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PubMed2003

Involvement of mast cell chymase in bleomycin-induced pulmonary fibrosis in mice.

The possible role of mast cell chymase in organ fibrosis was examined using a bleomycin-induced pulmonary fibrosis model in mice. Intratracheal injection of bleomycin to mice significantly increased not only hydroxyproline content but also chymase activity in the lung. Administration of a chymase inhibitor SUN C8077 (7-chloro-3-(3-amynophenyl) quinazoline-2, 4-dione methanesulfonate) dose-dependently reversed the bleomycin-induced increase in hydroxyproline content as well as chymase activity in the lung. Human chymase digested latent transforming growth factor-beta1 (TGF-beta1) to form mature TGF-beta1 in vitro, which was inhibited by SUN C8077. Human chymase, on the other hand, failed to stimulate DNA synthesis of human lung fibroblasts CCD-8Lu and LL97A. Taken together, it is suggested that mast cell chymase might participate in the pathogenesis of pulmonary fibrosis, and that the chymase-induced fibrosis might be mediated at least in part by TGF-beta1. Chymase inhibitor may be promising for treatment of pulmonary fibrosis in humans.

Animals↗
PubMed2001

Release of soluble tryptase but only minor amounts of chymase activity from cutaneous mast cells.

Tryptase and chymase are the major serine proteinases of skin mast cells but their biologic significance depends on their activity. In this study, we demonstrate the release of soluble activity of tryptase, but not markedly that of chymase, into skin blister fluids induced by freezing with liquid nitrogen as well as into supernatant during incubation of 8 whole skin specimens with compound 48/80 for up to 2 days followed by sonication. Incubation of 3 other skin specimens in compound 48/80 for up to 2 days revealed that the number of mast cells displaying tryptase activity decreased significantly on day 2, and the number of mast cells showing chymase activity (but not those showing chymase immunoreactivity) decreased significantly on day 1 but not thereafter on day 2. The results of 3 skin organ cultures for up to 14 days showed steady decrease in the number of tryptase-positive cells but persistence of mast cells containing chymase activity. Chymase in solution was sensitively inhibited by 0.01 mg/ml alpha1-antichymotrypsin but higher concentrations (0.3-3.0 mg/ml) were needed for inhibiting chymase on skin sections. In conclusion, after mast cell degranulation tryptase activity is substantially solubilized and it may potentially affect both local and distant skin structures. Instead, chymase is partially inactivated and the remaining chymase activity persists at the site of degranulation having only local effects.

Adult↗
PubMed2005

Mast cell chymase in the ischemic kidney of severe unilateral renovascular hypertension.

Chymase degrades angiotensin I (AI) to form angiotensin II (AII), probably constituting a bypass of the renin-angiotensin cascade. Chymase activity increases in some vascular diseases. In the kidney, an increase in chymase activity was reported in an animal model of ischemic kidney of renovascular hypertension (RVH); however, no such evidence has been provided in humans. We treated a 64-year-old patient with severe unilateral RVH and atherosclerosis, for whom removal of the ischemic kidney was the only option. Using immunohistochemical staining, we investigated chymase activity in the removed kidney and associated artery and vein. An increase in chymase activity, together with mast cells infiltrating the interstitium, was observed where interstitial fibrosis was seen. In the renal artery, where severe atherosclerosis was seen, and also in the vein, mast cell infiltration in the adventitia was accompanied by chymase. The captopril test showed an increase in serum aldosterone level, with a concomitant increase in plasma renin activity and decrease in blood pressure. Because the decrease in blood pressure implies a decrease in circulatory AII levels, it is plausible that in this patient, chymase had a role in AII formation in the adrenal gland to stimulate aldosterone secretion. Thus, by means of captopril, AI levels increased, and chymase may have produced AII in loci tissues, which, in turn, stimulated aldosterone secretion. This is the first report of an increase in chymase activity in the interstitium of an ischemic kidney and renal artery and vein in a patient with RVH and atherosclerosis.

