Search PubMed⌕ Search

Biomedical subjects

Mizuo Miyazaki

Publications and source records attributed to Mizuo Miyazaki.

At least 37 records · Page 2Linked to original sources
PubMed2005

Effect of chymase inhibition on the arteriovenous fistula stenosis in dogs.

It was hypothesized that chymase may participate in hemodialysis vascular access dysfunction, as chymase has been known to be an effective enzyme in the conversion of angiotensin I (Ang I) to Ang II and in the latent TGF-beta1 to the active form. An arteriovenous (AV) fistula was created between the brachial artery and vein in dogs. In the AV anastomosis, when the walls of the venous and arterial sides were compared, the eccentric neointimal formation was most evident in the venous wall. Compared with the venous side downstream of the AV anastomosis, a severe neointimal hyperplasia was found in the venous side upstream of the AV anastomosis (intima/media, 153 +/- 25%). The chymase- and TGF-beta-positive mast cells were markedly accumulated in the proliferous neointima and media. In association with the reduction of chymase expression, a marked decrease in Ang II-, AT(1) receptor-, and TGF-beta-positive areas was achieved by NK3201 (a chymase inhibitor) treatment, and the neointima formation (intima/media: region A, 53 +/- 9%, P < 0.001; region B, 54 +/- 14%, P < 0.001) was also significantly suppressed in this group. Although lisinopril treatment also provided some beneficial effects with regard to the prevention of neointimal formation, the degree was less than that seen with chymase inhibition. These findings indicate that mast cell-derived chymase plays an essential role in the pathogenesis of the AV fistula access failure and that chymase inhibition may be a therapeutic target for the treatment of hemodialysis vascular access dysfunction in clinic settings.

Acetamides↗
PubMed2005

Usefulness of serum mast cell-specific chymase levels for postmortem diagnosis of anaphylaxis.

Chymase, a serine protease, is stored mainly in secretory granules of human mast cells. Serum chymase concentration was examined in 8 autopsy cases with anaphylaxis as well as in 104 control cases without anaphylaxis. It was detected in all 8 cases with anaphylaxis (range 3-380 ng/ml, mean 89.8 ng/ml), while it was detected in only 2 of the 104 controls and was below a detectable level (<3 ng/ml) in the other 102. Serum tryptase levels are known to be a diagnostic indicator of anaphylaxis, therefore the relationship between serum chymase and tryptase levels was investigated in the 8 cases of anaphylactic death; a significant positive correlation was found (r=0.826, p=0.011). Furthermore, chymase was shown to be quite stable in serum. These results showed that measurement of serum chymase levels might be an additional tool for postmortem diagnosis of anaphylaxis.

Aged↗
PubMed2005

The relationship of tryptase- and chymase-positive mast cells to angiogenesis in stage I non-small cell lung cancer.

OBJECTIVE: There are two types of human mast cells, tryptase-positive mast cells (MC(T)) and tryptase- and chymase-positive mast cells (MC(TC)). Although MC(T) have been reported to be related to the generation of angiogenesis, little is known about the involvement of MC(TC) in tumor angiogenesis. In this study, to clarify the relationship between MC(TC) and lung cancer angiogenesis, we evaluated MC(TC), MC(T), and microvessel counts in normal, border, and central lung cancer regions. METHODS: Tumor sections from 32 cases of adenocarcinoma and 13 cases of squamous cell carcinoma were immunostained for chymase to evaluate MC(TC), tryptase to evaluate MC(T,) and CD34 to evaluate microvessel counts. RESULTS: Both MC(TC) and MC(T) counts in the border lung cancer region were significantly higher than in the central region, and the MC(TC) and MC(T) counts in the central region were significantly higher than those in the normal regions. The microvessel counts in the border region were higher than those in the central region. The ratio of MC(TC) to MC(T) in the border region, but not in the central region, was significantly higher than that in the normal region. In the border region, significant correlations not only between MC(T) and microvessel count, but also between MC(TC) and microvessel count were observed. In the central region, a significant correlation between MC(TC) and the microvessel count was observed, but there was no significant correlation between MC(T) and the microvessel count. CONCLUSIONS: These findings suggest that MC(TC) may be involved in the pathogenesis of angiogenesis in lung cancer.

