Abstract
It was hypothesized that celltocell interaction between human alveolar macrophages (AM) and alveolar epithelium, might be an important factor leading to nitric oxide synthase‐2 (NOS2) messenger ribonucleic acid (mRNA) and protein expression by constituent cells of the alveolar wall and/or AM.
NOS2 mRNA and the protein expression patterns of human AM and alveolar epithelial cells type II (AECII) isolated from normal parts of lung resections of patients with pulmonary malignancies were determined. In addition, NOS2 mRNA expression in human AM cocultured with autologous AECII in the presence of proinflammatory cytokines interleukin (IL)‐1β, tumour necrosis factor (TNF)‐α, interferon (IFN)‐γ or lipopolysaccharide (LPS) was investigated. The effect of human surfactant protein‐A (SP‐A) on IFN‐γ‐mediated NOS2 mRNA expression in human AM was also studied.
Neither NOS2 mRNA nor protein could be detected in freshly isolated, unstimulated or cytokinestimulated AECII. In contrast, freshly isolated AM from bronchoalveolar lavage or lung tissue samples expressed immunoreactivity for NOS2 protein, but no NOS2 mRNA could be detected by reverse transcriptase polymerase chain reaction. All stimuli tested failed to induce NOS2 mRNA expression in human AM in vitro. Only AMAECII coculture in the presence of IFN‐γ led to NOS2 mRNA and protein expression. In situ hybridization of NOS2 mRNA on lung tissue explants and immunohistochemical staining of cytospin preparations of AMAECII cocultures demonstrated that NOS2 is expressed in AM but not in AECII. This coculture effect could not be reproduced by substitution of AECII with SP‐A.
These data give evidence of a regulatory network controlling human nitric oxide synthase‐2 expression in the lower respiratory tract.
- alveolar epithelial cells type II
- alveolar macrophages
- cytokines
- nitric oxide synthase‐2
- reverse transcriptase polymerase chain reaction
- surfactant protein A
This study was supported in part by a grant from the Deutsche Forschungs gemeinschaft (No. Mu 6623/5‐5). D.V. Pechkovsky is a recipient of a research fellowship from the European Respiratory Society and the Borstel Foundation.
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