Increased replication of human cytomegalovirus in retinal pigment epithelial cells by valproic acid depends on histone deacetylase inhibition

Invest Ophthalmol Vis Sci. 2005 Sep;46(9):3451-7. doi: 10.1167/iovs.05-0369.

Abstract

Purpose: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylation
  • Antigens, Viral / genetics
  • Antigens, Viral / metabolism
  • Blotting, Western
  • Cells, Cultured
  • Cytomegalovirus / physiology*
  • Enzyme Inhibitors / pharmacology*
  • Histone Deacetylase Inhibitors*
  • Histones / metabolism
  • Humans
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Phosphorylation
  • Pigment Epithelium of Eye / enzymology
  • Pigment Epithelium of Eye / virology*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Valproic Acid / pharmacology*
  • Virus Replication / drug effects*

Substances

  • Antigens, Viral
  • Enzyme Inhibitors
  • Histone Deacetylase Inhibitors
  • Histones
  • Valproic Acid
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3