Ps. Herson et al., Hydrogen peroxide induces intracellular calcium overload by activation of a non-selective cation channel in an insulin-secreting cell line, J BIOL CHEM, 274(2), 1999, pp. 833-841
Fura-2 fluorescence was used to investigate the effects of H2O2 on [Ca2+](i
) in the insulin-secreting cell line CRI-G1. H2O2 (1-10 mM) caused a biphas
ic increase in free [Ca2+](i), an initial rise observed within 3 min and a
second, much larger rise following a 30-min exposure. Extracellular calcium
removal blocked the late, but not the initial, rise in [Ca2+](i), Thapsiga
rgin did not affect either response to H2O2, but activated capacitive calci
um entry, an action abolished by 10 mu M La3+, Simultaneous recordings of m
embrane potential and [Ca2+](i) demonstrated the same biphasic [Ca2+](i) re
sponse to H2O2 and showed that the late increase in [Ca2+](i) coincided tem
porally with cell membrane potential collapse. Buffering Ca-i(2+) to low na
nomolar levels prevented both phases of increased [Ca2+](i) and the H2O2-in
duced depolarization. The H2O2-induced late rise in [Ca2+](i) was prevented
by extracellular application of 100 mu M La3+. La3+ (100 mu M) inhibited t
he H2O2-induced cation current and NAD-activated cation (NSNAD) channel act
ivity in these cells. H2O2 increased the NAD/NADH ratio in intact CRI-G1 ce
lls, consistent with increased cellular [NAD], These data suggest that H2O2
increases [NAD], which, coupled with increased [Ca2+](i), activates NSNAD,
channels, causing unregulated Ca2+ entry and consequent cell death.