Review of various molecular targets on mast cells and its relation to obesity: A future perspective

Mast cells are stimulatory factors in prognosis of various immunogenic and allergic diseases in human body. These cells play an important role in various immunological and metabolic diseases. The aim of present article is to explore the molecular targets to suppress the over expression of mast cells in obesity. The last 20 years literature were searched by various bibliographic data bases like Pubmed, google Scholar, Scopus and web of Science. The data were collected by keywords like "Mast Cell" "obesity" and "role of mast cell or role in obesity". Articles and their abstract were reviewed with a counting of 827 publications, in which 87 publications were considered for study and remaining was excluded because of its specificity to the subject. This review explains the characteristics, molecular targets and role of mast cells in obesity and existing research with mast cells to the area of metabolic diseases.

Role of Chymase in the Development of Liver Cirrhosis and Its Complications: Experimental and Human Data

Background

Tissue Angiotensin II (Ang-II), produced through local non ACE-dependent pathways, stimulates liver fibrogenesis, renal vasoconstriction and sodium retention.

Aim

To highlight chymase-dependent pathway of Ang-II production in liver and kidney during cirrhosis development.

Methods

Liver histology, portal pressure, liver and kidney function, and hormonal status were investigated in rat liver cirrhosis induced through 13 weeks of CCl₄, with or without chymase inhibitor SF2809E, administered between 4^th and 13^th CCl₄ weeks; liver and kidney chymase immunolocation and Ang-II content were assessed. Chymase immunohistochemistry was also assessed in normal and cirrhotic human liver, and chymase mRNA transcripts were measured in human HepG2 cells and activated hepatic stellate cells (HSC/MFs) in vitro.

Results

Rats receiving both CCl₄ and SF2809E showed liver fibrotic septa focally linking portal tracts but no cirrhosis, as compared to ascitic cirrhotic rats receiving CCl₄. SF2809E reduced portal pressure, plasma bilirubin, tissue content of Ang-II, plasma renin activity, norepinephrine and vasopressin, and increased glomerular filtration rate, water clearance, urinary sodium excretion. Chymase tissue content was increased and detected in α-SMA-positive liver myofibroblasts and in kidney tubular cells of cirrhotic rats. In human cirrhosis, chymase was located in hepatocytes of regenerative nodules. Human HepG2 cells and HSC/MFs responded to TGF-β1 by up-regulating chymase mRNA transcription.

Conclusions

Chymase, through synthesis of Ang-II and other mediators, plays a role in the derangement of liver and kidney function in chronic liver diseases. In human cirrhosis, chymase is well-represented and apt to become a future target of pharmacological treatment.

Chymase mediates injury and mitochondrial damage in cardiomyocytes during acute ischemia/reperfusion in the dog

Cardiac ischemia and reperfusion (I/R) injury occurs because the acute increase in oxidative/inflammatory stress during reperfusion culminates in the death of cardiomyocytes. Currently, there is no drug utilized clinically that attenuates I/R injury in patients. Previous studies have demonstrated degranulation of mast cell contents into the interstitium after I/R. Using a dog model of I/R, we tested the role of chymase, a mast cell protease, in cardiomyocyte injury using a specific oral chymase inhibitor (CI). 15 adult mongrel dogs had left anterior descending artery occlusion for 60 min and reperfusion for 100 minutes. 9 dogs received vehicle and 6 were pretreated with a specific CI. In vivo cardiac microdialysis demonstrated a 3-fold increase in interstitial fluid chymase activity in I/R region that was significantly decreased by CI. CI pretreatment significantly attenuated loss of laminin, focal adhesion complex disruption, and release of troponin I into the circulation. Microarray analysis identified an I/R induced 17-fold increase in nuclear receptor subfamily 4A1 (NR4A1) and significantly decreased by CI. NR4A1 normally resides in the nucleus but can induce cell death on migration to the cytoplasm. I/R caused significant increase in NR4A1 protein expression and cytoplasmic translocation, and mitochondrial degradation, which were decreased by CI. Immunohistochemistry also revealed a high concentration of chymase within cardiomyocytes after I/R. In vitro, chymase added to culture HL-1 cardiomyocytes entered the cytoplasm and nucleus in a dynamin-dependent fashion, and promoted cytoplasmic translocation of NR4A1 protein. shRNA knockdown of NR4A1 on pre-treatment of HL-1 cells with CI significantly decreased chymase-induced cell death and mitochondrial damage. These results suggest that the beneficial effects of an orally active CI during I/R are mediated in the cardiac interstitium as well as within the cardiomyocyte due to a heretofore-unrecognized chymase entry into cardiomyocytes.

Mast cells and angiogenesis in wound healing

OBJECTIVE

To investigate the role of mast cells and vascular endothelial growth factor (VEGF) as a mediator of angiogenesis to promote wound healing in surgical and pathological scars.

