ETHNOPHARMACOLOGICAL RELEVANCE: Diabetic retinopathy (DR) is a severe microvascular complication of diabetes that is closely associated with hyperglycemia-induced mitochondrial dysfunction. Lishui Xiaozhong granules (LSXZ) are an empirical traditional Chinese medicine used to treat DR. However, its precise molecular targets and underlying mechanisms remain unclear.
AIM OF THE STUDY: This study investigated whether LSXZ protects retinal cells under hyperglycemic conditions by regulating PINK1/Parkin-mediated mitophagy.
MATERIALS AND METHODS: Human Müller cells were exposed to high glucose (HG; 50 mM) to establish an in vitro model and treated with LSXZ-containing serum and the mitophagy inhibitor cyclosporin A (CsA). Genetic knockdown via siRNA was performed to validate the necessity of the PINK1/Parkin pathway. A zebrafish DR model was induced using an HG, high-fat diet, and treated with different LSXZ concentrations. Cell viability, mitophagy, apoptosis, ferroptosis, mitochondrial function, and ultrastructural changes were assessed using CCK-8 assays, western blotting, qPCR, immunofluorescence, and transmission electron microscopy. Retinal histopathology, vascular diameter, inflammatory cell activation, oxidative stress, and gene expression profiles in zebrafish were assessed using hematoxylin-eosin staining, fluorescence microscopy, and transcriptomic sequencing.
RESULTS: LSXZ treatment reversed pathological changes by restoring PINK1/Parkin signaling, elevating LC3-II/LC3-I ratio, enhancing mitochondrial function, and suppressing apoptosis and ferroptosis-effects partially attenuated by CsA. Mitophagosomes increased after LSXZ treatment. Crucially, specific knockdown of PINK1 or Parkin significantly abolished LSXZ-induced cytoprotection, reversing the regulation of apoptotic/ferroptotic markers and mitochondrial recovery, thereby confirming the pivotal necessity of this pathway. In zebrafish, LSXZ alleviated hyperglycemia-induced retinal inner nuclear layer thinning, vascular dilation, excessive macrophage/astrocyte activation, and oxidative stress. These protective effects were mediated through upregulation of the TOMM40/TOMM20-PINK1/Parkin-MFN2 axis.
