Jordan A. Bairos , Uche Njoku , Maria Zafar , May G. Akl , Lei Li , Gunes Parlakgul , Ana Paula Arruda , Scott B. Widenmaier
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As cholesteryl esters localize to and accumulate in lipid droplets more readily than unesterified free cholesterol, we investigated whether cholesterol esterification by sterol O-acyltransferase (SOAT), also known as acyl co-A cholesterol acyltransferase (ACAT), is required for hepatocyte lipid droplet crystal formation.</p></div><div><h3>Method</h3><p>Cholesterol crystals were measured in cholesterol loaded Hep3B hepatocytes, RAW264.7 macrophages, and mouse liver using polarizing light microscopy. We examined the effect of blocking SOAT activity on crystal formation and compared these results to features of cholesterol metabolism and the progression to intracellular crystal deposits.</p></div><div><h3>Results</h3><p>Cholesterol loading of Hep3B cells caused robust levels of lipid droplet localized crystal formation in a dose- and time-dependent manner. Co-treatment with SOAT inhibitors and genetic ablation of <em>SOAT1</em> blocked crystal formation. SOAT inhibitor also blocked crystal formation in low density lipoprotein (LDL) treated Hep3B cells, acetylated LDL treated RAW 264.7 macrophages, and in the liver of mice genetically predisposed to hepatic cholesterol overload and in mice with cholesterol enriched diet-induced MASH.</p></div><div><h3>Conclusion</h3><p>SOAT1-mediated esterification may underlie cholesterol crystals associated with MASH by concentrating it in lipid droplets. These findings imply that inhibiting hepatocyte SOAT1 may be able to alleviate cholesterol associated MASH. Moreover, that either a lipid droplet localized cholesteryl ester hydrolase is required for cholesterol crystal formation, or the crystals are composed of cholesteryl ester.</p></div>","PeriodicalId":8815,"journal":{"name":"Biochimica et biophysica acta. 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引用次数: 0
摘要
目的：胆固醇储存过多会诱导肝细胞脂滴中胆固醇结晶的形成。这种结晶可将代谢功能障碍相关性脂肪性肝炎（MASH）与单纯性脂肪变性区分开来，并可能通过导致细胞损伤引发肝脏炎症而成为其发病机制的基础。胆固醇过量与其在脂滴中结晶的机制尚不清楚。由于胆固醇酯比未酯化的游离胆固醇更容易定位并在脂滴中积累，我们研究了肝细胞脂滴结晶的形成是否需要固醇 O-酰基转移酶（SOAT）（又称酰基共 A 胆固醇酰基转移酶（ACAT））对胆固醇进行酯化：方法：使用偏振光显微镜测量了装载胆固醇的 Hep3B 肝细胞、RAW264.7 巨噬细胞和小鼠肝脏中的胆固醇晶体。我们研究了阻断 SOAT 活性对晶体形成的影响，并将这些结果与胆固醇代谢特征和细胞内晶体沉积的进展进行了比较：结果：胆固醇负载Hep3B细胞可导致大量脂滴局部晶体形成，其形成具有剂量和时间依赖性。同时使用 SOAT 抑制剂和基因消融 SOAT1 可阻止晶体形成。SOAT 抑制剂还能阻止低密度脂蛋白（LDL）处理的 Hep3B 细胞、乙酰化 LDL 处理的 RAW 264.7 巨噬细胞、易患肝脏胆固醇过载的遗传小鼠肝脏以及胆固醇富集饮食诱导的 MASH 小鼠肝脏中晶体的形成：结论：SOAT1 介导的酯化作用可能是胆固醇在脂滴中浓缩而形成与 MASH 相关的胆固醇结晶的基础。这些发现意味着，抑制肝细胞 SOAT1 可减轻与胆固醇相关的 MASH。此外，胆固醇晶体的形成要么需要脂滴定位的胆固醇酯水解酶，要么晶体由胆固醇酯组成。
Sterol O-acyltransferase (SOAT/ACAT) activity is required to form cholesterol crystals in hepatocyte lipid droplets
Objective
Excess cholesterol storage can induce the formation of cholesterol crystals in hepatocyte lipid droplets. Such crystals distinguish metabolic dysfunction associated steatohepatitis (MASH) from simple steatosis and may underlie its pathogenesis by causing cell damage that triggers liver inflammation. The mechanism linking cholesterol excess to its crystallization in lipid droplets is unclear. As cholesteryl esters localize to and accumulate in lipid droplets more readily than unesterified free cholesterol, we investigated whether cholesterol esterification by sterol O-acyltransferase (SOAT), also known as acyl co-A cholesterol acyltransferase (ACAT), is required for hepatocyte lipid droplet crystal formation.
Method
Cholesterol crystals were measured in cholesterol loaded Hep3B hepatocytes, RAW264.7 macrophages, and mouse liver using polarizing light microscopy. We examined the effect of blocking SOAT activity on crystal formation and compared these results to features of cholesterol metabolism and the progression to intracellular crystal deposits.
Results
Cholesterol loading of Hep3B cells caused robust levels of lipid droplet localized crystal formation in a dose- and time-dependent manner. Co-treatment with SOAT inhibitors and genetic ablation of SOAT1 blocked crystal formation. SOAT inhibitor also blocked crystal formation in low density lipoprotein (LDL) treated Hep3B cells, acetylated LDL treated RAW 264.7 macrophages, and in the liver of mice genetically predisposed to hepatic cholesterol overload and in mice with cholesterol enriched diet-induced MASH.
Conclusion
SOAT1-mediated esterification may underlie cholesterol crystals associated with MASH by concentrating it in lipid droplets. These findings imply that inhibiting hepatocyte SOAT1 may be able to alleviate cholesterol associated MASH. Moreover, that either a lipid droplet localized cholesteryl ester hydrolase is required for cholesterol crystal formation, or the crystals are composed of cholesteryl ester.
期刊介绍：
BBA Molecular and Cell Biology of Lipids publishes papers on original research dealing with novel aspects of molecular genetics related to the lipidome, the biosynthesis of lipids, the role of lipids in cells and whole organisms, the regulation of lipid metabolism and function, and lipidomics in all organisms. Manuscripts should significantly advance the understanding of the molecular mechanisms underlying biological processes in which lipids are involved. Papers detailing novel methodology must report significant biochemical, molecular, or functional insight in the area of lipids.
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