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.

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.

Biological role of phosphatase PTEN in cancer and tissue injury healing.

PTEN (phosphatase and tensin homolog deleted on chromosome ten) also referred to as MMAC (mutated in multiple advanced cancers) was discovered as a tumor suppressor gene and later found to be a phospholipid phosphatase. PTEN negatively regulates Akt activation by preventing its phosphorylation. PTEN therefore inhibits the PI 3-kinase/Akt signaling pathway which is important for cell growth and survival.

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.

Despite activation of EGF-receptor-ERK signaling pathway, epithelial proliferation is impaired in portal hypertensive gastric mucosa: relevance of MKP-1, c-fos, c-myc, and cyclin D1 expression.

Portal hypertensive (PHT) gastric mucosa has increased susceptibility to injury and impaired mucosal healing. Our previous study demonstrated increased ERK activation and MAP kinase phosphatase-1 (MKP-1) overexpression in PHT gastric mucosa. However, it remains unknown which tyrosine kinase receptors are involved in ERK activation and whether ERK activation results in increased cell proliferation.

Defective mitogen-activated protein kinase (ERK2) signaling in gastric mucosa of portal hypertensive rats: potential therapeutic implications.

Portal hypertensive (PHT) gastropathy is a frequent, serious complication of liver cirrhosis. PHT gastric mucosa has numerous abnormalities such as reduced mucosal potential differences, reduced surface oxygenation, and increased susceptibility to injury caused by alcohol, aspirin, and other noxious factors. Because such mucosal injury is initially mediated by oxygen free radicals, and because mitogen-activated protein (MAP) kinase (ERK2) protects against cellular stress and induces cell proliferation, we postulated that oxidative stress-induced ERK2 activation is defective in PHT gastric mucosa.

Gene therapy for gastric ulcers with single local injection of naked DNA encoding VEGF and angiopoietin-1.

Background & Aims: Angiogenesis, formation of new capillary blood vessels, is crucial for gastroduodenal ulcer healing because it enables delivery of oxygen and nutrients to the healing site. Because angiogenesis is stimulated by vascular endothelial growth factor (VEGF) and angiopoietin-1 (Ang1), we studied whether local gene therapy with nonviral DNA encoding VEGF and/or Ang1 into the ulcer base could accelerate ulcer healing through enhanced angiogenesis.

Methods: Gastric ulcers were induced in rats by acetic acid applied to the serosal surface of the stomach, and the site around the ulcer was injected with nonviral plasmid-encoding full-length complementary DNA (cDNA) of human recombinant (rh) VEGF165, rhAng1, or their combination.

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.

Isolation and characterization of rat gastric microvascular endothelial cells as a model for studying gastric angiogenesis in vitro.

We have previously characterized morphologic features of wounding-induced angiogenesis that occurs in response to acute and chronic gastric mucosal injury. As a means of investigating the molecular mechanisms underlying gastric angiogenesis, microvascular endothelial cells were isolated from stomachs of normal (non-injured) rats. The isolation procedure adapted and combined aspects of previous methods and employed positive selection using magnetic beads coated with monoclonal antibody specific for rat CD31 (PECAM-1), a cell surface marker restricted to platelets, monocytes, T lymphocytes and endothelial cells.

ATP-induced CA2+-signaling enhances rat gastric microvascular endothelial cell migration.

The effects of exogenous ATP on Ca2+ signaling and wound healing were investigated in rat gastric microvascular endothelial cells (RGMEC). ATP (10 microM) triggered a significant rise in intracellular Ca2+ concentration ([Ca2+]i) from 46+/-2 nM at baseline to peak values averaging 283+/-31 nM (n = 5 experiments, 132 cells). Return to the basal [Ca2+]i was delayed by slowly declining plateau phase that persisted for 200+/-30 s.

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.

Antacid talcid activates in gastric mucosa genes encoding for EGF and its receptor. The molecular basis for its ulcer healing action.

In previous studies [Gut 35 (1994) 896-904], we demonstrated that antacid talcid (TAL) accelerates gastric ulcer healing and provides better quality of mucosal restoration within the scar than the omeprazole (OME). However, the mechanisms of TAL-induced ulcer healing are not clear. Since growth factors promote cell proliferation, re-epithelization, angiogenesis and ulcer healing, we studied whether TAL and/or OME affect expression of epidermal growth factor (EGF) and its receptors (EGF-R) in both normal and ulcerated gastric mucosae.

Isolation of morphologically and functionally intact gastric mucosal microvessels rapid communication.

Gastric mucosal microvessels were isolated after arterial perfusion of the rat stomach with magnetized iron oxide suspension. After homogenization of scrapped gastric mucosa, microvessels were initially separated with a high power magnet and further separated and purified by using a nylon sieve. Aliquots of purified microvessels were assessed for viability, histologic appearance, ultrastructure and generation of prostacyclin.

Expression of endothelin-1, and endothelin A and B receptors in portal hypertensive esophagus of rats.

Nitric oxide synthase is overexpressed in the portal hypertensive (PHT) esophagus, suggesting that expression of other vasoactive mediatora could also be affected. Therefore, in the present study we determined the expression of endothelin-1 (ET-1) and endothelin receptors, which could contribute to the regulation of the vascular tone in PHT esophagus. In esophageal specimens of PHT and sham operated rats, expression of ET-1 and its receptors A and B (ET(A)R and ET(B)R) mRNAs was studied by reverse transcription-polymerase chain reactions.

