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

The relationship between portal hypertension and portal hypertensive gastropathy

BACKGROUND AND AIM

Portal hypertensive gastropathy (PHG) most commonly occurs in the setting of increased portal pressure in patients with cirrhosis. Here, we aimed to understand the correlation between hepatic venous pressure gradient (HVPG) and the presence and severity of PHG in patients with cirrhosis.

METHODS

We examined patients with cirrhosis who underwent HVPG measurement at the Medical University of South Carolina between 2014 and 2020. Extensive demographic, clinical, laboratory, procedural (including precise grading of PHG severity using standard definitions), and outcome data were abstracted at the time of HVPG measurement.

RESULTS

Three hundred and ten patients with HVPG measurements and cirrhosis were identified. Seventy-three patients having endoscopy within 6 months of HVPG measurement were included (mean age 54 ± 11, 44% female). The most common causes of cirrhosis were alcohol (41%) and non-alcoholic steatohepatitis (32%). The average HVPG was 15 mmHg (±6) and 62 patients had clinically significant portal hypertension (CSPH) (HVPG ≥ 10 mmHg). Of the 73 patients with HVPG measured, 45 (62%) had PHG, including 40 (89%) of whom had CSPH. Out of the 45 patients with PHG, 41 and four had mild or severe PHG, respectively. MELD scores were similar in patients with and without PHG [15 ± 9 (SD) and 17 ± 9, respectively; p = .37]. HVPG was higher in patients with PHG (17 ± 7 mmHg) than those without PHG (13 ± 4 mmHg) (p = .01) but did not differ between mild and severe PHG.

CONCLUSION

A weak correlation exists between HVPG level and the presence of PHG.

An Update: Portal Hypertensive Gastropathy and Colopathy

Complications of portal hypertension include portal hypertensive gastropathy and colopathy. These disorders may cause chronic or acute gastrointestinal bleeding. The diagnosis is made endoscopically; therefore, there is great variability in their assessment. Portal hypertensive gastropathy can range from a mosaic-like pattern resembling snakeskin mucosa to frankly bleeding petechial lesions. Portal hypertensive colopathy has been less well-described and is variably characterized (erythema, vascular lesions, petechiae). Treatment is challenging and results are inconsistent. Currently, available evidence does not support the use of beta-blockers for primary prevention. Further investigation of the pathogenesis, natural history, and treatment of these disorders is needed.

Portal hypertensive gastropathy: A systematic review of the pathophysiology, clinical presentation, natural history and therapy

AIM

To describe the pathophysiology, clinical presentation, natural history, and therapy of portal hypertensive gastropathy (PHG) based on a systematic literature review.

METHODS

Computerized search of the literature was performed via PubMed using the following medical subject headings or keywords: "portal" and "gastropathy"; or "portal" and "hypertensive"; or "congestive" and "gastropathy"; or "congestive" and "gastroenteropathy". The following criteria were applied for study inclusion: Publication in peer-reviewed journals, and publication since 1980. Articles were independently evaluated by each author and selected for inclusion by consensus after discussion based on the following criteria: Well-designed, prospective trials; recent studies; large study populations; and study emphasis on PHG.

