Conference of DAAD-alumni. Bonn (2002)

INFLUENCE OF THE METABOLISM ON THE SUSCEPTIBILITY OF INSULIN-PRODUCING CELLS TO CYTOKINE-INDUCED APOPTOSIS
V.A. Goranov and Y.A. Haranava

During treatment of Rinm5f with IL-1 alone (or with TNF in concentrations between 0.1 – 10.0 pg/ml) we did not observe an increase of destructive processes in the cells. The amount of dead cells did not increase more than 15% during 20 h incubation. Treatment with glucose alone (24-48 h in concentrations up to 30 mM) did not cause an increase in the amount of apoptotic or necrotic cells.
The most reliable changes of insulinoma cell viability compared to the controls were registered when both cytokines (TNF and IL-1b) were given in identical concentrations. At concentrations between 5 – 10 pg/ml apoptosis was induced starting at 2 h. These concentrations of cytokines are apparently too high to observe the influence of glucose on the induction of apoptosis.
Cells treated with both cytokines at concentrations between 0.5 – 1.0 pg /ml demonstrated a specific dynamic behavior of apoptosis induction. During the first 1–2 h an increase of dying cells was not observed. This was registered especially in case of very low cytokine concentration (< 0.5 pg/ml). After 2 h the amount of apoptotic cells increased continuously, also depending on the concentration of the cytokines.
By pretreatment with glucose an increased rate of accumulation of apoptotic cells was observed. This effect was found to depend both on the concentration of glucose during pretreatment (between 18 and 30 µM) and on the concentration of the cytokines. The most dramatic increase of apoptotic cells was observed at 30 µM glucose.
The first observations of caspase-3 activation in cytokine-treated cells showed that the frequency of caspase-3 positive cells was not increased by a two hour treatment with cytokines with concentrations between 10 U and 30 U. However, an increase in the frequency of caspase-3 positive cells was found in those cells pretreated with glucose (18 µM). It can, therefore, be assumed that the induction of apoptosis in insulinoma cells is associated with caspase-3-dependent pathways.