Picolinic acid- or desferrioxamine-inducible autocrine activation of macrophages engineered to produce IFNγ: an approach for gene therapy

Abstract

Macrophage (Mf)-based vectors are highly mobile cellular shuttles designed to deliver therapeutic genes within the tissues. We engineered a mouse Mf cell line to express the murine interferon-g (IFNg) under the control of an inducible promoter containing the hypoxia-responsive element, which can be triggered by hypoxia and other stimuli. We show that this Mf vector can be induced to produce IFNg under normoxic conditions by stimulation with picolinic acid (PA), a catabolite of tryptophan, or desferrioxamine (DFX), an ironchelating drug. The Mf vector responds to IFNg with the induction of IRF-1 and of other IFNg-inducible genes, the expression of Ia antigens and induction of phagocytic activity.Inducible nitric oxygen synthase gene expression, nitric oxide production, as well as TNFa secretion were enhanced by PA or DFX as the sole stimuli. None of the above responses could be triggered individually by PA or DFX in control, normal Mf, indicating that the Mf vector overcame the need for costimulatory molecules derived from the immune system for its full activation. Furthermore, we demonstrate that extracellular iron can downregulate such response, thereby identifying an additional tool for the fine tuning of the Mf vector response to stimulation.

Monocytes and dendritic cells in a hypoxic environment: Spotlights on chemotaxis and migration

“…An additional level of complexity is given in vivo by the interaction of mononuclear phagocytes with other cells present in ischemic/diseased tissues and by the local balance between hypoxia and other microenvironmental alterations, such as glucose depletion, accumulation of lactate and other metabolic byproducts, and low PH (Crowther et al, 2001), or additional inflammatory co-stimuli, that include cytokines (TNF, IL-1), small metabolites (picolinic acid) and microbial products (LPS), which were reported to activate the HIF/HRE pathway and modulate transcription of hypoxia-responsive genes (Mi et al, 2007;Blouin et al, 2004;Peyssonnaux et al, 2005;Cramer et al, 2003;HellwigBurgel et al, 1999;Bosco et al, 2000;Pastorino et al, 2004). Examination of the effects of these factors in combination with hypoxia may yield a more complete picture of mononuclear phagocyte functions under pathological conditions.…”

Mechanisms of Fish Macrophage Antimicrobial Immunity

“…Notably, macrophage tryptophan degradation appears to also be coupled to production of nitric oxide. Picolinic acid, a catabolite of tryptophan degradation (Figure 3 ), synergizes with IFNγ to induce nitric oxide production in murine macrophages ( 298 – 302 ). Picolinic acid exerts this nitric oxide inducing potential via a hypoxic responsive element located in the 5’ flanking region of the murine iNOS gene, while mutation or deletion of this promoter sequence impairs picolinic acid-induced gene transcription of iNOS without affecting induction of nitric oxide synthase by LPS ( 300 ).…”

Hypoxia inhibits Moloney murine leukemia virus expression in activated macrophages

“…NO is produced by activated M [11] and can contribute to the antiviral effect of IFN-␥ [2,50]. However, we observed a similar reduction of retroviral mRNA under hypoxic conditions, when NO cannot be produced [51], and in response to PA, when high levels of NO are produced [36], indicating that this mechanism cannot account for hypoxia and PA silencing effects.…”

“…PA is a biologically active tryptophan metabolite with Mactivating properties, which mimics hypoxia in inducing gene expression [20,36]. We studied whether PA modulated viral promoter-driven gene expression.…”