AB0026 Pathophysiological hypoxia affects both redox state and il-2 signaling of human cd4+ t cells and concomitantly impairs survival and proliferation. (23rd January 2014)

• Record Type: Journal Article
• Authors: Gaber, T.; Tran, C. L.; Schellmann, S.; Hahne, M.; Strehl, C.; Jakstadt, M.; Burmester, G.-R.; Buttgereit, F.
• Is Part Of: Annals of the rheumatic diseases. Volume 72:Supplement 3(2013)
• Page Start: A793
• Page End: A793
• Publication Date: 2014-01-23
• Subjects: Rheumatism -- Periodicals; 616.723005
• DOI: 10.1136/annrheumdis-2013-eular.2349
• Languages: English
• ISSNs: 0003-4967

Abstract

Abstract : Background: Rheumatoid arthritis (RA) is a chronic inflammatory disease of diarthrodial joints, characterized by the infiltration of immune cells, alterations of cellular redox state and pathophysiological local tissue hypoxia (<1% O2 ). Objectives: We investigated the impact of different hypoxia levels on survival, proliferation, cytokine secretion, intracellular energy and redox state of quiescent and mitogen stimulated human CD4+ T cells. Methods: Isolated human CD4+ T cells were exposed to normoxia (18% O2 ), physiological hypoxia (5% O2 ) and pathophysiological hypoxia (<1% O2 ), respectively and cultured with or without PHA stimulation at defined periods of time (6h, 24, 48, and 72h). Cells were then analyzed by measuring IL-2R signaling (CD25 expression, phosphoSTAT5a), proliferation and the production of intracellular ROS (iROS) using flow cytometry. In addition, caspase-3/7 activity and ATP levels were determined by luminometric assays. Cellular oxidative damage and cytokine release were analyzed by ELISA based quantification of protein carbonylation (ROS damage) and IL2 production. Results: We found pathophysiological hypoxia (<1% O2 ) to decrease significantly CD4+ T cell survival after mitogenic stimulation. This effect was neither due to induced caspase-3/7-mediated apoptosis nor to increased ATP consumption or increased ATP depletion. However, the ability of stimulated T cells to proliferate was both delayed and suppressed under these hypoxic conditions, despite increased expression of CD25 and unchanged secreted IL-2 amounts. Hypoxia was also found to modify iROS levels in stimulated T cells over time, but without producing measurable effects on oxidative protein damage as compared to normoxia. In contrast, both normoxia (18% O2 ) and physiological hypoxia (5% O2 ) did not decrease CD4+ T cell survival and proliferation after mitogenic stimulation. Conclusions: We conclude that pathophysiological hypoxia (<1% O2 ) but not physiological hypoxia (5% O2 ) affects T cell proliferation and viability via disturbed IL-2R signaling downstream of STAT5a phosphorylation. However, the decreased T cell proliferation was not linked to an impaired cellular energy homeostasis. We suggest iROS links early events in T cell stimulation to the inhibition of the lymphoproliferative response under hypoxic conditions. The level of iROS may therefore act as a mediator of immune functions leading to down-regulation of long-term T cell activity in inflamed tissues. Disclosure of Interest: None Declared