title: Neutral endopeptidase regulates neurogenic inflammatory responses induced by stimulation of human oral keratinocytes with bacterial lipopolysaccharide and nicotine.
abstract: Neutral endopeptidase (NEP) is present on various epithelial cells and inactivates numerous physiologically active peptides. Neutral endopeptidase may regulate proinflammatory signals in oral mucosal epithelium. However, the function of NEP in oral mucosal epithelium is unknown. The present study investigated the action of NEP upon proinflammatory signals on human oral keratinocytes and the influence of endothelin-converting enzyme (ECE)-1, an enzyme similar to NEP, on the functions of NEP. Oral keratinocytes were cultured in medium containing inflammatory inducers [lipopolysaccharide (LPS) and nicotine], NEP inhibitors, and ECE-1/NEP inhibitors, either alone or in combination. The concentrations of substance P (SP) and interleukin-1β (IL-1β) were measured in the supernatant. Additionally, the concentrations of SP and IL-1β were measured in the supernatant of cells incubated with LPS or nicotine after transfection with NEP small interfering RNA (siRNA). The concentrations of SP and IL-1β were significantly increased in cells incubated with NEP inhibitors and, to a lesser extent, in cells incubated with ECE-1/NEP inhibitors, compared with controls (cells incubated with LPS or nicotine alone). The concentrations of SP and IL-1β in cells transfected with NEP siRNA were significantly augmented compared with controls. In conclusion, the present study demonstrated that NEP down-regulated the levels of SP and IL-1β produced from human oral keratinocytes, although ECE-1 may be partly related to the down-regulation.
authors.affiliation: Division of Community Oral Health Science, Department of Health Promotion, Kyushu Dental University, Kitakyushu, Japan.
authors.forename: Motoki
authors.initials: M
authors.lastname: Nakata
authors.forename: Shuji
authors.initials: S
authors.lastname: Awano
authors.forename: Naomasa
authors.initials: N
authors.lastname: Kinoshita
authors.forename: Akihiro
authors.initials: A
authors.lastname: Yoshida
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Ansai
mesh_terms: D016282:Aspartic Acid Endopeptidases / Q000378:metabolism*; D002460:Cell Line; D015536:Down-Regulation; D000072396:Endothelin-Converting Enzymes; D004847:Epithelial Cells / Q000201:enzymology; D006801:Humans; D007249:Inflammation / Q000139:chemically induced*; D053583:Interleukin-1beta / Q000032:analysis; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000009:adverse effects*; D008666:Metalloendopeptidases / Q000378:metabolism*; D009061:Mouth Mucosa / Q000201:enzymology; D015260:Neprilysin / Q000378:metabolism*; D009538:Nicotine / Q000494:pharmacology*; D011480:Protease Inhibitors / Q000378:metabolism*; D034741:RNA, Small Interfering; D013373:Substance P / Q000032:analysis
chemical_list: D053583:Interleukin-1beta; D008070:Lipopolysaccharides; D011480:Protease Inhibitors; D034741:RNA, Small Interfering; D013373:Substance P; D009538:Nicotine; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D015260:Neprilysin; C000606923:ECE1 protein, human; D000072396:Endothelin-Converting Enzymes
keywords: interleukin-1β; neutral endopeptidase; oral keratinocyte; small interfering RNA; substance P