The association of mast cells and atherosclerosis: a morphologic study of early atherosclerotic lesions in young people

Targeting gut microbiota and immune crosstalk: potential mechanisms of natural products in the treatment of atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory reaction that primarily affects large and medium-sized arteries. It is a major cause of cardiovascular disease and peripheral arterial occlusive disease. The pathogenesis of AS involves specific structural and functional alterations in various populations of vascular cells at different stages of the disease. The immune response is involved throughout the entire developmental stage of AS, and targeting immune cells presents a promising avenue for its treatment. Over the past 2 decades, studies have shown that gut microbiota (GM) and its metabolites, such as trimethylamine-N-oxide, have a significant impact on the progression of AS. Interestingly, it has also been reported that there are complex mechanisms of action between GM and their metabolites, immune responses, and natural products that can have an impact on AS. GM and its metabolites regulate the functional expression of immune cells and have potential impacts on AS. Natural products have a wide range of health properties, and researchers are increasingly focusing on their role in AS. Now, there is compelling evidence that natural products provide an alternative approach to improving immune function in the AS microenvironment by modulating the GM. Natural product metabolites such as resveratrol, berberine, curcumin, and quercetin may improve the intestinal microenvironment by modulating the relative abundance of GM, which in turn influences the accumulation of GM metabolites. Natural products can delay the progression of AS by regulating the metabolism of GM, inhibiting the migration of monocytes and macrophages, promoting the polarization of the M2 phenotype of macrophages, down-regulating the level of inflammatory factors, regulating the balance of Treg/Th17, and inhibiting the formation of foam cells. Based on the above, we describe recent advances in the use of natural products that target GM and immune cells crosstalk to treat AS, which may bring some insights to guide the treatment of AS.

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.

Inflammatory Cells in Atherosclerosis

Atherosclerosis is a chronic progressive disease that involves damage to the intima, inflammatory cell recruitment and the accumulation of lipids followed by calcification and plaque rupture. Inflammation is considered a key mediator of many events during the development and progression of the disease. Various types of inflammatory cells are reported to be involved in atherosclerosis. In the present paper, we discuss the involved inflammatory cells, their characteristic and functional significance in the development and progression of atherosclerosis. The detailed understanding of the role of all these cells in disease progression at different stages sheds more light on the subject and provides valuable insights as to where and when therapy should be targeted.

Innate and adaptive immunity: the understudied driving force of heart valve disease

Calcific aortic valve disease (CAVD), and its clinical manifestation that is calcific aortic valve stenosis, is the leading cause for valve disease within the developed world, with no current pharmacological treatment available to delay or halt its progression. Characterized by progressive fibrotic remodelling and subsequent pathogenic mineralization of the valve leaflets, valve disease affects 2.5% of the western population, thus highlighting the need for urgent intervention. Whilst the pathobiology of valve disease is complex, involving genetic factors, lipid infiltration, and oxidative damage, the immune system is now being accepted to play a crucial role in pathogenesis and disease continuation. No longer considered a passive degenerative disease, CAVD is understood to be an active inflammatory process, involving a multitude of pro-inflammatory mechanisms, with both the adaptive and the innate immune system underpinning these complex mechanisms. Within the valve, 15% of cells evolve from haemopoietic origin, and this number greatly expands following inflammation, as macrophages, T lymphocytes, B lymphocytes, and innate immune cells infiltrate the valve, promoting further inflammation. Whether chronic immune infiltration or pathogenic clonal expansion of immune cells within the valve or a combination of the two is responsible for disease progression, it is clear that greater understanding of the immune systems role in valve disease is required to inform future treatment strategies for control of CAVD development.

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.

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.

An autopsy case of sudden unexpected death with loxoprofen sodium-induced allergic eosinophilic coronary periarteritis

Although the cause of eosinophilic coronary periarteritis (ECPA) remains unclear, an allergic background is present in fewer patients than expected. A 50-year-old man with no history of allergy or symptoms suggestive of cardiac or respiratory disorders suddenly died shortly after oral administration of loxoprofen sodium. Autopsy showed eosinophilic coronary periarteritis in three main branches of the coronary arteries, characterized by eosinophil-predominant inflammation without fibrinoid necrosis or granulomatous change in the adventitia and its surroundings of the three main branches of the coronary arteries, in addition to the localized sign of bronchial asthma in the lung. Immunohistochemical examination showed that many mast cells positive for human mast cell tryptase were evident in the perivascular tissue containing peripheral nerve trunks. Whereas the blood concentration of loxoprofen sodium was within the therapeutic range, significant elevation of the serum histamine and tryptase levels was found. The present case suggests that eosinophilic coronary periarteritis may be caused by a type I allergic reaction in some patients and that loxoprofen sodium can trigger a life-threatening type I allergic reaction, including eosinophilic coronary periarteritis, leading to sudden unexpected death.

