AUTOPHAGY IN HUMAN SKIN FIBROBLASTS 19 improvement in autophagy function may also lead to amelioration in the visible signs of cutaneous aging. Interestingly, after UV irradiation of cells, we also observed a slight reinduction of the autophagosomal response in those cells derived from mature donors. Thus, our data indicate the possibility of restoring autophagosomal function in aged skin. Since a phase shift in the timing of autophagy was also observed, resynchronization as a treatment modality should also be investigated. Future research should include investigation into the downstream effects of UV exposure in skin such as the generation of reactive oxygen species and how they may contribute to the activation of intracellular damage removal. In addition, oxidation-sensitive signaling cascades, such as mitogen-activated protein kinases (MAPK), which can lead to genetic activation of antioxidant response elements, may also be a productive area for future stud- ies and the utilization of fi broblasts from more donors should strengthen our conclusions. In conclusion, we report for the fi rst time that autophagy levels peak at night in young fi broblasts, whereas in aged human skin fi broblasts, there is a reduction in autophagy. We further show the effect that environmental stress has on the expression of autophagic processes, and demonstrate how autophagy may be potentiated under these condi- tions, which emphasize its importance in maintaining healthy skin. Figure 5. UVA irradiation of fi broblasts did not signifi cantly affect LC3B/autophagy levels in young cells. However, UVA signifi cantly increased LC3B/autophagy in mature cells by 27.2% (±5.3% SEM) and phase shifted its peak expression to 1 h.

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