Diverse impact of a probiotic strain, Lacticaseibacillus paracasei Shirota, on peripheral mononuclear phagocytic cells in healthy Japanese office workers: a randomized, double-blind, controlled trial.

Mononuclear phagocytic cells (MPCs) are classified into monocytes (Mos)/macrophages and dendritic cells (DCs) based on their functions. Cells of MPCs lineage act as immune modulators by affecting effector cells, such as NK cells, T cells, and B cells. This study aimed to investigate the effects of Lacticaseibacillus paracasei strain Shirota (LcS) ingestion on peripheral MPCs, particularly on their expression of functional cell-surface molecules enhanced in healthy adults. Thus, twelve healthy office workers consumed a fermented milk drink containing 1.0 × 1011 cfu of LcS (LcS-FM) or a control unfermented milk drink (CM) once a day for 6 weeks. Peripheral blood mononuclear cells (PBMCs) were prepared from blood samples, and immune cells and functional cell-surface molecules were analyzed. We observed remarkable differences in the expression of HLAABC, MICA, CD40, and GPR43 in plasmacytoid DCs (pDCs) between the LcS-FM and CM groups, whereas no difference was found in CD86 or HLADR expression. The LcS-FM group exhibited higher CD40 expression in both conventional DCs (cDCs) and Mos, especially in type 2 conventional DCs (cDC2s) and classical monocytes (cMos); higher percentages of cMos, intermediate monocytes (iMos), and nonclassical monocytes; and higher numbers of cMos and iMos in PBMCs than the CM group. LcS ingestion increased the expression of HLAABC, MICA, CD40, and GPR43 in pDCs and CD40 in cDCs and Mos, particularly cDC2s and cMos. These results suggest that LcS modulates the function of MPCs that may lead to the regulation of immune effector functions in healthy adults.

Microbiota of the Small Intestine Is Selectively Engulfed by Phagocytes of the Lamina Propria and Peyer's Patches.

Phagocytes such as dendritic cells and macrophages, which are distributed in the small intestinal mucosa, play a crucial role in maintaining mucosal homeostasis by sampling the luminal gut microbiota. However, there is limited information regarding microbial uptake in a steady state. We investigated the composition of murine gut microbiota that is engulfed by phagocytes of specific subsets in the small intestinal lamina propria (SILP) and Peyer's patches (PP). Analysis of bacterial 16S rRNA gene amplicon sequences revealed that: 1) all the phagocyte subsets in the SILP primarily engulfed Lactobacillus (the most abundant microbe in the small intestine), whereas CD11bhi and CD11bhiCD11chi cell subsets in PP mostly engulfed segmented filamentous bacteria (indigenous bacteria in rodents that are reported to adhere to intestinal epithelial cells); and 2) among the Lactobacillus species engulfed by the SILP cell subsets, L. murinus was engulfed more frequently than L. taiwanensis, although both these Lactobacillus species were abundant in the small intestine under physiological conditions. These results suggest that small intestinal microbiota is selectively engulfed by phagocytes that localize in the adjacent intestinal mucosa in a steady state. These observations may provide insight into the crucial role of phagocytes in immune surveillance of the small intestinal mucosa.

Disturbance in the Mucosa-Associated Commensal Bacteria Is Associated with the Exacerbation of Chronic Colitis by Repeated Psychological Stress; Is That the New Target of Probiotics?

Psychological stress can exacerbate inflammatory bowel disease. However, the mechanisms underlying how psychological stress affects gut inflammation remain unclear. Here, we focused on the relationship between changes in the microbial community of mucosa-associated commensal bacteria (MACB) and mucosal immune responses induced by chronic psychological stress in a murine model of ulcerative colitis. Furthermore, we examined the effect of probiotic treatment on exacerbated colitis and MACB composition changes induced by chronic psychological stress. Repeated water avoidance stress (rWAS) in B6-Tcra-/- mice severely exacerbated colitis, which was evaluated by both colorectal tissue weight and histological score of colitis. rWAS treatment increased mRNA expression of UCN2 and IFN-γ in large intestinal lamina propria mononuclear cells (LI-LPMC). Interestingly, exacerbated colitis was associated with changes in the microbial community of MACB, specifically loss of bacterial species diversity and an increase in the component ratio of Clostridium, revealed by 16S rRNA gene amplicon analysis. Finally, the oral administration of a probiotic Lactobacillus strain was protective against the exacerbation of colitis and was associated with a change in the bacterial community of MACB in rWAS-exposed Tcra-/- mice. Taken together, these results suggested that loss of species diversity in MACB might play a key role in exacerbated colitis induced by chronic psychological stress. In addition, probiotic treatment may be used as a tool to preserve the diversity of bacterial species in MACB and alleviate gut inflammation induced by psychological stress.

