L-Arginine is not the limiting factor for nitric oxide synthesis by human alveolar macrophages in vitro

Unlike murine mononuclear phagocytes, human macrophages do not release high amounts of nitric oxide (NO) in vitro despite the presence of nitric oxide synthase (NOS). To determine whether this limited NO synthesis in vitro is due to limited availability of the NOS substrate L-arginine, and putative NOS inhibiting factors present in foetal serum preparations, both alveolar macrophages (AM) and monocyte derived macrophages (MDM) were incubated in various circumstances. Nitrite production measured using stimulated AM was typically It is concluded that the limited nitric oxide production of human macrophages in vitro can neither be explained by limited availability of L-arginine, nor by nitric oxide synthase inhibiting substances in foetal serum. Furthermore, it is shown that nitrite release from N omega -hydroxy-L-arginine by alveolar macrophages is nitric oxide synthase independent

Apocynin and 1400 W prevents airway hyperresponsiveness during allergic reactions in mice

1 The contribution of reactive nitrogen species to the development of airway hyperresponsiveness in a mouse model of allergic inflammation was investigated by the use of selective inhibitors of nitric oxide and superoxide formation. 2 Sensitized mice, repeatedly challenged with ovalbumin showed a significant (P <0.001, n = 9) increase in airway responsiveness measured using whole body plethysmography. This hyperresponsiveness was accompanied by an influx of eosinophils into the airway lumen and increased levels of ovalbumin-specific serum IgE. 3 Treatment of mice with the iNOS inhibitor 1400 W or the NADPH-oxidase inhibitor apocynin did not significantly alter cellular influx into the airway lumen nor serum ovalbumin specific IgE. In contrast, apocynin as well as 1400 W inhibited ovalbumin-induced airway hyperresponsiveness (P 4 These data suggest that the development of airway hyperresponsiveness during the airway inflammation upon ovalbumin challenge is dependent on the release of both superoxide and nitric oxide and is therefore likely to be dependent on reactive nitrogen species. This mechanism, however, is not reflected by 3-nitrotyrosine formation in the airways

Apocynin and 1400 W prevents airway hyperresponsiveness during allergic reactions in mice

1 The contribution of reactive nitrogen species to the development of airway hyperresponsiveness in a mouse model of allergic inflammation was investigated by the use of selective inhibitors of nitric oxide and superoxide formation. 2 Sensitized mice, repeatedly challenged with ovalbumin showed a significant (P <0.001, n = 9) increase in airway responsiveness measured using whole body plethysmography. This hyperresponsiveness was accompanied by an influx of eosinophils into the airway lumen and increased levels of ovalbumin-specific serum IgE. 3 Treatment of mice with the iNOS inhibitor 1400 W or the NADPH-oxidase inhibitor apocynin did not significantly alter cellular influx into the airway lumen nor serum ovalbumin specific IgE. In contrast, apocynin as well as 1400 W inhibited ovalbumin-induced airway hyperresponsiveness (P 4 These data suggest that the development of airway hyperresponsiveness during the airway inflammation upon ovalbumin challenge is dependent on the release of both superoxide and nitric oxide and is therefore likely to be dependent on reactive nitrogen species. This mechanism, however, is not reflected by 3-nitrotyrosine formation in the airways

Apocynin and 1400 W prevents airway hyperresponsiveness during allergic reactions in mice

1 The contribution of reactive nitrogen species to the development of airway hyperresponsiveness in a mouse model of allergic inflammation was investigated by the use of selective inhibitors of nitric oxide and superoxide formation. 2 Sensitized mice, repeatedly challenged with ovalbumin showed a significant (P <0.001, n = 9) increase in airway responsiveness measured using whole body plethysmography. This hyperresponsiveness was accompanied by an influx of eosinophils into the airway lumen and increased levels of ovalbumin-specific serum IgE. 3 Treatment of mice with the iNOS inhibitor 1400 W or the NADPH-oxidase inhibitor apocynin did not significantly alter cellular influx into the airway lumen nor serum ovalbumin specific IgE. In contrast, apocynin as well as 1400 W inhibited ovalbumin-induced airway hyperresponsiveness (P 4 These data suggest that the development of airway hyperresponsiveness during the airway inflammation upon ovalbumin challenge is dependent on the release of both superoxide and nitric oxide and is therefore likely to be dependent on reactive nitrogen species. This mechanism, however, is not reflected by 3-nitrotyrosine formation in the airways