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Effect of positive acceleration exposure on gut barrier in rats

With the development of modern high-performance fighter aircrafts, the requirement of acceleration is growing faster and higher, which is far beyond the tolerance of the pilots. In the process of flight, exposure to positive acceleration ( + Gz) is the most important threat to the tissues and organs of pilots. As we all know, the intestinal barrier is one of the significant barriers to prevent the endogenous pathogenic microorganisms and their toxins. This article reviews the impact of + Gz exposure on the gut barrier with regards to the establishment of + Gz models, the detection of related parameters of the gut barrier, and the damage of + Gz to the intestine, with an aim to improve the basic research of the gastrointestinal system in aviation medicine, and the pilot's health and flight safety.

Progress in understanding the relationship between food allergy and intestinal microflora

A food allergy is defined as a harmful immunological reaction to ingested food protein. According to 2007 CDC statistics, more than 3 million (3.9%) of children under 18 years old suffered from food allergy, and the morbidity is especially higher among children under 5 years old. Healthy intestinal microflora is very important for the development of mature human immune system. The composition of intestinal microflora differs significantly between children with and without food allergy. Food allergy in children may be closely associated with the immature development and damage of the intestinal mucosal barrier, intestinal dysbacteriosis and microflora disorder. Probiotics, as the balancer of intestinal microflora and regulator of intestinal mucosal immunity, can be used to prevent and treat allergic diseases; however, more larger randomized, controlled clinical studies are needed to verify its efficacy.

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.

Research advances in plateau hypoxia and gut barrier injury

Gut barrier function is an important feature of the intestinal tract. It consists of mechanical barrier, immune barrier, chemical barrier and organism barrier. Each barrier has different structures, molecular regulatory mechanisms and biologic functions, which are connected organically via their own signal paths simultaneously to protect the host from intruding of foreign antigen. The injury to these barriers in the plateau environment is a complex and inter-related process with many changes of inflammatory mediators and pathologic procedure. In this review, we focus on the barrier injury mechanisms under this special environment.

Effect of platelet activating factor receptor antagonist on tight junction associated protein between epithelial cells of intestinal mucosa in young rats

AIM: To investigate the effect of platelet acti-vating factor (PAF) receptor antagonist on the tight junction associated protein ZO-1 (zonula occludens-1) between epithelial cells of intestinal mucosa in young rats.

METHODS: Eighteen day-old Wistar rats were randomly assigned into lipopolysaccharide (LPS) group, PAF receptor antagonist (prevention and treatment) group and control group. The rats in LPS and control group were intraperitoneally injected with LPS (5 mg/kg) and normal saline (1 mL/kg), while the rats in prevention and treatment group were intraperitoneally injected with PAF receptor antagonist BN52021 (5 mg/kg) 30 min before and after LPS injection. Terminal ileum of each rat was collected for transmission electron microscopy. The expression of ZO-1 was determined by immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) at both protein and mRNA level.

RESULTS: Microvilli and tight junctions were intact in control group. Enlargement of tight junctions were observed in LPS group and microvilli were thin, rare or disrupt, and shed. The rough endoplasmic reticulum, mitochondria, and glycogen particles were damaged. The above changes were alleviated in PAF receptor antagonist group. The staining of ZO-1 in the control rats was similar to a honeycomb, which reflected a continuous and uniform distribution localized at the apical portion of cell-to-cell contact of the enterocytes. In LPS group, the signals of ZO-1 were disrupted and irregularly distributed at the outer enterocyte periphery. The content of ZO-1 was obviously lower in LPS group than that in the control group at 6 h (optical density: 0.198 5 ± 0.015 9 vs 0.224 7 ± 0.021 0, P < 0.01; mRNA: 0.16 ± 0.02 vs 1.18 ± 0.09, P < 0.01). The content of ZO-1 was also significantly decreased in prevention and treatment group in comparison with that in control group at 6 h (optical density: 0.199 2 ± 0.008 7, 0.203 8 ± 0.006 7 vs 0.224 7 ± 0.021 0, P < 0.01; mRNA: 0.47 ± 0.08, 0.53 ± 0.21 vs 1.18 ± 0.09, P < 0.01). Meanwhile, the level of ZO-1 in prevention and treatment group was higher than that in LPS group at different time points, but there were no marked differences.

CONCLUSION: PAF may decrease tight junction associated protein ZO-1 and thereby damage the function of intestinal barrier. PAF receptor antagonist can alleviate the degree of the damages to some extent.

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.