Cytoprotective effect of medical-grade honey against oxidative stress in retinal pigment epithelial cells

Abstract

Introduction: Age-related macular degeneration (AMD) is one of the leading causes of blindness. Dysfunction of the retinal pigment epithelium (RPE), attributed to oxidative stress and inflammation, is implicated in AMD. There are currently no curative treatments for AMD, so prevention remains the best strategy. The polyphenols in medical-grade honey constitute a potent antioxidant source and, owing to this property together with their anti-inflammatory and senolytic activity, they have been suggested as a potential agent for the management of AMD.

Objective: To evaluate the cytoprotective effect and antioxidant activity of medical-grade honey on the retinal pigment epithelium under oxidative stress.

Methods: Human retinal pigment epithelial cells (ARPE-19) were assigned to four groups: (1) untreated control, (2) incubated with 500 μmol/L t-BHP for 4 h, (3) incubated with medical-grade honey, and (4) incubated with t-BHP plus medical-grade honey (co-treatment); in addition, a pretreatment scheme with honey prior to t-BHP exposure was evaluated. Cell viability was determined using the alamarBlue assay, along with total ROS content, mitochondrial membrane potential (JC-1), and the mRNA expression levels of Nrf2 and HO-1. Data were expressed as the mean ± standard deviation of three independent experiments performed in triplicate. The normality of the distribution was verified with the Shapiro-Wilk test; comparisons among groups were performed by one-way ANOVA with the Tukey post hoc test. A value of p < 0.05 was considered statistically significant. The analysis was performed in GraphPad Prism 10.

Results: We established a cellular stress model in the ARPE-19 line with 500 μmol/L t-BHP. Treatment with medical-grade honey produced no significant effect on RPE cell death between 6 and 48 h, supporting its safety. In the co-treatment scheme, t-BHP plus medical-grade honey showed a significant decrease in total ROS generation from 4 h at a dose of 0.06 mg/mL. Pretreatment significantly reduced ROS levels at 24 h at doses of 1–2 mg/mL and increased the formation of JC-1 aggregates in ARPE-19 cells, in contrast to the predominance of monomer observed in the t-BHP-exposed group. The relative expression levels of Nrf2 and HO-1 increased, which is associated with the activation of the cytoprotective antioxidant response.

Conclusion: These results suggest that medical-grade honey exerts a cytoprotective effect against oxidative stress by modulating the antioxidant response in the retinal pigment epithelium. Preserving RPE function represents a preventive target against the visual disability associated with AMD and is therefore relevant to the comprehensive care of older adults in the field of visual rehabilitation.