Original Contribution
The effects of aging on pulmonary oxidative damage, protein nitration, and extracellular superoxide dismutase down-regulation during systemic inflammation

https://doi.org/10.1016/j.freeradbiomed.2010.11.013Get rights and content

Abstract

Systemic inflammatory response syndrome (SIRS), a serious clinical condition characterized by whole-body inflammation, is particularly threatening for elderly patients, who suffer much higher mortality rates than the young. A major pathological consequence of SIRS is acute lung injury caused by neutrophil-mediated oxidative damage. Previously, we reported an increase in protein tyrosine nitration (a marker of oxidative/nitrosative damage) and a decrease in the antioxidant enzyme extracellular superoxide dismutase (EC-SOD) in the lungs of young mice during endotoxemia-induced SIRS. Here we demonstrate that during endotoxemia, down-regulation of EC-SOD is significantly more profound and prolonged, whereas up-regulation of iNOS is augmented, in aged compared to young mice. Aged mice also showed 2.5-fold higher protein nitration levels, compared to young mice, with particularly strong nitration in the pulmonary vascular endothelium during SIRS. Additionally, by two-dimensional gel electrophoresis, Western blotting, and mass spectrometry, we identified proteins that show increased tyrosine nitration in age- and SIRS-dependent manners; these proteins (profilin-1, transgelin-2, LASP 1, tropomyosin, and myosin) include components of the actin cytoskeleton responsible for maintaining pulmonary vascular permeability. Reduced EC-SOD in combination with increased oxidative/nitrosative damage and altered cytoskeletal protein function due to tyrosine nitration may contribute to augmented lung injury in the aged with SIRS.

Section snippets

Animals

Young (4–6 months of age) and aged (24–26 months of age) male C57BL/6 mice were obtained from colonies of the National Institute on Aging (Bethesda, MD, USA). Mice were acclimated for at least 14 days in a 12:12-h light:dark cycle with free access to water and regular chow diet (LabDiet, Brentwood, MO, USA) before experiments began and throughout each experiment. All animal care and surgical procedures were approved by the Institutional Animal Care and Use Committees at the University of Texas

Exaggerated pulmonary inflammation and edema in aged mouse lung tissue after LPS-induced systemic inflammation

Upon LPS injection, both young and aged mice suffered hypothermia characteristic of LPS-mediated systemic inflammation [9] and a temporal appetite loss. Histology of H&E-stained lung tissues was compared among young (6-month) and aged (26-month) mice 24 h after LPS-induced systemic inflammation. Uninjected mice were used as controls. Fig. 1A shows the histologic characteristics of normal, healthy young lung tissue consisting of thin alveolar walls embedded with capillaries, alveolar cells, and

Discussion

Acute lung injury, a common consequence of oxidative damage during SIRS and sepsis, is a complex inflammatory syndrome characterized by hypoxemia, noncardiogenic pulmonary edema, and widespread capillary leakage resulting from endothelial barrier dysfunction [33]. We showed characteristic pathologic changes such as thickened alveolar walls, capillary dilation, and fluid-filled alveolar spaces that were more pronounced in the lung from aged mice during systemic inflammation, indicating an

Acknowledgments

The authors thank Dr. John E. Wiktorowicz, Mrs. Susan J. Stafford, and Dr. Zheng Wu of the Biomolecular Resource Facility at the University of Texas Medical Branch for technical advice and assistance with the 2D gel experiments and analysis. The authors also thank Dr. James D. Crapo at the National Jewish Medical and Research Center for providing the anti-EC-SOD antibody and Dr. Michael B. Reid of the Department of Physiology at the University of Kentucky for his thoughtful advice and critique

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    These authors contributed equally to this work.

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