Role of cathepsin S in ozone-induced airway hyperresponsiveness and inflammation

Proteomic signatures of eosinophilic and neutrophilic asthma from serum and sputum

BACKGROUND

Eosinophilic and neutrophilic asthma defined by high levels of blood and sputum eosinophils and neutrophils exemplifies the inflammatory heterogeneity of asthma, particularly severe asthma. We analysed the serum and sputum proteome to identify biomarkers jointly associated with these different phenotypes.

METHODS

Proteomic profiles (N = 1129 proteins) were assayed in sputum (n = 182) and serum (n = 574) from two cohorts (U-BIOPRED and ADEPT) of mild-moderate and severe asthma by SOMAscan. Using least absolute shrinkage and selection operator (LASSO)-penalised logistic regression in a stability selection framework, we sought sparse sets of proteins associated with either eosinophilic or neutrophilic asthma with and without adjustment for established clinical factors including oral corticosteroid use and forced expiratory volume.

FINDINGS

We identified 13 serum proteins associated with eosinophilic asthma, including 7 (PAPP-A, TARC/CCL17, ALT/GPT, IgE, CCL28, CO8A1, and IL5-Rα) that were stably selected while adjusting for clinical factors yielding an AUC of 0.84 (95% CI: 0.83-0.84) compared to 0.62 (95% CI: 0.61-0.63) for clinical factors only. Sputum protein analysis selected only PAPP-A (AUC = 0.81 [95% CI: 0.80-0.81]). 12 serum proteins were associated with neutrophilic asthma, of which 5 (MMP-9, EDAR, GIIE/PLA2G2E, IL-1-R4/IL1RL1, and Elafin) complemented clinical factors increasing the AUC from 0.63 (95% CI: 0.58-0.67) for the model with clinical factors only to 0.89 (95% CI: 0.89-0.90). Our model did not select any sputum proteins associated with neutrophilic status.

INTERPRETATION

Targeted serum proteomic profiles are a non-invasive and scalable approach for subtyping of neutrophilic and eosinophilic asthma and for future functional understanding of these phenotypes.

FUNDING

U-BIOPRED has received funding from the Innovative Medicines Initiative (IMI) Joint Undertaking under grant agreement no. 115010, resources of which are composed of financial contributions from the European Union's Seventh Framework Programme (FP7/2007-2013), and European Federation of Pharmaceutical Industries and Associations (EFPIA) companies' in-kind contributions (www.imi.europa.eu). ADEPT was funded by Johnson & Johnson/Janssen pharmaceutical Company.

Hemopexin Reverses Activation of Lung eIF2a and Decreases Mitochondrial Injury in Chlorine Exposed Mice

We assessed the mechanisms by which non-encapsulated heme, released in the plasma of mice post exposure to chlorine (Cl 2 ) gas, resulted in the initiation and propagation of acute lung injury. We exposed adult C57BL/6 male and female to Cl 2 (500 ppm for 30 min) in environmental chambers and returned them to room air and injected them intramuscularly with a single dose of human hemopexin (hHPX; 5 µg/ g BW), the most efficient scavenger of heme, 30-60 min post exposure. Concentrations of hHPX in plasma of air and Cl 2 exposed mice were 9081±900 vs. 1879± 293 at 6 h and 2966±463 vs. 1555±250 at 50 h post injection (ng/ml; X±1 SEM=3; p<0.01). Cl 2 exposed mice developed progressive acute lung injury post exposure characterized by increased concentrations of plasma heme, marked inflammatory response, respiratory acidosis and increased concentrations of plasma proteins in the alveolar space. Injection of hHPX decreased the onset of acute lung injury at 24 h post exposure; mean survival, for the saline and hHPX groups were 40 vs. 80% (P<0.001) at 15 d post exposure. Non-supervised global proteomics analysis of mouse lungs at 24 h post exposure, revealed the upregulation of 92 and downregulation of 145 lung proteins. Injection of hHPX at one h post exposure moderated the Cl 2 induced changes in eighty-three of these 237 lung proteins. System biology analysis of the global proteomics data showed that hHPX reversed changes in mitochondrial dysfunction and elF2 and integrin signaling. Western blot analysis of lung tissue showed significant increase of phosphorylated elF2 at 24 h post exposure in vehicle treated mice but normal levels in those injected with hHPX. Similarly, RT-PCR analysis of lung tissue showed that hHPX reversed the onset of mtDNA lesions. A form of recombinant human hemopexin generated in tobacco plants was equally effective in reversing acute lung and mtDNA injury. The results of this study offer new insights as to the mechanisms by which exposure to Cl 2 results in acute lung injury and to the therapeutic effects of hemopexin.

