Solar-simulated radiation and heat treatment induced metalloproteinase-1 expression in cultured dermal fibroblasts via distinct pathways: Implications on reduction of sun-associated aging

BackgroundSun exposure is an important environmental factor affecting human beings. Most knowledge regarding solar aging focused on light radiation (photoaging), and little emphasis has been placed on heat, a factor that is also closely associated with sun exposure.ObjectiveThis study was launched to evaluate the effects of simulated solar radiation (SSR) and environmental heat on skin fibroblasts in terms of dermal aging.MethodsCultured human dermal fibroblasts were treated with moderate amount of SSR (200 J/cm2) and heat (+2 °C). The metalloproteinase-1 (MMP-1) expression was used as a surrogate marker for dermal aging and the involved regulatory mechanisms were explored.ResultsBoth treatment conditions did not affect viability but significantly increased the expressions of MMP-1. In parallel, both treatments increased the intracellular levels of reactive oxygen species (ROS), but the increase induced by SSR is much greater than heat. In contrast, transient receptor potential vanilloid 1 (TRPV-1), the sensor of environmental heat, was upregulated by heat but not SSR treatment. Pretreating fibroblasts with antioxidant abrogated the SSR-induced MMP-1 but has limited effect on heat-induced MMP-1. On the other hand, TRPV-1 antagonist pretreatment reduced heat-induced MMP-1 in fibroblasts but not their SSR-treated counterparts.ConclusionBoth SSR and heat induced MMP-1 expression in dermal fibroblasts but through different pathways. As current strategies for reducing sun-related aging focused on filtering of light and use of antioxidants, future strategies design to reduce solar aging should also incorporate heat-induced aging into consideration.