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α 1 -Antitrypsin (AAT) is a 52-kDa circulating serine protease inhibitor. Production of AAT by the liver maintains 0.9-1.75 mg/mL circulating levels. During acute-phase responses, circulating AAT levels increase more than fourfold. In individuals with one of several inherited mutations in AAT, low circulating levels increase the risk for lung, liver and pancreatic destructive diseases, particularly emphysema. These individuals are treated with lifelong weekly infusions of human plasma-derived AAT. An increasing amount of evidence appears to suggest that AAT possesses not only the ability to inhibit serine proteases, such as elastase and proteinase-3 (PR-3), but also to exert antiinflammatory and tissue-protective effects independent of protease inhibition. AAT modifies dendritic cell maturation and promotes T regulatory cell differentiation, induces interleukin (IL)-1 receptor antagonist and IL-10 release, protects various cell types from cell death, inhibits caspases-1 and -3 activity and inhibits IL-1 production and activity. Importantly, unlike classic immunosuppressants, AAT allows undeterred isolated T-lymphocyte responses. On the basis of preclinical and clinical studies, AAT therapy for nondeficient individuals may interfere with disease progression in type 1 and type 2 diabetes, acute myocardial infarction, rheumatoid arthritis, inflammatory bowel disease, cystic fibrosis, transplant rejection, graft versus host disease and multiple sclerosis. AAT also appears to be antibacterial and an inhibitor of viral infections, such as influenza and human immunodeficiency virus (HIV), and is currently evaluated in clinical trials for type 1 diabetes, cystic fibrosis and graft versus host disease. Thus, AAT therapy appears to have advanced from replacement therapy, to a safe and potential treatment for a broad spectrum of inflammatory and immune-mediated diseases.

The rationale of α1-antitrypsin (AAT) augmentation therapy to treat progressive emphysema in AAT-deficient patients is based on inhibition of neutrophil elastase; however, the benefit of this treatment remains unclear. Here we show that clinical grade AAT (with elastase inhibitory activity) and a recombinant form of AAT (rAAT) without anti-elastase activity reduces lung inflammatory responses to LPS in elastase-deficient mice. WT and elastase-deficient mice treated with either native AAT or rAAT exhibited significant reductions in infiltrating neutrophils (23% and 68%), lavage fluid levels of TNF-α (70% and 80%), and the neutrophil chemokine KC (CXCL1) (64% and 90%), respectively. Lung parenchyma TNF-α, DNA damage-inducible transcript 3 and X-box binding protein-1 mRNA levels were reduced in both mouse strains treated with AAT; significantly lower levels of these genes, as well as IL-1β gene expression, were observed in lungs of AAT-deficient patients treated with AAT therapy compared with untreated patients. In vitro, LPS-induced cytokines from WT and elastase-deficient mouse neutrophils, as well as neutrophils of healthy humans, were similarly reduced by AAT or rAAT; human neutrophils adhering to endothelial cells were decreased by 60–80% (P < 0.001) with either AAT or rAAT. In mouse pancreatic islet macrophages, LPS-induced surface expression of MHC II, Toll-like receptor-2 and -4 were markedly lower (80%, P < 0.001) when exposed to either AAT or rAAT. Consistently, in vivo and in vitro, rAAT reduced inflammatory responses at concentrations 40- to 100-fold lower than native plasma-derived AAT. These data provide evidence that the anti-inflammatory and immunomodulatory properties of AAT can be independent of elastase inhibition.

