Pathophysiology of increased intestinal permeability in obstructive jaundice

Despite advances in preoperative evaluation and postoperative care, intervention, especially surgery, for relief of obstructive jaundice still carries high morbidity and mortality rates, mainly due to sepsis and renal dysfunction. The key event in the pathophysiology of obstructive jaundice-associated complications is endotoxemia of gut origin because of intestinal barrier failure. This breakage of the gut barrier in obstructive jaundice is multi-factorial, involving disruption of the immunologic, biological and mechanical barrier. Experimental and clinical studies have shown that obstructive jaundice results in increased intestinal permeability. The mechanisms implicated in this phenomenon remain unresolved, but growing research interest during the last decade has shed light in our knowledge in the field. This review summarizes the current concepts in the pathophysiology of obstructive jaundice-induced gut barrier dysfunction, analyzing pivotal factors, such as altered intestinal tight junctions expression, oxidative stress and imbalance of enterocyte proliferation and apoptosis. Clinicians handling patients with obstructive jaundice should not neglect protecting the intestinal barrier function before, during and after intervention for the relief of this condition, which may improve their patients’ outcome.     

紧密连接相关蛋白Occludin的研究进展

Occludin是紧密连接相关蛋白中最具有代表性的蛋白之一,它封闭细胞旁路,形成紧密连接的基础结构.Occludin的生理功能主要包括栅栏功能和细胞旁屏障功能,其表达低下可导致肺上皮屏障、血脑屏障、肠上皮屏障及血睾屏障的破坏,与多种疾病的发生、发展密切相关.因此,有关Occludin蛋白的调控机制及其临床意义已成为国内外研究的热点.     

谷氨酰胺对体外肠上皮细胞缺血再灌注损伤后occludin蛋白表达的影响

目的 探讨谷氨酰胺(GLN)对体外肠缺血再灌注损伤后肠上皮细胞活性及紧密连接蛋白occludin表达的影响,以研究GLN对肠黏膜保护作用的机制.方法 利用Caco-2细胞建立缺氧/复氧模型,模仿肠缺血再灌注,然后用含有不同浓度GLN的培养液继续培养.利用MTT检测细胞活性,利用RT-PCR和Western blot检测occludin蛋白的表达情况.结果 MTT结果显示,与0 mmol/L GLN组(0.635±0.041、0.690±0.032)相比,补充GLN后细胞OD值明显增加(4 mmol/L GLN组:0.716±0.040、0.904±0.089,8 mmol/L GLN组:0.768±0.040、0.856±0.073,P均<0.05).RT-PCR结果显示,与0 mmol/L GLN组(0.244±0.037、0.591±0.031)相比,GLN影响occludin蛋白mRNA的相对表达量(4 mmol/L GLN组:0.371±0.057、0.799±0.054,8 mmol/L GLN组:0.714±0.030、0.547±0.064,P均<0.05).Western blot结果显示,与0 mmol/L GLN组(35.056±2.313、74.309±1.528)相比,GLN可以增加紧密连接蛋白occludin表达(4 mmol/L GLN组:63.432±0.649、101.759±1.214,8 mmol/L GLN组:99.453±0.526、99.573±2.082,P均<0.05).结论 GLN促进肠上皮的增殖,同时在基因和蛋白水平上影响紧密连接蛋白occludin的表达.     

脑出血后血脑屏障紧密连接蛋白occludin的表达变化

目的 探讨脑出血后血脑屏障微血管内皮细胞间紧密连接蛋白occludin的表达变化. 方法 将SD雄性大鼠按随机数字表法分为正常对照组和脑出血组,再按时间因素将脑出血组分为出血后6h、24h、48h、72h、7d、14d6个亚组.采用脑内注入自体血法制作脑出血模型.HE染色观察脑出血后血肿周围脑组织的形态学改变;透射电镜观察脑出血后血肿周围紧密连接的超微结构改变;免疫荧光染色检测脑出血后血肿周围紧密连接蛋白occludin的表达分布状况;定量RT-PCR检测脑出血后血肿周围脑组织中occludin mRNA的表达状况. 结果 与正常对照组相比,脑出血组血肿周围脑组织出现水肿,在48 h左右尤为明显,局部可见明显脑细胞坏死及炎细胞浸润.脑出血后血肿周围紧密连接发生明显破坏,内皮细胞间出现裂隙.免疫荧光染色结果显示:正常对照组紧密连接蛋白occludin呈强阳性表达.脑出血后6hoccludin的表达即开始下降,呈阳性表达;脑出血后24～72h occludin的表达维持在较低水平,呈弱阳性表达.定量RT-PCR结果显示:脑出血后血肿周围脑组织中occludin mRNA相对含量明显降低,在6～72 h持续维持在较低水平,与正常对照组比较差异均有统计学意义(P＜0.05). 结论 脑出血发生后,紧密连接蛋白occludin 的表达下降,这可能是脑出血发生后血脑屏障破坏及脑水肿发生发展的重要分子基础之一.     

