20-HETE mediates ozone-induced, neutrophil-independent airway hyper-responsiveness in mice.
BACKGROUND
Ozone, a pollutant known to induce airway hyper-responsiveness (AHR), increases morbidity and mortality in patients with obstructive airway diseases and asthma. We postulate oxidized lipids mediate in vivo ozone-induced AHR in murine airways.


RESULTS
Male BALB/c mice were exposed to ozone (3 or 6 ppm) or filtered air (controls) for 2 h. Precision cut lung slices (PCLS; 250 microm thickness) containing an intrapulmonary airway ( approximately 0.01 mm(2) lumen area) were prepared immediately after exposure or 16 h later. After 24 h, airways were contracted to carbachol (CCh). Log EC(50) and E(max) values were then calculated by measuring the airway lumen area with respect to baseline. In parallel studies, dexamethasone (2.5 mg/kg), or 1-aminobenzotriazol (ABT) (50 mg/kg) were given intraperitoneal injection to naïve mice 18 h prior to ozone exposure. Indomethacin (10 mg/kg) was administered 2 h prior. Cell counts, cytokine levels and liquid chromatography-mass spectrometry (LC-MS) for lipid analysis were assessed in bronchoalveolar lavage (BAL) fluid from ozone exposed and control mice. Ozone acutely induced AHR to CCh. Dexamethasone or indomethacin had little effect on the ozone-induced AHR; while, ABT, a cytochrome P450 inhibitor, markedly attenuated airway sensitivity. BAL fluid from ozone exposed animals, which did not contain an increase in neutrophils or interleukin (IL)-6 levels, increased airway sensitivity following in vitro incubation with a naïve PCLS. In parallel, significant increases in oxidized lipids were also identified using LC-MS with increases of 20-HETE that were decreased following ABT treatment.


CONCLUSIONS
These data show that ozone acutely induces AHR to CCh independent of inflammation and is insensitive to steroid treatment or cyclooxygenase (COX) inhibition. BAL fluid from ozone exposed mice mimicked the effects of in vivo ozone exposure that were associated with marked increases in oxidized lipids. 20-HETE plays a pivotal role in mediating acute ozone-induced AHR.
Cooper
Philip R
PR
Department of Medicine and the Airways Biology Initiative, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania, United States of America.
Mesaros
A Clementina
AC
Zhang
Jie
J
Christmas
Peter
P
Stark
Christopher M
CM
Douaidy
Karim
K
Mittelman
Michael A
MA
Soberman
Roy J
RJ
Blair
Ian A
IA
Panettieri
Reynold A
RA
D000818:Animals; D016535:Bronchial Hyperreactivity; D002217:Carbachol / Q000494:pharmacology; D006893:Hydroxyeicosatetraenoic Acids / Q000032:analysis* / Q000276:immunology*; D015227:Lipid Peroxidation; D008297:Male; D013058:Mass Spectrometry; D051379:Mice; D008807:Mice, Inbred BALB C; D009504:Neutrophils; D010126:Ozone / Q000494:pharmacology*; D012130:Respiratory Hypersensitivity / Q000209:etiology*; D014230:Triazoles / Q000494:pharmacology
D006893:Hydroxyeicosatetraenoic Acids; D014230:Triazoles; C033020:1-aminobenzotriazole; D010126:Ozone; C055987:20-hydroxy-5,8,11,14-eicosatetraenoic acid; D002217:Carbachol