Antimicrobial Peptide (LL-37) Expression In Nasal Mucosa

Kim, Seon Tae; Chung, Yoo Sam; Cha, Heung Eog; Kim, Hyung Bok; Hwang, Yu Jin; Lee, Hee Seung; Lee, Heung Man

Abstract

BACKGROUND AND OBJECTIVES: Epithelial cells are the first line of defense in the innate immune system against microorganisms. The antimicrobial peptides are major participants in this system. LL-37, a kind of antimicrobial peptide, is the only cathelicidin protein so far identified in humans. Since the level of the peptide is known to increase in inflamed areas, we tried to find the correlation of the peptide with inflammation in nasal mucosa by examining the expression level of LL-37. Furthermore, we determined the mRNA expression level of IL-1beta and IL-8, both of which are known to be involved in inflammation.
MATERIALS AND METHODS
Nasal mucosa specimens were obtained from nasal polyps, chronic infective rhinitis, and normal inferior turbinate mucosa. The LL-37 protein was localized by immunohistochemical staining and mRNA expression of LL-37, IL-1beta, IL-8 were determined by reverse transcriptase polymerase chain reaction (RT-PCR).
RESULTS
In immunohistochemical study, LL-37 immunoreactive cells were primarily localized in the surface epithelia, the serous and mucous cells of the submucosal glands, and some stromal inflammatory cells. In normal tissue, 2 out of 6 samples (33%) studied exhibited immunoreactivity against LL-37 antibody, but in nasal polyps, 5 out of 8 (63%) and in infective rhinitis, 6 out of 7 (85%) showed positive reaction to the antibody. The number of positive cells were increased in inflammatory specimens, but there was no statistical difference between the normal and inflammatory specimens in epithelial layer, submucosal gland, and stromal inflammatory cells (p<0.05). In RT-PCR, LL-37 mRNA was detected in three of the six normal turbinate samples, but in all fifteen cases of inflammatory nasal tissues. The expression of LL-37 mRNA was correlated with the proinflammatory cytokines, IL-1beta and IL-8 mRNA.
CONCLUSIONS
Our results suggest that LL-37 is one of antimicrobial peptides found in the human nasal mucosa, and participates in the innate immune system of the nasal mucosa.