Evidence for a crucial role of neutrophil-derived serine proteases in the inactivation of interleukin-6 at sites of inflammation

Current Mouse Models of Intracranial Aneurysms: Analysis of Pharmacological Agents Used to Induce Aneurysms and Their Impact on Translational Research

Intracranial aneurysms (IAs) are rare vascular lesions that are more frequently found in women. The pathophysiology behind the formation and growth of IAs is complex. Hence, to date, no single pharmacological option exists to treat them. Animal models, especially mouse models, represent a valuable tool to explore such complex scientific questions. Genetic modification in a mouse model of IAs, including deletion or overexpression of a particular gene, provides an excellent means for examining basic mechanisms behind disease pathophysiology and developing novel pharmacological approaches. All existing animal models need some pharmacological treatments, surgical interventions, or both to develop IAs, which is different from the spontaneous and natural development of aneurysms under the influence of the classical risk factors. The benefit of such animal models is the development of IAs in a limited time. However, clinical translation of the results is often challenging because of the artificial course of IA development and growth. Here, we summarize the continuous improvement in mouse models of IAs. Moreover, we discuss the pros and cons of existing mouse models of IAs and highlight the main translational roadblocks and how to improve them to increase the success of translational IA research.

Interleukin-6 in Traumatic Brain Injury: A Janus-Faced Player in Damage and Repair

Traumatic brain injury (TBI) is a common and often devastating illness, with wide-ranging public health implications. In addition to the primary injury, victims of TBI are at risk for secondary neurological injury by numerous mechanisms. Current treatments are limited and do not target the profound immune response associated with injury. This immune response reflects a convergence of peripheral and central nervous system-resident immune cells whose interaction is mediated in part by a disruption in the blood-brain barrier (BBB). The diverse family of cytokines helps to govern this communication and among these, Interleukin (IL)-6 is a notable player in the immune response to acute neurological injury. It is also a well-established pharmacological target in a variety of other disease contexts. In TBI, elevated IL-6 levels are associated with worse outcomes, but the role of IL-6 in response to injury is double-edged. IL-6 promotes neurogenesis and wound healing in animal models of TBI, but it may also contribute to disruptions in the BBB and the progression of cerebral edema. Here, we review IL-6 biology in the context of TBI, with an eye to clarifying its controversial role and understanding its potential as a target for modulating the immune response in this disease.

Spatial localization of cathepsins: Implications in immune activation and resolution during infections

Cathepsins were first described, as endolysosomal proteolytic enzymes in reference to the organelles where they degrade the bulk of endogenous and exogenous substrates in a slightly acidic environment. These substrates include pathogens internalized via endocytosis and/or marked for destruction by autophagy. However, the role of cathepsins during infection far exceeds that of direct digestion of the pathogen. Cathepsins have been extensively investigated in the context of tumour associated immune cells and chronic inflammation. Several cathepsin-dependent immune responses develop in the endocytic pathway while others take place in the cytosol, the nucleus, or in the extracellular space. In this review we highlight the spatial localization of cathepsins and their implications in immune activation and resolution pathways during infection.

Neutrophil elastase promotes neointimal hyperplasia by targeting toll-like receptor 4 (TLR4)-NF-κB signalling

BACKGROUND AND PURPOSE

Neointimal hyperplasia (NIH) is the fundamental cause for vascular diseases and vascular smooth muscle cell (VSMC) dysregulation has been widely implicated in NIH. Neutrophil elastase is a potential therapeutic target for multiple diseases. We investigated the role of neutrophil elastase in VSMC functions and injury-induced NIH and explored the therapeutic potential of targeting neutrophil elastase in NIH.

EXPERIMENTAL APPROACH

VSMCs were used to analyse the effects of neutrophil elastase. Proteomic analysis was used to identify potential neutrophil elastase targets. Artery injury model and neutrophil elastase inhibitor GW311616A were used to investigate the role of neutrophil elastase in NIH.

KEY RESULTS

TNF-α up-regulated neutrophil elastase in VSMCs through modulating GAPBα/Runx1/CEBPα/c-Myb signalling. Up-regulated neutrophil elastase promoted VSMC migration, proliferation and inflammation. Toll-like receptor 4 (TLR4) was identified as a target protein for neutrophil elastase in VSMCs and the TLR4/MyD88/IRAK1/TRAF6/NF-κB regulatory axis was shown to be the signalling pathway for neutrophil elastase in VSMC pathology. Importantly, TLR4 inhibition abolished neutrophil elastase-mediated VSMC dysregulation. Injury-induced NIH was significantly reduced in both neutrophil elastase-deficient mice and mice treated with GW311616A. The formation of neutrophil extracellular traps was impaired in injured arteries from neutrophil elastase-deficient mice. Finally, a similar role for neutrophil elastase in human VSMC pathology was confirmed and we observed higher expression levels of neutrophil elastase but lower expression levels of TLR4 in human atherosclerotic lesions.

CONCLUSION AND IMPLICATIONS

We provide new insight into the molecular mechanisms underlying NIH and identify neutrophil elastase as a potential therapeutic target for vascular disease.

Colitis Linked to Endoplasmic Reticulum Stress Induces Trypsin Activity Affecting Epithelial Functions

BACKGROUND AND AIMS

Intestinal epithelial cells [IECs] from inflammatory bowel disease [IBD] patients exhibit an excessive induction of endoplasmic reticulum stress [ER stress] linked to altered intestinal barrier function and inflammation. Colonic tissues and the luminal content of IBD patients are also characterized by increased serine protease activity. The possible link between ER stress and serine protease activity in colitis-associated epithelial dysfunctions is unknown. We aimed to study the association between ER stress and serine protease activity in enterocytes and its impact on intestinal functions.

METHODS

The impact of ER stress induced by Thapsigargin on serine protease secretion was studied using either human intestinal cell lines or organoids. Moreover, treating human intestinal cells with protease-activated receptor antagonists allowed us to investigate ER stress-resulting molecular mechanisms that induce proteolytic activity and alter intestinal epithelial cell biology.

RESULTS

Colonic biopsies from IBD patients exhibited increased epithelial trypsin-like activity associated with elevated ER stress. Induction of ER stress in human intestinal epithelial cells displayed enhanced apical trypsin-like activity. ER stress-induced increased trypsin activity destabilized intestinal barrier function by increasing permeability and by controlling inflammatory mediators such as C-X-C chemokine ligand 8 [CXCL8]. The deleterious impact of ER stress-associated trypsin activity was specifically dependent on the activation of protease-activated receptors 2 and 4.

CONCLUSIONS

Excessive ER stress in IECs caused an increased release of trypsin activity that, in turn, altered intestinal barrier function, promoting the development of inflammatory process.

