Effect of cisapride on intestinal bacterial and endotoxin translocation in cirrhosis

AIM: To investigate the effects of cisapride on intestinal bacterial overgrowth (IBO), bacterial and endotoxin translocation, intestinal transit and permeability in cirrhotic rats. METHODS: All animals were assessed with variables including bacterial and endotoxin translocation, intestinal bacterial overgrowth, intestinal transit and permeability. Bacterial translocation (BT) was assessed by bacterial culture of MLN, liver and spleen, IBO by a jejunal bacterial count of the specific organism, intestinal permeability by determination of the 24-hour urinary (99m)Tc-DTPA excretion and intestinal transit by measurement of the distribution of (51)Cr in the intestine. RESULTS: Bacterial translocation (BT) and IBO was found in 48 % and 80 % cirrhotic rats respectively and none in control rats. Urinary excretion of (99m)Tc-DTPA in cirrhotic rats with BT (22.2+/-7.8) was greater than these without BT (10.5+/-2.9). Intestinal transit (geometric center ratio) was significantly delayed in cirrhotic rats (0.31+/-0.06) and further more delayed in cirrhotic rats with BT (0.24+/-0.06) than these without BT (0.38+/-0.11). Cirrhotic rats with IBO had significantly higher rates of intestinal bacterial and endotoxin translocation, slower intestinal transit time and higher intestinal permeability than those without IBO. It was also found that BT was closely associated with IBO and the injury of intestinal barrier. Compared with the placebo group, cisapride-treated rats had lower rates of bacterial/endotoxin translocation and IBO, which was closely associated with increased intestinal transit and improved intestinal permeability by cisapride. CONCLUSION: These results indicate that endotoxin and bacterial translocation in cirrhotic rats may be attributed to IBO and increased intestinal permeability. Cisapride that accelerates intestinal transit and improve intestinal permeability might be helpful in preventing intestinal bacterial and endotoxin translocation.     

急性肝损伤大鼠肠源性内毒素血症形成机理及其作用的实验研究

探讨急性肝损伤大鼠肠源性内毒素血症的形成机理及肠源性内毒素血症在急性肝损伤过程中的作用.采用皮下注射硫代乙酰胺（TAA）600 mg/kg制作大鼠急性肝损伤动物模型,取回肠内容物、肝、脾、淋巴结作细菌培养,检测血浆及回肠内容物内毒素含量.行血浆D-乳酸的检测.取肝脏和回肠作病理切片.结果显示TAA诱导大鼠急性肝损伤后,血浆及回肠内容物内毒素水平上升明显（P＜0.01）,血浆TNF-α含量升高明显（P＜0.01）,且与内毒素水平升高呈正相关（P＜0.01）.同时出现肠道菌群失调,肠道通透性增加,肠道细菌移位.回肠病理所示肠绒毛明显变短、破坏、炎性细胞浸润增多.因此肠道菌群失调、肠粘膜结构改变、肠道通透性增加及肠道细菌移位是形成肠源性内毒素血症的重要因素.内毒素可直接或通过诱导TNF-α加重肝损伤.     

Protective role of supplement with foreign Bifidobacterium and Lactobacillus in experimental hepatic ischemia-reperfusion injury

