ABL-N-induced apoptosis in human breast cancer cells is partially mediated by c-Jun NH2-terminal kinase activation.

INTRODUCTION: The present study was designed to determine the possibility of acetylbritannilactone (ABL) derivative 5-(5-(ethylperoxy)pentan-2-yl)-6-methyl-3-methylene-2-oxo-2,3,3a,4,7,7a-hexahydrobenzofuran-4-yl 2-(6-methoxynaphthalen-2-yl)propanoate (ABL-N) as a novel therapeutic agent in human breast cancers. METHODS: We investigated the effects of ABL-N on the induction of apoptosis in human breast cancer cells and further examined the underlying mechanisms. Moreover, tumor growth inhibition of ABL-N was done in xenograft models. RESULTS: ABL-N induced the activation of caspase-3 in estrogen receptor (ER)-negative cell lines MDA-MB-231 and MDA-MB-468, as evidenced by the cleavage of endogenous substrate Poly (ADP-ribose) polymerase (PARP). Pretreatment of cells with pan-caspase inhibitor z-VAD-fmk or caspase-3-specific inhibitor z-DEVD-fmk inhibited ABL-N-induced apoptosis. ABL-N treatment also resulted in an increase in the expression of pro-apoptotic members (Bax and Bad) with a concomitant decrease in Bcl-2. Furthermore, c-Jun-NH2-terminal kinase (JNK) and p38 mitogen-activated protein (MAP) kinase (p38) were activated in the apoptosis induced by ABL-N and JNK-specific inhibitor SP600125 and JNK small interfering RNA (siRNA) antagonized ABL-N-mediated apoptosis. However, the p38-specific inhibitor SB203580 had no effect upon these processes. Moreover, neither of the caspase inhibitors prevented ABL-N-induced JNK activation, indicating that JNK is upstream of caspases in ABL-N-initiated apoptosis. Additionally, in a nude mice xenograft experiment, ABL-N significantly inhibited the tumor growth of MDA-MB-231 cells. CONCLUSIONS: ABL-N induces apoptosis in breast cancer cells through the activation of caspases and JNK signaling pathways. Moreover, ABL-N treatment causes a significant inhibition of tumor growth in vivo. Therefore, it is thought that ABL-N might be a potential drug for use in breast cancer prevention and intervention.

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.

Baicalin inhibits PDGF-BB-stimulated vascular smooth muscle cell proliferation through suppressing PDGFRß-ERK signaling and increase in p27 accumulation and prevents injury-induced neointimal hyperplasia.

The increased proliferation and migration of vascular smooth muscle cells (VSMCs) are key events in the development of atherosclerotic lesions. Baicalin, an herb-derived flavonoid compound, has been previously shown to induce apoptosis and growth inhibition in cancer cells through multiple pathways. However, the potential role of baicalin in regulation of VSMC proliferation and prevention of cardiovascular diseases remains unexplored. In this study, we show that pretreatment with baicalin has a dose-dependent inhibitory effect on PDGF-BB-stimulated VSMC proliferation, accompanied with the reduction of proliferating cell nuclear antigen (PCNA) expression. We also show that baicalin-induced growth inhibition is associated with a decrease in cyclin E-CDK2 activation and increase in p27 level in PDGF-stimulated VSMCs, which appears to be at least partly mediated by blockade of PDGF receptor ß (PDGFRß)-extracellular signal-regulated kinase 1/2 (ERK1/2) signaling. In addition, baicalin was also found to inhibit adhesion molecule expression and cell migration induced by PDGF-BB in VSMCs. Furthermore, using an animal carotid arterial balloon-injury model, we found that baicalin significantly inhibited neointimal hyperplasia. Taken together, our results reveal a novel function of baicalin in inducing growth arrest of PDGF-stimulated VSMCs and suppressing neointimal hyperplasia after balloon injury, and suggest that the underlying mechanism involves the inhibition of cyclin E-CDK2 activation and the increase in p27 accumulation via blockade of the PDGFRß-ERK1/2 signaling cascade.