Calcium-Sensing Receptor and CPAP-Induced Neonatal Airway Hyperreactivity in Mice

BACKGROUND: Continuous positive airway pressure (CPAP) in preterm infants is initially beneficial, but animal models suggest longer term detrimental airway effects towards asthma. We used a neonatal CPAP mouse model and human fetal airway smooth muscle (ASM) to investigate the role of extracellular calcium sensing receptor (CaSR) in these effects. METHODS: Newborn wild type and smooth muscle-specific CaSR(−/−) mice were given CPAP for 7 days via a custom device (mimicking CPAP in premature infants), and recovered in normoxia for another 14 days (representing infants at 3–4 years). Airway reactivity was tested using lung slices, and airway CaSR quantified. Role of CaSR was tested using NPS2143 (inhibitor) or siRNA in WT mice. Fetal ASM cells stretched cyclically with/without static stretch mimicking breathing and CPAP were analyzed for intracellular Ca(2+) ([Ca(2+)](i)) responses, role of CaSR and signaling cascades. RESULTS: CPAP increased airway reactivity in WT but not CaSR(−/−) mice, increasing ASM CaSR. NPS2143 or CaSR siRNA reversed CPAP effects in WT mice. CPAP increased fetal ASM [Ca(2+)](I), blocked by NPS2143, and increased ERK1/2 and RhoA suggesting two mechanisms by which stretch increases CaSR. CONCLUSIONS: These data implicate CaSR in CPAP effects on airway function with implications for wheezing in former preterm infants.