Tailor-made inflammation: how neutrophil serine proteases modulate the inflammatory response

Neutrophil-Enriched Biomarkers and Long-Term Prognosis in Acute Coronary Syndrome: a Systematic Review and Meta-analysis

Activated neutrophils release a range of inflammatory products that represent potential biomarkers, and there is interest in the prognostic value of these in acute coronary syndrome (ACS) patients. We conducted a systematic review to examine neutrophil-enriched biomarkers and the occurrence of major adverse cardiovascular events (MACE) in patients with ACS. We identified twenty-seven studies including 17,831 patients with ACS. The most studied biomarkers were neutrophil gelatinase-associated lipocalin (NGAL) and myeloperoxidase (MPO). Meta-analyses showed that elevated NGAL was associated with higher MACE rates (unadjusted risk ratio (RR) 1.52, 95% CI 1.12-2.06, p = 0.006) as were elevated MPO levels (unadjusted RR 1.61, 95% CI 1.22-2.13, p = 0.01). There was limited data suggesting that increased levels of calprotectin, proteinase-3 and double-stranded DNA were also associated with MACE. These results suggest that higher levels of neutrophil-enriched biomarkers may be predictive of MACE in patients with ACS, although higher-quality studies are needed to confirm these observations.

Mechanisms of neutrophil extracellular trap in chronic inflammation of endothelium in atherosclerosis

Cardiovascular diseases are a primary cause of morbidity and mortality around the world. In addition, atherosclerosis (AS)-caused cardiovascular disease is the primary cause of death in human diseases, and almost two billion people suffer from carotid AS worldwide. AS is caused by chronic inflammation of the arterial vessel and is initiated by dysfunction of vascular endothelial cells. Neutrophils protect against pathogen invasion because they function as a component of the innate immune system. However, the contribution of neutrophils to cardiovascular disease has not yet been clarified. Neutrophil extracellular traps (NETs) represent an immune defense mechanism that is different from direct pathogen phagocytosis. NETs are extracellular web-like structures activated by neutrophils, and they play important roles in promoting endothelial inflammation via direct or indirect pathways. NETs consist of DNA, histones, myeloperoxidase, matrix metalloproteinases, proteinase 3, etc. Most of the components of NETs have no direct toxic effect on endothelial cells, such as DNA, but they can damage endothelial cells indirectly. In addition, NETs play a critical role in the process of AS; therefore, it is important to clarify the mechanisms of NETs in AS because NETs are a new potential therapeutic target AS. This review summarizes the possible mechanisms of NETs in AS.

Molecular Actors of Inflammation and Their Signaling Pathways: Mechanistic Insights from Zebrafish

Inflammation is a hallmark of the physiological response to aggressions. It is orchestrated by a plethora of molecules that detect the danger, signal intracellularly, and activate immune mechanisms to fight the threat. Understanding these processes at a level that allows to modulate their fate in a pathological context strongly relies on in vivo studies, as these can capture the complexity of the whole process and integrate the intricate interplay between the cellular and molecular actors of inflammation. Over the years, zebrafish has proven to be a well-recognized model to study immune responses linked to human physiopathology. We here provide a systematic review of the molecular effectors of inflammation known in this vertebrate and recapitulate their modes of action, as inferred from sterile or infection-based inflammatory models. We present a comprehensive analysis of their sequence, expression, and tissue distribution and summarize the tools that have been developed to study their function. We further highlight how these tools helped gain insights into the mechanisms of immune cell activation, induction, or resolution of inflammation, by uncovering downstream receptors and signaling pathways. These progresses pave the way for more refined models of inflammation, mimicking human diseases and enabling drug development using zebrafish models.

Selective decrease in alpha1-antitrypsin levels in diabetic retinopathy: Could the levels of it be playing a role in the pathophysiology of diabetic retinopathy?

Background & objectives

Type 2 diabetes mellitus (T2DM) is known to induce inflammation and activation of neutrophils causing the release of neutrophil elastase (NE), a pro-inflammatory proteinase. The activity of NE is regulated by endogenous inhibitors alpha₁-antitrypsin (α₁-AT) and alpha₂-macroglobulin (α₂-MG). Disrupted proteolytic homeostasis in T2DM patients is one of the causes for vascular complications. This study was carried out for evaluating the levels of plasma NE, α₁-AT, α₂-MG and NE-α₁-AT complex to understand their roles in the pathophysiology of diabetic nephropathy (DN) and diabetic retinopathy (DR).

Methods

A total of 240 participants (Control, n=60; T2DM, n=60; DN, n=60; and DR, n=60) were recruited after recording history, clinical examination and laboratory investigations. Retinopathy was confirmed by fundoscopy and nephropathy by urinary albumin excretion and serum creatinine levels. NE was measured using STANA. α₁-AT, α₂-MG and NE-α₁-AT complex were estimated by ELISA.

Results

Baseline clinical and laboratory findings were confirmatory to the study groups. The mean elastase activity was higher (P<0.0005) in diabetes groups (T2DM=0.73±0.31, DN=0.87±0.35, DR=0.76±0.41) than controls (0.35±0.20). The levels of α₁-AT were lower in DR (8.77±2.85) than DN (26.26±6.16) and T2DM (41.13±14.06) when juxtaposed with controls (122.95±25.71). The approximate fold decrease of α₁-AT levels was 15 for DR and four for DN compared to controls. The levels of α₂-MG were lowered in T2DM (167.29±30.45), DN (144.66±13.72), and DR (104.67±11.47) than controls (208.87±31.16). The NE-α₁-AT complex levels were: controls (215.83±13.61), T2DM (98.85±23.85), DN (129.26±20.40) and DR (153.25±17.11).

Interpretation & conclusions

Homeostasis of NE, α₁-AT and α₂-MG is disrupted in T2DM, DN and DR. Strikingly reduced levels of α₁-AT observed in DR are indicative of its possible role in the pathophysiology of retinopathy and emphasizes α₁-AT as a plausible therapeutic target.

Research Progress on the Immunogenicity and Regeneration of Acellular Adipose Matrix: A Mini Review

Acellular adipose matrix (AAM) has received increasing attention for soft tissue reconstruction, due to its abundant source, high long-term retention rate and in vivo adipogenic induction ability. However, the current decellularization methods inevitably affect native extracellular matrix (ECM) properties, and the residual antigens can trigger adverse immune reactions after transplantation. The behavior of host inflammatory cells mainly decides the regeneration of AAM after transplantation. In this review, recent knowledge of inflammatory cells for acellular matrix regeneration will be discussed. These advancements will inform further development of AAM products with better properties.

Combination therapy of Ulinastatin with Thrombomodulin alleviates endotoxin (LPS) - induced liver and kidney injury via inhibiting apoptosis, oxidative stress and HMGB1/TLR4/NF-κB pathway

Sepsis is a type of systemic inflammation response syndrome that leads to organ function disorders. Currently, there is no specific medicine for sepsis in clinical practice. Lipopolysaccharide (LPS) is an important endotoxin that causes sepsis. Here, we report an effective two-drug combination therapy to treat LPS-induced liver and kidney injury in endotoxic rats. Ulinastatin (UTI) and Thrombomodulin (TM) are biological macromolecules extracted from urine. In our study, combination therapy significantly improved LPS-induced liver and kidney pathological structure and functional injury, and significantly improved the survival rate of endotoxic rats. Results of TUNEL staining and Western blot showed that UTI combined with TM inhibited the excessive apoptosis of liver and kidney cells caused by LPS. The drug combination also promoted the proliferation of liver and kidney cells, reduced the levels of pro-inflammatory factors interleukin (IL)-6, IL-1β, tumor or necrosis factor (TNF)-α and nitric oxide, and down-regulated the expression of High Mobility Group Box 1 (HMGB1), Toll-like receptor (TLR) 4 and Nuclear Factor (NF)-κB phosphorylation to inhibit inflammation. In addition, the combination of UTI and TM also promoted the production of a variety of antioxidant enzymes in the tissues and inhibited the production of lipid peroxidation malondialdehyde (MDA) to enhance antioxidant defenses. Our experiments also proved that UTI combined with TM did not reduce the anticoagulant effect of TM. These results suggested that UTI combined with TM can improve endotoxin-induced liver and kidney damage and mortality by inhibiting liver and kidney cell apoptosis, promoting proliferation, and inhibiting inflammation and oxidative injury.

