A20 ameliorates advanced glycation end products-induced melanogenesis by inhibiting NLRP3 inflammasome activation in human dermal fibroblasts.

BACKGROUND: Advanced glycation end products (AGEs) promote melanogenesis through activating NLRP3 inflammasome in fibroblasts. Although A20 has been highlighted to inhibit NLRP3 inflammasome activation, its roles and mechanisms remain elusive in photoaging-associated pigmentation. OBJECTIVES: To determine the significance of fibroblast A20 in AGEs-induced NLRP3 inflammasome activation and pigmentation. METHODS: The correlation between A20 and AGEs or melanin was studied in sun-exposed skin and lesions of melasma and solar lentigo. We then investigated A20 level in AGEs-treated fibroblast and the effect of fibroblast A20 overexpression or knockdown on AGEs-BSA-induced NLRP3 inflammasome activation and pigmentation, respectively. Finally, the severity of NLRP3 inflammasome activation and pigmentation was evaluated after mice were injected intradermally with A20-overexpression adeno-associated virus and AGEs-BSA. RESULTS: Dermal A20 expression was decreased and exhibited negative correlation with either dermal AGEs deposition or epidermal melanin level in sun-exposed skin and pigmentary lesions. Moreover, both AGEs-BSA and AGEs-collagen robustly decreased A20 expression via binding to RAGE in fibroblasts. Further, A20 overexpression or depletion significantly decreased or augmented AGEs-BSA-induced activation of NF-κB pathway and NLRP3 inflammasome and IL-18 production and secretion in fibroblasts, respectively. Importantly, fibroblast A20 potently repressed AGEs-BSA-stimulated melanin content，tyrosinase activity，and expression of microphthalmia-associated transcription factor and tyrosinase in melanocytes. Particularly, fibroblast A20 significantly abrogated AGEs-BSA-promoted melanogenesis in ex vivo skin and mouse models. Additionally, fibroblast A20 inhibited AGEs-BSA-activated MAPKs in melanocytes and the epidermis of ex vivo skin. CONCLUSIONS: Fibroblast A20 suppresses AGEs-stimulate melanogenesis in photoaging-associated hyperpigmentation disorders by inhibiting NLRP3 inflammasome activation.

CircRNA-406918 enhances the degradation of advanced glycation end products in photoaged human dermal fibroblasts via targeting cathepsin D.

BACKGROUND: Lysosomal cathepsin D (CTSD) can degrade internalized advanced glycation end products (AGEs) in dermal fibroblasts. CTSD expression is decreased in photoaged fibroblasts, which contributes to intracellular AGEs deposition and further plays a role in AGEs accumulation of photoaged skin. The mechanism under downregulated CTSD expression is unclear. OBJECTIVE: To explore possible mechanism of regulating CTSD expression in photoaged fibroblasts. METHODS: Dermal fibroblasts were induced into photoaging with repetitive ultraviolet A (UVA) irradiation. The competing endogenous RNA (ceRNA) networks were constructed to predict candidate circRNAs or miRNAs related with CTSD expression. AGEs-BSA degradation by fibroblasts was studied with flow cytometry, ELISA, and confocal microscopy. Effects of overexpressing circRNA-406918 via lentiviral transduction on CTSD expression, autophagy, AGE-BSA degradation were analyzed in photoaged fibroblasts. The correlation between circRNA-406918 and CTSD expression or AGEs accumulation in sun-exposed and sun-protected skin was studied. RESULTS: CTSD expression, autophagy, and AGEs-BSA degradation were significantly decreased in photoaged fibroblasts. CircRNA-406918 was identified to regulate CTSD expression, autophagy, and senescence in photoaged fibroblasts. Overexpressing circRNA-406918 potently decreased senescence and increased CTSD expression, autophagic flux, and AGEs-BSA degradation in photoaged fibroblasts. Moreover, circRNA-406918 level was positively correlated with CTSD mRNA expression and negatively associated with AGEs accumulation in photodamaged skin. Further, circRNA-406918 was predicted to mediate CTSD expression through sponging eight miRNAs. CONCLUSION: These findings suggest that circRNA-406918 regulates CTSD expression and AGEs degradation in UVA-induced photoaged fibroblasts and might exert a role in AGEs accumulation in photoaged skin.

Advanced Glycation End Products Promote Melanogenesis by Activating NLRP3 Inflammasome in Human Dermal Fibroblasts.

Advanced glycation end product (AGE) accumulation is significantly increased in the dermis of photoaged skin and plays crucial roles in photoaging. Although AGEs have been found to contribute to the yellowish discoloration of photoaged skin, their roles in photoaging-associated hyperpigmentation disorders have not been extensively studied. In this study, we observed that AGEs, NLRP3, and IL-18 were increased in the dermis of sun-exposed skin and lesions of melasma and solar lentigo and that dermal deposition of AGE was positively correlated with epidermal melanin levels. In addition, we found that AGE-BSA potently activated NLRP3 inflammasome and promoted IL-18 production and secretion in cultured fibroblasts, which was mediated by receptor for AGE/NF-κB pathway. Moreover, AGE-BSA significantly promoted melanogenesis by increasing tyrosinase activity and expression of microphthalmia-associated transcription factor and tyrosinase, which was dependent on NLRP3 inflammasome activation and IL-18 secretion in fibroblasts. Notably, AGE-collagen could activate NLRP3 inflammasome in fibroblasts and enhance melanogenesis. Furthermore, we found that IL-18 enhanced melanogenesis by binding to its receptor and activating p38 MAPK and extracellular signal‒regulated kinase 1/2 signaling pathways in melanocytes. Importantly, the promelanogenesis of AGE-BSA was verified in ex vivo cultured skin and mouse models. These findings suggest that dermal AGEs stimulate melanogenesis and contribute to the development of photoaging-associated hyperpigmentation disorders.

Advanced glycation end products alter the m6A-modified RNA profiles in human dermal fibroblasts.

Background: To explore advanced glycation end products (AGEs)-induced m6A modification in fibroblasts and its potential role in photoaging. Methods: We studied m6A modification in AGEs-bovine serum albumin-treated fibroblasts with m6A-mRNA & lncRNA epitranscriptomic microarray and bioinformatics analysis. The m6A modification level was also investigated in skin samples. Results: m6A methylation microarray analysis revealed m6A modification profiles in AGEs-treated fibroblasts. Gene ontology, Kyoto Encyclopedia of Genes and Genomes, protein-protein interaction and competing endogenous RNA network analysis indicated that the genes of differentially methylated mRNAs and lncRNAs were mainly related to inflammation processes. We also found that AGEs-bovine serum albumin dose-dependently increased the m6A level and METTL14 expression in both fibroblasts and sun-exposed skin. Conclusion: Our study provided novel information regarding alterations of m6A modifications in AGEs-induced dermal fibroblasts and potential targets for treatment of photoaging.

Extracorporeal Shock Wave Therapy Promotes Osteogenic Differentiation in a Rabbit Osteoporosis Model.

Extracorporeal shock wave therapy (ESWT) has been identified to accelerate bone formation. However, detailed mechanism has not been fully explained. In this study, we found that ESWT promoted osteoblast formation in vitro. Local ESW treatment of femur increased bone formation in vivo. Furthermore, changing the density or frequency of energy, there was no statistical difference in osteogenic differentiation. Therapeutically, local ESW therapy relieved bone loss and increased the number of bone trabecular in a rabbit osteoporosis model and promoted endogenous levels of SMAD2 protein expression. Thus, ESWT may be a potential therapy by promoting osteoblast maturation through TGF-ß/SMAD2 pathway.