Synergic action between tumor necrosis factor and endotoxins or poly(A·U) on cultured bovine endothelial cells

Abstract

In order to investigate whether direct effects on tumor vasculature may contribute to induction of necrosis of solid tumors in vivo, agents and combinations with an established different capacity to induce tumor necrosis were studied for their effects on endothelial cells in vitro. Tumor necrosis serum caused a marked inhibition of [3H]thymidine incorporation by bovine umbilical cord endothelial cells after 4 h coincubation. Endotoxin was less inhibitory, whereas detoxified endotoxin and recombinant human tumor necrosis factor (rTNF) were hardly active in concentrations that can be achieved in vivo. Combinations of rTNF and (detoxified) endotoxin caused synergic inhibition. By 24 h effects of the separate agents and synergic effects of the combinations were much stronger. The nontoxic dsRNA, poly(A.U), also had inhibitory activity, and acted synergistically with rTNF. Morphologically, a combination of endotoxin and rTNF but not the separate constituents induced marked cell detachment by 24 h, an indication of cell death. Whereas both endotoxin and rTNF inhibited DNA synthesis of human endothelial cells, the agents did not act synergistically on these cells. The ability of the agents and the combinations to affect endothelial cells in culture appeared to be well in line with their capacity to induce tumor necrosis. Data suggest that direct (synergic) effects on endothelium may contribute to the induction of vascular damage in tumors by (combinations of) the agents. The fact that endothelial cell death is only induced by the combinations and not by the separate agents in vivo, may be a cause of the greater therapeutic activity of the combinations in vivo. The synergy between rTNF and the other agents indicates that the agents act by different mechanisms.

Role of tumour necrosis factor in the tumour-necrotizing activity of agents with diverging toxicity

“…In support of this are observations that endotoxin could induce necrosis of tumours that do not activate the mononuclear phagocyte system [8], while its degree of activation appeared to determine the degree of endotoxin-inducible TNF [4,9,12]. The basis of this synergy is still elusive, but may be related to a direct action of the agents on endothelial cells [21] as well as to their ability to induce mediators, other than TNF, active against tumour cells and/or the tumour vasculature. The inability of the antiserum to abrogate the antitumour action of the agents completely may be due to an inability of the antibodies to neutralize all TNF produced in the body, especially after treatment with the very potent TNF-inducing combination, MDP/lipid A.…”

“…The capacity of sera to inhibit the DNA synthesis of cultured MethA cells and bovine umbilical artery endothelial cells was determined as described previously [2,21 ]. The capacity of sera to inhibit the DNA synthesis of cultured MethA cells and bovine umbilical artery endothelial cells was determined as described previously [2,21 ].…”

Bovine herpesvirus 4 in bovine clinical mastitis

“…The number of lactating cows in the 10 different herds varied between 31 and 57, and the number of case/control pairs varied from one to 22 per herd (Table 1). Milk samples were examined for the presence of viruses, using four different types of cell cultures: embryonic bovine trachea cells ( ebtr ; a semipermanent cell line developed in the authors' laboratory, id ‐Lelystad); bovine epithelial udder cells (including fibroblasts) (Schmid and others 1983); bovine umbilical cord endothelial ( bue ) cells (Van de Wiel and others 1989); and bovine alveolar lung macrophages obtained from specific pathogen free ( spf ) cattle (Schrijver and others 1995).…”

Protective immunity to heartwater (Cowdria ruminantium infection) is acquired after vaccination with in vitro-attenuated rickettsiae

“…All vaccinated animals were challenged on day 30 postinoculum with virulent blood stabilate Crlll, which caused fatal heartwater in all nonvaccinated cor)trol animals ( Table 1). BUE cells were isolated from umbilical cord arteries (18), as described previously (9). Briefly, the cells were grown until confluency in RPMI 1640 medium supplemented with antibiotics, HEPES (N-2-hydroxyethylpiperazine-N'-2ethanesulfonic acid) buffer (20 mM, pH 7.0 to 7.3), L-glutamine (2 mM), and 10% newborn calf serum, and they were subcultured with trypsin-EDTA.…”