Role of interleukin-4 in down-regulation of endothelin-1 during gastric ulcer healing: effect of sucralfate.

BACKGROUND: The course of events associaed with healing gastric mucosal injury involves an orderly interplay between the array of signaling molecules that exert their influence on the processes leading to the restoration of the mucosal integrity. In this study, we investigated the effect of antiulcer agent, sucralfate, on the mucosal apoptotic processes during gastric ulcer healing by analyzing the expression of interleukin-4 (IL:4), endothelin-1 (ET-1), tumor necrosis factor-alpha (TNF-alpha), and the mucosal activity of capase-3, and constitutive (cNOS) and inducible nitric oxide synthase (NOS-2). METHODS: Rats with experimentally induced chronic gastric ulcers were administered twice daily for 14 days either sucralfate at 100 mg/kg or vehicle, and at different stages of treatment their stomachs were used for macroscopic and biochemical assessments. RESULTS: The ulcer onset was characterized by a massive epithelial apoptosis associated with a 33-fold increase in caspase-3 activity, 5.7-fold increase in TNF-alpha, 17.5-fold increase in NOS-2 and a 3.9-fold increase in ET-1, while the mucosal expression of cNOS activity showed a 7.6-fold drop and IL-4 expression fell by 37.2%. The healing was reflected in a rapid recovery in IL-4, and a decrease in apoptosis, caspase-3, TNF-alpha, ET-1 and NOS-2, and a slow recovery in cNOS activity, and the process was accelerated in the sucralfate-treated group. While in the absence of sucralfate the expression of IL-4 returned to that of the normal mucosa by the 7th day of healing and that of ET-1 and TNF-alpha by the 14th day, an accelerated ulcer healing with sucralfate treatment was associated with IL-4 recovery by the 4th day and that of ET-1 and TNF-alpha by the 10th day when the ulcer heated, while recovery in cNOS activity required 14 days. Yet, in both groups of animals the apoptotic DNA fragmentation rate, caspase-3 and the expression of NOS-2 activity remained significantly elevated even after the ulcer healed. CONCLUSIONS: The results suggest that a decrease in the mucosal expression of the regulatory cytokine IL-4 at the ulcer onset may well be a key factor causing dysregulation of ET-1 production, induction of TNF-alpha, and triggering the apoptotic events that affect the efficiency of mucosal repair process. We also show that accelerated ulcer healing by sucralfate may be the result of a rapid mucosal IL-4 generation that leads to the suppression of the mucosal apoptotic events.     

Effect of ebrotidine on gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide.

Helicobacter pylori lipopolysaccharide is a primary virulence factor responsible for eliciting acute mucosal inflammatory responses associated with H. pylori infection. In this study, we applied the animal model of H. pylori lipopolysaccharide-induced acute gastritis to assess the effect of antiulcer agent, ebrotidine, on the gastric mucosal inflammatory responses by analyzing the interplay between the activity of a key apoptotic caspase, caspase-3, epithelial cell apoptosis, and the expression of inducible nitric oxide synthase (NOS-2). METHODS: Rats, pretreated twice daily with ebrotidine at 100 mg/kg, or the vehicle, were subjected to intragastric application of H. pylori lipopolysaccharide at 50 microg/animal, and after 4 additional days on the antiulcer drug or vehicle regimen their mucosal tissue used for histologic assessment, assays of epithelial cells apoptosis, and the measurements of caspase-3 and NOS-2 activities. RESULTS: In the absence of antiulcer agent, H. pylori lipopolysaccharide induced acute reaction characterized by the inflammatory infiltration of the lamina propria, hyperemia, and epithelial hemorrhage. This was accompanied by an 11.2-fold increase in epithelial cell apoptosis, a 6.5-fold induction in mucosal expression of NOS-2, and a 5.4-fold increase in caspase-3 activity. Treatment with H2-receptor antagonist ebrotidine, also known for its gastroprotective effects, produced a 50.9% reduction in the extent of mucosal inflammatory changes elicited by H. pylori lipopolysaccharide and an 82.5% decrease in the epithelial cells apoptosis, while the activity of caspase-3 decreased by 33.7% and that of NOS-2 showed a 72.8% decline. CONCLUSIONS: The findings implicate caspase-3 involvement in gastric mucosal inflammatory responses to H. pylori lipopolysaccharide, and point towards participation of NOS-2 in the amplification of the cell death-signaling cascade. Our study also demonstrate that ebrotidine exerts modulatory effect on the H. pylori-induced mucosal inflammatory responses by interfering with the events propagated by NOS-2 and caspase-3.     

