Modification of Collagen by 3-Deoxyglucosone Alters Wound Healing through Differential Regulation of p38 MAP Kinase

Background: Wound healing is a highly dynamic process that requires signaling from the extracellular matrix to the fibroblasts for migration and proliferation, and closure of the wound. This rate of wound closure is impaired in diabetes, which may be due to the increased levels of the precursor for advanced glycation end products, 3-deoxyglucosone (3DG). Previous studies suggest a differential role for p38 mitogen-activated kinase (MAPK) during wound healing; whereby, p38 MAPK acts as a growth kinase during normal wound healing, but acts as a stress kinase during diabetic wound repair. Therefore, we investigated the signaling cross-talk by which p38 MAPK mediates wound healing in fibroblasts cultured on native collagen and 3DG-collagen. Methodology/Principal Findings: Using human dermal fibroblasts cultured on 3DG-collagen as a model of diabetic wounds, we demonstrated that p38 MAPK can promote either cell growth or cell death, and this was dependent on the activation of AKT and ERK1/2. Wound closure on native collagen was dependent on p38 MAPK phosphorylation of AKT and ERK1/2. Furthermore, proliferation and collagen production in fibroblasts cultured on native collagen was dependent on p38 MAPK regulation of AKT and ERK1/2. In contrast, 3DG-collagen decreased fibroblast migration, proliferation, and collagen expression through ERK1/2 and AKT downregulation via p38 MAPK. Conclusions/Significance: Taken together, the present study shows that p38 MAPK is a key signaling molecule that plays

Inhibitory Effect of Buah Merah Oil on Melanogenesis Via Degradation of Tyrosinase

Buah Merah (Pandanus conoideus) is exclusively distributed in Papua island and its neighboring areas. The extract oil from fruits (Buah Merah oil) contains rich in lipids, carotenoids and vitamin E.We assessed the effects of Buah Merah oil on melanogenesis in B16 melanoma cells. In the presence of alpha-melanocyte stimulating hormone (α-MSH), B16 melanoma cells are stimulated to enhance melanin synthesis. Buah Merah oil inhibited α-MSH-induced melanin synthesis with no cytotoxicity. This decrease in melanogenesis was correlated with reduced enzyme activity and decreased protein expression levels of tyrosinase. Tyrosinase is a type 1 membrane glycoprotein that is the critical rate-limiting enzyme involved in melanin synthesis. Furthermore, the Buah Merah oil-induced decrease in melanin content was accompanied by a decrease in the amount and activity of tyrosinase whereas the mRNA level of tyrosinase was unchanged. Moreover, treatment with proteasome inhibitor MG132 blocked the down-regulation of melanogenesis by Buah Merah oil. Immunoprecipitation analysis also revealed that treatment with Buah Merah oil modulated the ubiquitination of tyrosinase, that is Buah Merah oil increased the amount of ubiquitinated tyrosinase.Taken together, the present results indicate that the depigmenting effect of Buah Merah oil might be due to inhibition of tyrosinase expression through the ubiquitin proteasome-mediated degradation of tyrosinase