Pathology and new players in the pathogenesis of brain edema

Brain edema continues to be a major cause of mortality after diverse types of brain pathologies such as major cerebral infarcts, hemorrhages, trauma, infections and tumors. The classification of edema into vasogenic, cytotoxic, hydrocephalic and osmotic has stood the test of time although it is recognized that in most clinical situations there is a combination of different types of edema during the course of the disease. Basic information about the types of edema is provided for better understanding of the expression pattern of some of the newer molecules implicated in the pathogenesis of brain edema. These molecules include the aquaporins, matrix metalloproteinases and growth factors such as vascular endothelial growth factors A and B and the angiopoietins. The potential of these agents in the treatment of edema is discussed. Since many molecules are involved in the pathogenesis of brain edema, effective treatment cannot be achieved by a single agent but will require the administration of a “magic bullet” containing a variety of agents released at different times during the course of edema in order to be successful.     

不同胆汁引流方式对梗阻性黄疸大鼠肠黏膜屏障功能的影响及机制

目的：探讨不同胆汁引流方式对梗阻性黄疸（OJ）大鼠肠黏膜功能的影响及其机制。 方法：将60只SD大鼠采用胆总管结扎法制作OJ模型,1周后随机均分为无引流组（不行胆汁引流术）,内引流组（行胆汁内引流术）和外引流组（行胆汁外引流术）,引流时间1周。以20只假手术大鼠为对照组,实验共2周,结束时分别用ELISA法和Western blot法检测各组血清内毒素水平和小肠黏膜组织闭锁蛋白（occludin）及闭锁小带蛋白1（ZO-1）的表达,并观察小肠黏膜组织形态学改变。 结果：大鼠造模后出现明显的OJ表现,二次手术后,内引流组大鼠一般情况明显好于无引流组和外引流组。无引流组和外引流组OJ大鼠血清内毒素水平明显升高,与对照组比较,差异均有统计学意义（均P<0.01）,而无引流组与外引流组间内毒素水平差异无统计学意义（P>0.05）;内引流组OJ大鼠血清内毒素水平较无引流组和外引流组明显下降（均P<0.01）,与对照组水平无统计学差异（P>0.05）。与对照组比较,无引流组和外引流组OJ大鼠小肠黏膜组织occludin及ZO-1蛋白表达均明显降低（均P<0.01）,且外引流组两者表达水平降低较无引流组更为明显（均P<0.01）;内引流组OJ大鼠的occludin及ZO-1的表达水平明显高于无引流组和外引流组（均P<0.01）,且基本接近对照组（均P>0.05）。病理学观察显示,无引流组和外引流组OJ大鼠肠黏膜结构破坏,大量或中量炎性细胞浸润,而内引流组OJ大鼠组肠黏膜结构完整,仅见少量炎性细胞浸润。 结论：胆汁内引流对OJ大鼠肠黏膜屏障具有保护作用,其机制可能与胆汁维持肠黏膜上皮细胞间紧密连接相关蛋白的表达有关。     

