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. We examined whether EGF receptor (EGF-R) is involved in ERK activation and whether ERK activation triggers epithelial proliferation in PHT gastric mucosa. In gastric mucosa of PHT and sham-operated (SO) rats we studied: (1) EGF-R mRNA and protein expression as well as phosphorylation and membrane protein tyrosine kinase (PTK) activity; (2) ERK2 phosphorylation and activity; (3) MKP-1 mRNA and protein; (4) c-fos, c-myc and cyclin D1 mRNAs, and gastric epithelial proliferation. In PHT gastric mucosa: (1) EGF-R mRNA, protein and phosphorylation and membrane PTK activity were all significantly increased by 38%, 49%, 43% and 49%, respectively; (2) ERK2 phosphorylation and activity were significantly increased by 40% and 50 %, respectively; (3) MKP-1 mRNA and protein expression were significantly increased by 27% and 34%, respectively. In contrast, (4) c-fos, c-myc, and cyclin D1 mRNAs expression were all significantly decreased in PHT gastric mucosa by 36%, 33%, and 49%, respectively, and cell proliferation was significantly lower that in SO rats (11% in PHT vs. 18% in SO). These results suggest that in PHT gastric mucosa, ERK activation is mediated through EGF-R upregulation, but the gastric epithelial proliferation is impaired, possibly by MKP-1 overexpression, leading to reduction of c-fos, c-myc and cyclin D1.

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. Here we show that in PHT gastric mucosa, ERK2 activation by oxidative stress is impaired. This impairment is mediated by overexpression of MAP kinase phosphatase-1 (MKP-1), which results from the underlying and continual oxidative state associated with portal hypertension, and is ameliorated by inhibiting MKP-1. Furthermore, we found that supplementing vitamin E, a free radical scavenger, reduces the oxidative state in PHT gastric mucosa, normalizes MKP-1 expression, and thereby reverses impairment of oxidative stress-induced ERK2 activation. Finally, we show that orally administered vitamin E completely reverses the increased susceptibility of PHT gastric mucosa to alcohol injury. Our findings point to a new molecular and mechanistic basis for PHT gastropathy and provide a new therapeutic modality for protection of 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. For some studies, neutralizing anti-VEGF antibody was administered.

RESULTS

Single local injection of plasmids encoding VEGF165 and Ang1 significantly increased neovascularization and accelerated ulcer healing. A neutralizing anti-VEGF antibody significantly reduced the acceleration of ulcer healing resulting from the treatment. Coinjection of both plasmids encoding rhVEGF165 and rhAng1 resulted in formation of more mature vessels and to more complete restoration of gastric glandular structures within the ulcer scar. However, this did not result in further reduction of ulcer size.

CONCLUSIONS

VEGF and Ang1 gene therapy, with limited duration of target gene expression, significantly accelerates gastric ulcer healing. Coinjection of both plasmids leads to more complete structural restoration. Inhibition of accelerated healing by a neutralizing anti-VEGF antibody indicates an essential role for VEGF and enhanced angiogenesis in ulcer healing.

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.

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. Removal of extracellular Ca2+ did not significantly affect the peak rise in [Ca2+]i, but reduced the plateau. ATP (10 microM) also significantly increased the migration of RGMEC in a wounded monolayer. Addition of the non-subtype selective purinergic receptor antagonist, suramin, abrogated the effects of ATP on [Ca2+]i and migration. We conclude that local elevation of ATP acting through purinergic receptors induce Ca2+ signals in RGMEC and may contribute to endothelial cell migration.

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. The isolated microvascular endothelial cells expressed vascular endothelium-specific antigen and the endothelial-specific receptors, Tie2 and flt-1 (VEGFR1). When plated on growth factor-reduced matrigel, the isolated microvascular endothelial cells formed capillary-like structures reflecting in vitro angiogenesis. These cells were also responsive to vascular endothelial growth factor, VEGF, further verifying their endothelial nature. The rat microvascular endothelial cells isolated by this procedure should be useful in delineating molecular mechanisms and regulation of the angiogenesis that is essential for the healing of acute and chronic gastric 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.

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. ET-1 protein expression was assessed by immunostaining and enzyme immunoassay. In PHT esophagus, expression of ET-1, ET(A)R and ET(B)R mRNAs was significantly increased by 2.2-, 2.5- and 1.5-fold, respectively, compared with sham operated. The ET-1 protein was significantly increased by 2.2-fold vs. controls as measured by enzyme immunoassay. ET-1 protein was predominantly localized to endothelia of submucosal veins. Thus, portal hypertension induces over-expression of ET-1 in endothelia of esophageal submucosal vessels. Since ET-1 and its receptors could promote vascular proliferation and induce mucosal damage, the overexpressed ET-1 may play an important role in the development and rupture of esophageal varices in portal hypertension.

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. Rats with or without acetic acid-induced gastric ulcers (n = 64) received i.g. twice daily 1 mL of either: A) placebo (PLA); B) TAL 100 mg; or C) OME 50 mg x kg(-1) for 14 d. Studies of gastric specimens: 1) ulcer size; 2) quantitative histology; 3) expression of EGF mRNAs was determined by RT/PCR; 4) gastric sections were immunostained with antibodies against EGF and its receptors. In non-ulcerated gastric mucosa of placebo or omeprazole treated group, EGF expression was minimal, while EGF-R was localized to few cells in the mucosal proliferative zone. Gastric ulceration triggered overexpression of EGF and its receptor in epithelial cells of the ulcer margin and scar. In ulcerated gastric mucosa TAL treatment significantly enhanced (versus PLA and omeprazole) expression of EGF and EGF-R. OME treatment reduced expression of EGF in ulcerated mucosa by 55 +/- 2% (P < 0.01). It is concluded that: 1) treatment with TAL activates genes for EGF and its receptor in normal and ulcerated gastric mucosae; 2) since EGF promotes growth of epithelial cells and their proliferation and migration, the above actions of TAL provide the mechanism for its ulcer healing action and improved (versus OME) quality of mucosal restoration.

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. Microvessels were plated on Matrigel and cultured in DMEM with high glucose and 10% FBS for 1, 3 or 5 days. After 1, 3 and 5 days of culturing, endothelial viability was assessed with Fast green exclusion, and the basal and stimulated (with calcium ionophore) generation of prostacyclin was determined by assaying aliquots of the incubating medium for 6-keto PGF(1alpha). At 1 and 3 hrs after isolation, microvessels demonstrated intact morphologic structures as reflected by transmission EM and 92+/-4% of viable endothelial cells. The microvessels plated on Matrigel maintained good viability for at least 5 days and generated prostacyclin at the baseline and following ionophore stimulation. These data demonstrate that isolated microvessels cultured under optimal conditions are fully viable and functional.

