Activated mast cells induce endothelial cell apoptosis by a combined action of chymase and tumor necrosis factor-alpha

Recent advances in potential targets for myocardial ischemia reperfusion injury: Role of macrophages

Myocardial ischemia-reperfusion injury (MIRI) is a complex process that occurs when blood flow is restored after myocardium infarction (MI) with exacerbated tissue damage. Macrophages, essential cell type of the immune response, play an important role in MIRI. Macrophage subpopulations, namely M1 and M2, are distinguished by distinct phenotypes and functions. In MIRI, macrophages infiltrate in infarcted area, shaping the inflammatory response and influencing tissue healing. Resident cardiac macrophages interact with monocyte-derived macrophages in MIRI, and influence injury progression. Key factors including chemokines, cytokines, and toll-like receptors modulate macrophage behavior in MIRI. This review aims to address recent findings on the classification and the roles of macrophages in the myocardium, spanning from MI to subsequent MIRI, and highlights various signaling pathways implicated in macrophage polarization underlining the complexity of MIRI. This article will shed light on developing advanced therapeutic strategies for MIRI management.

Characterization of novel truncated apolipoprotein A-I in human high-density lipoprotein generated by sequential treatment with myeloperoxidase and chymase

High-density lipoprotein (HDL) cholesterol is a well-known biomarker, which has been associated with reduction in the risk of cardiovascular diseases (CVD). However, some HDL anti-atherosclerotic functions may be impaired without altered HDL-cholesterol (HDL-C) level via its dysfunctional proteins or other physiological reactions in vivo. We previously showed that activated mast cell-derived chymase could modestly cleave apolipoprotein A-I (apoA-I) in HDL3, and further easily cleave lipid-free apoA-I. In contrast, myeloperoxidase (MPO) secreted by macrophages, the main cell type in atherosclerotic plaques, could oxidize HDL proteins, which might modify their tertiary structures, increasing their susceptibility to other enzymes. Here we focused on the co-modification and impact of chymase and MPO, usually secreted during inflammation from cells with possible co-existence in atheromas, on HDL. Only after sequential treatment with MPO and then chymase, two novel truncated apoA-I fragments were generated from HDL. One fragment was 16.5 kDa, and the cleavage site by chymase after MPO modification was the C-terminal of Tyr100 in apoA-I, cross-validated by three different mass spectrometry methods. This novel apoA-I fragment can be trapped in HDL particles to avoid kidney glomerular filtration and has a specific site for antibody generation for ELISA tests. As such, its quantification can be useful in predicting patients with CVD having normal HDL-C levels.

Mast Cells in Cardiac Remodeling: Focus on the Right Ventricle

In response to various stressors, cardiac chambers undergo structural remodeling. Long-term exposure of the right ventricle (RV) to pressure or volume overload leads to its maladaptive remodeling, associated with RV failure and increased mortality. While left ventricular adverse remodeling is well understood and therapeutic options are available or emerging, RV remodeling remains underexplored, and no specific therapies are currently available. Accumulating evidence implicates the role of mast cells in RV remodeling. Mast cells produce and release numerous inflammatory mediators, growth factors and proteases that can adversely affect cardiac cells, thus contributing to cardiac remodeling. Recent experimental findings suggest that mast cells might represent a potential therapeutic target. This review examines the role of mast cells in cardiac remodeling, with a specific focus on RV remodeling, and explores the potential efficacy of therapeutic interventions targeting mast cells to mitigate adverse RV remodeling.

Mast Cell Dynamics in the Ovary Are Governed by GnRH and Prolactin

Gonadotrophin releasing hormone (GnRH) facilitates the migration of mast cells (MCs) into the involuting mammary gland. As GnRH is also expressed in the ovary, we examined changes in ovarian MCs. MCs in the ovary were mainly in interstitial tissue and their number increased during the estrous cycle to produce 2 peaks, one at diestrus 2 (20:00 hours) and another at proestrus (17:00 hours). Laser microdissection demonstrated that GnRH mRNA is expressed throughout ovarian tissues (corpora lutea, follicles, and interstitial tissues). GnRH immunoreactivity was also ubiquitous, but MCs were the most strongly immunostained. Analysis of GnRH mRNA in the ovary showed it to fluctuate similarly to the variation in MC number during the estrous cycle, and MCs also expressed GnRH. Local administration of a GnRH agonist (GnRHa) into the hemilateral ovarian bursa increased MCs in the administered ovary. MC number and GnRH mRNA were significantly lowered in the pregnant ovary. Prolactin administration suppressed the normal peaks in MC number in the ovary at both diestrus and proestrus. By contrast, a dopamine agonist, administered when prolactin was elevated during pseudopregnancy, increased ovarian MC number. Furthermore, prolactin inhibited GnRHa-induced peritoneal MC migration in a Transwell assay. These data clearly demonstrate that ovarian MC number is regulated positively by local GnRH expression and negatively by prolactin. The suppressive effect of prolactin on GnRH and MCs would be part of its luteotrophic action.

Mast cell-mediated immune regulation in health and disease

Mast cells are important components of the immune system, and they perform pro-inflammatory as well as anti-inflammatory roles in the complex process of immune regulation in health and disease. Because of their strategic perivascular localization, sensitivity and adaptability to the microenvironment, and ability to release a variety of preformed and newly synthesized effector molecules, mast cells perform unique functions in almost all organs. Additionally, Mast cells express a wide range of surface and cytoplasmic receptors which enable them to respond to a variety of cytokines, chemicals, and pathogens. The mast cell's role as a cellular interface between external and internal environments as well as between vasculature and tissues is critical for protection and repair. Mast cell interactions with different immune and nonimmune cells through secreted inflammatory mediators may also turn in favor of disease promoting agents. First and forefront, mast cells are well recognized for their multifaceted functions in allergic diseases. Reciprocal communication between mast cells and endothelial cells in the presence of bacterial toxins in chronic/sub-clinical infections induce persistent vascular inflammation. We have shown that mast cell proteases and histamine induce endothelial inflammatory responses that are synergistically amplified by bacterial toxins. Mast cells have been shown to exacerbate vascular changes in normal states as well as in chronic or subclinical infections, particularly among cigarette smokers. Furthermore, a potential role of mast cells in SARS-CoV-2-induced dysfunction of the capillary-alveolar interface adds to the growing understanding of mast cells in viral infections. The interaction between mast cells and microglial cells in the brain further highlights their significance in neuroinflammation. This review highlights the significant role of mast cells as the interface that acts as sensor and early responder through interactions with cells in systemic organs and the nervous system.

