SFRP5 inhibits melanin synthesis of melanocytes in vitiligo by suppressing the Wnt/b-catenin signaling

Secreted frizzled-related protein 5(SFRP5)plays a pivotal role in regulating the development of many tissues and organs,however,as an inhibitor of Wnt signaling,the role of SFRP5 in vitiligo remains unknown.Hence,we speculated that SFRP5 might be associated with melanogenesis in melanocytes by regulating Wnt signaling in vitiligo.In this study,we found that SFRP5 was overexpressed in the skin lesions of patients with vitiligo.Compared with that in normal epidermal melanocytes(PIG1),the expression of SFRP5 was increased in vitiligo melanocytes(PIG3V).To investigate the effect of SFRP5 on melanin synthesis,PIG1 cells were infected with recombinant SFRP5 adenovirus(AdSFRP5),and PIG3V cells were infected with recombinant siSFRP5 adenovirus(AdsiSFRP5).The results showed that SFRP5 overexpression inhibited melanin synthesis in PIG1 cells through downregulation of microphthalmia-associated transcription factor(MITF)and its target proteins via suppression of the Wnt/b-catenin signaling pathway.Accordingly,SFRP5 silencing increased melanin synthesis and activated the Wnt signaling pathway in PIG3V cells.Moreover,SFRP5 overexpression also downregulated the transcriptional activity of T cell factor/lymphoid enhancer factor(TCF/LEF)in PIG1 cells.Furthermore,this inhibitory effect of SFRP5 on melanin synthesis was reversed by treatment with the b-catenin agonist,SKL2001.The inhibitory action of SFRP5 in pigmentation was further confirmed in vivo using a nude mouse model.Hence,our results indicate that SFRP5 can inhibit melanogenesis in melanocytes.Additionally,our findings showed that SFRP5 plays a vital role in the development of vitiligo,and thus may serve as a potential therapeutic target for vitiligo.

Biomedical overview of melanin.2.Updating molecular modeling,synthesis mechanism,and supramolecular properties regarding melanoma therapy

Melanins represent one of the most ancient and important group of natural macromolecular pigments.They have multiple biological roles in almost all organisms across the Phyla,examples being photoprotection,anti-oxidative action,radical scavenger activity,and heavy metal removal.From the biomedical point of view,melanocytes are involved in the origin of melanoma tumors,and the main therapeutic advances for their treatment have been revised in Part 1 of this review.The chemical structure of eumelanin is a biological concern of great importance,and therefore,exploring theoretical molecular models and synthesis mechanisms will be here described,as well as molecular orbital features and supramolecular organization,which are responsible for the key properties that make these biological pigments so important,and so fascinating.Ultimately,this updated overview is devoted to describe present structural models and physico-chemical characteristics of eumelanin,in order to explain and utilize melanin properties on which new photothermal and ultrasonic protocols for melanoma treatment can be devised and applied.