Angiography, Digital Subtraction↗
PubMed2001

Chymase-dependent angiotensin II formation in the saphenous vein versus the internal thoracic artery.

OBJECTIVES: The great saphenous vein graft is known to be less patent than the internal thoracic artery graft. Recently, we reported that chymase-dependent angiotensin II formation plays an important role in the development of intimal hyperplasia in dog grafted veins. In this study we investigated the levels of angiotensin II-forming enzymes, angiotensin-converting enzyme, and chymase in human saphenous veins and internal thoracic arteries. METHODS: The saphenous vein and internal thoracic artery specimens were obtained from coronary artery bypass grafts of patients during surgical procedures (saphenous vein, n = 16; internal thoracic artery, n = 16). Activities of angiotensin-converting enzyme and chymase were determined by using the extract from the saphenous vein or internal thoracic artery. Sections of the saphenous vein or internal thoracic artery were stained with van Gieson's elastin stain and were immunostained with anti-human chymase antibody. RESULTS: The activities of angiotensin-converting enzyme in the saphenous vein and internal thoracic artery were 0.34 +/- 0.12 and 0.32 +/- 0.17 mU/mg protein, respectively, and the difference was not significant. The chymase activity in the saphenous vein was significantly higher than that in the internal thoracic artery (saphenous vein, 10.1 +/- 0.81 mU/mg protein; internal thoracic artery, 6.21 +/- 1.86 mU/mg protein). Chymase-positive cells in the saphenous vein were located in both the media and adventitia, and those in the internal thoracic artery were located only in the adventitia. The number of chymase-positive cells in the saphenous vein was about 2.6 times that in the internal thoracic artery. CONCLUSION: The chymase activity, but not the angiotensin-converting enzyme activity, was significantly higher in the saphenous vein, suggesting that the high levels of chymase activity may be related to the poorer performance of the saphenous vein for use as a bypass conduit.

Aged↗
PubMed1997

Selective reporter expression in mast cells using a chymase promoter.

Primate alpha-chymases are mast cell neutral proteases that are involved in regulating several regulatory peptides including angiotensin II. Because of significant substrate specificity differences among the chymase group of enzymes, animal models that overexpress primate chymases are crucial for delineating the in vivo function of these enzymes. Activation of alpha-prochymase requires processing enzymes and proteoglycans found in mast cell secretory granules. Thus, the development of models overexpressing active primate chymase requires a mast cell-specific promoter. We show that the 571-base pair (bp) 5'-upstream sequence of the baboon chymase gene, which encodes an alpha-chymase, coupled to the prokaryotic lacZ gene allows the targeting of beta-galactosidase to mast cells in transgenic mice. Tissue expression of the transgene is similar to the expression of the endogenous mouse alpha-chymase mouse mast cell protease-5. A mouse mast cell line that endogenously expresses mouse mast cell protease-5 (JKras mast cells) also selectively supports the expression of this transgene. In vitro transcription studies in JKras mast cells shows the critical role of a GATA cis-regulatory motif in baboon chymase promoter, located approximately 430-bp upstream of the transcription start site. These results suggest that the 571-bp domain of the baboon chymase promoter contains most, if not all, of the mast cell-specific region of the promoter. We describe here for the first time a promoter that directs expression of transgenes specifically to mouse mast cells. This promoter should be generally applicable for dominant expression of mast cell regulatory proteins.

3T3 Cells↗
PubMed2003

Albumin is a substrate of human chymase. Prediction by combinatorial peptide screening and development of a selective inhibitor based on the albumin cleavage site.