Wound healing requires a delicate balance between cellular and molecular factors, all affected by reactive oxygen species (ROS). While ROS decontaminate, they also might lead to impaired wound healing, as evident in radiation-exposed skin and in venous insufficiency. Human alpha-1 antitrypsin (hAAT) is a circulating antiprotease that is anti-inflammatory and tissue-protective. Accordingly, tissue repair is enhanced in hAAT-rich conditions. hAAT undergoes oxidative modification in high-ROS environments, which alters its functional properties. While its antiprotease function is lost, the consequences of oxidation on its anti-inflammatory and tissue-protective properties are still under investigation. To explore this, excisional skin wound closure rates were first examined on irradiated skin and then tested using an iron-loading venous insufficiency model. The former was tested on hAAT transgenic mice, the latter on wild-type mice using topical clinical-grade hAAT. In-vitro, hAAT was oxidized using H 2 O 2 (0.5, 5 and 25 mM), then tested for elastase inhibition and added to an in-vitro A549 epithelial cell gap closure assay and a RAW 264.7 macrophage cell response assay. ROS levels, inflammatory responses and NRF2/ARE activation were determined. Results demonstrated wound closure was impaired in wild-type mice by both radiation and iron. In contrast, hAAT-transgenic mice exhibited accelerated wound closure in both normal and irradiated skin, and topical hAAT improved wound healing in the venous insufficiency model. hAAT OX lacked elastase inhibition across the three oxidation levels, yet highly oxidized hAAT (hAAT OX 25mM ) impaired epithelial gap closure and weakly oxidized hAAT (hAAT OX 0.5mM ) enhanced gap closure. All forms of hAAT OX elevated ROS in macrophages, as well as the expression of iNOS and catalase, IL-1β, TNFα and CXCL-1. Unexpectedly, the NRF2/ARE pathway was activated by hAAT OX 25mM and suppressed by hAAT OX 0.5mM , and hAAT OX 0.5 mM induced IL-1 receptor antagonist expression. In conclusion, oxidation levels of hAAT modify its effects on inflammation and tissue repair. While protease inhibition is lost, anti-inflammatory and repair attributes are maintained under low oxidative conditions, suggesting a molecular profile that is physiologically attuned to local signals. Considering its safety record, the study proposes that hAAT therapy is poised for trials in the context of defective tissue repair under oxidative conditions.

Cytokines of the IL-1 family are important modulators of obesity-induced inflammation and the development of systemic insulin resistance. Here we show that IL-1 family member IL-37, recently characterized as an anti-inflammatory cytokine, ameliorates obesity-induced inflammation and insulin resistance. Mice transgenic for human IL-37 (IL-37tg) exhibit reduced numbers of adipose tissue macrophages, increased circulating levels of adiponectin and preserved glucose tolerance and insulin sensitivity after 16 weeks of HFD. In vitro treatment of adipocytes with recombinant IL-37 reduces adipogenesis and activates AMPK signalling. In humans, elevated steady-state IL-37 adipose tissue mRNA levels are positively correlated with insulin sensitivity and a lower inflammatory status of the adipose tissue. These findings reveal IL-37 as an important anti-inflammatory modulator during obesity-induced inflammation and insulin resistance in both mice and humans, and suggest that IL-37 is a potential target for the treatment of obesity-induced insulin resistance and type 2 diabetes. Inflammation is a hallmark of obesity and driver of various associated pathologies. Here the authors show that mice overexpressing the anti-inflammatory cytokine IL-37 are protected from the metabolic consequences of a high-fat diet, and that plasma levels of IL-37 correlate with insulin sensitivity in humans.

Acute graft-versus-host disease (GvHD) is a major complication that prevents successful outcomes after allogeneic bone marrow transplantation (BMT), an effective therapy for hematological malignancies. Several studies demonstrate that donor T cells and host antigen-presenting cells along with several proinflammatory cytokines are required for the induction of GvHD and contribute to its severity. Increasing evidence demonstrates that human serum-derived αalpha-1- anti-trypsin (AAT) reduces production of proinflammatory cytokines, induces anti-inflammatory cytokines, and interferes with maturation of dendritic cells. Using well-characterized mouse models of BMT, we have studied the effects of AAT on GvHD severity. Administration of AAT early after BMT decreased mortality in three models of GvHD and reduced serum levels of proinflammatory cytokines in the allogeneic recipients compared with vehicle (albumin) treated animals. AAT treatment reduced the expansion of alloreactive T effector cells but enhanced the recovery of T regulatory T cells, (Tregs) thus altering the ratio of donor T effector to T regulatory cells in favor of reducing the pathological process. However, despite altering the ratio in vivo, AAT had no direct effects on either the donor T effector cells or T regulatory cells Tregs in vitro. In contrast, AAT suppressed LPS-induced in vitro secretion of proinflammatory cytokines such as TNF-α and IL-1β, enhanced the production of the anti-inflammatory cytokine IL-10, and impaired NF-κB translocation in the host dendritic cells. In light of its long history of safety in humans, these findings suggest that administration of AAT represents a novel unique and viable strategy to mitigate clinical GvHD.

