多黏菌素E诱导肠道菌群失调对肠屏障功能和细菌易位的影响

目的:应用多黏菌素E给小鼠灌胃诱导建立肠道菌群失调动物模型,研究肠道菌群失调对肠黏膜屏障和细菌易位的影响。方法:将20只小鼠随机分为两组,每组10只。实验组采用多黏菌素E按0.2 g/kg加入0.2 ml等渗盐水灌胃,1次/d,连续7 d。对照组用等剂量等渗盐水灌胃,1次/d,连续7 d。实验结束次日观察两组小鼠回肠黏膜病理形态、肠道菌群、回肠黏膜组织紧密连接(TJ)蛋白表达和器官(肝、脾、肾、淋巴结)细菌易位率等。结果:实验组小鼠盲肠黏膜和盲肠内容物的肠杆菌数量显著减少。常规病理检查发现,实验组小鼠回肠黏膜充血明显,绒毛稀疏,尖端有少量上皮坏死脱落,与对照组比损伤明显。透射电镜显示,实验组小鼠回肠上皮TJ的电子致密物质明显减少,TJ破坏。回肠黏膜组织中TJ蛋白Claudin-1、Occludin和ZO-1的表达显著下降,器官细菌易位率显著高于对照组。结论:多黏菌素E灌胃能够诱导肠道菌群失调,且导致肠屏障功能损伤和细菌易位。     

肠屏障功能障碍

1肠屏障相关概念 1.1 肠屏障是指肠道能防止肠腔内的有害物质如细菌和毒素穿过肠黏膜进入体内其他组织器官和血液循环的结构和功能的总和.它包括:肠黏膜上皮、肠黏液、肠道菌群、分泌性免疫球蛋白、肠道相关淋巴组织(GALT)、胆盐、激素和胃酸等[1～3].一般将其归纳为三部分:①生态屏障即肠道内的常居菌群;②机械屏障即黏膜上皮;③免疫屏障即黏膜细胞的分泌性IgA、黏膜内及黏膜下各种免疫细胞(包括巨噬细胞、中性粒细胞、NK细胞、淋巴细胞-即IELs)、派尔集合淋巴结和肠系膜淋巴结(MLN).其中小肠黏膜上皮细胞非常重要,它在充满细菌和毒素的肠腔和其他组织及血循环之间构建了一个物理性屏障,一般意义上的肠屏障即指这层结构[3].     

全肠外营养对肠道免疫功能影响的研究

本研究采用ＳＰＦ大鼠ＴＰＮ支持模型，观察标准ＴＰＮ和改良ＴＰＮ不同营养模式对肠免疫屏障功能的影响，探讨ＴＰＮ导致肠粘膜免疫抑制的机理，进一步阐述ＴＰＮ导致肠湖泊性感染发生的综合机理。结果显示，标准ＴＰＮ由于缺乏肠粘膜必需氨基酸Ｇｌｎ和肠道刺激，引起肠粘膜免疫系统改变，肠腔细菌Ｓ－ｌｇＡ包被率下降，导致肠粘膜免疫抑制和肠道微生态紊乱、机械屏障损伤协同，至细菌粘附率和易位率上升。各改良组因添加肠道必需     

大鼠小肠RNA对受照小鼠肠黏膜损伤的修复作用

目的探讨外源大鼠RNA对受照小鼠肠黏膜损伤修复的影响。方法选用BALB/c雄性小鼠36只分为3组即正常对照、单纯照射组和小肠RNA组,每组12只。用11.5Gy60Coγ射线进行腹部一次照射,于照后1～3h采用局部肠腔扩张注入法给小鼠空肠肠腔内注入正常大鼠小肠RNA,于照后18h解剖取空肠段,检测各组肠腺存活率,扫描电镜和透射电镜将观察肠黏膜形态变化。结果与正常对照组相比,单纯照射组肠腺存活率显著降低(P<0.01);与单纯照射组相比,小肠RNA可明显提高受腹部照射小鼠空肠的肠腺存活率(P<0.01),减轻肠绒毛损伤,改善肠黏膜形态结构。结论大鼠小肠RNA对小鼠肠黏膜辐射损伤具有明显的修复作用。     

