune cell dysfunction in the development of lung disease in AATD. The authors discuss the role of AAT as a key modulator of TNF-α signaling firstly in the setting of AATD and secondly in other conditions where AAT augmentation therapy has potential utility as a novel therapy.

Low-density lipoprotein receptor-related protein 1 mediates α1-antitrypsin internalization in CD4+ T lymphocytes

In α1-antitrypsin-deficient HIV patients, an accelerated decline of CD4(+) T cell numbers is observed, suggesting that α1-antitrypsin is a potential endogenous HIV inhibitor. In infected T lymphocytes, α1-antitrypsin potently blocks NF-κB activation and HIV-1 replication by directly interacting with IκBα in the cytosol, thereby altering its ubiquitination pattern. However, the mechanism of α1-antitrypsin entry into the cytosol, where IκBα locates, remains unclear. In the present study, we investigated the mechanism of α1-antitrypsin internalization in CD4(+) T cells. Thus, primary CD4(+) T cells were infected with HIV-1 and then incubated with α1-antitrypsin to detect its internalization. We found that CD4(+) T cells internalized α1-antitrypsin through a clathrin-dependent endocytosis process. Next, intracellular α1-antitrypsin exerted the inhibitory effect on NF-κB activation and HIV-1 replication. On primary CD4(+) T cells, α1-antitrypsin interacted with low-density lipoprotein receptor-related protein 1 to initiate the internalization. Inside CD4(+) T lymphocytes, α1-antitrypsin was transported from the endosome to the lysosome and then released into the cytosol, where it is possible for α1-antitrypsin to directly interact with IκBα. These results together suggest that α1-antitrypsin internalization is a clathrin-dependent and low-density lipoprotein receptor-related protein 1-mediated endocytosis process. Internalized α1-antitrypsin is transported through the endosome-lysosome-cytosol routine to interact with cytosolic IκBα and block NF-κB activation and HIV-1 replication.

Scavenger receptor class B, type I-mediated uptake of A1AT by pulmonary endothelial cells

In addition to exerting a potent anti-elastase function, α-1 antitrypsin (A1AT) maintains the structural integrity of the lung by inhibiting endothelial inflammation and apoptosis. A main serpin secreted in circulation by hepatocytes, A1AT requires uptake by the endothelium to achieve vasculoprotective effects. This active uptake mechanism, which is inhibited by cigarette smoking (CS), involves primarily clathrin- but also caveola-mediated endocytosis and may require active binding to a receptor. Because circulating A1AT binds to high-density lipoprotein (HDL), we hypothesized that scavenging receptors are candidates for endothelial uptake of the serpin. Although the low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) internalizes only elastase-bound A1AT, the scavenger receptor B type I (SR-BI), which binds and internalizes HDL and is modulated by CS, may be involved in A1AT uptake. Transmission electron microscopy imaging of colloidal gold-labeled A1AT confirmed A1AT endocytosis in both clathrin-coated vesicles and caveolae in endothelial cells. SR-BI immunoprecipitation identified binding to A1AT at the plasma membrane. Pretreatment of human lung microvascular endothelial cells with SR-B ligands (HDL or LDL), knockdown of SCARB1 expression, or neutralizing SR-BI antibodies significantly reduced A1AT uptake by 30-50%. Scarb1 null mice exhibited decreased A1AT lung content following systemic A1AT administration and reduced lung anti-inflammatory effects of A1AT supplementation during short-term CS exposure. In turn, A1AT supplementation increased lung SR-BI expression and modulated circulating lipoprotein levels in wild-type animals. These studies indicate that SR-BI is an important mediator of A1AT endocytosis in pulmonary endothelium and suggest a cross talk between A1AT and lipoprotein regulation of vascular functions.