The impact of type 2 immunity and allergic diseases in atherosclerosis

Allergic diseases are allergen-induced immunological disorders characterized by the development of type 2 immunity and IgE responses. The prevalence of allergic diseases has been on the rise alike cardiovascular disease (CVD), which affects arteries of different organs such as the heart, the kidney and the brain. The underlying cause of CVD is often atherosclerosis, a disease distinguished by endothelial dysfunction, fibrofatty material accumulation in the intima of the artery wall, smooth muscle cell proliferation, and Th1 inflammation. The opposed T-cell identity of allergy and atherosclerosis implies an atheroprotective role for Th2 cells by counteracting Th1 responses. Yet, the clinical association between allergic disease and CVD argues against it. Within, we review different phases of allergic pathology, basic immunological mechanisms of atherosclerosis and the clinical association between allergic diseases (particularly asthma, atopic dermatitis, allergic rhinitis and food allergy) and CVD. Then, we discuss putative atherogenic mechanisms of type 2 immunity and allergic inflammation including acute allergic reactions (IgE, IgG1, mast cells, macrophages and allergic mediators such as vasoactive components, growth factors and those derived from the complement, contact and coagulation systems) and late phase inflammation (Th2 cells, eosinophils, type 2 innate-like lymphoid cells, alarmins, IL-4, IL-5, IL-9, IL-13 and IL-17).

Monocyte subsets, T cell activation profiles, and stroke in men and women: The Multi-Ethnic Study of Atherosclerosis and Cardiovascular Health Study

BACKGROUND AND AIMS

Despite mechanistic data implicating unresolving inflammation in stroke pathogenesis, data regarding circulating immune cell phenotypes - key determinants of inflammation propagation versus resolution - and incident stroke are lacking. Therefore, we aimed to comprehensively define associations of circulating immune phenotypes and activation profiles with incident stroke.

METHODS

We investigated circulating leukocyte phenotypes and activation profiles with incident adjudicated stroke in 2104 diverse adults from the Multi-Ethnic Study of Atherosclerosis (MESA) followed over a median of 16.6 years. Cryopreserved cells from the MESA baseline examination were thawed and myeloid and lymphoid lineage cell subsets were measured using polychromatic flow cytometry and intracellular cytokine activation staining. We analyzed multivariable-adjusted associations of cell phenotypes, as a proportion of parent cell subsets, with incident stroke (overall) and ischemic stroke using Cox regression models.

RESULTS

We observed associations of intermediate monocytes, early-activated CD4⁺ T cells, and both CD4⁺ and CD8⁺ T cells producing interleukin-4 after cytokine stimulation (T_h2 and T_c2, respectively) with higher risk for incident stroke; effect sizes ranged from 35% to 62% relative increases in risk for stroke. Meanwhile, differentiated and memory T cell phenotypes were associated with lower risk for incident stroke. In sex-stratified analyses, positive and negative associations were especially strong among men but null among women.

CONCLUSIONS

Circulating IL-4 producing T cells and intermediate monocytes were significantly associated with incident stroke over nearly two decades of follow-up. These associations were stronger among men and not among women. Further translational studies are warranted to define more precise targets for prognosis and intervention.

Quantitative Analysis of Tumor-Associated Mast Cells in Recurrent and Non-recurrent Urothelial Bladder Cancer in Stage pTa and pT1

Background

Urothelial carcinoma of the urinary bladder (UCUB) is a common malignancy in both genders with a very high recurrence rate. There has been increasing evidence for a correlation between tumor-associated mast cells (TAMC) and tumor growth and recurrence rates. In the present study, we set out to establish a link between TAMC and the clinical morphological characteristics of UCUB in stages pTa and pT1.

Methodology

A retrospective non-clinical approach was used, with two groups of patients with UCUB. A total of 163 patients were included, 95 in the non-recurrent group and 68 in the recurrent UCUB group. Estimation of TAMC was performed on histological slides from the initial biopsy material using Giemsa and Toluidine blue staining. The collected data were statistically analyzed using the Kaplan-Meier curve, Mann-Whitney test, receiver operating characteristic curve, and chi-square analysis.

Results

Statistical analysis revealed that TAMC in the tumor stroma shows a positive correlation with local recurrence, with no statistical significance to the time of recurrence. No correlation showed statistical significance with pT stage, grade, gender, and age.

Conclusions

The amount of TAMC in UCUB correlates positively with the rate of local recurrence. The depicted correlations are similar to those established in mammary carcinoma, some lymphoproliferative disorders, and pancreatic and prostate malignancies.

Morphological and Histopathological Study of Autopsied Patients with Atherosclerosis and HIV

BACKGROUND

Chronic infection by HIV evolves with a vascular inflammatory action causing endothelial dysfunction. The action of the virus, as well as the side effects of antiretroviral drugs, contribute to the progression of cardiovascular diseases. The present study aimed to evaluate the percentage of collagen fibers and the density of mast cells, chymase and tryptase, in aortas of patients with and without HIV, and also patients with and without atherosclerosis.

METHODS

Aortic fragments were obtained from autopsied patients aged 22-69 years and selected regardless of the cause of death or underlying disease. The samples were divided into four groups, (1) Group with HIV and with atherosclerosis; (2) Group with HIV and without atherosclerosis; (3) Group without HIV and with atherosclerosis; (4) Group without HIV and without atherosclerosis (Control). The percentage of collagen fibers was analyzed in the intima-media layer and the density of mast cells was analyzed in all aortic layers. Graphpad Prism 5.0^® software was used for statistical analysis.

RESULTS

There were more collagen fibers in HIV patients, with or without atherosclerosis. The group with HIV and atherosclerosis presented a higher density of chymase and tryptase mast cells. The correlation between collagen fibers and age was negative in the non-HIV group and with atherosclerosis.

CONCLUSION

The inflammatory process resulting from HIV infection may be relevant in the alteration of aortic collagen fibers and in triggering or accelerating atherosclerosis. The study is important because HIV patients have increased risks for the development of cardiovascular diseases, and follow-up is necessary to prevent such diseases.

Mast cells as a unique hematopoietic lineage and cell system: From Paul Ehrlich's visions to precision medicine concepts

The origin and functions of mast cells (MCs) have been debated since their description by Paul Ehrlich in 1879. MCs have long been considered 'reactive bystanders' and 'amplifiers' in inflammatory processes, allergic reactions, and host responses to infectious diseases. However, knowledge about the origin, phenotypes and functions of MCs has increased substantially over the past 50 years. MCs are now known to be derived from multipotent hematopoietic progenitors, which, through a process of differentiation and maturation, form a unique hematopoietic lineage residing in multiple organs. In particular, MCs are distinguishable from basophils and other hematopoietic cells by their unique phenotype, origin(s), and spectrum of functions, both in innate and adaptive immune responses and in other settings. The concept of a unique MC lineage is further supported by the development of a distinct group of neoplasms, collectively referred to as mastocytosis, in which MC precursors expand as clonal cells. The clinical consequences of the expansion and/or activation of MCs are best established in mastocytosis and in allergic inflammation. However, MCs have also been implicated as important participants in a number of additional pathologic conditions and physiological processes. In this article, we review concepts regarding MC development, factors controlling MC expansion and activation, and some of the fundamental roles MCs may play in both health and disease. We also discuss new concepts for suppressing MC expansion and/or activation using molecularly-targeted drugs.