BACKGROUND AND AIM: Intestinal microflora play a crucial role in some severe liver diseases. The purpose of this study was to evaluate the effects of a Lactobacillus strain and a Bifidobacterium strain on ischemia-reperfusion (I/R) liver injury. METHODS: Rats were divided into six groups. Each group received either Bifidobacterium Catenulatum ZYB0401; Lactobacillus Fermentum ZYL0401; a mixture of these two bacterial strains; gentamicin; or saline by daily gavage for 7 days. On the sixth day, all rats, except those in the control group, were subjected to 20 min of liver ischemia. After 22 h of hepatic reperfusion, liver enzymes and histology, malondialdehyde (MDA), superoxide dismutase (SOD), endotoxemia, serum tumor necrosis factor-alpha (TNF-alpha), intestinal bacteria, intestinal mucosal ultrastructure, and bacterial translocation were studied. RESULTS: All administered bacteria increased intestinal Bifidobacterium and Lactobacillus, decreased endotoxemia (P < 0.01), alanine aminotransferase (ALT) (P < 0.01), and markedly ameliorated liver histology and intestinal mucosal ultrastructure. Only rats treated with Bifidobacterium Catenulatum ZYB0401 and Lactobacillus Fermentum ZYL0401 showed reduced incidence of bacterial translocation to the kidney (P < 0.05), associated with decreased serum TNF-alpha and liver MDA (P < 0.05) and increased liver SOD (P < 0.05) compared to the I/R group. Gentamicin decreased almost all kinds of intestinal bacteria (P < 0.01) and decreased ALT (P < 0.01) and serum TNF-alpha, but failed to reduce both endotoxemia and the incidence of bacterial translocation and had no effects on liver MDA and SOD. CONCLUSION: Bifidobacterium Catenulatum ZYB0401 in combination with Lactobacillus Fermentum ZYL0401 could be useful in restoring intestinal microflora and in preventing liver injury in hepatic I/R of rats.     

Inhibition of Nitric Oxide Modulates the Effect of Oral Arginine Supplementation in Acute Liver Injury

Background: Arginine possesses numerous unique and advantageous biochemical and pharmacologic properties. We have previously shown that arginine supplementation in an acute liver injury model reduces both the extent of the liver injury and bacterial translocation. We therefore studied the role of nitric oxide on the effects of oral arginine supplementation in acute liver injury, bacterial translocation, ileal and cecal mucosal nucleotides, and RNA and DNA, to investigate pathogenetic mechanisms. Methods: Sprague-Dawley rats were divided into normal, liver injury control, N-nitro-L-arginine methyl ester (L-NAME), arginine, and L-NAME + arginine supplementation groups. Oral supplementation was performed daily through a nasogastric tube for 8 days. Acute liver injury was induced on the 8th day by intraperitoneal injection of D-galactosamine (1.1 g/kg body weight). Twenty-four hours after the liver injury, liver function tests, bacterial translocation, and ileal and cecal mucosal nucleotides, RNA, and DNA were evaluated. Results: Bilirubin and liver enzymes increased significantly in the L-NAME group compared with the arginine group, whereas the liver enzymes increased significantly compared wim the liver injury control group. In the L-NAME group the number of bacteria translocated to the portal and arterial blood increased significantly compared with all groups. In the arginine group the bacteria translocated to the liver and mesenteric lymph nodes decreased significantly compared with the liver injury control and L-NAME groups. The ileal and cecal mucosal nucleotides, RNA, and DNA in the arginine group increased significantly compared with the normal, liver injury, and L-NAME groups. Conclusions: Nitric oxide plays a role in the beneficial effect of the arginine supplementation in acute liver injury. It significantly improves the liver damage indicated by the increase of liver enzymes when its production was inhibited by L-NAME. Nitric oxide has a role in bacterial translocation since the number of bacteria significantly increased in arterial and portal blood when L-NAME was used to inhibit its production. Furthermore, arginine supplementation improved mucosal nucleotides, RNA, and DNA in ileum and colon.     

