Extracellular superoxide dismutase in the airways of transgenic mice reduces inflammation and attenuates lung toxicity following hyperoxia
Rodney J. Folz, … , Amir M. Abushamaa, Hagir B. Suliman
Rodney J. Folz, … , Amir M. Abushamaa, Hagir B. Suliman
Published April 1, 1999
Citation Information: J Clin Invest. 1999;103(7):1055-1066. https://doi.org/10.1172/JCI3816.
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Article

Extracellular superoxide dismutase in the airways of transgenic mice reduces inflammation and attenuates lung toxicity following hyperoxia

Abstract

Extracellular superoxide dismutase (EC-SOD, or SOD3) is the major extracellular antioxidant enzyme in the lung. To study the biologic role of EC-SOD in hyperoxic-induced pulmonary disease, we created transgenic (Tg) mice that specifically target overexpression of human EC-SOD (hEC-SOD) to alveolar type II and nonciliated bronchial epithelial cells. Mice heterozygous for the hEC-SOD transgene showed threefold higher EC-SOD levels in the lung compared with wild-type (Wt) littermate controls. A significant amount of hEC-SOD was present in the epithelial lining fluid layer. Both Tg and Wt mice were exposed to normobaric hyperoxia (>99% oxygen) for 48, 72, and 84 hours. Mice overexpressing hEC-SOD in the airways attenuated the hyperoxic lung injury response, showed decreased morphologic evidence of lung damage, had reduced numbers of recruited inflammatory cells, and had a reduced lung wet/dry ratio. To evaluate whether reduced numbers of neutrophil infiltration were directly responsible for the tolerance to oxygen toxicity observed in the Tg mice, we made Wt and Tg mice neutropenic using anti-neutrophil antibodies and subsequently exposed them to 72 hours of hyperoxia. Both Wt and Tg neutrophil-depleted (ND) mice have less severe lung injury compared with non-ND animals, thus providing direct evidence that neutrophils recruited to the lung during hyperoxia play a distinct role in the resultant acute lung injury. We conclude that oxidative and inflammatory processes in the extracellular lung compartment contribute to hyperoxic-induced lung damage and that overexpression of hEC-SOD mediates a protective response to hyperoxia, at least in part, by attenuating the neutrophil inflammatory response.

Authors

Rodney J. Folz, Amir M. Abushamaa, Hagir B. Suliman

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Western blot analysis of human and mouse EC-SOD from the lungs of wild-t...
Western blot analysis of human and mouse EC-SOD from the lungs of wild-type (Wt) and hEC-SOD transgenic (Tg) mice. Lung protein homogenates from Wt and Tg mice were electrophoresed in 12.5% SDS–polyacrylamide gel. The separated proteins were transferred to Immobilon-P and probed with the anti–hEC-SOD antibodies (WT474) or with anti–mouse EC-SOD (SS618) polyclonal antibodies. (a) Western blot of total lung protein (10 μg) probed with WT474. Lanes 1, 2, and 3 reflect lung homogenate from three independent Tg mice, whereas lanes 4, 5, and 6 are from Wt littermate controls. (b) An identical Western blot as in a was probed with SS618. Of note, hEC-SOD typically shows two bands with the lower-molecular-weight species representing a truncated COOH-terminus. Mouse EC-SOD typically shows three bands, with the lower two also representing COOH-terminal truncations (14).