Nitric Oxide, Aspirin-Triggered Lipoxins and NO-Aspirin in Gastric Protection

Gastroprotective effects of irsogladine maleate on ethanol/hydrochloric acid induced gastric ulcers in mice

BACKGROUND/AIMS

This study was conducted to investigate the inhibitory effect of irsogladine maleate (IM) on gastric ulcers induced by ethanol and hydrochloric acid (HCl).

METHODS

Mice were pretreated with IM for 1 hours before ulcer induction. Gastric ulcers were induced by oral administration of an ethanol/HCl mixture. To clarify the action mechanism of IM, the roles of 3'5'-cyclic adenosine monophosphate (cAMP), nitric oxide (NO), adenosine triphosphate-sensitive potassium (KATP) channels, prostaglandins and transient receptor potential cation channel subfamily V member 1 (TRPV1) were investigated, and lipid peroxidation in the stomach of IM-treated and -untreated animals was also measured.

RESULTS

IM significantly reduced the extent of ethanol/HCl mixture-induced gastric ulceration. It exhibited dose-related gastroprotection against the ethanol/ HCl-induced lesions, while pretreatment with glibenclamide but not N(ω)-nitro- L-arginine methyl ester, reversed this action. While pretreatment with the TRPV1 antagonist capsazepine failed to effectively block the gastroprotective effect of IM, the non-selective cyclooxygenase inhibitor indomethacin almost abolished it. IM also decreased the level of thiobarbituric acid reactive substances.

CONCLUSION

We concluded that IM exhibited significant gastroprotective effects in an ethanol/HCl-induced ulcer model, which appear to be mediated, at least in part, by NO, cAMP, endogenous prostaglandins, KATP channel opening, activation of TRPV1 channels, and antioxidant properties.

Antiulcer and Antioxidant Activity of a Lectin from Mucuna pruriens Seeds on Ethanol- induced Gastropathy: Involvement of Alpha-2 Adrenoceptors and Prostaglandins

Ethnopharmacological Relevance:

Mucuna pruriens (Mp) belongs to Leguminosae family, it is native of tropical regions and used to treat several maladies such as urinary, neurological, and menstruation disorders, constipation, edema, fever, tuberculosis, ulcers, diabetes, arthritis, dysentery, and cardiovascular diseases. Mp seeds are rich in bioactive compounds, for instance, lectins, a heterogeneous group of proteins and glycoproteins with a potential role as therapeutic tools for several conditions, including gastric disorders. This study investigated the acute toxicity, gastroprotective, and antioxidant activities of a lectin from Mucuna pruriens seeds (MpLec) on ethanol-induced gastropathy model in mice.

Materials & Methods:

Mice received MpLec (5 or 10 mg/kg; i.v.) and were observed for acute toxicity signs; in another experimental series, mice were pre-treated with MpLec (0.001; 0.01 or 0.1 mg/kg, i.v.), ranitidine (80 mg/kg, p.o.), or saline (0.3 mL/30g, i.v.) before ethanol 99.9% (0.2 mL/animal, p.o.), and euthanized 30 min after ethanol challenge. Macroscopic and microscopic gastric aspects, biochemical parameters (tissue hemoglobin levels, iron-induced lipid peroxidation, GSH content, SOD activity, and gastric mucosal PGE2) were measured. Additionally, pharmacological tools (yohimbine, indomethacin, naloxone, L-NAME) were opportunely used to clarify MpLec gastroprotective mechanisms of action.

Results:

No toxicity signs nor death were observed at acute toxicity tests. MpLec reduced ethanol-induced gastric damage, edema, and hemorrhagic patches formation, as well as decreased lipid peroxidation, SOD activity, and increased GSH content. Yohimbine and indomethacin prevented MpLec effects, suggesting the involvement of alpha-2 adrenoceptors and prostaglandins in the MpLec-mediated effects.

Conclusion:

MpLec does not present toxicity signs and shows gastroprotective and antioxidant activities via alpha-2 adrenoceptors and prostaglandins in the ethanol-induced gastropathy model.