A simple taurocholate-induced model of severe acute pancreatitis in rats

AIM: To investigate gut barrier damage and intestinal bacteria translocation in severe acute pancreatitis (SAP),a simple rat model of SAP was induced and studied.METHODS: Pancreatitis was induced by uniformly distributed injection of 3.8% Na taurocholate (1 mL/kg) beneath the pancreatic capsule. Rats in the control group were injected with normal saline in the identical location.RESULTS: Serum amylase, plasma endotoxin, intestinal permeability, and pancreatitis pathology scores were all markedly higher in the pancreatitis group than in the control group ( P < 0.01). The bacterial infection rate was significantly higher in the SAP group than in the control group ( P < 0.01), observed in parallel by both bacterial culture and real-time polymerase chain reaction. Acute damage of the pancreas was observed histologically in SAP rats, showing interstitial edema, leukocyte infiltration, acinar cell necrosis and hemorrhage. The microstructure of the intestinal mucosa of SAP rats appeared to be destroyed with loose, shortened microvilli and rupture of the intercellular junction, as shown by electron microscopy.CONCLUSION: Significant gut barrier damage and intestinal bacterial translocation were definitely observed with few potential study confounders in this SAP rat model, suggesting that it may be an appropriate animal model for study of gut barrier damage and bacterial translocation in SAP.     

Intestinal ischemia-reperfusion injury augments intestinal mucosal injury and bacterial translocation in jaundiced rats

BACKGROUND/AIMS: The aim of this study was to evaluate local effects and degree of bacterial translocation related with intestinal ischemia-reperfusion injury in a rat obstructive jaundice model. METHODOLOGY: Thirty adult Sprague-Dawley rats (200-250 g) were divided into three groups; including Group 1 (jaundice group), Group 2 (jaundice-ischemia group) and Group 3 (ischemia group). All rats had 2 laparotomies. After experimental interventions, tissue samples for translocation; liver and ileum samples for histopathological examination, 25 cm of small intestine for mucosal myeloperoxidase and malondialdehyde levels and blood samples for biochemical analysis were obtained. RESULTS: Jaundiced rats had increased liver enzyme levels and total and direct bilirubin levels (p<0.05). Intestinal mucosal myeloperoxidase and malondialdehyde levels were found to be high in intestinal ischemia-reperfusion groups (p<0.05). Intestinal mucosal damage was more severe in rats with intestinal ischemia-reperfusion after bile duct ligation (p<0.05). Degree of bacterial translocation was also found to be significantly high in these rats (p<0.05). CONCLUSIONS: Intestinal mucosa is disturbed more severely in obstructive jaundice with the development of ischemia and reperfusion. Development of intestinal ischemia-reperfusion in obstructive jaundice increases bacterial translocation.     

Intestinal barrier dysfunction and increased COX-2 gene expression in the gut of elderly rats with acute pancreatitis

Background/ObjectivesThe clinical course of acute pancreatitis can vary from mild to severe. In its most severe manifestation, acute pancreatitis is associated with an exacerbated systemic inflammatory response and high mortality rates. The severe form of acute pancreatitis is more frequent in elderly patients than in young patients, but the mechanisms underlying this difference are still under investigation.MethodsRats were divided into two groups as follows: Group 1, young rats; and Group 2, old rats. Acute pancreatitis group was induced by a retrograde injection of a sodium taurocholate solution into the biliopancreatic duct. Using this model of acute pancreatic injury, we designed a study to investigate possible differences in microbial translocation and characteristics of the intestinal barrier between elderly and young rats.ResultsThere was a significantly higher number of bacterial colonies in the pancreas of elderly rats compared with young rats following pancreas injury, which was associated with a more severe local intestinal inflammatory response that included elevated gene expression of COX-2 and a decreased gene expression of tight junction proteins.ConclusionsWe conclude that intestinal damage during acute pancreatitis is exacerbated in elderly rats compared with young rats and that COX-2 inhibition could be a potential therapeutic target to offer tailored treatment for acute pancreatitis in the elderly.     

Intestinal permeability in rats with CCI4-induced portal hypertension

AIM:To investigate the intestinal barrier changes in ratswith CCl_4-induced portal hypertension.METHODS:The permeability of intestinal barrier detectedby Lanthanum as a tracer was evaluated in rats,Bacterialtranslocation and plasma endotoxin were also determined.RESULTS:The incidence of bacterial translocation was85% in rats with CCl_4-induced portal hypertension,whichwas significantly higher than that in control rats(20%,P<0.01).Plasma endotoxin level was significantly higherin experimental group than in control group.Permeabilityof the epithelial mucosa and pathological alteration wereincreased in the ileum and the microvilli became shorterand thinner in rats with portal hypertension.CONCLUSION:Bacterial translocation occurs in ratswith CCl_4-induced portal hypertension and increasedpermeability between epithelial cells contributes to thetranslocation.     

