The UVA component of solar simulated radiation differentially degrades dermal proteins associated with photoageing

Chronic exposure to ultraviolet (UV) radiation causes remodelling of the dermal extracellular matrix (ECM) leading to photoageing. This remodelling may be driven by cell-derived proteases and/or photochemical mechanisms. We have previously shown that the amino acid composition of dermal ECM proteins correlates with their relative susceptibility to degradation by broadband UVB radiation. UV-chromophore-rich proteins such as fibrillin and fibronectin were preferentially degraded but not chromophore-poor collagen I and tropoelastin. In this study, we determine whether physiological doses of the UVA (315-400nm) component of solar radiation are capable of differentially degrading these ECM proteins. Suspensions of bovine collagen I and fibronectin, recombinant tropoelastin and human dermal fibroblast-derived fibrillin microfibrils were exposed to full spectrum Solar Simulated Radiation (SSR; 290-400nm: 0.8, 7.7 and 15.4J/cm2 and UVA (315-400nm): 1, 10 and 20J/cm2. The effects of SSR and UVA exposure on molecular structure were determined by reducing SDS-PAGE (collagen I, tropoelastin and fibronectin) and atomic force microscopy (fibrillin). Neither SSR nor UVA radiation affected the electrophoretic mobility of chromophore-poor collagen I and tropoelastin. However, both UV spectra induced dose-dependent aggregation of fibronectin (SSR: r2 0.99, UVA: r2 0.98). Similarly, both SSR and UVA radiation also significantly reduced the bead-to-bead distance of fibrillin microfibrils (SSR: mean±SD, 56.6±9.7nm [0J/cm2], 53.2±10.3nm [15.4J/cm2], p