STUDY DESIGN

The study was carried out on 40 patients who presented with active scar lesions. They were subdivided into 4 groups. They included granulation tissue (10 cases), surgical scar (10 cases), hypertrophic scar (10 cases), and keloid scar (10 cases). Also 10 healthy volunteers of the same age and sex were selected as a control group. Skin biopsies were taken from the patients and the control group. Skin biopsies from clinically assessed studied groups were processed for routine histology and embedded in paraffin. Four sections were prepared from each paraffin block. The first section was stained with hematoxylin and eosin for histological evaluation. The second and third sections were processed for immunostaining of mast cells that contain chymase (MCCs) and mast cells that contain tryptase (MCTs). The fourth section was processed for immunostaining of VEGF.

RESULTS

MCCs exhibited mild expression in normal tissue, granulation tissue, and surgical, hypertrophic and keloid scars. MCTs exhibited mild expression in normal tissue, granulation tissue and keloid, whereas moderate expression was exhibited in hypertrophic and surgical scars. VEGF expression was absent in normal tissue, mild in keloid, surgical and hypertrophic scars, and moderate in keloids and granulation tissue.

CONCLUSION

Mast cell expression variation among different scar types signals the pathological evolution of the lesion, and hence may guide the need for therapeutic intervention.

Involvement of chymase in allergic conjunctivitis of guinea pigs

It has been reported that chymase activity was increased in allergic conjunctivitis patients and this activity was correlated with the severity of the disease. However, the precise roles of chymase in allergic conjunctivitis are unclear, and whether chymase inhibitors are effective for allergic conjunctivitis has not been reported even in experimental animal models. In this study, the roles of chymase in the pathogenesis were evaluated using a selective chymase inhibitor, ONO-WH-236, in a guinea pig model of allergic conjunctivitis induced by cedar pollen. Sensitized guinea pigs were challenged by the pollen, followed by assessing redness and edema in the conjuntiva, and counting the frequency of eye scratching as an itch-associated response. Treatment with the ONO-WH-236 (40 and 80 mg/kg, p.o.) dose-dependently inhibited the induction of redness, edema and scratching behavior. An anti-histaminic drug, ketotifen (3 mg/kg, p.o.), also significantly inhibited conjunctivitis symptoms. Chymase activity was increased in ophthalmic lavage fluid immediately after the pollen challenge. The increase in chymase activity was inhibited by in vivo treatment with ONO-WH-236. Interestingly, increased histamine in the ophthalmic lavage fluid immediately after the challenge was also inhibited by the chymase inhibitor. Administration of human recombinant chymase by eye dropping (0.09 and 0.9 μg/eye) dose-dependently induced scratching behavior, which was inhibited by not only ONO-WH-236 but also ketotifen; however, chymase administration induced only weak redness in the conjunctiva, which was resistant to treatment with anti-histaminic drugs. In conclusion, it was suggested that chymase was released from mast cells after antigen challenge, followed by the induction of conjunctivitis symptoms through histamine release from mast cells. Thus, chymase could be a potential target for pharmacotherapy for allergic conjunctivitis.

Contributions of ACE and mast cell chymase to endogenous angiotensin II generation and leucocyte recruitment in vivo

AIMS

In vitro studies suggest that mast cell chymase (MCP) is more important than angiotensin-converting enzyme (ACE) for generating angiotensin II (Ang II) within the cardiovascular system. We investigated in vivo the relative contributions of ACE and MCP to leucocyte recruitment induced by endogenously generated Ang II.

METHODS AND RESULTS

Exposure of the murine cremasteric microcirculation of C57BL/6 mice to Ang I (100 nM for 4 h) induced leucocyte-endothelium interactions. Either losartan (an Ang II receptor-1 antagonist, AT(1)) or enalapril (an ACE inhibitor), but not chymostatin (a chymase inhibitor), inhibited Ang I-induced responses. Mast cell degranulation with compound 48/80 (CMP48/80, 1 μg/mL) also induced leucocyte adhesion but this was only weakly affected by the inhibitors. When Ang I and CMP48/80 were co-administered, AT(1B) receptor expression was increased, MCP-4 was found surrounding the vessel wall, and ACE was detected in the endothelium. Ang I + CMP48/80 induced enhanced leucocyte adhesion that was attenuated by losartan, enalapril, enalapril + chymostatin, and cromolyn (a mast cell stabilizer). The use of male mast cell-deficient WBB6F1/J-Kit(w)/Kit(w-v) mice (C57BL/6 background) confirmed these findings.

CONCLUSION

In vivo, Ang II is primarily generated by ACE under basal conditions, but in inflammatory conditions, the release of MCP amplifies local Ang II concentrations and the associated inflammatory process. Thus, AT(1) receptor antagonists may be more effective than ACE inhibitors for treating ongoing Ang II-mediated vascular inflammation.

