Monocytes and Macrophages in Alpha-1 Antitrypsin Deficiency

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.

Rare variants in alpha 1 antitrypsin deficiency: a systematic literature review

BACKGROUND

Alpha 1 Antitrypsin Deficiency (AATD) is a largely underrecognized genetic condition characterized by low Alpha 1 Antitrypsin (AAT) serum levels, resulting from variations in SERPINA1. Many individuals affected by AATD are thought to be undiagnosed, leading to poor patient outcomes. The Z (c.1096G > A; p.Glu366Lys) and S (c.863A > T; p.Glu288Val) deficiency variants are the most frequently found variants in AATD, with the Z variant present in most individuals diagnosed with AATD. However, there are many other less frequent variants known to contribute to lung and/or liver disease in AATD. To identify the most common rare variants associated with AATD, we conducted a systematic literature review with the aim of assessing AATD variation patterns across the world.

METHODS

A systematic literature search was performed to identify published studies reporting AATD/SERPINA1 variants. Study eligibility was assessed for the potential to contain relevant information, with quality assessment and data extraction performed on studies meeting all eligibility criteria. AATD variants were grouped by variant type and linked to the geographical region identified from the reporting article.

RESULTS

Of the 4945 articles identified by the search string, 864 contained useful information for this study. Most articles came from the United States, followed by the United Kingdom, Germany, Spain, and Italy. Collectively, the articles identified a total of 7631 rare variants and 216 types of rare variant across 80 counties. The F (c.739C > T; p.Arg247Cys) variant was identified 1,281 times and was the most reported known rare variant worldwide, followed by the I (c.187C > T; p.Arg63Cys) variant. Worldwide, there were 1492 Null/rare variants that were unidentified at the time of source article publication and 75 rare novel variants reported only once.

CONCLUSION

AATD goes far beyond the Z and S variants, suggesting there may be widespread underdiagnosis of patients with the condition. Each geographical region has its own distinctive variety of AATD variants and, therefore, comprehensive testing is needed to fully understand the true number and type of variants that exist. Comprehensive testing is also needed to ensure accurate diagnosis, optimize treatment strategies, and improve outcomes for patients with AATD.

A high α1-antitrypsin/interleukin-10 ratio predicts bacterial pneumonia in adults with community-acquired pneumonia: a prospective cohort study

BACKGROUND

Current microbiological tests fail to identify the causative microorganism in more than half of all pneumonia cases. We explored biomarkers that could be used for differentiating between bacterial and viral pneumonia in patients with community-acquired pneumonia (CAP).

METHODS

In this prospective cohort study conducted in Japan, data obtained from adult patients with bacterial pneumonia, including bacterial and viral coinfections (bacterial pneumonia [BP] group), and purely viral pneumonia (VP group) at diagnosis were analyzed using multivariate logistic regression analysis to identify predictors of bacterial pneumonia. Furthermore, a decision tree was developed using the predictors.

RESULTS

A total of 210 patients were analyzed. The BP and VP groups comprised 108 and 18 patients, respectively. The other 84 patients had no identified causative microorganism. The two groups shared similar characteristics, including disease severity; however, a significant difference (p < 0.05) was observed between the two groups regarding sputum type; sputum volume score; neutrophil counts; and serum levels of interleukin (IL)-8, IL-10, and α1-antitrypsin (AAT). Sputum volume score (p < 0.001), IL-10 (p < 0.001), and AAT (p = 0.008) were ultimately identified as predictors of BP. The area under the curve for these three variables on the receiver operating characteristic (ROC) curve was 0.927 (95% confidence interval [CI]: 0.881-0.974). The ROC curve for sputum volume score and an AAT/IL-10 ratio showed a diagnostic cutoff of 1 + and 65, respectively. Logistic regression analysis using dichotomized variables at the cutoff values showed that the odds ratios for the diagnosis of BP were 10.4 (95% CI: 2.2-50.2) for sputum volume score (absence vs. presence) and 19.8 (95% CI: 4.7-83.2) for AAT/IL-10 ratio (< 65 vs. ≥ 65).