Sequential expression of adrenomedullin and its receptor during gastric ulcer healing in rats.

Adrenomedullin (AM) is a potent vasodilatory peptide. While its growth-regulating action in some cultured cells has been recognized, expression of AM and its receptor during gastric ulcer healing has not been explored. Specimens of gastric walls from control rats or gastric ulcers were obtained at 1, 3, 7, and 14 days after gastric ulcer induction.

Inhibition of angiogenesis by nonsteroidal anti-inflammatory drugs: insight into mechanisms and implications for cancer growth and ulcer healing.

Angiogenesis, the formation of new capillary blood vessels, is essential not only for the growth and metastasis of solid tumors, but also for wound and ulcer healing, because without the restoration of blood flow, oxygen and nutrients cannot be delivered to the healing site. Nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, indomethacin and ibuprofen are the most widely used drugs for pain, arthritis, cardiovascular diseases and, more recently, the prevention of colon cancer and Alzheimer disease. However, NSAIDs produce gastroduodenal ulcers in about 25% of users (often with bleeding and/or perforations) and delay ulcer healing, presumably by blocking prostaglandin synthesis from cyclooxygenase (COX)-1 and COX-2 (ref.

Basic fibroblast growth factor stimulates repair of wounded hepatocyte monolayer: modulatory role of protein kinase A and extracellular matrix.

The two important repair mechanisms after hepatocyte injury are proliferation and migration of the nearby healthy hepatocytes. Although previous studies have shown that basic fibroblast growth factor (bFGF) levels are markedly elevated after liver injury, the role of bFGF in the repair of the wounded hepatocytes is not well understood. The aim of this study was to delineate the role of bFGF in the repair of the wounded hepatocyte monolayers.

Ethanol injury triggers activation of adrenomedullin and its receptor genes in gastric mucosa.

Adrenomedullin (AM) is a potent vasodilatory peptide, which is present in the stomach. However, its precise function in the gastric mucosa is unknown. The expression and localization of AM and its receptor in gastric mucosa injured by ethanol also have not been explored, forming the basis for this study.

Reduced adrenomedullin expression in gastric mucosa of portal hypertensive rats after ethanol-induced injury.

Objective: To determine the expression and localization of adrenomedullin (AM) and its receptor (AM-R) in portal hypertensive (PHT) gastric mucosa after intragastric ethanol administration.

Summary Background Data: The repair of gastric mucosal injury requires reestablishment of the microvascular network. The authors previously demonstrated impaired angiogenesis of PHT gastric mucosa after ethanol-induced injury.

Activation of VEGF and Ras genes in gastric mucosa during angiogenic response to ethanol injury.

Our previous studies demonstrated that ethanol injury triggers the angiogenic response in gastric mucosa bordering necrosis. The present study was aimed to determine whether vascular endothelial growth factor (VEGF) (a potent angiogenic peptide selectively acting on endothelial cells) and Ras (a mediator of cell proliferation and a putative regulator of VEGF expression) are involved in gastric angiogenesis after ethanol injury. We studied the angiogenic response and expression of VEGF and Ras in gastric mucosa after ethanol injury.

Induction of in vitro angiogenesis in the endothelial-derived cell line, EA hy926, by ethanol is mediated through PKC and MAPK.

We have previously shown that ethanol-induced injury to the gastric mucosa triggers increased expression of the angiogenic factors, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) and angiogenesis. To further investigate ethanol-induced angiogenesis, we used an in vitro angiogenesis model which employs the ability of an endothelial-derived cell line (EA hy926) to form tubelike structures resembling capillaries when plated on the matrix material, Matrigel. We report that serum-starved EA hy926 cells, incubated for as little as 5 minutes with ethanol concentrations of 1.

Expression of adrenomedullin in portal hypertensive gastric mucosa of rats.

We examined the expression and localization of adrenomedullin (AM) mRNA, AM receptor (AM-R) mRNA and AM protein in normal and portal hypertensive (PHT) rat gastric mucosa. Methods included competitive reverse transcription-polymerase chain reaction (RT/PCR), in situ hybridization and Western blot analysis. Both AM mRNA and AM-R mRNA were strongly expressed not only in normal rat gastric mucosa but also PHT rat gastric mucosa.

Partial portacaval shunt for variceal hemorrhage: longitudinal analysis of effectiveness.

Objective: To determine rates of survival, long-term patency, and recurrent variceal hemorrhage among patients with alcoholic cirrhosis treated by partial portacaval shunt.

Design: Single-institution cohort follow-up study of 72 consecutive patients who underwent small-diameter portacaval H-graft shunt with collateral ablation during a 10-year period (1981 through 1990). Subjects were enrolled and followed up for up to 15 years.

Induction of mitogen-activated protein kinase signal transduction pathway during gastric ulcer healing in rats.

Background & Aims: Previous studies have shown that gastric ulceration stimulates epithelial cell proliferation and overexpression of epidermal growth factor (EGF) and EGF receptor (EGF-R) in the mucosa bordering necrosis. The aim of this study was to investigate whether extracellular signal-regulated kinase (ERK) cascade is involved in the healing of experimental gastric ulcers.

Methods: We studied EGF-R levels, EGF-R phosphorylation levels, and ERK1 and ERK2 activity in normal and ulcerated rat gastric mucosa.

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.