Serosal Application Of Acetic Acid Research Articles

Physiological healing of chronic gastric ulcer is not impaired by the hydrogen sulphide (H2S)-releasing derivative of acetylsalicylic acid (ATB-340): functional and proteomic approaches.

Gastric ulcers affect approx. 10% of population. Non-steroidal anti-inflammatory drugs (NSAIDs), including acetylsalicylic acid (ASA) predispose to or impair the physiologically complex healing ofpre-existing ulcers. Since H2S is an endogenous cytoprotective molecule, we hypothesized that new H2S-releasing ASA-derivative (ATB-340) could overcome pathological impact of NSAIDs on GI regeneration.Clinically translational gastric ulcers were induced in Wistar rats using state-of-the-art microsurgical model employing serosal application of acetic acid. This was followed by 9 days long i.g. daily treatment with vehicle, ATB-340 (6-24mg/kg) or equimolar ASA doses (4-14mg/kg). Ulcer area was assessed macro- and microscopically. Prostaglandin (PG)E2 levels,indicating pharmacological activity of NSAIDsand 8-hydroxyguanozine content,reflecting nucleic acids oxidation in serum/gastric mucosa, were determined by ELISA. Qualitative and/or quantitative pathway-specific alterations at the ulcer margin were evaluated using real-time PCR and mass spectrometry-based proteomics.ASA, unlike ATB-340, dose-dependently delayed/impaired gastric tissue recovery, deregulating 310 proteins at the ulcer margin, including Ras signalling, wound healing or apoptosis regulators. ATB-340 maintained NSAIDs-specific cyclooxygenase-inhibiting capacity on systemic and GI level but in time-dependent manner. High dose of ATB-340 (24mg/kg daily), but not ASA, decreased nucleic acids oxidation and upregulated anti-oxidative/anti-inflammatory heme oxygenase-1, 24-dehydrocholesterol reductase or suppressor of cytokine signalling (SOCS3) at the ulcer margin.Thus, ASA impairs the physiological healing of pre-existing gastric ulcers, inducing the extensive molecularly functional and proteomic alterations at the wound margin. H2S-releasing ATB-340 maintains the target activity of NSAIDs with limited impact on gastric PGE2 signalling and physiological GI regeneration, enhancing anti-inflammatory and anti-oxidative response, andproviding the pharmacological advantage.

Evaluation of Therapeutic Efficacy of Stigma and Petal Extracts of Crocus sativus L. on Acetic Acid-Induced Gastric Ulcer in Rats

Saffron (Crocus sativus L.) has long been considered a medicinal plant in Traditional Persian Medicine (TPM) due to its therapeutic properties. Despite this interest, its effects on gastrointestinal disorders have not been completely taken into consideration. Hence, this study aimed to evaluate the pharmacological activity of ethanolic extracts of saffron stigma (SS) and saffron petal (SP) in acetic acid-induced gastric ulcer in rats. The gastric ulcer model was imitated by the serosal application of acetic acid in male Wistar rats. Then, the animals were orally fed with 100 mg/kg and 200 mg/kg of ethanolic extracts of SS or SP, omeprazole (40 mg/kg), or saline for 12 days. The macroscopic and microscopic appearances of gastric ulcers and the levels of malondialdehyde (MDA), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in gastric tissues were assessed. The highest anti-ulcer activity was observed in the omeprazole-treated animals with the lowest ulcer size (4.29 ± 1.78 mm2). SS could not reduce gastric ulcer size in rats. Compared to the untreated rats, SP treatment significantly decreased ulcer indices in a dose-dependent manner. The gastric levels of PGE2, VEGF, and MDA were significantly elevated in the untreated animals with gastric ulcers compared to rats in the control group. The SS extract suppressed the elevated PGE2 and VEGF levels at both doses, while SP did not have a significant influence. Both SS and SP treatments significantly ameliorated MDA levels in rats with gastric ulcers. Omeprazole treatment enhanced the PGE2 level and suppressed MDA contents, but it did not influence the VEGF level. In conclusion, our findings demonstrated that the saffron stigma has no significant effects on the gastric ulcer healing process, while its petals accelerate the process. This discrepancy can be attributed to the difference in the main secondary metabolites between saffron stigma and petals.