T cell transgressions: Tales of T cell form and function in diverse disease states

Insights into T cell form, function, and dysfunction are rapidly evolving. T cells have remarkably varied effector functions including protecting the host from infection, activating cells of the innate immune system, releasing cytokines and chemokines, and heavily contributing to immunological memory. Under healthy conditions, T cells orchestrate a finely tuned attack on invading pathogens while minimizing damage to the host. The dark side of T cells is that they also exhibit autoreactivity and inflict harm to host cells, creating autoimmunity. The mechanisms of T cell autoreactivity are complex and dynamic. Emerging research is elucidating the mechanisms leading T cells to become autoreactive and how such responses cause or contribute to diverse disease states, both peripherally and within the central nervous system. This review provides foundational information on T cell development, differentiation, and functions. Key T cell subtypes, cytokines that create their effector roles, and sex differences are highlighted. Pathological T cell contributions to diverse peripheral and central disease states, arising from errors in reactivity, are highlighted, with a focus on multiple sclerosis, rheumatoid arthritis, osteoarthritis, neuropathic pain, and type 1 diabetes.

Cathepsin C inhibition as a potential treatment strategy in cancer

Epidemiological studies established an association between chronic inflammation and higher risk of cancer. Inhibition of proteolytic enzymes represents a potential treatment strategy for cancer and prevention of cancer metastasis. Cathepsin C (CatC) is a highly conserved lysosomal cysteine dipeptidyl aminopeptidase required for the activation of pro-inflammatory neutrophil serine proteases (NSPs, elastase, proteinase 3, cathepsin G and NSP-4). NSPs are locally released by activated neutrophils in response to pathogens and non-infectious danger signals. Activated neutrophils also release neutrophil extracellular traps (NETs) that are decorated with several neutrophil proteins, including NSPs. NSPs are not only NETs constituents but also play a role in NET formation and release. Although immune cells harbor large amounts of CatC, additional cell sources for this protease exists. Upregulation of CatC expression was observed in different tissues during carcinogenesis and correlated with metastasis and poor patient survival. Recent mechanistic studies indicated an important interaction of tumor-associated CatC, NSPs, and NETs in cancer development and metastasis and suggested CatC as a therapeutic target in a several cancer types. Cancer cell-derived CatC promotes neutrophil recruitment in the inflammatory tumor microenvironment. Because the clinical consequences of genetic CatC deficiency in humans resulting in the elimination of NSPs are mild, small molecule inhibitors of CatC are assumed as safe drugs to reduce the NSP burden. Brensocatib, a nitrile CatC inhibitor is currently tested in a phase 3 clinical trial as a novel anti-inflammatory therapy for patients with bronchiectasis. However, recently developed CatC inhibitors possibly have protective effects beyond inflammation. In this review, we describe the pathophysiological function of CatC and discuss molecular mechanisms substantiating pharmacological CatC inhibition as a potential strategy for cancer treatment.

Origin and Expansion of the Serine Protease Repertoire in the Myelomonocyte Lineage

The deepest evolutionary branches of the trypsin/chymotrypsin family of serine proteases are represented by the digestive enzymes of the gastrointestinal tract and the multi-domain proteases of the blood coagulation and complement system. Similar to the very old digestive system, highly diverse cleavage specificities emerged in various cell lineages of the immune defense system during vertebrate evolution. The four neutrophil serine proteases (NSPs) expressed in the myelomonocyte lineage, neutrophil elastase, proteinase 3, cathepsin G, and neutrophil serine protease 4, collectively display a broad repertoire of (S1) specificities. The origin of NSPs can be traced back to a circulating liver-derived trypsin-like protease, the complement factor D ancestor, whose activity is tightly controlled by substrate-induced activation and TNFα-induced locally upregulated protein secretion. However, the present-day descendants are produced and converted to mature enzymes in precursor cells of the bone marrow and are safely sequestered in granules of circulating neutrophils. The potential site and duration of action of these cell-associated serine proteases are tightly controlled by the recruitment and activation of neutrophils, by stimulus-dependent regulated secretion of the granules, and by various soluble inhibitors in plasma, interstitial fluids, and in the inflammatory exudate. An extraordinary dynamic range and acceleration of immediate defense responses have been achieved by exploiting the high structural plasticity of the trypsin fold.

Bauhinia Protease Inhibitors Attenuate Gastric Ulcer by Blocking Neutrophil Enzymes

Proteases play a pivotal role in many signaling pathways; inhibitors of well-established proteases have shown a substantial therapeutic success. This study aimed to examine the in vivo effects of 3 protease inhibitors isolated from Bauhinia species: i) Bauhinia mollis elastase inhibitor, which blocks human neutrophil elastase (Ki_app 2.8 nM) and cathepsin G (Ki_app 1.0 nM) activities; ii) Bauhinia mollis trypsin inhibitor, a trypsin inhibitor (Ki_app 5.0 nM); and iii) Bauhinia bauhinioides cruzipain inhibitor, which inhibits elastase (Ki_app 2.6 nM), cathepsin G (Ki_app 160.0 nM), and the cysteine proteases cathepsin L (Ki_app 0.2 nM). Bauhinia bauhinioides cruzipain inhibitor, Bauhinia mollis elastase inhibitor, and Bauhinia mollis trypsin inhibitor were isolated using acetone and ammonium sulfate fractionations, DEAE-Sephadex, trypsin-Sepharose, and Resource-Q chromatographies. Mice and rats were treated intraperitoneally with 1 dose of inhibitor; gastric mucosal lesions were induced by cold-restraint stress. Oral pretreatment of mice with Bauhinia mollis elastase inhibitor or Bauhinia mollis trypsin inhibitor (1 - 10 mg/kg) did not show anti-ulcer effect, while Bauhinia bauhinioides cruzipain inhibitor (0.1 - 1.0 mg/kg) produced a similar reduction of the index of mucosal damage at all effective doses (30 to 33% < control). In rats at doses lower than those used in mice, Bauhinia mollis elastase inhibitor and Bauhinia bauhinioides cruzipain inhibitor reduced the index of mucosal damage by 66% and 54% of controls, respectively. The results indicate a protective effect against gastric mucosal lesions associated with elastase inhibition but not inhibition of trypsin activities. Moreover, the lack of Bauhinia mollis elastase inhibitor efficacy observed in mice may possibly be related to the reported structural differences of elastase in mice and rats.

Role of Neutrophils in the Pathogenesis of Nonalcoholic Steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) includes a spectrum of liver disorders, from fatty liver to nonalcoholic steatohepatitis (NASH), cirrhosis, and hepatocellular carcinoma. Compared with fatty liver, NASH is characterized by increased liver injury and inflammation, in which liver-infiltrating immune cells, with neutrophil infiltration as a hallmark of NASH, play a critical role in promoting the progression of fatty liver to NASH. Neutrophils are the first responders to injury and infection in various tissues, establishing the first line of defense through multiple mechanisms such as phagocytosis, cytokine secretion, reactive oxygen species production, and neutrophil extracellular trap formation; however, their roles in the pathogenesis of NASH remain obscure. The current review summarizes the roles of neutrophils that facilitate the progression of fatty liver to NASH and their involvement in inflammation resolution during NASH pathogenesis. The notion that neutrophils are potential therapeutic targets for the treatment of NASH is also discussed.

