title: Activation of the MAPK/Akt/Nrf2-Egr1/HO-1-GCLc axis protects MG-63 osteosarcoma cells against 15d-PGJ2-mediated cell death.
abstract: Despite considerable efforts to improve treatment modalities for osteosarcoma (OS), patient survival remains poor mainly due to pro-survival pathways in OS cells. Among others, prostaglandins (PGs) are the potent regulators of bone homoeostasis and OS pathophysiology. Therefore, the present study aimed to elucidate the impact of 15-deoxy-Δ(12,14)-PGJ2 (15d-PGJ2, a stable PGD2 degradation product) on cell death/cell survival pathways in p53-deficient MG-63 OS cells. Our findings show that 15d-PGJ2 induces generation of reactive oxygen species that promote p38 MAPK activation and subsequent Akt phosphorylation. This pathway induced nuclear expression of Nrf2 and Egr1, and increased transcription of haem oxygenase-1 (HO-1) and the catalytic subunit of glutamate cysteine ligase (GCLc), catalysing the first step in GSH synthesis. Silencing of Nrf2, Egr1 and HO-1 significantly elevated 15d-PGJ2-mediated reduction of cellular metabolic activity. Activation of cell survival genes including HO-1 and GCLc inhibited 15d-PGJ2-induced cleavage of pro-caspase-3 and PARP. Annexin V/propidium iodide staining showed an increase in early/late apoptotic cells in response to 15d-PGJ2. The observed 15d-PGJ2-mediated signalling events are independent of PGD2 receptors (DP1 and DP2) and PPARγ. In addition, the electrophilic carbon atom C9 is a prerequisite for the observed activity of 15d-PGJ2. The present data show that the intracellular redox imbalance acted as a node and triggered both death and survival pathways in response to 15d-PGJ2. Pharmacological or genetic interference of the pro-survival pathway, the p38 MAPK/Akt/Nrf2-Egr1/HO-1-GCLc axis, sensitizes MG-63 cells towards 15d-PGJ2-mediated apoptosis.
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Chintan N
authors.initials: CN
authors.lastname: Koyani
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria; Department of Pediatrics and Adolescence Medicine, Research Unit of Osteological Research and Analytical Mass Spectrometry, Medical University of Graz, Graz, Austria.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Kitz
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Christine
authors.initials: C
authors.lastname: Rossmann
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Eva
authors.initials: E
authors.lastname: Bernhart
authors.affiliation: Department of Pediatrics and Adolescence Medicine, Research Unit of Osteological Research and Analytical Mass Spectrometry, Medical University of Graz, Graz, Austria.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Huber
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Christopher
authors.initials: C
authors.lastname: Trummer
authors.affiliation: Department of Pediatrics and Adolescence Medicine, Research Unit of Osteological Research and Analytical Mass Spectrometry, Medical University of Graz, Graz, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Windischhofer
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sattler
authors.affiliation: Institute of Molecular Biology and Biochemistry, Medical University of Graz, Graz, Austria. Electronic address: ernst.malle@medunigraz.at.
authors.forename: Ernst
authors.initials: E
authors.lastname: Malle
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D051766:Early Growth Response Protein 1 / Q000235:genetics / Q000378:metabolism*; D020868:Gene Silencing; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism*; D051547:Heme Oxygenase-1 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000378:metabolism*; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D012516:Osteosarcoma / Q000378:metabolism / Q000473:pathology*; D010084:Oxidation-Reduction; D010766:Phosphorylation; D015230:Prostaglandin D2 / Q000031:analogs & derivatives* / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C477819:15-deoxyprostaglandin J2; C497325:EGR1 protein, human; D051766:Early Growth Response Protein 1; D051267:NF-E2-Related Factor 2; C495635:NFE2L2 protein, human; D017382:Reactive Oxygen Species; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; D051057:Proto-Oncogene Proteins c-akt; D020928:Mitogen-Activated Protein Kinases; D005721:Glutamate-Cysteine Ligase; D015230:Prostaglandin D2
keywords: 15d-PGJ(2); Chemotherapy; PI3K/Akt axis; Peroxisome proliferator-activated-receptor γ; Pro-survival signalling; ROS; Tumour protein p53