Experimental Model Of Portal Hypertension Research Articles

Clinical-experimental justification of the method of prevention and treatment of appendicular pylephlebitis

Taking into account the pathogenesis peculiarities of appendicular pylephlebitis, the risk group includes patients with a retrocecal location of the appendix, gangrenous and perforating appendicitis, the course of which was complicated by peritonitis or abscess. The purpose of our clinical-experimental study was to justify the method of pathogenetic treatment of acute appendicular pylephlebitis based on an experimental model of portal hypertension. Acute experiments were performed on male Wistar rats and outbred dogs. Clinical studies were prospectively-retrospective. In addition to traditional methods of treatment, we used the developed technique of draining the retroperitoneal space and introducing antibacterial compositions in a complex with a 10% dimethylsulfoxide (DMSO) solution was used. On the basis of experimental data, it was established that a 10% solution of DMSO complexed with a dye, when injected transperitoneally in the ileocecal angle area, preferentially penetrates the lymphatic and portal systems, even in conditions of portal hypertension. This is explained by the peculiarities of the anatomical structure. The use of the method of intraperitoneal administration of antibiotics in combination with DMSO is pathogenetically justified in patients with appendicular pylephlebitis, as it achieves local sanitation of the immediate source and primary ways of spreading the infection. Implementation of the developed method of prevention and treatment of acute pylephlebitis of appendicular genesis as part of improved treatment tactics allows to improve treatment results by likely reducing the frequency of postoperative complications from 18.7% to 2.7% (χ2 = 20.02, 95% CI 9.25-23.8) and the duration of hospitalization from 22.8 days to 8.5 days.

Experimental model of portal hypertension and esophagogastric varices in minipigs: pressure and endoscopic pilot study.

ABSTRACTIntroduction:Portal hypertension still represents an important health problem worldwide. In the search for knowledge regarding this syndrome, experimental studies with animal models have proven to be useful to point the direction to be taken in future randomized clinical trials.Purpose:To validate the experimental model of portal hypertension and esophagogastric varices in a medium-sized animal.Methods:This study included five minipigs br1. Midline laparotomy with dissection of the portal vein and production of a calibrated stenosis of this vein was performed. Measurement of pressure in the portal venous and digestive endoscopic were performed before and five weeks after the production of a stenosis.Results:All animals were 8 months old, average weight of 17 ± 2.5 kg. The mean pressure of the portal vein immediately before the partial ligation of the portal vein was 8.9 + 1.6 mm Hg, with 26.6 + 5.4 mm Hg in the second measurement five weeks later (p < 0.05). No gastroesophageal varices or hypertensive portal gastropathy were seen at endoscopy procedures in our sample at any time in the study.Conclusion:Portal vein ligation in minipigs has been validated in the production of portal hypertension, but not in the formation of esophageal varices.

Inflammatory bowel and oxidative stress changes in an experimental model of portal hypertension: action of N-acetylcysteine

IntroductionPortal hypertension (PH) is characterized by vasodilatation in the portal system and the bowel is one of the severely affected organs. N-acetylcysteine (NAC) is a molecule with important properties and widely used in clinical practice. ObjectiveTo evaluate NAC action in the bowel of animals submitted to the animal model of partial portal vein ligation (PPVL). Methods18 male Wistar rats were divided into three experimental groups (n=6): sham-operated (SO), PPVL, and PPVL+NAC. On the 8th day after surgery, N-acetylcysteine (10mg/kg, ip) was administered daily for 7 days. On the 15th day the animals’ bowel was collected for oxidative stress analysis, immunohistochemistry and Western blot. We evaluated the expression of NF-KB and TNF-α by immunohistochemistry and of iNOS by Western blot. Lipid peroxidation was assessed by TBARS technique, and the activities of antioxidant enzymes superoxide dismutase (SOD) and glutation peroxidase (GPx) were checked. ResultsWe observed an increased expression of NF-KB and TNF-α in PPVL group, and an increased iNOS expression assessed by Western blot. NAC reduced the expression of all proteins evaluated. We also observed an increase in oxidative stress in the bowel of mice PPVL group compared to controls (SO), and NAC was effective in reducing these values in PPVL+NAC group. Also, a reduction in the activity of SOD and GPx enzymes was observed in the diseased group, and NAC was able to restore the activity of the enzymes assessed. ConclusionWe suggest the anti-inflammatory and antioxidant action of NAC in the bowel of animals submitted to PPVL model.

Antioxidant properties of glutamine and its role in VEGF-Akt pathways in portal hypertension gastropathy.

