Neutral endopeptidase and endothelin-converting enzyme in human buccal mucosal epithelium

Objectives: This study investigated the expression of neutral endopeptidase (NEP) and endothelin-converting enzyme (ECE)-1 in human oral buccal mucosal epithelium, and verified whether their expression was related to oral and systemic health and life habits. Methods: Tissue samples were collected using a cotton swab from the oral buccal mucosal epithelium of patients who visited the hospital at Kyushu Dental College for dental treatment and oral care. The mRNA expression of NEP and ECE-1 isoforms a, b, and c in each sample was quantified using real-time RT-PCR. Results: NEP and the three ECE-1 isoforms were expressed in all samples. There were significant correlations between the expression of NEP and ECE-1a and 1b, and among the three ECE-1 isoforms (Pearson correlation analysis). The expression of NEP was enhanced significantly in males, but reduced significantly in subjects with diabetes (unpaired t-test). The ECE-1a gene was significantly overexpressed in the samples from subjects with hypertension or diabetes, and ECE-1c was significantly overexpressed in the subjects with diabetes. By contrast, the expression of ECE-1a and 1b was reduced significantly in the samples from subjects with a history of heart disease. Although there were no significant correlations between the gene expression and oral factors, such as the numbers of teeth and sites with probing depths greater than 4 mm (PD4) and bleeding on probing, and life habits, such as smoking and drinking alcohol, there were weak correlations between NEP expression and the numbers of teeth and teeth with PD4, and between the expression levels of NEP, ECE-1a and 1b and the number of teeth with PD4. Conclusion: The expression of NEP and ECE-1 in the human oral buccal mucosa might be related to differences in oral and systemic health.