Selective Inhibition of Inflammatory Gene Expression in Activated T Lymphocytes: A Mechanism of Immune Suppression by Thiopurines

• Published in: The Journal of pharmacology and experimental therapeutics 2005-02, Vol.312 (2), p.537-545
• Main Authors: Thomas, Carlton W, Myhre, Gennett M, Tschumper, Renee, Sreekumar, Raghavakaimal, Jelinek, Diane, McKean, David J, Lipsky, James J, Sandborn, William J, Egan, Laurence J
• Format: Article
• Language: English
• Subjects: Annexin A5; Apoptosis Regulatory Proteins; Azathioprine - pharmacology; Cells, Cultured; Coloring Agents; Dose-Response Relationship, Drug; Enzyme Inhibitors; Enzyme-Linked Immunosorbent Assay; Gene Expression - drug effects; Gene Expression Profiling; Humans; Immunity - genetics; Immunosuppressive Agents - pharmacology; Inflammation - genetics; Inflammation - metabolism; Interleukin-2 - metabolism; Lymphocyte Activation - drug effects; Membrane Glycoproteins - metabolism; Mercaptopurine - pharmacology; Oligonucleotide Array Sequence Analysis; Propidium; Reverse Transcriptase Polymerase Chain Reaction; T-Lymphocytes - drug effects; T-Lymphocytes - metabolism; TNF-Related Apoptosis-Inducing Ligand; Tumor Necrosis Factor-alpha - metabolism; Up-Regulation - drug effects
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.104.074815

Azathioprine and 6-mercaptopurine are antimetabolite thiopurine drugs that play important roles in the treatment of leukemia and in the management of conditions requiring immunosuppression, such as inflammatory bowel disease. The biochemical pharmacology of these drugs suggests that inhibition of purine nucleotide formation through the 6-thioguanine nucleotide metabolites is their key molecular mechanism. However, it is unclear how these metabolites suppress immunity. We hypothesized that azathioprine produces a selective inhibitory effect on activated but not quiescent T lymphocytes. We first established a model system of T lymphocyte culture with azathioprine that produced pharmacologically relevant concentrations of 6-thioguanine nucleotides. Using genome-wide expression profiling, we identified a group of azathioprine-regulated genes in quiescent and activated T lymphocytes. Several genes involved in immunity and inflammation were selectively down-regulated by azathioprine in stimulated but not quiescent cells. Quantitative reverse transcription-polymerase chain reaction for three of these genes, tumor necrosis factor-related apoptosis-inducing ligand, tumor necrosis factor receptor superfamily member 7, and α4-integrin, confirmed down-regulated expression of transcript levels. Tumor necrosis factor-related apoptosis-inducing ligand protein expression was further studied and found to be inhibited by azathioprine, 6-mercaptopurine, and 6-thioguanine, implying that the inhibitory effects of azathioprine on expression are mediated by 6-thioguanine nucleotides. These results therefore provide a previously unrecognized molecular mechanism for the immunosuppressive properties of thiopurine antimetabolite drugs.