What every clinician should know about inflammation in COPD

Inflammation drives COPD pathogenesis and exacerbations. Although the conceptual framework and major players in the inflammatory milieu of COPD have been long established, the nuances of cellular interactions and the etiological differences that create heterogeneity in inflammatory profiles and treatment response continue to be revealed. This wealth of data and understanding is not only a boon to the researcher but also provides guidance to the clinician, moving the field closer to precision medicine. It is through this lens that this review seeks to describe the inflammatory processes at play in COPD, relating inflammation to pathological and functional changes, identifying patient-specific and disease-related factors that may influence clinical observations, and providing current insights on existing and emerging anti-inflammatory treatments and treatment targets, including biological therapies and phosphodiesterase (PDE) inhibitors.

Monocyte NLRP3 inflammasome and interleukin-1β activation modulated by alpha-1 antitrypsin therapy in deficient individuals

INTRODUCTION

Altered complement component 3 (C3) activation in patients with alpha-1 antitrypsin (AAT) deficiency (AATD) has been reported. To understand the potential impact on course of inflammation, the aim of this study was to investigate whether C3d, a cleavage-product of C3, triggers interleukin (IL)-1β secretion via activation of NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome. The objective was to explore the effect of AAT augmentation therapy in patients with AATD on the C3d/complement receptor 3 (CR3) signalling axis of monocytes and on circulating pro-inflammatory markers.

METHODS

Inflammatory mediators were detected in blood from patients with AATD (n=28) and patients with AATD receiving augmentation therapy (n=19). Inflammasome activation and IL-1β secretion were measured in monocytes of patients with AATD, and following C3d stimulation in the presence or absence of CR3 or NLRP3 inhibitors.

RESULTS

C3d acting via CR3 induces NLRP3 and pro-IL-1β production, and through induction of endoplasmic reticulum (ER) stress and calcium flux, triggers caspase-1 activation and IL-1β secretion. Treatment of individuals with AATD with AAT therapy results in decreased plasma levels of C3d (3.0±1.2 µg/mL vs 1.3±0.5 µg/mL respectively, p<0.0001) and IL-1β (115.4±30 pg/mL vs 73.3±20 pg/mL, respectively, p<0.0001), with a 2.0-fold decrease in monocyte NLRP3 protein expression (p=0.0303), despite continued ER stress activation.

DISCUSSION

These results provide strong insight into the mechanism of complement-driven inflammation associated with AATD. Although the described variance in C3d and NLRP3 activation decreased post AAT augmentation therapy, results demonstrate persistent C3d and monocyte ER stress, with implications for new therapeutics and clinical practice.

Immunological and homeostatic pathways of alpha -1 antitrypsin: a new therapeutic potential

α -1 antitrypsin (A1AT) is a 52 kDa acute-phase glycoprotein belonging to the serine protease inhibitor superfamily (SERPIN). It is primarily synthesized by hepatocytes and to a lesser extent by monocytes, macrophages, intestinal epithelial cells, and bronchial epithelial cells. A1AT is encoded by SERPINA1 locus, also known as PI locus, highly polymorphic with at least 100 allelic variants described and responsible for different A1AT serum levels and function. A1AT inhibits a variety of serine proteinases, but its main target is represented by Neutrophil Elastase (NE). However, recent attention has been directed towards its immune-regulatory and homeostatic activities. A1AT exerts immune-regulatory effects on different cell types involved in innate and adaptive immunity. Additionally, it plays a role in metal and lipid metabolism, contributing to homeostasis. An adequate comprehension of these mechanisms could support the use of A1AT augmentation therapy in many disorders characterized by a chronic immune response. The aim of this review is to provide an up-to-date understanding of the molecular mechanisms and regulatory pathways responsible for immune-regulatory and homeostatic activities of A1AT. This knowledge aims to support the use of A1AT in therapeutic applications. Furthermore, the review summarizes the current state of knowledge regarding the application of A1AT in clinical and laboratory settings human and animal models.

Astrocyte-derived SerpinA3N promotes neuroinflammation and epileptic seizures by activating the NF-κB signaling pathway in mice with temporal lobe epilepsy

Impaired activation and regulation of the extinction of inflammatory cells and molecules in injured neuronal tissues are key factors in the development of epilepsy. SerpinA3N is mainly associated with the acute phase response and inflammatory response. In our current study, transcriptomics analysis, proteomics analysis, and Western blotting showed that the expression level of Serpin clade A member 3N (SerpinA3N) is significantly increased in the hippocampus of mice with kainic acid (KA)-induced temporal lobe epilepsy, and this molecule is mainly expressed in astrocytes. Notably, in vivo studies using gain- and loss-of-function approaches revealed that SerpinA3N in astrocytes promoted the release of proinflammatory factors and aggravated seizures. Mechanistically, RNA sequencing and Western blotting showed that SerpinA3N promoted KA-induced neuroinflammation by activating the NF-κB signaling pathway. In addition, co-immunoprecipitation revealed that SerpinA3N interacts with ryanodine receptor type 2 (RYR2) and promotes RYR2 phosphorylation. Overall, our study reveals a novel SerpinA3N-mediated mechanism in seizure-induced neuroinflammation and provides a new target for developing neuroinflammation-based strategies to reduce seizure-induced brain injury.

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.

Small airways disease in patients with alpha-1 antitrypsin deficiency

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder, characterized by panacinar emphysema mainly in the lower lobes, and predisposes to chronic obstructive pulmonary disease (COPD) at a younger age, especially in patients with concomitant cigarette smoking. Alpha-1 antitrypsin (a1-AT) is a serine protease inhibitor that mainly blocks neutrophil elastase and maintains protease/antiprotease balance in the lung and AATD is caused by mutations in the SERPINA1 gene that encodes a1-AT protein. PiZZ is the most common genotype associated with severe AATD, leading to reduced circulating levels of a1-AT. Besides its antiprotease function, a1-AT has anti-inflammatory and antioxidative effects and AATD results in defective innate immunity. Protease/antiprotease imbalance affects not only the lung parenchyma but also the small airways and recent studies have shown that AATD is associated with small airway dysfunction. Alterations in small airways structure with peripheral ventilation inhomogeneities may precede emphysema formation, providing a unique opportunity to detect early disease. The aim of the present review is to summarize the current evidence for the contribution of small airways disease in AATD-associated lung disease.