To investigate the effects of glutamine on oxidative/nitrosative stress and the vascular endothelial growth factor (VEGF)-Akt-endothelial nitric oxide synthase (eNOS) signaling pathway in an experimental model of portal hypertension induced by partial portal vein ligation (PPVL). Portal hypertension was induced by PPVL. The PPVL model consists of a partial obstruction of the portal vein, performed using a 20 G blunt needle as a guide, which is gently removed after the procedure. PPVL model was performed for 14 d beginning treatment with glutamine on the seventh day. On the fifteenth day, the mesenteric vein pressure was checked and the stomach was removed to test immunoreactivity and oxidative stress markers. We evaluated the expression and the immunoreactivity of proteins involved in the VEGF-Akt-eNOS pathway by Western blotting and immunohistochemical analysis. Oxidative stress was measured by quantification of the cytosolic concentration of thiobarbituric acid reactive substances (TBARS) as well as the levels of total glutathione (GSH), superoxide dismutase (SOD) activity, nitric oxide (NO) production and nitrotyrosine immunoreactivity. All data are presented as the mean ± SE. The production of TBARS and NO was significantly increased in PPVL animals. A reduction of SOD activity was detected in PPVL + G group. In the immunohistochemical analyses of nitrotyrosine, Akt and eNOS, the PPVL group exhibited significant increases, whereas decreases were observed in the PPVL + G group, but no difference in VEGF was detected between these groups. Western blotting analysis detected increased expression of phosphatidylinositol-3-kinase (PI3K), P-Akt and eNOS in the PPVL group compared with the PPVL + G group, which was not observed for the expression of VEGF when comparing these groups. Glutamine administration markedly alleviated oxidative/nitrosative stress, normalized SOD activity, increased levels of total GSH and blocked NO overproduction as well as the formation of peroxynitrite. Glutamine treatment demonstrated to reduce oxidative damage but does not reduce angiogenesis induced by PH in gastric tissue, demonstrating a beneficial role for the PI3K-Akt-eNOS pathway.

Beneficial Effect of Ultra-Low-Dose Aspirin in Platelet Activity Alterations and Haemorrhage Observed in Experimental Portal Hypertension

Ultra-low-dose aspirin has shown a prothrombotic effect in the laser-induced thrombosis model. Several studies of our laboratory have shown a positive effect in rats with two different experimental models of portal hypertension: portal vein ligation, a model with an almost normal liver, and 30 days of bile duct ligation, a model with cirrhosis and presence of ascitis. In both models of portal hypertensive rats, bleeding time was prolonged and thrombi formation, in a laser-induced model of thrombi production, decreased. The hypotheses of the presented studies were that ultra-low-dose aspirin could decrease the bleeding complications in these models and that the mechanism for these effects could act thorough the COX pathway. In different studies, ultra-low dose of aspirin normalized the induced hemorrhage time, thrombi production, and platelet-endothelial cell interaction. The possible beneficial role of these doses of aspirin and mechanism of COX 2 inhibition are discussed.

Gut-Brain Chemokine Changes in Portal Hypertensive Rats

Hepatic encephalopathy is a syndrome whose physiopathology is poorly understood; therefore, current diagnostic tests are imperfect and modern therapy is nonspecific. Particularly, it has been suggested that inflammation plays an important role in the pathogenesis of portal hypertensive encephalopathy in the rat. We have studied an experimental model of portal hypertension based on a triple partial portal vein ligation in the rat to verify this hypothesis. One month after portal hypertension we assayed in the splanchnic area (liver, small bowel and mesenteric lymph nodes) and in the central nervous system (hippocampus and cerebellum) fractalkine (CX3CL1) and stromal cell-derived factor alpha (SDF1-α) as well as their respective receptors (CX3CR1 and CXCR4) because of their key role in inflammatory processes. The significant increase of fractalkine in mesenteric lymph nodes (P<0.05) and its receptor (CX3CR1) in the small bowel (P<0.05) and hippocampus (P<0.01), associated with the increased expression of SDF1-α in the hippocampus (P<0.01) and the cerebellum (P<0.01) suggest that prehepatic portal hypertension in the rat induces important alterations in the expression of chemokines in the gut-brain axis. The present study revealed that portal hypertension is associated with splanchnic-brain inflammatory alterations mediated by chemokines.