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. AM and its receptor mRNAs expression were determined by reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. By RT-PCR, AM mRNA was increased by 167% at three days, while AM receptor mRNA was increased by 234% at seven days (both P < 0.05). By in situ hybridization, AM and AM receptor mRNAs were increased at ulcer margin from three days after ulcer induction. By immunohistochemistry, AM was increased in the ulcer margin at three and seven days. In separate in vitro studies using a rat gastric epithelial (RGM1) cell line, AM treatment significantly increased transforming growth factor-alpha mRNA expression and cell proliferation.

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. 10). The hypothesis that the gastrointestinal side effects of NSAIDs result from inhibition of COX-1, but not COX-2 (ref. 11), prompted the development of NSAIDs that selectively inhibit only COX-2 (such as celecoxib and rofecoxib). Our study demonstrates that both selective and nonselective NSAIDs inhibit angiogenesis through direct effects on endothelial cells. We also show that this action involves inhibition of mitogen-activated protein (MAP) kinase (ERK2) activity, interference with ERK nuclear translocation, is independent of protein kinase C and has prostaglandin-dependent and prostaglandin-independent components. Finally, we show that both COX-1 and COX-2 are important for the regulation of angiogenesis. These findings challenge the premise that selective COX-2 inhibitors will not affect the gastrointestinal tract and ulcer/wound healing.

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. Specifically, we examined the role of bFGF in cellular proliferation and migration of hepatocytes with an in vitro wound model. Standardized excisional wounds were created in clone 9 rat hepatocyte monolayers by a razor blade, and the extent of epithelial proliferation and migration was measured. After wound formation, bFGF (30 ng/mL) significantly stimulated proliferation of hepatocytes at the wound margin. bFGF also stimulated the migration of hepatocytes at the wound front. bFGF stimulation of hepatocyte migration correlated with increased formation of actin stress fibers and bFGF-receptor protein level. The bFGF stimulation of hepatocyte migration was abolished by various protein kinase A activating agents including 3-isobutyl-1-methylxanthine, 8-bromoadenosine-3', 5'-cyclic monophosphate, forskolin, and cholera toxin. In addition, protein kinase A activating agents almost completely prevented bFGF-induced actin stress fiber formation in the cells at the wound front. Varying the basement membrane composition of the extracellular matrix had a selective enhancing effect on the basal rates of hepatocyte migration (collagen IV > or = laminin > collagen I > fibronectin > control (plastic)). bFGF treatment resulted in a similar additive increase in hepatocyte migration across all coated surfaces studied. We conclude that bFGF promotes hepatocyte wound repair by stimulating both proliferation and migration of the hepatocyte at the margin of the wound.

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. Gastric samples of rats were obtained at 0 and 8 hr and 1, 2, and 4 days after intragastric administration of 100% ethanol. By RT-PCR, AM mRNA expression in gastric mucosa at 8 and 24 hr following ethanol injury was increased by 2-fold and by 2.5-fold (both P<0.01), respectively, and returned to normal at two days. AM receptor mRNA expression was increased by 2.7-fold, 2.3-fold, and 2.4-fold at 8, 24, and 48 hr, respectively (all P<0.01), and returned to normal at four days. By in situ hybridization, AM and AM receptor mRNAs were present in normal gastric mucosa and up-regulated in gastric mucosa following ethanol injury. The immunohistochemical signal for AM was significantly increased in the mucosa bordering erosion sites. We conclude that ethanol injury up-regulates the expression of both AM and AM receptor in gastric mucosa.

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. Because AM, a potent vasodilatory peptide, is also a novel growth and angiogenic factor, the authors hypothesized that AM is involved in the impaired repair of PHT gastric mucosa and its microvasculature after damage.

METHODS

Either PHT or sham-operated rats received intragastrically 100% ethanol, and the stomachs were excised at 1, 6, and 24 hours later. Expression and localization of AM and AM-R mRNA were examined by competitive reverse transcription-polymerase chain reaction and in situ hybridization. AM protein expression was examined by Western blot analysis.

RESULTS

One hour after ethanol administration, AM mRNA expression in PHT gastric mucosa was significantly decreased by 81%, especially in the superficial mucosa, compared with the gastric mucosa in sham-operated rats. The significant decrease lasted for 24 hours. AM protein expression was significantly decreased by 43% compared with the sham-operated gastric mucosa. Although AM-R mRNA expression in both groups was significantly increased 1 hour after ethanol administration and lasted for 24 hours compared with baseline, there were no differences between the two groups.

CONCLUSIONS

The expression of AM in PHT gastric mucosa after ethanol-induced injury is significantly decreased compared with controls. This finding could explain one mechanism for the impaired angiogenesis after injury of PHT gastric mucosa.

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. Ethanol damage triggered 1) angiogenesis in the gastric mucosa bordering necrosis, 2) significant increases in VEGF mRNA and protein expression, and 3) significant increases in the expression of Ki-ras mRNA and Ras proteins. Neutralizing anti-VEGF antibody significantly reduced (by greater than threefold) the angiogenic response to ethanol-induced injury. Moreover, mevastatin, an inhibitor of Ras activation, completely blocked the induction of VEGF expression in cultured primary endothelial cells. Because, in other tissues, VEGF is one of the most potent angiogenic factors and VEGF expression is dependent on Ras, our data indicate that Ras and VEGF are involved in gastric mucosal angiogenesis 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 1.0-2.5%, formed tubelike structures reflecting in vitro angiogenesis. Control cells, not incubated with ethanol, did not form tubelike structures. Incubation for 5 minutes with 2.5% ethanol resulted in increased activities of PKC and MAP kinase (ERK2) by 1.6-fold (p < 0.05) and 2.3-fold (P < 0.001), respectively. Furthermore, inhibitors of the MAPK kinase, MEK (PD98059) and PKC (GF 109203X) prevented the induction of in vitro angiogenesis by ethanol.

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. Shunt patency was assessed by portography and/or ultrasonography. We performed 7-year Kaplan-Meier analyses of survival (in 65 patients in Child classes A and B), shunt patency, and absence of variceal bleeding.

SETTING

Tertiary academic referral center of the US Department of Veterans Affairs.

