Chymase-independent vascular Ang-(1-12)/Ang II pathway and TXA2 generation are involved in endothelial dysfunction in the murine model of heart failure

The angiotensin (Ang)-(1-12)/Ang II pathway contributes to cardiac pathology. However, its involvement in the development of peripheral endothelial dysfunction associated with heart failure (HF) remains unknown. Therefore, this study aimed to characterise the effect of exogenous Ang-(1-12) and its conversion to Ang II on endothelial function using the murine model of HF (Tgαq*44 mice), focusing on the role of chymase and vascular-derived thromboxane A2 (TXA2). Ex vivo myographic assessments of isolated aorta showed impaired endothelium-dependent vasodilation in late-stage HF in 12-month-old Tgαq*44 mice. However, endothelium-dependent vasodilation was fully preserved in the early stage of HF in 4-month-old Tgαq*44 mice and 4- and 12-month-old FVB control mice. Ang-(1-12) impaired endothelium-dependent vasodilation in 4- and 12-month-old Tgαq*44 mice, that was associated with increased Ang II production. The chymase inhibitor chymostatin did not inhibit this response. Interestingly, TXA2 production reflected by TXB2 measurement was upregulated in response to Ang-(1-12) and Ang II in aortic rings isolated from 12-month-old Tgαq*44 mice but not from 4-month-old Tgαq*44 mice or age-matched FVB mice. Furthermore, in vivo magnetic resonance imaging showed that Ang-(1-12) impaired endothelium-dependent vasodilation in the aorta of Tgαq*44 mice and FVB mice. However, this response was inhibited by angiotensin I converting enzyme (ACE) inhibitor; perindopril, angiotensin II receptor type 1 (AT1) antagonist; losartan and TXA2 receptor (TP) antagonist-picotamide in 12-month-old-Tgαq*44 mice only. In conclusion, the chymase-independent vascular Ang-(1-12)/Ang II pathway and subsequent TXA2 overactivity contribute to systemic endothelial dysfunction in the late stage of HF in Tgαq*44 mice. Therefore, the vascular TXA2 receptor represents a pharmacotherapeutic target to improve peripheral endothelial dysfunction in chronic HF.

Human vascular smooth muscle cells utilise chymase for the atypical cleavage and activation of Interleukin-1β

BACKGROUND AND AIMS

Atherosclerosis and other cardiovascular diseases (CVD) are well established to be both instigated and worsened by inflammation. Indeed, CANTOS formally proved that targeting the inflammatory cytokine IL-1β only could reduce both cardiovascular events and death. However, due to the central role of IL-1β in host defence, blockade increased fatal infections, suggesting targeting key immune mediators over the long natural history of CVD is unsuitable. Thus, discovering alternative mechanisms that generate vascular inflammation may identify more actionable targets.

METHODS

We used primary human VSMCs and a combination of biochemical, pharmacological and molecular biological techniques to generate the data. Human carotid atherosclerotic plaques were also assessed histologically.

RESULTS

We showed that VSMCs expressed and efficiently processed pro-IL-1β to the active form after receiving a single stimulus via IL-1R1 or TLR4. Importantly, pro-IL-1β processing did not utilise inflammasomes or caspases. Unusually, we found that cathepsin C-activated chymase was responsible for cleaving IL-1β in VSMCs, and provided evidence for chymase expression in cultured VSMCs and in the fibrous cap of human plaques. Chymase also efficiently cleaved and activated recombinant pro-IL-1β.

CONCLUSIONS

Thus, VSMCs are efficient activators of IL-1β that do not use canonical inflammasomes or caspases. Hence, this alternative pathway could be targeted for long-term treatment of CVDs, as it is not central to everyday host defence.

Optimal molecular binding data and pharmacokinetic profiles of novel potential triple-action inhibitors of chymase, spleen tyrosine kinase, and prostaglandin D2 receptor in the treatment of asthma

BACKGROUND

Asthma is a chronic and complex pulmonary condition that affects the airways. A total of 250,000 asthma-related deaths are recorded annually and several proteins including chymase, spleen tyrosine kinase, and prostaglandin D2 receptor have been implicated in the pathophysiology of asthma. Different anti-inflammatory drugs have been developed for the treatment of asthma, particularly corticosteroids, but the associated adverse reactions cannot be overlooked. It is therefore of interest to identify and develop small molecule inhibitors of the integral proteins associated with asthma that have very little or no side effects. Herein, a molecular modeling approach was employed to screen the bioactive compounds in Chromolaena odorata and identify compounds with high binding affinity to the protein targets.

RESULTS

Five compounds were identified after rigorous and precise molecular screening namely (-)-epicatechin, chlorogenic acid, ombuine, quercetagetin, and quercetin 3-O-rutinoside. These compounds generally showed impressive binding to all the targets understudy. However, chlorogenic acid, quercetagetin, and quercetin 3-O-rutinoside showed better prospects in terms of triple-action inhibition. Further pulmonary and oral pharmacokinetics showed positive results for all the reported compounds. The generated pharmacophore model showed hydrogen bond donor, hydrogen bond acceptor, and aromatic rings as basic structural features required for triple action inhibition.

CONCLUSION

These findings suggest that these compounds could be explored as triple-action inhibitors of the protein targets. They are, therefore, recommended for further analysis.

Update on Mast Cell Proteases as Drug Targets

Mast cell granules are packed with proteases, which are released with other mediators by degranulating stimuli. Several of these proteases are targets of potentially therapeutic inhibitors based on hypothesized contributions to diseases, notably asthma and ulcerative colitis for β-tryptases, heart and kidney scarring for chymases, and airway infection for dipeptidyl peptidase-I. Small-molecule and antibody-based β-tryptase inhibitors showing preclinical promise were tested in early-phase human trials with some evidence of benefit. Chymase inhibitors were given safely in Phase II trials without demonstrating benefits, whereas dipeptidyl peptidase-I inhibitor improved bronchiectasis, in effects likely related to inactivation of the enzyme in neutrophils.

Two granzyme A/K homologs in Zebra mbuna have different specificities, one classical tryptase and one with chymase activity

Granzymes A and K are two highly homologous serine proteases expressed by mammalian cytotoxic T cells (CTLs) and natural killer (NK) cells. The locus encoding these two proteases is the first of the hematopoietic serine protease loci to appear during vertebrate evolution. This locus is found in all jawed vertebrates including the cartilaginous fishes. Granzyme A is the most abundant of the different granzymes expressed by CTLs and NK cells and its potential function has been studied extensively for many years. However, no clear conclusions concerning its primary role in the immune defense has been obtained. In all mammals, there are only one copy each of granzyme A and K, whereas additional copies are found in both cartilaginous and ray finned fishes. In cichlids two of these copies seem to encode new members of the granzyme A/K family. These two new members appear to have changed primary specificity and to be pure chymases based on the amino acids in their active site substrate binding pockets. Interestingly, one of these gene copies is located in the middle of the granzyme A/K locus, while the other copy is present in another locus, the met-ase locus. We here present a detailed characterization of the extended cleavage specificity of one of these non-classical granzymes, a Zebra mbuna granzyme positioned in the granzyme A/K locus. This enzyme, named granzyme A2, showed a high preference for tyrosine in the P1 position of substrates, thereby being a strict chymase. We have also characterized one of the classical granzyme A/Ks of the Zebra mbuna, granzyme A1, which is a tryptase with preference for arginine in the P1 position of substrates. Based on their extended specificities, the two granzymes showed major similarities, but also some differences in preferred amino acids in positions surrounding the cleavable amino acid. Fish lack one of the hematopoietic serine protease loci of mammals, the chymase locus, where one of the major mast cell enzymes is located. An interesting question is now if cichlids have by compensatory mechanisms generated a mast cell chymase from another locus, and if similar chymotryptic enzymes have appeared also in other fish species.

Secretory leukocyte protease inhibitor modulates FcεRI-dependent but not Mrgprb2-dependent mastocyte function in psoriasis

Psoriasis, which involves mast cells, is a chronic inflammatory skin disorder whose pathophysiology is still not fully understood. We investigated the role of secretory leukocyte protease inhibitor (SLPI), a potential inhibitor of mastocyte serine proteases, on mast cell-dependent processes of relevance to the skin barrier defense in psoriasis. Here, we demonstrate that the dermal mast cells of patients with psoriasis express SLPI but not those of healthy donors. Moreover, SLPI transcripts were found to be markedly upregulated in murine mast cells by mediators derived from psoriasis skin explant cultures. Using mast cells from SLPI-deficient mice and their SLPI+ wild-type controls, we show that SLPI inhibits the activity of serine protease chymase in mastocytes. SLPI was also found to enhance the degranulation of mast cells activated via anti-IgE Abs but not Mrgprb2 ligands. Finally, we demonstrate that the expression and function of Mrgprb2 in mast cells are suppressed by a normal and, to a larger extent, psoriatic skin environment. Together, these findings reveal mechanisms underlying FcεRI- and Mrgprb2-dependent mast cell function that have not been described previously.