Antiangiogenic therapies in portal hypertension: A breakthrough in hepatology

Portal hypertension is the most important complication that develops in patients with cirrhosis. Several studies have shown that angiogenesis (i.e. splanchnic neovascularization) driven by VEGF and other proangiogenic molecules, like PDGF, may be a major mechanism involved in portal hypertension, hyperdynamic splanchnic circulation and portosystemic collateralization. According with this, antiangiogenic therapies, like sorafenib or sunitinib, have been recently shown to reduce portosystemic collateral circulation, improve splanchnic hyperdynamics and decrease portal pressure in experimental model of portal hypertension. This effect was associated to a decrease in VEGF, PDGF expression and splanchnic neovascularization. In addition, these therapies were associated with a decrease in both splanchnic and intrahepatic inflammatory infiltrates, in hepatic stellate cell activation and in intrahepatic fibrosis. These data suggest that antiangiogenic therapies may therefore, by limiting liver fibrosis and inflammation in cirrhosis, prevent the occurrence of severe complications, such as portal hypertension and potentially liver cancer.

Partial hepatectomy, partial portal vein stenosis and mesenteric lymphadenectomy increase splanchnic mast cell infiltration in the rat

It is currently believed that portal hypertension induces an inflammatory response in which mast cells may be involved. The aim of this study was to verify the involvement of the intestinal submucosal and mesenteric lymph node mast cells in the splanchnic inflammatory response related to portal hypertension. Mast cell infiltration in the intestine (duodenum, jejunum, ileum, caecum and distal colon) and in the mesenteric lymph node complex (MLC) was measured using a stereological method in sham-operated rats (SO; n = 12), in two experimental models of portal hypertension, chronic (triple partial portal vein ligation, TPVL; n = 12) and transient (microsurgical partial hepatectomy; n = 12) and in rats in which the MLC was resected (n = 12). The small and large bowel submucosal infiltration increases in MLC-resected rats (p = 0.0001), in TPVL rats (p = 0.0001) and in rats with partial hepatectomy (p = 0.0001). An extensive mast cell infiltration in the MLC (p = 0.0001) was found in TPVL rats and in rats with partial hepatectomy (347.40+/-45.25 and 351.92+/-99.28/mm(3), respectively) in relation to sham-operated rats (135.27+/-30.28/mm(3)). We conclude that mast cells could be involved in the splanchnic alterations developed in the surgical experimental models of portal hypertension studied.

Beneficial effects of sorafenib on splanchnic, intrahepatic, and portocollateral circulations in portal hypertensive and cirrhotic rats

Portal hypertension, the most important complication in patients with cirrhosis of the liver, is a serious and life-threatening disease for which there are few therapeutic options. Because angiogenesis is a pathological hallmark of portal hypertension, the goal of this study was to determine the effects of sorafenib-a potent inhibitor of proangiogenic vascular endothelial growth factor receptor 2 (VEGFR-2), platelet-derived growth factor receptor beta (PDGFR-beta), and Raf kinases-on splanchnic, intrahepatic, systemic, and portosystemic collateral circulations in two different experimental models of portal hypertension: rats with prehepatic portal hypertension induced by partial portal vein ligation and rats with intrahepatic portal hypertension and secondary biliary cirrhosis induced by bile duct ligation. Such a comprehensive approach is necessary for any translational research directed toward defining the efficacy and potential clinical application of new therapeutic agents. Sorafenib administered orally once a day for 2 weeks in experimental models of portal hypertension and cirrhosis effectively inhibited VEGF, PDGF, and Raf signaling pathways, and produced several protective effects by inducing an approximately 80% decrease in splanchnic neovascularization and a marked attenuation of hyperdynamic splanchnic and systemic circulations, as well as a significant 18% decrease in the extent of portosystemic collaterals. In cirrhotic rats, sorafenib treatment also resulted in a 25% reduction in portal pressure, as well as a remarkable improvement in liver damage and intrahepatic fibrosis, inflammation, and angiogenesis. Notably, beneficial effects of sorafenib against tissue damage and inflammation were also observed in splanchnic organs. Taking into account the limitations of translating animal study results into humans, we believe that our findings will stimulate consideration of sorafenib as an effective therapeutic agent in patients suffering from advanced portal hypertension.