Analysis of mast cells and myocardial fibrosis in autopsied patients with hypertensive heart disease

OBJECTIVE

To analyze the percentage of collagen fibers and mast cell density in the left ventricular myocardium of autopsied patients with and without hypertensive heart disease.

METHODS

Thirty fragments of left ventricular myocardium were obtained from individuals autopsied at the Clinical Hospital of the Federal University of Triângulo Mineiro (UFTM) in the period from 1987 to 2017. Individuals were divided into two groups: those with hypertensive heart disease (HD) and those with no heart disease (ND). Subjects were also assessed according to age, gender and race (white and non-white). Collagen fibers were quantified by computed morphometry and mast cell density was assessed by immunohistochemical methods.

RESULTS

There were significantly more collagen fibers in the left ventricle in the HD group than in the ND group (p<0.001). Mast cell density was significantly higher in the left ventricle of individuals with HD immunolabeled with anti-chymase and anti-tryptase antibodies (p=0.02) and also of those immunolabeled only with anti-tryptase antibodies (p=0.03). Analyzing the HD group, there was a significant positive correlation between the percentage of collagen fibers in the left ventricle and mast cell density immunolabeled by anti-chymase and anti-tryptase antibodies (p=0.04) and also mast cell density immunolabeled only with anti-tryptase antibodies (p=0.02).

CONCLUSIONS

Mast cells are involved in the development of hypertensive heart disease, contributing to the remodeling of collagen fibers in this disease.

Ca2+ Flux: Searching for a Role in Efferocytosis of Apoptotic Cells in Atherosclerosis

In atherosclerosis, macrophages in the arterial wall ingest plasma lipoprotein-derived lipids and become lipid-filled foam cells with a limited lifespan. Thus, efficient removal of apoptotic foam cells by efferocytic macrophages is vital to preventing the dying foam cells from forming a large necrotic lipid core, which, otherwise, would render the atherosclerotic plaque vulnerable to rupture and would cause clinical complications. Ca2+ plays a role in macrophage migration, survival, and foam cell generation. Importantly, in efferocytic macrophages, Ca2+ induces actin polymerization, thereby promoting the formation of a phagocytic cup necessary for efferocytosis. Moreover, in the efferocytic macrophages, Ca2+ enhances the secretion of anti-inflammatory cytokines. Various Ca2+ antagonists have been seminal for the demonstration of the role of Ca2+ in the multiple steps of efferocytosis by macrophages. Moreover, in vitro and in vivo experiments and clinical investigations have revealed the capability of Ca2+ antagonists in attenuating the development of atherosclerotic plaques by interfering with the deposition of lipids in macrophages and by reducing plaque calcification. However, the regulation of cellular Ca2+ fluxes in the processes of efferocytic clearance of apoptotic foam cells and in the extracellular calcification in atherosclerosis remains unknown. Here, we attempted to unravel the molecular links between Ca2+ and efferocytosis in atherosclerosis and to evaluate cellular Ca2+ fluxes as potential treatment targets in atherosclerotic cardiovascular diseases.

Role of Allergic Inflammatory Cells in Coronary Artery Disease

Inflammation is an important player both for the initiation and progression of coronary artery disease and for coronary plaque instability. Moreover, inflammation contributes to stent thrombosis and in-stent restenosis after percutaneous coronary intervention. In the past several decades, most studies evaluated the involvement of cellular effectors of classic inflammatory responses, such as monocytes/macrophages, neutrophils, and T cells. Yet, besides classic inflammation, mounting evidence derived from both experimental and clinical studies suggests an important, often unrecognized, role for effector cells of allergic inflammation in both the pathogenesis of coronary artery disease and adverse events following stent implantation. In this review, we discuss the role of effector cells of allergic inflammation in the setting of coronary artery disease progression and instability, and in the occurrence of adverse events following stent implantation, as well. Moreover, we discuss possible therapeutic approaches targeting different specific pathways of allergic inflammatory activation.

Mast Cells in Cardiovascular Disease: From Bench to Bedside

Mast cells are pluripotent leukocytes that reside in the mucosa and connective tissue. Recent studies show an increased prevalence of cardiovascular disease among patients with mastocytosis, which is a hematological disease that is characterized by the accumulation of mast cells due to clonal proliferation. This association suggests an important role for mast cells in cardiovascular disease. Indeed, the evidence establishing the contribution of mast cells to the development and progression of atherosclerosis is continually increasing. Mast cells may contribute to plaque formation by stimulating the formation of foam cells and causing a pro-inflammatory micro-environment. In addition, these cells are able to promote plaque instability by neo-vessel formation and also by inducing intraplaque hemorrhage. Furthermore, mast cells appear to stimulate the formation of fibrosis after a cardiac infarction. In this review, the available data on the role of mast cells in cardiovascular disease are summarized, containing both in vitro research and animal studies, followed by a discussion of human data on the association between cardiovascular morbidity and diseases in which mast cells are important: Kounis syndrome, mastocytosis and allergy.

Multifunctional Role of Chymase in Acute and Chronic Tissue Injury and Remodeling

Chymase is the most efficient Ang II (angiotensin II)-forming enzyme in the human body and has been implicated in a wide variety of human diseases that also implicate its many other protease actions. Largely thought to be the product of mast cells, the identification of other cellular sources including cardiac fibroblasts and vascular endothelial cells demonstrates a more widely dispersed production and distribution system in various tissues. Furthermore, newly emerging evidence for its intracellular presence in cardiomyocytes and smooth muscle cells opens an entirely new compartment of chymase-mediated actions that were previously thought to be limited to the extracellular space. This review illustrates how these multiple chymase-mediated mechanisms of action can explain the residual risk in clinical trials of cardiovascular disease using conventional renin-angiotensin system blockade.

Morphological and histopathological evaluation of autopsied patients with hypertensive cardiopathy

BACKGROUND

Physiopathological processes in hypertensive heart disease are controlled by complex interactions between cardiomyocytes, extracellular matrix, microvasculature and other cells present in the myocardium.

OBJECTIVE

To analyze morphological changes in hypertensive cardiopathy and to describe and compare findings in order to help clarify determinant factors.

METHODS

42 fragments of the left ventricular myocardium and circumflex branch of the left coronary artery were obtained from individuals autopsied at the Clinical Hospital of the Federal University of Triângulo Mineiro (UFTM) in the period ranging from 1984 to 2018. Groups were split into individuals with hypertensive heart disease (HD) and individuals without heart disease (ND). Wall thickness was measured with a digital caliper and Computed Tomography. Quantification of collagen fibers was conducted by computerized morphometry and mast cell density was assessed by immunohistochemical methods.