Mast Cells as Potential Accelerators of Human Atherosclerosis-From Early to Late Lesions

Mast cells are present in atherosclerotic lesions throughout their development. The process of atherogenesis itself is characterized by infiltration and retention of cholesterol-containing blood-derived low-density lipoprotein (LDL) particles in the intimal layer of the arterial wall, where the particles become modified and ingested by macrophages, resulting in the formation of cholesterol-filled foam cells. Provided the blood-derived high-density lipoproteins (HDL) particles are able to efficiently carry cholesterol from the foam cells back to the circulation, the early lesions may stay stable or even disappear. However, the modified LDL particles also trigger a permanent local inflammatory reaction characterized by the presence of activated macrophages, T cells, and mast cells, which drive lesion progression. Then, the HDL particles become modified and unable to remove cholesterol from the foam cells. Ultimately, the aging foam cells die and form a necrotic lipid core. In such advanced lesions, the lipid core is separated from the circulating blood by a collagenous cap, which may become thin and fragile and susceptible to rupture, so causing an acute atherothrombotic event. Regarding the potential contribution of mast cells in the initiation and progression of atherosclerotic lesions, immunohistochemical studies in autopsied human subjects and studies in cell culture systems and in atherosclerotic mouse models have collectively provided evidence that the compounds released by activated mast cells may promote atherogenesis at various steps along the path of lesion development. This review focuses on the presence of activated mast cells in human atherosclerotic lesions. Moreover, some of the molecular mechanisms potentially governing activation and effector functions of mast cells in such lesions are presented and discussed.

Mast cell tryptase - Marker and maker of cardiovascular diseases

Mast cells are tissue-resident cells, which have been proposed to participate in various inflammatory diseases, among them the cardiovascular diseases (CVDs). For mast cells to be able to contribute to an inflammatory process, they need to be activated to exocytose their cytoplasmic secretory granules. The granules contain a vast array of highly bioactive effector molecules, the neutral protease tryptase being the most abundant protein among them. The released tryptase may act locally in the inflamed cardiac or vascular tissue, so contributing directly to the pathogenesis of CVDs. Moreover, a fraction of the released tryptase reaches the systemic circulation, thereby serving as a biomarker of mast cell activation. Actually, increased levels of circulating tryptase have been found to associate with CVDs. Here we review the biological relevance of the circulating tryptase as a biomarker of mast cell activity in CVDs, with special emphasis on the relationship between activation of mast cells in their tissue microenvironments and the pathophysiological pathways of CVDs. Based on the available in vitro and in vivo studies, we highlight the potential molecular mechanisms by which tryptase may contribute to the pathogenesis of CVDs. Finally, the synthetic and natural inhibitors of tryptase are reviewed for their potential utility as therapeutic agents in CVDs.

Immunobiology of Inherited Muscular Dystrophies

The immune response to acute muscle damage is important for normal repair. However, in chronic diseases such as many muscular dystrophies, the immune response can amplify pathology and play a major role in determining disease severity. Muscular dystrophies are inheritable diseases that vary tremendously in severity, but share the progressive loss of muscle mass and function that can be debilitating and lethal. Mutations in diverse genes cause muscular dystrophy, including genes that encode proteins that maintain membrane strength, participate in membrane repair, or are components of the extracellular matrix or the nuclear envelope. In this article, we explore the hypothesis that an important feature of many muscular dystrophies is an immune response adapted to acute, infrequent muscle damage that is misapplied in the context of chronic injury. We discuss the involvement of the immune system in the most common muscular dystrophy, Duchenne muscular dystrophy, and show that the immune system influences muscle death and fibrosis as disease progresses. We then present information on immune cell function in other muscular dystrophies and show that for many muscular dystrophies, release of cytosolic proteins into the extracellular space may provide an initial signal, leading to an immune response that is typically dominated by macrophages, neutrophils, helper T-lymphocytes, and cytotoxic T-lymphocytes. Although those features are similar in many muscular dystrophies, each muscular dystrophy shows distinguishing features in the magnitude and type of inflammatory response. These differences indicate that there are disease-specific immunomodulatory molecules that determine response to muscle cell damage caused by diverse genetic mutations. © 2018 American Physiological Society. Compr Physiol 8:1313-1356, 2018.

Inhibition of hepatic apolipoprotein A-I gene expression by histamine

In a recent high throughput analysis to identify drugs that alter hepatic apolipoprotein A-I (apo A-I) expression, histamine receptor one (H₁) antagonists emerged as potential apo A-1 inducing drugs. Thus the present study was undertaken to identify some of the underlying molecular mechanisms of the effect of antihistaminic drugs on apo AI production. Apo A-I levels were measured by enzyme immunoassay and Western blots. Apo A-I mRNA levels were measured by reverse transcription real-time PCR using glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA as the internal control. The effects of histamine and antihistamines on apo A-I gene were determined by transient transfection of plasmids containing the apo A-I gene promoter. Histamine repressed while (H₁) receptor antagonist azelastine increased apo A-I protein and mRNA levels within 48 h in a dose-dependent manner. Azelastine and histamine increased and suppressed, respectively, apo A-I gene promoter activity through a peroxisome proliferator activated receptor α response element. Treatment of HepG2 cells with other H₁ receptor antagonists including fexofenadine, cetirizine, and diphenhydramine increased apo A-I levels in a dose-dependent manner while treatment with H₂ receptor antagonists including cimetidine, famotidine, and ranitidine had no effect. We conclude that H₁ receptor signaling is a novel pathway of apo A1 gene expression and therefore could be an important therapeutic target for enhancing de-novo apo A-1 synthesis.

