Regulatory effects on the functions of neutrophils by human salivary antimicrobial peptides, histatins

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1. Quantitative determination of histatins and their characterization.The assay method for histatins in human saliva using a reversed-phase high performance liquid chromatography has been developed. The histatins have been bound to the high-molecular mass acid components in saliva. A mean value of the total histatins in whole saliva from healthy subjects was 28.6 muM and sex related differences for the histatin concentration was not observed. Diurnal changes of the histatin secretion did not show rhythms. Histatins in the saliva were autodegraded by proteolytic enzymes present in the saliva, as incubated at pH 7.0. In secreted saliva, histatin 5 was not generated from histatin 3.2. Inhibition by histatins on H_2O_2 generation from neutrophils.Neutrophils generated H_2O_2 in the addition of fMLP on the fibronectin-coated dish plate and this H_2O_2 production was inhibited by histatins dose-dependently, PMA-induced H_2O_2 generation was not inhibited by them. Histatins could inhibit the H_2O_2 generation via receptors on the neutrophils. On the other hand, histatins did not inhibit their chemotaxis and phagocytosis.These results suggest that antimicrobial histatins are secreted into the oral cavity constantly, and protect the oral mucous membrane from active oxygen generated by neutrophils.