Complexity of fatty acid distribution inside human macrophages on single cell level using Raman micro-spectroscopy
Complexity of fatty acid distribution inside human macrophages on single cell level using Raman micro-spectroscopy
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DOI：
10.1007/s00216-014-7927-0
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发表时间：
2014-11-01
影响因子：
4.3
通讯作者：
Popp, Juergen
中科院分区：
文献类型：
--
作者：
Stiebing, Clara;Matthaeus, Christian;Popp, Juergen
巨噬细胞是参与非特异性免疫防御的吞噬细胞。巨噬细胞的脂质摄取和储存行为在血管壁内动脉粥样硬化病变的发展中也发挥着关键作用。外源性脂质（例如脂肪酸）在血流中的分配决定了巨噬细胞内脂质的积累和数量。如果过度暴露，巨噬细胞会因细胞质中存在大量脂滴而转变为泡沫细胞。由于显微成像与光谱信息的结合，拉曼显微光谱是研究单细胞的强大工具。由于空间分辨率受衍射极限限制，因此可以可视化巨噬细胞内的脂滴。通过用氘对脂肪酸进行稳定同位素标记，可以研究外源提供的脂肪酸的吸收和储存。在这项研究中，我们展示了与氘代花生四烯酸一起孵育的单个 THP-1 巨噬细胞的时间依赖性拉曼光谱成像结果。多不饱和脂肪酸作为二十烷酸的前体，在细胞信号传导途径中发挥着重要作用。我们发现花生四烯酸储存在脂滴中，但泡沫细胞的形成不像其他脂肪酸那么明显。脂滴中的储存效率低于用氘化棕榈酸孵育的细胞中的储存效率。我们用气相色谱法验证了我们的结果，并获得了处理过的巨噬细胞中花生四烯酸及其代谢物的相对含量的信息。这些分析还提供了证据，表明大量的细胞内花生四烯酸被延长为肾上腺酸，但没有进一步代谢。氘代花生四烯酸和氘代棕榈酸的共同补充导致单细胞内脂滴的非均质存储模式。
Macrophages are phagocytic cells which are involved in the non-specific immune defense. Lipid uptake and storage behavior of macrophages also play a key role in the development of atherosclerotic lesions within walls of blood vessels. The allocation of exogenous lipids such as fatty acids in the blood stream dictates the accumulation and quantity of lipids within macrophages. In case of an overexposure, macrophages transform into foam cells because of the large amount of lipid droplets in the cytoplasm. Raman micro-spectroscopy is a powerful tool for studying single cells due to the combination of microscopic imaging with spectral information. With a spatial resolution restricted by the diffraction limit, it is possible to visualize lipid droplets within macrophages. With stable isotopic labeling of fatty acids with deuterium, the uptake and storage of exogenously provided fatty acids can be investigated. In this study, we present the results of time-dependent Raman spectroscopic imaging of single THP-1 macrophages incubated with deuterated arachidonic acid. The polyunsaturated fatty acid plays an important role in the cellular signaling pathway as being the precursor of icosanoids. We show that arachidonic acid is stored in lipid droplets but foam cell formation is less pronounced as with other fatty acids. The storage efficiency in lipid droplets is lower than in cells incubated with deuterated palmitic acid. We validate our results with gas chromatography and gain information on the relative content of arachidonic acid and its metabolites in treated macrophages. These analyses also provide evidence that significant amounts of the intracellular arachidonic acid is elongated to adrenic acid but is not metabolized any further. The co-supplementation of deuterated arachidonic acid and deuterated palmitic acid leads to a non-homogenous storage pattern in lipid droplets within single cells.