University of Arizona, Department of Pharmacology and Toxicology, Tucson, AZ, USA.
Endocyte, Inc., West Lafayette, IN, USA.
Toxicol Appl Pharmacol. 2019 Apr 1;368:49-54. doi: 10.1016/j.taap.2019.02.009. Epub 2019 Feb 19.
Nonalcoholic steatohepatitis (NASH) afflicts 20-36% of individuals with nonalcoholic fatty liver disease (NAFLD). A lipotoxic hepatic environment, altered innate immune signaling and inflammation are defining features of progression to NASH. Activated resident liver macrophages express folate receptor beta (FR-β) which may be an indicator of progression from steatosis to NASH. The goals of this study were to characterize FR-β protein expression in human NAFLD and rodent models of NASH, and demonstrate liver targeting of an FR-β imaging agent to the liver of a rodent NASH model using FR-β.
Rat liver lysates from methionine choline deficient (MCD) fed rats, high fat diet (HFD) and methionine choline sufficient (MC+) rat controls were analyzed for hepatic FR-β protein. The FR-β-targeted agent, Etarfolatide was injected into MCD and MC + -fed C57BL/6 mice for efficient FastSPECT hepatic imaging. Additionally, FR-β expression across the stages of human NAFLD from normal to NASH was assessed.
FastSPECT images show targeting of Etarfolatide to the liver of mice fed 8 weeks of MCD diet but not control-fed mice. The MCD rat model exhibited significantly increased protein expression of hepatic FR-β in contrast to HFD or normal samples. Similarly human liver samples categorized as NASH Fatty or NASH Not Fatty showed elevated FR-β protein when compared to normal liver. FR-β transcript expression levels were elevated across both NASH Fatty and NASH Not Fatty samples.
The findings in this study indicate that FR-β expression in NASH may be harnessed to target agents directly to the liver.
非酒精性脂肪性肝炎（NASH）影响 20-36%的非酒精性脂肪性肝病（NAFLD）患者。脂毒性肝环境、先天免疫信号改变和炎症是非酒精性脂肪性肝炎进展的特征。激活的固有肝巨噬细胞表达叶酸受体β（FR-β），这可能是从脂肪变性进展为 NASH 的一个指标。本研究的目的是描述人类 NAFLD 和 NASH 啮齿动物模型中 FR-β 蛋白的表达，并使用 FR-β 证明 FR-β 成像剂在 NASH 啮齿动物模型肝脏中的靶向性。
分析了用蛋氨酸胆碱缺乏（MCD）喂养的大鼠、高脂肪饮食（HFD）和蛋氨酸胆碱充足（MC+）大鼠对照的大鼠肝裂解物中的肝 FR-β 蛋白。将 FR-β 靶向剂 Etarfolatide 注射到 MCD 和 MC+喂养的 C57BL/6 小鼠体内，以进行高效的 FastSPECT 肝脏成像。此外，评估了从正常到 NASH 的人类 NAFLD 各个阶段的 FR-β 表达情况。
FastSPECT 图像显示 Etarfolatide 靶向 MCD 喂养 8 周的小鼠肝脏，但不靶向对照喂养的小鼠。与 HFD 或正常样本相比，MCD 大鼠模型中肝 FR-β 蛋白的表达显著增加。同样，与正常肝脏相比，被归类为 NASH 脂肪或 NASH 非脂肪的人类肝脏样本显示 FR-β 蛋白升高。NASH 脂肪和 NASH 非脂肪样本的 FR-β 转录表达水平均升高。
本研究的结果表明，NASH 中的 FR-β 表达可用于直接靶向肝脏的药物。
