title: Increased replication of human cytomegalovirus in retinal pigment epithelial cells by valproic acid depends on histone deacetylase inhibition.
abstract: OBJECTIVE
  Human cytomegalovirus (HCMV) replication depends on different cellular pathways, including histone acetylation and extracellular-signal regulated kinases 1 and 2 (Erk 1/2). In the present study, the influence of therapeutic valproic acid (VPA) concentrations was investigated on HCMV replication in retinal pigment epithelial (RPE) cells.
  
  
  METHODS
  HCMV antigen expression and replication were detected by immunostaining, real-time RT-PCR, and determination of virus titers. Histone acetylation and Erk 1/2 phosphorylation were detected by Western blot.
  
  
  RESULTS
  Pretreatment with VPA < or =1 mM enhanced HCMV antigen expression and replication by up to ninefold. In addition to histone deacetylase (HDAC) inhibition, VPA stimulated Erk 1/2 phosphorylation in RPE cells. Investigation of six VPA derivatives revealed that S-2-pentyl-4-pentynoic acid was the only derivative that induced histone hyperacetylation, indicating HDAC inhibition, in the observed concentrations < or =1 mM and that increased HCMV antigen expression. Other derivatives did not enhance HCMV replication in the tested concentrations, although some were found to induce Erk 1/2 phosphorylation. The mitogen-activated protein kinase kinase (MEK) inhibitor PD98059 inhibited VPA-induced Erk 1/2 phosphorylation but did not affect VPA-induced increased HCMV replication. In addition, the structurally nonrelated HDACI trichostatin A enhanced HCMV replication but did not affect Erk 1/2 phosphorylation in RPE cells.
  
  
  CONCLUSIONS
  The data demonstrate that VPA stimulates HCMV replication by HDAC inhibition independent of Erk 1/2 phosphorylation in therapeutic concentrations in RPE cells. Therefore, patients at risk of HCMV retinitis who are treated with VPA or other HDAC inhibitors should be carefully monitored.
authors.affiliation: Institut für Medizinische Virologie, Klinikum der J. W. Goethe-Universität, Paul-Ehrlich-Strasse 40, 60596 Frankfurt am Main, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Michaelis
authors.forename: Tatyana
authors.initials: T
authors.lastname: Suhan
authors.forename: Alexander
authors.initials: A
authors.lastname: Reinisch
authors.forename: Agnes
authors.initials: A
authors.lastname: Reisenauer
authors.forename: Corinna
authors.initials: C
authors.lastname: Fleckenstein
authors.forename: Daniel
authors.initials: D
authors.lastname: Eikel
authors.forename: Hermann
authors.initials: H
authors.lastname: Gümbel
authors.forename: Hans Wilhelm
authors.initials: HW
authors.lastname: Doerr
authors.forename: Heinz
authors.initials: H
authors.lastname: Nau
authors.forename: Jindrich
authors.initials: J
authors.lastname: Cinatl
mesh_terms: D000107:Acetylation; D000956:Antigens, Viral / Q000235:genetics / Q000378:metabolism; D015153:Blotting, Western; D002478:Cells, Cultured; D003587:Cytomegalovirus / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D056572:Histone Deacetylase Inhibitors; D006657:Histones / Q000378:metabolism; D006801:Humans; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010766:Phosphorylation; D010857:Pigment Epithelium of Eye / Q000201:enzymology / Q000821:virology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014635:Valproic Acid / Q000494:pharmacology*; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D000956:Antigens, Viral; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D014635:Valproic Acid; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3