Effect of TNF-α on tight junctions between the epithelial cells of intestinal mucosal barrier

The effect of T cell aging on the change of human tissue structure

The trend of aging of the global population is becoming more and more significant, and the incidence of age-related diseases continues to rise.This phenomenon makes the problem of aging gradually attracted wide attention of the society, and gradually developed into an independent research field.As a vital defense mechanism of the human body, the immune system changes significantly during the aging process.Age-induced changes in the body's immune system are considered harmful and are commonly referred to as immune aging, which may represent the beginning of systemic aging.Immune cells, especially T cells, are the biggest influencers and participants in age-related deterioration of immune function, making older people more susceptible to different age-related diseases.More and more evidence shows that T cells play an important role in the change of human tissue structure after aging, which fundamentally affects the health and survival of the elderly.In this review, we discuss the general characteristics of age-related T cell immune alterations and the possible effects of aging T cells in various tissue structures in the human body.

Glycyrrhizin inhibits LPS-induced inflammatory responses in goat ruminal epithelial cells in vitro

Inflammation plays a crucial role in the progression of Subacute Ruminal Acidosis (SARA). The experiment was designed to investigate anti-inflammatory effects of glycyrrhizin on goats ruminal epithelial cells (GREC) which were induced SARA by Lipopolysaccharide (LPS) in vitro. The GREC were induced SARA by adding LPS at the concentration of 5 μm and glycyrrhizin was added at different concentration of 0, 60, 90, 120, 150 μm. The structural integrity of LPS-induced GREC with the treatment of glycyrrhizin were observed by electron microscope; The levels of inflammatory factors TNF-α, IL-1β, IL-6, IL-8 and IL-12 were measured by ELISA; The number of Zo-1 and Occludin were measured, the expression of tight junction protein Occludin were measured by Western blot, and the mRNA expression of NF-κB, TNF-α, IL-1β, IL-6, IL-8 and IL-12 were measured in vitro. The results showed that higher concentration treatment of glycyrrhizin led to better morphology in LPS-induced GREC. Glycyrrhizin inhibited the growth of inflammatory factors TNF-α, IL-1β, IL-6, IL-8 and IL-12 in a dose-dependent manner. The number of ZO-1 and Occludin increased with the increase of adding of glycyrrhizin. Western blot analysis showed that the expression of tight junction protein Occludin in LPS-induced GREC increased with the adding of glycyrrhizin in a dose-dependent manner. Furthermore, the mRNA expression of NF-κB, TNF-α, IL-1β, IL-6, IL-8 and IL-12 decreased significantly with the increase treatment of glycyrrhizin. Glycyrrhizin significantly inhibits LPS-induced inflammatory mediators in GREC and the effects are better with the increase treatment of glycyrrhizin in vitro.

Curcumin protects against the intestinal ischemia-reperfusion injury: involvement of the tight junction protein ZO-1 and TNF-α related mechanism

Present study aimed to investigate the eff ect of curcumin-pretreatment on intestinal I/R injury and on intestinal mucosa barrier. Thirty Wistar rats were randomly divided into: sham, I/R, and curcumin groups (n=10). Animals in curcumin group were pretreated with curcumin by gastric gavage (200 mg/kg) for 2 days before I/R. Small intestine tissues were prepared for Haematoxylin & Eosin (H&E) staining. Serum diamine oxidase (DAO) and tumor necrosis factor (TNF)-α levels were measured. Expression of intestinal TNF-α and tight junction protein (ZO-1) proteins was detected by Western blot and/or immunohistochemistry. Serum DAO level and serum and intestinal TNF-α leves were signifi cantly increased after I/R, and the values were markedly reduced by curcumin pretreatment although still higher than that of sham group (p<0.05 or p<0.001). H&E staining showed the significant injury to intestinal mucosa following I/R, and curcumin pretreatment signifi cantly improved the histological structure of intestinal mucosa. I/R insult also induced significantly down-regulated expression of ZO-1, and the eff ect was dramatically attenuated by curcumin-pretreatment. Curcumin may protect the intestine from I/R injury through restoration of the epithelial structure, promotion of the recovery of intestinal permeability, as well as enhancement of ZO-1 protein expression, and this eff ect may be partly attributed to the TNF-α related pathway.