PATIENTS

Patients with alcoholic cirrhosis were considered for operation after at least 1 proven episode of variceal hemorrhage. Patients with portal vein thrombosis were excluded; patients in Child class C underwent operation only for compelling indications. Of the 72 who underwent partial shunting, 38 were in Child class A, 27 were in class B, and 7 were in class C.

INTERVENTIONS

Partial portacaval shunt (6-, 8- or 10-mm polytetrafluoroethylene H-graft with collateral ablation) and serial follow-up.

MAIN OUTCOME MEASURES

Study end points were death, recurrent variceal hemorrhage, and unavailability for follow-up. Other measures included graft patency and nonvariceal rebleeding.

RESULTS

Cumulative probability of 7-year patency for grafts at risk was 95%. The 7-year probability for absence of variceal bleeding in patients at risk was 92%. In 65 patients in Child classes A and B, operative mortality was 7.7% and the cumulative probability of 7-year survival was 54%.

CONCLUSION

For variceal bleeding associated with alcoholic cirrhosis, the small-diameter polytetrafluoroethylene portacaval H-graft with collateral ablation affords durable patency and protection against variceal rebleeding.

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. While total AM and AM-R mRNA abundance was similar in both normal and PHT stomachs, in the superficial mucosa-where major defense mechanisms are located-their expression was significantly reduced in PHT rats by 33% (AM mRNA) and 25% (AM-R mRNA) (both p .0.05). AM protein was also expressed similarly in both normal and PHT gastric mucosa. We conclude that AM and its receptor play a role in regulation of gastric mucosal microcirculation and thus gastric mucosal defense.

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. We also examined the effect of Tyrphostin A46 (potent inhibitor of EGF-R and EGF-R kinase-dependent proliferation) on the above parameters.

RESULTS

During the initial stages of healing (3 and 7 days), ulcerated mucosa showed significant increase (vs. controls) in protein tyrosine kinase activity, EGF-R levels (510% and 550%), EGF-R phosphorylation levels, ERK1 activity (430% and 880%), and ERK2 activity (550% and 990%). Tyrphostin A46 treatment significantly inhibited ulcer healing and reduced EGF-R levels, EGF-R phosphorylation, and ERK1 and ERK2 activity.

CONCLUSIONS

These findings indicate that experimental gastric ulcer healing involves activation of EGF-R-ERK signal transduction pathway.

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.

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.

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.

Overexpressed nitric oxide synthase in portal-hypertensive stomach of rat: a key to increased susceptibility to damage?

BACKGROUND & AIMS

Portal hypertension predisposes gastric mucosa to increased injury. The aim of this study was to determine whether overexpression of constitutive nitric oxide synthase (cNOS) is responsible for increased susceptibility of portal-hypertensive (PHT) gastric mucosa to damage.

METHODS

In gastric specimens from PHT and sham-operated rats, cNOS messenger RNA expression was determined by Northern blotting and cNOS protein expression by Western blotting, immunohistochemistry, and enzyme activity assay. Extent of ethanol-induced gastric mucosal necrosis, mucosal blood flow, and gastric NOS activity in PHT and sham-operated rats was determined after administration of N(omega)-nitro-L-arginine methyl ester (L-NAME) or saline.

RESULTS

cNOS messenger RNA level, cNOS enzyme activity, and fluorescence signals for cNOS were increased significantly in PHT rats compared with controls. Inhibition of overexpressed cNOS by L-NAME (5 mg/kg) significantly reduced ethanol-induced mucosal necrosis and normalized blood flow in PHT gastric mucosa, whereas this dose of L-NAME significantly increased mucosal necrosis in sham-operated rats.

CONCLUSIONS

Portal hypertension activates the cNOS gene with overexpression of cNOS protein in endothelia of gastric mucosal vessels. Excessive NO production by overexpressed cNOS may play an important role in the increased susceptibility of PHT gastric mucosa to damage.

Portal hypertension triggers local activation of inducible nitric oxide synthase gene in colonic mucosa

Recently a new clinical entity "portal hypertensive colopathy" has been reported. It involves vascular abnormalities and bleeding. Because nitric oxide may mediate these changes, we studied whether portal hypertension affects nitric oxide synthase in portal hypertensive colonic mucosa. In portal hypertensive and sham-operated rats the following studies were done: (1) colonic mucosal blood flow, (2) quantitative histologic examination, (3) reverse transcription-polymerase chain reaction for nitric oxide synthase mRNA, (4) nitric oxide synthase activity assay, and (5) immunostaining for nitric oxide synthase. In portal hypertensive rats, colonic mucosal blood flow and the number of submucosal veins were significantly increased in comparison to sham-operated rats. The mRNA expression and enzyme activity for inducible nitric oxide synthase (but not constitutive nitric oxide synthase) were significantly increased in portal hypertensive rats. Fluorescence signal intensity for inducible nitric oxide synthase in endothelia of mucosal and submucosal veins was significantly higher in portal hypertensive rats than in sham-operated rats. Portal hypertension activates inducible nitric oxide synthase gene and protein in colonic mucosal vessels. The excess of nitric oxide generated by overexpressed inducible nitric oxide synthase may play an important role in the development of vascular and hemodynamic abnormalities characterizing portal hypertensive colopathy.

Role of protein kinase a pathway in epidermal growth factor-induced liver cell repair

To gain a better understanding of the mechanisms that control the repair process in the injured liver, the actions of epidermal growth factor (EGF) and protein kinase A (PKA) were studied. Normal rat liver cells (clone 9) were grown to confluence. Standardized excisional wounds were made with a razor blade. The extent of hepatocyte migration into the wound was measured and determined at specific time intervals using a computerized digital analyzing system. Immunostaining of F-actin was performed with a fluorescein-labeled phalloidin. EGF significantly stimulated liver cell migration, whereas specific EGF-neutralizing antibody inhibited the EGF-induced migration. Agents that activate PKA at different stages of the PKA activation pathway, including 3-isobutyl-1-methylxanthine (IBMX), forskolin, and cholera toxin, inhibited EGF-induced migration. EGF triggered formation of actin stress fibers. PKA-activating agents inhibited actin stress fiber formation and stretching of cells at the wound margin. The following conclusions were drawn: (1) In excisional wounds of hepatocyte monolayers, both EGF and PKA exert action on actin microfilaments, which are stretched by EGF and inhibited by PKA; (2) the enhanced repair of wounded hepatocyte monolayers by EGF is blocked by activation of the PKA pathway at various levels; and (3) these actions of EGF and PKA indicate their important regulatory roles in controlling the rate of hepatocyte migration and restitution following the creation of excisional wounds.

