To evaluate the effects of a recombinant strain of Lactococcus lactis secreting bioactive heme oxygenase-1 (LL-HO-1) in a model of hyperoxia-induced lung injury in rat pups Intranasal administration with LL-HO-1 significantly reduced hyperoxia-induced lung injury as demonstrated by a decreased wet/dry ratio, myeloperoxidase activity in lung tissue, tumor necrosis factor alpha levels in bronchoalveolar lavage (BAL) fluid, and attenuated lung injury scores. Although expression of HO-1 and NADPH oxidase-1 and production of superoxide in lung tissue were not affected by LL-HO-1 treatment, HO-1 levels in nasal mucosa and interleukin-10 concentrations in BAL fluid significantly increased compared with the hyperoxia control group Intranasal administration of LL-HO-1 protects against hyperoxia-induced lung damage, apparently through attenuation of inflammation.