Impaired oxygenation of gastric mucosa in portal hypertension. The basis for increased susceptibility to injury

Epidemiology of asymptomatic peptic ulcer disease diagnosed during screening endoscopy in patients with cirrhosis

OBJECTIVE

Asymptomatic peptic ulcer disease (PUD) is frequently overlooked in patients with cirrhosis, who are at increased risk for gastrointestinal complications that can lead to increased morbidity and mortality. We aimed to determine the prevalence and associated factors of asymptomatic PUD identified during screening endoscopy in patients with cirrhosis.

METHODS

We conducted a retrospective cross-sectional study among patients with cirrhosis at St. Paul's Hospital Millennium Medical College in Ethiopia. Data were collected using a structured questionnaire from patients' medical charts. A logistic regression model was used to identify predictors of peptic ulcer.

RESULTS

This study included 296 patients, revealing that 19.6% had PUD (95% confidence interval: 13.5-26.4). Significant associations were found between peptic ulcer and Helicobacter pylori infection, moderate and heavy alcohol consumption, and Child-Pugh class C cirrhosis.

CONCLUSION

We found that patients with liver cirrhosis are more likely to have asymptomatic peptic ulcers. Asymptomatic PUD was linked to H. pylori infection, greater alcohol consumption, and Child-Pugh class C liver disease, highlighting the need for targeted prevention and management strategies to reduce morbidity in patients with cirrhosis, such as eradication therapy for H. pylori and counseling on alcohol use.

Clinical significance of small-bowel villous edema in patients with liver cirrhosis: A capsule endoscopy study

BACKGROUND AND AIM

The relationship between the presence of villous edema (VE) in portal hypertensive enteropathy and clinical factors remains unclear. The aim of this study was to reveal the clinical factors related to VE in patients with liver cirrhosis (LC), and investigate the clinical significance of VE.

METHODS

Between February 2009 and September 2016, 363 consecutive patients with LC underwent capsule endoscopy for diagnosing portal hypertensive enteropathy at Hiroshima University Hospital. We evaluated the relationship between the presence of VE and patients' clinical characteristics, findings of esophagogastroduodenoscopy and computed tomography, and survival time.

RESULTS

Villous edema was observed in 131 patients (36%), and severe lesions were found in 71 (20%). The presence of VE was significantly greater in patients with Child-Pugh classification B or C, esophageal varices, portal hypertensive gastropathy (PHG), ascites, portal vein thrombosis (PVT), and splenomegaly. In multivariate analysis, Child-Pugh class B or C, esophageal varices, PVT, and splenomegaly were significant predictive factors for the presence of VE. Severe VE was significantly greater in patients with Child-Pugh class B or C, serum albumin level ≤ 3.2 mg/dL, PHG, and PVT. In multivariate analysis, PHG, Child-Pugh class B or C, PVT, were significant predictive factors for severe VE.

CONCLUSIONS

Clinical factors related to portal hypertension were significantly correlated with VE. In particular PVT was correlated with the appearance and exacerbation of VE. Periodic capsule endoscopy in LC patients may lead to early detection of portal hypertension and PVT.

Portal hypertensive gastropathy and gastric antral vascular ectasia

Portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE) are gastric mucosal lesions that mostly present as chronic anemia and rarely cause the acute gastrointestinal hemorrhage. Despite similar clinical manifestations, their pathophysiology and management are entirely different. PHG is seen exclusively in patients with portal hypertension, but GAVE can also be observed in patients with other conditions. Their diagnosis is endoscopic, and although generally each of them has a characteristic endoscopic appearance and distribution, there are cases in which the differential is difficult and must rely on histology. This review focuses on the management of both entities. The mainstay of management of PHG is based on portal-hypotensive pharmacological treatment while GAVE benefits from hormonal therapy, endoscopic Nd:YAG laser, and argon plasma coagulation. More invasive options should be reserved for refractory cases.

Peptic ulcer disease in liver cirrhosis and chronic hepatitis: impact of portal hypertension

OBJECTIVE

The pathophysiology of peptic ulcer disease (PUD) in liver cirrhosis (LC) and chronic hepatitis has not been established. The aim of this study was to assess the role of portal hypertension from PUD in patients with LC and chronic hepatitis.

MATERIALS AND METHODS

We analyzed the medical records of 455 hepatic vein pressure gradient (HVPG) and esophagogastroduodenoscopy patients who had LC or chronic hepatitis in a single tertiary hospital. The association of PUD with LC and chronic hepatitis was assessed by univariate and multivariate analysis.

RESULTS

A total of 72 PUD cases were detected. PUD was associated with LC more than with chronic hepatitis (odds ratio [OR]: 4.13, p = 0.03). In the univariate analysis, taking an ulcerogenic medication was associated with PUD in patients with LC (OR: 4.34, p = 0.04) and smoking was associated with PUD in patients with chronic hepatitis (OR: 3.61, p = 0.04). In the multivariate analysis, taking an ulcerogenic medication was associated with PUD in patients with LC (OR: 2.93, p = 0.04). However, HVPG was not related to PUD in patients with LC or chronic hepatitis.

CONCLUSION

According to the present study, patients with LC have a higher risk of PUD than those with chronic hepatitis. The risk factor was taking ulcerogenic medication. However, HVPG reflecting portal hypertension was not associated with PUD in LC or chronic hepatitis (Clinicaltrial number NCT01944878).

Small bowel abnormalities in patients with compensated liver cirrhosis

BACKGROUND

Although capsule endoscopy is available as a minimally invasive imaging technique that contributes significantly to the detection of small bowel lesions, there are only a very few published descriptions of small bowel abnormalities in patients with portal hypertension.

AIMS

The aim of this study was to characterize the occurrence of small bowel lesions by means of capsule endoscopy in patients with portal hypertension, particularly those with compensated liver cirrhosis and associated anemia.

METHODS

Sixty consecutive patients who met our criteria underwent capsule endoscopy. The frequency, type, and distribution of small bowel lesions were determined, and clinical factors associated with the lesions were examined.

RESULTS

Small bowel abnormalities were found in 40 patients (67 %), including erythema (n = 32, 53 %), erosion (n = 10, 17 %), angioectasia (n = 9, 15 %), varices (n = 4, 7 %), and villous edema (n = 4, 7 %). Most lesions were located in the proximal or middle small bowel. Factors associated with the lesions were Child-Pugh class B (vs. class A, P = 0.0023), ascites (vs. no ascites, P = 0.0085), and portal hypertensive gastropathy (vs. no portal hypertensive gastropathy, P = 0.0434).

CONCLUSIONS

We found capsule endoscopy to be a useful diagnostic modality for detecting clinically significant small bowel lesions in patients with compensated liver cirrhosis. Based on our results, we suggest that this procedure should be especially considered for patients with Child-Pugh class B disease, ascites, and/or portal hypertensive gastropathy if they show evidence of gastrointestinal blood loss and/or iron-deficiency anemia.

The diminished expression of proangiogenic growth factors and their receptors in gastric ulcers of cirrhotic patients

Objectives

The pathogenesis of the higher occurrence of peptic ulcer disease in cirrhotic patients is complex. Platelets can stimulate angiogenesis and promote gastric ulcer healing. We compared the expressions of proangiogenic growth factors and their receptors in the gastric ulcer margin between cirrhotic patients with thrombocytopenia and those of non-cirrhotic patients to elucidate possible mechanisms.

Methods

Eligible cirrhotic patients (n = 55) and non-cirrhotic patients (n = 55) who had gastric ulcers were enrolled. Mucosa from the gastric ulcer margin and non-ulcer areas were sampled and the mRNA expressions of the proangiogenic growth factors (vascular endothelial growth factor [VEGF], platelet derived growth factor [PDGF], basic fibroblast growth factor [bFGF]) and their receptors (VEGFR1, VEGFR2, PDGFRA, PDGFRB, FGFR1, FGFR2) were measured and compared. Platelet count and the expressions of these growth factors and their receptors were correlated with each other.

Results

The two groups were comparable in terms of gender, ulcer size and infection rate of Helicobacter pylori. However, the cirrhotic group were younger in age, had a lower platelet count than those in the non-cirrhotic group (p<0.05). The cirrhotic patients had diminished mRNA expressions of PDGFB, VEGFR2, FGFR1, and FGFR2 in gastric ulcer margin when compared with those of the non-cirrhotic patients (p<0.05). Diminished expressions of PDGFB and VEGFR2, FGFR1, and FGFR2 were well correlated with the degree of thrombocytopenia in these cirrhotic patients (ρ>0.5, p<0.001).

Conclusions

Our findings implied that diminished activity of proangiogenic factors and their receptors may contribute to the pathogenesis of gastric ulcers in cirrhotic patients.

