Attenuation of gastric mucosal inflammation induced by aspirin through activation of A2A adenosine receptor in rats

Dendrobium officinale Polysaccharides as a Natural Functional Component for Acetic-Acid-Induced Gastric Ulcers in Rats

Dendrobium officinale is an important edible and medicinal plant, with the Dendrobium officinale polysaccharide (DOP) being its primary active constituent, known for its diverse biological activities. In this study, DOP was extracted and characterized for its structural properties. The potential of DOP to ameliorate gastric ulcers (GUs) was investigated using an acetic-acid-induced GU model in rats. The results demonstrated that DOP exerted a multifaceted protective effect against GU, mitigating the deleterious impact on food intake and body weight in rats. DOP exhibited its protective action by attenuating cellular damage attributed to oxidative stress and inflammatory reactions mediated by enhanced activities of SOD, GSH, and GSH-PX, coupled with a downregulation in the expression of pro-inflammatory cytokines, including IL-1β, IL-6, and TNF-α. Furthermore, DOP effectively inhibited apoptosis in gastric mucosa cells of acetic-acid-induced GU rat models and facilitated the self-repair of damaged tissues. Remarkably, the DOP-200 and DOP-400 groups outperformed omeprazole in reducing the expression of IL-6 and malondialdehyde (MDA) in tissues, as well as IL-1β, IL-6, and TNF-α in serum. These groups also exhibited an improved expression of SOD in tissues and SOD, GSH, and GSH-PX in serum. A Western blot analysis of gastric mucosa demonstrated that the DOP-200 and DOP-400 groups significantly reduced the expression of NF-κBp65, phosphorylated NF-κBp65, FoxO3a, and Bim. The observed antagonism to GU appeared to be associated with the NF-κB cell pathway. Additionally, qRT-PCR results indicate that DOP reduced the mRNA transcription levels of IL-6, and TNF-α, which shows that the healing of GU is related to the reduction in the inflammatory reaction by DOP. However, the expression of EGF and VEGF decreased, suggesting that the mechanism of DOP inhibiting GU may not be directly related to EGF and VEGF, or there is an uncertain competitive relationship between them, so further research is needed.

Drugs targeting adenosine signaling pathways: A current view

Adenosine is an endogenous nucleoside that regulates many physiological and pathological processes. It is derived from either the intracellular or extracellular dephosphorylation of adenosine triphosphate and interacts with cell-surface G-protein-coupled receptors. Adenosine plays a substantial role in protecting against cell damage in areas of increased tissue metabolism and preventing organ dysfunction in pathological states. Targeting adenosine metabolism and receptor signaling may be an effective therapeutic approach for human diseases, including cardiovascular and central nervous system disorders, rheumatoid arthritis, asthma, renal diseases, and cancer. Several lines of evidence have shown that many drugs exert their beneficial effects by modulating adenosine signaling pathways but this knowledge urgently needs to be summarized, and most importantly, actualized. The present review collects pharmaceuticals and pharmacological or diagnostic tools that target adenosine signaling in their primary or secondary mode of action. We overviewed FDA-approved drugs as well as those currently being studied in clinical trials. Among them are already used in clinic A2A adenosine receptor modulators like istradefylline or regadenoson, but also plenty of anti-platelet, anti-inflammatory, or immunosuppressive, and anti-cancer drugs. On the other hand, we investigated dozens of specific adenosine pathway regulators that are tested in clinical trials to treat human infectious and noninfectious diseases. In conclusion, targeting purinergic signaling represents a great therapeutic challenge. The actual knowledge of the involvement of adenosinergic signaling as part of the mechanism of action of old drugs has open a path not only for drug-repurposing but also for new therapeutic strategies.

Protein profiling identified mitochondrial dysfunction and synaptic abnormalities after dexamethasone intervention in rats with traumatic brain injury

Dexamethasone has been widely used after various neurosurgical procedures due to its anti-inflammatory property and the abilities to restore vascular permeability, inhibit free radicals, and reduce cerebrospinal fluid production. According to the latest guidelines for the treatment of traumatic brain injury in the United States, high-dose glucocorticoids cause neurological damage. To investigate the reason why high-dose glucocorticoids after traumatic brain injury exhibit harmful effect, rat controlled cortical impact models of traumatic brain injury were established. At 1 hour and 2 days after surgery, rat models were intraperitoneally administered dexamethasone 10 mg/kg. The results revealed that 31 proteins were significantly upregulated and 12 proteins were significantly downregulated in rat models of traumatic brain injury after dexamethasone treatment. The Ingenuity Pathway Analysis results showed that differentially expressed proteins were enriched in the mitochondrial dysfunction pathway and synaptogenesis signaling pathway. Western blot analysis and immunohistochemistry results showed that Ndufv2, Maob and Gria3 expression and positive cell count in the dexamethasone-treated group were significantly greater than those in the model group. These findings suggest that dexamethasone may promote a compensatory increase in complex I subunits (Ndufs2 and Ndufv2), increase the expression of mitochondrial enzyme Maob, and upregulate synaptic-transmission-related protein Gria3. These changes may be caused by nerve injury after traumatic brain injury treatment by dexamethasone. The study was approved by Institutional Ethics Committee of Beijing Neurosurgical Institute (approval No. 201802001) on June 6, 2018.

