Hyperoxia is an important cause of acute lung injury. To determine whether IL-13 is protective in hyperoxia, we compared the survival in 100% O2 of transgenic mice that overexpress IL-13 in the lung and of nontransgenic littermate controls. IL-13 enhanced survival in 100% O2. One hundred percent of nontransgenic mice died in 4-5 days, whereas 100% of IL-13-overexpressing mice lived for more than 7 days, and many lived 10-14 days. IL-13 also stimulated VEGF accumulation in mice breathing room air, and it interacted with 100% O2 to increase VEGF accumulation further. The 164-amino acid isoform was the major VEGF moiety in bronchoalveolar lavage from transgenic mice in room air, whereas the 120- and 188-amino acid isoforms accumulated in these mice during hyperoxia. In addition, antibody neutralization of VEGF decreased the survival of IL-13-overexpressing mice in 100% O2. These studies demonstrate that IL-13 has protective effects in hyperoxic acute lung injury. They also demonstrate that IL-13, alone and in combination with 100% O2, stimulates pulmonary VEGF accumulation, that this stimulation is isoform-specific, and that the protective effects of IL-13 are mediated, in part, by VEGF.
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