Normal human gingival fibroblasts undergo cytostasis and apoptosis after long-term exposure to butyric acid.

The causes of periodontal disease are complex. Butyric acid, a metabolite of periodontopathic bacteria such as Porphyromonas gingivalis, acts as a histone deacetylase inhibitor that has a direct effect on mRNA expression. Butyric acid produced by Clostridium butyricum in the intestinal tract induces differentiation of regulatory T cells, thereby suppressing inflammation in the gut. Mice lacking Clostridium butyricum in the intestinal tract suffer from colitis. By contrast, butyric acid in the oral cavity worsens periodontal disease. Periodontal disease is a chronic condition in which periodontal tissue is exposed to virulence factors (such as butyric acid); however, no study has examined the effects of long-term exposure to butyric acid. The present study demonstrated that long-term exposure of human gingival fibroblasts (HGFs) to butyric acid induced cytostasis and apoptosis via the intrinsic and extrinsic pathways. Butyric acid inhibited the division of HGFs by altering expression of mRNAs encoding cyclins. Butyric acid induced apoptosis in HGFs via the intrinsic pathway, followed by activation of caspase 9; there was no DNA damage or p53 activation. Butyric acid also upregulated expression of TNF-α mRNA and protein by HGFs. Furthermore TNF-α induced apoptosis by activating caspase 8 (the extrinsic pathway) and by inducing production of pro-inflammatory cytokines. Taken together, the results show that butyric acid induced cytostasis and apoptosis in HGFs, accompanied by production of pro-inflammatory cytokines. It thus acts as a death ligand and plays a critical role as a prophlogistic substance.

Long-term exposure to butyric acid induces excessive production of matrix metalloproteases in human gingival fibroblasts.

OBJECTIVE: The purpose of this study was to clarify the relationship between bacteria-induced butyric acid and periodontal disease progression. DESIGN: Normal human gingival fibroblasts were exposed to butyric acid (0, 1, 5, 10, and 15 mM) adjusted to a pH of 7.2-7.4 using sodium hydroxide for 0-96 h and cell viability was evaluated. In addition, the effects of butyric acid on the production of matrix metalloproteinases (MMPs) and tissue inhibitors of matrix metalloproteinases (TIMPs) in gingival fibroblasts were analyzed by real-time RT-PCR, ELISA, western blotting, and stromelysin zymography. RESULTS: Butyric acid reduced the viability of gingival fibroblasts in a concentration- and time-dependent manner. Furthermore, butyric acid promoted production of MMP-1, MMP-3, and MMP-10 in gingival fibroblasts and suppressed TIMP-2 protein production. CONCLUSIONS: Butyric acid promoted overproduction of MMPs, resulting in a disruption of the balance between MMPs and TIMPs expression in gingival fibroblasts. Our study suggests that the butyric acid produced by causative bacteria stimulates excessive MMP expression in periodontal tissue, leading to destruction of the tissue.

Relationship between periodontal disease and butyric acid produced by periodontopathic bacteria.

BACKGROUND: Periodontopathic bacteria such as Porphyromonas gingivalis produce a large amount of butyric acid as a metabolite. Though butyric acid has been reported to have an anti-inflammatory effect on inflammatory diseases in the gastrointestinal tract, it has been suggested to contribute to the progression of periodontal disease in the oral cavity. The concentration of butyric acid in periodontal tissue of patients with periodontitis patients is reported to increase with the progress of the periodontal disease state. However, the influence of butyric acid on periodontal disease progression is not well known. MAIN TEXT: In this review, we have considered the relationship between butyric acid and periodontal disease with respect to the findings reported till date and the knowledge we newly obtained [Shirasugi M et al. Biochem Biophys Res Commun, 2017]. We have studied the relationship between butyric acid and periodontal disease by analyzing the effect of butyric acid on normal human gingival fibroblasts, which are a major component of periodontal tissue. We observed that gingival fibroblasts underwent cytostasis and apoptosis via extrinsic and intrinsic pathways upon long-term exposure to butyric acid. In addition, we showed that TNF-α produced by gingival fibroblasts treated with butyric acid plays an important role in inducing exogenous apoptosis. CONCLUSION: Butyric acid produced by periodontopathic bacteria may promote progress of the periodontal disease state. Butyric acid is known to act as an HDAC inhibitor. Thus, we believe that advanced epigenetic analysis of the effects of butyric acid on gingival fibroblasts will help elucidate the periodontal disease pathology and facilitate discovery of new targets for periodontal disease treatment.