Antibacterial Effects of Eel Galectin on Periodontopathic Bacteria

Objectives: Periodontitis is an infectious disease associated with microorganisms in the oral biofilm. Recently, a number of natural substances which exert an antibacterial effect on oral pathogens have been investigated. In this study, we investigated the inhibitory effect of galectin purified from mucus on Japanese eel skin on biofilm formation by periodontal pathogens and the cytokine-inducing activities of endotoxins from those periodontal pathogens.

Methods: Galectin AJL-1 purified from the mucus on Japanese eel skin (Anguilla japonica) was used in this study. The inhibitory effect of AJL-1 on biofilm formation by the following periodontal pathogens was determined on 96-well culture plates: Porphyromonas gingivalis, Prevotella intermedia and Aggregatibacter actinomycetemcomitans. These strains were cultured in Trypticase soy broth containing 25, 50 or 100 μg/ml of AJL-1, respectively, under anaerobic conditions. After staining adherent bacteria with crystal violet, biofilm formation was quantified. In order to confirm that inhibition of biofilm formation was due to AJL-1-mediated antibacterial activity, ATP-bioluminescent assay was carried out. We investigated the effect of AJL-1 on cytokine induction in human umbilical vascular endothelial cells (HUVECs) by A. actinomycetemcomitans lipopolysaccharide (LPS).

Results: AJL-1 significantly inhibited biofilm formation by all the A. actinomycetemcomitans strains tested in a dose-dependent manner (p<0.05), but did not inhibit biofilm formation by P. gingivalis or P. intermedia strains. ATP assay revealed a very weak bactericidal effect. It suppressed IL-6 (p<0.01) and IL-8 (p<0.05) induction by A. actinomycetemcomitans LPS in HUVECs.

Conclusion: The present study showed that eel galectin AJL-1 effectively inhibited biofilm formation by A. actinomycetemcomitans and inflammatory cytokine induction by its LPS. We intend to confirm these effects in vivo and apply them clinically.