Omeprazole fails to suppress up-regulation of gastric mucosal endothelin-converting enzyme-1 by Helicobacter pylori lipopolysaccharide.

BACKGROUND: Endothelin-1, a key mediator of inflammatory processes, is produced from its biologically inactive precursor, big ET- by the action of endothelin converting enzyme-1(ECE-1). In this study, we applied the animal model of H. pylori lipopolysaccharide-induced gastritis to assess the effect of three different types of antiulcer agents on the gastric mucosal expression of ECE-1 activity. METHODS: Rats, pretreated twice daily for 3 days with proton pump inhibitor, omeprazole at 40 mg/kg, gastroprotective agent, sulglycotide at 200 mg/kg, H2-receptor antagonist, ebrotidine at 100 mg/kg or the vehicle, were subjected to intragastric application of H. pylori lipopolysaccharide at 50 microg/animal, and after 2, and 4 additional days on the drug or vehicle regimen their mucosal tissue used for histologic and biochemical assessment. RESULTS: In the absence of antiulcer agents, H. pylori lipopolysaccharide elicited a pattern of mucosal inflammatory responses resembling that of acute gastritis which reached a maximum by the 4th day and were accompanied by a 4.1-fold increase in the mucosal expression of ECE-1 activity and an 8.8-fold enhancement in TNF-alpha. Treatment with sulglycotide led to a 56.7% reduction in the extent of mucosal inflammatory involvement, the mucosal expression of ECE-1 activity fell by a 40.5% and the level of TNF-alpha declined by a 69%. Ebrotidine produced a 50.9% decrease in the extent of mucosal inflammatory involvement, a 33.6% decrease in the expression of ECE-1 activity and a 64.1% decline in TNF-alpha, whereas omeprazole elicited a 37.6% reduction in the extent of mucosal inflammatory involvement and a 29.5% decrease in TNF-alpha, but had no effect on the lipoploysaccharide-induced increase in the mucosal expression of ECE-1 activity. CONCLUSIONS: The findings implicate up-regulation of ECE-1 in triggering the induction of TNF-alpha and propagation of gastric mucosal inflammatory responses to H. pylori. We also show that omeprazole, in contrast to sulglycotide and ebrotidine, fails to counter the enhancement in the mucosal expression of ECE-1 caused by H. pylori- lipopolysaccharide.     

Downregulation of endothelin-1 by interleukin-4 during gastric ulcer healing.

We investigated the course of events associated with gastric ulcer healing by analyzing mucosal expression of interleukin-4 (IL-4), endothelin-1 (ET-1), tumor necrosis factor-alpha (TNF-alpha), and the activity of constitutive (cNOS) and inducible nitric oxide synthase (NOS-2). Ulcer onset was characterized by a massive epithelial apoptosis associated with a 5.7-fold increase in TNF-alpha, a 17.5-fold increase in NOS-2, and a 3.9-fold increase in ET-1, while mucosal expression of cNOS showed a 7.6-fold drop and IL-4 fell by 37.2%. Healing was accompanied by a rapid raise in IL-4; decrease in apoptosis, TNF-alpha, ET-1, and NOS-2; and a slow recovery in cNOS. The expression of IL-4 returned to control levels by the 7th day of healing and that of ET-1 and TNF-alpha by the 14th day, while apoptotic DNA fragmentation and the activity of NOS-2 remained significantly elevated beyond the 14-day period. The results suggest that a decrease in the mucosal level of IL-4 at ulcer onset may well be a key factor causing dysregulation of ET-1 production, induction of TNF-alpha, and triggering the apoptotic events that affect the efficiency of mucosal repair.     

