Preventive Effect of Lactobacillus helveticus SBT2171 on Collagen-Induced Arthritis in Mice.

We recently reported that the intraperitoneal inoculation of Lactobacillus helveticus SBT2171 inhibited the development of collagen-induced arthritis (CIA), a murine model of rheumatoid arthritis (RA). In the present study, we evaluated the effect of the oral administration of L. helveticus SBT2171 on CIA development and on the regulation of antigen-specific antibody production and inflammatory immune cells, which have been implicated in the development of RA. Both oral administration and intraperitoneal inoculation of L. helveticus SBT2171 reduced joint swelling, body weight loss, and the serum level of bovine type II collagen (CII)-specific antibodies in the CIA mouse model. The intraperitoneal inoculation also decreased the arthritis incidence, joint damage, and serum level of interleukin (IL)-6. In addition, the numbers of total immune cells, total B cells, germinal center B cells, and CD4+ T cells in the draining lymph nodes were decreased following intraperitoneal inoculation of L. helveticus SBT2171. These findings demonstrate the ability of L. helveticus SBT2171 to downregulate the abundance of immune cells and the subsequent production of CII-specific antibodies and IL-6, thereby suppressing the CIA symptoms, indicating its potential for use in the prevention of RA.

Lactobacillus helveticus SBT2171 Attenuates Experimental Autoimmune Encephalomyelitis in Mice.

We recently reported that Lactobacillus helveticus SBT2171 (LH2171) inhibited the proliferation and inflammatory cytokine production of primary immune cells in vitro, and alleviated collagen-induced arthritis (CIA) in mice, a model of human rheumatoid arthritis (RA). In this study, we newly investigated whether LH2171 could relieve the severity of experimental autoimmune encephalomyelitis (EAE), a murine model of multiple sclerosis (MS), which is an autoimmune disease, but develop the symptoms by different mechanisms from RA. In MS and EAE, main cause of the disease is the abnormality in CD4+ T cell immunity, whereas in RA and CIA, is that in antibody-mediated immunity. The intraperitoneal administration of LH2171 significantly decreased the incidence and clinical score of EAE in mice. LH2171 also reduced the numbers of pathogenic immune cells, especially Th17 cells, in the spinal cord at the peak stage of disease severity. Interestingly, before the onset of EAE, LH2171 administration remarkably decreased the ratio of Th17 cells to CD4+ T cells in the inguinal lymph nodes (LNs), where pathogenic immune cells are activated to infiltrate the central nervous system, including the spinal cord. Furthermore, the expression of interleukin (IL)-6, an inflammatory cytokine essential for Th17 differentiation, decreased in the LNs of LH2171-administered mice. Moreover, LH2171 significantly inhibited IL-6 production in vitro from both DC2.4 and RAW264.7 cells, model cell lines of antigen-presenting cells. These findings suggest that LH2171 might down-regulate IL-6 production and the subsequent Th17 differentiation and spinal cord infiltration, consequently alleviating EAE symptoms.

Administration of Lactobacillus gasseri SBT2055 suppresses macrophage infiltration into adipose tissue in diet-induced obese mice.

Administration of Lactobacillus gasseri SBT2055 (LG2055) has been shown to prevent body weight gain and it also down-regulates the expression of the Ccl2 gene in adipose tissue in diet-induced obese mice. The CC chemokine ligand 2 has a crucial role in macrophage infiltration into adipose tissue, which is known to exacerbate inflammation. However, it is not yet known how LG2055 affects the invasion of macrophages into adipose tissue. C57BL/6J male mice were fed a normal-fat diet (10 % energy fat), high-fat diet (HFD; 45 % energy fat), or HFD containing LG2055 for 12 weeks. After the feeding period, gene expression and macrophage population in adipose tissue were analysed by real-time PCR and flow cytometry, respectively. Body weight and abdominal fat weight were not altered by feeding LG2055. Flow cytometry analysis revealed that the population of macrophages in adipose tissue was significantly reduced by feeding LG2055 compared with HFD only. Furthermore, the ratio of classically activated inflammatory macrophages (M1 macrophages) to total macrophages was significantly decreased in the LG2055-fed group. The expressions of Ccl2, Ccr2 and Lep were down-regulated and that of Il6, Tnf and Nos2 tended to be down-regulated in adipose tissue by feeding LG2055. In addition, fasting glucose levels were significantly decreased in the LG2055-fed group. These data suggest that administration of LG2055 might attenuate inflammation, which is caused by the intake of an HFD, through the inhibition of macrophage invasion into adipose tissue.

