The role of erythropoietin-producing hepatoma receptor tyrosine kinase A2 on ventilator-induced lung injury

Abstract

Background: The erythropoietin-producing hepatoma (Eph) receptor tyrosine kinases and their ligand ephrins have diverse biological functions and influence cellular behaviors during embryogenesis and adult life. Among these, EphA2 receptor and the ligand ephrinA1 play a pivotal role in inflammation and tissue injury by modulating epithelial and endothelial barrier integrity. However, the role of EphA2/ephrinA1 in the process of ventilator-induced lung injury (VILI) remains unclear. Therefore, we hypothesized that the blockade of EphA2/ephrinA1 signaling using an EphA2 receptor antibody (Ab) would result in decreased inflammation and injury in VILI model. Methods: Wild type male C57BL/6J mice were randomly assigned to four experimental groups (n = 4/group); (1) non-ventilated mice as a control group, (2) immunoglobulin G (IgG) (1 hour before mechanical ventilation) + high tidal volume (HTV) ventilation group, (3) EphA2 receptor Ab (1 hour before mechanical ventilation) + HTV ventilation group, and (4) HTV ventilation + EphA2 receptor Ab (2 hours after mechanical ventilation) group. Injury was assessed by bronchoalveolar lavage fluid analysis, lung injury scoring, and transmission electron micrographic evaluation. Western blotting for EphA2/ephrinA1/phosphoinositide 3-kinase γ (PI3Kγ)/protein kinase B (Akt)/NF-kB/P70S6 kinase and enzyme-linked immunoassay for interleukin (IL)-1β/IL-6/keratinocyte chemoattractant (KC/CXCL1) were performed on lung lysates. Results: EphA2/EphrinA1 expression was higher in HTV ventilation group rather than in control group and decreased by pre- or post-treatment with EphA2 receptor Ab. EphA2 receptor Ab also ameliorated the extent of lung injury and downregulated the expression of PI3Kγ/Akt/NF-kB and mammalian target of rapamycin (mTOR). EphA2 receptor Ab did not influence on the proinflammatory cytokine/chemokine levels. Conclusion: These findings suggest that EphA2/ephrinA1 may be involved in the pathogenesis of VILI, partly through PI3Kγ/Akt/NF-kB signaling pathway and possibly via mTOR pathway. Our data provide an evidence for EphA2/ehprinA1 as a promising therapeutic target for modulating VILI.