(Hypertension. 1997;29:1309-1313.)
© 1997 American Heart Association, Inc.
Articles |
From The First Department of Internal Medicine, Osaka City (Japan) University Medical School.
Correspondence to Masakazu Kohno, MD, Division of Hypertension and Atherosclerosis, The First Department of Internal Medicine, Osaka City University Medical School, 1-5-7 Asahi-machi, Abeno-ku, Osaka 545, Japan.
| Abstract |
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Key Words: adrenomedullin angiotensin II cell movement muscle, smooth
| Introduction |
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Adrenomedullin, a potent vasorelaxant peptide, has recently been isolated from the acid extract of human pheochromocytoma.9 10 This peptide, consisting of 52 amino acids, has one intracellular disulfide bond and shows homology with calcitonin generelated peptide.9 10 This peptide stimulates cAMP formation in cultured rat vascular SMCs via specific receptors.11 12 13 Recently, we showed that rat adrenomedullin potently inhibits fetal calf seruminduced or platelet-derived growth factorinduced migration in cultured rat aortic SMCs.14 Subsequently, we showed that adrenomedullin modestly but significantly suppresses fetal calf seruminduced proliferation in cultured rat aortic SMCs.15 However, the role of adrenomedullin in the regulation of human coronary artery SMC migration and the interaction of this peptide and the RAS remain to be fully clarified.
Accordingly, the objectives of the current study were to determine whether Ang II stimulates migration of cultured SMCs derived from human coronary artery and, if so, to examine the possible effect of human adrenomedullin on Ang IIinduced migration in these cells. In addition, we examined the mechanism of the interaction of adrenomedullin and Ang II on human coronary artery SMC migration.
| Methods |
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Culture of Human Coronary Artery SMCs
Human coronary artery SMCs were cultured in SmBM
containing human epidermal growth factor (0.5 ng/mL), human fibroblast
growth factor (2 ng/mL), insulin (5 µg/mL), 5% fetal bovine serum,
50 µg/mL gentamicin sulfate, and 50 µg/mL amphotericin-B. Cells
were identified as SMCs according to their morphological and growth
characteristics.16 17 Cultures were maintained at 37°C
with atmospheric air and 5% CO2. Cells were subcultured
after treatment with 0.25% trypsin and 0.02% EDTA. Subconfluent SMCs
between passages 4 and 8 were used for the experiments.
Migration Assay
We assayed SMC migration with a modification of Boyden's
chamber method using microchemotaxis chambers (Neuro Probe Inc) and
polycarbonate filters (Nucleopore Corp), as previously
reported.14 In this experiment, polycarbonate filters with
12-µm-diameter pores were used. Cultured SMCs were trypsinized and
suspended at a concentration of approximately 5.0x105
cells/mL in SmBM supplemented with 0.5% fetal calf serum. Cell number
was counted with an electronic cell counter (model ZB1, Coulter
Electronics). A 200-µL volume of SMC suspension was placed in the
upper chamber, and 40 µL of medium and 0.4% bovine serum
albumin containing 10-9,
10-8, 10-7, and
10-6 mol/L Ang II was placed in the lower
chamber. The chamber was incubated at 37°C under 5% CO2
in air for 3, 6, and 9 hours. After incubation, SMCs on the upper side
of the filter were scraped off, and the filter was removed. The SMCs
that had migrated to the lower side of the filter were fixed in
ethanol, stained with Diff-Quick staining solution, and counted under a
microscope (x400 magnification) for quantification of SMC migration.
Migration activity was calculated as the mean number of migrated cells
observed in four high-power fields and given as the mean value of four
measurements.
Ang IIinduced migration may be separated into chemotactic and chemokinetic components. The chemotactic component was determined by the addition of 10-7 mol/L Ang II to the lower chamber only, and the chemokinetic component was determined with 10-7 mol/L Ang II added to either the upper chamber only or to both the upper and lower chambers.18
To determine the effects of Ang II receptor antagonists on SMC migration, 10-7 mol/L Ang II with or without 10-6 and 10-7 mol/L of the AT1 receptor antagonist losartan and the AT2 receptor antagonist PD 123319 was added to the lower chamber. To determine the effects of human adrenomedullin on Ang IIinduced SMC migration, various concentrations (10-9, 10-8, 10-7, and 10-6 mol/L) of adrenomedullin were added to the lower chamber in addition to 10-7 or 10-8 mol/L Ang II. In separate experiments, to determine the effects of 8-bromo-cAMP or forskolin on Ang IIstimulated SMC migration, these agents were added to the lower chamber in addition to 10-7 mol/L Ang II.
