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.
Wheeler
H R
HR
Department of Clinical Oncology, Royal North Shore Hospital, Sydney, Australia.
Rockett
E J
EJ
Clark
I
I
Geczy
C L
CL
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