Alpha-1 antitrypsin reduces severity of pseudomonas pneumonia in mice and inhibits epithelial barrier disruption and pseudomonas invasion of respiratory epithelial cells

Alpha-1 antitrypsin targeted neutrophil elastase protects against sepsis-induced inflammation and coagulation in mice via inhibiting neutrophil extracellular trap formation

AIMS

Sepsis pathophysiology is complex and identifying effective treatments for sepsis remains challenging. The study aims to identify effective drugs and targets for sepsis through transcriptomic analysis of sepsis patients, repositioning analysis of compounds, and validation by animal models.

MAIN METHODS

GSE185263 obtained from the GEO database that includes gene expression profiles of 44 healthy controls and 348 sepsis patients categorized by severity. Bioinformatic algorithms revealed the molecular, function, and immune characteristics of the sepsis, and constructed sepsis-related protein-protein interaction networks. Subsequently, Random Walk with Restart analysis was applied to identify candidate drugs for sepsis, which were tested in animal models for survival, inflammation, coagulation, and multi-organ damage.

KEY FINDINGS

Our analysis found 1862 genes linked to sepsis development, enriched in functions like neutrophil extracellular trap formation (NETs) and complement/coagulation cascades. With disease progression, immune activation-associated cells were inhibited, while immune suppression-associated cells were activated. Next, the drug repositioning method identified candidate drugs, such as alpha-1 antitrypsin, that may play a therapeutic role by targeting neutrophil elastase (NE) to inhibit NETs. Animal experiments proved that alpha-1 antitrypsin treatment can improve the survival rate, reduce sepsis score, reduce the levels of inflammation markers in serum, and alleviate muti-organ morphological damage in mice with sepsis. The further results showed that α-1 antitrypsin can inhibit the NETs by suppressing the NE for the treatment of sepsis.

SIGNIFICANCE

Alpha-1 antitrypsin acted on the NE to inhibit NETs thereby protecting mice from sepsis-induced inflammation and coagulation.

Alpha1-antitrypsin improves survival in murine abdominal sepsis model by decreasing inflammation and sequestration of free heme

Background

Excessive inflammation, hemolysis, and accumulation of labile heme play an essential role in the pathophysiology of multi-organ dysfunction syndrome (MODS) in sepsis. Alpha1-antitrypsin (AAT), an acute phase protein with heme binding capacity, is one of the essential modulators of host responses to inflammation. In this study, we evaluate the putative protective effect of AAT against MODS and mortality in a mouse model of polymicrobial abdominal sepsis.

Methods

Polymicrobial abdominal sepsis was induced in C57BL/6N mice by cecal ligation and puncture (CLP). Immediately after CLP surgery, mice were treated intraperitoneally with three different forms of human AAT-plasma-derived native (nAAT), oxidized nAAT (oxAAT), or recombinant AAT (recAAT)-or were injected with vehicle. Sham-operated mice served as controls. Mouse survival, bacterial load, kidney and liver function, immune cell profiles, cytokines/chemokines, and free (labile) heme levels were assessed. In parallel, in vitro experiments were carried out with resident peritoneal macrophages (MPMΦ) and mouse peritoneal mesothelial cells (MPMC).

Results

All AAT preparations used reduced mortality in septic mice. Treatment with AAT significantly reduced plasma lactate dehydrogenase and s-creatinine levels, vascular leakage, and systemic inflammation. Specifically, AAT reduced intraperitoneal accumulation of free heme, production of cytokines/chemokines, and neutrophil infiltration into the peritoneal cavity compared to septic mice not treated with AAT. In vitro experiments performed using MPMC and primary MPMΦ confirmed that AAT not only significantly decreases lipopolysaccharide (LPS)-induced pro-inflammatory cell activation but also prevents the enhancement of cellular responses to LPS by free heme. In addition, AAT inhibits cell death caused by free heme in vitro.

Conclusion

Data from the septic CLP mouse model suggest that intraperitoneal AAT treatment alone is sufficient to improve sepsis-associated organ dysfunctions, preserve endothelial barrier function, and reduce mortality, likely by preventing hyper-inflammatory responses and by neutralizing free heme.

Alpha-1 antitrypsin inhibits fractalkine-mediated monocyte-lung endothelial cell interactions

