College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China.
Key Laboratory of Agricultural Animal Genetics, Breeding, and Reproduction, Ministry of Education, College of Animal Science and Technology and College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
Life Sci. 2022 May 1;296:120438. doi: 10.1016/j.lfs.2022.120438. Epub 2022 Feb 25.
Nonalcoholic fatty liver disease (NAFLD) has become a global epidemic, but its pathogenesis is unclear. STEAP4, a member of six transmembrane protein family, integrates inflammatory and metabolic responses. Our present aim is to explore the roles of STEAP4 in maintaining cellular homeostasis and improving high-fat-diet (HFD)-caused oxidative stress in hepatocytes.
NAFLD model was established by HFD-feeding mice. The effects of over-nutrition on liver were detected by serum biochemical analysis and bulk RNA-seq. The levels of gene expression were measured by QPCR and Western Blot. Immunofluorescent staining was applied to determine the localization of STEAP4. AMPK agonist was employed to investigate the link between STEAP4 and AMPK pathway.
Sus scrofa STEAP4 (sSTEAP4) relieved oxidative stress and rescued the viability of hepatocytes. sSTEAP4 increased AKT phosphorylation and SOD2 level in hepatocytes, whether or not treated with HO, suggesting sSTEAP4 has regulatory effects on insulin signaling and antioxidant pathways. However, sSTEAP4 inhibited AMPK phosphorylation and Beclin1/LC3 expression under HO-deficiency situation, but the results were conversed with HO stimulation. The cellular ER stress was aggravated with the increased energy during oxidative stress, indicating that sSTEAP4 might regulate the energetic communication between ER and mitochondria by intervening mitochondrial energy production. In addition, sSTEAP4 was demonstrated to localize in the membranes of plasma and ER in HepG2 hepatocytes.
Our results reveal that sSTEAP4 based on the needs of cell itself to improve hepatic oxidative stress and HFD-caused NAFLD, which might provide a new therapeutic scheme for NAFLD.
非酒精性脂肪性肝病（NAFLD）已成为全球性流行病，但其发病机制尚不清楚。STEAP4 是六跨膜蛋白家族的成员，整合了炎症和代谢反应。我们目前的目的是探讨 STEAP4 在维持细胞内稳态和改善高脂肪饮食（HFD）引起的肝细胞氧化应激中的作用。
通过 HFD 喂养小鼠建立 NAFLD 模型。通过血清生化分析和 bulk RNA-seq 检测过度营养对肝脏的影响。通过 QPCR 和 Western Blot 测量基因表达水平。免疫荧光染色用于确定 STEAP4 的定位。使用 AMPK 激动剂研究 STEAP4 与 AMPK 通路之间的联系。
Sus scrofa STEAP4（sSTEAP4）缓解了氧化应激并挽救了肝细胞的活力。sSTEAP4 增加了肝细胞中 AKT 的磷酸化和 SOD2 水平，无论是否用 HO 处理，表明 sSTEAP4 对胰岛素信号和抗氧化途径具有调节作用。然而，在 HO 缺乏的情况下，sSTEAP4 抑制了 AMPK 的磷酸化和 Beclin1/LC3 的表达，但在 HO 刺激下结果相反。在氧化应激过程中，由于能量增加，细胞内质网应激加剧，表明 sSTEAP4 可能通过干预线粒体能量产生来调节内质网和线粒体之间的能量通讯。此外，在 HepG2 肝细胞中，sSTEAP4 被证明定位于质膜和内质网膜上。
我们的结果表明，sSTEAP4 根据细胞自身的需要来改善肝氧化应激和 HFD 引起的 NAFLD，这可能为 NAFLD 提供新的治疗方案。