Increased oxidative stress may lead to impaired adaptive cytoprotection in the gastric mucosa of portal hypertensive rat

BACKGROUND AND AIMS

In the gastric mucosa of portal hypertensive rats, adaptive cytoprotection against ethanol-induced damage is impaired. The aim of this study was to determine relation between impaired adaptive cytoprotection and oxidative stress.

METHODS

Portal hypertension was produced in male Sprague-Dawley rats by inducing staged portal vein occlusion. Oxidative stress levels were evaluated by measuring malondialdehyde and nitrotyrosine levels in the rat gastric mucosa with or without 10% ethanol pretreatment. Inhibition of oxidative stress by an anti-oxidant agent was estimated, and glutathione levels were also measured. Adaptive cytoprotection to 70% ethanol treatment was evaluated by measuring the gastric mucosal injury index in the presence or absence of the anti-oxidant.

RESULTS

The portal hypertensive gastric mucosa pretreated with 10% ethanol had significantly higher oxidative stress levels than the mucosa not pretreated with 10% ethanol. However, the sham-operated gastric mucosa pretreated with 10% ethanol had significantly lower oxidative stress levels than the mucosa not pretreated with 10% ethanol. Pretreatment with 10% ethanol increased glutathione levels in the sham-operated but not in the portal hypertensive gastric mucosa. Administration of the anti-oxidant agent prior to 10% ethanol pretreatment significantly reduced oxidative stress levels, increased glutathione levels, and decreased the injury index in response to 70% ethanol in the portal hypertensive gastric mucosa.

CONCLUSION

Increased oxidative stress may lead to impaired adaptive cytoprotection in the gastric mucosa of portal hypertensive rats, probably through damage to the system of endogenous anti-oxidant production.

Nonpeptic ulcer, nonvariceal gastrointestinal bleeding in hemodialysis patients

OBJECTIVES

Hemodialysis patients carry a higher risk of peptic ulcer bleeding. Whether hemodialysis patients also have a higher occurrence of nonpeptic ulcer, nonvariceal gastrointestinal bleeding needs further evaluation.

METHODS

Using Taiwan's National Health Insurance research database, the occurrence of nonpeptic ulcer, nonvariceal gastrointestinal bleeding was compared among the hemodialysis patients, chronic kidney disease patients, and controls using log-rank test. Risk factors were identified by Cox regression analysis.

RESULTS

A total of 20,830 patients were enrolled, including 8210 hemodialysis and 4190 chronic kidney disease patients and 8430 age- and sex-matched controls in a 2:1:2 ratio. In the 7-year follow-up period, hemodialysis patients had a significantly higher cumulative hazard of nonpeptic ulcer, nonvariceal gastrointestinal bleeding than chronic kidney disease patients and controls (P <.001, by log-rank test). The hazard also was significantly higher in the chronic kidney disease patients than in controls. Cox regression analysis revealed that older age, the comorbidities of diabetes mellitus, cirrhosis, and chronic obstructive pulmonary disease, history of uncomplicated peptic ulcer disease, chronic kidney disease (hazard ratio 5.17), hemodialysis (hazard ratio 9.43), and use of selective serotonin reuptake inhibitors were independent risk factors for nonpeptic ulcer, nonvariceal gastrointestinal bleeding in all study patients. Old age, diabetes mellitus, cirrhosis, chronic obstructive pulmonary disease, history of uncomplicated peptic ulcer disease, and use of selective serotonin reuptake inhibitors were independent risk factors in hemodialysis patients.

CONCLUSIONS

There is a higher risk of developing nonpeptic ulcer, nonvariceal gastrointestinal bleeding in hemodialysis patients after adjustments for age, sex, underlying comorbidities, and ulcerogenic medication. The risk has increased since patients had chronic kidney disease.

Cirrhotic patients at increased risk of peptic ulcer bleeding: a nationwide population-based cohort study

BACKGROUND

Few large population-based studies have compared the occurrence of peptic ulcer bleeding (PUB) in cirrhotic and noncirrhotic patients.

AIMS

To investigate if cirrhotic patients have higher risk of PUB than the general population and to identify possible risk factors of PUB in cirrhotic patients.

METHODS

Using the National Health Insurance Research Database, a nationwide population-based dataset in Taiwan and matching age, gender, comorbidities and ulcerogenic medication by propensity score, 4013 cirrhotic patients, 8013 chronic hepatitis patients and 7793 normal controls were compared. The log-rank test was used to analyse differences in accumulated PUB-free survival rates between the groups. Cox proportional hazard regressions were performed to evaluate independent risk factors for PUB in all patients and identified risk factors of PUB in cirrhotic patients.

RESULTS

During the 7-year follow-up, cirrhotic patients had significantly higher incidences of PUB than chronic hepatitis patients and controls, respectively (P < 0.001 by log-rank test). By Cox proportional hazard regression analysis, cirrhosis was independently associated with increased risk of PUB (hazard ratio: 4.22; 95% CI 3.37-5.29, P < 0.001) after adjusting for age, gender, economic status, underlying comorbidities and ulcerogenic medication. Age, male, diabetes, chronic renal disease, history of gastro-oesophageal variceal bleeding and use of nonsteroidal anti-inflammatory drugs were risk factors for PUB in cirrhotic patients.

CONCLUSION

Cirrhotic patients have a significantly higher risk of peptic ulcer bleeding after adjustments for possible confounding factors like age, gender, economic status, underlying comorbidities and ulcerogenic medication.

The management of portal hypertensive gastropathy and gastric antral vascular ectasia

Portal hypertensive gastropathy and gastric antral vascular ectasia are gastric mucosal lesions that can cause chronic gastrointestinal haemorrhage and, consequently, chronic anaemia, in patients with cirrhosis. Although chronic anaemia is the most common clinical manifestation, these entities may also lead to acute gastrointestinal bleeding. Despite similar clinical manifestations, their pathophysiology and management are entirely different. Their diagnosis is endoscopic and although generally each of them has a characteristic endoscopic appearance and distribution, there are cases in which the differential is difficult and must rely on histology. This review focuses on the management of both entities. The mainstay of management of portal hypertensive gastropathy is based on portal-hypotensive pharmacological treatment whilst gastric antral vascular ectasia benefits from endoscopic therapy. More invasive options should be reserved for refractory cases.

Management of gastropathy and gastric vascular ectasia in portal hypertension

Portal hypertensive gastropathy and gastric antral vascular ectasia may cause gastrointestinal hemorrhage in patients with portal hypertension. Whereas the former presents exclusively in patients with portal hypertension, gastric antral vascular ectasia can also be observed in patients with other conditions. Diagnosis is established with upper gastrointestinal endoscopy, although some cases may require a biopsy to confirm the diagnosis. The most frequent manifestation is ferropenic anemia, which may become transfusion dependent. Treatment in portal hypertensive gastropathy is focused on portal pressure reducing drugs, mainly nonselective beta-blockers, whereas in gastric antral vascular ectasia treatment is based on endoscopic ablation. More invasive options can be used if first-line therapies fail, although these should be evaluated on a case-by-case basis.

Effect of laparoscopic splenectomy on portal hypertensive gastropathy in cirrhotic patients with portal hypertension

AIM

This study investigated the relationship between portal hypertensive gastropathy (PHG) and splenomegaly, and the effect of laparoscopic splenectomy on PHG in cirrhotic patients with portal hypertension.

METHODS

Seventy patients with liver cirrhosis and portal hypertension were prospectively studied. Indication for laparoscopic splenectomy was bleeding tendency in 10 patients, induction of interferon in 45, treatment of hepatocellular carcinoma in seven, and treatment for endoscopic injection sclerotherapy-resistant esophagogastric varices in eight. The severity of PHG was classified into none, mild, or severe according to the classification by McCormack et al. The severity of liver disease was classified using the Child-Pugh score. All patients underwent upper gastrointestinal endoscopy before and 1 month after the operation.

RESULTS

The prevalence of PHG was significantly correlated with the severity of liver disease using the Child-Pugh score. The severity of PHG was significantly correlated with the resected spleen volume. One month after the operation, PHG was improved in 16 of 17 patients with severe PHG and in 12 of 32 with mild PHG. The Child-Pugh score showed a significant improvement (6.8 +/- 1.4 to 6.2 +/- 1.2) at 3 months after laparoscopic splenectomy (P < 0.0001).

CONCLUSIONS

PHG may be associated with splenomegaly, and laparoscopic splenectomy may have a beneficial effect on PHG, at least for a short time.

Increased heat-shock protein 90 expression contributes to impaired adaptive cytoprotection in the gastric mucosa of portal hypertensive rats

BACKGROUND AND AIMS

Portal hypertensive (PHT) gastropathy results in an increased susceptibility to damage. Adaptive cytoprotection against ethanol-induced damage is impaired in the gastric mucosa of rats with portal hypertension. Excessive nitric oxide (NO) production occurs in portal hypertension and is mediated in part via heat-shock protein (Hsp)90 production. The aim of this study was to investigate the relation between adaptive cytoprotection after exposure to ethanol and gastric expression of Hsp90 in PHT rats.

