The Department of Clinical Biochemistry and Pharmacology, Faculty of Health Sciences, Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel; The National Institute of Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel.
The National Institute of Biotechnology in the Negev (NIBN), Ben-Gurion University of the Negev, Beer-Sheva 84103, Israel; Department of Life Sciences, Ben-Gurion University of the Negev, Beer-Sheva, Israel.
Biochim Biophys Acta Mol Cell Biol Lipids. 2017 Sep;1862(9):1001-1012. doi: 10.1016/j.bbalip.2017.06.012. Epub 2017 Jun 23.
Obesity promotes the biogenesis of adipose tissue (AT) foam cells (FC), which contribute to AT insulin resistance. Autophagy, an evolutionarily-conserved house-keeping process, was implicated in cellular lipid handling by either feeding and/or degrading lipid-droplets (LDs). We hypothesized that beyond phagocytosis of dead adipocytes, AT-FC biogenesis is supported by the AT microenvironment by regulating autophagy. Non-polarized ("M0") RAW264.7 macrophages exposed to AT conditioned media (AT-CM) exhibited a markedly enhanced LDs biogenesis rate compared to control cells (8.3 Vs 0.3 LDs/cells/h, p<0.005). Autophagic flux was decreased by AT-CM, and fluorescently following autophagosomes over time revealed ~20% decline in new autophagic vesicles' formation rate, and 60-70% decrease in autophagosomal growth rate, without marked alternations in the acidic lysosomal compartment. Suppressing autophagy by either targeting autophagosome formation (pharmacologically, with 3-methyladenine or genetically, with Atg12±Atg7-siRNA), decreased the rate of LD formation induced by oleic acid. Conversely, interfering with late autophago-lysosomal function, either pharmacologically with bafilomycin-A1, chloroquine or leupeptin, enhanced LD formation in macrophages without affecting LD degradation rate. Similarly enhanced LD biogenesis rate was induced by siRNA targeting Lamp-1 or the V-ATPase. Collectively, we propose that secreted products from AT interrupt late autophagosome maturation in macrophages, supporting enhanced LDs biogenesis and AT-FC formation, thereby contributing to AT dysfunction in obesity.
肥胖促进脂肪组织（AT）泡沫细胞（FC）的发生，而这些细胞会导致 AT 胰岛素抵抗。自噬是一种进化上保守的细胞内物质处理过程，它可以通过吞噬和/或降解脂滴（LDs）来参与细胞内脂质处理。我们假设，除了吞噬死亡的脂肪细胞外，AT 微环境还可以通过调节自噬来支持 AT-FC 的发生。与对照细胞相比，未极化（“M0”）RAW264.7 巨噬细胞暴露于 AT 条件培养基（AT-CM）中时，LDs 发生率明显增加（8.3 比 0.3 LDs/细胞/小时，p<0.005）。AT-CM 降低了自噬通量，通过荧光追踪自噬体随时间的变化，发现新的自噬小泡形成率下降了约 20%，自噬体生长率下降了 60-70%，而酸性溶酶体腔没有明显改变。通过靶向自噬体形成（药理学上用 3-甲基腺嘌呤，或遗传学上用 Atg12±Atg7-siRNA）抑制自噬，会降低油酸诱导的 LD 形成率。相反，通过药理学方法用巴弗洛霉素 A1、氯喹或亮抑蛋白酶肽干扰晚期自噬溶酶体功能，会增强巨噬细胞中的 LD 形成，但不会影响 LD 降解率。同样，用 Lamp-1 或 V-ATPase 的 siRNA 靶向也会诱导 LD 生物发生率的增强。综上所述，我们提出 AT 分泌的产物会中断巨噬细胞晚期自噬体的成熟，从而支持增强的 LDs 生物发生和 AT-FC 的形成，导致肥胖时 AT 功能障碍。
