Defective signal-transduction pathways in T-cells from autoimmune MRL-lpr/lpr mice are associated with increased polyamine concentrations

• Published in: Biochemical journal Vol. 311 ( Pt 1); no. 1; pp. 175 - 182
• Main Authors: Thomas, T J, Gunnia, U B, Seibold, J R, Thomas, T
• Format: Journal Article
• Language: English
• Published: England 01.10.1995
• Subjects: AIDS/HIV; Animals; Autoimmune Diseases - physiopathology; Blotting, Western; Calcium - metabolism; CD4-CD8 Ratio; Concanavalin A - pharmacology; Eflornithine - pharmacology; Female; Inositol Phosphates - metabolism; Lupus Erythematosus, Systemic - physiopathology; Mice; Mice, Inbred BALB C; Ornithine Decarboxylase - metabolism; Phosphorylation; Phosphotyrosine - metabolism; Polyamines - antagonists & inhibitors; Polyamines - metabolism; Signal Transduction; Spleen - cytology; T-Lymphocytes - drug effects; T-Lymphocytes - pathology; T-Lymphocytes - physiology
• ISSN: 0264-6021; 1470-8728
• DOI: 10.1042/bj3110175

We previously reported that difluoromethylornithine (DFMO), an inhibitor of polyamine biosynthesis, exerted significant beneficial effects on the lifespan and disease expression of MRL-lpr/lpr mice, which spontaneously develop a lupus-like syndrome. Polyamine levels in splenic T-cells of MRL-lpr/lpr mice were significantly higher than those of Balb/c mice. In the present investigation, we examined the role of endogenous polyamines in transmembrane Ca2+ influx, generation of InsP3 and tyrosine phosphorylation of the p56lck protein in concanavalin A-stimulated splenic T-cells. Cytosolic free calcium concentrations ([Ca2+]i) in concanavalin A-stimulated T-cells of MRL-lpr/lpr and Balb/c mice were 250 +/- 25 and 450 +/- 42 nM respectively. Treatment of MRL-lpr/lpr mice with DFMO increased [Ca2+]i to 360 +/- 30 nM (P < 0.05). InsP3 levels of concanavalin A-stimulated MRL-lpr/lpr splenic T-cells were only 20% higher than those of unstimulated controls, whereas those of Balb/c T-cells were 90% higher. DFMO treatment increased InsP3 levels in concanavalin A-treated MRL-lpr/lpr T-cells to 67%. Western-blot analysis showed a 7-fold higher level of p56lck phosphorylation of MRL-lpr/lpr splenic T-cells than that of Balb/c mice. DFMO treatment reduced tyrosine phosphorylation of p56lck of MRL-lpr/lpr mice significantly (P < 0.001). Two-colour flow-cytometric analysis revealed no significant difference in the CD4+/CD8+ ratio in splenic T-cells of MRL-lpr/lpr mice after DFMO treatment. Polyamine levels in splenocytes were significantly reduced by DFMO treatment. These data show that DFMO treatment could alter signal-transduction pathways of splenic T-cells of MRL-lpr/lpr mice. Increased levels of polyamines in T-cells of untreated lpr mice contribute to defective signal-transduction pathways and the pathogenesis of lupus-like symptoms.