CONCLUSIONS

Considering that obtaining a definitive etiologic diagnosis with the current testing methods is difficult and time consuming, a decision tree with two predictors, namely sputum volume and the AAT/IL-10 ratio, can be useful in predicting BP among patients diagnosed with CAP and facilitating the appropriate use of antibiotics.

TRIAL REGISTRATION

UMIN000034673 registered on November 29, 2018.

NAFLD and AATD Are Two Diseases with Unbalanced Lipid Metabolism: Similarities and Differences

Non-alcoholic fatty liver disease (NAFLD) is a type of steatosis commonly associated with obesity, dyslipidemia, hypertension, and diabetes. Other diseases such as inherited alpha-1 antitrypsin deficiency (AATD) have also been related to the development of liver steatosis. The primary reasons leading to hepatic lipid deposits can be genetic and epigenetic, and the outcomes range from benign steatosis to liver failure, as well as to extrahepatic diseases. Progressive hepatocellular damage and dysregulated systemic immune responses can affect extrahepatic organs, specifically the heart and lungs. In this review, we discuss the similarities and differences between the molecular pathways of NAFLD and AATD, and the putative value of hepatic organoids as novel models to investigate the physio pathological mechanisms of liver steatosis.

The Anti-Inflammatory Effect of Lactose-Modified Hyaluronic Acid Molecules on Primary Bronchial Fibroblasts of Smokers

The progression of smoking-related diseases is characterized by macrophage-mediated inflammation, which is responsible for an increased expression of proinflammatory cytokines and galectins, molecules that bind specifically to β-galactoside sugars. This study aimed to assess the anti-inflammatory and antioxidant effects of a broad selection of differently lactose-modified hyaluronic acids (HA) named HYLACH^®, which are able to bind proinflammatory galectins. The best HYLACH ligands for Gal-3 were selected in silico and their activities were tested in vitro on primary human bronchial fibroblasts obtained from smokers and inflamed with the conditioned medium of activated U937 monocytes. Changes in cell viability, ROS generation, proinflammatory mediators, and MMP expression, at both gene and protein levels, were analyzed. The in silico results show that HYLACH with a percentage of lactosylation of 10-40% are the best ligands for Gal-3. The in vitro study revealed that HYLACH compounds with 10, 20, and 40% lactosylation (HYLACH-1-2-3) administrated to inflamed cell cultures counteracted the oxidative damage and restored gene and protein expression for IL-1β, TNF-α, IL-6, Gal-1, Gal-3, and MMP-3 to near baseline values. The evidence that HYLACH attenuated macrophage-induced inflammation, inhibited MMP expression, and exhibited antioxidative effects provide an initial step toward the development of a therapeutic treatment suitable for smoking-related diseases.

Connecting single-nucleotide polymorphisms, glycosylation status, and interactions of plasma serine protease inhibitors

Understanding the combined impacts of genetic variances and post-translational modifications requires new approaches. Here, we delineate proteoforms of plasma serine protease inhibitors and relate specific proteoforms to their interactions in complexes through the use of native mass spectrometry (MS). First, we dissect the proteoform repertoire of an acute-phase plasma protein, serine protease inhibitor A1 (SERPINA1), resolving four SERPINA1 variants (M1V, M1A, M2, and M3) with common single-nucleotide polymorphisms (SNPs). Investigating the glycosylation status of these variants and their ability to form complexes with a serine protease, elastase, we find that fucosylation stabilizes the interaction of the SERPINA1 M1V variant through its core fucosylation on Asn271. In contrast, antennary fucosylation on Asn271 destabilizes SERPINA1-elastase interactions. We unveil the same opposing effects of core and antennary fucosylation on SERPINA3 interactions with chymotrypsin. Together, our native MS results highlight the modulating effects of fucosylation with different linkages on glycoprotein interactions.

The role of lung macrophages in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) as a common, preventable and treatable chronic respiratory disease in clinic, gets continuous deterioration and we can't take effective intervention at present. Lung macrophages (LMs) are closely related to the occurrence and development of COPD, but the specific mechanism is not completely clear. In this review we will focus on the role of LMs and potential avenues for therapeutic targeting for LMs in COPD.

