Cudraflavanone A, a Flavonoid Isolated from the Root Bark of Cudrania tricuspidata, Inhibits Vascular Smooth Muscle Cell Growth via an Akt-Dependent Pathway

Abstract

In previous studies of the root bark of Cudrania tricuspidata, various isoprenylated xanthones and flavonoids were isolated, some of which have anticancer, hepatoprotective, and antiperoxidative activities. Cytokines and growth factors are involved in the regulation of vascular smooth muscle cells (VSMCs) in atherosclerotic plaques. To assess whether cudraflavanone A isolated from the root bark of C. tricuspidata may be useful in the prevention of atherosclerosis or restenosis after angioplasty, we investigated the ability of cudraflavanone A to inhibit VSMCs growth under 25 ng/mL platelet-derived growth factor BB (PDGF-BB)-stimulated conditions. Cudraflavanone A (0.1 - 1 μM) significantly inhibited PDGF-BB-induced cell numbers in a concentration-dependent manner. The antigrowth effects of cudraflavanone A on VSMCs were also examined in [3H]-thymidine incorporation and cell cycle assays. Consistent with the inhibitory effect on cell number, PDGF-BB-stimulated [3H]-thymidine incorporation and cell cycle progression in VSMCs was also concentration-dependently reduced by cudraflavanone A. Furthermore, PDGF-BB markedly activated PDGF-beta receptor (PDGF-Rβ) tyrosine kinase activity, leading to activation of intracellular signals required for VSMC growth. However, PDGF-BB-induced this kinase activity was not affected by cudraflavanone A. PDGF-BB also increased the activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), Akt, and phospholipase C gamma (PLCγ)1, which are important signaling molecules in cell growth. Cudraflavanone A (0.1 - 1 μM) suppressed PDGF-BB-stimulated Akt activation, which is involved in cell survival, but had no effect on the activation of ERK1/2 and PLCγ1. Selective modification of Akt activation by cudraflavanone A in VSMCs may suppress intimal thickening after angioplasty and plaque formation in atherosclerosis. These results suggest that cudraflavanone A from C. tricuspidata inhibits PDGF-BB-induced rat aortic VSMC growth via an Akt-dependent pathway.

Cudrania tricuspidata - Moraceae - cudraflavanone A - vascular smooth muscle cell - Akt

