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

Ironing out macrophages in atherosclerosis

<p indent="0mm">The most common cause of death worldwide is atherosclerosis and related cardiovascular disorders. Macrophages are important players in the pathogenesis of atherosclerosis and perform critical functions in iron homeostasis due to recycling iron by phagocytosis of senescent red blood cells and regulating iron availability in the tissue microenvironment. With the growth of research on the "iron hypothesis" of atherosclerosis, macrophage iron has gradually become a hotspot in the refined iron hypothesis. Macrophages with the M1, M2, M(Hb), Mox, and other phenotypes have been defined with different iron-handling capabilities related to the immune function and immunometabolism of macrophages, which influence the progression of atherosclerosis. In this review, we focus on macrophage iron and its effects on the development of atherosclerosis. We also cover the contradictory discoveries and propose a possible explanation. Finally, pharmaceutical modulation of macrophage iron is discussed as a promising target for atherosclerosis therapy.</p>.

An integrated cytokine and kynurenine network as the basis of neuroimmune communication

Two of the molecular families closely associated with mediating communication between the brain and immune system are cytokines and the kynurenine metabolites of tryptophan. Both groups regulate neuron and glial activity in the central nervous system (CNS) and leukocyte function in the immune system, although neither group alone completely explains neuroimmune function, disease occurrence or severity. This essay suggests that the two families perform complementary functions generating an integrated network. The kynurenine pathway determines overall neuronal excitability and plasticity by modulating glutamate receptors and GPR35 activity across the CNS, and regulates general features of immune cell status, surveillance and tolerance which often involves the Aryl Hydrocarbon Receptor (AHR). Equally, cytokines and chemokines define and regulate specific populations of neurons, glia or immune system leukocytes, generating more specific responses within restricted CNS regions or leukocyte populations. In addition, as there is a much larger variety of these compounds, their homing properties enable the superimposition of dynamic variations of cell activity upon local, spatially limited, cell populations. This would in principle allow the targeting of potential treatments to restricted regions of the CNS. The proposed synergistic interface of 'tonic' kynurenine pathway affecting baseline activity and the superimposed 'phasic' cytokine system would constitute an integrated network explaining some features of neuroimmune communication. The concept would broaden the scope for the development of new treatments for disorders involving both the CNS and immune systems, with safer and more effective agents targeted to specific CNS regions.

Ironing out Macrophage Immunometabolism

Over the last decade, increasing evidence has reinforced the key role of metabolic reprogramming in macrophage activation. In addition to supporting the specific immune response of different subsets of macrophages, intracellular metabolic pathways also directly control the specialized effector functions of immune cells. In this context, iron metabolism has been recognized as an important component of macrophage plasticity. Since macrophages control the availability of this essential metal, changes in the expression of genes coding for the major proteins of iron metabolism may result in different iron availability for the macrophage itself and for other cells in the microenvironment. In this review, we discuss how macrophage iron can also play a role in immunometabolism.

Mechanisms of Fish Macrophage Antimicrobial Immunity

Overcrowding conditions and temperatures shifts regularly manifest in large-scale infections of farmed fish, resulting in economic losses for the global aquaculture industries. Increased understanding of the functional mechanisms of fish antimicrobial host defenses is an important step forward in prevention of pathogen-induced morbidity and mortality in aquaculture setting. Like other vertebrates, macrophage-lineage cells are integral to fish immune responses and for this reason, much of the recent fish immunology research has focused on fish macrophage biology. These studies have revealed notable similarities as well as striking differences in the molecular strategies by which fish and higher vertebrates control their respective macrophage polarization and functionality. In this review, we address the current understanding of the biological mechanisms of teleost macrophage functional heterogeneity and immunity, focusing on the key cytokine regulators that control fish macrophage development and their antimicrobial armamentarium.

The delicate balance of macrophages in colorectal cancer; their role in tumour development and therapeutic potential

Most tumours are heavily infiltrated by immune cells. This has been correlated with either a good or a bad patient prognosis, depending on the (sub) type of immune cells. Macrophages represent one of the most prominent leukocyte populations in the majority of tumours. Functions of macrophages range from cytotoxicity, to stimulation of tumour growth by secretion of cytokines, growth and angiogenic factors, or suppressing immune responses. In most tumours macrophages are described as cells with immune suppressing, and wound healing properties, which aids tumour development. Yet, increasing evidence shows that macrophages are potent inhibitors of tumour growth in colorectal cancer. Macrophages in this respect show high plasticity. The presence of high macrophage numbers in the tumour may therefore become advantageous, if cells can be reprogrammed from tumour promoting macrophages into potent effector cells. Enhancing cytotoxic properties of macrophages by microbial products, pro-inflammatory cytokines or monoclonal antibody therapy are promising possibilities, and are currently tested in clinical trials.

Hypoxia inhibits Moloney murine leukemia virus expression in activated macrophages

Hypoxia, a local decrease in oxygen tension, occurring in many pathological processes, modifies macrophage (Mphi) gene expression and function. Here, we provide the first evidence that hypoxia inhibits transgene expression driven by the Moloney murine leukemia virus-long terminal repeats (MoMLV-LTR) in IFN-gamma-activated Mphi. Hypoxia silenced the expression of several MoMLV-LTR-driven genes, including v-myc, enhanced green fluorescence protein, and env, and was effective in different mouse Mphi cell lines and on distinct MoMLV backbone-based viruses. Down-regulation of MoMLV mRNA occurred at the transcriptional level and was associated with decreased retrovirus production, as determined by titration experiments, suggesting that hypoxia may control MoMLV retroviral spread through the suppression of LTR activity. In contrast, genes driven by the CMV or the SV40 promoter were up-regulated or unchanged by hypoxia, indicating a selective inhibitory activity on the MoMLV promoter. It is interesting that hypoxia was ineffective in suppressing MoMLV-LTR-controlled gene expression in T or fibroblast cell lines, suggesting a Mphi lineage-selective action. Finally, we found that MoMLV-mediated gene expression in Mphi was also inhibited by picolinic acid, a tryptophan catabolite with hypoxia-like activity and Mphi-activating properties, suggesting a pathophysiological role of this molecule in viral resistance and its possible use as an antiviral agent.