Galectin-3, a damage-associated molecular pattern, in tears of patients with vernal keratoconjunctivitis

PURPOSE

Galectin-3 is a damage-associated molecular pattern (DAMPs), released from damaged or dying cells. In this study, we investigated the concentration and source of galectin-3 in the tears of patients with vernal keratoconjunctivitis (VKC) and evaluated whether the concentration of galectin-3 in tears represents a biomarker of corneal epithelial damage.

STUDY DESIGN

Clinical and experimental.

METHODS

We measured the concentration of galectin-3 in tear samples from 26 patients with VKC and 6 healthy controls by enzyme-linked immunosorbent assay (ELISA). The expression of galectin-3 in cultured human corneal epithelial cells (HCEs) stimulated with or without tryptase or chymase was investigated by polymerase chain reaction (PCR), ELISA, and Western blotting. We also estimated the concentration of galectin-3 in the supernatants of cultured HCEs induced to necrosis. Finally, we investigated whether recombinant galectin-3 induced the expression of various genes related to cell migration or the cell cycle in HCEs by using microarray analysis.

RESULTS

High concentrations of galectin-3 were detected in the tears of patients with VKC. The concentration showed significant correlation with the severity of corneal epithelial damage. Stimulation of cultured HCEs with various concentrations of tryptase or chymase had no effect on the expression of galectin-3. However, high concentrations of galectin-3 were detected in the supernatants of necrotic HCEs. Recombinant human galectin-3 induced various cell migration- and cell cycle-related genes.

CONCLUSION

The concentrations of galectin-3 in the tears of patients with VKC may represent a biomarker of the severity of corneal epithelial damage.

Mast cell chymase is in contact with melanoma cells in vivo and it detaches melanoma cells from the substratum in vitro

Background

Mast cell chymase, a chymotryptic serine proteinase, is a powerful enzyme that may liberate adherent tumor cells thereby promoting tumor spread.

Methods

This study investigated interactions between cells containing immunoreactive chymase and melanoma cells in 101 melanoma and 50 nevus specimens as well as used recombinant human (rh)-chymase and WM115 and G361 primary melanoma cell lines in culture.

Results

Rh-chymase at low concentration (0.1 µg/mL) detached both melanoma cell lines from noncoated or collagen-coated plastic surface, but this effect was regulated by heparin and heparinase. After prolonged treatment at high rh-chymase (1-5 µg/mL) the growth pattern of detached and re-seeded cells was abnormal. Decreased migration and proliferation at up to 0.005-0.01 µg/mL rh-chymase was noticed in WM115 cells, while rh-chymase at 1-5 µg/mL partially reduced the viability of G361 cells. Of importance is the finding that melanoma cell lines are not uniform as there was variation between cell lines with regard to the concentration of rh-chymase needed for these effects. Sonicates prepared from the cell lysates did not inhibit the enzymatic activity of rh-chymase. The interactions were confirmed morphologically by detecting apparent contacts between chymase+ cells and melanoma cells in melanoma specimens.

Conclusions

These results suggest that chymase can detach melanoma cells from the tumor, but this effect is regulated by heparin, and their proliferation, migration or viability can be reduced by chymase. Thus, the effect of chymase may be antitumorigenic, rather than protumorigenic.

Investigation into the Health Effects of Reduced Chymase Function Using Predicted Loss-of-Function Mutations in CMA1

Tissue remodelling and fibrosis which occur in response to injury play a central role in the development of many diseases. Chymase is a key enzyme believed to mediate these pathological processes. As such, chymase inhibitors have been under active development for the treatment of a number of conditions. To investigate the impact of reduced chymase function, we constructed a genetic score from two pLoF mutations in the gene encoding chymase and tested its association with diseases and biomarkers. Our study found no association between the genetically-predicted reduced chymase function score and heart failure, chronic kidney disease or other predefined conditions. We additionally found no association of the score with any physical measurements or biomarkers. Our results provide no evidence in support of chymase inhibition as a novel therapeutic strategy for the treatment or prevention of heart failure, chronic kidney disease or major cardiovascular events, as previously proposed.

Distribution of decidual mast cells in fetal growth restriction and stillbirth at (near) term

INTRODUCTION

Placental pathology and pregnancy complications are associated with unfavorable regulation of the maternal immune system. Although much research has been performed towards the role of immune cells like macrophages and T cells in this context, little is known about the presence and function of mast cells (MC). MC can be sub classified in tryptase-positive (MC_T) and tryptase- and chymase-positive (MC_TC). This study investigates the presence of MC in the decidua of pregnancies complicated by fetal growth restriction (FGR) and stillbirth (SB).

METHODS

Placental tissue from FGR (n = 250), SB (n = 64) and healthy pregnancies (n = 42) was included. Histopathological lesions were classified according to the Amsterdam Placental Workshop Group criteria. Tissue sections were stained for tryptase and chymase. Decidual MC were counted manually, and the results were expressed as number of cells/mm² decidual tissue.

RESULTS

A significant lower median number of MC_TC was found in the decidua of FGR (0.40 per mm²; p < 0.001) and SB (0.51 per mm²; p < 0.05) compared to healthy controls (1.04 per mm²). No difference in MC_T number (1.19 per mm², 1.88 per mm² and 1.37 per mm² respectively) was seen between the groups. There was no difference in number of MC_T and MC_TC between placental pathological lesions.

DISCUSSION

Our findings suggest a shift in decidual MC balance towards MC_T in pregnancy complications. No difference in numbers of MC subtypes was found to be related to histopathologic lesions.

Mast Cells in Human Cutaneous Neurofibromas: Density, Subtypes, and Association with Clinical Features in Neurofibromatosis 1

BACKGROUND

Cutaneous neurofibromas (cNFs) are hallmarks of neurofibromatosis 1 (NF1) and cause the main disease burden in adults with NF1. Mast cells are a known component of cNFs. However, no comprehensive characterization of mast cells in cNFs is available, and their contributions to cNF growth and symptoms such as itch are not known.

METHODS

We collected 60 cNFs from ten individuals with NF1, studied their mast cell proteinase content, and compared the mast cell numbers to selected clinical features of the tumors and patients. The tumors were immunolabeled for the mast cell markers CD117, tryptase, and chymase, and the percentage of immunopositive cells was determined using computer-assisted methods.

RESULTS

The median proportions of positive cells were 5.5% (range 0.1-14.4) for CD117, 4.0% (1.2-7.0) for tryptase, and 5.0% (1.1-15.9) for chymase. The median densities of cells immunopositive for CD117, tryptase, and chymase were 280, 243, and 250 cells/mm2, respectively. Small tumors, growing tumors, and tumors from patients below the median age of 33 years displayed a high proportion of mast cells. Cells expressing both tryptase and chymase were the predominant mast cell type in cNFs, followed by cells expressing chymase only.

CONCLUSION

The results highlight the abundance of mast cells in cNFs and that their number and subtypes clearly differ from those previously reported in unaffected skin.

Role of chymase in blood pressure control, plasma and tissue angiotensin II, renal Haemodynamics, and excretion in spontaneously hypertensive rats

Background: Chymase generates angiotensin II (ANG II) independently of angiotensin-converting enzyme in tissues and it contributes to vascular remodeling and development of hypertension, however the exact mechanism of its action is unclear. Methods: Hence, the effects of chymase inhibition were examined in anesthetized spontaneously hypertensive rats (SHR) in two stages of the disease development, ie. pre-hypertensive (SHR7) and with established hypertension (SHR16). Chymostatin, a commercial chymase inhibitor, was infused intravenously alone or in subsequent groups co-infused with captopril. Results: Mean blood pressure (MBP), total renal blood flow (RBF) and ANG II content (plasma and tissues) were measured. In SHR16 chymase blockade significantly decreased MBP (-6%) and plasma (-38%), kidney (-71%) and heart (-52%) ANG II levels. In SHR7 chymostatin did not influence MBP or RBF, but significantly decreased heart ANG II level. Conclusion: Jointly, functional studies and ANG II determinations support the evidence that in SHR chymase can raise plasma ANG II and contribute to blood pressure elevation. We propose that addition of chymase blockade to ACE inhibition could be a promising approach in the treatment of hypertensive patients resistant to therapy with ACE-inhibitors alone.