Ginger-derived compounds exert in vivo and in vitro anti-asthmatic effects by inhibiting the T-helper 2 cell-mediated allergic response

6-Shogaol (SHO) and 6-gingerol (GIN), naturally derived compounds of ginger (Zingiber officinale Roscoe), have been found to have anti-allergic effects on dermatitis-like skin lesions and rhinitis. Although SHO and GIN have demonstrated a potential in various inflammatory diseases, their efficacy and mechanism in asthma have not been largely examined. Therefore, the present study demonstrated the anti-asthmatic effects of SHO and GIN on the T-helper (Th) 2 cell-mediated allergic response pathway in an ovalbumin (OVA)-induced asthma mouse model. The asthma mouse model was established with an intraperitoneal (i.p.) injection of 50 µg OVA and 1 mg aluminum hydroxide with or without an i.p. injection of SHO and GIN (10 mg/kg) before treatment with OVA. In addition, the current study assessed mast cell degranulation in antigen-stimulated RBL-2H3 cells under different treatment conditions (SHO or GIN at 0, 10, 25, 50 and 100 nM) and determined the mRNA and protein levels of anti-oxidative enzymes [superoxide dismutase (SOD)1, SOD2, glutathione peroxidase-1/2, catalase] in lung tissues. SHO and GIN inhibited eosinophilia in the bronchoalveolar lavage fluids and H&E-stained lung tissues. Both factors also decreased mucus production in periodic acid-Schiff-stained lung tissues and the levels of Th2 cytokines in these tissues. GIN attenuated oxidative stress by upregulating the expression levels of anti-oxidative proteins. In an in vitro experiment, the degranulation of RBL-2H3 rat mast cells was significantly decreased. It was found that SHO and GIN effectively suppressed the allergic response in the mouse model by inhibiting eosinophilia and Th2 cytokine production. Collectively, it was suggested that SHO can inhibit lung inflammation by attenuating the Th2 cell-mediated allergic response signals, and that GIN can inhibit lung inflammation and epithelial cell remodeling by repressing oxidative stress. Therefore, SHO and GIN could be used therapeutically for allergic and eosinophilic asthma.

Roles of microRNAs in chronic pediatric diseases and their use as potential biomarkers: A review

MicroRNAs (miRNAs) are small non-coding highly conserved RNA molecules that can act as master regulators of gene expression in a sequence-specific manner either by translation repression or mRNA degradation, influencing a wide range of biologic processes that are essential for the maintenance of cellular homeostasis. Chronic pediatric diseases are the leading cause of death worldwide among children and the recent evidence indicates that aberrant miRNA expression significantly contributes to the development of chronic pediatric diseases. This review focuses on the role of miRNAs in five major chronic pediatric diseases including bronchial asthma, congenital heart diseases, cystic fibrosis, type 1 diabetes mellitus, and epilepsy, and their potential use as novel biomarkers for the diagnosis and prognosis of these disorders.

Cigarette smoke induces overexpression of active human cathepsin S in lungs from current smokers with or without COPD

Cigarette smoking has marked effects on lung tissue, including induction of oxidative stress, inflammatory cell recruitment, and a protease/antiprotease imbalance. These effects contribute to tissue remodeling and destruction resulting in loss of lung function in chronic obstructive pulmonary disease (COPD) patients. Cathepsin S (CatS) is a cysteine protease that is involved in the remodeling/degradation of connective tissue and basement membrane. Aberrant expression or activity of CatS has been implicated in a variety of diseases, including arthritis, cancer, cardiovascular, and lung diseases. However, little is known about the effect of cigarette smoking on both CatS expression and activity, as well as its role in smoking-related lung diseases. Here, we evaluated the expression and activity of human CatS in lung tissues from never-smokers and smokers with or without COPD. Despite the presence of an oxidizing environment, CatS expression and activity were significantly higher in current smokers (both non-COPD and COPD) compared with never-smokers, and correlated positively with smoking history. Moreover, we found that the exposure of primary human bronchial epithelial cells to cigarette smoke extract triggered the activation of P2X7 receptors, which in turns drives CatS upregulation. The present data suggest that excessive CatS expression and activity contribute, beside other proteases, to the deleterious effects of cigarette smoke on pulmonary homeostasis.