Heme oxygenase-1-mediated autophagy protects against pulmonary endothelial cell death and development of emphysema in cadmium-treated mice

Pulmonary exposure to cadmium, a major component of cigarette smoke, has a dramatic impact on lung function and the development of emphysema. Cigarette smoke exposure induces heme oxygenase-1 (HO-1), a cytoprotective enzyme. In this study, we employed a truncated mouse model of emphysema by intratracheal instillation of cadmium (CdCl2) solution (0.025% per 1 mg/kg body wt) in HO-1(+/+), HO-1(-/-), and overexpressing humanized HO-1 bacterial artificial chromosome (hHO-1BAC) mice. We evaluated the role of HO-1 in cadmium-induced emphysema in mice by analyzing histopathology, micro-computed tomography scans, and lung function tests. CdCl2-exposed HO-1(-/-) mice exhibited more severe emphysema compared with HO-1(+/+) or hHO-1BAC mice. Loss of pulmonary endothelial cells (PECs) from the alveolar capillary membrane is recognized to be a target in emphysema. PECs from HO-1(+/+), HO-1(-/-), and hHO-1BAC were employed to define the underlying molecular mechanism for the protection from emphysema by HO-1. Electron microscopy, expression of autophagic markers (microtubule-associated protein 1B-light chain 3 II, autophagy protein 5, and Beclin1) and apoptotic marker (cleaved caspase 3) suggested induction of autophagy and apoptosis in PECs after CdCl2 treatment. CdCl2-treated HO-1(-/-) PECs exhibited downregulation of autophagic markers and significantly increased cleaved caspase 3 expression and activity (∼4-fold higher). Moreover, hHO-1BAC PECs demonstrated upregulated autophagy and absence of cleaved caspase 3 expression or activity. Pretreatment of HO-1(+/+) PECs with rapamycin induced autophagy and resulted in reduced cell death upon cadmium treatment. Induction of autophagy following CdCl2 treatment was found to be protective from apoptotic cell death. HO-1 induced protective autophagy in PECs and mitigated cadmium-induced emphysema.

Acute-phase protein α1-anti-trypsin: diverting injurious innate and adaptive immune responses from non-authentic threats

One would assume that the anti-inflammatory activity of α1-anti-trypsin (AAT) is the result of inhibiting neutrophil enzymes. However, AAT exhibits tolerogenic activities that are difficult to explain by serine-protease inhibition or by reduced inflammatory parameters. Targets outside the serine-protease family have been identified, supporting the notion that elastase inhibition, the only functional factory release criteria for clinical-grade AAT, is over-emphasized. Non-obvious developments in the understanding of AAT biology disqualify it from being a straightforward anti-inflammatory agent: AAT does not block dendritic cell activities, nor does it promote viral and tumour susceptibilities, stunt B lymphocyte responses or render treated patients susceptible to infections; accordingly, outcomes of elevated AAT do not overlap those attained by immunosuppression. Aside from the acute-phase response, AAT rises during the third trimester of pregnancy and also in advanced age. At the molecular level, AAT docks onto cholesterol-rich lipid-rafts and circulating lipid particles, directly binds interleukin (IL)-8, ADAM metallopeptidase domain 17 (ADAM17) and danger-associated molecular pattern (DAMP) molecules, and its activity is lost to smoke, high glucose levels and bacterial proteases, introducing a novel entity - 'relative AAT deficiency'. Unlike immunosuppression, AAT appears to help the immune system to distinguish between desired responses against authentic threats, and unwanted responses fuelled by a positive feedback loop perpetuated by, and at the expense of, inflamed injured innocent bystander cells. With a remarkable clinical safety record, AAT treatment is currently tested in clinical trials for its potential benefit in a variety of categorically distinct pathologies that share at least one common driving force: cell injury.

Acute-Phase Protein α1-Antitrypsin—A Novel Regulator of Angiopoietin-like Protein 4 Transcription and Secretion

