ABSTRACT
Enterococcus faecalis is a resident lactic acid bacterium in the human intestine. Its immunostimulatory action was reported to be enhanced by heat sterilization. To investigate its beneficial actions, we evaluated the ability of 10 E. faecalis strains to induce interleukin-12 (IL-12) production in a mouse macrophage cell line, J774.1 and found that the strain, E. faecalis IC-1, had a potent IL-12-inducing ability. Furthermore, we investigated the underlying mechanism by treating IC-1 cells with RNase or lysozyme. Its activity almost disappeared and an antagonist of Toll-like receptor (TLR) 7 inhibited this activity. Moreover, lysozyme-treated IC-1 bacteria were not phagocytized by J774.1 cells, and did not induce IL-12 production. Based on our results, we propose that macrophages recognize the cell wall components of IC-1, leading to phagocytosis. The IC-1 RNA is then recognized by TLR7, which induces the production of IL-12.
Subject(s)
Cell Wall/immunology , Enterococcus faecalis/immunology , Interleukin-12/immunology , Macrophages/immunology , RNA, Bacterial/immunology , Animals , Cell Line , Cell Wall/chemistry , Cell Wall/drug effects , Coculture Techniques , Enterococcus faecalis/chemistry , Enterococcus faecalis/drug effects , Gene Expression , Interleukin-12/biosynthesis , Macrophages/cytology , Macrophages/drug effects , Membrane Glycoproteins/antagonists & inhibitors , Membrane Glycoproteins/genetics , Membrane Glycoproteins/immunology , Mice , Muramidase/chemistry , Muramidase/pharmacology , Oligonucleotides/pharmacology , Phagocytosis/drug effects , RNA, Bacterial/chemistry , Ribonucleases/chemistry , Ribonucleases/pharmacology , Toll-Like Receptor 7/antagonists & inhibitors , Toll-Like Receptor 7/genetics , Toll-Like Receptor 7/immunologyABSTRACT
BACKGROUND: Green tea is a beverage with potential effects on cognitive dysfunction, as indicated by results of experimental studies. However, its effects in humans, especially at real-world (typical) consumption levels, are unclear. METHODS: A double-blind, randomized controlled study was conducted to assess the effects of green tea consumption on cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score <28) in Japan. Participants were randomly allocated to the green tea or placebo group, and consumed either 2 g/day of green tea powder (containing 220.2 mg of catechins) or placebo powder (containing 0.0 mg of catechins), respectively, for 12 months. Cognitive function assessments were performed every 3 months using the MMSE-J and laboratory tests. RESULTS: Thirty-three nursing home residents with cognitive dysfunction were enrolled (four men, 29 women; mean age ± SD, 84.8 ± 9.3; mean MMSE-J score ± SD, 15.8 ± 5.4), of whom 27 completed the study. Changes of MMSE-J score after 1 year of green tea consumption were not significantly different compared with that of the placebo group (-0.61 [-2.97, 1.74], least square mean (LSM) difference [95 % CI]; P = 0.59). However, levels of malondialdehyde-modified low-density lipoprotein (U/L), a marker of oxidative stress, was significantly lower in the green tea group (-22.93 [-44.13, -1.73], LSM difference [95 % CI]; P = 0.04). CONCLUSIONS: Our results suggest that 12 months green tea consumption may not significantly affect cognitive function assessed by MMSE-J, but prevent an increase of oxidative stress in the elderly population. Additional long-term controlled studies are needed to clarify the effects. TRIAL REGISTRATION: UMIN000011668.
Subject(s)
Cognitive Dysfunction/epidemiology , Tea , Aged , Aged, 80 and over , Catechin/administration & dosage , Cognition/drug effects , Cognitive Dysfunction/drug therapy , Double-Blind Method , Female , Humans , Japan/epidemiology , Male , Nursing Homes , Oxidative Stress , Placebos , Plant Extracts/administration & dosage , Surveys and Questionnaires , Tea/chemistryABSTRACT
Green tea is known to have various health benefits for humans. However, the effect of green tea consumption on cognitive dysfunction remains to be clinically verified. We conducted a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Twelve elderly nursing home residents with cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score: <28) participated in the study (2 men, 10 women; mean age, 88 years). The participants consumed green tea powder 2 g/day for 3 months. After three months of green tea consumption, the participants' MMSE-J scores were significantly improved (before, 15.3 ± 7.7; after, 17.0 ± 8.2; p = 0.03). This result suggests that green tea consumption may be effective in improving cognitive function or reducing the progression of cognitive dysfunction; however, long-term large-scale controlled studies are needed to further clarify the effect.