Innate Immune Cells and Hypertension: Neutrophils and Neutrophil Extracellular Traps (NETs)

Uncontrolled immune system activation amplifies end-organ injury in hypertension. Nonetheless, the exact mechanisms initiating this exacerbated inflammatory response, thereby contributing to further increases in blood pressure (BP), are still being revealed. While participation of lymphoid-derived immune cells has been well described in the hypertension literature, the mechanisms by which myeloid-derived innate immune cells contribute to T cell activation, and subsequent BP elevation, remains an active area of investigation. In this article, we critically analyze the literature to understand how monocytes, macrophages, dendritic cells, and polymorphonuclear leukocytes, including mast cells, eosinophils, basophils, and neutrophils, contribute to hypertension and hypertension-associated end-organ injury. The most abundant leukocytes, neutrophils, are indisputably increased in hypertension. However, it is unknown how (and why) they switch from critical first responders of the innate immune system, and homeostatic regulators of BP, to tissue-damaging, pro-hypertensive mediators. We propose that myeloperoxidase-derived pro-oxidants, neutrophil elastase, neutrophil extracellular traps (NETs), and interactions with other innate and adaptive immune cells are novel mechanisms that could contribute to the inflammatory cascade in hypertension. We further posit that the gut microbiota serves as a set point for neutropoiesis and their function. Finally, given that hypertension appears to be a key risk factor for morbidity and mortality in COVID-19 patients, we put forth evidence that neutrophils and NETs cause cardiovascular injury post-coronavirus infection, and thus may be proposed as an intriguing therapeutic target for high-risk individuals. © 2021 American Physiological Society. Compr Physiol 11:1575-1589, 2021.

Neutrophil elastase promotes macrophage cell adhesion and cytokine production through the integrin-Src kinases pathway

There are a number of respiratory diseases characterized by the presence of excess neutrophil elastase (NE) activity in tissues, including cystic fibrosis and chronic obstructive pulmonary disease (COPD). NE is considered a primary contributor to disease development, but the precise mechanism has yet to be fully determined. We hypothesized that NE alters the function of macrophages (Mɸ) which play a critical role in many physiological processes in healthy lungs. We demonstrate that monocyte-derived Mɸ exposed to NE releases active matrix metalloproteinases (MMPs), increase expression of pro-inflammatory cytokines TNFα, IL-1β, and IL-8, and reduce capacity to phagocytose bacteria. Changes in Mɸ function following NE treatment were accompanied by increased adhesion and cytoskeleton re-arrangement, indicating the possibility of integrin involvement. To support this observation, we demonstrate that NE induces phosphorylation of kinases from the Src kinase family, a hallmark of integrin signaling activation. Moreover, pretreatment of Mɸ with a specific Src kinase inhibitor, PP2 completely prevents NE-induced pro-inflammatory cytokine production. Taken together these findings indicate that NE participates in lung destruction not only through direct proteolytic degradation of matrix proteins, but also through activation of Mɸ inflammatory and proteolytic functions.

The Role of Neutrophils and Neutrophil Elastase in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a severe vasculopathy characterized by the presence of fibrotic lesions in the arterial wall and the loss of small distal pulmonary arteries. The vasculopathy is accompanied by perivascular inflammation and increased protease levels, with neutrophil elastase notably implicated in aberrant vascular remodeling. However, the source of elevated elastase levels in PAH remains unclear. A major source of neutrophil elastase is the neutrophil, an understudied cell population in PAH. The principal function of neutrophils is to destroy invading pathogens by means of phagocytosis and NET formation, but proteases, chemokines, and cytokines implicated in PAH can be released by and/or prime and activate neutrophils. This review focuses on the contribution of inflammation to the development and progression of the disease, highlighting studies implicating neutrophils, neutrophil elastase, and other neutrophil proteases in PAH. The roles of cytokines, chemokines, and neutrophil elastase in the disease are discussed and we describe new insight into the role neutrophils potentially play in the pathogenesis of PAH.

Membrane-Associated Proteinase 3 on Granulocytes and Acute Myeloid Leukemia Inhibits T Cell Proliferation

Proteinase 3 (P3), a serine protease expressed by myeloid cells, localized within azurophil granules, and also expressed on the cellular membrane of polymorphonuclear neutrophils (PMN), is the target of autoimmunity in granulomatosis with polyangiitis. PR1, an HLA-A2 restricted nonameric peptide derived from P3, has been targeted effectively in myeloid leukemia. We previously showed (Molldrem et al. 2003. JClinInvest 111: 639-647) that overexpression of P3 in chronic myeloid leukemia induces apoptosis of high-affinity PR1-specific T cells, leading to deletional tolerance and leukemia outgrowth. In this study, we investigated the effect of membrane P3 (mP3)-expressing PMN and acute myeloid leukemia (AML) blasts on the proliferation of CD4 and CD8 T cells in vitro. We demonstrate that mP3-expressing PMN significantly inhibits autologous healthy donor T cell proliferation but does not affect cytokine production in activated T cells and that this effect requires cell proximity and was abrogated by P3 blockade. This inhibition required P3 enzyme activity. However, suppression was not reversed by either the addition of catalase or the inhibition of arginase I. In addition to P3 blockade, anti-low density lipoprotein receptor-related protein 1 (LRP1) Ab also restored T cells' capacity to proliferate. Last, we show dose-dependent inhibition of T cell proliferation by mP3-expressing AML blasts. Together, our findings demonstrate a novel mechanism whereby PMN- and AML-associated mP3 inhibits T cell proliferation via direct LRP1 and mP3 interaction, and we identify P3 as a novel target to modulate immunity in myeloid leukemia and autoimmune disease.

Genetic and Pharmacologic Inhibition of the Neutrophil Elastase Inhibits Experimental Atherosclerosis

Background

To investigate whether neutrophil elastase (NE) plays a causal role in atherosclerosis, and the molecular mechanisms involved.

Methods and Results

NE genetic–deficient mice (Apolipoprotein E^−/−/NE^−/− mice), bone marrow transplantation, and a specific NE inhibitor (GW311616A) were employed in this study to establish the causal role of NE in atherosclerosis. Aortic expression of NE mRNA and plasma NE activity was significantly increased in high‐fat diet (HFD)–fed wild‐type (WT) (Apolipoprotein E^−/−) mice but, as expected, not in NE‐deficient mice. Selective NE knockout markedly reduced HFD‐induced atherosclerosis and significantly increased indicators of atherosclerotic plaque stability. While plasma lipid profiles were not affected by NE deficiency, decreased levels of circulating proinflammatory cytokines and inflammatory monocytes (Ly6C^hi/CD11b⁺) were observed in NE‐deficient mice fed with an HFD for 12 weeks as compared with WT. Bone marrow reconstitution of WT mice with NE^−/− bone marrow cells significantly reduced HFD‐induced atherosclerosis, while bone marrow reconstitution of NE^−/− mice with WT bone marrow cells restored the pathological features of atherosclerotic plaques induced by HFD in NE‐deficient mice. In line with these findings, pharmacological inhibition of NE in WT mice through oral administration of NE inhibitor GW311616A also significantly reduced atherosclerosis. Mechanistically, we demonstrated that NE promotes foam cell formation by increasing ATP‐binding cassette transporter ABCA1 protein degradation and inhibiting macrophage cholesterol efflux.