Grass carp SERPINA1 inhibits GCRV infection through degrading CF2

SERPINA1, a member of the serine protease inhibitor family, plays a role in viral infection and inflammation by regulating the activities of serine and cysteine proteases. To date, there have been no reports on the immune function of SERPINA1 in fishes. In this study, we first cloned the serpina1 gene of grass carp (Ctenopharyngodon idellus) and found that it could respond rapidly to the infection of Grass carp reovirus (GCRV), and overexpression of serpina1 could enhance the antiviral response of CIK cells. A polyclonal antibody of SERPINA1 was prepared, and the protein interacting with SERPINA1 was screened by CoIP/MS in grass carp hepatopancreas tissue. It was found that SERPINA1 interacted with coagulation factor 2 (CF2) and could degrade it in a dose-dependent manner. In addition, overexpression of cf2 contributed to the infection of GCRV in CIK cells, whereas co-expression of serpina1 and cf2 in grass carp reduced the copy number of GCRV in cells. The results showed that grass carp SERPINA1 could inhibit GCRV infection by degrading CF2. This study proposes that SERPINA1 can inhibit viral infection through interaction with the coagulation factor, providing new insights into the molecular mechanism of SERPINA1’s antiviral function.

Alpha-1 antitrypsin in autoimmune diseases: Roles and therapeutic prospects

Alpha-1 antitrypsin (A1AT) is a protease inhibitor in the serum. Its primary function is to inhibit the activity of a series of proteases, including proteinase 3, neutrophil elastase, metalloproteases, and cysteine-aspartate proteases. In addition, A1AT also has anti-inflammatory, anti-apoptotic, anti-oxidative stress, anti-viral, and anti-bacterial activities and plays essential roles in the regulation of tissue repair and lymphocyte differentiation and activation. The overactivation of the immune system characterizes the pathogenesis of autoimmune diseases. A1AT treatment shows beneficial effects on patients and animal models with autoimmune diseases such as rheumatoid arthritis and systemic lupus erythematosus. This review summarizes the functions and therapeutic prospects of A1AT in autoimmune diseases.

Alu RNA induces NLRP3 expression through TLR7 activation in α-1-antitrypsin-deficient macrophages

α-1 antitrypsin (AAT) is a serine protease inhibitor that plays a pivotal role in maintaining lung homeostasis. The most common AAT allele associated with AAT deficiency (AATD) is PiZ. Z-AAT accumulates in cells due to misfolding, causing severe AATD. The major function of AAT is to neutralize neutrophil elastase in the lung. It is generally accepted that loss of antiprotease function is a major cause of COPD in individuals with AATD. However, it is now being recognized that the toxic gain-of-function effect of Z-AAT in macrophage likely contributes to lung disease. In the present study, we determined that TLR7 signaling is activated in Z-MDMs, and the expression level of NLRP3, one of the targets of TLR7 signaling, is significantly higher in Z- compared with M-MDMs. We also determined that the level of endosomal Alu RNA is significantly higher in Z-compared with M-MDMs. Alu RNA is a known endogenous ligand that activates TLR7 signaling. Z-AAT likely induces the expression of Alu elements in MDMs and accelerates monocyte death, leading to the higher level of endosomal Alu RNA in Z-MDMs. Taken together,this study identifies a mechanism responsible for the toxic gain of function of Z-AAT macrophages.

Differential expression profiles of miRNA in granulomatous lobular mastitis and identification of possible biomarkers

The etiology and pathogenesis of granulomatous lobular mastitis (GLM) remain largely elusive and the expression levels and regulatory roles of microRNAs (miRNAs or miRs) in GLM have remained mostly undetermined. In the present study, the miRNAs that were differentially expressed in breast biopsy samples from patients with GLM and normal tissue adjacent to fibroadenoma were analyzed, a comprehensive differential expression profile of miRNAs was provided and potential biomarkers were screened out. The expression profile of miRNAs was determined by high-throughput sequencing in the tissues of patients with GLM and healthy controls. Significantly differentially expressed miRNAs were screened by threshold setting and cluster analysis and their target genes were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. Finally, circulating differentially expressed miRNAs between the GLM and control groups were further analyzed by reverse transcription-quantitative PCR (RT-qPCR). A total of 31,077 miRNAs were detected by high-throughput sequencing. By using the cutoff criteria of |log2 fold change|>2.5 and q<0.001, 13 miRNAs that were indicated to be GLM biomarkers were screened out. The expression levels of these 13 miRNAs in the GLM group were higher than those in the control group. GO and KEGG enrichment analyses suggested that the occurrence and development of GLM may be associated with autoimmune inflammation, metabolism and pathogenic organisms. miR-451a and miR-5571-3p were confirmed to be significantly increased in the serum of patients with GLM compared with their levels in the serum of healthy volunteers, which suggests that they may be used as biomarkers of GLM. To the best of our knowledge, the present study was the first report detailing genome-wide miRNA profiling of patients with GLM compared with controls. The possible targets and pathways of GLM were evaluated by bioinformatics analysis. The present study identified 13 differentially expressed miRNAs with important theoretical significance and potential application. Furthermore, miR-451a and miR-5571-3p were verified by RT-qPCR as possible biomarkers of GLM.

Alpha-1 Antitrypsin Therapy Modifies Neutrophil Adhesion in Patients with Obstructive Lung Disease

Alpha-1 antitrypsin (AAT) deficiency (AATD) is characterized by neutrophil-dominated inflammation resulting in emphysema. The cholesterol-rich neutrophil outer plasma membrane plays a central role in adhesion and subsequent transmigration to underlying tissues. This study aimed to investigate mechanisms of increased neutrophil adhesion in AATD, and whether AAT augmentation therapy abrogates this effect. Plasma and blood neutrophils were donated by healthy controls (n=20), AATD (n=30) and AATD patients post AAT augmentation therapy (n=6). Neutrophil membrane protein expression was investigated using liquid chromatography-tandem mass spectrometry. The effect of once weekly intravenous AAT augmentation therapy was assessed by ELISAs, and calcium fluorometric, μ-calpain and cell adhesion assays. Decreased neutrophil plasma membrane cholesterol content (P=0.03), yet increased abundance of integrin alpha-M (fold change 1.91), integrin alpha-L (fold change 3.76) and cytoskeletal adaptor proteins including talin-1 (fold change 4.04), were detected on AATD neutrophil plasma membrane fractions. The described inflammatory induced structural changes were a result of >2 fold increased cytosolic calcium levels (P=0.02), leading to significant calcium dependent μ-calpain activity (3.5 fold change, P=0.005), resulting in proteolysis of the membrane cholesterol trafficking protein caveolin-1. Treatment of AAT-deficient individuals with AAT augmentation therapy resulted in increased caveolin-1 and membrane cholesterol content (111.8 ± 15.5 vs 64.18 ± 7.8 µg/ 2x10⁷ cells pre- and post-treatment respectively, P=0.02), with concurrent decreased neutrophil integrin expression and adhesion. Results demonstrate an auxiliary benefit of AAT augmentation therapy, evident by a decrease in circulating inflammation and controlled neutrophil adhesion.

