Phillyrin improves pulmonary epithelial barrier dysfunction in LPS-induced acute lung injury through the RhoA/ROCK signaling pathway

Abstract Objective Forsythiae Fructus, the fruit of Forsythia suspensa (Thunb.) Vahl, is a traditional Chinese medicine widely used for clearing heat and detoxifying and for treating inflammatory conditions such as fever and respiratory infection. Its effective ingredients include phillyrin, a lignan component with pharmacological properties, including anti-inflammation and antioxidation. This study investigated the effects of phillyrin on epithelial barrier dysfunction caused by acute lung injury (ALI) and key signaling pathways in rats with lipopolysaccharide (LPS)-induced ALI to explore its mechanism of attenuating ALI. Results Analysis of the lung wet/dry weight ratio, myeloperoxidase activity, pathological sections, and proinflammatory factor levels in vivo revealed that phillyrin could alleviate LPS-induced ALI. Network pharmacology showed 125 hub targets between phillyrin and ALI and indicated that the Rho activator (RhoA) was the main target in the enriched pathway, and the RhoA/Rho-associated protein kinase (ROCK) was pivotal in phillyrin’s therapeutic effects against ALI. Phillyrin improved tight junctions in the rats with LPS-induced ALI. In addition, western blot analyses revealed that phillyrin inhibited ALI-induced increments in RhoA, Rho-associated protein kinase 1, and myosin light-chain kinase proteins. Inhibitor experiments demonstrated that after fasudil inhibited the signaling pathway, phillyrin did not increase its inhibitory effect on key pathway proteins and its improvement effect on epithelial dysfunction. Conclusions Phillyrin inhibits pulmonary edema, suppresses inflammation and oxidative stress in ALI rats, and improves LPS-induced alveolar epithelial barrier dysfunction by inhibiting RhoA/ROCK pathways.