全肠外营养相关肠黏膜免疫屏障损伤小鼠模型的建立

目的:建立一种稳定有效的小鼠模型,为进一步研究全肠外营养(TPN)相关肠黏膜屏障损伤的机制和干预措施。方法:将22只小鼠随机分为对照组(n=10)和TPN组(n=12)。小鼠经颈内静脉置管后,对照组给予正常饮食,用微量泵持续输注等渗盐水;TPN组给予禁食后用微量泵持续输注PN液。5 d后比较两组小鼠生存率、肠道菌群易位情况、肠道杯状细胞数量以及潘氏细胞变化。结果:两组小鼠的生存率无显著性差异。TPN组肠道菌群淋巴结易位率增加(6/10 vs 1/10,P0.05),杯状细胞数量减少[(61.6±6.5)个vs(33.0±7.8)个,P0.01)],隐窝处潘氏细胞内抗菌多肽颗粒明显减少,溶菌酶和黏蛋白2(MUC2)含量显著降低。结论:TPN组小鼠能作为后期研究TPN诱导肠黏膜免疫屏障受损的模型,用于患病机制、药物治疗的观察和研究。     

谷氨酰胺在预防细菌易位和肠上皮细胞损伤中的作用

小肠粘膜的损伤是发生细菌易位的主要机制，而谷氨酰胺在肠粘膜结构与屏障功能的维持中起重要作用。本文通过细胞株、活体肠袢水平的观察来了解谷氨酰胺在减轻细菌易位及肠上皮细胞损伤中的作用。１材料和方法从坏死性肠炎（ＮＥＣ）的婴儿体内分离出的大肠杆菌菌落用在Ｃ...     

艾司洛尔对脓毒症大鼠肠黏膜屏障的影响

目的:探讨艾司洛尔对脓毒症大鼠肠黏膜屏障的保护作用. 方法:建立脓毒症大鼠模型,将大鼠随机分为对照组(脓毒症组)和艾司洛尔组(脓毒症模型+艾司洛尔组),每组8只.观察大鼠的基本生命体征、体外肠道的通透性和血清内毒素变化.同时,通过肝、脾和肠系膜淋巴结细菌培养观察细菌易位情况.最后,根据H-E染色结果评估大鼠肠道损伤. 结果:艾司洛尔组大鼠心率明显低于基础值(P＜0.05).与对照组比,艾司洛尔组大鼠细菌易位减少,体外肠道通透性降低.两组大鼠血清内毒素水平无显著性差异.艾司洛尔组大鼠肠道病理评分明显低于对照组. 结论:艾司洛尔能保护脓毒症大鼠肠黏膜屏障,减轻肠损伤.     

乳杆菌对致病性大肠杆菌感染小鼠肠黏膜屏障功能的影响

目的:研究乳杆菌对致病性大肠杆菌感染小鼠肠黏膜屏障的保护作用.方法:将BALB/c小鼠随机分为对照组、致病性大肠杆菌感染组、乳杆菌JCM1081灌胃组、乳杆菌治疗组等,实验进行14 d.观察各组小鼠肠黏膜形态变化、肠道菌群变化、细菌移位以及肠黏膜钙黏蛋白表达的差异.结果:致病性大肠杆菌感染组小鼠与对照组相比,肠黏膜形态有明显改变,肠道内厌氧菌数量显著下降,肠杆菌和肠球菌数量明显增加,在肝、脾、肾以及肠系膜淋巴结中有细菌存在,但肠黏膜钙黏蛋白无明显变化.乳杆菌灌胃组小鼠各项指标无显著变化.乳杆菌治疗组小鼠各项指标变化程度较致病性大肠杆菌感染组显著减轻.结论:乳杆菌能黏附定植于肠黏膜并形成生物屏障,起着保护肠黏膜免受损伤的作用.     

人芽囊原虫不同感染途径对免疫抑制小鼠肠黏膜的影响

目的 探讨人芽囊原虫(B.hominis)经口和经直肠感染免疫功能低下小鼠后在肠道内寄生和对肠黏膜的损伤情况.方法 将昆明小鼠60只应用免疫抑制剂制备为免疫功能低下小鼠后,随机分为6组.其中4组分别经口和直肠感染15×103、20×103剂量的虫体,其他两组为阴性对照组.感染后d2观察各组小鼠症状并粪便检查感染情况.感染7d后处死动物,分段将肠内容物涂片检查虫体寄生情况,同时取回盲部肠黏膜观察光镜下的病理结构改变和电镜的超微病理变化.结果 经口和直肠感染均显示该虫主要寄生在回盲部和盲肠,主要附着在肠腔和肠黏膜表面.光学和电子显微镜检查显示经口感染小鼠肠黏膜组织病理变化较轻,经直肠感染小鼠肠黏膜病理改变较重,不同感染剂量之间小鼠肠黏膜病理变化无明显差异.正常对照组小鼠肠腔内未见虫体,组织病理检查未见异常改变.结论 人芽囊原虫对小鼠肠黏膜损伤程度与感染途径有关,经直肠感染病理变化较重.该虫主要寄生在小鼠回盲部的肠腔和黏膜表面.     