NF-κB inhibitors that prevent foam cell formation and atherosclerotic plaque accumulation

The transformation of monocyte-derived macrophages into lipid-laden foam cells is one inflammatory process underlying atherosclerotic disease. Previous studies have demonstrated that fullerene derivatives (FDs) have inflammation-blunting properties. Thus, it was hypothesized that FD could inhibit the transformation process underlying foam cell formation. Fullerene derivatives inhibited the phorbol myristic acid/oxidized low-density lipoprotein-induced differentiation of macrophages into foam cells as determined by lipid staining and morphology.Lipoprotein-induced generation of TNF-α, C5a-induced MC activation, ICAM-1 driven adhesion, and CD36 expression were significantly inhibited in FD treated cells compared to non-treated cells. Inhibition appeared to be mediated through the NF-κB pathway as FD reduced expression of NF-κB and atherosclerosis-associated genes. Compared to controls, FD dramatically inhibited plaque formation in arteries of apolipoprotein E null mice. Thus, FD may be an unrecognized therapy to prevent atherosclerotic lesions via inhibition of foam cell formation and MC stabilization.

Low-density lipoprotein transport through an arterial wall under hypertension - A model with time and pressure dependent fraction of leaky junction consistent with experiments

The influence of hypertension on low-density lipoproteins intake into the arterial wall is an important factor for understanding mechanisms of atherosclerosis. It has been experimentally observed that the increased pressure leads to the higher level of the LDL inside the wall. In this paper we attempt to construct a model of the LDL transport which reproduces quantitatively experimental outcomes. We supplement the well-known four-layer arterial wall model to include two pressure induced effects: the compression of the intima tissue and the increase of the fraction of leaky junctions. We demonstrate that such model can reach the very good agreement with experimental data.

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.

Selective IgE deficiency and cardiovascular diseases

Selective immunoglobulin E (IgE) deficiency (IgED) is defined as serum levels of IgE more than or equal to 2 kIU/L and is associated with immune dysregulation and autoimmunity. This study aimed to investigate a prevalence of atherosclerotic cardiovascular disease (ASCVD) in population with IgED. Within the electronic patient record (EPR) database of Leumit Health Care Services (LHS) in Israel, data capture was performed using IBM Cognos 10.1.1 BI Report Studio software. The case samples were drawn from the full study population (n = 18,487), having any allergy-related symptoms and/or those requesting antiallergy medications and performed serum total IgE measurement during 2012 at LHS. All subjects aged more than or equal to 40 years old, with serum total IgE less than 2 kIU/L were included in case group. Control group was randomly sampled from the remained subjects, with a case-control ratio of 10 controls for each case (1:10). The comorbid cardiovascular diseases during less than or equal to 10 years before serum total IgE testing were identified and retrieved using specific International Classification of Diseases, 9th Revision, Clinical Modification diagnostic codes. There were 103 in case and 1030 subjects in control group. Compared with control group patients, the case group had significantly more arterial hypertension [34 (37.7%) versus 187 (18.2%), p < 0.001], ischemic heart disease (IHD) [26 (25.2%) versus 87 (8.4%), p < 0.001], carotid stenosis [5 (4.9%) versus 7 (0.7%), p = 0.003], cerebrovascular disease (CVD) [3 (2.9%) versus 5 (0.5%), p = 0.029], and peripheral vascular disease (PVD) [4 (3.9%) versus 9 (0.9%), p = 0.024]. IgED is associated with higher prevalence of arterial hypertension and ASCVD.

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.

Chronic ingestion of H1-antihistamines increase progression of atherosclerosis in apolipoprotein E-/- mice

Although increased serum histamine levels and H1R expression in the plaque are seen in atherosclerosis, it is not known whether H1R activation is a causative factor in the development of the disease, or is a host defense response to atherogenic signals. In order to elucidate how pharmacological inhibition of histamine receptor 1 (H1R) signaling affects atherogenesis, we administered either cetirizine (1 and 4 mg/kg. b.w) or fexofenadine (10 and 40 mg/kg. b.w) to ApoE^−/− mice maintained on a high fat diet for three months. Mice ingesting a low dose of cetirizine or fexofenadine had significantly higher plaque coverage in the aorta and cross-sectional lesion area at the aortic root. Surprisingly, the higher doses of cetirizine or fexofenadine did not enhance atherosclerotic lesion coverage over the controls. The low dose of fexofenadine, but not cetirizine, increased serum LDL cholesterol. Interestingly, the expression of iNOS and eNOS mRNA was increased in aortas of mice on high doses of cetirizine or fexofenadine. This may be a compensatory nitric oxide (NO)-mediated vasodilatory mechanism that accounts for the lack of increase in the progression of atherosclerosis. Although the administration of cetirizine did not alter blood pressure between the groups, there was a positive correlation between blood pressure and lesion/media ratio at the aortic root in mice receiving the low dose of cetirizine. However, this association was not observed in mice treated with the high dose of cetirizine or either doses of fexofenadine. The macrophages or T lymphocytes densities were not altered by low doses of H1-antihistamines, whereas, high doses decreased the number of macrophages but not T lymphocytes. The number of mast cells was decreased only in mice treated with low dose of fexofenadine. These results demonstrate that chronic ingestion of low therapeutic doses of cetirizine or fexofenadine enhance progression of atherosclerosis.

