PSAT1 is upregulated by METTL3 to attenuate high glucose-induced retinal pigment epithelial cell apoptosis and oxidative stress.

Background: Diabetic retinopathy (DR) is a major ocular complication of diabetes mellitus, and a significant cause of visual impairment and blindness in adults. Phosphoserine aminotransferase 1 (PSAT1) is an enzyme participating in serine synthesis, which might improve insulin signaling and insulin sensitivity. Furthermore, it has been reported that the m6A methylation in mRNA controls gene expression under many physiological and pathological conditions. Nevertheless, the influences of m6A methylation on PSAT1 expression and DR progression at the molecular level have not been reported.

Methods: High-glucose (HG) was used to treat human retinal pigment epithelial cells (ARPE-19) to construct a cell injury model. PSAT1 and Methyltransferase-like 3 (METTL3) levels were detected by real-time quantitative polymerase chain reaction (RT-qPCR). PSAT1, B-cell lymphoma-2 (Bcl-2), Bcl-2 related X protein (Bax), and METTL3 protein levels were examined by western blot assay. Cell viability and apoptosis were detected by Cell Counting Kit-8 (CCK-8) and TUNEL assays. Reactive oxygen species (ROS), malondialdehyde (MDA), and Glutathione peroxidase (GSH-Px) levels were examined using special assay kits. Interaction between METTL3 and PSAT1 was verified using methylated RNA immunoprecipitation (MeRIP) and dual-luciferase reporter assay.

Results: PSAT1 and METTL3 levels were decreased in DR patients and HG-treated ARPE-19 cells. Upregulation of PSAT1 might attenuate HG-induced cell viability inhibition and apoptosis and oxidative stress promotion in ARPE-19 cells. Moreover, PSAT1 was identified as a downstream target of METTL3-mediated m6A modification. METTL3 might improve the stability of PSAT1 mRNA via m6A methylation.

Conclusion: METTL3 might mitigate HG-induced ARPE-19 cell damage partly by regulating the stability of PSAT1 mRNA, providing a promising therapeutic target for DR.