DEFECTIVE SIGNAL-TRANSDUCTION PATHWAYS IN T-CELLS FROM AUTOIMMUNE MRL-LPR LPR MICE ARE ASSOCIATED WITH INCREASED POLYAMINE CONCENTRATIONS/

We previously reported that difluoromethylornithine (DFMO), an inhibit or of polyamine biosynthesis, exerted significant beneficial effects o n the lifespan and disease expression of MRL-lpr/lpr mice, which spont aneously develop a lupus-like syndrome. Polyamine levels in splenic T- cells of MRL-lpl/lpr mice were significantly higher than those of Balb /c mice. In the present investigation, we examined the role of endogen ous polyamines in transmembrane Ca2+ influx, generation of InsP(3) and tyrosine phosphorylation of the p56(lck) protein in concanavalin A-st imulated splenic T-cells. Cytosolic free calcium concentrations ([Ca2](i)) in concanavalin A-stimulated T-cells of MRL-lpr/lpr and Balb/c m ice were 250+/-25 and 450+/-42 nM respectively. Treatment of MRL-lpr/l pr mice with DFMO increased [Ca2+](i) to 360+/-30 nM (P < 0.05). InsP( 3) levels of concanavalin A-stimulated MRL-lpr/lpr splenic T-cells wer e only 20% higher than those of unstimulated controls, whereas those o f Balb/c T-cells were 90% higher. DFMO treatment increased InsP(3) lev els in concanavalin A-treated MRL-lpr/lpr T-cells to 67%. Western-blot analysis showed a 7-fold higher level of p56(lck) phosphorylation of MRL-lpr/lpr. splenic T-cells than that of Balb/c mice. DFMO treatment reduced tyrosine phosphorylation of p56(lck) of MRL-lpr/lpr mice signi ficantly (P < 0.001). Two-colour flow-cytometric analysis revealed no significant difference in the CD4(+)/CD8(+) ratio in splenic T-cells o f MRL-lpr/lpr mice after DFMO treatment. Polyamine levels in splenocyt es were significantly reduced by DFMO treatment. These data show that DFMO treatment could alter signal-transduction pathways of splenic T-c ells of MRL-lpr/lpr mice. Increased levels of polyamines in T-cells of untreated lpr mice contribute to defective signal-transduction pathwa ys and the pathogenesis of lupus-like symptoms.