Protective effects of histamine on Gq-mediated relaxation in regenerated endothelium

In the porcine coronary artery, regenerated endothelium is dysfunctional as regards the responses to endothelium-dependent agonists. The current study aimed to determine the possible involvement of histamine in such dysfunction. Pigs were treated chronically with pyrilamine (H1 receptor inhibitor, 2 mg·kg−1·day−1) with part of their coronary endothelium and allowed to regenerate for 28 days after balloon denudation. The results showed a reduction in relaxation to bradykinin (Gq protein dependent) only in the pyrilamine-treated group (area under the curve, 269.7 ± 13.4 vs. 142.0 ± 31.0, native endothelium vs. regenerated endothelium) but not in the control group (253.0 ± 22.1 vs. 231.9 ± 29.5, native endothelium vs. regenerated endothelium). The differences in the relaxation to serotonin (Gi protein dependent) between native and regenerated endothelium were not affected by the pyrilamine treatment (control group, 106.3 ± 17.0 vs. 55.61 ± 12.7; and pyrilamine group, 106.0 ± 8.20 vs. 49.30 ± 6.31, native endothelium vs. regenerated endothelium). These findings indicate that during regeneration of the endothelium, the activation of H1 receptors by endogenous histamine may be required to maintain the endothelium-dependent Gq protein-mediated relaxation to bradykinin, suggesting a beneficial role of the monoamine in the process of endothelial regeneration.

Mast cells in human carotid atherosclerotic plaques are associated with intraplaque microvessel density and the occurrence of future cardiovascular events

AIMS

Human autopsy, animal, and cell culture studies together have merged in a concept suggesting participation of mast cells (MCs) in the generation of atherosclerotic plaques. More specifically, these studies have suggested MC-induced intraplaque neovascularization as one mechanism by which MCs may render the plaques vulnerable. The present study was designed to assess the association between MC numbers and neovascularization in human atherosclerotic plaques, and to relate the abundance of plaque MCs to the occurrence of adverse cardiovascular events during the follow-up.

METHODS AND RESULTS

Atherosclerotic plaques of 270 patients suffering from carotid artery stenosis were stained for the presence of MCs (MC tryptase). Furthermore, during a follow-up of 3 years, cardiovascular-related endpoints were assessed in 253 patients. On average a high number of MCs were observed per plaque cross-section [median 108 (55-233) cells per section]. Plaques with high MC numbers revealed an unstable lipid-rich inflammatory phenotype and were associated with symptomatic patients. In addition, MC numbers were positively associated with microvessel density (r = 0.416, P < 0.001). Patients with high intraplaque MC numbers showed significantly more cardiovascular events during the follow-up (58/142 vs. 31/111 events, P = 0.029). In a multivariate analysis with correction for the main risk factors of cardiovascular diseases, MCs remained independently associated with adverse cardiovascular events (P = 0.025).

CONCLUSION

Mast cells are highly prevalent in human carotid atherosclerotic lesions and associated with plaque microvessel density. Furthermore, intraplaque MC numbers associate with future cardiovascular events.

Mast cells and vascular diseases

Mast cells are increasingly being recognized as effector cells in many cardiovascular conditions. Many mast-cell-derived products such as tryptase and chymase can, through their enzymic action, have detrimental effects on blood vessel structure while mast cell-derived mediators such as cytokines and chemokines can perpetuate vascular inflammation. Mice lacking mast cells have been developed and these are providing an insight into how mast cells are involved in cardiovascular diseases and, as knowledge increase, mast cells may become a viable therapeutic target to slow progression of cardiovascular disease.

Effects of probiotic Lactobacillus rhamnosus GG and Propionibacterium freudenreichii ssp. shermanii JS supplementation on intestinal and systemic markers of inflammation in ApoE*3Leiden mice consuming a high-fat diet

A high-fat diet disturbs the composition and function of the gut microbiota and generates local gut-associated and also systemic responses. Intestinal mast cells, for their part, secrete mediators which play a role in the orchestration of physiological and immunological functions of the intestine. Probiotic bacteria, again, help to maintain the homeostasis of the gut microbiota by protecting the gut epithelium and regulating the local immune system. In the present study, we explored the effects of two probiotic bacteria, Lactobacillus rhamnosus GG (GG) and Propionibacterium freudenreichii spp. shermanii JS (PJS), on high fat-fed ApoE*3Leiden mice by estimating the mast cell numbers and the immunoreactivity of TNF-α and IL-10 in the intestine, as well as plasma levels of several markers of inflammation and parameters of lipid metabolism. We found that mice that received GG and PJS exhibited significantly lower numbers of intestinal mast cells compared with control mice. PJS lowered intestinal immunoreactivity of TNF-α, while GG increased intestinal IL-10. PJS was also observed to lower the plasma levels of markers of inflammation including vascular cell adhesion molecule 1, and also the amount of gonadal adipose tissue. GG lowered alanine aminotransferase, a marker of hepatocellular activation. Collectively, these data demonstrate that probiotic GG and PJS tend to down-regulate both intestinal and systemic pro-inflammatory changes induced by a high-fat diet in this humanised mouse model.

Correlation of lifetime progress of atherosclerosis and morphologic markers of severity in humans: new tools for a more sensitive evaluation

OBJECTIVES

To describe the morphological features of atherosclerosis in the aortas of autopsied patients (ranging from young adults to the elderly), thus providing new tools for a more sensitive morphological evaluation.

