Psoralen alleviates acute lung injury by covalently targeting Cys106 of HMGB1 in macrophages to inhibit inflammatory responses

Background Acute lung injury (ALI) is a critical pathophysiological response in various respiratory diseases characterized by alveolar damage and excessive inflammation. It can progress to acute respiratory distress syndrome, with current treatments showing limited efficacy and considerable side effects. Psoralen (Pso), derived from Psoralea corylifolia L., has anti-inflammatory properties, but its role in ALI remains fully elucidated. Purpose This study aimed to investigate the therapeutic effects of Pso on ALI, and to explore its therapeutic targets and mechanisms. Methods The therapeutic potential of Pso was assessed using a model of ALI induced by lipopolysaccharide (LPS). The direct target was investigated using alkynyl-Psoralen (A-Pso) for chemical proteomic analysis, and a series of molecular biology methods were used to explore the underlying mechanism. Results Pso treatment significantly alleviated LPS-induced lung injury in mice, targeted macrophages, and inhibited the LPS-induced activation of macrophages. Target-fishing experiments identified high-mobility group box-1 (HMGB1) as a direct target of Pso in macrophages. FTS and CETSA confirmed Pso binding to HMGB1, and LC-MS/MS analysis indicated a covalent interaction between Pso and Cys106 of HMGB1. Furthermore, Pso covalently targeted Cys106, affecting HMGB1 binding to TLR4 and downregulating the phosphorylation of NF-κB, indicating the inhibition of the TLR4/NF-κB signaling pathway both in macrophages and in lung tissues of ALI mice. These findings suggest that Pso exerts its therapeutic effects by covalently targeting HMGB1 in macrophages and modulating the TLR4/NF-κB signaling pathway. Conclusion This study not only found that Pso improves LPS-induced ALI inflammation by targeting macrophages, but also verified that this mechanism of action is mainly caused by Pso covalently targeting Cys106 of HMGB1, inhibiting the HMGB1-TLR4 interaction, and thereby suppressing cytokine storm generation. As the first naturally derived HMGB1 covalent inhibitor with a clear binding site, Pso plays an important role in HMGB1 induced inflammatory diseases and is an active precursor for the development of new HMGB1 covalent inhibitors.