Profilaxis preprimaria de la hemorragia por varices

Portosystemic collateral formation, particularly at the gastroesophageal junction, is a most serious consequence of portal hypertension. Increased portal pressure is the most significant force underlying gastroesophageal variceal formation, to which end portal pressure (estimated from the hepatic venous pressure gradient) must reach at least 10 mmHg. Subsequently, splanchnic hyperemia also contributes to variceal development. Portoystemic collaterals result from repermeabilization of pre-extant vessels, vascular remodeling, and angiogenesis. The goal of pre-primary prophylaxis is preventing or delaying the formation of gastroesophageal varices. In experimental models of portal hypertension, early administration of splanchnic vasoconstrictors such as beta-blockers, nitric oxide synthesis inhibitors, or antiangiogenic substances inhibits portosystemic collateral formation. However, clinical trials of beta-blockers in patients with cirrhosis and no varices to delay variceal formation have failed to yield expected results.

Prehepatic portal hypertension produces increased mast cell density in the small bowel and in mesenteric lymph nodes in the rat

Because most of the characteristics of the portal hypertensive enteropathy can be explained on the basis of increased levels of mast cell mediators, the purpose of the present paper was to study mast cell splanchnic infiltration. Duodenum, jejunum, ileum and mesenteric lymph node complex infiltration by mast cells was assayed by a stereological technique in control rats (group I; n = 5) and in an experimental model of portal hypertension (the portal vein-stenosed rat, group II; n = 5) at 6 weeks after operation. Intestinal and mesenteric lymph node complex infiltration by mast cells increased in the animals with partial portal vein ligation. The mast cell density progressively increased distally along the small bowel. The mast cell increase in the mesenteric lymph node complex in portal vein-stenosed rats was greater than in the duodenum (P = 0.001), jejunum (P = 0.006) and ileum. The rise of mast cells density in the small bowel and mesenteric lymph node complex in rats with partial portal vein ligation suggests that these cells are involved in the etiopathogenesis of experimental portal prehepatic hypertensive enteropathy.

Impaired mesenteric leukocyte recruitment in experimental portal hypertension in the rat.

Increased incidence of septic complications in human and experimental portal hypertension has been documented. Because development of an inflammatory response is essential in defense against infectious agents, the aim of this study was to assess leukocyte-endothelial cell interactions in an experimental model of portal hypertension. Intravital microscopy studies showed that under baseline conditions, leukocyte rolling, adhesion, and emigration in mesenteric venules were similar in control, sham operated (SO), and partial portal vein ligated (PPVL) rats. Compared with either control or SO rats, PPVL animals exhibited a markedly reduced recruitment of rolling, adherent, and emigrated leukocytes in response to leukotriene B(4) (LTB(4)) stimulation. Similarly, platelet-activating factor (PAF) superfusion, which induced a large increment in leukocyte rolling and adherence in control and SO rats, was without any effect in PPVL animals. Endothelial P-selectin expression in control rats, as measured by the double radio-labeled monoclonal antibody (mAb) technique, was not modified by LTB(4), but significantly increased in response to PAF. PPVL rats had a significantly lower expression of P-selectin after stimulation with PAF. Neutrophils isolated from PPVL rats exhibited increased L-selectin shedding and CD11b up-regulation in response to PAF and LTB(4), compared with neutrophils isolated from SO rats. These observations indicate that portal hypertension is associated with a defective inflammatory response, which is manifested as a decreased recruitment of rolling leukocytes, and subsequently reduced adhesion/emigration. This defect appears to result from a reduced endothelial P-selectin up-regulation and increased L-selectin shedding.

Vascular nitric oxide production during the development of two experimental models of portal hypertension

Background/Aims: The aim of this study was to determine the relative roles of constitutive NOS (NOS3) and inducible NOS (NOS2) isoforms during the development of two models ofportal hypertension in rats. Methods: Vascular reactivity of aortic rings for norepinephrine was performed in control, sham-operated, portal-vein-stenosed and secondary biliary cirrhotic rats 1, 4, 7, 14 and 28 days after surgery. NOS activity and nitrate plasma levels were also measured. Results: An impaired response to norepinephrine observed in sham-operated, portal-vein-stenosed and cirrhotic rats at days 1 and 4 compared with controls was reversed after L-NNA and aminoguanidine. Portal hypertensive rats remained hyporeactive at days 7, 14 and 28 compared with sham-oprated rats. At days 7 and 14 in portal-vein-stenosed rats, vascular hyporeactivity was reversed by L-NNA and W7. At days 14 and 28 in cirrhotic rats, vascular hyporeactivity was reversed by L-NNA and W7. Nitrate levels increased at day 1 in the 3 groups, and increased at days 14 and 28 in portal hypertensive rats. Total NOS-activity increased in cirrhotic rats at day 28, in portal-vein-stenosed rats at day 14, and in sham-operated rats at day 1 compared to controls. NOS2 activity increased only in sham-operated rats at day 1. Conclusions: This study shows that for two models of portal hypertension, increased NO production in the first days is related to NOS2 induction secondary to surgery. On the other hand, when portal hypertension has fully developed, the NOS3 isoform appears to play the major role.

