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The scope of this thesis is the immunomodulation by macrophages by metabolites and mRNA analogues used in vaccines. Human blood monocyte-derived macrophages are used as a model to study immune function. The work of this thesis shows how both the pro- and anti-inflammatory functions of macrophages are affected by different compounds with potential therapeutic applications. In chapter 2, we characterise the responses of macrophages to a new mRNA nucleotide analogue: 5-ethynyl uridine. This is particularly interesting because the mRNA is equipped with a chemical group from click-chemistry. The Nobel prize for click-chemistry was awarded this year to (among others) Carolyn Bertozzi. This technique will aid the development of mRNA vaccines by adding modality to mRNA therapies. The rest of the thesis focuses on the interaction of these immune cells with surrounding metabolites for potential therapeutic development. For instance, we found that the metabolite itaconate can contribute to a wound-healing phenotype, which could be interesting for wound treatment.

5-methoxy tryptophan (5-MTP) is an anti-fibrotic metabolite made by fibroblasts and epithelial cells, present in a micromolar concentrations in human blood, and is associated with the progression of fibrotic kidney disease, but the mechanism is unclear. Here, we show by microscopy and functional assays that 5-MTP influences mitochondria in human peripheral blood monocyte-derived macrophages. As a result, the mitochondrial membranes are more rigid, more branched, and are protected against oxidation. The macrophages also change their metabolism by reducing mitochondrial import of acyl-carnitines, intermediates of fatty acid metabolism, driving glucose import. Moreover, 5-MTP increases the endocytosis of collagen by macrophages, and experiments with inhibition of glucose uptake showed that this is a direct result of their altered metabolism. However, 5-MTP does not affect the macrophages following pathogenic stimulation, due to 5-MTP degradation by induced expression of indole-amine oxygenase-1 (IDO-1). Thus, 5-MTP is a fibrosis-protective metabolite that, in absence of pathogenic stimulation, promotes collagen uptake by anti-inflammatory macrophages by altering the physicochemical properties of their mitochondrial membranes.

Contains fulltext : 201259.pdf (publisher's version ) (Open Access)