Mast cell tissue inhibitor of metalloproteinase-1 is cleaved and inactivated extracellularly by alpha-chymase

The mast cell: A Janus in kidney transplants

Mast cells (MCs) are innate immune cells with a versatile set of functionalities, enabling them to orchestrate immune responses in various ways. Aside from their known role in allergy, they also partake in both allograft tolerance and rejection through interaction with regulatory T cells, effector T cells, B cells and degranulation of cytokines and other mediators. MC mediators have both pro- and anti-inflammatory actions, but overall lean towards pro-fibrotic pathways. Paradoxically, they are also seen as having potential protective effects in tissue remodeling post-injury. This manuscript elaborates on current knowledge of the functional diversity of mast cells in kidney transplants, combining theory and practice into a MC model stipulating both protective and harmful capabilities in the kidney transplant setting.

Cut loose TIMP-1: an emerging cytokine in inflammation

Appreciation of the entire biological impact of an individual protein can be hampered by its original naming based on one function only. Tissue inhibitor of metalloproteinases-1 (TIMP-1), mostly known for its eponymous function to inhibit metalloproteinases, exhibits only a fraction of its cellular effects via this feature. Recently, TIMP-1 emerged as a potent cytokine acting via various cell-surface receptors, explaining a so-far under-appreciated role of TIMP-1-mediated signaling on immune cells. This, at least partly, resolved why elevated blood levels of TIMP-1 correlate with progression of numerous inflammatory diseases. Here, we emphasize the necessity of unbiased name-independent recognition of structure-function relationships to properly appreciate the biological potential of TIMP-1 and other cytokines in complex physiological processes such as inflammation.

Mast Cell Chymase and Kidney Disease

A sizable part (~2%) of the human genome encodes for proteases. They are involved in many physiological processes, such as development, reproduction and inflammation, but also play a role in pathology. Mast cells (MC) contain a variety of MC specific proteases, the expression of which may differ between various MC subtypes. Amongst these proteases, chymase represents up to 25% of the total proteins in the MC and is released from cytoplasmic granules upon activation. Once secreted, it cleaves the targets in the local tissue environment, but may also act in lymph nodes infiltrated by MC, or systemically, when reaching the circulation during an inflammatory response. MC have been recognized as important components in the development of kidney disease. Based on this observation, MC chymase has gained interest following the discovery that it contributes to the angiotensin-converting enzyme’s independent generation of angiotensin II, an important inflammatory mediator in the development of kidney disease. Hence, progress regarding its role has been made based on studies using inhibitors but also on mice deficient in MC protease 4 (mMCP-4), the functional murine counterpart of human chymase. In this review, we discuss the role and actions of chymase in kidney disease. While initially believed to contribute to pathogenesis, the accumulated data favor a more subtle view, indicating that chymase may also have beneficial actions.

Mast cell chymase: morphofunctional characteristics

During degranulation, mast cells secrete a specific set of mediators defined as "secretome" including the preformed mediators that have already been synthesized by a cell and contained in the cytoplasmic granules. This group includes serine proteases, in particular, chymase and tryptase. Biological significance of chymase depends on the mechanisms of degranulation and is characterized by selective effects on the cellular and non-cellular components of the specific tissue microenvironment. Chymase is known to be closely involved in the mechanisms of inflammation and allergy, angiogenesis, and oncogenesis, remodeling of the extracellular matrix of the connective tissue and changes in organ histoarchitectonics. Number of chymase-positive mast cells in the intra-organ population, and the mechanisms of biogenesis and secretome degranulation appear to be the informative criteria for interpreting the state of the internal organs, characterizing not only the diagnostic efficacy but also the properties of targets of pharmacotherapy. In this review, we discussed the current state of knowledge about mast cell chymase as one of the mast cell secretome proteases. Main issues of the reviewed publications are highlighted with our microscopic images of mast cell chymase visualized using immunohistochemical staining.

Mast Cell Cytonemes as a Defense Mechanism against Coxiella burnetii

Mast cells (MCs) are found in tissues that are in close contact with external environment, such as skin, lungs, or intestinal mucosa but also in the placenta during pregnancy. If their role in mediating allergic conditions is established, several studies now highlight their importance during infection with extracellular pathogens. This study showed a new and effective antimicrobial mechanism of MCs against Coxiella burnetii, an intracellular bacterium whose infection during pregnancy is associated with abortion, preterm labor, and stillbirth. The data reveal that in response to C. burnetii, MCs release extracellular actin filaments that contain antimicrobial agents and are capable to trap and kill bacteria. We show that this mechanism is dependent on the cooperation of two membrane receptors, CD36 and Toll-like receptor 4, and may occur in the placenta during pregnancy by using ex vivo placental MCs. Overall, this study reports an unexpected role for MCs during infection with intracellular bacteria and suggests that MC response to C. burnetii infection is a protective defense mechanism during pregnancy.

Mast cells (MCs) are critical mediators of inflammation; however, their microbicidal activity against invading pathogens remains largely unknown. Here, we describe a nonpreviously reported antibacterial mechanism used by MCs against Coxiella burnetii, the agent of Q fever. We show that C. burnetii interaction with MCs does not result in bacterial uptake but rather induces the formation of extracellular actin filaments named cytonemes. MC cytonemes express cathelicidin and neutrophil elastase and mediate the capture and destruction of entrapped bacteria. We provide evidence that MC cytoneme formation and microbicidal activity are dependent on the cooperation of the scavenger receptor CD36 and Toll-like receptor 4. Taken together, our results suggest that MCs use an extracellular sophisticated mechanism of defense to eliminate intracellular pathogens, such as C. burnetii, before their entry into host cells.

Mouse mast cell protease 4 suppresses scar formation after traumatic spinal cord injury

Spinal cord injury (SCI) triggers the formation of a glial and fibrotic scar, which creates a major barrier for neuroregenerative processes. Previous findings indicate that mast cells (MCs) protect the spinal cord after mechanical damage by suppressing detrimental inflammatory processes via mouse mast cell protease 4 (mMCP4), a MC-specific chymase. In addition to these immunomodulatory properties, mMCP4 also plays an important role in tissue remodeling and extracellular matrix degradation. Therefore, we have investigated the effects of mMCP4 on the scarring response after SCI. We demonstrate that the decrease in locomotor performance in mMCP4^-/- mice is correlated with excessive scar formation at the lesion. The expression of axon-growth inhibitory chondroitin sulfate proteoglycans was dramatically increased in the perilesional area in mMCP4^-/- mice compared to wild type mice. Moreover, the fibronectin-, laminin-, and collagen IV-positive scar was significantly enlarged in mMCP4^-/- mice at the lesion center. A degradation assay revealed that mMCP4 directly cleaves collagen IV in vitro. On the gene expression level, neurocan and GFAP were significantly higher in the mMCP4^-/- group at day 2 and day 28 after injury respectively. In contrast, the expression of fibronectin and collagen IV was reduced in mMCP4^-/- mice compared to WT mice at day 7 after SCI. In conclusion, our data show that mMCP4 modulates scar development after SCI by altering the gene and protein expression patterns of key scar factors in vivo. Therefore, we suggest a new mechanism via which endogenous mMCP4 can improve recovery after SCI.

Japanese encephalitis virus neuropenetrance is driven by mast cell chymase

Japanese encephalitis virus (JEV) is a leading cause of viral encephalitis. However, the mechanisms of JEV penetration of the blood-brain-barrier (BBB) remain poorly understood. Mast cells (MCs) are granulated innate immune sentinels located perivascularly, including at the BBB. Here we show that JEV activates MCs, leading to the release of granule-associated proteases in vivo. MC-deficient mice display reduced BBB permeability during JEV infection compared to congenic wild-type (WT) mice, indicating that enhanced vascular leakage in the brain during JEV infection is MC-dependent. Moreover, MCs promoted increased JEV infection in the central nervous system (CNS), enhanced neurological deficits, and reduced survival in vivo. Mechanistically, chymase, a MC-specific protease, enhances JEV-induced breakdown of the BBB and cleavage of tight-junction proteins. Chymase inhibition reversed BBB leakage, reduced brain infection and neurological deficits during JEV infection, and prolonged survival, suggesting chymase is a novel therapeutic target to prevent JEV encephalitis.

How Japanese encephalitis virus (JEV) penetrates the blood-brain barrier (BBB) remains unclear. Here, using a genetic mouse model and a virulent JEV strain, the authors show that perivascular mast cells (MC) mediate JEV neuroinvasion and identify the MC-protease chymase as a potential therapeutic target.