Lipid Changes in Hepatic Microsomes and its Relationship to P-Nitrophenol Glucuronidation in an Experimental Model of Portal Hypertension

The liver is responsible for the most important metabolic pathway of non polar compounds. The aim of the present work was to study the p-nitrophenol glucuronidation and its relationship with lipidic composition of microsomal membrane in a model of hepatic portal hypertension and hepatocellular damage induced by monocrotaline. A global increment in liver microsomal phospholipids as well as changes in the phospholipid pattern (phosphatidylethanolamine and sphingomyelin increased up to 156 ± 13 and 195 ± 14% respectively) were detected in monocrotaline intoxicated rats when it were compared to control rats. The microsomal cholesterol content showed a decrease in monocrotaline intoxicated rats. (4.1 ± 0.7 against 6.6 ± 1.5 µg/mg of microsomal protein, in control rats). When p-nitrophenol activity was measured, Km from monocrotaline intoxicated rats was 0.137 mM, and Vmax was 2.9 nmol of p-nitrophenol/ mg microsomal protein since in control group Km was 0,322 mM, and Vmax was 4,5 nmol of p-nitrophenol/ mg microsomal protein. It is concluded that monocrotaline intoxicated rats showed a different behavior in the kinetics of p-nitrophenol UDP-glucuronyltransferase, as well as a different microsomal lipidic profile, when compared to control group.

Intrahepatic portal occlusion by microspheres: a new model of portal hypertension in the rat.

Available experimental models of portal hypertension are based either on cirrhosis or externally applied portal vein constricting devices. A new method is described of raising portal pressure, which uses intraportally injected microspheres to block intrahepatic portal radicles, which has the advantages of retaining normal liver architecture and providing a more clinically relevant intrahepatic obstruction to portal flow. Measured aliquots of microspheres (15, 25, 50, 90 microns) or equivalent volumes of saline were injected into a peripheral portal tributary (caecal vein) of 22 normal rats. The resultant changes in arterial, portal, and splenic pulp pressures were monitored. Sequential microsphere injections produced graduated rises in portal pressure up to a peak of 18.5-22.5 mm Hg (8.7-12.4 mm Hg increase from basal), which declined gradually to a steady state pressure of 13.3-15.1 mm Hg (4.0-5.0 mm Hg increase). There was no significant difference between pressure increases produced by microspheres of differing sizes. It is concluded that portal hypertension can be produced acutely by blocking portal radicles with microspheres. The maximum pressure achieved, however, is substantially less than that obtained by total portal vein occlusion (mean: 57.6 mm Hg). This suggests the existence of functional intrahepatic portal systemic shunts not previously described in the normal liver.

Effects of pentobarbital sodium anesthesia on splanchnic hemodynamics of normal and portal-hypertensive rats.

To determine the effect of pentobarbital sodium anesthesia on the rat with portal hypertension due to portal vein stenosis, four groups of rats were studied. Cardiac output and regional blood flow were measured by radioactive microspheres in anesthetized and conscious sham-operated and portal-hypertensive rats. Anesthesia markedly decreased cardiac output in both sham-operated (109.7 +/- 4.6 vs. 77.8 +/- 1.4 ml/min, P less than 0.001) and portal-hypertensive rats (130.1 +/- 7.6 vs. 93.8 +/- 5.3 ml/min, P less than 0.01). In spite of this diminution in cardiac output, pentobarbital did not significantly change absolute blood flow values of splanchnic organs in either group. However, the fractions of cardiac output perfusing the splanchnic organs were significantly increased by pentobarbital in both groups because of the decrease in cardiac output: sham operated, anesthetized, 22.86 +/- 1.19% vs. conscious, 14.83 +/- 1.02%, P less than 0.001; and portal hypertensive, anesthetized, 26.67 +/- 0.71% vs. conscious, 19.07 +/- 1.44%, P less than 0.001. The hyperdynamic circulation of the portal vein-stenosed rat compared with the sham-operated rat continued to manifest itself with significantly increased portal pressure, cardiac output, and splanchnic blood flow, whether the animal was anesthetized or awake. We conclude that, despite marked hemodynamic changes induced by pentobarbital, the rat with portal vein stenosis remains a useful experimental model of portal hypertension.