LOCALIZATION OF NEUTRAL ENDOPEPTIDASE (NEP) MESSENGER-RNA IN HUMAN BRONCHI

Neutral endopeptidase (NEP) may regulate peptide-induced inflammation in the respiratory tract, It is of interest to determine which respira tory resident cells express NEP. Trachea and bronchi from seven nonsmo king, nonasthmatic subjects were examined, NEP messenger ribonucleic a cid (mRNA) was characterized by Northern blot hybridization of culture d human tracheobronchial epithelial and smooth muscle cells, and rever se transcriptase-polymerase chain reaction (RT-PCR) in trachea and bro nchi. In situ hybridization with biotin- and S-35-labelled antisense c omplementary ribonucleic acid (cRNA) probes was used to determine the distribution of NEP mRNA in human bronchial mucosa NEP-immunoreactive material was detected using MEK10 murine monoclonal antibodies and the inmunogold method with silver enhancement. NEP mRNA was 4.5 kb in siz e in the cultured human smooth muscle and epithelial cells by Northern blot analysis, No evidence was found by RT-PCR for truncated, alterna tively spliced NEP mRNAs, such as del exon 16 or del exons 5-18 in hum an bronchus. NEP mRNA was detected by in situ hybridization in epithel ial cells, submucosal glands, bronchial smooth muscle and endothelium. NEP-immunoreactive material was identified in the epithelium, submuco sal glands, bronchial smooth muscle, and endothelium, demonstrating an excellent correlation between the distribution of NEP mRNA and the ce ll surface protein. NEP mRNA and immunoreactive material were excluded from epithelial goblet cell and submucosal gland mucous cell vacuoles . We conclude that the various sites of NEP protein and mRNA expressio n correlate with the locations of peptide receptors and NEP enzyme fun ction, and are consistent with the hypothesis that NEP may regulate pe ptide-induced inflammation in human bronchi.