Psoriasis is a kind of chronic inflammatory skin disorder, while the long-term use of conventional therapies for this disease are limited by severe adverse effects. Novel small molecules associated with new therapeutic mechanisms are greatly needed. It is known that phosphodiesterase 4 (PDE4) plays a central role in regulating inflammatory responses through hydrolyzing intracellular cyclic adenosine monophosphate (cAMP), making PDE4 to be an important target for the treatment of inflammatory diseases (e.g. psoriasis). In our previous work, we identified a series of novel PDE4 inhibitors with a tetrahydroisoquinoline scaffold through structure-based drug design, among which compound 1 showed moderate inhibition activity against PDE4. In this study, a series of novel tetrahydroisoquinoline derivatives were developed based on the crystal structure of PDE4D in complex with compound 1. Anti-inflammatory effects of these compounds were evaluated, and compound 36, with high safety, permeability and selectivity, exhibited significant inhibitory potency against the enzymatic activity of PDE4D and the TNF-α release from the LPS-stimulated RAW 264.7 and hPBMCs. Moreover, an in vivo study demonstrated that a topical administration of 36 achieved more significant efficacy than calcipotriol to improve the features of psoriasis-like skin inflammation. Overall, our study provides a basis for further development of tetrahydroisoquinoline-based PDE4 inhibitors against psoriasis.

银屑病是一种慢性炎症性皮肤病，而长期使用传统疗法治疗该疾病受到严重不良影响的限制。迫切需要与新的治疗机制相关的新型小分子。已知磷酸二酯酶4（PDE4）通过水解细胞内环状单磷酸腺苷（cAMP）在调节炎症反应中起着核心作用，使PDE4成为治疗炎性疾病（如牛皮癣）的重要靶标。在我们之前的工作中，我们通过基于结构的药物设计鉴定了一系列具有四氢异喹啉骨架的新型PDE4抑制剂，其中化合物1表现出对PDE4的中等抑制活性。在这项研究中，基于与化合物1络合的PDE4D的晶体结构，开发了一系列新型的四氢异喹啉衍生物。评估了这些化合物的抗炎作用，具有高安全性，通透性和选择性的化合物36对PDE4D的酶促活性以及从LPS刺激的RAW 264.7和hPBMC中释放的TNF-α表现出显着的抑制作用。此外，一项体内研究表明，局部给药36与卡泊三醇相比，在改善银屑病样皮肤炎症的特征方面取得了更显着的疗效。总体而言，我们的研究为进一步开发基于四氢异喹啉的抗银屑病PDE4抑制剂提供了基础。