Therapeutic potential of Ferula foetida(Bunge) Regel on gastric ulcer model in rats.

The plant Ferula foetida(Bunge) Regel (FFBR) has a long history in Asian traditional medicine. This study aimed to evaluate the ulcer healing potential of FFBR umbel ethanolic extract on acetic acid-induced chronic gastric ulcer in rats. First, the gastric ulcer model was imitated by serosal application of acetic acid in male Wistar rats. Then, the animals were orally fed by ethanolic extract of FFBR umbel (100 mg/kg, 200 mg/kg, and 300 mg/kg), omeprazole (40 mg/kg), or saline for 12 days. Eventually, on the 13th day, animals were sacrificed, and their stomachs were taken out. The macroscopic and microscopic appearances of gastric ulcers and the levels of malondialdehyde (MDA), vascular endothelial growth factor (VEGF), and prostaglandin E2 (PGE2) in gastric tissues were assessed. In addition, the expression of NF-κB p65 was investigated by immunohistochemistry. Compared to the untreated rats with gastric ulcer, FFBR extract significantly decreased ulcer area even superior to omeprazole in a dose-dependent manner. Moreover, histological examination revealed that the extract (300 mg/kg) accelerated the epithelialization and differentiation of proliferative cells to mucosal tissue. The FFBR extract (300 mg/kg) increased tissue levels of VEGF and PGE2, but it did not affect MDA levels in rats with gastric ulcers. FFBR treatment (all doses) could significantly inhibit the expression of NF-κB p65 in gastric tissue. Taken together, experimental findings suggested that FFBR could accelerate the healing process of gastric ulcers in rats through mediating NF-κB and VEGF/PGE2 pathways.

Carbon monoxide released from its pharmacological donor, tricarbonyldichlororuthenium (II) dimer, accelerates the healing of pre-existing gastric ulcers.

Carbon monoxide (CO), a gaseous mediator produced by haem oxygenases (HOs), has been shown to prevent stress-, ethanol-, aspirin- and alendronate-induced gastric damage; however, its role in gastric ulcer healing has not been fully elucidated. We investigated whether CO released from tricarbonyldichlororuthenium (II) dimer (CORM-2) can affect gastric ulcer healing and determined the mechanisms involved in this healing action. Gastric ulcers were induced in Wistar rats by serosal application of acetic acid. Animals received 9days of treatment with RuCl3 [2.5mg·kg-1 intragastrically (i.g.)], haemin (5mg·kg-1 i.g.), CORM-2 (0.1-10mg·kg-1 i.g.) administered alone or with zinc protoporphyrin IX (ZnPP, 10mg·kg-1 i.g.), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 5mg·kg-1 i.g.), NG -nitro-l-arginine (l-NNA, 15mg·kg-1 i.g.), indomethacin (5mg·kg-1 i.g.) or glibenclamide (10mg·kg-1 i.g.). Gastric ulcer area and gastric blood flow (GBF) were assessed planimetrically, microscopically and by laser flowmeter respectively. Gastric mRNA/protein expressions of EGF, EGF receptors, VEGFA, HOs, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), COX-2, hypoxia-inducible factor (HIF)-1α and pro-inflammatory iNOS, IL-1β and TNF-α were determined by real-time PCR or Western blots. CORM-2 and haemin but not RuCl3 or ZnPP decreased ulcer size while increasing GBF. These effects were reduced by ODQ, indomethacin, l-NNA and glibenclamide. CORM-2 significantly decreased the expression of pro-inflammatory markers, Nrf2/HO1 and HIF-1α, and up-regulated EGF. CO released from CORM-2 or endogenously produced by the HO1/Nrf2 pathway accelerates gastric ulcer healing via an increase in GBF, an up-regulation in EGF expression and down-regulation of the inflammatory response.