Neutrophil elastase and endogenous inhibitors in Behçet's disease saliva

Behçet's disease (BD) is a vasculitis of unknown aetiology typified by chronic recurrent oral ulcers and systemic inflammatory manifestations. Neutrophils, and specifically their protease neutrophil elastase (NE), have been implicated in its pathology. Although NE is an effective anti-microbial, excessive NE can damage host tissue. Recurrent oral ulceration is a primary BD symptom, therefore we hypothesized that excessive neutrophil infiltration evidenced by increased NE and a reduction in specific endogenous inhibitors, secretory leucocyte protease inhibitor (SLPI) and alpha1-anti-trypsin (α1AT) contributes to BD mucosal instability. NE, SLPI and α1AT were quantified in saliva from BD patients with active oral ulcers (BDa) and quiet without ulcers (BDq), recurrent aphthous stomatitis (RASa; RASq) and healthy controls (HC). Although BDq saliva had marginally higher median NE levels (1112 ng/ml) compared to both RASq (1043 ng/ml) and HC (999 ng/ml), SLPI was significantly reduced in BDq (P < 0·01). Despite decreased SLPI protein, mRNA expression was significantly increased in BDq buccal epithelial swabs compared to RASq and HC (P < 0·05, P < 0·001). NE remained enzymatically active, although α1AT levels were at least eight times higher than SLPI in all groups, suggesting that α1AT does not have a primary role in counteracting NE in saliva. Furthermore, NE levels in BDa patients medicated with both azathioprine (AZA) and colchicine (COLC) were significantly lower than those on COLC (P = 0·0008) or neither (P = 0·02), indicating that combining AZA + COLC may help to regulate excessive NE during ulceration. This study showed that enzymatically active NE coupled with reduced SLPI in BD saliva may contribute to recurrent oral ulcerations.

Neutrophil elastase triggers the development of autoimmune diabetes by exacerbating innate immune responses in pancreatic islets of non-obese diabetic mice

Type 1 diabetes is an autoimmune disease resulted from self-destruction of insulin-producing pancreatic β cells. However, the pathological pathways that trigger the autoimmune destruction remain poorly understood. Clinical studies have demonstrated close associations of neutrophils and neutrophil elastase (NE) with β-cell autoimmunity in patients with Type 1 diabetes. The present study aims to investigate the impact of NE inhibition on development of autoimmune diabetes in NOD mice. NE pharmacological inhibitor (sivelestat) or biological inhibitor (elafin) was supplemented into NOD mice to evaluate their effects on islet inflammation and diabetogenesis. The impact of NE inhibition on innate and adaptive immune cells was measured with flow cytometry and immunohistochemistry. A significant but transient increase in neutrophil infiltration accompanied with elevated NE activity was observed in the neonatal period of NOD mice. Treatment of NOD mice with sivelestat or elafin at the early age led to a marked reduction in spontaneous development of insulitis and autoimmune diabetes. Mechanistically, inhibition of NE significantly attenuated infiltration of macrophages and islet inflammation, thus ameliorating cytotoxic T cell-mediated autoimmune attack of pancreatic β cells. In vitro studies showed that NE directly induced inflammatory responses in both min6 β cells and RAW264.7 macrophages, and promoted macrophage migration. These findings support an important role of NE in triggering the onset and progression of β-cell autoimmunity, and suggest that pharmacological inhibition of NE may represent a promising therapeutic strategy for treatment of autoimmune diabetes.

Evolution of multifunctionality through a pleiotropic substitution in the innate immune protein S100A9

Multifunctional proteins are evolutionary puzzles: how do proteins evolve to satisfy multiple functional constraints? S100A9 is one such multifunctional protein. It potently amplifies inflammation via Toll-like receptor four and is antimicrobial as part of a heterocomplex with S100A8. These two functions are seemingly regulated by proteolysis: S100A9 is readily degraded, while S100A8/S100A9 is resistant. We take an evolutionary biochemical approach to show that S100A9 evolved both functions and lost proteolytic resistance from a weakly proinflammatory, proteolytically resistant amniote ancestor. We identify a historical substitution that has pleiotropic effects on S100A9 proinflammatory activity and proteolytic resistance but has little effect on S100A8/S100A9 antimicrobial activity. We thus propose that mammals evolved S100A8/S100A9 antimicrobial and S100A9 proinflammatory activities concomitantly with a proteolytic 'timer' to selectively regulate S100A9. This highlights how the same mutation can have pleiotropic effects on one functional state of a protein but not another, thus facilitating the evolution of multifunctionality.

Protective effect of rhubarb combined with ulinastatin for patients with sepsis

BACKGROUND

Sepsis is the leading cause of death in critically ill patients. Ulinastatin (UTI), a protease inhibitor, and rhubarb, used as a traditional Chinese medication, are proved to be effective in treating sepsis, but the effect of the combination therapy of these two drugs on sepsis remains unclear. This study aimed to investigate the effect of the combination treatment of UTI and rhubarb on sepsis patients.

METHODS

A total of 75 septic patients were randomly divided into control group, UTI group, Rhubarb group, and UTI plus Rhubarb group. Clinical data and score of Acute Physiology and Chronic Health Evaluation II (APACHE II) were collected; lymphocyte subtypes in the peripheral blood were analyzed before and after the 5-day treatment in the Intensive Care Unit.

RESULTS

All the therapeutic interventions (UTI alone, rhubarb alone, or UTI plus rhubarb) significantly reduced the levels of C-Reactive protein, white blood cell density, lactic acid, and APACH II scores, and elevated the levels of CD4/CD8, but only UTI plus rhubarb treatment obviously decreased the level of procalcitonin.

CONCLUSION

This study suggested that the combination of UTI and rhubarb may be a promising therapeutic scheme to ameliorate sepsis.

On the Process of Discovering Leads That Target the Heparin-Binding Site of Neutrophil Elastase in the Sputum of Cystic Fibrosis Patients

Cystic fibrosis (CF) is a disease of dysregulated salt and fluid homeostasis that results in the massive accumulation of neutrophil elastase, resulting in lung degradation and death. The current CF therapy relies on inhaled deoxyribonuclease and hypertonic saline but does not address the elastolytic degradation of the lung. We reasoned that allosteric agents targeting the heparin-binding site of neutrophil elastase would offer a therapeutic paradigm. Screening a library of 60 nonsaccharide glycosaminoglycan mimetics (NSGMs) led to the discovery of 23 hits against neutrophil elastase. To identify a lead NSGM that works in sync with the current CF-relieving agents, we developed a rigorous protocol based on fundamental computational, biochemical, mechanistic, and adverse effect studies. The lead NSGM so identified neutralized neutrophil elastase present in the sputum of CF patients in the presence of deoxyribonuclease and high-salt conditions. Our work presents the process for discovering potent, small, synthetic, allosteric, anti-CF agents, while also identifying a novel lead for further studies in animal models of CF.

An ancient mechanism of arginine-specific substrate cleavage: What's 'up' with NSP4?

The recently discovered neutrophil serine protease 4 (NSP4) is the fourth member of the NSP family, which includes the well-studied neutrophil elastase, proteinase 3 and cathepsin G. Like the other three NSP members, NSP4 is synthesized by myeloid precursors in the bone marrow and, after cleavage of the two-amino acid activation peptide, is stored as an active protease in azurophil granules of neutrophils. Based on its primary amino acid sequence, NSP4 is predicted to have a shallow S1 specificity pocket with elastase-like substrate specificity. However, NSP4 was found to preferentially cleave after an arginine residue. Structural studies resolved this paradox by revealing an unprecedented mechanism of P1-arginine recognition. In contrast to the canonical mechanism in which the P1-arginine residue points down into a deep S1 pocket, the arginine side chain adopts a surface-exposed 'up' conformation in the NSP4 active site. This conformation is stabilized by the Phe190 residue, which serves as a hydrophobic platform for the aliphatic portion of the arginine side chain, and a network of hydrogen bonds between the arginine guanidium group and the NSP4 residues Ser192 and Ser216. This unique configuration allows NSP4 to cleave even after naturally modified arginine residues, such as citrulline and methylarginine. This non-canonical mechanism, characterized by the hallmark 'triad' Phe190-Ser192-Ser216, is largely preserved throughout evolution starting with bony fish, which appeared about 400 million years ago. Although the substrates and physiological role of NSP4 remain to be determined, its remarkable evolutionary conservation, restricted tissue expression and homology to other neutrophil serine proteases anticipate a function in immune-related processes.