Conclusions

We outlined a pathogenic role for NE in foam cell formation and atherosclerosis development. Consequently, inhibition of NE may represent a potential therapeutic approach to treating cardiovascular disease.

Neutrophils in cancer

Neutrophils play an important role in cancer. This does not only relate to the well-established prognostic value of the presence of neutrophils, either in the blood or in tumor tissue, in the context of cancer progression or for the monitoring of therapy, but also to their active role in the progression of cancer. In the current review, we describe what is known in general about the role of neutrophils in cancer. What is emerging is a complex, rather heterogeneous picture with both pro- and anti-tumorigenic roles, which apparently differs with cancer type and disease stage. Furthermore, we will discuss the well-known role of neutrophils as myeloid-derived suppressor cells (MDSC), and also on the role of neutrophils as important effector cells during antibody therapy in cancer. It is clear that neutrophils contribute substantially to cancer progression in multiple ways, and this includes both direct effects on the cancer cells and indirect effect on the tumor microenvironment. While in many cases neutrophils have been shown to promote tumor progression, for instance by acting as MDSC, there are also protective effects, particularly when antibody immunotherapy is performed. A better understanding of the role of neutrophils is likely to provide opportunities for immunomodulation and for improving the treatment of cancer patients.

Meprin metalloproteases: Molecular regulation and function in inflammation and fibrosis

The zinc-endopeptidases meprin α and meprin β are extracellular proteases involved in connective tissue homeostasis, intestinal barrier function and immunological processes. Meprins are unique among other extracellular proteases with regard to cleavage specificity and structure. Meprin α and meprin β have a strong preference for negatively charged amino acids around the scissile bond, reflected by cleavage sites identified in procollagen I, the amyloid precursor protein (APP) and the interleukin-6 receptor (IL-6R). In this review we report on recent findings that summarize the complex molecular regulation of meprins, particular folding, activation and shedding. Dysregulation of meprin α and meprin β is often associated with pathological conditions such as neurodegeneration, inflammatory bowel disease and fibrosis. Based on mouse models and patient data we suggest meprins as possible key regulators in the onset and progression of fibrotic disorders, leading to severe diseases such as pulmonary hypertension. This article is part of a Special Issue entitled: Proteolysis as a Regulatory Event in Pathophysiology edited by Stefan Rose-John.

Trypsin differentially modulates the surface expression and function of channel catfish leukocyte immune-type receptors

Channel catfish (Ictalurus punctatus) leukocyte immune-type receptors (IpLITRs) are immunoregulatory proteins that control innate immune cellular responses. Previously, we demonstrated that two representative IpLITR forms, IpLITR 2.6b and IpLITR 1.1b, engage distinct components of the phagocytic machinery resulting in unique target capture and engulfment phenotypes. IpLITR-induced phagocytic mechanisms were also differentially susceptible to temperature and pharmacological inhibitors of canonical signaling mediators. In the present study, we examined the sensitivity of IpLITR-mediated phagocytosis to the endogenous serine-protease trypsin, a well-known mediator of immunoregulatory receptor functions. Trypsin selectively reduced IpLITR 1.1b cell surface expression and phagocytic activity in a dose-dependent manner. We also observed a significant alteration of the IpLITR 1.1b phagocytic phenotype post-trypsin exposure; whereas, the IpLITR 2.6b-mediated target engulfment phenotype was unchanged. Recovery experiments suggested that trypsin-induced inhibition of IpLITR 1.1b-dependent phagocytosis was reversible and that the re-establishment of phagocytic function was associated with a recovery of receptor surface expression. Cell-surface biotinylation and immunoprecipitation studies demonstrated that IpLITR 1.1b normally exists as a mature (∼70 kDa) protein on the cell surface. However, trypsin treatment reduced expression of the mature receptor and processed IpLITR 1.1b into an ∼60 kDa form. The trypsin-generated and putative immature IpLITR 1.1b form was not present on the cell surface; suggesting that the cleaved receptor may have been internalized, post-processing, by regulated endocytosis. Taken together, these results reveal a unique role for trypsin as a selective modulator of IpLITR-mediated phagocytosis and highlight a conserved role for serine proteases as potent immunomodulatory factors.

Protease inhibition as new therapeutic strategy for GI diseases

The GI tract is the most exposed organ to proteases, both in physiological and pathophysiological conditions. For digestive purposes, the lumen of the upper GI tract contains large amounts of pancreatic proteases, but studies have also demonstrated increased proteolytic activity into mucosal tissues (both in the upper and lower GI tract), associated with pathological conditions. This review aims at outlining the evidences for dysregulated proteolytic homeostasis in GI diseases and the pathogenic mechanisms of increased proteolytic activity. The therapeutic potential of protease inhibition in GI diseases is discussed, with a particular focus on IBDs, functional GI disorders and colorectal cancer.

Meprin metalloproteases inactivate interleukin 6

Meprins have been implicated in the pathogenesis of several inflammatory diseases, including inflammatory bowel disease, in which the cytokine IL-6 is a prominent effector molecule. Because IL-6 levels are elevated markedly in meprin α and α/β knockout mice in an experimental model of inflammatory bowel disease, the interaction between meprins and IL-6 was studied. The results demonstrate that rodent and human meprin A and B cleave IL-6 to a smaller product and, subsequently, are capable of extensive degradation of the cytokine. Analysis of the limited degradation product formed by meprin A indicated that three to five amino acids are removed from the C terminus of the cytokine. Meprin A and meprin B cleaved IL-6 with micromolar affinities (Km of 4.7 and 12.0 μM, respectively) and with high efficiencies (kcat/Km of 0.2 and 2.5 (M(-1)/s(-1)) × 10(6), respectively). These efficiency constants are among the highest for known meprin substrates. Madin-Darby canine kidney cells transiently transfected with meprin α or meprin β constructs also cleave exogenous IL-6. Both human and murine IL-6 cleaved by meprin A or B are inactivated, as demonstrated by their decreased capability to stimulate proliferation of B9 cells. These results are consistent with the proposition that one function of meprin metalloproteases is to modulate inflammation by inactivating IL-6.