Adenocarcinoma↗
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↗
PubMed2005

Mast cell chymase decreases the barrier function and inhibits the migration of corneal epithelial cells.

PURPOSE: We investigated the in vitro effects of human mast cell chymase on corneal epithelial cells. METHODS: Human corneal epithelial cells were incubated with human chymase at activity levels that were likely to exist in the tears of patients with vernal keratoconjunctivitis. RESULTS: Incubation of chymase resulted in a decrease of barrier function of corneal epithelium. Occludin protein was cleaved by chymase. In the wound assay, incubation with chymase resulted in an inhibition of cell migration. CONCLUSION: Human chymase causes the proteolysis of occludin and fibronectin, resulting in a decrease of barrier function and inhibition of the migration of corneal epithelial cells.

Blotting, Western↗
PubMed2005

Mast cell chymase induces conjunctival epithelial cell apoptosis by a mechanism involving degradation of fibronectin.

PURPOSE: To determine the mechanism of conjunctival epithelial injury in vernal keratoconjunctivitis, we investigated the effects of human chymase on conjunctival epithelial cells in vitro. METHODS: Human conjunctival epithelial cells were incubated with human chymase for 24 or 48 hr at levels of activity that were likely to exist in the tear fluid of patients with vernal keratoconjunctivitis. Morphologic changes of the cells were observed by phase contrast microscopy. To determine the number of detached cells, we used an automated cell counter, while apoptotic cells were quantitated by flow cytometry. The level of soluble fibronectin in conditioned medium was measured by ELISA. RESULTS: Most of the cells in the incubation with chymase were detached by 24 hr. However, chymase-mediated apoptosis was a slower process and was only detected after incubation of cells with chymase for 36 to 48 hr. Both cell detachment and apoptosis were blocked when cells were incubated in fibronectin-coated plates. The increase of soluble fibronectin was dependent on the amount of chymase added and the exposure time. A caspase inhibitor (antiapoptotic agent) rescued cells from apoptosis but did not prevent cell detachment. These results indicate that chymase-induced apoptosis of conjunctival epithelial cells represents anoikis, which is a slowly occurring apoptotic process induced by lack of adhesion to an extracellular matrix. CONCLUSIONS: Human mast cell chymase caused conjunctival epithelial cell detachment by degrading fibronectin, and this led to secondary apoptosis.

Apoptosis↗
PubMed2005

The regressive effect of an angiotensin II receptor blocker on formed fatty streaks in monkeys fed a high-cholesterol diet.

OBJECTIVES: To clarify the regressive effect of an angiotensin II type 1 receptor blocker (ARB) on already formed fatty streaks, we investigated the effect of the administration of an ARB, olmesartan, on formed fatty streaks in monkeys fed a high-cholesterol diet. METHODS: After the monkeys were fed a high-cholesterol diet for 6 months, intimal hyperplasia was clearly observed on intravascular ultrasound. For the next 6 months, the high-cholesterol diet was continued, and olmesartan (3 mg/kg per day) or placebo was administered. A control group was fed a normal diet for 12 months. RESULTS: Olmesartan did not significantly affect blood pressure or plasma cholesterol levels throughout the experiment. After 6 months of treatment with olmesartan, intimal hyperplasia was significantly lower than before treatment. Acetylcholine-induced relaxation in isolated carotid arteries was significantly less in the high-cholesterol diet placebo-treated group compared to the normal diet group, whereas its response was improved by olmesartan. Serum levels of monocyte chemoattractant protein were significantly increased with a high cholesterol load, but they were significantly suppressed by olmesartan. CONCLUSIONS: We have demonstrated for the first time that an ARB, olmesartan, was found to have a regressive effect on formed fatty streaks in monkeys.

