Isopropyl 3-(3, 4-Dihydroxyphenyl)-2-hydroxypropanoate, A Novel Metabolite from Salvia Miltiorrhiza, Protects Against LPS-induced Acute Lung Injury in Mice by Attenuating the Canonical and Non-canonical Inflammatory Pathways of Pyroptosis

Abstract BackgroundThe pathological characteristics of acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) are pulmonary edema resulting from pulmonary permeability increasing. The main cause is uncontrolled inflammatory response leading to the damage of pulmonary vascular endothelial and alveolar epithelial barriers. However, there has not been effective drugs against ALI. In this study, we investigated the function of Isopropyl 3-(3, 4-dihydroxypheny l)-2-hydroxypropanoate (IDHP), a novel metabolite of Danshen dripping pill having anti-inflammatory effect, in lipopolysaccharide (LPS) induced ALI in mice, and its underlying mechanisms.MethodsPretreatment of IDHP in LPS-induced acute lung injury in mice were observed on survival rate, pulmonary morphologic changes, total protein content in bronchoalveolar lavage fluid (BALF), and inflammatory cytokines in lung tissue and BALF. To further explore its mechanism on ALI, THP-1 macrophages was studied to analyse pyroptosis related proteins and co-culture with epithelial or endothelial cells to assess protection function of IDHP in vitro.ResultsAs revealed by survival study, pretreatment with high dose of IDHP reduced the mortality of mice from ALI. IDHP pretreatment significantly improved LPS-induced lung pathological changes, reduced protein leakage and lung myeloperoxidase activity. IDHP also inhibited the release of inflammatory mediators TNFα, IL-1β, IL-6 and IL-18 in BALF and lung tissue. Meanwhile, IDHP decreased the expression of active-caspase1 (in canonical pyroptosis pathway), caspase4/5 (non-canonical pyroptosis pathway), Nrlp3, mature IL-1β, mature IL-18, Asc speck formation, and cleaved Gsdmd, all these are required for pyroptosis, in LPS stimulated THP-1 macrophages. Moreover, IDHP also decreased ROS production in LPS-stimulated THP-1 macrophages, inhibited the expression of tight junction proteins (Occludin, Zo-1) in endothelial cells, and decreased lactate dehydrogenase activity in supernatants of epithelial or endothelial cells, co-cultured with LPS-stimulated THP-1 macrophages. ConclusionsPretreatment of IDHP improves survival rate and ameliorates LPS-induced ALI in mice possibly via inhibiting canonical and non-canonical pyroptosis pathways.