Targeting mast cell as a neuroprotective strategy

Background: Mast cells (MCs) are perivascularly located immune cells of haematopoietic origin. Emerging evidences suggest that the activation of MCs play important roles in the pathogenesis of blood brain barrier disruption, neuroinflammation, and neurodegeneration. Objectives: In this review, we aimed to discuss the detrimental effects of MCs in response to various types of brain injury, as well as the therapeutic potential and neuroprotective effects of targeting the activation and degranulation of MCs, particularly in the management of the acute phase. Methods: An extensive online literature search was conducted through Pubmed/Central on March 2018. Then, we comprehensively summarized the effects of the activation of brain MCs in acute brain injury along with current pharmacological strategies targeting at the activation of MCs. Results: The review of the current literature indicated that the activation and degranulation of brain MCs significantly contribute to the acute pathological process following different types of brain injury including focal and global cerebral ischaemia, intracerebral haemorrhage, subarachnoid haemorrhage, and traumatic brain injury. Conclusions: Brain MCs significantly contribute to the acute pathological processes following brain injury. In that regard, targeting brain MCs may provide a novel strategy for neuroprotection.

The role of tryptase and anti-type II collagen antibodies in the pathogenesis of idiopathic epiretinal membranes

Purpose

To investigate the pathogenesis of idiopathic epiretinal membrane (ERM) from a biochemical perspective, the relationships between ERM and tryptase activity, a serine protease, and the levels of anti-type II collagen (anti-IIC) antibodies in the serum.

Patients and methods

Vitreous samples for measurement of tryptase activity were obtained from 54 eyes of 54 patients who underwent a vitrectomy for vitreoretinal disease, ie, 14 eyes of 14 patients with idiopathic macular hole, 14 eyes of 14 patients with proliferative diabetic retinopathy (PDR), 13 eyes of 13 patients with ERM, and 13 eyes of 13 patients with rhegmatogenous retinal detachment (RRD). Tryptase activity was measured by spectrophotometry. Anti-IIC antibodies were measured in the serum obtained from 17 patients with ERM, eight patients who underwent cataract surgery, 12 patients with PDR, and nine patients with RRD. In these 46 patients, the anti-IIC antibodies were measured using a Human/Monkey Anti-Type I and Type II Collagen IgG Assay Kit.

Results

Vitreal tryptase activity (mean ± standard deviation [SD]) in macular hole, PDR, ERM, and RRD was 0.0146±0.0053, 0.0018±0.0018, 0.0166±0.0046, and 0.0117±0.0029 mU/mg protein, respectively. Vitreal tryptase activity was significantly higher in macular hole and ERM than in PDR and RRD (P<0.05, Fisher’s protected least significant difference). The serum levels of anti-IIC immunoglobulin G (IgG) antibody (mean ± SD) in ERM, cataract surgery, PDR, and RRD were 58.222±30.986, 34.890±18.165, 55.760±26.008, and 35.453±12.769 units/mL, respectively. The serum levels of anti-IIC IgG antibody were significantly higher in ERM and PDR than in cataract surgery and RRD (P<0.05, Fisher’s protected least significant difference, two-sided).

Conclusion

In the pathogenesis of ERM, increased vitreal tryptase activity may be involved in tissue fibrosis, and elevated serum anti-IIC antibodies may lead to an immune response at the vitreoretinal interface, thus resulting in membrane formation.

The Role of Mast Cell Specific Chymases and Tryptases in Tumor Angiogenesis

An association between mast cells and tumor angiogenesis is known to exist, but the exact role that mast cells play in this process is still unclear. It is thought that the mediators released by mast cells are important in neovascularization. However, it is not known how individual mediators are involved in this process. The major constituents of mast cell secretory granules are the mast cell specific proteases chymase, tryptase, and carboxypeptidase A3. Several previous studies aimed to understand the way in which specific mast cell granule constituents act to induce tumor angiogenesis. A body of evidence indicates that mast cell proteases are the pivotal players in inducing tumor angiogenesis. In this review, the likely mechanisms by which tryptase and chymase can act directly or indirectly to induce tumor angiogenesis are discussed. Finally, information presented here in this review indicates that mast cell proteases significantly influence angiogenesis thus affecting tumor growth and progression. This also suggests that these proteases could serve as novel therapeutic targets for the treatment of various types of cancer.

Vitreous estrogen levels in patients with an idiopathic macular hole

Purpose

Estrogen, a female hormone, activates collagenase and might be associated with the pathogenesis of vitreoretinal collagen fiber disease. The purpose of the present study was to investigate the vitreous levels of estrone (E1) and estradiol (E2) in subjects with an idiopathic macular hole (IMH).

Methods

Vitreous samples were obtained from ten female patients with an IMH and from nine female patients with other retinal diseases (six with rhegmatogenous retinal detachment and three with age-related macular degeneration) as a control at the time of vitreous surgery. E1 and E2 levels in the vitreous samples were then determined using the Coat-A-Count^® Estradiol Radioimmunoassay (RIA) Kit and the DSL-70 Estrone RIA Kit, respectively.

Results

The mean vitreous levels of E1 and E2 in the subjects with IMH were 1.83±2.00 pg/mL and 7.03±2.97 pg/mL, respectively, whereas in the control subjects they were 2.42±1.25 pg/mL and 4.90±2.90 pg/mL, respectively. Thus, the vitreous E2 levels in the subjects with IMH were significantly higher than in the controls (P<0.05).

Conclusion

The findings of this study suggest that E2 might be associated with the pathogenesis of IMH, but further investigation is needed to elucidate that association.

Expression of recombinant human mast cell chymase with Asn-linked glycans in glycoengineered Pichia pastoris

Recombinant human mast cell chymase (rhChymase) was expressed in secreted form as an active enzyme in the SuperMan5 strain of GlycoSwitch® Pichia pastoris, which is engineered to produce proteins with (Man)5(GlcNAc)2 Asn-linked glycans. Cation exchange and heparin affinity chromatography yielded 5mg of active rhChymase per liter of fermentation medium. Purified rhChymase migrated on SDS-PAGE as a single band of 30 kDa and treatment with peptide N-glycosidase F decreased this to 25 kDa, consistent with the established properties of native human chymase (hChymase). Polyclonal antibodies against hChymase detected rhChymase by Western blot. Active site titration with Eglin C, a potent chymase inhibitor, quantified the concentration of purified active enzyme. Kinetic analyses with succinyl-Ala-Ala-Pro-Phe (suc-AAPF) p-nitroanilide and thiobenzyl ester synthetic substrates showed that heparin significantly reduced KM, whereas heparin effects on kcat were minor. Pure rhChymase with Asn-linked glycans closely resembles hChymase. This bioengineering approach avoided hyperglycosylation and provides a source of active rhChymase for other studies as well as a foundation for production of recombinant enzyme with human glycosylation patterns.

Analysis of genes causing hypertension and stroke in spontaneously hypertensive rats: gene expression profiles in the brain

Spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP) are frequently used as rat models not only of essential hypertension and stroke, but also of attention-deficit hyperactivity disorder (ADHD). Normotensive Wistar-Kyoto rats (WKY) are used as the control rats in these cases. An increasing number of studies has demonstrated the critical role of the central nervous system in the development and maintenance of hypertension. In a previous study, we analyzed the gene expression profiles in the adrenal glands of SHR. Thus, in this study, we analyzed gene expression profiles in the brains of SHR in order to identify the genes responsible for causing hypertension and stroke, as well as those involved in ADHD. Using genome-wide microarray technology, we examined the gene expression profiles in the brains of 3 rat strains (SHR, SHRSP and WKY) when the rats were 3 and 6 weeks of age, a period in which the rats are considered to be in a pre-hypertensive state. Gene expression profiles in the brain were compared between SHR and WKY, and between SHRSP and SHR. A total of 179 genes showing a >4- or <-4-fold change in expression were isolated, and candidate genes were selected using two different web tools: the first tool was the Database for Annotation, Visualization and Integrated Discovery (DAVID), which was used to search for significantly enriched genes, and categorized them using Gene Ontology (GO) terms, and the second was the network explorer of Ingenuity Pathway Analysis (IPA), which was used to search for interaction networks among SHR- and SHRSP-specific genes. The IPA of SHR-specific genes revealed that prostaglandin E receptor 4 (Ptger4) is one of the candidate genes responsible for causing hypertension in SHR, and that albumin (Alb) and chymase 1 (Cma1) are also responsible for causing hypertension in SHR in the presence of angiotensinogen (Agt). Similar analyses of SHRSP-specific genes revealed that the angiotensin II receptor-associated gene (Agtrap) interacts with the FBJ osteosarcoma oncogene (Fos), and with the angiotensin II receptor type-1b (Agtr1b). As Agtrap and Agtr1b not only participate in the 'uptake of norepinephrine' and 'blood pressure', but also in the 'behavior' of SHRSP at 6 weeks of age, our data demonstrate a close association between hypertension and ADHD.