Human chymase is a chymotryptic serine peptidase stored and secreted by mast cells. Compared with other chymotryptic enzymes, such as cathepsin G and chymotrypsin, it is much more slowly inhibited by serum serpins. Although chymase hydrolyzes several peptides and proteins in vitro, its target repertoire is limited compared with chymotrypsin because of selective interactions in an extended substrate-binding site. The best-known natural substrate, angiotensin I, is cleaved to generate vasoactive angiotensin II. Selectivity of angiotensin cleavage depends in major part on interactions involving substrate residues on the carboxyl-terminal (P1'-P2') side of the cleaved bond. To identify new targets based on interactions with residues on the aminoterminal (P4-P1) side of the site of hydrolysis, we profiled substrate preferences of recombinant human chymase using a combinatorial, fluorogenic peptide substrate library. Data base queries using the peptide (Arg-Glu-Thr-Tyr-X) generated from the most preferred amino acid at each subsite identify albumin as the sole, soluble, human extracellular protein containing this sequence. We validate the prediction that this site is chymase-susceptible by showing that chymase hydrolyzes albumin uniquely at the predicted location, with the resulting fragments remaining disulfide-linked. The site of hydrolysis is highly conserved in vertebrate albumins and is near predicted sites of metal cation binding, but nicking by chymase does not alter binding of Cu2+ or Zn2+. A synthetic peptidic inhibitor, diphenyl N alpha-benzoxycarbonyl-l-Arg-Glu-Thr-PheP-phosphonate, was designed from the preferred P4-P1 substrate sequence. This inhibitor is highly potent (IC50 3.8 nM) and 2,700- and 1,300-fold selective for chymase over cathepsin G and chymotrypsin, respectively. In summary, these findings reveal albumin to be a substrate for chymase and identify a potentially useful new chymase inhibitor.

Albumins↗
PubMed2005

Species differences in angiotensin II generation and degradation by mast cell chymases.

Although chymases are known to exhibit species differences in regard to angiotensin (Ang) II generation and degradation, their properties have never been compared under the same experimental conditions. We analyzed the processing of Ang I by chymases of a variety of species (human chymase, dog chymase, hamster chymase-1, rat mast cell protease-1 [rMCP-1], mouse mast cell protease-4 [mMCP-4]) at physiological ionic strength and under neutral pH conditions. Human chymase generated Ang II from Ang I without further degradation, whereas the chymases of other species generated Ang II, followed by degradation at the Tyr4-Ile5 site in a time-dependent manner. Kinetic analysis showed that in terms of Ang II generating activity (analyzed by cleavage of the Phe8-His9 bond using the model peptide Ang(5-10), Ile5-His6-Pro7-Phe8-His9-Leu10), the chymases ranked as follows: dog > human > hamster > mouse > rat (kcat/Km: 18, 11, 0.69, 0.059, 0.030 microM-1min-1), and that in terms of Ang II degrading activity (i.e., cleavage of the Tyr4-Ile5 bond of Ang II), the order was hamster > rat > mouse > dog (kcat/Km: 5.4, 4.8, 0.39, 0.29 microM-lmin-1). These results suggest species differences in the contribution of chymases to local Ang II generation and degradation.

Angiotensin II↗
PubMed2004

An antiarrhythmic effect of a chymase inhibitor after myocardial infarction.

Chymase plays an important role in the regulation of local angiotensin (Ang) II formation in the cardiac tissue. We recently found that cardiac chymase was activated significantly and survival rate markedly improved by treatment with chymase inhibitors after myocardial infarction (MI) in hamsters. However, the mechanisms for this effect have not been established. Because lethal arrhythmias are generally believed to contribute to sudden cardiac death, we assessed whether inhibition of cardiac chymase would provide an antiarrhythmic effect during the 8-h ischemic period after 2-[4-(5-fluoro-3-methylbenzo-[b]thiophen-2-yl)sulfonamide-3-methanesulfonylphenyl]oxazole-4-carboxylicacid (TY51184) (a specific chymase inhibitor, 1 mg/kg i.v.) treatment by ligation of left anterior descending coronary artery (LAD) in dogs. Effects of candesartan (an Ang II type 1 receptor antagonist, 1 mg/kg i.v.) in this model were also assessed. Total Ang II-forming activity and chymase activity in the infarcted heart were increased significantly 8 h after LAD ligation. A time-dependent elevation of Ang II in plasma was also observed. A decrease in plasma Ang II levels after TY51184 treatment occurred concomitantly with suppression of cardiac chymase activity. LAD ligation resulted in a large number of ventricular arrhythmias (VAs). TY51184 and candesartan treatments largely suppressed the appearance of VAs, and the efficacy of the two agents was similar. These findings demonstrate that chymase inhibition can provide an antiarrhythmic effect after MI, and the reduction of Ang II by TY51184 may be mainly responsible for this beneficial effect. An antiarrhythmic effect of chymase inhibitors may contribute to reductions in the mortality rate during the acute phase after MI.

