Melatonin inhibits fibroblast cell functions and hypertrophic scar formation by enhancing autophagy through the MT2 receptor-inhibited PI3K/Akt /mTOR signaling. Melatonin inhibits fibroblast cell functions and hypertrophic scar formation by enhancing autophagy through the MT2 receptor-inhibited PI3K/Akt /mTOR signaling

Hypertrophic scar (HS) is a fibrotic skin condition and characterized by abnormal proliferation of myofibroblasts and accumulation of extracellular matrix. Melatonin, an endogenous hormone, can alleviate fibrosis in multiple models of diseases. This study examined the effect of melatonin on fibrosis in primary fibroblasts from human HS (HSFs) and a rabbit ear model and potential mechanisms. Melatonin treatment significantly decreased the migration and contraction capacity, collagen and α-smooth muscle actin (α-SMA) production in HSFs. RNA-sequencing and bioinformatic analyses indicated that melatonin modulated the expression of genes involved in autophagy and oxidative stress. Mechanistically, melatonin treatment attenuated the AKT/mTOR activation through affecting the binding of MT2 receptor with PI3K to enhance autophagy, decreasing fibrogenic factor production in HSFs. Moreover, melatonin treatment inhibited HS formation in rabbit ears by enhancing autophagy. The anti-fibrotic effects of melatonin were abrogated by treatment with an autophagy inhibitor (3-methyladenine, 3-MA), an Akt activator (SC79), or an MT2 selective antagonist (4-phenyl-2propionamidotetralin, 4-P-PDOT). Therefore, melatonin may be a potential drug for prevention and treatment of HS. Overall design: RNA-seq of hypertrophic scar fibroblasts were treated with or without melatonin

增生性瘢痕（Hypertrophic Scar, HS）是一类纤维化性皮肤疾病，以肌成纤维细胞异常增殖及细胞外基质堆积为特征。褪黑素（Melatonin）作为一种内源性激素，可在多种疾病模型中缓解纤维化。本研究探究了褪黑素对人增生性瘢痕原代成纤维细胞（HSFs）及兔耳模型中纤维化的影响及其潜在作用机制。褪黑素处理可显著降低HSFs的迁移与收缩能力，减少胶原蛋白及α-平滑肌肌动蛋白（α-smooth muscle actin, α-SMA）的生成。RNA测序（RNA-sequencing）与生物信息学分析显示，褪黑素可调控自噬与氧化应激相关基因的表达。机制层面，褪黑素处理可通过影响MT2受体与PI3K的结合，减弱AKT/mTOR通路激活，从而增强自噬，减少HSFs中纤维化因子的生成。此外，褪黑素处理可通过增强自噬抑制兔耳的瘢痕形成。自噬抑制剂3-甲基腺嘌呤（3-methyladenine, 3-MA）、AKT激活剂SC79或MT2选择性拮抗剂4-苯基-2-丙酰胺基四啉（4-phenyl-2propionamidotetralin, 4-P-PDOT）均可抵消褪黑素的抗纤维化作用。因此，褪黑素有望成为预防与治疗增生性瘢痕的潜在药物。实验整体设计：对经褪黑素处理与未处理的增生性瘢痕成纤维细胞进行RNA测序。