Neutral endopeptidase activity and concentration of sensory neuropeptide in the human nasal mucosa

Human nasal mucosa biopsy samples were studied by biochemical and histological methods to determine whether the concentration of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) as a marker of sensory nerves was dependent on the activity of neutral endopeptidase-like enzyme (NEP-LE). Mucosal samples from the middle turbinate were obtained from 32 patients undergoing functional endoscopic nasal surgery for non-allergic chronic rhinosinusitis. The degree of symptoms related to nasal obstruction, rhinorrhea and headaches was recorded. The number of inflammatory cells in each biopsy sample was evaluated by conventional histopathological examination. CGRP-LI was measured by radioimmunoassay. The activity of NEP-LE was evaluated in vitro using [3H] Leu5-enkephalin as substrate. A good correlation was observed between increased concentrations of CGRP, abundant inflammatory cells and the intensity of symptoms (R2 = 0.80). A low activity of NEP-LE was associated with a high concentration of both inflammatory cells and CGRP, suggesting that NEP-LE activity was reduced during inflammation. These observations further support the hypothesis that reduced degradation of sensory neuropeptides could be involved in the pathophysiological mechanisms of non-specific chronic rhinosinusitis.