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Rationale: Inhaled nitric oxide (NO) has been used to prevent bronchopulmonary dysplasia, but with variable results. Ethyl nitrite (ENO) forms S-nitrosothiols more readily than does NO, and resists higher-order nitrogen oxide formation. Because S-nitrosylation is a key pathway mediating many NO biological effects, treatment with inhaled ENO may better protect postnatal lung development from oxidative stress than NO. Objectives: To compare inhaled NO and ENO on hyperoxia-impaired postnatal lung development. Methods: We treated newborn rats beginning at birth to air or 95% O 2 ؎ 0.2-20.0 ppm ENO for 8 days, or to 10 ppm NO for 8 days. Pups treated with the optimum ENO dose, 10 ppm, and pups treated with 10 ppm NO were recovered in room air for 6 more days. Measurements and Main Results: ENO and NO partly prevented 95% O 2 -induced airway neutrophil influx in lavage, but ENO had a greater effect than did NO in prevention of lung myeloperoxidase accumulation, and in expression of cytokine-induced neutrophil chemoattractant-1. Treatment with 10 ppm ENO, but not NO, for 8 days followed by recovery in air for 6 days prevented 95% O 2 -induced impairments of body weight, lung compliance, and alveolar development. Conclusions: Inhaled ENO conferred protection superior to inhaled NO against hyperoxia-induced inflammation. ENO prevented hyperoxia impairments of lung compliance and postnatal alveolar development in newborn rats. Keywords: bronchopulmonary dysplasia; O-nitrosoethanol; S-nitrosylationInhaled nitric oxide (NO) has been used to prevent and treat bronchopulmonary dysplasia (BPD) in premature newborns, with mixed success (1-4). The rationale underlying clinical trials has included improvement of ventilation-perfusion matching through classical effects on guanylyl cylase-mediated pulmonary vascular tone and remodeling (5), alveolar capillary development (6), and reducing inflammation (7). However, many, if not most NO biological effects are mediated through reversible S-nitrosylation of critical thiols that govern multiple biological pathways (8-10).Inhaled agents preferentially forming S-nitrosothiols may "deliver" NO biological effects more efficiently, which may be of particular benefit in treating patients subjected to high levels of inhaled oxygen, as NO tends to rapidly form peroxynitrite in What This Study Adds to the FieldInhaled ethyl nitrite dose-dependently prevents hyperoxiainduced lung inflammation in newborn rats, and, at an equivalent dose, afforded better protection of postnatal lung function and development than nitric oxide. the presence of superoxide. Inhaled ethyl nitrite (ENO) has been used to treat newborns with pulmonary hypertension (11), and efficiently achieves S-nitrosation of glutathione compared with NO, without releasing significant amounts of reactive• NO species (12), so it should be less susceptible to forming higherorder nitrogen oxides.We therefore compared the effects of inhaled NO and ENO in hyperoxia-exposed newborn rats, which we have previously shown to develop an acute inf...

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Hypersecretion of mucus characterizes many inflammatory airway diseases, including asthma, chronic bronchitis, and cystic fibrosis. Excess mucus causes airway obstruction, reduces pulmonary function, and can lead to increased morbidity and mortality. MicroRNAs are small non-coding pieces of RNA which regulate other genes by binding to a complementary sequence in the target mRNA. The microRNA miR-21 is upregulated in many inflammatory conditions and, interestingly, miR-21 has been shown to target the mRNA of Myristoylated Alanine-Rich C Kinase Substrate (MARCKS), a protein that is an important regulator of airway mucin (the solid component of mucus) secretion. In these studies, we determined that exposure of primary, well-differentiated, normal human bronchial epithelial (NHBE) cells to the pro-inflammatory stimulus lipopolysaccharide (LPS) increased expression of both miR-21 and MARCKS in a time-dependent manner. To investigate whether miR-21 regulation of MARCKS played a role in mucin secretion, two separate airway epithelial cell lines, HBE1 (papilloma virus transformed) and NCI-H292 (mucodepidermoid derived) were utilized, since manipulation of miR-21 is performed via transfection of commercially-available miR-21 inhibitors and mimics/activators. Treatment of HBE1 cells with LPS caused concentration-dependent increases in expression of both miR-21 and MARCKS mRNA and protein. The miR-21 inhibitor effectively reduced levels of miR-21 in the cells, coincident with an increase in MARCKS mRNA expression over time as well as enhanced mucin secretion, while the miR-21 mimic/activator increased levels of miR-21, which coincided with a decrease in expression of MARCKS and a decrease in mucin secretion. These results suggest that miR-21 is increased in airway epithelial cells following exposure to LPS, and that miR-21 downregulates expression of MARCKS, which may decrease mucin secretion by the cells. Thus, miR-21 may act as a negative feedback regulator of mucin secretion in airway epithelial cells, and may do so, at least in part, by downregulating expression of MARCKS.

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