A tumor necrosis factor mimetic peptide activates a murine macrophage cell line to inhibit mycobacterial growth in a nitric oxide-dependent fashion.
The control of mycobacterial infections depends on the cytokine-mediated activation of mononuclear phagocytes to inhibit the growth of intracellular mycobacteria. Optimal activation requires the presence of T-cell-derived gamma interferon (IFN-gamma) and other signals, including tumor necrosis factor (TNF). Recently, an 11-mer peptide based on amino acids 70 to 80 of the human TNF sequence, TNF(70-80), was found to have TNF mimetic properties, which include the activation of human and mouse neutrophils to kill Plasmodia spp. Therefore, we investigated the capacity of TNF(70-80) to activate the murine macrophage cell line RAW264.7 infected with the vaccine strain Mycobacterium bovis bacillus Calmette-Guérin (BCG). When RAW264.7 cells were pretreated with human TNF or TNF(70-80) in the presence of IFN-gamma, there was a dose-dependent reduction in the replication of BCG as measured by the uptake of 3H-labeled uracil and a concomitant release of nitric oxide as measured by the nitrite in the culture supernatants. TNF- or TNF(70-80)-induced macrophage activation was dependent on IFN-gamma and was inhibited by neutralizing monoclonal antibody to human TNF and by anti-IFN-gamma antisera. Both nitrite release and BCG growth inhibition were abrogated by competitive inhibitors of L-arginine, which blocked the activation of inducible nitric oxide synthase. A soluble form of the Type 1 TNF receptor blocked the activation of BCG-infected macrophages by human TNF and TNF(70-80), demonstrating that the effect of TNF(70-80) is dependent on signaling through TNF receptor I. The mimetic effects of TNF(70-80) on macrophage activation in vitro suggest that treatment with TNF(70-80) may modulate mycobacterial infections in vivo.
Britton
W J
WJ
Centenary Institute of Cancer Medicine and Cell Biology, Newtown, New South Wales, Australia. wbritton@medicine.usyd.edu.au
Meadows
N
N
Rathjen
D A
DA
Roach
D R
DR
Briscoe
H
H
D000818:Animals; D002460:Cell Line; D006801:Humans; D007371:Interferon-gamma / Q000494:pharmacology; D008262:Macrophage Activation / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects*; D051379:Mice; D009163:Mycobacterium bovis / Q000187:drug effects* / Q000254:growth & development; D009569:Nitric Oxide / Q000502:physiology*; D010446:Peptide Fragments / Q000494:pharmacology*; D018124:Receptors, Tumor Necrosis Factor / Q000502:physiology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D010446:Peptide Fragments; D018124:Receptors, Tumor Necrosis Factor; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D007371:Interferon-gamma