Developing a device that protects xenogeneic islets to allow treatment and potentially cure of diabetes in large mammals has been a major challenge in the past decade. Using xenogeneic islets for transplantation is required in light of donor shortage and the large number of diabetic patients that qualify for islet transplantation. Until now, however, host immunoreactivity against the xenogeneic graft has been a major drawback for the use of porcine islets. Our study demonstrates the applicability of a novel immunoprotective membrane that allows successful xenotransplantation of rat islets in diabetic minipigs without immunosuppressive therapy. Rat pancreatic islets were encapsulated in highly purified alginate and integrated into a plastic macrochamber covered by a poly-membrane for subcutaneous transplantation. Diabetic Sinclair pigs were transplanted and followed for up to 90 days. We demonstrated a persistent graft function and restoration of normoglycemia without the need for immunosuppressive therapy. This concept could potentially offer an attractive strategy for a more widespread islet replacement therapy that would restore endogenous insulin secretion in diabetic patients without the need for immunosuppressive drugs and may even open up an avenue for safe utilization of xenogeneic islet donors.

Background. Severe bacterial infection can cause sepsis, multiple organ dysfunction syndrome (MODS), and death. Human α₁-antitrypsin (hAAT) is an antiinflammatory, immune-modulating, and tissue-protective circulating serine-protease inhibitor, with levels that increase during acute-phase responses. It is currently being evaluated as a therapeutic agent for individuals with diabetes and graft-versus-host disease. However, the concern of opportunistic bacterial infections has yet to be addressed. Therefore, we investigated host immune cell responses during acute bacterial infections under conditions of elevated hAAT levels. Methods. Peritonitis and sepsis models were created using wild-type mice and hAAT-transgenic mice. Bacterial loads, MODS, leukopenia, neutrophil infiltration, immune cell activation, circulating cytokine levels, and survival rates were then assessed. Results. hAAT significantly reduced infection-induced leukopenia and liver, pancreas, and lung injury, and it significantly improved 24-hour survival rates. Unexpectedly, bacterial load was reduced. Levels of early proinflammatory mediators and neutrophil influx were increased by hAAT soon after infection but not during sterile peritonitis. Conclusions. hAAT reduces the bacterial burden after infection. Since hAAT does not block bacterial growth in culture, its effects might rely on host immune cell modulation. These outcomes suggest that prolonged hAAT treatment in patients without hAAT deficiency is safe. Additionally, hAAT treatment may be considered a preemptive therapeutic measure for individuals who are at risk for bacterial infections.

α(1)-Antitrypsin (AAT) is a 52-kDa circulating serine protease inhibitor. Production of AAT by the liver maintains 0.9-1.75 mg/mL circulating levels. During acute-phase responses, circulating AAT levels increase more than fourfold. In individuals with one of several inherited mutations in AAT, low circulating levels increase the risk for lung, liver and pancreatic destructive diseases, particularly emphysema. These individuals are treated with lifelong weekly infusions of human plasma-derived AAT. An increasing amount of evidence appears to suggest that AAT possesses not only the ability to inhibit serine proteases, such as elastase and proteinase-3 (PR-3), but also to exert antiinflammatory and tissue-protective effects independent of protease inhibition. AAT modifies dendritic cell maturation and promotes T regulatory cell differentiation, induces interleukin (IL)-1 receptor antagonist and IL-10 release, protects various cell types from cell death, inhibits caspases-1 and -3 activity and inhibits IL-1 production and activity. Importantly, unlike classic immunosuppressants, AAT allows undeterred isolated T-lymphocyte responses. On the basis of preclinical and clinical studies, AAT therapy for nondeficient individuals may interfere with disease progression in type 1 and type 2 diabetes, acute myocardial infarction, rheumatoid arthritis, inflammatory bowel disease, cystic fibrosis, transplant rejection, graft versus host disease and multiple sclerosis. AAT also appears to be antibacterial and an inhibitor of viral infections, such as influenza and human immunodeficiency virus (HIV), and is currently evaluated in clinical trials for type 1 diabetes, cystic fibrosis and graft versus host disease. Thus, AAT therapy appears to have advanced from replacement therapy, to a safe and potential treatment for a broad spectrum of inflammatory and immune-mediated diseases.