Animals↗
PubMed1999

Tranilast suppresses vascular chymase expression and neointima formation in balloon-injured dog carotid artery.

BACKGROUND: Activation of vascular chymase plays a major role in myointimal hypertrophy after vascular injury by augmenting the production of angiotensin (ANG) II. Because chymase is synthesized mainly in mast cells, we assumed that the chymase-dependent ANG II formation could be downregulated by tranilast, a mast cell-stabilizing antiallergic agent. We have assessed inhibitory effects of tranilast on neointima formation after balloon injury in the carotid artery of dogs, which share a similar ANG II-forming chymase with humans, and further explored the pathophysiological significance of vascular chymase. METHODS AND RESULTS: Either tranilast (50 mg/kg BID) or vehicle was orally administered to beagles for 2 weeks before and 4 weeks after balloon injury. Four weeks after the injury, remarkable neointima was formed in the carotid arteries of vehicle-treated dogs. Chymase mRNA levels and chymaselike activity of vehicle-treated injured arteries were increased 10.2- and 4.8-fold, respectively, those of uninjured arteries. Angiotensin-converting enzyme (ACE) activity was slightly increased in the injured arteries, whereas ACE mRNA levels were not. Tranilast treatment completely prevented the increase in chymaselike activity, reduced the chymase mRNA levels by 43%, and decreased the carotid intima/media ratio by 63%. In vehicle-treated injured arteries, mast cell count in the adventitia showed a great increase, which was completely prevented by the tranilast treatment. Vascular ACE activity and mRNA levels were unaffected by tranilast. CONCLUSIONS: Tranilast suppressed chymase gene expression, which was specifically activated in the injured arteries, and prevented neointima formation. Suppression of the chymase-dependent ANG II-forming pathway may contribute to the beneficial effects of tranilast.

Animals↗
PubMed2001

Mast cell chymase inhibits smooth muscle cell growth and collagen expression in vitro: transforming growth factor-beta1-dependent and -independent effects.

In the vulnerable areas of fibrous caps of advanced atherosclerotic lesions, chymase-containing mast cells are present. In such areas, the numbers of smooth muscle cells (SMCs) and the content of collagen are reduced. In this in vitro study, we found that the addition of chymase, isolated and purified from rat serosal mast cells, to cultured rat aortic SMCs of the synthetic phenotype (s-SMCs) inhibited their proliferation by blocking the G(0)/G(1)-->S transition in the cell cycle. Rat chymase and recombinant human chymase inhibited the expression of collagen type I and type III mRNA in s-SMCs and in human coronary arterial SMCs. The growth-inhibitory effect of chymase was partially reversed by addition to the culture medium of an antibody capable of neutralizing the activity of transforming growth factor-beta1 (TGF-beta1). Immunocytochemistry showed that the s-SMCs expressed and synthesized extracellular matrix-associated TGF-beta1. On exposure to mast cell chymase, the extracellular matrix-associated latent TGF-beta1 was released and activated, as demonstrated by immunoblotting and by an ELISA with TGF-beta1 type II receptor for capture. When added to s-SMCs, such chymase-released TGF-beta1 was capable of inhibiting their growth. In contrast, the inhibitory effect of chymase on collagen synthesis by s-SMCs did not depend on TGF-beta1. Taken together, the findings support the hypothesis that chymase released from activated mast cells in atherosclerotic plaques contributes to cap remodeling.

Animals↗
PubMed1999

Increased expression of mast cell chymase in the lungs of patients with congenital heart disease associated with early pulmonary vascular disease.

