Directly blocking the Keap1–Nrf2 pathway is a promising strategy for the mitigation of acute lung injury (ALI). Peptide Keap1–Nrf2 inhibitors have been reported to have a high Keap1 binding affinity. However, these inhibitors showed weak activity in cells and/or animals. In this study, we designed a series of linear peptides from an Nrf2-based 9-mer Ac-LDEETGEFL-NH₂. To improve the cellular activity, we further designed cyclic peptides based on the crystal complex of Keap1 with a linear peptide. Among them, cyclic 9-mer ZC9 targeting Keap1 showed a better affinity (K_D2 = 51 nM). Specifically, it exhibited an acceptable water solubility (>38 mg/mL), better cell permeability, cell activity, and metabolic stability (serum t_1/2 > 24 h). In the in vitro LPS-induced oxidative damages and ALI model, ZC9 showed significant dose–response reversal activity without apparent toxicity. In conclusion, our results suggested ZC9 as a lead cyclic peptide targeting the Keap1–Nrf2 pathway for ALI clinical treatment.

中文翻译：

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环肽 Keap1-Nrf2 蛋白-蛋白相互作用抑制剂：设计、合成和急性肺损伤的体内治疗

直接阻断 Keap1-Nrf2 通路是缓解急性肺损伤 (ALI) 的一种有前景的策略。据报道，肽 Keap1-Nrf2 抑制剂具有高 Keap1 结合亲和力。然而，这些抑制剂在细胞和/或动物中表现出较弱的活性。在本研究中，我们从基于 Nrf2 的 9 聚体 Ac-LDEETGEFL-NH ₂设计了一系列线性肽。为了提高细胞活性，我们进一步设计了基于Keap1与线性肽晶体复合物的环肽。其中，靶向Keap1的环状9聚体ZC9表现出更好的亲和力（K _D2 = 51 nM）。具体来说，它表现出可接受的水溶性（>38 mg/mL）、更好的细胞通透性、细胞活性和代谢稳定性（血清t _1/2 > 24 h）。在体外 LPS 诱导的氧化损伤和 ALI 模型中，ZC9显示出显着的剂量反应逆转活性，而没有明显的毒性。总之，我们的结果表明ZC9作为针对 ALI 临床治疗的 Keap1-Nrf2 通路的先导环肽。