Role of Proteases in Inflammatory Lung Diseases

Proteases are enzymes that have the capacity to hydrolyze peptide bonds and degrade other proteins. Proteases can promote inflammation by regulating expression and activity of different pro-inflammatory cytokines, chemokines and other immune components in the lung compartment. They are categorized in three major subcategories: serine proteases, metalloproteases and cysteine proteases especially in case of lung diseases. Neutrophil-derived serine proteases (NSPs), metalloproteases and some mast cell-derived proteases are mainly focused here. Their modes of actions are different in different diseases for e.g. NE induces the release of IL-8 from lung epithelial cells through a MyD88/IRAK/TRAF-6-dependent pathway and also through EGFR MAPK pathway. NSPs contribute to immune regulation during inflammation through the cleavage and activation of specific cellular receptors. MMPs can also influence the progression of various inflammatory processes and there are many non-matrix substrates for MMPs, such as chemokines, growth factors and receptors. During lung inflammation interplay between NE and MMP is an important significant phenomenon. They have been evaluated as therapeutic targets in several inflammatory lung diseases. Here we review the role of proteases in various lung inflammatory diseases with emphasis on their mode of action and contribution to immune regulation during inflammation.

Inactivation of IL-6 and soluble IL-6 receptor by neutrophil derived serine proteases in cystic fibrosis

The ability of IL-6 to signal via both membrane bound and soluble receptors is thought to explain the capacity of this cytokine to act in both the initiation and resolution of acute inflammatory responses. In cystic fibrosis (CF), poorly resolved neutrophillic inflammation of the lungs is a primary cause of morbidity and mortality. Expression of IL-6 has been reported to be low in CF lung secretions, despite ongoing inflammation, but the status of soluble IL-6 receptor (sIL-6R) in these patients is unknown. We hypothesised that sIL-6R may be an important potentiator of IL-6 activity in CF associated lung disease. IL-6, sIL-6R and sgp130 (a natural antagonist of responses mediated by the sIL-6R) were analysed by ELISA and Western blot in bronchoalveolar lavage fluid (BALF) from 28 paediatric CF patients and nine non-CF controls. Total cell counts in CF were four fold higher compared to controls (median: 1.4 x 10(6) cells/ml v. 0.35 x 10(6) cells/ml in controls) (p<0.001) and the infiltrate was dominated by neutrophils which were elevated by 89 fold (0.62 x 10(6) cells/ml v. 0.007 x 10(6) cells/ml in controls) (p<0.001). Other markers of inflammation such as IL-8 and MCP-1 were elevated 17.5 and 3.8 fold respectively (IL-8; median: 1122 pg/ml v. 64 pg/ml in controls, p<0.01 and MCP-1; median: 692 pg/ml v. 182 pg/ml in controls, p<0.05). IL-6, although present in 23/32 CF BALF specimens compared to 1/9 controls (p<0.01), was weakly expressed (median: 50 pg/ml). Expression of sIL-6R and sgp130 in CF was no different to control patients. We tested whether weak expression of all three molecules was due to degradation by CF BALF. Degradative activity was observed in association with BALF elastase activity and could be specifically blocked by serine protease inhibitors. Degradation of sIL-6R by purified serine proteases (elastase, cathepsin G and proteinase 3) was also observed leading to a loss of trans-signalling activity. Interestingly, sIL-6R was protected from proteolysis by interaction with IL-6. Our data identify and define a novel protease mediated deficiency of IL-6 signalling in the CF lung.

Diverse regulatory roles for lysosomal proteases in the immune response

The innate and adaptive immune system utilise endocytic protease activity to promote functional immune responses. Cysteine and aspartic proteases (cathepsins) constitute a subset of endocytic proteases, the immune function of which has been described extensively. Although historically these studies have focused on their role in processes such as antigen presentation and zymogen processing within the endocytic compartment, recent discoveries have demonstrated a critical role for these proteases in other intracellular compartments, and within the extracellular milieu. It has also become clear that their pattern of expression and substrate specificities are more diverse than was first envisaged. Here, we discuss recent advances addressing the role of lysosomal proteases in various aspects of the immune response. We pay attention to reports demonstrating cathepsin activity outside of its canonical endosome/lysosome microenvironment.

Activated protein C attenuates leukocyte elastase-induced lung injury in mice

Leukocyte elastase (LE), a neutrophil serine protease, is known to cause alveolar wall destruction and alveolar hemorrhage in the lung, but recent evidence suggests that it may also produce a significant inflammatory response. The purpose of the current study was to (1) examine the relationship between LE-induced lung injury and specific markers of inflammation and cytokine/chemokine, and to (2) determine the potential of activated protein C (APC), a potent immunomodulator, to block the inflammatory response to LE. We treated the C57BL/6 mice with LE (10 U/kg, i.t.) and assessed the lung inflammation over 72 h. Total cells, total protein, and neutrophils were increased and peaked at 16 h in bronchial alveolar lavage fluid. Macrophages were also increased and peaked at 24 h. Administration of LE up-regulated the synthesis of proinflammatory cytokines, IL-1beta and IL-6, chemokines, keratinocyte-derived chemokine, and macrophage inflammatory protein 2 in bronchial alveolar lavage fluid, and their peaks were at 6 h. Furthermore, the mice were treated with APC at 0.2, 2.0, and 10 mg/kg (i.v.) after instillation of LE. Therapeutic treatment of APC at 2.0 and 10 mg/kg significantly attenuated the increases in all these parameters. Lung histology revealed that, in addition to inflammation, alveolar hemorrhage and alveolar wall destruction induced by LE were also attenuated by APC. Finally, the expression of tissue plasminogen activator and plasminogen activator inhibitor in whole lung of mice exposed to LE, detected by means of reverse-transcriptase-polymerase chain reaction, were not influenced by the treatment with APC. These data demonstrate that intratracheal administration of LE to mice causes a transient inflammatory response, and APC can play a protective role against LE-induced lung injury.

Targeting neutrophil elastase in cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is a lethal hereditary disease characterised by neutrophil-dominated lung inflammation. These abundant neutrophils produce neutrophil elastase (NE), a destructive serine protease that has direct actions on extracellular matrix proteins and has a role in the host response to inflammation and infection.

OBJECTIVE

This review examines the prospect of developing novel therapies for CF by targeting NE. The authors explore the functions of NE and of naturally-occurring and synthetic NE inhibitors.

METHODS

A literature search was conducted exploring the functions of NE and inhibitors of NE; naturally occurring and synthetic.

CONCLUSIONS

Targeting NE in CF offers therapeutic potential, but optimal inhibitors that can be delivered safely and effectively to the lung are still under development.