RESULTS

There was a significant increase of heart weight in the HD group compared to the ND group, (p = 0.0002). There was a significant increase of thickness of the middle third of the free wall in the HD group compared to the ND group, (p = 0.04). There was a significant increase of collagen fibers in the left ventricle in the HD group compared to the ND group, (p < 0.0001). Concerning mast cell density, there was a significant increase in the left ventricle of individuals with HD immuno-labeled by the set anti-chymase/anti-tryptase (p < 0.0001). There was a significant increase of mast cell density in the circumflex branch of the left coronary artery of individuals with HD immuno-labeled by the set anti-chymase/anti-tryptase (p = 0.01).

CONCLUSIONS

Mast cells are involved in the development of hypertensive heart disease, contributing to the remodeling of collagen fibers in this disease.

MFAP5 suppression inhibits migration/invasion, regulates cell cycle and induces apoptosis via promoting ROS production in cervical cancer

Cervical cancer is one of the most lethal types of cancer among female. Microfibrillar-associated protein 5 (MFAP5) is an extracellular matrix (ECM) glycoprotein, and is confirmed to be involved in cell signaling during microfibril assembly, elastinogenesis and cell survival. However, the role of MFAP5 in cervical cancer development and progression remains poorly understood. In the study, MFAP5 was over-expressed in human cervical cancers, and in different cervical cancer cell lines. Patients suffering from cervical cancer with low MFAP5 expression exhibited better survival rate. Suppressing MFAP5 in cervical cancer cells markedly reduced the cell proliferation, migration and invasion by modulating epithelial-mesenchymal transition (EMT)-related signaling pathway. In addition, MFAP5 knockdown induced large number of cells distributed in G2/M phase, along with reduced Cyclin B1, Cyclin D1 and cyclin-dependent kinase 4 (CDK4) expressions, and enhanced p21 and p53 levels. Moreover, apoptosis was highly induced by MFAP5 silence through reducing Bcl-xl and Bcl-2 expressions, and promoting Bax, cleaved Caspase-3 and poly (ADP-Ribose) polymerase (PARP) expressions in cervical cancer cells. Reactive oxygen species (ROS) production levels were also higher in MFAP5-knockdown cells, along with Jun-N-terminal kinase (JNK) activation. Importantly, we found that MFAP5 knockdown-inhibited cervical cancer cell growth was dependent on ROS production. Finally, the depletion of MFAP5 prevented cervical cancer progression in vivo. In summary, our study identified a critical role played by MFAP5 in the progression of cervical cancer and the potential mechanisms by which exerted its effects, indicating that targeting MFAP5-related pathways could be conducive to the therapies for cervical cancer.

Mast Cell Interaction with Neutrophils in Human Gastric Carcinomas: Ultrastructural Observations

Aim. The role of mast cells in cell-cell immune interactions has received increasing attention, although their functional interaction with neutrophils still remains to be clarified in tumors. The aim of the present study was to investigate the association between mast cells and neutrophils in a series of gastric carcinomas (GC). Patients and Methods. 52 surgically resected GC specimens were routinely processed for both light and electron microscopy. Only cases showing both mast cells and neutrophils in the tumor stroma were considered in the analysis. Results. Only 9 GC (M : F = 5 : 4; age range: 50–82 years) showed both mast cells and neutrophils in the tumor stroma. At ultrathin sections, we identified heterotypic aggregation and intermingling of mast cells and neutrophils. Mast cells had mature phenotype and showed full complement of granules with homogeneous, scroll, particle, and mixed pattern. In addition, we found normal-appearing or early apoptosis showing neutrophils. Conclusion. Our histological findings showed the likely interaction between mast cells and neutrophils in GC. We hypothesize that the granular content of mast cells may be released in small quantity through a mechanism called “kiss-and-run fusion,” which is alternative to well-known massive anaphylactic or piecemeal degranulation.

Mast cells and acute coronary syndromes: relationship between serum tryptase, clinical outcome and severity of coronary artery disease

Objective

To assess the relationship between serum tryptase and the occurrence of major cardiovascular and cerebrovascular events (MACCE) at 2-year follow-up in patients admitted with acute coronary syndrome (ACS). To compare serum tryptase to other validated prognostic markers (maximum high-sensitivity troponin (hs-Tn), C reactive protein (CRP) levels at admission, Synergy between percutaneous coronary intervention with Taxus and Cardiac Surgery (SYNTAX) score).

Methods

We measured serum tryptase at admission in 140 consecutive patients with ACS and in 50 healthy controls. The patients’ follow-up was maintained for 2 years after discharge. The predictive accuracy of serum tryptase for 2-year MACCE was assessed and compared with hs-Tn, CRP and SYNTAX score.

Results

Serum tryptase levels at admission were significantly higher in patients with ACS compared with the control group (p=0.0351). 2 years after discharge, 28/140 patients (20%) experienced MACCE. Serum tryptase levels, maximum hs-Tn measurements and SYNTAX score were higher in patients who experienced MACCE compared with those without (p<0.0001). Conversely, we found no significant association between MACCE and CRP. The predictive accuracy of serum tryptase for MACCE was set at the cut-off point of 6.7 ng/mL (sensitivity 46%, specificity 84%).

Conclusions

In patients with ACS, serum tryptase measured during index admission is significantly correlated to the development of MACCE up to 2 years, demonstrating a possible long-term prognostic role of this biomarker.

Interaction between allergic asthma and atherosclerosis

Prior studies have established an essential role of mast cells in allergic asthma and atherosclerosis. Mast cell deficiency or inactivation protects mice from allergen-induced airway hyper-responsiveness and diet-induced atherosclerosis, suggesting that mast cells share pathologic activities in both diseases. Allergic asthma and atherosclerosis are inflammatory diseases that contain similar sets of elevated numbers of inflammatory cells in addition to mast cells in the airway and arterial wall, such as macrophages, monocytes, T cells, eosinophils, and smooth muscle cells. Emerging evidence from experimental models and human studies points to a potential interaction between the 2 seemingly unrelated diseases. Patients or mice with allergic asthma have a high risk of developing atherosclerosis or vice versa, despite the fact that asthma is a T-helper (Th)2-oriented disease, whereas Th1 immunity promotes atherosclerosis. In addition to the preferred Th1/Th2 responses that may differentiate the 2 diseases, mast cells and many other inflammatory cells also contribute to their pathogenesis by more than just T cell immunity. Here, we summarize the different roles of airway and arterial wall inflammatory cells and vascular cells in asthma and atherosclerosis and propose an interaction between the 2 diseases, although limited investigations are available to delineate the molecular and cellular mechanisms by which 1 disease increases the risk of the other. Results from mouse allergic asthma and atherosclerosis models and from human population studies lead to the hypothesis that patients with atherosclerosis may benefit from antiasthmatic medications or that the therapeutic regimens targeting atherosclerosis may also alleviate allergic asthma.