Up-regulation of endothelin-converting enzyme-1 in gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Endothelin-1 (ET-1) is a vasoactive peptide produced from a biologically inactive big ET-1 by the action of endothelin-converting enzyme-1 (ECE-1). We investigated gastric mucosal expression of ECE-1 during a 10-day course of inflammatory responses associated with acute gastritis elicited by Helicobacter pylori lipopolysaccharide. The ECE-1 activity was associated with microsomal fraction and the level of its expression reflected the extent of mucosal inflammatory involvement. The histologic pattern of inflammation reached a maximum on the 4th day following the lipopolysaccharide and was accompanied by a 4.1-fold enhancement in the expression of ECE-1 activity and a significant elevation in ET-1 (3.1-fold), TNF-alpha (8.8-fold), and apoptosis (11.6-fold). A 41.5% decrease in the severity of mucosal inflammation by the 10th day following the lipopolysaccharide was reflected in a 62.3% reduction in the mucosal expression of ECE-1 and a decline in TNF-alpha, ET-1, and apoptosis. Thus, H. pylori infection causes up-regulation of gastric mucosal ECE-1 expression, which leads to the enhancement of ET-1 production, induction of TNF-alpha, and triggering the apoptotic events that exacerbate the inflammatory process.     

Involvement of endothelin-1 in up-regulation of gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

In this study, we investigated gastric mucosal inflammatory responses during Helicobacter pylori lipopolysaccharide-induced gastritis by analyzing the interplay between mucosal expression of endothelin-1 (ET-1), interleukin-4 (IL-4) and tumor necrosis factor-alpha (TNF-alpha). The assays conducted 4 days after intragastric dose of H. pylori lipopolysaccharide demonstrated a pattern of acute mucosal reaction characterized by the inflammatory infiltration of the lamina propria, hyperemia, and epithelial hemorrhage. This was accompanied by a 3.1-fold increase in the mucosal expression of ET-1 and a 9-fold enhancement in TNF-alpha, while the level of IL-4 showed a 20.8% decline. The results implicate ET-1 in gastric mucosal responses to H. pylori, and suggest that an increase in its level, combined with a loss of compensatory action by IL-4, may be responsible for the induction of TNF-alpha and triggering apoptotic events that exacerbate the inflammatory process.     

Endothelin-1, interleukin-4 and nitric oxide synthase modulators of gastric mucosal injury by indomethacin: effect of antiulcer agents.

Endothelin-1 (ET-1), nitric oxide, and cytokines are recognized mediators of the inflammatory processes associated with gastric mucosal injury. In this study, we investigated mucosal expression of ET-1, interleukin-4 (IL-4), and the activity of constitutive nitric oxide synthase (cNOS) during indomethacin-induced gastric mucosal injury, and evaluated the effect of antiulcer agents on this process. The experiments were conducted with groups of rats pretreated intragastrically with ranitidine (100 mg/kg), ebrotidine (100 mg/kg), sulglycotide (200 mg/kg) or vehicle, followed 30 min later by an intragastric dose of indomethacin (60 mg/kg). The animals were killed 2 h later and their mucosal tissue subjected to macroscopic damage assessment and the measurements of epithelial cell apoptosis, ET-1, IL-4, and cNOS. In the absence of antiulcer agents, indomethacin caused multiple hemorrhagic lesions and extensive epithelial cell apoptosis, accompanied by a 20.7% reduction in IL-4, a 3.1-fold increase in mucosal expression of ET-1 and a 4.2-fold decline in cNOS. Pretreatment with H2-receptor antagonist, ranitidine produced a 15.7% reduction in the mucosal damage caused by indomethacin, 29.5% decrease in epithelial cell apoptosis and a 19.6% reduction in ET-1, while the expression of IL-4 increased by 10.8% and that of cNOS showed a 2-fold increase. The H2-blocker, ebrotidine, also known for its gastroprotective effects, reduced the indomethacin-induced lesions by 90.2%, epithelial cell apoptosis decreased by 61% and ET-1 showed a 58.2% decline, while IL-4 increased by 30.6% and that of cNOS showed a 3.1-fold increase. Pretreatment with gastroprotective agent, sulglycotide, led to a 51.2% reduction in the extent of mucosal damage caused by indomethacin, a 43.9% decrease in apoptosis, and a 63.5% decrease in ET-1, while the expression of cNOS increased by 3.4-fold and the level of IL-4 showed a 32.2% increase. The results suggest that an increase in vasoconstrictive ET-1 level combined with a decrease in regulatory cytokine, IL-4, and a loss of compensatory action by cNOS may be responsible for gastric mucosal injury caused by indomethacin. Our findings also point to a value of ebrotidine and sulglycotide in countering the untoward gastrointestinal side effects of NSAID therapy.     