Chronic Psychological Stress Disrupted the Composition of the Murine Colonic Microbiota and Accelerated a Murine Model of Inflammatory Bowel Disease.

The effect of psychological stress on the gastrointestinal microbiota is widely recognized. Chronic psychological stress may be associated with increased disease activity in inflammatory bowel disease, but the relationships among psychological stress, the gastrointestinal microbiota, and the severity of colitis is not yet fully understood. Here, we examined the impact of 12-week repeated water-avoidance stress on the microbiota of two inbred strains of T cell receptor alpha chain gene knockout mouse (background, BALB/c and C57BL/6) by means of next-generation sequencing of bacterial 16S rRNA genes. In both mouse strains, knockout of the T cell receptor alpha chain gene caused a loss of gastrointestinal microbial diversity and stability. Chronic exposure to repeated water-avoidance stress markedly altered the composition of the colonic microbiota of C57BL/6 mice, but not of BALB/c mice. In C57BL/6 mice, the relative abundance of genus Clostridium, some members of which produce the toxin phospholipase C, was increased, which was weakly positively associated with colitis severity, suggesting that expansion of specific populations of indigenous pathogens may be involved in the exacerbation of colitis. However, we also found that colitis was not exacerbated in mice with a relatively diverse microbiota even if their colonic microbiota contained an expanded phospholipase C-producing Clostridium population. Exposure to chronic stress also altered the concentration of free immunoglobulin A in colonic contents, which may be related to both the loss of bacterial diversity in the colonic microbiota and the severity of the colitis exacerbation. Together, these results suggest that long-term exposure to psychological stress induces dysbiosis in the immunodeficient mouse in a strain-specific manner and also that alteration of microbial diversity, which may be related to an altered pattern of immunoglobulin secretion in the gastrointestinal tract, might play a crucial role in the development of chronic stress-induced colitis.

Enhanced differentiation of intraepithelial lymphocytes in the intestine of polymeric immunoglobulin receptor-deficient mice.

To clarify the effect of secretory IgA (sIgA) deficiency on gut homeostasis, we examined intraepithelial lymphocytes (IELs) in the small intestine (SI) of polymeric immunoglobulin receptor-deficient (pIgR(-/-) ) mice. The pIgR(-/-) mice exhibited the accumulation of CD8αß(+) T-cell receptor (TCR)-αß(+) IELs (CD8αß(+) αß-IELs) after weaning, but no increase of CD8αß(+) γδ-IELs was detected in pIgR(-/-) TCR-ß(-/-) mice compared with pIgR(+/+) TCR-ß(-/-) mice. When 5-bromo-2'-deoxyuridine (BrdU) was given for 14 days, the proportion of BrdU-labelled cells in SI-IELs was not different between pIgR(+/+) mice and pIgR(-/-) mice. However, the proportion of BrdU-labelled CD8αß(+) -IELs became higher in pIgR(-/-) mice than pIgR(+/+) mice 10 days after discontinuing BrdU-labelling. Intravenously transferred splenic T cells migrated into the intraepithelial compartments of pIgR(+/+) TCR-ß(-/-) mice and pIgR(-/-) TCR-ß(-/-) mice to a similar extent. In contrast, in the case of injection of immature bone marrow cells, CD8αß(+) αß-IELs increased much more in the SI of pIgR(-/-) TCR-ß(-/-) mice than pIgR(+/+) TCR-ß(-/-) mice 8 weeks after the transfer. αß-IELs from pIgR(-/-) mice could produce more interferon-γ and interleukin-17 than those of pIgR(+/+) mice, and intestinal permeability tended to increase in the SI of pIgR(-/-) mice with aging. Taken together, these results indicate that activated CD8αß(+) αß-IELs preferentially accumulate in pIgR(-/-) mice through the enhanced differentiation of immature haematopoietic precursor cells, which may subsequently result in the disruption of epithelial integrity.

