A potential role for oxygen in the photodegradation of fibrillin microfibrils by UVB radiation

Exposure to ultraviolet radiation is thought to accelerate skin ageing via the activation and/or the enhanced expression of extracellular matrix (ECM) proteases. Whilst such enzyme-mediated pathways may play a role in photoageing, we have previously demonstrated that key ECM components (fibrillin microfibrils, fibronectin and type I collagen) are differentially degraded by UVB in enzyme-free environments. However, it remains unclear whether this UVB-induced damage occurs directly by photon absorption or indirectly via reactive oxygen species (ROS) intermediates. In this study we have characterised the effects of UVB irradiation in both ambient-oxygen and depleted-oxygen environments on microfibril structure. Aliquots of Cos-1 cell-derived microfibrils were adsorbed to hydrophilic mica substrates either: i) without any exposure to UVB radiation, ii) following exposure to 500mJ/cm2 UVB radiation (TL12; 280-315nm) in ambient-oxygen conditions or iii) after exposure to the same UVB dose in an depleted-oxygen environment (achieved by bubbling with N2 for 10min). Adsorbed microfibrils were subsequently imaged by atomic force microscopy. Relative microfibril flexibility (quantified via the angle between adjacent microfibril beads) was significantly increased (Mann-Whitney U test, p =