The innate immune system in demyelinating disease

Demyelinating diseases such as multiple sclerosis are chronic inflammatory autoimmune diseases with a heterogeneous clinical presentation and course. Both the adaptive and the innate immune systems have been suggested to contribute to their pathogenesis and recovery. In this review, we discuss the role of the innate immune system in mediating demyelinating diseases. In particular, we provide an overview of the anti-inflammatory or pro-inflammatory functions of dendritic cells, mast cells, natural killer (NK) cells, NK-T cells, γδ T cells, microglial cells, and astrocytes. We emphasize the interaction of astroctyes with the immune system and how this interaction relates to the demyelinating pathologies. Given the pivotal role of the innate immune system, it is possible that targeting these cells may provide an effective therapeutic approach for demyelinating diseases.

Secretomic analysis identifies alpha-1 antitrypsin (A1AT) as a required protein in cancer cell migration, invasion, and pericellular fibronectin assembly for facilitating lung colonization of lung adenocarcinoma cells

Metastasis is a major obstacle that must be overcome for the successful treatment of lung cancer. Proteins secreted by cancer cells may facilitate the progression of metastasis, particularly within the phases of migration and invasion. To discover metastasis-promoting secretory proteins within cancer cells, we used the label-free quantitative proteomics approach and compared the secretomes from the lung adenocarcinoma cell lines CL1-0 and CL1-5, which exhibit low and high metastatic properties, respectively. By employing quantitative analyses, we identified 660 proteins, 68 of which were considered to be expressed at different levels between the two cell lines. High levels of A1AT were secreted by CL1-5, and the roles of A1AT in the influence of lung adenocarcinoma metastasis were investigated. Molecular and pathological confirmation demonstrated that altered expression of A1AT correlates with the metastatic potential of lung adenocarcinoma. The migration and invasion properties of CL1-5 cells were significantly diminished by reducing the expression and secretion of their A1AT proteins. Conversely, the migration and invasion properties of CL1-0 cells were significantly increased through the overexpression and secretion of A1AT proteins. Furthermore, the assembly levels of the metastasis-promoting pericellular fibronectin (FN1), which facilitates colonization of lung capillary endothelia by adhering to the cell surface receptor dipeptidyl peptidase IV (DPP IV), were higher on the surfaces of suspended CL1-5 cells than on those of the CL1-0 cells. This discovery reflects previous findings in breast cancer. In line with this finding, FN1 assembly and the lung colonization of suspended CL1-5 cells were inhibited when endogenous A1AT protein was knocked down using siRNA. The major thrust of this study is to demonstrate the effects of coupling the label-free proteomics strategy with the secretomes of cancer cells that differentially exhibit invasive and metastatic properties. This provides a new opportunity for the effective identification of metastasis-associated proteins that are secreted by cancer cells and promote experimental metastasis.

Cerebral mast cells mediate blood-brain barrier disruption in acute experimental ischemic stroke through perivascular gelatinase activation

BACKGROUND AND PURPOSE

Perivascularly positioned cerebral mast cells (MC) have been shown to participate in acute blood-brain barrier disruption and expansive brain edema following experimental transient cerebral ischemia. However, the underlying molecular mechanisms remain unknown. Because proteolytic gelatinase enzymes, matrix metalloproteinases (MMP)-2 and MMP-9, are thought to have a central role in compromising the integrity of the blood-brain barrier following ischemia, we examined whether cerebral MCs influence gelatinase activity in ischemic cerebral microvasculature.

METHODS

Rats underwent 60 minutes of middle cerebral artery occlusion followed by 3-hour reperfusion, and were treated with a MC-stabilizing (cromoglycate), or MC-degranulating (compound 48/80) agent, or vehicle. Genetically manipulated, MC-deficient WsRc(Ws/Ws) rats and their wild-type littermates (WT) underwent the same procedures. Cerebral edema and extravasation of Evans blue albumin were measured. Gelatinase activity was visualized by in situ zymography and was quantified with computerized high-throughput image and data analysis.

RESULTS

Activated MCs showed secretion of gelatinase-positive granules. Genetic MC deficiency decreased global gelatinase-active area (-69%, compared with WT; P<0.001) and the mean gelatinase activity of the ischemic microvasculature (-57% compared with WT; P=0.002). MC stabilization with cromoglycate decreased the percentage of microvessels with high gelatinase activity (-36% compared with saline; P<0.05). Compound 48/80 showed increased area of in situ zymography activity in the ischemic lesion (+55% compared with saline; P<0.001). Microvascular gelatinase activity correlated with brain swelling (r=0.84; P<0.001; and r=0.61; P=0.02).

CONCLUSIONS

Our data demonstrate that cerebral MCs participate in regulation of acute microvascular gelatinase activation and consequent blood-brain barrier disruption following transient cerebral ischemia.

Mast cell proteases as protective and inflammatory mediators

Proteases are the most abundant class of proteins produced by mast cells. Many of these are stored in membrane-enclosed intracellular granules until liberated by degranulating stimuli, which include cross-linking of high affinity IgE receptor F(c)εRI by IgE bound to multivalent allergen. Understanding and separating the functions of the proteases is important because expression differs among mast cells in different tissue locations. Differences between laboratory animals and humans in protease expression also influence the degree of confidence with which results obtained in animal models of mast cell function can be extrapolated to humans. The inflammatory potential of mast cell proteases was the first aspect of their biology to be explored and has received the most attention, in part because some of them, notably tryptases and chymases, are biomarkers of local and systemic mast cell degranulation and anaphylaxis. Although some of the proteases indeed augment allergic inflammation and are potential targets for inhibition to treat asthma and related allergic disorders, they are protective and even anti-inflammatory in some settings. For example, mast cell tryptases may protect from serious bacterial lung infections and may limit the "rubor" component of inflammation caused by vasodilating neuropeptides in the skin. Chymases help to maintain intestinal barrier function and to expel parasitic worms and may support blood pressure during anaphylaxis by generating angiotensin II. In other life-or-death examples, carboxypeptidase A3 and other mast cell peptidases limit systemic toxicity of endogenous peptideslike endothelin and neurotensin during septic peritonitis and inactivate venom-associated peptides. On the other hand, mast cell peptidase-mediated destruction of protective cytokines, like IL-6, can enhance mortality from sepsis. Peptidases released from mast cells also influence nonmast cell proteases, such as by activating matrix metalloproteinase cascades, which are important in responses to infection and resolution of tissue injury. Overall, mast cell proteases have a variety of roles, inflammatory and anti-inflammatory, protective and deleterious, in keeping with the increasingly well-appreciated contributions of mast cells in allergy, tissue homeostasis and innate immunity.

Beneficial effects of astragalus polysaccharides treatment on cardiac chymase activities and cardiomyopathy in diabetic hamsters

Over-activation of the local chymase-angiotensin II (Ang II) system has a dominant role in diabetic cardiomyopathy. Astragalus polysaccharides (APS) are used in traditional Chinese medicine to boost immunity. In this study, we investigated the effects of APS treatment on cardiac function, myocardial collagen expression, cardiac ultrastructure, cardiac matrix metalloproteinase (MMP) activity, levels of plasma glycosylated serum protein (GSP), and myocardial enzymes, and the expression of Ang II, chymase, and angiotensin-converting enzyme (ACE) in the diabetic hamster myocardium. Diabetes was induced by a single injection of streptozotocin (60 mg/kg ip). The experimental groups consisted of normal control (n = 15), diabetic (n = 15), insulin-treated diabetic (n = 15, NPH 1-2 U/day ip), and APS-treated diabetic (n = 30, APS 1-2 g/kg/day orally for 10 weeks) hamsters. Diabetic hamsters treated with insulin or APS exhibited significantly decreased blood glucose, plasma GSP, and myocardial enzymes, as well as improvements in cardiac function and cardiac ultrastructure. Compared with insulin treatment, APS treatment significantly reduced myocardial collagen (type I and III) expression and lowered cardiac MMP-2 activity, myocardial Ang II levels, myocardial chymase expression, and p-ERK1/2 kinase expression. In diabetic hamsters, myocardial ACE expression and plasma Ang II levels was not altered by insulin or APS treatment. These results indicate that treatment of diabetic hamsters with APS inhibited the local chymase-Ang II system and improved markers of diabetic cardiomyopathy.

