Crocin Protects Against Retinal Ischemia–Reperfusion Injury via Regulating Sirt6-Mediated Nrf2/HO-1 Pathway in Rats

Purpose: To examine if crocin protects retinal ganglion cells (RGCs) from retinal ischemia-reperfusion (RIR) injury by activating the Sirt6-mediated Nrf2/HO-1 signaling pathway. Methods: Primary RGCs were isolated and treated with crocin (8-12 µM) under oxygen and glucose deprivation/reperfusion (OGD/R) conditions, and rats received intraperitoneal crocin (10-50 mg/kg) after RIR induction. Cell viability, apoptosis, endoplasmic reticulum stress (ERS), inflammatory responses, and reactive oxygen species (ROS) levels were assessed using Cell Counting Kit-8 (CCK-8) assays, flow cytometry, 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining, western blotting, and quantitative reverse-transcription PCR (qRT-PCR). Sirt6 and Nrf2 were silenced via siRNA transfection, and the Nrf2 inhibitor ML385 was used in vivo to validate pathway involvement. Results: Crocin significantly improved RGC viability, reduced apoptosis, and attenuated ROS accumulation, ERS (GRP78, p-PERK, CHOP), and pro-inflammatory cytokine expression (TNF-α, IL-1β, IL-6) in OGD/R-treated cells and RIR-injured retinas. Mechanistically, crocin upregulated Sirt6 expression, promoted Nrf2 nuclear translocation, and enhanced HO-1 levels, activating the Sirt6-Nrf2/HO-1 axis. Silencing Sirt6 or Nrf2 abrogated the protective effects of crocin, whereas ML385 reversed crocin-mediated retinal protection in vivo, confirming Nrf2 as a downstream effector of Sirt6. Conclusions: Crocin protects RGCs against RIR injury through the Sirt6-Nrf2/HO-1 pathway, alleviating ERS, inflammation, apoptosis, and oxidative stress. These findings suggest that crocin may be a possible therapeutic agent for retinal ischemic diseases.