Ameliorating gut microenvironment through staphylococcal nuclease-mediated intestinal NETs degradation for prevention of type 1 diabetes in NOD mice

AIMS

Recent studies have revealed that neutrophil extracellular traps (NETs) provide negative feedback in the progression to chronic inflammation and contribute to the pathogenesis of multiple autoimmune diseases including type 1 diabetes (T1D). In addition, accumulating evidences suggest that gut immunity play a key role in T1D pathogenesis. Our study aimed to evaluate whether staphylococcal nuclease (SNase) targeting intestinal NETs can ameliorate the intestinal inflammatory environment and protect against T1D development in non-obese diabetic(NOD) mice.

MAIN METHODS

Degradation of NETs with SNase in vitro was examined using SYTOX green assay. NOD/LtJ mice were oral administration of Lactococcus lactisl (L. lactis) pCYT: SNase and blood glucose levels were monitored weekly. Several biomarkers of NETs formation, gut leakage and inflammation were determined using a commercial ELISA kit. T Cell phenotypes in peripheral immune system were analyzed in flow cytometry and fecal samples were isolated to investigate intestinal microbiota.

KEY FINDINGS

The oral delivery of SNase by L. lactis can decrease the NETs levels and ameliorate inflammation both in the intestine and pancreatic islets and finally effectively regulate the blood glucose levels of NOD mice. Meanwhile, zonulin and lipopolysaccharide levels also reduced in SNase-fed NOD mice, suggesting SNase could improve gut barrier function via intestinal NETs degradation. Furthermore, the abundances of the intestinal microbiota and butyrate-producing gut bacteria were also increased with SNase treatment.

SIGNIFICANCE

SNase shows potential for intestinal NETs to prevent T1D based on the gut-pancreas axis.

000Synthesis of new α-aminophosphonates: Evaluation as anti-inflammatory agents and QSAR studies

In this paper, we report the synthesis of a new series of α-aminophosphonates derivatives based in an efficient three-component reaction. All compounds prepared showed significant anti-inflammatory activity, being the compounds 1a, 1c, 1d, 1f, 2b and 2c the most promising ones, in terms of maximal efficacy (over 95%), potency (ED₅₀ range between 0.7 and 10.1 mg/ear) and relative potency (range from 0.04 to 0.67). Compounds 1a, 1c, 1d and 1f significantly decrease the number of neutrophils (range from 46.7 to 63.0%) and monocytes (18.9-34.1%) in blood samples from the orbital sinus. Additionally, QSAR model revealed that the spherical molecular shape and the location of the HOMO on the phenyl ring improves the anti-inflammatory activity of the compounds. The values of R², Q², s and F statistical parameters and the QUIK, asymptotic Q² and Overfitting rules validate the descriptive and predictive ability of the QSAR model. Altogether these results suggest that these new α-aminophosphonates are potential agents for the treatment of inflammation.

Protease-activated receptor 4 activity promotes platelet granule release and platelet-leukocyte interactions

Human platelets express two protease-activated receptors (PARs), PAR1 (F2R) and PAR4 (F2RL3), which are activated by a number of serine proteases that are generated during pathological events and cause platelet activation. Recent interest has focused on PAR4 as a therapeutic target, given PAR4 seems to promote experimental thrombosis and procoagulant microparticle formation, without a broadly apparent role in hemostasis. However, it is not yet known whether PAR4 activity plays a role in platelet-leukocyte interactions, which are thought to contribute to both thrombosis and acute or chronic thrombo-inflammatory processes. We sought to determine whether PAR4 activity contributes to granule secretion from activated platelets and platelet-leukocyte interactions. We performed in vitro and ex vivo studies of platelet granule release and platelet-leukocyte interactions in the presence of PAR4 agonists including PAR4 activating peptide, thrombin, cathepsin G, and plasmin in combination with small-molecule PAR4 antagonists. Activation of human platelets with thrombin, cathepsin G, or plasmin potentiated platelet dense granule secretion that was specifically impaired by PAR4 inhibitors. Platelet-leukocyte interactions and platelet P-selectin exposure the following stimulation with PAR4 agonists were also impaired by activated PAR4 inhibition in either a purified system or in whole blood. These results indicate PAR4-specific promotion of platelet granule release and platelet-leukocyte aggregate formation and suggest that pharmacological control of PAR4 activity could potentially attenuate platelet granule release or platelet-leukocyte interaction-mediated pathological processes.

Proteinase 3; a potential target in chronic obstructive pulmonary disease and other chronic inflammatory diseases

Chronic Obstructive Pulmonary Disease (COPD) is a common, multifactorial lung disease which results in significant impairment of patients' health and a large impact on society and health care burden. It is believed to be the result of prolonged, destructive neutrophilic inflammation which results in progressive damage to lung structures. During this process, large quantities of neutrophil serine proteinases (NSPs) are released which initiate the damage and contribute towards driving a persistent inflammatory state.Neutrophil elastase has long been considered the key NSP involved in the pathophysiology of COPD. However, in recent years, a significant role for Proteinase 3 (PR3) in disease development has emerged, both in COPD and other chronic inflammatory conditions. Therefore, there is a need to investigate the importance of PR3 in disease development and hence its potential as a therapeutic target. Research into PR3 has largely been confined to its role as an autoantigen, but PR3 is involved in triggering inflammatory pathways, disrupting cellular signalling, degrading key structural proteins, and pathogen response.This review summarises what is presently known about PR3, explores its involvement particularly in the development of COPD, and indicates areas requiring further investigation.

Effect of bacterial components of mixed culture supernatants of planktonic and biofilm Pseudomonas aeruginosa with commensal Escherichia coli on the neutrophil response in vitro

Pseudomonas aeruginosa (PA) responsible for acute and chronic infections often forms a well-organized bacterial population with different microbial species including commensal strains of Escherichia coli. Bacterial extracellular components of mixed culture can modulate the influence of bacteria on the neutrophil functions. The objective of this study was to compare the effect of pyocyanin, pyoverdine, LPS, exopolysaccharide of single species and mixed culture supernatants of PA strains and E. coli K12 on microbicidal, secretory activity of human neutrophils in vitro. Bacterial components of E. coli K12 in mixed supernatants with 'biofilm' PA strains (PA ATCC, PA BALG) enhanced short-term microbicidal mechanisms and inhibited neutrophil secretion delayed in time. The influence of 'planktonic' PA (PA 9-3) exometabolites in mixed culture is almost mimicked by E. coli K12 effect on functional neutrophil changes. This investigation may help to understand some of the mechanisms of neutrophil response to mixed infections of different PA with other bacteria species.

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.

Preservation with α1-antitrypsin improves primary graft function of murine lung transplants

BACKGROUND

Vascular damage and primary graft dysfunction increase with prolonged preservation times of transplanted donor lungs. Hence, storage and conservation of donated lungs in protein-free, dextran-containing electrolyte solutions, like Perfadex, is limited to about 6 hours. We hypothesized that transplanted lungs are protected against neutrophil-mediated proteolytic damage by adding α₁-anti-trypsin (AAT), a highly abundant human plasma proteinase inhibitor, to Perfadex.