Targeting of cathepsin S reduces cystic fibrosis-like lung disease

Cathepsin S (CatS) is upregulated in the lungs of patients with cystic fibrosis (CF). However, its role in CF lung disease pathogenesis remains unclear.In this study, β-epithelial Na⁺ channel-overexpressing transgenic (βENaC-Tg) mice, a model of CF-like lung disease, were crossed with CatS null (CatS^-/-) mice or treated with the CatS inhibitor VBY-999.Levels of active CatS were elevated in the lungs of βENaC-Tg mice compared with wild-type (WT) littermates. CatS^-/-βENaC-Tg mice exhibited decreased pulmonary inflammation, mucus obstruction and structural lung damage compared with βENaC-Tg mice. Pharmacological inhibition of CatS resulted in a significant decrease in pulmonary inflammation, lung damage and mucus plugging in the lungs of βENaC-Tg mice. In addition, instillation of CatS into the lungs of WT mice resulted in inflammation, lung remodelling and upregulation of mucin expression. Inhibition of the CatS target, protease-activated receptor 2 (PAR2), in βENaC-Tg mice resulted in a reduction in airway inflammation and mucin expression, indicating a role for this receptor in CatS-induced lung pathology.Our data indicate an important role for CatS in the pathogenesis of CF-like lung disease mediated in part by PAR2 and highlight CatS as a therapeutic target.

Effects of ozone repeated short exposures on the airway/lung inflammation, airway hyperresponsiveness and mucus production in a mouse model of ovalbumin-induced asthma

OBJECTIVE

The purpose of this study is to explore the influence of ozone repeated short exposures on airway/lung inflammation, airway hyperresponsiveness (AHR) and airway hypersecretion in ovalbumin (OVA) sensitized/challenged asthmatic mouse model.

METHODS

OVA sensitization was performing by intraperitoneal injection. Ozone exposures (3ppm for 3hours) were given one hour after aerosolized OVA challenges (once every other day, 4 times totally). Methacholine (MCH) bronchial provocation tests, Liu's staining of BALF cell smears, hematoxylin-eosin (HE) staining and Periodic Acid-Schiff (PAS) staining of lung tissue were performed. Interleukins (ILs; IL-4, IL-13, IL-1β, and IL-18) protein (ELISA) and mRNA expression levels (RT-qPCR) in murine lung, 8-hydroxy-2'-deoxyguanosine (8-OHdG, ELISA), malondialdehyde (MDA, thiobarbituric acid assay), reduced glutathione (GSH, spectrophotometric method) in bronchoalveolar lavage fluid (BALF), and GSH1 mRNA relative expression levels (RT-qPCR) in lung tissue were analyzed.

RESULT

Repeated ozone exposures down-regulated the AHR to MCH in mice undergoing OVA sensitization and challenge, however not all parameters associated with asthma were decreased since obvious mucus hypersecretion was induced and airway inflammation increased slightly, especially around small airways. Following ozone co-exposure, the increase of IL-4 and IL-13 levels in murine lung caused by OVA sensitization/challenge were reversed. Instead, levels of IL-1β in BALF remained, higher than negative control group. Ozone repeated short exposures also induced significant increase of 8-OHdG in BALF in OVA sensitized and challenged mice.

CONCLUSION

For asthmatic mice undergoing ozone exposures, AHR is not an accurate indicator of the severity of asthma. Repeated short ozone exposures increase mucus hypersecretion, possibly via an increase in oxidative stress and immune dysregulation.

Inflammation and host-pathogen interaction: Cause and consequence in cystic fibrosis lung disease

Cystic Fibrosis (CF) lung disease is associated with dysregulation of host defence systems, which ultimately disrupts the balance between inflammation and resolution and leaves the host susceptible to repeated infection. However, the mechanisms underlying these defects are complex and continue to garner significant interest among the CF research community. This review explores emerging data on novel aspects of innate host defence with promising biomarker and therapeutic potential for CF lung disease. Improved understanding of inflammation and host defence against pathogens in patients and animal models during the progression of CF lung disease is pivotal for the discovery of new therapeutics that can limit and/or prevent damage from birth.

