Role of mitochondria and mitochondrial cytochrome c in tubeimoside I-mediated apoptosis of human cervical carcinoma HeLa cell line

Background: Tubeimoside I (TBMS1), a triterpenoid saponin, isolated from the tubers of Bolbostemma paniculatum, showed potent antitumor and antitumor-promoting effects. The objective of this study is to investigate the role of mitochondria and mitochondria cytochrome c in TBMS1-mediated apoptosis of human cervical carcinoma HeLa cell line. Methods: Viability of HeLa cells was measured by MTT assay. Apoptotic induction by TBMS1 was determined by fluorescence microscopy, flow cytometry and gel electrophoresis of fragmented DNA. Mitochondrial transmembrane potential (triangle psi m) was assayed by flow cytometry. Cytochrome c (Cyt c) was detected by Western blotting. Results: The results showed that Cyclosporin A (CsA) partly protected HeLa cells from growth inhibitory effect of TBMS1, and partly countered the ability of TBMS1 to rapidly induce apoptosis in HeLa cells, and that TBMS1 decreased triangle psi m and induced Cyt c release by a mechanism inhibited by CsA, and that TBMS1 induced apoptosis of HeLa cells dose-dependently in accordance with increase of cytosolic Cyt c. Conclusions: TBMS1 opens the permeability transition (PT) pore, thereby decreasing triangle psi m, releasing Cyt c from mitochondria, and further causing a series of events consistent with established mechanistic models of apoptosis.