METHODS

A realistic clinically oriented murine model of lung transplantation was used to simulate the ischemia-reperfusion process. Lung grafts were stored at 4°C in Perfadex solution supplemented with AAT or an AAT mutant devoid of elastase-inhibiting activity for 18 hours. We examined wild-type and proteinase 3/neutrophil elastase (PR3/NE) double-deficient mice as graft recipients. Gas exchange function and infiltrating neutrophils of the transplanted lung, as well as protein content and neutrophil numbers in the bronchoalveolar lavage fluid, were determined.

RESULTS

AAT as a supplement to Perfadex reduced the extent of primary graft dysfunction and early neutrophil responses after extended storage for 18 hours at 4°C and 4-hour reperfusion in the recipients. Double-knockout recipients that lack elastase-like activities in neutrophils were also protected from early reperfusion injury, but not lung grafts that were perfused with a reactive center mutant of AAT devoid of elastase-inhibiting activity.

CONCLUSIONS

PR3 and NE, the principal targets of AAT, are major triggers of post-ischemic reperfusion damage. Their effective inhibition in the graft and recipient is a promising strategy for organ usage after storage for >6 hours.

Pharmacological Stimulation of Phagocytosis Enhances Amyloid Plaque Clearance; Evidence from a Transgenic Mouse Model of ATTR Neuropathy

Hereditary ATTR V30M amyloidosis is a lethal autosomal dominant sensorimotor and autonomic neuropathy caused by deposition of aberrant transthyretin (TTR). Immunohistochemical examination of sural nerve biopsies in patients with amyloidotic neuropathy show co-aggregation of TTR with several proteins; including apolipoprotein E, serum amyloid P and components of the complement cascade. Complement activation and macrophages are increasingly recognized to play a crucial role in amyloidogenesis at the tissue bed level. In the current study we test the effect of two C5a receptor agonists and a C5a receptor antagonist (PMX53) on disease phenotype in ATTR V30M mice. Our results indicate that amyloid deposition was significantly reduced following treatment with the C5a receptor agonists, while treatment with the antagonist resulted in a significant increase of amyloid load. Administration of the C5a receptor agonists triggered increased recruitment of phagocytic cells resulting in clearance of amyloid deposits.

Inhibitors and Antibody Fragments as Potential Anti-Inflammatory Therapeutics Targeting Neutrophil Proteinase 3 in Human Disease

Proteinase 3 (PR3) has received great scientific attention after its identification as the essential antigenic target of antineutrophil cytoplasm antibodies in Wegener's granulomatosis (now called granulomatosis with polyangiitis). Despite many structural and functional similarities between neutrophil elastase (NE) and PR3 during biosynthesis, storage, and extracellular release, unique properties and pathobiological functions have emerged from detailed studies in recent years. The development of highly sensitive substrates and inhibitors of human PR3 and the creation of PR3-selective single knockout mice led to the identification of nonredundant roles of PR3 in cell death induction via procaspase-3 activation in cell cultures and in mouse models. According to a study in knockout mice, PR3 shortens the lifespan of infiltrating neutrophils in tissues and accelerates the clearance of aged neutrophils in mice. Membrane exposure of active human PR3 on apoptotic neutrophils reprograms the response of macrophages to phagocytosed neutrophils, triggers secretion of proinflammatory cytokines, and undermines immune silencing and tissue regeneration. PR3-induced disruption of the anti-inflammatory effect of efferocytosis may be relevant for not only granulomatosis with polyangiitis but also for other autoimmune diseases with high neutrophil turnover. Inhibition of membrane-bound PR3 by endogenous inhibitors such as the α-1-protease inhibitor is comparatively weaker than that of NE, suggesting that the adverse effects of unopposed PR3 activity resurface earlier than those of NE in individuals with α-1-protease inhibitor deficiency. Effective coverage of PR3 by anti-inflammatory tools and simultaneous inhibition of both PR3 and NE should be most promising in the future.

Role of Proteases in Lung Disease: A Brief Overview

Proteases play an important role in health and disease of the lung. In the normal lungs, proteases maintain their homeostatic functions that regulate processes like its regeneration and repair. Dysregulation of proteases–antiproteases balance is crucial in the manifestation of different types of lung diseases. Chronic inflammatory lung pathologies are associated with a marked increase in protease activities. Thus, in addition to protease activities, inhibition of anti-proteolytic control mechanisms are also important for effective microbial infection and inflammation in the lung. Herein, we briefly summarize the role of different proteases and to some extent antiproteases in regulating a variety of lung diseases.

Serine Protease Zymography: Low-Cost, Rapid, and Highly Sensitive RAMA Casein Zymography

To detect serine protease activity by zymography, casein and CBB stain have been used as a substrate and a detection procedure, respectively. Casein zymography has been using substrate concentration at 1 mg/mL and employing conventional CBB stain. Although ordinary casein zymography provides reproducible results, it has several disadvantages including time-consuming and relative low sensitivity. Improved casein zymography, RAMA casein zymography, is rapid and highly sensitive. RAMA casein zymography completes the detection process within 1 h after incubation and increases the sensitivity at least by tenfold. In addition to serine protease, the method also detects metalloprotease 7 (MMP7, Matrilysin) with high sensitivity.

Neutrophil serine proteases and their endogenous inhibitors in coronary artery ectasia patients

Objective:

Proteolytic enzymes possibly contribute to coronary artery ectasia (CAE). This study aimed to determine whether neutrophils, neutrophil serine proteases (NSPs), and their endogenous inhibitors participated in the pathological process of CAE.

Methods:

The study consisted of 30 patients with CAE, 30 patients with coronary artery disease (CAD), and 29 subjects with normal coronary arteries (Control). The following circulating items were measured: the main NSPs, including human neutrophil elastase (HNE), cathepsin G (CG), and proteinase 3 (PR3); soluble elastin (sElastin), which was a degradation product of elastin fibres; NSP inhibitors such as α1-protease inhibitor (α1-PI), α2-macroglobulin (α2-MG), secretory leucoprotease inhibitor (SLPI), and elafin; as well as two neutrophil activation markers (myeloperoxidase and lactoferrin) and three classic neutrophil activators [tumor necrosis factor-α (TNF-α), interleukin-8 (IL-8), and bacterial endotoxin].

Results:

The levels of HNE, CG, and sElastin were elevated in the CAE group. The levels of α1-PI and α2-MG were also significantly increased in the CAE group. The levels of myeloperoxidase and lactoferrin were higher in the CAE group. The levels of TNF-α, IL-8, and endotoxin were unchanged in the CAE group compared with those in the CAD group.

Conclusion:

Neutrophils may participate in the process of vessel extracellular matrix destruction and coronary ectasia by releasing NSPs in a non-classical manner.

Cathepsin G Controls Arterial But Not Venular Myeloid Cell Recruitment

BACKGROUND

Therapeutic targeting of arterial leukocyte recruitment in the context of atherosclerosis has been disappointing in clinical studies. Reasons for such failures include the lack of knowledge of arterial-specific recruitment patterns. Here we establish the importance of the cathepsin G (CatG) in the context of arterial myeloid cell recruitment.

METHODS

Intravital microscopy of the carotid artery, the jugular vein, and cremasteric arterioles and venules in Apoe^-/-and CatG-deficient mice (Apoe^-/-Ctsg^-/-) was used to study site-specific myeloid cell behavior after high-fat diet feeding or tumor necrosis factor stimulation. Atherosclerosis development was assessed in aortic root sections after 4 weeks of high-fat diet, whereas lung inflammation was assessed after inhalation of lipopolysaccharide. Endothelial deposition of CatG and CCL5 was quantified in whole-mount preparations using 2-photon and confocal microscopy.