RESULTS

PHG is diagnosed by characteristic endoscopic findings of small polygonal areas of variable erythema surrounded by a pale, reticular border in a mosaic pattern in the gastric fundus/body in a patient with cirrhotic or non-cirrhotic portal hypertension. Histologic findings include capillary and venule dilatation, congestion, and tortuosity, without vascular fibrin thrombi or inflammatory cells in gastric submucosa. PHG is differentiated from gastric antral vascular ectasia by a different endoscopic appearance. The etiology of PHG is inadequately understood. Portal hypertension is necessary but insufficient to develop PHG because many patients have portal hypertension without PHG. PHG increases in frequency with more severe portal hypertension, advanced liver disease, longer liver disease duration, presence of esophageal varices, and endoscopic variceal obliteration. PHG pathogenesis is related to a hyperdynamic circulation, induced by portal hypertension, characterized by increased intrahepatic resistance to flow, increased splanchnic flow, increased total gastric flow, and most likely decreased gastric mucosal flow. Gastric mucosa in PHG shows increased susceptibility to gastrotoxic chemicals and poor wound healing. Nitrous oxide, free radicals, tumor necrosis factor-alpha, and glucagon may contribute to PHG development. Acute and chronic gastrointestinal bleeding are the only clinical complications. Bleeding is typically mild-to-moderate. Endoscopic therapy is rarely useful because the bleeding is typically diffuse. Acute bleeding is primarily treated with octreotide, often with concomitant proton pump inhibitor therapy, or secondarily treated with vasopressin or terlipressin. Nonselective β-adrenergic receptor antagonists, particularly propranolol, are used to prevent bleeding after an acute episode or for chronic bleeding. Iron deficiency anemia from chronic bleeding may require iron replacement therapy. Transjugular-intrahepatic-portosystemic-shunt and liver transplantation are highly successful ultimate therapies because they reduce the underlying portal hypertension.

CONCLUSION

PHG is important to recognize in patients with cirrhotic or non-cirrhotic portal hypertension because it can cause acute or chronic GI bleeding that often requires pharmacologic therapy.

Strawberry phytochemicals inhibit azoxymethane/dextran sodium sulfate-induced colorectal carcinogenesis in Crj: CD-1 mice

Human and experimental colon carcinogenesis are enhanced by a pro-inflammatory microenvironment. Pharmacologically driven chemopreventive agents and dietary variables are hypothesized to have future roles in the prevention of colon cancer by targeting these processes. The current study was designed to determine the ability of dietary lyophilized strawberries to inhibit inflammation-promoted colon carcinogenesis in a preclinical animal model. Mice were given a single i.p. injection of azoxymethane (10 mg kg⁻¹ body weight). One week after injection, mice were administered 2% (w/v) dextran sodium sulfate in drinking water for seven days and then an experimental diet containing chemically characterized lyophilized strawberries for the duration of the bioassay. Mice fed control diet, or experimental diet containing 2.5%, 5.0% or 10.0% strawberries displayed tumor incidence of 100%, 64%, 75% and 44%, respectively (p < 0.05). The mechanistic studies demonstrate that strawberries reduced expression of proinflammatory mediators, suppressed nitrosative stress and decreased phosphorylation of phosphatidylinositol 3-kinase, Akt, extracellular signal-regulated kinase and nuclear factor kappa B. In conclusion, strawberries target proinflammatory mediators and oncogenic signaling for the preventive efficacies against colon carcinogenesis in mice. This works supports future development of fully characterized and precisely controlled functional foods for testing in human clinical trials for this disease.

Review article: the management of portal hypertensive gastropathy and gastric antral vascular ectasia in cirrhosis

BACKGROUND

Portal hypertensive gastropathy (PHG) and gastric antral vascular ectasia (GAVE) are important causes of both acute and chronic gastrointestinal bleeding in patients with cirrhosis.

AIM

To review the current management of PHG and GAVE.

METHODS

PubMed was searched for English language articles using the key words 'GAVE', 'gastric antral vascular ectasia', 'cirrhosis', 'gastrointestinal bleeding', 'acute', 'chronic', 'portal hypertensive gastropathy', 'watermelon stomach', 'radiofrequency ablation', 'band ligation', 'thermoablation' and 'TIPSS'.

RESULTS

GAVE and PHG are both encountered in patients with cirrhosis. They can be seen in asymptomatic patients and in those with either acute or chronic gastrointestinal bleeding. PHG, by definition, requires the presence of portal hypertension, with or without cirrhosis, whereas GAVE requires neither cirrhosis nor portal hypertension. They can often be diagnosed on endoscopic appearance alone, but may require biopsy in certain cases. The treatment of PHG is aimed at reducing hepatic venous pressure gradients, most often by pharmacologic means, but may require shunt procedures in severe cases. Management of GAVE on the other hand is predominantly endoscopic, focusing on various ablative techniques.