Modulating macrophage function to reinforce host innate resistance against Mycobacterium avium complex infection

Mycobacterium avium complex (MAC) is the main causative agent of infectious diseases in humans among nontuberculous mycobacteria (NTM) that are ubiquitous organisms found in environmental media such as soil as well as in domestic and natural waters. MAC is a primary causative agent of NTM-lung disease that threaten immunocompromised or structural lung disease patients. The incidence and the prevalence of M. tuberculosis infection have been reduced, while MAC infections and mortality rates have increased, making it a cause of global health concern. The emergence of drug resistance and the side effects of long-term drug use have led to a poor outcome of treatment regimens against MAC infections. Therefore, the development of host-directed therapy (HDT) has recently gained interest, aiming to accelerate mycobacterial clearance and reversing lung damage by employing the immune system using a novel adjuvant strategy to improve the clinical outcome of MAC infection. Therefore, in this review, we discuss the innate immune responses that contribute to MAC infection focusing on macrophages, chief innate immune cells, and host susceptibility factors in patients. We also discuss potential HDTs that can act on the signaling pathway of macrophages, thereby contributing to antimycobacterial activity as a part of the innate immune response during MAC infection. Furthermore, this review provides new insights into MAC infection control that modulates and enhances macrophage function, promoting host antimicrobial activity in response to potential HDTs and thus presenting a deeper understanding of the interactions between macrophages and MACs during infection.

Cigarette smoke exposed airway epithelial cell-derived EVs promote pro-inflammatory macrophage activation in alpha-1 antitrypsin deficiency

BACKGROUND

Alpha-1 antitrypsin deficiency (AATD) is a genetic disorder most commonly secondary to a single mutation in the SERPINA1 gene (PI*Z) that causes misfolding and accumulation of alpha-1 antitrypsin (AAT) in hepatocytes and mononuclear phagocytes which reduces plasma AAT and creates a toxic gain of function. This toxic gain of function promotes a pro-inflammatory phenotype in macrophages that contributes to lung inflammation and early-onset COPD, especially in individuals who smoke cigarettes. The aim of this study is to determine the role of cigarette exposed AATD macrophages and bronchial epithelial cells in AATD-mediated lung inflammation.

METHODS

Peripheral blood mononuclear cells from AATD and healthy individuals were differentiated into alveolar-like macrophages and exposed to air or cigarette smoke while in culture. Macrophage endoplasmic reticulum stress was quantified and secreted cytokines were measured using qPCR and cytokine ELISAs. To determine whether there is "cross talk" between epithelial cells and macrophages, macrophages were exposed to extracellular vesicles released by airway epithelial cells exposed to cigarette smoke and their inflammatory response was determined.

RESULTS

AATD macrophages spontaneously produce several-fold more pro-inflammatory cytokines as compared to normal macrophages. AATD macrophages have an enhanced inflammatory response when exposed to cigarette smoke-induced extracellular vesicles (EVs) released from airway epithelial cells. Cigarette smoke-induced EVs induce expression of GM-CSF and IL-8 in AATD macrophages but have no effect on normal macrophages. Release of AAT polymers, potent neutrophil chemo attractants, were also increased from AATD macrophages after exposure to cigarette smoke-induced EVs.

CONCLUSIONS

The expression of mutated AAT confers an inflammatory phenotype in AATD macrophages which disposes them to an exaggerated inflammatory response to cigarette smoke-induced EVs, and thus could contribute to progressive lung inflammation and damage in AATD individuals.

Secretion of functional α1-antitrypsin is cell type dependent: Implications for intramuscular delivery for gene therapy

Heterologous expression of proteins is used widely for the biosynthesis of biologics, many of which are secreted from cells. In addition, gene therapy and messenger RNA (mRNA) vaccines frequently direct the expression of secretory proteins to nonnative host cells. Consequently, it is crucial to understand the maturation and trafficking of proteins in a range of host cells including muscle cells, a popular therapeutic target due to the ease of accessibility by intramuscular injection. Here, we analyzed the production efficiency for α1-antitrypsin (AAT) in Chinese hamster ovary cells, commonly used for biotherapeutic production, and myoblasts (embryonic progenitor cells of muscle cells) and compared it to the production in the major natural cells, liver hepatocytes. AAT is a target protein for gene therapy to address pathologies associated with insufficiencies in native AAT activity or production. AAT secretion and maturation were most efficient in hepatocytes. Myoblasts were the poorest of the cell types tested; however, secretion of active AAT was significantly augmented in myoblasts by treatment with the proteostasis regulator suberoylanilide hydroxamic acid, a histone deacetylase inhibitor. These findings were extended and validated in myotubes (mature muscle cells) where AAT was transduced using an adeno-associated viral capsid transduction method used in gene therapy clinical trials. Overall, our study sheds light on a possible mechanism to enhance the efficacy of gene therapy approaches for AAT and, moreover, may have implications for the production of proteins from mRNA vaccines, which rely on the expression of viral glycoproteins in nonnative host cells upon intramuscular injection.

