Porcine epithelial beta-defensin 1 is expressed in the dorsal tongue at antimicrobial concentrations

Epithelial cells and phagocytes contain antimicrobial polypeptides that par ticipate in innate host defense, A recently cloned porcine beta-defensin, P BD-1, was detected by Northern organ blots exclusively in the tongue epithe lium. We generated recombinant PBD-1 peptide by using a baculovirus-insect cell expression system and obtained two forms (PBD-1(42) and PBD-1(38)), wh ich differed by N-terminal truncation, Only PBD-1(42) was found in scraping s of the surface of the dorsal tongue or the buccal mucosa, Immunohistochem ical staining with antibody to PBD-1(42) revealed that PBD-1 was highly con centrated in an similar to 0.1-mm-thick layer in the cornified tips of the filiform (but not fungiform) papillae of the dorsal tongue and in the super ficial squamous cell layers of the buccal mucosa, By scraping, extraction, and semiquantitative Western blotting, the concentration of PBD-1 in the do rsal tongue surface and the buccal mucosa was estimated at 20 to 100 mu g/m l. PBD-1 had antibacterial activity against Escherichia coli, Salmonella ty phimurium, Listeria monocytogenes, and Candida albicans in 10 mM sodium pho sphate buffer (pH 7.4), Added NaCl progressively inhibited the activity of PBD-1 against E. coli and C. albicans, In 10 mM sodium phosphate with 125 m M NaCl, the combinations of sublethal concentrations of PBD-1 and the porci ne neutrophil peptide PG-3, PR-39, or PR-26 showed synergistic activity aga inst E. coli or the multidrug-resistant S. typhimurium DT104. At its physio logic concentration, PBD-1 has antimicrobial effects under both low- and hi gh-salt conditions encountered in the oral cavity and may contribute to the antimicrobial barrier properties of the dorsal tongue and oral epithelium.