In Vivo and In Vitro Study of Immunostimulation by Leuconostoc lactis-Produced Gluco-Oligosaccharides

Temperature-regulated cascade reaction for homogeneous oligo-dextran synthesis using a fusion enzyme

Based on the principle of cascade reaction, a fusion enzyme of dextransucrase and dextranase was designed without linker to catalyze the production of oligo-dextran with homogeneous molecular weight from sucrose in one catalytic step. Due to the different effects of temperature on the two components of the fusion enzyme, temperature served as the "toggle switch" for the catalytic efficiency of the two-level fusion enzyme, regulating the catalytic products of the fusion enzyme. Under optimal conditions, the fusion enzyme efficiently utilized 100 % of the sucrose, and the yield of oligo-dextran with a homogeneous molecular weight reached 70 %. The product has been purified and characterized. The probiotic potential of the product was evaluated by analyzing the growth of 10 probiotic species. Its cytotoxic and anti-inflammatory activities were also determined. The results showed that the long-chain oligo-dextran in this study had significantly better probiotic potential and anti-inflammatory activity compared to other oligosaccharides. This study provides a strategy for the application of oligo-dextran in the food and pharmaceutical industries.

Synergistic Immunostimulatory Activities of Probiotic Strains, Leuconostoc lactis and Weissella cibaria, and the Prebiotic Oligosaccharides They Produce

Synbiotics contain health-beneficial bacteria, i.e., probiotics and prebiotics selectively utilized by the probiotics. Herein, three probiotic strains, Leuconostoc lactis CCK940, L. lactis SBC001, and Weissella cibaria YRK005, and the oligosaccharides produced by these strains (CCK, SBC, and YRK, respectively) were used to prepare nine synbiotic combinations. Macrophages (RAW 264.7) were treated with these synbiotic combinations and the corresponding lactic acid bacteria and oligosaccharides alone to evaluate the treatments' immunostimulatory activities. The level of nitric oxide (NO) production was significantly higher in the macrophages treated with the synbiotics than in those treated with the corresponding probiotic strains and the oligosaccharide alone. The immunostimulatory activities of the synbiotics increased regardless of the probiotic strain and the type of oligosaccharide used. The expressions of tissue necrosis factor-α, interleukin-1β, cyclooxygenase-2, inducible NO synthase genes, and extracellular-signal-regulated and c-Jun N-terminal kinases were significantly higher in the macrophages treated with the three synbiotics than in those treated with the corresponding strains or with the oligosaccharides alone. These results indicate that the synergistic immunostimulatory activities of probiotics and the prebiotics they produced in the studied synbiotic preparations resulted from the activation of the mitogen-activated protein-kinase-signaling pathway. This study suggests the combined use of these probiotics and prebiotics in the development of synbiotic preparations as health supplements.

Neoadjuvant PD-1 blockade plus chemotherapy induces a high pathological complete response rate and anti-tumor immune subsets in clinical stage III gastric cancer

First-line PD-1 blockade plus chemotherapy significantly improves the survival benefits in late-stage gastric cancer (GC) patients. However, the pathological response rate and effects on the immune microenvironment of neoadjuvant PD-1 blockade plus chemotherapy in patients with cTNM-stage III GC remain to be elucidated. Patients with cTNM-stage III GC who underwent neoadjuvant PD-1 blockade plus chemotherapy and surgery were enrolled. Four in vivo models bearing GC were jointly established to investigate the specific roles of chemotherapy and PD-1 blockade for GC treatment. The tumor immune microenvironment was analyzed by hematoxylin and eosin (H&E) and IHC staining, multicolor flow cytometry and immunofluorescence. A total of 75 patients with cTNM-stage III (cT2-4N1-3M0) gastric cancer who received neoadjuvant PD-1 blockade plus chemotherapy (SOX/XELOX) were included in this study. After treatment, 21 (28.0%) and 57 (76.0%) patients achieved pathological complete response (pCR) and post-therapy pathological downstaging. Subgroup analyses revealed that patients with CPS >1 (32.6% vs 8.3%) and dMMR (35.7% vs 25.4%) subtype had better efficacy. Additionally, the resected specimens showed more anti-tumor immune infiltration indicating a response to neoadjuvant PD-1 blockade plus chemotherapy. Multicolor immunofluorescence and in vivo experiments on mouse models revealed that elevated M1/M2 ratio of macrophages, CD8 + T cells and plasma cells indicated effective response to treatment. Furthermore, neoadjuvant PD-1 blockade plus chemotherapy neither delayed surgery nor increased postoperative complication rate. The analyses indicate neoadjuvant PD-1 blockade plus chemotherapy is a promising therapeutic strategy in patients with cTNM-stage III GC with an encouraging pCR rate.

