Modulation of Airway Remodeling by PF543, a Sphingosine Kinase 1 Inhibitor, in a Mouse Model of Bronchopulmonary Dysplasia

Abstract

Bronchopulmonary dysplasia (BPD) is a chronic lung disease affecting extreme preterm newborn survivors with serious long‐term sequela of wheezing. Oxygen therapy, which is inevitable for the survival of such extremely premature infants, is partly responsible for the development of BPD and associated airway remodeling (AWRM). Altered Sphingosine‐1‐phosphate (S1P)/Sphingosine kinase 1 (SPHK1) signaling have been implicated in the pathophysiology of a number of lung diseases; however, the role of SPHK1/S1P signaling in BPD and AWRM is not well understood. The neonatal mice were subjected to hyperoxia (HO) at 95% oxygen (postnatal day 3 to 10) and allowed to grow as adults for 8 weeks. During exposure to room air (RA) or HO, the mice received 5mg/kg of PF543, a specific inhibitor of SPHK1, intraperitoneally on alternate days. Lungs were then collected and prepared for histology as well as morphometry of alveoli/airways. Lung function studies were performed using a ventilator and methacholine challenge was used to measure airway hyper reactivity (AHR). Levels of S1P and sphingoid bases in bronchoalveolar lavage (BAL) fluids and lung tissues were measured by LC‐MS/MS. In vitro mechanistic studies on HO‐induced AWRM and the protective effect of PF543 were performed using small airway epithelial cells (SAEC).The exposure of neonatal mice to hyperoxia resulted in AWRM in adults, as evidenced by increased peribronchial fibrosis and smooth muscle hypertrophy. These changes were significantly less in Sphk1 knock out (Sphk1−/−) mice exposed to HO indicating a potential role of SPHK1 in the pathogenesis of AWRM. Subsequent experiments using a specific SPHK1 inhibitor, PF543, during neonatal HO prevented alveolar simplification and, more significantly, ameliorated AWRM in adult mice. Lung function studies revealed AHR in adult mice that were exposed to neonatal HO. Interestingly, PF543 therapy reduced methacholine‐induced AHR and airway constriction along with a reduction in AWRM. Exposure of neonatal mice to HO showed epithelial mesenchymal transition (EMT) ‐like changes, which was reduced by PF543 treatment. Inhibition of SPHK1 with PF543 in SAECs ameliorated HO‐induced loss of E‐cadherin and gain of N‐cadherin and vimentin, markers of EMT.In conclusion, our data indicate a novel role for SPHK1/S1P signaling in HO‐induced BPD and AWRM, and amelioration by PF543.Support or Funding InformationThis work is supported by NIH/NICHD R01 HD090887‐01 A1 and AHA 18TPA34230095 to AH.