Porcine Epithelial β-Defensin 1 Is Expressed in the Dorsal Tongue at Antimicrobial Concentrations

Epithelial cells and phagocytes contain antimicrobial polypeptides that participate in innate host defense. A recently cloned porcine β-defensin, PBD-1, was detected by Northern organ blots exclusively in the tongue epithelium. 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)), which differed by N-terminal truncation. Only PBD-1(42) was found in scrapings of the surface of the dorsal tongue or the buccal mucosa. Immunohistochemical staining with antibody to PBD-1(42) revealed that PBD-1 was highly concentrated in an ∼0.1-mm-thick layer in the cornified tips of the filiform (but not fungiform) papillae of the dorsal tongue and in the superficial squamous cell layers of the buccal mucosa. By scraping, extraction, and semiquantitative Western blotting, the concentration of PBD-1 in the dorsal tongue surface and the buccal mucosa was estimated at 20 to 100 μg/ml. PBD-1 had antibacterial activity against Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, and Candida albicans in 10 mM sodium phosphate 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 mM NaCl, the combinations of sublethal concentrations of PBD-1 and the porcine neutrophil peptide PG-3, PR-39, or PR-26 showed synergistic activity against E. coli or the multidrug-resistant S. typhimurium DT104. At its physiologic concentration, PBD-1 has antimicrobial effects under both low- and high-salt conditions encountered in the oral cavity and may contribute to the antimicrobial barrier properties of the dorsal tongue and oral epithelium.