METHOD

We collected 141 aorta samples. We assessed the macroscopic degree of atherosclerosis, thickness of the intima and media, lipid and collagen depositions in the intima, and the infiltration of mast cells into the layers of the aorta. We correlated the findings with gender, age, race and cause of death.

RESULTS

The degree of atherosclerosis was significantly higher in the elderly. The aorta was thicker in the elderly and in cases with a cardiovascular cause of death. The thickness of the intima was significantly greater in the elderly, in males and in cases with a cardiovascular cause of death. The lipid content in the intima of the aorta was significantly higher in Caucasians. Older people and men had a significantly higher number of mast cells.

CONCLUSION

A macroscopic evaluation is a good indicator of the severity of atherosclerosis, but a more detailed analysis, namely evaluating the thickness of the layers of the aorta and the number of mast cells, may further elucidate the changes in the constituents of this vessel.

Mast cell deficiency attenuates progression of atherosclerosis and hepatic steatosis in apolipoprotein E-null mice

Mast cells are important cells of the immune system and are recognized as participants in the pathogenesis of atherosclerosis. In this study, we evaluated the role of mast cells on the progression of atherosclerosis and hepatic steatosis using the apolipoprotein E-deficient (ApoE(-/-)) and ApoE(-/-)/mast cell-deficient (Kit(W-sh/W-sh)) mouse models maintained on a high-fat diet. The en face analyses of aortas showed a marked reduction in plaque coverage in ApoE(-/-)/Kit(W-sh/W-sh) compared with ApoE(-/-) after a 6-mo regimen with no significant change noted after 3 mo. Quantification of intima/media thickness on hematoxylin and eosin-stained histological cross sections of the aortic arch revealed no significant difference between ApoE(-/-) and ApoE(-/-)/Kit(W-sh/W-sh) mice. The high-fat regimen did not induce atherosclerosis in either Kit(W-sh/W-sh) or wild-type mice. Mast cells with indications of degranulation were seen only in the aortic walls and heart of ApoE(-/-) mice. Compared with ApoE(-/-) mice, the serum levels of total cholesterol, low-density lipoprotein and high-density lipoprotein were decreased by 50% in ApoE(-/-)/Kit(W-sh/W-sh) mice, whereas no appreciable differences were noted in serum levels of triglycerides or very low density lipoprotein. ApoE(-/-)/Kit(W-sh/W-sh) mice developed significantly less hepatic steatosis than ApoE(-/-) mice after the 3-mo regimen. The analysis of Th1/Th2/Th17 cytokine profile in the sera revealed significant reduction of interleukin (IL)-6 and IL-10 in ApoE(-/-)/Kit(W-sh/W-sh) mice compared with ApoE(-/-) mice. The assessment of systemic generation of thromboxane A(2) (TXA(2)) and prostaglandin I(2) (PGI(2)) revealed significant decrease in the production of PGI(2) in ApoE(-/-)/Kit(W-sh/W-sh) mice with no change in TXA(2). The decrease in PGI(2) production was found to be associated with reduced levels of cyclooxygenase-2 mRNA in the aortic tissues. A significant reduction in T-lymphocytes and macrophages was noted in the atheromas of the ApoE(-/-)/Kit(W-sh/W-sh) mice. These results demonstrate the direct involvement of mast cells in the progression of atherosclerosis and hepatic steatosis.

Association of polymorphisms in prolylcarboxypeptidase and chymase genes with essential hypertension in the Chinese Han population

INTRODUCTION

The prolylcarboxypeptidase (PRCP) gene encodes a membrane protein that acts on angiotensin II (Ang II) and kallikrein to release vasoactive peptides. The chymase (CMA1) gene is important for Ang II generation. Therefore, the two genes might be involved in the pathogenesis of essential hypertension (EH).

MATERIALS AND METHODS

Eleven tag single nucleotide polymorphisms (SNPs) in the PRCP gene and four tag SNPs and G-1903A (rs1800875) polymorphism in the CMA1 gene were genotyped in the Chinese Han population (n=1020) using a polymerase chain reaction-restriction fragment length polymorphism method.

RESULTS

In the PRCP gene, single site analyses indicated that the rs7104980 G allele was a susceptible factor for EH (adjusted odds ratio (OR)=1.98, 95% confidence interval (CI) 1.62-2.43, p=0.3×10(-10)). The protective effect of Hap3 GAGCACTAACA was observed without carrying the susceptible rs7104908 G allele (OR=0.67, 95% CI 0.56-0.81, p=0.3×10(-4)) by haplotype analyses. In the case of the CMA1 gene, no associations with EH were found through single site analyses. However, haplotype analyses showed that Hap16 TTTA significantly increased the risk of EH with OR=3.15 (p=0.0002) which may be driven by interaction with a nearby SNP combination.

CONCLUSIONS

The present results indicated PRCP rs7104980 can be considered as a marker for EH and Hap3 GAGCACTAACA (PRCP) and Hap16 TTTA (CMA1) might be associated with EH in Chinese Han population.

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.

