Mechanistic and therapeutic aspects of spin trap inhalation to protect the obese lung

DARIO C. RAMIREZ; SANDRA E. GOMEZ-MEJIBA

Denver

Congreso; Amercian Thoracic Society Annual Meeting; 2011

ats

D. C. Ramirez1, S. E. Gomez-Mejiba2 1Oklahoma Medical Research Foundation, Oklahoma City, OK, 2Oklahoma Medical Research Foundation, Oklahoma City Corresponding author's email: dariocramirez@yahoo.com Lung inflammation caused by inhalation of air pollutants might play a pathogenic role in obesity by increasing systemic inflammation, which is thought to increase the incidence of insulin resistance and cardiovascular diseases in this population. We found that the lung from mice fed a high-fat diet for 20 weeks has more neutrophils and myeloperoxidase (MPO) than mice fed a control chow. This led us to hypothesize that inahlation of air pollutants makes the obese lung an important source of systemic inflammation due to local MPO-related oxidative processes. Herein we used only lean animals to test whether and how the nitrone spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO) can affect neutrophil homing in the lung of mice exposed to lipopolysaccharide (LPS). We used male B6 mice with acute intratracheal instillation of either 50 ml of vehicle (saline) or LPS (50, 125, 250, 500 mg/mouse), with fifty ml of DMPO (0.05, 0.25, 0.5, 2.5 nmol/mouse) or vehicle intratracheally instilled 1 h before and 23 h after the instillation of LPS. Twenty four h after the LPS instillation, the bronchoalvelolar lavage fluid (BALF), blood and lung tissue were collected. LPS, DMPO or a combination of both at the doses and follow-up time used did not cause death of animals; however, mice instilled with LPS became cachexic and asthenic. Interestingly, DMPO treatment greatly improved these conditions. Cytospin preparation and differential cytology of the BALF showed a cell population mainly composed of neutrophils which were reduced in a dose-dependent manner by DMPO. LPS increased markers of oxidative stress (carbonyls, nitrotyrosine and chlorotyrosine), inflammation (TNF-a, IL-1b, nitrite/nitrate, and IL-6) and tissue damage (lactic dehydrogenase) in the BALF supernatant, serum and lung tissue homogenates; these changes were prevented by DMPO. Histology of the lung tissue of mice instilled with LPS and DMPO showed increased protein-DMPO nitrone adduct formation along with reduced ICAM-1 expression and TNF-a in the lung parenchyma. Protein nitrone adducts also increased in BALF supernatant and serum, indicating that because of its pharmacokinetic properties DMPO might act locally and systemically to trap protein-centered radicals or that proteins tagged with DMPO in the lung can reach systemic circulation. These results suggest that DMPO blocks inflammation caused by endotoxin by trapping protein-centered radicals, suppressing ICAM-1/chemokine expression, and/or blocking further inflammatory effects of oxidized proteins. Delivery of DMPO into the lung might be a potential preventive therapy against metabolic complications in obese patients exposed to air pollution. 5R00ES015415-04 This abstract is funded by: NIEHS 5R00ES015415-04