cGMP regulates mechanosensitive TRPV4 channels in lung endothelial cells

Previously, we and others have demonstrated that endothelial Ca 2+ influx via activated TRPV4 channels promotes hydrostatic edema formation. Here, we used real‐time microscopy and patch clamp analyses to study the regulation of this mechanosensitive channel by NO/cGMP pathway. In vivo, we tested the ability of sildenafil which prevents the degradation of cGMP by inhibition of phosphodiesterase 5 to attenuate hydrostatic edema in a rat model of left anterior descending coronary artery (LAD) occlusion. In isolated perfused rat lungs, elevation of left atrial pressure from 5 to 15 cmH 2 O induced an increase in endothelial Ca 2+ concentration ([Ca 2+ ] i ) from 105±6 to 173±10 nM. This [Ca 2+ ] i response was blocked by TRPV4 inhibitor ruthenium red (RuR; 1 μM), NO donor GSNO (250μM), or cGMP analog 8Br‐cGMP (100 μM) (n=5 each, p<0.05). Activation of TRPV4 by 4αPDD (10 μM) induced an [Ca 2+ ] i increase from 103±4 to 172±20 nM which was again blocked by RuR and 8Br‐cGMP (p<0.05). In pulmonary microvascular endothelial cells, 4αPDD activated an inward current that reversed near +20 mV and was blocked by 8Br‐cGMP. In vivo, sildenafil (1 mg/kg bw) reduced lung wet/dry weight ratio and improved arterial pO 2 after LAD occlusion. Our data demonstrate that cGMP attenuates Ca 2+ influx via TRPV4 in lung microvascular endothelial cells. This regulatory pathway may present a new therapeutic target for the treatment of hydrostatic lung edema.