Direct effects of mast cell proteases, tryptase and chymase, on bronchial epithelial integrity proteins and anti-viral responses

BACKGROUND

Mast cells (MCs) are known to contribute to both acute and chronic inflammation. Bronchial epithelial cells are the first line of defence against pathogens and a deficient anti-viral response has been suggested to play a role in the pathogenesis of asthma exacerbations. However, effects of MC mediators on bronchial epithelial immune response have been less studied. The aim of this study is to investigate the direct effects of stimulation with MC proteases, tryptase and chymase, on inflammatory and anti-viral responses in human bronchial epithelial cells (HBECs).

METHOD

Cultured BEAS-2b cells and primary HBECs from 3 asthmatic patients were stimulated with tryptase or chymase (0.1 to 0.5 μg/ml) for 1, 3, 6 and 24 h. To study the effects of MC mediators on the anti-viral response, cells were stimulated with 10 μg/ml of viral mimic Poly (I:C) for 3 and 24 h following pre-treatment with 0.5 μg/ml tryptase or chymase for 3 h. Samples were analysed for changes in pro-inflammatory and anti-viral mediators and receptors using RT-qPCR, western blot and Luminex.

RESULTS

Tryptase and chymase induced release of the alarmin ATP and pro-inflammatory mediators IL-8, IL-6, IL-22 and MCP-1 from HBECs. Moreover, tryptase and chymase decreased the expression of E-cadherin and zonula occludens-1 expression from HBECs. Pre-treatment of HBECs with tryptase and chymase further increased Poly (I:C) induced IL-8 release at 3 h. Furthermore, tryptase significantly reduced type-I and III interferons (IFNs) and pattern recognition receptor (PRR) expression in HBECs. Tryptase impaired Poly (I:C) induced IFN and PRR expression which was restored by treatment of a serine protease inhibitor. Similar effects of tryptase on inflammation and anti-viral responses were also confirmed in primary HBECs from asthmatic patients.

CONCLUSION

MC localization within the epithelium and the release of their proteases may play a critical role in asthma pathology by provoking pro-inflammatory and alarmin responses and downregulating IFNs. Furthermore, MC proteases induce downregulation of epithelial junction proteins which may lead to barrier dysfunction. In summary, our data suggests that mast cells may contribute towards impaired anti-viral epithelial responses during asthma exacerbations mediated by the protease activity of tryptase.

The Angiotensin-(1-12)/Chymase axis as an alternate component of the tissue renin angiotensin system

The identification of an alternate extended form of angiotensin I composed of the first twelve amino acids at the N-terminal of angiotensinogen has generated new knowledge of the importance of noncanonical mechanisms for renin independent generation of angiotensins. The human sequence of the dodecapeptide angiotensin-(1-12) [N-Asp¹-Arg²-Val³-Tyr⁴-Ile⁵-His⁶-Pro⁷-Phe⁸-His⁹-Leu¹⁰-Va^l1-Ile¹²-COOH] is an endogenous substrate that in the rat has been documented to be present in multiple organs including the heart, brain, kidney, gut, adrenal gland, and the bone marrow. Newer studies have confirmed the existence of Ang-(1-12) as an Ang II-forming substrate in the blood and heart of normal and diseased patients. Studies to-date document that angiotensin II generation from angiotensin-(1-12) does not require renin participation while chymase rather than angiotensin converting enzyme shows high catalytic activity in converting this tissue substrate into angiotensin II directly.

Effect of Guanxin V in animal model of acute myocardial infarction

Background

Acute myocardial infarction (AMI) is the most serious and lethal manifestation of coronary heart disease worldwide, presenting extremely high disability and mortality. Our previous studies have shown that Guanxin V (GXV) could significantly improve the cardiac function and the blood flow dynamics, and reduce serum levels of inflammatory factors in AMI rats, thus triggering ventricular remodeling (VR) at post-AMI.

Methods

An in vivo AMI model was established in Syrian hamsters by performing the ligation of the left anterior descending coronary artery. Syrian hamsters were randomly divided into four groups, namely Sham operation group (n = 12), AMI group (n = 12), GXV group (GXV 6 g/Kg/d, n = 12), and Tranilast group (Tra 105 mg/Kg/d, n = 12). Drug intervention was conducted for consecutive 8 weeks. Relative biological indicators were measured in the 4th and 8th week, respectively.

Results

Cardiac functions were improved, and the infarcted size and heart weight index were limited in Syrian hamsters of GXV and Tra groups compared with those in AMI group. Furthermore, GXV was able to decrease the number of mast cells and chymase level in Syrian hamsters with AMI. Administration of GXV remarkably inactivated the renin-angiotension-aldosterone system, and alleviated myocardial fibrosis and cardiomyocyte apoptosis, thus slowing down VR at post-AMI.

Conclusion

GXV slows down the process of VR at post-AMI by reducing chymase level and mast cells number, as well as inactivating the reninangiotension-aldosterone system..

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03211-7.

Protease profile of normal and neoplastic mast cells in the human bone marrow with special emphasis on systemic mastocytosis

Mast cells (MC) are immune cells that produce a variety of mediators, such as proteases, that are important in the body's immune responses. MC proteases have pronounced multifunctionality and in many respects determine the biological characteristics of the organ-specific MC population. Although, increased numbers of MC are one of the objective mastocytosis signs, a detailed assessment of the proteases biogenesis and excretion mechanisms in the bone marrow (BM) has not yet been carried out. Here, we performed an analysis of the expression of proteases in patients with various forms of systemic mastocytosis. We presented data on intracellular protease co-localization in human BM MCs and discussed their implication in secretory pathways of MCs in the development of the disease. Systemic mastocytosis, depending on the course, is featured by the formation of definite profiles of specific proteases in various forms of atypical mast cells. Intragranular accumulation of tryptase, chymase and carboxypeptidases in the hypochromic phenotype of atypical mast cells is characterized. Characterization of MC proteases expression during mastocytosis can be used to refine the MC classification, help in a prognosis, and increase the effectiveness of targeted therapy.

Tranilast prevents doxorubicin-induced myocardial hypertrophy and angiotensin II synthesis in rats

An increase in oxidative stress is an important pathological mechanism of heart injury induced by doxorubicin (DOX). Tranilast is an anti-allergy drug that has been shown to possess good antioxidant activity in previous studies. The overexpression and secretion of chymase by mast cells (MCs) increase the pathological overexpression of angiotensin II (Ang II), which plays a crucial role in myocardial hypertrophy and the deterioration of heart disease. The MC stabilizer tranilast (N-(3,4-dimethoxycinnamoyl) anthranilic acid; tran) prevents mast cells from degranulating, which may reduce DOX-induced Ang II synthesis. Therefore, in the present study, we hypothesized that tranilast will protect rats from DOX-induced myocardial damage via its antioxidant activity, thereby inhibiting Ang II expression. Thirty male Wistar rats were divided into three groups (n = 10 in each group) that received DOX, a combination of DOX and tranilast or saline (the control group) to test this hypothesis. Tranilast suppressed chymase expression, reduced Ang II levels and prevented the myocardial hypertrophy and the deterioration of heart function induced by DOX. Based on the findings of the present study, the suppression of chymase-dependent Ang-II production and the direct effect of tranilast on the inhibition of apoptosis and fibrosis because of its antioxidant stress capacity may contribute to the protective effect of tranilast against DOX-induced myocardial hypertrophy.

Mechanism of Albuminuria Reduction by Chymase Inhibition in Diabetic Mice

Chymase has several functions, such as angiotensin II formation, which can promote diabetic kidney disease (DKD). In this study, we evaluated the effect of the chymase inhibitor TY-51469 on DKD in diabetic db/db mice. Diabetic mice were administered TY-51469 (10 mg/kg/day) or placebo for 4 weeks. No significant difference was observed in body weight and fasting blood glucose between TY-51469- and placebo-treated groups. However, a significant reduction in urinary albumin/creatinine ratio was observed in the TY-51469-treated group compared with the placebo-treated group. In the renal extract, chymase activity was significantly higher in placebo-treated mice than in non-diabetic db/m mice, but it was reduced by treatment with TY-51469. Both NADPH oxidase 4 expression and the oxidative stress marker malondialdehyde were significantly augmented in the placebo-treated group, but they were attenuated in the TY-51469-treated group. Significant increases of tumor necrosis factor-α and transforming growth factor-β mRNA levels in the placebo-treated group were significantly reduced by treatment with TY-51469. Furthermore, the expression of nephrin, which is a podocyte-specific protein, was significantly reduced in the placebo-treated group, but it was restored in the TY-51469-treated group. These findings demonstrated that chymase inhibition reduced albuminuria via attenuation of podocyte injury by oxidative stress.

