Cold-induced injury to lung epithelial cells can be inhibited by iron chelators - implications for lung preservation

Hypothermia has been shown to lead to cell death via an iron-dependent formation of reactive oxygen species (ROS) in diverse cell types. The susceptibility of lung cells to this injury is unknown - but is of great interest as oxygen is used in lung preservation. Therefore, we studied whether preservation injury to lung epithelial cells can be influenced by iron chelators.

A549 lung epithelial cells were preserved at 4°C for varying periods in either cell culture medium (Dulbecco's Modified Eagle Medium, DMEM), Bretschneider histidine-tryptophan-ketoglutarate (HTK), modified HTK, Celsior, or low potassium dextran (LPD) solution with/without the iron chelators 2,2'-dipyridyl, deferoxamine, or LK 614 and then rewarmed in cell culture medium (for 3h). Lethal cell injury (lactate dehydrogenase (LDH) release or propidium iodide uptake), metabolic activity, morphological alterations, and lipid peroxidation (thiobarbituric acid-reactive substances, TBARS) were assessed.

Lung epithelial cells sustained substantial damage after cold storage/rewarming (LDH release: DMEM 66±12% and 97±1%, HTK 73±14% and 97±1%, Celsior 81±16% and 97±1%, LPD 39±14% and 96±1% after 24h, n=7, and 7 days, n=6, respectively). TBARS were increased. Iron chelators strongly inhibited the damage in all solutions (LDH release after 7 days' cold storage in the presence of 2,2'-dipyridyl: below 8% in all solutions except LPD, LPD 15±4%). This was confirmed using the other iron chelators and the other parameters of injury.

Hypothermic storage of lung cells leads to iron-dependent oxidative cell injury. These results suggest that the addition of iron chelators to existing or novel preservation solutions might decrease lung preservation injury, and this should now be tested in experimental lung transplantation.