Zinc and copper play a role in coaggregation inhibiting action of Porphyromonas gingivalis

We investigated the mechanisms of adherence of salivary and serum proteins, which mimic gingival crevicular fluid (GCF), to Porphyromonas gingivalis, and the effects of these adhered proteins on coaggregation and hemagglutination properties.The amounts of salivary and serum proteins adhering to P. gingivalis were determined using (3)H-labeled and non-labeled proteins. The coaggregation between P. gingivalis and Streptococcus oralis or Streptococcus gordonii was observed. Hemagglutination was evaluated using sheep erythrocytes. Proteins that interacted with zinc or copper in saliva and serum and on P. gingivalis were examined using sodium dodecyl sulfate-polyacrylamide gel electrophoresis.The amount of salivary or serum proteins that adhered to the surface of P. gingivalis strains was increased by cations, especially zinc and copper ions. The pretreatment of bacterial cells with salivary or serum proteins before the assay inhibited coaggregation with gram-positive bacteria and hemagglutination. These phenomena were enhanced by the presence of zinc or copper ions during the pretreatment of P. gingivalis with proteins. We detected protein bands that were related to these cations in saliva and serum and on P. gingivalis.Our findings suggest that zinc and copper ions markedly enhanced the adhesion and accumulation of salivary and serum proteins on cells of P. gingivalis and inhibited the coaggregation and hemagglutination of P. gingivalis. These cations might be useful for limiting the settlement of P. gingivalis in the gingival sulcus with the goal of preventing periodontal disease.