Methanolic Extract of Distemonanthus benthamianus (Caesalpiniaceae) Stem Bark Suppresses Ethanol/Indomethacin-Induced Chronic Gastric Injury in Rats

Distemonanthus benthamianus (Caesalpiniaceae) is a plant from the Cameroon pharmacopoeia very widely used in the treatment of many pathologies among which are gastrointestinal disorders. The main purpose of this study was to assess the healing properties of gastric ulcer from the methanolic extract of Distemonanthus benthamianus and its mechanisms of action. The healing properties of gastric ulcers (chronic ulcer model induced by ethanol and indomethacin) were evaluated in vivo in adult male rats, while the mechanisms of action were evaluated in vitro by anti-inflammatory assay (protein denaturation, cyclooxygenase, and lipoxygenase assays) and immunomodulatory assay (ROS production (using technical chemiluminescence), cytokine (TNF-α, IL-1β, IL-6) production (using ELISA), proliferation of T cells (using liquid scintillation counter), and cytotoxicity (using MTT assay)). The methanolic extract of Distemonanthus benthamianus inhibited protein denaturation (75.63%) and the activities of cyclooxygenase (78.92%) and 5-lipoxygenase (81.54%). The extract also significantly (p < 0.001) inhibited intracellular and extracellular ROS production and T cell proliferation and reduced significantly (p < 0.01, p < 0.001) TNF-α, IL-1β, IL-6, and PGE2 production. At all doses (125, 250, and 500 mg/kg), the extract significantly reduces the ulceration index and the area of ulceration and significantly increases the mass of gastric mucus. In addition, the extract significantly decreases the level of MDA, significantly increases the activities of catalase and glutathione, and then improves the hematological parameters in sick animals. Histological micrographs show that in the presence of the extract, there is advanced reepithelialization with recovery of the ulcerated epithelium. Thus, the extract of Distemonanthus benthamianus has healing properties against gastric ulcers which are associated with its anti-inflammatory, immunomodulatory, and antioxidant effects.

Protective Effect of Polydeoxyribonucleotide Against CCl4-Induced Acute Liver Injury in Mice

Purpose

Polydeoxyribonucleotide (PDRN) is a substance known to suppress inflammation and accelerate wound healing. In this experiment, the effect of PDRN treatment on carbon tetrachloride (CCl₄)-evoked acute liver injury (ALI) was investigated using mice.

Methods

We analyzed the levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and conducted hematoxylin and eosin staining in accompany with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Western blot analysis was also conducted to assess the expressions of tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, adenosine A_2A receptor, Bcl-2-associated X protein (Bax), and B-cell lymphoma 2 (Bcl-2). The mice were received intraperitoneal injection of 10-mL/kg CCl₄, 4 times, once every 2 days. The mice in the PDRN treatment groups received intraperitoneal injection of 200-μL distilled water comprising each concentration of PDRN for 7 days starting 1 day after first CCl₄ injection.

Results

ALT and AST concentrations in the serum were reduced and TNF-α, IL-1β, and IL-6 expressions were decreased by PDRN injection in CCl₄-evoked ALI mice. PDRN injection suppressed Bax versus Bcl-2 ratio and reduced the percentage of TUNE-positive cells in CCl₄-evoked ALI mice. PDRN injection overexpressed adenosine A_2A receptor in CCl₄-evoked ALI mice.

Conclusions

The therapeutic efficacy of PDRN also can be expected for CCl₄-evoked acute urogenital injury in addition to ALI. The current research suggests that PDRN may be used for the therapeutic agent of CCl₄-evoked ALI.

Combination Therapy With Polydeoxyribonucleotide and Pirfenidone Alleviates Symptoms of Acute Respiratory Distress Syndrome in Human Lung Epithelial A549 Cells

PURPOSE

Acute respiratory distress syndrome (ARDS) is characterized by its acute onset of symptoms such as bilateral pulmonary infiltrates, severe hypoxemia, and pulmonary edema. Many patients with ARDS survive in the acute phase, but then die from significant lung fibrosis.

METHODS

The effect of combination therapy with polydeoxyribonucleotide (PDRN) and pirfenidone on ARDS was investigated using human lung epithelial A549 cells. ARDS environment was induced by treatment with lipopolysaccharide and transforming growth factor (TGF)-β. Enzyme-linked immunoassay for connective tissue growth factor (CTGF) and hydroxyproline were conducted. Western blot for collagen type I, fibroblast growth factor (FGF), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 was performed.