Role of CX3CR1 in repair of injured intestinal epithelial cells by bone marrow mesenchymal stem cells

AIM: To investigate the role of chemokine receptor CX3CR1 in the repair of injured intestinal epithelial cells by bone marrow mesenchymal stem cells (BM-MSCs).

METHODS: BM-MSCs were cultured and identified in vitro. Caco-2 cells were exposed to tumor necrosis factor alpha (TNF-α) to establish a cell model of injured intestinal epithelium. Cells were divided into six groups: BM-MSCs, Caco-2 cells, Caco-2 cells treated with TNF-α, co-cultured BM-MSCs and Caco-2 cells, co-cultured BM-MSCs and Caco-2 cells treated with TNF-α, and co-cultured BM-MSCs and Caco-2 cells treated with anti-CX3CR1 and TNF-α. The expression of tight junction proteins and mRNAs in Caco-2 cells, and CX3CR1 protein and mRNA in BM-MSCs was detected by immunofluorescence, Western blot and RT-PCR.

RESULTS: We selected 100 ng/mL TNF-α for 48 h to establish the injured model, because the expression of zonula occluden 1(ZO-1) and Occludin was reduced significantly at this time point (P < 0.05). The protein and mRNA levels of ZO-1, Occludin and CX3CR1 had no significant changes when BM-MSCs were co-cultured with untreated Caco-2 cells, but increased when BM-MSCs were co-cultured with injured Caco-2 cells (P < 0.05). When CX3CR1 was blocked, the protein and mRNA levels of ZO-1 and Occludin decreased significantly.

CONCLUSION: CX3CR1 participates in the repair of injured intestinal epithelial cells by BM-MSCs.

Relative expression of cholesterol transport-related proteins and inflammation markers through the induction of 7-ketosterol-mediated stress in Caco-2 cells

Human diets contain sterol oxidation products that can induce cytotoxic effects, mainly caused by cholesterol oxides. However, phytosterol oxides effects have been less extensively investigated. This study evaluates the production of inflammatory biomarkers (IL-1β, IL-8, IL-10, TNFα) and the influence of gene expression transporters and enzymes related to cholesterol absorption and metabolism (NPC1L1, ABCG5/8, HMGCoA, ACAT) produced by 7-ketosterols (stigmasterol/cholesterol) in Caco-2 cells. These effects were linked to intracellular signaling pathways by using several inhibitors. Results showed 7-ketostigmasterol to have a greater proinflammatory potential than 7-ketocholesterol. In non-pre-treated cells, only efflux transporters were down-regulated by 7-ketosterols, showing a greater influence upon ABCG5 expression. Cell-pre-incubation with bradykinin induced changes in ABCG expression levels after 7-ketostigmasterol-incubation; however, the energetic metabolism inhibition reduced NPC1L1 expression only in 7-ketocholesterol-incubated cells. In non-pre-treated cells, HMG-CoA was up-regulated by both 7-ketosterols. However, exposure to inhibitors down-regulated the expression levels, mainly in 7-ketocholesterol-incubated cells. While ACAT expression values in non-pre-treated cells were unchanged, exposure to inhibitors caused down-regulation of mRNA levels. These results suggest that internalization and excretion of 7-ketostigmasterol is probably influenced by [Ca]i, which also could mediate HMGCoA activity in POPs metabolism. However, energetic metabolism and reducing equivalents exert different influences upon the 7-ketosterol internalization.

Congestion preconditioning protects against intestinal mucosal hyperpermeability induced by congestion-reperfusion injury in rats

AIM: To investigate the effects of congestion preconditioning on intestinal barrier dysfunction caused by portal occlusion in rats.

METHODS: Sprague-Dawley rats were divided into three groups: congestion-reperfusion group (CR group), congestion preconditioning group (CP group) and sham operation group (SO group). In the CR group, portal vein flow was occluded using a micro-clamp for 45 min and then unclamped by removing the micro-clamp. In the CP group, the portal vein was clamped for 5 min and then unclamped for 5 min, followed by one repeat of this procedure before portal vein flow occlusion for 45 min. In the SO group, all the procedures were conducted except for the clamping of the portal vein. Portal blood samples were collected at baseline, 12 h and 24 h after the portal procedure for measurement of plasma endotoxin and TNF-α concentrations. Meanwhile, the intestine was loaded with 5 mL FITC-dextran 4400 (FD4, 0.2%). One hour later. portal blood samples were taken for detection of intestinal mucosal permeability by measuring the appearance of fluorescent probe FD4 in portal plasma.

