Diabetes-induced decrease of adenosine kinase expression impairs the proliferation potential of diabetic rat T lymphocytes.
The proliferative response of T lymphocytes is a crucial step in cell-mediated immunity. This study was undertaken to investigate the mechanisms leading to the impaired proliferative response of diabetic T lymphocytes. T cells that had been isolated from the spleen of normal rats and cultured in medium containing 20 mm glucose and no insulin displayed the same degree of proliferative impairment as cells isolated from diabetic rats. The rate of T-cell proliferation, when induced with concanavalin A or anti-CD3 and anti-CD28 antibodies, was not affected by the inhibition of nucleoside transporters. T cells cultured at high glucose concentrations in the absence of insulin displayed decreased expression of adenosine kinase, and released measurable extracellular quantities of adenosine. Under resting conditions, the level of cAMP was 5.9-fold higher in these cells compared to cells grown in low glucose and in the presence of insulin. Experiments with specific adenosine receptor agonists and antagonists showed that adenosine-induced suppression of diabetic T cell proliferation was mediated by the A2A adenosine receptor, but not by the A2B receptor. Treatment of diabetic T cells with 10 microm H-89, a specific protein kinase A inhibitor, restored T-cell proliferation. These results show that suppressed proliferation of diabetic T lymphocytes is evoked by the decreased expression of adenosine kinase, leading to the outflow of adenosine from the cell. Extracellular adenosine then stimulates the A2A receptor and induces cAMP production, leading to the activation of protein kinase A, and suppression of T-cell proliferation.
Sakowicz-Burkiewicz
Monika
M
Department of Molecular Medicine, University of Gdansk, Gdansk, Poland.
Kocbuch
Katarzyna
K
Grden
Marzena
M
Szutowicz
Andrzej
A
Pawelczyk
Tadeusz
T
D000248:Adenosine Kinase / Q000276:immunology / Q000378:metabolism*; D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000276:immunology; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology* / Q000276:immunology*; D005786:Gene Expression Regulation / Q000276:immunology; D006943:Hyperglycemia / Q000201:enzymology / Q000276:immunology; D007108:Immune Tolerance / Q000187:drug effects; D007111:Immunity, Cellular; D007328:Insulin / Q000276:immunology; D008297:Male; D033703:Nucleoside Transport Proteins / Q000276:immunology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D043705:Receptor, Adenosine A2A / Q000276:immunology; D018047:Receptors, Purinergic P1 / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology; D013154:Spleen / Q000276:immunology; D013601:T-Lymphocytes / Q000201:enzymology* / Q000276:immunology
D007328:Insulin; D033703:Nucleoside Transport Proteins; D047428:Protein Kinase Inhibitors; D012333:RNA, Messenger; D043705:Receptor, Adenosine A2A; D018047:Receptors, Purinergic P1; D000242:Cyclic AMP; D000248:Adenosine Kinase; D017868:Cyclic AMP-Dependent Protein Kinases