METHODS

Portal hypertension was induced in rats by staged portal vein occlusion. Adaptive cytoprotection to 70% ethanol was evaluated by assessing the injury index of the gastric mucosa with or without pretreatment with 10% ethanol. Expression of Hsp90 mRNA was evaluated by real-time polymerase chain reaction, and expression of Hsp90 protein was evaluated by western blotting. The effect of Hsp90 inhibition in PHT rats was evaluated by administration of geldanamycin.

RESULTS

Gastric Hsp90 mRNA expression in PHT rats was significantly less than that in sham-operated (SO) controls. However, after 10% ethanol pretreatment, Hsp90 mRNA expression was significantly greater in PHT rats than in SO controls. In PHT rats, gastric Hsp90 protein expression after 10% ethanol pretreatment was significantly greater than that without the pretreatment. However, the pretreatment had no effect on the injury index compared to SO rats. Administration of geldanamycin prior to 10% ethanol pretreatment significantly decreased the injury index in response to 70% ethanol in the PHT rats.

CONCLUSIONS

These results show that 10% ethanol pretreatment markedly increases gastric Hsp90 expression in PHT rats. Excessive production of Hsp90 may contribute impaired adaptive cytoprotection.

Pathogenesis of portal hypertensive gastropathy: translating basic research into clinical practice

Portal hypertensive gastropathy (PHG) is often seen in patients with portal hypertension, and can lead to transfusion-dependent anemia as well as acute, life-threatening bleeding episodes. This Review focuses on the mechanisms that underlie the pathogenesis of PHG that provide reasonable grounds for the treatment of this condition, and ultimately enable translation of basic research into clinical practice. Increased portal pressure associated with cirrhosis and liver dysfunction is critical for the development of clinically significant PHG, and leads to impaired gastric mucosal defense mechanisms that render the stomach susceptible to mucosal injury. The use of pharmacological agents such as beta-blockers reduces the frequency of bleeding episodes in PHG. As a last resort, surgical decompression of the portal system, transjugular intrahepatic stent placement and liver transplantation can resolve this condition. Elimination of known risk factors for gastric injury such as alcohol, aspirin and traditional NSAIDs is critical. The role of Helicobacter pylori colonization of the gastric mucosa in PHG is not clear. Careful and critical interpretation of human and experimental data can be helpful to establish a rationale for the medical management of this important condition.

Significance of ERK nitration in portal hypertensive gastropathy and its therapeutic implications

Portal hypertensive (PHT) gastric mucosa increases susceptibility to injury and delayed mucosal healing. It is possible that nitration of ERK by peroxynitrite might alter MAPK (ERK) signaling in PHT gastric mucosa, leading to delayed mucosal healing, since excessive nitric oxide production is implicated in PHT gastric mucosa and MAPK (ERK) signaling induces cell proliferation and leads to gastric mucosal healing in response to injury. Portal hypertension was produced by staged portal vein ligation, and sham-operation (SO) rats served as controls. Lipid peroxide (LPO) and nitrotyrosine increased significantly in PHT gastric mucosa compared with SO rats. ERK activation was impaired in PHT gastric mucosa in response to ethanol injury, whereas no significant difference in the phosphorylation of MEK, an upstream molecule of ERK, was seen between the two groups. The nitration of ERK by peroxynitrite, as detected by the coimmunoprecipitation of ERK and nitrotyrosine, was significantly enhanced in PHT gastric mucosa. Administration of rebamipide, a gastroprotective drug that acts as an oxygen-derived free radical scavenger, significantly decreased LPO and nitrotyrosine as well as the nitration of ERK by peroxynitrite in PHT gastric mucosa, therefore normalizing ERK activation and restoring the gastric mucosal healing response to ethanol injury. Enhanced nitration of ERK by peroxynitrite is involved in the impaired MAPK (ERK) signaling in PHT gastric mucosa. These findings demonstrate a new molecular mechanism in which PHT gastric mucosa is predisposed to injury and impaired healing.

Gastric mucosal defense and cytoprotection: bench to bedside

The gastric mucosa maintains structural integrity and function despite continuous exposure to noxious factors, including 0.1 mol/L HCl and pepsin, that are capable of digesting tissue. Under normal conditions, mucosal integrity is maintained by defense mechanisms, which include preepithelial factors (mucus-bicarbonate-phospholipid "barrier"), an epithelial "barrier" (surface epithelial cells connected by tight junctions and generating bicarbonate, mucus, phospholipids, trefoil peptides, prostaglandins (PGs), and heat shock proteins), continuous cell renewal accomplished by proliferation of progenitor cells (regulated by growth factors, PGE(2) and survivin), continuous blood flow through mucosal microvessels, an endothelial "barrier," sensory innervation, and generation of PGs and nitric oxide. Mucosal injury may occur when noxious factors "overwhelm" an intact mucosal defense or when the mucosal defense is impaired. We review basic components of gastric mucosal defense and discuss conditions in which mucosal injury is directly related to impairment in mucosal defense, focusing on disorders with important clinical sequelae: nonsteroidal anti-inflammatory drug (NSAID)-associated injury, which is primarily related to inhibition of cyclooxygenase (COX)-mediated PG synthesis, and stress-related mucosal disease (SRMD), which occurs with local ischemia. The annual incidence of NSAID-associated upper gastrointestinal (GI) complications such as bleeding is approximately 1%-1.5%; and reductions in these complications have been demonstrated with misoprostol, proton pump inhibitors (PPIs) (only documented in high-risk patients), and COX-2 selective inhibitors. Clinically significant bleeding from SRMD is relatively uncommon with modern intensive care. Pharmacologic therapy with antisecretory drugs may be used in high-risk patients (eg, mechanical ventilation >or=48 hours), although the absolute risk reduction is small, and a decrease in mortality is not documented.

Avoiding pitfalls: what an endoscopist should know in liver transplantation--part 1

Cirrhosis is associated with global homodynamic changes, but the majority of the complications are usually manifested through the gastrointestinal tract. Therefore, Gastrointestinal Endoscopy has become an important tool in the multidisciplinary approach in the management of these patients. With the ever growing number of cirrhotic patients requiring pre-transplant endoscopic management, it is imperative that the community endoscopists are well aware of the pathologies that can be potentially noted on Gastrointestinal Endoscopy. Their timely management is also considered to have the utmost importance in being able to stabilize the patient until their transfer to a Liver Transplant Center. The aim of this manuscript is to give a comprehensive update and review of various endoscopic findings that a non-transplant endoscopist will encounter in the pre-transplant setting.

Aging gastropathy-novel mechanisms: hypoxia, up-regulation of multifunctional phosphatase PTEN, and proapoptotic factors

BACKGROUND & AIMS

Aging gastric mucosa has impaired mucosal defense and increased susceptibility to injury. Our aims were to determine the mechanisms responsible for above abnormalities.

METHODS

We used Fisher F-344 rats, 3 and 24 months of age. We measured gastric mucosal blood flow; visualized mucosal hypoxia; examined expression of early growth response-1 transcription factor and phosphatase and tensin homologue deleted on chromosome 10 (PTEN); assessed apoptosis; and determined expression of caspase-3, caspase-9, and survivin. We also examined susceptibility of gastric mucosa of young and aging rats to ethanol injury and whether down-regulation of PTEN affects susceptibility of aging gastric mucosa to injury. To determine human relevance, we examined expression of PTEN and survivin in human gastric specimens of young and aging individuals.

RESULTS

Gastric mucosa of aging (vs young) rats has a 60% reduction in mucosal blood flow; prominent hypoxia; and increased early growth response-1 transcription factor and PTEN messenger RNAs, and proteins. It also has increased expression of proapoptotic proteins caspase-3 and capase-9, reduced survivin, and a 6-fold increased apoptosis vs mucosa of young rats. Ethanol-induced gastric mucosal injury in aging (vs young) rats was significantly increased. The down-regulation of PTEN in gastric mucosa of aging rats completely reversed its increased susceptibility to ethanol injury. In aging human gastric mucosa, PTEN expression was significantly increased, whereas survivin was significantly reduced.

CONCLUSIONS

(1) Gastric mucosa of aging rats has significantly reduced blood flow, tissue hypoxia, activation of Egr-1, PTEN; increased caspases; and reduced survivin. (2) These changes increase susceptibility of aging gastric mucosa to injury.