Endothelin receptor antagonist macitentan or deletion of mouse mast cell protease 4 delays lesion development in atherosclerotic mice

AIMS

To determine the impact of mixed endothelin receptor antagonist and mouse mast cell protease-4 (mMCP-4) in the development of atherosclerosis in the mouse model.

MATERIALS AND METHODS

Apolipoprotein E (ApoE) KO mice were crossed with mMCP-4 KO mice to generate ApoE/mMCP-4 double KO mice. Atherosclerosis was induced with a normal- or high-fat diet for 12, 27 or 52weeks. Macitentan (30mg/kg/day), a dual ETA/ETB receptor antagonist, was given orally for 6weeks (27week protocol). At sacrifice, aortas and brachiocephalic arteries (BCAs) were collected. En face Sudan IV staining was performed on aortas and BCA sections were subjected to Masson's trichrome stain and α-smooth muscle actin labeling.

KEY FINDINGS

Under normal diet, both macitentan treatment and the absence of mMCP-4 reduced the development of aortic atherosclerotic lesions in 27-week old ApoE KO mice, but mMCP-4 deletion failed to maintain this effect on 52-week old mice. Under high-fat diet (WD), macitentan, but not the absence of mMCP-4, reduced aortic lesion development in ApoE KO mice. On BCA lesions of 27-week old WD mice, macitentan treatment had a small impact while mMCP-4 deletion showed improved features of plaque stability.

SIGNIFICANCE

These results suggest that the inhibition of mMCP-4 reduces lesion spreading in the earlier phases of atherosclerosis development and can help stabilise the more advanced plaque. Macitentan treatment was more effective to prevent lesion spreading but did not improve plaque features to the same extent.

Mast Cell: A Multi-Functional Master Cell

Mast cells are immune cells of the myeloid lineage and are present in connective tissues throughout the body. The activation and degranulation of mast cells significantly modulates many aspects of physiological and pathological conditions in various settings. With respect to normal physiological functions, mast cells are known to regulate vasodilation, vascular homeostasis, innate and adaptive immune responses, angiogenesis, and venom detoxification. On the other hand, mast cells have also been implicated in the pathophysiology of many diseases, including allergy, asthma, anaphylaxis, gastrointestinal disorders, many types of malignancies, and cardiovascular diseases. This review summarizes the current understanding of the role of mast cells in many pathophysiological conditions.

The impact of mast cells on cardiovascular diseases

Mast cells comprise an innate immune cell population, which accumulates in tissues proximal to the outside environment and, upon activation, augments the progression of immunological reactions through the release and diffusion of either pre-formed or newly generated mediators. The released products of mast cells include histamine, proteases, as well as a variety of cytokines, chemokines and growth factors, which act on the surrounding microenvironment thereby shaping the immune responses triggered in various diseased states. Mast cells have also been detected in the arterial wall and are implicated in the onset and progression of numerous cardiovascular diseases. Notably, modulation of distinct mast cell actions using genetic and pharmacological approaches highlights the crucial role of this cell type in cardiovascular syndromes. The acquired evidence renders mast cells and their mediators as potential prognostic markers and therapeutic targets in a broad spectrum of pathophysiological conditions related to cardiovascular diseases.

Chymase inhibition improves vascular dysfunction and survival in stroke-prone spontaneously hypertensive rats

OBJECTIVE

To clarify the role of chymase in hypertension, we evaluated the effect of a chymase inhibitor, TY-51469, on vascular dysfunction and survival in stroke-prone spontaneously hypertensive rats (SHR-SP).

METHODS

SHR-SP were treated with TY-51469 (1 mg/kg per day) or placebo from 4 to 12 weeks old or until death. Wistar-Kyoto rats were used as a normal group.

RESULTS

SBP was significantly higher in both the placebo and TY-51469 groups than in the normal group, but there was no significant difference between the two treatment groups. Plasma renin, angiotensin-converting enzyme activity and angiotensin II levels were not different between the placebo and TY-51469 groups. In contrast, vascular chymase-like activity was significantly higher in the placebo than in the normal group, but it was reduced by TY-51469. Acetylcholine-induced vascular relaxation was significantly higher in the TY-51469 group than in the placebo group. There was significant augmentation of the number of monocytes/macrophages and matrix metalloproteinase-9 activity in aortic tissue from the placebo group compared with the normal group, and these changes were attenuated by TY-51469. There were also significant increases in mRNA levels of monocyte chemoattractant protein-1 and tumor necrosis factor-α in the placebo group that were attenuated by TY-51469. Cumulative survival was significantly prolonged in the TY-51469 group compared with the placebo group.

CONCLUSION

Chymase might play an important role in vascular dysfunction via augmentation both of matrix metalloproteinase-9 activity and monocyte/macrophage accumulation in SHR-SP, and its inhibition may be useful for preventing vascular remodeling and prolonging survival.

IgE actions on CD4+ T cells, mast cells, and macrophages participate in the pathogenesis of experimental abdominal aortic aneurysms

Immunoglobulin E (IgE) activates mast cells (MCs). It remains unknown whether IgE also activates other inflammatory cells, and contributes to the pathogenesis of abdominal aortic aneurysms (AAAs). This study demonstrates that CD4⁺ T cells express IgE receptor FcεR1, at much higher levels than do CD8⁺ T cells. IgE induces CD4⁺ T-cell production of IL6 and IFN-γ, but reduces their production of IL10. FcεR1 deficiency (Fcer1a^−/−) protects apolipoprotein E-deficient (Apoe^−/−) mice from angiotensin-II infusion-induced AAAs and reduces plasma IL6 levels. Adoptive transfer of CD4⁺ T cells (but not CD8⁺ T cells), MCs, and macrophages from Apoe^−/− mice, but not those from Apoe^−/−Fcer1a^−/− mice, increases AAA size and plasma IL6 in Apoe^−/−Fcer1a^−/− recipient mice. Biweekly intravenous administration of an anti-IgE monoclonal antibody ablated plasma IgE and reduced AAAs in Apoe^−/− mice. Patients with AAAs had significantly higher plasma IgE levels than those without AAAs. This study establishes an important role of IgE in AAA pathogenesis by activating CD4⁺ T cells, MCs, and macrophages and supports consideration of neutralizing plasma IgE in the therapeutics of human AAAs.

