ABSTRACT
BACKGROUND: The heat produced by exposure to infrared radiation (IR) has been demonstrated to modulate the expression of tropoelastin and fibrillin-1, the two main components of elastic fibers in human skin in vivo. However, the effect of IR range of radiations on tropoelastin and fibrillin-1 expression has not been thoroughly investigated. METHODS: Eighteen volunteers were enrolled in this study involving three trials. Time-dependent, dose-dependent and cumulative effects of IR were investigated, respectively. Tropoelastin and fibrillin-1 expression was measured by immunohistochemical staining on skin biopsy samples from volunteers. In addition, we also measured tropoelastin mRNA expression by a real-time RT-polymerase chain reaction. RESULTS: A single dose of IR (2 minimal heating dose) induced a time-dependent increase in tropoelastin expression at the protein level. An inverse correlation was found between the alterations of tropoelastin and fibrillin-1. Furthermore, IR was found to increase tropoelastin expression in a dose-dependent manner at both the mRNA and the protein level. Repeated low doses of IR increased tropoelastin expression and decreased fibrillin-1 expression at the protein level in the dermis. Meanwhile, the number of both fibers along the dermal-epidermal junction was increased. CONCLUSION: IR can alter the expression of tropoelastin and fibrillin-1, which may result in abnormal elastic fiber formation.