RESULTS

In this study, 8-μg/mL PDRN enhanced cell viability. Combination therapy with PDRN and pirfenidone and pirfenidone monotherapy suppressed expressions of CTGF and hydroxyproline and inhibited expressions of collagen type I and FGF. Combination therapy with PDRN and pirfenidone and PDRN monotherapy suppressed expression of TNF-α and IL-1β.

CONCLUSION

The combination therapy with PDRN and pirfenidone exerted stronger therapeutic effect against lipopolysaccharide and TGF-β-induced ARDS environment compared to the PDRN monotherapy or pirfenidone monotherapy. The excellent therapeutic effect of combination therapy with PDRN and pirfenidone on ARDS was shown by promoting the rapid anti-inflammatory effect and inhibiting the fibrotic processes.

Role and Function of Adenosine and its Receptors in Inflammation, Neuroinflammation, IBS, Autoimmune Inflammatory Disorders, Rheumatoid Arthritis and Psoriasis

The physiological effects of endogenous adenosine on various organ systems are very complex and numerous which are elicited upon activation of any of the four G-protein-coupled receptors (GPCRs) denoted as A1, A2A, A2B and A3 adenosine receptors (ARs). Several fused heterocyclic and non-xanthine derivatives are reported as a possible target for these receptors due to physiological problems and lack of selectivity of xanthine derivatives. In the present review, we have discussed the development of various new chemical entities as a target for these receptors. In addition, compounds acting on adenosine receptors can be utilized in treating diseases like inflammation, neuroinflammation, autoimmune and related diseases.

Evaluating the mucoprotective effect of polydeoxyribonucleotide against indomethacin-induced gastropathy via the MAPK/NF-κB signaling pathway in rats

Non-steroidal anti-inflammatory drugs (NSAIDs) cause gastric mucosal damage and gastric ulceration. Among the most commonly used NSAIDs, indomethacin upregulates mucosal tumor necrosis factor-α, which activates nuclear factor-kappa B (NF-κB), and mitogen-activated protein kinases (MAPK) to induce various pro-inflammatory mediators. Polydeoxyribonucleotide (PDRN) is an adenosine A_2A receptor agonist that exerts anti-inflammatory effects. In this study, we evaluated the efficacy of PDRN in the initial treatment of gastropathy against that of ecabet sodium and irsoglandin maleate, which are commonly used medications. The rats were administrated indomethacin once a day for 7 days after 24 h of fasting to induce gastropathy. Rats in the drug-treated groups were orally administrated 500 μl of distilled water containing the drug once daily for 7 days 1 h after indomethacin administration. Indomethacin administration caused mucosal damage and increased pro-inflammatory cytokine release. Both NF-κB and MAPK cascade factors were increased by indomethacin administration. PDRN therapy more potently suppressed the expressions of NF-κB and MAPK cascade factors compared to other drugs. The expression of cyclic adenosine-3',5'-monophosphate was also increased by PDRN treatment in the indomethacin-induced gastropathy rats. These changes led to a reduction in pro-inflammatory cytokines and apoptotic factors, which ultimately promote recovery of damaged gastric tissue. Therefore, PDRN may serve as a new therapeutic option in the initial treatment of NSAIDs-induced gastropathy.

The relatively selective cyclooxygenase-2 inhibitor nimesulide: What's going on?

Nimesulide is a relatively selective cyclooxygenase (COX)-2 inhibitor, non-steroidal anti-inflammatory drug; it has been discovered in 1971 and firstly commercialized in Italy in 1985. There is much evidence that the pharmacological profile of nimesulide is peculiar and not shared with the other COX-2 selective inhibitors, suggesting that other molecular mechanisms besides inhibition of COX-2 derived prostaglandins are involved. Similarly, experimental data suggest that the gastrointestinal safety of nimesulide cannot be ascribed only to a COX-1 sparing effect. On the inflammatory process, the efficacy of nimesulide is dependent upon a wide spectrum of actions, due to the combination of effects on immune and non-immune cells. Early data demonstrated a central role for cyclic AMP (cAMP) in the anti-inflammatory effect of nimesulide; more recently, we have shown the involvement of the pathway ecto-5'-nucleotidase/adenosine A_2A receptor. To date, the molecular mechanism(s) that confers uniqueness to nimesulide have not yet been defined. To go inside the mechanism of action of an existing drug, such as nimesulide, would be helpful to refine its therapeutic use but also to identify new targets for novel therapeutic anti-inflammatory approach. Here, we focus on accumulated evidence for a peculiar pharmacological profile of nimesulide.

Combination therapy with polydeoxyribonucleotide and proton pump inhibitor enhances therapeutic effectiveness for gastric ulcer in rats

AIMS

The main action of proton pump inhibitors (PPIs) is to inhibit gastric acid secretion, and PPIs are widely used to treat gastric ulcer (GU). However, if the action of promoting gastric mucosal regeneration is added, the effectiveness of GU treatment can be enhanced. Thus, in order to improve the therapeutic effect on GU, we tried to develop combination therapy promoting regeneration in injured tissue besides suppressing gastric acid secretion.