4-Hydroxy-2-nonenal-modified glyceraldehyde-3-phosphate dehydrogenase is degraded by cathepsin G

Degradation of oxidized or oxidatively modified proteins is an essential part of the antioxidant defenses of cells. 4-Hydroxy-2-nonenal (HNE), a major reactive aldehyde formed by lipid peroxidation, causes many types of cellular damage. It has been reported that HNE-modified proteins are degraded by the ubiquitin-proteasome pathway or, in some cases, by the lysosomal pathway. However, our previous studies using U937 cells showed that HNE-modified glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is degraded by an enzyme that is sensitive to a serine protease inhibitor, diisopropyl fluorophosphate (DFP), but not a proteasome inhibitor, MG-132, and that its degradation is not catalyzed in the acidic pH range where lysosomal enzymes are active. In the present study, we purified an HNE-modified GAPDH-degrading enzyme from a U937 cell extract to a final active fraction containing two proteins of 28 kDa (P28) and 27 kDa (P27) that became labeled with [(3)H]DFP. Using peptide mass fingerprinting and a specific antibody, P28 and P27 were both identified as cathepsin G. The degradation activity was inhibited by cathepsin G inhibitors. Furthermore, a cell extract from U937 cells transfected with a cathepsin G-specific siRNA hardly degraded HNE-modified GAPDH. These results suggest that cathepsin G plays a role in the degradation of HNE-modified GAPDH.

Angiogenic activity of bFGF and VEGF suppressed by proteolytic cleavage by neutrophil elastase

Neutrophil elastase (NE), a serine protease released from the azurophil granules of activated neutrophil, proteolytically cleaves multiple cytokines, and cell surface proteins. In the present study, we examined whether NE affects the biological abilities of angiogenic growth factors such as basic-fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF). NE degraded bFGF and VEGF in a time- and concentration-dependent manner, and these degradations were suppressed by sivelestat, a synthetic inhibitor of NE. The bFGF- or VEGF-mediated proliferative activity of human umbilical vein endothelial cells was inhibited by NE, and the activity was recovered by sivelestat. Furthermore, NE reduced the bFGF- or VEGF-induced tubulogenic response of the mice aortas, ex vivo angiogenesis assay, and these effects were also recovered by sivelestat. Neutrophil-derived NE degraded potent angiogenic factors, resulting in loss of their angiogenic activity. These findings provide additional insight into the role played by neutrophils in the angiogenesis process at sites of inflammation.

The role of T helper 17 (Th17) and regulatory T cells (Treg) in human organ transplantation and autoimmune disease

Uncommitted (naive) murine CD4+ T helper cells (Thp) can be induced to differentiate towards T helper 1 (Th1), Th2, Th17 and regulatory (Treg) phenotypes according to the local cytokine milieu. This can be demonstrated most readily both in vitro and in vivo in murine CD4+ T cells. The presence of interleukin (IL)-12 [signalling through signal transduction and activator of transcription (STAT)-4] skews towards Th1, IL-4 (signalling through STAT-6) towards Th2, transforming growth factor (TGF)-beta towards Treg and IL-6 and TGF-beta towards Th17. The committed cells are characterized by expression of specific transcription factors, T-bet for Th1, GATA-3 for Th2, forkhead box P3 (FoxP3) for Tregs and RORgammat for Th17 cells. Recently, it has been demonstrated that the skewing of murine Thp towards Th17 and Treg is mutually exclusive. Although human Thp can also be skewed towards Th1 and Th2 phenotypes there is as yet no direct evidence for the existence of discrete Th17 cells in humans nor of mutually antagonistic development of Th17 cells and Tregs. There is considerable evidence, however, both in humans and in mice for the importance of interferon (IFN)-gamma and IL-17 in the development and progression of inflammatory and autoimmune diseases (AD). Unexpectedly, some models of autoimmunity thought traditionally to be solely Th1-dependent have been demonstrated subsequently to have a non-redundant requirement for Th17 cells, notably experimental allergic encephalomyelitis and collagen-induced arthritis. In contrast, Tregs have anti-inflammatory properties and can cause quiescence of autoimmune diseases and prolongation of transplant function. As a result, it can be proposed that skewing of responses towards Th17 or Th1 and away from Treg may be responsible for the development and/or progression of AD or acute transplant rejection in humans. Blocking critical cytokines in vivo, notably IL-6, may result in a shift from a Th17 towards a regulatory phenotype and induce quiescence of AD or prevent transplant rejection. In this paper we review Th17/IL-17 and Treg biology and expand on this hypothesis.

Neutrophil serine proteases: specific regulators of inflammation

Neutrophils are essential for host defence against invading pathogens. They engulf and degrade microorganisms using an array of weapons that include reactive oxygen species, antimicrobial peptides, and proteases such as cathepsin G, neutrophil elastase and proteinase 3. As discussed in this Review, the generation of mice deficient in these proteases has established a role for these enzymes as intracellular microbicidal agents. However, I focus mainly on emerging data indicating that, after release, these proteases also contribute to the extracellular killing of microorganisms, and regulate non-infectious inflammatory processes by activating specific receptors and modulating the levels of cytokines.

Heparin cofactor II-thrombin complex in MPS I: a biomarker of MPS disease

The mucopolysaccharidoses are a clinically heterogeneous group of lysosomal storage disorders presenting with broad multi-system disease and a continuous range of phenotypes. Currently, there are no objective biomarkers of MPS disease that clearly reflect disease severity or therapeutic responsiveness. Using proteomic studies in the murine MPS I model, we have identified the formation of the heparin cofactor II-thrombin (HCII-T) complex, a well-known serine protease inhibitor (serpin)-serine protease complex, as an informative biomarker for MPS I. MPS I patients showed a range of serum HCII-T concentrations from 46,000-208,600 pM, whereas the control values varied from 115.1-398.0 pM. HCII-T complex was also elevated in plasma from MPS I patients and mice. The degree of HCII-T complex formation appears to correlate with disease severity and is responsive to therapy. In addition to its role as a biomarker, the discovery of increased serpin-serine protease complex formation provides a valuable insight into possible pathophysiological mechanisms of MPS disease.

Quantum proteolytic activation of chemokine CCL15 by neutrophil granulocytes modulates mononuclear cell adhesiveness

Monocyte infiltration into inflammatory sites is generally preceded by neutrophils. We show here that neutrophils may support this process by activation of CCL15, a human chemokine circulating in blood plasma. Neutrophils were found to release CCL15 proteolytic activity in the course of hemofiltration of blood from renal insufficiency patients. Processing of CCL15 immunoreactivity (IR) in the pericellular space is suggested by a lack of proteolytic activity in blood and blood filtrate, but a shift of the retention time (t(R)) of CCL15-IR, detected by chromatographic separation of CCL15-IR in blood and hemofiltrate. CCL15 molecules with N-terminal deletions of 23 (delta23) and 26 (delta26) aa were identified as main proteolytic products in hemofiltrate. Neutrophil cathepsin G was identified as the principal protease to produce delta23 and delta26 CCL15. Also, elastase displays CCL15 proteolytic activity and produces a delta21 isoform. Compared with full-length CCL15, delta23 and delta26 isoforms displayed a significantly increased potency to induce calcium fluxes and chemotactic activity on monocytes and to induce adhesiveness of mononuclear cells to fibronectin. Thus, our findings indicate that activation of monocytes by neutrophils is at least in part induced by quantum proteolytic processing of circulating or endothelium-bound CCL15 by neutrophil cathepsin G.

