Antibacterial effects of salivary proteins [Tükürük proteinlerinin antibakteriyal etkileri]

Abstract

The mouth is a unique part of the body. It represents a multifunctional interface: it is an entrance for the external environment and acts as a part of the upper airway. It is clear that such an environment provides ideal conditions where specific microorganism may flourish. The ingested food may also cause damage to the hard and soft tissues. It is therefore not surprising that saliva contains several components which are involved in a wide range of protective systems. Saliva is produced by a great number of salivary glands which empty their secretion fluids into the oral cavity. Three pairs of major types of glands can be distinguished: the parotid, the submandibular and the sublingual glands, which are responsible for the major part of saliva production. In addition, the minor salivary glands, located in the mucous membranes aligning the oral cavity, contribute to only small amounts of human whole saliva. The macromolecules of saliva consist almost exclusively of proteins and glycoproteins. Almost all salivary proteins are in one way or another involved in protection of tissues of the oral cavity. Particularly salivary mucins are playing a crucial protective role for oral tissues. Since saliva is one of the natural resources, function will be unappreciated until problems, like e.g. a shortage of saliva, will occur. This can be illustrated by patients suffering from xerostomia of which the salivary contribution is diminished from normally 500-600 mL/day to 20 mL/day or less. These patients are suffering from soreness, mucosal ulceration, difficulty in deglutition, and a rampant increase in dental caries as well as non specific oral infections. These affections can be attributed for a large part to the lack of salivary mucins. As mucins are covering all epithelial surfaces of the mouth, they have major function in lubrication and protection against desiccation and exogenous insults. In addition, in a soluble state they can bind bacteria, playing a role in the clearance of these organisms. The tooth surface is covered by a layer consisting of selectively adsorbed salivary proteins designated the acquired pellicle. The physiological role of the pellicle is thought to protect the teeth against bacterial insults caused by their metabolic products (acids) and hydrolytic enzymes secreted. In addition, the pellicle reduces friction between the tooth surfaces during chewing and facilitates the lubrication of the surrounding soft tissues. Moreover, the pellicle proteins provide a matrix for remineralization by binding both phosphate and calcium. Major pellicle proteins (mucins, prolin-rich proteins, statherin) and many minor salivary components (amiylase, albumin, cysteine-rich phoshoprotein, fibronectin, glycosyltransferase, histidine-rich proteins, lactoferrin, lysozyme, prolin-rich glycoprotein, slgA, IgG) are found in variable amounts on the tooth surface. A number of salivary proteins, like lysozym and lactoferrin and the peroxidase system, exert an immediate effect on oral bacteria. They are working particularly cooperatively with other salivary proteins. Their joint effects are clear: interference with the colonization and multiplication of bacteria or even them. Detection of salivary components will provide various oral or systemic diseases. Thereby the increase of anticariogenic agents will lead to reduced caries incidence. Those antibacterial properties of saliva inspired the researchers to develop similar oral hygiene products.