The angiopoietin-like protein 4 (angptl4, also known as peroxisome proliferator–activated receptor [PPAR]γ–induced angiopoietin-related protein) is a multifunctional protein associated with acute-phase response. The mechanisms accounting for the increase in angptl4 expression are largely unknown. This study shows that human α1-antitrypsin (A1AT) upregulates expression and release of angplt4 in human blood adherent mononuclear cells and in primary human lung microvascular endothelial cells in a concentration- and time-dependent manner. Mononuclear cells treated for 1 h with A1AT (from 0.1 to 4 mg/ml) increased mRNA of angptl4 from 2- to 174-fold, respectively, relative to controls. In endothelial cells, the maximal effect on angptl4 expression was achieved at 8 h with 2 mg/ml A1AT (11-fold induction versus controls). In 10 emphysema patients receiving A1AT therapy (Prolastin), plasma angptl4 levels were higher relative to patients without therapy (nanograms per milliliter, mean [95% confidence interval] 127.1 [99.5–154.6] versus 76.8 [54.8–98.8], respectively, p = 0.045) and correlated with A1AT levels. The effect of A1AT on angptl4 expression was significantly diminished in cells pretreated with a specific inhibitor of ERK1/2 activation (UO126), irreversible and selective PPARγ antagonist (GW9662), or genistein, a ligand for PPARγ. GW9662 did not alter the ability of A1AT to induce ERK1/2 phosphorylation, suggesting that PPARγ is a critical mediator in the A1AT-driven angptl4 expression. In contrast, the forced accumulation of HIF-1α, an upregulator of angptl4 expression, enhanced the effect of A1AT. Thus, acute-phase protein A1AT is a physiological regulator of angptl4, another acute-phase protein.

RG, Campos M, Petrache I. Active trafficking of alpha 1 antitrypsin across the lung endothelium

The homeostatic lung protective effects of alpha-1 antitrypsin (A1AT) may require the transport of circulating proteinase inhibitor across an intact lung endothelial barrier. We hypothesized that uninjured pulmonary endothelial cells transport A1AT to lung epithelial cells. Purified human A1AT was rapidly taken up by confluent primary rat pulmonary endothelial cell monolayers, was secreted extracellularly, both apically and basolaterally, and was taken up by adjacent rat lung epithelial cells co-cultured on polarized transwells. Similarly, polarized primary human lung epithelial cells took up basolaterally-, but not apically-supplied A1AT, followed by apical secretion. Evidence of A1AT transcytosis across lung microcirculation was confirmed in vivo by two-photon intravital microscopy in mice. Time-lapse confocal microscopy indicated that A1AT co-localized with Golgi in the endothelium whilst inhibition of the classical secretory pathway with tunicamycin significantly increased intracellular retention of A1AT. However, inhibition of Golgi secretion promoted non-classical A1AT secretion, associated with microparticle release. Polymerized A1AT or A1AT supplied to endothelial cells exposed to soluble cigarette smoke extract had decreased transcytosis. These results suggest previously unappreciated pathways of A1AT bidirectional uptake and secretion from lung endothelial cells towards the alveolar epithelium and airspaces. A1AT trafficking may determine its functional bioavailablity in the lung, which could be impaired in individuals exposed to smoking or in those with A1AT deficiency.

α₁-Antitrypsin modulates lung endothelial cell inflammatory responses to TNF-α

α₁-Antitrypsin (A1AT) is an acute-phase reactant, but also a major protective factor against the development of chronic obstructive pulmonary disease, a complex disease with sustained chronic inflammation. The lung-protective effects of A1AT have been attributed to the inhibition of proteases involved in lung matrix fragmentation, macrophage activation, and endothelial-cell apoptosis. More recently, A1AT has been shown to directly interact with or modulate the actions of cytokines such as TNF-α or IL-1 in inflammatory cells, but its effect on the lung endothelium, an active participant in the amplification and resolution of inflammation, has received little attention. An important role of A1AT in modulating lung endothelial inflammatory responses is expected, given the high concentrations of circulating A1AT during inflammation and its active uptake by endothelial cells. We investigated the role of A1AT in primary lung microvascular endothelial cell activation by relevant cytokines such as TNF-α or IL-1β. Despite an initial marked augmentation of TNF-α self-induced transcription, A1AT inhibited TNF-α receptor 1 up-regulation and significantly reduced TNF-α secretion, effects that were associated with inhibition of TNF-α-converting enzyme activity. Furthermore, A1AT inhibited calpain activity, whose activation by TNF-α contributed to decreased intracellular A1AT concentrations. These data indicate that A1AT initially facilitates acute responses of the endothelium to TNF-α, followed by selective inhibition of TNF-α-induced-self amplification, which may assist the vasculature in the resolution of chronic inflammation.