Regional vascular response to ProAngiotensin-12 (PA12) through the rat arterial system

ProAngiotensin-12 (PA12) is the most recent peptide to be identified as a functional component of the renin-angiotensin system (RAS). PA12 is reported to constrict rat coronary arteries and the aorta, dependent upon angiotensin II-converting enzyme 1 (ACE1) and chymase. The current study employed myography to determine the direct vascular effects of PA12 on a range of isolated rat arteries extending from the core to periphery. PA12 significantly constricted the descending thoracic aorta, right and left common carotid arteries, abdominal aorta and superior mesenteric artery, with little effect on the femoral and renal arteries. AngII was found to produce similar responses to PA12 when administered at the same dose. A potency gradient in response to PA12 was clearly apparent, with vessels in closest proximity to the heart responding with the greatest constriction; while constrictive potency was lost further form the heart. Inhibition of ACE1 and chymase both significantly attenuated PA12-induced vasoconstriction, with chymostatin displaying lesser potency. We postulate ACE1 primarily regulates RAS activity within the circulation, while chymase may have an important role in local, tissue-based RAS activity.

The intracellular renin-angiotensin system: a new paradigm

More than a century after its discovery, the physiological implications of the renin-angiotensin system (RAS) continue to expand, with the identification of new components, functions and subsystems. These advancements have led to better management and understanding of a broad range of cardiovascular and metabolic disorders. The RAS has traditionally been viewed as a circulatory system, involved in the short-term regulation of volume and blood pressure homeostasis. Recently, local RASs have been described as regulators of chronic tissue effects. Most recently, studies have provided evidence of a complete, functional RAS within cells, described as an 'intracrine' or intracellular system. A more comprehensive understanding of the intracellular RAS provides for new strategies in system regulation and a more efficacious approach to the management of RAS-related diseases.

The chymotrypsin-like protease complex of Treponema denticola ATCC 35405 mediates fibrinogen adherence and degradation

Treponema denticola is an anaerobic spirochete strongly associated with human periodontal disease. T. denticola bacteria interact with a range of host tissue proteins, including fibronectin, laminin, and fibrinogen. The latter localizes in the extracellular matrix where tissue damage has occurred, and interactions with fibrinogen may play a key role in T. denticola colonization of the damaged sites. T. denticola ATCC 35405 showed saturable binding of fluid-phase fibrinogen to the cell surface and saturable adherence to immobilized fibrinogen. Levels of fibrinogen binding were enhanced in the presence of the serine protease inhibitor phenylmethylsulfonyl fluoride. The Aalpha and Bbeta chains of fibrinogen, but not the gamma chains, were specifically recognized by T. denticola. Following fibrinogen affinity chromatography analysis of cell surface extracts, a major fibrinogen-binding component (polypeptide molecular mass, approximately 100 kDa), which also degraded fibrinogen, was purified. Upon heating at 100 degrees C, the polypeptide was dissociated into three components (apparent molecular masses, 80, 48, and 45 kDa) that did not individually bind or degrade fibrinogen. The native 100-kDa polypeptide complex was identified as chymotrypsin-like protease (CTLP), or dentilisin. In an isogenic CTLP(-) mutant strain, CKE, chymotrypsin-like activity was reduced >90% compared to that in the wild type and fibrinogen binding and hydrolysis were ablated. Isogenic mutant strain MHE, deficient in the production of Msp (major surface protein), showed levels of CTLP reduced 40% relative to those in the wild type and exhibited correspondingly reduced levels of fibrinogen binding and proteolysis. Thrombin clotting times in the presence of wild-type T. denticola cells, but not strain CKE (CTLP(-)) cells, were extended. These results suggest that interactions of T. denticola with fibrinogen, which may promote colonization and modulate hemostasis, are mediated principally by CTLP.

Enhanced mast cell chymase expression in human idiopathic interstitial pneumonia

Previous studies have shown that mast cell chymase induces and promotes fibrogenesis in injured tissues. We studied the roles of mast cell chymase in the fibritic processes of human idiopathic interstitial pneumonias. Frozen tissue sections from human lungs with usual interstitial pneumonia (n=7), nonspecific interstitial pneumonia (n=4) and normal lungs (n=10) were studied immunohistochemically. Monoclonal antibodies against mast cell chymase, tryptase, interleukin-4, and smooth muscle actin were used. Stained cells or areas were quantified by computer-aided morphometry. The numbers of both tryptase-positive mast cells and chymase-positive mast cells were significantly greater in lung tissues with idiopathic interstitial pneumonia than in normal lung tissues. The increase in the number of chymase-positive mast cells in the diseased lung tissues was closely related to an increase in interleukin-4-positive cells, and also to an accumulation of smooth muscle cells and myofibroblasts. Because smooth muscle cell and myofibroblast proliferation is a principal pathological change in idiopathic interstitial pneumonias, these observations suggest that mast cell chymase, possibly induced by interleukin-4-dependent phenotypic modulation, may be an important mediator in the inflammatory and fibrotic processes of idiopathic interstitial pneumonia in humans.