A Review of Alpha-1 Antitrypsin Binding Partners for Immune Regulation and Potential Therapeutic Application

Alpha-1 antitrypsin (AAT) is the canonical serine protease inhibitor of neutrophil-derived proteases and can modulate innate immune mechanisms through its anti-inflammatory activities mediated by a broad spectrum of protein, cytokine, and cell surface interactions. AAT contains a reactive methionine residue that is critical for its protease-specific binding capacity, whereby AAT entraps the protease on cleavage of its reactive centre loop, neutralises its activity by key changes in its tertiary structure, and permits removal of the AAT-protease complex from the circulation. Recently, however, the immunomodulatory role of AAT has come increasingly to the fore with several prominent studies focused on lipid or protein-protein interactions that are predominantly mediated through electrostatic, glycan, or hydrophobic potential binding sites. The aim of this review was to investigate the spectrum of AAT molecular interactions, with newer studies supporting a potential therapeutic paradigm for AAT augmentation therapy in disorders in which a chronic immune response is strongly linked.

In vitro and in vivo modulation of NADPH oxidase activity and reactive oxygen species production in human neutrophils by α1-antitrypsin

Oxidative stress from innate immune cells is a driving mechanism that underlies COPD pathogenesis. Individuals with α-1 antitrypsin (AAT) deficiency (AATD) have a dramatically increased risk of developing COPD. To understand this further, the aim of this study was to investigate whether AATD presents with altered neutrophil NADPH oxidase activation, due to the specific lack of plasma AAT.

Experiments were performed using circulating neutrophils isolated from healthy controls and individuals with AATD. Superoxide anion (O₂⁻) production was determined from the rate of reduction of cytochrome c. Quantification of membrane NADPH oxidase subunits was performed by mass spectrometry and Western blot analysis. The clinical significance of our in vitro findings was assessed in patients with AATD and severe COPD receiving intravenous AAT replacement therapy.

In vitro, AAT significantly inhibited O₂⁻ production by stimulated neutrophils and suppressed receptor stimulation of cyclic adenosine monophosphate and extracellular signal-regulated kinase (ERK)1/2 phosphorylation. In addition, AAT reduced plasma membrane translocation of cytosolic phox components of the NADPH oxidase. Ex vivo, AATD neutrophils demonstrated increased plasma membrane-associated p67^phox and p47^phox and significantly increased O₂⁻ production. The described variance in phox protein membrane assembly was resolved post-AAT augmentation therapy in vivo, the effects of which significantly reduced AATD neutrophil O₂⁻ production to that of healthy control cells.

These results expand our knowledge on the mechanism of neutrophil-driven airways disease associated with AATD. Therapeutic AAT augmentation modified neutrophil NADPH oxidase assembly and reactive oxygen species production, with implications for clinical use in conditions in which oxidative stress plays a pathogenic role.

Circulating neutrophils in COPD due to α₁-antitrypsin deficiency illustrate increased NADPH oxidase assembly and reactive oxygen species production, a defect corrected by α₁-antitrypsin augmentation therapyhttps://bit.ly/38NNTzM

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.

Alpha-1 Antitrypsin Augmentation Inhibits Proteolysis of Neutrophil Membrane Voltage-Gated Proton Channel-1 in Alpha-1 Deficient Individuals

Background and Objectives: Alpha-1 antitrypsin is a serine protease inhibitor that demonstrates an array of immunomodulatory functions. Individuals with the genetic condition of alpha-1 antitrypsin deficiency (AATD) are at increased risk of early onset emphysematous lung disease. This lung disease is partly driven by neutrophil mediated lung destruction in an environment of low AAT. As peripheral neutrophil hyper-responsiveness in AATD leads to excessive degranulation and increased migration to the airways, we examined the expression of the membrane voltage-gated proton channel-1 (HVCN1), which is integrally linked to neutrophil function. The objectives of this study were to evaluate altered HVCN1 in AATD neutrophils, serine protease-dependent degradation of HVCN1, and to investigate the ability of serum AAT to control HVCN1 expression. Materials and Methods: Circulating neutrophils were purified from AATD patients (n = 20), AATD patients receiving AAT augmentation therapy (n = 3) and healthy controls (n = 20). HVCN1 neutrophil expression was assessed by flow cytometry and Western blot analysis. Neutrophil membrane bound elastase was measured by fluorescence resonance energy transfer. Results: In this study we demonstrated that HVCN1 protein is under-expressed in AATD neutrophils (p = 0.02), suggesting a link between reduced HVCN1 expression and AAT deficiency. We have demonstrated that HVCN1 undergoes significant proteolytic degradation in activated neutrophils (p < 0.0001), primarily due to neutrophil elastase activity (p = 0.0004). In addition, the treatment of AATD individuals with AAT augmentation therapy increased neutrophil plasma membrane HVCN1 expression (p = 0.01). Conclusions: Our results demonstrate reduced levels of HVCN1 in peripheral blood neutrophils that may influence the neutrophil-dominated immune response in the AATD airways and highlights the role of antiprotease treatment and specifically AAT augmentation therapy in protecting neutrophil membrane expression of HVCN1.