Immunostimulatory Activity of Lactic Acid Bacteria Cell-Free Supernatants through the Activation of NF-κB and MAPK Signaling Pathways in RAW 264.7 Cells

Lactic acid bacteria (LAB) can improve host health and has strong potential for use as a health functional food. Specific strains of LAB have been reported to exert immunostimulatory effects. The primary goal of this study was to evaluate the immunostimulatory activities of novel LAB strains isolated from humans and foods and to investigate the probiotic properties of these strains. Cell-free supernatants (CFS) obtained from selected LAB strains significantly increased phagocytosis and level of nitric oxide (NO) and pro-inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 in RAW264.7 macrophage cells. The protein expression of inducible NO synthase (iNOS) and cyclooxygenase (COX)-2, which are immunomodulators, was also upregulated by CFS treatment. CFS markedly induced the phosphorylation of nuclear factor-κB (NF-κB) and MAPKs (ERK, JNK, and p38). In addition, the safety of the LAB strains used in this study was demonstrated by hemolysis and antibiotic resistance tests. Their stability was confirmed under simulated gastrointestinal conditions. Taken together, these results indicate that the LAB strains selected in this study could be useful as probiotic candidates with immune-stimulating activity.

Immunostimulatory Activity of Synbiotics Using Lactococcus lactis SG-030 and Glucooligosaccharides from Weissella cibaria YRK005

Much attention has been recently paid to the health benefits of synbiotics, a combination of probiotics and prebiotics. In this study, synbiotics were prepared by combining lactic acid bacteria with potential as probiotics and purified glucooligosaccharides, and their immunostimulatory activity was evaluated using RAW 264.7 macrophage cells. A lactic acid bacteria strain with high antioxidant activity, acid and bile salt tolerance, adhesion to Caco-2 cells, and nitric oxide (NO) production was selected as a potential probiotic strain. The selected strain, isolated from forsythia, was identified as Lactococcus lactis SG-030. The purified glucooligosaccharides produced from Weissella cibaria YRK005 were used as prebiotics. RAW 264.7 cells were treated with synbiotics in two ways. One way was a simultaneous treatment with lactic acid bacteria and glucooligosaccharides. The other way was to pre-culture the lactic acid bacteria with glucooligosaccharides followed by treatment with synbiotic culture broth or synbiotic culture supernatant. In both cases, synbiotics synergistically increased NO production in RAW 264.7 cells. In addition, synbiotics treatment increased the expression of tissue necrosis factor-α, interleukin (IL)-1β, IL-6, and inducible nitric oxide synthase genes. Synbiotics also increased the expression of P38, extracellular signal-regulated kinases, c-Jun N-terminal kinases, phosphoinositide 3-kinase, and Akt proteins. The results confirmed that the synbiotics prepared in this study exhibited synergistic immunostimulatory activity.

Transcriptome Analysis Reveals Possible Immunomodulatory Activity Mechanism of Chlorella sp. Exopolysaccharides on RAW264.7 Macrophages

