Cystic fibrosis transmembrane conductance regulator and sphingolipids regulate hypoxic pulmonary vasoconstriction

Background: Gene mutations of cystic fibrosis transmembrane conductance regulator(CFTR) cause cystic fibrosis, which is associated with profound pulmonary ventilation-perfusion (V A /Q) mismatches. Hypoxic pulmonary vasoconstriction(HPV) minimizes V A /Q inequalities. However, chronic hypoxemia-associated lung diseases frequently result in pulmonary hypertension (PH). Aims and objectives: We hypothesized that CFTR may mediate HPV potentially by modulating the response to sphingolipidsas mediators of HPV. Methods: HPV and V A /Q mismatch were analyzed in isolated mouse lungs or in vivo . Ca 2+ mobilization, transient receptor potentialcanonical 6 ( TRPC6) translocation to caveolaeand the interaction between CFTR and TRPC6were studied in pulmonary arterial smooth muscle cells (PASMC). The role of CFTR in long-term vascular adaptation to chronic hypoxia was analyzed in CFTR -/- mice. Results: CFTR deficiency diminished HPV, aggravated V A /Q mismatch and partially protected from hypoxic PH. In PASMC, hypoxia caused CFTR/ TRPC6complex formation, while CFTR inhibition attenuated hypoxia-induced TRPC6translocation to caveolaeand Ca 2+ mobilization. Inhibition of neutral sphingomyelinase (nSMase) blocked HPV, while exogenous nSMase caused CFTR-dependent TRPC6translocation and vasoconstriction. nSMase and hypoxia-induced vasoconstriction, yet not TRPC6translocation were blocked by inhibition or deficiency of sphingosine kinase 1(SphK1) or antagonism of S1P receptors 2 and 4 (S1P 2/4 ). S1P and nSMase had synergistic effects on vasoconstrictionthat involved TRPC6, phospholipase C, and rho kinase. Conclusions: These findings demonstrate a central role of CFTR and sphingolipidsin HPV.