Human pancreatic islet transplantation offers diabetic patients tight glucose control but has low graft survival rates. The immunosuppressive drugs that are administered to graft recipients lack the antiinflammatory benefits of corticosteroids because of their diabetogenic effects. The serum protease inhibitor α1-antitrypsin (AAT) possesses antiinflammatory properties and reduces cytokine-mediated islet damage. In the present study, diabetic mice were grafted with allogeneic islets and treated with AAT monotherapy (n = 24). After 14 days of treatment, mice remained normoglycemic and islet allografts were functional for up to 120 treatment-free days. After graft removal and retransplantation, mice accepted same-strain islets but rejected third-strain islets, thus confirming that specific immune tolerance had been induced. Explanted grafts exhibited a population of T regulatory cells in transplant sites. According to RT-PCR, grafts contained high levels of mRNA for foxp3, cytotoxic T lymphocyte antigen-4, TGF-β, IL-10, and IL-1 receptor antagonist; expression of proinflammatory mediators was low or absent. After implantation of skin allografts, AAT-treated mice had greater numbers of foxp3-positive cells in draining lymph nodes (DLNs) compared with control treatment mice. Moreover, dendritic cells in DLNs exhibited an immature phenotype with decreased CD86 activation marker. Although the number of CD3 transcripts decreased in the DLNs, AAT did not affect IL-2 activity in vitro. Thus, AAT monotherapy provides allografts with antiinflammatory conditions that favor development of antigen-specific T regulatory cells. Because AAT treatment in humans is safe, its use during human islet transplantation may be considered.

Regulation of inflammation and re-epithelialization are critical for efficient wound healing. This study explores the role of human α1-antitrypsin (hAAT), an immunomodulatory protein, in modulating inflammation and promoting re-epithelialization across various epithelial cell types. , epithelial gap closure and migration assays were performed using two human epithelial cell lines-HaCaT and A549 cells with and without mitomycin C treatment. These cell lines were also used in an gel-directed epithelial migration assay. Cells were treated with hAAT, and the gap area was measured using image analysis. Gene expression of inflammatory markers (IL-1β, IL-6, and TNFα) and adhesion molecules (desmoglein-1, plectin, and integrin α6β4) were analyzed using qPCR. , corneal abrasions were induced in C57BL/6 mice using an Ophthalmic Burr. Mice received topical hAAT treatment immediately after injury and every 6 hours thereafter. Wound closure was assessed by applying the standard ophthalmic staining technique, fluorescein, and image analysis. Inflammatory markers and adhesion molecule expression were evaluated using qPCR and immunohistochemistry. , hAAT accelerated epithelial gap closure and increased migration distance, independent of cell proliferation. hAAT-treated cells also exhibited earlier peak expressions of IL-1β and IL-6. , hAAT treatment accelerated corneal wound closure and resulted in a preference for IL-1Ra over IL-1β expression. hAAT also enhanced the expression of desmoglein-1, plectin, and integrin α6β4, both and , and increased desmoglein-1 expression in the epithelial migration zone of mouse cornea. hAAT enhances re-epithelialization by modulating inflammation, promoting epithelial cell migration, and regulating expression of adhesion molecules.