The role of mast cells in atherosclerosis

Rupture of an atherosclerotic plaque is the major underlying cause of adverse cardiovascular events such as myocardial infarction or stroke. Therapeutic interventions should therefore be directed towards inhibiting growth of atherosclerotic lesions as well as towards prevention of lesion destabilization. Interestingly, the presence of mast cells has been demonstrated in both murine and human plaques, and multiple interventional murine studies have pointed out a direct role for mast cells in early and late stages of atherosclerosis. Moreover, it has recently been described that activated lesional mast cells correlate with major cardiovascular events in patients suffering from cardiovascular disease. This review focuses on the effect of different mast cell derived mediators in atherogenesis and in late stage plaque destabilization. Also, possible ligands for mast cell activation in the context of atherosclerosis are discussed. Finally, we will elaborate on the predictive value of mast cells, together with therapeutic implications, in cardiovascular disease.

Tumor necrosis factor-related apoptosis-inducing ligand in vascular inflammation and atherosclerosis: a protector or culprit?

In addition to inducing tumor cell apoptosis, tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) shows broad biological functions both in vitro and in vivo. TRAIL gene deletion enhanced atherogenesis in hyperlipidemic mice, supporting that endogenous TRAIL has protective actions in maintaining blood vessel homeostasis and repressing atherosclerosis. The mechanisms of this beneficial effect are not understood. It remains to be determined whether the athero-protective action of TRAIL is via direct impacts on residential vascular cells or indirectly by modulating systemic immune functions. However, in vitro experiments indicate that excessive TRAIL may stimulate endothelial cell apoptosis, smooth muscle proliferation and migration, and inflammatory responses. Moreover, TRAIL can stimulate lipid uptake and foam cell formation in cultured macrophages. Here we provide a critical review on the potential relationships between TRAIL and atherosclerosis. We propose that increased TRAIL production may also have potential detrimental effects on vascular inflammation and atherosclerosis. Further in vivo experiments are warranted to elucidate the effects of exogenous TRAIL on atherogenesis.

Mast cells as effectors in atherosclerosis

The mast cell is a potent immune cell known for its functions in host defense responses and diseases, such as asthma and allergies. In the past years, accumulating evidence established the contribution of the mast cell to cardiovascular diseases as well, in particular, by its effects on atherosclerotic plaque progression and destabilization. Through its release not only of mediators, such as the mast cell-specific proteases chymase and tryptase, but also of growth factors, histamine, and chemokines, activated mast cells can have detrimental effects on its immediate surroundings in the vessel wall. This results in matrix degradation, apoptosis, and enhanced recruitment of inflammatory cells, thereby actively contributing to cardiovascular diseases. In this review, we will discuss the current knowledge on mast cell function in cardiovascular diseases and speculate on potential novel therapeutic strategies to prevent acute cardiovascular syndromes via targeting of mast cells.

An agent-based model of the response to angioplasty and bare-metal stent deployment in an atherosclerotic blood vessel

PURPOSE

While animal models are widely used to investigate the development of restenosis in blood vessels following an intervention, computational models offer another means for investigating this phenomenon. A computational model of the response of a treated vessel would allow investigators to assess the effects of altering certain vessel- and stent-related variables. The authors aimed to develop a novel computational model of restenosis development following an angioplasty and bare-metal stent implantation in an atherosclerotic vessel using agent-based modeling techniques. The presented model is intended to demonstrate the body's response to the intervention and to explore how different vessel geometries or stent arrangements may affect restenosis development.

METHODS

The model was created on a two-dimensional grid space. It utilizes the post-procedural vessel lumen diameter and stent information as its input parameters. The simulation starting point of the model is an atherosclerotic vessel after an angioplasty and stent implantation procedure. The model subsequently generates the final lumen diameter, percent change in lumen cross-sectional area, time to lumen diameter stabilization, and local concentrations of inflammatory cytokines upon simulation completion. Simulation results were directly compared with the results from serial imaging studies and cytokine levels studies in atherosclerotic patients from the relevant literature.

RESULTS

The final lumen diameter results were all within one standard deviation of the mean lumen diameters reported in the comparison studies. The overlapping-stent simulations yielded results that matched published trends. The cytokine levels remained within the range of physiological levels throughout the simulations.

CONCLUSION

We developed a novel computational model that successfully simulated the development of restenosis in a blood vessel following an angioplasty and bare-metal stent deployment based on the characteristics of the vessel cross-section and stent. A further development of this model could ultimately be used as a predictive tool to depict patient outcomes and inform treatment options.

Generation of a new congenic mouse strain with enhanced chymase expression in mast cells

Mast cells are effector cells best known for their roles in IgE-associated allergy, but they also play a protective role in defense against pathogens. These cells express high levels of proteases including chymase, tryptase and carboxypeptidase. In the present study, we identified a congenic strain of C57BL/6 mice expressing an extraordinarily high level of chymases Mcp-2 and Mcp-4 in mast cells. The overexpression was associated with variant Mcp-2 and Mcp-4 genes originated from DBA/2 mice that also expressed high levels of the two enzymes. Real time PCR analysis revealed that Mcp-2 and Mcp-4 were selectively overexpressed as tryptases, Cpa3 and several other chymases were kept at normal levels. Reporter gene assays demonstrated that single-nucleotide polymorphisms (SNPs) in the promoter region of Mcp-2 gene may be partly responsible for the increased gene transcription. Our study provides a new model system to study the function of mast cell chymases. The data also suggest that expression of chymases differs considerably in different strains of mice and the increased chymase activity may be responsible for some unique phenotypes observed in DBA/2 mice.

Relationship between numerous mast cells and early follicular development in neonatal MRL/MpJ mouse ovaries

In the neonatal mouse ovary, clusters of oocytes called nests break into smaller cysts and subsequently form individual follicles. During this period, we found numerous mast cells in the ovary of MRL/MpJ mice and investigated their appearance and morphology with follicular development. The ovarian mast cells, which were already present at postnatal day 0, tended to localize adjacent to the surface epithelium. Among 11 different mouse strains, MRL/MpJ mice possessed the greatest number of ovarian mast cells. Ovarian mast cells were also found in DBA/1, BALB/c, NZW, and DBA/2 mice but rarely in C57BL/6, NZB, AKR, C3H/He, CBA, and ICR mice. The ovarian mast cells expressed connective tissue mast cell markers, although mast cells around the surface epithelium also expressed a mucosal mast cell marker in MRL/MpJ mice. Some ovarian mast cells migrated into the oocyte nests and directly contacted the compressed and degenerated oocytes. In MRL/MpJ mice, the number of oocytes in the nest was significantly lower than in the other strains, and the number of oocytes showed a positive correlation with the number of ovarian mast cells. The gene expression of a mast cell marker also correlated with the expression of an oocyte nest marker, suggesting a link between the appearance of ovarian ? 4mast cells and early follicular development. Furthermore, the expression of follicle developmental markers was significantly higher in MRL/MpJ mice than in C57BL/6 mice. These results indicate that the appearance of ovarian mast cells is a unique phenotype of neonatal MRL/MpJ mice, and that ovarian mast cells participate in early follicular development, especially nest breakdown.