RESULTS: The concentrations of FD4, endotoxin and TNF-α in portal plasma in the CR group were significantly higher than those in the SO group (24 h: 0.621 mg/L ± 0.074 mg/L vs 0.107 mg/L ± 0.015 mg/L, P < 0.01; 0.636 EU/mL ± 0.064 EU/mL vs 0.056 EU/mL ± 0.019 EU/mL, P < 0.01; 107.14 ng/L ± 15.71 ng/L vs 11.98 ng/L ± 3.15 ng/L, P < 0.01). Plasma endotoxin concentration was positively correlated with FD4 level in portal plasma (r = 0.9118, P < 0.01). The levels of FD4, endotoxin and TNF-α in portal plasma in the CP group were remarkably attenuated compared with those in the CR group (24 h: 0.391 mg/L ± 0.070 mg/L vs 0.621 mg/L ± 0.074 mg/L, P < 0.01; 0.452 EU/mL ± 0.048 EU/mL vs 0.636 EU/mL ± 0.064 EU/mL, P < 0.01; 73.38 ng/L ± 5.37 ng/L vs 107.14 ng/L ± 15.71 ng/L, P < 0.01).

CONCLUSION: Congestion preconditioning has a protective effect against intestinal mucosal hyperpermeability induced by congestion-reperfusion injury and could therefore alleviate endotoxemia and systemic inflammatory reaction.

Relationship between occludin expression in intestinal epithelial cells and tumor necrosis factor-α level in rats with nonalcoholic fatty liver disease

AIM: To investigate the expression of tight junction protein occludin in intestinal epithelial cells and to analyze its relationship with tumor necrosis factor-α (TNF-α) level in rats with nonalcoholic fatty liver disease (NAFLD).

METHODS: Thirty male Sprague-Dawley rats were divided into two groups: control group and model group. The control group was fed a normal diet while the model group was fed a high-fat diet. All the animals were sacrificed after 12 wk of feeding. Hematoxylin & eosin staining of hepatic tissue was performed to confirm if NAFLD was induced successfully. Serum TNF-α level was determined by radioimmunoassay. The expression of TNF-α in hepatic cells and occludin in intestinal epithelial cells was detected by immunohistochemistry. Intestinal epithelial tight junctions were observed by electron microscopy.

RESULTS: Serum TNF-α level in the model group was significantly higher than that in the control group (3.21 µg/L ± 0.45 µg/Lvs 2.10 µg/L ± 0.29 µg/L, t = -6.157, P < 0.01). In the model group, TNF-α was mainly distributed in the cytoplasm of liver cells, presenting with brownish-yellow fine granules, whereas only scattered positive cells were seen in the control group. Immunohistochemistry analysis showed that occludin was localized to the apical region of the intestinal lateral plasma membrane and distributed in a continuous pattern in the control group but significantly down-regulated and distributed in a non-continuous pattern in the model group. Electron microscopy analysis demonstrated that tight junctions were significantly shorter in the model group than in the control group (0.50 µm ± 0.21 µm vs 0.78 µm ± 0.19 µm, P < 0.05).

CONCLUSION: TNF-α may inhibit the expression of tight junction protein occludin in intestinal epithelial cells, which may result in intestinal barrier dysfunction and promote the development and progression of NAFLD.

The roles of tumor necrosis factor-alpha in colon tight junction protein expression and intestinal mucosa structure in a mouse model of acute liver failure

Background

Spontaneous bacterial peritonitis (SBP) is a common clinical disease and one of the most severe complications of acute liver failure (ALF). Although the mechanism responsible for SBP is unclear, cytokines play an important role. The aim of this study was to investigate the effects of tumor necrosis factor-alpha (TNF-α) on the structure of the intestinal mucosa and the expression of tight junction (Zona Occludens 1; ZO-1) protein in a mouse model of ALF.

Methods

We induced ALF using D-galactosamine/lipopolysaccharide (GalN/LPS) or GalN/TNF-α and assessed the results using transmission electron microscopy, immunohistochemistry, Western blotting, ELISA and real-time quantitative PCR. The effects of administration of anti-TNF-α IgG antibody or anti-TNF-α R1 antibody before administration of GalN/LPS or GalN/TNF-α, respectively, on TNF-α were also assessed.