High-Mobility Group Box 1 Inhibits Gastric Ulcer Healing through Toll-Like Receptor 4 and Receptor for Advanced Glycation End Products

High-mobility group box 1 (HMGB1) was initially discovered as a nuclear protein that interacts with DNA as a chromatin-associated non-histone protein to stabilize nucleosomes and to regulate the transcription of many genes in the nucleus. Once leaked or actively secreted into the extracellular environment, HMGB1 activates inflammatory pathways by stimulating multiple receptors, including Toll-like receptor (TLR) 2, TLR4, and receptor for advanced glycation end products (RAGE), leading to tissue injury. Although HMGB1’s ability to induce inflammation has been well documented, no studies have examined the role of HMGB1 in wound healing in the gastrointestinal field. The aim of this study was to evaluate the role of HMGB1 and its receptors in the healing of gastric ulcers. We also investigated which receptor among TLR2, TLR4, or RAGE mediates HMGB1’s effects on ulcer healing. Gastric ulcers were induced by serosal application of acetic acid in mice, and gastric tissues were processed for further evaluation. The induction of ulcer increased the immunohistochemical staining of cytoplasmic HMGB1 and elevated serum HMGB1 levels. Ulcer size, myeloperoxidase (MPO) activity, and the expression of tumor necrosis factor α (TNFα) mRNA peaked on day 4. Intraperitoneal administration of HMGB1 delayed ulcer healing and elevated MPO activity and TNFα expression. In contrast, administration of anti-HMGB1 antibody promoted ulcer healing and reduced MPO activity and TNFα expression. TLR4 and RAGE deficiency enhanced ulcer healing and reduced the level of TNFα, whereas ulcer healing in TLR2 knockout (KO) mice was similar to that in wild-type mice. In TLR4 KO and RAGE KO mice, exogenous HMGB1 did not affect ulcer healing and TNFα expression. Thus, we showed that HMGB1 is a complicating factor in the gastric ulcer healing process, which acts through TLR4 and RAGE to induce excessive inflammatory responses.

SITAGLIPTIN IMPAIRS HEALING OF EXPERIMENTALLY INDUCED GASTRIC ULCERS VIA INHIBITION OF INOS AND COX-2 EXPRESSION

Gastric ulcer healing is a complex process that is regulated by several promoting factors including COX-2 and iNOS. Diabetes mellitus is usually associated with delayed gastric ulcer healing. Hence, the current study was designed to investigate the effect of sitagliptin (dipeptidyl peptidase-4 inhibitor) on gastric ulcer healing and expression of iNOS and COX-2 in rat stomach.The study was conducted on 30 rats divided into three equal groups. Group 1 served as normal control group. Gastric ulcer was induced, by serosal application of acetic acid, in group 2 (ulcer model group) and group 3 (sitagliptin-treated group). Sitagliptin was administrated from day 3 to day 10 in group 3. All rats were sacrificed on day 10 and stomachs were removed for pathological examination and immunohistochemical assessment of COX-2 and iNOS expression. Pathological examination revealed that gastric ulcer healing was significantly impaired in the sitagliptin-treated group as evidenced by the significantly larger ulcerated area and ulcer base maturation impairment.COX-2 and iNOS expression as well as mean MVD were significantly diminished in the sitagliptin-treated group as compared to the ulcer model group. A significant positive correlation was found between COX-2 and iNOS implying their synergistic action. We conclude that sitagliptin significantly impairs gastric ulcer healing in rats possibly through inhibition of iNOS and COX-2 expression. Our results raise the question of whether sitagliptin is advisable in diabetic patients with pre-existing gastric ulcer. Our preliminary experimental findings need to be substantiated by future human studies.

