Editorial [Hot Topic: Antimicrobial Peptides, Mainly Defensins in Oral Cavity (Executive Editors: S. Vardar-Sengul and D. Mercola)]

Ever since the first observations that certain endogenously produced cystein-rich peptides have significant antibacterial and antifungal activity, interest has grown and evidence has accumulated that they may play multiple roles in maintaining oral health. Oral epithelium is constantly exposed to microbial agents. It is clear that the oral epithelium is not only a physical barrier but also has chemical defense mechanisms containing antimicrobial peptides such as the defensins. Epithelial cells secrete interleukin-8 and other cytokines that attract neutrophils and other cell types, and also they produce antimicrobial peptides against microorganisms and their products. Therefore, antimicrobial peptides of the oral epithelium belong to the first line of host defense mechanisms against infections in epithelial tissue. As part of innate immune system, antimicrobial peptides helping keep the balance between health and disease in the complex environment of oral cavity are small cationic antimicrobial peptides and have broad spectrum antimicrobial and antifungal activity. Thus, epithelial cells are active participants in antimicrobial activity and in interacting with innate and acquired immune responses. This theme issue of Current Pharmaceutical Design focuses on antimicrobial peptides, mainly on defensins in oral cavity. We asked numerous questions to explore and understand the importance and role of defensins in oral health and disease, to create new insights to the pharmaceutical discovery field, and to find out new treatment strategies for oral diseases. We are delighted to have Michael E. Selsted's introductory manuscript to the defensin research field in this issue of Current Pharmaceutical Design. Defensin amino acid sequences and term defensin first published by M. Selsted, T. Ganz and R. Lehrer more than 20 years ago and Lehrer Laboratory in UCLA pioneered defensin research in the world. Dr. Selsted's introduction provides a fascinating historical review of the development of the field as a whole, shares his insights into some of the determining factors in the directions of research that have evolved and provides observations on the context for the contributions of this issue. Humans have defense mechanisms in the oral cavity including the natural defenses of saliva and the host innate immune responses as well as the ability to generate antibodies by acquired immune responses. Saliva contains a large number of protective proteins, such as lactoferrin, lysozome, peroxidases, immunoglobulins, agglutinin and mucins, and several types of antimicrobial peptides, including histatins, defensins and cathelicidin/LL-37 that have an important role in innate host defense. In this issue, Drs. Abiko and Saitoh from University of Hokkaido review salivary defensins and discuss their importance in oral health and disease. Salivary defensins which protect mucosal epithelium are possibly derived from salivary ductal cells, oral epithelial cells and some blood cells. The antimicrobial activity of defensins may be affected by the components of saliva, which in turn may poteniate the protective role of saliva. The authors suggest that salivary defensin levels can be altered in oral diseases and therefore their level may be a useful marker for risk assessment, salivary diagnosis and new therapeutic strategies. Dr. Chung et al. from University of Washington, in their review article, create a picture of the role played by various antimicrobial peptides that are expressed in periodontal tissues and how they function in periodontal health and periodontal diseases. They also provide an overview of the differential regulation of human beta defensin expression as a host innate immune response to commensal vs. pathogenic bacteria. Dr. Chung and co-authors suggest that understanding how the expression of antimicrobial peptides is regulated in oral epithelia will lead us to discover new therapeutic targets to prevent and treat periodontal diseases.......