[Portal hypertension in mansonic schistosomiasis: repercussions of surgical treatment on the histomorphometric profile of the gastric mucosa]

The repercussions from surgical treatment for controlling portal hypertension and its effects on the gastric vasculature of young patients with mansonic schistosomiasis were investigated by digital image analysis. The study included five patients at the preoperative stage and 27 patients who had undergone surgical intervention at different times in the past: 0-2 years ago, n=4; 2-6 years ago, n=13, and more than 6 years ago, n=10. Endoscopic biopsies were taken from the mucosa of the gastric antrum and body endoscopic mucosa and the samples underwent routine histological tests after embedding in paraffin blocks. Histological thin sections were used for histomorphometric analysis of the following parameters: mean number of vessels per field, and mean diameter and thickness of the vessel walls. The results showed that, between the patients whose operation was not more than two years ago and those whose operation was more than six years ago, there was a significant decrease in the density and diameter of the vessels. These findings give support to the concept that the surgical treatment administered decreases specific histological alterations like hemorrhage and ectasia, over the long term.

Zinc L-carnosine protects against mucosal injury in portal hypertensive gastropathy through induction of heat shock protein 72

BACKGROUND AND AIMS

Increased susceptibility to gastric mucosal injury is observed in portal hypertensive gastropathy (PHG). In this study, the effects of zinc L-carnosine, an anti-ulcer drug, were evaluated on expression of heat shock protein (hsp) 72 and cytoprotection in gastric mucosa in a rat model of PHG.

METHODS

Portal hypertensive gastropathy with liver cirrhosis was induced by bile duct ligation for 4 weeks in male Sprague-Dawley rats. Expression of gastric mucosal hsp72 was evaluated by Western blotting at 6 h after intragastric administration of L-carnosine, zinc sulfate, or zinc L-carnosine. Blood was also collected for determination of serum zinc level. Mucosal protective abilities against hydrochloric acid (HCl) (0.6N) followed by pretreatment with L-carnosine, zinc sulfate or zinc L-carnosine were also studied.

RESULTS

L-carnosine, zinc sulfate, and zinc L-carnosine induced hsp72 in gastric mucosa of rats with bile duct ligation. Zinc sulfate and zinc L-carnosine suppressed HCl-induced mucosal injury. However, L-carnosine could not suppress HCl-induced mucosal injury. Serum zinc levels were significantly elevated after zinc L-carnosine administration. Furthermore, pretreatment with zinc L-carnosine (30-300 mg/kg) increased the expression of hsp72 in gastric mucosa and prevented HCl-induced mucosal injury in rats with bile duct ligation in a dose-dependent manner.

CONCLUSIONS

Zinc derivatives, especially zinc L-carnosine, protected portal hypertensive gastric mucosa with increased hsp72 expression in cirrhotic rats. It is postulated that zinc L-carnosine may be beneficial to the mucosal protection in PHG as a 'chaperone inducer'.

L3 and adult Ostertagia (Teladorsagia) circumcincta exhibit cyanide sensitive oxygen uptake

Oxygen consumption by L3 and adult Ostertagia (Teladorsagia) circumcincta was examined in vitro to determine whether oxygen can be utilised in metabolism. The oxygen concentration in the abomasal fluid of sheep infected with O. circumcincta was also measured. Rates of consumption (in nmol O2/h/1000 worms) were 13+/-1 in sheathed L3, 34+/-6 in ex-sheathed L3, and 1944+/-495 in adult worms. Constant rates of consumption were maintained until media oxygen concentration dropped to between 10 and 20 microM. Consumption was inhibited 95% by cyanide in L3 and 74% in adults. Oxygen concentration in abomasal fluid varied between 10 and 30 microM in both infected and uninfected animals. During infection, oxygen concentration decreased slightly with increased abomasal pH, though the correlation between the two was poor (r=-0.30). In conclusion, O. circumcincta can consume oxygen and oxygen concentration at the infection site is sufficient to support at least some aerobic metabolism.

Expression of endothelin receptors in the gastric mucosa of portal hypertensive rats

BACKGROUND

Portal hypertensive gastropathy is an abnormal circulatory state in gastric mucosa with vascular dilatation due to portal hypertension. The aim of the present study was to evaluate expression of endothelin receptors and their roles in the portal hypertensive gastric mucosa.

METHODS

Portal hypertensive rats were generated by staged portal vein occlusion. Expression of endothelin-A receptor and endothelin-B receptor mRNA was examined by reverse transcriptase-polymerase chain reaction, and protein were examined by immunohistochemistry. The changes of mucosal microcirculation by endothelin receptor antagonists were measured with in vivo microscope.

RESULTS

Expression of endothelin-A receptor mRNA was increased significantly in portal hypertensive rats in comparison with sham-operated control rats (P < 0.05). There was no significant difference between the two groups in endothelin-B receptor mRNA expression. Vessels of the gastric mucosa were dilated, and intravessel blood flow was increased significantly in the portal hypertensive group (P < 0.05). Diameters of mucosal vessels and blood flow were increased significantly by endothelin-A receptor antagonist (BQ-485) in the portal hypertensive rats. Endothelin-B receptor antagonist (IRL-1038) had no significant effect on mucosal microcirculation.

CONCLUSION

These data suggest that increased expression of endothelin-A receptor in the portal hypertensive gastric mucosa may be related to the regulation of gastric microcirculation.

Factors predisposing to peptic ulcer disease in asymptomatic cirrhotic patients

BACKGROUND

There is a high prevalence of peptic ulcer in cirrhotic patients, but the pathogenesis of peptic ulcer in cirrhosis remains inconclusive.

AIM

To investigate factors associated with peptic ulcer and to evaluate peptic ulcer prevalence in asymptomatic cirrhotic patients.

METHODS

A total of 130 cirrhotics were recruited into the study for endoscopic screening. Data were collected and biochemical tests were done. Doppler ultrasound was used to assess the portal vein velocity and size. Patients underwent endoscopy for the presence of varices and peptic ulcer. Helicobacter pylori infection was confirmed by urease test, histology and 14C-urea breath test. Statistical analysis was performed.

RESULTS

Peptic ulcer was detected in 50 (39%) cases. Between peptic ulcer and non-peptic ulcer groups, there were no significant differences in age, sex, alcoholic drinking, smoking, non-steroidal anti-inflammatory drug use, portal vein velocity and size, except for H. pylori infection (P = 0.006), serum albumin (P = 0.02) and Child-Pugh score (P = 0.03). By multivariate analysis, H. pylori infection (OR: 3.26; 95% CI: 1.49-7.13; P = 0.003), Child-Pugh classes B (OR: 2.48; 95% CI: 1.04-5.91; P = 0.04) and C (OR: 3.26; 95% CI: 1.2-8.81; P = 0.02) were independently associated with peptic ulcer.

CONCLUSION

H. pylori infection and advanced cirrhosis are important factors associated with active peptic ulcer.

Selective cyclooxygenase (COX) inhibition causes damage to portal hypertensive gastric mucosa: roles of nitric oxide and NF-kappaB

Portal hypertension (PHT) is associated with increased susceptibility of the gastric mucosa to injury by a variety of factors, including nonsteroidal anti-inflammatory drugs (NSAIDs) that nonselectively inhibit both isoforms of cyclooxygenase (COX-1 and -2). PHT gastric mucosa also has excessive nitric oxide (NO) production that contributes to the general increased susceptibility to injury. Using a rat model of PHT, we studied whether selective COX inhibition, which does not damage normal (normotensive) gastric mucosa, is sufficient to cause PHT gastric damage and, if so, whether and how excessive NO is involved. Indomethacin, a nonselective NSAID, caused 2.4-fold more gastric injury to PHT vs. normotensive sham-operated (SO) control rats. Neither NS-398 nor celecoxib, selective COX-2 inhibitors, caused gastric damage in either SO or PHT rats. SC-560, a selective COX-1 inhibitor, did not cause gastric damage in SO rats but dose-dependently caused gastric damage in PHT rats. There was a compensatory increase in COX-2 expression and activity in SC-560-treated SO rats but not SC-560-treated PHT rats. Partial inhibition of NO production restored gastric COX-2 expression and activity levels in SC-560-treated PHT rats to those of SC-560-treated SO rats, by a mechanism consistent with induction of NF-kappaB, and significantly reduced gastric damage. These studies indicate that, in contrast to normotensive gastric mucosa, inhibition of COX-1 alone is sufficient to cause PHT gastric damage as a result of excessive NO that prevents the induction of NF-kappaB and the compensatory increase in COX-2.

An endoscopic study of upper-GI mucosal changes in patients with congestive heart failure

BACKGROUND

Congestive heart failure results in an increase in systemic venous pressure that is transmitted to the inferior vena cava and to the hepatic veins. This can cause GI vascular and mucosal congestion. The aim of this study was to define upper-GI mucosal changes in patients with congestive heart failure.