Methionine sulfoxide and proteolytic cleavage contribute to the inactivation of cathepsin G by hypochlorous acid: an oxidative mechanism for regulation of serine proteinases by myeloperoxidase

Using myeloperoxidase and hydrogen peroxide, activated neutrophils produce high local concentrations of hypochlorous acid (HOCl). They also secrete cathepsin G, a serine protease implicated in cytokine release, receptor activation, and degradation of tissue proteins. Isolated cathepsin G was inactivated by HOCl but not by hydrogen peroxide in vitro. We found that activated neutrophils lost cathepsin G activity by a pathway requiring myeloperoxidase, suggesting that oxidants generated by myeloperoxidase might regulate cathepsin G activity in vivo. Tandem mass spectrometric analysis of oxidized cathepsin G revealed that loss of a peptide containing Asp108, which lies in the active site, associated quantitatively with loss of enzymatic activity. Catalytic domain peptides containing Asp108 were lost from the oxidized protein in concert with the conversion of Met110 to the sulfoxide. Release of this peptide was blocked by pretreating cathepsin G with phenylmethylsulfonyl fluoride, strongly implying that oxidation introduced proteolytic cleavage sites into cathepsin G. Model system studies demonstrated that methionine oxidation can direct the regiospecific proteolysis of peptides by cathepsin G. Thus, oxidation of Met110 may contribute to cathepsin G inactivation by at least two distinct mechanisms. One involves direct oxidation of the thioether residue adjacent to the aspartic acid in the catalytic domain. The other involves the generation of new sites that are susceptible to proteolysis by cathepsin G. These observations raise the possibility that oxidants derived from neutrophils restrain pericellular proteolysis by inactivating cathepsin G. They also suggest that methionine oxidation could render cathepsin G susceptible to autolytic cleavage. Myeloperoxidase may thus play a previously unsuspected role in regulating tissue injury by serine proteases during inflammation.

Neutrophil serine proteases: potential key regulators of cell signalling during inflammation

The serine proteases cathepsin G, human leucocyte elastase and proteinase 3 are major contents of neutrophils and are released at sites of inflammation. The common picture of their function was that they do not degrade extracellular proteins specifically. Recent studies provided evidence that these proteases are able to activate specifically pro-inflammatory cytokines and lead to the activation of different receptors. Neutrophil serine proteases might therefore be important regulators of inflammatory processes and are interesting targets for new therapeutic approaches against inflammatory disorders. This review summarizes the current knowledge on the regulation of cell signalling by neutrophil serine proteases.

Proteolysis of macrophage inflammatory protein-1alpha isoforms LD78beta and LD78alpha by neutrophil-derived serine proteases

Macrophage inflammatory protein-1alpha (MIP-1alpha) is a chemokine that leads to leukocyte recruitment and activation at sites of infection. Controlling chemokine activity at sites of infection is important, since excess accumulation of leukocytes may contribute to localized tissue damage. Neutrophil-derived serine proteases modulate the bioactivity of chemokine and cytokine networks through proteolytic cleavage. Because MIP-1alpha is temporally expressed with neutrophils at sites of infection, we examined proteolysis of MIP-1alpha in vitro by the neutrophil-derived serine proteases: cathepsin G, elastase, and proteinase 3. Recombinant human MIP-1alpha isoforms LD78beta and LD78alpha were expressed and purified, and the protease cleavage sites were analyzed by mass spectrometry and peptide sequencing. Chemotactic activities of parent and cleavage molecules were also compared. Both LD78beta and LD78alpha were cleaved by neutrophil lysates at Thr16-Ser17, Phe24-Ile25, Tyr28-Phe29, and Thr31-Ser32. This degradation was inhibited by serine protease inhibitors phenylmethylsulfonyl fluoride and 4-(2-aminoethyl)-benzenesulfonyl fluoride. Incubation of the substrates with individual proteases revealed that cathepsin G preferentially cleaved at Phe24-Ile25 and Tyr28-Phe29, whereas elastase and proteinase 3 cleaved at Thr16-Ser17 and Thr31-Ser32. Proteolysis of LD78beta resulted in loss of chemotactic activity. The role of these proteases in LD78beta and LD78alpha degradation was confirmed by incubation with neutrophil lysates from Papillon-Lefevre syndrome patients, demonstrating that the cell lysates containing inactivated serine proteases could not degrade LD78beta and LD78alpha. These findings suggest that severe periodontal tissue destruction in Papillon-Lefevre syndrome may be related to excess accumulation of LD78beta and LD78alpha and dysregulation of the microbial-induced inflammatory response in the periodontium.

Effects of elastase and cathepsin G on the levels of membrane and soluble TNFα

Neutrophil elastase (NE) and cathepsin G (CG), the proteolytic enzymes localized in azurophil granules of neutrophils (PMN), are involved in PMN responses to various stimuli. When released at sites of inflammation, they participate in the degradation of numerous proteins involved in the regulation of the immune response. In this study, we employed ADAM17(-/-) fibroblasts stably transfected with cDNA of human pro-tumor necrosis factor alpha (proTNFalpha) (ADAM17(-/-)TNF(+)) to investigate the effects of NE and CG on shedding and degradation of TNFalpha. Both NE and CG were found to diminish the level of membrane TNFalpha (mTNFalpha) as measured by flow cytometry. This process was accompanied by the accumulation of biologically active soluble TNFalpha (sTNFalpha) in the culture medium, as determined by an increase in both the cytotoxic activity of TNFalpha and its ability to serve as a co-stimulator in the induction of inducible nitric oxide synthase (iNOS). However, in contrast to CG, NE at high concentrations was able to degrade sTNFalpha released from the cell surface. Using soluble recombinant human TNFalpha, we identified Val(93)-Ala(94) and Val(117)-Glu(118) as the NE cleavage sites within the sTNFalpha molecule. Taken together, the ability of NE and CG to modulate levels of membrane and soluble forms of TNFalpha may contribute to the proinflammatory activity of neutrophils.

