Cathepsin G-regulated release of formyl peptide receptor agonists modulate neutrophil effector functions

Identification and Validation of CXCL2 as a Key Gene for Childhood Obesity

This study aims to identify the key genes and their regulatory networks by bioinformatics, increasing understanding of childhood obesity. The data comes from the GEO and Immport database. The immune microenvironment was explored in GSE104815. Key genes were identified by intersection of DEGs with the immune gene set. Enrichment analysis revealed gene-related functions and correlation analysis explored the relationship. Regulatory networks were constructed based on miRcode, TarBase and TargetScan databases. GSE29718 was used to validate our findings. Intercellular communication and cell differentiation trends were further explored using single-cell data from GSE153643. Based on our research, the immune microenvironment in the obese group showed higher immune infiltration. We found 962 DEGs and CXCL2 was identified as the key gene. The co-regulatory network of lncRNA-miRNA-mRNA suggested that obtaining TM4SF19-AS1, GUSBP11, AC105020.1, LINC00189, COL4A2-AS2, VIPR1-AS1 and LINC00242 may regulate CXCL2 (r > 0.9 and P < 0.01). Differential expression of CXCL2 was validated in GSE29718 (P < 0.05) and CXCL2 was identified as a biomarker for childhood obesity (AUC = 0.885). GSVA enrichment analysis revealed many pathways of high group obtaining the TNF-α signaling via NF-κB pathway and interferon γ response pathway. In GSE153643, 11 cell types were identified and CXCL2 was highly expressed in monocyte, macrophage, endothelial cell and pericyte. In CXCL2 high expressing macrophages, there was a tendency for cells to polarize toward M1 macrophages (P < 0.05). In summary, we identified CXCL2 as a potential biomarker of childhood obesity. The development of childhood obesity may be associated with the activation of immune infiltration of macrophage M1 polarization by CXCL2 expression.

Joint multi-omics discriminant analysis with consistent representation learning using PANDA

Integrative multi-omics analysis provides deeper insight and enables better and more realistic modeling of the underlying biology and causes of diseases than does single omics analysis. Although several integrative multi-omics analysis methods have been proposed and demonstrated promising results in integrating distinct omics datasets, inconsistent distribution of the different omics data, which is caused by technology variations, poses a challenge for paired integrative multi-omics methods. In addition, the existing discriminant analysis-based integrative methods do not effectively exploit correlation and consistent discriminant structures, necessitating a compromise between correlation and discrimination in using these methods. Herein we present PAN-omics Discriminant Analysis (PANDA), a joint discriminant analysis method that seeks omics-specific discriminant common spaces by jointly learning consistent discriminant latent representations for each omics. PANDA jointly maximizes between-class and minimizes within-class omics variations in a common space and simultaneously models the relationships among omics at the consistency representation and cross-omics correlation levels, overcoming the need for compromise between discrimination and correlation as with the existing integrative multi-omics methods. Because of the consistency representation learning incorporated into the objective function of PANDA, this method seeks a common discriminant space to minimize the differences in distributions among omics, can lead to a more robust latent representations than other methods, and is against the inconsistency of the different omics. We compared PANDA to 10 other state-of-the-art multi-omics data integration methods using both simulated and real-world multi-omics datasets and found that PANDA consistently outperformed them while providing meaningful discriminant latent representations. PANDA is implemented using both R and MATLAB, with codes available at https://github.com/WuLabMDA/PANDA.

Neutrophil proteases are protective against SARS-CoV-2 by degrading the spike protein and dampening virus-mediated inflammation

Studies on severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) have highlighted the crucial role of host proteases for viral replication and the immune response. The serine proteases furin and TMPRSS2 and lysosomal cysteine proteases facilitate viral entry by limited proteolytic processing of the spike (S) protein. While neutrophils are recruited to the lungs during COVID-19 pneumonia, little is known about the role of the neutrophil serine proteases (NSPs) cathepsin G (CatG), elastase (NE), and proteinase 3 (PR3) on SARS-CoV-2 entry and replication. Furthermore, the current paradigm is that NSPs may contribute to the pathogenesis of severe COVID-19. Here, we show that these proteases cleaved the S protein at multiple sites and abrogated viral entry and replication in vitro. In mouse models, CatG significantly inhibited viral replication in the lung. Importantly, lung inflammation and pathology were increased in mice deficient in NE and/or CatG. These results reveal that NSPs contribute to innate defenses against SARS-CoV-2 infection via proteolytic inactivation of the S protein and that NE and CatG limit lung inflammation in vivo. We conclude that therapeutic interventions aiming to reduce the activity of NSPs may interfere with viral clearance and inflammation in COVID-19 patients.

