title: Heme oxygenase-1 attenuates cadmium-induced mitochondrial-caspase 3- dependent apoptosis in human hepatoma cell line.
abstract: BACKGROUND
  Cadmium (Cd) is a well known environmental and industrial toxicant causing damaging effects in numerous organs. In this study, we examined the role of heme oxygenase-1 (HO-1) in modulating the Cd-induced apoptosis in human hepatoma (HepG2) cells after 24 h exposure.
  
  
  METHODS
  HepG2 cells were exposed to 5 and 10 μM Cd as CdCl2 for 24 h while other sets of cells were pre-treated with either 10 μM Cobalt protoporphyrin (CoPPIX) or 10 μM Tin protoporphyrin (SnPPIX) for 24 h, or 50 μM Z-DEVD-FMK for 1 h before exposure to 5 and 10 μM CdCl2 for 24 h. Expressions of caspase 3, cytosolic cytochrome c, mitochondrial Bax and anti-apoptotic BCL-xl proteins were assessed by western blot. Intracellular reactive oxygen species (ROS) production was determined using the dihydrofluorescein diacetate (H2DFA) method. Cell viability was assessed by MTT assay, while a flow cytometry method was used to assess the level of apoptosis in the cell populations.
  
  
  RESULTS
  Our results show that there were a significant increase in the expression of cytosolic cytochrome c, mitochondrial Bax protein, and caspase 3 at 5 and 10 μM compared to the control, but these increases were attenuated by the presence of CoPPIX. The presence of SnPPIX significantly enhanced Cd-induced caspase 3 activities. CoPPIX significantly decreased the level of ROS production by 24.6 and 22.2 % in 5 and 10 μM CdCl2, respectively, but SnPPIX caused a significant increase in ROS production in the presence of CdCl2. HepG2 cell viability was also significantly impaired by 13.89 and 32.53 % in the presence of 5 and 10 μM CdCl2, respectively, but the presence of CoPPIX and Z-DEVD-FMK significantly enhanced cell survival, while SnPPIX enhanced Cd-impaired cell viability. The presence of CoPPIX and Z-DEVD-FMK also significantly decreased the population of apoptotic and necrotic cells compared with Cd.
  
  
  CONCLUSIONS
  In summary, the present study showed that HO-1 attenuates the Cd-induced caspase 3 dependent pathway of apoptosis in HepG2 cells, probably by modulating Cd-induced oxidative stress.
authors.affiliation: Oxidative Stress Research Centre, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville Campus, Bellville, 7535, South Africa. tolekan@hotmail.com.|Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, G1 1XW, Glasgow, UK. tolekan@hotmail.com.
authors.forename: Akeem O
authors.initials: AO
authors.lastname: Lawal
authors.affiliation: Oxidative Stress Research Centre, Faculty of Health and Wellness Sciences, Cape Peninsula University of Technology, Bellville Campus, Bellville, 7535, South Africa.|Institute of Biomedical and Microbial Biotechnology, Cape Peninsula University of Technology, Bellville Campus, Bellville, 7535, South Africa.
authors.forename: Jeanine L
authors.initials: JL
authors.lastname: Marnewick
authors.affiliation: Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, G1 1XW, Glasgow, UK.
authors.forename: Elizabeth M
authors.initials: EM
authors.lastname: Ellis
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D002104:Cadmium / Q000494:pharmacology*; D006528:Carcinoma, Hepatocellular / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D003600:Cytosol / Q000187:drug effects / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D008665:Metalloporphyrins / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D009842:Oligopeptides / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: D015853:Cysteine Proteinase Inhibitors; D008665:Metalloporphyrins; D009842:Oligopeptides; D011524:Protoporphyrins; D017382:Reactive Oxygen Species; D051028:bcl-2-Associated X Protein; C110772:benzoylcarbonyl-aspartyl-glutamyl-valyl-aspartyl-fluoromethyl ketone; D002104:Cadmium; C007095:cobaltiprotoporphyrin; D045304:Cytochromes c; C032628:tin protoporphyrin IX; D051547:Heme Oxygenase-1; D053148:Caspase 3