CALCIUM SIGNALING RESTITUTION PREVENTS T-CELL PROLIFERATIVE SUPPRESSION BY PROSTAGLANDIN E2

Abstract

Previous studies from our laboratory have implicated a role for Ca2+ in prostaglandin E2 (PGE2)-induced suppression in T-cell proliferation during sepsis. The present study further elucidated the mechanism of PGE2-induced suppression in T-cell proliferation. We assessed whether prevention of the suppression in Ca2+ mobilization in PGE2-treated T-cells would restore proliferation. Rat splenic T-cell Ca2+ mobilization and proliferation were measured after stimulation of cells with concanavalin A (Con A) employing Fura-2 spectroscopy and cellular [3H]thymidine uptake techniques, respectively. PGE2 and other agents that directly up-regulate the PGE2-mediated cell signaling events (e.g., cholera toxin and forskolin), substantially suppressed both Con A-induced proliferation (p < .01) and Ca2+ mobilization in T-cells (p < .01). When stimulated with Con A plus ionomycin, [Ca2+]i in PGE2 treated T-cells (395 +/- 21, nM) was not significantly different (p > .05) from that observed in Con A-stimulated T-cells without the PGE2 exposure (351 +/- 8.6). The stimulation of PGE2-treated T-cells with ionomycin and Con A also significantly (p < .025), if not completely, prevented the PGE2-induced suppression in T-cell proliferation. These results suggest that the cross-talk between the TCR- and PGE2-mediated signaling in T-cells negatively modulates the TCR signals at the Ca2+ mobilization step and/or earlier to it.