Human Gingival Fibroblasts Rescue Butyric Acid-Induced T-Cell Apoptosis

Abstract

We previously demonstrated that butyric acid, an extracellular metabolite from periodontopathic bacteria, induces cytotoxicity and apoptosis in murine thymocytes, splenic T cells, and human Jurkat T cells. In this study, we used a cell-to-cell interaction system to examine the contribution of gingival fibroblasts to the regulation of T-cell death induced by butyric acid. Butyric acid slightly suppressed fibroblast viability in a concentration-dependent fashion. However, DNA fragmentation assays indicated that butyric acid did not induce apoptosis for up to 21 h in human gingival fibroblasts (Gin 1, F41-G, and H. pulp cells). The culture supernatants were assayed for interleukin 1␣ (IL-1␣), IL-1␤, IL-6, IL-8, IL-11, tumor necrosis factor alpha, and transforming growth factor ␤, but only the IL-6, IL-8, and IL-11 levels were significantly increased by addition of butyric acid. Butyric acid-or Fas-induced Jurkat-cell apoptosis was attenuated when Jurkat cells were cocultured with either F41-G or Gin 1 cells that had been preincubated for 6 h with butyric acid. IL-8 slightly stimulated butyric acid-or Fas-induced Jurkat-cell apoptosis in a dose-dependent manner, although a low dose of IL-8 had a mildly inhibitory effect on apoptosis. In contrast, IL-6 and IL-11 significantly suppressed butyric acid-or Fas-induced apoptosis in a dose-dependent fashion. Furthermore, the addition of monoclonal antibodies against human IL-6 and IL-11 to cocultures of gingival fibroblasts and Jurkat cells partially eliminated T-cell recovery. These results suggest that the proinflammatory cytokines such as IL-6 and IL-11, produced in fibroblasts stimulated with butyric acid, are involved in the attenuation of T-cell apoptosis by gingival fibroblasts.

Butyric acid induces apoptosis in both human monocytes and lymphocytes equivalently

“…We previously demonstrated that short-chain fatty acids (SCFAs), an extracellular metabolites from periodontopathic bacteria, greatly inhibit proliferation and cytokine production of T and B cells (4). Among SCFAs, butyric acid particularly induces apoptosis in mouse and human T cells (5), B-cells (6), monocytes and macrophages (7), whereas, oral epithelial cells and healthy gingival fibroblasts (8) are resistant to butyric acid-induced apoptosis. Interestingly, inflamed gingival fibroblasts from adults with periodontitis are highly susceptible to butyric acid-induced apoptosis (9).…”

Apoptosis induced by Short-chain Fatty Acids Modulates Immunoresponses: Role of Cell-to-cell Communication in Inhibiting Butyric Acid-induced T Cell Apoptosis

“…Butyric acid treatment primarily resulted in increased expression of proapoptotic genes such as Bax, Bad, Bak, and caspase-3, -6, -7, -8, and -9, whereas the expression of antiapoptotic mediators such as Bcl-2 and glutathione was decreased (Table 1). Furthermore, among the MAPKs, the repression profile of butyric acid-treated Jurkat cells was confirmed by means of cDNA array (6).…”

“…A sustained phosphorylation was down-regulated after 6 h following treatment with butyric acid. Thus, butyric acid activates the JNK and p38 pathways and at the same time downregulates ERK in Jurkat cells (6).…”

“…Butyric acid-treated cells showed higher basal levels of reactive oxygen species (ROS) compared with untreated cells (6). Furthermore, antioxidants NAC and 3AB showed a protective effect against butyric acid-induced apoptosis in a dose-dependent manner.…”

Effects of butyric acid on the periodontal tissue

“…We have reported that human gingival fibroblasts rescue butyric acidinduced T-cell apoptosis via proinflammatory cytokines such as interleukin (IL) -6 and IL-11, which are produced by fibroblasts stimulated with butyric acid [30]. The number of Jurkat T-cells adherent to HGFs was significantly increased following the addition of butyric acid.…”