title: Inhibition of GTPase Rac1 in endothelium by 6-mercaptopurine results in immunosuppression in nonimmune cells: new target for an old drug.
abstract: Azathioprine and its metabolite 6-mercaptopurine (6-MP) are well established immunosuppressive drugs. Common understanding of their immunosuppressive properties is largely limited to immune cells. However, in this study, the mechanism underlying the protective role of 6-MP in endothelial cell activation is investigated. Because 6-MP and its derivative 6-thioguanosine-5'-triphosphate (6-T-GTP) were shown to block activation of GTPase Rac1 in T lymphocytes, we focused on Rac1-mediated processes in endothelial cells. Indeed, 6-MP and 6-T-GTP decreased Rac1 activation in endothelial cells. As a result, the compounds inhibited TNF-α-induced downstream signaling via JNK and reduced activation of transcription factors c-Jun, activating transcription factor-2 and, in addition, NF κ-light-chain-enhancer of activated B cells (NF-κB), which led to decreased transcription of proinflammatory cytokines. Moreover, 6-MP and 6-T-GTP selectively decreased TNF-α-induced VCAM-1 but not ICAM-1 protein levels. Rac1-mediated generation of cell membrane protrusions, which form docking structures to capture leukocytes, also was reduced by 6-MP/6-T-GTP. Consequently, leukocyte transmigration was inhibited after 6-MP/6-T-GTP treatment. These data underscore the anti-inflammatory effect of 6-MP and 6-T-GTP on endothelial cells by blocking Rac1 activation. Our data provide mechanistic insight that supports development of novel Rac1-specific therapeutic approaches against chronic inflammatory diseases.
authors.affiliation: Department of Medical Biochemistry, Academic Medical Center, University of Amsterdam, 1105 AZ Amsterdam, The Netherlands;
authors.forename: Goran
authors.initials: G
authors.lastname: Marinković
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Kroon
authors.forename: Mark
authors.initials: M
authors.lastname: Hoogenboezem
authors.forename: Kees A
authors.initials: KA
authors.lastname: Hoeben
authors.forename: Matthijs S
authors.initials: MS
authors.lastname: Ruiter
authors.forename: Kondababu
authors.initials: K
authors.lastname: Kurakula
authors.forename: Iker
authors.initials: I
authors.lastname: Otermin Rubio
authors.forename: Mariska
authors.initials: M
authors.lastname: Vos
authors.forename: Carlie J M
authors.initials: CJ
authors.lastname: de Vries
authors.forename: Jaap D
authors.initials: JD
authors.lastname: van Buul
authors.forename: Vivian
authors.initials: V
authors.lastname: de Waard
mesh_terms: D015153:Blotting, Western; D002448:Cell Adhesion / Q000187:drug effects; D002478:Cells, Cultured; D018920:Coculture Techniques; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D015122:Mercaptopurine / Q000494:pharmacology*; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D059467:Transcriptome; D057705:Transendothelial and Transepithelial Migration / Q000187:drug effects; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D007166:Immunosuppressive Agents; C107953:RAC1 protein, human; D015122:Mercaptopurine; D020830:rac1 GTP-Binding Protein