Classical Activation of Macrophages Leads to Lipid Droplet Formation Without de novo Fatty Acid Synthesis

Rosas-Ballina, Mauricio; Guan, Xue Li; Schmidt, Alexander; Bumann, Dirk

doi:10.3389/fimmu.2020.00131

Cited by 48 publications

(28 citation statements)

References 67 publications

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“…This was an interesting finding as triacylglycerol represents an energy storage and might thus play an important role in the metabolism of DCs. Our finding is consistent with previously shown data that triacylglycerol and lipid droplets are accumulating after activation of myeloid cells, indicating an influence on the metabolism of DCs after TLR stimulation (116)(117)(118). Overall, lipids accomplish complex functions in DCs, depending on the maturation state of the cell.…”

Section: Discussionsupporting

confidence: 92%

Maturation of Monocyte-Derived DCs Leads to Increased Cellular Stiffness, Higher Membrane Fluidity, and Changed Lipid Composition

et al. 2020

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Dendritic cells (DCs) are professional antigen-presenting cells of the immune system. Upon sensing pathogenic material in their environment, DCs start to mature, which includes cellular processes, such as antigen uptake, processing and presentation, as well as upregulation of costimulatory molecules and cytokine secretion. During maturation, DCs detach from peripheral tissues, migrate to the nearest lymph node, and find their way into the correct position in the net of the lymph node microenvironment to meet and interact with the respective T cells. We hypothesize that the maturation of DCs is well prepared and optimized leading to processes that alter various cellular characteristics from mechanics and metabolism to membrane properties. Here, we investigated the mechanical properties of monocyte-derived dendritic cells (moDCs) using real-time deformability cytometry to measure cytoskeletal changes and found that mature moDCs were stiffer compared to immature moDCs. These cellular changes likely play an important role in the processes of cell migration and T cell activation. As lipids constitute the building blocks of the plasma membrane, which, during maturation, need to adapt to the environment for migration and DC-T cell interaction, we performed an unbiased high-throughput lipidomics screening to identify the lipidome of moDCs. These analyses revealed that the overall lipid composition was significantly changed during moDC maturation, even implying an increase of storage lipids and differences of the relative abundance of membrane lipids upon maturation. Further, metadata analyses demonstrated that lipid changes were associated with the serum low-density lipoprotein (LDL) and cholesterol levels in the blood of the donors. Finally, using lipid packing imaging we found that the membrane of mature moDCs revealed a higher fluidity compared to immature moDCs. This comprehensive and quantitative characterization of maturation associated changes in moDCs sets the stage for improving their use in clinical application.

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Section: Discussionsupporting

confidence: 92%

Maturation of Monocyte-Derived DCs Leads to Increased Cellular Stiffness, Higher Membrane Fluidity, and Changed Lipid Composition

et al. 2020

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“…The macrophage cell is finally overlaid with lipid droplets which are indicated as black dots and the fluorescence image of the AuNPs are marked in red to characterize the in vitro biodistribution of the AuNP-loaded macrophage cell. Figure 2b is a time-lapsed image for the AuNP-loaded macrophages indicating cellular uptake and release of AuNPs in the macrophages during continual exposure to AuNP for 24 h. The emergence of lipid droplets explains the morphology activation of macrophage to phagocyte [22]. AuNP and lipid droplet detections confirm the activation and AuNP internalization of macrophages.…”

Section: Characterization Of Aunp-loaded Macrophagementioning

confidence: 80%

Intercellular Bioimaging and Biodistribution of Gold Nanoparticle-Loaded Macrophages for Targeted Drug Delivery

et al. 2020

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In order to effectively apply nanoparticles to clinical use, macrophages have been used as vehicles to deliver genes, drugs or nanomaterials into tumors. In this study, the effectiveness of macrophage as a drug delivery system was validated by biodistribution imaging modalities at intercellular and ex vivo levels. We focused on biodistribution imaging, namely, the characterization of the gold nanoparticle-loaded macrophages using intracellular holotomography and target delivery efficiency analysis using ex vivo fluorescence imaging techniques. In more detail, gold nanoparticles (AuNPs) were prepared with trisodium citrate method and loaded into macrophage cells (RAW 264.7). First, AuNPs loading into macrophages was confirmed using the conventional ultraviolet-visible (UV-VIS) spectroscopy and inductively coupled plasma-mass spectrometry (ICP-MS). Then, the holotomographic imaging was employed to characterize the intracellular biodistribution of the AuNPs-loaded macrophages. The efficacy of target delivery of the well AuNPs uptake macrophages was studied in a mouse model, established via lipopolysaccharide (LPS)-induced inflammation. The fluorescent images and the ex vivo ICP-MS evaluated the delivery efficiency of the AuNPs-loaded macrophages. Results revealed that the holotomographic imaging techniques can be promising modalities to understand intracellular biodistribution and ex vivo fluorescence imaging can be useful to validate the target delivery efficacy of the AuNPs-loaded macrophages.