The involvement of mast cells and mast cell proteinases in the intestinal response to equine cyathostomin infection

Cyathostomins (Cyathostominae) are regarded as the most pathogenic equine nematode worldwide. These nematodes are difficult to control in equine populations due to emerging anthelmintic resistance and evasion of encysted larval cyathostomins to regular modern anthelmintics. Mast cells and their proteinases have been shown to play a role in the mammalian immune response to nematode infections. Involvement of mast cells and mast cell proteinases in the equine immune response to cyathostomin infection is proposed. A technique was established to perform immunohistochemical staining using polyclonal rabbit anti-equine mast cell proteinase-1 (eqMCP-1) and anti-equine tryptase on formalin-fixed large intestinal sections, from horses classified as cyathostomin positive and negative at the time of death based upon larval enumeration. Quantitative analysis of antibody labelled mast cells was used to detect mast cell proteinases in equine large intestinal sections positive and negative for cyathostomin larvae. This demonstrated an increase in equine tryptase labelled mucosal and submucosal mast cells in cyathostomin positive horses. This study has established an immunohistochemical technique to demonstrate mast cell proteinases in formalin-fixed large intestinal sections. This technique may be used to determine possible involvement of mast cells and their proteinases in the equine immune response to cyathostomin larvae. Further studies are required to define a specific role.

The Significance of Chymase in the Progression of Abdominal Aortic Aneurysms in Dogs

In this study, we investigated the effect of a specific chymase inhibitor, NK3201, in the progression of abdominal aortic aneurysm in a dog experimental model. Abdominal aortic aneurysms were induced in dogs by injecting elastase into the abdominal aorta. NK3201 (1 mg/kg per day, p.o.) or a placebo was started 3 days before elastase injection and continued for 8 weeks after the injection. On abdominal ultrasound, the aortic diameter was seen to gradually expand in the placebo-treated group, but not in the NK3201-treated group. Eight weeks after elastase injection, the ratio of the medial area to the total area in the placebo-treated group was significantly smaller than that in the normal group, but it was significantly larger than that in the NK3201-treated group. In addition to chymase activity, angiotensin II-forming and matrix metalloproteinase-9 activities were significantly higher in the placebo-treated group than in the normal group; in the NK3201-treated group, all of these activities were significantly decreased. On immunohistochemical analyses, there was a significantly greater number of chymase-positive cells in the placebo-treated group than in the normal group, but the number was significantly smaller in the NK3201-treated group than in the placebo-treated group. Thus, chymase inhibition may become a useful strategy for preventing abdominal aortic aneurysms.

Murine model of food allergy after epicutaneous sensitization: role of mucosal mast cell protease-1

OBJECTIVE

Studies of the pathological mechanisms of food allergy have been impeded by the lack of relevant animal models. The purpose of this study was to develop a physiological model of food allergy that was not dependent on immunostimulatory adjuvants.

MATERIAL AND METHODS

Balb/c mice were epicutaneously sensitized four times at varying intervals over a 22-day period, and challenged orally from day 40, 6 times every 1-3 days with either saline or ovalbumin.

RESULTS

After sensitization (day 35) but before the oral challenges, the ovalbumin-sensitized groups showed increased specific IgE and IgG1 production when compared with the sham-sensitized groups. Mucosal mast cell protease-1 (MMCP-1) was undetectable in serum before the intragastric challenge. MMCP-1 concentrations were increased after the first ovalbumin dose, solely in the ovalbumin-sensitized and -challenged group. After the challenge period, the mean serum MMCP-1 concentration increased from an undetectable level in controls to an over 44-fold level in the ovalbumin-sensitized and -challenged mice. In this group, MMCP-1-positive cells were present in the small intestine and expressions of IFN-gamma and CXCL-9 mRNA were decreased in the ileum, suggesting an impaired Th-1-type response. Within one hour of the last ovalbumin challenge, 5 out of 6 mice developed diarrhea in the ovalbumin-sensitized and -challenged group, but there was no diarrhea in the other groups.

CONCLUSIONS

A murine model of food allergy based on sensitization via epicutaneous exposure to allergen without immunostimulatory adjuvants was developed. Effective production of MMCP-1 together with specific IgE and IgG1 suggests a breakdown in oral tolerance to the allergen. Intragastric challenges were accompanied by mast cell-dependent immunopathological changes and diarrhea.