CONCLUSIONS

Gastric antral vascular ectasia and portal hypertensive gastropathy are distinct entities and are both encountered in cirrhotic patients. Management of portal hypertensive gastropathy is centred on reduction in portal pressures, whereas treatment of gastric antral vascular ectasia is predominantly endoscopic.

Resveratrol suppresses colitis and colon cancer associated with colitis

Resveratrol is a naturally occurring polyphenol that exhibits pleiotropic health beneficial effects, including anti-inflammatory, cardio-protective, and cancer-protective activities. It is recognized as one of the more promising natural molecules in the prevention and treatment of chronic inflammatory and autoimmune disorders. Ulcerative colitis is an idiopathic, chronic inflammatory disease of the colon associated with a high colon cancer risk. Here, we used a dextran sulfate sodium (DSS) mouse model of colitis, which resembles human ulcerative colitis pathology. Resveratrol mixed in food ameliorates DSS-induced colitis in mice in a dose-dependent manner. Resveratrol significantly improves inflammation score, downregulates the percentage of neutrophils in the mesenteric lymph nodes and lamina propria, and modulates CD3(+) T cells that express tumor necrosis factor-alpha and IFN-gamma. Markers of inflammation and inflammatory stress (p53 and p53-phospho-Ser(15)) are also downregulated by resveratrol. Because chronic colitis drives colon cancer risk, we carried out experiments to determine the chemopreventive properties of resveratrol. Tumor incidence is reduced from 80% in mice treated with azoxymethane (AOM) + DSS to 20% in mice treated with AOM + DSS + resveratrol (300 ppm). Tumor multiplicity also decreased with resveratrol treatment. AOM + DSS-treated mice had 2.4 +/- 0.7 tumors per animal compared with AOM + DSS + 300 ppm resveratrol, which had 0.2 +/- 0.13 tumors per animal. The current study indicates that resveratrol is a useful, nontoxic complementary and alternative strategy to abate colitis and potentially colon cancer associated with colitis.

Downregulation of cyclooxygenase-1 is involved in gastric mucosal apoptosis via death signaling in portal hypertensive rats

Portal hypertension (PHT) gastropathy is a frequent complication of liver cirrhosis and one of the leading causes of death from cirrhosis. Apoptosis is widely considered to be an active energy-dependent mode of cell death and a distinct entity from necrotic cell death. It is unclear whether gastric mucosal apoptosis is involved in PHT gastropathy. Prostaglandins (PGs) produced through cyclooxygenase (COX) are thought to play a key role in protection of the gastrointestinal mucosa from injury and apoptosis. However, the role of COX in PHT gastropathy is still not clearly understood. The aims of this study were to investigate whether (1) gastric mucosal apoptosis is involved in PHT gastropathy and (2) downregulation of COX contributes to this apoptosis. In this study, we show that gastric mucosal apoptosis was remarkably increased while mucosal proliferation was inhibited in PHT rats. Gastric mucosal COX-1 was significantly suppressed at both the mRNA and protein levels, and PGE(2) was reduced in PHT rats. Further, PGE(2) treatment suppressed gastric mucosal apoptosis in PHT rats. However, gastric mucosal COX-2 levels did not differ between sham-operated rats and PHT rats. Gastric mucosal levels of tumor necrosis factor-alpha (TNF-alpha) and Fas ligand, but not TNF-related apoptosis-inducing ligand, were increased, and activated caspase-8 and caspase-3 levels were upregulated in PHT rats. The release of cytochrome c from the mitochondria to the cytosol was not observed in PHT rats. Our data indicate that downregulation of COX-1 is involved in gastric mucosal apoptosis via death signaling-mediated type-I cell death in PHT rats.