The Contribution of Antimicrobial Peptides to Immune Cell Function: A Review of Recent Advances

The development of novel antimicrobial agents to replace antibiotics has become urgent due to the emergence of multidrug-resistant microorganisms. Antimicrobial peptides (AMPs), widely distributed in all kingdoms of life, present strong antimicrobial activity against a variety of bacteria, fungi, parasites, and viruses. The potential of AMPs as new alternatives to antibiotics has gradually attracted considerable interest. In addition, AMPs exhibit strong anticancer potential as well as anti-inflammatory and immunomodulatory activity. Many studies have provided evidence that AMPs can recruit and activate immune cells, controlling inflammation. This review highlights the scientific literature focusing on evidence for the anti-inflammatory mechanisms of different AMPs in immune cells, including macrophages, monocytes, lymphocytes, mast cells, dendritic cells, neutrophils, and eosinophils. A variety of immunomodulatory characteristics, including the abilities to activate and differentiate immune cells, change the content and expression of inflammatory mediators, and regulate specific cellular functions and inflammation-related signaling pathways, are summarized and discussed in detail. This comprehensive review contributes to a better understanding of the role of AMPs in the regulation of the immune system and provides a reference for the use of AMPs as novel anti-inflammatory drugs for the treatment of various inflammatory diseases.

Quantitative Proteomic Characterization of Foreign Body Response towards Silicone Breast Implants Identifies Chronological Disease-Relevant Biomarker Dynamics

The etiology of exaggerated fibrous capsule formation around silicone mammary implants (SMI) is multifactorial but primarily induced by immune mechanisms towards the foreign material silicone. The aim of this work was to understand the disease progression from implant insertion and immediate tissue damage response reflected in (a) the acute wound proteome and (b) the adsorption of chronic inflammatory wound proteins at implant surfaces. An intraindividual relative quantitation TMT-liquid chromatography-tandem mass spectrometry approach was applied to the profile wound proteome formed around SMI in the first five days post-implantation. Compared to plasma, the acute wound profile resembled a more complex composition comprising plasma-derived and locally differentially expressed proteins (DEPs). DEPs were subjected to a functional enrichment analysis, which revealed the dysregulation of signaling pathways mainly involved in immediate inflammation response and ECM turnover. Moreover, we found time-course variations in protein enrichment immediately post-implantation, which were adsorbed to SMI surfaces after 6-8 months. Characterization of the expander-adhesive proteome by a label-free approach uncovered a long-term adsorbed acute wound and the fibrosis-associated proteome. Our findings propose a wound biomarker panel for the early detection and diagnosis of excessive fibrosis that could potentially broaden insights into the characteristics of fibrotic implant encapsulation.

Resolution Pharmacology: Focus on Pro-Resolving Annexin A1 and Lipid Mediators for Therapeutic Innovation in Inflammation

Chronic diseases that affect our society are made more complex by comorbidities and are poorly managed by the current pharmacology. While all present inflammatory etiopathogeneses, there is an unmet need for better clinical management of these diseases and their multiple symptoms. We discuss here an innovative approach based on the biology of the resolution of inflammation. Studying endogenous pro-resolving peptide and lipid mediators, how they are formed, and which target they interact with, can offer innovative options through augmenting the expression or function of pro-resolving pathways or mimicking their actions with novel targeted molecules. In all cases, resolution offers innovation for the treatment of the primary cause of a given disease and/or for the management of its comorbidities, ultimately improving patient quality of life. By implementing resolution pharmacology, we harness the whole physiology of inflammation, with the potential to bring a marked change in the management of inflammatory conditions.