急性胰腺炎患者肠黏膜屏障功能损害相关研究

目的探讨急性胰腺炎(AP)患者肠黏膜屏障功能改变机制。方法 61例AP患者按病情程度分为重症组(n=31)和轻型组(n=30),另选肠镜检查志愿者作为对照组(n=30),电镜观察肠黏膜超微结构变化,比较血清内毒素、白细胞介素-18(IL-18)及肠黏膜ZO-1、Occludin的变化。结果对照组ZO-1和Occludin蛋白为棕黄色,染色较强,成点状聚集;轻型组和重症组患者肠黏膜ZO-1和Occludin蛋白的染色变浅。轻型组和重症组患者肠黏膜ZO-1和Occludin蛋白光密度水平较对照组下降(P<0.05,0.01)。与轻型组比较,重症组患者肠黏膜光密度水平降低(P<0.05)。轻型组和重症组患者肠黏膜ZO-1、Occludin基因水平较对照组下降(P<0.05,0.01);重症组患者肠黏膜ZO-1、Occludin基因水平较轻型组下降(P<0.05)。轻型组和重症组患者内毒素和IL-18水平均高于对照组,差异有统计学意义(P<0.05,P<0.01)。重症组患者肠黏膜内毒素和IL-18水平高于轻型组,差异有统计学意义(P<0.05)。血清内毒素、IL-18水平与ZO-1蛋白和Occludin蛋白表达均呈负相关(r=-0.79、-0.64、-0.71、-0.61,P<0.05)。结论 AP患者早期肠黏膜受损,肠黏膜通透性增加。内毒素和IL-18可能协同或单独参与肠黏膜的破坏。     

Bile acids permeabilize the blood brain barrier after bile duct ligation in rats via Rac1-dependent mechanisms

BackgroundThe blood brain barrier tightly regulates the passage of molecules into the brain and becomes leaky following obstructive cholestasis. The aim of this study was to determine if increased serum bile acids observed during cholestasis permeabilize the blood brain barrier.MethodsRats underwent bile duct ligation or deoxycholic or chenodeoxycholic acid injections and blood brain barrier permeability assessed. In vitro, the permeability of rat brain microvessel endothelial cell monolayers, the expression and phosphorylation of occludin, ZO-1 and ZO-2 as well as the activity of Rac1 was assessed after treatment with plasma from cholestatic rats, or bile acid treatment, in the presence of a Rac1 inhibitor.ResultsBlood brain barrier permeability was increased in vivo and in vitro following bile duct ligation or treatment with bile acids. Associated with the bile acid-stimulated increase in endothelial cell monolayer permeability was elevated Rac1 activity and increased phosphorylation of occludin. Pretreatment of endothelial cell monolayers with a Rac1 inhibitor prevented the effects of bile acid treatment on occludin phosphorylation and monolayer permeability.ConclusionsThese data suggest that increased circulating serum bile acids may contribute to the increased permeability of the blood brain barrier seen during obstructive cholestasis via disruption of tight junctions.     

C1q肿瘤坏死因子相关蛋白6破坏大鼠脑缺血再灌注损伤后血脑屏障的机制研究

目的 探讨C1q肿瘤坏死因子相关蛋白6（C1q and tumor necrosis factor related protein 6，C1QTNF6） 对大鼠大脑中动脉缺血再灌注（middle cerebral artery occlusion reperfusion，MCAO/R）后血脑屏障及内皮细胞闭合蛋白（occludin）和闭锁小带蛋白-1（zonula occludens 1，ZO-1）表达的影响。      

ω-3不饱和脂肪酸对肝部分切除大鼠残肝的保护作用及机制

目的：探讨ω-3不饱和脂肪酸（ω-3PUFA）对肝部分切除大鼠残肝的保护作用和机制。方法：雄性SD大鼠96只随机分为:假手术组,模型组（肝部分切除+生理盐水），低剂量ω-3PUFA治疗组（肝部分切除+1 mL/kg ω-3PUFA），高剂量ω-3PUFA治疗组（肝部分切除+2 mL/kg ω-3PUFA）。术后1，2，3，5 d光镜下动态观察肝脏病理形态学改变，并检测术后3 d肝细胞Occludin蛋白的表达和超微结构改变。结果：病理学检查可见模型组肝细胞组织形态受损明显，而两个剂量的ω-3PUFA治疗组肝细胞受损情况明显减轻，但其两者间差异较小；术后3 d，两个剂量的ω-3PUFA治疗组Occludin蛋白表达较模型组明显升高，但其两者间差异不明显；电镜发现模型组肝细胞紧密连接严重受损，两个剂量的ω-3PUFA治疗组受损程度明显减轻，且高剂量组作用优于低剂量组。结论：肝切除术后大鼠围手术期应用ω-3PUFA可能通过增加Occludin蛋白表达和维持肝细胞间紧密连接，从而产生保护肝脏屏障的效果。