Role of the endothelium on vasoactive agents in patients with liver cirrhosis

BACKGROUND AND AIM

Patients with liver cirrhosis exhibit peripheral vasodilatation and decreased vasoconstrictor responsiveness. We investigated the role of the endothelium in these patients.

METHODS

Nine patients with cirrhosis and seven controls were recruited. Responses to acetylcholine, bradykinin and sodium nitroprusside were obtained using forearm plethysmography. Responses to norepinephrine (100 ng/min) were obtained in the absence and combined presence of the cyclo-oxygenase inhibitor, indomethacin, and the nitric oxide (NO) synthase inhibitor, N(G)-monomethyl-L-arginine.

RESULTS

Responses to acetylcholine (area under curve: controls vs cirrhotic, 10326 +/- 1400 vs 18490 +/- 2787 units; P = 0.036), but not to bradykinin (15619 +/- 3557 vs 12415 +/- 3823 units) or sodium nitroprusside, were significantly higher in patients with cirrhosis. Responses to norepinephrine were significantly dampened in cirrhotics (percentage increase in forearm blood flow; controls vs cirrhotics, -50.50 +/- 2.69 vs-26.39 +/- 5.44; P = 0.036) but this blunted response was no longer apparent following the administration of both blockers.

CONCLUSIONS

We conclude that: (i) there is an increased response to acetylcholine but not to bradykinin; and (ii) that an enhanced production of prostacyclin and/or NO is responsible for the dampened response to norepinephrine.

Expression of TNF-α and VEGF in the esophagus of portal hypertensive rats

AIM: To investigate the expression of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) in the development of esophageal varices in portal hypertensive rats.

METHODS: Thirty male Sprague-Dawley (SD) rats in the model group in which a two-stage ligation of portal vein plus ligation of the left adrenal vein was performed, were divided into three subgroups (M₇, M₁₄, and M₂₁) in which the rats were kiued on the seventh day, the 14^th d and the 21 d after the complete portal ligation. Thirty male SD rats, which underwent the sham operation in the control group, were also separated into three subgroups (C₇, C₁₄ and C₂₁) corresponding to the models. The expression of TNF-α and VEGF in the esophagus of all the six subgroups of rats were measured with immunohistochemical SP technique.

RESULTS: The portal pressure in the three model subgroups was significantly higher than that in the corresponding control subgroups (23.82±1.83 vs 11.61±0.86 cmH₂O, 20.90±3.27 vs 11.43±1.55 cmH₂O and 20.68±2.27 vs 11.87±0.79 cmH₂O respectively, P<0.01), as well as the number (9.3±1.6 vs 5.1±0.8, 11.1±0.8 vs 5.4±1.3 and 11.7±1.5 vs 5.2±1.1 respectively, P<0.01) and the total vascular area (78972.6±3527.8 vs 12993.5±4994.8 μm², 107207.5±46461.4 vs 11862.6±5423.2 μm² and 110241.4±49262.2 vs 11973.7±3968.5 μm² respectively, P<0.01) of submucosal veins in esophagus. Compared to the corresponding controls, the expression of TNF-α and VEGF in M₂₁ was significantly higher (2.23±0.30 vs 1.13±0.28 and 1.65±0.38 vs 0.56±0.30 for TNF-α and VEGF respectively, P <0.01), whereas there was no difference in M₇ (1.14±0.38 vs 1.06±0.27 and 0.67±0.35 vs 0.50±0.24 for TNF-α and VEGF respectively, P>0.05) and M₁₄ (1.20±0.25 vs 1.04±0.26 and 0.65±0.18 vs 0.53±0.25 for TNF-α and VEGF respectively, P>0.05). And the expression of TNF-α and VEGF in M₂₁ was significantly higher than that in M₇ (2.23±0.30 vs 1.14±0.38 and 1.65±0.38 vs 0.67±0.35 for TNF-α and VEGF respectively, P<0.01) and M₁₄ (2.23±0.30 vs 1.20±0.25 and 1.65±0.38 vs 0.65±0.18 for TNF-α and VEGF respectively, P<0.01), but there was no difference between M₇ and M₁₄ (1.14±0.38 vs 1.20±0.25 and 0.67±0.35 vs 0.65±0.18 for TNF-α and VEGF respectively, P >0.05).