Role of Activation of 5′-Adenosine Monophosphate-Activated Protein Kinase in Gastric Ulcer Healing in Diabetic Rats

Background: The potential utility of 5′-adenosine monophosphate-activated protein kinase (AMPK)-activating agents, such as metformin, in inducing angiogenesis, could be a promising approach to promote healing of gastric ulcers complicated by diabetes mellitus. The aim of the present study was to assess the effect of a drug that activates AMPK, namely metformin, in gastric ulcer healing in streptozotocin-induced diabetic rats. Methods: Forty male Wistar albino rats were made diabetic by intraperitoneal (i.p.) streptozotocin injection and 10 rats were injected i.p. by a single dose of physiological saline. Six weeks following streptozotocin or saline injection, gastric ulcers were induced by serosal application of acetic acid. Three days after acetic acid application, rats were divided into group 1 (nondiabetic control), group 2 (streptozotocin-injected rats), groups 3–5 (streptozotocin-injected rats treated with metformin or metformin and an inhibitor of AMPK, namely compound C or pioglitazone) for 7 days following acetic acid application. Results: Administration of metformin, but not pioglitazone, resulted in a significant decrease in the gastric ulcer area, a significant increase in epithelial regeneration assessed histologically, a significant increase in the number of microvessels in the ulcer margin, a significant increase in gastric vascular endothelial growth factor concentration and gastric von Willebrand factor as well as a significant increase in gastric phospho-AMPK. Compound C, an inhibitor of AMPK, blocked metformin-induced changes in assessed parameters suggesting that the effect of metformin was mediated mainly through activation of AMPK. Conclusion: Our results suggest the feasibility of a novel treatment strategy, namely drugs activating AMPK, for patients in whom impairment of ulcer healing constitutes a secondary complication of diabetes mellitus.

Stimulation of gastric ulcer healing by heat shock protein 70

It is important in treatment of gastric ulcers to not only prevent further ulcer formation but also enhance ulcer healing. When cells are exposed to gastric irritants, expression of heat shock proteins (HSPs) is induced, making the cells resistant to the irritants. We recently reported direct evidence that HSPs, especially HSP70, are preventive against irritant-induced gastric ulcer formation. Gastric ulcer healing is a process involving cell proliferation and migration at the gastric ulcer margin and angiogenesis in granulation tissue. In this study, we have examined the role of HSP70 in gastric ulcer healing. Gastric ulcers were produced by focal and serosal application of acetic acid. Expression of HSP70 was induced in both the gastric ulcer margin and granulation tissue. Compared with wild-type mice, gastric ulcer healing was accelerated in transgenic mice expressing HSP70, and both cell proliferation at the gastric ulcer margin and angiogenesis in granulation tissue were enhanced. Oral administration of geranylgeranylacetone, an inducer of HSPs, to wild-type mice, either prior to or after ulcer formation, not only induced expression of HSP70 in the stomach but also accelerated gastric ulcer healing. On the other hand, oral administration of purified recombinant HSP70 prior to the ulcer formation, but not after formation, stimulated gastric ulcer healing. This study provides the first evidence that HSP70 accelerates gastric ulcer healing. The results also suggest that both the HSP70 produced prior to ulcer formation and released from damaged cells, and the HSP70 produced after ulcer formation are involved in this accelerated healing process.

Delayed healing of chronic gastric ulcer after Helicobacter pylori infection in mice.

It has been suggested that there is a close relationship between Helicobacter pylori and the onset or recurrence of gastroduodenal disease. The aim of this study was to examine the effect of H. pylori on the healing of chronic gastric ulcers induced in mice. H. pylori administered to nude mice delayed the healing of experimental acetic acid-induced gastric ulcers. Histological examination showed the occurrence of high densities of H. pylori on the surface of epithelial cells and in the ulcerated area. Repeated administration of amoxicillin (10 mgkg(-1) daily for 5 days) eradicated H. pylori and increased the rate of healing of gastric ulcers in H. pylori-infected mice, but metronidazole, which also eradicated the organisms, did not significantly affect the rate of healing. In conclusion, H. pylori-infection delayed the healing of gastric ulcers induced by the serosal application of acetic acid in mice, possibly by aggravation or prolongation of the mucosal inflammation. Amoxicillin eradicated H. pylori and promoted gastric ulcer healing in mice infected with H. pylori.