MAIN METHODS

Polydeoxyribonucleotide (PDRN) was selected to evaluate tissue regeneration, and pantoprazole was chosen as one of the PPIs. GU was induced by oral administration of indomethacin once a day for 7 days. Rats in drug-administered groups were intraperitoneally injected with 100 μL normal saline, containing each drug at the indicated concentration, once a day for 14 days after inducing GU.

KEY FINDINGS

PDRN and PPI combination therapy potently improved tissue regeneration and inhibited production of pro-inflammatory cytokines. PDRN treatment with or without PPI increased the concentration of cyclic adenosine-3,5'-monophosphate (cAMP) and the ratio of phosphorylated cAMP response element-binding protein (p-CREB) to cAMP response element-binding protein (CREB). PDRN treatment with or without PPI also increased the expressions of vascular endothelial growth factor (VEGF) and adenosine A_2A receptor.

SIGNIFICANCE

PDRN and PPI combination therapy showed more potent therapeutic effect on GU compared to the PDRN monotherapy or PPI monotherapy. The excellent therapeutic effect of PDRN and PPI combination therapy on GU appeared by promoting regeneration of damaged tissue as well as inhibiting gastric acid secretion.

Polydeoxyribonucleotide Ameliorates Lipopolysaccharide-Induced Lung Injury by Inhibiting Apoptotic Cell Death in Rats

Lung injury is characterized by diffuse lung inflammation, alveolar-capillary destruction, and alveolar flooding, resulting in respiratory failure. Polydexyribonucleotide (PDRN) has an anti-inflammatory effect, decreasing inflammatory cytokines, and suppressing apoptosis. Thus, we investigated its efficacy in the treatment of lung injury, which was induced in rats using lipopolysaccharide (LPS). Rats were randomly divided into three groups according to sacrifice time, and each group split into control, lung injury-induced, and lung injury-induced + PDRN-treated groups. Rats were sacrificed 24 h and 72 h after PDRN administration, according to each group. Lung injury was induced by intratracheal instillation of LPS (5 mg/kg) in 0.2 mL saline. Rats in PDRN-treated groups received a single intraperitoneal injection of 0.3 mL distilled water including PDRN (8 mg/kg), 1 h after lung injury induction. Percentages of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive, cleaved caspase-3-, -8-, and -9-positive cells, the ratio of Bcl-2-associated X protein (Bax) to B-cell lymphoma 2 (Bcl-2), and expressions of inflammatory cytokines (tumor necrosis factor-α, interleukin-6) were decreased by PDRN treatment in the LPS-induced lung injury rats. Therefore, treatment with PDRN reduced lung injury score. This anti-apoptotic effect of PDRN can be ascribed to the enhancing effect of PDRN on adenosine A_2A receptor expression. Based on these results, PDRN might be considered as a new therapeutic agent for the treatment of lung injury.

Potential Therapeutic Applications of Adenosine A2A Receptor Ligands and Opportunities for A2A Receptor Imaging

Adenosine A_2A receptors (A_2A Rs) are highly expressed in the human striatum, and at lower densities in the cerebral cortex, the hippocampus, and cells of the immune system. Antagonists of these receptors are potentially useful for the treatment of motor fluctuations, epilepsy, postischemic brain damage, or cognitive impairment, and for the control of an immune checkpoint during immunotherapy of cancer. A_2A R agonists may suppress transplant rejection and graft-versus-host disease; be used to treat inflammatory disorders such as asthma, inflammatory bowel disease, and rheumatoid arthritis; be locally applied to promote wound healing and be employed in a strategy for transient opening of the blood-brain barrier (BBB) so that therapeutic drugs and monoclonal antibodies can enter the brain. Increasing A_2A R signaling in adipose tissue is also a potential strategy to combat obesity. Several radioligands for positron emission tomography (PET) imaging of A_2A Rs have been developed in recent years. This review article presents a critical overview of the potential therapeutic applications of A_2A R ligands, the use of A_2A R imaging in drug development, and opportunities and limitations of PET imaging in future research.

Astragaloside IV protects rat gastric mucosa against aspirin-induced damage

Aspirin (Asp) is commonly used as an anti-inflammatory drug, but the long-term usage of Asp can lead to severe gastrointestinal damage. Thus the co-administering of Asp with another drug that can suppress its side effect while having no impact on its anti-inflammatory activity would be ideal. Astragaloside IV (AST-IV) is a natural anti-inflammatory compound that has been shown to protect rat gastric mucosa from anhydrous ethanol-inflicted damage. In this study, we investigated whether AST-IV could protect rat gastric mucosa against Asp-induced gastric mucosal damage. Wistar rats administered 150mg/kg Asp showed significant damage to the gastric mucosa, as revealed by gastric damage score and histological evaluation. However, this was largely abolished by co-administering Asp and 25mg/kg or 50mg/kg AST-IV. The protective mechanism of AST-IV involved the suppression of Asp-induced inhibition of cycloxygenase-1 (COX-1) expression, prostaglandin E₂ (PGE₂) production, superoxide dismutase (SOD) activity and nitric oxide (NO) production. AST-IV blocked Asp-induced inhibition of SOD activity through preventing Asp from inhibiting the expression of SOD-1, both at the mRNA and protein levels. AST-IV did not appear to interfere with the anti-inflammatory activity of Asp since COX-2 level in model gastritis rats treated with Asp plus AST-IV was equally suppressed as in model gastritis rats treated with Asp alone. The results clearly showed that AST-IV could neutralize the toxicity of Asp while having no impact on its anti-inflammatory activity. AST-IV could therefore be considered as a potential drug for relieving the side effect associated with the long-term usage of Asp.