Determinants of affinity and proteolytic stability in interactions of Kunitz family protease inhibitors with mesotrypsin

An important functional property of protein protease inhibitors is their stability to proteolysis. Mesotrypsin is a human trypsin that has been implicated in the proteolytic inactivation of several protein protease inhibitors. We have found that bovine pancreatic trypsin inhibitor (BPTI), a Kunitz protease inhibitor, inhibits mesotrypsin very weakly and is slowly proteolyzed, whereas, despite close sequence and structural homology, the Kunitz protease inhibitor domain of the amyloid precursor protein (APPI) binds to mesotrypsin 100 times more tightly and is cleaved 300 times more rapidly. To define features responsible for these differences, we have assessed the binding and cleavage by mesotrypsin of APPI and BPTI reciprocally mutated at two nonidentical residues that make direct contact with the enzyme. We find that Arg at P(1) (versus Lys) favors both tighter binding and more rapid cleavage, whereas Met (versus Arg) at P'(2) favors tighter binding but has minimal effect on cleavage. Surprisingly, we find that the APPI scaffold greatly enhances proteolytic cleavage rates, independently of the binding loop. We draw thermodynamic additivity cycles analyzing the interdependence of P(1) and P'(2) substitutions and scaffold differences, finding multiple instances in which the contributions of these features are nonadditive. We also report the crystal structure of the mesotrypsin·APPI complex, in which we find that the binding loop of APPI displays evidence of increased mobility compared with BPTI. Our data suggest that the enhanced vulnerability of APPI to mesotrypsin cleavage may derive from sequence differences in the scaffold that propagate increased flexibility and mobility to the binding loop.

Astragalus polysaccharides inhibited diabetic cardiomyopathy in hamsters depending on suppression of heart chymase activation

Diabetic cardiomyopathy is associated with high morbidity and mortality of heart failure. Overactivation of the local chymase-Ang II system plays a dominant role in diabetic cardiomyopathy. Astragalus polysaccharide (APS) is used in traditional Chinese medicine to boost immunity. To study the effect of APS on local system of chymase-Ang II in diabetic cardiomyopathy, we investigated APS/normal saline (NS)-administrated streptozotocin-induced diabetic hamsters. After APS/NS administration at a dose of 1 g/kg per day for 10 weeks, hemodynamic parameters, levels of insulin (INS), C-peptide (C-P), glycosylated serum protein (GSP), lipoproteins, myocardial enzymes, and Ang II (plasma and myocardial) were tested; myocardial collagen (type I and III), myocardial ultrastructure, and activities of matrix metalloproteinase (MMPs) were measured; activities and expression of cardiac chymase and ACE were detected by using quantitative real-time RT-PCR and RIA; protein expression of cardiac phosphoric extracellular signal-regulated kinase 1/2 (p-ERK1/2) was measured by Western blot. AP-administrated diabetic hamsters had lower levels of GSP, lipoproteins, myocardial enzymes, myocardial Ang II, expression of collagen I and I/ III, activities of pro-MMP-2 and MMP-2, activities and expression of chymase, and expression of p-ERK1/2 than NS-administrated diabetic hamsters and could better protect the myocardial ultrastructure. There was no difference in hemodynamic parameters between two groups. These results indicate that APS could inhibit diabetic cardiomyopathy in hamsters depending on the suppression of the local cardiac chymase-Ang II system.

Mast cells as early responders in the regulation of acute blood-brain barrier changes after cerebral ischemia and hemorrhage

The inflammatory response triggered by stroke has been viewed as harmful, focusing on the influx and migration of blood-borne leukocytes, neutrophils, and macrophages. This review hypothesizes that the brain and meninges have their own resident cells that are capable of fast host response, which are well known to mediate immediate reactions such as anaphylaxis, known as mast cells (MCs). We discuss novel research suggesting that by acting rapidly on the cerebral vessels, this cell type has a potentially deleterious role in the very early phase of acute cerebral ischemia and hemorrhage. Mast cells should be recognized as a potent inflammatory cell that, already at the outset of ischemia, is resident within the cerebral microvasculature. By releasing their cytoplasmic granules, which contain a host of vasoactive mediators such as tumor necrosis factor-alpha, histamine, heparin, and proteases, MCs act on the basal membrane, thus promoting blood-brain barrier (BBB) damage, brain edema, prolonged extravasation, and hemorrhage. This makes them a candidate for a new pharmacological target in attempts to even out the inflammatory responses of the neurovascular unit, and to stabilize the BBB after acute stroke.

Mast cell peptidases: chameleons of innate immunity and host defense

Mast cells make and secrete an abundance of peptidases, which are stored in such large amounts in granules that they comprise a high fraction of all cellular protein. Perhaps no other immune cell is so generously endowed with peptidases. For many years after the main peptidases were first described, they were best known as markers of degranulation, for they are released locally in response to mast cell stimulation and can be distributed systemically and detected in blood. The principal peptidases are tryptases, chymases, carboxypeptidase A3, and dipeptidylpeptidase I (cathepsin C). Numerous studies suggest that these enzymes are important and even critical for host defense and homeostasis. Endogenous and allergen or pathogen-associated targets have been identified. Belying the narrow notion of peptidases as proinflammatory, several of the peptidases limit inflammation and toxicity of endogenous peptides and venoms. The peptidases are interdependent, so that absence or inactivity of one enzyme can alter levels and activity of others. Mammalian mast cell peptidases--chymases and tryptases especially--vary remarkably in number, expression, biophysical properties, and specificity, perhaps because they hyper-evolved under pressure from the very pathogens they help to repel. Tryptase and chymase involvement in some pathologies stimulated development of therapeutic inhibitors for use in asthma, lung fibrosis, pulmonary hypertension, ulcerative colitis, and cardiovascular diseases. While animal studies support the potential for mast cell peptidase inhibitors to mitigate certain diseases, other studies, as in mice lacking selected peptidases, predict roles in defense against bacteria and parasites and that systemic inactivation may impair host defense.

Alterations in lung mast cell populations in patients with chronic obstructive pulmonary disease

RATIONALE

Mast cells have important roles in innate immunity and tissue remodeling but have remained poorly studied in inflammatory airway diseases like chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To perform a detailed histological characterization of human lung mast cell populations at different severities of COPD, comparing with smoking and never-smoking control subjects.

METHODS

Mast cells were analyzed in lung tissues from patients with mild to very severe COPD, GOLD I-IV (n = 25, 10 of whom were treated with corticosteroids). Never-smokers and smokers served as controls. The density, morphology, and molecular characteristics of mucosal and connective tissue mast cells (MC(T) and MC(TC), respectively) were analyzed in several lung regions.

MEASUREMENTS AND MAIN RESULTS

In all compartments of COPD lungs, especially at severe stages, the MC(TC) population increased in density, whereas the MC(T) population decreased. The net result was a reduction in total mast cell density. This phenomenon was paralleled by increased numbers of luminal mast cells, whereas the numbers of terminal transferase dUTP nick end labeling (TUNEL)(+) apoptotic mast cells remained unchanged. In COPD lungs, the MC(T) and MC(TC) populations showed alterations in morphology and expression of CD88 (C5a-R), transforming growth factor (TGF)-beta, and renin. Statistically significant correlations were found between several COPD-related mast cell alterations and lung function parameters.

CONCLUSIONS

As COPD progresses to its severe stages, the mast cell populations in the lung undergo changes in density, distribution, and molecular expression. In COPD lungs, these novel histopathological features were found to be correlated to lung function and they may thus have clinical consequences.

Measurement of activities in two different angiotensin II generating systems, chymase and angiotensin-converting enzyme, in the vitreous fluid of vitreoretinal diseases: A possible involvement of chymase in the pathogenesis of macular hole patients

PURPOSE

To investigate possible involvement of chymase and angiotensin-converting enzyme (ACE) in the pathogenesis of vitreoretinal diseases, both of which are related to the production of angiotensin II.

METHODS

We measured chymase and ACE activities in the vitreous in the 54 affected eyes of 54 patients who had undergone vitreous surgery for idiopathic macular holes (MH, n = 14), proliferative diabetic retinopathy (PDR, n = 14), idiopathic epiretinal membranes (ERM, n = 13), and rhegmatogenous retinal detachment (RRD, n = 13).

