title: The induction and suppression of the apoptotic response of HSV-1 in human corneal epithelial cells.
abstract: OBJECTIVE
  HSV-1 has been shown to block apoptosis in some cell lines when the cells are exposed to exogenous agents (e.g., sorbitol). The purpose of this study was to determine whether HSV-1 infection of human corneal epithelial (HCE) cells alone induces an early proapoptotic response and whether this response is subsequently downregulated during the infection.
  
  
  METHODS
  HCE cells were infected with HSV-1 or subjected to osmotic shock (sorbitol). Fluorescent staining for annexin V binding, mitochondrial membrane potential, and DNA condensation and assays for caspase 8, 9, and 3 activity and cytokeratin 18 cleavage were performed, to assess the apoptotic pathway.
  
  
  RESULTS
  HSV-1 infection of HCE cells induced a rapid proapoptotic response, characterized by translocation of phosphatidylserine to the external membrane, activation of caspases 8 and 3 within 2 hours, and cleavage of cytokeratin 18. However, the induced response was downregulated during the infection, and later stages of the apoptotic responses (e.g., DNA condensation) were not produced. Sorbitol treatment led to terminal apoptosis by 12 hours, as indicated by DNA condensation of treated cells and reduction in the number of viable cells.
  
  
  CONCLUSIONS
  HSV-1 can induce and subsequently suppress the apoptotic pathway in HCE. Suppression of apoptosis occurred only during HSV-1 infection and not after treatment with sorbitol, suggesting that the suppression of apoptosis may be a mechanism of viral survival.
authors.affiliation: Vision Cooperative Research Centre, Sydney, Australia.
authors.forename: David H
authors.initials: DH
authors.lastname: Miles
authors.forename: Archana
authors.initials: A
authors.lastname: Thakur
authors.forename: Nerida
authors.initials: N
authors.lastname: Cole
authors.forename: Mark D P
authors.initials: MD
authors.lastname: Willcox
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D015536:Down-Regulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019573:Epithelium, Corneal / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000821:virology*; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D053538:Keratin-18 / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial; D008856:Microscopy, Fluorescence; D009997:Osmotic Pressure; D010718:Phosphatidylserines / Q000378:metabolism; D021381:Protein Transport; D013012:Sorbitol / Q000494:pharmacology
chemical_list: D017304:Annexin A5; D004791:Enzyme Inhibitors; D053538:Keratin-18; D010718:Phosphatidylserines; D013012:Sorbitol; D004247:DNA; D053148:Caspase 3; D053181:Caspase 8