Docosahexaenoic acid modulates oxidative stress-induced apoptosis via PI3K/Akt m-TOR/p70S6K pathways in human RPE cells

Oxidative stress (OS) plays a critical role in the pathogenesis of age-related macular degeneration (AMD), especially by targeting the retinal pigment epithelium (RPE). Dietary habits with high consumption of long-chain omega-3 polyunsaturated fatty acids, including docosahexaenoic acid (DHA), have been reported to prevent the development and progression of AMD. Nevertheless, it is still unclear how DHA affects AMD, although the conversion of DHA into neuroprotective metabolites has been demonstrated to participate in this effect, at least experimentally. The present study aimed to investigate the involvement of the phosphatidylinositol 3-kinase (PI3K)/Akt and mammalian target of rapamycin complex (m-TOR)/p70S6K pathways in human RPE cells in response to OS, and then to assess the effect of DHA in the signaling pathways and protection against RPE cell death. For this purpose, we used ARPE-19 cells exposed to the prooxidant agent, tert-butyl hydroperoxide (t-BHP). We found that exposing cells to t-BHP inhibited the activation of Akt and p70S6K. However, in cells enriched with DHA and then exposed to t-BHP, we demonstrated that Akt and p70S6K remained phosphorylated for a longer time after stress. In addition, DHA reduced the percentage of apoptotic cells induced by OS. This study suggests that: (i) PI3K/Akt and m-TOR/P70S6K pathways are involved in the response of RPE to OS; and that (ii) DHA protected RPE cells from apoptosis triggered by OS by enhancing the phosphorylation of Akt and P70S6K. Practical applicationsOxidative stress plays a critical role in age-related macular degeneration. DHA has been reported to prevent the development and evolution of AMD. An understanding of the PI3K/Akt and m-TOR/P70S6K pathways involved in the response of RPE to OS may contribute to treatments involving the protection of RPE cells from apoptosis through enhancing the phosphorylation of Akt/P70S6K. Docosahexaenoic acid protected RPE cells from apoptosis triggered by oxidative stress by enhancing the phosphorylation of Akt and P70S6K.