Alpha-1-antitrypsin inhibits nitric oxide production

NO is an endogenously produced gas that regulates inflammation, vascular tone, neurotransmission, and immunity. NO production can be increased by exposing cells to several endogenous and exogenous proinflammatory mediators, including IFN-γ, TNF-α, IL-1β, and LPS. As AAT has been shown to inhibit cell activation and suppress cytokine production associated with proinflammatory stimulation, we examined AAT for NO-suppressive function. In RAW 264.7 murine macrophagic cells, physiological AAT concentrations significantly inhibited combined LPS- and IFN-γ-induced NO synthesis, and NO synthesis inhibition was associated with decreased expression of iNOS, suppressed NF-κB activation, and reduced translocation of extracellular AAT into the interior of RAW 264.7 cells. CE-2072, a synthetic inhibitor of serine proteases, also suppressed NO production, iNOS expression, and NF-κB activation. However, AAT did not alter activation of intracellular MAPKs. In subjects with genetic AAT deficiency, exhaled NO was increased significantly compared with exhaled NO in healthy controls. These in vitro and in vivo studies suggest that AAT is an endogenous inhibitor of NO production. Administering AAT or AAT-like molecules may have use as a treatment for diseases associated with excessive NO production.

Pathogenesis of abdominal aortic aneurysms: role of nicotine and nicotinic acetylcholine receptors

Inflammation, proteolysis, smooth muscle cell apoptosis, and angiogenesis have been implicated in the pathogenesis of abdominal aortic aneurysms (AAAs), although the well-defined initiating mechanism is not fully understood. Matrix metalloproteinases (MMPs) such as MMP-2 and -9 and other proteinases degrading elastin and extracellular matrix are the critical pathogenesis of AAAs. Among the risk factors of AAAs, cigarette smoking is an irrefutable one. Cigarette smoke is practically involved in various aspects of the AAA pathogenesis. Nicotine, a major alkaloid in tobacco leaves and a primary component in cigarette smoke, can stimulate the MMPs expression by vascular SMCs, endothelial cells, and inflammatory cells in vascular wall and induce angiogenesis in the aneurysmal tissues. However, for the inflammatory and apoptotic processes in the pathogenesis of AAAs, nicotine seems to be moving in just the opposite direction. Additionally, the effects of nicotine are probably dose dependent or associated with the exposure duration and may be partly exerted by its receptors—nicotinic acetylcholine receptors (nAChRs). In this paper, we will mainly discuss the pathogenesis of AAAs involving inflammation, proteolysis, smooth muscle cell apoptosis and angiogenesis, and the roles of nicotine and nAChRs.

Autologous carotid artery reconstruction for the extracranial internal carotid artery aneurysm in a patient combined with pulmonary bulla

INTRODUCTION

Aneurysm of the extracranial internal carotid artery (AEICA) is extremely rare catastrophic pathology associated with cerebral embolism and rupture. There was no report on AEICA associated with bullous lung disease.

REPORT

We report a case of AECIA in a 44-year-old female patient combined with asymptomatic pulmonary bulla, and successfully treated by autologous carotid artery reconstruction.

CONCLUSION

The possibility of a relationship between AEICA and bullous lung disease is discussed about the level of alpha 1-antitrypsin (α1-AT). The using of external carotid artery (ECA) replace of the internal carotid artery (ICA) combined with resection of the AEICA is an autologous reconstruction to restore arterial continuity and avoiding the use of synthetic or vein graft with their potential complications.

What can in vitro models of COPD tell us?

Chronic obstructive pulmonary disease (COPD) is a progressive lung disease characterised by chronic bronchitis, largely irreversible remodelling of the small airways, and emphysematous destruction of the alveoli. COPD is projected to be the third leading cause of death worldwide by 2020. COPD often results from prolonged exposure to irritants such as cigarette smoke or inhaled particulates. Current pharmacotherapies for COPD are unable to reverse the pathological changes of this disease, and this is partially due to a limited understanding of the intricate mechanisms by which chronic exposure lead to the different pathological components of COPD. This review examines how the mechanisms that underlie various components of COPD can be modelled in vitro, specifically using cigarette smoke extract with cells cultured from primary human lung tissue, and how the effectiveness of current and novel pharmacotherapies on successfully attenuating these pathological changes can also be examined in vitro.

