Activation of ARE/Nrf2 and inhibition of NFkB are involved in the protective effect of phytonutrients and estradiol in human skin cells under mitochondria-generated oxidative stress

During cell aging, mitochondrial ROS (mtROS) cause mitochondrial DNA mutations, which lead to mitochondrial dysfunction. This causes an increased production of mtROS, creating a vicious cycle and leading to accelerated aging. We used rotenone, a complex I inhibitor, to cause mitochondrial dysfunction in dermal fibroblasts, which resulted in high mitochondrial and cytosolic ROS levels, apoptotic cell death, increased matrix metalloproteinase-1 secretion, and decreased collagen secretion. Pre-treatment with carotenoid-rich tomato extracts, rosemary extract, and estradiol reversed these effects. The aim of the current study was to evaluate the effect of rotenone and phytonutrients and estradiol on mitochondrial respiration and cell senescence and to analyze the mechanisms involved in these effects. Rotenone caused a substantial reduction in mitochondrial respiration and ATP levels and increased the number of senescent cells. These effects were reversed by phytonutrients and estradiol. The enhanced mitochondrial respiration as a result of the phytonutrient and estradiol treatment was associated with increased mitochondrial biogenesis. Rotenone treatment was associated with an increased activity of NFƙB and AP-1 transcription systems, whereas the phytonutrients and estradiol caused an inhibition of these activities and an activation of antioxidant response element (ARE/Nrf2) transcriptional activity. To determine whether the activation of ARE/Nrf2 and inhibition of NFƙB are crucial for cell protection, we inhibited these pathways by the Nrf2 inhibitors ML385 and ochratoxin A and by the NFƙB inhibitors IKK-16 and JSH-23. Inhibition of ARE/Nrf2 markedly reduced the protective effects of the phytonutrients and estradiol by diminishing their potential to reduce mtROS and the ATP level. Inhibition of NFƙB markedly reduced rotenone-induced cell damage, similar to the effects of the phytonutrients and estradiol, suggesting that NFkB inhibition is important for skin cell protection. The presented results indicate that tomato carotenoids, rosemary extract, and estradiol protect dermal fibroblasts from damage caused by mtROS and may thus delay skin cell senescence and improve skin health.