RESULTS

Our observations elucidated a crucial role for CatG during arterial leukocyte adhesion, an effect not found during venular adhesion. Consequently, CatG deficiency attenuates atherosclerosis but not acute lung inflammation. Mechanistically, CatG is immobilized on arterial endothelium where it activates leukocytes to firmly adhere engaging integrin clustering, a process of crucial importance to achieve effective adherence under high-shear flow. Therapeutic neutralization of CatG specifically abrogated arterial leukocyte adhesion without affecting myeloid cell adhesion in the microcirculation. Repetitive application of CatG-neutralizing antibodies permitted inhibition of atherogenesis in mice.

CONCLUSIONS

Taken together, these findings present evidence of an arterial-specific recruitment pattern centered on CatG-instructed adhesion strengthening. The inhibition of this process could provide a novel strategy for treatment of arterial inflammation with limited side effects.

Neutrophil elastase enhances the proliferation and decreases apoptosis of leukemia cells via activation of PI3K/Akt signaling

Neutrophil elastase (NE) is a neutrophil-derived serine proteinase with specificity for a broad range of substrates. NE has been reported to be associated with the pathogenesis of several conditions, particularly that of pulmonary diseases. Previous studies have shown that NE can cleave the pro-myelocyte - retinoic acid receptor-alpha chimeric protein and is important for the development of acute pro-myelocytic leukemia. To further elucidate the role of NE in acute pro-myelocytic leukemia, the present study successfully constructed a lentiviral vector containing the NE gene (LV5-NE), which was transfected into NB4 acute pro-myelocytic leukemia cells. The effects of NE overexpression in NB4 cells were detected using a Cell-Counting Kit-8 assay, flow cytometry and western blot analysis. The results showed that NE significantly promoted the proliferation of NB4 cells, inhibited cell apoptosis and apoptotic signaling, and led the activation of Akt. In an additional experiment, a vector expressing small hairpin RNA targeting NE was constructed to assess the effects of NE knockdown in U937 cells. Western blot analysis revealed that apoptotic signaling was increased, while Akt activation was decreased following silencing of NE. The results of the present study may indicate that NE activates the phosphoinositide-3 kinase/Akt signaling pathway in leukemia cells to inhibit apoptosis and enhance cell proliferation, and may therefore represent a molecular target for the treatment of pro-myelocytic leukemia.

Extracellular granzyme K mediates endothelial activation through the cleavage of protease-activated receptor-1

Granzymes are a family of serine proteases that were once thought to function exclusively as mediators of cytotoxic lymphocyte-induced target cell death. However, non-apoptotic roles for granzymes, including granzyme K (GzK), have been proposed. As recent studies have observed elevated levels of GzK in the plasma of patients diagnosed with clinical sepsis, we hypothesized that extracellular GzK induces a proinflammatory response in endothelial cells. In the present study, extracellular GzK proteolytically activated protease-activated receptor-1 leading to increased interleukin 6 and monocyte chemotactic protein 1 production in endothelial cells. Enhanced expression of intercellular adhesion molecule 1 along with an increased capacity for adherence of THP-1 cells was also observed. Characterization of downstream pathways implicated the mitogen-activated protein kinase p38 pathway for intercellular adhesion molecule 1 expression, and both the p38 and the extracellular signal-regulated protein kinases 1 and 2 pathways in cytokine production. GzK also increased tumour necrosis factor α-induced inflammatory adhesion molecule expression. Furthermore, the physiological inhibitor of GzK, inter-α-inhibitor protein, significantly inhibited GzK activity in vitro. In summary, extracellular GzK promotes a proinflammatory response in endothelial cells.

N-Arylacyl O-sulfonated aminoglycosides as novel inhibitors of human neutrophil elastase, cathepsin G and proteinase 3

The balance between neutrophil serine proteases (NSPs) and protease inhibitors (PIs) in the lung is a critical determinant for a number of chronic inflammatory lung diseases such as chronic obstructive pulmonary disease, cystic fibrosis and acute lung injury. During activation at inflammatory sites, excessive release of NSPs such as human neutrophil elastase (HNE), proteinase 3 (Pr3) and cathepsin G (CatG), leads to destruction of the lung matrix and continued propagation of acute inflammation. Under normal conditions, PIs counteract these effects by inactivating NSPs; however, in chronic inflammatory lung diseases, there are insufficient amounts of PIs to mitigate damage. Therapeutic strategies are needed to modulate excessive NSP activity for the clinical management of chronic inflammatory lung diseases. In the study reported here, a panel of N-arylacyl O-sulfonated aminoglycosides was screened to identify inhibitors of the NSPs. Dose-dependent inhibitors for each individual serine protease were identified. Select compounds were found to inhibit multiple NSPs, including one lead structure that is shown to inhibit all three NSPs. Two lead compounds identified during the screen for each individual NSP were further characterized as partial mixed inhibitors of CatG. Concentration-dependent inhibition of protease-mediated detachment of lung epithelial cells is demonstrated.

Ulinastatin- and thymosin α1-based immunomodulatory strategy for sepsis: A meta-analysis

OBJECTIVE

This meta-analysis was performed to evaluate the efficacy of ulinastatin (UTI) and thymosin α1 (Tα1) based immunomodulatory strategy in sepsis patients.

METHODS

A systematic search was made of MEDLINE, Cochrane, ISI Web of Science and SCOPUS databases. Randomized clinical trials on treatment of sepsis with the combination of ulinastatin and Tα1, compared with placebo, were reviewed. Studies were pooled to relative risk (RR) and weighted mean differences (WMD), with 95% confidence interval (CI).

RESULTS

Six trials (enrolling 915 participants) met the inclusion criteria. Compared with placebo, the combination of ulinastatin and Tα1 presented significant effects on 28-day all-cause mortality (RR 0.67; 95% CI 0.57 to 0.80), 90-day all-cause mortality (RR 0.75; 95% CI 0.61 to 0.93), TNF-α (WMD -73.86ng/L; 95% CI -91.00 to -56.73ng/L), IL-6 (WMD -55.04ng/L; 95% CI -61.22 to -48.85ng/L), and duration of mechanical ventilation (WMD -2.26days; 95% CI -2.79 to -1.73days).

CONCLUSIONS

Immunomodulatory therapy that combines ulinastatin and Tα1 significantly improves all-cause mortality, inflammatory mediators and duration of mechanical ventilation in subjects with sepsis.

Conserved Amblyomma americanum tick Serpin19, an inhibitor of blood clotting factors Xa and XIa, trypsin and plasmin, has anti-haemostatic functions

Tick saliva serine protease inhibitors (serpins) facilitate tick blood meal feeding through inhibition of protease mediators of host defense pathways. We previously identified a highly conserved Amblyomma americanum serpin 19 that is characterised by its reactive center loop being 100% conserved in ixodid ticks. In this study, biochemical characterisation reveals that the ubiquitously transcribed A. americanum serpin 19 is an anti-coagulant protein, inhibiting the activity of five of the eight serine protease blood clotting factors. Pichia pastoris-expressed recombinant (r) A. americanum serpin 19 inhibits the enzyme activity of trypsin, plasmin and blood clotting factors (f) Xa and XIa, with stoichiometry of inhibition estimated at 5.1, 9.4, 23.8 and 28, respectively. Similar to typical inhibitory serpins, recombinant A. americanum serpin 19 forms irreversible complexes with trypsin, fXa and fXIa. At a higher molar excess of recombinant A. americanum serpin 19, fXIIa is inhibited by 82.5%, and thrombin (fIIa), fIXa, chymotrypsin and tryptase are inhibited moderately by 14-29%. In anti-hemostatic functional assays, recombinant A. americanum serpin 19 inhibits thrombin but not ADP and cathepsin G activated platelet aggregation, delays clotting in recalcification and thrombin time assays by up to 250s, and up to 40s in the activated partial thromboplastin time assay. Given A. americanum serpin 19 high cross-tick species conservation, and specific reactivity of recombinant A. americanum serpin 19 with antibodies to A. americanum tick saliva proteins, we conclude that recombinant A. americanum serpin 19 is a potential candidate for development of a universal tick vaccine.

