title: Increased stress-induced generation of reactive oxygen species and apoptosis in human keratoconus fibroblasts.
abstract: OBJECTIVE
  To determine whether keratoconus (KC) corneal fibroblast cultures have increased reactive oxygen species (ROS) production and are more susceptible to stress-related challenges.
  
  
  METHODS
  Normal (n = 9) and KC (n = 10) stromal fibroblast cultures were incubated in either neutral- or low-pH conditions, with or without hydrogen peroxide. Catalase activities were measured with a fluorescent substrate assay. Superoxide and ROS/reactive nitrogen species (RNS) productions were determined with an amine-reactive green-dye assay and 2',7'-dichlorodihydrofluorescein diacetate (H2DCFDA) dye assay, respectively. Cell viability was analyzed by a dye-exclusion assay. Caspase 3 activity was measured by a fluorochrome inhibitor of caspase (FLICA) assay. A cationic (green) dye was used to measure the mitochondrial membrane potential (delta psi m).
  
  
  RESULTS
  KC fibroblasts had increased superoxide and ROS/RNS production (6.2-fold, P < 0.001 and 1.8-fold, P < 0.001, respectively) and catalase activity (P < 0.01) with higher concentrations of H2O2 compared with normal cultures (P = 0.16). After a low-pH stress challenge, KC fibroblasts maintained higher ROS/RNS levels (3.3-fold, P < 0.02), showed higher caspase-3 activity (7.5-fold, P < 0.02) and decreased delta psi m (2.6-fold, P < 0.04), and had decreased cell viability (37%, P < 0.005 vs. 20%, P < 0.27) compared with normal fibroblasts.
  
  
  CONCLUSIONS
  Under identical conditions, KC fibroblasts had increased basal generation of ROS/RNS and were more susceptible to stressful challenges (low-pH and/or H2O2 conditions) than were normal fibroblasts. In addition, the stressed KC fibroblasts possessed characteristics similar to those found in the intact KC corneas (increased catalase activity, ROS production, and apoptosis). These properties may play a role in the pathogenesis of KC.
authors.affiliation: Department of Ophthalmology, University of California Irvine Medical Center, Irvine, California, USA.
authors.forename: Marilyn
authors.initials: M
authors.lastname: Chwa
authors.forename: Shari R
authors.initials: SR
authors.lastname: Atilano
authors.forename: Vinitha
authors.initials: V
authors.lastname: Reddy
authors.forename: Nicole
authors.initials: N
authors.lastname: Jordan
authors.forename: Dae W
authors.initials: DW
authors.lastname: Kim
authors.forename: M Cristina
authors.initials: MC
authors.lastname: Kenney
mesh_terms: D000328:Adult; D017209:Apoptosis; D002374:Catalase / Q000378:metabolism; D018929:Cell Culture Techniques; D002470:Cell Survival; D003315:Cornea / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D006861:Hydrogen Peroxide / Q000633:toxicity; D006863:Hydrogen-Ion Concentration; D007640:Keratoconus / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008875:Middle Aged; D008928:Mitochondria / Q000378:metabolism; D018384:Oxidative Stress; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism
chemical_list: D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species; D013481:Superoxides; D006861:Hydrogen Peroxide; D002374:Catalase