Novel Insight into the in vivo Function of Mast Cell Chymase: Lessons from Knockouts and Inhibitors

Mast cells are now recognized as key players in diverse pathologies, but the mechanisms by which they contribute in such settings are only partially understood. Mast cells are packed with secretory granules, and when they undergo degranulation in response to activation the contents of the granules are expelled to the extracellular milieu. Chymases, neutral serine proteases, are the major constituents of the mast cell granules and are hence released in large amounts upon mast cell activation. Following their release, chymases can cleave one or several of a myriad of potential substrates, and the cleavage of many of these could potentially have a profound impact on the respective pathology. Indeed, chymases have recently been implicated in several pathological contexts, in particular through studies using chymase inhibitors and by the use of chymase-deficient animals. In many cases, chymase has been shown to account for mast cell-dependent detrimental effects in the respective conditions and is therefore emerging as a promising drug target. On the other hand, chymase has been shown to have protective roles in other pathological settings. More unexpectedly, chymase has also been shown to control certain homeostatic processes. Here, these findings are reviewed.

Differential Expression of the Angiotensin-(1-12)/Chymase Axis in Human Atrial Tissue

BACKGROUND

Heart chymase rather than angiotensin (Ang)-converting enzyme has higher specificity for Ang I conversion into Ang II in humans. A new pathway for direct cardiac Ang II generation has been revealed through the demonstration that Ang-(1-12) is cleaved by chymase to generate Ang II directly. Herein, we address whether Ang-(1-12), chymase messenger RNA (mRNA), and activity levels can be differentiated in human atrial tissue from normal and diseased hearts and if these measures associate with various pathologic heart conditions.

MATERIALS AND METHODS

Atrial appendages were collected from 11 nonfailing donor hearts and 111 patients undergoing heart surgery for the correction of valvular heart disease, resistant atrial fibrillation, or ischemic heart disease. Chymase mRNA was analyzed by real-time polymerase chain reaction and enzymatic activity by high-performance liquid chromatography using Ang-(1-12) as the substrate. Ang-(1-12) levels were determined by immunohistochemical staining.

RESULTS

Chymase gene transcripts, chymase activity, and immunoreactive Ang-(1-12) expression levels were higher in left atrial tissue compared with right atrial tissue, irrespective of cardiac disease. In addition, left atrial chymase mRNA expression was significantly higher in stroke versus nonstroke patients and in cardiac surgery patients who had a history of postoperative atrial fibrillation versus nonatrial fibrillation. Correlation analysis showed that left atrial chymase mRNA was positively related to left atrial enlargement, as determined by echocardiography.

CONCLUSIONS

As Ang-(1-12) expression and chymase gene transcripts and enzymatic activity levels were positively linked to left atrial size in patients with left ventricular heart disease, an important alternate Ang II forming pathway, via Ang-(1-12) and chymase, in maladaptive atrial and ventricular remodeling in humans is uncovered.

Mouse connective tissue mast cell proteases tryptase and carboxypeptidase A3 play protective roles in itch induced by endothelin-1

Background

Itch is an unpleasant sensation that can be debilitating, especially if it is chronic and of non-histaminergic origin, as treatment options are limited. Endothelin-1 (ET-1) is a potent endogenous vasoconstrictor that also has the ability to induce a burning, non-histaminergic pruritus when exogenously administered, by activating the endothelin A receptor (ET_AR) on primary afferents. ET-1 is released endogenously by several cell-types found in the skin, including macrophages and keratinocytes. Mast cells express ET_ARs and can thereby be degranulated by ET-1, and mast cell proteases chymase and carboxypeptidase A3 (CPA3) are known to either generate or degrade ET-1, respectively, suggesting a role for mast cell proteases in the regulation of ET-1-induced itch. The mouse mast cell proteases (mMCPs) mMCP4 (chymase), mMCP6 (tryptase), and CPA3 are found in connective tissue type mast cells and are the closest functional homologs to human mast cell proteases, but little is known about their role in endothelin-induced itch.

Methods

In this study, we evaluated the effects of mast cell protease deficiency on scratching behavior induced by ET-1. To investigate this, mMCP knock-out and transgenic mice were injected intradermally with ET-1 and their scratching behavior was recorded and analyzed.

Results

CPA3-deficient mice and mice lacking all three proteases demonstrated highly elevated levels of scratching behavior compared with wild-type controls. A modest increase in the number of scratching bouts was also seen in mMCP6-deficient mice, while mMCP4-deficiency did not have any effect.

Conclusion

Altogether, these findings identify a prominent role for the mast cell proteases, in particular CPA3, in the protection against itch induced by ET-1.

The novel mechanism of valproate to prevent peritoneal adhesion formation

PURPOSE

A novel pharmacological mechanism of valproate was analyzed using a hamster model of adhesion.

METHODS

Valproate or placebo was administered just after cecal injury and adhesion severity scores and histological were analyzed.

RESULTS

The adhesion severity scores in the placebo- and valproate-treated groups were 2.67 ± 0.42 and 1.0 ± 0.37, respectively, with a significant difference between the groups. A significant increase in mast cell numbers was observed in the placebo-treated group vs. the sham-operated group; however, the mast cell number in the adhesive lesion was significantly lower in the valproate-treated group than in the placebo-treated group. The number of cells positive for chymase, an enzyme in mast cells, in the adhesive lesion was significantly higher in the placebo-treated group, but its increase was attenuated significantly by treatment with valproate. The myeloperoxidase gene expression level in the cecum was significantly higher in the placebo-treated group than in the sham-operated group, but there was no significant difference in the myeloperoxidase gene expression level between the sham-operated and valproate-treated groups in. In an in vitro experiment, valproate inhibited purified human and hamster chymases dose-dependently.

CONCLUSION

The chymase inhibitory effect of valproate may contribute to prevent adhesion formation after abdominal injury.

Elevated chymase-dependent angiotensin II-forming activity in circulating mononuclear leukocytes was observed in the patient of atrial fibrillation

Chymase is an angiotensin II-forming serine proteinase and elevation of its tissue activity occurs in various cardiovascular diseases. Several authors have suggested that there is an association between the renin-angiotensin system and atrial fibrillation (AF). Chymase-dependent angiotensin II-forming activity in circulating mononuclear leukocytes (CML chymase dAIIFA) was investigated in patients with AF and patients in sinus rhythm. Consecutive outpatients were recruited at our hospital. CML chymase dAIIFA was measured using a Nma/Dnp-type fluorescence-quenching substrate of modified angiotensin I in the presence or absence of a specific serine proteinase inhibitor. To search the independent contributing factor of existence of AF, the analysis between groups was carried out using multivariate analysis after univariate analysis. The patients were classified into a sinus rhythm (SR) group (n = 459) or an AF group (n = 48). CML chymase dAIIFA was significantly higher in the AF group (622 pmol/min/mg) compared with the SR group (488 pmol/min/mg) (p < 0.001). Logistic regression analysis revealed that high CML chymase dAIIFA was an independent determinant of the existence of AF (p < 0.001). Elevation of CML chymase dAIIFA was associated with AF. Activation of chymase might be linked to atrial structural and electrical remodeling.

Detection of Mast Cells and Basophils by Immunohistochemistry

Staining cells or tissues with basic dyes was the mainstay of mast cell and basophil detection methods for more than a century following the first identification of these cell types using such methods. These techniques have now been largely supplanted by immunohistochemical procedures with monoclonal antibodies directed against unique constituents of these cell types. Immunohistochemistry with antibodies specific for the granule protease tryptase provides a more sensitive and discriminating means for detecting mast cells than using the classical histochemical procedures, and using antibodies specific for products of basophils (2D7 antigen and basogranulin) has allowed detection of basophils that infiltrate into tissues. The application of immunohistochemistry to detect more than one marker in the same cell has underpinned concepts of mast cell heterogeneity based on differential expression of chymase and other proteases. The double labeling procedures employed have also provided a means for investigating the expression of cytokines and a range of other products. Protocols are here set out that have been used for immunohistochemical detection of mast cells and basophils and their subpopulations in human tissues. Consideration is given to pitfalls to avoid and to a range of alternative approaches.

Association between chymase gene polymorphisms and atrial fibrillation in Chinese Han population

Background

Chymase is the major angiotensin II (Ang II)-forming enzyme in cardiovascular tissue, with an important role in atrial remodeling. This study aimed to examine the association between chymase 1 gene (CMA1) polymorphisms and atrial fibrillation (AF) in a Chinese Han population.

Methods

This case-control study enrolled 126 patients with lone AF and 120 age- and sex-matched healthy controls, all from a Chinese Han population. Five CMA1 polymorphisms were genotyped.

