Protection of intestinal occludin tight junction protein by dietary gangliosides in lipopolysaccharide-induced acute inflammation

Antimicrobial peptide Cathelicidin-BF prevents intestinal barrier dysfunction in a mouse model of endotoxemia

Intestinal barrier functions are altered during the development of sepsis. Cathelicidin antimicrobial peptides, such as LL-37 and mCRAMP, can protect animals against intestinal barrier dysfunction. Cathelicidin-BF (C-BF), a new cathelicidin peptide purified from the venom of the snake Bungarus fasciatus, has been shown to have both antimicrobial and anti-inflammatory properties. This study investigated whether C-BF pretreatment could protect the intestinal barrier against dysfunction in a mouse model of endotoxemia, induced by intraperitoneal injection of LPS (10mg/kg). Mice were treated with low or high dose C-BF before treatment with LPS, and samples were collected 5h after LPS treatment. C-BF reduced LPS induced intestinal histological damage and gut permeability to 4 KD Fluorescein-isothiocyanate-conjugated dextran. Pretreatment with C-BF prevented LPS induced intestinal tight junction disruption and epithelial cell apoptosis. Moreover, C-BF down regulated the expression and secretion of TNF-α, a process involving the NF-κB signaling pathway. C-BF also reduced LPS induced TNF-α expression through the NF-κB signaling pathway in mouse RAW 264.7 macrophages. These findings indicate that C-BF can prevent gut barrier dysfunction induced by LPS, suggesting that C-BF may be used to develop a prophylactic agent for intestinal injury in endotoxemia.

Porcine β-defensin 2 attenuates inflammation and mucosal lesions in dextran sodium sulfate-induced colitis

Intestinal permeability plays a critical role in the etiopathogenesis of ulcerative colitis. Defensins, including porcine β-defensin (pBD)2, are crucial antimicrobial peptides for gut protection owing to their antibacterial and immunomodulatory activities. The purpose of this study was to investigate the protective effects of pBD2 on mucosal injury and the disruption of the epithelial barrier during the pathological process of dextran sodium sulfate (DSS)-induced colitis. The effects and mechanism of pBD2 were evaluated both using a DSS-induced C57BL/6 mouse model and, in vitro, using Caco-2 and RAW264.7 cells. DSS-induced colitis was characterized by higher disease activity index, shortened colon length, elevated activities of myeloperoxidase and eosinophil peroxidase, histologic evidence of inflammation, and increased expression levels of TNF-α, IL-6, and IL-8. pBD2 increased the expression of zonula occludens-1, zonula occludens-2, claudin-1, mucin-1, and mucin-2 mRNA and proteins, and it decreased permeability to FITC-D, as well as apoptosis, in DSS-treated mice. pBD2 also decreased inflammatory infiltrates of the colon epithelium. In Caco-2 cells, pBD2 increased transepithelial electrical resistance and mucin mRNA expression, and it decreased the permeability of FITC-D while preserving the structural integrity of the tight junctions. The effects of pBD2 appeared to be through upregulation of the expression of genes associated with tight junctions and mucins, and by suppressing DSS-induced increases in inflammation, inducible NO synthase, cyclooxygenase-2, and apoptosis. These results show that pBD2 improves DSS-induced changes in mucosal lesions and paracellular permeability, possibly by affecting the activation of NF-κB signaling. The present study demonstrates that intrarectal administration of pBD2 may be a novel preventive option for ulcerative colitis.

GM1 and GD1a gangliosides modulate toxic and inflammatory effects of E. coli lipopolysaccharide by preventing TLR4 translocation into lipid rafts

Exogenous gangliosides are known to inhibit the effects of Escherichia coli lipopolysaccharide (LPS) in different cells exhibiting anti-inflammatory and immunosuppressive activities. The mechanisms underlying ganglioside action are not fully understood. Because LPS recognition and receptor complex formation occur in lipid rafts, and gangliosides play a key role in their maintenance, we hypothesize that protective effects of exogenous gangliosides would depend on inhibition of LPS signaling via prevention of TLR4 translocation into lipid rafts. The effect of GM1 and GD1a gangliosides on LPS-induced toxic and inflammatory reactions in PC12 cells, and in epithelial cells isolated from the frog urinary bladder, was studied. In PC12 cells, GD1a and GM1 significantly reduced the effect of LPS on the decrease of cell survival and on stimulation of reactive oxygen species production. In epithelial cells, gangliosides decreased LPS-stimulated iNOS expression, NO, and PGE2 production. Subcellular fractionation, in combination with immunoblotting, showed that pretreatment of cells with GM1, GD1a, or methyl-β-cyclodextrin, completely eliminated the effect of LPS on translocation of TLR4 into lipid rafts. The results are consistent with the hypothesis that ganglioside-induced prevention of TLR4 translocation into lipid rafts could be a mechanism of protection against LPS in various cells.