Mast cell chymase and tryptase as targets for cardiovascular and metabolic diseases

Mast cells are critical effectors in inflammatory diseases, including cardiovascular and metabolic diseases and their associated complications. These cells exert their physiological and pathological activities by releasing granules containing histamine, cytokines, chemokines, and proteases, including mast cell-specific chymases and tryptases. Several recent human and animal studies have shown direct or indirect participation of mast cell-specific proteases in atherosclerosis, abdominal aortic aneurysms, obesity, diabetes, and their complications. Animal studies have demonstrated the beneficial effects of highly selective and potent chymase and tryptase inhibitors in several experimental cardiovascular and metabolic diseases. In this review, we summarize recent discoveries from in vitro cell-based studies to experimental animal disease models, from protease knockout mice to treatments with recently developed selective and potent protease inhibitors, and from patients with preclinical disorders to those affected by complications. We hypothesize that inhibition of chymases and tryptases would benefit patients suffering from cardiovascular and metabolic diseases.

Involvement of mast cell chymase in burn wound healing in hamsters

Mast cells play a significant role in the late stage of wound healing following burn injuries. In the present study, the possible role of mast cell chymase in burn wound healing was examined using a mast cell membrane stabilizer, ketotifen, in hamsters. A total of 28 hamsters were randomly divided into two groups (n=14), termed as the control and ketotifen groups. A deep partial-thickness burn injury was made on the back skin of the hamsters. The control group was orally administered physiological saline (1 ml) and the ketotifen group was orally administered ketotifen (4 mg/kg) once daily, two days prior to and two days subsequent to the burn. The results showed that concentrations of angiotensin II (Ang II), TGF-β1, collagens I and III and interleukin (IL)-1β were significantly decreased in the ketotifen group compared with those in the control group. However, there was no significant difference in fibroblast apoptosis between the two groups. The release of mast cell chymase was inhibited by the mast cell membrane stabilizer ketotifen. Taken together, these results suggest that mast cell chymase may participate in the process of burn wound healing. Chymase may therefore be a promising therapeutic target for the treatment of burn wounds.

Complement factor C5a as mast cell activator mediates vascular remodelling in vein graft disease

AIMS

Failure of vein graft conduits due to vein graft thickening, accelerated atherosclerosis, and subsequent plaque rupture is applicable to 50% of all vein grafts within 10 years. New potential therapeutic targets to treat vein graft disease may be found in components of the innate immune system, such as mast cells and complement factors, which are known to be involved in atherosclerosis and plaque destabilization. Interestingly, mast cells can be activated by complement factor C5a and, therefore, a direct role for C5a-mediated mast cell activation in vein graft disease is anticipated. We hypothesize that C5a-mediated mast cell activation is involved in the development and destabilization of vein graft lesions.

METHODS AND RESULTS

Mast cells accumulated in time in murine vein graft lesions, and C5a and C5a-receptor (CD88) expression was up-regulated during vein graft disease in apolipoprotein E-deficient mice. Mast cell activation with dinitrophenyl resulted in a profound increase in vein graft thickening and in the number of plaque disruptions. C5a application enhanced vein graft lesion formation, while treatment with a C5a-receptor antagonist resulted in decreased vein graft disease. C5a most likely exerts its function via mast cell activation since the mast cell inhibitor cromolyn totally blocked C5a-enhanced vein graft disease.

CONCLUSION

These data provide evidence that complement factor C5a-induced mast cell activation is highly involved in vein graft disease, which identifies new targets to prevent vein graft disease.

Mast cell chymase and tryptase in abdominal aortic aneurysm formation

Mast cells (MCs) are implicated in the pathogenesis of atherosclerosis and abdominal aortic aneurysm (AAA). MC-specific chymase and tryptase play important roles in inducing endothelial cell expression of adhesion molecules and chemokines to promote leukocyte recruitment, degrading matrix proteins and activating protease-activated receptors to trigger smooth muscle cell apoptosis, and activating other proteases to degrade medial elastin and to enhance angiogenesis. In experimental AAA, the absence or pharmacological inhibition of chymase or tryptase reduced AAA formation and associated arterial pathologies, proving that these MC proteases participate directly in AAA formation. Increased levels of these proteases in human AAA lesions and in plasma from AAA patients suggest that these proteases are also essential to human AAA pathogenesis. Development of chymase or tryptase inhibitors or their antibodies may have therapeutic potential among affected human subjects.

Chemokine (C-C motif) receptor 2 mediates mast cell migration to abdominal aortic aneurysm lesions in mice

AIMS

Mast cells participate importantly in abdominal aortic aneurysms (AAAs) by releasing inflammatory cytokines to promote vascular cell protease expression and arterial wall remodelling. Mast cells accumulate in AAA lesions during disease progression, but the exact chemokines by which mast cells migrate to the site of vascular inflammation remain unknown. This study tested the hypothesis that mast cells use chemokine (C-C motif) receptor 2 (CCR2) for their accumulation in experimental mouse AAA lesions.

METHODS AND RESULTS

We generated mast cell and apolipoprotein E double-deficient (Apoe(-/-)Kit(W-sh/W-sh)) mice and found that they were protected from angiotensin II (Ang II) chronic infusion-induced AAAs compared with Apoe(-/-) littermates. Using bone-marrow derived mast cells (BMMC) from Apoe(-/-) mice and CCR2 double-deficient (Apoe(-/-)Ccr2(-/-)) mice, we demonstrated that Apoe(-/-)Kit(W-sh/W-sh) mice receiving BMMC from Apoe(-/-)Ccr2(-/-) mice, but not those from Apoe(-/-) mice, remained protected from AAA formation. Adoptive transfer of BMMC from Apoe(-/-) mice into Apoe(-/-)Kit(W-sh/W-sh) mice also increased lesion content of macrophages, T cells, and MHC class II-positive cells; there was also increased apoptosis, angiogenesis, cell proliferation, elastin fragmentation, and medial smooth muscle cell loss. In contrast, adoptive transfer of BMMC from Apoe(-/-)Ccr2(-/-) mice into Apoe(-/-)Kit(W-sh/W-sh) mice did not affect these variables.

CONCLUSIONS

The increased AAA formation and associated lesion characteristics in Apoe(-/-)Kit(W-sh/W-sh) mice after receiving BMMC from Apoe(-/-) mice, but not from Apoe(-/-)Ccr2(-/-) mice, suggests that mast cells use CCR2 as the chemokine receptor for their recruitment in Ang II-induced mouse AAA lesions.