References

• 1 Ross R. The pathogenesis of atherosclerosis: a perspective for the 1990s.  Nature. 1993;  362 801-9.
• 2 Maresta A, Balducelli M, Cantini L, Casari A, Chioin R, Fabbri M. et al . Trapidil (triazolopyrimidine), a platelet-derived growth factor antagonist, reduces restenosis after percutaneous transluminal coronary angioplasty. Results of the randomized, double-blind STARC study. Studio Trapidil versus Aspirin nella Restenosi Coronarica.  Circulation. 1994;  90 2710-5.
• 3 Ko Y, Totzke G, Graack G H, Heidgen F J, Meyer zu Brickwedde M K, Dusing R. et al . Action of dihydropyridine calcium antagonists on early growth response gene expression and cell growth in vascular smooth muscle cells.  J Hypertens. 1993;  11 1171-8.
• 4 Kumar M S, Owens G K. Combinatorial control of smooth muscle-specific gene expression.  Arterioscler Thromb Vasc Biol. 2003;  23 737-47.
• 5 Kim T J, Yun Y P. Antiproliferative activity of NQ304, a synthetic 1,4-naphthoquinone, is mediated via the suppressions of the PI3K/Akt and ERK1/2 signaling pathways in PDGF-BB-stimulated vascular smooth muscle cells.  Vasc Pharmacol. 2007;  46 43-51.
• 6 Myllarniemi M, Frosen J, Calderon Ramirez L G, Buchdunger E, Lemstrom K, Hayry P. Selective tyrosine kinase inhibitor for the platelet-derived growth factor receptor in vitro inhibits smooth muscle cell proliferation after reinjury of arterial intima in vivo .  Cardiovasc Drugs Ther. 1999;  13 159-68.
• 7 Kim J H, Jin Y R, Park B S, Kim T J, Kim S Y, Lim Y. et al . Luteolin prevents PDGF-BB-induced proliferation of vascular smooth muscle cells by inhibition of PDGF beta-receptor phosphorylation.  Biochem Pharmacol. 2005;  69 1715-21.
• 8 Heldin C H, Ostman A, Ronnstrand L. Signal transduction via platelet-derived growth factor receptors.  Biochim Biophys Acta. 1998;  1378 F79-113.
• 9 Graf K, Xi X P, Yang D, Fleck E, Hsueh W A, Law R E. Mitogen-activated protein kinase activation is involved in platelet-derived growth factor-directed migration by vascular smooth muscle cells.  Hypertension. 1997;  29 334-9.
• 10 Pyles J M, March K L, Franklin M, Mehdi K, Wilensky R L, Adam L P. Activation of MAP kinase in vivo follows balloon overstretch injury of porcine coronary and carotid arteries.  Circ Res. 1997;  81 904-10.
• 11 Seo W G, Pae H O, Oh G S, Chai K Y, Yun Y G, Kwon T O. et al . Inhibitory effect of ethyl acetate fraction from Cudrania tricuspidata on the expression of nitric oxide synthase gene in RAW 264.7 macrophages stimulated with interferon-gamma and lipopolysaccharide.  Gen Pharmacol. 2000;  35 21-8.
• 12 Lee B W, Lee J H, Lee S T, Lee H S, Lee W S, Jeong T S. et al . Antioxidant and cytotoxic activities of xanthones from Cudrania tricuspidata .  Bioorg Med Chem Lett. 2005;  15 5548-52.
• 13 An R B, Sohn D H, Kim Y C. Hepatoprotective compounds of the roots of Cudrania tricuspidata on tacrine-induced cytotoxicity in Hep G2 cells.  Biol Pharm Bull. 2006;  29 838-40.
• 14 Park K H, Park Y D, Han J M, Im K R, Lee B W, Jeong I Y. et al . Anti-atherosclerotic and anti-inflammatory activities of catecholic xanthones and flavonoids isolated from Cudrania tricuspidata .  Bioorg Med Chem Lett. 2006;  16 5580-3.
• 15 Lee B W, Gal S W, Park K M, Park K H. Cytotoxic xanthones from Cudrania tricuspidata .  J Nat Prod. 2005;  68 456-8.
• 16 Zou Y S, Hou A J, Zhu G F. Isoprenylated xanthones and flavonoids from Cudrania tricuspidata .  Chem Biodivers. 2005;  2 131-8.
• 17 Fujimoto T, Nomura T. Components of root bark of Cudrania tricuspidata; 3. Isolation and structure studies on the flavonoids.  Planta Med. 1985;  51 190-3.
• 18 Kim T J, Zhang Y H, Kim Y, Lee C K, Lee M K, Hong J T. et al . Effects of apigenin on the serum- and platelet-derived growth factor-BB-induced proliferation of rat aortic vascular smooth muscle cells.  Planta Med. 2002;  68 605-9.
• 19 Chamley-Campbell J, Campbell G R, Groschel-Stewart U, Burnstock G. FITC-labelled antibody staining of tropomyosin-containing fibrils in smooth, cardiac and skeletal muscle cells, prefusion myoblasts, fibroblasts, endothelial cells and 3T3 cells in culture.  Cell Tissue Res. 1977;  183 153-66.
• 20 Laemmli U K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4.  Nature. 1970;  227 680-5.
• 21 Higaki M, Shimokado K. Phosphatidylinositol 3-kinase is required for growth factor-induced amino acid uptake by vascular smooth muscle cells.  Arterioscler Thromb Vasc Biol. 1999;  19 2127-32.
• 22 Downward J. Signal transduction. New exchange, new target.  Nature. 1998;  396 416-7.

1 Both authors contributed equally to this work