Analysis of T cell apoptosis induced by volatile fatty acids

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(1) Volatile fatty acids, especially butyric acid, metabolic by-products of periodontopathic bacteria, induced apoptosis in murine thymocytes, splenic T cells, human peripheral blood mononuclear cells (PBMC), and Jurkat cells. The apoptosis sensitivity of these cells to butyric acid was thymocytes > Jurkat cells> splenic T cells> PBMC.(2) Western blotting analysis which was used to study the expression of bcl-2, Bax, Fas and FasL, involved in the response to DNA damage and the induction of apoptosis, indicated that expression of bcl-2 was reduced and phosphorylated bcl-2 was also disappeared in butyric acid-treated cells. No changes in Bax, Fas and Fas-L was demonstrated. FACS analysis revealed that butyric acid suppressed the ratio of bcl-2^+ cells but not of Fas^+ cells.(3) RT-PCR and Western blotting analysis indicated that there was no increase in p53 expression in butyric acid-induced T cell apoptosis. The DNA fragmentation assay indicated that T cell blasts derived from mice containing a germ-line deficiency of the p53 tumor suppressor gene were susceptible to butyric acid-induced apoptosis to the same degree as wild-type T cells.(4) Annexin V binding experiments in flow cytometly revealed that butyric acid increased the number of early- and late-stage apoptotic cells.(5) Butyric acid-induced T cell apoptosis was accompanied by Caspase 3 and Caspase 6 protease activities but not by Caspase 1 and Caspase 8 protease activities.