Flos Lonicera ameliorates obesity and associated endotoxemia in rats through modulation of gut permeability and intestinal microbiota

BACKGROUND AND AIM

Increasing evidence has indicated a close association of host-gut flora metabolic interaction with obesity. Flos Lonicera, a traditional herbal medicine, is used widely in eastern Asia for the treatment of various disorders. The aim of this study was to evaluate whether unfermented or fermented formulations of Flos Lonicera could exert a beneficial impact to combat obesity and related metabolic endotoxemia.

METHODS

Obesity and metabolic endotoxemia were induced separately or together in rats through feeding a eight-week high fat diet either alone (HFD control group) or in combination with a single LPS stimulation (intraperitoneal injection, 0.75 mg/kg) (LPS control group). While, the mechanism of action of the Lonicera formulations was explored in vitro using RAW 264.7 and HCT 116 cell lines as models.

RESULTS

In cell-based studies, treatment with both unfermented Flos Lonicera (UFL) and fermented Flos Lonicera (FFL) formulations resulted in suppression of LPS-induced NO production and gene expression of vital proinflammatory cytokines (TNF-α, COX-2, and IL-6) in RAW 264.7 cells, reduced the gene expression of zonula occludens (ZO)-1 and claudin-1, and normalized trans epithelial electric resistance (TEER) and horseradish peroxidase (HRP) flux in LPS-treated HCT-116 cells. In an animal study, treatment of HFD as well as HFD+LPS groups with UFL or FFL resulted in a notable decrease in body and adipose tissue weights, ameliorated total cholesterol, HDL, triglyceride, aspartate transaminase and endotoxin levels in serum, reduced the urinary lactulose/mannitol ratio, and markedly alleviated lipid accumulation in liver. In addition, exposure of HFD as well as HFD+LPS groups with UFL or FFL resulted in significant alteration of the distribution of intestinal flora, especially affecting the population of Akkermansia spp. and ratio of Bacteroidetes and Firmicutes.

CONCLUSION

This evidence collectively demonstrates that Flos Lonicera ameliorates obesity and related metabolic endotoxemia via regulating distribution of gut flora and gut permeability.

Dietary GD3 ganglioside reduces the incidence and severity of necrotizing enterocolitis by sustaining regulatory immune responses

OBJECTIVES

Gangliosides are glycosphingolipids, rich in colostrum and in membrane microdomains, which promote enterocyte growth and differentiation, and modulate TH1/TH2 responses. In an in vitro intestinal explant model of necrotizing enterocolitis (NEC), gangliosides have been shown to ameliorate intestinal injury; however, possible immunomodulatory mechanisms associated with this observation, as well as potential in vivo protective effects of gangliosides, remain unknown. The present study evaluates the effects of dietary GD3, the predominant ganglioside in neonatal rat intestine, both on the clinicopathologic expression of disease and on ileal Foxp3+ T regulatory cell immune responses in an experimental NEC model.

METHODS

Newborn rat pups were fed gavage formula (NEC) or formula supplemented with 15 μg/mL GD3 (GD3-NEC). Dam-fed (DF) littermates served as controls. NEC was induced by asphyxia and cold stress. At 96 hours, ileal gross and histologic changes were evaluated, and ileal cytokine profiles, Foxp3 expression, and Foxp3+ cell numbers were determined.

RESULTS

GD3 decreased the incidence and gross and histopathologic severity of NEC. Ileal Foxp3 expression and Foxp3+ cell numbers were significantly decreased in the NEC group compared with DF. GD3 increased ileal Foxp3 expression and Foxp3+ cell numbers, in association with upregulation of anti-inflammatory cytokine interleukin (IL)-10 and chemokines, tissue inhibitor of metalloproteinases 1, IL-1 receptor antagonist (IL-1ra), and suppressed proinflammatory mediators.

CONCLUSIONS

These data suggest that dietary GD3 protects newborn rats from NEC, in part, by augmenting mucosal Foxp3+ T regulatory immune responses.

Protective role of 1,25(OH)2 vitamin D3 in the mucosal injury and epithelial barrier disruption in DSS-induced acute colitis in mice

Background

Intestinal hyper-permeability plays a critical role in the etiopathogenesis of inflammatory bowel disease (IBD) by affecting the penetration of pathogens, toxic compounds and macromolecules. 1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃], the active form of vitamin D, has been shown to be an important regulator of IBD and recent epidemiology suggests that patients with IBD have an impaired vitamin D status. The purpose of this study is to investigate the possible protective effects of 1,25(OH)₂D₃ on mucosal injury and epithelial barrier disruption on dextran sulfate sodium (DSS)-induced acute colitis model.

