Increase of collagen synthesis by obovatol through stimulation of the TGF-β signaling and inhibition of matrix metalloproteinase in UVB-irradiated human fibroblast

Background: Alterations of the extracellular matrix (ECM) is critical in the photo and age-damaged skin. Thus any compounds keep ECM can protected from photo and aged-damaged skin. ECM is predominantly composed of type I and type III collagens in the dermis. Transforming growth factor (TGF-beta)s play important roles in cellular biosynthesis of extracellular matrix. Activator protein 1 (AP-1) and Smad are significant factors that mediate TGF-beta. Objective: We have investigated increasing effects of obovatol, a biphenolic compound isolated from leaves of Magnolia obovata on the collagen synthesis through stimulation of the TGF-beta signaling and inhibition of matrix metalloproteinase, thereby protect against from UV damages via maintain of collagen in the UVB irradiated human fibroblast cells. Methods: The fibroblasts were pretreated with obovatol for 24 h and then the cells were irradiated with UVB. UVB-exposed cells were further cultured for 24 h. Type I procollagen, MMP-3, TGF-beta and Smad as well as phosphorylation of MAN family expression were determined by Western blot. The activation of AP-1 was investigated using EMSA. The released type I procollagen and TGF-beta into cell culture medium were determined by Western blot after concentration of these proteins. Results: The results showed that obovatol stimulated type I procollagen, TGF-beta, and Smad expression and inhibited matrix metalloproteinase-3 (MMP-3) in dose-dependent manner (1-5 mu M) in UVB-irradiated human fibroblast cells. Obovatol also inhibited UVB-induced activation of AP-1 and MAP kinases. Conclusion: These results suggest that obovatol increases collagen synthesis through stimulation of the TGF-beta signaling and inhibition of matrix metalloproteinase in UVB-irradiated human fibroblast, thus obovatol could be effective against photo damaged skin. (C) 2007 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.