RESULTS

Chymase activities in the vitreous from patients with MH, PDR, ERM, and RRD were 1.87 +/- 0.53, 0.06 +/- 0.04, 0.40 +/- 0.12, and 0.08 +/- 0.03 (mean +/- SE) mU/mg protein, respectively, and ACE activities in the vitreous humor were 0.18 +/- 0.09, 0.30 +/- 0.07, 0.01 +/- 0.01, and 0.03 +/- 0.02 (mean +/- SE) mU/mg protein, respectively. Chymase activity was significantly elevated in MH among these diseases (p < 0.01, Scheffe), and ACE was significantly activated in PDR compared to ERM and RRD (p < 0.05, Scheffe).

CONCLUSIONS

Our results suggest that two different angiotensin II generating systems are activated in human vitreous humor; an increased activity of chymase may play a possible role in the formation of macular holes.

Delineating protease functions during cancer development

Much progress has been made in understanding how matrix remodeling proteases, including metalloproteinases, serine proteases, and cysteine cathepsins, functionally contribute to cancer development. In addition to modulating extracellular matrix metabolism, proteases provide a significant protumor advantage to developing neoplasms through their ability to modulate bioavailability of growth and proangiogenic factors, regulation of bioactive chemokines and cytokines, and processing of cell-cell and cell-matrix adhesion molecules. Although some proteases directly regulate these events, it is now evident that some proteases indirectly contribute to cancer development by regulating posttranslational activation of latent zymogens that then directly impart regulatory information. Thus, many proteases act in a cascade-like manner and exert their functionality as part of a proteolytic pathway rather than simply functioning individually. Delineating the cascade of enzymatic activities contributing to overall proteolysis during carcinogenesis may identify rate-limiting steps or pathways that can be targeted with anti-cancer therapeutics. This chapter highlights recent insights into the complexity of roles played by pericellular and intracellular proteases by examining mechanistic studies as well as the roles of individual protease gene functions in various organ-specific mouse models of cancer development, with an emphasis on intersecting proteolytic activities that amplify programming of tissues to foster neoplastic development.

Chymase activity is closely related with plaque vulnerability in a hamster model of atherosclerosis

OBJECTIVE

To test the hypothesis that stimulation of chymase secretion may contribute to plaque vulnerability and inhibition of chymase activity may enhance plaque stability.

METHODS AND RESULTS

Sixty eight-week-old male Syrian golden hamsters were randomly divided into normal control group, high-cholesterol (HC) treated group, HC+ovalbumin treated group and HC+tranilast treated group. The normal control group received a normal diet while the other three intervention groups received a high-cholesterol diet for 15 weeks. Hamsters in the HC+ovalbumin treated group underwent transcatheter pharmacological triggering at the end of week 15 after antigen sensitization and those in the HC+tranilast treated group were given tranilast intragastrically for 3 weeks before euthanasia. Serological, ultrasonographic, pathologic, immunohistochemical, and gene expression studies were performed in all animals. The total number of mast cells, proportion of degranulated mast cells and the number of extracellular granules in plaques, the apoptosis rate of vascular smooth cells, the local activities of chymase, the concentration of Ang II and the expression levels of inflammatory markers as well as plaque vulnerability index all increased significantly in HC+ovalbumin treated group, but remarkably decreased in HC+tranilast treated group, in comparison with the HC treated group. These results suggest that stimulation of chymase secretion contributes to plaque vulnerability while inhibition of chymase activity enhances plaque stability. We conclude that chymase activity provides a promising therapeutic target in the stabilization of atherosclerotic plaques.

An emerging role of mast cells in cerebral ischemia and hemorrhage

Mast cells (MCs) are perivascularly located resident cells of hematopoietic origin, recognized as effectors in inflammation and immunity. Their subendothelial location at the boundary between the intravascular and extravascular milieus, and their ability to rapidly respond to blood- and tissue-borne stimuli via release of potent vasodilatatory, proteolytic, fibrinolytic, and proinflammatory mediators, render MCs with a unique status to act in the first-line defense in various pathologies. We review experimental evidence suggesting a role for MCs in the pathophysiology of brain ischemia and hemorrhage. In new-born rats, MCs contributed to brain damage in hypoxic-ischemic insults. In experimental cerebral ischemia/reperfusion, MCs regulated permeability of the blood-brain barrier, brain edema formation, and the intensity of local neutrophil infiltration. MCs were reported to play a role in the tissue plasminogen activator-mediated cerebral hemorrhages after experimental ischemic stroke, and to be involved in the expansion of hematoma and edema following intracerebral hemorrhage. Importantly, the MC-stabilizing drug cromoglycate inhibited MC-mediated adverse effects on brain pathology and improved survival of experimental animals. This brings us to a position to consider MC stabilization as a novel initial adjuvant therapy in the prevention of brain injuries in hypoxia-ischemia in new-borns, as well as in ischemic stroke and intracerebral hemorrhage in adults.

Mast cells in vulnerable atherosclerotic plaques--a view to a kill

The aim of the present review is to discuss the participation of mast cells in the pathogenesis of erosion and rupture of atherosclerotic plaques, the major causes behind acute coronary syndromes and myocardial infarction. We present ex vivo observations describing mast cells and their activation in human atherosclerotic plaques and discuss in vitro and in vivo data showing that mast cells are potential regulators of inflammation, immunity and adverse remodeling, including matrix remodeling and cell death. Furthermore, we focus on studies that have been performed with human tissues and human mast cells, but when appropriate, we also discuss observations made in animal models. Finally, we present potential pharmacological means to modulate mast cell responses in the arterial vessel walls.

The extended cleavage specificity of the rodent beta-chymases rMCP-1 and mMCP-4 reveal major functional similarities to the human mast cell chymase

In rat and mouse the phylogenetic homologues of the human mast cell alpha-chymase (rMCP-5 and mMCP-5) have lost their chymase activity and instead become elastases. To investigate whether rodents hold enzymes with equivalent function as the primate alpha-chymases, we have determined the extended cleavage specificity of the major connective tissue mast cell beta-chymases in rat and mouse, rMCP-1 and mMCP-4. By using a phage display approach we determined the enzyme/substrate interaction in seven positions, both N- and C-terminal of the cleaved bond. The two proteases were found to display rather similar specificities. Both enzymes prefer Phe in position P1, and aliphatic amino acids are favoured N-terminal of the cleaved bond, i.e. Leu in P2 and Val in P3 and P4. Val and Leu are overrepresented also in positions P1' and P3'. The two enzymes differ clearly only in one position, the P2' residue, where mMCP-4 strongly prefers negatively charged amino acids while rMCP-1 favours Ser. Interestingly, Asp and Glu are often present in position P2' of known substrates for the human chymase. Overall, these two rodent beta-chymases have very similar amino acid preferences as the human chymase, particularly mMCP-4, which most likely have a very similar function as the human chymase. This finding indicates that rodent and primate connective tissue mast cells seem to have relatively similar proteolytic repertoires, although they express different sets of serine proteases.

Mast Cell Stabilization Reduces Hemorrhage Formation and Mortality After Administration of Thrombolytics in Experimental Ischemic Stroke

Background— Thrombolysis with tissue plasminogen activator (tPA) improves stroke outcome, but hemorrhagic complications and reperfusion injury occasionally impede favorable prognosis after vessel recanalization. Perivascularly located cerebral mast cells (MCs) release on degranulation potent vasoactive, proteolytic, and fibrinolytic substances. We previously found MCs to increase ischemic and hemorrhagic brain edema and neutrophil accumulation. This study examined the role of MCs in tPA-mediated hemorrhage formation (HF) and reperfusion injury.

Methods and Results— Exposure to tPA in vitro induced strong MC degranulation. In vivo experiments in a focal cerebral ischemia/reperfusion model in rats showed 70- to 100-fold increase in HF after postischemic tPA administration ( P <0.001). Pharmacological MC stabilization with cromoglycate led to significant reduction in tPA-mediated HF at 3 (97%), 6 (76%), and 24 hours (96%) compared with controls ( P <0.01, P <0.001, and P <0.01, respectively). Furthermore, genetically modified MC-deficient rats showed similarly robust reduction of tPA-mediated HF at 6 (92%) and 24 (89%) hours compared with wild-type littermates ( P <0.01 and P <0.001, respectively). MC stabilization and MC deficiency also significantly reduced other hallmarks of reperfusion injury, such as brain swelling and neutrophil infiltration. These effects of cromoglycate and MC deficiency translated into significantly better neurological outcome ( P <0.01 and P <0.05, respectively) and lower mortality ( P <0.05 and P <0.05, respectively) after 24 hours.