Nitroxides prevent exacerbation of indomethacin-induced gastric damage in adjuvant arthritis rats

Nonsteroidal anti-inflammatory drugs are the drugs of choice in the treatment of rheumatoid arthritis (RA) because of their rapid analgesic effect. However, they induce severe gastric damage in RA patients and animals by a process mediated by reactive oxygen species (ROS). Nitroxides (nitroxyl radicals) are widely used as imaging agents and antioxidants to explore the role of ROS generation in the pathogenesis of disease. In this study, the effectiveness of the newly synthesized nitroxides 8-aza-7,7,9,9-tetramethyl-1,4-dioxaspiro[4.5]undecan-8-oxyl (compound 1) and 4-oxo-2,2,6,6-tetraethylpiperidine-1-oxyl (compound 2) in the prevention of gastric ulcers in adjuvant arthritis rats treated with indomethacin was evaluated by monitoring the reaction of reactive oxygen species in gastric tissue with Overhauser-enhanced magnetic resonance imaging (OMRI). Pretreatment with all tested nitroxides suppressed the ulcers induced by indomethacin treatment in arthritic rats. OMRI using compounds 1 and 2 as well as 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) demonstrated a redox imbalance in the stomach of these rats. Lipid peroxide and interleukin (IL)-1β levels in the gastric mucosa were significantly suppressed by compound 1 and TEMPOL, whereas CINC/gro, a member of the IL-8 family, was significantly suppressed by compound 1 only. These results suggest that the preventive effects of nitroxides on gastric ulcers may operate by different mechanisms.

CGS 21680, an agonist of the adenosine (A2A) receptor, decreases acute lung inflammation

Adenosine A(2A) receptor agonists may be important regulators of inflammation. The aim of this study was to investigate the effects of CGS 21680 (0.1mg/kgi.p.), an agonist of the adenosine (A(2A)) receptor, in a mouse model of carrageenan-induced pleurisy. Injection of carrageenan into the pleural cavity of mice elicited an acute inflammatory response characterised by: infiltration of neutrophils in lung tissues and subsequent lipid peroxidation, increased production of nitric oxide (NO), cytokines such as tumour necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and increased expression of intercellular adhesion molecule (ICAM-1) and platelet-adhesion molecule (P-selectin). Furthermore, carrageenan induced the expression of nuclear factor-κB (NF-κB), inducible nitric oxide synthase (iNOS), nitrotyrosine, the activation of poly-ADP-ribosyl polymerase (PARP), as well as induced apoptosis (FAS-ligand expression, Bax and Bcl-2 expression) in the lung tissues. Administration of CGS 21680, 30 min prior to challenge with carrageenan, caused a significant reduction of all the parameters of inflammation measured. In addition, to confirm the anti-inflammatory effect of CGS 21680, we have also evaluated the effects of CGS 21680 post-treatment (30 min after the challenge with carrageenan) and we have demonstrated that also it caused a reduction of neutrophil infiltration and the degree of lung injury. Thus, based on these findings we propose that adenosine A(2A) receptor agonists such as CGS 21680 may be useful in the treatment of various inflammatory diseases.

Octreotide ameliorates gastric lesions in chronically mild stressed rats

AIM: To evaluate the effect of chronic mild stress (CMS) on the emergence of gastric ulcers and possible modulation by octreotide, a synthetic somatostatin analogue.

METHODS: Adult male Wistar rats were subjected to nine different unpredictable random stress procedures for 21 d, a multifactorial interactional animal model for CMS. Octreotide was administered daily for 21 d at two dose levels (50 and 90 μg/kg) before exposure to stress procedure. Macro- and microscopical assessments were made, in addition to quantification of plasma corticosterone and gastric mucosal inflammatory, oxidative stress, and apoptotic biomarkers.