Portacaval shunt for portal hypertensive gastropathy

Portal hypertensive gastropathy is a vascular disorder of the gastric mucosa distinguished by ectasia of the mucosal capillaries and submucosal veins without inflammation. During 1988 to 1993, 12 patients with biopsyproven cirrhosis (10 alcoholic, 2 posthepatitic) were evaluated and treated prospectively by portacaval shunt for active bleeding from severe portal hypertensive gastropathy. Eleven patients had been hospitalized for bleeding three to nine times previously, and one was bleeding uncontrollably for the first time. Requirement for blood transfusions ranged from 11 to 39 units cumulatively, of which 8 to 30 units were required specifically to replace blood lost from portal hypertensive gastropathy. Admission findings were ascites in 9 patients, jaundice in 8, severe muscle wasting in 10, hyperdynamic state in 9. Child's risk class was C in 7, B in 4, A in 1. Ten of the 12 patients had previously received repetitive endoscopic sclerotherapy for esophageal varices, which has been reported to precipitate portal hypertensive gastropathy. Eight patients had failed propranolol therapy for bleeding. Portacaval shunt was performed emergently in 11 patients and electively in 1, and permanently stopped bleeding in all by reducing the mean portal vein-inferior vena cava pressure gradient from 251 to 16 mm saline. There were no operative deaths, and two unrelated late deaths after 13 and 24 months. During 1 to 6.75 years of followup, all shunts remained patent by ultrasonography, the gastric mucosa reverted to normal On serial endoscopy, and there was no gastrointestinal bleeding. Recurrent portal-systemic encephalopathy developed in only 8% of patients. Quality of life was generally good. It is concluded that portacaval shunt provides definitive treatment of bleeding portal hypertensive gastropathy by eliminating the underlying cause, and makes possible prolonged survival with an acceptable quality of life.

Reduced expression of basic fibroblast growth factor and its receptor mRNAs and proteins in portal hypertensive esophageal mucosa: a mechanism responsible for muscularis mucosae thinning and variceal rupture

BACKGROUND

Basic fibroblast growth factor (bFGF) enhances cell migration, proliferation, and tissue integrity. This especially pertinent to the smooth muscle cells in which it stimulates cell proliferation and promotes their growth. The aim of this study was to determine whether expression of bFGF and its receptors (FGFR-1 and -2) is altered in portal hypertensive esophageal mucosa, especially in the muscularis mucosal layer, which constitutes a physical barrier to variceal rupture.

METHODS

Portal hypertension (PHT) was produced by staged portal vein ligation. In 30 PHT rats and 30 sham-operated controls 2 weeks after operation, specimens of lower esophagus were obtained for (1) quantitative histologic assessment including thickness of epithelium and muscularis mucosae; (2) immunostaining with specific antibodies against bFGF and its receptors 1 and 2 (intensity of bFGF, FGFR-1 and FGFR-2 immunostaining in esophageal structures was measured with a video image system); and (3) expression of bFGF and FGFR-1 and -2 mRNAs was assessed with reverse transcription-polymerase chain reaction.

RESULTS

The esophageal muscularis mucosae and epithelium overlaying large submucosal veins in PHT rats significatly thinner than those in controls (muscularis mucosae, 28.3 +/- 1.4 versus 52.2 +/- 8.0 micrometer, respectively, p<0.05); epithelium, 39.0+/- 7.1 versus 49.3 +/- 1.9 micrometer, respectively, p<0.05). The immunostaining intensity of bFGF and FGFR-2 was significantly reduced in PHT rats (42.1 +/- 2.3 and 71.3 +/- 6.5 units, respectively) versus controls (49.5 +/- 5.6 and 78.6 +/- 5.7 units, respectively, p< 0.05). Expressions of bFGF and FGFR-2 mRNAs in PHT esophageal mucosa were significantly reduced versus controls by 30.8% and 30.3%, respectively (p < 0.01, p 0.05).

CONCLUSIONS

(1) Esophageal mucosa of PHT rats has thinner muscularis mucosae and reduced bFGF and FGFR-2 mRNAs and proteins. (2) Because bFGF stimulates smooth muscle cell proliferation and their growth, our findings can explain thinning of esophageal muscularis mucosae in PHT rats, thus indicating a possible mechanism for rupture of varices in the esophagus.

Portal hypertension activates the nitric oxide synthase genes in the esophageal mucosa of rats

BACKGROUND & AIMS

Nitric oxide is associated with hyperdynamic circulation and development of collaterals in portal hypertension. The aim of this study was to investigate whether NO synthase is activated in the portal-hypertensive esophagus.

METHODS

In esophageal specimens after portal ligation or sham operation, the expression of constitutive and inducible NO synthase messenger RNA was assessed by reverse transcription-polymerase chain reactions. NO synthase protein at 14 postoperative days was visualized with immunofluorescence staining with specific antibodies against constitutive and inducible NO synthase.

RESULTS

The esophageal muscularis mucosae and epithelium overlying large submucosal veins in portal-hypertensive rats were significantly thinner than in controls (muscularis mucosae, 24.3% thinner, P < 0.01; epithelium, 23.0% thinner, P < 0.05). Expression of NO synthase proteins in endothelia of submucosal veins was significantly higher in portal-hypertensive rats than in controls (constitutive NO synthase, 17.6%; inducible NO synthase, 18.0% increased over controls, respectively; P < 0.01). Expression of both constitutive and inducible NO synthase messenger RNA in portal-hypertensive rats was significantly increased (constitutive NO synthase, 10-fold; inducible NO synthase, 20-fold at 14 days vs. controls; P < 0.01).

CONCLUSIONS

Portal hypertension triggers overexpression of NO synthase messenger RNA and protein in the rat esophageal mucosa. This phenomenon, combined with the thinness of muscularis mucosae and epithelium, may facilitate development and rupture of esophageal varices.