Conclusions— MCs appear to play an important role in HF and reperfusion injury after tPA administration. Pharmacological stabilization of MCs could offer a novel type of therapy to improve the safety of administration of thrombolytics.

Bronchoalveolar matrix metalloproteinase 9 relates to restrictive lung function impairment in systemic sclerosis

Systemic sclerosis (SSc) is frequently associated with interstitial lung disease (ILD) often leading to lung fibrosis. In this study we investigated whether matrix metalloproteinase 9 (MMP-9) and its natural inhibitor; the tissue inhibitor of matrix metalloproteinase 1 (TIMP-1), would be associated with remodelling in ILD in SSc. Levels of total MMP-9, pro-MMP-9 and TIMP-1 were measured in bronchoalveolar lavage (BAL) fluid from nine SSc patients with ILD, seven SSc patients without ILD and 16 age- and sex-matched healthy controls. Total MMP-9 and pro-MMP-9 levels were significantly elevated in SSc patients with ILD, compared to levels in SSc patients without ILD and healthy controls. In SSc patients with ILD calculated active MMP-9 levels were significantly higher than in SSc patients without ILD and tended to be higher than in healthy controls. TIMP-1 levels were elevated in both patient groups compared to healthy controls. Total-, pro- and active MMP-9 levels as well as pro-MMP-TIMP-1 and active MMP-9/TIMP-1 ratios were inversely associated with total lung capacity. The present study suggests that MMP-9 plays a pathophysiological role in the remodelling in ILD and lung fibrosis associated with SSc, and may represent a new therapeutic target in this condition.

Mast cell tryptases and chymases in inflammation and host defense

Tryptases and chymases are the major proteins stored and secreted by mast cells. The types, amounts, and properties of these serine peptidases vary by mast cell subtype, tissue, and mammal of origin. Membrane-anchored gamma-tryptases are tryptic, prostasin-like, type I peptidases that remain membrane attached on release and act locally. Soluble tryptases, including their close relatives, mastins, form inhibitor-resistant oligomers that act more remotely. Befitting their greater destructive potential, chymases are quickly inhibited after release, although some gain protection by associating with proteoglycans. Most chymase-like enzymes, including mast cell cathepsin G, hydrolyze chymotryptic substrates, an uncommon capability in the proteome. Some rodent chymases, however, have mutations resulting in elastolytic activity. Secreted tryptases and chymases promote inflammation, matrix destruction, and tissue remodeling by several mechanisms, including destroying procoagulant, matrix, growth, and differentiation factors and activating proteinase-activated receptors, urokinase, metalloproteinases, and angiotensin. They also modulate immune responses by hydrolyzing chemokines and cytokines. At least one chymase protects mice from intestinal worms. Tryptases and chymases can also oppose inflammation by inactivating allergens and neuropeptides causing inflammation and bronchoconstriction. Thus, like mast cells themselves, mast cell serine peptidases play multiple roles in host defense, and any accounting of benefit versus harm is necessarily context specific.

Mast cells and inflammatory kidney disease

Inflammatory kidney disease involves a complex network of interactions between resident kidney and infiltrating hematopoietic cells. Mast cells (MCs) are constitutively found in kidneys in small numbers but increase considerably in various renal diseases. While this increase is usually interpreted as a sign of pathological involvement, recent data using MC-deficient animals show their ability to restore kidney homeostasis. In anti-glomerular basement membrane antibody-induced glomerulonephritis, MCs are protective by initiating repair and remodeling functions counteracting the devastating effects of glomerular injury. Protection may also include immunoregulatory capacities to limit autoreactive T-cell responses. MCs also control tubulointerstitial fibrosis by activating tissue remodeling and neutralizing fibrotic factors. Release of mediators by MCs during inflammation, however, could also promote unwanted responses that ultimately lead to destruction of kidney structure, as exemplified by data showing either protection or aggravation in related renal disease models. Similarly, while the action of proteases may initially be beneficial, the generation of fibrosis-promoting angiotensin II by chymase also shows the limits of adaptive responses to achieve homeostasis. Thus, it is likely the physiological context involving the interaction with other cells and inflammatory mediators that determines the final action of MCs in the development of kidney disease.

Involvement of mast cells in the regulation of matrix metalloproteinase-9 and tissue inhibitor of metalloproteases-1 in 12-O-tetradecanoylphorbolacetate-induced inflammation in mice

In this study, we investigated the involvement of mast cells in the regulation of matrix metalloproteinase-9 (MMP-9) in 12-O-tetradecanoylphorbolacetate (TPA)-induced inflammation, using mast cell-deficient (W/W(v)) mice and control (+/+) mice. Topical application of TPA to the ears induced acute inflammation, accompanied by mast cell degranulation in +/+ mice, which peaked at 6-12 h. There was no significant difference in ear thickness between the groups until 12 h, but the swelling was greater in W/W(v) mice than +/+ mice at 24-36 h. Western blot analysis revealed that TPA-induced marked increases in levels of proMMP-9 and tissue inhibitor of metalloproteinases-1 (TIMP-1), which existed as complexes with proMMP-9. The amount of proMMP-9-TIMP-1 complex was markedly smaller in +/+ mice than W/W(v) mice at 6 and 24 h, but had almost returned to control levels in both groups at 48 h. The free form of proMMP-9 was also slightly less abundant in +/+ mice than W/W(v) mice at 6, 24, and 48 h. Gelatin zymographic analysis revealed that levels of the active species of MMP-9 (approximately 74 and 83 kD), as well as free form of proMMP-9, increased time-dependently after the application of TPA and peaked at 24 h in +/+ mice. The 74-kD band was detected only in +/+ mice at 6 h. Our results therefore suggested that during inflammation degranulation of mast cells results in a reduction of the proMMP-9-TIMP-1 complex levels, together with a fall in the amount of free proMMP-9.

Mast Cell Proteases

Mast cells (MCs) are traditionally thought of as a nuisance for its host, for example, by causing many of the symptoms associated with allergic reactions. In addition, recent research has put focus on MCs for displaying harmful effects during various autoimmune disorders. On the other hand, MCs can also be beneficial for its host, for example, by contributing to the defense against insults such as bacteria, parasites, and snake venom toxins. When the MC is challenged by an external stimulus, it may respond by degranulation. In this process, a number of powerful preformed inflammatory "mediators" are released, including cytokines, histamine, serglycin proteoglycans, and several MC-specific proteases: chymases, tryptases, and carboxypeptidase A. Although the exact effector mechanism(s) by which MCs carry out their either beneficial or harmful effects in vivo are in large parts unknown, it is reasonable to assume that these mediators may contribute in profound ways. Among the various MC mediators, the exact biological function of the MC proteases has for a long time been relatively obscure. However, recent progress involving successful genetic targeting of several MC protease genes has generated powerful tools, which will enable us to unravel the role of the MC proteases both in normal physiology as well as in pathological settings. This chapter summarizes the current knowledge of the biology of the MC proteases.

Effects of Chymase on the Macular Region in Monkeys and Porcine Müller Cells: Probable Involvement of Chymase in the Onset of Idiopathic Macular Holes

OBJECTIVES

To investigate chymase involvement in idiopathic macular hole onset, the effects of chymase on monkey eyes and cultured Muller cells were investigated.

METHODS

Immunohistochemistry using antinestin and antiglial fibrillary acidic protein antibodies was performed in a normal monkey eye. After chymase was injected into the monkey vitreous, histological changes in the retina were evaluated using the TdT-mediated dUTP nick-end labeling (TUNEL) assay. Expression of c-kit, a stem cell factor receptor, and nestin was examined in porcine Muller cells cultured with basic fibroblast growth factor. The effects of chymase on proliferation and TUNEL staining in Muller cells were also examined.

RESULTS

The number of nestin and glial fibrillary acidic protein-positive cells was higher in the macula than in other regions. Thickening of the posterior hyaloid membrane and some apoptotic cells were found in the macula of chymase-treated eyes. The expression of c-kit and nestin in Muller cells was shown and enhanced when cultured with basic fibroblast growth factor. Exposure to chymase inhibited Muller cell proliferation and produced TUNEL-positive cells.

