Antimicrobial peptide LL-37 is upregulated in chronic nasal inflammatory disease

Objective - LL-37 is one of the antimicrobial peptides and the only member of the cathelicidin family identified so far in humans. We attempted to find a correlation between LL-37 peptide and inflammation of the nasal mucosa. Material and methods - Nasal mucosa specimens were obtained from 15 chronic infective rhinitis patients and 6 normal controls. Immunohistochemical staining was used to examine the localization of LL-37 and reverse transcriptase polymerase chain reaction (RT-PCR) was used to determine the levels of LL-37, IL-1β and IL-8 in tissue. Results - LL-37 peptide was primarily localized in the surface of the epithelia, in the serous and mucous cells of the submucosal glands and in stromal inflammatory cells. The number of LL-37 immunoreactive cells in inflammatory nasal mucosa was significantly increased compared with normal nasal tissue. Using RT-PCR, LL-37 mRNA was detected in 3/6 normal turbinate samples but in all cases with inflammatory nasal tissues. IL-1β and IL-8 transcripts exhibited a similar pattern to that of LL-37. Conclusions - We suggest that LL-37 is one of the antimicrobial peptides found in human nasal mucosa and that it participates in the innate immune system of the nasal mucosa.