Neuronal nitric oxide synthase is associated with airway obstruction in BALB/c mice exposed to ozone.
BACKGROUND
The functional role of nitric oxide (NO) and the various nitric oxide synthase (NOS) isoforms in asthma is controversial.


OBJECTIVE
To investigate the role of NO in mice exposed to ozone, three known isoforms of NOS [inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS)] were studied.


METHODS
The expression of iNOS, nNOS, and eNOS was determined in lung by Western blot analysis after exposure to filtered air and ozone (0.12, 0.5, 1 or 2 ppm) for 3 h. Using barometric whole-body plethysmography and increase in enhanced pause (P(enh)) as an index of airway obstruction, we measured airway responses to ozone exposure. Bronchoalveolar lavage (BAL) was performed. Nitrate and nitrite were measured using a modified Griess reaction.


RESULTS
The nitrate concentration in BAL fluid, which indicates the in vivo generation of NO in airways, from the ozone-exposed group was significantly greater than that from the group exposed to filtered air (631.0 +/- 86.4 vs. 152.1 +/- 16.9 micromol/l, p < 0.05). The nitrate concentration in BAL fluid was increased more in mice exposed to 2-ppm ozone than that in mice exposed to filtered air or 0.12-, 0.5-, or 1-ppm ozone. Increases in P(enh) after exposure to ozone or filtered air were significantly higher in the ozone-exposed groups than in the group exposed to filtered air (p < 0.01). Increases in P(enh) were dependent on the ozone concentration. Although the protein levels of eNOS and iNOS determined were within normal levels, the amount of nNOS protein was markedly elevated in airway tissue homogenates of the group exposed to 2-ppm ozone.


CONCLUSIONS
These findings demonstrate that the nNOS isoform may be involved in airway obstruction in mice exposed to ozone.
Jang
An-Soo
AS
Department of Internal Medicine, Cheju National University College of Medicine, Jeju, Republic of Korea. jas877@cheju.ac.kr
Choi
Inseon-S
IS
Lee
Jong-Un
JU
D000402:Airway Obstruction / Q000139:chemically induced / Q000378:metabolism*; D000818:Animals; D015153:Blotting, Western; D018893:Bronchoalveolar Lavage; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D005260:Female; D007527:Isoenzymes; D051379:Mice; D008807:Mice, Inbred BALB C; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000096:biosynthesis*; D010083:Oxidants, Photochemical / Q000633:toxicity*; D010126:Ozone / Q000633:toxicity*; D010991:Plethysmography; D018709:Statistics, Nonparametric
D007527:Isoenzymes; D010083:Oxidants, Photochemical; D010126:Ozone; D019001:Nitric Oxide Synthase