New Pharmacological Tools to Target Leukocyte Trafficking in Lung Disease

Infection and inflammation of the lung results in the recruitment of non-resident immune cells, including neutrophils, eosinophils and monocytes. This swift response should ensure clearance of the threat and resolution of stimuli which drive inflammation. However, once the threat is subdued this influx of immune cells should be followed by clearance of recruited cells through apoptosis and subsequent efferocytosis, expectoration or retrograde migration back into the circulation. This cycle of cell recruitment, containment of threat and then clearance of immune cells and repair is held in exquisite balance to limit host damage. Advanced age is often associated with detrimental changes to the balance described above. Cellular functions are altered including a reduced ability to traffic accurately towards inflammation, a reduced ability to clear pathogens and sustained inflammation. These changes, seen with age, are heightened in lung disease, and most chronic and acute lung diseases are associated with an exaggerated influx of immune cells, such as neutrophils, to the airways as well as considerable inflammation. Indeed, across many lung diseases, pathogenesis and progression has been associated with the sustained presence of trafficking cells, with examples including chronic diseases such as Chronic Obstructive Pulmonary Disease and Idiopathic Pulmonary Fibrosis and acute infections such as Pneumonia and Pneumonitis. In these instances, there is evidence that dysfunctional and sustained recruitment of cells to the airways not only increases host damage but impairs the hosts ability to effectively respond to microbial invasion. Targeting leukocyte migration in these instances, to normalise cellular responses, has therapeutic promise. In this review we discuss the current evidence to support the trafficking cell as an immunotherapeutic target in lung disease, and which potential mechanisms or pathways have shown promise in early drug trials, with a focus on the neutrophil, as the quintessential trafficking immune cell.

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.

Potential Roles of Acute Phase Proteins in Cancer: Why Do Cancer Cells Produce or Take Up Exogenous Acute Phase Protein Alpha1-Antitrypsin?

An association between acute-phase proteins (APPs) and cancer has long been established and there are numerous reports correlating altered levels and/or molecular forms of APPs with different types of cancers. Many authors have shown a positive correlation between high levels of APPs, like alpha1-antitrypsin (AAT), and unfavorable clinical outcome in cancers. Conversely, others proposed that high levels of APPs are probably just a part of nonspecific inflammatory response to cancer development. However, this might not be always true, because many cancerous cells produce or take up exogenous APPs. What is the biological significance of this and what benefit do cancer cells have from these proteins remains largely unknown. Recent data revealed that some APPs, including AAT, are able to enhance cancer cell resistance against anticancer drug-induced apoptosis and autophagy. In this review, we specifically discuss our own findings and controversies in the literature regarding the role of AAT in cancer.

Alpha-1 antitrypsin deficiency-associated panniculitis

BACKGROUND

Panniculitis represents a rare and potentially lethal manifestation of alpha-1 antitrypsin deficiency (AATD). Evidence regarding management is limited to case reports and small case series. We sought to clarify typical features and investigation of AATD-associated panniculitis and assess the evidence regarding therapeutic options.

SEARCH METHODOLOGY

Articles and abstracts published between 1970 and 2020 were identified by searches of MEDLINE, PubMed, and secondary searches of references from relevant articles using the search terms "panniculitis," "alpha-1," "antitrypsin," "deficiency," and "Weber-Christian."

FINDINGS

We identified 117 cases of AATD-associated panniculitis. In 1 series, AATD was present in 15% of all cases of biopsy-proven panniculitis. Failure to achieve clinical response was seen in all instances of systemic steroid use. Dapsone, although effective and accessible, is frequently associated with failure to achieve remission. In these instances, intravenous AAT augmentation therapy generally resulted in response.

CONCLUSIONS

AATD may be more prevalent among patients presenting with panniculitis than previously thought. Patients presenting with panniculitis and systemic illness show high mortality risk. Although most cases are associated with the severe ZZ-genotype, moderate genotypes may also predispose to panniculitis. Dapsone remains the most cost-effective therapeutic option, whereas intravenous AAT augmentation remains the most efficacious. Finally, glucocorticoids appear ineffective in this setting.

Monocytes and Macrophages in Alpha-1 Antitrypsin Deficiency

Alpha-1 antitrypsin deficiency (AATD) is a genetic condition characterised by low circulating levels of alpha-1 antitrypsin (AAT), a serine proteinase inhibitor. The most common deficiency variants are the S and Z mutations, which cause the accumulation of misfolded AAT in hepatocytes resulting in endoplasmic reticular stress and insufficient release of AAT into the circulation (<11μmol/L). This leads to liver disease, as well as an increased risk of emphysema due to unopposed proteolytic activity of neutrophil-derived serine proteinases in the lungs. AATD has been traditionally viewed as an inflammatory disorder caused directly by a proteinase-antiproteinase imbalance in the lung, but increasing evidence suggests that low AAT levels may affect other cellular functions. Recently, AAT polymers have been identified in both monocytes and macrophages from AATD patients and evidence is building that these cells may also play a role in the development of AATD lung disease. Alveolar macrophages are phagocytic cells that are important in the lung immune response but are also implicated in driving inflammation. This review explores the potential implications of monocyte and macrophage involvement in non-liver AAT synthesis and the pathophysiology of AATD lung disease.

Alpha 1 Antitrypsin-Deficient Macrophages Have Impaired Efferocytosis of Apoptotic Neutrophils

Alpha 1 antitrypsin deficiency (AATD) is an autosomal co-dominant disorder characterized by a low level of circulating AAT, which significantly reduces protection for the lower airways against proteolytic burden caused by neutrophils. Neutrophils, which are terminally differentiated innate immune cells and play a critical role to clear pathogens, accumulate excessively in the lung of AATD individuals. The neutrophil burden in AATD individuals increases the risk for early-onset destructive lung diseases by producing neutrophil products such as reactive oxygen radicals and various proteases. The level of AAT in AATD individuals is not sufficient to inhibit the activity of neutrophil chemotactic factors such as CXCL-8 and LTB4, which could lead to alveolar neutrophil accumulation in AATD individuals. However, as neutrophils have a short lifespan, and apoptotic neutrophils are rapidly cleared by alveolar macrophages that outnumber the apoptotic neutrophils in the pulmonary alveolus, the increased chemotaxis activity does not fully explain the persistent neutrophil accumulation and the resulting chronic inflammation in AATD individuals. Here, we propose that the ability of alveolar macrophages to clear apoptotic neutrophils is impaired in AATD individuals and it could be the main driver to cause neutrophil accumulation in their lung. This study demonstrates that Z-AAT variant significantly increases the expression of pro-inflammatory cytokines including CXCL-8, CXCL1, LTB4, and TNFα in LPS-treated macrophages. These cytokines play a central role in neutrophil recruitment to the lung and in clearance of apoptotic neutrophils by macrophages. Our result shows that LPS treatment significantly reduces the efferocytosis ability of macrophages with the Z-AAT allele by inducing TNFα expression. We incubated monocyte-derived macrophages (MDMs) with apoptotic neutrophils and found that after 3 h of co-incubation, the expression level of CXCL-8 is reduced in M-MDMs but increased in Z-MDMs. This result shows that the expression of inflammatory cytokines could be increased by impaired efferocytosis. It indicates that the efferocytosis ability of macrophages plays an important role in regulating cytokine expression and resolving inflammation. Findings from this study would help us better understand the multifaceted effect of AAT on regulating neutrophil balance in the lung and the underlying mechanisms.

