Antimicrobial Effects of Ginsenosides on Monospecies and Multispecies Cariogenic Biofilms

Objectives:
Within biofims, microbes are more obstinate than planktonic cells, leading to persistent infection. Until now, the report regarding the application of ginseng extracts against multispecies oral biofilms is not available. Therefore, we investigated whether the ginseng extract ginsenoside Rh2 can inhibit and eliminate multispecies cariogenic dental plaques. Meanwhile, we sought to figure out the in depth mechanism about the antimicrobial effects of Rh2 on cariogenic biofilms.
Methods: We investigated what effects ginsenoside Rh2 had on monospecies and multispecies biofilm formed by cariogenic bacteria Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus) and Streptococcus sanguinis (S. sanguinis) in vitro. Cytotoxicity of Rh2 was examined by cell counting kit (CCK-8). Rh2’s effects on bacterial walls were also observed through transmission electron microscopy (TEM). To explore the mechanism of Rh2 in inhibiting their biofilm, isobaric tags for relative and absolute quantification (iTRAQ) were used to profile the common proteins with differential expression. SD rats were used for establishing caries model. Micro-CT was used for calculating the volume of teeth defect.
Results: The results were verified by reverse transcription and quantification polymerase chain reaction (RT-QPCR). In general, Rh2 application to cariogenic oral biofilms not only significantly decreased biomass accumulation, but also prevented the formed biofilm from developing by inhibiting bacterial growth and extracellular polysaccharide synthesis. Moreover, Rh2 was essentially non-cytotoxic to periodontal ligament cells at 50% biofilm inhibitory concentration (IC50). TEM imaging showed Rh2 could disrupt membrane function and disturb the physiology of these bacteria. Itraq results indicated the levels of mannose-specific IIC/D and acetaldehyde/alcohol dehydrogenase were down-regulated dramatically, while mRNA expression of these corresponding genes were significantly changed. Rats treated with Rh2 achieved lower caires scores than the control group.
Conclusions: Our data revealed a potential protection for Rh2 in dental caries, by inhibiting and eliminating biofilms formed by cariogenic bacteria.