Results

The CMA1 polymorphism rs1800875 (G-1903A) was associated with AF. The frequency of the GG genotype was significantly higher in AF patients compared with controls (p = 0.009). Haplotype analysis further demonstrated an increased risk of AF associated with the rs1800875-G haplotype (Hap8 TGTTG, odds ratio (OR) = 1.668, 95% CI 1.132–2.458, p = 0.009), and a decreased risk for the rs1800875-A haplotype (Hap5 TATTG, OR = 0.178, 95% CI 0.042–0.749, p = 0.008).

Conclusions

CMA1 polymorphisms may be associated with AF, and the rs1800875 GG genotype might be a susceptibility factor for AF in the Chinese Han population.

Angiotensin-(1-12)/chymase axis modulates cardiomyocyte L-type calcium currents in rats expressing human angiotensinogen

BACKGROUND

Activation of the intracrine renin angiotensin systems (RAS) is increasingly recognized as contributing to human pathologies, yet non-canonical renin-independent mechanisms for angiotensin II (Ang II) biosynthesis remain controversial. Direct Ang II generation from angiotensin-(1-12) [Ang-(1-12)] by chymase is an essential intracrine source for regulation of cardiac function. Using a transgenic rat model that overexpresses the human angiotensinogen gene [TGR(hAGT)L1623] and displays increased cardiac Ang II levels, this study aimed to provide evidence for intracrine activation of L-type calcium currents (I_Ca-L) mediated by the Ang-(1-12)/chymase axis.

METHODS AND RESULTS

On patch clamp, I_Ca-L density was significantly higher in TGR(hAGT)L1623 (-6.4 ± 0.3 pA/pF) compared to Sprague Dawley (SD) cardiomyocytes (-4.8, ± 0.5 pA/pF). Intracellular administration of Ang II and Ang-(1-12) elicited a I_Ca-L increase in both SD and TGR(hAGT)L1623 cardiomyocytes, albeit blunted in transgenic cells. I_Ca-L activation by intracellular Ang II and Ang-(1-12) was abolished by the specific Ang II type 1 receptor blocker E-3174. Co-administration of a chymase inhibitor prevented activation of I_Ca-L by Ang-(1-12). Confocal micrographs revealed abundant chymase (mast cell protease 5) immunoreactive protein in SD and TGR(hAGT)L1623 cardiomyocytes.

CONCLUSIONS

Our data demonstrate the existence in cardiomyocytes of a calcium channel modulatory activity responsive to Ang II generated by the Ang-(1-12)/chymase axis that signals via intracellular receptors. Chronically elevated Ang II in TGR(hAGT)L1623 hearts leading to increased intracellular calcium through I_Ca-L suggests that activation of this Ang-(1-12)/chymase-governed cardiac intracrine RAS may contribute to the pathological phenotypes observed in the humanized model of chronic hypertension and cardiac hypertrophy.

Giardia excretory-secretory proteins modulate the enzymatic activities of mast cell chymase and tryptase

BACKGROUND

Mast cells are involved in the host immune response controlling infection with the non-invasive intestinal protozoan parasite Giardia intestinalis. Experimental infections in rodents with G. intestinalis showed increased intestinal expression of mucosal and connective mast cell specific proteases suggesting that both mucosal and connective tissue mast cells are recruited and activated during infection. During infection Giardia excretory-secretory proteins (ESPs) with immunomodulatory capacity are released. However, studies investigating potential interactions between Giardia ESPs and the connective tissue mast cell specific serine proteases, i.e. human chymase and mouse mast cell protease (mMCP)-4 and, human and mouse tryptase (mMCP-6) remain scarce.

RESULTS

We first investigated if soluble Giardia proteins (sGPs), which over-lap extensively in protein content with ESP fractions, from the isolates GS, WB and H3, could induce mast cell activation. sGPs induced a minor activation of bone marrow derived mucosal-like mast cells, as indicated by increased IL-6 secretion and no degranulation. Furthermore, sGPs were highly resistant to degradation by human tryptase while human chymase degraded a 65 kDa sGP and, wild-type mouse ear tissue extracts degraded several protein bands in the 10 to 75 kDa range. In striking contrast, sGPs and ESPs were found to increase the enzymatic activity of human and mouse tryptase and to reduce the activity of human and mouse chymase.

CONCLUSION

Our finding suggests that Giardia ssp. via enhancement or reduction of mast cell protease activity may modulate mast cell-driven intestinal immune responses. ESP-mediated modulation of the mast cell specific proteases may also increase degradation of tight junctions, which may be beneficial for Giardia ssp. during infection.

Reversal of angiotensin-(1-12)-caused positive modulation on left ventricular contractile performance in heart failure: Assessment by pressure-volume analysis

BACKGROUND

Angiotensin-(1-12) [Ang-(1-12)] is a renin-independent precursor for direct angiotensin-II production by chymase. Substantial evidence suggests that heart failure (HF) may alter cardiac Ang-(1-12) expression and activity; this novel Ang-(1-12)/chymase axis may be the main source for angiotensin-II deleterious actions in HF. We hypothesized that HF alters cardiac response to Ang-(1-12). Its stimulation may produce cardiac negative modulation and exacerbate left ventricle (LV) systolic and diastolic dysfunction.

METHODS AND RESULTS

We assessed the effects of Ang-(1-12) (2 nmol/kg/min, iv, 10 min) on LV contractility, LV diastolic filling, and LV-arterial coupling (AVC) in 16 SD male rats with HF-induced by isoproterenol (3 mo after 170 mg/kg sq. for 2 consecutive days) and 10 age-matched male controls. In normal controls, versus baseline, Ang-(1-12) increased LV end-systolic pressure, without altering heart rate, arterial elastance (E_A), LV end-diastolic pressure (P_ED), the time constant of LV relaxation (τ) and ejection fraction (EF). Ang-(1-12) significantly increased the slopes (E_ES) of LV end-systolic pressure (P)-volume (V) relations and the slopes (M_SW) of LV stroke wok-end-diastolic V relations, indicating increased LV contractility. AVC (quantified as E_ES/E_A) improved. In contrast, in HF, versus HF baseline, Ang-(1-12) produced a similar increase in P_ES, but significantly increased τ, E_A, and P_ED. The early diastolic portion of LV PV loop was shifted upward with reduced in EF. Moreover, Ang-(1-12) significantly decreased E_ES and M_SW, demonstrating decreased LV contractility. AVC was decreased by 43%.

CONCLUSIONS

In both normal and HF rats, Ang-(1-12) causes similar vasoconstriction. In normal, Ang-(1-12) increases LV contractile function. In HF, Ang-(1-12) has adverse effects and depresses LV systolic and diastolic functional performance.

Mast cell peptidases (carboxypeptidase A and chymase)-mediated hydrolysis of human angiotensin-(1-12) substrate

Angiotensin processing peptidases (carboxypeptidase A (CPA) and chymase) are stored in cardiac mast cell (MC) secretory granules in large quantity and are co-released into the extracellular environment after activation/degranulation. In the human heart, chymase is primarily responsible for angiotensin II (Ang II) generation from the alternate substrate angiotensin-(1-12) (Ang-(1-12)). We investigated the individual and combined hydrolytic specificity of CPA and chymase enzymes (1:1 and 1:⅓ ratio) in the processing of the human Ang-(1-12) (hAng-(1-12)) substrate. To determine the K_m and V_max, the CPA and recombinant human chymase (rhChymase) enzymes were incubated with increasing concentrations of hAng-(1-12) substrate (0-300 μM). We found that CPA alone sequentially metabolized hAng-(1-12) substrate into angiotensin-(1-9) (Ang-(1-9), 53%), Ang II (22%) and angiotensin-(1-7) (Ang-(1-7), 11%) during a 15 min incubation. In the presence of rhChymase alone, ¹²⁵I-hAng-(1-12) was directly metabolized into Ang II (89%) and no further hydrolysis of Ang II was detected. In the presence of both CPA + rhChymase enzymes (1:1 or 1:⅓ ratio), the amount of Ang II formation from ¹²⁵I-hAng-(1-12) within a 5 min incubation period were 68% or 65%, respectively. In the presence of both (CPA + rhChymase), small amounts of Ang-(1-9) and Ang-(1-7) were generated from ¹²⁵I-hAng-(1-12). The K_m and V_max values were 150 ± 5 μM and 384 ± 23 nM/min/mg of CPA and 40 ± 9 μM and 116 ± 20 nM/min/mg of rhChymase. The catalytic efficiency (V_max/K_m ratio) was higher for rhChymase/hAng-(1-12) compared to CPA/hAng-(1-12). Compared to CPA, chymase has a much higher affinity to hydrolyze the hAng-(1-12) substrate directly into Ang II. In addition, Ang II and Ang-(1-7) are the end products of chymase and CPA, respectively. Overall, our findings suggest that the Ang II generation from hAng-(1-12) is primarily mediated by chymase rather than CPA.

