title: The role of p38 signaling and poly(ADP-ribosyl)ation-induced metabolic collapse in the osteogenic differentiation-coupled cell death pathway.
abstract: Osteogenic differentiation is a multistep process regulated by a diverse set of morphogenic and transcription factors. Previously we identified endogenous hydrogen peroxide-induced poly(ADP-ribose) polymerase-1 (PARP1) activation as a mediator of osteodifferentiation and associated cell death. Here we set out to investigate whether or not activation of PARP1 is dependent on DNA breaks and how PARP1 mediates cell death during osteodifferentiation of mesenchymal stem cells and SAOS-2 cells. Here we show that the MAP kinases p38, JNK, and ERK1/2 become activated during the differentiation process. However, only p38 activation depended both on hydrogen peroxide production and on PARP1 activation as the hydrogen peroxide decomposing enzyme catalase, the PARP inhibitor PJ34, and the silencing of PARP1 suppressed p38 activation. Inhibition of p38 suppressed cell death and inhibited osteogenic differentiation (calcium deposition, alkaline phosphatase activity, and marker gene expression) providing further support for the close coupling of osteodifferentiation and cell death. Metabolic collapse appears to be central in the hydrogen peroxide-PARP1-p38 pathway as silencing PARP1 or inhibition of p38 prevented differentiation-associated loss of cellular NAD, inhibition of mitochondrial respiration, and glycolytic activity. We also provide evidence that endogenous hydrogen peroxide produced by the differentiating cells is sufficient to cause detectable DNA breakage. Moreover, p38 translocates from the cytoplasm to the nucleus where it interacts and colocalizes with PARP1 as detected by immunoprecipitation and immunofluorescence, respectively. In summary, hydrogen peroxide-induced PARP1 activation leads to p38 activation and this pathway is required both for the successful completion of the differentiation process and for the associated cell death.
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; Department of Environmental Pollution Biophysics, Faculty of Biology and Environmental Protection, University of Lodz, Poland.
authors: Agnieszka
authors: A
authors: Robaszkiewicz
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: Zsuzsanna
authors: Z
authors: Valkó
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, Debrecen, Hungary.
authors: Katalin
authors: K
authors: Kovács
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: Csaba
authors: C
authors: Hegedűs
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
authors: Edina
authors: E
authors: Bakondi
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, Debrecen, Hungary; Research Center for Molecular Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Lendület Laboratory of Cellular Metabolism Research Group, Debrecen, Hungary.
authors: Péter
authors: P
authors: Bai
authors: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, Debrecen, Hungary. Electronic address: lvirag@med.unideb.hu.
authors: László
authors: L
authors: Virág
mesh_terms: D017209:Apoptosis; D015153:Blotting, Western; D001859:Bone Neoplasms / Q000378:metabolism / Q000473:pathology; D002454:Cell Differentiation; D049109:Cell Proliferation; D002478:Cells, Cultured; D002823:Chorion / Q000378:metabolism / Q000473:pathology; D020552:Comet Assay; D004249:DNA Damage; D004734:Energy Metabolism; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D059630:Mesenchymal Stem Cells / Q000378:metabolism / Q000473:pathology*; D048052:Mitogen-Activated Protein Kinase 3 / Q000235:genetics / Q000378:metabolism*; D010012:Osteogenesis / Q000502:physiology*; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology*; D018384:Oxidative Stress; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction
chemical_list: D012333:RNA, Messenger; D011065:Poly(ADP-ribose) Polymerases; D048052:Mitogen-Activated Protein Kinase 3
keywords: Cell death; Hydrogen peroxide; Osteogenic differentiation; PARP1; Poly(ADP-ribosyl)ation; p38 MAP kinase