Role of mast cell chymase and tryptase in the progression of atherosclerosis: study in 44 autopsied cases

The aim of this study was to describe the role of mast cell chymase and tryptase in the progression of atherosclerosis. Forty-four sections of aortas were obtained from autopsies. We assessed the macroscopic degree of atherosclerosis, microscopic intensity of lipid deposition in the tunica intima, percentage of collagen in the tunica intima, and density of immunostained mast cells. There was no significant difference between the density of mast cell tryptase and chymase concerning ethnicity, sex, cause of death, or degree of atherosclerosis. The density of mast cell chymase was significantly higher in the nonelderly group. The percentage of collagen was significantly higher in elderly patients. There was a positive and significant correlation between the degree of macroscopic atherosclerosis and lipidosis, the density of mast cell chymase and the percentage of collagen, the density of mast cell tryptase and the percentage of collagen, and lipidosis and the density of mast cell tryptase. The degree of macroscopic lesion of atherosclerosis increased proportionally with the increase in the density of mast cell chymase and tryptase and in the intensity of lipid deposition and with the percentage of collagen in the atherosclerotic plaques. Thus, mast cells may play a crucial role in aggravating atherosclerotic lesions.

Emerging role of mast cells and macrophages in cardiovascular and metabolic diseases

Mast cells are essential in allergic immune responses. Recent discoveries have revealed their direct participation in cardiovascular diseases and metabolic disorders. Although more sophisticated mechanisms are still unknown, data from animal studies suggest that mast cells act similarly to macrophages and other inflammatory cells and contribute to human diseases through cell-cell interactions and the release of proinflammatory cytokines, chemokines, and proteases to induce inflammatory cell recruitment, cell apoptosis, angiogenesis, and matrix protein remodeling. Reduced cardiovascular complications and improved metabolic symptoms in animals receiving over-the-counter antiallergy medications that stabilize mast cells open another era of mast cell biology and bring new hope to human patients suffering from these conditions.

Tributyltin impairs the coronary vasodilation induced by 17β-estradiol in isolated rat heart

Triorganotins, such as tributyltin (TBT), are environmental contaminants that are commonly used as antifouling agents for boats. However, TBT is also known to alter mammalian reproductive functions. Although the female sex hormones are primarily involved in the regulation of reproductive functions, 17β-estradiol also protects against cardiovascular diseases, in that this hormone reduces the incidence of coronary artery disease via coronary vasodilation. The aim of this study was to examine the influence of 100 ng/kg TBT administered daily by oral gavage for 15 d on coronary functions in female Wistar rats. Findings were correlated with changes in sex steroids concentrations. Tributyltin significantly increased the baseline coronary perfusion pressure and impaired vasodilation induced by 17β-estradiol. In addition, TBT markedly decreased serum 17β-estradiol levels accompanied by a significant rise in serum progesterone levels. Tributyltin elevated collagen deposition in the heart interstitium and number of mast cells proximate to the cardiac vessels. There was a positive correlation between the increase in coronary perfusion pressure and incidence of cardiac hypertrophy. In addition, TBT induced endothelium denudation (scanning electron microscopy) and accumulation of platelets. Moreover, TBT impaired coronary vascular reactivity to estradiol (at least in part), resulting in endothelial denudation, enhanced collagen deposition and elevated number of mast cells. Taken together, the present results demonstrate that TBT exposure may be a potential risk factor for cardiovascular disorders in rats.

Association between SNP rs1800875, serum chymase and immunoglobulin E levels in patients with coronary heart disease

OBJECTIVE

The gene for mast cell chymase (CMA1) is an ideal candidate for investigating the genetic predisposition to coronary heart disease (CHD), as activated mast cells have been found to be present in a greater proportion in the shoulder region of atheroma than in normal coronary intimae. Previous studies have indicated that CMA1 promoter polymorphism rs1800875 may be involved in regulating immunoglobulin E (IgE) levels in patients with eczema, and it is associated with the progression of immunoglobulin A nephropathy.

METHODS

The association between single nucleotide polymorphism (SNP) rs1800875, serum chymase, and serum IgE levels was examined in 175 CHD subjects and 95 non-CHD subjects.

RESULTS

Statistical analysis indicated no significant difference in allele frequency between CHD and non-CHD. However, a significant association was found between CMA1 genotypes and total IgE levels in CHD subjects. Meanwhile, crossover analysis revealed that, in GG homozygotes, CHD risk was nearly six times higher in those with IgE (U/ml) level <2.58 (natural logarithm conversion), while no association was found with chymase level.

CONCLUSIONS

Polymorphism rs1800875 of CMA1 may be associated with serum IgE level in CHD subjects, but not with chymase level in both groups. In GG homozygotes, high IgE level is a protective factor against coronary disease.

Cysteinyl cathepsins and mast cell proteases in the pathogenesis and therapeutics of cardiovascular diseases

The initiation and progression of cardiovascular diseases involve extensive arterial wall matrix protein degradation. Proteases are essential to these pathological events. Recent discoveries suggest that proteases do more than catabolize matrix proteins. During the pathogenesis of atherosclerosis, abdominal aortic aneuryms, and associated complications, cysteinyl cathepsins and mast cell tryptases and chymases participate importantly in vascular cell apoptosis, foam cell formation, matrix protein gene expression, and pro-enzyme, latent cytokine, chemokine, and growth factor activation. Experimental animal disease models have been invaluable in examining each of these protease functions. Deficiency and pharmacological inhibition of cathepsins or mast cell proteases have allowed their in vivo evaluation in the setting of pathological conditions. Recent discoveries of highly selective and potent inhibitors of cathepsins, chymase, and tryptase, and their applications in vascular diseases in animal models and non-vascular diseases in human trials, have led to the hypothesis that selective inhibition of cathepsins, chymases, and tryptase will benefit patients suffering from cardiovascular diseases. This review highlights recent discoveries from in vitro cell-based studies to experimental animal cardiovascular disease models, from protease knockout mice to treatments with recently developed selective and potent protease inhibitors, and from patients with cathepsin-associated non-vascular diseases to those affected by cardiovascular complications.

Mast cells in atherosclerosis

The mast cell, a potent inflammatory cell type, is widely distributed over several tissues, but particularly prominent at the interface exposed to the environment to act in the first line of defense against pathogens. Upon activation mast cells release granules, which contain a large panel of mediators, including neutral proteases (e.g. chymase and tryptase), cathepsins, heparin, histamine and a variety of cytokines and growth factors. While mast cells have been demonstrated to be critically involved in a number of Th2 dominated diseases such as asthma and allergy, recent investigations have now also implicated mast cells in the pathogenesis of atherosclerosis and acute cardiovascular syndromes. In this review, we will discuss the contribution of mast cells to the initiation and progression of atherosclerosis and gauge the therapeutic opportunities of mast cell targeted intervention in acute cardiovascular syndromes.