Methods

We used DSS-induced acute colitis model to investigate the protective effects of 1,25(OH)₂D₃ on mucosal injury and epithelial barrier integrity. Severity of colitis was evaluated by disease activity index (DAI), body weight (BW) change, colon length, histology, myeloperoxidase (MPO) activity, and proinflammatory cytokine production including tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ). In vitro the protective role of 1,25(OH)₂D₃ was assessed by incubating Caco-2 cells with or without DSS and measuring transepithelial electrical resistance (TEER) and fluorescein isothiocyanate dextran (FITC-D). The intestinal permeability was analyzed by FITC-D, bacterial translocation and measurement of lipopolysaccharide (LPS). Ultrastructural features of the colon tissue and Caco-2 cell monolayer were observed by electron microscopy. Expressions of tight junction (TJ) proteins in the colon mucosa and Caco-2 cells were detected by immunohistochemistry, immunofluorescence, Western blot and real-time fluorescent quantitative PCR, respectively.

Results

DSS-induced acute colitis model was characterized by a reduced BW, AUC of BW, serum calcium, higher DAI, AUC of DAI, shortened colon length, elevated MPO activity, worsened histologic inflammation, increased mononuclear cell numbers in mesenteric lymph nodes (MLNs) and colonic lamina propria (LP), and enhanced proteins and mRNA levels of TNF-α and IFN-γ. 1,25(OH)₂D₃ markedly increased expressions of TJ proteins and mRNA and decreased the FITC-D permeability and the level of LPS. Furthermore, 1,25(OH)₂D₃ abrogated bacterial translocation to MLNs and ameliorated ultrastructural features of the colon epithelium by scanning electron microscopy (SEM). In vitro, 1,25(OH)₂D₃ increased TEER, TJ proteins and mRNA expressions, decreased the FITC-D permeability, and preserved structural integrity of the TJ in Caco-2 cells.

Conclusions

1,25(OH)₂D₃ may play a protective role in mucosal barrier homeostasis by maintaining the integrity of junction complexes and in healing capacity of the colon epithelium. 1,25(OH)₂D₃ may represent an attractive and novel therapeutic agent for the adjuvant therapy of IBD.

Dietary ganglioside reduces proinflammatory signaling in the intestine

Gangliosides are integral to the structure and function of cell membranes. Ganglioside composition of the intestinal brush border and apical surface of the colon influences numerous cell processes including microbial attachment, cell division, differentiation, and signaling. Accelerated catabolism of ganglioside in intestinal disease results in increased proinflammatory signaling. Restoring proper structure and function to the diseased intestine can resolve inflammation, increase resistance to infection, and improve gut integrity to induce remission of conditions like necrotizing enterocolitis (NEC) and Crohn's disease (CD). Maintaining inactive state of disease may be achieved by reducing the rate that gangliosides are degraded or by increasing intake of dietary ganglioside. Collectively, the studies outlined in this paper indicate that the amount of gangliosides GM3 and GD3 in intestinal mucosa is decreased with inflammation, low level of GM3 is associated with higher production of proinflammatory signals, and ganglioside content of intestinal mucosa can be increased by dietary ganglioside.

Moving beyond "good fat, bad fat": the complex roles of dietary lipids in cellular function and health: session abstracts

The International Life Science Institute North America and the American Society for Nutrition annual Functional Foods for Health Symposium was held 9 April 2011. Evidence that foods and their components offer health benefits beyond basic nutrition continues to captivate the interest of the scientific community, government agencies, and the general public. This paper is comprised of extended abstracts from the session and addresses issues related to emerging lipid nutrition science, including active roles of lipids in modulating physiological pathways. Identified pathways underlie the development of obesity, cognitive development, and inflammation, the latter of which is thought to relate to multiple disease processes. These data point to a new way of thinking about the role of lipids in health and disease.

Advances in research of intestinal epithelial tight junctions and intestinal permeability

Intestinal epithelial tight junctions are a structural basis for the intestinal barrier and play an important role in the regulation of intestinal permeability. Increased intestinal permeability caused by the destruction of tight junctions may result in bacterial translocation, systemic inflammatory response, and multiple organ dysfunction syndrome. In this paper, we review the structure and function of tight junctions, factors affecting intestinal permeability, and measures for improving the dysfunction in intestinal permeability.