INTERLEUKIN-10 EXPRESSION IS INDUCED BY INCREASE OF INTRACELLULAR CALCIUM LEVELS IN THE MONOCYTIC CELL-LINE U937

The regulation of interleukin-10 (IL-10) expression after treatment wi th a high, exponential, electric pulse was investigated in the monocyt ic cell line U937. Recently, we showed IL-IO protein production in the monocytic cell lines U937 and THP-I after exposure to a single, high exponential electric pulse [Lehmann MH, Hoffken It, Berg H (1996) Bioe lectrochem. Bioenerg. 41: 227-229]. In the present study, the specific ity of this process was proven by semiquantitative reverse-transcripta se polymerase chain reaction. It was found that the presence of calciu m in the culture medium during the pulse is essential for IL-IO protei n production. Only a small amount of IL-10 protein was produced in cal cium free medium. The calcium specific chelator EGTA prevented IL-10 p rotein production induced by the electric pulse in a dose-dependent ma nner. Additionally, IL-10 mRNA transcription could be induced in U937 cells without pulse application by means of the calcium ionophore iono mycin. No IL-10 protein could be detected by ELISA. However, down-regu lation of TNF-alpha mRNA levels after ionomycin stimulation provided a n indirect proof that IL-10 protein production occurred.