HYPERTONIC SALINE ACTIVATES PROTEIN-TYROSINE KINASES AND MITOGEN-ACTIVATED PROTEIN-KINASE P38 IN T-CELLS

Objectives: In previous in vitro studies, we have found that hypertoni c saline (HTS) can augment T-cell proliferation and restore the functi on of suppressed T-cells. Our animal models have shown that HTS resusc itation reverses immunosuppression after hemorrhage and reduces mortal ity from sepsis, In the present study, we investigated if and how HTS may influence T-cell signaling and function on a subcellular level. De sign: Human peripheral blood mononuclear cells (PBMC) were used to det ermine the effect of HTS on T-cell interleukin 2 (IL-2) production and proliferation, Human Jurkat T-cells were used to study the effects of HTS on T-cell signal transduction, IL-2 mRNA transcription, and IL-2 expression. Material and Methods: The effect of HTS on T-cell prolifer ation and IL-2 production was measured with PBMC and Jurkat T-cells, I L-2 mRNA transcription in HIS-treated Jurkat cells was measured by rev erse transcriptase polymerase chain reaction, HTS-induced protein tyro sine phosphorylation in Jurkat T-cells was determined by immunoblottin g with anti-phosphotyrosine antibodies, Expression in Jurkat cells of the mitogen-activated protein kinase p38 (MAPK p38), a signal transduc tion protein that is activated by osmotic stress, was determined by im munoblotting with anti-MAPK p38 antibodies, HTS-induced MAPK p38 activ ation in Jurkat cells was measured with an immune-complex kinase assay using ATF-2 as a substrate. Measurements and Main Results: Proliferat ion of activated human PBMC increased significantly upon addition of H TS to the culture medium, This effect of HTS was paralleled by enhance d IL-2 production of activated PBMC and Jurkat cells and IL-2 mRNA tra nscription of Jurkat cells, HTS exposure of Jurkat cells caused tyrosi ne phosphorylation of a number of cellular proteins, We found that Jur kat T-cells expressed MAPK p38 and that it was activated in the presen ce of HTS, All these effects of HTS on T-cell signaling and function w ere observed at NaCl concentrations that were within physiologically r elevant levels (20-100 mmol/L hypertonicity). Conclusions: In T-cells, HTS triggers a signaling pathway that includes increased tyrosine pho sphorylation of several cellular proteins and activation of MAPK p38, HTS alone does not result in IL-2 mRNA transcription, IL-2 expression, or T-cell proliferation, However, in combination with other stimuli, HTS augments T-cell IL-2 expression and proliferation, We speculate th at HTS could ''resuscitate'' suppressed T-cells in trauma patients by circumvention of, or substituting for, blocked signaling pathways.