Chronic obstructive pulmonary disease (COPD) is characterized by nonresolving inflammation fueled by breach in the endothelial barrier and leukocyte recruitment into the airspaces. Among the ligand-receptor axes that control leukocyte recruitment, the full-length fractalkine ligand (CX3CL1)-receptor (CX3CR1) ensures homeostatic endothelial-leukocyte interactions. Cigarette smoke (CS) exposure and respiratory pathogens increase expression of endothelial sheddases, such as a-disintegrin-and-metalloproteinase-domain 17 (ADAM17, TACE), inhibited by the anti-protease α-1 antitrypsin (AAT). In the systemic endothelium, TACE cleaves CX3CL1 to release soluble CX3CL1 (sCX3CL1). During CS exposure, it is not known whether AAT inhibits sCX3CL1 shedding and CX3CR1+ leukocyte transendothelial migration across lung microvasculature. We investigated the mechanism of sCX3CL1 shedding, its role in endothelial-monocyte interactions, and AAT effect on these interactions during acute inflammation. We used two, CS and lipopolysaccharide (LPS) models of acute inflammation in transgenic Cx3cr1gfp/gfp mice and primary human endothelial cells and monocytes to study sCX3CL1-mediated CX3CR1+ monocyte adhesion and migration. We measured sCX3CL1 levels in plasma and bronchoalveolar lavage (BALF) of individuals with COPD. Both sCX3CL1 shedding and CX3CR1+ monocytes transendothelial migration were triggered by LPS and CS exposure in mice, and were significantly attenuated by AAT. The inhibition of monocyte-endothelial adhesion and migration by AAT was TACE-dependent. Compared with healthy controls, sCX3CL1 levels were increased in plasma and BALF of individuals with COPD, and were associated with clinical parameters of emphysema. Our results indicate that inhibition of sCX3CL1 as well as AAT augmentation may be effective approaches to decrease excessive monocyte lung recruitment during acute and chronic inflammatory states.NEW & NOTEWORTHY Our novel findings that AAT and other inhibitors of TACE, the sheddase that controls full-length fractalkine (CX3CL1) endothelial expression, may provide fine-tuning of the CX3CL1-CX3CR1 axis specifically involved in endothelial-monocyte cross talk and leukocyte recruitment to the alveolar space, suggests that AAT and inhibitors of sCX3CL1 signaling may be harnessed to reduce lung inflammation.

AAT: does it have a place in acute leukemia?

Aim: In this study, the authors aimed to investigate the change of AAT, its effect on the response to induction and its effects on the treatment process in acute myeloid leukemia and acute lymphoblastic leukemia patients. Materials & methods: This study included 94 patients who were hospitalized and followed up in Istanbul Training and Research Hospital, Hematology Clinic, between October 2019 and December 2021. Results: Patients with a complete response had higher serum AAT levels than those with a non-complete response (p < 0.05). The mean serum AAT level was found to be significantly higher in patients without Gram-positive growth than in patients with Gram-positive growth. Conclusion: It can be thought that AAT can play a role during the course of acute leukemia management.

A comprehensive overview of investigational elastase inhibitors for the treatment of acute respiratory distress syndrome

INTRODUCTION

Excessive activity of neutrophil elastase (NE), the main enzyme present in azurophil granules in the neutrophil cytoplasm, may cause tissue injury and remodeling in various lung diseases, including acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), in which it is crucial to the immune response and inflammatory process. Consequently, NE is a possible target for therapeutic intervention in ALI/ARDS.

AREAS COVERED

The protective effects of several NE inhibitors in attenuating ALI/ARDS in several models of lung injury are described. Some of these NE inhibitors are currently in clinical development, but only sivelestat has been evaluated as a treatment for ALI/ARDS.

EXPERT OPINION

Preclinical research has produced encouraging information about using NE inhibitors. Nevertheless, only sivelestat has been approved for this clinical indication, and only in Japan and South Korea because of the conflicting results of clinical trials and likely also because of the potential adverse events. Identifying subsets of patients with ARDS most likely to benefit from NE inhibitor treatment, such as the hyperinflammatory phenotype, and using a more advanced generation of NE inhibitors than sivelestat could enable better clinical results than those obtained with elastase inhibitors.

Alpha-1-antitrypsin antagonizes COVID-19: a review of the epidemiology, molecular mechanisms, and clinical evidence

Alpha-1-antitrypsin (AAT), a serine protease inhibitor (serpin), is increasingly recognized to inhibit SARS-CoV-2 infection and counter many of the pathogenic mechanisms of COVID-19. Herein, we reviewed the epidemiologic evidence, the molecular mechanisms, and the clinical evidence that support this paradigm. As background to our discussion, we first examined the basic mechanism of SARS-CoV-2 infection and contend that despite the availability of vaccines and anti-viral agents, COVID-19 remains problematic due to viral evolution. We next underscored that measures to prevent severe COVID-19 currently exists but teeters on a balance and that current treatment for severe COVID-19 remains grossly suboptimal. We then reviewed the epidemiologic and clinical evidence that AAT deficiency increases risk of COVID-19 infection and of more severe disease, and the experimental evidence that AAT inhibits cell surface transmembrane protease 2 (TMPRSS2) - a host serine protease required for SARS-CoV-2 entry into cells - and that this inhibition may be augmented by heparin. We also elaborated on the panoply of other activities of AAT (and heparin) that could mitigate severity of COVID-19. Finally, we evaluated the available clinical evidence for AAT treatment of COVID-19.

