UVA‐activated synthesis of metalloproteinases 1, 3 and 9 is prevented by a broad‐spectrum sunscreen

Abstract Background Specific sunscreens against ultraviolet ( UV ) A and B radiations are essential to prevent matrix degradation and the activation of intracellular signaling pathways involved in photoaging and photocarcinogenesis. Matrix degradation results from UVA ‐induced production of matrix metalloproteinases ( MMP ) and activation of intracellular pathways in fibroblasts and keratinocytes. In particular, in keratinocytes, UVA radiation induces β‐catenin nuclear translocation and stimulates MMP gene transcription. Our study was aimed at assessing the efficacy of a specific broad‐spectrum sunscreen in preventing β‐catenin translocation and MMPs enhanced expression in cultured keratinocytes after UVA irradiation. Methods Sunscreen or the vehicle was spread on quartz sheet. Irradiation of HaCaT cells with 6 J/cm 2 UVA was performed through the sheet, and cells were collected for β‐catenin immunostaining then visualization by confocal microscopy, and quantitative real‐time polymerase chain reaction analysis of MMP ‐1, ‐3 and ‐9 gene expression. Results As shown by immunostaining and confocal microscopy, the sunscreen abrogated UVA ‐induced beta‐catenin translocation to the nucleus, in comparison with control groups. MMP ‐1, ‐3 and ‐9 mRNA expression was enhanced by 7, 7 and 4 folds ( P < 0.0001, P < 0.001 and P < 0.01, respectively) in unprotected UVA ‐irradiated cells compared to the non‐irradiated control. Sunscreen protection of the cells significantly reduced UVA ‐induced expression of MMP ‐1, ‐3 and ‐9 by 83% ( P < 0.01), 80% ( P < 0.01) and 65% ( P < 0.05), respectively. Conclusion This study demonstrated the efficacy of this broad‐spectrum sunscreen in preventing UVA ‐induced effects on the markers of photoaging and photocarcinogenesis in vitro . It was able to protect HaCaT keratinocytes from UVA ‐induced β‐catenin translocation to the nucleus and MMPs expression.