Muc-2–Deficient Mice Display a Sex-Specific, COX-2–Related Impairment of Gastric Mucosal Repair

Mucus is known to contribute significantly to the prevention and repair of mucosal damage throughout the gastrointestinal tract. Although not normally expressed in the stomach, mucin-2 (MUC-2, encoded by the MUC2 gene) is expressed in certain disease states. The aim of this study was to determine in a mouse model whether the absence of Muc-2 would result in impaired susceptibility to and healing of gastric mucosal injury. Acute gastric damage was induced in mice deficient in Muc-2 and in wild-type controls, through oral administration of indomethacin. Chronic gastric ulcers were induced by serosal application of acetic acid. The extent of injury and the extent of healing of the damage over time were examined in both models. Indomethacin administration caused similar levels of gastric damage in Muc-2-deficient and wild-type mice, but the erosions healed more slowly in the former. Acetic acid-induced gastric ulcers were initially similar in size in Muc-2-deficient and wild-type mice of both sexes, but ulcer healing was significantly impaired in male Muc-2-deficient mice. Induction of cyclooxygenase-2 in the stomach, in response to indomethacin- or acetic acid-induced ulceration, was significantly reduced in male Muc-2-deficient mice. This phenomenon, and the sex specificity, was also apparent in bone marrow-derived macrophages stimulated with endotoxin. These results demonstrate a marked impairment of gastric mucosal repair in male Muc-2-deficient mice that may be related to an insufficient induction of cyclooxygenase-2, an enzyme known to contribute to mucosal repair.

884 The Role of the Ferric Uptake Regulator (Fur) in Helicobacter pylori Resistance to Metronidazole

G A A b st ra ct s induced gastric lesions at 6, 12 and 24 h upon 3.5 h of WRS exposure (series B). In separate series, rats with chronic gastric ulcers induced by serosal application of acetic acid (ulcer area=28 mm2) were treated daily for 9 and 15 days with: 1) vehicle (saline); 2) Hp2-20 (0.5 25 mg/kg i.g.) or 3) control peptide Hp1 (10 mg/kg i.g.) with or without non-selective and selective inhibitors of cNOS and iNOS, L-NNA (20 mg/kg-d i.p.) and L-Nil (5 mg/kgd i.p.) without or with the combination with L-arginine (200 mg/kg-d s.c.). The gastric juice was collected for acid output assessment and the number and area of WRS lesions and ulcers were determined planimetrically, the gastric blood flow (GBF) was determined by H2-gas clearance technique and luminal NOx concentration, plasma VEGF levels, the expression of mRNAs for VEGF and FPR mRNA and protein were assessed by ELISA, RTPCR and Western Blot. Hp2-20 dose-dependently inhibited the gastric acid secretion and decreased the number of WRS-induced gastric lesions at 6h, 12 h and 24 h by 16%, 38% and 46%, respectively. Hp2-20 reduced the area of acetic acid ulcers; the dose inhibiting by 50% (ID50) of ulcer area at day 9 upon ulcer induction being 10 mg/kg and this was accompanied by the rise in GBF at ulcer margin, luminal NOx levels and VEGF concentration. Treatment with L-NNA and L-Nil which by themselves increased the area of gastric ulcer significantly reduced the healing effects of Hp2-20 and accompanying rise in the GBF and plasma NOx concentration. These increase in the area of gastric ulcers and accompanying fall in GBF and NOx content induced by L-NNA and L-Nil were reversed by L-arginine added to NOS inhibitors. Upregulation of mRNA and protein for VEGF and FPR at ulcer marginwas observed inHp2-20-treated animals and these effects were significantly attenuated by L-NNA or L-Nil. We conclude that Hp2-20 enhances the mucosal recovery from WRSinduced lesions and accelerates the healing of preexisting gastric ulcers due to upregulation of FRP receptors via mechanism involving inhibition of gastric acid secretion, an activation of NO/NOS pathway and an overexpression and release of VEGF at the ulcer margin responsible for new microvessels formation.

