Interferon‐γ and tumor necrosis factor induce the L‐arginine‐dependent cytotoxic effector mechanism in murine macrophages^*

Abstract

We tested several monokines and muramyl dipeptide (MDP) to determine whether they induce the L-arginine-dependent effector mechanism in cultured murine macrophages. Recombinant interferon-gamma (rIFN-gamma) and recombinant tumor necrosis factor (rTNF) synergize to induce nitrite (NO2-) and nitrate (NO3-) synthesis from L-arginine as well as to cause inhibition of the iron-dependent enzyme aconitase in macrophages. Unlike rTNF, recombinant interleukin 1 (rIL 1) and rIL 6/B cell stimulatory factor 2 (rIL 6/BSF-2) did not act as cofactors when added to macrophages in the presence of rIFN-gamma. rIFN-gamma plus MDP induced the L-arginine-dependent effector mechanism in murine macrophages. However, induction by rIFN-gamma plus MDP was inhibited by anti-rTNF antibodies which suppressed both NO2-/NO3- synthesis and aconitase inhibition. This result indicates that endogenously produced TNF is involved in the induction of the L-arginine-dependent effector mechanism when MDP is the co-stimulant with rIFN-gamma. In contrast, anti-rTNF antibodies did not fully suppress the effect of combining rIFN-gamma and lipopolysaccharide, suggesting that, in this case, activation of the L-arginine-dependent effector pathway may involve more than induction of TNF synthesis by the macrophages. These results provide information, at a biochemical level, on a mechanism through which combination of IFN-gamma and TNF can modulate macrophage functions involved in the control of cell proliferation.

Nitric oxide is an important mediator for tumoricidal activity in vivo.

“…We also demonstrate that IFN-y, but not TNF-a, is an important mediator of the BCG-induced nonspecific host resistance against syngeneic ovarian tumor cells in vivo. This observation is contrary to in vitro studies in which IFN-y was thought to be important for the priming of macrophages and TNF-a was thought to be necessary for full induction of activated macrophage cytotoxicity (8,9). Furthermore, others (14) showed that neutralization of either IFN--y or TNF-a blocked the BCG-induced in vivo synthesis of nitrogen oxides from L-arginine as well as the protection against Francisella tularensis.…”

“…NO produced by the activated macrophages is responsible for this cytostatic and/or cytolytic activity (1)(2)(3). Interferon 'y (IFN-y) is important for the priming of macrophages, and tumor necrosis factor a (TNF-a) or some other cytokine or bacterial lipopolysaccharide (LPS) is necessary for full induction of activated macrophage cytotoxicity (6)(7)(8)(9). However, the role of NO in mediating tumoricidal activity in vivo is not known.…”

Role of tumour necrosis factor in the induction of nitric oxide synthase in a rat model of endotoxin shock

“…Like LPS, TNF also induces the calcium-independent isoform of NOS in vitro (Drapier et al, 1988;Kilbourn & Belloni, 1990). Systemic administration of TNF increases NO production (Kosaka et al, 1992) and causes NO-mediated vasodilatation and vascular hyporeactivity to vasoconstrictors in vivo (Vicaut & Baundry, 1992) and ex vivo (Takahashi et al, 1992;Foulkes & Shaw, 1992).…”

Antitumour responses to flavone-8-acetic acid and 5,6-dimethylxanthenone-4-acetic acid in immune deficient mice

“…It has improved antitumour activity and 12-fold higher dose potency when compared to FAA, and is a candidate drug for clinical trial. FAA and 5,6-MeXAA share many properties with endotoxin: they induce the synthesis of tumour necrosis factor (TNF) (North & Havell, 1988;Mace et al, 1990) and stimulate the formation of nitric oxide, both in vitro (Drapier et al, 1988;Thomsen et al, 1990) and in vivo (Stuehr & Marletta, 1985;Thomsen et al, 1991). There are two main facets to the action of these agents.…”