RESULTS: Exposure to CMS elevated plasma corticosterone (28.3 ± 0.6 μg/dL, P = 0.002), an event that was accompanied by gastric lesions (6.4 ± 0.16 mm, P = 0.01) and confirmed histopathologically. Moreover, the insult elevated gastric mucosal lipid peroxides (13 ± 0.5 nmol/g tissue, P = 0.001), tumor necrosis factor-α (3008.6 ± 78.18 pg/g tissue, P < 0.001), prostaglandin E2 (117.1 ± 4.31 pg/g tissue, P = 0.002), and caspase-3 activity (2.4 ± 0.14 OD/mg protein, P = 0.002). Conversely, CMS mitigated interleukin-10 (627.9 ± 12.82 pg/g tissue, P = 0.001). Furthermore, in animals exposed to CMS, octreotide restored plasma corticosterone (61% and 71% from CMS, P = 0.002) at both dose levels. These beneficial effects were associated with a remarkable suppression of gastric lesions (38% and 9% from CMS, P = 0.01) and reversal of derangements in gastric mucosa.

CONCLUSION: The current investigation provides evidence that exposure to CMS induces gastric ulceration, which was alleviated by administration of octreotide possibly possessing antioxidant, anti-inflammatory, and anti-apoptotic actions.

Protective Effects of Ginger against Aspirin-Induced Gastric Ulcers in Rats

We investigated the mechanism underlying the protective effects of ginger against gastric damage induced by aspirin in rats. Gastric mucosal lesions were produced by orally administering 200 mg/kg aspirin suspended in 1% carboxymethylcellulose solution to pyloric-ligated male Wistar rats. Ginger powder (200 mg/kg) markedly reduced the aspirin-induced gastric hemorrhagic ulcer area. The total acidity of gastric juice was not significantly influenced by aspirin or ginger. Ginger powder did not affect the aspirin-induced reduction in mucosal prostaglandin E2 (PGE2) content; however, it did ameliorate the aspirin-induced increases in mucosal activity of the inducible form of NO synthase (iNOS) and plasma tumor necrosis factor (TNF)-α and interleukin (IL)-1β levels. In the next experiment, high and low doses of 6-gingerol and 6-shogaol were used instead of ginger powder in the same experimental model to examine their roles in the anti-ulcer mechanism of ginger. Both 6-gingerol and 6-shogaol reduced aspirin induced ulcer formation, mucosal iNOS and plasma TNF-α and IL-1β levels. In conclusion, ginger powder prevents the aspirin induced gastric ulcer formation by reducing mucosal iNOS activity and the plasma levels of inflammatory cytokines but does not affect gastric juice or acid production or mucosal PGE2 content. This protective effect of ginger powder against gastric ulcers may be attributable to both gingerol and shogaol.

Relationship between low-dose aspirin-induced gastric mucosal injury and intragastric pH in healthy volunteers

BACKGROUND AND AIMS

Gastric acid plays an important role in the pathogenesis of gastric mucosal lesions. We investigated whether aspirin-induced gastric mucosal injury might have any association with the intragastric pH.

MATERIALS AND METHODS

Fifteen healthy, Helicobacter pylori-negative volunteers randomly underwent the four different 7-day regimens: (1) aspirin 100 mg, (2) rabeprazole 10 mg, (3) aspirin 100 mg + rabeprazole 10 mg, and (4) aspirin 100 mg + rabeprazole 40 mg. Gastric mucosal injury based on the modified Lanza score (MLS), 24-h intragastric pH, and histopathology of gastric mucosa were evaluated prior to the start and on day 7 of each regimen.

RESULTS

The median MLSs were 0 in the baseline and the rabeprazole 10 mg regimen. The median MLS in the aspirin regimen was 3, while those in both aspirin + rabeprazole 10 mg and aspirin + rabeprazole 40 mg regimens were 0. Rabeprazole significantly prevented the gastric mucosal injury by aspirin (P = 0.001 for rabeprazole 10 mg and P = 0.005 for rabeprazole 40 mg). The MLSs were negatively correlated with the 24-h intragastric pH (P = -0.711, < 0.001), whereas aspirin had no effect on the intragastric pH. Aspirin expanded the mean diameter of the microvessels of the gastric mucosa, which, in turn, was negatively correlated with the intragastric pH.

CONCLUSIONS

Aspirin might induce gastric mucosal injury by affecting the mucosal microvessels in an acid-dependent manner. Sustained maintenance of the intragastric pH at an elevated value is necessary to prevent gastric mucosal damage induced by aspirin.

Adenosine A(2A) agonist and A(2B) antagonist mediate an inhibition of inflammation-induced contractile disturbance of a rat gastrointestinal preparation

