Inhibition of LRP5/6-mediated Wnt/β-catenin signaling by Mesd attenuates hyperoxia-induced pulmonary hypertension in neonatal rats

BACKGROUND: Hyperoxia-induced neonatal lung injury is associated with activation of Wnt/beta-catenin signaling. Low-density lipoprotein receptor related proteins 5 and 6 (LRP5/6) are Wnt coreceptors that bind to Wnt ligands and mediate canonical Wnt/beta-catenin signaling. We hypothesized that inhibition of LRP5/6 by their universal inhibitor, Mesd, would attenuate hyperoxia-induced lung injury. METHODS: Newborn rat pups were randomly exposed to normoxia or hyperoxia at 90% FiO(2) and injected intraperitoneally with placebo or Mesd every other day for 14 d. On day 15, phosphorylation of LRP5/6 (pLRP5/6), expression of Wnt/beta-catenin target genes, cyclin D1 and Wnt-induced signaling protein-1 (WISP-1), right-ventricular systolic pressure (RVSP), right-ventricular hypertrophy (RVH), pulmonary vascular remodeling, alveolarization, and vascularization were measured. RESULTS: Hyperoxia exposure markedly induced pLRP5/6, cyclin D1, and WISP-1 expression in the lungs of placebo animals, but they were significantly attenuated by the administration of Mesd. Mesd also significantly attenuated hyperoxia-induced pulmonary hypertension (PH) and pulmonary vascular remodeling. However, there was no effect on alveolarization or vascularization after Mesd administration. CONCLUSION:This study demonstrates that LRP5/6 mediates pulmonary vascular remodeling and PH in hyperoxia-induced neonatal lung injury, thereby suggesting a potential therapeutic target to alleviate PH in neonates with severe bronchopulmonary dysplasia.