Effect of teprenone on portal hypertensive gastric mucosa

Teprenone (geranylgeranylacetone) is a gastric mucosal protective drug used clinically in Japan for treatment of gastric ulcers and gastritis. Its effect on portal hypertensive (PHT) gastric mucosa which has impaired defensive mechanisms is not known. In 20 PHT and 20 sham-operated rats, we studied the effects of teprenone or placebo on: (1) portal pressure; (2) gastric pH; (3) gastric mucosal blood flow using laser doppler flowmetry, and (4) hexosamine content in gastric mucosa. The gastric mucosal blood flow was significantly higher in the PHT + teprenone group than in the PHT + placebo group (463 +/- 75 and 381 +/- 82 perfusion units, respectively; p < 0.05). The hexosamine content was significantly lower in PHT rats than in sham-operated controls (12.6 +/- 2.3 vs. 14.3 +/- 2.2 micrograms/mg, respectively). Teprenone treatment significantly increased the gastric mucosal hexosamine concentration in both sham-operated and PHT rats (17.2 +/- 3.1 and 15.6 +/- 3.6 micrograms/mg, respectively). These effects of teprenone, combined with its known prostaglandin-stimulating action, suggest a potential role for this agent in the treatment of PHT gastric mucosal abnormalities.

The effect of Polyethylene Glycol-Superoxide Dismutase on gastric mucosa and survival in shock with tissue injury

Oxygen-derived free radicals may play an important role in the pathogenesis of organ injury and death following hemorrhagic shock. This study was designed to test the effects of Polyethylene Glycol-Superoxide Dismutase (PEG-SOD) on gastric mucosal injury and survival in an animal model of hemorrhagic shock and tissue trauma. Reproducible tissue trauma was produced by IM injection of turpentine (1.4 microliters/g). A standardized hemorrhagic shock model with an LD 90 was employed. This model consisted of the following sequence of events: phlebotomy to 60 per cent blood volume, 45-minute shock period, resuscitation using Lactated Ringers (LR) at two times shed volume over 60 minutes. Twenty rats were randomly assigned to receive LR (control) or PEG-SOD (5.36 mg/kg). Immediately following the death or at 72 hours, the stomach was removed. Computer image analysis was used to determine the lesion area as a per cent of total gastric mucosal surface area. Our results show no statistical difference in gastric mucosal lesion area between groups (1.83% vs 1.75%, respectively). Survival at 72 hours was significantly higher for PEG-SOD animals vs controls (70% vs 10%, P = 0.0001). This data suggests that IV administration of PEG-SOD during resuscitation is a potentially effective means of improving survival following severe hemorrhagic shock and tissue injury.

Collateral ablation improves portal perfusion after partial portacaval shunt

Small-diameter portacaval H-grafts (partial shunts) effectively abolish bleeding from esophageal varices. Goals are 1) to prevent variceal hemorrhage by subtotal portal decompression, and 2) to minimize postshunt encephalopathy by maintaining substantial residual pressure and prograde flow in the portal vein. To reduce spontaneous shunting of portal blood away from the liver, we advocate ablation of collateral vessels after partial shunts. Others have performed partial shunts without collateral ablation. We postulated that ablation of collateral vessels would augment portal perfusion pressure and preserve prograde portal flow after partial shunts. In 15 patients undergoing 8 or 10 mm portacaval H-grafts, portal pressure was measured intraoperatively before and after ligation of principal venous collaterals. In another 13 patients, collateral embolization was performed during postoperative portography. The degree of portal perfusion was scored. Pressure measurements demonstrated a mean rise in portal pressure of 2.8 cm saline after ligation (P = 0.025). Angiographic perfusion scores after embolization improved by a mean of 0.57 points on a 4 point scale (P = 0.032). We conclude that intraoperative collateral ligation augments residual portal pressures and that postoperative collateral embolization improves portal flow patterns. Since both observed effects have been associated with decreased postshunt encephalopathy rates, ablation of collateral vessels must be an integral component of the partial portacaval shunt.

Surgical management of portal hypertension

Portal hypertension is frequently complicated by upper gastrointestinal tract bleeding and ascites. Hemorrhage from esophageal varices is the most common cause of death from portal hypertension. Medical treatment, including resuscitation, vasoactive drugs, and endoscopic sclerosis, is the preferred initial therapy. Patients with refractory hemorrhage frequently are referred for immediate surgical intervention (usually emergency portacaval shunt). An additional cohort of patients with a history of at least 1 episode of variceal hemorrhage is likely to benefit from elective shunt operations. Shunt operations are classified as total, partial, or selective shunts based on their hemodynamic characteristics. Angiographically created shunts have been introduced recently as an alternative to operative shunts in certain circumstances. Devascularization of the esophagus or splenectomy is done for specific indications. Medically intractable ascites is a separate indication for surgical intervention. Liver transplantation has been advocated for patients whose portal hypertension is a consequence of end-stage liver disease. In the context of an increasingly complex set of treatment options, we present an overview of surgical therapy for complications of portal hypertension.

Analysis of nutrient hepatic blood flow after 8-mm versus 16-mm portacaval H-grafts in a prospective randomized trial

BACKGROUND

In previous unrandomized studies, we demonstrated that patients undergoing 8-mm diameter portacaval H-grafts with collateral ablation (partial shunts) have lower rates of portasystemic encephalopathy (PSE) postoperatively than patients undergoing total portacaval shunts. We postulated that nutrient hepatic blood flow was greater after partial shunts because 8-mm grafts preserved some portal flow.

METHODS

To test this hypothesis, we analyzed hepatic hemodynamics in 18 of 30 randomized patients who consented to be studied after complete operative recovery, grouped according to shunt size. We measured nutrient hepatic blood flow using 99m-Tc-Mebrofenin tracer elimination kinetics, and fractionated it into its portal venous and hepatic arterial components. PSE was assessed by blinded observers. Stepwise logistic regression was used to select the variable that best predicted encephalopathy. From 1989 to 1993, we conducted a randomized, prospective trial of partial (8 mm) versus total (16 mm) portacaval H-grafts. Group differences were compared using one-way analysis of variance (ANOVA).

RESULTS

Hepatic encephalopathy occurred in 2 of 10 patients with partial shunts versus 5 of 8 patients with total shunts. Nutrient hepatic blood flow was significantly higher for partial shunts compared with total shunts (403 +/- 601 versus 243 +/- 17mL/min). Three variables--nutrient hepatic blood flow, portal blood flow, and hepatic arterial flow--were analyzed by stepwise logistic regression. Nutrient hepatic blood flow was selected as the best predictor of hepatic encephalopathy. In this series, PSE did not occur in any patient with more than 325 mL/min of nutrient hepatic blood flow.

CONCLUSION

These findings provide a physiologic basis for clinical observations demonstrating a lower incidence of PSE with partial shunts and indicates the superiority of partial over total shunts. Partial shunts, by preserving portal flow, maintain higher nutrient hepatic blood flow than total shunts and thus minimize PSE rates.