Nonsteroidal anti-inflammatory drugs impair oral mucosal repair by eliciting disturbances in endothelin-converting enzyme-1 and constitutive nitric oxide synthase.

Although the use of nonsteroidal anti-inflammatory drugs (NSAIDs) is known to cause the impairment in mucosal defenses that are well recognized and clinically emphasized with respect to the gastrointestinal tract, less apparent is the extent of their interference with the repair of soft oral tissue. As the disturbances in nitric oxide generation and the release of endothelin-1 (ET-1) are the early signs of injury by NSAIDs, we investigated oral mucosal ulcer healing in the presence of NSAID administration by analyzing the expression of endothelin-converting enzyme-1(ECE-1), responsible for ET-1 generation, and the mucosal activity of inducible (NOS-2) and constitutive (cNOS) nitric oxide synthase responsible for nitric oxide production. Groups of rats with acetic-induced buccal mucosal ulcers were subjected twice daily for up to 10 days to intragastric administration of either indomethacin (5 mg/kg), aspirin (20 mg/kg), or the vehicle and their mucosal tissue subjected to macroacopic assessment of ulcer healing rate and biochemical measurements. While in the control group the ulcer healed by the tenth day, only a 57.2% reduction in the ulcer crater area was attained in the animals subjected to indomethacin and a 54.8% reduction in ulcer occurred in the presence of aspirin administration. Futhermore, by the tenth day, the delay in healing in the presence of indomethacin was manifested by a 4.9-fold higher rate of apoptosis, a 2.7-fold higher expression of ECE-1 activity, a 3.9-fold higher expression of NOS-2 activity and a 2.2-fold decline in cNOS activity, while the interference in ulcer healing by aspirin was characterized by a 5.6-fold higher rate of apoptosis, a 2.8-fold expressiom of ECE-1 activity, a 3.7-fold higher expression of NOS-2 activity and a 2.3-fold lower expression of cNOS activity. Our findings demonstrate that NSAIDs not only pose a well-known risk of gastrointestinal injury, but also interfere with soft oral tissue repair. The impairment in buccal mucosal ulcer healing by NSAID ingestion is manifested in up-regulation in the expression of ECE-1 responsible for ET-1 generation, suppression in cNOS, and amplification of apoptotic events that delay the healing process.     

Platelet-activating factor modulates gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Platelet-activating factor (PAF) is a phospholipid messenger implicated in mediation of inflammatory events associated with the resolution of inflammation. We applied the animal model of Helicobacter pylori LPS-induced gastritis in conjunction with prophylactic and therapeutic administration of a specific PAF antagonist, BN52020, to investigate the role of PAF in gastric mucosal responses to H. pylori infection. Prophylactic BN52020 administration produced up to 73.6% reduction in the severity of the LPS-induced inflammatory changes, whereas up to 38.4% increase in the severity of mucosal involvement occurred with BN52020 administered therapeutically. The prophylactic effects of BN52020 were accompanied by a drop in apoptosis and the expression of TNF-alpha and NOS-2, while BN52020 administered therapeutically caused a marked upregulation in apoptosis, TNF-alpha, and NOS-2. The untoward therapeutic effects of BN52020, moreover, were potentiated further in the presence of COX-2 inhibitor, whereas NOS-2 inhibitor caused a reduction in the extent of inflammatory changes. Our findings point to PAF as a key mediator of gastric mucosal inflammatory responses to H. pylori and suggest its modulatory role in the expression of COX-2 derived anti-inflammatory prostaglandins that are involved in controlling the extent of NOS-2 induction.     

Induction of endothelin-converting enzyme-1 in gastric mucosal injury by idomethacin

Endothelin-1 (ET-1) is a 21-amino acid vasoactive peptide produced from a 39-amino acid biologically inactive peptide, big ET-1, by the action of endothelin-converting enzyme-1 (ECE-1). We investigated gastric mucosal expression of ECE-1 during a 16 h course of inflammatory responses associated with gastric mucosal injury caused by indomethacin. The extent of gastric mucosal damage reached a maximum 4 h following the drug, and was accompanied by a 3.9-fold enhancement in the expression of ECE-1 activity and a significant elevation in ET-1 (4.5-fold), TNF-alpha (11.3-fold), and apoptosis (29.9-fold). A 37.2% decrease in the severity of lesion 16 h following the drug was associated with a 44.5% reduction in the mucosal expression of ECE-1 activity and a decline in TNF-alpha (64%), ET-1 (65.2%), and apoptosis (72.3%). The results demonstrate that gastric mucosal injury by indomethacin is associated with up-regulation of ECE-1 expression, which leads to the enhancement of ET-1 production, induction of TNF-alpha, and triggering apoptotic events that disrupt gastric mucosal homeostasis.     

