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(Hypertension. 2000;36:638.)
© 2000 American Heart Association, Inc.
Colin Johnston - A Celebration |
Hypothesis Regarding the Pathophysiological Role of Alternative Pathways of Angiotensin II Formation in Atherosclerosis
From the Department of Internal Medicine, School of Medicine, Fukuoka University, Fukuoka, Japan.
Correspondence to Hidenori Urata, MD, Department of Internal Medicine, Fukuoka University, 7-45-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan. E-mail uratah{at}fukuoka-u.ac.jp
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Abstract |
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 Top Abstract IntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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Abstract—The renin-angiotensin system has been studied and recognized as one of the major blood pressure–regulating systems for the past century. In the last quarter century, however, many alternative pathways of angiotensin II formation have been found, and among them, chymase has been a focus of interest because of its specificity and potency in the human cardiovascular system. Chymase evidently is not involved in functional regulation of blood pressure at least in the short term, but evidence is accumulating that it may be involved in structural remodeling of the cardiovascular system. We found increased vascular chymase activity in atherosclerotic lesions of the human aorta as well as in cardiac remodeling after myocardial infarction. We found a significant positive correlation between serum total or LDL cholesterol levels and arterial chymase-dependent angiotensin II–forming activity in patients who were undergoing coronary artery bypass operation, suggesting that high serum cholesterol may trigger upregulation of vascular chymase and facilitate the development of atherosclerosis. This hypothesis was tested in Syrian hamsters fed a high cholesterol diet containing 0.5% cholesterol: A marked lipid deposition in the aortic cusp developed and the plasma cholesterol levels were positively correlated with aortic chymase activity. An orally active nonpeptide chymase inhibitor almost canceled this lipid deposition. These clinical and experimental data indicated an association between cholesterol and vascular chymase upregulation that may facilitate the development of atherosclerosis.
Key Words: kallikrein • angiotensin-converting enzyme • atherosclerosis • cardiovascular diseases
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Introduction |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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Locally formed angiotensin (Ang) II is thought to play some pathological roles in the development of hypertensive heart disease, congestive heart failure, and acute myocardial infarction. This is substantiated by the fact that the introduction of ACE inhibitors improved the morbidity and mortality rates of patients with various cardiovascular diseases. In the last quarter century, however, many other Ang II–forming enzymes have been found.1 We have found that trypsin2 as well as kallikrein3 generates Ang II not only in test tubes but in ischemic dog heart4 and ischemic human leg5 and even normal healthy individuals when exercised.6 Among these Ang II–forming enzymes, chymase is most potent in human tissues including heart, aorta, lung, liver, and so forth.7 It is now evident, however, that chymase is not involved in blood pressure regulation,8 but evidence has been accumulating that it may be involved in cardiovascular remodeling. Two recent reports suggested that in the heart and vasculature, ACE-independent Ang II formation takes place in vivo.9 10 We further investigated how human chymase is involved in cardiovascular diseases.
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Clinical Evidence for Involvement of Chymase in Atherogenesis |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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We have found an increased activity of arterial chymase in atherosclerotic lesions of the human aorta.11 We determined aortic Ang II–forming activity (AIIFA) and the histochemical localization of each Ang II–forming enzyme in the atheromatous human aorta. Specimens of normal (n=9), atherosclerotic (n=8), and aneurysmal (n=6) human aortas were obtained at autopsy or cardiovascular surgery. Total AIIFA was significantly higher in atherosclerotic and aneurysmal lesions than in normal aorta (Figure 1). Most (80% to 90%) AIIFA in the human aorta in vitro was chymase dependent in normal as well as in atherosclerotic aortas (Figure 1). Immunocytochemical staining of the corresponding aortic sections with anti-chymase, anti-tryptase, or anti-ACE antibodies showed that chymase-positive mast cells were located in the tunica adventitia of normal and atheromatous aortas, whereas ACE-positive cells were localized in endothelial cells of normal aorta and in macrophages and smooth muscle cells of atheromatous neointima. The number of activated mast cells in the aneurysmal lesions (18%) was significantly higher than in atherosclerotic (5%) and normal aortas (1%).11 These results suggest that local Ang II formation appears to be increased in atherosclerotic lesions and that chymase is primarily responsible for this increase. The histological localization and potential roles of chymase in the development of atherosclerotic lesions appear to be different from those of ACE.