Beneficial Effects of Citrus Juice Fermented with Lactobacillus plantarum YIT 0132 on Japanese Cedar Pollinosis.

Recently, the prevalence of allergies in Japan has been increasing. Certain types of fruit juice and lactic acid bacteria are known to alleviate allergic symptoms. Therefore, we examined whether citrus juice fermented by a specific lactic acid bacteria can improve the symptoms of Japanese cedar pollinosis (JCPsis). Lactobacillus plantarum YIT 0132 (LP0132) was selected based on its high proliferative activity in citrus juice and anti-inflammatory interleukin-10-inducing activity. Dietary administration of heat-killed LP0132 cells or citrus juice fermented with LP0132 was found to significantly suppress nasal rubbing in a JCPsis mouse model, indicating relief of allergy symptoms. To evaluate the effects of LP0132-fermented citrus juice on pollinosis symptoms and quality of life (QOL) in humans with JCPsis, a single-blind, placebo-controlled, parallel-group clinical trial was conducted. The participants were 42 adults with JCPsis. They ingested 100 mL of sterilized LP0132-fermented citrus juice (active group) or unfermented citrus juice (placebo group) once daily for 8 weeks. Immediately after the pollen peak when allergy symptoms and QOL loss were most severe, itchy eyes, itchy skin, and QOL loss by JCPsis were alleviated in the active group compared with the placebo group. At 10 weeks after starting the intervention, increased the levels of blood eosinophils were significantly suppressed in the active group compared with the placebo group. We conclude that continuous ingestion of citrus juice fermented with LP0132 may help alleviate the allergy symptoms and impaired QOL caused by JCPsis.

Immune deviation and alleviation of allergic reactions in mice subjected to dietary restriction.

We examined cytokine production and allergic reactions in mice fed ad libitum (AL) and subjected to dietary restriction (DR). DR retarded the increase in body weight, and peripheral blood T cells in the DR mice produced less IFN-gamma and more IL-4 in response to immobilized anti-CD3 mAb. Systemic immunization and intranasal challenge with ovalbumin (OVA) induced accumulation of leukocytes into the lung, increase in IL-4 level in bronchoalveolar lavage fluid (BALF), and rise in serum IgE in the AL mice. In contrast, these allergic symptoms were alleviated in the DR mice. Furthermore, the relative proportion of IL-4-producing T cells responsive to OVA was less in the DR mice than the AL mice. DR tended to decrease the proportion and cytolytic activity of NK cells in the spleen, especially in younger mice. These results indicate that DR can prevent the expansion of allergen-specific IL-4-producing T cells followed by suppression of the allergic reaction, but might dampen NK cell activity.

Accumulation of intestinal intraepithelial lymphocytes in association with lack of polymeric immunoglobulin receptor.

Immunoglobulin A (IgA) is transported by the polymeric immunoglobulin receptor (pIgR) through epithelial cells of the gut, the airways, the tear and salivary glands, and the lactating mammary gland, and IgA accumulates in serum and the intestinal lamina propria of pIgR-deficient (pIgR(-/-)) mice. Intraepithelial lymphocytes (IEL) increased in number and Thy-1(+)CD8alphabeta(+)TCRalphabeta(+) IEL preferentially expanded in the small intestine (SI) of pIgR(-/-) mice. Cytotoxic activity of SI-IEL was comparable in pIgR(+/+) and pIgR(-/-) mice. Accumulation and cytotoxic activity of SI-IEL was attenuated in germ-free pIgR(-/-) mice. Furthermore, Thy-1(+)CD8alphabeta(+) IEL did not expand in pIgR(-/-)TCRbetadelta(-/-) mice compared with TCRbetadelta(-/-) mice, and SI-IEL from pIgR(-/-)TCRbetadelta(-/-) mice as well as TCRbetadelta(-/-) mice expressed perforin and granzyme B mRNA and serine esterase. The proliferative status of SI-IEL from pIgR(+/+) and pIgR(-/-) mice was similar, but adoptive transfer experiment showed that SI-IEL from pIgR(-/-) mice might have a stronger tendency to migrate into the intestinal epithelia than those from pIgR(+/+) mice. These results demonstrate that the accumulation of Thy-1(+)CD8alphabeta(+)TCRalphabeta(+) IEL in pIgR(-/-) mice triggered by intestinal microorganisms needed the expression of functional TCR and might be caused by lymphocyte migration into the intestinal epithelia.