Denan Jin

Increased local angiotensin II formation in aneurysmal aorta.

We investigated the levels and locations of angiotensin II-forming enzymes, angiotensin converting enzyme (ACE) and chymase, in aneurysmal and normal aortas. Aneurysmal aortic specimens (n = 14) were obtained at the time of operative aneurysm repair from 14 patients ranging in age from 57 to 84 y. Normal aortic specimens (n = 16) were obtained from 16 patients (48 to 72 y) who underwent coronary artery bypass surgery. The ACE and chymase activities were determined using each specimen. Sections of each specimen were immunostained with antibodies for ACE and chymase. The ACE activities in the aneurysmal and normal aortas were 0.82 +/- 0.10 and 0.14 +/- 0.05 mU/mg protein, respectively, and this difference was significant. The chymase activities in the aneurysmal and normal aortas were 17.9 +/- 2.40 and 1.02 +/- 0.18 mU/mg protein, respectively, and this difference was also significant. In the aneurysmal aorta, ACE-positive cells were detected with macrophages in the intima and media and chymase-positive cells were detected with mast cells in the media and adventitia, whereas positive ACE and chymase cells in the normal aorta were located only in the endothelium and adventitia, respectively. Angiotensin II-forming enzymes, chymase and ACE, were significantly increased in the aneurysmal aorta, and increased angiotensin II may be associated with the development of aneurysmal formations.

Oral administration of a specific chymase inhibitor, NK3201, inhibits vascular proliferation in grafted vein.

Chymase may play an important role in vascular proliferation, as shown by in-vitro experiments, but the role of chymase in vivo has been unclear. In this study, we investigated the effect of a novel chymase inhibitor, NK3201, on this proliferation in dog grafted veins. NK3201 inhibited human and dog chymases, but not rabbit ACE. NK3201 suppressed the Ang I-induced vascular contraction in isolated dog arteries in the presence of an ACE inhibitor, and the IC50 value of chymostatin and NK3201 in dog artery was 320 nM. In dog, the concentration of NK3201 in blood was about 10 microM at 24 h after oral administration of the drug (5 mg/kg). In the group treated with NK3201, each dog was administered orally 5 mg/kg per day from 5 days before to the day before the removal of the grafted veins. Each dog underwent right common carotid artery bypass grafting with the ipsilaterial external jugular vein. By 28 days after grafting, a significant vascular proliferation was observed in the grafted veins and the chymase activity was also increased significantly. Treatment with chymase inhibitor significantly suppressed the proliferation of the grafted veins and the increased chymase activity. In this study, we demonstrate for the first time that oral administration of a specific chymase inhibitor, NK3201, appears useful for preventing vascular proliferation.

Different angiotensin II-forming pathways in human and rat vascular tissues

We studied the angiotensin II-forming pathways in extracts from human and rat vascular tissues. In the extract from human artery, angiotensin I mainly converted to two products, angiotensin-(1-9) and angiotensin II, while in the extract from rat artery, the major angiotensin I products were angiotensin II and angiotensin-(5-10). The concentrations of angiotensin II and angiotensin-(1-9) generated in the human extract (1 mg protein/ml) after incubation for 30 min were 3.2 and 2.5 nmol, respectively, and that of angiotensin II and angiotensin-(5-10) generated in the rat extract (1 mg protein/ml) were 0.28 and 2.3 nmol, respectively. In the extract from human vascular tissues, the angiotensin II formation was inhibited by 8% with lisinopril and by 95% with chymostatin. The other product, angiotensin-(1-9) was inhibited completely by carboxypeptidase inhibitor. In the extract from rat vascular tissues, the angiotensin II formation was suppressed to 4% by lisinopril, but not by chymostatin. The angiotensin-(5-10) formation was completely inhibited by chymostatin. These findings suggest clearly that human vascular tissues contain two angiotensin II-forming enzymes, angiotensin-converting enzyme and chymase, but rat vascular tissues have no chymase-dependent angiotensin II-forming pathway.

Beneficial effects of cardiac chymase inhibition during the acute phase of myocardial infarction

Recently, the presence of the chymase-dependent angiotensin (Ang) II-generating system in hamsters, dogs, monkeys, as well as human cardiovascular tissues has been identified. We have reported that the activation of cardiac chymase was more prominent than that of angiotensin converting enzyme (ACE) and that AT1 receptor antagonist treatment rather than ACE inhibitor treatment alone provided significant beneficial effects on cardiac function and survival after MI in hamsters. The aim of the present study was to determine whether this different effects between AT1 receptor antagonist and ACE inhibitor were due to the activation of cardiac chymase after MI in hamsters by using 4-[1-[[bis-(4-methyl-pheny)-methyl]-carbamoyl]-3-(2-ethoxy-benzyl)-4-oxo-azetidine-2-yloxy]-benzoic acid (BCEAB), a novel, orally active and specific chymase inhibitor. The ACE and chymase activities in the infarcted left ventricle were significantly increased 3 days after MI. BCEAB (100 mg/kg/day, p.o.) treatment starting 3 days before MI significantly suppressed the cardiac chymase activity, while it did not affect the plasma and cardiac ACE activities 3 days after MI. A significant improvement in hemodynamics (maximal negative and positive rates of pressure development; left ventricular systolic pressure) was observed for the treatment with BCEAB 3 days after MI. BCEAB (100 mg/kg/day, p.o.) treatment starting 3 days before MI significantly reduced the mortality rate during 14 days of observation following MI (vehicle, 61.1%, n = 18; BCEAB, 27.8%, n = 18; P < 0.05). These findings demonstrated for the first time that cardiac chymase participates directly in the pathophysiologic state after MI in hamsters.

12-Hydroxyeicosatetraenoic acid potentiates angiotensin II-induced pressor response in rats

We studied whether 12-hydroxyeicosatetraenoic acid (HETE) affected the angiotensin II-induced pressor response in rats. After intravenous administration of 1 and 3 microg/kg 12-HETE, the angiotensin II-induced pressor response was not potentiated. However, 10, 20 and 30 min after the administration of 10 microg/kg 12-HETE, the angiotensin II-induced pressor responses were increased by 7.5, 6.8 and 4.8 mm Hg, respectively. The significant pressor response was observed at 10 and 20 min after the administration. In this study, we clearly demonstrated that 12-HETE potentiated the angiotensin II-induced pressor response.