METHODS

A total of 57 patients with congestive heart failure presenting with GI symptoms underwent upper endoscopy. Echocardiography was performed in all patients to determine the ejection fraction and the degree of tricuspid regurgitation. Transabdominal US was performed to measure the diameters of the hepatic veins, the inferior vena cava, and the portal vein. The presence and the severity of gastropathy and duodenopathy were compared with the parameters relating to severity of cardiac failure.

RESULTS

Of the 57 patients studied, gastric mucosal changes were observed in 50 (88%), duodenal mucosal changes in 31 (54%), and esophageal mucosal changes in none. Gastric mucosal changes were the following: mosaic-like pattern (n = 50), punctate spots (n = 34), thickened folds (n = 5), watermelon stomach (n = 3), and telangiectasia (n = 10). Duodenal mucosal changes were the following: mosaic-like pattern (n = 29), thickened folds (n = 8), and telangiectasia (n = 2). Upper-GI symptoms were associated with gastropathy ( p = 0.027) and duodenopathy ( p = 0.003). The presence and the severity of duodenopathy showed a high degree of positive correlation with the presence and the severity of gastropathy (gamma value 0.690; p value <0.001). Patients with gastropathy and duodenopathy had higher mean inferior vena cava and hepatic vein diameters than those without gastropathy and duodenopathy. The severity of duodenopathy but not that of gastropathy was significantly associated with increasing severity of tricuspid regurgitation ( p = 0.001), larger portal vein diameter ( p = 0.02), and lower ejection fraction ( p = 0.008).

CONCLUSIONS

Among patients with congestive cardiac failure with GI symptoms, changes of congestive gastropathy are evident in 88% and duodenopathy in 54%. The presence and the severity of duodenopathy was significantly associated with increasing severity of features of congestive heart failure.

Helicobacter pylori density and cagA status in cirrhotic patients: a case-control study

BACKGROUND AND AIM

Despite a similar Helicobacter pylori prevalence, peptic ulcer is more frequent in cirrhotic patients than in controls. We evaluated whether cirrhotic patients had an increased bacterial density and/or a higher prevalence of H. pylori cagA-positive strains than controls.

METHODS

A total of 36 dyspeptic cirrhotic patients with H. pylori infection and 72 matched controls were enrolled. H. pylori infection was detected at histology on Giemsa staining, bacterial density was assessed using difference over baseline (DOB) values at 13C urea breath test, and cagA status was established at serology.

RESULTS

Overall, both DOB values and prevalence of cagA did not significantly differ between cirrhotic patients and controls. However, peptic ulcer controls showed significantly higher DOB value (27.9 +/- 17.4 vs 19.4 +/- 9.3, respectively; P = 0.009) and cagA positive rate (85%vs 48%; P = 0.01) than non-ulcer dyspepsia patients. Although not statistically significant, a similar trend was observed in cirrhotic patients with peptic ulcer for DOB values (26.5 +/- 16.3 vs 18.3/1000 +/- 9.2, respectively; P = 0.07), whereas the cagA-positive rate was similar between peptic ulcer and non-ulcer dyspepsia patients (60%vs 50%; P = 0.30).

CONCLUSIONS

The present data showed that both bacterial density and cagA prevalence did not differ between cirrhotic patients and controls.

Abnormal PTEN expression in portal hypertensive gastric mucosa: a key to impaired PI 3-kinase/Akt activation and delayed injury healing?

Phosphatase and tensin homologue deleted on chromosome ten (PTEN) is a dual-specificity phosphatase that has activity toward both phosphorylated peptides and phospholipids. PTEN inhibits activation of Akt, the downstream effector of PI 3-kinase, which is integral to cell proliferation, migration, survival, and angiogenesis essential for tissue injury healing. PTEN expression and activation during injury healing remain unexplored. Portal hypertensive (PHT) gastric mucosa has impaired injury healing, but the underlying mechanisms remain unknown. We investigated whether impaired healing of injured PHT gastric mucosa is due to abnormal PTEN expression/activation that leads to decreased Akt activation. We also investigated the possible involvement of Egr-1, which regulates PTEN in some cells (e.g., fetal kidney epithelial cells), and TNF-alpha, which can induce Egr-1 expression. In PHT gastric mucosa 6 h after injury, PTEN protein levels were increased by 2.7-fold; unphosphorylated PTEN (reflecting activated PTEN) was increased by 2.4-fold; Akt phosphorylation (reflecting Akt activation) was reduced by 2-fold; and Egr-1 expression was increased by 3.3-fold vs. normal gastric mucosa. TNF-alpha neutralization reversed all of the above abnormalities in PHT gastric mucosa, reduced mucosal injury, and enhanced healing. We conclude that, in injured PHT gastric mucosa, overexpressed/activated PTEN leads to the reduced activation of the PI 3-kinase/Akt pathway that results in impaired injury healing.

Gastroduodenal and intestinal permeability in primary biliary cirrhosis

OBJECTIVES

To evaluate gastrointestinal permeability in primary biliary cirrhosis (PBC), using a sensitive method to detect epithelial damage, and to correlate it with the Mayo score, histological stage, ascites, spontaneous bacterial peritonitis, endoscopic signs of portal hypertension and Helicobacter pylori infection.

METHODS

Fifty consecutive patients with PBC and 39 patients with cirrhosis of other aetiologies (non-PBC) were enrolled in the study. Coeliac disease was initially ruled out in all participants. Permeability was assessed using sucrose (gastro-duodenum) and lactulose-mannitol (intestine).

RESULTS

Sucrose excretion was above the limit in both PBC and non-PBC patients. Twenty-two per cent of PBC patients had an increased result for the lactulose-mannitol test compared to 12.8% of non-PBC cirrhotic patients. PBC patients had high sucrose excretion levels irrespective of the presence of any oesophageal varices, which significantly increased the gastroduodenal permeability in non-PBC patients only when associated with hypertensive gastropathy. Sucrose excretion was significantly enhanced by hypertensive gastropathy in non-PBC patients (P < 0.001) but not in PBC patients. No significant correlation was found in either group between gastrointestinal permeability and the other parameters.

CONCLUSIONS

Gastrointestinal permeability is increased in PBC. Portal hypertension contributes to altered gastric mucosal permeability in non-PBC cirrhosis, whereas different epithelial dysfunction can be hypothesized in PBC.

Helicobacter pylori infection in patients with liver cirrhosis: facts and fictions

Helicobacter pylori infection could play a role in different clinical alterations observed in cirrhosis, from gastroduodenal lesions to hepatic encephalopathy. Although its prevalence in cirrhotics is similar to that in controls, H. pylori infection is responsible for the increased prevalence of peptic ulcer observed in these patients. The ammonia production by H. pylori urease does not seem to increase blood ammonia levels during cirrhosis, indicating that its role in hepatic encephalopathy could be marginalized in clinical practice. Dual and triple therapies have been shown to be equally effective for H. pylori eradication in these patients.

Portal Hypertensive gastropathy

Portal hypertensive gastropathy (PHG), a term used to describe the endoscopic appearance of gastric mucosa with a characteristic mosaic-like pattern with or without red spots, is a common finding in patients with portal hypertension. Current classification systems that describe the severity of PHG have many limitations, but it appears that simple grading systems have better inter- and intraobserver agreement. The wide variation in the reported prevalence of PHG is probably related to selection bias, absence of uniform criteria and classification, and more importantly, the differences in inter- and intraobserver variation. Pathogenesis of PHG is not clearly defined, but there is a very close relationship between portal hypertension and development of PHG. GAVE is a separate entity from PHG, but patients with severe PHG may have a GAVE-like appearance in the gastric antrum. Acute bleeding from PHG, seen usually in the presence of severe PHG, is often mild and self-limiting. Currently, the only treatment that could be recommended for prophylaxis of bleeding from PHG is nonselective B-blockers.

Gastric motility in patients with presinusoidal portal hypertension

OBJECTIVE

The aim of this study was to evaluate the consequences of portal hypertension (PH) for the motor functions of the human stomach.

METHODS

The PH model used was the hepatosplenic form of mansonic schistosomiasis, as this is a condition characterized by PH but with considerably preserved hepatocellular function. The study included 15 patients with PH and 25 healthy volunteers who served as controls. The adaptive relaxation of the stomach was studied in 12 patients with PH and in 10 controls by a manometric method during rapid insufflation (25-30 s) of 700 ml of air into the gastric fundus. The gastric emptying of a liquid solution (15 patients with PH and 20 controls) and of a solid-liquid meal (nine patients with PH and 12 controls) was determined by gamma scintigraphy. The thickness of the gastric antrum wall was measured by ultrasonography in 12 patients with PH and in 10 controls.