CONCLUSION: In the development of esophageal varices in portal hypertensive rats, increased TNF-α and VEGF may be not an early event, and probably play a role in weakening the esophageal wall and the rupture of esophageal varices.

Effects of tumor necrosis factor, endothelin and nitric oxide on hyperdynamic circulation of rats with acute and chronic portal hypertension

AIM: To evaluate the effect of tumor necrosis factor (TNF), endothelin (ET) and nitric oxide (NO) on hyperdynamic circulation (HC) of rats with acute and chronic portal hypertension (PHT).

METHODS: Chronic portal hypertension was induced in Wistar rats by injection of carbon tetrachloride. After two weeks of cirrhosis formation, L-NMMA (25 mg/kg) was injected into one group of cirrhotic rats via femoral vein and the experiment was begun immediately. Another group of cirrhotic rats was injected with anti-rat TNFα (300 mg/kg) via abdominal cavity twice within 48 h and the experiment was performed 24 h after the second injection. The blood concentrations of TNFα, ET-1 and NO in portal vein and the nitric oxide synthase (NOS) activity in hepatic tissue were determined pre-and post-injection of anti-rat TNFα or L-NMMA. Stroke volume (SV), cardiac output (CO), portal pressure (PP), superior mesenteric artery blood flow (SMA flow) and iliac artery blood flow (IAflow) were measured simultaneously. Acute portal hypertension was established in Wistar rats by partial portal-vein ligation (PVL). The parameters mentioned above were determined at 0.5 h, 24 h, 48 h, 72 h and 120 h after PVL. After the formation of stable PHT, the PVL rats were injected with anti-rat TNFα or L-NMMA according to different groups, the parameters mentioned above were also determined.

RESULTS: In cirrhotic rats, the blood levels of TNFα, NO in portal vein and the liver NOS activity were significantly increased (P < 0.05) while the blood level of ET-1 was not statistically different (P > 0.05) from the control animals (477.67 ± 83.81 pg/mL vs 48.87 ± 32.79 pg/mL, 278.41 ± 20.11 µmol/L vs 113.28 ± 14.51 µmol/L, 1.81 ± 0.06 u/mg·prot vs 0.87 ± 0.03 u/mg·prot and 14.33 ± 4.42 pg/mL vs 8.72 ± 0.79 pg/mL, respectively). After injection of anti-rat TNFα, the blood level of TNFα was lower than that in controls (15.17 ± 18.79 pg/mL vs 48.87 ± 32.79 pg/mL). The blood level of NO and the liver NOS activity were significantly decreased, but still higher than those of the controls. The blood level of ET-1 was not significantly changed. PP, SV, CO, SMAflow and IAflow were ameliorated. After injection of L-NMMA, the blood level of NO and the liver NOS activity were recovered to those of the controls. PP and CO were also recovered to those of the controls. SV, SMAflow and IAflow were ameliorated. In PVL rats, the blood levels of TNFα, NO in portal vein and the liver NOS activity were gradually increased and reached the highest levels at 48 h after PVL. The blood level of ET-1 among different staged animals was not significantly different from the control animals. PP among different staged animals (2.4 ± 0.18 kPa at 0.5 h, 1.56 ± 0.08 kPa at 24 h, 1.74 ± 0.1 kPa at 48 h, 2.38 ± 0.05 kPa at 72 h, 2.39 ± 0.16 kPa at 120 h) was significantly higher than that in controls (0.9 ± 0.16 kPa). After injection of anti-rat TNFα in 72 h PVL rats, the blood level of TNFα was lower than that in controls (14 ± 14 pg/mL vs 48.87 ± 32.79 pg/mL). The blood level of NO and the liver NOS activity were significantly decreased, but still higher than those of the controls. The blood level of ET-1 was not significantly changed. PP was decreased from 2.38 ± 0.05 kPa to 1.68 ± 0.12 kPa, but significantly higher than that in controls. SV, CO, SMAflow and IAflow were ameliorated. After injection of L-NMMA in 72 h PVL rats, the blood level of NO and the liver NOS activity were recovered to those of the controls. PP, SV, CO, SMAflow and IAflow were also recovered to those of the controls.

