title: Enhancement of catalase activity by repetitive low-grade H2O2 exposures protects fibroblasts from subsequent stress-induced apoptosis.
abstract: Exposure of Chinese hamster V79 fibroblasts to mild and repetitive H2O2 doses in culture for 15 weeks produced no change in lipid peroxidation status, GSH/GSSG ratio and glutathione peroxidase activity of these cells (VST cells). In contrast, in VST cells catalase levels underwent a prominent increase which could be significantly inhibited and brought down to control levels after treatment with the catalase inhibitor 3-aminotriazole (3-AT). When control (VC) cells were exposed to UV radiation (UVC 5 J/m2) or H2O2 (7.5mM, 15 min), intracellular reactive oxygen species (ROS) levels rose prominently with significant activation of caspase-3. Marked nuclear fragmentation and lower cell viability were also noted in these cells. In contrast, VST cells demonstrated a significantly lower ROS level, an absence of nuclear fragmentation and an unchanged caspase-3 activity after exposure to UVC or H2O2. Cell viability was also significantly better preserved in VST cells than VC cells after UV or H2O2 exposures. Following 3-AT treatment of VST cells, UVC radiation or H2O2 brought about significantly higher elevations in intracellular ROS, increases in caspase-3 activity, significantly lowered cell viability and marked nuclear fragmentation, indicating the involvement of high catalase levels in the cytoprotective effects of repetitive stress. Therefore, upregulation of the antioxidant defense after repetitive oxidative stress imparted a superior ability to cope with subsequent acute stress and escape apoptotic death and loss of viability.
authors.affiliation: Crystallography & Molecular Biology Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata-700064, India.
authors.forename: Prosenjit
authors.initials: P
authors.lastname: Sen
authors.forename: Sebanti
authors.initials: S
authors.lastname: Mukherjee
authors.forename: Gayaram
authors.initials: G
authors.lastname: Bhaumik
authors.forename: Pradeep
authors.initials: P
authors.lastname: Das
authors.forename: Sandipan
authors.initials: S
authors.lastname: Ganguly
authors.forename: Nandini
authors.initials: N
authors.lastname: Choudhury
authors.forename: Sanghamitra
authors.initials: S
authors.lastname: Raha
mesh_terms: D000640:Amitrole / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002374:Catalase / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D005978:Glutathione / Q000378:metabolism; D019803:Glutathione Disulfide / Q000378:metabolism; D005982:Glutathione Transferase / Q000187:drug effects / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D006861:Hydrogen Peroxide; D002374:Catalase; D005982:Glutathione Transferase; D005978:Glutathione; D019803:Glutathione Disulfide; D000640:Amitrole