The molecular mechanism involved in pulmonary vascular disease (PVD) associated with congenital heart disease (CHD) remains uncertain. Evidence suggesting that angiotensin converting enzyme plays an important role in pulmonary vascular pathology led us to hypothesize that mast cell chymase, another angiotensin I converting enzyme, also had the potential to contribute to the development of PVD in CHD. Twenty-three patients 3 mo to 45 yr of age with atrial or ventricular or both septal defects with increased pulmonary arterial blood flow and pressure, with pulmonary vascular resistance ranging from 1.3 to 8.1 units/m(2), were studied. Mast cells and mast cell chymase were immunohistochemically identified in the lung biopsy tissues obtained during corrective surgery. There was a significant difference in numbers of total mast cells between patients (n = 23) and control subjects (n = 10) with normal pulmonary circulation (p < 0.01). Moreover, chymase-containing mast cells in the lung tissues of patients with CHD showed striking differences from those of control subjects. In the patients, 72% of lung mast cells contained chymase, compared with only 15% in control subjects (p < 0.0001). Chymase-containing mast cells predominantly appeared in the media and adventitia of vessel walls. Importantly, angiotensin II was immunohistochemically detected in perivascular lesions where chymase was present, but not in the lesions where chymase was sparsely seen. Furthermore, the number of chymase-containing mast cells was correlated with pulmonary vascular resistance (r = 0.64). These findings suggest a possible role of mast cell chymase in the development of early-stage PVD in patients with CHD.

Adult↗
PubMed2001

A novel vascular smooth muscle chymase is upregulated in hypertensive rats.

While greater than 80% of angiotensin II (Ang II) formation in the human heart and greater than 60% in arteries appears to result from chymase activity, no cardiovascular cell-expressed chymase has been previously reported. We now describe the cloning of a full-length cDNA encoding a novel chymase from rat vascular smooth muscle cells. The cDNA encompasses 953 nucleotides, encodes 247 amino acids, and exhibits 74% and 80% homology in amino acid sequence to rat mast cell chymase I and II, respectively. Southern blot analysis indicates that the rat vascular chymase is encoded by a separate gene. This chymase was induced in hypertrophied rat pulmonary arteries, with 11-fold and 8-fold higher chymase mRNA levels in aortic and pulmonary artery smooth muscle cells from spontaneously hypertensive than in corresponding tissues from normotensive rats. We assayed the activity of the endogenous enzyme and of a recombinant, epitope-tagged chymase in transfected smooth muscle cells and showed that Ang II production from Ang I can be inhibited with chymostatin, but not EDTA or captopril. Spontaneously hypertensive rats show elevated chymase expression and increased chymostatin-inhibitable angiotensin-converting activity, suggesting a possible role for this novel enzyme in the pathophysiology of hypertension.

Amino Acid Sequence↗
PubMed1998

[Angiotensin II formation by chymase in the cardiovascular tissue].

Angiotensin-converting enzyme (ACE) inhibitors attenuated the contractile responses to angiotensin (Ang) I of arterial strips of humans, monkeys, and dogs, as can be expected. Unexpectedly, however, the response was not abolished by sufficient doses of ACE inhibitors, the facts suggesting the Ang I conversion by a non-ACE enzyme(s). HPLC analysis of the incubation product of Ang I with vascular tissues revealed that Ang II was yet formed despite complete ACE inhibition, and the ACE inhibitor-insensitive Ang II formation was blocked by chymostatin. The disclosed Ang II-forming enzyme was identified as chymase, which was later found in abundance in the human heart. Another notable discovery by us is the species difference in chymase processing of Ang I: chymases of primates, dog, and hamster convert Ang I to Ang II, while chymases of rat, rabbit, and probably mouse do not. Accumulating evidence indicating that Ang II is not merely a vasopressor agent but also a growth-promoting factor, which leads to tissue hypertrophy and fibrosis, together with the results our studies lead us to propose the tissue-remodeling roles of chymase-formed Ang II in various cardiovascular diseases: dog neointimal proliferation after angioplasty, hamster cardiomyopathy, etc., in which chymase mRNA is increased concordantly with tissue remodeling. The fact that Ang II receptor antagonists, not ACE inhibitors, suppress the tissue remodeling supports our argument that Ang II is formed predominantly by chymase in diseased tissues. Orally active chymase inhibitors, evolving in our study, should help explore the actual roles of chymase as well as the rational treatment of tissue-remodeling disorders.