Regulation of ozone-induced lung inflammation by the epidermal growth factor receptor in mice

Human exposure to the highly reactive oxidant gas Ozone (O₃ ) is associated with inflammatory responses in the airway epithelium. The mechanisms responsible have not been fully elucidated. Epidermal growth factor receptor (EGFR) has previously been shown to play a critical role in the pathogenesis of lung inflammation. To define the role of EGFR in O₃ -induced lung inflammation in mice. 40 BALB/c mice were exposed to filtered air (FA) or (0.25, 0.5, 1.00 ppm) O₃ for 3 h per day for 7 consecutive days. Levels of reactive oxygen species (ROS), EGF, and transforming growth factor α (TGF-α) in the bronchoalveolar lavage fluid (BALF) of mice were measured using ELISA. BALB/c mice were intratracheally instilled with the EGFR kinase inhibitor PD153035 2 h prior to O₃ exposure and every other day thereafter. Phosphorylation of EGFR (Y1068) in lung sections was determined using immunohistochemical staining and western blot 24 h after exposure. Inhalation of O₃ induced pronounced lung inflammation in a dose-dependent manner. Levels of ROS, TGF-α, and total proteins and cells in the BALF of mice exposed to 0.5 ppm or 1.0 ppm of O₃ were markedly elevated relative to those in the BALF of the mice exposed to FA. In addition, exposure to O₃ induced EGFR(Y1068) phosphorylation in the airway epithelium. Administration of PD153035 resulted in a significantly reduced lung inflammation as well as EGFR phosphorylation induced by O₃ exposure. Inhalation of O₃ leads to inflammatory responses that are dependent on the activation the EGFR in the airway epithelium. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 2016-2027, 2016.

Antimicrobial proteins and peptides in human lung diseases: A friend and foe partnership with host proteases

Lung antimicrobial proteins and peptides (AMPs) are major sentinels of innate immunity by preventing microbial colonization and infection. Nevertheless bactericidal activity of AMPs against Gram-positive and Gram-negative bacteria is compromised in patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and asthma. Evidence is accumulating that expression of harmful human serine proteases, matrix metalloproteases and cysteine cathepsins is markedely increased in these chronic lung diseases. The local imbalance between proteases and protease inhibitors compromises lung tissue integrity and function, by not only degrading extracellular matrix components, but also non-matrix proteins. Despite the fact that AMPs are somewhat resistant to proteolytic degradation, some human proteases cleave them efficiently and impair their antimicrobial potency. By contrast, certain AMPs may be effective as antiproteases. Host proteases participate in concert with bacterial proteases in the degradation of key innate immunity peptides/proteins and thus may play immunomodulatory activities during chronic lung diseases. In this context, the present review highlights the current knowledge and recent discoveries on the ability of host enzymes to interact with AMPs, providing a better understanding of the role of human proteases in innate host defense.

miR-31 dysregulation in cystic fibrosis airways contributes to increased pulmonary cathepsin S production

RATIONALE

Cathepsin S (CTSS) activity is increased in bronchoalveolar lavage (BAL) fluid from patients with cystic fibrosis (CF). This activity contributes to lung inflammation via degradation of antimicrobial proteins, such as lactoferrin and members of the β-defensin family.

OBJECTIVES

In this study, we investigated the hypothesis that airway epithelial cells are a source of CTSS, and mechanisms underlying CTSS expression in the CF lung.

METHODS

Protease activity was determined using fluorogenic activity assays. Protein and mRNA expression were analyzed by ELISA, Western blotting, and reverse-transcriptase polymerase chain reaction.

MEASUREMENTS AND MAIN RESULTS

In contrast to neutrophil elastase, CTSS activity was detectable in 100% of CF BAL fluid samples from patients without Pseudomonas aeruginosa infection. In this study, we identified epithelial cells as a source of pulmonary CTSS activity with the demonstration that CF airway epithelial cells express and secrete significantly more CTSS than non-CF control cells in the absence of proinflammatory stimulation. Furthermore, levels of the transcription factor IRF-1 correlated with increased levels of its target gene CTSS. We discovered that miR-31, which is decreased in the CF airways, regulates IRF-1 in CF epithelial cells. Treating CF bronchial epithelial cells with a miR-31 mimic decreased IRF-1 protein levels with concomitant knockdown of CTSS expression and secretion.

CONCLUSIONS

The miR-31/IRF-1/CTSS pathway may play a functional role in the pathogenesis of CF lung disease and may open up new avenues for exploration in the search for an effective therapeutic target.