Neutrophils and Platelets: Immune Soldiers Fighting Together in Stroke Pathophysiology

Neutrophils and platelets exhibit a diverse repertoire of functions in thromboinflammatory conditions such as stroke. Most cerebral ischemic events result from longstanding chronic inflammation secondary to underlying pathogenic conditions, e.g., hypertension, diabetes mellitus, obstructive sleep apnea, coronary artery disease, atrial fibrillation, morbid obesity, dyslipidemia, and sickle cell disease. Neutrophils can enable, as well as resolve, cerebrovascular inflammation via many effector functions including neutrophil extracellular traps, serine proteases and reactive oxygen species, and pro-resolving endogenous molecules such as Annexin A1. Like neutrophils, platelets also engage in pro- as well as anti-inflammatory roles in regulating cerebrovascular inflammation. These anucleated cells are at the core of stroke pathogenesis and can trigger an ischemic event via adherence to the hypoxic cerebral endothelial cells culminating in aggregation and clot formation. In this article, we review and highlight the evolving role of neutrophils and platelets in ischemic stroke and discuss ongoing preclinical and clinical strategies that may produce viable therapeutics for prevention and management of stroke.

The impact of thrombo-inflammation on the cerebral microcirculation

The intertwined processes of thrombosis and inflammation (termed "thrombo-inflammation") are significant drivers of cerebrovascular diseases, and as such, they represent prime targets for drug discovery programs focusing on treatment and management of cerebrovascular diseases. Most cerebrovascular events result from chronic systemic microcirculatory dysfunction due to underlying conditions, for example, hypertension, diabetes mellitus, coronary artery disease, dyslipidemia, and sickle cell disease. Immune cells especially neutrophils play a critical role in the onset and maintenance of neuroinflammatory responses in the microcirculation. Neutrophils have the ability to drive both inflammatory and anti-inflammatory/pro-resolution effects depending on the underlying vascular state (physiological vs. pathological). In this article, we highlight the pathophysiological role of neutrophils in stroke and discuss ongoing pharmacotherapeutic strategies that are focused on identifying potential therapeutic targets for enhancing neuroprotection, mitigating inflammatory pathways, and enabling resolution.

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.

Identification of an immune-related long non-coding RNA signature and nomogram as prognostic target for muscle-invasive bladder cancer

To identify an immune-related prognostic signature based on long non-coding RNAs (lncRNAs) and find immunotherapeutic targets for bladder urothelial carcinoma, we downloaded RNA-sequencing data from The Cancer Genome Atlas (TCGA) dataset. Functional enrichment analysis demonstrated bladder urothelial carcinoma was related to immune-related functions. We obtained 332 immune-related genes and 262 lncRNAs targeting immune-related genes. We constructed a signature based on eight lncRNAs in training cohort. Patients were classified as high-risk and low-risk according to signature risk score. High-risk patients had poor overall survival compared with low-risk patients (P < 0.001). Multivariate Cox regression suggested the signature was an independent prognostic indicator. The findings were further validated in testing, entire TCGA and external validation cohorts. Gene set enrichment analysis indicated significant enrichment of immune-related phenotype in high-risk group. Immunohistochemistry and online analyses validated the functions of 4 key immune-related genes (LIG1, TBX1, CTSG and CXCL12) in bladder urothelial carcinoma. Nomogram proved to be a good classifier for muscle-invasive bladder cancer through combining the signature. In conclusion, our immune-related prognostic signature and nomogram provided prognostic indicators and potential immunotherapeutic targets for muscle-invasive bladder cancer.

Ischemia-Reperfusion Injury in Sickle Cell Disease: From Basics to Therapeutics

Sickle cell disease (SCD) is one of the most common hereditary hemoglobinopathies worldwide, affecting almost 400,000 newborns globally each year. It is characterized by chronic hemolytic anemia and endothelial dysfunction, resulting in a constant state of disruption of the vascular system and leading to recurrent episodes of ischemia-reperfusion injury (I/RI) to multiple organ systems. I/RI is a fundamental vascular pathobiological paradigm and contributes to morbidity and mortality in a wide range of conditions, including myocardial infarction, stroke, acute kidney injury, and transplantation. I/RI is characterized by an initial restriction of blood supply to an organ, which can lead to ischemia, followed by the subsequent restoration of perfusion and concomitant reoxygenation. Recent advances in the pathophysiology of SCD have led to an understanding that many of the consequences of this disease can be explained by mechanisms associated with I/RI. The following review focuses on the evolving pathobiology of SCD, how various complications of SCD can be attributed to I/RI, and the role of timely therapeutic intervention(s) based on targeting mediators or pathways that influence I/R insult.