西沙比利对肝硬化大鼠小肠细菌及内毒素转位的影响

目的：研究西沙比利对肝硬化大鼠小肠细菌过度生长(IBO)，细菌及内毒素转位，小肠转运时间及小肠通透性的作用。方法：正常对照组大鼠25只，肝硬化对照组大鼠25只，肝硬化治疗组20只(用等渗盐水)，另20只肝硬化大鼠用西沙比利治疗，动物均测定各种参数如细菌和内毒素转位，小肠细菌过度生长，小肠转运时间及通透性。结果：48％肝硬化大鼠发生细菌转位，与无IBO肝硬化大鼠比较，IBO肝硬化大鼠的内毒素和细菌转位发生率高，肠转远时间延长，小肠通透性增高。BT的细菌与IBO主菌群一致。与对照组比较，西沙比利处理的肝硬化大鼠肠细菌和内毒素转位及IBO发生率降低，这与肠转运时间增快及通透性降低密切相关。结论：肝硬化大鼠内毒素和细菌转位可能是由于IBO和肠通透性增加的结果，而IBO的发生可能是由于肠转运时间延长所致。西沙比利可加速小肠转运时间，改善小肠通透性，这有助于防治小肠细菌和内毒素转位。     

Effect of artesunate supplementation on bacterial translocation and dysbiosis of gut microbiota in rats with liver cirrhosis

AIM: To evaluate the effect of artesunate(AS) supplementation on bacterial translocation(BT) and gut microbiota in a rat model of liver cirrhosis. METHODS: Fifty-four male Sprague-Dawley rats were randomly divided into a normal control group(N), a liver cirrhosis group(M) and a liver cirrhosis group intervened with AS(MA). Each group was sampled at 4, 6 and 8 wk. Liver cirrhosis was induced by injection of carbon tetrachloride(CCl4), intragastric administration of 10% ethanol, and feeding a high fat diet. Rats in the MA group were intragastrically administered with AS(25 mg/kg body weight, once daily). Injuries of the liver and intestinal mucosa were assessed by hematoxylineosin or Masson's trichrome staining. Liver index was calculated as a ratio of the organ weight(g) to body weight(g). The gut microbiota was examined by automated ribosomal intergenic-spacer analysis of fecal DNA. BT was assessed by standard microbiological techniques in the blood, mesenteric lymph nodes(MLNs), liver, spleen, and kidney. RESULTS: Compared to group N, the body weight was reduced significantly in groups M and MA due to the development of liver cirrhosis over the period of 8 wk. The body weight was higher in group MA than in group M. The liver indices were significantly elevated at 4, 6 and 8 wk in groups M and MA compared to group N. AS supplementation partially decreased the liver indices in group MA. Marked histopathologic changes in the liver and small intestinal mucosa in group M were observed, which were alleviated in group MA. Levels of pro-inflammatory interleukin-6 and tumor necrosis factor-α were significantly elevated at 8 wk in ileal homogenates in group M compared to group N, which were decreased after AS supplementation in group MA. The dysbiosis of gut microbiota indicated by the mean diversity(Shannon index) and mean similarity(Sorenson index) was severe as the liver cirrhosis developed, and AS supplementation had an apparent intervention effect on the dysbiosis of gut microbiota at 4 wk. The occurrence of BT was increased in the liver of group M compared to that of group N. AS supplementation reduced BT in group MA at 8 wk. BT also occurred in the MLNs, spleen, and kidney, which was reduced by AS supplementation. BT was not detected in the blood in any group.CONCLUSION: Dysbiosis of gut microbiota, injury of intestinal mucosal barrier and BT occurred as liver cirrhosis progressed, which might enhance inflammation and aggravate liver injury. AS may have other nonantimalarial effects that modulate gut microbiota,inhibit BT and alleviate inflammation, resulting in a reduction in CCl4, alcohol and high fat-caused damages to the liver and intestine.     