Circulating oxidative stress and acute phase protein levels in horses infested with ticks

Ticks have saliva rich in immunoregulatory molecules that interfere with the host's physiology in order to feed. This study aimed to evaluate the concentration of acute phase proteins and circulating oxidative stress in response to infestation by Amblyomma sculptum and Dermacentor nitens in two breed horses, Mangalarga Marchador and Breton Postier, to define resistance or susceptibility to ticks. Among the oxidative stress markers, we observed lower malondialdehyde and nitric oxide in horses with tick infestation, consequently not altering the antioxidant enzymes. Breton Postier with tick infestation showed a reduction in the ferric reducing ability of plasma (FRAP), which may be due to lower feeding of the host due to the stress caused by the infestation or even to sequestration of components induced by the tick during blood feeding. The alpha-1-antitrypsin, an acute phase protein, showed an increase in Mangalarga Marchador with tick infestation; curiously it is related to a protective action against tissue damage, pathogens and parasites. We could assume that Mangalarga Marchador showed a better response to ticks when compared to Breton Postier. However, it is still early to define the resistance or susceptibility to ticks, as we did not observe significant changes in most of the analyzed variables. Further studies are needed to understand the compounds and mechanisms of action of the tick saliva in the acute phase proteins and the possible relationships of oxidative stress in the host and the tick during blood feeding.

Synthetic neutrophil extracellular traps dissect bactericidal contribution of NETs under regulation of α-1-antitrypsin

Deciphering the complex interplay of neutrophil extracellular traps (NETs) with the surrounding environment is a challenge with notable clinical implications. To bridge the gap in knowledge, we report our findings on the antibacterial activity against Pseudomonas aeruginosa of synthetic NET-mimetic materials composed of nanofibrillated DNA-protein complexes. Our synthetic system makes component-by-component bottom-up analysis of NET protein effects possible. When the antimicrobial enzyme neutrophil elastase (NE) is incorporated into the bactericidal DNA-histone complexes, the resulting synthetic NET-like structure exhibits an unexpected reduction in antimicrobial activity. This critical immune function is rescued upon treatment with alpha-1-antitrypsin (AAT), a physiological tissue-protective protease inhibitor. This suggests a direct causal link between AAT inhibition of NE and preservation of histone-mediated antimicrobial activity. These results help better understand the complex and, at times, contradictory observations of in vivo antimicrobial effects of NETs and AAT by excluding neutrophil, cytokine, and chemoattractant contributions.

α1-Antitrypsin Binds to the Glucocorticoid Receptor with Anti-Inflammatory and Antimycobacterial Significance in Macrophages

α1-Antitrypsin (AAT), a serine protease inhibitor, is the third most abundant protein in plasma. Although the best-known function of AAT is irreversible inhibition of elastase, AAT is an acute-phase reactant and is increasingly recognized to have a panoply of other functions, including as an anti-inflammatory mediator and a host-protective molecule against various pathogens. Although a canonical receptor for AAT has not been identified, AAT can be internalized into the cytoplasm and is known to affect gene regulation. Because AAT has anti-inflammatory properties, we examined whether AAT binds the cytoplasmic glucocorticoid receptor (GR) in human macrophages. We report the finding that AAT binds to GR using several approaches, including coimmunoprecipitation, mass spectrometry, and microscale thermophoresis. We also performed in silico molecular modeling and found that binding between AAT and GR has a plausible stereochemical basis. The significance of this interaction in macrophages is evinced by AAT inhibition of LPS-induced NF-κB activation and IL-8 production as well as AAT induction of angiopoietin-like 4 protein, which are, in part, dependent on GR. Furthermore, this AAT-GR interaction contributes to a host-protective role against mycobacteria in macrophages. In summary, this study identifies a new mechanism for the gene regulation, anti-inflammatory, and host-defense properties of AAT.

Bitter taste signaling in tracheal epithelial brush cells elicits innate immune responses to bacterial infection

Constant exposure of the airways to inhaled pathogens requires efficient early immune responses protecting against infections. How bacteria on the epithelial surface are detected and first-line protective mechanisms are initiated are not well understood. We have recently shown that tracheal brush cells (BCs) express functional taste receptors. Here we report that bitter taste signaling in murine BCs induces neurogenic inflammation. We demonstrate that BC signaling stimulates adjacent sensory nerve endings in the trachea to release the neuropeptides CGRP and substance P that mediate plasma extravasation, neutrophil recruitment, and diapedesis. Moreover, we show that bitter tasting quorum-sensing molecules from Pseudomonas aeruginosa activate tracheal BCs. BC signaling depends on the key taste transduction gene Trpm5, triggers secretion of immune mediators, among them the most abundant member of the complement system, and is needed to combat P. aeruginosa infections. Our data provide functional insight into first-line defense mechanisms against bacterial infections of the lung.

