Antiproliferative action of cudraflavone B, isolated from Cudrania tricuspidata, through the downregulation of pRb phosphorylation in aortic smooth muscle cell proliferation signaling.
Cudrania tricuspidata has been proposed to possess anti-inflammatory, antioxidant, hepatoprotective, and antitumor activities. Although cudraflavone B, isolated from the root bark of C. tricuspidata, has a variety of pharmacological effects, its effects on rat aortic smooth muscle cells (RASMCs) are unclear. In the present study, cudraflavone B was found to inhibit cell proliferation and DNA synthesis in cultured RASMCs. Pretreatment with cudraflavone B (0.1-4 microM) suppressed platelet-derived growth factor-BB (PDGF-BB)-stimulated cell number in a concentration-dependent manner. The inhibition percentages were 19.7%, 36.4%, 52.3%, and 99.1% at concentrations of 0.1, 1, 2, and 4 microM, respectively. Moreover, cudraflavone B inhibited [H]-thymidine incorporation into DNA in RASMCs in response to 25 ng/mL PDGF-BB. PDGF-BB-stimulated DNA synthesis was significantly reduced by 15.9%, 31.7%, 43.1%, and 78.2% at concentrations of 0.1, 1, 2, and 4 muM, respectively. Thus, cudraflavone B blocked the PDGF-BB-inducible progression through G0/G1 to S phase of the cell cycle in synchronized cells. Furthermore, PDGF-BB-induced phosphorylation of retinoblastoma protein (pRb), the hyperphosphorylation of which is a hallmark of the G1-S transition in the cell cycle, was significantly inhibited by cudraflavone B. Because pRb phosphorylation is regulated by cyclin-dependent kinases (CDKs), we investigated the expression of CDK2, CDK4, cyclin E, and cyclin D1 and the CDK inhibitors p21 and p27. Treatment with cudraflavone B downregulated the cyclins and CDKs and upregulated the expression of p21 and p27, a CDK inhibitor. These findings suggest that cudraflavone B inhibits RASMC proliferation via the induction of p21 and p27 expression and subsequent cell cycle arrest with reduction of pRb phosphorylation at the G1-S phase.
Kim
Tack-Joong
TJ
Division of Biological Science and Technology, Institute of Biomaterials, Yonsei University, Wonju, Korea.
Han
Hyeong-Jun
HJ
Lim
Yong
Y
Song
Min-Cheol
MC
Kim
Jihee
J
Hong
Jin-Tae
JT
Yoo
Hwan-Soo
HS
Pyo
Myoung-Yun
MY
Hwang
Bang-Yeon
BY
Lee
Myoung-Koo
MK
Yun
Yeo-Pyo
YP
D000818:Animals; D001011:Aorta / Q000166:cytology; D049109:Cell Proliferation / Q000187:drug effects*; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D005419:Flavonoids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D015394:Molecular Structure; D029586:Moraceae / Q000737:chemistry*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D024301:Plant Bark / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D051381:Rats; D016160:Retinoblastoma Protein / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013997:Time Factors
D016895:Culture Media, Serum-Free; D005419:Flavonoids; D010982:Platelet-Derived Growth Factor; D016160:Retinoblastoma Protein; C542041:cudraflavone B