| 1. |
- Robciuc, A., et al.
(författare)
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Hyperosmolarity-induced lipid droplet formation depends on ceramide production by neutral sphingomyelinase 2
- 2012
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Ingår i: Journal of Lipid Research. - : American Society for Biochemistry and Molecular Biology. - 0022-2275 .- 1539-7262. ; 53:11, s. 2286-2295
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Tidskriftsartikel (refereegranskat)abstract
- Hyperosmolarity (HO) imposes a remarkable stress on membranes, especially in tissues in direct contact with the external environment. Our efforts were focused on revealing stress-induced lipid changes that precede the inflammatory cytokine response in human corneal epithelial cells exposed to increasing osmolarity. We used a lipidomic analysis that detected significant and systematic changes in the lipid profile, highly correlated with sodium concentrations in the medium. Ceramides and triglycerides (TGs) were the most-responsive lipid classes, with gradual increases of up to 2- and 3-fold, respectively, when compared with control. The source of ceramide proved to be sphingomyelin hydrolysis, and neutral sphingomyelinase 2 (NSM2) activity showed a 2-fold increase 1 h after HO stress, whereas transcription increased 3-fold. Both TG accumulation and IL-8 secretion were shown to be dependent on ceramide production by specific knock-down of NSM2. In HCE cells, diglyceride acyltransferase 1 was responsible for the TG synthesis, but the enzyme activity had no effect on cytokine secretion. Hence, NSM2 plays a key role in the cellular response to hyperosmolar stress, and its activity regulates both cytokine secretion and lipid droplet formation.
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| 2. |
- Wiedmer, S. K., et al.
(författare)
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Chromatographic lipid profiling of stress-exposed cells
- 2012
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Ingår i: Journal of Separation Science. - : Wiley-VCH Verlagsgesellschaft. - 1615-9306 .- 1615-9314. ; 35:15, s. 1845-1853
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Tidskriftsartikel (refereegranskat)abstract
- Lipidomics is an emerging field of science not only due to its integral part of cell biology and biophysics but also due to the key role of lipids in the modulation of membrane physical properties, signaling, and cell death regulation. The aim of this study was to characterize changes in N-palmitoyl ceramide concentration and in the global lipid profile in macrophages challenged by oxidized low-density lipoprotein and nutrient deprived hepatocytes. For this purpose, a quantitative targeted method based on gas chromatography-mass spectrometry for the determination of total N-palmitoyl ceramide concentrations in the cellular membranes of cells under stress was used. Ultrahigh-performance liquid chromatography-quadrupole-time of flight mass spectrometry was applied for the comprehensive profiling of lipids. In essence, we found that both models of cellular stress caused an increase in N-palmitoyl ceramide levels. In addition, increased levels of other ceramides were observed as well as up- and down-regulation of several other lipid species.
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