Mast cell chymase: morphofunctional characteristics

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

Physiological Roles of Mast Cells: Collegium Internationale Allergologicum Update 2019

Mast cells are immune cells which have a widespread distribution in nearly all tissues. These cells and their mediators are canonically viewed as primary effector cells in allergic disorders. However, in the last years, mast cells have gained recognition for their involvement in several physiological and pathological conditions. They are highly heterogeneous immune cells displaying a constellation of surface receptors and producing a wide spectrum of inflammatory and immunomodulatory mediators. These features enable the cells to act as sentinels in harmful situations as well as respond to metabolic and immune changes in their microenvironment. Moreover, they communicate with many immune and nonimmune cells implicated in several immunological responses. Although mast cells contribute to host responses in experimental infections, there is no satisfactory model to study how they contribute to infection outcome in humans. Mast cells modulate physiological and pathological angiogenesis and lymphangiogenesis, but their role in tumor initiation and development is still controversial. Cardiac mast cells store and release several mediators that can exert multiple effects in the homeostatic control of different cardiometabolic functions. Although mast cells and their mediators have been simplistically associated with detrimental roles in allergic disorders, there is increasing evidence that they can also have homeostatic or protective roles in several pathophysiological processes. These findings may reflect the functional heterogeneity of different subsets of mast cells.

Mast cell chymase in synovial fluid of collagen-induced-arthritis rats regulates gelatinase release and promotes synovial fibroblasts proliferation via FAK/p21 signaling pathway

Mast cells (MCs) were accumulated in synovial tissue of rheumatoid arthritis (RA) patients. MC activation releases numerous mediators including MC-chymase. Synovial fibroblast shows a dramatic hyperplasia in RA articular cavity, but the effects of MC-chymase on synovial fibroblast are unknown. In this study, the collagen-induced-arthritis (CIA) rat model was employed to evaluate the dynamic changes of MC-chymase activity and other inflammatory factors during CIA development in-vivo. The fresh primary synovial fibroblasts from normal or CIA rats were extracted to compare the differences of these two cell-types, and to investigate the effects of MC-chymase on both-types of synovial fibroblast. The data showed that the dynamic changes in chymase activity in synovial fluids of CIA rats before and after immunizations were companied with the changes of tryptase, MMP-2/-9, TNF-α, IL-6, Co-II IgG, total protein, paw-thickness and body weight in-vivo. The baseline differences in cell grow rates, expression levels of p21, FAK, MMP-9 between normal and CIA-SFB have been seen. Compared to the normal synovial fibroblasts, CIA-SFB increased the percentage of the cells transferred to S or G2/M phases in cell cycle in-vivo; CIA-SFB become more proliferative with high-expression MMP-2/9 during CIA development. MC-chymase in-vitro promoted both types of synovial fibroblast proliferation and induced cell cycle changes, but CIA-synovial fibroblasts exhibited much stronger responses to MC-chymase stimulation by increased expression levels of p21, FAK, MMP-9 which associated with cell adhesion and migration. This study might give a new insight that the activated mast cell can be an important target cell for RA treatment and suggest that MC-chymase needs well attention for therapeutic aims.

High Fib4 index in patients with suspected NASH is associated with elevation of chymase-dependent angiotensin II-forming activity in circulating mononuclear leucocytes

Fatal hepatic disease is closely related to non-alcoholic fatty liver disease, especially non-alcoholic steatohepatitis (NASH). NASH is associated with cardiovascular events because it develops on the background of lifestyle-related diseases. Chymase-dependent angiotensin II-forming activity (dAIIFA) in circulating mononuclear leucocytes (CML) is a marker of local angiotensin II production and inflammation. This study investigated the association between CML chymase dAIIFA and NASH. Cardiovascular outpatients were recruited and the Fib4 index (F4I) was calculated. Patients with an F4I > 2.67 were classified into the high F4I group and these patients were strongly suspected to have NASH, while patients with an F4I < 1.30 were classified into the low F4I group. Patient background factors were compared between these groups. CML chymase dAIIFA was measured by ELISA using Nma/Dnp-modified angiotensin I. Among 499 patients, 16% were classified into the high F4I group. Compared with the low F4I group, the high F4I group had a significantly higher age, pancytopenia, more frequent diabetes mellitus, lower diastolic blood pressure, lower estimated glomerular filtration rate, higher brain natriuretic peptide, lower plasma aldosterone concentration, higher total AIIFA, higher CML chymase dAIIFA, and higher pulse wave velocity. Contrary to expectations, the body mass index, triglycerides, and low-density lipoprotein cholesterol were relatively low in the high F4I group. Many cardiovascular outpatients have a high F4I and can probably be categorized as NASH. The high F4I patients had few features of metabolic syndrome and were suspected to have elevated tissue chymase dAIIFA contributing to inflammation in the liver as well as in cardiovascular organs.

Structure-based virtual screening for novel chymase inhibitors by in silico fragment mapping

The term chymase refers to a family of chymotrypsin-like serine proteases stored within the secretory granules of mast cells. Recently, a variety of small molecule inhibitors for chymase have been developed with a primary focus on the treatment of cardiovascular diseases. Despite the expected therapeutic benefit of these chymase inhibitors, they have not been used clinically. Here, we attempted to identify new chymase inhibitors using a multistep structure-based virtual screening protocol combined with our knowledge-based in silico fragment mapping technique. The mapping procedure identified fragments with novel modes of interaction at the oxyanion hole of chymase. Next, we constructed a three-dimensional (3D) pharmacophore model and retrieved eight candidate chymase inhibitors from a commercial database that included approximately five million compounds. This selection was achieved using a multistep virtual screening protocol, which combined a 3D pharmacophore-based search, docking calculations, and analyses of binding free energy. One of the eight compounds exhibited concentration-dependent chymase inhibitory activity, which could be further optimized to develop more potent chymase inhibitors.

Extended cleavage specificity of sheep mast cell protease-2: A classical chymase with preference to aromatic P1 substrate residues

Serine proteases constitute the major protein content of mammalian mast cell granules and the selectivity for substrates by these proteases is of major importance for the role of mast cells in immunity. In order to address this subject, we present here the extended cleavage specificity of sheep mast cell protease-2 (MCP2), a chymotrypsin-type serine protease. Comparison of the extended specificity results to a panel of mammalian mast cell chymases show, in almost all aspects, the same cleavage characteristics. This includes preference for aromatic residues (Phe, Tyr, Trp) in the P1 position of substrates and a preference for aliphatic residues in most other substrate positions around the cleavage site. MCP2 also cleaved, albeit relatively low efficiency, after Leu in the P1 position. In contrast to the human, mouse, hamster and opossum chymases that show a relatively strong preference for negatively charged amino acids in the P2'position, the sheep MCP2, however, lacked that preference. Therefore, together with the rat chymase (rMCP1), sheep MCP2 can be grouped to a small subfamily of mammalian chymases that show fairly unspecific preference in the P2'position. In summary, the results here support the view of a strong evolutionary conservation of a potent chymotrypsin-type protease as a key feature of mammalian mast cells.

Role of cardiac mast cells in exercise training-mediated cardiac remodeling in angiotensin II-infused ovariectomized rats

AIMS

Regular exercise is recommended in postmenopausal women to prevent the development of heart disease, but mechanism underlying the protection is not completely understood. Many studies have suggested that exercise training notably mediated whole body immune and inflammatory functions. Whether exercise training prevents cardiac dysfunction after deprivation of female sex hormones by inhibiting cardiac immune activation is therefore interesting.

MAIN METHODS

Nine-week treadmill running program was introduced in sham-operated and ovariectomized rats. In addition, chronic angiotensin II infusion was further challenged to activate pathological cardiac remodeling. Cardiac remodeling in associated with the density and degranulation of cardiac mast cells was then evaluated.

KEY FINDINGS

With exogenous angiotensin II-induced hypertension, cardiac hypertrophy with myocardial fibrosis was shown similarly in both sham-operated controls and ovariectomized rats. Although exercise training did not prevent cardiac hypertrophy, myocardial fibrosis was abolished by exercise. While ovariectomy increased both cardiac mast cell density and degranulation percentage, angiotensin II infusion only enhanced mast cell density. Exercise training could not decrease the density of mast cells, but it did normalize the percentage of degranulation in all groups. Correlation analysis suggested that cardiac mast cell activation is inversely associated with cardiomyocyte hypertrophy due to exercise training but is directly correlated to cardiac hypertrophy by angiotensin II infusion.

SIGNIFICANCE

Exercise training could attenuate cardiac mast cell hyperactivation induced by either deprivation of female sex hormones or excessive angiotensin II. Additionally, cardiac mast cells could be a solution in the distinction between physiological and pathological hypertrophic development.

