Dysregulation of cathepsin S (Cat S), a cysteine protease involved in extracellular-matrix and basement membrane (BM) degradation, is a concomitant feature of several inflammatory skin diseases. Therefore, Cat S has been suggested as a potential therapeutic target. Flavonoids, which were identified as regulatory molecules of various proteolytic enzymes, exert beneficial effects on skin epidermis. Herein, thirteen flavonoid compounds were screened in vitro and in silico and neohesperidin dihydrochalcone (NHDC) was identified as a potent, competitive, and selective inhibitor (K_i=8±1 µM) of Cat S. Furthermore, Cat S-dependent hydrolysis of nidogen-1, a keystone protein of BM architecture, as well elastin, collagens I and IV was impaired by NHDC, while both expression and activity of Cat S were significantly reduced in NHDC-treated human keratinocytes. Moreover, a reconstructed human skin model showed a significant decrease of both mRNA and protein levels of Cat S after NHDC treatment. Conversely, the expression of nidogen-1 was significantly increased. NHDC raised IL-10 expression, an anti-inflammatory cytokine, and mediated STAT3 signaling pathway, which in turn dampened Cat S expression. Our findings support that NHDC may represent a valuable scaffold for structural improvement and development of Cat S inhibitors to preserve the matrix integrity and favor skin homeostasis during inflammatory events.

组织蛋白酶 S (Cat S) 的失调是一种参与细胞外基质和基底膜 (BM) 降解的半胱氨酸蛋白酶，是几种炎症性皮肤病的伴随特征。因此，Cat S 已被建议作为潜在的治疗靶点。黄酮类化合物被鉴定为各种蛋白水解酶的调节分子，对皮肤表皮产生有益作用。在此，13 种黄酮类化合物在体外和计算机中进行了筛选，新橙皮苷二氢查耳酮 (NHDC) 被鉴定为一种有效的、竞争性和选择性的抑制剂 (K _i=8±1 µM) Cat S。此外，Nidogen-1（BM 结构的关键蛋白）以及弹性蛋白、胶原蛋白 I 和 IV 的 Cat S 依赖性水解受到 NHDC 的损害，而 Cat S 的表达和活性在 NHDC 处理的人角质形成细胞中显着减少。此外，重建的人体皮肤模型显示，在 NHDC 处理后，Cat S 的 mRNA 和蛋白质水平均显着降低。相反，nidogen-1的表达显着增加。NHDC 提高了抗炎细胞因子 IL-10 的表达，并介导了 STAT3 信号通路，这反过来又抑制了 Cat S 的表达。我们的研究结果支持 NHDC 可能代表了一种有价值的支架，可用于结构改进和 Cat S 抑制剂的开发，以在炎症事件期间保持基质完整性并有利于皮肤稳态。