Increased expression of heme oxygenase-1 in human lung transplantation.

Heme oxygenase-1 (HO-1) has been found to be a cytoprotective protein, and has recently been identified as a graft survival gene. This study demonstrates that HO-1 expression is increased in human lung allografts with acute cellular rejection and obliterative bronchiolitis. HO-1 expression was correlated with increased tissue iron and/or ferritin expression and increased inflammatory/oxidant load as measured by myeloperoxidase expression. Although the trigger for increased HO-1 expression in this setting is unknown, it may be related to hemorrhage and/or oxidative stress associated with rejection.