Konjac Glucomannan Oligosaccharides Prevent Intestinal Inflammation Through SIGNR1-Mediated Regulation of Alternatively Activated Macrophages.

SCOPE: Konjac glucomannan oligosaccharides (KMOS) are prebiotics and may improve intestinal immunity through modulation of macrophage function. However, the underlying molecular mechanisms were unclear. METHODS AND RESULTS: Using a mouse model of dextran sulfated sodium (DSS)-induced acute colitis, the study demonstrates here that KMOS (400 mg-1 kg-1 d-1 ) can ameliorate intestinal inflammation in a macrophage dependent manner. Oral exposure to KMOS prevents DSS-induced intestinal pathology, improves epithelial integrity, and decreases accumulation of colonic inflammatory leukocytes and cytokines. The therapeutic effects of KMOS are dependent on the function of macrophages, as depletion of macrophages abolished the effects. In colonic lamina propria of DSS-treated mice, as well as in vitro culture of bone marrow derived macrophages (BMDMs), KMOS skews reprogramming of classically activated macrophages (CAM/M1) into alternatively activated macrophages (AAM/M2). The study further determines that the activation of SIGNR1/phospho-c-Raf (S338)/phospho-p65 (S276)/acetyl-p65 (K310) pathway is responsible for KMOS-induced AAM/M2 polarization. Blockage of SIGNR1 abolishes KMOS-induced AAM/M2 polarization of activated macrophages, expression of phospho-p65 (S276) in colonic macrophages, and alleviation of DSS-induced colitis in mice, suggesting that SIGNR1 is critical for macrophage responses to KMOS. CONCLUSIONS: This study reveals a SIGNR1-mediated macrophage-dependent pathway that supports regulatory function of KMOS in host immunity and intestinal homeostasis.

Curdlan (Alcaligenes faecalis) (1→3)-ß-d-Glucan Oligosaccharides Drive M1 Phenotype Polarization in Murine Bone Marrow-Derived Macrophages via Activation of MAPKs and NF-κB Pathways.

Functional oligosaccharides, particularly curdlan (1→3)-ß-d-glucan oligosaccharides (GOS), play important roles in modulating host immune responses. However, the molecular mechanisms underlying the immunostimulatory effects of GOS on macrophage polarization are not clear. In this work, GOS (5-1000 µg/mL) were non-toxic to bone marrow-derived macrophages (BMDMs) with improved pinocytic and bactericidal capacities. Incubation with GOS (100 µg/mL) induced M1 phenotype polarization of BMDMs as evidenced by increased CD11c+/CD86+ (10.1%) and M1 gene expression of inducible nitric oxide synthase, interleukin (IL)-1ß, and chemokine C-C-motif ligand 2. Accordingly, the secretion of cytokines IL-1ß, IL-6, monocyte chemotactic protein-1, and tumor necrosis factor-α, as well as the nitrite release of BMDMs were increased by GOS (100 µg/mL). Expression of mitogen-activated protein kinases (MAPKs) of phosphorylated (p)-c-Jun amino-terminal kinase, p-extracellular signal regulated kinase, and p-p38 in BMDMs were increased by GOS, as well as the p-Stat1. Moreover, nuclear factor-kappa B (NF-κB) p-p65 expression in BMDMs was promoted by GOS while it suppressed IκBα expression. Receptor blocking with anti-CR3 (CD11b/CD18) and anti-toll-like receptor (TLR) 2 antibodies diminished GOS induced M1 phenotype polarization with reduced mRNA expression of M1 genes, decreased cytokine and nitrite releases, and suppressed signaling pathway activation. Thus, CR3 (CD11b/CD18) and TLR2 mediated activation of MAPKs and NF-κB pathways are responsible for GOS induced polarization of BMDMs.

Curdlan oligosaccharides having higher immunostimulatory activity than curdlan in mice treated with cyclophosphamide.

This study evaluated the immunostimulatory activity of curdlan oligosaccharides (GOS) in cyclophosphamide (CTX)-induced immunosuppressed mice and in RAW264.7 cells. GOS was able to stimulate the release of nitric oxide (NO), cytokines (IL-1ß, IL-6 and TNF-α) and improve the phagocytic rate of peritoneal macrophages and RAW264.7 cells. It further enhanced immunoglobulins (Ig) release (IgG by 50.6%-74.7%, IgA by 31.3%-34.9%, IgM by 28.3%-66.7%), splenic lymphocyte proliferation (by 74.8%-91.3%), nature killer cells cytotoxicity (by 32.0%-49.6%), immunophenotypes of splenic lymphocytes (from 1.7 to 2.4, 2.2 and 2.7) in immunosuppressed mice. Compared with curdlan, higher immunostimulatory activity of GOS was found in CTX-treated mice. Moreover, GOS could activate nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways through toll-like receptor 2 (TLR2) and complement receptor 3 (CR3). These results indicated that GOS may be a favorable candidate of functional food in regulating immune responses.

Disruption of chaperone-mediated autophagy-dependent degradation of MEF2A by oxidative stress-induced lysosome destabilization.

Oxidative stress has been implicated in both normal aging and various neurodegenerative disorders and it may be a major cause of neuronal death. Chaperone-mediated autophagy (CMA) targets selective cytoplasmic proteins for degradation by lysosomes and protects neurons against various extracellular stimuli including oxidative stress. MEF2A (myocyte enhancer factor 2A), a key transcription factor, protects primary neurons from oxidative stress-induced cell damage. However, the precise mechanisms of how the protein stability and the transcriptional activity of MEF2A are regulated under oxidative stress remain unknown. In this study, we report that MEF2A is physiologically degraded through the CMA pathway. In pathological conditions, mild oxidative stress (200 µM H 2O 2) enhances the degradation of MEF2A as well as its activity, whereas excessive oxidative stress (> 400 µM H 2O 2) disrupts its degradation process and leads to the accumulation of nonfunctional MEF2A. Under excessive oxidative stress, an N-terminal HDAC4 (histone deacetylase 4) cleavage product (HDAC4-NT), is significantly induced by lysosomal serine proteases released from ruptured lysosomes in a PRKACA (protein kinase, cAMP-dependent, catalytic, α)-independent manner. The production of HDAC4-NT, as a MEF2 repressor, may account for the reduced DNA-binding and transcriptional activity of MEF2A. Our work provides reliable evidence for the first time that MEF2A is targeted to lysosomes for CMA degradation; oxidative stress-induced lysosome destabilization leads to the disruption of MEF2A degradation as well as the dysregulation of its function. These findings may shed light on the underlying mechanisms of pathogenic processes of neuronal damage in various neurodegenerative-related diseases.

Protective effects of a wheat germ peptide (RVF) against H2O 2-induced oxidative stress in human neuroblastoma cells.

RVF (Arg-Val-Phe), a peptide derived from wheat germ, shows antioxidant properties. Here, the neuroprotective efficacies of RVF were investigated in human neuroblastoma cells (SH-SY5Y) that were pretreated with RVF (150-250 µM, 4 h) and exposed to H2O2 (200 µM). RVF increased viable cell numbers by 37 % and reduced the release of lactate dehydrogenase. Pretreatment with RVF also inhibited H2O2-induced accumulation of reactive oxygen species and maintained the mitochondrial transmembrane potential as well as preventing intracellular Ca(2+) dysregulation during H2O2 exposure. Furthermore, pretreatment with RVF increased the Bcl-2/Bax ratio and blocked cleavage poly(ADP-ribose) polymerase by inhibiting caspase-3 activation, thus decreasing apoptosis.