title: Downregulation of tumor necrosis factor receptors on macrophages and endothelial cells by microtubule depolymerizing agents.
abstract: Exposure of murine and human macrophages and human umbilical vein endothelial cells to micromolar concentrations of five microtubule (MT)-depolymerizing agents (colchicine, nocodazole, podophyllotoxin, vincristine, and vinblastine) resulted in a loss of binding sites for iodinated TNF-alpha. The reduction amounted to 40-60% by 1 h and approximately 75% by 2-4 h. In 1 h, specific binding was reduced 50% by 0.1-5 microM of these drugs at 37 degrees C, but not at 4 degrees C. Inactive isomers of colchicine were ineffective, as were microfilament-destabilizing cytochalasins. The active agents did not compete with TNF-alpha R for binding. Antiserum against TNF-alpha did not neutralize the effect of colchicine and nocodazole. PGE1 and dibutyryl-cAMP could not mimic, and cyclooxygenase inhibitors could not prevent the drug effects. All the binding sites were regenerated within 3 h after removal of nocodazole, which binds tubulin reversibly, whereas little recovery was found even 18 h after the removal of colchicine, which binds tubulin irreversibly. These findings suggested that MT disassembly was responsible for the observed downregulation of TNF-alpha R. The protein synthesis inhibitor cycloheximide inhibited binding of TNF-alpha to a similar extent and with a similar time course as colchicine in the absence of added ligand. Neither drug affected binding of IFN-gamma to macrophages, nor binding of TNF-alpha to human polymorphonuclear leukocytes. Thus, an intact MT network appears to be important in maintenance of the steady state of TNF-alpha R on those cells in which TNF-alpha R turns over rapidly in the absence of ligand. The antiinflammatory actions of MT-depolymerizing agents may result in part from their interference with the ability of such cells to respond to TNF-alpha.
authors.affiliation: Beatrice and Samuel A. Seaver Laboratory, Department of Medicine, Cornell University Medical College, New York, New York 10021.
authors.forename: A H
authors.initials: AH
authors.lastname: Ding
authors.forename: F
authors.initials: F
authors.lastname: Porteu
authors.forename: E
authors.initials: E
authors.lastname: Sanchez
authors.forename: C F
authors.initials: CF
authors.lastname: Nathan
mesh_terms: D000818:Animals; D003078:Colchicine / Q000494:pharmacology; D003513:Cycloheximide / Q000494:pharmacology; D015536:Down-Regulation; D004727:Endothelium / Q000032:analysis / Q000187:drug effects*; D006801:Humans; D008070:Lipopolysaccharides / Q000502:physiology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000032:analysis / Q000187:drug effects*; D051379:Mice; D008870:Microtubules / Q000187:drug effects*; D009504:Neutrophils / Q000032:analysis / Q000187:drug effects; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D011956:Receptors, Cell Surface / Q000032:analysis / Q000187:drug effects* / Q000502:physiology; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D011956:Receptors, Cell Surface; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D011451:Prostaglandin-Endoperoxide Synthases; D003078:Colchicine