Cathepsins: a new culprit behind abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a fatal disease defined as an abdominal aortic diameter of 3.0 cm or more, where the abdominal aorta exceeds the normal diameter by more than 50%. Histopathological changes of AAA mainly include extracellular matrix (ECM) remodeling at the abdominal aorta wall, but there is lack of specific drugs to treat AAA. Recent studies have reported that lysosomal cathepsins could induce vascular remodeling and AAA formation by regulating vascular inflammation, medial smooth muscle cell apoptosis, neovascularization, and protease expression. Thus, cathepsins are expected to become a new therapeutic target for AAA treatment.

Inhibition of cathepsin S produces neuroprotective effects after traumatic brain injury in mice

Cathepsin S (CatS) is a cysteine protease normally present in lysosomes. It has long been regarded as an enzyme that is primarily involved in general protein degradation. More recently, mounting evidence has shown that it is involved in Alzheimer disease, seizures, age-related inflammatory processes, and neuropathic pain. In this study, we investigated the time course of CatS protein and mRNA expression and the cellular distribution of CatS in a mouse model of traumatic brain injury (TBI). To clarify the roles of CatS in TBI, we injected the mice intraventricularly with LHVS, a nonbrain penetrant, irreversible CatS inhibitor, and examined the effect on inflammation and neurobehavioral function. We found that expression of CatS was increased as early as 1 h after TBI at both protein and mRNA levels. The increased expression was detected in microglia and neurons. Inhibition of CatS significantly reduced the level of TBI-induced inflammatory factors in brain tissue and alleviated brain edema. Additionally, administration of LHVS led to a decrease in neuronal degeneration and improved neurobehavioral function. These results imply that CatS is involved in the secondary injury after TBI and provide a new perspective for preventing secondary injury after TBI.

Impact of aging on pulmonary responses to acute ozone exposure in mice: role of TNFR1

CONTEXT

Chamber studies in adult humans indicate reduced responses to acute ozone with increasing age. Age-related changes in TNFα have been observed. TNFα induced inflammation is predominantly mediated through TNFR1.

OBJECTIVE

To examine the impact of aging on inflammatory responses to acute ozone exposure in mice and determine the role of TNFR1 in age-related differences.

MATERIALS AND METHODS

Wildtype and TNFR1 deficient (TNFR1(-/-)) mice aged 7 or 39 weeks were exposed to ozone (2 ppm for 3 h). Four hours after exposure, bronchoalveolar lavage (BAL) was performed and BAL cells, cytokines, chemokines, and protein were examined.

RESULTS

Ozone-induced increases in BAL neutrophils and in neutrophil chemotactic factors were lower in 39- versus 7-week-old wildtype, but not (TNFR1(-/-)) mice. There was no effect of TNFR1 genotype in 7-week-old mice, but in 39-week-old mice, BAL neutrophils and BAL concentrations of MCP-1, KC, MIP-2, IL-6 and IP-10 were significantly greater following ozone exposure in TNFR1(-/-) versus wildtype mice. BAL concentrations of the soluble form of the TNFR1 receptor (sTNFR1) were substantially increased in 39-week-old versus 7-week-old mice, regardless of exposure.

DISCUSSION AND CONCLUSION

The data suggest that increased levels of sTNFR1 in the lungs of the 39-week-old mice may neutralize TNFα and protect these older mice against ozone-induced inflammation.

Identification of differentially expressed genes in lung tissues of nickel-exposed rats using suppression subtractive hybridization

Occupational exposure to nickel compound, such as nickel refining, electroplating, and in conjunction with other metals, is harmful to the health, causing respiratory distress, and lung and nasal cancer. In this work, the different gene expression patterns of lung tissues from nickel-exposed rats and controls were investigated. The suppression subtractive hybridization (SSH) method was used to generate two subtracted cDNA libraries with gene transcripts differentially expressed after nickel inducing. Dot-blot hybridizations were used to confirm differential ratios of expression of obtained SSH clones. Out of 768 unique SSH clones, which were chosen randomly from the two subtraction libraries (384 of each), 319 could be verified as differentially expressed. According to blast screening and functional annotation, 28% genes in nickel-induced cDNA library were related to cell differentiation, whereas 21% in driver library were related to oxygen transport. Two novel expressed sequence tags (ESTs; NCBI Accession No. FC809414 and No. FC809411) in nickel-induced cDNA library were obtained. The genes detected in the present study are probably important genes associated with nickel-induced lung cancer.