Acetylcholine↗
PubMed2005

Role of chymase-dependent angiotensin II formation in regulating blood pressure in spontaneously hypertensive rats.

Vascular smooth muscle cells in spontaneously hypertensive rats (SHR) express angiotensin II-forming chymase (rat vascular chymase [RVCH]), which may contribute to blood pressure regulation. In this study, we studied whether chymase-dependent angiotensin II formation contributes to the regulation of blood pressure in SHR. The systolic blood pressure in 16-week-old Wistar-Kyoto (WKY) rats was 113 +/- 9 mmHg, compared to 172 +/- 3 mmHg in SHR. Using synthetic substrates for measuring angiotensin-converting enzyme (ACE) and chymase activities, it was found that both ACE and chymase activities in extracts from SHR aortas were significantly higher than in those from WKY rat aortas. Using angiotensin I as a substrate, angiotensin II formation in SHR was found to be significantly higher than that in WKY rats, and its formation was completely suppressed by an ACE inhibitor, but not by a chymase inhibitor. RVCH mRNA expression could not be detected in aorta extracts from either WKY rats or SHR. In carotid arteries isolated from WKY rats and SHR, angiotensin I-induced vasoconstriction was completely suppressed by an ACE inhibitor, but not by a chymase inhibitor. Angiotensin I-induced pressor responses in both WKY rats and SHR were also completely inhibited by an ACE inhibitor, but they were not affected by a chymase inhibitor. In SHR, an ACE inhibitor and an angiotensin II receptor blocker showed equipotent hypotensive effects, but a chymase inhibitor did not have a hypotensive effect. These results indicated that chymase-dependent angiotensin II did not regulate blood pressure in SHR in the present study.

Angiotensin I↗
PubMed2005

Significance of angiotensin II receptor blocker lipophilicities and their protective effect against vascular remodeling.

Although the lipophilicities of the various angiotensin II receptor blockers (ARBs) are very different, the relationship between lipophilicity and the protective effect against vascular remodeling is unclear. In this study, we compared the protective effects of a highly lipophilic ARB, telmisartan, and an ARB with low lipophilicity, losartan, on vascular function and oxidative stress in stroke-prone spontaneously hypertensive rats (SHR-SP). SHR-SP received oral placebo, 1 mg/kg telmisartan, or 10 mg/kg losartan for 2 weeks. The blood pressure (BP) in SHR-SP was significantly higher than that in Wistar-Kyoto (WKY) rats before treatment, and the BP was reduced equally in telmisartan- and losartan-treated SHR-SP compared to placebo-treated SHR-SP. Acetylcholine-induced vasorelaxation in isolated carotid arteries was significantly weaker in SHR-SP than in WKY rats, but in both telmisartan- and losartan-treated SHR-SP, acetylcholine-induced vasorelaxation was significantly higher than in placebo-treated SHR-SP. Moreover, acetylcholine-induced vasorelaxation in telmisartan-treated rats was significantly stronger than in losartan-treated SHR-SP. The expression of the endothelial nitric oxide synthase gene was significantly higher in telmisartan- and losartan-treated rats than in placebo-treated SHR-SP, and was significantly higher in telmisartan-treated rats than in losartan-treated rats. In contrast, the expression of the NAD(P)H oxidase subunit p22phox gene in telmisartan-treated SHR-SP was significantly lower than that in losartan-treated SHR-SP. Immunohistochemistry showed that angiotensin II expression in the aorta was significantly lower in telmisartan-treated SHR-SP than in losartan-treated SHR-SP. In conclusion, a highly lipophilic ARB, telmisartan, may be useful for preventing NAD(P)H oxidase activity, and thereby for conferring vascular protection.

Angiotensin II↗
PubMed2004

Therapeutic applications of chymase inhibitors in cardiovascular diseases and fibrosis.