Enoxaparin augments alpha-1-antitrypsin inhibition of TMPRSS2, a promising drug combination against COVID-19

The cell surface serine protease Transmembrane Protease 2 (TMPRSS2) is required to cleave the spike protein of SARS-CoV-2 for viral entry into cells. We determined whether negatively-charged heparin enhanced TMPRSS2 inhibition by alpha-1-antitrypsin (AAT). TMPRSS2 activity was determined in HEK293T cells overexpressing TMPRSS2. We quantified infection of primary human airway epithelial cells (hAEc) with human coronavirus 229E (HCoV-229E) by immunostaining for the nucleocapsid protein and by the plaque assay. Detailed molecular modeling was undertaken with the heparin-TMPRSS2-AAT ternary complex. Enoxaparin enhanced AAT inhibition of both TMPRSS2 activity and infection of hAEc with HCoV-229E. Underlying these findings, detailed molecular modeling revealed that: (i) the reactive center loop of AAT adopts an inhibitory-competent conformation compared with the crystal structure of TMPRSS2 bound to an exogenous (nafamostat) or endogenous (HAI-2) TMPRSS2 inhibitor and (ii) negatively-charged heparin bridges adjacent electropositive patches at the TMPRSS2-AAT interface, neutralizing otherwise repulsive forces. In conclusion, enoxaparin enhances AAT inhibition of both TMPRSS2 and coronavirus infection. Such host-directed therapy is less likely to be affected by SARS-CoV-2 mutations. Furthermore, given the known anti-inflammatory activities of both AAT and heparin, this form of treatment may target both the virus and the excessive inflammatory consequences of severe COVID-19.

Ceruletide and Alpha-1 Antitrypsin as a Novel Combination Therapy for Ischemic Stroke

Ischemic stroke is a primary cause of morbidity and mortality worldwide. Beyond the approved thrombolytic therapies, there is no effective treatment to mitigate its progression. Drug repositioning combinational therapies are becoming promising approaches to identify new uses of existing drugs to synergically target multiple disease-response mechanisms underlying complex pathologies. Here, we used a systems biology-based approach based on artificial intelligence and pattern recognition tools to generate in silico mathematical models mimicking the ischemic stroke pathology. Combinational treatments were acquired by screening these models with more than 5 million two-by-two combinations of drugs. A drug combination (CA) formed by ceruletide and alpha-1 antitrypsin showing a predicted value of neuroprotection of 92% was evaluated for their synergic neuroprotective effects in a mouse pre-clinical stroke model. The administration of both drugs in combination was safe and effective in reducing by 39.42% the infarct volume 24 h after cerebral ischemia. This neuroprotection was not observed when drugs were given individually. Importantly, potential incompatibilities of the drug combination with tPA thrombolysis were discarded in vitro and in vivo by using a mouse thromboembolic stroke model with t-PA-induced reperfusion, revealing an improvement in the forepaw strength 72 h after stroke in CA-treated mice. Finally, we identified the predicted mechanisms of action of ceruletide and alpha-1 antitrypsin and we demonstrated that CA modulates EGFR and ANGPT-1 levels in circulation within the acute phase after stroke. In conclusion, we have identified a promising combinational treatment with neuroprotective effects for the treatment of ischemic stroke.

Correlation between α1-Antitrypsin Deficiency and SARS-CoV-2 Infection: Epidemiological Data and Pathogenetic Hypotheses

The most common hereditary disorder in adults, α1-antitrypsin deficiency (AATD), is characterized by reduced plasma levels or the abnormal functioning of α1-antitrypsin (AAT), a major human blood serine protease inhibitor, which is encoded by the SERine Protein INhibitor-A1 (SERPINA1) gene and produced in the liver. Recently, it has been hypothesized that the geographic differences in COVID-19 infection and fatality rates may be partially explained by ethnic differences in SERPINA1 allele frequencies. In our review, we examined epidemiological data on the correlation between the distribution of AATD, SARS-CoV-2 infection, and COVID-19 mortality rates. Moreover, we described shared pathogenetic pathways that may provide a theoretical basis for our epidemiological findings. We also considered the potential use of AAT augmentation therapy in patients with COVID-19.

α1-Antitrypsin: Key Player or Bystander in Acute Respiratory Distress Syndrome?

Acute respiratory distress syndrome is characterized by hypoxemia, altered alveolar-capillary permeability, and neutrophil-dominated inflammatory pulmonary edema. Despite decades of research, an effective drug therapy for acute respiratory distress syndrome remains elusive. The ideal pharmacotherapy for acute respiratory distress syndrome should demonstrate antiprotease activity and target injurious inflammatory pathways while maintaining host defense against infection. Furthermore, a drug with a reputable safety profile, low possibility of off-target effects, and well-known pharmacokinetics would be desirable. The endogenous 52-kd serine protease α1-antitrypsin has the potential to be a novel treatment option for acute respiratory distress syndrome. The main function of α1-antitrypsin is as an antiprotease, targeting neutrophil elastase in particular. However, studies have also highlighted the role of α1-antitrypsin in the modulation of inflammation and bacterial clearance. In light of the current SARS-CoV-2 pandemic, the identification of a treatment for acute respiratory distress syndrome is even more pertinent, and α1-antitrypsin has been implicated in the inflammatory response to SARS-CoV-2 infection.