Modulation of mouse macrophage proteome induced by Toxoplasma gondii tachyzoites in vivo

Toxoplasma gondii is an obligate intracellular protozoan parasite, which can invade and multiply within the macrophages of humans and most warm-blooded animals. Macrophages are important effector cells for the control and killing of intracellular T. gondii, and they may also serve as long-term host cells for the replication and survival of the parasite. In the present study, we explored the proteomic profile of macrophages of the specific pathogen-free Kunming mice at 24 h after infection with tachyzoites of the virulent T. gondii RH strain using two-dimensional gel electrophoresis combined with matrix-assisted laser desorption ionization time-of-flight (TOF)/TOF tandem mass spectrometry. Totally, 60 differentially expressed protein spots were identified. Among them, 52 spots corresponded to 38 proteins matching to proteins of the mouse, including actin, enolase, calumenin, vimentin, plastin 2, annexin A1, cathepsin S, arginase-1, arachidonate 12-lipoxygenase, and aminoacylase-1. Functional prediction using Gene Ontology database showed that these proteins were mainly involved in metabolism, structure, protein fate, and immune responses. The findings provided an insight into the interactive relationship between T. gondii and the host macrophages, and will shed new lights on the understanding of molecular mechanisms of T. gondii pathogenesis.

Trypanosoma cruzi infection induces a global host cell response in cardiomyocytes

Chagas' disease, caused by the hemoflagellate protozoan Trypanosoma cruzi, affects millions of people in South and Central America. Chronic chagasic cardiomyopathy, the most devastating manifestation of this disease, occurs in approximately one-third of infected individuals. Events associated with the parasite's tropism for and invasion of cardiomyocytes have been the focus of intense investigation in recent years. In the present study, we use murine microarrays to investigate the cellular response caused by invasion of primary murine cardiomyocytes by T. cruzi trypomastigotes. These studies identified 353 murine genes that were differentially expressed during the early stages of invasion and infection of these cells. Genes associated with the immune response, inflammation, cytoskeleton organization, cell-cell and cell-matrix interactions, apoptosis, cell cycle, and oxidative stress are among those affected during the infection. Our data indicate that T. cruzi induces broad modulations of the host cell machinery in ways that provide insight into how the parasite survives, replicates, and persists in the infected host and ultimately defines the clinical outcome of the infection.

Lack of cathepsin activities alter or prevent the development of lung granulomas in a mouse model of sarcoidosis

BACKGROUND

Remodeling of lung tissues during the process of granuloma formation requires significant restructuring of the extra-cellular matrix and cathepsins K, L and S are among the strongest extra-cellular matrix degrading enzymes. Cathepsin K is highly expressed in various pathological granulomatous infiltrates and all three enzymes in their active form are detected in bronchoalveolar lavage fluids from patients with sarcoidosis. Granulomatous inflammation is driven by T-cell response and cathepsins S and L are actively involved in the regulation of antigen presentation and T-cell selection. Here, we show that the disruption of the activities of cathepsins K, L, or S affects the development of lung granulomas in a mouse model of sarcoidosis.

METHODS

Apolipoprotein E-deficient mice lacking cathepsin K or L were fed Paigen diet for 16 weeks and lungs were analyzed and compared with their cathepsin-expressing littermates. The role of cathepsin S in the development of granulomas was evaluated using mice treated for 8 weeks with a potent and selective cathepsin S inhibitor.

RESULTS

When compared to wild-type litters, more cathepsin K-deficient mice had lung granulomas, but individually affected mice developed smaller granulomas that were present in lower numbers. The absence of cathepsin K increased the number of multinucleated giant cells and the collagen content in granulomas. Cathepsin L deficiency resulted in decreased size and number of lung granulomas. Apoe-/- mice treated with a selective cathepsin S inhibitor did not develop lung granulomas and only individual epithelioid cells were observed.

CONCLUSIONS

Cathepsin K deficiency affected mostly the occurrence and composition of lung granulomas, whereas cathepsin L deficiency significantly reduced their number and cathepsin S inhibition prevented the formation of granulomas.