Quality of gastric ulcer healing. Is it influenced by antiulcer drugs?

BACKGROUND

Chronic administration of sucralfate (SCR), a non-systemic ulcer-healing drug, exerts a trophic action on the gastric mucosa and prevents or reduces ulcer recurrence. The aim of this study was to determine whether SCR and/or the acid inhibiting drug omeprazole (OME) may affect the quality of ulcer healing, i.e., restoration of mucosal architecture.

METHODS

Gastric ulcers were produced in male rats by serosal application of acetic acid. Rats were gavaged twice daily for 14 days with 2 ml of: (a) Placebo (PLA), (b) SCR 500 mg/kg, or (c) OME, 50 mg/kg starting 48 h after ulcer induction. We determined ulcer size under a dissecting microscope, and performed quantitative histologic assessment of quality of healing score (QS) on a scale from 0 (normal) to 5 (most abnormal).

RESULTS

Ulcer size was 1.4 +/- 0.15 mm in the PLA group, 0.61 +/- 0.1 mm in the SCR group and 0.86 +/- 0.13 mm in the OME group (both OME and SCR p < 0.01 versus PLA). In the PLA group, histology showed (in rats with ulcers) a well-developed ulcer margin with cystically dilated glands. The QS of the ulcer scar in the PLA group was 3.3 +/- 0.22. IN the SCR-treated group, within the scar gastric glands were less dilated, more vertically oriented and the healing zone and granulation tissue were well developed and organized. The QS was 1.6 +/- 0.2, p < 0.001 versus PLA and OME. In the OME group, the ulcer margin and the scar were thinner-reduction of mucosal thickness by 43 +/- 2% (p < 0.005) and 18 +/- 1%, respectively, versus SCR and PLA groups. The number of dilated glands and connective tissue components in the scar was increased by 60%. The QS was 3.6 +/- 0.3.

CONCLUSIONS

(1) Both SCR and OME significantly reduced the size of the experimental gastric ulcer. (2) Restoration of mucosal architecture, assessed quantitatively, was much better in the SCR than in the OME and PLA-treated groups. (3) a trophic action of SCR on the gastric mucosa may be the basis of better quality of ulcer healing with SCR.

Cellular and molecular mechanisms of gastric ulcer healing. Is the quality of mucosal scar affected by treatment?

BACKGROUND

Ulcer healing, i.e. the reconstruction of the mucosal architecture, is an active process of filling the mucosal defect with proliferating and migrating epithelial cells and connective tissue.

METHODS

This article represents a summary of histologic and ultrastructural assessment of the cellular events occurring during healing of experimental gastric ulcer.

RESULTS

Mucosa adjacent to the ulcer crater forms a 'healing' zone. The gastric glands in this zone dilate and the epithelial cells lining these glands de-differentiate, express epidermal growth factor receptor, and proliferate. The latter is the result of local activation of genes encoding for EGF and its receptors. At the ulcer margin, proliferating and dividing epithelial cells migrate onto the granulation tissue to cover (re-epithelialize) the ulcer and bud into granulation tissue to reconstruct glandular structures within the ulcer scar. Re-epithelialization and reconstruction of epithelial structures is under control of epidermal growth factor (EGF) and related peptides which are produced locally by regenerating cells. Under control of fibroblast growth factors, granulation connective tissue grows extensively supplying (a) microvessels for restoration of the microvascular network and (b) connective tissue cells for restoration of the lamina propria within the mucosal scar. The final outcome of the healing process reflects a dynamic interaction between the epithelial component for the 'healing' zone at the ulcer margin and the connective tissue component (including microvessels) originating from the granulation tissue. Depending on these interactions, mucosal scar can be of good quality (restoration close to normal) or poor quality. While a number of pharmacologic agents affect gastric ulcer healing, it is unknown whether these drugs affect the quality of mucosal architecture reconstruction. In previous studies, we demonstrated that sucralfate exerts a trophic effect on gastric mucosa and, compared with omeprazole, improves the quality of restored mucosal structures within the scar of healed gastric ulcers. In the most recent studies, we demonstrated that treatment with sucralfate activates genes for EGF, bFGF, and their receptors, significantly increasing (vs placebo and omeprazole) expression of EGF and its receptor in ulcerated gastric mucosa.

CONCLUSION

Thus, the superior quality of ulcer healing by sucralfate (versus omeprazole) is most likely based on its capacity to induce and stimulate expression of EGF, bFGF, and their receptors.

The role of extracellular matrix in injury to gastric mucosa by indomethacin

The extracellular matrix components fibronectin, collagen IV, and laminin provide structural support for the gastric mucosal cells and influence cell migration, attachment, differentiation, and proliferation. Because little is known about the effect of indomethacin on the extracellular matrix, we studied the expression and distribution of extracellular matrix components in the gastric mucosa before and sequentially during indomethacin injury. A total of 32 male Sprague-Dawley rats were treated with placebo or indomethacin 100 mg intraperitoneally. One, 4, and 18 h later, stomachs were excised and gastric specimens were immunostained with specific antibodies against fibronectin (FN), collagen IV (CIV), laminin (LM), fibronectin receptor (FNR), and vimentin (VM). Gross necrosis, quantitative histology, and expression of FN, CIV, LM, FNR, and VM were analyzed using a videoimage analysis system. In the mucosa treated with indomethacin, the expression of VM and LM was decreased by 54% (p < 0.01) and 52% (p < 0.01), respectively, within 1 h vs. control mucosa. The former reflected damage to endothelial cells. Expression of FN, FNR, and CIV was decreased by 50, 25, and 50%, respectively, at 1 h after indomethacin, reflecting significant damage to the extracellular matrix. However, at 1 h, no gross necrosis and no histologic damage were seen in the gastric mucosa. We conclude that expression of extracellular matrix components in the gastric mucosa is significantly reduced during indomethacin injury and that damage to extracellular matrix and microvascular endothelium precedes injury of glandular epithelial cells.

Partial versus total portacaval shunt in alcoholic cirrhosis. Results of a prospective, randomized clinical trial

OBJECTIVE

Results of the first prospective randomized clinical trial comparing partial and total portacaval shunt for variceal hemorrhage are reported.

SUMMARY BACKGROUND DATA

Total portacaval shunts produce subnormal portal pressures, completely diverting hepatic portal flow. Partial shunts maintain higher pressures and preserve hepatopedal flow. No randomized trials of these two approaches have been performed.

