We previously reported that the major component of Enterococcus faecalis strain EC-12 (EC-12) inducing production of Interleukin (IL)-12 in mouse/human immune cells was its own RNA. This study aimed to investigate if RNase A-treated EC-12 could also produce IL-10 and to evaluate the possible effects of IL-10 produced by RNase A-treated EC-12. Three experiments were conducted: (1) Assessment of the effect of RNase A-treated EC-12 on transcriptome profiles and biological pathways in human peripheral blood mononuclear cells; (2) Determination of cytokine concentration in its culture supernatants; and (3) Supplementation of RNase A-treated EC-12 (RN) to mice with dextran sodium sulfate-induced colitis. Treatment of EC-12 with RNase A inhibited inflammatory response including the potency to induce IL-12 production, while it did not affect IL-10 production (Experiment 1 and 2). Colitis symptoms were milder in RN than in PBS-supplemented controls (Experiment 3). RNase A-treated EC-12 likely became an anti-inflammatory agent primarily inducing IL-10 production.
Keywords: Lactic acid bacteria; anti-inflammatory effect; bacterial RNA; colitis; mouse.