Characterization of the Inflammatory Response to Severe COVID-19 Illness

Rationale: Coronavirus disease (COVID-19) is a global threat to health. Its inflammatory characteristics are incompletely understood.Objectives: To define the cytokine profile of COVID-19 and to identify evidence of immunometabolic alterations in those with severe illness.Methods: Levels of IL-1β, IL-6, IL-8, IL-10, and sTNFR1 (soluble tumor necrosis factor receptor 1) were assessed in plasma from healthy volunteers, hospitalized but stable patients with COVID-19 (COVIDstable patients), patients with COVID-19 requiring ICU admission (COVIDICU patients), and patients with severe community-acquired pneumonia requiring ICU support (CAPICU patients). Immunometabolic markers were measured in circulating neutrophils from patients with severe COVID-19. The acute phase response of AAT (alpha-1 antitrypsin) to COVID-19 was also evaluated.Measurements and Main Results: IL-1β, IL-6, IL-8, and sTNFR1 were all increased in patients with COVID-19. COVIDICU patients could be clearly differentiated from COVIDstable patients, and demonstrated higher levels of IL-1β, IL-6, and sTNFR1 but lower IL-10 than CAPICU patients. COVID-19 neutrophils displayed altered immunometabolism, with increased cytosolic PKM2 (pyruvate kinase M2), phosphorylated PKM2, HIF-1α (hypoxia-inducible factor-1α), and lactate. The production and sialylation of AAT increased in COVID-19, but this antiinflammatory response was overwhelmed in severe illness, with the IL-6:AAT ratio markedly higher in patients requiring ICU admission (P < 0.0001). In critically unwell patients with COVID-19, increases in IL-6:AAT predicted prolonged ICU stay and mortality, whereas improvement in IL-6:AAT was associated with clinical resolution (P < 0.0001).Conclusions: The COVID-19 cytokinemia is distinct from that of other types of pneumonia, leading to organ failure and ICU need. Neutrophils undergo immunometabolic reprogramming in severe COVID-19 illness. Cytokine ratios may predict outcomes in this population.

The clinical and inflammatory relationships between periodontitis and chronic obstructive pulmonary disease

AIM

To investigate associations between periodontitis and chronic obstructive pulmonary disease (COPD) with and without alpha-1 antitrypsin deficiency (AATD), including neutrophil functions implicated in tissue damage.

METHODS

The presence and severity of periodontitis (using two international criteria) and lung disease were assessed in 156 COPD patients with and without AATD accounting for common confounding factors. Saliva and systemic inflammatory markers were measured by ELISA together with neutrophil migration.

RESULTS

COPD and AATD patients exhibited higher prevalence of periodontitis (COPD 95%; AATD 88%) than reported in unselected community-dwelling populations even when risk factors (age, smoking history, socio-economic status and dental habits) were considered. Periodontitis severity associated with lung disease severity (AATD, periodontitis versus no periodontitis; FEV1 = 56% versus 99% predicted; TLCO = 59% versus 81% predicted, p < .0001 for both). Neutrophil migratory accuracy declined in stage II-IV periodontitis patients with COPD or AATD compared to COPD or AATD with no or stage I periodontitis. Improved dental habits appeared to be associated with a reduction in exacerbation frequency in COPD.

CONCLUSION

The results support shared pathophysiology between periodontitis and COPD, especially when associated with AATD. This may reflect an amplification of neutrophilic inflammation and altered neutrophil functions, already described in periodontitis, COPD and AATD.

Neutrophil Modulation in Alpha-1 Antitrypsin Deficiency

Neutrophils have been implicated in the pathogenesis of alpha-1 antitrypsin deficiency (AATD) since the first descriptions of the disease. Neutrophil proteinases can cause all lung manifestations of AATD, from small airways destruction, to emphysema, to chronic bronchitis and airflow obstruction. Initially, it was proposed that neutrophil functions were normal in AATD, responding in an initially physiological manner to a high burden of pulmonary inflammation. More recent studies have shed new light on this, describing changes in neutrophil responses (a modulation of usual cellular functions) in the presence of inflammation or infection which might enhance tissue damage while impeding bacterial clearance, providing some evidence to support there being an AATD neutrophil phenotype. Many facets of neutrophil function in AATD can be explained by the loss of alpha-1 antitrypsin (AAT) in diverse biological processes. If this were the only reason for altered neutrophil functions, one would predict similar disease presentation across affected people. However, this is not the case. Despite similar (low) levels of AAT, lung disease is extremely variable in AATD, with some patients suffering a significant burden of lung disease and some much less, irrespective of smoking habits and, in some cases, despite augmentation therapy. This review will explore how complex neutrophil responses are and how they are altered with age, inflammation and AATD. Further, it will discuss the need to understand more completely which aspects of AATD-associated disease are driven by neutrophils and how patients more susceptible to neutrophil dysfunction could be identified to potentially stratify treatment approaches.

