title: Isoorientin induces apoptosis through mitochondrial dysfunction and inhibition of PI3K/Akt signaling pathway in HepG2 cancer cells.
abstract: Isoorientin (ISO) is a flavonoid compound that can be extracted from several plant species, such as Phyllostachys pubescens, Patrinia, and Drosophyllum lusitanicum; however, its biological activity remains poorly understood. The present study investigated the effects and putative mechanism of apoptosis induced by ISO in human hepatoblastoma cancer (HepG2) cells. The results showed that ISO induced cell death in a dose-dependent manner in HepG2 cells, but no toxicity in human liver cells (HL-7702) and buffalo rat liver cells (BRL-3A) treated with ISO at the indicated concentrations. ISO-induced cell death included apoptosis which characterized by the appearance of nuclear shrinkage, the cleavage of poly (ADP-ribose) polymerase (PARP) and DNA fragmentation. ISO significantly (p<0.01) increased the Bax/Bcl-2 ratio, disrupted the mitochondrial membrane potential (MMP), increased the release of cytochrome c, activated caspase-3, and enhanced intracellular levels of reactive oxygen species (ROS) and nitric oxide (NO). In addition, ISO effectively inhibited the phosphorylation of Akt and increased FoxO4 expression. The PI3K/Akt inhibitor LY294002 enhanced the apoptosis-inducing effect of ISO. However, LY294002 markedly quenched ROS and NO generation and diminished the protein expression of heme peroxidase enzyme (HO-1) and inducible nitric oxide synthase (iNOS). Furthermore, the addition of a ROS inhibitor (N-acetyl cysteine, NAC) or iNOS inhibitor (N-[3-(aminomethyl) benzyl] acetamidine, dihydrochloride, 1400W) significantly diminished the apoptosis induced by ISO and also blocked the phosphorylation of Akt. These results demonstrated for the first time that ISO induces apoptosis in HepG2 cells and indicate that this apoptosis might be mediated through mitochondrial dysfunction and PI3K/Akt signaling pathway, and has no toxicity in normal liver cells, suggesting that ISO may have good potential as a therapeutic and chemopreventive agent for liver cancer.
authors.affiliation: Laboratory of Nutrition and Functional Factors, College of Food Science and Engineering, Northwest A & F University, Yangling, China.
authors.forename: Li
authors.initials: L
authors.lastname: Yuan
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Haifang
authors.initials: H
authors.lastname: Xiao
authors.forename: Chunxia
authors.initials: C
authors.lastname: Xiao
authors.forename: Yutang
authors.initials: Y
authors.lastname: Wang
authors.forename: Xuebo
authors.initials: X
authors.lastname: Liu
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002867:Chromones / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D006801:Humans; D047311:Luteolin / Q000633:toxicity*; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects*; D051336:Mitochondrial Membranes / Q000187:drug effects; D009025:Morpholines / Q000494:pharmacology; D009569:Nitric Oxide / Q000096:biosynthesis / Q000502:physiology; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*
chemical_list: D000975:Antioxidants; D002867:Chromones; D009025:Morpholines; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D045304:Cytochromes c; C057912:homoorientin; D052247:Nitric Oxide Synthase Type II; D051057:Proto-Oncogene Proteins c-akt; D047311:Luteolin