Probing cathepsin S activity in whole blood by the activity-based probe BIL-DMK: cellular distribution in human leukocyte populations and evidence of diurnal modulation

Using the cell-permeable, radioiodinated, irreversible inhibitor BIL-DMK, we probed active cysteine cathepsins in blood. Incubation of the probe in human whole blood followed by separation of white blood cells by dextran sedimentation led to the labeling of one major band at 24kDa. Two-dimensional gel electrophoresis showed that the band resolved in a single protein spot and corresponded to cathepsin S based on its molecular mass, isoelectric point, and Western blot analysis using anti-human cathepsin S antibodies. Cathepsin S activity in human whole blood was dependent on the time of blood collection, suggesting that cathepsin S activity is subject to circadian variations. Separation of white blood cell populations using a magnetic cell sorter and further characterization by FACS (fluorescent-activated cell sorting) analysis demonstrated that the majority of active cathepsin S resided in the monocyte and neutrophil populations, whereas on a cell basis cathepsin S activity in granulocytes is 10-fold lower than that in monocytes. A whole blood cathepsin S assay was developed and used to measure cathepsin S inhibition in both in vitro and ex vivo conditions. To determine the correlation between the in vitro and ex vivo assays, a reversible cathepsin S inhibitor was dosed intravenously to a rhesus monkey. The inhibitor concentration required to inhibit 50% of the cathepsin S activity ex vivo correlated well with the concentration required to inhibit the enzyme in rhesus monkey whole blood in vitro. The results reported here demonstrate the utility of the activity-based probe BIL-DMK for the ex vivo assessment of cathepsin S inhibition.

Genetic and pharmacological evaluation of cathepsin s in a mouse model of asthma

Cathepsin S (Cat S) is predominantly expressed in antigen-presenting cells and is up-regulated in several preclinical models of antigen-induced inflammation, suggesting a role in the allergic response. Prophylactic dosing of an irreversible Cat S inhibitor has been shown to attenuate pulmonary eosinophilia in mice, supporting the hypothesis that Cat S inhibition before the initiation of airway inflammation is beneficial in airway disease. In addition, Cat S has been shown to play a role in more distal events in the allergic response. To determine where Cat S inhibition may affect the allergic response, we used complementary genetic and pharmacological approaches to investigate the role of Cat S in the early and downstream allergic events in a murine model of antigen-induced lung inflammation. Cat S knockout mice did not develop ovalbumin-induced pulmonary inflammation, consistent with a role for Cat S in the development of the allergic response. Alternatively, wild-type mice were treated with a reversible, highly selective Cat S inhibitor in prophylactic and therapeutic dosing paradigms and assessed for changes in airway inflammation. Although both treatment paradigms resulted in potent Cat S inhibition, only prophylactic Cat S inhibitor dosing blocked lung inflammation, consistent with our findings in Cat S knockout mice. The findings indicate that although Cat S is up-regulated in allergic models, it does not appear to play a significant role in the downstream effector inflammatory phase in this model; however, our results demonstrate that Cat S inhibition in a prophylactic paradigm would ameliorate airway inflammation.

Serum cathepsin S is associated with serum C-reactive protein and interleukin-6 independently of obesity in elderly men

OBJECTIVE

Cathepsin S has been suggested provide a mechanistic link between obesity and atherosclerosis, possibly mediated via adipose tissue-derived inflammation. Previous data have shown an association between circulating cathepsin S and inflammatory markers in the obese, but to date, community-based reports are lacking. Accordingly, we aimed to investigate the association between serum levels of cathepsin S and markers of cytokine-mediated inflammation in a community-based sample, with prespecified subgroup analyses in nonobese participants.

METHODS

Serum cathepsin S, C-reactive protein (CRP), and IL-6 were measured in a community-based cohort of elderly men (Uppsala Longitudinal Study of Adult Men; mean age 71 years, n = 991). CRP and IL-6 were also measured at a reexamination after 7 yr.

RESULTS

After adjustment for age, body mass index, fasting plasma glucose, diabetes treatment, systolic blood pressure, diastolic blood pressure, hypertension treatment, serum cholesterol, serum high-density lipoprotein cholesterol, prior cardiovascular disease, smoking, and leisure time physical activity, higher cathepsin S was associated with higher CRP (regression coefficient for 1 sd increase, 0.13; 95% confidence interval 0.07-0.19; P < 0.001) and higher serum IL-6 (regression coefficient for 1 sd increase, 0.08; 95% confidence interval 0.01-0.14; P = 0.02). These associations remained similar in normal-weight participants (body mass index <25 kg/m(2), n = 375). In longitudinal analyses, higher cathepsin S at baseline was associated with higher serum CRP and IL-6 after 7 yr.

CONCLUSIONS

These results provide additional evidence for the interplay between cathepsin S and inflammatory activity and suggest that this association is present also in normal-weight individuals in the community.