METHODS

Alcoholic patients with cirrhosis (n = 30) and variceal hemorrhage treated at one institution were randomized to receive partial (8-mm diameter portacaval H grafts with collateral ablation, n = 14) or total shunts (16-mm diameter grafts, n = 16). Portography was performed after operation and then yearly. Investigators blinded to shunt type assessed encephalopathy; hospitalizations were reviewed.

RESULTS

Child's class, age, and operative urgency were similar for the two groups. Two patients (with total shunts) died within 30 days. Hepatopedal flow was maintained in 13 partial and 0 total shunt patients (p < 0.0001). Shunt gradients were 16 +/- 5 compared with 6 +/- 3 cm saline after partial and total shunts (p < 0.0001). There were no shunt thromboses or variceal hemorrhages. Encephalopathy-free survival was significantly greater after partial shunts (p = 0.013; life table analysis). Five total compared with zero partial shunt patients required hospitalization for coma (p = 0.02). Long-term survival was not different for the two groups of patients.

CONCLUSIONS

Partial shunts control variceal hemorrhage while maintaining hepatopedal flow and elevated portal pressures. By minimizing encephalopathy rates, partial shunts provide improved quality of survival compared with total shunts.

Distorted microangioarchitecture and impaired angiogenesis in gastric mucosa of portal hypertensive rats

BACKGROUND/AIMS

Portal hypertensive (PHT) gastropathy is now recognized as a distinct entity, but the size of microvessels has been a subject of controversy. Angiogenesis in PHT gastric mucosa has not been explored. The aim of this study was to examine the angioarchitecture of PHT and non-PHT gastric mucosae before and after ethanol-induced injury utilizing microvascular cast techniques.

METHODS

Portal hypertension was produced by staged portal vein occlusion. Fourteen days later, gastric vascular casts were made in both PHT and control (sham-operated) rats by Mercox resin infusion. After tissue dissolution, casts were examined under a scanning electron microscope. To examine angiogenesis in injured gastric mucosa, the above study was repeated in PHT and control rats 18 hours after intragastric administration of 100% ethanol.

RESULTS

The capillary casts in PHT gastric mucosa (mean diameter, 6.3 +/- 0.03 microns) were significantly narrower than those of controls (mean diameter, 8.6 +/- 0.02 microns; P < 0.01). After ethanol injury, 5.5% +/- 0.3% of microvessels in gastric mucosa of sham-operated rats contained buds, showing angiogenesis. In contrast, PHT gastric mucosa had a paucity of capillary angiogenesis (buds in only 0.4% +/- 0.2% of microvessels; P < 0.01 vs. control).

CONCLUSIONS

This study shows prominent persistent abnormalities in the microangioarchitecture of PHT gastric mucosa. Moreover, PHT gastric mucosal microvessels have a marked impairment of angiogenic response to ethanol injury.

Narrow-diameter portacaval shunts for management of variceal bleeding

Over the past decade, we have developed and refined a method for partial portosystemic shunting for the control of bleeding esophageal varices in alcoholic cirrhotic patients. The narrow-diameter interposition portacaval H-graft using 8 mm polytetrafluoroethylene has been performed in 32 patients at our institution with low operative mortality (6.3%) and nearly complete cessation of variceal bleeding (96.7%) over a mean follow-up period of 43 months. In comparison with total shunts, diminished rates of postshunt encephalopathy (13% versus 40%) have been observed. Prograde portal blood flow has been preserved in 90% of 30 patients studied by perioperative portography. Shunt patency with continued prograde flow has been demonstrated at up to 9 years of follow-up. Investigators at three other centers have studied partial shunting using substantially similar techniques, with similar findings. Based on these results, we conclude that narrow-diameter shunts provide effective, long-lasting treatment for variceal hemorrhage due to portal hypertension in the alcoholic.

Increased susceptibility to injury and normal reactivity to prostaglandin protection of mucous cells isolated from gastric mucosa of portal hypertensive rats

We examined the susceptibility of mucous cells isolated from gastric mucosa of portal hypertensive rats to ethanol injury. In addition, we assessed their response to protective action of prostaglandin against ethanol injury in vitro. Ethanol significantly decreased cell viability in calcium-containing medium. The injury of mucous cells isolated from portal hypertensive rats was more extensive than those isolated from sham-operated rats. Ethanol-induced cell injury was reduced similarly in both groups by pretreatment with 16,16-dimethyl prostaglandin E2. These results suggest that mucous cells isolated from portal hypertensive gastric mucosa are more susceptible to ethanol injury and this susceptibility is dependent on extracellular calcium. The cells from portal hypertensive gastric mucosa retain, however, sensitivity to protective action of 16,16-dimethyl prostaglandin E2.

Comparison of continuous single layer polypropylene anastomosis with double layer and stapled anastomoses in elective colon resections

The documented leak rate of the continuous single layer polypropylene (CSLP) anastomosis in elective colon resection is 0-6 per cent. It is more cost effective than stapling (S), and should be faster and easier to perform than the double-layer (DL) technique. However, there have been no reported series comparing the outcome of the CSLP anastomosis with the DL and S techniques. We reviewed the charts of 100 patients with elective colon resections. Eighty-four had data sufficient for analysis. There were 44 CSLP, 21 DL, and 19 S. The groups were comparable with respect to 12 preoperative variables. Proportionately more large-small bowel anastomoses were performed in the S group, and no patient in the S group was actively taking steroids. Clinical outcome was assessed. All leaks were clinically apparent and documented with contrast enema or laparotomy. The leak rate for the CSLP was 6.8 per cent (3/44). Two of the three patients with leaks were taking steroids. There were two leaks in the DL group (9.5%), one of which was taking steroids, and no leaks in the S group. The difference in leak rate between the three groups was not statistically significant. The average cost for CSLP at our institution is $4.00 compared with $8.00 and $35.00 for the DL and S, respectively. We conclude that the CSLP is a reasonable and safe alternative to DL and S anastomoses.