Cardiovascular and musculskeletal co-morbidities in patients with alpha 1 antitrypsin deficiency

Background

Determining the presence and extent of co-morbidities is fundamental in assessing patients with chronic respiratory disease, where increased cardiovascular risk, presence of osteoporosis and low muscle mass have been recognised in several disease states. We hypothesised that the systemic consequences are evident in a further group of subjects with COPD due to Alpha-1 Antitrypsin Deficiency (A1ATD), yet are currently under-recognised.

Methods

We studied 19 patients with PiZZ A1ATD COPD and 20 age, sex and smoking matched controls, all subjects free from known cardiovascular disease. They underwent spirometry, haemodynamic measurements including aortic pulse wave velocity (aPWV), an independent predictor or cardiovascular risk, dual energy X-ray absorptiometry to determine body composition and bone mineral density.

Results

The aPWV was greater in patients: 9.9(2.1) m/s than controls: 8.5(1.6) m/s, p = 0.03, despite similar mean arterial pressure (MAP). The strongest predictors of aPWV were age, FEV₁% predicted and MAP (all p < 0.01). Osteoporosis was present in 8/19 patients (2/20 controls) and was previously unsuspected in 7 patients. The fat free mass and bone mineral density were lower in patients than controls (p < 0.001).

Conclusions

Patients with A1ATD related COPD have increased aortic stiffness suggesting increased risk of cardiovascular disease and evidence of occult musculoskeletal changes, all likely to contribute hugely to overall morbidity and mortality.

Effects of major human antiprotease alpha-1-antitrypsin on the motility and proliferation of stromal cells from human exfoliated deciduous teeth

AIM

Intrinsic tissue regeneration mechanisms are still not fully understood. The destruction/reconstruction processes are usually in fine balance; however, this can be easily destroyed, for example in the environment of chronic inflammation. One of the major proteins present at the inflammatory sites is the multifunctional protein alpha-1-antitrypsin (AAT). In this study, potential therapeutic effects of this major human antiprotease on progenitor cells are assessed.

MATERIALS & METHODS

Stromal cells from human exfoliated deciduous teeth (SHEDs) were used, which are similar to the mesenchymal stromal cells isolated from other tissues. SHEDs were cultivated in the presence of subphysiological, physiological and inflammatory concentrations of AAT, and their proliferation and motility traits were assayed. Some intracellular signaling pathways, AAT internalization by SHEDs and their matrix metalloprotease profile were studied in parallel.

RESULTS

Physiologic and inflammatory concentrations of AAT significantly increased the cell proliferation rate, induced phosphorylation of several key protein kinases and increased the amount of secreted active gelatinases. Moreover, cells exposed to physiologic and inflammatory levels of AAT were able to invade and migrate more efficiently. Subphysiologic AAT levels did not change cell behavior significantly.

CONCLUSION

AAT at physiologic and inflammatory concentrations positively modulates the proliferation and motility of SHEDs in vitro. These results suggest the importance of AAT in the maintenance and regulation of tissue progenitor cells in vivo.

Proteases and antiproteases in chronic neutrophilic lung disease - relevance to drug discovery

Chronic inflammatory lung diseases such as cystic fibrosis and emphysema are characterized by higher-than-normal levels of pulmonary proteases. While these enzymes play important roles such as bacterial killing, their dysregulated expression or activity can adversely impact on the inflammatory process. The existence of efficient endogenous control mechanisms that can dampen or halt this overexuberant protease activity in vivo is essential for the effective resolution of inflammatory lung disease. The function of pulmonary antiproteases is to fulfil this role. Interestingly, in addition to their antiprotease activity, protease inhibitors in the lung also often possess other intrinsic properties that contribute to microbial killing or termination of the inflammatory process. This review will outline important features of chronic inflammation that are regulated by pulmonary proteases and will describe the various mechanisms by which antiproteases attempt to counterbalance exaggerated protease-mediated inflammatory events. These proteases, antiproteases and their modifiers represent interesting targets for therapeutic intervention.