Neutrophil Cathepsin G and Tumor Cell RAGE Facilitate Neutrophil Anti-Tumor Cytotoxicity

Neutrophils are a heterogeneous population of myeloid cells which may either promote or hinder tumor growth and progression. Anti-tumor neutrophils have the capacity to kill tumor cells in a contact-dependent manner. However, the molecular mechanisms underlying tumor cell recognition by neutrophils remained unexplored. Tumor cells were shown to express aberrant glycosylation patterns and neutrophils are equipped with receptors capable of recognizing such glycosylations. Accordingly, we hypothesized that the receptor for advanced glycation end products (RAGE) may facilitate neutrophil recognition of tumor cells. Indeed, RAGE decoy receptors and RAGE-specific blocking antibodies dramatically reduce tumor cell susceptibility to neutrophil cytotoxicity. Unexpectedly, we found that tumor cell RAGE rather than neutrophil RAGE is important for the killing process. We further identified neutrophil Cathepsin G as the neutrophil component interacting with tumor cell RAGE. Cathepsin G-deficient neutrophils show impaired ability to kill tumor cells, suggesting that RAGE-Cathepsin G interaction is required for neutrophil cytotoxicity. These data unravel new aspects of neutrophil anti-tumor activity and identify a novel role for RAGE and Cathepsin G in neutrophil-mediated cytotoxicity.

Evaluation of Neutrophil Activation Status According to the Phenotypes of Adult Asthma

Purpose

Neutrophils are considered key effector cells in the pathogenic mechanisms of airway inflammation in asthma. This study assessed the activation status of neutrophils in adult asthmatics, and the therapeutic potential of FTY720, a synthetic sphingosine-1-phosphate analog, on activated neutrophils using an in vitro stimulation model.

Methods

We isolated peripheral blood neutrophils (PBNs) from 59 asthmatic patients (including 20 aspirin-exacerbated respiratory disease [AERD] and 39 aspirin-tolerant asthma [ATA] groups). PBNs were stimulated with N-formyl-methionyl-leucyl-phenylalanine (fMLP) or lipopolysaccharide (LPS) and their activation status was determined based on reactive oxygen species (ROS) production, cell surface expression of CD11b, interleukin (IL)-8 and matrix metallopeptidase (MMP)-9 release. PBNs were primed with FTY720 to evaluate its anti-inflammatory action.

Results

In vitro PBN stimulation with fMLP or LPS induced a significant increase in ROS/CD11b/IL-8/MMP-9 levels (P < 0.05 for all). In asthmatics, fMLP-induced ROS level was significantly correlated with values of forced expiratory volume in 1 second/forced vital capacity (r = −0.278; P = 0.036), maximal mid-expiratory flow (r = −0.309; P = 0.019) and PC20 methacholine (r = −0.302; P = 0.029). In addition, ROS levels were significantly higher in patients with AERD and in those with severe asthma than in those with ATA or non-severe asthma (P < 0.05 for all). FTY720 treatment could suppress ROS/CD11b levels, and LPS-induced IL-8 and MMP-9 levels (P < 0.05 for all). Responders to FTY720 treatment had significantly higher neutrophil counts in sputum (P = 0.004).

Conclusions

Our findings suggest a useful in vitro PBN stimulation model for evaluating the neutrophil functional status and the therapeutic potentials of neutrophil-targeting candidates in asthmatics.

The role of neutrophil granule proteins in neuroinflammation and Alzheimer's disease

Neutrophils are the innate immune system’s first line of defense. Neutrophils play a critical role in protecting the host against infectious pathogens, resolving sterile injuries, and mediating inflammatory responses. The granules of neutrophils and their constituent proteins are central to these functions. Although neutrophils may exert a protective role upon acute inflammatory conditions or insults, continued activity of neutrophils in chronic inflammatory diseases can contribute to tissue damage. Neutrophil granule proteins are involved in a number of chronic inflammatory conditions and diseases. However, the functions of these proteins in neuroinflammation and chronic neuroinflammatory diseases, including Alzheimer’s disease (AD), remain to be elucidated. In this review, we discuss recent findings from our lab and others that suggest possible functions for neutrophils and the neutrophil granule proteins, CAP37, neutrophil elastase, and cathepsin G, in neuroinflammation, with an emphasis on AD. These findings reveal that neutrophil granule proteins may exert both neuroprotective and neurotoxic effects. Further research should determine whether neutrophil granule proteins are valid targets for therapeutic interventions in chronic neuroinflammatory diseases.