α1 Antitrypsin therapy modulates the neutrophil membrane proteome and secretome

Obstructive pulmonary disease in patients with α₁ antitrypsin (AAT) deficiency (AATD) occurs earlier in life compared with patients without AATD. To understand this further, the aim of this study was to investigate whether AATD presents with altered neutrophil characteristics, due to the specific lack of plasma AAT, compared with non-AATD COPD.This study focussed on the neutrophil plasma membrane and, by use of label-free tandem mass spectrometry, the proteome of the neutrophil membrane was compared in forced expiratory volume in 1 s (FEV₁)-matched AATD, non-AATD COPD and in AATD patients receiving weekly AAT augmentation therapy (n=6 patients per cohort). Altered protein expression in AATD was confirmed by Western blot, ELISA and fluorescence resonance energy transfer analysis.The neutrophil membrane proteome in AATD differed significantly from that of COPD as demonstrated by increased abundance and activity of primary granule proteins including neutrophil elastase on the cell surface in AATD. The signalling mechanism underlying increased degranulation involved Rac2 activation, subsequently resulting in proteinase-activated receptor 2 activation by serine proteinases and enhanced reactive oxygen species production. In vitro and ex vivo, AAT reduced primary granule release and the described plasma membrane variance was resolved post-AAT augmentation therapy in vivo, the effects of which significantly altered the AATD neutrophil membrane proteome to that of a non-AATD COPD cell.These results provide strong insight into the mechanism of neutrophil driven airways disease associated with AATD. Therapeutic AAT augmentation modified the membrane proteome to that of a typical COPD cell, with implications for clinical practice.

The Biological Effects of Double-Dose Alpha-1 Antitrypsin Augmentation Therapy. A Pilot Clinical Trial

Rationale: Augmentation therapy with intravenous AAT (alpha-1 antitrypsin) is the only specific therapy for individuals with pulmonary disease from AAT deficiency (AATD). The recommended standard dose (SD; 60 mg/kg/wk) elevates AAT trough serum levels to around 50% of normal; however, outside of slowing emphysema progression, its effects in other clinical outcomes have not been rigorously proven.

Objectives: To evaluate the biological effects of normalizing AAT trough levels with double-dose (DD) therapy (120 mg/kg/wk) in subjects with AATD already receiving SD therapy.

Methods: Clinically stable subjects were evaluated after 4 weeks of SD therapy, followed by 4 weeks of DD therapy, and 4 weeks after return to SD therapy. At the end of each phase, BAL fluid (BALF) and plasma samples were obtained.

Measurements and Main Results: DD therapy increased trough AAT levels to normal and, compared with SD therapy, reduced serine protease activity in BALF (elastase and cathepsin G), plasma elastase footprint (Aα-Val³⁶⁰), and markers of elastin degradation (desmosine/isodesmosine) in BALF. DD therapy also further downregulated BALF ILs and cytokines including Jak-STAT (Janus kinases–signal transducer and activator of transcription proteins), TNFα (tumor necrosis factor-α), and T-cell receptor signaling pathways, cytokines involved in macrophage migration, eosinophil recruitment, humoral and adaptive immunity, neutrophil activation, and cachexia. On restarting SD after DD treatment, a possible carryover effect was seen for several biological markers.

Conclusions: Subjects with AATD on SD augmentation therapy still exhibit inflammation, protease activity, and elastin degradation that can be further improved by normalizing AAT levels. Higher AAT dosing than currently recommended may lead to enhanced clinical benefits and should be explored further.

Clinical trial registered with www.clinicaltrials.gov (NCT 01669421).

The Role of ALDH2 in Sepsis and the To-Be-Discovered Mechanisms

Sepsis, defined as life-threatening tissue damage and organ dysfunction caused by a dysregulated host response to infection, is a critical disease which imposes global health burden. Sepsis-induced organ dysfunction, including circulatory and cardiac dysfunction, hepatic dysfunction, renal dysfunction, etc., contributes to high mortality and long-term disability of sepsis patients. Altered inflammatory response, ROS and reactive aldehyde stress, mitochondrial dysfunction, and programmed cell death pathways (necrosis, apoptosis, and autophagy) have been demonstrated to play crucial roles in septic organ dysfunction. Unfortunately, except for infection control and supportive therapies, no specific therapy exists for sepsis. New specific therapeutic targets are highly warranted. Emerging studies suggested a role of potential therapeutic target of ALDH2, a tetrameric enzyme located in mitochondria to detoxify aldehydes, in septic organ dysfunction. In this article, we will review the presentations and pathophysiology of septic organ dysfunction, as well as summarize and discuss the recent insights regarding ALDH2 in sepsis.

Neutrophil phenotypes in chronic lung disease

Introduction: Neutrophils are the most abundant inflammatory cells in the lungs of patients with chronic lung diseases, especially COPD, yet despite this, patients often experience repeated chest infections. Neutrophil function may be altered in disease, but the reasons are unclear. In chronic disease, sequential pro-inflammatory and pro-repair responses appear distorted. As understanding of neutrophil heterogeneity has expanded, it is suggested that different neutrophil phenotypes may impact on health and disease. Areas covered: In this review, the definition of cellular phenotype, the implication of neutrophil surface markers and functions in chronic lung disease and the complex influences of external, local and genetic factors on these changes are discussed. Literature was accessed up to the 19 July 2019 using: PubMed, US National Library of Medicine National Institutes of Health and the National Centre for Biotechnology Information. Expert opinion: As more is learned about neutrophils, the further we step from the classical view of neutrophils being unrefined killing machines to highly complex and finely tuned cells. Future therapeutics may aim to normalize neutrophil function, but to achieve this, knowledge of phenotypes in humans and how these relate to observed pathology and disease processes is required.

Understanding the role of neutrophils in chronic inflammatory airway disease

Airway neutrophilia is a common feature of many chronic inflammatory lung diseases and is associated with disease progression, often regardless of the initiating cause. Neutrophils and their products are thought to be key mediators of the inflammatory changes in the airways of patients with chronic obstructive pulmonary disease (COPD) and have been shown to cause many of the pathological features associated with disease, including emphysema and mucus hypersecretion. Patients with COPD also have high rates of bacterial colonisation and recurrent infective exacerbations, suggesting that neutrophil host defence mechanisms are impaired, a concept supported by studies showing alterations to neutrophil migration, degranulation and reactive oxygen species production in cells isolated from patients with COPD. Although the role of neutrophils is best described in COPD, many of the pathological features of this disease are not unique to COPD and also feature in other chronic inflammatory airway diseases, including asthma, cystic fibrosis, alpha-1 anti-trypsin deficiency, and bronchiectasis. There is increasing evidence for immune cell dysfunction contributing to inflammation in many of these diseases, focusing interest on the neutrophil as a key driver of pulmonary inflammation and a potential therapeutic target than spans diseases. This review discusses the evidence for neutrophilic involvement in COPD and also considers their roles in alpha-1 anti-trypsin deficiency, bronchiectasis, asthma, and cystic fibrosis. We provide an in-depth assessment of the role of the neutrophil in each of these conditions, exploring recent advances in understanding, and finally discussing the possibility of common mechanisms across diseases.

