FATP4 inactivation in cultured macrophages attenuates M1- and ER stress-induced cytokine release via a metabolic shift towards triacylglycerides

Abstract

Fatty acid transport protein 4 (FATP4) belongs to a family of acyl-CoA synthetases which activate long-chain fatty acids into acyl-CoAs subsequently used in specific metabolic pathways. Patients with FATP4 mutations and Fatp4-null mice show thick desquamating skin and other complications, however, FATP4 role on macrophage functions has not been studied. We here determined whether the levels of macrophage glycerophospholipids, sphingolipids including ceramides, triacylglycerides, and cytokine release could be altered by FATP4 inactivation. Two in vitro experimental systems were studied: FATP4 knockdown in THP-1-derived macrophages undergoing M1 (LPS + IFNγ) or M2 (IL-4) activation and bone marrow-derived macrophages (BMDMs) from macrophage-specific Fatp4-knockout (Fatp4M−/−) mice undergoing tunicamycin (TM)-induced endoplasmic reticulum stress. FATP4-deficient macrophages showed a metabolic shift towards triacylglycerides and were protected from M1- or TM-induced release of pro-inflammatory cytokines and cellular injury. Fatp4M−/− BMDMs showed specificity in attenuating TM-induced activation of inositol-requiring enzyme1α, but not other unfolded protein response pathways. Under basal conditions, FATP4/Fatp4 deficiency decreased the levels of ceramides and induced an up-regulation of mannose receptor CD206 expression. The deficiency led to an attenuation of IL-8 release in THP-1 cells as well as TNF-α and IL-12 release in BMDMs. Thus, FATP4 functions as an acyl-CoA synthetase in macrophages and its inactivation suppresses the release of pro-inflammatory cytokines by shifting fatty acids towards the synthesis of specific lipids.

Macrophages and Metabolic Reprograming in the Tumor Microenvironment

“…However, the relationship between TAM and tumor remains to be clarified: (1) With the development of studies in mononuclear phagocyte lineage, the mechanism of proliferation needs to be reexamined, especially source and maintenance levels of macrophages in human cancers. (2) The integrity of the tumor and the surrounding environment and heterogeneity and subject characteristics, all cells in the environment of in situ research are particularly important in time and space. Different space should be more widely studied to observe the change in the cells during different stages with the overall objective of examining the occurrence of tumor development.…”

“…Increasing evidence has shown that there is connection with energy regulation, immune surveillance and vital organ functions. Cancer changes the relationship with the immune state in various ways, such as the production of certain cytokines ( 2 ), antigen presentation ( 3 ), the immune response ( 4 ), checkpoint expression ( 5 ), and immune exhaustion ( 6 ). The function of immune cells depends on the normal process of nutrient metabolism.…”

Myeloid-specific fatty acid transport protein 4 deficiency induces a sex-dimorphic susceptibility for nonalcoholic steatohepatitis in mice fed a high-fat, high-cholesterol diet

“…Lipids from BMDMs were extracted by using hexane:isopropanol (3:2 vol/vol) containing internal standards according to our published procedure ( 22 ). The profile of 164 phospholipids (PLs) and sphingolipids (SPLs) was obtained by liquid-chromatography mass spectrometry (LC-MS/MS) with running conditions described previously ( 22 ).…”

“…Lipids from BMDMs were extracted by using hexane:isopropanol (3:2 vol/vol) containing internal standards according to our published procedure ( 22 ). The profile of 164 phospholipids (PLs) and sphingolipids (SPLs) was obtained by liquid-chromatography mass spectrometry (LC-MS/MS) with running conditions described previously ( 22 ). Internal standards were phosphatidylcholine (PC)-17:0/17:0, phosphatidylethanolamine (PE)-12:0/12:0, phosphatidylserine (PS)-17:0/17:0, phosphatidylinositol (PI)-17:0/17:0, and Cer-17:0 (Avanti Polar Lipids, Alabaster, AL).…”

“…As adult patients with FATP4 mutations manifest allergies and eosinophilia ( 9 ), we therefore have been investigating the role of FATP4 in myeloid cells including macrophages (MΦ) since FATP4 is expressed in human monocytes ( 19 ), human monocytic leukemia THP-1 cells ( 20 ), and mouse bone-marrow-derived macrophages (BMDMs) ( 21 ). We have shown that BMDMs from male myeloid-specific Fatp4-deficient (Fatp4 M−/− ) mice showed a decrease in Cer containing VLFAs associated with an attenuation of proinflammatory TNFα at basal conditions and during tunicamycin-induced stress ( 22 ). We hypothesized that such alteration in MΦ polarization may render an alteration in metabolic response during NASH, we therefore aimed to investigate whether these Fatp4 M−/− mice could show phenotypic alterations in cultured MΦ and during NASH in vivo.…”