Abstract
Upon oxidative stress and aging, Nrf2 (NFE2-related factor2) triggers antioxidant defense genes to defends against homeostatic failure. Using human(h) or rat(r) lens epithelial cells (LECs) and aging human lenses, we showed that a progressive increase in oxidative load during aging was linked to a decline in Prdx6 expression. DNA binding experiments using gel-shift and ChIP assays demonstrated a progressive reduction in Nrf2/ARE binding (−357/−349) of Prdx6 promoter. The promoter (−918) with ARE showed a marked reduction in young vs aged hLECs, which was directly correlated to decreased Nrf2/ARE binding. A Nrf2 activator, Sulforaphane (SFN), augmented Prdx6, catalase and GSTπ expression in dose-dependent fashion, and halted Nrf2 dysregulation of these antioxidants. SFN reinforced Nrf2/DNA binding and increased promoter activities by enhancing expression and facilitating Nrf2 translocalization in nucleus. Conversely, promoter mutated at ARE site did not respond to SFN, validating the SFN-mediated restoration of Nrf2/ARE signaling. Furthermore, SFN rescued cells from UVB-induced toxicity in dose-dependent fashion, which was consistent with SFN’s dose-dependent activation of Nrf2/ARE interaction. Importantly, knockdown of Prdx6 revealed that Prdx6 expression was prerequisite for SFN-mediated cytoprotection. Collectively, our results suggest that loss of Prdx6 caused by dysregulation of ARE/Nrf2 can be attenuated through a SFN, to combat diseases associated with aging.
Highlights
A prominent feature of biological aging is a progressive decline in antioxidant defense mechanisms, which are crucial to protecting cells and tissues from many oxidative, chemical and pathological stresses[1,2,3,4,5,6]
Age-related increased oxidative load in lens epithelial cells (LECs) was linked to progressive decline in Nrf[2], Cat and Prdx[6] expression
Data analysis revealed that lens/hLECs mRNA expression of Prdx[6], Cat and Nrf[2] declined with aging, and this loss was more significant in aged cells (Fig. 1B–D)
Summary
A prominent feature of biological aging is a progressive decline in antioxidant defense mechanisms, which are crucial to protecting cells and tissues from many oxidative, chemical and pathological stresses[1,2,3,4,5,6]. Using eye lens and lens epithelial cells (LECs), one of the best biological systems for study of molecular mechanisms of age-related diseases, we found that an age-associated decline in Prdx[6] expression was linked to the loss of Nrf[2]. This dysregulation of Nrf[2] was reflected in its reduced expression and DNA-binding activity to ARE. We propose that SFN mediates activation of this molecular switch, and that restoration of the Nrf2/Prdx[6] pathway provides a proof of concept that SFN can be considered as a therapeutic chemo-protectant to repair and reverse age-related diseases, such as cataractogenesis
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