Platelet-activating factor mediates Helicobacter pylori lipopolysaccharide interference with gastric mucin synthesis

Platelet-activating factor (PAF) is now recognized as the most proximal mediator of cellular events triggered by bacterial infection. In this study, we report that a specific PAF antagonist, BN52020, impedes the reduction in mucin synthesis evoked in gastric mucosal cells by H. pylori LPS. The impedance by BN52020 of the LPS inhibitory effect on mucin synthesis was blocked by wortmannin, an inhibitor of phosphatidylinositol 3-kinase (P13K), which also obviated the inhibitory effect of BN52020 on the LPS-induced upregulation in apoptosis, TNF-alpha, and NO generation. A reduction in the impedance by BN52020 of the LPS detrimental effect on mucin synthesis was also attained with cNOS inhibitor, L-NNA, whereas NOS-2 inhibitor, 1400W caused a potentiation in the impedance effect of BN52020. However, while 1400W and BN52020 countered the potentiating effect of wortmannin on the LPS-induced decrease in mucin synthesis, a further exacerbation of the potentiating effect of wortmannin was attained in the presence of cNOS inhibitor, L-NNA. Our findings suggest that PAF, through the interference with PI3K-dependent cNOS activation, plays a critical role in influencing the extent of pathological consequences of H. pylori infection on the synthesis of gastric mucin.     

Endothelin-1-dependent leptin induction in gastric mucosal inflammatory responses to Helicobacter pylori lipopolysaccharide

Leptin, a multifunctional hormone that regulates food intake and energy expenditure, has emerged recently as an important modulator of gastric mucosal responses to Helicobacter pylori infection. We applied the animal model of H. pylori LPS-induced gastritis to investigate the role of endothelin-1 (ET-1) in the mucosal leptin production. We show that the histologic pattern of inflammation reached a maximum on the fourth day following the LPS and was reflected in a marked increase in the mucosal level of ET-1 and leptin. Therapeutic administration of phosphoramidon, an inhibitor of ECE-1 activity, led to a 61.2% decline in the mucosal ET-1 level and a 64.1% reduction in leptin, while the severity of mucosal inflammatory involvement increased by 28.6%. A drop in the level of leptin and the increase in severity of the inflammatory involvement elicited by the LPS was also attained in the presence of ET(A) receptor antagonist BQ610, but not the ET(B) receptor antagonist BQ788. Moreover, administration of ERK inhibitor, PD98059, in the presence of ET(B) receptor antagonist, but not the ET(A) receptor antagonist, caused reduction in the mucosal leptin level. Our findings are the first to implicate ET-1 as a key factor in up-regulation of gastric mucosal leptin-associated H. pylori infection. We also show that the effect of ET-1 on leptin production is a consequence of ET(A) receptor activation.     

Suppression of caspase-3 and nitric-oxide synthase-2 during buccal mucosal ulcer healing: effect of chronic alcohol ingestion

In this study, we analyzed the effect of chronic alcohol ingestion on the expression of constitutive (cNOS) and inducible (NOS-2) nitric-oxide synthase and the activity of an apoptotic protease, caspase-3, during buccal mucosal ulcer healing in rats maintained for 5 weeks on alcohol-containing or control liquid diet. In comparison with the controls, the ulcer onset in the alcohol group was characterized by a 2.5-fold greater epithelial cells apoptosis, 2.1-fold greater expression of caspase-3 activity, and a 1.4-fold greater enhancement in NOS-2, but expression of cNOS showed a 1.3-fold decrease. In both groups the ulcer healing was accompanied by a gradual decline in apoptosis, caspase-3, and NOS-2 and a recovery in cNOS activity, but the changes were considerably slower in the alcohol diet group, as manifested by a 40%(4 days) delay in ulcer healing. These results suggest that chronic alcohol ingestion interferes with the suppression of NOS-2 and the apoptotic events propagated by caspase-3 and hence affects the efficiency of oral mucosal repair process.     