Serum progranulin levels are elevated in dermatomyositis patients with acute interstitial lung disease, predicting prognosis

Introduction

Progranulin (PGRN), a pleiotropic growth factor, has emerged as an immunoregulatory molecule. Because the roles of PGRN in dermatomyositis (DM) are still unknown, we investigated whether serum PGRN levels are associated with disease activity and prognosis in DM patients, particularly in those with DM complicated with interstitial lung disease (ILD).

Methods

The serum levels of PGRN were measured by enzyme-linked immunosorbent assay in patients with DM (n =57; acute/subacute interstitial pneumonia (A/SIP): n =17, chronic interstitial pneumonia (CIP): n =24, without ILD: n =16), polymyositis (PM, n =21; including 6 with ILD) and normal healthy controls (NHCs, n =60). We assessed the correlation between the serum PGRN levels and the activity indexes of ILD or prognosis in DM patients with ILD.

Results

Serum PGRN levels were significantly higher in DM patients than in PM patients (P =0.0025) and in NHCs (P <0.0001). In DM patients, the levels were significantly higher in patients with A/SIP than in those with CIP (P <0.0001) or without ILD (P =0.0003). The serum PGRN levels in DM patients with ILD significantly correlated with serum ferritin (r_S =0.77, P <0.0001), lactate dehydrogenase (r_S =0.54, P =0.0003) and C-reactive protein (r_S =0.48, P =0.0015) levels. Moreover, in DM patients with ILD, the cumulative survival rate for 6 months was significantly lower in the group with serum PGRN levels ≥200 ng/ml (67%) than in the group with serum PGRN levels <200 ng/ml (100%) (P =0.0009).

Conclusions

Serum PGRN is associated with disease activity and prognosis of DM with ILD. PGRN may play a role in the pathogenesis of DM and could be a useful biomarker.

Proteinase 3 and Serpin B1: a novel pathway in the regulation of caspase-3 activation, neutrophil spontaneous apoptosis, and inflammation

Neutrophils are the first responders of the inflammatory response. They are characterized by their potent cytotoxic content but also by their limited lifetime. This short half-life is thought to be a self-protecting mechanism for the host, as highlighted by the numerous pathologies associated with imbalanced neutrophil survival. Neutrophil spontaneous death is the prototype of programmed cell death, harboring all the phenotypic hallmarks of apoptosis and dependent on the activation of the effector caspase-3. However, the pathways regulating neutrophil spontaneous death remain ill-defined. In a recent publication, we determined that in aging neutrophils, the cleavage and activation of caspase-3 was mediated by the serine protease Proteinase 3 (PR3), and was independent of the canonical extrinsic and intrinsic apoptosis pathways. In mature neutrophils, PR3 was stored in granules and progressively released to the cytosol during neutrophil aging. The release of PR3 was dependent on lysosomal membrane permeabilization (LMP). Once in the cytosol, PR3 cleaved procaspase-3 at a site upstream of the caspase-9 cleavage site, leading to caspase-3 activation. Inhibition, knockdown or knockout of PR3 delayed neutrophil apoptosis in vitro and in vivo. The adoptive transfer of both WT and PR3-deficient neutrophils to WT mice revealed that the delayed death of neutrophils lacking PR3 in vivo was due to an altered intrinsic apoptosis/survival pathway and not to difference in the inflammatory microenvironment. The cytosolic inhibitor of serine proteases serpin b1 counterbalanced the activity of PR3 in the cytosol of neutrophils, and the deletion of serpinb1 in neutrophils accelerated their spontaneous death. In summary, our results reveal that PR3 and serpinB1 are part of a newly characterized apoptosis pathway, regulating caspase-3 activation and neutrophil spontaneous death and the survival of neutrophils during inflammation.

Neutrophil serine proteases in antibacterial defense

Neutrophil serine proteases (NSPs) are critical for the effective functioning of neutrophils and greatly contribute to immune protection against bacterial infections. Thanks to their broad substrate specificity, these chymotrypsin-like proteases trigger multiple reactions that are detrimental to bacterial survival such as direct bacterial killing, generation of antimicrobial peptides, inactivation of bacterial virulence factors and formation of neutrophil extracellular traps. Recently, the importance of NSPs in antibacterial defenses has been further underscored by discoveries of unique bacterial evasion strategies to combat these proteases. Bacteria can indirectly disarm NSPs by protecting bacterial substrates against NSP cleavage, but also produce inhibitory molecules that potently block NSPs. Here we review recent insights in the functional contribution of NSPs in host protection against bacterial infections and the elegant strategies that bacteria use to counteract these responses.

The adaptor ASC exacerbates lethal Listeria monocytogenes infection by mediating IL-18 production in an inflammasome-dependent and -independent manner

Listeria monocytogenes induces the formation of inflammasomes and subsequent caspase-1 activation, and the adaptor apoptosis-associated speck-like protein containing a CARD (ASC) is crucial for this response. However, the role of ASC in L. monocytogenes infection in vivo is unclear. In this study, we demonstrate that ASC has a detrimental effect on host defense against L. monocytogenes infection at a lethal dose (10(6) CFU), but not at a sublethal dose (10(3) CFU). During lethal L. monocytogenes infection, serum levels of IL-18 and IL-10 were markedly elevated in WT mice, but not in ASC KO mice. IL-18 KO mice were more resistant to lethal L. monocytogenes infection than WT mice and had lower levels of serum IL-10. Furthermore, blockade of IL-10 receptor resulted in a reduction in bacterial counts, suggesting that ASC and IL-18 might exacerbate L. monocytogenes infection through induction of IL-10. We noticed that maturation of IL-18 during lethal infection was partially independent of caspase-1, but was critically dependent on ASC. ASC was required for the elevation of serum neutrophil serine protease activity, which correlated with caspase-1-independent IL-18 maturation and IL-10 production. Collectively, these results suggest that ASC plays a detrimental role in lethal L. monocytogenes infection through IL-18 production in an inflammasome-dependent and -independent manner.

Proteinase 3-dependent caspase-3 cleavage modulates neutrophil death and inflammation

Caspase-3-mediated spontaneous death in neutrophils is a prototype of programmed cell death and is critical for modulating physiopathological inflammatory responses; however, the underlying regulatory pathways remain ill defined. Here we determined that in aging neutrophils, the cleavage and activation of caspase-3 is independent of the canonical caspase-8- or caspase-9-mediated pathway. Instead, caspase-3 activation was mediated by serine protease proteinase 3 (PR3), which is present in the cytosol of aging neutrophils. Specifically, PR3 cleaved procaspase-3 at a site upstream of the canonical caspase-9 cleavage site. In mature neutrophils, PR3 was sequestered in granules and released during aging via lysosomal membrane permeabilization (LMP), leading to procaspase-3 cleavage and apoptosis. Pharmacological inhibition or knockdown of PR3 delayed neutrophil death in vitro and consistently delayed neutrophil death and augmented neutrophil accumulation at sites of inflammation in a murine model of peritonitis. Adoptive transfer of both WT and PR3-deficient neutrophils revealed that the delayed death of neutrophils lacking PR3 is due to an altered intrinsic apoptosis/survival pathway, rather than the inflammatory microenvironment. The presence of the suicide protease inhibitor SERPINB1 counterbalanced the protease activity of PR3 in aging neutrophils, and deletion of Serpinb1 accelerated neutrophil death. Taken together, our results reveal that PR3-mediated caspase-3 activation controls neutrophil spontaneous death.

