title: Role of Bax in death of uninfected retinal cells during murine cytomegalovirus retinitis.
abstract: OBJECTIVE
  Extensive death of uninfected bystander neuronal cells is an important component of the pathogenesis of cytomegalovirus retinitis. Our previous results have shown that caspase 3-dependent and -independent pathways are involved in death of uninfected bystander cells during murine cytomegalovirus (MCMV) retinitis and also that Bcl-2, an important inhibitor of apoptosis via the Bax-mediated mitochondrial pathway, is downregulated during this process. The purpose of this study was to determine whether Bax-mediated mitochondrial damage has a significant role in the death of uninfected retinal cells.
  
  
  METHODS
  BALB/c mice, Bax(-/-) mice, or Bax(+/+) mice were immunosuppressed with methylprednisolone and infected with 5 × 10(3) plaque-forming units (PFU) of the K181 strain of MCMV via the supraciliary route. Injected eyes were analyzed by plaque assay, electron microscopy, hematoxylin and eosin (H&E) staining, TUNEL assay, Western blot (for caspase 3, caspase 12, Bax, receptor interacting protein-1 [RIP1] and receptor interacting protein-3 [RIP3]), as well as immunohistochemical staining for MCMV early antigen and cleaved caspase 3.
  
  
  RESULTS
  Significantly more Bax was detected in mitochondrial fractions of MCMV-infected eyes than in mitochondrial fractions of mock-infected control eyes. Furthermore, the level of cleaved caspase 3 was significantly lower in MCMV-infected Bax(-/-) eyes than in MCMV-infected Bax(+/+) eyes. However, more caspase 3-independent cell death of uninfected bystander retinal cells and more cleaved RIP1 were observed in Bax(-/-) than in Bax(+/+) eyes.
  
  
  CONCLUSIONS
  During MCMV retinitis, Bax is activated and has an important role in death of uninfected bystander retinal cells by caspase 3-dependent apoptosis. Although the exact mechanism remains to be deciphered, active Bax might also prevent death of some types of uninfected retinal cells by a caspase 3-independent pathway.
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Juan
authors.initials: J
authors.lastname: Mo
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Brendan
authors.initials: B
authors.lastname: Marshall
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Jason
authors.initials: J
authors.lastname: Covar
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Nancy Y
authors.initials: NY
authors.lastname: Zhang
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Sylvia B
authors.initials: SB
authors.lastname: Smith
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States The James and Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Sally S
authors.initials: SS
authors.lastname: Atherton
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States The James and Jean Culver Vision Discovery Institute, Medical College of Georgia, Georgia Regents University, Augusta, Georgia, United States.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhang
mesh_terms: D000818:Animals; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D016923:Cell Death; D017726:Cytomegalovirus Retinitis / Q000378:metabolism / Q000473:pathology* / Q000821:virology; D004195:Disease Models, Animal; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D051379:Mice; D008807:Mice, Inbred BALB C; D008854:Microscopy, Electron; D012165:Retinal Ganglion Cells / Q000378:metabolism / Q000648:ultrastructure* / Q000821:virology; D051028:bcl-2-Associated X Protein / Q000502:physiology*
chemical_list: C494827:Bax protein, mouse; D051028:bcl-2-Associated X Protein; D053148:Caspase 3
keywords: Bax; apoptosis; murine cytomegalovirus; retinitis