热毒清对内毒素所致DIC大鼠肝损伤的防护作用

目的:观察热毒清抗内毒素DIC大鼠肝损伤的作用。方法:用内毒素诱发大鼠DIC模型观察热毒清对肝组织病理学和丙氨酸氨基转移酶(ALT)的影响。结果:和模型组相比,热毒清组的ALT水平明显降低,差别有显著意义(P<0.01)。病理学改变也明显减轻。结论:热毒清对内毒素DIC大鼠肝损伤有一定的改善作用。     

Ingestion of resistant starch protects endotoxin influx from the intestinal tract and reduces D-galactosamine-induced liver injury in rats

BACKGROUND AND AIMS: The aim of the present study was to examine the protective effect of a dietary high-amylose cornstarch (HAS) against D-galactosamine (D-GalN)-induced liver injury, focusing specifically on intestinal endotoxin translocation. METHODS: Male Wistar rats fed a HAS-free basal diet or a 30% HAS-supplemented diet were injected intraperitoneally with D-GalN. Serum transaminase activities, serum concentrations of tumor necrosis factor (TNF)-alpha, and portal venous endotoxin concentrations were determined at various time points. Ileal mucosal proliferation, small intestinal immunoglobulin (Ig)A and mucin, and the size of the cecal short-chain fatty acids (SCFA) pool were also determined. RESULTS: High-amylose cornstarch ingestion significantly reduced the increase in serum transaminase activities at 22 h after the injection of D-GalN. Rats fed the HAS diet showed a greater cecal SCFA production as measured by pool size than those fed the basal diet. Luminal IgA and mucin content were significantly greater in rats fed the HAS diet. Protein, DNA and RNA contents in the ileal mucosa were also higher in rats fed the 30% HAS diet. In a further experiment, portal venous endotoxin concentrations in rats fed the basal diet reached 72 ng/L at 4 h after D-GalN administration, but endotoxin was not detected in rats fed the HAS diet. At this time, portal endotoxin concentrations were significantly and positively correlated with the serum concentrations of TNF-alpha and serum alanine aminotransferase activities. CONCLUSION: These data support the view that HAS ingestion may reduce D-GalN-induced liver injury as a result of an inhibitory effect on endotoxin influx from the intestinal tract, at least in part as a result of alterations in the mucosal barrier functions.     

Pectin-Supplemented Enteral Diet Reduces the Severity of Methotrexate-Induced Enterocolitis in Rats

Background: Administration of methotrexate (MTX) to rats fed an elemental diet results in a high mortality from severe enterocolitis. Previous studies have shown that pectin is an important precursor of substrates for intestinal structure and function and may facilitate intestinal recovery after enterocolitis. The aim of this study is to evaluate the effect of pectin on MTX-induced enterocolitis in rats. Methods: Rats received intragastric infusion of either 1% pectin-supplemented or pectin-free elemental diet from the beginning of the study via a gastrostomy. On the 4th day animals received either MTX, 20 mg/kg intraperitoneally, or saline injection and were killed on the 7th day for sampling. Results: Pectin supplementation significantly decreased body weight loss, organ water content, and intestinal myeloperoxidase levels and increased mucosal protein, DNA, and RNA content in enterocolitis rats. The intestinal permeability was increased by administration of MTX, and pectin supplementation significantly reversed the increased permeability in the distal small bowel and colon. Pectin supplementation also lowered the magnitude of bacterial translocation, decreased plasma endotoxin levels, and restored bowel microecology. Conclusions: Pectin significantly decreased MTX-induced intestinal injury and improved bowel integrity.     

