Schepens Eye Research Institute of Mass, Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, MA 02134, USA.
Int J Mol Sci. 2021 Apr 29;22(9):4701. doi: 10.3390/ijms22094701.
PGC-1α, a key orchestrator of mitochondrial metabolism, plays a crucial role in governing the energetically demanding needs of retinal pigment epithelial cells (RPE). We previously showed that silencing induced RPE to undergo an epithelial-mesenchymal-transition (EMT). Here, we show that induction of EMT in RPE using transforming growth factor-beta 2 (TGFβ2) suppressed expression. Correspondingly, TGFβ2 induced defects in mitochondrial network integrity with increased sphericity and fragmentation. TGFβ2 reduced expression of genes regulating mitochondrial dynamics, reduced citrate synthase activity and intracellular ATP content. High-resolution respirometry showed that TGFβ2 reduced mitochondrial OXPHOS levels consistent with reduced expression of . The reduced mitochondrial respiration was associated with a compensatory increase in glycolytic reserve, glucose uptake and gene expression of glycolytic enzymes (, , ). Treatment with ZLN005, a selective small molecule activator of PGC-1α, blocked TGFβ2-induced upregulation of mesenchymal genes (, , , ) and TGFβ2-induced migration using the scratch wound assay. Our data show that EMT is accompanied by mitochondrial dysfunction and a metabolic shift towards reduced OXPHOS and increased glycolysis that may be driven by PGC-1α suppression. ZLN005 effectively blocks EMT in RPE and thus serves as a novel therapeutic avenue for treatment of subretinal fibrosis.
PGC-1α 是线粒体代谢的关键调节因子，在调节视网膜色素上皮细胞（RPE）的高能量需求方面起着至关重要的作用。我们之前的研究表明，沉默 可诱导 RPE 发生上皮间质转化（EMT）。在这里，我们发现使用转化生长因子-β 2（TGFβ2）诱导 RPE 中的 EMT 会抑制 表达。相应地，TGFβ2 诱导的线粒体网络完整性缺陷表现为球形度增加和碎片化。TGFβ2 降低了调节线粒体动态的基因的表达，降低了柠檬酸合酶活性和细胞内 ATP 含量。高分辨率呼吸测定显示，TGFβ2 降低了线粒体 OXPHOS 水平，与 的表达减少一致。减少的线粒体呼吸与糖酵解储备、葡萄糖摄取和糖酵解酶的基因表达（ 、 、 ）的代偿性增加相关。用 ZLN005（PGC-1α 的选择性小分子激活剂）治疗可阻断 TGFβ2 诱导的间充质基因（ 、 、 、 ）上调和划痕实验中 TGFβ2 诱导的迁移。我们的数据表明，EMT 伴随着线粒体功能障碍和代谢向减少的 OXPHOS 和增加的糖酵解转变，这可能是由 PGC-1α 抑制驱动的。ZLN005 可有效阻断 RPE 中的 EMT，因此是治疗视网膜下纤维化的新的治疗途径。