Molecular network, pathway, and functional analysis of time-dependent gene changes related to cathepsin G exposure in neonatal rat cardiomyocytes

The molecular pathways activated in response to acute cathepsin G (CG) exposure, as well as the mechanisms involved in activation of signaling pathways that culminate in myocyte detachment and apoptosis remain unclear. This study aimed to determine the changes in gene expression patterns associated with time dependent CG exposure to neonatal rat cardiomyocytes (NRCMs). Microarray analysis revealed a total of 451, 572 and 1127 differentially expressed genes after CG exposure at 1, 4 and 8 h respectively. A total of 54 overlapped genes at each time point were mapped by Ingenuity Pathway Analysis (IPA). The top up-regulated genes included Hamp, SMAD6, NR4A1, FOSL2, ID3 and SLAMF7, and down-regulated genes included CYR61, GDF6, Olr640, Vom2r36, DUSP6 and MMP20. Our data suggest that there are multiple deregulated pathways associated with cardiomyocyte death after CG exposure, including JAK/Stat signaling, IL-9 signaling and Nur77 signaling. In addition, we also generated the molecular network of expressed gene and found most of the molecules were connected to ERK1/2, caspase, BCR (complex) and Cyclins. Our study reveals the ability to assess time-dependent changes in gene expression patterns in NRCMs associated with CG exposure. The global gene expression profiles may provide insight into the cellular mechanism that regulates CG dependent myocyte apoptosis. In future, the pathways important in CG response, as well as the genes found to be differentially expressed might represent the therapeutic targets for myocyte survival in heart failure.

Exogenous murine antimicrobial peptide CRAMP significantly exacerbates Ovalbumin-induced airway inflammation but ameliorates oxazolone-induced intestinal colitis in BALB/c mice

Cathelicidin has been reported to be multifunctional. The current study aimed to investigate the influences of exogenous cathelicidin-related antimicrobial peptide (CRAMP) on inflammatory responses in different disease models. In OVA-induced allergic airway inflammation, CRAMP significantly enhanced the infiltration of inflammatory cells and accumulation of proinflammatory Th2 cytokine IL-13 and IL-33 in bronchial alveolar lavage fluid (BALF), exacerbated lung tissue inflammation and airway goblet cell hyperplasia, and elevated OVA-specific IgE level in serum. In oxazolone-induced intestinal colitis, the expression levels of CRAMP and its receptor FPR2 significantly increased in comparison with those of TNBS-induced mice, vesicle and normal controls. Exogenous CRAMP significantly prevented the development of ulcerative colitis, evidenced by improved body weight regain, decreased colons weight/length ratio, elevated epithelial integrity, and ameliorated colon tissue inflammation. In addition, pro-inflammatory cytokines TNF-α, IL-1β, IL-4 and IL-13, as well as chemokines CXCL2 and CXCL5 for neutrophils recruitment were significantly decreased in CRAMP-treated mice, and epithelial repair-related factors MUC2 and Claudin1 were increased, determined by real time-PCR and ELISAs. The results indicated that although CRAMP has pro-inflammatory effects in airway, local application of exogenous CRAMP might be a potential approach for the treatment of ulcerative colitis.

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.

Annexin A1 localization and its relevance to cancer

Annexin A1 (ANXA1) is a Ca(2+)-regulated phospholipid-binding protein involved in various cell processes. ANXA1 was initially widely studied in inflammation resolution, but its overexpression was later reported in a large number of cancers. Further in-depth investigations have revealed that this protein could have many roles in cancer progression and act at different levels (from cancer initiation to metastasis). This is partly due to the location of ANXA1 in different cell compartments. ANXA1 can be nuclear, cytoplasmic and/or membrane associated. This last location allows ANXA1 to be proteolytically cleaved and/or to become accessible to its cognate partners, the formyl-peptide receptors. Indeed, in some cancers, ANXA1 is found at the cell surface, where it stimulates formyl-peptide receptors to trigger oncogenic pathways. In the present review, we look at the different locations of ANXA1 and their association with the deregulated pathways often observed in cancers. We have specifically detailed the non-classic pathways of ANXA1 externalization, the significance of its cleavage and the role of the ANXA1-formyl-peptide receptor complex in cancer progression.