CONCLUSION: NO plays a critical role in the development and maintenance of HC in acute PHT and is a key factor for maintenance of HC in chronic PHT. TNFα may not participate in the hemodynamic changes of HC directly, while play an indirect role by inducing the production of NO through activating NOS. No evidence that circulating ET-1 plays a role in both models of portal hypertension has been found.

The role of nitric oxide synthase isoforms in extrahepatic portal hypertension: studies in gene-knockout mice

BACKGROUND & AIMS

Considerable debate exists concerning which isoform of nitric oxide synthase (NOS) is responsible for the increased production of NO in PHT. We used the portal vein ligation model of PHT in wild-type and eNOS- or iNOS-knockout mice to definitively determine the contribution of these isoforms in the development of PHT.

METHODS

The portal vein of wild-type mice, or those with targeted mutations in the nos2 gene (iNOS) or the nos3 gene (eNOS), was ligated and portal venous pressure (Ppv), abdominal aortic blood flow (Qao), and portosystemic shunt determined 2 weeks later.

RESULTS

In wild-type mice, as compared with sham-operated controls, portal vein ligation (PVL) resulted in a time-dependent increase in Ppv (7.72 +/- 0.37 vs 17.57 +/- 0.51 cmH(2)O, at 14 days) concomitant with a significant increase in Qao (0.12 +/- 0.003 vs 0.227 +/- 0.005 mL/min/g) and portosystemic shunt (0.47% +/- 0.01% vs 84.13% +/- 0.09% shunt). Likewise, PVL in iNOS-deficient mice resulted in similar increases in Ppv, Qao, and shunt development. In contrast, after PVL in eNOS-deficient animals, there was no significant change in Ppv (7.52 +/- 0.22 vs 8.07 +/- 0.4 cmH(2)0) or Qao (0.111 +/- 0.01 vs 0.14 +/-.023 mL/min/g). However, eNOS (-/-) mice did develop a substantial portosystemic shunt (0.33% +/- 0.005% vs 84.53% +/- 0.19% shunt), comparable to that seen in wild-type animals after PVL.

CONCLUSIONS

These data support a key role for eNOS, rather than iNOS, in the pathogenesis of PHT.

Comparison of the efficacy of octreotide, vasopressin, and omeprazole in the control of acute bleeding in patients with portal hypertensive gastropathy: a controlled study

BACKGROUND

Portal hypertensive gastropathy is an important complication of liver cirrhosis and it contributes to acute gastric bleeding. Effective management of this condition remains a clinical challenge. We assessed and compared the efficacy of octreotide, vasopressin, and omeprazole in the treatment of acute bleeding in patients with portal hypertensive gastropathy.

METHODS

Sixty-eight patients with portal hypertensive gastropathy were randomized into Octreotide, Vasopressin, and Omeprazole groups. Bleeding was monitored by observing the contents of the nasogastric tube. Blood transfusion requirements and side-effects of drugs were recorded. Repeat endoscopies were scheduled 2 weeks after treatment.