RESULTS

Patients with PH showed the following: 1) reduction of the adaptive relaxation of the stomach (p < 0.0001); 2) acceleration of gastric emptying of the test solution (T 1/2, p = 0.0316), which became particularly expressive 25, 30, 40, and 50 min after ingestion (p = 0.0181, 0.0215, 0.0181, and 0.0215, respectively); 3) no alteration in gastric emptying of the solid-liquid meal as judged by T 1/2 values (p = 0.9170) or lag-phase values (p = 0.7544); and 4) a conspicuous increase in gastric wall thickness as determined by antrum wall measurements (p = 0.0008).

CONCLUSIONS

The reduced gastric adaptive relaxation demonstrated in patients with PH and normal hepatocellular function leads us to consider this condition as a cause of diastolic dysfunction of the stomach. In this disease, the motor alteration may be explained as a consequence of the reduction of gastric wall compliance, probably resulting from edema and vascular ectasia, which were indirectly detected by the increase thickness of the gastric antrum wall. The discrete acceleration of liquid gastric may be also related to the reduced gastric wall compliance.

Activation of eNOS in rat portal hypertensive gastric mucosa is mediated by TNF-alpha via the PI 3-kinase-Akt signaling pathway

Activation of endothelial nitric oxide synthase (eNOS) in portal hypertensive (PHT) gastric mucosa leads to hyperdynamic circulation and increased susceptibility to injury. However, the signaling mechanisms for eNOS activation in PHT gastric mucosa and the role of TNF-alpha in this signaling remain unknown. In PHT gastric mucosa we studied (1) eNOS phosphorylation (at serine 1177) required for its activation; (2) association of the phosphatidylinositol 3-kinase (PI 3-kinase), and its downstream effector Akt, with eNOS; and, (3) whether TNF-alpha neutralization affects eNOS phosphorylation and PI 3-kinase-Akt activation. To determine human relevance, we used human microvascular endothelial cells to examine directly whether TNF-alpha stimulates eNOS phosphorylation via PI 3-kinase. PHT gastric mucosa has significantly increased (1) eNOS phosphorylation at serine 1177 by 90% (P <.01); (2) membrane translocation (P <.05) and phosphorylation (P <.05) of p85 (regulatory subunit of PI 3-kinase) by 61% and 85%, respectively; (3) phosphorylation (P <.01) and activity (P <.01) of Akt by 40% and 52%, respectively; and (4) binding of Akt to eNOS by as much as 410% (P <.001). Neutralizing anti-TNF-alpha antibody significantly reduced p85 phosphorylation, phosphorylation and activity of Akt, and eNOS phosphorylation in PHT gastric mucosa to normal levels. Furthermore, TNF-alpha stimulated eNOS phosphorylation in human microvascular endothelial cells. In conclusion, these findings show that in PHT gastric mucosa, TNF-alpha stimulates eNOS phosphorylation at serine 1177 (required for its activation) via the PI 3-kinase-Akt signal transduction pathway.

Modulation of acid secretion in common bile duct ligation-related gastropathy in Wistar rats

BACKGROUND

Portal hypertensive gastropathy is associated with fundic gland atrophy, resulting in a decrease in chief and parietal cells, and diminished acid secretion.

METHODS

Acid secretion by isolated parietal cells was measured (acridine orange retention), along with the levels of various second messengers (intracellular Ca(2+), cyclic adenosine monophosphate and protein kinase C) in the common bile duct, ligated portal hypertensive rats and compared with sham-operated controls.

RESULTS

There was a significant decrease in the response of isolated parietal cells to the secretagogues histamine and carbachol. This resulted in the blunted acid secretion in the common bile duct ligated group. In addition, all the second messengers studied were significantly decreased as compared with the sham-operated controls.

CONCLUSION

These results suggest that the blunted acid secretory response in the portal hypertensive rat is caused by an alteration in the intracellular signal transduction mechanism.

Immunohistochemical localization of vascular endothelial growth factor in the rat portal hypertensive gastropathy

BACKGROUND AND AIMS

Portal hypertensive gastropathy (PHG) is now recognized to be a distinct entity. Recently, angiogenesis has been noticed as a key factor in clarifying the pathophysiology of various diseases. Angiogenesis in the PHT of explored gastric mucosa has yet to be explored. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor. The aim of the present study was thus to investigate whether the hypoxic state exists in PHG, and whether VEGF appears more strongly in PHG than in normal gastric mucosa and, if so, what exactly is the role of the hypoxic state and VEGF in PHG.

METHODS

At 1, 3, 7 and 14 days after either a portal ligation or sham operation, the portal venous pressure, the gastric mucosal blood flow volume and the blood gas were measured and, the expression of VEGF and antiproliferating cell nuclear antigen (PCNA) in gastric mucosal specimens was immunohistochemically assessed.

RESULTS

The portal pressure (PP) and the gastric mucosal blood flow (GMBF) in the PHT rats were significantly greater than in the control (CTR). Both the SaO2 and PaO2 of the arterial blood gas were lower in the PHT rats than in the control rats. The percentage of VEGF expression in the PHG was found to be higher than that in the control gastric mucosa. The percentage of PCNA expression in the PHG was higher than that in the control gastric mucosa.

CONCLUSION

The levels of SaO2 and PaO2 were lower in the PHT rats. There is a possibility that a kind of portal hypertensive gastric change may trigger an enhanced histochemical expression of VEGF. The increased activity of VEGF may have a possibility of the hypoxic gastric mucosal state caused by the presence of active congestion. This damaged mucosal state 'PHG' may thus facilitate the fragility in PHG and such lesions may be slow and insidious, which may therefore lead to sudden and severe anemia, thus causing massive and sometimes fatal hemorrhaging.

Portal hypertensive gastric mucosa has reduced activation of MAP kinase (ERK2) in response to alcohol injury: a key to impaired healing?

Portal hypertensive (PHT) gastric mucosa has increased susceptibility to injury and impaired mucosal healing. Because our previous study showed that ulcer-induced activation of mitogen-activated protein (MAP) kinase (ERK) plays a pivotal role in gastric mucosal healing, we investigated whether ERK activation is altered in PHT gastric mucosa following alcohol injury. We studied ERK2 phosphorylation and activity and expression of MAP kinase phosphatase-1 (MKP-1) in gastric mucosa of PHT and sham-operated (SO) normal rats both at baseline and following alcohol injury. In SO gastric mucosa, ERK2 phosphorylation and activity were significantly increased time-dependently following alcohol injury: by 221% and 137%, respectively at 24 h vs. baseline. In contrast, in PHT gastric mucosa following alcohol injury, neither ERK2 phosphorylation nor activity was increased versus baseline. In PHT gastric mucosa, MKP-1 mRNA and protein expression were increased at baseline versus SO rats and were increased further following alcohol injury with values higher by 20%-40% at each study time versus SO rats. Because ERK2 is crucial for mucosal healing, reduced ERK2 activation resulting from the overexpression of MKP-1 might be the basis for the impaired mucosal healing in PHT gastric mucosa.

Gastric mucosal resistance to acute injury in experimental portal hypertension

1. The gastric mucosa of portal hypertensive rats exhibits important microvascular changes and a nitric oxide (NO)-dependent hyperemia. This study analyses whether portal hypertensive mucosa exhibits changes in its ability to withstand aggression. 2. Portal hypertension was induced by partial portal vein ligation (PPVL) or common bile duct ligation (CBDL) and gastric damage was induced by oral administration of ethanol or aspirin. Experiments were performed in conscious or anaesthetized rats and some animals were pre-treated with the NO-synthesis inhibitor L-NAME. 3. Conscious PPVL or CBDL rats showed an increased resistance to the damaging effects of ethanol. Oral administration of aspirin produced less gastric damage in PPVL conscious rats than in the control group. 4. The protective effects of portal hypertension were maintained in animals anaesthetized with ketamine and absent when pentobarbital was employed. 5. Pre-treatment with L-NAME restored the damaging effects of ethanol and aspirin in PPVL rats without modifying the level of damage in control animals. 6. Gastric bleeding induced by oral aspirin, as measured by the luminal release of (51)Cr-labelled erythrocytes, was significantly greater in PPVL rats than in control animals. 7. Semi-quantitative analysis by RT--PCR of the mRNA for endothelial NO-synthase (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) levels showed that the expression of iNOS was slightly increased in both the gastric mucosa and smooth muscle of PPVL rats. No changes were observed in eNOS and nNOS expression. 8. Conscious portal hypertensive rats exhibit an enhanced resistance to acute gastric damage which is absent under the influence of some types of anaesthesia and seems related to an increased synthesis of nitric oxide. However, mucosal lesions in these animals show an augmented bleeding per area of injury.