Genetic overexpression of Serpina3n attenuates muscular dystrophy in mice

Muscular dystrophy (MD) is associated with mutations in genes that stabilize the myofiber plasma membrane, such as through the dystrophin-glycoprotein complex (DGC). Instability of this complex or defects in membrane repair/integrity leads to calcium influx and myofiber necrosis leading to progressive dystrophic disease. MD pathogenesis is also associated with increased skeletal muscle protease levels and activity that could augment weakening of the sarcolemma through greater degradation of cellular attachment complexes. Here, we observed a compensatory increase in the serine protease inhibitor Serpina3n in mouse models of MD and after acute muscle tissue injury. Serpina3n muscle-specific transgenic mice were generated to model this increase in expression, which reduced the activity of select proteases in dystrophic skeletal muscle and protected muscle from both acute injury with cardiotoxin and from chronic muscle disease in the mdx or Sgcd(-/-) MD genetic backgrounds. The Serpina3n transgene mitigated muscle degeneration and fibrosis, reduced creatine kinase serum levels, restored running capacity on a treadmill and reduced muscle membrane leakiness in vivo that is characteristic of mdx and Sgcd(-/-) mice. Mechanistically, we show that increased Serpina3n promotes greater sarcolemma membrane integrity and stability in dystrophic mouse models in association with increased membrane residence of the integrins, the DGC/utrophin-glycoprotein complex of proteins and annexin A1. Hence, Serpina3n blocks endogenous increases in the activity of select skeletal muscle resident proteases during injury or dystrophic disease, which stabilizes the sarcolemma leading to less myofiber degeneration and increased regeneration. These results suggest the use of select protease inhibitors as a strategy for treating MD.

Up-regulation of Cathepsin G in the Development of Chronic Postsurgical Pain

Background:

Proteases have been shown to modulate pain signaling in the spinal cord and may contribute to the development of chronic postsurgical pain. By using peripheral inflammation in rats as a chronic pain model, the authors identified the deregulation of proteases and their inhibitors as a hallmark of chronic pain development using a genome-wide screening approach.

Methods:

A microarray analysis was performed and identified spinal cathepsin G (CTSG) as the most up-regulated gene in rats with persistent hyperalgesia after intraplantar injection of complete Freund’s adjuvant (n = 4). Further experiments were performed to elucidate the mechanisms of CTSG-induced hyperalgesia by intrathecally applying specific CTSG inhibitor (n = 10). The authors also evaluated the association between CTSG gene polymorphisms and the risk of chronic postsurgical pain in 1,152 surgical patients.

Results:

CTSG blockade reduced heat hyperalgesia, accompanied by a reduction in neutrophil infiltration and interleukin 1β levels in the dorsal horns. In the gene association study, 246 patients (21.4%) reported chronic postsurgical pain at 12-month follow-up. Patients with AA genotypes at polymorphisms rs2070697 (AA-15.3%, GA-24.1%, and GG-22.3%) or rs2236742 (AA-6.4%, GA-20.4%, and GG-22.6%) in the CTSG gene had lower risk for chronic postsurgical pain compared with wild-types. The adjusted odds ratios were 0.67 (95% CI, 0.26 to 0.99) and 0.34 (95% CI, 0.21 to 0.98), respectively.

Conclusions:

This study demonstrated that CTSG is a pronociceptive mediator in both animal model and human study. CTSG represents a new target for pain control and a potential marker to predict patients who are prone to develop chronic pain after surgery.

P2X7 Receptor Regulates Internalization of Antimicrobial Peptide LL-37 by Human Macrophages That Promotes Intracellular Pathogen Clearance

Bioactive peptide LL-37/hCAP18, the only human member of the cathelicidin family, plays important roles in killing various pathogens, as well as in immune modulation. We demonstrate that LL-37 is internalized by human macrophages in a time-, dose-, temperature-, and peptide sequence-dependent endocytotic process. Both clathrin- and caveolae/lipid raft-mediated endocytosis pathways are involved in LL-37 internalization. We find that the P2X7 receptor (P2X7R) plays an important role in LL-37 internalization by human macrophages because significantly less internalized LL-37 was detected in macrophages pretreated with P2X7R antagonists or, more specifically, in differentiated THP-1 cells in which the P2X7R gene had been silenced. Furthermore, this P2X7R-mediated LL-37 internalization is primarily connected to the clathrin-mediated endocytosis pathway. In addition, our results demonstrate that internalized LL-37 traffics to endosomes and lysosomes and contributes to intracellular clearance of bacteria by human macrophages, coinciding with increased reactive oxygen species and lysosome formation. Finally, we show that human macrophages have the potential to import LL-37 released from activated human neutrophils. In conclusion, our study unveils a novel mechanism by which human macrophages internalize antimicrobial peptides to improve their intracellular pathogen clearance.