Adenosine can show anti-inflammatory as well as pro-inflammatory activities. The contribution of the specific adenosine receptor subtypes in various cells, tissues and organs is complex. In this study, we examined the effect of the adenosine A(2A) receptor agonist CGS 21680 and the A(2B)R antagonist PSB-1115 on acute inflammation induced experimentally by 2,4,6-trinitrobenzenesulfonic acid (TNBS) on rat ileum/jejunum preparations. Pre-incubation of the ileum/jejunum segments with TNBS for 30 min resulted in a concentration-dependent inhibition of acetylcholine (ACh)-induced contractions. Pharmacological activation of the A(2A)R with CGS 21680 (0.1-10 microM) pre-incubated simultaneously with TNBS (10 mM) prevented concentration-dependently the TNBS-induced inhibition of the ACh contractions. Stimulation of A(2B)R with the selective agonist BAY 60-6583 (10 microM) did neither result in an increase nor in a further decrease of ACh-induced contractions compared to the TNBS-induced inhibition. The simultaneous pre-incubation of the ileum/jejunum segments with TNBS (10 mM) and the selective A(2B)R antagonist PSB-1115 (100 microM) inhibited the contraction-decreasing effect of TNBS. The effects of the A(2A)R agonist and the A(2B)R antagonist were in the same range as the effect induced by 1 microM methotrexate. The combination of the A(2A)R agonist CGS 21680 and the A(2B)R antagonist PSB-1115 at subthreshold concentrations of both agents found a significant amelioration of the TNBS-diminished contractility. Our results demonstrate that the activation of A(2A) receptors or the blockade of the A(2B) receptors can prevent the inflammation-induced disturbance of the ACh-induced contraction in TNBS pre-treated small intestinal preparations. The combination of both may be useful for the treatment of inflammatory bowel diseases.

Attenuation of gastric mucosal inflammation induced by indomethacin through activation of the A2A adenosine receptor in rats

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) such as indomethacin induce gastric mucosal lesions in part by the activation of inflammatory cells and the production of proinflammatory cytokines. The activation of adenosine A(2A) receptors inhibits inflammation by increasing cyclic AMP in leukocytes and reducing both the production of various proinflammatory cytokines and neutrophil chemotaxis. The aim of present study was to determine whether administration of an orally active adenosine A(2A) receptor agonist (4-[3-[6-amino-9-(5-cyclopropylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]-prop-2-ynyl]-piperidine-1-carboxylic acid methyl ester; ATL-313) ameliorated indomethacin-induced gastric mucosal lesions in rats.

METHODS

Gastric lesions were produced by oral gavage of indomethacin (30 mg/kg). ATL-313 (1-10 microg/kg) was given orally just before the indomethacin administration.

RESULTS

The ulcer index induced by indomethacin was significantly (>50%) reduced by pretreatment with ATL-313 and this effect was blocked completely by the addition of equimolar ZM241385, a selective A(2A) receptor antagonist. The gastric content of myeloperoxidase (MPO) and proinflammatory cytokines was significantly reduced by 10 microg/kg ATL-313, but gastric mucosal prostaglandin 2 (PGE2) was not affected.

CONCLUSION

We conclude that ATL-313 does not inhibit the mucosal damaging effect of indomethacin, but it does block secondary injury due to stomach inflammation. A(2A) agonists may represent a class of new therapeutic drugs for NSAID-induced gastric ulcers.

Adenosine deaminase and adenosine receptor polymorphisms in aspirin-intolerant asthma

In asthmatic airways, adenosine is a potent bronchoconstrictor with either pro- or anti-inflammatory effects depending on receptor interactions. While aspirin has been suggested to mediate adenosine action, the roles of adenosine and its receptors in aspirin-intolerant asthma (AIA) are not well-defined. Therefore, we evaluated associations between genetic polymorphisms of adenosine deaminase and the four adenosine receptors (A(1), A(2A), A(2B), and A(3)) with the AIA phenotype. The genes for adenosine deaminase (ADA) and the four adenosine receptors (ADORA1, ADORA2A, ADORA2B, and ADORA3) were screened by direct sequencing, and 13 single nucleotide polymorphisms (SNPs) were selected among 23 polymorphisms. Using multivariate logistic regression analysis, we compared the frequencies of SNP genotypes and haplotypes among 136 patients with AIA, 181 patients with aspirin-tolerant asthma (ATA), and 183 normal individuals. We found significant differences between normal and patients with AIA in the ADORA1 SNP genotype frequencies for 1405C>T (P=0.001) and A102A (P=0.013). No other significant associations were detected for the other SNPs. In the haplotype analysis, ht[C-T-G] (P=0.003) and ht[A-C-G] (P=0.032) in ADORA1 and ht[A-T] in ADORA2 (P=0.013) were significantly associated with AIA. Genetic polymorphisms of adenosine receptors A(1) and A(2A) were associated with AIA, suggesting that adenosine might play a crucial role in the development of AIA through interactions with the A(1) and A(2A) receptors.

Irsogladine maleate suppresses indomethacin-induced elevation of proinflammatory cytokines and gastric injury in rats

AIM: To investigate the mucosal protective effect and the mechanisms of action of the anti-ulcer drug irsogladine maleate in gastric injury induced by indomethacin in rats.

METHODS: Gastric mucosal injury was induced in male Hos:Donryu rats by oral administration of indomethacin at a dose of 48 mg/kg. One hour before indomethacin treatment, animals were orally pretreated with irsogladine maleate at doses of 1 mg/kg, 3 mg/kg or 10 mg/kg. Four hours after indomethacin administration, the animals were sacrificed and their stomachs were rapidly removed and processed for the evaluation of gastric mucosal damage and the determination of the concentrations of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), IL-8 and myeloperoxidase (MPO) in mucosal tissues.