Inflammation, Ageing and Diseases of the Lung: Potential therapeutic strategies from shared biological pathways

Lung diseases disproportionately affect elderly individuals. The lungs form a unique environment: a highly elastic organ with gaseous exchange requiring the closest proximity of inhaled air containing harmful agents and the circulating blood volume. The lungs are highly susceptible to senescence, with age and "inflammageing" creating a pro-inflammatory environment with a reduced capacity to deal with challenges. Whilst lung diseases may have disparate causes, the burden of ageing and inflammation provides a common process which can exacerbate seemingly unrelated pathologies. However, these shared pathways may also provide a common route to treatment, with increased interest in drugs which target ageing processes across respiratory diseases. In this review, we will examine the evidence for the increased burden of lung disease in older adults, the structural and functional changes seen with advancing age and assess what our expanding knowledge of inflammation and ageing pathways could mean for the treatment of lung disease.

Polymerization of misfolded Z alpha-1 antitrypsin protein lowers CX3CR1 expression in human PBMCs

Expression levels of CX3CR1 (C-X3-C motif chemokine receptor 1) on immune cells have significant importance in maintaining tissue homeostasis under physiological and pathological conditions. The factors implicated in the regulation of CX3CR1 and its specific ligand CX3CL1 (fractalkine) expression remain largely unknown. Recent studies provide evidence that host’s misfolded proteins occurring in the forms of polymers or amyloid fibrils can regulate CX3CR1 expression. Herein, a novel example demonstrates that polymers of human ZZ alpha-1 antitrypsin (Z-AAT) protein, resulting from its conformational misfolding due to the Z (Glu342Lys) mutation in SERPINA1 gene, strongly lower CX3CR1 mRNA expression in human peripheral blood mononuclear cells (PBMCs). This parallels with increase of intracellular levels of CX3CR1 and Z-AAT proteins. Presented data indicate the involvement of the CX3CR1 pathway in the Z-AAT-related disorders and further support the role of misfolded proteins in CX3CR1 regulation.

Proteins can lose their structure and form polymers because of mutations or changes in their immediate environment which can lead to cell damage and disease. Interestingly, polymers formed by a variety of proteins can reduce the levels of CX3C chemokine receptor 1 (CX3CR1 for short) that controls the behaviour of immune cells and is implicated in a range of illnesses.

Inherited ZZ alpha-1 antitrypsin deficiency is a rare genetic condition that highly increases the risk of liver and lung diseases. This disorder is characterised by mutant alpha-1 antitrypsin proteins (AAT for short) reacting together to form polymers; yet it remains unclear how the polymers affect different cells or organs, and lead to diseases. To investigate this question, Tumpara et al. examined whether polymers of mutant AAT influence the level of the CX3CR1 protein in specific classes of immune cells.

Experiments revealed that in people with AAT deficiency, certain blood immune cells express lower levels of CX3CR1. Regardless of age, clinical diagnosis, or treatment regimen, all individuals with ZZ alpha-1 antitrypsin deficiency had AAT polymers circulating in their blood: the higher the levels of polymers measured, the lower the expression of CX3CR1 recorded in the specific immune cells. When Tumpara et al. added polymers of mutant AAT to the immune cells of healthy donors, the expression of CX3CR1 dropped in a manner dependent on the polymer concentration. According to microscopy data, AAT polymers occurred inside cells alongside the CX3CR1 protein, suggesting that the two molecular actors interact. In the future, new drugs that remove these polymers, either from inside cells or as they circulate in the body, could help patients suffering from conditions associated with this abnormal protein aggregation.