Insulin-like growth factor I improves intestinal barrier function in cirrhotic rats

BACKGROUND AND AIMS: In liver cirrhosis, disruption of the intestinal barrier facilitates bacterial translocation and spontaneous bacterial peritonitis. Insulin-like growth factor I (IGF-I) is an anabolic hormone synthesised by hepatocytes that displays hepatoprotective activities and trophic effects on the intestine. The aim of this study was to investigate the effect of IGF-I on intestinal barrier function in cirrhotic rats. METHODS: In rats with carbon tetrachloride induced cirrhosis, we investigated the effect of IGF-I therapy on: (a) portal pressure; (b) intestinal histology and permeability to endotoxin and bacteria; (c) intestinal expression of cyclooxygenase 2 (COX-2) and tumour necrosis factor alpha (TNF-alpha), two factors that influence in a positive and negative manner, respectively, the integrity of the intestinal barrier; (d) intestinal permeability to 3H-mannitol in rats with bile duct ligation (BDL); and (e) transepithelial electrical resistance (TER) of polarised monolayers of rat small intestine epithelial cells. RESULTS: IGF-I therapy reduced liver collagen expression and portal pressure in cirrhotic rats, induced improvement in intestinal histology, and caused a reduction in bacterial translocation and endotoxaemia. These changes were associated with diminished TNF-alpha expression and elevated COX-2 levels in the intestine. IGF-I reduced intestinal permeability in BDL rats and enhanced barrier function of the monolayers of epithelial intestinal cells where lipopolysaccharide (LPS) caused a decrease in TER that was reversed by IGF-I. This effect of IGF-I was associated with upregulation of COX-2 in LPS treated enterocytes. CONCLUSIONS: IGF-I enhances intestinal barrier function and reduces endotoxaemia and bacterial translocation in cirrhotic rats. IGF-I therapy might be useful in the prevention of spontaneous bacterial peritonitis in liver cirrhosis.     

The mRNA expression patterns of tumor necrosis factor-α and TNFR-I in some vital organs after thermal injury

AIM: To investigate changes of tumor necrosis factor-α (TNF-α and TNFR-I expression in vital organs and their significance in the pathogenesis of multiple organ damage associated with endogenous endotoxin following major burns.METHODS: Wistar rats subjected to a 35% full-thickness scald injury were sacrificed at 12h, 24h, 48h, and 72 hpostburn, respectively. Meanwhile, eight rats were taken as normal controls. Tissue samples from liver, spleen, kidney,lung and intestine were collected to assay tissue endotoxin levels and measure TNF-α and TNFR-I expression. In addition, blood samples were obtained for the determination of organ function parameters.RESULTS: Endotoxin levels in liver, spleen and lung increased markedly after thermal injury, with the highest level in liver. The gene expression of TNF-α in liver, lung and kidney was up-regulated after thermal injury, while the TNFR-I mRNA expression in liver, lung, kidney and intestine was shown decreased throughout the observation period. Thus, the mRNA expression ratio of TNF-α to TNFR-I was significantly increased postburn, particularly in pulmonary tissue (67-fold). In addition, the significant correlations between the expression of TNFR-I or the expression ratio of TNF-α/TNFR mRNA in liver tissue and serum aspartate aminotransferase levels were noted (P&lt;0.05-0.01). Similar results were also obtained between pulmonary TNF-α mRNA expression and myeloperoxidase activities (P&lt;0.01), whereas there was a highly negative correlation between levels of renal TNFR-I mRNA expression and serum creatinine.CONCLUSION: Burn injury could result in the translocation of gut-derived endotoxin that was mainly distributed in the liver, spleen and lung. The translocated endotoxin then made the expression of TNF-α and TNFR-I mRNA up-regulated and down-regulated respectively in various organs, which might be involved in the pathogenesis of multiple organ damage following burns.     