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P<0.01 vs chymase dAIIFA in normal aorta. This figure
is modified from Reference 11. |
Development of Human Chymase ELISA and Arterial Chymase Levels |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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We have produced a monoclonal antibody by immunizing Balb/c mice with recombinant human chymase purified from culture medium of Chinese hamster ovarian cells transfected by human chymase cDNA. Anti-human chymase polyclonal antibody was also produced by immunizing the same antigen to rabbits. With the use of these antibodies, a sandwich ELISA was developed. The detectable range of chymase concentration by this ELISA was 0.27 to 200 ng/mL. Because a significant correlation was found between the ELISA data and the enzymatic activity of chymase in homogenates of human artery, it appears that our monoclonal antibody against recombinant human chymase specifically recognizes native human chymase. Using this chymase ELISA, we analyzed arterial samples from many patients and found that regional differences in chymase levels of aortic branch arteries were not significantly varied, but they apparently differed by individual patients. Aortic chymase immunoreactivity was significantly higher in patients with macroscopic atherosclerotic lesions than without such legions. These results indicate that high chymase levels in the arterial wall may be associated with the development of atherogenesis.12
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Positive Correlation of Arterial Chymase Activity and Plasma Total or LDL Cholesterol Levels |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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The association between vascular AIIFA in the human internal thoracic artery (ITA) and various clinical parameters was studied with ITA obtained from 32 patients who underwent coronary artery bypass grafting. Only serum total and LDL cholesterol levels but no other risk factors significantly correlated with chymase-dependent (r=0.60, P<0.001) (Figure 2a) and ACE-dependent (r=0.35, P<0.05) AIIFA, respectively. The LDL cholesterol level was also correlated with chymase-dependent AIIFA (r=0.47, P<0.05) (Figure 2b).13 These data led us to hypothesize that an increased plasma LDL cholesterol level induces increased arterial chymase as well as ACE activity, which may in turn lead to arterial remodeling such as atherogenic changes.
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Prevention of Aortic Lipid Deposit With an Orally Active Nonpeptidic Chymase Inhibitor |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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We examined in a hamster model what we found in human ITA, that is, the association between cholesterol and arterial chymase activity. When Syrian hamsters were fed a high cholesterol diet containing 0.5% cholesterol, a marked lipid deposition in the aortic cusp developed and the plasma cholesterol levels were positively correlated with aortic chymase activity.14 When an orally active nonpeptide chymase inhibitor (SUN-C8257) was given for 12 weeks together with a high cholesterol diet in this model, the aortic lipid deposition visualized by oil red O stain was almost canceled. On the other hand, the levels of systolic blood pressure and serum total and LDL cholesterol of these chymase inhibitor–treated hamsters did not change significantly. These facts indicated that the chymase inhibitor SUN-C8257 did not affect cholesterol absorption or blood pressure. Further study is necessary to elucidate the mechanism for the elimination of lipid deposit by a chymase inhibitor.
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Pathological Involvement of Human Chymase in Atherogenesis |
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TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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Our clinical and experimental data indicated a close association between cholesterol level and arterial chymase upregulation together with development of atherogenesis. Our current hypothesis is as follows (Figure 3): Hypercholesterolemia may activate adventitial mast cells containing chymase, which in turn release chymase and increase adventitial Ang II and interleukin-1ß concentration.15 These cytokines are known to be proatherogenic and probably may facilitate intimal lipid deposition observed in our experimental model. In addition, chymase by itself is known to have a number of proatherogenic direct actions by degrading the extracellular matrix,16 17 modifying apolipoprotein AI or B,18 and producing endothelin (1-31).19 These direct actions of chymase may also cooperate, at least in part, in the atherogenic process.
