title: Defective signal-transduction pathways in T-cells from autoimmune MRL-lpr/lpr mice are associated with increased polyamine concentrations.
abstract: 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.
authors.affiliation: Clinical Research Center, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Thomas
authors.forename: U B
authors.initials: UB
authors.lastname: Gunnia
authors.forename: J R
authors.initials: JR
authors.lastname: Seibold
authors.forename: T
authors.initials: T
authors.lastname: Thomas
mesh_terms: D000818:Animals; D001327:Autoimmune Diseases / Q000503:physiopathology*; D015153:Blotting, Western; D016516:CD4-CD8 Ratio; D002118:Calcium / Q000378:metabolism; D003208:Concanavalin A / Q000494:pharmacology; D000518:Eflornithine / Q000494:pharmacology; D005260:Female; D007295:Inositol Phosphates / Q000378:metabolism; D008180:Lupus Erythematosus, Systemic / Q000503:physiopathology; D051379:Mice; D008807:Mice, Inbred BALB C; D009955:Ornithine Decarboxylase / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011073:Polyamines / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000187:drug effects / Q000473:pathology / Q000502:physiology*
chemical_list: D007295:Inositol Phosphates; D011073:Polyamines; D003208:Concanavalin A; D019000:Phosphotyrosine; D009955:Ornithine Decarboxylase; D002118:Calcium; D000518:Eflornithine