Apoptosis-inducing effects of extracts from desert plants in HepG2 human hepatocarcinoma cells

Objective:To investigat the mechanism of antitumor efficacy of Origanum clayi(O.clayi) and Ochradenus baccatus(O.baccatus) extracts by exploring apoptosis-inducing potential.Methods:The aqueous extracts of aerial parts of aforementioned plants were prepared and used for this study.HepG2 cells were treated with varying concentrations(0,2 and 5 mg/mL)of each plant extract for 24 or 48 h.Cell apoptosis was measured by annexin V-fluorescein isothiocyanate binding assay and flow cytometry.The expression levels of various apoptosisrelated genes were determined by semi-quantitative reverse transcription-polymerase chain reaction.Results:O.clayi and O.baccatus extracts exerted apoptotic effects on HepG2 cells for 48 h following treatment.O.clayi extract was found to be a better apoptosis-inducing agent than O.baccatus extract as the former delivered greater efficacy at a lower concentration.Both extracts manifested upregulation of Bax,Bad.cytochrome c.caspase-3,caspase-7.caspase-9 and poly(adenosine diphosphate-ribose) polymerase.Conclusions:The aqueous extracts of O.clayi and O.baccatus are capable of inducing apoptosis in HepG2 cells through modulation of mitochondrial pathway which explains their antitumor activities.These desert plants may serve as useful resources to develop effective remedies for hepatocellular carcinoma and other human malignancies.

Metformin Modulates GLP-1- and GIP-Mediated Intracellular Signaling under Normoglycemic Conditions

GLP-1 and GIP promote insulin secretion from pancreatic β-cells by inducing intracellular signals such as Ca2+ and cAMP. Metformin primarily acts by inhibiting glucogenesis in the liver and promoting glucose metabolism in the muscle. It is used as a concomitant drug with the incretin in the treatment of T2D. We focused on intracellular signals under various glucose concentrations and assessed the effects of metformin on incretin signaling in MIN6 β-cells. Metformin inhibited incretin-induced [Ca2+]i in the presence of 5.5 mM glucose but not 16.7 mM glucose. In accordance with low [Ca2+]i, insulin secretion from MIN6 cells declined, despite enhanced incretin-induced cAMP production. Abundant expressions of Adcy 6 and 9, which are negatively controlled by Ca2+ signals, were detected in MIN6 cells. Thus, increasing cAMP production was associated with the inhibition of Ca2+ mobilization by metformin. However, we show that metformin controls insulin secretion by inhibiting incretin-mediated [Ca2+]i under normoglycemic conditions.