High vascular pressure leads to P450 epoxygenase‐dependent TRPV4 activation and endothelial injury in mouse lung

We have shown that activation of the vanilloid transient receptor potential channel TRPV4 increases lung endothelial permeability. The current study tested the hypothesis that TRPV4 mediates the Ca2+ entry-dependent permeability response in lung to high venous pressure (HiPv). Isolated lungs from TRPV4+/+ mice (WT) or TRPV4−/− (KO) littermates were perfused with buffer/4% albumin (33 °C). Endothelial permeability was measured by the filtration coefficient (Kf), via 15-min elevation in Pv: 5→15 cmH2O (baseline) and 5→ 30 cmH2O (HiPv). Baseline Kf was no different in WT vs KO groups (0.0104±0.0005 vs 0.0092±0.0006 ml/min/cmH2O/g dry wt, mean±SEM). In WT lungs (n=6), HiPv increased Kf 3.9-fold (p<0.001). This response, but not baseline Kf, was attenuated at 26 °C (n=6). In low Ca2+ buffer (0.02 mM, n=5), HiPv had no impact on Kf, though Kf increased in these lungs after Ca2+ add-back (2.2 mM, p<0.01). HiPv did not significantly increase Kf in WT lungs pretreated with the TRPV antagonist ruthenium red (3 μM, n=4) nor in KO lungs (n=7). The WT response to HiPv was also blocked by inhibitors of phospholipase A2 (methyl arachidonyl fluorophosphonate, 2.5 μM, n=4) or P450 epoxygenase (propargyloxyphenyl hexanoic acid, 50 μM, n=6). These findings support a role for P450-derived epoxyeicosatrienoic acid-dependent regulation of Ca2+ entry via TRPV4 in the permeability response to HiPv. Supported by HL066299, HL081851.