Human mast cells (HMC-1 5C6) enhance interleukin-6 production by quiescent and lipopolysaccharide-stimulated human coronary artery endothelial cells

We examined the effect of intact human mast cells (HMC-1 5C6) and their selected mediators on interleukin-6 (IL-6) production and bone morphogenetic protein-2 (BMP-2) expression in human coronary artery endothelial cells (HCAEC) in the presence and absence of lipopolysaccharide (LPS). Scanning electron microscopy showed that HMC-1 5C6 cells adhere to HCAEC in cocultures. Addition of HMC-1 5C6 cells markedly enhanced the IL-6 production by quiescent and LPS-activated HCAEC even at the maximal concentration of LPS. Furthermore, mast cell-derived histamine and proteases accounted for the direct and synergistic effect of mast cells on IL-6 production that was completely blocked by the combination of histamine receptor-1 antagonist and protease inhibitors. Another novel finding is that histamine was able to induce BMP-2 expression in HCAEC. Collectively, our results suggest that endotoxin and mast cell products synergistically amplify vascular inflammation and that histamine participates in the early events of vascular calcification.

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.

Mast cells: pivotal players in cardiovascular diseases

The clinical outcome of cardiovascular diseases as myocardial infarction and stroke are generally caused by rupture of an atherosclerotic plaque. However, the actual cause of a plaque to rupture is not yet established. Interestingly, pathology studies have shown an increased presence of the mast cell, an important inflammatory effector cell in allergy and host defense, in (peri)vascular tissue during plaque progression, which may point towards a causal role for mast cells. Very recent data in mouse models show that mast cells and derived mediators indeed can profoundly impact plaque progression, plaque stability and acute cardiovascular syndromes such as vascular aneurysm or myocardial infarction. In this review, we discuss recent evidence on the role of mast cells in the progression of cardiovascular disorders and give insight in the therapeutic potential of modulation of mast cell function in these processes to improve the resilience of a plaque to rupture.

Current understanding of Kounis syndrome

Inflammatory mediators, adhesion molecules of neutrophils and monocytes, have been shown to be increased in the plasma of patients presenting with acute coronary syndromes. Anaphylaxis is a systemic, immediate hypersensitivity reaction caused by rapid IgE-mediated release of mediators from mast cells and basophils. Kounis syndrome is the coincidental occurrence of these two distinct conditions accompanied by clinical and laboratory findings of angina pectoris caused by inflammatory mediators released during an allergic insult. Allergic angina can progress to acute myocardial infarction, which is termed 'allergic myocardial infarction'. There are several causes reported to be capable of inducing Kounis syndrome. These include a number of conditions, several drugs, foods and insect stings, among others. In this article, the clinical aspects, diagnosis, pathogenesis, incidence and epidemiology, related conditions and therapeutic management of this important syndrome are discussed.

Combined pathological effects of cocaine abuse and HIV infection on the cardiovascular system: an autopsy study of 187 cases from the Fulton County Medical Examiner's office

This autopsy study evaluates the possible cumulative effects of cocaine use in HIV-infected adult individuals on cardiovascular tissue. A total of 187 autopsy case reports and available H&E sections of myocardium and coronary arteries were reviewed. Four major study groups were defined: (A) a total of 63 cases positive for cocaine and negative for HIV (COC); (B) 40 cases positive for HIV/AIDS and negative for cocaine (HIV), (C) 23 cases both HIV/AIDS and cocaine (HIV/COC), and (D) a control group of 61 age-, sex- and race-matched, negative for cocaine and for HIV (CONT). The following morphologic and demographic data were analyzed: heart weight, left ventricular hypertrophy, myocardial fibrosis, thickening of the intramyocardial vessels, myocarditis, acute or remote myocardial infarcts (MI), age, sex, and race. Increased frequency of coronary wall and adventitial infiltrates, myocarditis, and thickened intramyocardial vessels present in HIV/COC group (14.5%, 17.4%, and 17.4% vs. 6.5%, 3.3%, and 0% in CONT group) may indicate possible combined and/or cumulative effects of HIV and cocaine on cardiovascular pathology.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Adventitial mast cells contribute to pathogenesis in the progression of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is histologically characterized by medial degeneration and various degrees of chronic adventitial inflammation, although the mechanisms for progression of aneurysm are poorly understood. In the present study, we carried out histological study of AAA tissues of patients, and interventional animal and cell culture experiments to investigate a role of mast cells in the pathogenesis of AAA. The number of mast cells was found to increase in the outer media or adventitia of human AAA, showing a positive correlation between the cell number and the AAA diameter. Aneurysmal dilatation of the aorta was seen in the control (+/+) rats following periaortic application of calcium chloride (CaCl2) treatment but not in the mast cell-deficient mutant Ws/Ws rats. The AAA formation was accompanied by accumulation of mast cells, T lymphocytes and by activated matrix metalloproteinase 9, reduced elastin levels and augmented angiogenesis in the aortic tissue, but these changes were much less in the Ws/Ws rats than in the controls. Similarly, mast cells were accumulated and activated at the adventitia of aneurysmal aorta in the apolipoprotein E-deficient mice. The pharmacological intervention with the tranilast, an inhibitor of mast cell degranulation, attenuated AAA development in these rodent models. In the cell culture experiment, a mast cell directly augmented matrix metalloproteinase 9 activity produced by the monocyte/macrophage. Collectively, these data suggest that adventitial mast cells play a critical role in the progression of AAA.

Free cholesterol in atherosclerotic plaques: where does it come from?