Lactobacillus helveticus SBT2171 inhibits lymphocyte proliferation by regulation of the JNK signaling pathway.

Lactobacillus helveticus SBT2171 (LH2171) is a lactic acid bacterium with high protease activity and used in starter cultures in the manufacture of cheese. We recently reported that consumption of cheese manufactured using LH2171 alleviated symptoms of dextran sodium sulfate (DSS)-induced colitis in mice. In this study, we have examined whether LH2171 itself exerts an inhibitory effect on the excessive proliferation of lymphocytes. We found that LH2171 inhibited the proliferation of LPS-stimulated mouse T and B cells, and the human lymphoma cell lines, Jurkat and BJAB. Cell cycle analysis showed an accumulation of LH2171-treated BJAB cells in the G2/M phase. Further, phosphorylation of c-Jun N-terminal kinase (JNK) and c-Jun was reduced by LH2171 in BJAB cells. Subsequently, expression of cell division cycle 2 (CDC2), regulated by the JNK signaling pathway and essential for G2/M phase progression, was inhibited by LH2171. It was also demonstrated that intraperitoneal administration of LH2171 strongly alleviated symptoms of collagen-induced arthritis (CIA) in mice. These findings suggest that LH2171 inhibits the proliferation of lymphocytes through a suppression of the JNK signaling pathway and exerts an immunosuppressive effect in vivo.

Lactobacillus gasseri SBT2055 induces TGF-ß expression in dendritic cells and activates TLR2 signal to produce IgA in the small intestine.

Probiotic bacteria provide benefits in enhancing host immune responses and protecting against infection. Induction of IgA production by oral administration of probiotic bacteria in the intestine has been considered to be one reason for this beneficial effect, but the mechanisms of the effect are poorly understood. Lactobacillus gasseri SBT2055 (LG2055) is a probiotic bacterium with properties such as bile tolerance, ability to improve the intestinal environment, and it has preventive effects related to abdominal adiposity. In this study, we have found that oral administration of LG2055 induced IgA production and increased the rate of IgA(+) cell population in Peyer's patch and in the lamina propria of the mouse small intestine. The LG2055 markedly increased the amount of IgA in a co-culture of B cells and bone marrow derived dendritic cells (BMDC), and TLR2 signal is critical for it. In addition, it is demonstrated that LG2055 stimulates BMDC to promote the production of TGF-ß, BAFF, IL-6, and IL-10, all critical for IgA production from B cells. Combined stimulation of B cells with BAFF and LG2055 enhanced the induction of IgA production. Further, TGF-ß signal was shown to be critical for LG2055-induced IgA production in the B cell and BMDC co-culture system, but TGF-ß did not induce IgA production in a culture of only B cells stimulated with LG2055. Furthermore, TGF-ß was critical for the production of BAFF, IL-6, IL-10, and TGF-ß itself from LG2055-stimulated BMDC. These results demonstrate that TGF-ß was produced by BMDC stimulated with LG2055 and it has an autocrine/paracrine function essential for BMDC to induce the production of BAFF, IL-6, and IL-10.

Overexpression of the yeast transcription activator Msn2 confers furfural resistance and increases the initial fermentation rate in ethanol production.