cAMP Measurement
After preincubation, cell monolayers were washed twice with
phosphate-buffered saline and stimulated for 30 minutes with different
concentrations of human adrenomedullin dissolved in SmBM that contained
5x10-4 mol/L IBMX. The reaction was stopped
by rapid aspiration and addition of 2 mL ice-cold 65% ethanol, as
previously described.19 After evaporation by a centrifugal
evaporator, the dry residue was dissolved in an assay buffer. cAMP
levels were determined by radioimmunoassay with a cAMP assay kit, as
previously described.13
Calculations and Analysis
The statistical significance of differences was evaluated with
an unpaired ANOVA, and probability values were calculated by
Scheffé's method.20 All values are expressed as
mean±SD.
| Results |
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Ang IIinduced migration can be separated into two components:
chemotaxis and chemokinesis. The chemotactic component was determined
by the addition of Ang II to the lower chamber only, and the
chemokinetic effect was measured with Ang II added to either the upper
chamber only or to both the upper and lower chambers. Evaluation of Ang
IIinduced SMC migration showed that the migration-stimulating effect
of Ang II was chemotactic in nature for cultured human coronary
artery SMCs (Fig 2
).
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Effects of Ang II Receptor Antagonist on SMC
Migration
Effects of losartan and PD 123319 on Ang IIstimulated
SMC migration are shown in Fig 3
. The
migration-stimulating effect of Ang II was clearly blocked by the
AT1 receptor antagonist losartan, but
it was not blocked by the AT2 receptor
antagonist PD 123319. This suggests that the
AT1 receptor is coupled to Ang IIinduced migration in
cultured human coronary artery SMCs.
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Effect of Adrenomedullin on Ang IIInduced SMC Migration
Fig 4A
shows effects of various concentrations
(10-9, 10-8,
10-7, and 10-6 mol/L)
of human adrenomedullin on SMC migration induced by
10-7 or 10-8 mol/L
Ang II. Human adrenomedullin significantly inhibited Ang IIinduced
migration in a concentration-dependent manner between
10-8 and 10-6
mol/L.
|
Effects of adrenomedullin on cellular cAMP level in cells treated with
10-7 or 10-8 mol/L
Ang II are shown in Fig 4B
. In parallel with the inhibition by
adrenomedullin of Ang IIinduced SMC migration, cellular cAMP
increased after treatment with adrenomedullin (Fig 4A
and 4B
).
Effects of 8-Bromo-cAMP and Forskolin on Ang IIInduced
SMC Migration
To elucidate whether the inhibitory effect of
adrenomedullin on Ang IIinduced SMC migration is causally linked to
the increase in cellular cAMP, we examined the effect of 8-bromo-cAMP,
a cAMP analogue, on Ang IIinduced SMC migration. Inhibition of Ang
IIinduced SMC migration by adrenomedullin could be reproduced by this
analogue at concentrations of 10-5 and
10-4 mol/L (Fig 5A
).
Furthermore, we examined the effect of forskolin, an
activator of adenylate cyclase, on Ang II
induced SMC migration. The addition of forskolin also reduced Ang
IIinduced SMC migration at concentrations of
10-6 and 10-5 mol/L
(Fig 5B
).
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| Discussion |
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Evaluation of Ang IIinduced migration showed that the migration-stimulatory effect of Ang II was chemotactic rather than chemokinetic in nature for cultured human coronary artery SMCs. This finding seems to be compatible with the report by Dubey and coworkers8 that Ang II stimulates the migration of rat aortic SMCs.
In the balloon injury model, Ang II has been found to contribute importantly to intimal lesion formation.3 4 Interestingly, in the rat intimal lesion, development can be reduced by inhibition of SMC migration alone, in the absence of an effect on SMC proliferation.21 22 Actually, angiotensin-converting enzyme inhibitors have been shown to reduce intimal lesion size by inhibiting SMC migration without affecting SMC proliferation in the balloon injury model.4 Although we have no direct evidence, these observations and our data raise the possibility that Ang IIinduced SMC migration contributes to the development of restenotic lesions in humans after angioplasty.
