Abstract Rationale Radiation-induced lung injury (RILI) is a potential complication of thoracic radiation associated with significant morbidity although the cellular mechanisms responsible for these effects have not been fully characterized. TRPM2 (transient receptor potential (melastatin) 2), an oxidant sensitive, non-selective cation channel is known to regulate cellular responses to radiation injury in general and is expressed in the lung endothelium. Thus, we hypothesized that TRPM2 is an important mediator of RILI via effects on lung endothelial cell (EC) responses to radiation. Methods To assess the role of endothelial TRPM2 in RILI, TRPM2-/- and wildtype mice were subjected to single dose thoracic irradiation (20 Gy). Bronchoalveolar lavage (BAL) fluid was collected 12 wks after radiation to assess protein and total cell counts, markers of increased lung vascular permeability and inflammation consistent with RILI. In parallel experiments with the same conditions, lungs were harvested at 16 wks and used for histology. Separately, lung homogenates from wildtype and TRPM2-/- mice harvested at 12 wks after irradiation were used for Western blotting for Bax and caspase-3, markers of apoptosis. To assess the role of TRPM2 on EC barrier function, lung EC from wildtype and TRPM2-/- mice were used in assays of transendothelial electrical resistance and FITC-dextran transwell flux. Results RILI was markedly attenuated in TRPM2-/- mice compared to controls as assessed by BAL protein and total cell counts at 12 wks and evidence of decreased inflammatory cells and interstitial edema on lung histology at 16 wks. In addition, radiation-induced apoptosis was significantly reduced in lung EC isolated from TRPM2-/- mice compared to controls. Finally, TRPM2 depletion was associated with a significant attenuation of thrombin-induced EC barrier disruption as assessed by both TER and FITC-dextran transwell flux. Conclusion Our data confirm that TRPM2 is an important mediator of lung EC responses to radiation and suggest that the inhibition of TRPM2 may prove to be a novel and effective therapeutic strategy in patients with or at risk for RILI. This abstract is funded by: none
Chen et al. (Fri,) studied this question.