Down-regulation of TNF-alpha receptors by conophylline in human T-cell leukemia cells

Int J Oncol. 2003 Nov;23(5):1373-9.


In the course of our screening for tumor necrosis factor-alpha (TNF-alpha) function inhibitors, conophylline, a vinca alkaloid isolated from the plant Ervatamia microphylla, was found to inhibit TNF-alpha-induced NF-kappaB activation. We studied the effect of conophylline on TNF-alpha-induced NF-kappaB and JNK activations in human T-cell leukemia Jurkat cells. Conophylline inhibited both of these TNF-alpha-induced activations. It also inhibited phosphorylation and degradation of I-kappaB-alpha. Moreover, a receptor binding assay using [125I]-TNF-alpha showed that this inhibitory effect was due to a decrease in the binding of TNF-alpha to the cells. Scatchard analysis of the binding data indicated that conophylline induced only a small change in the affinity of the receptors but a significant change in the receptor number. FACS analysis showed that conophylline reduced the expression of CD120a/TNFR1, the high-affinity receptor for TNF-alpha, on the cell surface. On the other hand, conophylline did not affect the kinetics of internalization and degradation of TNF-alpha/receptor complexes or the half-life of TNF-alpha binding sites. These results indicate that conophylline down-regulates the expression of the TNF-alpha receptors on the cell surface.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, CD / biosynthesis
  • Binding Sites
  • Cell Membrane / metabolism
  • Cell Nucleus / metabolism
  • Cell Separation
  • Dose-Response Relationship, Drug
  • Down-Regulation*
  • Enzyme Activation
  • Flow Cytometry
  • HL-60 Cells
  • Humans
  • I-kappa B Proteins / metabolism
  • Jurkat Cells
  • Kinetics
  • Leukemia, T-Cell / drug therapy*
  • Leukemia, T-Cell / metabolism*
  • Models, Chemical
  • NF-KappaB Inhibitor alpha
  • NF-kappa B / metabolism
  • Phosphorylation
  • Protein Binding
  • Receptors, Tumor Necrosis Factor / biosynthesis*
  • Receptors, Tumor Necrosis Factor, Type I
  • Recombinant Proteins / metabolism
  • Time Factors
  • Vinca Alkaloids / pharmacology*


  • Antigens, CD
  • I-kappa B Proteins
  • NF-kappa B
  • NFKBIA protein, human
  • Receptors, Tumor Necrosis Factor
  • Receptors, Tumor Necrosis Factor, Type I
  • Recombinant Proteins
  • Vinca Alkaloids
  • conophylline
  • NF-KappaB Inhibitor alpha