Second, we showed for the first time that human adrenomedullin strongly inhibits Ang IIinduced migration of human coronary artery SMCs in a concentration-dependent manner. In fact, SMC migration induced by 10-7 and 10-8 mol/L Ang II was significantly inhibited by human adrenomedullin-(1-52) at concentrations of 10-8 to 10-6 mol/L. Human adrenomedullin-(1-52) at 10-6 mol/L inhibited migration induced by 10-7 and 10-8 mol/L Ang II by approximately 65% and 55%, respectively. Although human adrenomedullin-(1-52) is a major circulating form in humans,23 24 25 the normal plasma concentrations (approximately 10-10 to 10-11 mol/L) are much lower than concentrations of synthetic adrenomedullin, which can inhibit SMC migration.23 24 25 However, plasma adrenomedullin concentrations are found to be high in hypertensive individuals with organ damage24 25 and in individuals with severe congestive heart failure.26 Furthermore, local levels of adrenomedullin in coronary vascular tissues may be much higher than plasma concentrations of adrenomedullin, because it has recently been shown that a considerable amount of adrenomedullin is synthesized in and secreted from vascular endothelial cells.27 With this matter taken into account, our results suggest that adrenomedullin, by acting locally as a paracrine factor, inhibits the migration of human coronary artery SMCs when the RAS is activated in coronary vascular tissues. Previously, we showed that adrenomedullin had a modest antiproliferative effect on rat aortic SMCs.15 Consequently, human adrenomedullin may antagonize the development of intimal thickening induced by Ang II in the coronary artery in certain pathological conditions, for example, after angioplasty. However, the present experiment was done on cultured SMCs; therefore, extrapolation to in vivo conditions should be made with caution.
We have obtained some evidence for a causal link between cAMP production and inhibition of Ang IIinduced SMC migration. First, human adrenomedullin increased cAMP levels, and this effect paralleled the inhibition of migration. Second, a cAMP analogue, 8-bromo-cAMP, and an activator of adenylate cyclase, forskolin, significantly inhibited Ang IIinduced migration. These results suggest that human adrenomedullin inhibits Ang IIinduced migration of human coronary artery SMCs at least partly through a cAMP-dependent mechanism. However, further studies are necessary to elucidate the involvement of cAMP and its related systems in the inhibition by human adrenomedullin of Ang IIinduced migration of human coronary artery SMCs.
Overall, the present work suggests that Ang II stimulates human coronary artery SMC migration via AT1 receptors and human adrenomedullin potently inhibits this stimulation. Taken together with the findings that adrenomedullin is synthesized in and secreted from vascular endothelial cells,27 possibly in coronary vascular tissues, this peptide may antagonize the development of intimal lesions in certain pathological conditions. However, more studies will be necessary to elucidate the exact role of endogenous adrenomedullin on intimal thickening during the process of RAS-related coronary atherosclerosis.
| Selected Abbreviations and Acronyms |
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| Acknowledgments |
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Received October 4, 1996; first decision October 21, 1996; accepted November 18, 1996.
| References |
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|
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2. Ross R. The pathogenesis of atherosclerosis: an update. N Engl J Med. 1986;314:488-500.[Medline] [Order article via Infotrieve]
3. Bell L, Madri JA. Influence of the angiotensin system on endothelial and smooth muscle cell migration. Am J Pathol. 1990;137:7-12.[Abstract]
4. Prescott MF, Webb RL, Reidy MA. Angiotensin-converting enzyme inhibitor versus angiotensin II, AT1 receptor antagonist: effects on smooth muscle cell migration and proliferation after balloon catheter injury. Am J Pathol. 1991;139:1291-1296.[Abstract]
5.
Van Kleef EM, Smits JFM, De Mey JGR, Cleutjens JPM,
Lombardi DM, Schwartz SM, Daemen MJAP.
1-Adrenoreceptor blockade reduces the
angiotensin IIinduced vascular smooth muscle cell DNA
synthesis in the rat thoracic aorta and carotid artery.
Circ Res. 1992;70:1122-1127.
6. Bunkenburg B, van Amelsvoort T, Rogg H, Wood JM. Receptor-mediated effects of angiotensin II on growth of vascular smooth muscle cells from spontaneously hypertensive rats. Hypertension. 1992;20:749-754.
7.
Janiak P, Pillon A, Prost JF, Vilaine JP. Role
of angiotensin subtype 2 receptor in neointima
formation after vascular injury. Hypertension. 1992;20:737-745.
8. Dubey RK, Jackson EK, Lüscher TF. Nitric oxide inhibits angiotensin II-induced migration of rat aortic smooth muscle cell. J Clin Invest. 1995;96:141-149.
9. Kitamura K, Kangawa K, Kawamoto M, Ichiki Y, Nakamura S, Matsuo H, Eto T. Adrenomedullin: a novel hypotensive peptide isolated from human pheochromocytoma. Biochem Biophys Res Commun. 1993;192:553-560.[Medline] [Order article via Infotrieve]
10. Ishiyama Y, Kitamura K, Ichiki Y, Nakamura S, Kida O, Kangawa K, Eto T. Hemodynamic effects of a novel hypotensive peptide, human adrenomedullin, in rats. Eur J Pharmacol. 1993;241:271-273.[Medline] [Order article via Infotrieve]
11. Ishizaka Y, Tanaka M, Kitamura K, Kangawa K, Minamino N, Matsuo H, Eto T. Adrenomedullin stimulates cyclic AMP formation in rat vascular smooth muscle cells. Biochem Biophys Res Commun. 1994;200:642-646.[Medline] [Order article via Infotrieve]
12. Eguchi S, Hirata Y, Kano H, Sato K, Watanabe Y, Watanabe TX, Nakajima K, Sakakibara S, Marumo F. Specific receptors for adrenomedullin in cultured rat vascular smooth muscle cells. FEBS Lett. 1994;340:226-230.[Medline] [Order article via Infotrieve]
13.