Human serum inactivates non-glycosylated but not glycosylated granulocyte colony stimulating factor by a protease dependent mechanism: significance of carbohydrates on the glycosylated molecule

It has previously been reported that the biological activity of the human hematopoetic cytokine granulocyte colony stimulating factor (G-CSF) was reduced following incubation with human serum. The mechanism of action of serum has remained elusive although a number of possible mechanisms have been suggested including inactivation due to binding to the serum protein alpha(2)-macroglobulin (alpha(2)M) and degradation by serum proteases. The aim of this study was to clarify the conditions required by serum to reduce the biological activity of the cytokine and to define the mechanism involved. It has also been noted that G-CSF obtained from a CHO expression system (and therefore considered a glycosylated molecule) was resistant to serum inactivation unlike G-CSF obtained from an E. coli expression system (considered to be non-glycosylated). We used an enzymatic approach to remove the carbohydrate residues from glycosylated G-CSF and tested this material for its stability in serum. We additionally used a mutated G-CSF lacking glycosylation sites. We concluded that glycosylation was important in protecting against serum inactivation. We observed that serum reduced the biological activity of non-glycosylated G-CSF in a dose, and temperature dependent manner and deduced that the mechanism of action was dependent upon alpha(2)M bound serum protease enzymes.

Role of soluble gp130 in the tumour necrosis factor-alpha expression and its production by peripheral blood mononuclear cells

BACKGROUND

In our previous study we found that rhsIL-6R, along with recombinant human interleukin-6, plays a regulatory role in the immune response by modulating the tumour necrosis factor-alpha(TNF-alpha) expression and its production by peripheral blood mononuclear cells (PBMC). We also suggested that sIL-6R with IL-6 secreted by human PMN (neutrophils) influenced the TNF-alpha expression and its production by autologous PBMC.

AIMS

Since soluble gp130 (sgp130) is a natural inhibitor for sIL-6R/interleukin-6 responses, in the present study we estimated an effect of exogenous recombinant human sgp130 and sgp130 secreted by PMN on the TNF-alpha expression and its production by PBMC.

METHODS

Cells were isolated from whole blood of healthy persons. The PMN were cultured in 96-well plates for 1 h at 37 degrees C in a humidified incubator with 5% CO2. After the incubation, the culture supernatant of PMN was removed and added to the PBMC. PBMC were incubated for 1 h at 37 degrees C in the same conditions. Cytoplasmic protein fractions of PMN and, for comparative purpose of PBMC, were analysed for presence of sgp130 by western blotting with the use of monoclonal antibody capable of detecting this protein. In the culture supernatants of PMN we examined the concentrations of sgp130 by human enzyme-linked immunosorbent assay. TNF-alpha was measured at the protein levels as well as the mRNA levels.

RESULTS AND CONCLUSIONS

The present results revealed that exogenous recombinant human sgp130modulates the TNF-alpha expression and production by PBMC. In contrast, we did not find any effect of sgp130 secreted by PMN on the TNF-alpha expression and its production by autologous PBMC.

The significance of carbohydrates on G-CSF: differential sensitivity of G-CSFs to human neutrophil elastase degradation

It has been reported recently that granulocyte-colony stimulating factor (G-CSF) is degraded upon exposure to human neutrophil elastase (HNE), and this has a negative effect on the ability of the cytokine to promote the in vitro proliferation and maturation of CD34+ cells. This has important implications on the possible in vivo role of elastase in providing negative feedback to granulopoiesis by the direct antagonism of G-CSF. The cytokine used in that study was expressed in Escherichia coli [and was nonglycosylated (NG)], unlike the naturally occurring cytokine, which is an O-linked glycoprotein. As a Chinese hamster ovary-derived (glycosylated) cytokine is available, we compared the susceptibility of NG and glycosylated G-CSF to elastase degradation by incubating the cytokines with HNE and assessing its impact by sodium dodecyl sulfate gel electrophoresis and bioassay. We confirmed the ability of elastase to degrade NG G-CSF in a time- and concentration-dependent manner and found this was associated with a reduction in biological activity of the cytokine. Glycosylated G-CSF, however, was more resistant to elastase degradation, although prolonged exposure did lead to degradation and decreased biological activity. The significance of sugar residues on glycosylated G-CSF in providing protection against the effects of elastase was investigated using enzymatically deglycosylated G-CSF and a mutated form of the G-CSF molecule that was expressed in yeast but was NG. The possible role of HNE in serum-induced inactivation of NG G-CSF was also considered.

Principles of interleukin (IL)-6-type cytokine signalling and its regulation

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed.

Principles of interleukin (IL)-6-type cytokine signalling and its regulation

The IL (interleukin)-6-type cytokines IL-6, IL-11, LIF (leukaemia inhibitory factor), OSM (oncostatin M), ciliary neurotrophic factor, cardiotrophin-1 and cardiotrophin-like cytokine are an important family of mediators involved in the regulation of the acute-phase response to injury and infection. Besides their functions in inflammation and the immune response, these cytokines play also a crucial role in haematopoiesis, liver and neuronal regeneration, embryonal development and fertility. Dysregulation of IL-6-type cytokine signalling contributes to the onset and maintenance of several diseases, such as rheumatoid arthritis, inflammatory bowel disease, osteoporosis, multiple sclerosis and various types of cancer (e.g. multiple myeloma and prostate cancer). IL-6-type cytokines exert their action via the signal transducers gp (glycoprotein) 130, LIF receptor and OSM receptor leading to the activation of the JAK/STAT (Janus kinase/signal transducer and activator of transcription) and MAPK (mitogen-activated protein kinase) cascades. This review focuses on recent progress in the understanding of the molecular mechanisms of IL-6-type cytokine signal transduction. Emphasis is put on the termination and modulation of the JAK/STAT signalling pathway mediated by tyrosine phosphatases, the SOCS (suppressor of cytokine signalling) feedback inhibitors and PIAS (protein inhibitor of activated STAT) proteins. Also the cross-talk between the JAK/STAT pathway with other signalling cascades is discussed.

Structure of homo- and hetero-oligomeric meprin metalloproteases. Dimers, tetramers, and high molecular mass multimers

Meprin A and B, metalloproteases consisting of evolutionarily related alpha and/or beta subunits, are membrane-bound and secreted enzymes expressed by kidney and intestinal epithelial cells, leukocytes, and cancer cells. Previous work established that the multidomain meprin subunits (each approximately 80 kDa) form disulfide-bridged homo- and heterodimers, and differ in substrate and peptide bond specificities. The work herein clearly demonstrates that meprin dimers differ markedly in their ability to oligomerize. Electrophoresis, light scattering, size exclusion chromatography, and electron microscopy were used to characterize quaternary structures of recombinant rat meprins. Meprin B, consisting of meprin beta subunits only, was dimeric under a wide range of conditions. By contrast, meprin alpha homodimers formed heterogeneous multimers (ring-, circle-, spiral-, and tube-like structures) containing up to 100 subunits, with molecular masses at protein peaks ranging from approximately 1.0 to 6.0 MDa. The size of the meprin alpha homo-oligomers was dependent on protein concentration, ionic strength, and activation state. Meprin alphabeta heterodimers tended to form tetramers but not higher oligomers. Thus, the presence of meprin beta, which has a transmembrane domain in vivo, restricts the oligomerization potential of meprin molecules and localizes meprins to the plasma membrane. By contrast, the propensity of secreted meprin alpha homodimers to self-associate concentrates proteolytic potential into high molecular mass multimers and thus allows for autocompartmentalization. The work indicates that different mechanisms exist to localize and concentrate the proteolytic activity of membrane-bound and secreted meprin metalloproteinases.

