Neuroprotective Effects of the SIRT3/AMPK Axis in Experimental Glaucoma

Glaucoma is a major cause of irreversible blindness, characterized by the progressive degeneration of retinal ganglion cells (RGCs), with oxidative stress and apoptosis playing central roles in its pathogenesis. Sirtuin 3 (SIRT3) has demonstrated antioxidant and anti-apoptotic effects in various neurodegenerative diseases; however, its precise role in glaucoma remains unclear. This study aimed to elucidate the neuroprotective function and mechanistic basis of the SIRT3/AMP-activated protein kinase (AMPK) axis in glaucoma.

A rat model of chronic ocular hypertension (COH) was generated using cross-linked hydrogel injection, while an N-methyl-D-aspartate (NMDA)-induced RGC injury model was developed in vitro. SIRT3 overexpression was achieved using adeno-associated virus (AAV) transfection, either alone or combined with the AMPK inhibitor Compound C. Functional and molecular analyses were performed, including intraocular pressure (IOP) measurement, hematoxylin-eosin (H&E) staining, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, immunofluorescence, Cell Counting Kit-8 (CCK-8) cell viability assay, flow cytometry, Quantitative real-time PCR (qRT-PCR), and western blotting.

In the COH model, both SIRT3 expression and the p-AMPK/AMPK ratio were significantly reduced at weeks 2, 4, and 6 (p < 0.05). Overexpression of SIRT3 lowered IOP, preserved retinal thickness, and decreased the number of TUNEL-positive cells (p < 0.001), while Compound C partially reversed these effects (p < 0.05). In addition, SIRT3 overexpression markedly educed reactive oxygen species (ROS) accumulation (p < 0.001) and restored the p-AMPK/AMPK ratio (p < 0.001), both of which were partially inhibited by Compound C. In NMDA-induced RGCs, SIRT3 overexpression significantly increased SIRT3 mRNA levels (p < 0.01), enhanced cell viability (p < 0.001), and suppressed apoptosis (p < 0.001), with these effects attenuated by Compound C (p < 0.01). The reduction of ROS and activation of AMPK by SIRT3 in this model were also partly reversed by AMPK inhibition (p < 0.01).

This study provides the first comprehensive in vivo and in vitro evidence in glaucoma models that SIRT3 confers neuroprotection in experimental glaucoma, primarily through activation of the AMPK signaling pathway. These findings identify the SIRT3/AMPK axis as a novel mechanistic target and suggest a promising therapeutic strategy for IOP-independent neuroprotection in glaucoma.