Mechanism of alpha-1 antitrypsin endocytosis by lung endothelium

The integrity of lung alveoli is maintained by proper circulating levels of alpha-1 antitrypsin (A1AT). Next to cigarette smoking, A1AT deficiency is a major risk factor for lung emphysema development. We recently reported that in addition to neutralizing neutrophil elastases in the extracellular compartment, A1AT is internalized by lung endothelial cells and inhibits apoptosis. We hypothesized that the intracellular uptake of A1AT by endothelial cells may be required for its protective function; therefore, we studied the mechanisms of A1AT internalization by primary rat lung microvascular endothelial cells and the effect of cigarette smoke on this process both in vitro and in vivo (in mice). Purified A1AT was taken up intracellularly by endothelial cells in a time-dependent, dose-dependent, and conformer-specific manner and was detected in the cytoplasm of endothelial cells of nondiseased human lung sections. Despite a critical role for caveoli in endothelial cell endocytosis in general, specific inhibition of clathrin-mediated, but not caveoli-mediated, endocytosis profoundly decreased A1AT internalization and reversed the A1AT's antiapoptotic action. Further more, A1AT associated with clathrin heavy chains, but not with caveolin-1 in the plasma membrane fraction of endothelial cells. Interestingly, cigarette smoke exposure significantly inhibited A1AT uptake both in endothelial cells and in the mouse lung and altered the intracellular distribution of clathrin heavy chains. Our results suggest that clathrin-mediated endocytosis regulates A1AT intracellular function in the lung endothelium and may be an important determinant of the serpin's protection against developing cigarette smoke-induced emphysema.

Safety and efficacy of alpha-1-antitrypsin augmentation therapy in the treatment of patients with alpha-1-antitrypsin deficiency

Alpha-1-antitrypsin deficiency (AATD), also known as alpha1-proteinase inhibitor deficiency, is an autosomal co-dominant condition. The genotypes associated with AATD include null, deficient, and dysfunctional alpha-1-antitrypsin (A1AT) variants, which result in low levels of circulating functional A1AT, unbalanced protease activity, and an increased risk of developing lung emphysema, the leading cause of morbidity in these patients. Furthermore, the most common abnormal genotype, Pi*ZZ may also cause trapping of abnormally folded protein polymers in hepatocytes causing liver dysfunction. A major focus of therapy for patients with lung disease due to AATD is to correct the A1AT deficiency state by augmenting serum levels with intravenous infusions of human plasma-derived A1AT. This strategy has been associated with effective elevations of A1AT levels and function in serum and lung epithelial fluid and observational studies suggest that it may lead to attenuation in lung function decline, particularly in patients with moderate impairment of lung function. In addition, an observational study suggests that augmentation therapy is associated with a reduction of mortality in subjects with AATD and moderate to severe lung impairment. More recent randomized placebo-controlled studies utilizing computer scan densitometry suggest that this therapy attenuates lung tissue loss. Augmentation therapy has a relative paucity of side effects, but it is highly expensive. Therefore, this therapy is recommended for patients with AATD who have a high-risk A1AT genotype with plasma A1AT below protective levels (11 μM) and evidence of obstructive lung disease. In this article, we review the published evidence of A1AT augmentation therapy efficacy, side effects, and safety profile.

HDL antielastase activity prevents smooth muscle cell anoikis, a potential new antiatherogenic property

Various studies using proteomic approaches have shown that HDL can carry many proteins other than its constitutive apolipoprotein A-I (apoA-I). Using mass spectrometry and Western blotting, we showed the presence of alpha(1)-antitrypsin (AAT) (SERPINA1, serpin peptidase inhibitor, clade A, an elastase inhibitor) in HDL, isolated either by ultracentrifugation or by selected-affinity immunosorption using an anti-apoA-I column. Furthermore, we report that HDL possesses potent antielastase activity. We further showed that only HDL but not LDL is able to bind AAT. HDL-associated AAT was able to inhibit extracellular matrix degradation, cell detachment, and apoptosis induced by elastase in human vascular smooth muscle cells (VSMCs) and in mammary artery cultured ex vivo. Degradation of fibronectin by elastase used as a marker of pericellular proteolysis was prevented by addition of HDL. Elastase present in aortic abdominal aneurysm (AAA) thrombus samples was also able to induce apoptosis of VSMCs in culture. This phenomenon was prevented by addition of HDL but not of LDL. Finally, we report that the proportion of AAT in HDL isolated from patients with an AAA is decreased relative to that from matched control subjects, suggesting a reduced capacity of HDL to inhibit elastase in these patients. In conclusion, our data provide evidence of a new potential antiatherogenic property of HDL attributable to AAT and its antielastase activity.