表皮生长因子增强TPN减少放射性肠炎细菌易位及其机理的实验研究

腹部受辐射 ( abdominal rdiation,AR)致放射性肠炎常导致肠粘膜屏障损害和细菌易位。接受长期 TPN( total parenteral nutrition,TPN)改善营养的同时 ,可加重细菌易位 ,并导致多器官功能衰竭等致死性并发症。即使给予肠粘膜代谢所需的谷氨酰胺 ( Glutamine,Gln)亦不能完全防治其损伤。EGF( epidermal growth factor)是胃肠道粘膜上皮生长和增殖的介质。本研究在 SD大鼠放射性肠炎模型上观察了 EGF增强 TPN对放射性肠炎细菌易位及对损伤的肠粘膜修复的影响 ,结果发现 ,经 EGF增强的 TPN治疗大鼠放射性肠炎 ,大鼠死亡率、细菌易位率均较不用 TPN及应用不含 EGF的 TPN组明显下降 ,体重、粘膜 /肠段重量比、绒毛高度、面积、小肠 Gln摄取率及 DNA含量均明显升高。机理为 :EGF对小肠粘膜有明显的滋养作用。EGF增强 TPN在提供较完善营养及肠道充分休息 ,促进创伤愈合的同时 ,通过提高肠粘膜对 Gln的摄取能力 ,维持肠粘膜上皮的正常代谢 ,加速修复损伤的肠粘膜屏障 ,降低细菌易位率 ,从而降低死亡率     

肠道粘膜屏障的损伤与保护

肠道依靠其机械、免疫屏障及正常的微生态环境等,能有效阻止肠道细菌移位和内毒素血症.但在创伤、应激等情况下,其结构和功能可受到严重损害,从而引起一系列病理生理的变化,充分认识肠粘膜屏障损伤的危害性,探讨其发生的机制及采取积极有效地保护措施,有助于防止疾病的发生和多器官功能障碍.     

Impaired intestinal immunity and barrier function: a cause for enhanced bacterial translocation in alcohol intoxication and burn injury.

Alcohol intoxication is being recognized increasingly as the major factor in pathogenesis after burn injury. Findings from multiple studies support the suggestion that, in comparison with burn-injured patients who sustained injury in the absence of alcohol intoxication, burn-injured patients who sustained injury under the influence of alcohol exhibit higher rates of infection and are more likely to die. Thus, infection becomes the primary cause of death in burn-injured patients. Because the intestine is considered to be a major source of bacteria, studies in experimental animals have been designed to examine whether alcohol intoxication before burn injury enhances bacterial translocation from the intestine. Results of these studies have shown a several-fold increase in bacterial translocation from the intestine in the group of animals receiving combined insult of alcohol intoxication and burn injury compared with findings for the groups receiving either insult alone. Alcohol intoxication and burn injury independent of each other have also been shown to cause an increase in bacterial translocation. The gastrointestinal tract normally maintains a physical mucosal and immunologic barrier that provides an effective defense in keeping bacteria within the intestinal lumen. However, in injury conditions these defense mechanisms are impaired. Intestinal bacteria consequently gain access to extraintestinal sites. Intestine-derived bacteria are implicated in causing systemic infection and in subsequent multiple organ dysfunction in both immunocompromised patients and patients with injury, such as burn and trauma. In this article, we discuss three potential mechanisms that are likely to contribute to the increase in bacterial translocation in alcohol intoxication and burn injury: (1) increase in bacterial growth in the intestine, (2) physical disruption of mucosal barrier of the intestine, and (3) suppression of the immune defense in the intestine.     

Effects of protein malnutrition and endotoxin on the intestinal mucosal barrier to the translocation of indigenous flora in mice

Since protein malnourished or endotoxemic patients are at increased risk of developing nosocomial infections with enteric organisms, we investigated the effects of these risk factors alone and in combination on the intestinal mucosal barrier to bacteria. Protein malnutrition resulted in severe ileal atrophy that was directly related to the length of time the mice were protein malnourished. Although protein malnutrition did not promote bacterial translocation from the gut to systemic organs, the protein-malnourished mice were more susceptible to endotoxin-induced bacterial translocation than normally nourished mice (p less than 0.01). Since the gross epithelial damage documented after endotoxin administration in normally nourished mice was diminished after protein malnutrition, there was no correlation between the gross appearance of the epithelial mucosal barrier and the extent of endotoxin-induced bacterial translocation. These results suggest that the synergistic effect of endotoxin plus protein malnutrition on bacterial translocation is not primarily related to failure of the gut mucosal barrier. Nonetheless, it appears that protein-malnourished mice are less able to clear translocating bacteria than normally nourished mice.     