Angiotensin II↗
PubMed1999

[Involvement of chymase in angiogenesis in hamster sponge granulomas].

We investigated the angiogenic effect of chymase, an alternative angiotensin II-generating enzyme, on angiogenesis using hamster sponge implant model. Exogenous administration of angiotensin II (Ang II) or angiotensin I (Ang I) directly into the sponges enhanced angiogenesis, as determined from the hemoglobin contents in the sponge granuloma tissues. Chymostatin, an inhibitor of chymase, inhibited angiogenesis induced by Ang I but not by Ang II, suggesting the presence of a chymase-like Ang II-generating activity in the sponge granuloma. TCV-116 (5 mg/kg p.o.), an antagonist of Ang II type 1 receptor, and chymostatin suppressed bFGF-induced angiogenesis, suggesting the significance of the endogenous angiotensin system. Chymase activity in the sponge granuloma increased in parallel with the rise in hemoglobin contents induced by bFGF. We also examined the effects of direct administration of human pro-chymase gene or purified hamster chymase, and demonstrated that in vivo human pro-chymase gene transfection and direct injection of purified chymase enhanced angiogenesis, which was 50% inhibited by TCV-116. Sponge granulomas treated with Ang II was supressed by vascular endothelial growth factor (VEGF) antisense. Our results suggest that chymase enhanced angiogenesis partly through the local production of Ang II, followed by up-regulation of VEGF.

Angiotensin I↗
PubMed2000

Characterization of recombinant human chymase expressed in Escherichia coli.

We compared recombinant human chymase expressed in Escherichia coli with human chymase purified from vascular tissues. The recombinant chymase, the structure of which was NH2-enterokinase cleavage site-chymase-COOH, was expressed in Escherichia coli and then was solubilized and renatured. The protein did not have a chymase activity, but gained this activity after the cleavage of the N-terminal site by enterokinase. The enzyme was purified by heparin affinity and gel filtration columns. The N-terminal sequence of the protein was identical to the sequence for human chymase. The molecular weights of the recombinant chymase and chymase purified from human vascular tissues were 26 and 30 kDa, respectively, and the 4 kDa difference was thought to be due to the presence or absence of glycan. The optimum pH of the recombinant enzyme activity was between 7.5 and 9.0. The activity of the recombinant enzyme was inhibited by chymostatin, soybean trypsin inhibitor and phenylmethylsulfonyl fluoride, but not by ethylenediaminetetraacetic acid and aprotinin. This enzyme cleaved specifically the Phe8-His9 bond of angiotensin (Ang) I to form Ang II and that of big endothelin (ET)-1 to form ET-1-(1-31). These findings demonstrated that the enzymatic characteristics of the recombinant enzyme were identical to that of native human chymase.

Amino Acid Sequence↗
PubMed2002

Development of the chymase inhibitor as an anti-tissue-remodeling drug: myocardial infarction and some other possibilities.

Chymase leading to tissue remodeling is expected to be a potent pharmaceutical target. Its functions in vivo are still unclear, because of lack of orally available inhibitors. Recently, however, the chymase inhibitor NK3201 (2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidin-1-yl)-N-[[3,4-dioxo-1-phenyl-7-(2-pyridyloxy)]-2-heptyl] acetamide) was demonstrated to have oral activity against neointimal hyperplasia in dog models (Takai S. et al., Life Sci 69, 1725 - 1732 (2001)). In this review, by showing the efficacy of NK3201 in some hamster models, chymase functions in vivo are summarized, and the potency of this chymase inhibitor is introduced. In vitro study, NK3201 showed potent chymase specific inhibitory activity, and Dixon plot analysis indicated competitive inhibition. Oral administration of NK3201 into normal rats resulted in rapid spread over every tissue except the brain, and sufficient activity to inhibit tissue chymase was detected even after 24 h. In passive cutaneous anaphylaxis, myocardial infarction and bleomycin-induced pulmonary fibrosis models, orally administered NK3201 showed potent inhibition of inflammatory response, tissue angiotensin II formation, and fibrosis, respectively. These data suggest that chymase has a vital role in tissue remodeling through promotion of the inflammatory response, tissue angiotensin II and tissue fibrosis. Our recent data indicated chymase participation in bladder fibrosis, like interstitial cystitis. Therefore, the orally active chymase inhibitor NK3201 may have protective effects on tissue remodeling in several diseases.