Lignocellulosic biomass is a promising source for bioethanol production, because it is abundant worldwide and has few competing uses. However, the treatment of lignocelllulosic biomass with weak acid to release cellulose and hemicellulose generates many kinds of byproducts including furfural and 5-hydroxymethylfurfural, which inhibit fermentation by yeast, because they generate reactive oxygen species (ROS) in cells. In order to acquire high tolerance to oxidative stress in bioethanol yeast strains, we focused on the transcription activator Msn2 of Saccharomyces cerevisiae, which regulates numerous genes involved in antioxidative stress responses, and constructed bioethanol yeast strains that overexpress Msn2 constitutively. The Msn2-overexpressing bioethanol strains showed tolerance to oxidative stress, probably due to the high-level expression of various antioxidant enzyme genes. Unexpectedly, these strains showed ethanol sensitivity compared with the control strain, probably due to imbalance of the expression level between Msn2 and Msn4. In the presence of furfural, the engineered strains exhibited reduced intracellular ROS levels, and showed rapid growth compared with the control strain. The fermentation test in the presence of furfural revealed that the Msn2-overexpressing strains showed improvement of the initial rate of fermentation. Our results indicate that overexpression of the transcription activator Msn2 in bioethanol yeast strains confers furfural tolerance by reducing the intracellular ROS levels and enhances the initial rate of fermentation in the presence of furfural, suggesting that these strains are capable of adapting rapidly to various compounds that inhibit fermentation by inducing ROS accumulation. Our results not only promise to improve bioethanol production from lignocellulosic biomass, but also provide novel insights for molecular breeding of industrial yeast strains.

Metabolic engineering of Saccharomyces cerevisiae for astaxanthin production and oxidative stress tolerance.

The red carotenoid astaxanthin possesses higher antioxidant activity than other carotenoids and has great commercial potential for use in the aquaculture, pharmaceutical, and food industries. In this study, we produced astaxanthin in the budding yeast Saccharomyces cerevisiae by introducing the genes involved in astaxanthin biosynthesis of carotenogenic microorganisms. In particular, expression of genes of the red yeast Xanthophyllomyces dendrorhous encoding phytoene desaturase (crtI product) and bifunctional phytoene synthase/lycopene cyclase (crtYB product) resulted in the accumulation of a small amount of beta-carotene in S. cerevisiae. Overexpression of geranylgeranyl pyrophosphate (GGPP) synthase from S. cerevisiae (the BTS1 gene product) increased the intracellular beta-carotene levels due to the accelerated conversion of farnesyl pyrophosphate to GGPP. Introduction of the X. dendrorhous crtS gene, encoding astaxanthin synthase, assumed to be the cytochrome P450 enzyme, did not lead to astaxanthin production. However, coexpression of CrtS with X. dendrorhous CrtR, a cytochrome P450 reductase, resulted in the accumulation of a small amount of astaxanthin. In addition, the beta-carotene-producing yeast cells transformed by the bacterial genes crtW and crtZ, encoding beta-carotene ketolase and hydroxylase, respectively, also accumulated astaxanthin and its intermediates, echinenone, canthaxanthin, and zeaxanthin. Interestingly, we found that these ketocarotenoids conferred oxidative stress tolerance on S. cerevisiae cells. This metabolic engineering has potential for overproduction of astaxanthin and breeding of novel oxidative stress-tolerant yeast strains.

Efficient screening for astaxanthin-overproducing mutants of the yeast Xanthophyllomyces dendrorhous by flow cytometry.

Astaxanthin possesses higher antioxidant activity than other carotenoids and, for this and other reasons, has great commercial potential for use in the aquaculture, pharmaceutical, and food industries. The basidiomycetous yeast Xanthophyllomyces dendrorhous is one of the best natural producers of astaxanthin, but wild-type cells accumulate only a small amount of astaxanthin. In this study, we developed an efficient flow cytometry method to screen for astaxanthin-overproducing mutants of X. dendrorhous. We first examined the relationship between cellular astaxanthin content and the intensity of fluorescence emitted from the cell. Although the fluorescence emission maximum of astaxanthin dissolved in acetone occurred at 570 nm, intracellular astaxanthin content correlated better with emission at around 675 nm in different X. dendrorhous strains. Using this emission wavelength, we screened cells mutagenized with ethyl methanesulfonate and successfully isolated mutants that produced 1.5-3.8-fold more astaxanthin than parent cells. This method enabled us to obtain overproducers five times more efficient than conventional screening from plate culture.