Estrogen modulates the differential expression of cardiac myocyte chymase isoforms and diastolic function

Chymases, a family of serine proteases with chymotryptic activity, play a significant role in cardiac angiotensin II (Ang II) formation from its substrate Ang-(1-12) in both human and rodent models. No studies, to date, have assessed the differences in enzymatic activity among these isoforms in Ang II formation, particularly in the cardiomyocyte (CM). Using PCR and DNA sequencing, we demonstrated that MCP-1, MCP-2, MCP-4, and MCP-5 mRNAs are expressed in the CM of both spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). While rMCP-1 and rMCP-5 gene transcripts were higher than that of other isoforms in both rat strains, WKY CM exhibits higher levels of rMCP-1 and rMCP-5 mRNAs compared to the SHR CM. Ovariectomy (OVX) increased the expression of rMCP-1 and rMCP-5 mRNAs in WKY. In SHR, OVX was associated with a blunted increase in rMCP-1 mRNA compared to OVX normotensive WKY. Chymase activity, measured as Ang II formation from Ang-(1-12), significantly correlated with rMCP-1 and rMCP-5 mRNA expression in both rat strains. Both rMCP-1 and rMCP-5 mRNA expressions were positively correlated with progressive diastolic dysfunction (increasing the ratio of early mitral inflow velocity-to-early mitral annular velocity, E/e') and expanding chamber dimensions or increasing left ventricular internal diameter end diastole. These data show rMCP-1 and rMCP-5 as the Ang II forming chymase isoforms participating in the loss of normal cardiac function due to OVX in rodents.

Increase of chymase-dependent angiotensin II-forming activity in circulating mononuclear leukocytes after acute myocardial infarction chymase activity after acute myocardial infarction

A previous clinical study revealed elevation of chymase- and cathepsin G-dependent angiotensin II-forming activity (AIIFA) in the myocardium after acute myocardial infarction (AMI). This study examined the time course of chymase- and cathepsin G-dependent AIIFA in circulating mononuclear leukocytes (CML) after AMI. Consecutive patients with AMI were recruited. Chymase- and cathepsin G-dependent AIIFA in CML were assayed using a modified angiotensin I substrate with Nma/Dnp fluorescence quenching. The changes of CML AIIFA were monitored over time in the patients. Fifteen consecutive AMI patients admitted to our hospital were recruited. At 1 day after the admission, CML chymase- and cathepsin G-dependent AIIFA were 2.9- and 1.7-fold higher than at discharge, respectively. The ratio of chymase-dependent AIIFA to total AIIFA was significantly increased. AIIFA gradually decreased over time after the admission. The peak value of chymase- and cathepsin G-dependent AIIFA was significantly correlated with the maximum levels of aspartate aminotransferase (r = 0.53, 0.64), lactate dehydrogenase (r = 0.57, 0.62), and creatine kinase (r = 0.60, 0.65). This is the first evidence that chymase- and cathepsin G-dependent AIIFA is elevated in CML after AMI. Our data suggested that chymase-dependent AIIFA is increased in CML as well as in the myocardium after AMI, and that the level of chymase-dependent AIIFA might reflect the severity of infarction.

Prospective single-arm observational study of human chymase inhibitor Polygonum hydropiper L in subjects with hypertension

Background and Purpose: Human chymase (h-chymase) is a serine protease that forms local angiotensin II and has been proven to be related to onset of hypertension, arteriosclerosis, and post myocardial infarction cardiac remodeling. Since no chymase inhibitor was clinically available, an extensive screening for inhibition of h-chymase in three different extracts (water, hot water,  and ethanol) of approximately 800 food ingredients had been performed and we identified Polygonum hydropiper L (Polygonum). Using a dried and powdered Polygonum, we conducted a prospective, single-arm, pilot study to investigate its safety and antihypertensive effect in subjects with normal high blood pressure to moderate hypertension.Methods: First, a single oral dose of Polygonum powder (4000 mg) was administered to assess acute toxicity. Then, a pilot study was conducted in 11 subjects using the sequence of placebo and Polygonum for 2 weeks each. The dose of Polygonum was increased sequentially (200-2000 mg/day). Home blood pressure and pulse rate were monitored.Results: Oral administration of Polygonum (4000 mg) did not cause any adverse events. In the dose-escalation phase, evening systolic blood pressure was significantly decreased at 800 mg, 2000 mg doses post-treatment (p < 0.05, and p < 0.05, respectively). Depressor responders to Polygonum intake had significantly higher salt intake in spot urine (p < 0.05). No adverse events or reactions occurred.Conclusion: This was the first investigation that an h-chymase inhibitory Polygonum intake for safety and tolerability was proven and, in addition, chymase inhibitory Polygonum appeared to have depressor effect especially in a hypertensive subject with excessive salt intake.

Endothelins in inflammatory neurological diseases

Endothelins were discovered more than thirty years ago as potent vasoactive compounds. Beyond their well-documented cardiovascular properties, however, the contributions of the endothelin pathway have been demonstrated in several neuroinflammatory processes and the peptides have been reported as clinically relevant biomarkers in neurodegenerative diseases. Several studies report that endothelin-1 significantly contributes to the progression of neuroinflammatory processes, particularly during infections in the central nervous system (CNS), and is associated with a loss of endothelial integrity at the blood brain barrier level. Because of the paucity of clinical trials with endothelin-1 antagonists in several infectious and non-infectious neuroinflammatory diseases, it remains an open question whether the 21 amino acid peptide is a mediator/modulator rather than a biomarker of the progression of neurodegeneration. This review focuses on the potential roles of endothelins in the pathology of neuroinflammatory processes, including infectious diseases of viral, bacterial or parasitic origin in which the synthesis of endothelins or its pharmacology have been investigated from the cell to the bedside in several cases, as well as in non-infectious inflammatory processes such as neurodegenerative disorders like Alzheimers Disease or central nervous system vasculitis.

Critical role of the chymase/angiotensin-(1-12) axis in modulating cardiomyocyte contractility

BACKGROUND

Angiotensin-(1-12) [Ang-(1-12)] is a chymase-dependent source for angiotensin II (Ang II) cardiac activity. The direct contractile effects of Ang-(1-12) in normal and heart failure (HF) remain to be demonstrated. We assessed the hypothesis that Ang-(1-12) may modulate [Ca²⁺]_i regulation and alter cardiomyocyte contractility in normal and HF rats.

METHODS AND RESULTS

We compared left ventricle (LV) myocyte contractile and calcium transient ([Ca²⁺]_iT) responses to angiotensin peptides in 16 SD rats with isoproterenol-induced HF and 16 age-matched controls. In normal myocytes, versus baseline, Ang II (10^-6 M) superfusion significantly increased myocyte contractility (dL/dt_max: 40%) and [Ca²⁺]_iT (29%). Ang-(1-12) (4 × 10^-6 M) caused similar increases in dL/dt_max (34%) and [Ca²⁺]_iT (25%). Compared with normal myocytes, superfusion of Ang II and Ang-(1-12) in myocytes obtained from rats with isoproterenol-induced HF caused similar but significantly attenuated positive inotropic actions with about 42% to 50% less increases in dL/dt_max and [Ca²⁺]_iT. Chymostatin abolished Ang-(1-12)-mediated effects in normal and HF myocytes. The presence of an inhibitory cAMP analog, Rp-cAMPS prevented Ang-(1-12)-induced inotropic effects in both normal and HF myocytes. Incubation of HF myocytes with pertussis toxin (PTX) further augmented Ang II-mediated contractility.

CONCLUSIONS

Ang-(1-12) stimulates cardiomyocyte contractile function and [Ca²⁺]_iT in both normal and HF rats through a chymase mediated action. Altered inotropic responses to Ang-(1-12) and Ang II in HF myocytes are mediated through a cAMP-dependent mechanism that is coupled to both stimulatory G and inhibitory PTX-sensitive G proteins.