Chymase activates not only angiotensin I to angiotensin II but also latent transforming growth factor-beta-binding protein to transforming growth factor-beta. In dog grafted veins, chymase activity and angiotensin II concentration along with vascular proliferation were significantly increased, while they were significantly suppressed by a chymase inhibitor. After balloon injury in dog arteries, chymase activity was significantly increased in the injured artery, and a chymase inhibitor and an angiotensin AT(1) receptor antagonist were effective in preventing the vascular proliferation, but an angiotensin-converting enzyme inhibitor was ineffective. In fibrotic models, the tissue fibrosis was reduced by chymase inhibitors. In adhesion models, the transforming growth factor-beta concentration and adhesion formation were suppressed by chymase inhibitors. Therefore, chymase inhibitors may be useful for preventing cardiovascular diseases and fibrosis via inhibition of angiotensin II formation and transforming growth factor-beta activation.

Animals↗
PubMed2004

A specific chymase inhibitor, NK3201, suppresses bleomycin-induced pulmonary fibrosis in hamsters.

We evaluated whether a chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[(3,4-dioxo-1-phenyl-7-(2-pyridyloxy))-2-heptyl]acetamide (NK3201), suppressed bleomycin-induced pulmonary fibrosis. Hamsters were orally administered NK3201 (30 mg/kg per day) or placebo, beginning 5 days before intratracheal instillation of bleomycin (10 mg/kg). Four weeks after the instillation of bleomycin, pulmonary chymase activity in placebo-treated hamsters was significantly higher than in control hamsters, whereas the activity in NK3201-treated hamsters was significantly lower than in placebo-treated hamsters. The ratio of fibrotic area to total area in NK3201-treated hamsters was significantly decreased to 54.0% of the ratio in placebo-treated hamsters. Therefore, NK3201 may be useful in the prevention of pulmonary fibrosis.

Acetamides↗
PubMed2004

A specific chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[[3,4-dioxo-1-phenyl-7-(2-pyridyloxy)]-2-heptyl]acetamide (NK3201), suppresses development of abdominal aortic aneurysm in hamsters.

In this study, we investigated the effect of a specific chymase inhibitor, 2-(5-formylamino-6-oxo-2-phenyl-1,6-dihydropyrimidine-1-yl)-N-[[3,4-dioxo-1-phenyl-7-(2-pyridyloxy)]-2-heptyl]acetamide (NK3201), in the development of abdominal aortic aneurysm in a hamster experimental model. The abdominal aortic aneurysm was induced by application of elastase onto the abdominal aorta in hamster. Each hamster was administered NK3201 (30 mg/kg/day p.o.) or placebo beginning 4 days before application of elastase and continuing through the experiments. Sham-operated hamsters received saline application onto the abdominal aorta. Two weeks after application of elastase, the aortic diameter in the placebo-treated group was significantly increased to 1.6-fold compared with the value for the sham-operated group, whereas that in the NK3201-treated group was significantly reduced. The chymase activities in the sham-operated and the placebo-treated groups were 0.35 +/- 0.01 and 3.44 +/- 0.62 mU/mg protein, respectively, and this difference was significant. NK3201 significantly reduced the chymase activity in the placebo-treated group. Here, we demonstrated for the first time that a chymase inhibitor prevented the development of abdominal aortic aneurysm in a hamster experimental model.

Acetamides↗
PubMed2004

Significance of chymase inhibition for prevention of adhesion formation.

To clarify the role of chymase in adhesion formation, we investigated whether a chymase inhibitor could prevent adhesion formation after surgery in hamsters. Hamsters received a lesion produced by uterus scraping. A specific chymase inhibitor, 2-[4-(5-fluoro-3-methylbenzo[b]thiophen-2-yl)sulfonamido-3-methanesulfonylphenyl]oxazole-4-carboxylicacid (TY-51184), or placebo was injected into the abdomen before closing and scores for adhesion formation were assessed at 1, 4, and 12 weeks. A single peritoneal administration of TY-51184 significantly decreased the adhesion scores even at 12 weeks (placebo, 2.80+/-0.20; chymase inhibitor, 1.60+/-0.31). Thus, chymase inhibitors may be a novel strategy to prevent adhesion formation.