The role of neutrophil elastase in acute lung injury

Beside its physiological function as a powerful host defense, neutrophil elastase is also known as one of the most destructive enzymes in the body. Current notion holds that neutrophil elastase is able to escape from regulation by multiple protease inhibitors at inflammatory sites. Once unregulated, this enzyme disturbs the function of the lung permeability barrier and induces the release of pro-inflammatory cytokines. These actions then cause symptoms that are typical in the pathophysiology of acute lung injury. In this article, we review recent progress in the understanding of the physiological activity of neutrophil elastase and its role in acute lung injury. Evidence in this review that supports the involvement of neutrophil elastase in the pathophysiology of acute lung injury includes: (1) neutrophil elastase levels are increased in both clinical and animal models of acute lung injury; (2) topical or systemic administration of neutrophil elastase produces typical symptoms of acute lung injury both in vitro and in vivo; and (3) inhibition of increased neutrophil elastase activity reduces symptoms of acute lung injury in animal models. A greater understanding of the role of this enzyme in the pathophysiology of acute lung injury will lead to better treatments for this complicated disease.

Proteinase-3, a serine protease which mediates doxorubicin-induced apoptosis in the HL-60 leukemia cell line, is downregulated in its doxorubicin-resistant variant

We report here that expression of proteinase 3 (PR3), a serine protease, is down-regulated in the HL60/ADR multidrug resistant variant of the human myelogenous leukemia cell line HL-60, and that down-regulation of PR3 is associated with doxorubicin (DOX) resistance in these cells. To determine whether PR3 is involved in DOX-induced apoptosis in HL-60 cells, and whether its loss causes resistance to DOX, we inhibited PR3 expression by an anti-sense PR3 oligodeoxynucleotide and showed that inhibition of PR3 expression results in a significant reduction in DOX-induced DNA fragmentation and increased resistance to DOX-induced apoptosis. Our results revealed that PR3-mediated DOX-induced apoptosis in HL-60 cells is independent of the loss of mitochondrial membrane potential (deltapsi(m)) and activation of the caspase-8 and -9 pathways. Moreover, while PR3 is involved in the cleavage of caspase-3, PR3-mediated DOX-induced DNA fragmentation and apoptosis were not prevented by a specific inhibitor of caspase-3. These data suggest that activation of caspase-3 alone is not sufficient to trigger PR3-mediated DOX-induced apoptosis. Treatment with an anti-PR3 oligomer significantly decreased reactive oxygen species (ROS) generation in cells treated with low concentrations of DOX, revealing a role for PR3 in enhancing production of DOX-induced ROS. Moreover, DOX-induced apoptosis at 0.001-0.01 microM was only inhibited in HL-60 cells pre-treated with the antioxidant N-acetyl-cysteine in the absence of anti-PR3, revealing that DOX-induced apoptosis in these cells is PR3- and ROS-dependent. Our results show that PR3 is involved in DOX-induced ROS-dependent apoptosis and that its loss is associated with resistance to DOX in HL-60 cells.

Induction of anaphylatoxin C5a receptors in rat hepatocytes by lipopolysaccharide in vivo: mediation by interleukin-6 from Kupffer cells

BACKGROUND & AIMS

In normal rat liver, anaphylatoxin C5a induces glucose output from hepatocytes indirectly via prostanoids released from Kupffer cells. Correspondingly, it was found that hepatocytes, in contrast to Kupffer cells, did not express C5a receptors. Lipopolysaccharide (LPS) has been reported to enhance C5a receptor expression in murine livers. This might be the result of de novo expression in hepatocytes.

METHODS

C5a receptor expression was investigated in hepatocytes after in vivo treatment of rats with LPS and in vitro stimulation of isolated cells with LPS and proinflammatory cytokines on messenger RNA (mRNA) and protein level, and functionally in isolated hepatocytes and perfused liver.

RESULTS

In vivo treatment of rats with LPS induced C5a receptor mRNA and protein in hepatocytes with a maximum after 8-10 hours. At this time-point, C5a directly activated glycogen phosphorylase in isolated hepatocytes and enhanced glucose output in perfused livers without the involvement of prostanoids. LPS failed to induce C5a receptors in cultured hepatocytes in vitro, whereas interleukin (IL) 6 and IL-1beta, which are known to be released from Kupffer cells on stimulation with LPS, did so. In cocultures of hepatocytes with Kupffer cells, LPS induced C5a receptors in hepatocytes in an IL-6-dependent manner.

CONCLUSIONS

Thus, IL-6 from Kupffer cells appears to be the main mediator of LPS-induced de novo expression of C5a receptors in hepatocytes.

Association of alpha(1)-antichymotrypsin deficiency with milder lung disease in patients with cystic fibrosis

BACKGROUND

Cystic fibrosis (CF) is characterised by an excess of free proteinases that destroy lung tissue. Despite this, previous studies have shown that patients with CF with a mild deficiency variant of the proteinase inhibitor alpha(1)-antitrypsin have less, rather than more, severe pulmonary disease. Alpha(1)-antichymotrypsin is another important serine proteinase inhibitor that protects the lung against proteolytic attack, and point mutations in the alpha(1)-antichymotrypsin gene that result in plasma deficiency are associated with chronic obstructive pulmonary disease.

METHODS

The effect of alpha(1)-antichymotrypsin deficiency and the -15 alpha(1)-antichymotrypsin signal peptide genotype on lung function was assessed in patients with CF.

RESULTS

One hundred and fifty seven patients with CF were screened and 10 were identified with a plasma deficiency of alpha(1)-antichymotrypsin (plasma concentration <0.2 g/l). In a multivariate analysis these individuals had significantly less severe lung disease than those who had normal or raised levels of alpha(1)-antichymotrypsin: forced expiratory volume in one second (FEV(1)) 69.9% predicted versus 53. 2% predicted (p=0.04) and chest radiographic score of 7.2 versus 9.7 (p=0.03) for those with and without alpha(1)-antichymotrypsin deficiency, respectively. The -15 signal peptide genotype did not affect plasma levels, but the -15 Ala/Ala signal peptide genotype was over-represented in individuals with CF compared with healthy blood donor controls.

CONCLUSION

These data indicate that deficiency of alpha(1)-antichymotrypsin is associated with less severe pulmonary disease in patients with CF, and support our previous observations that mild genetic deficiency of a proteinase inhibitor is associated with an improved outcome.