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Despite the considerable amount of evidence regarding
pathophysiological roles of chymase, several
investigators have suggested that unlike ACE, chymase contribution in
the local Ang II formation in vivo is limited because of the existence
of endogenous serine proteinase inhibitors in
the interstitial fluid.20 21 It is obvious
that chymase activity in plasma is completely inhibited by circulating
endogenous serine proteinase inhibitors such as
2-macroglobulin and 1–anti-trypsin.22 23 On the
other hand, a majority of tissue chymase exists as a bound form by its
basic ionic charge to the extracellular matrixes including proteoglycan
or heparan sulfate.24 Since the bound-form chymase appears
to be resistant to endogenous serine proteinase
inhibitors, tissue chymase is likely to be enzymatically
active to produce Ang II.9 25 Our recent observation
supported this concept because treatment with an orally active chymase
inhibitor decreased Ang II immunoreactivity in the
adventitia of the hamster aorta, whereas those in the intima and media
remained unchanged (Uehara and Urata, et al, unpublished observation,
2000). This result suggests that aortic chymase contributes adventitial
Ang II formation in vivo.
In conclusion, several alternative Ang II–forming serine proteinases (chymase, kallikrein, and cathepsin G) are activated in several pathological conditions such as ischemia, hypercholesterolemia, hypertension, and local noninfectious inflammation. Since these alternative Ang II–forming enzymes appear not to play a major role in blood pressure regulation, their main role appears to be associated with the development of structural tissue remodeling including post–myocardial infarction, atherosclerosis, and local inflammation.
Received March 27, 2000; first decision July 24, 2000; accepted July 28, 2000.
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References |
|---|
|
TopAbstractIntroductionClinical Evidence for...Development of Human Chymase...Positive Correlation of Arterial...Prevention of Aortic Lipid...Pathological Involvement of...References |
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1. Arakawa K. Serine protease angiotensin II systems. J Hypertens. 1996;14:S3–S7.
2.
Arakawa K, Ikeda M, Fukuyama J, Sakai T. A pressor
formation by trypsin from renin-denatured human plasma protein.
J Clin Endocrinol Metab. 1976;42:599–602.
3. Arakawa K, Maruta H. Ability of kallikrein to generate angiotensin II-like pressor substance and a proposed "kinin-tensin enzyme system." Nature. 1980;288:705–706.[Medline] [Order article via Infotrieve]
4. Gondo M, Maruta H, Arakawa K. Direct formation of angiotensin II without renin or converting enzyme in the ischemic dog heart. Jpn Heart J. 1989;30:219–229.[Medline] [Order article via Infotrieve]
5. Urabe Y, Ideishi M, Sasaguri M, Ikeda M, Arakawa K. Beneficial effects of a serine protease inhibitor in peripheral vascular disease. Am J Cardiol. 1993;72:218–222.[Medline] [Order article via Infotrieve]
6. Miura S, Ideishi M, Sakai T, Motoyama M, Kinoshita A, Sasaguri M, Tanaka H, Shindo M, Arakawa K. Angiotensin II formation by an alternative pathway during exercise in humans. J Hypertens. 1994;12:1177–1181.[Medline] [Order article via Infotrieve]
7.
Akasu M, Urata H, Kinoshita A, Sasaguri M, Ideishi M,
Arakawa K. Differences in tissue angiotensin II-forming
pathways by species and organs in vitro. Hypertension. 1998;32:514–520.
8. Nakayama S, Uehara Y, Urata H, Kinoshita A, Noda K, Sasaguri M, Ideishi M, Suzumiya J, Kikuchi M, Arakawa K. Differential regulation of angiotensin II-forming enzymes by tissues in 2-kidney 1 clip hypertensive hamster. J Hypertens. 1998;16(suppl 2):S124. Abstract.
9.
Wei CC, Meng QC, Palmer R, Hageman GR, Durand J,
Bradley WE, Farrell DM, Hankes GH, Oparil S, Dell’Italia LJ. Evidence
for angiotensin-converting enzyme- and chymase-mediated
angiotensin II formation in the interstitial
fluid space of the dog heart in vivo. Circulation. 1999;99:2583–2589.
10.
Suzuki H, Caughey GH, Gao XP, Rubinstein I. Mast cell
chymase-like protease(s) modulates Escherichia coli
lipopolysaccharide-induced vasomotor dysfunction in skeletal
muscle in vivo. J Pharmacol Exp Ther. 1998;284:1156–1164.
