Figure 1.

Schematic diagram showing the role of MMPs in photoaging. UV-induced excess intracellular reactive oxygen species (ROS) activates mitogen-activated protein kinases (MAPKs) and nuclear factor-kappa B (NF-κB), culminating in the transcriptional regulation of MMPs, and results in the degradation of collagen and elastin, subsequently leading to photoaging. In addition to collagen and elastin degradation, AP-1 inhibits transforming growth factor beta (TGF-β) signaling, causing a reduction in procollagen synthesis.