Concentration of arginine and optimal time of hypertonic saline in restoration of T-cell dysfunction

Background: Hypertonic saline (HS) restores prostaglandin E₂ (PGE₂)-induced T-cell suppression in the presence of 1100 μM arginine. However, under arginine-free culture conditions, HS dose not restore T-cell proliferation. Therefore, we wanted to determine if HS can restore PGE₂-induced T-cell suppression in the presence of 80 μM of arginine, the physiologically relevant arginine concentration. We also wanted to determine the concentration of arginine that induces HS restoration of PGE ₂-suppressed T-cell proliferation and whether HS restoration of T-cell dysfunction is dependent on the injection time of HS. Materials and Methods: Jurkat cells were cultured in media containing 0, 40, 80, 400, 800, or 1100 μM arginine. In both the PGE₂-stimulated and HS-treated group, we measured cell proliferation using MTT assay and arginase activity. We also measured cell proliferation relative to HS injection time. Results: In 80 μM arginine, HS did not restore Jurkat cell proliferation that had been suppressed by PGE₂. Increased concentrations of arginine in the media increased MTT cell proliferation. In 800 μM arginine media, HS restored PGE₂-suppressed Jurkat cell proliferation to normal. HS restored PGE₂-suppressed Jurkat cell proliferation when it was added at 2 h, similar to at same time and 1 h after PGE₂ stimulation. Conclusions: In order to restore PGE₂-suppressed Jurkat cell proliferation, HS requires at least 800 μM arginine. HS restored PGE₂-suppressed Jurkat cell proliferation even though HS was added at 2 h after PGE₂ stimulation.