Anti-inflammatory effect of two isoforms of COX in H. pylori-induced gastritis in mice: possible involvement of PGE2

Neutrophil infiltration mediated by TNF-alpha is associated with various types of gastric injury, whereas PGs play a crucial role in gastric defense. We examined roles of two isoforms of cyclooxygenase (COX) and PGE2 in Helicobacter pylori-induced gastritis in mice. Mice infected with H. pylori were given selective COX-1 inhibitor SC-560 (10 mg/kg), selective COX-2 inhibitor NS-398 (10 mg/kg), or nonselective COX inhibitor indomethacin (2 mg/kg) with or without 16,16-dimethyl PGE2 for 1 wk. H. pylori infection increased levels of mRNA for COX-1 and -2 in gastric tissue by 1.2-fold and 3.3-fold, respectively, accompanied by a significant increase in PGE2 production by gastric tissue. H. pylori infection significantly elevated MPO activity, a marker of neutrophil infiltration, and epithelial cell apoptosis in the stomach. SC-560 augmented MPO activity and epithelial cell apoptosis with associated reduction in PGE2 production, whereas NS-398 had the same effects without affecting PGE2 production. Inhibition of both COX-1 and -2 by indomethacin or concurrent treatment with SC-560 and NS-398 resulted in a stronger increase in MPO activity and apoptosis than inhibition of either COX-1 or -2 alone. H. pylori infection elevated TNF-alpha mRNA expression in the stomach, which was further increased by indomethacin. Effects of COX inhibitors on neutrophil infiltration, apoptosis, and TNF-alpha expression in H. pylori-infected mice were abolished by exogenous 16,16-dimethyl PGE2. In conclusion, PGE2 derived from either COX-1 or -2 is involved in regulation of gastric mucosal inflammation and contributes to maintenance of mucosal integrity during H. pylori infection via inhibition of TNF-alpha expression.     

Role of endothelin-1 and interleukin-4 in buccal mucosal ulcer healing: effect of chronic alcohol ingestion

We investigated the effect of chronic alcohol ingestion on buccal mucosal ulcer healing by analyzing the interplay between mucosal expression of tumor necrosis factor-alpha (TNF-alpha), endothelin-1 (ET-1), and interleukin-4 (IL-4). Chronic ulceration was induced in rats maintained for 5 weeks on alcohol-containing or control liquid diet. In both groups, the ulcer onset was characterized by a massive increase (6.5-8.9-fold) in TNF-alpha and ET-1 (1.6-4.0-fold), and a decrease (1.4-1.5-fold) in IL-4. However, the group on the alcohol diet exhibited a 38.3% higher mucosal expression of TNF-alpha, a 26. 2% higher ET-1 level, and a 6.5% lower content of IL-4. While in both groups the ulcer healing was accompanied by an increase in buccal mucosal expression of IL-4, and a decline in ET-1 and TNF-alpha, the changes were significantly slower in the alcohol diet group and manifested by a 4 day delay in ulcer healing. The results suggest that chronic alcohol ingestion exerts detrimental effects on the buccal mucosal IL-4 expression, causing dysregulation of ET-1 production, induction of TNF-alpha, and triggering apoptotic events that delay the mucosal repair.     

Impedance of Helicobacter pylori lipopolysaccharide interference with gastric mucin synthesis by peroxisome proliferator-activated receptor gamma activation involves phosphatidylinositol 3-kinase/ERK pathway

Peroxisome proliferator-activated receptor gamma (PPARgamma) plays a critical role in the regulation of the expression of genes associated with inflammation. In this study, we report that PPARgamma activation leading to the impedance of H. pylori lipopolysaccharide (LPS) inhibitory effect on gastric mucin synthesis occurs with the involvement of phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) pathways. Using gastric mucosal cells in culture, we show that activation of PPARgamma with a specific synthetic agonist, ciglitazone, prevents in a dose-dependent fashion (up to 90.2%) the LPS-induced reduction in mucin synthesis, and the effect is reflected in a marked decrease in the LPS-induced apoptosis (72.4%), NO generation (80.1%), and the expression of NOS-2 activity (90%). The impedance by ciglitazone of the LPS-induced reduction in mucin synthesis was blocked by wortmannin, a specific inhibitor of P13K and PD98059, an inhibitor of ERK. Both inhibitors, moreover, caused further enhancement in the LPS-induced NO generation and countered the inhibitory effect of ciglitazone on the LPS-induced upregulation in NOS-2. Our findings point to PI3K and ERK as mediators of PPARgamma agonist effect leading to the impedance of H. pylori LPS inhibition on gastric mucin synthesis.     

