Depletion of intracellular GTP results in nuclear factor-kappaB activation and intercellular adhesion molecule-1 expression in human endothelial cells.
The expression of the intercellular adhesion molecule 1 (ICAM-1) on the surface of endothelial cells plays an important role in immune-mediated processes. The induction by the proinflammatory cytokine interleukin (IL)-1beta is regulated by nuclear transcription factor kappaB (NF-kappaB). We studied the effect of an inosine-5'-monophosphate dehydrogenase (IMPDH) inhibitor, mycophenolic acid (MPA), on constitutive and IL-1beta-induced expression of ICAM-1 in human umbilical vein endothelial cells (HUVECs). Unexpectedly, pretreatment with MPA enhanced the constitutive expression and potentiated the induction of ICAM-1 by IL-1beta, as detected by flow cytometry. Northern blot analysis revealed an increase in ICAM-1 mRNA levels in cells treated with MPA. This was associated with an increase in phosphorylation of IkappaB-alpha (an inhibitor of NF-kappaB), nuclear translocation of the NF-kappaB subunits p50 and p65 and their binding to DNA as detected by Western blotting, confocal microscopy, and electrophoretic mobility shift assay. The up-regulation of ICAM-1 by MPA was prevented by high doses (100 microM) of guanine or guanosine but not by physiological doses (0.1 microM), indicating that guanylates are involved in endothelial responses to IL-1beta. Cultivation of HUVECs in the absence of guanine enhanced further ICAM-1 expression during IMPDH inhibition. These results demonstrate that cytokine-mediated endothelial ICAM-1 expression can be modulated by IMPDH inhibition. We believe this represents a novel interaction between endothelial guanylate metabolism, NF-kappaB activation, and adhesion molecule expression.
Department of Cardiothoracic Surgery, Research Laboratories, University of Vienna, Vienna, Austria. guenter.weigel@akh-wein.ac.at
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D002478:Cells, Cultured; D004347:Drug Interactions; D004730:Endothelium, Vascular / Q000378:metabolism*; D015870:Gene Expression; D006160:Guanosine Triphosphate / Q000172:deficiency / Q000378:metabolism*; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D007168:IMP Dehydrogenase / Q000037:antagonists & inhibitors; D015151:Immunoblotting; D018799:Intercellular Adhesion Molecule-1 / Q000096:biosynthesis* / Q000235:genetics; D007375:Interleukin-1 / Q000494:pharmacology; D009173:Mycophenolic Acid / Q000494:pharmacology; D016328:NF-kappa B / Q000378:metabolism*; D010766:Phosphorylation; D020871:RNA Stability; D012333:RNA, Messenger / Q000096:biosynthesis
D020672:I-kappa B Proteins; D007375:Interleukin-1; D016328:NF-kappa B; D012333:RNA, Messenger; D018799:Intercellular Adhesion Molecule-1; D006160:Guanosine Triphosphate; D007168:IMP Dehydrogenase; D009173:Mycophenolic Acid