Treatment with a neutrophil elastase inhibitor and ofloxacin reduces P. aeruginosa burden in a mouse model of chronic suppurative otitis media

Chronic suppurative otitis media (CSOM) is a widespread, debilitating problem with poorly understood immunology. Here, we assess the host response to middle ear infection over the course of a month post-infection in a mouse model of CSOM and in human subjects with the disease. Using multiparameter flow cytometry and a binomial generalized linear machine learning model, we identified Ly6G, a surface marker of mature neutrophils, as the most informative factor of host response driving disease in the CSOM mouse model. Consistent with this, neutrophils were the most abundant cell type in infected mice and Ly6G expression tracked with the course of infection. Moreover, neutrophil-specific immunomodulatory treatment using the neutrophil elastase inhibitor GW 311616A significantly reduces bacterial burden relative to ofloxacin-only treated animals in this model. The levels of dsDNA in middle ear effusion samples are elevated in both humans and mice with CSOM and decreased during treatment, suggesting that dsDNA may serve as a molecular biomarker of treatment response. Together these data strongly implicate neutrophils in the ineffective immune response to P. aeruginosa infection in CSOM and suggest that immunomodulatory strategies may benefit drug-tolerant infections for chronic biofilm-mediated disease.

Hypothesis: Alpha-1-antitrypsin is a promising treatment option for COVID-19

No definitive treatment for COVID-19 exists although promising results have been reported with remdesivir and glucocorticoids. Short of a truly effective preventive or curative vaccine against SARS-CoV-2, it is becoming increasingly clear that multiple pathophysiologic processes seen with COVID-19 as well as SARS-CoV-2 itself should be targeted. Because alpha-1-antitrypsin (AAT) embraces a panoply of biologic activities that may antagonize several pathophysiologic mechanisms induced by SARS-CoV-2, we hypothesize that this naturally occurring molecule is a promising agent to ameliorate COVID-19. We posit at least seven different mechanisms by which AAT may alleviate COVID-19. First, AAT is a serine protease inhibitor (SERPIN) shown to inhibit TMPRSS-2, the host serine protease that cleaves the spike protein of SARS-CoV-2, a necessary preparatory step for the virus to bind its cell surface receptor ACE2 to gain intracellular entry. Second, AAT has anti-viral activity against other RNA viruses HIV and influenza as well as induces autophagy, a known host effector mechanism against MERS-CoV, a related coronavirus that causes the Middle East Respiratory Syndrome. Third, AAT has potent anti-inflammatory properties, in part through inhibiting both nuclear factor-kappa B (NFκB) activation and ADAM17 (also known as tumor necrosis factor-alpha converting enzyme), and thus may dampen the hyper-inflammatory response of COVID-19. Fourth, AAT inhibits neutrophil elastase, a serine protease that helps recruit potentially injurious neutrophils and implicated in acute lung injury. AAT inhibition of ADAM17 also prevents shedding of ACE2 and hence may preserve ACE2 inhibition of bradykinin, reducing the ability of bradykinin to cause a capillary leak in COVID-19. Fifth, AAT inhibits thrombin, and venous thromboembolism and in situ microthrombi and macrothrombi are increasingly implicated in COVID-19. Sixth, AAT inhibition of elastase can antagonize the formation of neutrophil extracellular traps (NETs), a complex extracellular structure comprised of neutrophil-derived DNA, histones, and proteases, and implicated in the immunothrombosis of COVID-19; indeed, AAT has been shown to change the shape and adherence of non-COVID-19-related NETs. Seventh, AAT inhibition of endothelial cell apoptosis may limit the endothelial injury linked to severe COVID-19-associated acute lung injury, multi-organ dysfunction, and pre-eclampsia-like syndrome seen in gravid women. Furthermore, because both NETs formation and the presence of anti-phospholipid antibodies are increased in both COVID-19 and non-COVID pre-eclampsia, it suggests a similar vascular pathogenesis in both disorders. As a final point, AAT has an excellent safety profile when administered to patients with AAT deficiency and is dosed intravenously once weekly but also comes in an inhaled preparation. Thus, AAT is an appealing drug candidate to treat COVID-19 and should be studied.

Exacerbations of Lung Disease in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) is an important risk factor for development of chronic obstructive pulmonary disease (COPD). Patients with AATD classically develop a different pattern of lung disease from those with usual COPD, decline faster and exhibit a range of differences in pathogenesis, all of which may be relevant to phenotype and/or impact of exacerbations. There are a number of definitions of exacerbation, with the main features being worsening of symptoms over at least 2 days, which may be associated with a change in treatment. In this article we review the literature surrounding exacerbations in AATD, focusing, in particular, on ways in which they may differ from such events in usual COPD, and the potential impact on clinical management.