In this study, the exopolysaccharides of Chlorella sp. (CEP) were isolated to obtain the purified fraction CEP4. Characterization results showed that CEP4 was a sulfated heteropolysaccharide. The main monosaccharide components of CEP4 are glucosamine hydrochloride (40.8%) and glucuronic acid (21.0%). The impact of CEP4 on the immune activity of RAW264.7 macrophage cytokines was detected, and the results showed that CEP4 induced the production of nitric oxide (NO), TNF-α, and IL-6 in a dose-dependent pattern within a range of 6 μg/mL. A total of 4824 differentially expressed genes (DEGs) were obtained from the results of RNA-seq. Gene enrichment analysis showed that immune-related genes such as NFKB1, IL-6, and IL-1β were significantly upregulated, while the genes RIPK1 and TLR4 were significantly downregulated. KEGG pathway enrichment analysis showed that DEGs were significantly enriched in immune-related biological processes, including toll-like receptor (TLR) signaling pathway, cytosolic DNA-sensing pathway, and C-type lectin receptor signaling pathway. Protein–protein interaction (PPI) network analysis showed that HSP90AB1, Rbx1, ISG15, Psmb6, Psmb3, Psmb8, PSMA7, Polr2f, Rpsa, and NEDD8 were the hub genes with an essential role in the immune activity of CEP4. The preliminary results of the present study revealed the potential mechanism of CEP4 in the immune regulation of RAW264.7 macrophages, suggesting that CEP4 is a promising immunoregulatory agent.

Production Optimization, Structural Analysis, and Prebiotic- and Anti-Inflammatory Effects of Gluco-Oligosaccharides Produced by Leuconostoc lactis SBC001

Leuconostoc lactis SBC001, isolated from chive, produces glucansucrase and synthesizes oligosaccharides through its enzymatic activity. This study was conducted to optimize oligosaccharide production using response surface methodology, analyze the structure of purified oligosaccharides, and investigate the prebiotic effect on 24 bacterial and yeast strains and the anti-inflammatory activity using RAW 264.7 macrophage cells. The optimal conditions for oligosaccharide production were a culture temperature of 30 °C and sucrose and maltose concentrations of 9.6% and 7.4%, respectively. Based on ¹H-NMR spectroscopic study, the oligosaccharides were identified as gluco-oligosaccharides that consisted of 23.63% α-1,4 glycosidic linkages and 76.37% α-1,6 glycosidic linkages with an average molecular weight of 1137 Da. The oligosaccharides promoted the growth of bacterial and yeast strains, including Lactobacillus plantarum, L. paracasei, L. johnsonii, Leuconostoc mesenteroides, L. rhamnosus, and Saccharomyces cerevisiae. When lipopolysaccharide-stimulated RAW 264.7 cells were treated with the oligosaccharides, the production of nitric oxide was decreased; the expression of inducible nitric oxide synthase, tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-10 was suppressed; and the nuclear factor-kappa B signaling pathway was inhibited. In conclusion, the gluco-oligosaccharides obtained from Leu. lactis SBC001 exhibited a prebiotic effect on six bacterial and yeast strains and anti-inflammatory activity in RAW 264.7 macrophage cells.

Immunomodulatory Activity of Lactococcus lactis GCWB1176 in Cyclophosphamide-Induced Immunosuppression Model

Recently, Lactococcus lactis subsp. lactis has been reported to have immunostimulating properties in an immunosuppressed-animal model. However, the immunological activities of Lactococcus lactis and the molecular mechanisms remain unclear. In this report, we evaluated the immunostimulating activity and associated mechanisms of Lactococcus lactis subsp. lactis GCWB1176 (GCWB1176) in macrophages and cyclophosphamide (CTX)-induced immunosuppressed mice. In a series of safety tests, GCWB1176 was found to have a negative response to hemolysis, as well as susceptibility to antibiotics. Administration of GCWB1176 elevated natural killer (NK) cell activities; concanavalin A-induced T cell proliferation; and serum levels of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, interleukin (IL)-2, IL-4, IL-10 and IL-12 in CTX-induced immunosuppressed mice. In RAW264.7 macrophages, treatment with GCWB1176 induced phagocytic activity and increased the production of nitric oxide (NO) and expression of inducible NO synthase. Simultaneously, GCWB1176 increased the production of TNF-α, IFN-γ, IL-1β, IL-10 and IL-12 from mouse splenocytes and RAW264.7 cells. In addition, GCWB1176 significantly increased the transcriptional activities of NF-κB and iNOS. Taken together, GCWB1176 improved immune function through the activation of macrophages and NK cells. These findings suggest that dietary supplementation of GCWB1176 may be used to enhance immunity.