严重腹部创伤休克时肠损伤后不同手术方式对肠黏膜屏障的影响

目的:对照研究严重腹部创伤休克时肠道损伤后不同手术方法对术后肠黏膜屏障的影响.方法:雌性杂种猪麻醉后,建立多发肠管损伤并发酸中毒、低体温、凝血障碍"致死三联征"的严重腹部创伤实验模型,随机分为三组,每组7只.即①对照组:手术修补(修补)组行肠管损伤修补吻合术,7号线双层关闭腹腔;②肠道结扎(结扎)组行肠管损伤段丝线结扎...     

谷氨酰胺对创伤后肠粘膜通透性的影响

在创伤的情况下,肠道通透性将发生改变,继而引起细菌移位和内毒素血症。谷氨酰胺可以通过降低肠粘膜通透性来减少细菌移位、减轻内毒素血症。     

大黄和早期肠内营养对肠缺血-再灌注损伤大鼠肠屏障功能的影响

目的:观察大黄和早期肠内营养(EEN)对大鼠肠缺血-再灌注损伤(IRI)后肠黏膜屏障的影响.方法:将32只大鼠随机分为对照组、EN组、大黄组、大黄+EN组.在大鼠肠IRI模型上观察再灌注24h后肠黏膜形态学的变化、血清内毒素和细菌易位指标. 结果:肠IRI可导致肠黏膜发生严重损伤.肠IRI后24h,大黄组大鼠内毒素水平...     

微生物酵素预防治疗肠道细菌易位的实验研究

目的探讨微生物酵素对他克莫司(FK506)作用下肠道细菌易位情况的影响。方法健康雄性Wistar大鼠84只,体重180～220g,随机分为对照组、免疫抑制组和预防治疗组;比较3组间肝和肠系膜淋巴结细菌培养阳性率、肠黏膜病理分析。结果免疫抑制组第5、7天脏器细菌培养阳性率分别为28.57%、42.86%,显著高于对照组的0、0(P<0.05);各时间点肠黏膜损伤评分均显著高于对照组(P<0.05);预防治疗组第7天脏器细菌培养阳性率为7.14%,显著低于免疫抑制组的0(P<0.05);第3、5、7天肠黏膜损伤评分均显著低于免疫抑制组(P<0.05)。结论 FK506可以引起肠黏膜上皮损伤,肠道机械屏障功能破坏,肠黏膜通透性增高,发生肠道细菌易位;应用微生物酵素在一定程度上能够减轻FK506引起的肠黏膜上皮损害,保护肠黏膜机械屏障功能,降低肠黏膜通透性,减少肠道细菌易位的发生。     

益生菌在肠内营养中的应用及研究进展

防治肠源性感染的关键在于防止肠内细菌和(或)内毒素的移位,纠正肠内菌群平衡的紊乱和失调,改善肠黏膜屏障功能以及提高肠道局部的免疫功能。而益生菌是具有维持肠内菌群平衡、防止肠黏膜屏障的破坏、增强局部免疫功能、促进和改善消化道蠕动以及吸收等作用的非致病性微生物,可治疗和预防肠源性感染。以下综述益生菌在肠内营养的作用及研究进展。     

Bulk prevents bacterial translocation induced by the oral administration of total parenteral nutrition solution

The effects of a fat and glutamine-free orally administered total parenteral nutrition (TPN) solution on intestinal mucosal mass, morphology, barrier function, and cecal bacterial population levels were measured in CD-1 mice. Ileal mucosal protein content decreased by 63% (p less than 0.01) in the oral TPN-fed mice, although they gained weight on this diet. These TPN-fed mice also exhibited changes in mucosal structure and the normal ecology of their cecal microflora was disrupted leading to overgrowth with Gram-negative enteric bacilli. These changes in intestinal mucosal mass, morphology, and gut bacterial ecology were associated with an increased incidence of bacterial translocation (BT) (TPN group 70% BT vs control group 15% BT: p less than 0.01). The administration of cellulose fiber or kaolin (bulk-forming agents), but not of citrus-pectin (a fully-fermentable, nonresidue fiber) reduced the incidence of BT in the TPN-fed mice to control levels. The beneficial effects of these bulk-forming agents appeared to be due to their ability to prevent TPN-induced disruption of the intestinal microflora and alterations in intestinal morphology, even though they did not prevent ileal mucosal protein levels from decreasing. These results suggest that the administration of bulk forming agents will prevent the loss of intestinal barrier function against luminal bacteria that occurs in mice fed an oral TPN solution.