Granulocyte-targeted therapies for airway diseases

The average respiration rate for an adult is 12-20 breaths per minute, which constantly exposes the lungs to allergens and harmful particles. As a result, respiratory diseases, which includes asthma, chronic obstructive pulmonary disease (COPD) and acute lower respiratory tract infections (LTRI), are a major cause of death worldwide. Although asthma, COPD and LTRI are distinctly different diseases with separate mechanisms of disease progression, they do share a common feature - airway inflammation with intense recruitment and activation of granulocytes and mast cells. Neutrophils, eosinophils, basophils, and mast cells are crucial players in host defense against pathogens and maintenance of lung homeostasis. Upon contact with harmful particles, part of the pulmonary defense mechanism is to recruit these cells into the airways. Despite their protective nature, overactivation or accumulation of granulocytes and mast cells in the lungs results in unwanted chronic airway inflammation and damage. As such, understanding the bright and the dark side of these leukocytes in lung physiology paves the way for the development of therapies targeting this important mechanism of disease. Here we discuss the role of granulocytes in respiratory diseases and summarize therapeutic strategies focused on granulocyte recruitment and activation in the lungs.

Human serum proteins bind to Sporothrix schenckii conidia with differential effects on phagocytosis

Serum is an important source of proteins that interact with pathogens. Once bound to the cell surface, serum proteins can stimulate the innate immune system. The phagocytosis of Sporothrix schenckii conidia by human macrophages is activated through human serum opsonisation. In this study, we have attempted to characterise human blood serum proteins that bind to the cell wall of S. schenckii conidia. We systematically observed the same four proteins independent of the plasma donor: albumin, serum amyloid protein (SAP), α-1 antitrypsin (AAT), and transferrin were identified with the help of tandem mass spectrometry. Phagocytosis depended on the concentration of the SAP or α-1 antitrypsin that was used to opsonise the conidia; however, transferrin or albumin did not have any effect on conidia internalisation. The presence of mannose did not affect macrophage phagocytosis of the conidia opsonised with SAP or α-1 antitrypsin, which suggests that these proteins are not recognised by the mannose receptor.

Alpha-1-Antitrypsin Deficiency and Bronchiectasis: A Concomitance or a Real Association?

Alpha-1-antitrypsin deficiency (AATd) is a hereditary disease, mainly characterized by early onset and the lower lobes' predominant emphysema. Bronchiectasis is characterized by dilatation of the bronchial wall and a clinical syndrome whose features are a cough, sputum production and frequent respiratory exacerbations. In the literature, there are many papers concerning these two clinical entities, but there is still a lot of debate about a possible association between them, in particular about the frequency of their association and causal links. The aim of this short communication is to show the literature reports about the association between AATd and bronchiectasis to establish the state of the art and possible future developments in this research field.

Antithrombin plus alpha-1 protease inhibitor does not affect coagulation and inflammation in two murine models of acute lung injury

Background

In acute respiratory distress syndrome (ARDS), uncontrolled production of activators of coagulation and proinflammatory mediators results in a shift from an adequate local innate immune response to hypercoagulability and inflammation. This study aimed to investigate whether the protease inhibitors antithrombin (AT) and alpha-1 protease inhibitor (A1PI) may attenuate an exaggerated pulmonary immune response.

Methods

Lung injury was induced either by single intranasal administration of lipopolysaccharide (LPS) (5 mg/kg) in BALB/c mice or by combination of an intravenous injection of LPS (10 mg/kg) with subsequent injurious ventilation using high tidal volumes (12–15 ml/kg) for 4 h in RccHan Wistar rats. Animals received either a single bolus of AT (250 IU/kg) or A1PI (60 mg/kg) alone or in combination, with or without intravenous low-dose heparin (100 U/kg). Control animals received saline. Additional controls received neither LPS, nor ventilation, nor treatment. Endpoints were local and systemic markers of coagulation, e.g., thrombin–antithrombin complexes (TATc), and inflammation, e.g., interleukin-6.

Results

Both lung injury models resulted in a pronounced immune response within the pulmonary compartment shown by elevated levels of markers of coagulation and inflammation. The two-hit lung injury model also induced profound systemic coagulopathy and inflammation. Monotherapy with AT or A1PI did not reduce pulmonary coagulopathy or inflammation in any lung injury model. Nor did combination therapy with AT and A1PI result in a decrease of coagulation or inflammatory parameters. AT markedly reduced systemic levels of TATc in the two-hit lung injury model. Systemic inflammation was not affected by the different interventions. Additional administration of heparin did not lead to macroscopic bleeding incidences.

Conclusions

In two different murine models of acute lung injury, neither single therapy with AT or A1PI nor combination of both agents attenuates the pronounced pulmonary coagulation or inflammatory response.

Alpha-1-Antitrypsin Enhances Primary Human Macrophage Immunity Against Non-tuberculous Mycobacteria

Rationale: The association between non-tuberculous mycobacterial lung disease and alpha-1-antitrypsin (AAT) deficiency is likely due, in part, to underlying emphysema or bronchiectasis. But there is increasing evidence that AAT itself enhances host immunity against microbial pathogens and thus deficiency could compromise host protection.