Role of modulation of vascular endothelial growth factor and tumor necrosis factor-alpha in gastric ulcer healing in diabetic rats

The aim of the present study was to assess the effect of drugs that increase gastric vascular endothelial growth factor (VEGF) and suppress gastric tumor necrosis factor-alpha (TNF-α) in gastric ulcer healing in streptozotocin-induced diabetic rats. Sixty male albino rats were made diabetic by intraperitoneal (i.p.) streptozotocin injection and ten rats were injected i.p. by a single dose of saline. Six weeks following streptozotocin or saline injection, gastric ulcers were induced by serosal application of acetic acid. Three days after acetic acid application, rats were divided into: group I (non-diabetic control), group II (streptozotocin-injected), groups III–VII (streptozotocin-injected rats treated with insulin, insulin and pentoxifylline, insulin and simvastatin, pentoxifylline as well as simvastatin, respectively, for 7 days following acetic acid application. The use of insulin, combinations of insulin and pentoxifylline or simvastatin resulted in a significant decrease in gastric ulcer area, significant increase in epithelial regeneration assessed histologically, significant increase in gastric VEGF concentration, and gastric von Willebrand factor (vWF) as well as significant decrease in gastric TNF-α. A significant difference in gastric ulcer area as well as in gastric TNF-α, VEGF and vWF levels could be observed between rats that received combinations of insulin and pentoxifylline or simvastatin compared to rats that received either drug alone. Our results suggest the feasibility of a novel treatment strategy, namely pentoxifylline and simvastatin, for patients in whom impairment of ulcer healing constitutes a secondary complication of diabetes mellitus.

Leptin Promotes Gastric Ulcer Healing via Upregulation of Vascular Endothelial Growth Factor

Background and Aim: Leptin, a key hormone in regulation of food intake and energy expenditure, exerts pleiotropic cytokine-like biological effects. Its role in gastric ulcer healing is unclear. In this study, we investigated the role of leptin in gastric ulcer healing. Methods: Experimental gastric ulcer was induced by focal serosal application of acetic acid in leptin-deficient ob/ob mice and wild-type mice. Healing of gastric ulcer and angiogenesis in the ulcer tissue was evaluated. Results: Gastric ulcer healing was delayed in ob/ob mice compared with that in wild-type mice. The impairment of ulcer healing observed in ob/ob mice was characterized by reduced expression of vascular endothelial growth factor (VEGF) and impairment of angiogenesis. Systemic administration of leptin to ob/ob mice reversed the impairment of gastric ulcer healing; this reversal was accompanied by an increase in VEGF expression and angiogenesis. Although mRNA for leptin was not expressed in normal gastric mucosa and not induced in ulcerous tissue, leptin receptor expression was markedly upregulated in gastric epithelial cells at ulcer margins, and was colocalized with VEGF. Conclusion: These findings suggest that leptin promotes gastric ulcer healing by induction of angiogenesis in the granular tissue of ulcers via upregulation of VEGF expression.

Acetic Acid Induced Ulceration in Rats Is Not Affected by Infection with Hymenolepis diminuta

Analysis of rodent models of inflammatory bowel disease, airways hyper-reactivity, diabetes, and multiple sclerosis has shown that infection with helminth parasites can significantly reduce the severity of the disease. Here, we assessed whether rats infected with the tapeworm Hymenolepis diminuta were protected from gastric ulceration induced by the serosal application of acetic acid. All rats gavaged with infective cysticercoids harbored adult worms when assessed 6 wk later, and acetic acid evoked the expected gastric ulceration. However, infection with H. diminuta did not affect the degree of gastric ulceration at either 3 or 7 days post-acetic acid application, as gauged by ulcer area or histopathology. While the data do not dismiss the possibility that infection with other helminths could be anti-ulcerogenic, they illustrate that 'helminth therapy' for inflammatory disease is likely to be both disease- and helminth-specific.

Dynamic physiological and molecular changes in gastric ulcer healing achieved by melatonin and its precursor L‐tryptophan in rats

