Abstract:

Objective To investigate the effects of MST1/2 inhibitor XMU-MP-1 blocking the Hippo signaling pathway on hyperoxia-induced lung injury neonatal rats with bronchopulmonary dysplasia （BPD）. Methods Neonatal rats were randomly divided into four groups： control group， XMU-MP-1 group， BPD model group， and BPD + XMU-MP-1 group， with 10 rats in each group. Rats in the BPD model group and BPD + XMU-MP-1 group were exposed to 85% O₂ in a hyperoxia chamber for 14 consecutive days to establish the BPD model， while those in the control group and XMU-MP-1 group were kept in normal air. From the first day of modeling， rats in the XMU-MP-1 group and BPD + XMU-MP-1 group received daily intraperitoneal injections of the MST1/2 kinase inhibitor XMU-MP-1 （1 mg/kg）， whereas those in the control group and BPD model group received equal volumes of normal saline， for 7 consecutive days. Body weight was monitored during the modeling period. At the end of the modeling period， lung tissue sections were stained with hematoxylin and eosin （HE） for histopathological evaluation， and the extent of alveolarization was quantified by radial alveolar count （RAC）. Western blot and immunofluorescence staining were used to detect the expression levels of Hippo signaling pathway proteins （MST1/2， p-YAP）， epithelial-mesenchymal transition-related markers （E-cadherin， Vimentin）， and the fibroblast activation marker Thy-1. TUNEL staining was employed to detect pulmonary cell apoptosis， and Sirius Red staining was used to assess pulmonary collagen deposition. Results Compared with the control group， the BPD model group exhibited significantly decreased body weight （P < 0.05）； typical BPD pathological changes， characterized by significantly decreased RAC （P < 0.05）； significantly increased pulmonary cell apoptosis rate and collagen deposition area （all P < 0.05）； and significantly upregulated protein expression of MST1/2， p-YAP and Vimentin， as well as significantly downregulated expression of E-cadherin and Thy-1 （all P < 0.05）. Compared with the BPD model group， the BPD + XMU-MP-1 group showed significantly restored body weight （P < 0.05）， and the aforementioned pulmonary pathological damage， protein expression abnormalities， cell apoptosis， and collagen deposition were all significantly ameliorated （all P < 0.05）. Conclusions The Hippo signaling pathway is abnormally activated in hyperoxia-induced BPD model of neonatal rats， participating in lung cell apoptosis， epithelial⁃mesenchymal transition and collagen deposition. Blocking this pathway with the MST1/2 inhibitor XMU-MP-1 alleviates BPD lung injury， suggesting that the Hippo pathway is a potential therapeutic target for BPD.

Key words: bronchopulmonary dysplasia, Hippo signaling pathway, apoptosis, epithelial-mesenchymal transition, collagen deposition