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.