Actinomycin D upregulates lipopolysaccharide induction of macrophage procoagulant expression and tumour necrosis factor-alpha production.
The antitumour antibiotic actinomycin D (Act D) and the aminosugar D-galactosamine both enhance the sensitivity of animals to bacterial lipopolysaccharide (LPS). Lipopolysaccharide stimulates macrophage membrane-bound procoagulant activity (MPCA) and tumour necrosis factor-alpha (TNF-alpha) production in vitro. We investigated the effects of LPS combined with either Act D or D-galactosamine on procoagulant and TNF-alpha production in vitro. Actinomycin D directly induced procoagulant on the malignant monocytoid cell line WEHI 265, and synergized with LPS to enhance MPCA on both WEHI 265 cells and thioglycollate-induced peritoneal exudate macrophages. In the presence of Act D, exudate macrophages expressed procoagulant in response to concentrations of LPS 100,000-fold lower than normally required. Pulsing experiments demonstrated that LPS primed these cells within 4 h to respond to Act D, whereas 4 h priming with Act D inhibited subsequent procoagulant induction by LPS. Although its effects on TNF-alpha production were less intense, low levels of Act D more than doubled TNF-alpha produced by LPS-stimulated exudate macrophages. Procoagulant expression and TNF-alpha production were not always co-ordinately expressed; interferon-gamma (IFN-gamma) synergized with LPS to enhance both responses but when IFN-gamma was combined with Act D only procoagulant was upregulated. D-galactosamine failed to affect these macrophage responses. Results indicate different in vivo mechanisms of enhancement of LPS toxicity by these two agents.
Department of Clinical Oncology, Royal North Shore Hospital, Sydney, Australia.
H R
HR
Wheeler
E J
EJ
Rockett
I
I
Clark
C L
CL
Geczy
D000818:Animals; D001779:Blood Coagulation Factors / Q000096:biosynthesis*; D003609:Dactinomycin / Q000008:administration & dosage*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004731:Endotoxins / Q000008:administration & dosage*; D004926:Escherichia coli; D005688:Galactosamine / Q000494:pharmacology; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D051379:Mice; D008815:Mice, Inbred Strains; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis*
D001779:Blood Coagulation Factors; D004731:Endotoxins; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; C045072:macrophage procoagulant activity; D003609:Dactinomycin; D005688:Galactosamine; D007371:Interferon-gamma