BioProject

When macrophages are activated by sensing bacterial lipopolysaccharides (LPS), they greatly increase their motility, mRNA synthesis and protein production. More...

When macrophages are activated by sensing bacterial lipopolysaccharides (LPS), they greatly increase their motility, mRNA synthesis and protein production. Most of the ATP needed for these responses is derived from the uptake and catabolism of glucose, a relatively inefficient ATP source. Although the stimulated cells also increase their uptake of free fatty acids, they store a large fraction as triglycerides (TAG). We report here that both Toll-like receptor 4 (TLR4) and TLR2 agonists stimulate prolonged TAG retention by primary murine and human macrophages. Agonist-induced TAG storage lasted at least 72-96 hrs in vitro and was associated with increases in fatty acid (FA) uptake, FA esterification, and FA incorporation into TAG; FA oxidation decreased. The results of expression and inhibitor studies support a prominent role for increases in long chain acyl CoA synthase 1 (ACSL1) and diacylglycerol acyltransferase-2 (DGAT2) during the sustained response to TLR2/4 activation; decreases in adipose triglyceride lipase (ATGL, Pnpla2) and monoacylglycerol lipase (MgII) may also contribute. Stimulated murine macrophages that retained TAG carried out phagocytosis more effectively and were protected from saturated fatty acid-induced cell death (lipotoxicity). TLR agonist-induced TAG retention in macrophages is thus an active, sustained process that may have important adaptive functions. It may also contribute to the persistence of lipid-laden macrophages in infected tissues, host susceptibility to some microbial pathogens, and the pathogenesis of atherosclerosis. Overall design: RNA from macrophage loaded with Fatty Acids, stimulated with bacterial lipopolysaccharides (LPS), or both compared to untreated controls (FA, LPS, FA+LPS, untreated). Replicates from 4 independent experiments. Less...