Objectives: The goal of this project is to determine if AAT could augment macrophage activity against non-tuberculous mycobacteria.

Methods: We compared the ability of monocyte-derived macrophages cultured in autologous plasma that were obtained immediately before and soon after AAT infusion—given to individuals with AAT deficiency—to control an ex vivo Mycobacterium intracellulare infection.

Measurements and Main Results: We found that compared to pre-AAT infused monocyte-derived macrophages plus plasma, macrophages, and contemporaneous plasma obtained after a session of AAT infusion were significantly better able to control M. intracellulare infection; the reduced bacterial burden was linked with greater phagosome-lysosome fusion and increased autophagosome formation/maturation, the latter due to AAT inhibition of both M. intracellulare–induced nuclear factor-kappa B activation and A20 expression. While there was a modest increase in apoptosis in the M. intracellulare-infected post-AAT infused macrophages and plasma, inhibiting caspase-3 in THP-1 cells, monocyte-derived macrophages, and alveolar macrophages unexpectedly reduced the M. intracellulare burden, indicating that apoptosis impairs macrophage control of M. intracellulare and that the host protective effects of AAT occurred despite inducing apoptosis.

Conclusion: AAT augments macrophage control of M. intracellulare infection through enhancing phagosome-lysosome fusion and autophagy.

Alpha-1 Antitrypsin Substitution for Extrapulmonary Conditions in Alpha-1 Antitrypsin Deficient Patients

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder which most commonly manifests as pulmonary emphysema. Accordingly, alpha-1 antitrypsin (AAT) augmentation therapy aims to reduce the progression of emphysema, as achieved by life-long weekly slow-drip infusions of plasma-derived affinity-purified human AAT. However, not all AATD patients will receive this therapy, due to either lack of medical coverage or low patient compliance. To circumvent these limitations, attempts are being made to develop lung-directed therapies, including inhaled AAT and locally-delivered AAT gene therapy. Lung transplantation is also an ultimate therapy option. Although less common, AATD patients also present with disease manifestations that extend beyond the lung, including vasculitis, diabetes and panniculitis, and appear to experience longer and more frequent hospitalization times and more frequent pneumonia bouts. In the past decade, new mechanism-based clinical indications for AAT therapy have surfaced, depicting a safe, anti-inflammatory, immunomodulatory and tissue-protective agent. Introduced to non-AATD individuals, AAT appears to provide relief from steroid-refractory graft-versus-host disease, from bacterial infections in cystic fibrosis and from autoimmune diabetes; preclinical studies show benefit also in multiple sclerosis, ulcerative colitis, rheumatoid arthritis, acute myocardial infarction and stroke, as well as ischemia-reperfusion injury and aberrant wound healing processes. While the current augmentation therapy is targeted towards treatment of emphysema, it is suggested that AATD patients may benefit from AAT augmentation therapy geared towards extrapulmonary pathologies as well. Thus, development of mechanism-based, context-specific AAT augmentation therapy protocols is encouraged. In the current review, we will discuss extrapulmonary manifestations of AATD and the potential of AAT augmentation therapy for these conditions.

Neutrophil Fates in Bronchiectasis and Alpha-1 Antitrypsin Deficiency

The neutrophil is a powerful cellular defender of the vulnerable interface between the environment and pulmonary tissues. This cell's potent weapons are carefully calibrated in the healthy state to maximize effectiveness in fighting pathogens while minimizing tissue damage and allowing for repair of what damage does occur. The three related chronic airway disorders of cystic fibrosis, non-cystic fibrosis bronchiectasis, and alpha-1 antitrypsin deficiency all demonstrate significant derangements of this homeostatic system that result in their respective pathologies. An important shared feature among them is the inefficient resolution of chronic inflammation that serves as a central means for neutrophil-driven lung damage resulting in disease progression. Examining the commonalities and divergences between these diseases in the light of their immunopathology is informative and may help guide us toward future therapeutics designed to modulate the neutrophil's interplay with the pulmonary environment.

Alpha-1 antitrypsin supplementation improves alveolar macrophages efferocytosis and phagocytosis following cigarette smoke exposure