Depressor effect of the young leaves of Polygonum hydropiper Linn. in high-salt induced hypertensive mice

A novel chymase inhibitor has been reported to have depressor effect in salt-induced hypertension. Therefore, we examined the hypothesis that chymase inhibitory dried young leaves of Polygonum hydropiper (PPH) or young leaves extract of Polygonum hydropiper (PHE) could reduce salt-induced hypertension. In this study, 8-wk old wild-type mice were allocated into three experiments and experiment I included groups, I- normal water drinking, II- high salt (2% NaCl) water (HSW) drinking, and III- HSW plus PPH (500 mg kg^-1, orally) for 12-wk. Blood pressure (BP) and heart rate (HR) were measured at baseline and weekly up to wk-12. In experiment II, mice were given HSW for 12-wk followed by 8-wk treatment with PPH plus HSW (62.5, 125, 250 and 500 mg kg^-1 for groups I, II, III and IV, respectively). BP and HR were measured at baseline and monthly until wk-12, following weekly for 8-wk. Experiment III comprised of four groups of mice for 12-wk HSW and 8-wk treatment with PHE plus HSW (2.5, 5, 10 and 20 mg kg^-1 for groups I-IV, respectively). BP and HR were measured at baseline and monthly up to wk-12, following weekly for 8-wk. Significant reduction in BP and HR were observed in mice treated with PPH (500 mg kg^-1) compared to HSW control. PPH reduced BP and HR dose dependently in hypertensive mice and the higher dose showed maximum reduction. PHE at its maximum dose (20 mg kg^-1) significantly suppressed BP and HR. Over all, we found that the young leaves of Polygonum hydropiper suppressed salt-induced hypertension.

Mast cell heterogeneity and anti-inflammatory annexin A1 expression in leprosy skin lesions

Mast cells (MCs) have important immunoregulatory roles in skin inflammation. Annexin A1 (ANXA1) is an endogenous anti-inflammatory protein that can be expressed by mast cells, neutrophils, eosinophils, monocytes, epithelial and T cells. This study investigated MCs heterogeneity and ANXA1 expression in human dermatoses with special emphasis in leprosy. Sixty one skin biopsies from 2 groups were investigated: 40 newly diagnosed untreated leprosy patients (18 reaction-free, 11 type 1 reaction/T1R, 11 type 2 reaction/T2R); 21 patients with other dermatoses. Tryptase/try+ and chymase/chy + phenotypic markers and toluidine blue stained intact/degranulated MC counts/mm² were evaluated. Try⁺/chy⁺ MCs and ANXA1 were identified by streptavidin-biotin-peroxidase immunostaining and density was reported. In leprosy, degranulated MCs outnumbered intact ones regardless of the leprosy form (from tuberculoid/TT to lepromatous/LL), leprosy reactions (reactional/reaction-free) and type of reaction (T1R/T2R). Compared to other dermatoses, leprosy skin lesions showed lower numbers of degranulated and intact MCs. Try⁺ MCs outnumbered chy⁺ in leprosy lesions (reaction-free/reactional, particularly in T2R), but not in other dermatoses. Compared to other dermatoses, ANXA1 expression, which is also expressed in mast cells, was higher in the epidermis of leprosy skin lesions, independently of reactional episode. In leprosy, higher MC degranulation and differential expression of try⁺/chy⁺ subsets independent of leprosy type and reaction suggest that the Mycobacterium leprae infection itself dictates the inflammatory MCs activation in skin lesions. Higher expression of ANXA1 in leprosy suggests its potential anti-inflammatory role to maintain homeostasis preventing tissue and nerve damage.

Structure-based design, synthesis, and binding mode analysis of novel and potent chymase inhibitors

Based on insight from the X-ray crystal structure of human chymase in complex with compound 1, a lactam carbonyl of the diazepane core was exchanged with O-substituted oxyimino group, leading to amidoxime derivatives. This modification resulted in highly potent chymase inhibitors, such as O-phenylamidoxime 5f. X-ray crystal structure analysis indicated that compound 5f induced movement of the Leu99 and Tyr94 side chains at the S2 site, and the increase in inhibitory activity of O-phenyl amidoxime derivatives suggested that the O-phenyl moiety interacted with the Tyr94 residue. Surface plasmon resonance experiments showed that compound 5f had slower association and dissociation kinetics and the calculated residence time of compound 5f to human chymase was extended compared to that of amide compound 1.

Novel Cardiac Intracrine Mechanisms Based on Ang-(1-12)/Chymase Axis Require a Revision of Therapeutic Approaches in Human Heart Disease

PURPOSE OF THE REVIEW

Drugs targeting the renin-angiotensin system (RAS), namely angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are the most commonly prescribed drugs for patients with or at risk for cardiovascular events. However, new treatment strategies aimed at mitigating the rise of the heart failure pandemic are warranted because clinical trials show that RAS blockers have limited benefits in halting disease progression. The main goal of this review is to put forward the concept of an intracrine RAS signaling through the novel angiotensin-(1-12)/chymase axis as the main source of deleterious angiotensin II (Ang II) in cardiac maladaptive remodeling leading to heart failure (HF).

RECENT FINDINGS

Expanding traditional knowledge, Ang II can be produced in tissues independently from the circulatory renin-angiotensin system. In the heart, angiotensin-(1-12) [Ang-(1-12)], a recently discovered derivative of angiotensinogen, is a precursor of Ang II, and chymase rather than ACE is the main enzyme contributing to the direct production of Ang II from Ang-(1-12). The Ang-(1-12)/chymase axis is an independent intracrine pathway accounting for the trophic, contractile, and pro-arrhythmic Ang II actions in the human heart. Ang-(1-12) expression and chymase activity have been found elevated in the left atrial appendage of heart disease subjects, suggesting a pivotal role of this axis in the progression of HF. Recent meta-analysis of large clinical trials on the use of ACE inhibitors and angiotensin receptor blockers in cardiovascular disease has demonstrated an imbalance between patients that significantly benefit from these therapeutic agents and those that remain at risk for heart disease progression. Looking to find an explanation, detailed investigation on the RAS has unveiled a previously unrecognized complexity of substrates and enzymes in tissues ultimately associated with the production of Ang II that may explain the shortcomings of ACE inhibition and angiotensin receptor blockade. Discovery of the Ang-(1-12)/chymase axis in human hearts, capable of producing Ang II independently from the circulatory RAS, has led to the notion that a tissue-delimited RAS signaling in an intracrine fashion may account for the deleterious effects of Ang II in the heart, contributing to the transition from maladaptive cardiac remodeling to heart failure. Targeting intracellular RAS signaling may improve current therapies aimed at reducing the burden of heart failure.

Chymase inhibitor prevents the development and progression of non-alcoholic steatohepatitis in rats fed a high-fat and high-cholesterol diet

The effect of the chymase inhibitor TY-51469 on the development and progression of non-alcoholic steatohepatitis (NASH) was evaluated in rats fed a high-fat and high-cholesterol (HFC) diet. To evaluate the preventive effect of TY-51469 on the development of NASH, stroke-prone spontaneously hypertensive rat 5 (SHRSP5)/Dmcr rats were fed either a normal or HFC diet for 8 weeks, and concurrently administered either placebo or TY-51469 (1 mg/kg per day). To evaluate the effect of TY-51469 on the survival rate, TY-51469 was administered either concurrently with HFC diet (pretreated group) or 8 weeks after HFC diet at which point NASH had developed (posttreated group). Eight weeks after HFC diet, significant increases of steatosis, fibrosis and chymase-positive cells were observed in liver from the placebo-treated rats. Significant increases of myeloperoxidase, transforming growth factor-β, matrix metalloproteinase-9, and collagen I mRNA levels were also observed. However, all parameters were significantly attenuated in the TY-51469-treated group. A survival rate of the placebo-treated group fed the HFC diet was 0% at 14 weeks. In comparison, the rates of TY-51469-pretreated and TY-51469-posttreated groups were 100% and 50% at 14 weeks, respectively. Chymase inhibitor may be applicable to preventing the development and progression of NASH.

Cardiovascular effect of inflammation and nonsteroidal anti-inflammatory drugs on renin-angiotensin system in experimental arthritis

A co-morbidity of inflammatory conditions is increased cardio-renal risks. Additionally, nonsteroidal anti-inflammatory drugs (NSAIDs) which are used to treat pain and inflammation are also associated with increase in such risks. We hypothesized that inflammation and NSAIDs impose the cardio-renal risk through the activation of the renin-angiotensin-system (RAS), a regulating pathway of the renal and cardiovascular homeostasis. We investigated the effect of adjuvant arthritis and NSAIDs on the RAS. Western blotting and ELISA were used to measure the RAS components. Inflammation caused significant imbalances in the cardiac and renal angiotensin converting enzymes, their biologically active angiotensin peptides (AngII and Ang1-7) and the target proteins involved in the peptide-receptor binding (AngII type 1 and type 2, and Ang1-7 receptor, Mas) toward cardio-renal toxicity. However, 7 days treatment of arthritic animals with NSAIDs (rofecoxib, meloxicam, celecoxib and flurbiprofen) restored the constitutive balances, perhaps due to their anti-inflammatory properties. Inflammation exerts its cardio-renal effects by causing imbalance in the RAS. NSAIDs through their anti-inflammatory effect restore this imbalance. Thus, mechanisms other than imbalances in the RAS may be involved in the NSAIDs cardiotoxicity.