Expression of non-steroidal anti-inflammatory drug-activated gene-1 in human nasal mucosa and cultured nasal epithelial cells: a preliminary investigation.
OBJECTIVE
Non-steroidal anti-inflammatory drug-activated gene-1 (NAG-1) is a recently discovered transforming growth factor-beta superfamily cytokine. The localization and functions of NAG-1 have not been thoroughly studied. The aims of this study were to investigate its expression and localization in human nasal mucosa and also the change in NAG-1 expression as a function of mucociliary and squamous differentiation.


METHODS
Anterior and middle portions of human inferior turbinate were used and immunohistochemical studies were performed using NAG-1 antibody. Passage-2 normal human nasal epithelial (NHNE) cell culture was performed for 14 days using the air-liquid interface method and the cells were divided into retinoic acid (RA)-sufficient and -deficient groups. Each group of cells was stained with hematoxylin-eosin to study the degree of differentiation. Western blot analysis for NAG-1 expression was performed in each group after 0, 7 and 14 days.


RESULTS
NAG-1 expression in mucociliated epithelium was noted in ciliated cells and serous acini, but was not found in goblet cells or mucous acini. In squamous epithelium, NAG-1 expression was weaker than that in mucociliated epithelium. In RA-sufficient culture, NHNE cells were differentiated into ciliated epithelium, but in RA-deficient culture, keratinizing squamous epithelium was noted. Western blot analysis showed that NAG-1 expression was significantly higher in RA-sufficient than -deficient culture (three-fold difference) and this expression was time-dependent.


CONCLUSIONS
NAG-1 may be involved in differentiation and apoptotic processes of nasal epithelial cells. However, it is still unclear whether NAG-1 is an inducer or a byproduct of differentiation or apoptosis. The role of NAG-1 protein remains to be solved.
Kim
Kyung-Su
KS
Department of Otorhinolaryngology, Yonsei University College of Medicine, Seoul, South Korea.
Shin
Ji-Hyun
JH
Baek
Seung Joon
SJ
Yoon
Joo-Heon
JH
D017209:Apoptosis; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000737:chemistry; D002454:Cell Differentiation; D002478:Cells, Cultured; D016207:Cytokines / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D005786:Gene Expression Regulation; D015972:Gene Expression Regulation, Neoplastic; D055436:Growth Differentiation Factor 15; D006801:Humans; D007150:Immunohistochemistry; D009297:Nasal Mucosa / Q000166:cytology / Q000378:metabolism*
D016207:Cytokines; C526140:GDF15 protein, human; D055436:Growth Differentiation Factor 15