The Role of Bystander Effect in Ultraviolet A Induced Photoaging

Abstract

Background: Exposure to sunlight, mainly UVA, leads to typical changes in the features of the skin known as photoaging. UVA irradiation induces the expression of proteases that are responsible for the degradation of the extracellular matrix proteins to results in photoaging; it also downregulates the expression of proteins that are needed for the skin structure. Since, it is known that cells in the neighborhood of irradiated cells, but not directly exposed to it, often manifest responses like their irradiated counterparts, it is important to evaluate if these bystander cells too, can contribute to photoaging.Methods and Results: UVA induced cell cycle arrest have been associated with photoaging, from ow cytometry analysis we found that there was an induction of cell cycle arrest at the G 1 /S phase in the UVAbystander cells. The expression of some key photoaging marker genes likes, matrix metalloproteinases (MMP-1, MMP-3, MMP-9), cyclooxygenase-2 (COX-2), collagen1 and elastin were assessed from qRT-PCR.Upregulation of MMP-1 and COX-2, downregulation of collagen1 and elastin, along with suppression below normal expression for MMP-3 and MMP-9 was observed in the UVA-bystander A375 cells. Conclusion: Our ndings for the rst time suggest the contribution of UVA-bystander cells to the process of photoaging. HighlightsG 1 /S cell cycle arrest was observed in UVA-bystander A375 cells.The expression of MMP-1 & COX-2 was upregulated in UVA-bystander A375 cells.Collagen 1 & elastin expression was also downregulated in these bystander cells.Expression of MMP-3 & -9 in the UVA-bystander cells lower than that in control cells.