New nature-inspired hybrids activating the Nrf2-HO1 pathway in retinal pigment epithelial cells and their potential use in pathologies featured by oxidative stress

Purpose: Among the earliest factors triggering Age-related Macular Degeneration (AMD) is the degeneration of retinal pigment epithelium (RPE). A primary system used by RPE to neutralize oxidative stress and maintain cellular homeostasis is the nuclear factor E2-related factor 2 (Nrf2) pathway. We aimed to further test some novel Nature-Inspired Hybrids (NIH) endowed with anti-oxidant properties, in order to evaluate their capability to activate Nrf2-pathway and to promote protection in RPE cells. Methods: ARPE-19 cells were exposed to NIH (5μM) for increasing times (from 3 to 48 hours). Dimethyl-fumarate (DMF; 10μM), a well-known Nrf2 activator, was used as a positive control. The Nrf2-pathway activation was evaluated by studying Nrf2 protein nuclear translocation and Heme-Oxygenase 1 (HO-1) expression (mRNA and protein, with real time PCR and Western blotting, respectively). Cell viability of ARPE-19 exposed to the NIH in the presence/absence of AMD-related stressors was evaluated by various techniques (MTT, LDH and PrestoBlue® assay). Results: The NIH are well tolerated by ARPE-19 cells. The NIH presenting in their structure the chemical active group(s) responsible for the Nrf2-pathway activation (catechol group and/or Michael acceptor) induce Nrf2 nuclear translocation, suggesting an interference in Nrf2 protein degradation process. The same NIH upregulate HO-1 expression, although with levels and/or time-courses that vary among molecules, with potential outcomes on the cellular stress response. Conclusion: A positive modulation of Nrf2-pathway by NIH may be protective in RPE cells, encouraging further studies on their potential use in pathologies featured by oxidative stress.