oxidants and antioxidants in biology - Oxygen Club of California

The effects of tocopherols on the Ca 2+ -response under xanthine
oxidase-catalyzed ROS and thapsigargin-induced [Ca 2+ ] i -
oscillations in endothelial cells
BETTINA BUSCHLE*, HANS KONRAD BIESALSKI,
AND DONATUS NOHR
University of Hohenheim, Institute of Biological Chemistry & Nutrition,
Fruwirthstr. 12, D-70593 Stuttgart, Germany
The major area of interest concerning vitamin E lies essentially
in its antioxidative capacity. In our study we investigated xanthine
oxidase (XO)-catalyzed reactive oxygen species (ROS) on human
microvascular endothelial cells (HMEC-1) and the influence of α-,
β- or γ-tocopherol on XO-catalyzed ROS. In dependence of XO
concentration ROS generation caused varying increases in cytosolic
Ca 2+ ([Ca 2+ ] i ) levels. XO showed a dose dependent increase in
[Ca 2+ ] i . Dependent on the XO concentration tocopherol was able to
lower the oxidative stress induced increases in ([Ca 2+ ] i ).
On thapsigargin (TG) stimulated [Ca 2+ ] i -oscillations in HMEC-
1 ROS generation resulted in considerable variations. Preincubation
with physiological concentrations of any of the different tocopherols
had no influence on this stress response. However, the frequency
of the TG-induced oscillations was changed in both directions
in comparison to control cells due to the respective tocopherol
applied. The regulation of the frequency of ([Ca 2+ ] i ) oscillations
may provide cells with a specific mechanism to control signalling
and may have advantages in controlling cellular responses.
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