title: The combined effects of irradiation and herpes simplex virus type 1 infection on an immortal gingival cell line.
abstract: BACKGROUND
  Oral mucosa is frequently exposed to Herpes simplex virus type 1 (HSV-1) infection and irradiation due to dental radiography. During radiotherapy for oral cancer, the surrounding clinically normal tissues are also irradiated. This prompted us to study the effects of HSV-1 infection and irradiation on viability and apoptosis of oral epithelial cells.
  
  
  METHODS
  Immortal gingival keratinocyte (HMK) cells were infected with HSV-1 at a low multiplicity of infection (MOI) and irradiated with 2 Gy 24 hours post infection. The cells were then harvested at 24, 72 and 144 hours post irradiation for viability assays and qRT-PCR analyses for the apoptosis-related genes caspases 3, 8, and 9, bcl-2, NFκB1, and viral gene VP16. Mann-Whitney U-test was used for statistical calculations.
  
  
  RESULTS
  Irradiation improved the cell viability at 144 hours post irradiation (P = 0.05), which was further improved by HSV-1 infection at MOI of 0.00001 (P = 0.05). Simultaneously, the combined effects of infection at MOI of 0.0001 and irradiation resulted in upregulation in NFκB1 (P = 0.05). The combined effects of irradiation and HSV infection also significantly downregulated the expression of caspases 3, 8, and 9 at 144 hours (P = 0.05) whereas caspase 3 and 8 significantly upregulated in non-irradiated, HSV-infected cells as compared to uninfected controls (P = 0.05). Infection with 0.0001 MOI downregulated bcl-2 in non-irradiated cells but was upregulated by 27% after irradiation when compared to non-irradiated infected cells (P = 0.05). Irradiation had no effect on HSV-1 shedding or HSV gene expression at 144 hours.
  
  
  CONCLUSIONS
  HSV-1 infection may improve the viability of immortal cells after irradiation. The effect might be related to inhibition of apoptosis.
authors.affiliation: Institute of Dentistry, Department of Oral Pathology, University of Turku, Lemminkäisenkatu 2, 20520 Turku, Finland. asturu@utu.fi.
authors.forename: Aaro
authors.initials: A
authors.lastname: Turunen
authors.forename: Veijo
authors.initials: V
authors.lastname: Hukkanen
authors.forename: Michaela
authors.initials: M
authors.lastname: Nygårdas
authors.forename: Jarmo
authors.initials: J
authors.lastname: Kulmala
authors.forename: Stina
authors.initials: S
authors.lastname: Syrjänen
mesh_terms: D017209:Apoptosis / Q000235:genetics; D020169:Caspases / Q000235:genetics; D002461:Cell Line, Transformed; D002470:Cell Survival / Q000528:radiation effects; D005881:Gingiva / Q000166:cytology / Q000528:radiation effects* / Q000821:virology*; D006561:Herpes Simplex / Q000821:virology; D017405:Herpes Simplex Virus Protein Vmw65 / Q000235:genetics; D018259:Herpesvirus 1, Human / Q000502:physiology*; D006801:Humans; D015603:Keratinocytes / Q000528:radiation effects / Q000821:virology; D009061:Mouth Mucosa / Q000166:cytology / Q000528:radiation effects* / Q000821:virology*; D009062:Mouth Neoplasms / Q000532:radiotherapy; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics; D011861:Radiography, Dental / Q000009:adverse effects; D011878:Radiotherapy / Q000009:adverse effects; D014779:Virus Replication; D017201:Virus Shedding
chemical_list: D017405:Herpes Simplex Virus Protein Vmw65; D019253:Proto-Oncogene Proteins c-bcl-2; D020169:Caspases