Acetamides↗
PubMed2003

Human chymase expression in a mice induces mild hypertension with left ventricular hypertrophy.

A number of in vitro studies have suggested potential pathophysiological roles of human (h-) chymase. However, the lack of an appropriate animal model has left the in vivo roles of chymase unclear. To approach this problem, a transgenic mouse (TGM) model carrying the h-chymase gene was established. The h-chymase cDNA transgene was constructed with the chicken beta actin promoter and cytomegalovirus immediate early gene enhancer, and injected into mouse oocytes. Homozygous mice with a high copy number of the h-chymase gene suffered from intrauterine death. In three heterozygous TGM lines, h-chymase transgene expression was detected in entire organs, including the heart, vessels, skin, liver, lung, and brain. The h-chymase immunoreactivity was localized in the extracellular matrices of each organ, especially on the basement membranes of vessels. Aortic and hepatic chymase-dependent angiotensin II formations were significantly higher than those in the wild-type littermates. Three independent TGM lines showed the same phenotypic changes: elevation of blood pressure, left ventricular hypertrophy, emaciation with reduction in the lipid tissue, leukocytosis, and oligotrichia. The angiotensin II subtype 1 (AT1) receptor antagonist valsartan suppressed the elevated blood pressure completely and left ventricular hypertrophy incompletely, but did not affect the other phenotypes. These data suggested that in vivo expression of h-chymase caused mild hypertension (AT1 receptor-dependent) with left ventricular hypertrophy (partially AT1 receptor-dependent), and also chronic inflammatory changes (AT1 receptor-independent).

Animals↗
PubMed2006

Effect of Angiotensin II Type 1 receptor blocker on cardiac angiotensin-converting enzyme and chymase-like activities, and cardiac fibrosis in cardiomyopathic hamsters.

It has been reported that cardiac chymase has an effect on cardiac fibrosis through the Angiotensin (Ang) II formation and an Ang II-independent mechanism. In the present study, Ang II type 1 (AT1) receptor blocker (candesartan cilexetil) was administered to dilated cardiomyopathic (DCM; Bio TO2) hamsters for 4 weeks to study the effect of AT1 receptor blocker on cardiac chymase-like activity and cardiac fibrosis. Echocardiography, histological examination, and assessment of cardiac angiotensin-converting enzyme (ACE)/chymase-like activities were conducted. Hamsters showed cardiac dysfunction due to increased left ventricular dimensions and decreased ventricular wall thickness, significant increase in cardiac chymase-like activity, and fibrosis. This result indicates that the cardiac chymase-like activity is responsible for cardiac fibrosis. When candesartan cilexetil was administered to Bio TO2 hamsters, cardiac chymase-like activity increased significantly, whereas cardiac fibrosis decreased significantly. Cardiac ACE and chymase-like activities were unchanged in non-DCM hamsters with candesartan cilexetil. This suggests that the cardiac Ang II formation mechanism was stimulated by suppressing the effect of cardiac Ang II, and cardiac chymase-like activity could be increased. Moreover, this mechanism may be more highly activated if cardiac Ang II is activated in the heart. In conclusion, we demonstrated that AT1 receptor blocker reduced cardiac fibrosis, although cardiac chymase-like activity increased. Because the Ang II-forming pathway and the effect of chymase in hamsters is similar to that in dogs, the results of the present study may supplement the available information for dogs.

Angiotensin II Type 1 Receptor Blockers↗