Vorapaxar proven to be a promising candidate for pulmonary fibrosis by intervening in the PAR1/JAK2/STAT1/3 signaling pathway-an experimental in vitro and vivo study.

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease, and its 5-year mortality rate is even higher than the mortality rate of some cancers. Fibrosis can cause irreversible damage to lung structure and function. Treatment options for IPF remain limited, and there is an urgent need to develop effective therapeutic drugs. Protease activated receptor-1 (PAR-1) is a G-protein-coupled receptor and is considered a potential target for the treatment of fibrotic diseases. Vorapaxar is a clinically approved PAR-1 antagonist for cardiovascular protection. The purpose of this study was to explore the potential effect and mechanism of Vorapaxar on pulmonary fibrosis in vivo and in vitro. In the experimental animal model, Vorapaxar can effectively alleviate bleomycin (BLM)-induced pulmonary fibrosis. Treatment with 2.5, 5 or 10 mg/kg Vorapaxar once a day reduced the degree of fibrosis in a dose-dependent manner. The expression of fibronectin, collagen and α smooth muscle actin decreased significantly at the messenger RNA (mRNA) and protein levels in treated mice. In vitro, our results showed that Vorapaxar could inhibit the activation of fibroblasts induced by thrombin in a dose-dependent manner. In terms of mechanism, Vorapaxar inhibits the signal transduction of JAK2/STAT1/3 by inhibiting the activation of protease activated receptor 1, which reduces the expression of HSP90ß and the interaction between HSP90ß and transforming growth factor-ß (TGFß) receptor II and inhibits the TGFß/Smad signaling pathway. In conclusion, Vorapaxar inhibits the activation of pulmonary fibroblasts induced by thrombin by targeting protease activated receptor 1 and alleviates BLM-induced pulmonary fibrosis in mice.

Myricetin reverses epithelial-endothelial transition and inhibits vasculogenic mimicry and angiogenesis of hepatocellular carcinoma by directly targeting PAR1.

Most antiangiogenic inhibitors targeting endothelium-dependent vessels cannot inhibit tumor growth but promote tumor invasion and metastasis in some patients. Vasculogenic mimicry (VM) employs mechanisms that differ from those used to construct endothelium-dependent vessels. Inhibiting VM may be a novel antiangiogenic strategy against alternative tumor vascularization. In this paper, myricetin was selected from among several flavonoid compounds as an effective PAR1 antagonist. In two different hepatocellular carcinoma (HCC) cell lines high-expressed PAR1, myricetin inhibited cell migration, invasion and VM formation and reversed the expression of epithelial-endothelial transition (EET) markers by inhibiting PAR1 activation. Knockout of PAR1 inhibited HCC cell invasion and metastasis and weakened the inhibitory effect of myricetin on HCC cells. The migration, invasion and tube formation ability of PLC-PRF-5 cells were enhanced after PAR1 overexpression, and the inhibitory effect of myricetin was enhanced. A docking assay revealed that myricetin binds to Leu258 and Thr261 in the PAR1 activity pocket. Mutation of Leu258 and Thr261 inhibited the antitumor effect of myricetin in vitro and in vivo. In summary, myricetin reverses PAR1-mediated EET and inhibits HCC cell invasion, metastasis, VM formation and angiogenesis by targeting PAR1, and Leu258 and Thr261 of PAR1 participate in VM and angiogenesis in HCC tissues.

Pinocembrin relieves lipopolysaccharide and bleomycin induced lung inflammation via inhibiting TLR4-NF-κB-NLRP3 inflammasome signaling pathway.

Inflammation is a defense response of the body to stimuli. Lung injury caused by external stimuli can stimulate inflammatory cells to accumulate at the site of injury and secrete cytokines. Pinocembrin is a flavonoid with anti-inflammatory effects. Based on previous studies, we further explored the anti-inflammatory mechanisms of pinocembrin in vitro and in vivo. In vitro studies indicated that pinocembrin inhibited lipopolysaccharide (LPS)-stimulated inflammatory response in macrophages. In vivo studies also showed that pinocembrin could reduce LPS and bleomycin (BLM) induced lung inflammatory response in mice. Further mechanistic studies indicated that pinocembrin could regulate the TLR4-NF-κB signaling pathway and suppressed the activation and assembly of NLRP3 inflammasomes. In summary, pinocembrin could relieve pulmonary inflammatory response induced by LPS and BLM mainly via inhibiting TLR4-NF-κB-NLRP3 inflammasome axis. These results contribute to the understanding of the anti-inflammatory mechanisms of pinocembrin and serve as reference for future research on pinocembrin.