Mast cell proteases as pharmacological targets

Mast cells are rich in proteases, which are the major proteins of intracellular granules and are released with histamine and heparin by activated cells. Most of these proteases are active in the granule as well as outside of the mast cell when secreted, and can cleave targets near degranulating mast cells and in adjoining tissue compartments. Some proteases released from mast cells reach the bloodstream and may have far-reaching actions. In terms of relative amounts, the major mast cell proteases include the tryptases, chymases, cathepsin G, carboxypeptidase A3, dipeptidylpeptidase I/cathepsin C, and cathepsins L and S. Some mast cells also produce granzyme B, plasminogen activators, and matrix metalloproteinases. Tryptases and chymases are almost entirely mast cell-specific, whereas other proteases, such as cathepsins G, C, and L are expressed by a variety of inflammatory cells. Carboxypeptidase A3 expression is a property shared by basophils and mast cells. Other proteases, such as mastins, are largely basophil-specific, although human basophils are protease-deficient compared with their murine counterparts. The major classes of mast cell proteases have been targeted for development of therapeutic inhibitors. Also, a human β-tryptase has been proposed as a potential drug itself, to inactivate of snake venins. Diseases linked to mast cell proteases include allergic diseases, such as asthma, eczema, and anaphylaxis, but also include non-allergic diseases such as inflammatory bowel disease, autoimmune arthritis, atherosclerosis, aortic aneurysms, hypertension, myocardial infarction, heart failure, pulmonary hypertension and scarring diseases of lungs and other organs. In some cases, studies performed in mouse models suggest protective or homeostatic roles for specific proteases (or groups of proteases) in infections by bacteria, worms and other parasites, and even in allergic inflammation. At the same time, a clearer picture has emerged of differences in the properties and patterns of expression of proteases expressed in human mast cell subsets, and in humans versus other mammals. These considerations are influencing prioritization of specific protease targets for therapeutic inhibition, as well as options of pre-clinical models, disease indications, and choice of topical versus systemic routes of inhibitor administration.

Prostaglandin E2 resistance in granulocytes from patients with aspirin-exacerbated respiratory disease

BACKGROUND

Aspirin-exacerbated respiratory disease (AERD) is an inflammatory condition of the respiratory tract and is characterized by overproduction of leukotrienes (LT) and large numbers of circulating granulocyte-platelet complexes. LT production can be suppressed by prostaglandin E(2) (PGE(2)) and the cyclic AMP-dependent protein kinase A (PKA).

OBJECTIVE

To determine if PGE(2)-dependent control of LT production by granulocytes is dysregulated in AERD.

METHODS

Granulocytes from well-characterized patients with and without AERD were activated ex vivo and subjected to a range of functional and biochemical analyses.

RESULTS

Granulocytes from subjects with AERD generated more LTB4 and cysteinyl LTs than did granulocytes from controls with aspirin-tolerant asthma and controls without asthma. When compared with controls, granulocytes from subjects with AERD had comparable levels of EP(2) protein expression and PGE(2)-mediated cAMP accumulation, yet were resistant to PGE(2)-mediated suppression of LT generation. Percentages of platelet-adherent neutrophils correlated positively with LTB4 generation and inversely with responsiveness to PGE(2)-mediated suppression of LTB(4). The PKA inhibitor H89 potentiated LTB4 generation by control granulocytes but was inactive in granulocytes from individuals with AERD and had no effect on platelet P-selectin induction. Both tonic PKA activity and levels of PKA catalytic gamma subunit protein were significantly lower in granulocytes from individuals with AERD relative to those from controls.

CONCLUSIONS

Impaired granulocyte PKA function in AERD may lead to dysregulated control of 5-lipoxygenase activity by PGE(2), whereas adherent platelets lead to increased production of LTs, which contributes to the features of persistent respiratory tract inflammation and LT overproduction.