The Multifaceted Effects of Alpha1-Antitrypsin on Neutrophil Functions

Neutrophils are the predominant immune cells in human blood possessing heterogeneity, plasticity and functional diversity. The activation and recruitment of neutrophils into inflamed tissue in response to stimuli are tightly regulated processes. Alpha1-Antitrypsin (AAT), an acute phase protein, is one of the potent regulators of neutrophil activation via both -protease inhibitory and non-inhibitory functions. This review summarizes our current understanding of the effects of AAT on neutrophils, illustrating the interplay between AAT and the key effector functions of neutrophils.

The impact of alpha-1 antitrypsin augmentation therapy on neutrophil-driven respiratory disease in deficient individuals

Alpha-1 antitrypsin (AAT) is the most abundant serine protease inhibitor circulating in the blood. AAT deficiency (AATD) is an autosomal codominant condition affecting an estimated 3.4 million individuals worldwide. The clinical disease associated with AATD can present in a number of ways including COPD, liver disease, panniculitis and antineutrophil cytoplasmic antibody vasculitis. AATD is the only proven genetic risk factor for the development of COPD, and deficient individuals who smoke are disposed to more aggressive disease. Principally, AAT is a serine protease inhibitor; however, over the past number of years, the assessment of AAT as simply an antiprotease has evolved, and it is now recognized that AAT has significant anti-inflammatory properties affecting a wide range of cells, including the circulating neutrophil.

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.

New Concepts in Alpha-1 Antitrypsin Deficiency Disease Mechanisms

Alpha-1 antitrypsin deficiency is predominantly caused by point mutations that alter the protein's folding. These mutations fall into two broad categories: those that destabilize the protein dramatically and lead to its post-translational degradation and those that affect protein structure more subtly to promote protein polymerization within the endoplasmic reticulum (ER). This distinction is important because it determines the cell's response to each mutant. The severely misfolded mutants trigger an unfolded protein response (UPR) that promotes improved protein folding but can kill the cell in the chronic setting. In contrast, mutations that permit polymer formation fail to activate the UPR but instead promote a nuclear factor-κB-mediated ER overload response. The ability of polymers to increase a cell's sensitivity to ER stress likely explains apparent inconsistencies in the alpha-1 antitrypsin-signaling literature that have linked polymers with the UPR. In this review we discuss the use of mutant serpins to dissect each signaling pathway.

Neutrophil Membrane Cholesterol Content is a Key Factor in Cystic Fibrosis Lung Disease

Background

Identification of mechanisms promoting neutrophil trafficking to the lungs of patients with cystic fibrosis (CF) is a challenge for next generation therapeutics. Cholesterol, a structural component of neutrophil plasma membranes influences cell adhesion, a key step in transmigration. The effect of chronic inflammation on neutrophil membrane cholesterol content in patients with CF (PWCF) remains unclear. To address this we examined neutrophils of PWCF to evaluate the cause and consequence of altered membrane cholesterol and identified the effects of lung transplantation and ion channel potentiator therapy on the cellular mechanisms responsible for perturbed membrane cholesterol and increased cell adhesion.

Methodology

PWCF homozygous for the ΔF508 mutation or heterozygous for the G551D mutation were recruited (n = 48). Membrane protein expression was investigated by mass spectrometry. The effect of lung transplantation or ivacaftor therapy was assessed by ELISAs, and calcium fluorometric and μ-calpain assays.

Findings

Membranes of CF neutrophils contain less cholesterol, yet increased integrin CD11b expression, and respond to inflammatory induced endoplasmic reticulum (ER) stress by activating μ-calpain. In vivo and in vitro, increased μ-calpain activity resulted in proteolysis of the membrane cholesterol trafficking protein caveolin-1. The critical role of caveolin-1 for adequate membrane cholesterol content was confirmed in caveolin-1 knock-out mice. Lung transplant therapy or treatment of PWCF with ivacaftor, reduced levels of circulating inflammatory mediators and actuated increased caveolin-1 and membrane cholesterol, with concurrent normalized neutrophil adhesion.

Interpretation

Results demonstrate an auxiliary benefit of lung transplant and potentiator therapy, evident by a reduction in circulating inflammation and controlled neutrophil adhesion.

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This study explored neutrophil adhesion in cystic fibrosis.

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Altered membrane cholesterol lead to increased adhesion.

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Circulating inflammatory mediators caused increased calpain activity and reduced membrane cholesterol content.

In patients with cystic fibrosis (CF), chronic inflammation in the circulation, in part originating from the pulmonary compartment, leads to decreased membrane cholesterol in circulating neutrophils, resulting in increased cell adhesion. The mechanism of action involves proteolytic down-regulation of the cholesterol trafficking protein caveolin-1. The overall effect of lung transplant therapy, or CFTR potentiator treatment, was to significantly diminish the circulating inflammatory burden thereby permitting caveolin-1 expression, with concomitant decreased CF cell adhesion and significant clinical improvement.

Cationic Nanoliposomes Meet mRNA: Efficient Delivery of Modified mRNA Using Hemocompatible and Stable Vectors for Therapeutic Applications

Synthetically modified mRNA is a unique bioactive agent, ideal for use in therapeutic applications, such as cancer vaccination or treatment of single-gene disorders. In order to facilitate mRNA transfections for future therapeutic applications, there is a need for the delivery system to achieve optimal transfection efficacy, perform with durable stability, and provide drug safety. The objective of our study was to comprehensively analyze the use of 3β-[N-(N',N'-dimethylaminoethane) carbamoyl](DC-Cholesterol)/dioleoylphosphatidylethanolamine (DOPE) liposomes as a potential transfection agent for modified mRNAs. Our cationic liposomes facilitated a high degree of mRNA encapsulation and successful cell transfection efficiencies. More importantly, no negative effects on cell viability or immune reactions were detected posttransfection. Notably, the liposomes had a long-acting transfection effect on cells, resulting in a prolonged protein production of alpha-1-antitrypsin (AAT). In addition, the stability of these mRNA-loaded liposomes allowed storage for 80 days, without the loss of transfection efficacy. Finally, comprehensive analysis showed that these liposomes are fully hemocompatible with fresh human whole blood. In summary, we present an extensive analysis on the use of DC-cholesterol/DOPE liposomes as mRNA delivery vehicles. This approach provides the basis of a safe and efficient therapeutic strategy in the development of successful mRNA-based drugs.