Following induction of gastric ulcer in rats by serosal application of acetic acid, local mucosal necrosis ensues accompanied by a reduction in mucosal microcirculation and by almost immediate expression of inducible nitric oxide (NO) synthase (iNOS) and proinflammatory cytokines. Daily application of melatonin (20 mg/kg) or l-tryptophan (100 mg/kg) accelerates ulcer healing by affecting the cyclooxygenase-2 (COX-2)-prostaglandin (PG) system with excessive production of protective PG, especially in later period of ulcer healing. Furthermore, expression of hypoxia inducible factor, vascular-endothelial growth factor, an activation of cNOS-NO system and the stimulation of sensory nerves with the expression and release of calcitonin gene related peptide (CGRP) appear to aid the restoration of mucosal repair and microcirculation in the ulcer bed. The enhanced expression of the melatonin MT(2) receptors (MT(2)-R) combined with overexpression of key enzymes involved in biosynthesis of melatonin such as N-acetyltransferase and hydroxyindole-O-methyltransferase contribute to the acceleration of ulcer healing by this indole. Melatonin-induced acceleration of ulcer healing is also mediated by release of gastrin and ghrelin, the most potent stimulants of gastric mucosal cell proliferation and mucosal repair. These sequential steps in ulcer healing accelerated by melatonin can be interfered with by the blockade of MT(2)R, COX-2/PG and cNOS/NO systems, and by reduction in the inflammatory iNOS/NO system. Thus, melatonin and its precursor l-tryptophan, trigger the cascade of molecular events leading to the functional improvement in ulcer healing.

A vascular endothelial growth factor mimetic accelerates gastric ulcer healing in an iNOS-dependent manner

Angiogenesis is crucial to all types of wound healing, including gastric ulcer healing. The most potent promoter of angiogenesis is vascular endothelial growth factor (VEGF). We hypothesized that a 15-amino acid peptide designed to mimic the angiogenic action of VEGF would accelerate gastric ulcer healing. Gastric ulcers were induced in mice by serosal application of acetic acid. Treatment with the VEGF mimetic accelerated gastric ulcer healing when administered orally or intraperitoneally, at a dose of 50 ng/kg or greater. Such healing was not observed when the reverse sequence pentadecapeptide or the full-length VEGF protein was administered. Contrary to our hypothesis, the VEGF mimetic did not significantly increase angiogenesis in the ulcerated stomach. The enhancement of ulcer healing by the VEGF mimetic occurred independently of cyclooxygenase-2 (COX-2) activity but was blocked by inhibitors of inducible nitric oxide synthase (iNOS). These results demonstrate that a VEGF mimetic is a potent stimulus for gastric ulcer healing, even when given orally. The effects of the mimetic were independent of stimulatory effects on angiogenesis and COX-2 activity but were dependent on iNOS-derived NO production.

Annexin-1 modulates repair of gastric mucosal injury

Annexin-1 is a glucocorticoid-inducible protein that plays an important effector role in the resolution of inflammation and has recently been shown to contribute to the resistance of the stomach to injury. Using an integrated genetic and pharmacological approach, we have tested the hypothesis that annexin-1 contributes to the healing of mucosal injury, given that such injury is accompanied by an inflammatory response, which is often associated with an overexpression of annexin-1 expression. Gastric ulcers were induced in mice through serosal application of acetic acid. Annexin-1 expression during the healing of the ulcers was examined. The effects on gastric ulcer healing of treatment with an annexin-1 mimetic (Ac2-26), an antagonist of the annexin-1 receptor (Boc2), or a glucocorticoid (dexamethasone) were examined. Finally, susceptibility to and healing of indomethacin-induced gastric lesions were compared in wild-type and annexin-1-deficient mice. Expression of annexin-1 was significantly increased in the gastric ulcer margin throughout the healing process. Treatment with an annexin-1 mimetic (Ac2-26) significantly enhanced gastric ulcer healing. In contrast, both dexamethasone and an formyl peptide receptor-like-1 (FPRL-1) antagonist impaired the early phase of ulcer healing. Annexin-1-deficient mice exhibited the same susceptibility as wild-type mice to indomethacin-induced gastric damage, but the healing of that damage was impaired in the former. These data support the hypothesis that annexin-1 contributes significantly to the process of healing of gastric mucosal damage.