Kohno M, Kano H, Horio T, Yokokawa K, Yasunari K,
Takeda T. Inhibition of endothelin production by
adrenomedullin in the vascular smooth muscle cells.
Hypertension. 1995;25:1185-1190.
14.
Horio T, Kohno M, Kano H, Ikeda M, Yasunari K, Yokokawa
K, Minami M, Takeda T. Adrenomedullin as a novel antimigration
factor of vascular smooth muscle cells. Circ Res. 1995;77:660-664.
15. Kano H, Kohno M, Yasunari K, Yokokawa K, Horio T, Ikeda M, Minami M, Hanehira T, Takeda T, Yoshikawa J. Adrenomedullin as a novel antiproliferative factor of vascular smooth muscle cells. J Hypertens. 1996;14:209-213.[Medline] [Order article via Infotrieve]
16.
Yasunari K, Kohno M, Murakawa K, Yokokawa K, Horio T,
Takeda T. Phorbol ester and atrial natriuretic
peptide receptor response on vascular smooth muscle.
Hypertension. 1992;19:314-319.
17.
Yasunari K, Kohno M, Murakawa K, Yokokawa K, Horio T,
Takeda T. Interaction between a phorbol ester and dopamine DA1
receptors on vascular smooth muscle. Am J
Physiol. 1993;264:F24-F30.
18. Ikeda M, Kohno M, Yasunari K, Yokokawa K, Horio T, Ueda M, Morisaki N, Yoshikawa J. Natriuretic peptide family as a novel antimigration factor of vascular smooth muscle cells. Arterioscler Thromb Vasc Biol. In press.
19. Kohno M, Yasunari K, Yokokawa K, Murakawa K, Horio T, Takeda T. Inhibition by atrial and brain natriuretic peptides of endothelin-1 secretion after stimulation with angiotensin II and thrombin of cultured human endothelial cells. J Clin Invest. 1991;87:1999-2004.
20.
Wallenstein S, Zucker CL, Fleiss JL. Some
statistical methods useful in circulation research. Circ
Res. 1980;47:1-9.
21. Fingerle J, Johnson R, Clowes AW, Majesky MW, Reidy MA. The role of platelets in smooth muscle cell proliferation and migration after vascular injury in the rat carotid artery. Proc Natl Acad Sci U S A. 1981;86:8412-8416.
22.
Ferns GAA, Raines EW, Sprugel KH, Montaini AS, Reidy
MA, Ross R. Inhibition of neointimal smooth muscle
cell accumulation after angioplasty by an antibody to PDGF.
Science. 1991;253:1129-1132.
23. Kitamura K, Ichiki Y, Tanaka M, Kawamoto M, Emura J, Sakakibara S, Kangawa K, Matsuo H, Eto T. Immunoreactive adrenomedullin in human plasma. FEBS Lett. 1994;341:288-290.[Medline] [Order article via Infotrieve]
24.
Kohno M, Hanehira T, Kano H, Horio T, Yokokawa K, Ikeda
M, Minami M, Yasunari K, Yoshikawa J. Plasma adrenomedullin
concentrations in essential hypertension.
Hypertension. 1996;27:102-107.
25. Ishimitsu T, Nishikimi T, Saito Y, Kitamura K, Eto T, Kangawa K, Matsuo H, Omae T, Matsuoka H. Plasma levels of adrenomedullin, a newly identified hypotensive peptide, in patients with hypertension and renal failure. J Clin Invest. 1994;94:2158-2161.
26. Kato J, Kobayashi K, Etoh T, Tanaka M, Kitamura K, Imamura T, Koiwaya Y, Kangawa K, Eto T. Plasma adrenomedullin concentration in patients with heart failure. J Clin Endocrinol Metab. 1996;81:180-183.[Abstract]
27. Sugo S, Minamino N, Kangawa K, Miyamoto K, Kitamura K, Sakata J, Eto T, Matsuo H. Endothelial cells activity synthesize and secrete adrenomedullin. Biochem Biophys Res Commun. 1990;168:863-870.[Medline] [Order article via Infotrieve]
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