Tempol 对肝硬化大鼠肝门阻断后肠道菌群移位及内毒素血症的作用

目的：探讨4-羟基-2,2,6,6-四甲基哌啶（Tempol）对肝硬化大鼠肝门阻断后肠道细菌移位和内毒素血症的作用。方法选择SD大鼠30只,采用四氯化碳诱导行肝硬化建模,将建模大鼠随机均分为假手术组（不阻断肝门）、对照组（阻断肝门）、实验组（阻断肝门前后静注Tempol ）。3组均取门静脉、腔静脉血检测血清内毒素,取肠系膜淋巴结、肝组织、肺组织行细菌培养,以及小肠黏膜形态与细胞凋亡检测。结果与假手术组及对照组比较,实验组可明显减少肝门阻断后的肠道细菌移位及血清内毒素水平（ P均＜0．05）。结论 Tempo1可有效地预防肝硬化大鼠肝门阻断后的肠道细菌移位和内毒素血症。     

Effects of glutamine supplementation on gut barrier, glutathione content and acute phase response in malnourished rats during inflammatory shock

AIM: To evaluate the effect of glutamine on intestinal mucosa integrity,glutathione stores and acute phase response in protein-depleted rats during an inflammatory shock. METHODS: Plasma acute phase proteins (APP),jejunal APP mRNA levels,liver and jejunal glutathione concentrations were measured before and one,three and seven days after turpentine injection in 4 groups of control,protein-restricted,protein-restricted rats supplemented with glutamine or protein powder. Bacterial translocation in mesenteric lymph nodes and intestinal morphology were also assessed. RESULTS: Protein deprivation and turpentine injection significantly reduced jejunal villus height,and crypt depths. Mucosal glutathione concentration significantly decreased in protein-restricted rats. Before turpentine oil,glutamine supplementation restored villus heights and glutathione concentration (3.24 ± 1.05 vs 1.72 ± 0.46 μmol/g tissue,P < 0.05) in the jejunum,whereas in the liver glutathione remained low. Glutamine markedly increased jejunal α1-acid glycoprotein mRNA level after turpentine oil but did not affect its plasma concentration. Bacterial translocation in protein-restricted rats was not prevented by glutamine or protein powder supplementation. CONCLUSION: Glutamine restored gut glutathione stores and villus heights in malnourished rats but had no preventive effect on bacterial translocation in our model.     

Phosphatidylcholine Reverses Ethanol-Induced Increase in Transepithelial Endotoxin Permeability and Abolishes Transepithelial Leukocyte Activation

Background:  Chronic alcohol abuse increases both intestinal bacterial overgrowth and intestinal permeability to macromolecules. Intestinal permeability of endotoxin, a component of the outer cell membrane of Gram-negative bacteria, plays a crucial role in the development of alcohol-induced liver disease (ALD). As impaired bile flow leads to endotoxemia and the bile component phosphatidylcholine (PC) is therapeutically active in ALD, we tested the hypothesis that conjugated primary bile salts (CPBS) and PC inhibit ethanol-enhanced transepithelial permeability of endotoxin and the subsequent transepithelial activation of human leukocytes.
Methods:  For this purpose, we used a model in which intestinal epithelial cells (Caco-2) were basolaterally cocultivated with mononuclear leukocytes. Cells were challenged apically with endotoxin from Escherichia coli K12 and were incubated with or without the addition of CPBS (1.5 mM), PC (0.38 mM), pooled human bile (2%) in combination with ethanol (0 to 66 mM).
Results:  Ethanol decreased integrity of intestinal epithelial cell monolayer and enhanced transepithelial permeability of endotoxin. Both the transepithelial permeability of endotoxin and the transepithelial stimulation of leukocytes were nearly completely abolished after the apical supplementation of PC with CPBS, but not by CPBS alone. Ethanol up to 66 mM was not able to reverse this effect.
Conclusions:  A considerable part of the therapeutic and preventive effect of PC supplementation in ALD might result from a reduction of ethanol-enhanced permeability of endotoxin through the intestinal barrier.