Cytotoxic effects of short-chain carboxylic acids on human gingival epithelial cells

Previous studies showed that foods that are retained on the dentition can accumulate high levels of short-chain carboxylic acids (acetic, formic, lactic and propionic). Since gingival epithelium is the first periodontal tissue to be challenged by oral factors, a study was undertaken to determine whether short-chain carboxylic acids can affect epithelial cells in vitro. Immortalized human oral epithelial cells were grown in supplemented keratinocyte growth medium at 37 degrees C, and the effects of short-chain carboxylic acids were determined with tetrazolium-based and trypan blue exclusion assays. Low concentrations of short-chain carboxylic acids inhibited the growth of human oral epithelial cells, while higher concentrations led to cell death. The effects of short-chain carboxylic acids on the cells were dose-dependent and varied among the individual acids (propionate > formate > lactate > acetate). Growth inhibition was partly reversible and growth resumed after removal of the acids. However, the time needed for recovery of the cells increased with short-chain carboxylic acids concentration, consistent with progressively greater damage to the cells at higher short-chain carboxylic acids concentrations. The observed effects of short-chain carboxylic acids on gingival cells in vitro supported our hypothesis that short-chain carboxylic acids can damage the integrity of gingival epithelium in situ.