Gastric mucosal protection by sucralfate involves phosphoinositides participation

1. The mechanism of gastroprotective action of an antiulcer drug, sucralfate, was investigated. Studies in vivo were conducted with groups of rats with and without indomethacin pretreatment, and the animals received sucralfate followed by ethanol. In the in vitro system, gastric mucosa was cultured in the presence of sucralfate with and without indomethacin. 2. The in vivo experiments revealed that ethanol caused extensive gastric lesions which were significantly reduced following sucralfate pretreatment. Furthermore, sucralfate was also capable of preventing the detrimental effect of indomethacin on gastric mucus gel dimension and its mucin content. 3. The data with gastric mucosal culture showed that the sucralfate elicited increase in mucin was accompanied by the enhanced turnover of mucosal phosphoinositides. 4. Regardless of the inclusion of indomethacin, sucralfate evoked 23% reduction in phosphatidylinositol, 24% increase in inositol-1-phosphate and 3.4-fold increase in inositol-1,4,5-trisphosphate, thus indicating the activation of phosphoinositide-specific phospholipase C. 5. The results demonstrate that the gastric mucosal protective action of sucralfate is not mediated by endogenous prostaglandins, but appears to involve the metabolism of phosphoinositide-derived messenger molecules.     

Aspirin ingestion impairs oral mucosal ulcer healing by inducing membrane-bound tumor necrosis factor-alpha release

Among the early manifestations of impairment by nonsteroidal anti-inflammatory drugs in mucosal tissue repair is the enhancement in tumor necrosis factor-alpha (TNF-alpha). We investigated the effect of aspirin ingestion on the processing of TNF-alpha in rat soft oral tissue during buccal ulcer healing. While in the control group, the ulcer healed by the 10th day; only a 54.8% reduction in the ulcer area was attained in the presence of aspirin administration. Moreover, by the 10th day, the delay in ulcer healing by aspirin was manifested in a 5.6-fold higher rate of apoptosis and a 5.2-fold higher level of soluble TNF-alpha, yet the expression of membrane-bound TNF-alpha showed a 38% decline. Treatment with metalloprotease inhibitor, Zincov, produced dose-dependent reduction (56.9%) in aspirin-induced increase in the mucosal expression of soluble TNF-alpha, evoked a 62% decrease in the rate of epithelial cell apoptosis, and led to a marked reversal (56.9%) in aspirin-induced delay in ulcer healing. Our findings indicate that the impairment in buccal ulcer healing by aspirin is a result of upregulation in the processing of soluble TNF-alpha from its membrane-bound precursor that leads to the amplification of apoptotic events and potentiation of the mucosal inflammatory responses that interfere with healing process.     

Suppression of endothelin-converting enzyme-1 during buccal mucosal ulcer healing: effect of chronic alcohol ingestion

Among the factors affecting the efficiency of soft oral tissue healing is endothelin-1 (ET-1), a potent vasoactive peptide produced from a biologically inactive big ET-1 by the action of endothelin-converting enzyme-1 (ECE-1). We investigated the expression of ECE-1 during buccal mucosal ulcer healing in rats maintained for 5 weeks on alcohol containing or control diet. The mucosal activity of ECE-1, characterized by sensitivity to phosphoramidon, was associated with microsomal fraction and showed an elevated (3.1-fold) level in the alcohol diet group. Moreover, the ulcer onset in the alcohol group was reflected in a 39% greater expression of ECE-1 activity, and was accompanied by a 1.4-fold greater increase in TNF-alpha and a 2.5-fold greater enhancement in epithelial cell apoptosis. While in both groups the ulcer healing was associated with a decrease in buccal mucosal expression of ECE-1, as well as a decline in TNF-alpha and apoptosis, the changes were significantly slower in the alcohol diet group and manifested by a 40% delay in healing. Thus, chronic alcohol ingestion leads to up-regulation of ECE-1 expression, induction of TNF-alpha, and triggering apoptotic events that delay the mucosal repair.