Topical transplantation of mesenchymal stem cells accelerates gastric ulcer healing in rats

Mesenchymal stem cells (MSCs), a subpopulation of adult somatic stem cells, are an attractive stem cell source in regenerative medicine because of their multipotentiality. We examined the effects of MSC transplantation on gastric ulcer healing. Putative MSCs, isolated from bone marrow aspirates of male rats by dish adherence and expanded in culture, were characterized by flow cytometry and reverse transcription-polymerase chain reaction. Gastric ulcers were induced by serosal application of acetic acid on the anterior wall of the stomach in female rats. Either MSCs (labeled with PKH67; 1x10(7) cells) or vehicle was injected into the gastric wall surrounding the ulcer. The healing process of the ulcer and the influence of anti-vascular endothelial growth factor (VEGF) antibody were examined. CD29-positive, CD90-positive, CD34-negative, and CD45-negative MSCs expressed mRNAs for VEGF and hepatocyte growth factor (HGF). The MSCs were transplantable to the gastric tissue surrounding the ulcer, where a majority of the engrafted cells were positive for vimentin. The transplantation significantly accelerated gastric ulcer healing compared with controls. The engrafted MSCs also expressed VEGF and HGF. Administration of anti-VEGF neutralizing antibody dose dependently reduced the MSC-induced promotion of ulcer healing. In conclusion, MSC transplantation accelerated gastric ulcer healing, possibly through the induction of angiogenesis in the gastric mucosa via the secretion of VEGF. The beneficial effects of MSCs might be mediated not only by their differentiation into gastric interstitial cells, but also by their ability to supply angiogenic factors.

Effect of dopamine on the healing of acetic acid-induced gastric ulcers in rats

Dopamine, as a neurotransmitter in the brain, is also present in the gastroduodenal mucosa and has been implicated in several functions in these tissues. Recent study showed that dopamine acts as a potent antitumor/angiogenic activity through suppression of growth factor expression. Since growth factors are known to play a crucial role in the mechanism of wound healing, it is possible that dopamine has a deleterious influence on the healing of gastric ulcers. In the present study, we examined the effect of dopamine on the healing of acetic acid-induced gastric ulcers in rats. Gastric ulcers were induced in male SD rats by serosal application of acetic acid for 60 sec. Dopamine was subcutaneously given twice daily for 7 days, starting 3 days after ulceration. In some case, the osmotic mini-pump filled with dopamine was implanted into the dorsal subcutaneous space in rats for 7 days. VEGF and Flk-1 mRNA expressions were determined by RT-PCR. Dopamine (3, 10 and 30 mg/kg) given subcutaneously for 7 days did not significantly affect the healing of gastric ulcers. The expression of VEGF and Flk-1 mRNA in the ulcerated mucosa was up-regulated after ulceration, and these expressions were not affected by dopamine. Likewise, dopamine (0.6 mg/kg/hr) infused continuously using the osmotic mini-pump also had no effect on the healing of these ulcers. These results suggest that dopamine, although reportedly shows a potent antitumor/angiogenic activity, does not cause any influence on the healing of the pre-existing gastric ulcers in rats.

Hydrogen sulfide enhances ulcer healing in rats

Hydrogen sulfide is an endogenous mediator that relaxes vascular smooth muscle, exhibits several antiinflammatory activities, and contributes to gastric mucosal defense. This study was performed to examine the role of hydrogen sulfide in the resolution of injury; specifically, the healing of gastric ulcers. Ulcers were induced in rats by serosal application of acetic acid. This elicited a marked increase in gastric expression of the two key enzymes in hydrogen sulfide synthesis (cystathionine-beta-synthase and cystathionine-gamma-lyase) and in hydrogen sulfide synthesis. Twice-daily treatment for a week with hydrogen sulfide donors significantly increased the extent of healing of gastric ulcers as compared to vehicle-treatment. Similar treatment with L-cysteine, a precursor for hydrogen sulfide, also accelerated healing of the ulcers, and the effect was abolished by cotreatment with an inhibitor of cystathionine-gamma-lyase. The beneficial effects of hydrogen sulfide on ulcer healing were not dependent on nitric oxide synthesis, nor did they appear to occur through activation of ATP-sensitive K+ channels. These results suggest that hydrogen sulfide is produced in the gastric mucosa in response to injury and acts to promote healing. The results further suggest that drugs releasing hydrogen sulfide could be employed to accelerate healing of gastric ulcers, and possibly of other wounds.