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Oxidant Injury in PC12 Cells—A Possible Model of Calcium “Dysregulation” in Aging: I. Selectivity of Protection Against Oxidative Stress
Author(s) -
Joseph J. A.,
Strain J. G.,
Jimenez N. D.,
Fisher D.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.69031252.x
Subject(s) - intracellular , oxidative stress , antagonist , chemistry , depolarization , nifedipine , biophysics , calcium , calcium in biology , trolox , channel blocker , pharmacology , endocrinology , medicine , biochemistry , receptor , biology , organic chemistry , antioxidant capacity
Previous research has suggested that the initial effects of cellular free radical neurotoxic insult involve large increases in intracellular Ca 2+ . However, the exact role of oxidative stress on the various parameters involved in these increases has not been specified. The present experiments were performed to examine these parameters in PC12 cells exposed to 5, 25, or 300 µ M H 2 O 2 for 30 min in growth medium alone or containing either nifedipine (L‐type Ca 2+ antagonist), conotoxin (N‐type antagonist), Trolox (vitamin E analogue), or α‐phenyl‐ n ‐ tert ‐butylnitrone (nitrone trapping agent; PBN). The concentrations of H 2 O 2 were chosen by examining the degree of cell killing induced by exposure to graded concentrations of H 2 O 2 . The 5 and 25 µ M concentrations of H 2 O 2 produced no significant cell killing at either 30 min or 24 h after treatment, whereas the 300 µ M concentration produced a moderate degree of cell killing that did not increase between the two times. Fluorescent imaging was used to visualize intracellular Ca 2+ changes in fura‐2‐loaded cells. Baseline (pre‐30 m M KCI) Ca 2+ levels were increased significantly by H 2 O 2 treatment (e.g., 300 µ M , 200%), but the rise in the level of free intracellular Ca 2+ after KCI stimulation (i.e., peak) was decreased (e.g., 300 µ M , 50%) and the cell's ability to sequester or extrude the excess Ca 2+ (i.e., Ca 2+ recovery time) after depolarization was decreased significantly. All compounds prevented baseline Ca 2+ increases and, with the exception of conotoxin, antagonized the peak decreases in Ca 2+ . It is interesting that after 300 µ M H 2 O 2 exposure, only Trolox was partially effective in preventing these deficits in recovery. Conotoxin increased the decrement recovery in the absence of H 2 O 2 . However, in cells exposed to 5 or 25 µ M H 2 O 2 , conotoxin as well as the other agents were effective in preventing the deficits in recovery.