Lan Jingjing, Huang Xianyin, Li Hongpeng, Lin Shen, Huang Jingqian, Yang Weixin, Ouyang Mengting, Fang Jiaqi, Xu Qingfang
Department of Dermato-Venereology, Third Affiliated Hospital of Sun Yat-Sen University, Guangzhou, 510630, P. R. China.
Inflammation. 2025 Apr;48(2):919-934. doi: 10.1007/s10753-024-02097-0. Epub 2024 Jul 16.
Fibroblast A20 suppresses advanced glycation end products (AGEs)-induced melanogenesis by inhibiting NLRP3 inflammasome activation. AGEs repress A20 expression and significantly m6A-methylate A20 mRNA in fibroblasts. YTHDF2 is the most studied m6A reader protein and can accelerate degradation of m6A-modified mRNA. Whether YTHDF2 regulates AGEs-induced A20 expression and pigmentation is unknown. In this study, we confirmed that YTHDF2 inversely regulated AGEs-BSA-inhibited A20 expression but facilitated AGEs-BSA-activated NF-κB signaling and NLRP3 inflammasome in fibroblasts via YTHDF2 knockdown and overexpression experiments. Mechanistically, YTHDF2 bound to m6A-modified A20 mRNA induced by AGEs-BSA and increased its degradation. Moreover, fibroblast YTHDF2 robustly promoted AGEs-BSA-induced IL-18 level in coculture supernatants and melanin content, tyrosinase activity, and expression of microphthalmia-associated transcription factor and tyrosinase in melanocytes, which were significantly blocked by IL-18 binding protein. Further, fibroblast YTHDF2 markedly increased AGEs-BSA-induced epidermal melanin level in cocultured ex vivo skin and MAPKs activation in melanocytes. Importantly, upregulated dermal YTHDF2 expression was negatively correlated with dermal A20 level and positively associated with both epidermal melanin and dermal AGEs content in sun-exposed skin and lesions of melasma and solar lentigo. These findings suggest that fibroblast YTHDF2 positively regulates AGEs-induced melanogenesis mainly via A20/ NF-κB /NLRP3 inflammasome/ IL-18 /MAPKs axis in an m6A-dependent manner and functions in photoaging-induced hyperpigmentation skin disorders.
成纤维细胞A20通过抑制NLRP3炎性小体激活来抑制晚期糖基化终末产物（AGEs）诱导的黑色素生成。AGEs抑制成纤维细胞中A20的表达，并使其mRNA发生显著的m6A甲基化。YTHDF2是研究最多的m6A阅读蛋白，可加速m6A修饰的mRNA降解。YTHDF2是否调节AGEs诱导的A20表达和色素沉着尚不清楚。在本研究中，我们通过YTHDF2敲低和过表达实验证实，YTHDF2反向调节AGEs-BSA抑制的A20表达，但促进了成纤维细胞中AGEs-BSA激活的NF-κB信号传导和NLRP3炎性小体。机制上，YTHDF2与AGEs-BSA诱导的m6A修饰的A20 mRNA结合并增加其降解。此外，成纤维细胞YTHDF2强烈促进共培养上清液中AGEs-BSA诱导的IL-18水平以及黑色素含量、酪氨酸酶活性，以及黑素细胞中小眼畸形相关转录因子和酪氨酸酶的表达，而IL-18结合蛋白可显著阻断这些作用。此外，成纤维细胞YTHDF2显著增加共培养的离体皮肤中AGEs-BSA诱导的表皮黑色素水平以及黑素细胞中的MAPKs激活。重要的是，在暴露于阳光的皮肤以及黄褐斑和日光性雀斑样痣病变中，真皮YTHDF2表达上调与真皮A20水平呈负相关，与表皮黑色素和真皮AGEs含量均呈正相关。这些发现表明，成纤维细胞YTHDF2主要通过A20/NF-κB/NLRP3炎性小体/IL-18/MAPKs轴以m6A依赖的方式正向调节AGEs诱导的黑色素生成，并在光老化诱导的色素沉着性皮肤疾病中发挥作用。