CONCLUSIONS

There might be Muller cells possessing atypical properties near the macular region and chymase might cause fibrosis and apoptosis through these cells. These findings suggest that increased chymase activity may result in idiopathic macular hole onset.

Human Mast Cell-Derived Gelatinase B (Matrix Metalloproteinase-9) Is Regulated by Inflammatory Cytokines: Role in Cell Migration

Mast cells are key effectors in the pathogenesis of inflammatory and tissue destructive diseases such as rheumatoid arthritis (RA). These cells contain specialized secretory granules loaded with bioactive molecules including cytokines, growth factors, and proteases that are released upon activation. This study investigated the regulation of matrix metalloproteinase MMP-9 (gelatinase B) in human mast cells by cytokines that are known to be involved in the pathogenesis of RA. Immunohistochemical staining of synovial tissue showed abundant expression of MMP-9 by synovial tissue mast cells in patients with RA but not in normal controls. The expression, activity, and production of MMP-9 in mast cells was confirmed by RT-PCR, zymography, and Western blotting using cord blood-derived human mast cells (CB-HMC). Treatment of CB-HMC with TNF-alpha significantly increased the expression of MMP-9 mRNA and up-regulated the activity of MMP-9 in a time- and dose-dependent manner. By contrast, IFN-gamma inhibited MMP-9 mRNA and protein expression. The cytokine-mediated regulation of MMP-9 was also apparent in the human mast cell line (HMC-1) and in mouse bone marrow-derived mast cells. Furthermore, TNF-alpha significantly increased the invasiveness of CB-HMC across Matrigel-coated membranes while the addition of IFN-gamma, rTIMP-1, or pharmacological MMP inhibitors significantly reduced this process. These observations suggest that MMP-9 is not a stored product in mast cells but these cells are capable of producing this enzyme under inflammatory conditions that may facilitate the migration of mast cell progenitors to sites of inflammation and may also contribute to local tissue damage.

A Pulmonary Perspective on GASPIDs: Granule-Associated Serine Peptidases of Immune Defense

Airways are protected from pathogens by forces allied with innate and adaptive immunity. Recent investigations establish critical defensive roles for leukocyte and mast cell serine-class peptidases garrisoned in membrane-bound organelles-here termed Granule-Associated Serine Peptidases of Immune Defense, or GASPIDs. Some better characterized GASPIDs include neutrophil elastase and cathepsin G (which defend against bacteria), proteinase-3 (targeted by antineutrophil antibodies in Wegener's vasculitis), mast cell beta-tryptase and chymase (which promote allergic inflammation), granzymes A and B (which launch apoptosis pathways in infected host cells), and factor D (which activates complement's alternative pathway). GASPIDs can defend against pathogens but can harm host cells in the process, and therefore become targets for pharmaceutical inhibition. They vary widely in specificity, yet are phylogenetically similar. Mammalian speciation supported a remarkable flowering of these enzymes as they co-evolved with specialized immune cells, including mast cells, basophils, eosinophils, cytolytic T-cells, natural killer cells, neutrophils, macrophages and dendritic cells. Many GASPIDs continue to evolve rapidly, providing some of the most conspicuous examples of divergent protein evolution. Consequently, students of GASPIDs are rewarded not only with insights into their roles in lung immune defense but also with clues to the origins of cellular specialization in vertebrate immunity.

Mast cell-mediated remodeling and fibrinolytic activity protect against fatal glomerulonephritis

Mast cells are detrimental in several inflammatory diseases; however, their physiological roles are also increasingly recognized. Recent data suggest that mast cells may also be involved in renal diseases. We therefore used congenitally mast cell-deficient W/W(v) mice and normal +/+ littermates to assess their role in anti-glomerular basement membrane-induced glomerulonephritis. Following administration of anti-glomerular basement membrane Abs, W/W(v) mice exhibited increased mortality as compared with +/+ mice owing to rapid deterioration of renal function. Reconstitution of the mast cell population in W/W(v) mice restored protection. This was independent of activating FcgammaR, as protection was also obtained using mast cells deficient in FcRgamma. Comparative histological analysis of kidneys showed that deterioration of renal function was caused by the presence of thick layers of subendothelial glomerular deposits in W/W(v) mice, while +/+ mice or mast cell-reconstituted W/W(v) mice showed significantly less. Deposits appeared during the early phase of disease and persisted thereafter, and were accompanied by enhanced macrophage recruitment. Immunohistochemical analysis revealed increased amounts of fibrin and type I collagen in W/W(v) mice, which were also unable to maintain high tissue plasminogen activator and urinary-type plasminogen activator activity in urine in the heterologous phase of disease. Our results indicate that mast cells by their ability to mediate remodeling and repair functions are protective in immune complex-mediated glomerulonephritis.

Cerebral mast cells regulate early ischemic brain swelling and neutrophil accumulation

We previously observed degranulated mast cells (MC) in association with perivascular brain edema formation during focal cerebral ischemia. Brain MC are typically located perivascularly and contain potent fast-acting vasoactive and proteolytic substances. We examined in a rat model of transient middle cerebral artery occlusion (MCAO) whether, in the early phase of ischemia, MC regulate microcirculation, the blood-brain barrier (BBB) permeability, and edema formation. First, animals received MC inhibitor (cromoglycate), MC-degranulating drug (compound 48/80), or saline. Thereafter, we performed transient MCAO in gene-manipulated MC-deficient rats and their wild-type (WT) littermates, calculating brain swelling, visualizing BBB leakage by intravenously administered Evans blue albumin, and determining neutrophil infiltration with light microscopy. Cerebral blood flow, monitored by laser-Doppler flowmetry in separate experiments, was similar among pharmacological treatments. Ischemic swelling resulted in increased hemispheric volume of 13.4%+/-1.0% in controls, 8.1%+/-0.4% (39% reduction) after cromoglycate, and 25.2%+/-2.0% (89% increase) after compound 48/80 (P<0.05). Early ischemic BBB leakage was reduced by 51% after cromoglycate, and 50% enhanced by compound 48/80 (P<0.05). The cromoglycate group showed 37% less postischemic neutrophil infiltration than did controls (P<0.05). Furthermore, MC-deficient rats responded to focal ischemia with 58% less brain swelling (6.7%+/-1.2%) than did their WT littermates (15.8%+/-1.4%, P<0.05). Blood-brain barrier damage was 47% lower in MC-deficient rats than in the WT (P<0.05). Neutrophil infiltration after MCAO was decreased 47% in MC-deficient rats in comparison to WT (P<0.05). Pharmacological MC inhibition thus appears to deserve further investigation regarding reduction of brain swelling and inflammation early after stroke.

Expression of chymase-positive cells in gastric cancer and its correlation with the angiogenesis

BACKGROUND AND OBJECTIVES

Chymase is expressed in mast cells and induces angiogenesis via activation of angiotensin II and matrix metalloproteinase-9. However, it has been unclear whether chymase is involved in the pathophysiology of angiogenesis in gastric cancer. To clarify the contribution of chymase to angiogenesis in gastric cancer, we assessed the relationship between chymase-positive cells and tumor angiogenesis.

METHODS

We evaluated chymase-positive cells and microvessels using anti-human chymase and anti-CD34 antibodies in 168 cases of gastric cancer, respectively.

RESULTS

Chymase-positive cells in gastric tumor region were significantly higher than the cells in normal region. The number of chymase-positive cells in the undifferentiated type of gastric tumor region was significantly higher than the one in the differentiated type. Specimens from patients with advanced histological stages of disease had more chymase-positive cells than those with early-stage disease. There was a significant positive correlation between chymase-positive cells and microvessels in gastric cancer specimens. Postoperative survival curves revealed that patients with a high number of chymase-positive cells had a poor prognosis.

CONCLUSIONS

These results suggest that accumulation of chymase-positive cells in gastric cancer may lead to an increase of tumor angiogenesis, and may contribute to tumor growth and progression.

Transcript signatures of lymphocytic bronchitis in lung allograft biopsy specimens

BACKGROUND

Rejection and obliterative bronchiolitis are barriers to sustained graft function in recipients of transplanted lungs. Early detection is hindered by inadequate tests and an incomplete understanding of the molecular events preceding or accompanying graft deterioration.

METHODS

Hypothesizing that genes involved in immune responses and tissue remodeling produce biomarkers of rejection, we measured the expression of 192 selected genes in 72 sets of biopsy specimens from human lung allografts. Gene transcripts were quantified using a 2-step, multiplex, real-time polymerase chain reaction approach in endobronchial and transbronchial biopsy specimens from transplant recipients without acute infections undergoing routine surveillance bronchoscopy.