RESULTS

Complete bleeding control after 48 h of drug infusion was achieved in all patients receiving octreotide (100%), 14/22 patients receiving vasopressin (64%), and 13/22 patients receiving Omeprazole (59%). Octreotide required much less time and significantly fewer blood transfusions to control bleeding. Patients receiving vasopressin experienced more side-effects than those receiving octreotide and omeprazole. In the 17 patients whose bleeding was not controlled within 48 h by either vasopressin or omeprazole, complete bleeding control was achieved by combined use of these two agents. Follow-up endoscopy showed dramatic improvement in gastric mucosal erosions, superficial ulceration and erythema.

CONCLUSIONS

Octreotide appeared to be more effective in controlling acute bleeding in patients with hypertensive gastropathy, with significantly rapid action, smaller transfusion requirements, and minor side-effects. Simultaneous administration of vasopressin and omeprazole appeared to have additive effects.

Endothelial dysfunction in cirrhosis and portal hypertension

Portal hypertension (PHT) is a common clinical syndrome associated with chronic liver diseases; it is characterized by a pathological increase in portal pressure. Pharmacotherapy for PHT is aimed at reducing both intrahepatic vascular tone and elevated splanchnic blood flow. Due to the altered hemodynamic profile in PHT, dramatic changes in mechanical forces, both pressure and flow, may play a pivotal role in controlling endothelial and vascular smooth muscle cell signaling, structure, and function in cirrhotics. Nitric oxide, prostacyclin, endothelial-derived contracting factors, and endothelial-derived hyperpolarizing factor are powerful vasoactive substances released from the endothelium in response to both humoral and mechanical stimuli that can profoundly affect both the function and structure of the underlying vascular smooth muscle. This review will examine the contributory role of hormonal- and mechanical force-induced changes in endothelial function and signaling and the consequence of these changes on the structural and functional response of the underlying vascular smooth muscle. It will focus on the pivotal role of hormonal and mechanical force-induced endothelial release of vasoactive substances in dictating the reactivity of the underlying vascular smooth muscle, i.e., whether hyporeactive or hyperreactive, and will examine the extent to which these substances may exert a protective and/or detrimental influence on the structure of the underlying vascular smooth muscle in both a normal hemodynamic environment and following hemodynamic perturbations typical of PHT and cirrhosis. Finally, it will discuss the intracellular processes that regulate the release/expression of these vasoactive substances and that control the transformation of this normally protective cell to one that may promote the development of vasculopathy in PHT.

Protective role of intracellular glutathione against nitric oxide-induced necrosis in rat gastric mucosal cells

BACKGROUND

Nitric oxide synthase activity is increased in the stomach in association with Helicobacter pylori infection and portal hypertension, but the mechanism by which nitric oxide contributes to mucosal damage remains unclear.

AIM

To examine whether nitric oxide injures gastric mucosal cells and whether cellular glutathione affects nitric oxide-induced cytotoxicity.

METHODS

A confluent monolayer of RGM-1 gastric mucosal cells was exposed to nitric oxide donors (NOC5 or NOC12). Cell viability was determined by trypan blue dye exclusion, lactate dehydrogenase release and supravital staining with Hoechst 33342 and propidium iodide. The kinetics of the reduced/oxidized forms of glutathione were also measured, as well as the effect of glutathione-depletion or glutathione-precursor treatment on nitric oxide-induced cytotoxicity.

RESULTS

Excess exogenous nitric oxide produced by NOC5 or NOC12 induced necrosis in RGM-1 cells in a time- and concentration-dependent manner. The level of reduced glutathione drastically decreased prior to the loss of cell viability and remained low, but oxidized glutathione was not affected. Glutathione depletion increased necrosis of both NOCs in an NOC-concentration-related fashion, while pre-treatment with gamma-glutamylcysteine ethyl ester reduced their necrotic susceptibility.

CONCLUSION

Exogenous nitric oxide induced necrosis in gastric mucosal cells, and intracellular reduced glutathione protects gastric mucosal cells from damage by nitric oxide.