New insights into impairment of mucosal defense in portal hypertensive gastric mucosa

Portal hypertension (PHT) increases susceptibility of the gastric mucosa to injury. The aim of this study was to investigate whether PHT affects rat gastric mucosal defense mechanisms in vivo at the pre-epithelial, epithelial, and/or post-epithelial levels. PHT was produced in rats by staged portal vein ligation and sham-operated (SO) rats served as controls. The gastric mucosa was exposed, chambered, and continuously superfused with buffers under in vivo microscopy. We measured gastric mucosal gel layer thickness, surface epithelial cell intracellular pH (pHi), mucosal blood flow, and mucosal/serosal oxygenation. In PHT rats, gastric mucosal gel layer thickness was significantly reduced (88 +/- 16 microm in PHT rats vs. 135 +/- 25 microm in SO rats; P <0.0001), and the surface epithelial cell pHi was significantly decreased (6.80 +/- 0.11 in PHT rats vs. 7.09 +/- 0.21 in SO rats; P <0.01). Although total gastric mucosal blood flow was significantly increased in PHT rats by 72% (P <0.05), the oxygenation of the gastric mucosal surface was decreased by 42% (P <0.05) compared with SO rats. PHT impairs pre-epithelial (mucosal gel layer thickness), epithelial (pHi), and post-epithelial (maldistribution of blood flow) components of the gastric mucosal barrier. These findings can explain the increased susceptibility of portal hypertensive gastric mucosa to injury.

Portal-hypertensive gastropathy

In the present article we describe updated information concerning the clinical feature of portal-hypertensive gastropathy (PHG), which is characterized by mucosal and submucosal vascular dilatation without inflammation. Although this lesion represents non-variceal bleeding, there is a wide variation of its prevalence. Portal pressure and some humoral factors may play important roles in its pathogenesis. Gastric acid secretory activity is reduced, whereas the gastric mucosal barrier is impaired. With regard to gastric mucosal haemodynamics, whether 'overflow' (i.e. active congestion) or 'stasis' (i.e. passive congestion) cause gastric mucosal hyperaemia is not known. A severe lesion is a potential source of bleeding, while mild lesions are of little clinical significance and endoscopic variceal obliteration aggravates PHG in some patients. In the treatment of PHG, pharmacological (e.g. propranolol), surgical (e.g. portosystemic shunt) and radiological (e.g. transjugular intrahepatic portosystemic shunt) procedures may be useful in preventing bleeding from PHG.

Alterations in colonic mucosal vessels in patients with cirrhosis and noncirrhotic portal hypertension

Changes in intestinal mucosal microvasculature as a cause of lower gastrointestinal hemorrhage in patients with portal hypertension have been well documented clinically, but the analogous histomorphological changes have not been well characterized. The goal of this study was to evaluate qualitative and quantitative changes in colonic mucosal vessels in patients with cirrhosis or clinically evident portal hypertension and to correlate these changes with endoscopic and clinical findings. Colon biopsy or resection specimen slides from 46 patients with biopsy-proven cirrhosis (44 patients) or noncirrhotic portal hypertension (two patients) were reviewed. Immunoperoxidase stain for CD34 antigen was used to facilitate visualization of mucosal vessels, and vessel diameter was measured with a micrometer. Patients with inflammatory bowel disease were excluded. Twenty-four normal colon biopsy specimens served as controls. Mucosal vessels were divided into superficial, intermediate, and deep layers. As a group, the cirrhotic patients had a significantly higher mean diameter of vessels in all three layers. Qualitatively, increased numbers of small vessels and prominent branching were noted, especially in the superficial and intermediate layers. Tortuous, thick-walled vessels, suggesting arterialization of venules, were present in some cases. Eleven patients had endoscopic findings suggestive of vascular abnormalities, including erythematous mucosal patches, red macules, and telangiectasias. Eighteen had esophageal varices, and five had portal gastropathy. Nineteen patients had gastrointestinal (GI) bleeding, localized to the lower GI tract in 11. These qualitative and quantitative findings suggest that colonic mucosal vascular lesions are common in portal hypertension and may represent a potential source of clinically significant lower GI hemorrhage in these patients.

Tumor necrosis factor alpha regulates nitric oxide synthase expression in portal hypertensive gastric mucosa of rats

Anti-tumor necrosis factor alpha (TNF-alpha) treatment decreases nitric oxide (NO) synthesis and ameliorates the hyperdynamic circulation in portal hypertensive rats. We have recently demonstrated that nitric oxide synthase isoform 3 (NOS3) is overexpressed in portal hypertensive gastric mucosa and that resultant NO overproduction probably is responsible for the increased susceptibility of the mucosa to damage. In the present study, we examined whether TNF-alpha is overexpressed in portal hypertensive gastric mucosa and whether anti-TNF-alpha treatment affects gastric NOS3 messenger RNA (mRNA) and protein expression. We examined plasma concentrations of TNF-alpha and its protein expression in gastric specimens from portal hypertensive and sham-operated rats using Western blotting and immunohistochemistry. We also measured gastric mucosal blood flow, gastric expression of NOS3 mRNA and protein, and NOS3 enzyme activity in rats with and without TNF-alpha-neutralizing antibody treatment. The TNF-alpha protein levels in portal hypertensive stomachs were significantly increased by 57% compared with levels in sham-operated controls. TNF-alpha antibody treatment normalized gastric mucosal blood flow in portal hypertensive stomachs and significantly reversed overexpression of gastric NOS3 mRNA, protein, and its enzyme activity in portal hypertensive rats by 48%, 45%, and 33%, respectively. These results suggest that TNF-alpha may regulate NOS3 expression in the portal hypertensive stomach and that anti-TNF-alpha treatment may ameliorate the pathophysiological abnormalities of portal hypertensive gastric mucosa.

Underlying mechanisms of portal hypertensive gastropathy

Gastric mucosal lesions are frequently observed in patients with liver cirrhosis and portal hypertension. Similar lesions can be observed in experimental portal hypertension. This review summarizes our current knowledge of the pathophysiology of portal hypertensive gastropathy, with a particular focus on the microcirculatory disturbances that characterize this condition. The stomach of cirrhotic patients exhibits an increased susceptibility to injury induced by several irritants. Similarly, the stomach of portal hypertensive animals is less resistant to injury. One of the most important factors contributing to the increased susceptibility to damage is an impaired hyperemic response when the epithelium is exposed to irritants. This appears to be related to a reduction in mucosal prostaglandin production and to altered microcirculatory responsiveness to nitric oxide. Nitric oxide overproduction in portal hypertension may have direct effects on gastric blood flow regulation. Elevated production of tumor necrosis factor-alpha by gastric mucosa in portal hypertensive rats has also been shown to contribute to mucosal injury. A better understanding of the pathogenesis of portal hypertensive gastropathy may lead to development of specific therapeutic interventions for this condition.

Thickened gastric mucosal capillary wall: a histological marker for portal hypertension

To evaluate whether the diameter or thickness of the wall of mucosal capillaries in the stomach could be a useful histological marker of portal hypertension, gastric mucosal biopsies were taken from the fundus and antrum of 73 patients with cirrhosis of the liver and 64 healthy volunteers. The mean +/- SD diameter of mucosal capillaries in the fundus of patients was not significantly different from that in the control group (59.4 +/- 16.8 microns vs 53.5 +/- 16.5 microns, respectively; P = NS). However, the mean +/- SD diameter of the antral mucosal capillaries was significantly greater in patients compared to controls (61.3 +/- 18.1 microns vs 47.6 +/- 12.7 microns, respectively; P < 0.001). The mean +/- SD thickness of the fundal and antral capillary wall in the patients group (6.8 +/- 2.4 microns and 7.2 +/- 2.4 microns, respectively) was significantly greater than that in the control group (3.5 +/- 1.5 microns and 3.3 +/- 1.5 microns, respectively) (P < 0.001 for each). The overall diagnostic accuracy of antral mucosal capillary diameter to diagnose portal hypertension was 50%, while that of thickened fundal and antral mucosal capillary wall was 84% and 85%, respectively. It is concluded that the gastric mucosal capillary walls are thicker in patients with portal hypertension and that this is a more reliable histological marker of portal hypertension than dilated gastric mucosal capillaries.

Overexpression of endothelin-1 mRNA and protein in portal hypertensive gastric mucosa of rats: a key to increased susceptibility to damage?

BACKGROUND

Portal hypertension predisposes gastric mucosa to increased injury by various noxious factors. Because endothelin-1 (ET-1) is a potent vasoconstrictor that enhances gastric mucosal injury, we examined ET-1 expression in the portal hypertensive (PHT) gastric mucosa and its possible role in increased mucosal susceptibility to damage.

METHODS

In gastric specimens of PHT or sham-operated rats, ET-1 mRNA expression was studied by S1-nuclease protection assay and ET-1 protein by enzyme immunoassay and immunostaining. We also determined the extent of ethanol-induced gastric mucosal necrosis in PHT and sham-operated rats after administering either a placebo or FR 139317, a selective ETA receptor antagonist.

