Abstract
BACKGROUND: Lung ischemia-reperfusion injury (IRI), involving severe inflammation and edema, is a major cause of primary graft dysfunction after transplant. Activation of transient receptor potential vanilloid 4 (TRPV4) channels modulates vascular permeability. Thus, this study tests the hypothesis that endothelial TRPV4 channels mediate lung IRI. METHODS: A left lung hilar-ligation model was used to induce lung IR in C57BL/6 wild-type (WT), Trpv4(-/-), tamoxifen-inducible endothelial Trpv4 knockout (Trpv4(EC)(-/-)), and tamoxifen-treated control (Trpv4(fl/fl)) (n ≥ 6 mice/group). WT mice were also treated with GSK2193874 (WT+GSK219), a TRPV4-specific inhibitor (1 mg/kg). Partial pressure of arterial oxygen, edema (wet-to-dry weight ratio), compliance, neutrophil infiltration, and cytokine concentrations in bronchoalveolar lavage fluid were assessed. Pulmonary microvascular endothelial cells were characterized in vitro after exposure to hypoxia-reoxygenation. RESULTS: Compared with WT, partial pressure of arterial oxygen after IR was significantly improved in Trpv4(-/-) mice (133.1 ± 43.9 vs 427.8 ± 83.1 mm Hg, P < .001) and WT+GSK219 mice (133.1 ± 43.9 vs 447.0 ± 67.6 mm Hg, P < .001). Pulmonary edema and neutrophil infiltration were also significantly reduced after IR in Trpv4(-/-) and WT+GSK219 mice vs WT. Trpv4(EC)(-/-) mice after IR demonstrated significantly improved oxygenation vs control (109.2 ± 21.6 vs 405.3 ± 41.4 mm Hg, P < .001) as well as significantly improved compliance and significantly less edema, neutrophil infiltration, and proinflammatory cytokine production (tumor necrosis factor-a, chemokine [C-X-C motif] ligand 1, interleukin 17, interferon-γ). Hypoxia-reoxygenation-induced permeability and chemokine (C-X-C motif) ligand 1 expression by pulmonary microvascular endothelial cells were significantly attenuated by TRPV4 inhibitors. CONCLUSIONS: Endothelial TRPV4 plays a key role in vascular permeability and lung inflammation after IR. TRPV4 channels may be a promising therapeutic target to mitigate lung IRI and decrease the incidence of primary graft dysfunction after transplant.