Biology subjects

van Teijlingen Bakker, N.

Publications and source records attributed to van Teijlingen Bakker, N..

2 recordsLinked to original sources

bioRxiv2022

In macrophages fatty acid oxidation spares glutamate for use in diverse metabolic pathways required for alternative activation

Fatty acid oxidation (FAO) is upregulated in IL-4-stimulated (alternatively activated) macrophages (M(IL-4)). We examined the effect of loss of function of the enzyme Cpt1a, which facilitates the entry of long chain fatty acids (FA) into mitochondria for FAO, on alternative activation. Expression of M(IL-4) markers ARG1, CD301 and RELM, was impaired in tamoxifen-treated ERT2Cre x Cpt1afl/fl macrophages and in macrophages expressing shRNA targeting Cpt1a (Cpt1a-shRNA). In contrast, VaviCre x Cpt1afl/fl and LysmCre x Cpt1afl/fl M(IL-4) responded normally to IL-4. Reduced alternative activation due to Cpt1a loss of function was linked to decreased cellular pools of -ketoglutarate, glutamate, and glutathione, diminished commitment of glucose carbon to serine/glycine synthesis, and decreased expression of genes in the Nrf2-oxidative stress response pathway. Consistent with this, reactive oxygen species were increased. Restoration of glutathione pools with N-acetyl cysteine normalized oxidative stress and allowed alternative activation in the face of Cpt1a-deficiency, pointing to a role for FAO in the control of ROS and as being important for alternative activation. In VaviCre x Cpt1afl/fl M(IL-4), glutamine uptake was increased, compensating for the loss of FAO to meet necessary metabolic demands, to allow alternative activation. The data indicate that macrophages are able to regulate glutamine metabolism to compensate for chronic disruption of FAO to meet metabolic needs.

immunology↗

bioRxiv2020

Triacylglycerol synthesis enhances macrophage inflammatory function

Macrophages are integral to most tissues. Foam cells, macrophages with lipid droplets (LDs) which are stores of triacylglycerols (TGs) and cholesterol esters (CEs), are found in various disease states1. LDs can act as energy stores since TG lipolysis releases fatty acids (FAs) for mitochondrial oxidation (FAO), a process that relies on long-chain FA conversion into acylcarnitines by the enzyme Cpt1a2. However, in macrophages, proinflammatory signals result in diminished FAO and increased TG synthesis with LD development3,4. We explored the significance of LDs in cells that do not utilize FAO. We show that macrophages stimulated with lipopolysaccharide (LPS) plus interferon-{gamma} (IFN{gamma}) accumulate TGs in LDs, and long-chain acylcarnitines. In these cells, inhibition of TG synthesis results in diminished LD development, and increased long chain acylcarnitine levels, suggesting that FA fate is balanced between TG and acylcarnitine synthesis. Nevertheless, TG-synthesis is required for inflammatory macrophage function, since its inhibition negatively affects production of proinflammatory IL-1{beta}, IL-6 and PGE2, and phagocytic capacity, and protects against LPS-induced shock in vivo. Failure to make PGE2 is critical for this phenotype, since exogenous PGE2 reverses the anti-inflammatory effects of TG-synthesis inhibition. These findings place LDs in a position of central functional importance in inflammatory macrophages.

immunology↗