PURPOSE OF REVIEW

Free cholesterol in plaques is an emerging contributing factor to lesion instability and, until recently, apoptosis of lipid-laden macrophages was considered the major source of free cholesterol. The validity of this concept is beginning to be challenged since there is recent evidence of erythrocyte membrane-derived cholesterol in plaques. Therefore, intraplaque hemorrhage may not be a passive event, as once considered as studies continue to support the relationship of intraplaque hemorrhage and necrotic core expansion.

RECENT FINDINGS

The association of intraplaque hemorrhage, accumulated free cholesterol, and necrotic core expansion is beginning to unfold and recent MRI studies suggest the value of intraplaque hemorrhage as a predictor of recurrent cerebrovascular events. The amount of erythrocyte membrane-derived cholesterol is also suggested to be a measure of lesion vulnerability in acute coronary syndromes. Recent inhibitors studies of vascular permeability factors further emphasize the importance of intraplaque hemorrhage in plaque progression. Finally, DNA microarray analysis is starting to reveal key molecules involved in the accumulation of free cholesterol that are selectively induced in high-risk plaques.

SUMMARY

These recent findings emphasize the importance of intraplaque hemorrhage as a contributor of free cholesterol in plaques and point to its provocative role in lesion destabilization.

Mast cells: multipotent local effector cells in atherothrombosis

Our understanding of the relationship between the proatherogenic activities of arterial mast cells (MCs) and the development of atherosclerotic lesions is advancing. Atherosclerosis is a chronic inflammatory disease in which cholesterol and other lipids of circulating low-density lipoprotein (LDL) particles accumulate both extracellularly and intracellularly in the innermost layer of the arterial wall, the intima. One prerequisite for the proatherogenic activity of the LDL particles is their retention and proteolytic modification within the extracellular matrix of the intima. Experimental studies with activated chymase-secreting MCs have provided us fundamental insights into the molecular mechanisms of these processes. High-density lipoprotein (HDL) particles, again, remove cholesterol from the intracellular stores and carry it back to the circulation. MC chymase and tryptase actively degrade HDL and thus generate functionally defective particles that are unable to initiate cholesterol efflux from the arterial wall. In advanced atherosclerotic plaques, the accumulated lipids are separated from the circulation by a collagenous cap. By inducing apoptosis of endothelial cells (ECs), subendothelial MCs may induce detachment of ECs from the cap (plaque erosion). Moreover, MCs may weaken the cap if they disturb local collagen turnover by inducing apoptosis of the collagen-secreting smooth muscle cells or when they promote collagen degradation by activating matrix metalloproteinases. Plaques with a weak cap are vulnerable to rupture. The exposed subendothelial tissue at eroded and ruptured sites of plaques triggers local development of a platelet-rich thrombus. As regulators of the collagen-induced platelet activation and fibrin formation/fibrinolysis, the MCs may retard or accelerate the growth of the plaque-associated thrombus and ultimately participate in the wound-healing response of the injured plaque. We propose that by promoting cholesterol accumulation and plaque vulnerability and by locally regulating hemostasis, MCs in atherosclerotic lesions have the potential to contribute to the clinical outcomes of atherosclerosis, such as myocardial infarction and stroke.

Mast cell distribution, activation, and phenotype in xanthoma

BACKGROUND

Activated mast cells enhance the uptake of mast cell-derived proteoglycan-low-density lipoprotein complexes by macrophages.

OBJECTIVE

We sought to investigate mast cell contribution to the pathogenesis of xanthoma.

METHODS

Twenty cases of xanthelasma palpebrarum and 6 cases of tuberous xanthoma lesions were analyzed using immunohistochemical staining.

RESULTS

Xanthelasma lesions contained up to 5-fold more tryptase-stained mast cells than tuberous xanthoma lesions. Tuberous xanthoma lesions especially showed extensive staining of tryptase around mast cells and within some macrophages and foam cells. More than 99% of mast cells in xanthelasma lesions contained both tryptase and chymase. Approximately 60% of mast cells represented only tryptase in tuberous xanthoma lesions where the ratio of macrophages to tryptase-stained mast cells was extremely high (15:1) as compared with xanthelasma lesions (2:1).

LIMITATIONS

A change in mast cell phenotype has not been necessarily proven.

CONCLUSION

Mast cells are activated under the microenvironment in which macrophages predominate rather than mast cells, which thus reflects the clinical phenotypes of xanthoma lesions.

Shear stress-induced changes in atherosclerotic plaque composition are modulated by chemokines

We previously found that low shear stress (LSS) induces atherosclerotic plaques in mice with increased lipid and matrix metalloproteinase content and decreased vascular smooth muscle and collagen content. Here, we evaluated the role of chemokines in this process, using an extravascular device inducing regions of LSS, high shear stress, and oscillatory shear stress (OSS) in the carotid artery. One week of shear stress alterations induced expression of IFN-gamma-inducible protein-10 (IP-10) exclusively in the LSS region, whereas monocyte chemoattractant protein-1 (MCP-1) and the mouse homolog of growth-regulated oncogene alpha (GRO-alpha) were equally upregulated in both LSS and OSS regions. After 3 weeks, GRO-alpha and IP-10 were specifically upregulated in LSS regions. After 9 weeks, lesions with thinner fibrous caps and larger necrotic cores were found in the LSS region compared with the OSS region. Equal levels of MCP-1 expression were observed in both regions, while expression of fractalkine was found in the LSS region only. Blockage of fractalkine inhibited plaque growth and resulted in striking differences in plaque composition in the LSS region. We conclude that LSS or OSS triggers expression of chemokines involved in atherogenesis. Fractalkine upregulation is critically important for the composition of LSS-induced atherosclerotic lesions.