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“…While we have not yet examined whether ADJaided LBs directly affect antigen processing, our lipidomic studies highlight the unique composition of lipids within ADJ-treated DCs, which shows accumulations of 18:2 and 18:3 acyl tails and ceramides, presumably due to uptake of ADJ itself. Because ADJ upregulates CD36 expression in DCs, it is conceivable that ADJ enhances the uptake of external lipid without de novo fatty acid synthesis derived from glucose (Rosas-Ballina et al, 2020). In line with low metabolic profiles in ADJ-stimulated DCs, the formation of intracellular LBs using external fatty acids could be a more efficient pathway to store intracellular lipids since it requires minimal energy and overall metabolic activities.…”

Section: How Does Adj Enhance DC Cross-presentation and Potentiate Cdmentioning

confidence: 99%

Carbomer-based Nano-Emulsion Adjuvant Enhances Dendritic Cell Cross-presentation via Lipid Body Formation Independent of Glycolysis

Suresh

Lee

Kingstad-Bakke

et al. 2020

Preprint

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ADJ induces inflammasome activation in DCs, but deficiency for NLRP3, ASC or caspase 1 did not affect ADJ-mediated cross-presentationNext, we examined the effects of ADJ on the expression profiles of cytokines, chemokines and canonical cell surface markers of DC activation. Compared to untreated DCs, ADJ-treated DCs showed statistically significant, yet modest increases in expression of CD40, CD80, and CD86; no significant differences in expression were observed for MHC-I, MHC-II, or CCR7 (Fig. 1C).ADJ-treated DCs produced higher levels of IL-12 (p70), TNF-, IL-1, CCL3, CCL4, CXCL1, and RANTES, as compared to untreated DCs; no significant differences in expression were observed for IL-6, IL-10, and IFN- (Fig. 1D). Particularly, ADJ-stimulated DCs also produced significantly elevated levels of IL-1 and IL-18 (Fig. 1D), which is suggestive of inflammasome activation. Since inflammasome activation has been implicated in modulation of antigen presentation by DCs (Sokolovska et al., 2013, Li et al., 2019, we performed B3Z assays using DCs deficient in NLRP3, ASC, or caspase 1 to interrogate whether inflammasome activation is required for ADJ-induced cross-presentation in BMDCs. Surprisingly, loss of NLRP3, ASC or caspase 1 activity did not affect ADJ-induced cross-presentation by DCs, in vitro (Fig. 1E). To validate whether caspase 1 is required for cross-presentation in vivo, we immunized cohorts of wild type (WT) and caspase 1-deficient mice with ADJ+OVA, and quantified OVA SIINFEKLspecific CD8 T cells in spleens using MHC I tetramers at day 8 after immunization. Consistent with our results from B3Z assays, caspase 1 deficiency did not significantly affect the activation of SIINFEKL-specific CD8 T cells in spleens (Fig. 1F), suggesting that caspase 1 is not essential for ADJ-driven cross-presentation to CD8 T cells in vivo.

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Classical Activation of Macrophages Leads to Lipid Droplet Formation Without de novo Fatty Acid Synthesis

Cited by 48 publications

References 67 publications

Maturation of Monocyte-Derived DCs Leads to Increased Cellular Stiffness, Higher Membrane Fluidity, and Changed Lipid Composition

Maturation of Monocyte-Derived DCs Leads to Increased Cellular Stiffness, Higher Membrane Fluidity, and Changed Lipid Composition

Intercellular Bioimaging and Biodistribution of Gold Nanoparticle-Loaded Macrophages for Targeted Drug Delivery

Carbomer-based Nano-Emulsion Adjuvant Enhances Dendritic Cell Cross-presentation via Lipid Body Formation Independent of Glycolysis

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