Neutrophil elastase causes tissue damage that decreases host tolerance to lung infection with burkholderia species

Two distinct defense strategies can protect the host from infection: resistance is the ability to destroy the infectious agent, and tolerance is the ability to withstand infection by minimizing the negative impact it has on the host's health without directly affecting pathogen burden. Burkholderia pseudomallei is a Gram-negative bacterium that infects macrophages and causes melioidosis. We have recently shown that inflammasome-triggered pyroptosis and IL-18 are equally important for resistance to B. pseudomallei, whereas IL-1β is deleterious. Here we show that the detrimental role of IL-1β during infection with B. pseudomallei (and closely related B. thailandensis) is due to excessive recruitment of neutrophils to the lung and consequent tissue damage. Mice deficient in the potentially damaging enzyme neutrophil elastase were less susceptible than the wild type C57BL/6J mice to infection, although the bacterial burdens in organs and the extent of inflammation were comparable between C57BL/6J and elastase-deficient mice. In contrast, lung tissue damage and vascular leakage were drastically reduced in elastase-deficient mice compared to controls. Bradykinin levels were higher in C57BL/6 than in elastase-deficient mice; administration of a bradykinin antagonist protected mice from infection, suggesting that increased vascular permeability mediated by bradykinin is one of the mechanisms through which elastase decreases host tolerance to melioidosis. Collectively, these results demonstrate that absence of neutrophil elastase increases host tolerance, rather than resistance, to infection by minimizing host tissue damage.

Network analyses reveal pervasive functional regulation between proteases in the human protease web

Network modeling of interactions between proteases and their inhibitors reveals a network of new protein connections and cascades in the protease web.

Proteolytic processing is an irreversible posttranslational modification affecting a large portion of the proteome. Protease-cleaved mediators frequently exhibit altered activity, and biological pathways are often regulated by proteolytic processing. Many of these mechanisms have not been appreciated as being protease-dependent, and the potential in unraveling a complex new dimension of biological control is increasingly recognized. Proteases are currently believed to act individually or in isolated cascades. However, conclusive but scattered biochemical evidence indicates broader regulation of proteases by protease and inhibitor interactions. Therefore, to systematically study such interactions, we assembled curated protease cleavage and inhibition data into a global, computational representation, termed the protease web. This revealed that proteases pervasively influence the activity of other proteases directly or by cleaving intermediate proteases or protease inhibitors. The protease web spans four classes of proteases and inhibitors and so links both recently and classically described protease groups and cascades, which can no longer be viewed as operating in isolation in vivo. We demonstrated that this observation, termed reachability, is robust to alterations in the data and will only increase in the future as additional data are added. We further show how subnetworks of the web are operational in 23 different tissues reflecting different phenotypes. We applied our network to develop novel insights into biologically relevant protease interactions using cell-specific proteases of the polymorphonuclear leukocyte as a system. Predictions from the protease web on the activity of matrix metalloproteinase 8 (MMP8) and neutrophil elastase being linked by an inactivating cleavage of serpinA1 by MMP8 were validated and explain perplexing Mmp8^−/− versus wild-type polymorphonuclear chemokine cleavages in vivo. Our findings supply systematically derived and validated evidence for the existence of the protease web, a network that affects the activity of most proteases and thereby influences the functional state of the proteome and cell activity.

Proteases modify the structure and activity of all proteins by peptide bond hydrolysis and are increasingly recognized as integral regulatory components of numerous biological mechanisms. Deregulated protease activity is a common characteristic of many diseases. However, protease drug development is complicated by an incomplete understanding of protease biology. One missing piece in this puzzle is the interplay between proteases: Some proteases activate other proteases, whereas some proteases inactivate inhibitors, leading to currently unpredictable cleavage of additional proteins. Using database annotations we mathematically modeled protease interactions. Our model includes 1,230 proteins and shows connections between 141,523 pairs of proteases, substrates, and inhibitors. Thus, proteases interact on a large scale to form the protease web, which links most studied groups of proteases and their inhibitors, indicating that the potential of regulation through this network is very large. We found that this interplay is robust to targeted or untargeted pruning of the protease web and that protease inhibitors are central to network connectivity. Our model was used to decipher proteolytic pathways that drive inflammatory processes in vivo. Consequently, protease regulatory interactions should be recognized and explored further to understand in vivo roles and to select better drug targets that avoid side effects arising from inhibition of unexpected activities.

Intravenous administration of ulinastatin (human urinary trypsin inhibitor) in severe sepsis: a multicenter randomized controlled study

Purpose

Ulinastatin, a serine protease inhibitor, inhibits several pro-inflammatory proteases and decreases inflammatory cytokine levels and mortality in experimental sepsis. We studied the effect of ulinastatin on 28-day all-cause mortality in a double-blind trial in patients with severe sepsis in seven Indian hospitals.

Methods

Patients with sepsis were randomized within 48 h of onset of one or more organ failures to receive intravenous administration of ulinastatin (200,000 IU) or placebo 12 hourly for 5 days.

Results

Of 122 randomized subjects, 114 completed the study (55 receiving ulinastatin, 59 receiving placebo). At baseline, the mean APACHE II score was 13.4 (SD = 4.4), 48 (42 %) patients were receiving mechanical ventilation, 58 (51 %) were on vasopressors, and 35 % had multiple organ failure. In the modified intention-to-treat analysis (patients receiving six or more doses of study drugs), 28-day all-cause mortality was 7.3 % with ulinastatin (4 deaths) versus 20.3 % (12 deaths) with placebo (p = 0.045). On multivariate analysis too, treatment with ulinastatin (odds ratio 0.26, 95 % CI 0.07–0.95; p = 0.042) independently decreased 28-day all-cause mortality. However, the mortality difference did not reach statistical significance in the intention-to-treat analysis [10.2 % (6/59 deaths) with ulinastatin versus 20.6 % (13/63 deaths) in the placebo group; p = 0.11]. The ulinastatin group had lower incidence of new-onset organ failure (10 vs. 26 patients, p = 0.003), more ventilator-free days (mean ± SD 19.4 ± 10.6 days vs. 10.2 ± 12.5 days, p = 0.019), and shorter hospital stay (11.8 ± 7.1 days vs. 24.2 ± 7.2 days, p < 0.001).

Conclusions

In this pilot study, intravenous administration of ulinastatin reduced mortality in patients with severe sepsis in the modified intention-to-treat analysis, but not in the intention-to-treat analysis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-014-3278-8) contains supplementary material, which is available to authorized users.

Progranulin is a substrate for neutrophil-elastase and proteinase-3 in the airway and its concentration correlates with mediators of airway inflammation in COPD

Progranulin (PGRN) is an anti-inflammatory protein, yet its digestion by neutrophil-derived proteinases generates products that can stimulate epithelial cell lines to secrete the neutrophil chemoattractant interleukin (IL)-8. Because dysregulated neutrophilic inflammation is implicated in the pathophysiology of chronic obstructive pulmonary disease (COPD), the possible influence of PGRN and digestion products may be of relevance to understanding and treating inflammation in the disease. PGRN was measured in sputum sol-phase samples from patients with a clinical diagnosis of COPD and chronic sputum production in a clinically stable state; PGRN correlated negatively with bacterial load (colony-forming units/ml) ( r = −0.446, P = 0.003, n = 43) and markers of neutrophilic inflammation, including neutrophil elastase (NE, nM) ( r = −0.562, P = 0.008, n = 21) and proteinase-3 (PR3, nM) ( r = −0.515, P = 0.017, n = 21). Products of PGRN digestion were detected in sputum sol phase, and PGRN conversion activity in sputum sol phase was inhibited with the serine proteinase inhibitor α1-antitrypsin. Digested PGRN at concentrations likely to be present in the airways did not stimulate IL-8 secretion from normal human bronchial epithelial (NHBE) cells. Infection of NHBE cells with live Haemophilus influenzae significantly increased PGRN secretion compared with untreated cells ( P ≤ 0.001). The concentration of PGRN relates negatively to the amplified airway inflammation associated with bacterial colonization in clinically stable COPD. This relationship is driven by the proteolytic action of the neutrophil-derived proteinases NE and PR3; the products released by this action are unlikely to stimulate significant IL-8 secretion from epithelial cells in the airways.