Exogenous Interferon-γ Induces Endogenous Synthesis of Interferon-α and -β by Murine Macrophages for Induction of Nitric Oxide Synthase

Abstract

Murine macrophages (M phi) are activated either by interferon-gamma (IFN-gamma) or interferon-alpha/beta (IFN-alpha/beta) in combination with bacterial lipopolysaccharide (LPS) to induce synthesis of tumor necrosis factor alpha (TNF-alpha) and nitric oxide synthase (iNOS) mRNA synthesis for generation of tumor cytotoxic nitric oxide (NO). In the present study, the effect of exogenous IFN-gamma on the induction of endogenous mRNA synthesis and secretion of IFN-alpha/beta by murine M phi was investigated. Neutralizing antibodies to IFN-alpha/beta reversed TNF-alpha and NOS mRNA synthesis, as well as nitric oxide (NO)-mediated tumor cytotoxicity. Quantitative reverse transcription polymerase chain reaction (RT-PCR) revealed that treatment of M phi with IFN-gamma induced increases in both IFN-alpha and IFN-beta mRNA synthesis by approximately 2-fold and 10-fold, respectively, which corresponded to a 2-fold increase in secretion of IFN-alpha/beta by ELISA. These data indicate that exogenous IFN-gamma induces endogenous synthesis and secretion of IFN-alpha/beta by M phi, which appears to act in concert with endogenously synthesized TNF-alpha for the autocrine induction of NOS mRNA synthesis.

Anti-inflammatory action of type I interferons deduced from mice expressing interferon β

“…To characterize better this process, we investigated the activation of NF-B and Stat1␣ as transcription factors integrating the early pro-inflammatory stimulation involved in the transcriptional activation of genes that participate in the onset of inflammation. 8,[30][31][32][33] As Figure 6 shows, NF-B activation in macrophages from animals challenged in vivo with LPS and IFN-␥ was impaired in Tg-1 when compared with the corresponding controls, at least during the initial 2-h period after stimulation. Analysis of the bands by supershift assays suggested the presence of p65.p50 and p50.p50 complexes in the upper and lower bands, respectively.…”

“…For example, using these animals, it has been reported that hIFN-␤ favors the development of a pre-diabetic state that was evidenced after administration of low doses of streptozotocin. 25 Tg-1 mice released relatively large amounts of hIFN-␤, but because of the much lower affinity of the human cytokine for the murine type I IFN receptor, it exerts systemic effects outside the pancreas where the cytokine is produced, 8 a condition which constitutes an advantage of this model over a murine IFN-␤-expressing alternative. We detected levels of hIFN-␤ that are in the range of 4-5 ng/ml of serum as deduced by ELISA assays.…”

“…3,4 In addition to the antiviral effects of type I IFNs, cumulative evidence supports the view that these cytokines exert an inhibitory or regulatory action on the activation of cells of the immune system, in particular macrophages. [5][6][7][8] Expression of inducible nitric oxide synthase (iNOS) constitutes a key step for commitment of the physiological functions of activated macrophages. [9][10][11] Multiple proinflammatory cytokines and bacterial cell wall products are involved in the expression of iNOS, acting in a concerted cooperative pathway.…”

“…13,14 However, controversy exists about the mechanism of action of type I IFNs in the transcriptional control of iNOS: IFN-␣ and -␤ are synthesized by macrophages stimulated with LPS and IFN-␥, and neutralizing antibodies against type I IFNs decreased the expression of iNOS. 8 Alternatively, challenge of macrophages with IFN-␣/␤ before IFN-␥ stimulation impaired the transcription of iNOS through a mechanism that involved a decreased activity of NF-B and inhibition of IFN-␥-dependent signaling. Interestingly, these effects were observed only during the initial 2-h period of stimulation, indicating that type I IFNs inhibited the recruitment or the function of the transcription factors responsible for the activation of the iNOS promoter, but they did not affect the stability of the iNOS mRNA and protein.…”

Biodegradable polymer-based interleukin-12 gene delivery: role of induced cytokines, tumor infiltrating cells and nitric oxide in anti-tumor activity

“…27 However, it has not been found to be as effective as IL-12 both in terms of its own production in vivo, as well as in terms of anti-tumor and anti-metastatic activity. 28 In the earlier paper, we reported that in vitro transfection of PAGA/pmIFN-␥ into cultured CT-26 tumor cells generates similar expression levels of mIFN-␥ in comparison with mIL-12 induced mIFN-␥.…”