RESULTS

In PHT stomachs ET-1 mRNA expression and protein concentration were significantly increased compared with sham-operated controls: mRNA expression (ET-1/glyceraldehyde-3-phosphate-dehydrogenase ratio), 0.54 +/- 0.18 versus 0.30 +/- 0.08; protein concentration, 7.36 +/- 2.21 pg/mg versus 3.93 +/- 0.40 pg/mg, respectively; both p < 0.01. Immunofluorescence signal of ET-1 protein was predominantly localized to endothelia of gastric mucosal and submucosal vessels. In PHT stomachs FR 139317 significantly reduced mucosal necrosis (percentage of necrotic area, from 24.9 +/- 5.9% to 10.8 +/- 4.0%; p < 0.01), although it had no effect on sham-operated controls.

CONCLUSIONS

Portal hypertension activates the ET-1 gene with overexpression of ET-1 protein in the gastric mucosa. Protection of PHT gastric mucosa by ETA receptor antagonist against damage indicates that overexpression of ET-1 plays an important role in increased susceptibility of PHT gastric mucosa to injury.

Cytoprotective activity in the gastric mucosa of rats exposed to carbon tetrachloride-induced liver injury

The present study was undertaken to evaluate the cytoprotective activity in the gastric mucosa of rats subjected to CCl4-induced liver injury. Response of gastric mucosa to absolute ethanol insult or acid (pylorus ligation) after CCl4 challenge was analyzed. Intraperitoneal administration of CCl4 increased plasma AST and ALT, but liver protein and glycogen levels were decreased; in addition, gastric acid secretion was significantly increased with respect to control animals (1541 +/- 266 vs. 629 +/- 25 mu eq H+; p < 0.001). Microscopical gastric erosions were observed in 3/10 animals after CCl4 challenge. Pylorus-ligated as well as CCl4-challenged rats developed increased susceptibility to gastric lesions, compared to control (lesion indices: 4.6 +/- 0.20 vs 2.8 +/- 0.13; p < 0.05), while showing increased resistance to absolute ethanol-induced gastric damage (30.4 +/- 11.2 vs 89.7 +/- 9.7 mm, p < 0.01). PGE2 levels in the gastric mucosa were not influenced by exposure to CCl4. Ultrastructural studies revealed the presence of continuous ethanol-resistant and apparently more adherent layer of mucus in CCl4-challenged animals. Morphological evaluation revealed an increase in Alcian blue-stained mucus. A dual condition of enhanced sensitivity to HCl with increased tolerance to ethanol was observed in gastric mucosa of CCl4-treated animals. These observations could be explained by the amount and/or composition of protective mucus layer in the gastric mucosa.

Tumor necrosis factor-alpha regulates inducible nitric oxide synthase gene expression in the portal hypertensive gastric mucosa of the rat

Increased expression of both nitric oxide synthase (NOS) and tumor necrosis factor-alpha (TNF-alpha) have been implicated in the hyperdynamic circulation of portal hypertension. Since overexpression of these proteins would affect gastric mucosal defenses, which are impaired in portal hypertension, we examined the expression and interrelationships of TNF-alpha and NOS in the gastric mucosa of portal hypertensive rats. Following staged portal vein ligation, gastric strips from portal hypertensive rats were incubated in organ culture medium with or without TNF-alpha antibody. The expression of TNF-alpha and NOS mRNAs was assessed by reverse transcription-polymerase chain reaction (RT-PCR) at baseline and after 1, 2, and 6 hours of incubation. RT-PCR demonstrated a threefold increase in inducible NOS mRNA and a 50% increase in TNF-alpha mRNA expression at baseline in portal hypertensive animals as compared to sham-operated animals. In tissue incubated with TNF-alpha neutralizing antibody, inducible NOS mRNA expression was significantly decreased by 40%, 70%, and 80% after 1, 2, and 6 hours, respectively. Since increased TNF-alpha and NOS production could potentially impair gastric mucosal defenses, our findings suggest a major role for these proteins in the development of portal hypertensive gastropathy.

Gastric mucus generation in cirrhotic patients with portal hypertension. Effects of tetraprenylacetone

We have evaluated gastric mucus generation (study 1) and the effects of tetraprenylacetone on gastric mucus generation (study 2) in cirrhotic patients with portal hypertension. Study 1: Included were 50 noncirrhotics (group A), 25 cirrhotics without portal hypertension (group B), and 25 cirrhotics with portal hypertension (group C). The antrum, corpus, and fundus mucus generation was assessed by hexosamine concentration using biopsy specimens. In groups A and B, the antrum hexosamine concentration was significantly higher compared with the corpus (P < 0.01, P < 0.01) and the fundus (P < 0.01). In contrast, the hexosamine concentration at each location was similar in group C. Furthermore, the antrum hexosamine concentration of group C was significantly lower compared with that of group A (P < 0.05). In study 2, a double-blind design, 300 mg of tetraprenylacetone was administered for four weeks in 10 cirrhotics with portal hypertension and placebo in 10. The regional hexosamine concentrations were measured before and after drug administration. Placebo administration did not change hexosamine concentration at each location. In contrast, tetraprenylacetone increased the antrum and corpus hexosamine concentration (P < 0.01, P < 0.05), although the fundus concentration did not change. These data suggest that cirrhotics with portal hypertension have reduced gastric antral mucus generation and tetraprenylacetone normalizes this.

Vasopressin plus oxygen vs vasopressin alone in cirrhotic patients with portal-hypertensive gastropathy: effects on gastric mucosal haemodynamics and oxygenation

The effects of vasopressin plus oxygen and vasopressin alone on gastric mucosal perfusion and oxygenation were studied using reflectance spectrophotometry and laser Doppler velocimetry in 23 cirrhotic patients with portal-hypertensive gastropathy. The measurements were performed under basal conditions and after double-blinded administration of placebo (n = 7), vasopressin (0.3 U/min; n = 8) or vasopressin (0.3 U/min) plus nasal oxygen (4 L/min; n = 8). No significant effects on gastric mucosal haemodynamics and oxygenation were observed after placebo. In contrast, vasopressin and vasopressin plus oxygen induced a similar reduction in haemoglobin content (-26 +/- 2 and -21 +/- 4%, respectively P < 0.01), and laser Doppler signal (-23 +/- 2 and -22 +/- 2%, respectively, P < 0.01). Although each treatment induced a significant reduction in oxygen saturation (-21 +/- 2 and -7 +/- 1%, respectively P < 0.01), the effect was less pronounced in patients receiving the combination than in those receiving vasopressin alone (P < 0.01). These data suggest that vasopressin and vasopressin plus oxygen reduce gastric mucosal hyperaemia and that the oxygen supplement partially protects against gastric mucosal hypoxia during vasopressin infusion in cirrhotic patients with portal-hypertensive gastropathy.

Gastric and colonic inflammatory and vasoactive mediators in experimental portal hypertension

Rats with portal hypertension and experimental liver disease may exhibit increased susceptibility of the gastric mucosa to damage by noxious agents, and increased bacterial translocation through the bowel wall. The aim of this study was to determine mucosal gastric and colonic generation of vasoactive substances, because they may contribute to the altered mucosal function. Rats with partial vein ligation (n = 7), complete bile duct ligation (n = 6) and sham-operated rats (n = 10) were studied. Three weeks following surgery rats were anesthetized, splenic pulp pressure was measured, stomachs and colons were removed and mucosa was extracted for determination of prostaglandin E2, thromboxane B2, leukotriene B4, leukotriene C4 and endothelin-1 by radioimmunoassay (ng/g) and platelet activating factor activity (pg/10 mg) by platelet aggregation. Pulp pressure was > 13 mmHg in partial vein ligated rats and bile duct ligated rats and 6 mmHg in sham-operated rats. No macroscopic or microscopic lesions were seen any of the removed tissues. Gastric mucosal prostaglandin E2 and thromboxane B2 generation were decreased by 35% and 7%, respectively, in bile duct ligated rats (bile duct ligated versus sham-operated, p < 0.05 for prostaglandin E2 and thromboxane B2). Gastric leukotriene B4 and C4 generation, platelet activating factor activity and endothelin-1 content did not differ significantly among the three groups. A different pattern of changes was observed in the colon. Colonic leukotriene B4 generation and endothelin-1 content were increased in bile duct ligated rats by 105% and 210%, respectively (bile duct ligated versus sham-operated, p < 0.05 for leukotriene B4 and endothelin-1). The decreased gastric mucosal prostaglandin E2 generation of bile duct ligated rats may render the gut mucosa of these animals relatively ischemic and vulnerable to damage by noxious agents. The increased colonic leukotriene B4 generation and the increased endothelin-1 content of the colonic mucosa of bile duct ligated rats may promote inflammatory and ischemic changes in the colonic mucosa and may enable bacterial translocation.