RESULTS

Comparisons of histopathology in parallel biopsy specimens identified 6 genes correlating with rejection as manifested by lymphocytic bronchitis, a suspected harbinger of obliterative bronchiolitis. For example, beta2-defensin and collagenase transcripts in inflamed bronchi increased 37-fold and 163-fold, respectively. By contrast, these transcripts did not correlate with acute rejection in transbronchial specimens. Further, no correspondence was noted between histopathologic bronchitis and parenchymal rejection when endobronchial and transbronchial samples were obtained from the same patient.

CONCLUSIONS

Our highly sensitive method permits quantitation of many gene transcripts simultaneously in small, bronchoscopically acquired biopsy specimens of allografts. Transcript signatures obtained by this approach suggest that airway and alveolar responses to rejection differ and that endobronchial biopsy specimens assess lymphocytic bronchitis and chronic rejection but are not proxies for transbronchial biopsy specimens. Further, they reveal changes in airway expression of the specific genes involved in host defense and remodeling and suggest that the measurement of transcripts correlating with lymphocytic bronchitis may be diagnostic adjuncts to histopathology.

c-Kit immunophenotyping and metalloproteinase expression profiles of mast cells in interstitial lung diseases

Diverse interstitial lung diseases (ILD) demonstrate mesenchymal infiltration by an abundance of activated mast cells whose role in parenchymal fibrogenesis remains unclear. Since mast cells differentiate in a dynamic, tissue-specific manner via signals transduced by c-Kit receptor, we examined the effect of ILD microenvironments on c-Kit expression and metalloproteinase phenotypes of mesenchymal mast cell populations. Immunohistochemical and flow cytometric analyses characterized surface expression of c-Kit on mast cells in tissues obtained from patients with idiopathic pulmonary fibrosis, systemic sclerosis, sarcoidosis, and lymphangioleiomyomatosis, thus identifying a unique immunophenotype not shared by normal lung mast cells. Isolation of c-Kit+/FcepsilonRI+/CD34- mast cells via immunocytometric sorting of heterogeneous cell populations from mechanically disaggregated lung tissues permitted analysis of gene expression patterns by two-step real-time polymerase chain reaction. Transcriptional profiling identified expression of c-Kit and the neutral serine proteases, tryptase and chymase, establishing the identity of sorted populations as mature mast cells. Mast cells harvested from ILD tissues demonstrated characteristic metalloproteinase phenotypes which included expression of matrix metalloproteinase (MMP)-1 and a disintegrin and metalloproteinase (ADAM)-9, -10, and -17. Immunohistochemical co-localization guided by gene profiling data confirmed expression of chymase, MMP-1, and ADAM-17 protein in subpopulations of mast cells in remodelling interstitium. Gene profiling of harvested mast cells also showed increased transcript copy numbers for TNFalpha and CC chemokine receptor 2, which play critical roles in lung injury. We conclude that ILD microenvironments induce unique c-Kit receptor and metalloproteinase mast cell phenotypes.

Diffuse expression of heparan sulfate proteoglycan and connective tissue growth factor in fibrous septa with many mast cells relate to unresolving hepatic fibrosis of congenital hepatic fibrosis

BACKGROUND AND AIMS

Congenital hepatic fibrosis (CHF) is characterized by dense portal/septal fibrosis and bile duct proliferation and tortuosity. In this study, the roles and significance of fibrosis-related cells and molecules in the process of progressive and unresolving fibrosis of CHF were examined in comparison with other fibrotic liver diseases.

METHODS

Seven CHF livers were examined, and a total of 74 control livers (chronic viral hepatitis (CVH), alcoholic fibrosis/cirrhosis (F/C), extrahepatic biliary obstruction and livers showing non-specific reactive changes) were used as controls. All of these livers were wedge biopsied or surgically resected ones, and were formalin fixed and paraffin embedded. In addition to histologic observations, expression of heparan sulfate proteoglycan (HSPG), connective tissue growth factor (CTGF), mast cell-specific tryptase, alpha-smooth muscle actin for activated hepatic stellate cells (HSC) or myofibroblasts (MF) were immunohistochemically surveyed. HSPG and CTGF at mRNA were also examined by in situ hybridization.

RESULTS

Portal/septal fibrosis of CHF were mature collagenous and elastic fiber poor, when compared with controls. HSPG and CTGF were diffusely abundant in fibrous portal tracts/septa in CHF, while they were more or less accentuated at periportal areas in alcoholic F/C and CVH. In CHF, the number of interface and portal/septal MF was increased from mild-to-moderate degree, while their increase was moderate to marked in alcoholic F/C and CVH, particularly F3/F4. While activated HSC were frequent in alcoholic F/C and CVH and they were continuous with interface MF, activated HSC in CHF were scanty. Instead, mast cells were increased in portal/septal fibrosis of CHF. Portal mononuclear cells and endothelial cells were positive for HSPG mRNA, and mononuclear cells for CTGF mRNA, and such cells were accentuated around proliferated bile ducts and ductules in CHF.

CONCLUSIONS

Abundant CTGF retained diffusely in HSPG in the fibrous portal tracts/septa may be responsible for non-resolving hepatic fibrosis in CHF, and many mast cells and portal MF not related to HSC may causally relate to such characteristic finding in CHF.

Exposure to tobacco-derived materials induces overproduction of secreted proteinases in mast cells

Mast cells reside at interfaces with the environment, including the mucosa of the respiratory and gastrointestinal tracts. This localization exposes mast cells to inhaled, or ingested, environmental challenges. In the airways of smokers, resident immune cells will be in contact with the condensed components of cigarette smoke. Mast cells are of particular interest due to their ability to promote airway remodeling and mucus hypersecretion. Clinical data show increased levels of mast cell-secreted tryptase and increased numbers of degranulated mast cells in the lavage and bronchial tissue of smokers. Since mast cell-secreted proteinases (MCPTs), including tryptases, contribute to pathological airway remodeling, we investigated the relationship between mast cell proteinases and smoke exposure. We exposed a mast cell line to cigarette smoke condensate (CSC). We show that CSC exposure increases MCPT levels in mast cells using an assay for tryptase-type MCPT activity. We hypothesized that this increase in MCPT activity reflects a CSC-induced increase in the cytosolic pool of proteinase molecules, via stimulation of MCPT transcription. Transcript array data suggested that mRNA changes in response to CSC were limited in number and peaked after 3 h of CSC exposure. However, we noted marked transcriptional regulation of several MCPT genes. CSC-induced changes in the mRNA levels for MCPTs were confirmed using quantitative RT-PCR. Taken together, our data suggest that chronic exposure to cigarette smoke up-regulates MCPT levels in mast cells at both the protein and the mRNA level. We suggest that the pathological airway remodeling that has been described in clinical studies of smoke inhalation may be attributable to MCPT overproduction in vivo.

Role of mast cells and their mediators in failing myocardium under mechanical ventricular support

BACKGROUND

Mast cells have been implicated in tissue remodeling and fibroblast stimulation. We explored the effect of mechanical support by left ventricular assist device (LVAD) in failing myocardium and looked into grade and distribution of interstitial fibrosis, mast cell density, mast cell phenotypes and basic fibroblast growth factor (bFGF) expression pre- and post-LVAD.

METHODS

Myocardial tissue was obtained from 20 patients with end-stage cardiomyopathy at the time of LVAD implantation and LVAD removal and from 7 donor hearts not used for transplantation. Tissue sections were stained for mast cells using tryptase as a marker and the myocardial fibrosis was measured. Double staining for tryptase and chymase was performed for detection of chymase-positive mast cells. Fluorescent microscopy showed the relationship of mast cells to bFGF, and bFGF expression was quantified by Western blot.

RESULTS

There was a significant increase in mast cells in heart failure vs normal myocardium. A secondary increase in mast cells occurred after long-term (>40 days) support compared with matched pre-LVAD samples (mean +/- SEM; 57.4 +/- 8.6 cells/10 fields vs 45.1 +/- 7.6 SEM cells/10 fields, p < 0.01). The secondary increase in mast cells was associated specifically with an increase in chymase-negative mast cells (p < 0.01). These findings are statistically significant with concurrent decreased expression of bFGF and decreased fibrosis in the same patient tissues (p < 0.01).

CONCLUSIONS

We suggest that, under long-term support, there is a change in phenotypic expression in mast cells, which can alter fibroblast functions. The decreased myocardial bFGF levels might be the result of these phenotypically altered mast cells.