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

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 b-catenin nuclear translocation and stimulates MMP gene transcription. Our study was aimed at assessing the efficacy of a specific broad-spectrum sunscreen in preventing b-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 b-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 b-catenin translocation to the nucleus and MMPs expression.