Serum α-1 Antitrypsin (AAT) antagonizes intrinsic apoptosis induction in neutrophils from patients with systemic inflammatory response syndrome

Excessive neutrophil activation accompanied by delayed apoptotic cell death in inflammatory conditions causes progressive damage of cells and tissues, leading to life-threatening multiple organ dysfunction syndrome. Previous work suggested that circulating serum factors during inflammation are critically involved in the suppression of neutrophil cell death although the identity of these antiapoptotic mediators remained elusive. In this study, we identified the acute phase protein α-1 Antitrypsin (AAT) as a potent suppressor of staurosporine (STS)-induced apoptosis in human neutrophils through a mechanism implicating caspases-independent pathways. We show here that serum levels of AAT, potentially in part released by stimulated neutrophils, are markedly elevated in major trauma patients suffering from systemic inflammatory response syndrome (SIRS). Notably, AAT depletion from serum increased sensitivity of human neutrophils for STS-induced cell death. In fact, AAT was demonstrated to confer intrinsic apoptosis resistance by preventing PKC/Akt inactivation and subsequent proteasomal degradation of antiapoptotic Mcl-1 protein in response to STS treatment. Neither MAP kinase ERK1/2 nor caspases were found to be involved in AAT-triggered antiapoptotic pathways in neutrophils. In summary, these results establish a novel pivotal role of circulating AAT in mediating survival by antagonizing the proapoptotic action of the PKC inhibitor STS and should be considered for AAT augmentation therapies in future.

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.

α1-Antitrypsin deficiency

α1-Antitrypsin deficiency (A1ATD) is an inherited disorder caused by mutations in SERPINA1, leading to liver and lung disease. It is not a rare disorder but frequently goes underdiagnosed or misdiagnosed as asthma, chronic obstructive pulmonary disease (COPD) or cryptogenic liver disease. The most frequent disease-associated mutations include the S allele and the Z allele of SERPINA1, which lead to the accumulation of misfolded α1-antitrypsin in hepatocytes, endoplasmic reticulum stress, low circulating levels of α1-antitrypsin and liver disease. Currently, there is no cure for severe liver disease and the only management option is liver transplantation when liver failure is life-threatening. A1ATD-associated lung disease predominately occurs in adults and is caused principally by inadequate protease inhibition. Treatment of A1ATD-associated lung disease includes standard therapies that are also used for the treatment of COPD, in addition to the use of augmentation therapy (that is, infusions of human plasma-derived, purified α1-antitrypsin). New therapies that target the misfolded α1-antitrypsin or attempt to correct the underlying genetic mutation are currently under development.

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.

Alpha-1-antitrypsin deficiency: increasing awareness and improving diagnosis

Alpha-1-antitrypsin deficiency (AATD) is a hereditary disorder that is characterized by a low serum level of alpha-1-antitrypsin (AAT). The loss of anti-inflammatory and antiproteolytic functions, together with pro-inflammatory effects of polymerized AAT contribute to protein degradation and increased inflammation resulting in an increased risk of developing chronic obstructive pulmonary disease (COPD) and emphysema, especially in smokers. AATD is a rare disease that is significantly underdiagnosed. According to recent data that are based on extrapolations, in many countries only 5-15% of homozygous individuals have been identified. Furthermore, the diagnostic delay typically exceeds 5 years, resulting in an average age at diagnosis of about 45 years. Although the American Thoracic Society/European Respiratory Society recommendations state that all symptomatic adults with persistent airway obstruction should be screened, these recommendations are not being followed. Potential reasons for that include missing knowledge about the disease and the appropriate tests, and the low awareness of physicians with regard to the disorder. Once the decision to initiate testing has been made, a screening test (AAT serum level or other) should be performed. Further diagnostic evaluation is based on the following techniques: polymerase chain reaction (PCR) for frequent and clinically important mutations, isoelectric focusing (IEF) with or without immunoblotting, and sequencing of the gene locus coding for AAT. Various diagnostic algorithms have been published for AATD detection (severe deficiency or carrier status). Modern laboratory approaches like the use of serum separator cards, a lateral flow assay to detect the Z-protein, and a broader availability of next-generation sequencing are recent advances, likely to alter existing algorithms.

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.

In Vitro Evaluation of a Novel mRNA-Based Therapeutic Strategy for the Treatment of Patients Suffering from Alpha-1-Antitrypsin Deficiency

In single-gene disorders, like alpha-1-antitrypsin deficiency (AATD), a gene mutation causes missing or dysfunctional protein synthesis. This, in turn, can lead to serious complications for the patient affected. Furthermore, single-gene disorders are associated with severe early-onset conditions and necessitate expensive lifelong care. Until nowadays, therapeutic treatment options are still limited, cost-intensive, or lack effectiveness. For these reasons, we aim to develop a novel mRNA-based therapeutic strategy for the treatment of single-gene disorders, such as AATD, which is based on the induction of de novo synthesis of the functional proteins. Therefore, an alpha-1-antitrypsin (AAT) encoding mRNA was generated by in vitro transcription. After in vitro delivery of the mRNA to different cells, protein expression and functionality, as well as adverse effects and mRNA serum stability, were analyzed. Our results show that the AAT mRNA-transfected cells express the AAT protein in high amounts within the first 24 h. Moreover, the expressed AAT protein is highly functional, since the activity of elastase is significantly inhibited. Our data also show that mRNA concentrations up to 1 μg per 150,000 cells have no adverse effects on cell viability and immune activation. Furthermore, the encapsulated AAT encoding mRNA is stable and functional in human serum for up to 30 min. Overall, the proposed project provides an innovative, highly promising, and safe therapeutic approach and, thus, promises a novel progress in the treatment of single-gene disorders, whereby affected patients could greatly benefit.