Epidermal growth factor protects gastric mucosa against ischemia-reperfusion injury

Epidermal growth factor (EGF) protects gastric mucosa against many injurious factors, but no study has examined whether EGF may protect against ischemia-reperfusion (I-R)-induced gastric mucosal injury. We assessed the effect of EGF pretreatment on the extent of ischemia-reperfusion-induced gastric mucosal damage in rats. Assessment of injury and protection included: the extent of macroscopic necrosis; qualitative and quantitative histology with measurement of deep mucosal necrosis; microvascular permeability after injection of fluorescein-conjugated albumin; and transmission electron microscopy. After I-R, saline-pretreated rats (placebo group) had macroscopic necrosis involving 40 +/- 6% of total gastric mucosal area. Histology revealed exfoliation of the surface epithelial cells, mucosal hemorrhages, microvascular injury, and extensive deep mucosal necrosis involving 7 +/- 5% of mucosal strips. Microvascular permeability assessed by fluorescein-conjugated albumin was significantly increased to 327 +/- 29% of that in normal rats (without ischemia-reperfusion). Transmission electron microscopy showed severe microvascular injury. EGF pretreatment significantly reduced gross mucosal necrosis to 17 +/- 6% and deep histologic mucosal necrosis to 2 +/- 1% (both p < 0.01 versus saline pretreated). Integrity of the mucosal microvessels was preserved and microvascular permeability was close to normal. This study demonstrates that EGF significantly reduces ischemia-reperfusion injury to the rat gastric mucosa and that this effect of EGF may be mediated by its protection of the mucosal microvessels.

Surgical treatment of enteric 'bud' fistulas in contaminated wounds. A riskless extraperitoneal method using split-thickness skin grafts

We describe methods and results of a local extraperitoneal method of repairing enterocutaneous "bud" fistulas in abdominal-wall defects. The method is performed with local anesthesia and involves an extraperitoneal closure with skin-graft coverage. Of the nine fistulas so treated, five healed. No patient's postoperative course was set back by the repairs that failed since the method precludes intraperitoneal entrance. Two of three high-output fistulas were successfully repaired with the extraperitoneal method, reversing an otherwise stormy clinical course. We conclude that for epithelialized enterocutaneous fistulas, little is lost if our method of repair fails and much is gained if it is successful in these critically ill patients.

Epidermal growth factor protects portal hypertensive gastric mucosa in ischemia/reperfusion: the role of capillary endothelia and prostaglandins

BACKGROUND

Epidermal growth factor (EGF) protects gastric mucosa against a variety of injurious agents, but the mechanism is unclear. Because the abnormal microvasculature of portal hypertensive (PHT) gastric mucosa is a major target of ischemia/reperfusion (I/R) injury, we used this model to assess EGF's protective role at the microvascular level.

METHODS

Rats with PHT (staged portal vein ligation) received either EGF, 20 micrograms/kg, or saline solution intravenously, with or without indomethacin pretreatment (20 mg/kg subcutaneously). I/R was produced by withdrawing blood to systemic pressures of 30 mm Hg for 20 minutes and reinfusing it. Stomachs were excised 20 minutes later and evaluated for gross and histologic necrosis, microvascular permeability, mucosal ultrastructure and vimentin, and cyclooxygenase immunofluorescence.

RESULTS

In saline-treated rats, gross and histologic damage involved 46% +/- 3% of glandular mucosa and 23% +/- 3% of mucosal sections, respectively. Microvascular permeability was increased 43-fold over that of normal control rats. Vimentin immunofluorescence intensity was reduced to 36% +/- 4% that of normal control rats. EGF pretreatment reduced histologic necrosis to 2% +/- 1% (p less than 0.01). Microvascular permeability and vimentin intensity were almost normalized. Indomethacin partially reversed the mucosal protection induced by EGF.

CONCLUSIONS

EGF significantly reduces I/R injury to PHT gastric mucosa. Microvascular endothelia of PHT gastric mucosa are the major target of I/R injury and the site of EGF's protective action. Prostaglandins in part mediate EGF's protective action.

Increased expression of epidermal growth factor receptor during gastric ulcer healing in rats

Expression of epidermal growth factor receptor (EGFR) was studied immunohistochemically in rat gastric mucosa during healing of acetic acid-induced ulcers. In normal control gastric oxyntic mucosa, EGFR was expressed in proliferative zone cells and in some parietal cells. In mucosa of the ulcer margin, at 3, 7, and 16 days after ulcer induction, there was a 75-fold increase (over controls) in the number of cells expressing EGFR. Seventy percent of ulcers healed by the 16th day, and all were healed by the 25th day. The mucosal scar that replaced the ulcer was composed of dilated glands lined with poorly or aberrantly differentiated cells showing persistence of increased EGFR expression. An increased EGFR expression indicates an important role of EGF in ulcer healing and scar formation.

Adaptation of gastric mucosa to chronic alcohol administration is associated with increased mucosal expression of growth factors and their receptor

In our previous study we found that chronic, intragastric administration of ethanol to rats produces adaptation of the gastric mucosa to subsequent challenge with an acute dose of 50% ethanol. The mechanism of this mucosal tolerance remains unexplained. Epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) stimulate cells growth and proliferation in the gastric mucosa with noted trophic effect, protect the gastric mucosa against acute injury and accelerate healing of injured mucosa. Many of these effects are exerted through EGF and TGF alpha action on their common receptor (EGFR). The aim of the present study was to determine the effect of chronic alcohol administration on cell proliferation and gastric mucosal expression and distribution of EGF, TGF alpha and EGFR. Chronic administration of ethanol (1 ml, 50% ethanol, twice daily) significantly increased the extent of gastric mucosal mucous and proliferative cell zones, the number of proliferating (DNA synthesizing) cells and mucosal expression of EGF, TGF alpha and EGFR by 13, 6, and 20-fold, respectively. Thus, adaptation of gastric mucosa to chronic alcohol administration is associated with increased cell proliferation and increased expression of mucosal EGF, TGF alpha and EGFR.

Increased susceptibility of the portal hypertensive gastric mucosa to damage

Portal hypertensive gastropathy has recently been recognized as a unique entity distinct from other gastropathies involving the normotensive gastric mucosa. To delineate the pathophysiology of this disorder, we developed a rat model of portal hypertension using two-staged portal vein ligation. In this model, features of the portal hypertensive mucosa include increased luminal hydrogen ion loss, reduced electronegativity of potential difference, and increased submucosal edema. Ultrastructurally, the portal hypertensive gastric mucosa has marked endothelial hypertrophy of capillaries resulting in prominent compromise of microvascular lumina. Combined with the submucosal edema, the microvasculopathy results in reduced oxygenation of the surface gastric mucosa. This is associated with diminished prostaglandin production, which impairs gastric mucosal protection in portal hypertension. These observations are strengthened by experiments that demonstrated significantly increased gastric mucosal damage by alcohol, bile acids, aspirin, and shock/reperfusion in portal hypertensive rats compared to normotensive sham-operated controls. Many of our experimental findings have been confirmed clinically; however, much more research in this area is clearly needed.