of cell cycle, the percentage of cells in S phase was significantly decreased, while the percentage of cells in G 1 phase was increased. Flow cytometry assay also showed that ESB had a positive effect on apoptosis. Typical apoptotic morphologies such as condensation and fragmentation of nuclei and blebbing membrane of apoptotic cells could be observed under transmission electron microscope and fluorescence microscope. To further investige the molecular mechanism behind ESB-induced apoptosis, ESB-treated cells rapidly lost their mitochondrial transmembrane potential, released mitochondrial cytochrome C into cytosol, and induced caspase-3 activity in a dose-dependent manner. CONCLUSION: ESB can effectively inhibit the proliferation and induce apoptosis of H22 cells involving loss of mitochondrial transmembrane potential, release of cytochrome C, and activation of caspase-3.
INTRODUCTIONScutellaria barbata D.Don (S. barbata) is a perennial herb, also known as Ban-Zhi-Lian (barbat sskullcap) in traditional Chinese medicine. It is mainly distributed in southern China and has been used as an antitumor agent for lung cancer, digestive system cancer, hepatoma, breast cancer, and chorioepithelioma as well as an anti-inflammatory agent and a diuretic in China and Korea [1][2][3][4][5][6][7][8][9] . Extracts from S. barbata (ESB) have in vitro growth inhibitory effects on a number of human cancers including leukemia, colon cancer, hepatoma and skin cancer [4][5][6][7][8][9][10] . However, its antitumor mechanism still remains unclear.It was reported that many Chinese herbs have anticancer properties and induce apoptosis [11] . Three apoptotic pathways have been addressed, including the mitochondrial pathway [12,13] , death receptor pathway [14] , and endoplasmic reticulum stress-mediated apoptosis pathway [15] . The mitochondrial pathway initiates apoptosis in most physiological and pathological situations. Permeabilization outside mitochondrial membrane plays the most important role in mitochondrial apoptosis. In the mitochondria-initiated pathway, mitochondria undergoing permeability transition release apoptogenic proteins such as cytochrome C or apoptosis-inducing factor from the mitochondrial intermembrane space into the cytosol [16] . Released cytochrome C can activate caspase-9, and activated caspase-9 in turn cleaves and activates executioner caspase-3. After caspase-3 activation, some specific substrates for caspase-3 such as poly (ADP-ribose) and polymerase (PARP) are cleaved, and eventually lead to apoptosis [17] . In this study, S. barbata extract showed anti-tumor activity in vitro and could inhibit the growth of mouse H22 hepatoma cells by inhibiting cell apoptosis and cytotoxic effects, demonstrating that the extract from S. barbata can strongly inhibit cell proliferation and induce apoptosis of H22 cells through the mitochondrial dysfunction pathway.
MATERIALS AND METHODSReagents and animals N e w b ov i n e s e r u m ( G i b c o, U S A ) , R P M I -1 6 4 0 medium(Gibco, USA), propidium iodide (PI) (Sigma, ...