title: Cytotoxic effect of hemin in colonic epithelial cell line: involvement of 18 kDa translocator protein (TSPO).
abstract: OBJECTIVE
  The aim of this study is to investigate the effect of hemin in colonic epithelial cells (Caco-2) cell proliferation and if this effect was due to a direct modulation of 18-kDa translocator protein (TSPO) and/or heme oxygenase type 1 (HO-1).
  
  
  METHODS
  The main methods are as follow: cell proliferation and cell cytotoxic assays on Caco-2 cell lines treated with hemin in the presence or not of 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK 11195) and Sn-protoporphyrin IX (Sn-PPIX), and immunoblotting for TSPO and HO-1 protein analysis, siRNA directed against TSPO.
  
  
  RESULTS
  Hemin was shown to be toxic for the Caco-2 cell line in a concentration and time dependent manner. Although hemin was able to induce HO-1 in a dose dependent manner, a specific HO-1 inhibitor, Sn-PPIX, was unable to interfere with the effect of hemin on Caco-2 cells. Instead, PK 11195, a specific TSPO ligand, was able to counteract the effect of hemin, suggesting an important role of TSPO in the hemin activity. Cell viability assay further confirms the high cytotoxic effects exerted by hemin on Caco-2 cells expressing TSPO compared to the siRNA-TSPO targeted cells. In addition, hemin was able to decrease significantly the TSPO protein density in a dose dependent manner after 24h of incubation.
  
  
  CONCLUSIONS
  The interaction and the consecutive down regulation of TSPO by hemin played an important role in the control of Caco-2 cell viability. The presented data suggest that TSPO might contribute to protect cells from potential toxic compounds such as free tetrapyrroles, candidating this receptor as a survival receptor protein.
authors.affiliation: Department of Life Sciences University of Modena and Reggio Emilia, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Gemelli
authors.affiliation: Department of Life Sciences University of Modena and Reggio Emilia, Italy.
authors.forename: Bendjedith Momo
authors.initials: BM
authors.lastname: Dongmo
authors.affiliation: Department of Life Sciences University of Modena and Reggio Emilia, Italy.
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Ferrarini
authors.affiliation: Department of Life Sciences University of Modena and Reggio Emilia, Italy.
authors.forename: Alexis
authors.initials: A
authors.lastname: Grande
authors.affiliation: Department of Life Sciences University of Modena and Reggio Emilia, Italy. Electronic address: corsi.lorenzo@unimore.it.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Corsi
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D015153:Blotting, Western; D018938:Caco-2 Cells / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D051547:Heme Oxygenase-1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D006427:Hemin / Q000494:pharmacology*; D006801:Humans; D007546:Isoquinolines / Q000494:pharmacology; D008665:Metalloporphyrins / Q000494:pharmacology; D011524:Protoporphyrins / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000235:genetics; D018079:Receptors, GABA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D008665:Metalloporphyrins; D011524:Protoporphyrins; D034741:RNA, Small Interfering; D018079:Receptors, GABA; C499229:TSPO protein, human; D006427:Hemin; C032628:tin protoporphyrin IX; D051547:Heme Oxygenase-1; C037850:PK 11195
keywords: Cell proliferation; HO-1; Hemin; PK 11195; Sn-PPIX; TSPO; si-RNA