Cigarette smoking (CS), the main risk factor for COPD (chronic obstructive pulmonary disease) in developed countries, decreases alveolar macrophages (AM) clearance of both apoptotic cells and bacterial pathogens. This global deficit of AM engulfment may explain why active smokers have worse outcomes of COPD exacerbations, episodes characterized by airway infection and inflammation that carry high morbidity and healthcare cost. When administered as intravenous supplementation, the acute phase-reactant alpha-1 antitrypsin (A1AT) reduces the severity of COPD exacerbations in A1AT deficient (AATD) individuals and of bacterial pneumonia in murine models, but the effect of A1AT on AM scavenging functions has not been reported. Apoptotic cell clearance (efferocytosis) was measured in human AM isolated from patients with COPD, in primary rat AM or differentiated monocytes exposed to CS ex vivo, and in AM recovered from mice exposed to CS. A1AT (100 μg/mL, 16 h) significantly ameliorated efferocytosis (by ~50%) in AM of active smokers or AM exposed ex vivo to CS. A1AT significantly improved AM global engulfment, including phagocytosis, even when cells were simultaneously challenged with apoptotic and Fc-coated (bacteria-like) targets. The improved efferocytosis in A1AT-treated macrophages was associated with inhibition of tumor necrosis factor-α converting enzyme (TACE) activity, decreased mannose receptor shedding, and markedly increased abundance of efferocytosis receptors (mannose- and phosphatidyl serine receptors and the scavenger receptor B2) on AM plasma membrane. Directed airway A1AT treatment (via inhalation of a nebulized solution) restored in situ airway AM efferocytosis after CS exposure in mice. The amelioration of CS-exposed AM global engulfment may render A1AT as a potential therapy for COPD exacerbations.

T Helper Subsets, Peripheral Plasticity, and the Acute Phase Protein, α1-Antitrypsin

The traditional model of T helper differentiation describes the naïve T cell as choosing one of several subsets upon stimulation and an added reciprocal inhibition aimed at maintaining the chosen subset. However, to date, evidence is mounting to support the presence of subset plasticity. This is, presumably, aimed at fine-tuning adaptive immune responses according to local signals. Reprograming of cell phenotype is made possible by changes in activation of master transcription factors, employing epigenetic modifications that preserve a flexible mode, permitting a shift between activation and silencing of genes. The acute phase response represents an example of peripheral changes that are critical in modulating T cell responses. α1-antitrypsin (AAT) belongs to the acute phase responses and has recently surfaced as a tolerogenic agent in the context of adaptive immune responses. Nonetheless, AAT does not inhibit T cell responses, nor does it shutdown inflammation per se; rather, it appears that AAT targets non-T cell immunocytes towards changing the cytokine environment of T cells, thus promoting a regulatory T cell profile. The present review focuses on this intriguing two-way communication between innate and adaptive entities, a crosstalk that holds important implications on potential therapies for a multitude of immune disorders.

Alpha-1-anti-trypsin-Fc fusion protein ameliorates gouty arthritis by reducing release and extracellular processing of IL-1β and by the induction of endogenous IL-1Ra

OBJECTIVES

In the present study, we generated a new protein, recombinant human alpha-1-anti-trypsin (AAT)-IgG1 Fc fusion protein (AAT-Fc), and evaluated its properties to suppress inflammation and interleukin (IL)-1β in a mouse model of gouty arthritis.

METHODS

A combination of monosodium urate (MSU) crystals and the fatty acid C16.0 (MSU/C16.0) was injected intra-articularly into the knee to induce gouty arthritis. Joint swelling, synovial cytokine production and histopathology were determined after 4 h. AAT-Fc was evaluated for inhibition of MSU/C16.0-induced IL-1β release from human blood monocytes and for inhibition of extracellular IL-1β precursor processing.

RESULTS

AAT-Fc markedly suppressed MSU/C16.0-induced joint inflammation by 85-91% (p<0.001). Ex vivo production of IL-1β and IL-6 from cultured synovia were similarly reduced (63% and 65%, respectively). The efficacy of 2.0 mg/kg AAT-Fc in reducing inflammation was comparable to 80 mg/kg of plasma-derived AAT. Injection of AAT-Fc into mice increased circulating levels of endogenous IL-1 receptor antagonist by fourfold. We also observed that joint swelling was reduced by 80%, cellular infiltration by 95% and synovial production of IL-1β by 60% in transgenic mice expressing low levels of human AAT. In vitro, AAT-Fc reduced MSU/C16.0-induced release of IL-1β from human blood monocytes and inhibited proteinase-3-mediated extracellular processing of the IL-1β precursor into active IL-1β.

CONCLUSIONS

A single low dose of AAT-Fc is highly effective in reducing joint inflammation in this model of acute gouty arthritis. Considering the long-term safety of plasma-derived AAT use in humans, subcutaneous AAT-Fc emerges as a promising therapy for gout attacks.

Host-pathogen interplay in the respiratory environment of cystic fibrosis

Significant advances have been made in the understanding of disease progression in cystic fibrosis (CF), revealing a complex interplay between host and pathogenic organisms. The diverse CF microbiota within the airway activates an aberrant immune response that is ineffective in clearing infection. An appreciation of how the CF host immune system interacts with these organisms is crucial to understanding the pathogenesis of CF pulmonary disease. Here we discuss the microbial complexity present in the lungs of individuals with CF, review emerging concepts of innate and adaptive immune responses to pathogens that chronically inhabit the CF lung, and discuss therapies that target the aberrant inflammatory response that characterizes CF. A greater understanding of the underlying mechanisms will shed light on pathogenesis and guide more targeted therapies in the future that serve to reduce infection, minimize lung pathology, and improve the quality of life for patients with CF.