Animals↗
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↗
PubMed2004

Effect of chymase-dependent transforming growth factor beta on peritoneal adhesion formation in a rat model.

PURPOSE: To clarify the role of chymase produced from mast cells, which are closely related to adhesion formation, we investigated the preventive effect of a chymase inhibitor on adhesion formation in a rat model. METHODS: A lesion was created in rats by uterus scraping, and a chymase inhibitor, Suc-Val-Pro-Phep(OPh)2 (10 microM), or a placebo was injected into the abdomen. The level of transforming growth factor beta (TGF-beta) in the peritoneal fluid was also measured. RESULTS: By 2 weeks after the operation, the scores for adhesion formation in the chymase inhibitor-treated group were significantly lower than those in the placebo-treated group, at 1.64 +/- 0.34 and 3.27 +/- 0.19, respectively (P < 0.01). After scraping the uterus, the level of TGF-beta in the peritoneal fluid was significantly higher in the placebo-treated group, whereas it was significantly suppressed by the chymase inhibitor. CONCLUSIONS: Chymase may play an important role in adhesion formation aided by TGF-beta.

Animals↗
PubMed2004

Role of chymase on growth of cultured canine Tenon's capsule fibroblasts and scarring in a canine conjunctival flap model.

Chymase is a chymotrypsin-like serine protease contained in the secretory granules of mast cells. Recently, we reported that chymase activity and the number of chymase-positive mast cells in conjunctival tissues were significantly increased during the wound healing process in a hamster model of glaucoma surgery. However, it has been unclear the role of chymase on conjunctival scarring. In the present study, we evaluated the effect of dog chymase on cell proliferation of fibroblasts established from canine Tenon's capsule and the effect of a chymase inhibitor on scarring in a canine conjunctival flap model. After a fibroblast cell culture was established from canine Tenon's capsules, the fibroblasts were incubated in the presence of dog chymase (5-20 ng ml(-1)). Cell proliferation was evaluated by bromodeoxyuridine incorporation. In a canine conjunctival flap model, a sponge treated with a chymase inhibitor, Suc-Val-Pro-Phe(P)(OPh)(2), or placebo was placed in between the conjunctiva and sclera and the conjunctival incision was closed. One week after the surgery, adhesion degree was assessed, and chymase activities in the conjunctival lesion and in the areas of the conjunctiva and sclera were measured. In cultured canine Tenon's capsule fibroblasts, dog chymase significantly increased cell proliferation, and this chymase-dependent proliferation was completely suppressed by the chymase inhibitor. In the canine surgical model, chymase activity in placebo-treated eyes was significantly increased compared to control eyes, while it was significantly decreased by treatment with the chymase inhibitor. Scores for adhesion degree in the chymase inhibitor-treated eyes were significantly decreased in comparison with those in placebo-treated eyes. The conjunctival area in the chymase inhibitor-treated eyes was also suppressed to 52.6% compared with that in placebo-treated treated eyes. In conclusion, chymase stimulates proliferation of fibroblasts derived from canine Tenon's capsule and chymase may play an important role in scarring after glaucoma surgery.

Animals↗
PubMed2004

Chymase as a novel target for the prevention of vascular diseases.

In vascular tissues, chymase catalyzes the production of angiotensin II, which plays a crucial role in vascular diseases. Recent clinical studies and animal models of vascular proliferation and atherosclerosis have provided evidence that angiotensin II formed by chymase is involved in these processes. These observations suggest that chymase might promote the development of vascular proliferation and atherosclerosis. Chymase also activates matrix metalloproteinase 9, which promotes aortic aneurysm and angiogenesis, and thus chymase inhibitors might also prevent the progression of abdominal aortic aneurysm and angiogenesis. We propose that chymase is a novel target for preventing vascular diseases.

Animals↗