Acetylbritannilactone induces G1 arrest and apoptosis in vascular smooth muscle cells.
BACKGROUND
The present study was designed to determine the effects of Acetylbritannilactone (ABL), a naturally occurring Inula britannica L., on vascular smooth muscle cell (VSMC) proliferation and apoptosis.


METHODS
In vitro experiments were performed to evaluate the effects of ABL on the VSMC cycle and apoptosis stimulated by chemoattractant. In addition, to examine the effects of ABL in vivo, balloon injury to rat carotid arteries was performed.


RESULTS
ABL treatment inhibited platelet-derived growth factor (PDGF) induced DNA synthesis and proliferation in cultured VSMC. Such growth-inhibitory effects of ABL were associated with G1 phase arrest, which were correlated with reduction of cyclins D1, A, and E expression and cyclin-dependent kinase (CDK) 2, CDK4, and CDK6 proteins, increased the CDK inhibitory protein p21cip1 expression, and enhanced the binding of p21cip1 to CDKs. In addition, ABL also induced apoptosis in proliferative VSMCs, as evidenced by the induction of a higher ratio of Bax/Bcl-2, activation of caspase-9, caspase-3, and the cleavage of endogenous substrate Poly (ADP-ribose) polymerase. However, pretreatment with pan-caspases inhibitor (z-VAD-fmk) only partially reversed ABL-induced apoptosis, suggesting the involvement of both caspase-dependent and caspase-independent pathways in these processes. Furthermore, the effects of ABL on VSMCs were associated with the downregulation of extracellular signal-regulated kinase (ERK) 1/2 signaling pathways. In vivo, ABL (26 mg/kg/day) significantly suppressed injury-induced ERK1/2 phosphorylation, and increased VSMC apoptosis 14 days after balloon injury.


CONCLUSIONS
Our findings demonstrated that ABL was capable of suppressing the abnormal VSMC proliferation, accompanied by the induction of apoptosis in vivo and in vitro. It suggested that ABL could be considered a pharmacological candidate for the prevention of restenosis after balloon angioplasty.
Liu
Bin
B
Department of Biochemistry and Molecular Biology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang, PR China.
Han
Mei
M
Sun
Rong-Hua
RH
Wang
Jun-Jie
JJ
Liu
Yue-Ping
YP
Wen
Jin-Kun
JK
D000800:Angioplasty, Balloon / Q000009:adverse effects; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D020212:Carotid Artery Injuries / Q000188:drug therapy / Q000473:pathology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors; D016213:Cyclins / Q000037:antagonists & inhibitors; D004195:Disease Models, Animal; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D016193:G1 Phase / Q000187:drug effects* / Q000502:physiology; D038143:Inula; D007783:Lactones / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects*; D028321:Plant Preparations / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism
C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D007783:Lactones; D028321:Plant Preparations; C487680:acetylbritannilatone; D017479:Receptors, Platelet-Derived Growth Factor; D018844:Cyclin-Dependent Kinases; D048049:Extracellular Signal-Regulated MAP Kinases