Neutrophils enhance expression of inducible nitric oxide synthase in human normal but not cystic fibrosis bronchial epithelial cells.
The bronchial epithelium in cystic fibrosis (CF) expresses very low levels of the inducible form of nitric oxide synthase (iNOS). The product of iNOS, nitric oxide (NO), mediates anti-microbial effects and can reduce neutrophil sequestration in the lung. Heavy neutrophilic infiltration of the pulmonary epithelium is a major feature of the end-stage CF lung. This study hypothesized that the system whereby the pulmonary epithelium protects itself against exaggerated neutrophilic infiltration by producing NO is compromised in CF. Human neutrophils were activated by incubation with cytokines, added to monolayers of normal (16HBE14o-) and CF (CFBE41o-) bronchial epithelial cells and co-cultured for up to 72 h. Marked up-regulation of iNOS protein expression was seen in normal bronchial epithelial cells following neutrophil co-culture but the CF cells showed a significantly smaller increase (p<0.001). To determine whether the relative lack of protein was due to a defect in translation, RT-PCR of iNOS mRNA was carried out and a pattern of mRNA expression was seen paralleling that of the protein. The reduced production of NO by CF compared with normal epithelium was shown by the presence of significantly (p<0.001) less accumulated nitrites in medium after co-culture with neutrophils. In summary, this study shows that the normal production of NO by bronchial epithelium in response to contact with neutrophils is lacking in CF. As NO has been shown to oppose neutrophil sequestration, its relative lack in CF may underlie the heavy neutrophilic infiltration that characterizes the disease.
Meng
Q H
QH
Department of Histochemistry, Imperial College School of Medicine, Hammersmith Hospital, London, UK.
Polak
J M
JM
Edgar
A J
AJ
Chacon
M R
MR
Evans
T J
TJ
Gruenert
D C
DC
Bishop
A E
AE
D001980:Bronchi / Q000201:enzymology*; D018929:Cell Culture Techniques; D002460:Cell Line; D003550:Cystic Fibrosis / Q000201:enzymology*; D004847:Epithelial Cells / Q000201:enzymology; D015870:Gene Expression; D006801:Humans; D007124:Immunoenzyme Techniques; D009504:Neutrophils / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction
D009573:Nitrites; D012333:RNA, Messenger; D009569:Nitric Oxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II