11.
Ihara M, Urata H, Kinoshita A, Suzumiya J, Sasaguri M,
Kikuchi M, Ideishi M, Arakawa K. Increased chymase-dependent
angiotensin II formation in human atherosclerotic aorta.
Hypertension. 1999;33:1399–1405.
12. Okamoto T, Urata H, Ideishi M, Arakawa K. Development and clinical application of ELISA for human chymase. FASEB J. 2000;13:A482. Abstract.
13.
Uehara Y, Urata H, Sasaguri M, Ideishi M, Sakata N,
Tashiro T, Kimura M, Arakawa K. Increased chymase activity in internal
thoracic artery of patients with
hypercholesterolemia. Hypertension. 2000;35:55–60.
14. Uehara Y, Urata H, Koga T, Okamoto T, Ideishi M, Arakawa K. Chymase inhibitor decrease aortic cholesterol deposition in high cholesterol-fed hamster. Circulation. 1999;100(suppl I):I-473. Abstract.
15.
Mizutani H, Schechter N, Lazarus G, Black RA, Kupper
TS. Rapid and specific conversion of precursor interleukin 1ß
(IL-1ß) to an active IL-1 species by human mast cell chymase. J
Exp Med. 1991;174:821–825.
16.
Saarinen J, Kalkkinen N, Welgus HG, Kovanen PT.
Activation of human interstitial
procollagenase through direct cleavage of the
Leu83-Thr84 bond by mast
cell chymase. J Biol Chem. 1994;269:18134–18140.
17.
Kofford MW, Schwartz LB, Schechter NM, Yager DR,
Diegelmann RF, Graham MF. Cleavage of type I procollagen by human mast
cell chymase initiates collagen fibril formation and generates a unique
carboxyl-terminal propeptide. J Biol Chem. 1997;272:7127–7131.
18. Lindstedt L, Lee M, Castro GR, Fruchart JC, Kovanen PT. Chymase in exocytosed rat mast cell granules effectively proteolyzes apolipoprotein Al-containing lipoproteins, so reducing the cholesterol efflux-inducing ability of serum and aortic intimal fluid. J Clin Invest. 1996;97:2174–2182.[Medline] [Order article via Infotrieve]
19. Nakano A, Kishi F, Minami K, Wakabayashi H, Nakaya Y, Kido H. Selective conversion of big endothelins to tracheal smooth muscle-constricting 31-amino acid-length endothelins by chymase from human mast cells. J Immunol. 1997;159:1987–1992.[Abstract]
20. Zisman LS, Abraham WT, Meixell GE, Vamvakias BN, Quaife RA, Lowes BD, Roden RL, Peacock SJ, Groves BM, Raynolds MV, Bristow MR, Perryman MB. Angiotensin II formation in the intact human heart. J Clin Invest. 1995;96:1490–1498.
21.
Kokkonen JO, Saarinen J, Kovanen PT. Regulation of
local angiotensin II formation in the human heart in the
presence of interstitial fluid: inhibition of chymase by
protease inhibitors of interstitial fluid and
of angiotensin-converting enzyme by Ang-(1-9) formed by
heart carboxypeptidase A-like activity. Circulation. 1997;95:1455–1463.
22.
Urata H, Kinoshita A, Misono KS, Bumpus FM, Husain A.
Identification of a highly specific chymase as the major
angiotensin II-forming enzyme in the human heart.
J Biol Chem. 1990;265:22348–22357.
23. Urata H, Graten D. Cardiac angiotensin II formation: the angiotensin-I converting enzyme and human chymase. Eur Heart J. 1993;14:177–182.
24. Urata H, Boehm KD, Philip A, Kinoshita A, Gabrovsek J, Bumpus FM, Husain A. Cellular localization and regional distribution of an angiotensin II-forming chymase in the heart. J Clin Invest. 1993;91:1269–1281.
25.
Takai S, Jin D, Sakaguchi M, Miyazaki M.
Chymase-dependent angiotensin II formation in human
vascular tissue. Circulation. 1999;100:654–658.
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