Results

Morphological abnormalities in the intestinal mucosa of ALF mice were positively correlated with serum TNF-α level. Electron microscopic analysis revealed tight junction (TJ) disruptions, epithelial cell swelling, and atrophy of intestinal villi. Gut bacteria invaded the body at sites where TJ disruptions occurred. Expression of ZO-1 mRNA was significantly decreased in both ALF models, as was the level of ZO-1 protein. Prophylactic treatment with either anti-TNF-α IgG antibody or anti-tumor necrosis factor-a receptor1 (anti-TNF-α R1) antibody prevented changes in intestinal tissue ultrastructure and ZO-1 expression.

Conclusion

TNF-α affects the structure of the intestinal mucosa, decreases expression of ZO-1, and affects the morphology of the colon in a mouse model of ALF. It also may participate in the pathophysiological mechanism of SBP complicated to ALF.

Anti-infection effect of hydrolysates from conglycinin on E.coli in mice

AIM: To elucidate anti-infection effect of hydrolysates from conglycinin on E.coli in mice.

METHODS: Male KM mice were assigned randomly in five treatments. After feeding basal diet three days, E.coliO₁₃₈ was fed in five treatments from 2×10¹¹ to 2×10⁷CFU/L, diluted (in decuple) ordinally. The LD₅₀ of mice feeding E.coliO₁₃₈ after 56 h was 4.73×10¹⁰ CFU/L. Two batch of Male KM mice were randomly assigned to six treatments respectively: normal (NOR) group, feeding-E.coli control (FEC), Basal diet + physiological saline, Basal diet + Hcl-full hydrolysis of conglycinin (HCL-FHC), Basal diet + conglycinin (Conglycinin), Basal diet + pepsin-hydrolysate conglycinin (PTC), and Basal diet + purified fraction B of pepsin hydrolysates of conglycinin (P2-PTC) group. The mice were fed with a dose of 0.2 mL /g (containing equal amount of nitrogen) except the ones in NOR and FEC group. Twenty days after feeding, each mouse in FEC, HCL-FHC, Conglycinin, PTC and P2-PTC group was fed with E.coliO₁₃₈ (2×10⁹ CFU/L and 2×10¹¹ CFU/L for the two batch, respectively, 0.2 mL/g) in the 22^nd day (midday). The actions of the mice were observed until 48 h after feeding with E.coliO₁₃₈. Then all the mice were killed. The blood, spleen and the whole length of intestines were collected. The immune index was determined by radioimmunoassay.

RESULTS: The KM mice reacted differently when infected with different levels of E.coli after feeding the pepsin-hydrolysate conglycinin. In mice fed with 2×10⁹ CFU/L of E.coliO₁₃₈, the pepsin-hydrolysate conglycinin significantly increased the level of spleen IL-2 (19.2±9.6 μg/g vs 11.5±4.7 μg/g in P2-PTC and NOR group respectively, P<0.05; 19.2±9.6 μg/g vs 9.4±3.7 μg/g in P2-PTC and FEC group respectively, P<0.01), the intestinal sIgA concentration, and significantly decreased spleen IL-6 (127.1±52.8 ng/g vs 276.4±60.1 ng/g in P2-PTC and NOR respectively, P<0.01; 127.1±52.8 ng/g vs 224.5±38.9 ng/g in P2-PTC and FEC respectively, P<0.05) and TNF-α (9.1±2.0 μg/g vs 16.3±3.9 μg/g in PTC and NOR group respectively, P<0.05) level, but had no significant effect on serum IL-2. In mice fed with 2×10¹¹ CFU/L of E.coliO₁₃₈, the pepsin-hydrolysate conglycinin significantly increased the levels of spleen IL-6 (480.5±184.7 ng/g vs 206.7±72.3 ng/g in P2-PTC and NOR respectively, P<0.05) and TNF-α (43.3±5.8 μg/g vs 10.5±4.1 μg/g in P2-PTC and NOR group respectively, P<0.01; 43.3±5.8 μg/g vs 19.7±9.0 μg/g in P2-PTC and FEC group respectively, P<0.01), and decreased the serum IL-6 and TNF-α (P2-PTC group 2.8±1.0 μg/L vs FEC group 4.6±2.0 μg/L in P2-PTC and FEC group respectively, P<0.05) concentrations.

CONCLUSION: The hydrolysates from conglycinin with pepsin can increase the immune function in mice, defend the invasion of E.coli and keep the gut healthy.