Cytotoxic mechanisms of butyrate on human pulp cells in vitro

Objectives: Butyrate, a short chain fatty acid, is a metabolic lipid-byproduct of various root canal pathogens, such as Poryromonas endodontalis. However, little is known about the effects of butyrate on cultured human pulp cells. Methods: Human pulp cells were cultured using an explant technique obtained from impacted third molars with informed consent. The cytotoxic mechanism of butyrate toward human pulp cells were analyzed by using tetrazolium bromide reduction assay, flow cytometry, and protein synthesis analysis. Results: Butyrate exhibited cytotoxic effects on human pulp cells in a concentration- and time-dependent manner (p<0.05). The concentrations of butyrate higher than 4 mM led cell cycle arrest to G0/G1. The concentration of butyrate up to 8 mM resulted in G2/M phase arrest. Butyrate also inhibited protein synthesis at 2 mM and higher concentrations in a dose-dependent manner (p<0.05). Conclusions: These results indicate that butyrate is cytotoxic to human pulp cells by inhibiting cell growth, cell cycle, and protein synthesis. This study was supported by NSC 95-2314-B-040-017.