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Published on: January 7, 2020
Increased lipid rafts and accelerated lipopolysaccharide-induced tumor necrosis factor-alpha secretion in
Masahiro Koseki1, Ken-Ichi Hirano, Daisaku Masuda
1Department of Metabolic Medicine, Graduate School of Medicine, Osaka University, Suita, Osaka, Japan. koseki@imed2.med.osaka-u.ac.jp
Abstract:
Lipid rafts on the cell surface are believed to be very important as platforms for various cellular functions. The aim of this study was to know whether defective lipid efflux may influence lipid rafts on the cell surface and their related cellular functions. We investigated macrophages with defective lipid efflux from ATP binding cassette transporter A1-deficient (Abca1-KO) mice. Lipid rafts were evaluated by the following two novel probes: a biotinylated and protease (subtilisin Carlsberg)-nicked derivative of theta-toxin and a fluorescein ester of polyethylene glycol-derived cholesterol. Lipid rafts in Abca1-KO macrophages were increased, as demonstrated by both probes. Moreover, activities of nuclear factor kappaB, mRNA and intracellular distribution, and secretion of tumor necrosis factor-alpha (TNF-alpha) were examined after stimulation by lipopolysaccharides (LPSs). LPS-induced responses of the activation of nuclear factor kappaB and TNF-alpha were more prompt and accelerated in the Abca1-KO macrophages compared with wild-type macrophages. Modification of lipid rafts by cyclodextrin and nystatin corrected the abnormal response, suggesting an association between the increased lipid rafts and abnormal TNF-alpha secretion. We report here that Abca1-KO macrophages with defective lipid efflux exhibited increased lipid rafts on the cell surface and accelerated TNF-alpha secretion.
Insights
Defective lipid efflux in macrophages from ATP binding cassette transporter A1-deficient (Abca1-KO) mice leads to increased lipid rafts. This results in accelerated tumor necrosis factor-alpha (TNF-alpha) secretion upon lipopolysaccharide (LPS) stimulation.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Lipid rafts are crucial cell surface platforms regulating various cellular functions.
- Defective lipid efflux, particularly via ATP binding cassette transporter A1 (Abca1), may impact cellular processes.
- Understanding the role of lipid rafts in macrophages with impaired lipid efflux is essential.
Purpose of the Study:
- To investigate the influence of defective lipid efflux on cell surface lipid rafts.
- To determine the functional consequences of altered lipid rafts on macrophage responses.
- To examine the relationship between lipid rafts and tumor necrosis factor-alpha (TNF-alpha) secretion.
Main Methods:
- Utilized ATP binding cassette transporter A1-deficient (Abca1-KO) mice macrophages to model defective lipid efflux.
- Employed novel probes, including a modified theta-toxin and a cholesterol derivative, to evaluate lipid rafts.
- Assessed lipopolysaccharide (LPS)-induced activation of nuclear factor kappaB (NF-κB) and TNF-alpha production and secretion.
Main Results:
- Abca1-KO macrophages exhibited significantly increased lipid rafts compared to wild-type controls.
- LPS stimulation resulted in more rapid activation of NF-κB and accelerated TNF-alpha secretion in Abca1-KO macrophages.
- Modulating lipid rafts with cyclodextrin and nystatin normalized the abnormal TNF-alpha secretion, confirming the association.
Conclusions:
- Defective lipid efflux in Abca1-KO macrophages is associated with an increase in cell surface lipid rafts.
- Increased lipid rafts contribute to accelerated TNF-alpha secretion in response to inflammatory stimuli.
- Targeting lipid rafts may offer therapeutic potential for inflammatory conditions associated with lipid metabolism defects.