Histamine differentially interacts with tumor necrosis factor-alpha and thrombin in endothelial tissue factor induction: the role of c-Jun NH2-terminal kinase

BACKGROUND

Histamine plays an important role in vascular disease. Tissue factor (TF) expression is induced in vascular inflammation and acute coronary syndromes.

OBJECTIVES

This study examined the effect of histamine on tumor necrosis factor-alpha- (TNF-alpha-) vs. thrombin-induced endothelial TF expression.

METHODS AND RESULTS

Histamine (10(-8)-10(-5) mol L-1), TNF-alpha (5 ng mL-1), and thrombin (1 U mL-1) induced TF expression in human endothelial cells. Although TF expression by TNF-alpha and thrombin was identical, histamine augmented TNF-alpha-induced expression 7.0-fold, but thrombin-induced expression only 2.6-fold. Similar responses occurred with TF activity. The H1-receptor antagonist mepyramine abrogated these effects. Differential augmentation by histamine was also observed at the mRNA level. Histamine-induced p38 activation preceded a weak second activation to both TNF-alpha and thrombin. Histamine-induced c-Jun NH2-terminal kinase (JNK) activation was followed by a strong second activation to TNF-alpha, and less to thrombin. Selective inhibition of this second JNK activation by SP600125 reduced TF induction to histamine plus TNF-alpha by 67%, but to histamine plus thrombin by only 32%. Histamine augmented TNF-alpha- and thrombin-induced vascular cell adhesion molecule 1 (VCAM-1) expression to a similar extent. Consistent with this observation, VCAM-1 induction to TNF-alpha and thrombin was mediated by p38, but not by JNK.

CONCLUSIONS

Histamine differentially augments TNF-alpha- vs. thrombin-induced TF expression and activity, which is mediated by the H1-receptor, occurs at the mRNA level, and is related to differential JNK activation.

Histamine Network in Atherosclerosis

Histamine is a low-molecular-weight amine, synthesized from l-histidine by histidine decarboxylase. It has been suggested that the histamine is produced in the atherosclerotic lesion although the activity of histamine has not been clarified completely. To avoid the pharmacologic problems, genetically engineered mice are useful. We recently observed the histidine decarboxylase-gene knockout mice ameliorates' atherosclerotic region, compared with that of the wild-type control mice. The source of histamine in atherosclerotic lesion should be clarified in details; however, it could be macrophage, endothelial cells, and mast cells. All four types of histamine receptors (H1-H4) have the possibilities to be involved in the atherosclerotic regions. Because H1 and H2 receptors are discovered previously, the activities through those receptors are investigated relatively well, but as the other two types of receptors have been cloned recently, their involvement in atherosclerotic lesion should be investigated further.

Human gastroepiploic artery has greater chymase activity than the internal thoracic artery

OBJECTIVE

Recent reports have demonstrated that long-term patency of the gastroepiploic artery (GEA) in coronary artery bypass grafting (CABG) is less satisfactory compared with the internal thoracic artery (ITA). However, the reason has not been fully elucidated. Angiotensin II is known to play an important role in the development of intimal hyperplasia, we hypothesized that the GEA is different from the ITA with respect to angiotensin II-forming ability. Accordingly, we measured activities of angiotensin II-forming enzymes, angiotensin-converting enzyme (ACE) and chymase, in human GEA and ITA.

METHODS

Remnant of the GEAs and ITAs were obtained from 24 patients who underwent CABG in which both conduits were used simultaneously. Activities of ACE and chymase were measured by using the extract form the GEA or ITA. Sections of the GEA or ITA were immunohistochemically stained with anti-human chymase antibody.

RESULTS

The ACE activity of the GEA (0.28+/-0.16 mU/mg protein) was greater than that of the ITA (0.18+/-0.11, p < 0.001). The chymase activity of the GEA (11.11+/-7.15 mU/mg protein) was also greater than that in the ITA (7.13+/-4.89, p < 0.001). The density of chymase-positive cells in the GEA (3.8+/-4.2 cells/mm2) was greater than that in the ITA (1.1+/-1.2, p < 0.01).

CONCLUSION

Activities of both ACE and chymase were significantly greater in the GEA compared with the ITA. The GEA may be different from the ITA with respect to potential ability of angiotensin II-formation.

Systemic Mastocytosis: Clinical Manifestations and Differential Diagnosis

Mast cells produce symptoms by local and remote effects of mediator release and by their presence in increased numbers in normal tissue and bone marrow, where they damage and impair normal organ function. Moreover, mast cells are long-lived and heterogeneous in their response to secretagogues and to inhibitors of mediator release. Clinicians sorting out the diagnosis of SM on the basis of presenting signs and symptoms continue to have their diagnostic skills challenged because of the rarity of this disorder, the fact that many symptoms of SM are present in more common disorders, and the multiple guises that SM may assume at the time of presentation.