RESULTS: Linear hemorrhagic mucosal lesions were observed primarily in the glandular stomach 4 h after oral administration of indomethacin. Pretreatment with irsogladine maleate markedly reduced the number and severity of these lesions in a dose-dependent manner. The mucosal concentrations of proinflammatory cytokines (TNF-α, IL-1β, and IL-8) and MPO, which indicates the degree of mucosal infiltration by neutrophils, increased concomitantly with the occurrence of gastric injury in the indomethacin-treated rats. Pretreatment with irsogladine maleate significantly decreased the levels of these inflammatory factors in gastric tissue elicited by indomethacin.

CONCLUSION: The mucosal protective effects afforded by irsogladine maleate on gastric injury induced by indomethacin are mediated by inhibition of mucosal proinflammatory cytokine production and neutrophil infiltration, leading to suppression of mucosal inflammation and subsequent tissue destruction.

Purinergic receptors and gastrointestinal secretomotor function

Secretomotor reflexes in the gastrointestinal (GI) tract are important in the lubrication and movement of digested products, absorption of nutrients, or the diarrhea that occurs in diseases to flush out unwanted microbes. Mechanical or chemical stimulation of mucosal sensory enterochromaffin (EC) cells triggers release of serotonin (5-HT) (among other mediators) and initiates local reflexes by activating intrinsic primary afferent neurons of the submucous plexus. Signals are conveyed to interneurons or secretomotor neurons to stimulate chloride and fluid secretion. Inputs from myenteric neurons modulate secretory rates and reflexes, and special neural circuits exist to coordinate secretion with motility. Cellular components of secretomotor reflexes variably express purinergic receptors for adenosine (A1, A2a, A2b, or A3 receptors) or the nucleotides adenosine 5'-triphosphate (ATP), adenosine diphosphate (ADP), uridine 5'-triphosphate (UTP), or uridine diphosphate (UDP) (P2X(1-7), P2Y(2), P2Y(4), P2Y(6), P2Y(12) receptors). This review focuses on the emerging concepts in our understanding of purinergic regulation at these receptors, and in particular of mechanosensory reflexes. Purinergic inhibitory (A(1), A(3), P2Y(12)) or excitatory (A(2), P2Y(1)) receptors modulate mechanosensitive 5-HT release. Excitatory (P2Y(1), other P2Y, P2X) or inhibitory (A(1), A(3)) receptors are involved in mechanically evoked secretory reflexes or "neurogenic diarrhea." Distinct neural (pre- or postsynaptic) and non-neural distribution profiles of P2X(2), P2X(3), P2X(5), P2Y(1), P2Y(2), P2Y(4), P2Y(6), or P2Y(12) receptors, and for some their effects on neurotransmission, suggests their role in GI secretomotor function. Luminal A(2b), P2Y(2), P2Y(4), and P2Y(6) receptors are involved in fluid and Cl(-), HCO(3) (-), K(+), or mucin secretion. Abnormal receptor expression in GI diseases may be of clinical relevance. Adenosine A(2a) or A(3) receptors are emerging as therapeutic targets in inflammatory bowel diseases (IBD) and gastroprotection; they can also prevent purinergic receptor abnormalities and diarrhea. Purines are emerging as fundamental regulators of enteric secretomotor reflexes in health and disease.

A selective adenosine A2A receptor agonist, ATL-146e, prevents concanavalin A-induced acute liver injury in mice

BACKGROUND AND AIMS

Concanavalin A (Con A) activates T lymphocytes and induces CD4+ T cell-mediated hepatic injury in mice. Pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma), and interleukin-6 (IL-6), are critical mediators in this experimental model. Activation of adenosine A2A receptors reduces the production of various pro-inflammatory cytokines and suppresses T cell activation. A selective adenosine A2A receptor agonist (ATL-146e) has been shown to be a potent inhibitor of inflammation by increasing intracellular cyclic AMP (cAMP) in leukocytes. The aim of the present study was to determine whether ATL-146e could ameliorate Con A-induced hepatic injury, reduction of pro-inflammatory cytokine production.

METHODS

Balb/c mice were injected with 25mg/kg Con A with or without a single injection of ATL-146e (0.5-50 microg/kg), 5 min prior to Con A administration. Liver enzymes, histology, and serum levels of tumor necrosis factor-alpha, interferon-gamma, and interleukin-6 were examined. We also assessed the effects of ATL-146e on pro-inflammatory cytokine production with CD4+ T cell.

RESULTS

Pretreatment with ATL-146e significantly reduced serum levels of liver enzymes (P<0.001). The serum pro-inflammatory cytokines were all increased after Con A administration and reduced to near normal levels by ATL-146e. ATL-146e also inhibited CD4+ T cell pro-inflammatory cytokine production.

CONCLUSION

A selective adenosine A2A receptor agonist, ATL-146e, can prevent concanavalin A-induced hepatic injury that is presumably mediated by its anti-inflammatory properties.