Nitric oxide-donating aspirin (NO-Aspirin) suppresses lung tumorigenesis in vitro and in vivo and these effects are associated with modulation of the EGFR signaling pathway

Although regular aspirin use has been shown to lower the risk of colorectal cancer, its efficacy against lung cancer is weak or inconsistent. Moreover, aspirin use increases the risk of ulcers and stomach bleeding. In this study, we determined the efficacy of nitric oxide-donating aspirin (NO-Aspirin), a safer form of aspirin in which the parent drug is linked to a nitric oxide-releasing moiety through a spacer, to suppress lung tumorigenesis. Under in vitro conditions, NO-Aspirin significantly reduced the proliferation and survival of tumorigenic bronchial cell line (1170) and non-small cell lung cancer (NSCLC) cell lines (A549, H1650, H1975 and HCC827) and colony formation by NSCLC cells at sub- or low micromolar concentrations (≤1 µM for 1170 cells and ≤6 µM for NSCLC cells) in a COX-2 independent manner. These effects were paralleled by suppression of phospho-epidermal growth factor receptor (EGFR), -STAT3, -Akt and -ERK and enhanced caspase 3 and PARP cleavage. Among NSCLC cells, EGFR mutant cells (H1650, H1975 and HCC827) were more sensitive than cells expressing wild-type EGFR (A549) and H1650 cells were the most sensitive. Moreover, NO-Aspirin sensitized H1650 and H1975 cells to the antiproliferative effects of erlotinib, a tyrosine kinase inhibitor. In in vivo studies using 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) + lipopolysaccharide (LPS)-induced model of lung tumorigenesis, NO-Aspirin significantly reduced the number and size of lung tumors, expression of phospho-EGFR and -Akt as well as the pro-inflammatory molecules TNF-α and interferon-gamma. Overall, these results indicate the potential of NO-Aspirin for the chemoprevention of lung cancer in high risk populations.

Investigational drugs targeting the prostaglandin E2 signaling pathway for the treatment of inflammatory pain

Non-steroidal anti-inflammatory drugs (NSAID) are the most commonly used drugs for the treatment of pain, inflammation and fever. Although they are effective for a huge number of users, their analgesic properties are not sufficient for several patients and the occurrence of side effects still constitutes a big challenge during long term therapy. Areas covered: This review gives an overview about the first and second generations of NSAIDs (COX1/2 non-selective, COX-2 selective), and their main side effects which gave still an urgent need for safer drugs and for the establishment of novel treatment strategies (improved safety, tolerability, patient convenience). The current developments of a possible third generation NSAID class comprise changes in the formulation of already approved drugs, combination therapies, dual cyclooxygenase-lipoxygenase inhibitors, NO- and H₂S-releasing NSAIDs, prostaglandin synthase inhibitors and EP receptor modulators, respectively. Literature search has been done with PubMed NCBI. Expert opinion: Currently, there is no newly developed drug that is superior to the already approved selective and non-selective NSAIDs. Several novel approaches show promising analgesic efficacy but side effects are still an important problem. Solutions might be constituted by combination therapies allowing administration of lower drug doses or by individualized therapies targeting molecules apart from COX, respectively.

Effects of n-3 PUFAs on Intestinal Mucosa Innate Immunity and Intestinal Microbiota in Mice after Hemorrhagic Shock Resuscitation

n-3 polyunsaturated fatty acids (PUFAs) can improve the function of the intestinal barrier after damage from ischemia-reperfusion or hemorrhagic shock resuscitation (HSR). However, the effects of n-3 PUFAs on intestinal microbiota and the innate immunity of the intestinal mucosa after HSR remain unclear. In the present study, 40 C57BL/6J mice were randomly assigned to five groups: control, sham, HSR, HSR + n-3 PUFAs and HSR + n-6 PUFAs. Mice were sacrificed 12 h after HSR. Liver, spleen, mesenteric lymph nodes and terminal ileal tissues were collected. Intestinal mucosae were scraped aseptically. Compared with the HSR group, the number of goblet cells increased, expression of mucin 2 was restored and disturbed intestinal microbiota were partly stabilized in the PUFA-administered groups, indicating that both n-3 and n-6 PUFAs reduced overproliferation of Gammaproteobacteria while promoting the growth of Bacteroidetes. Notably, n-3 PUFAs had an advantage over n-6 PUFAs in improving ileal tissue levels of lysozyme after HSR. Thus, PUFAs, especially n-3 PUFAs, partly improved the innate immunity of intestinal mucosa in mice after HSR. These findings suggest a clinical rationale for providing n-3 PUFAs to patients recovering from ischemia-reperfusion.

The Preventive Effect on Ethanol-Induced Gastric Lesions of the Medicinal Plant Plumeria rubra: Involvement of the Latex Proteins in the NO/cGMP/K ATP Signaling Pathway

Plumeria rubra (Apocynaceae) is frequently used in folk medicine for the treatment of gastrointestinal disorders, hepatitis, and tracheitis, among other infirmities. The aim of this study was to investigate the gastroprotective potential of a protein fraction isolated from the latex of Plumeria rubra (PrLP) against ethanol-induced gastric lesions and describe the underlying mechanisms. In a dose-dependent manner, the pretreatment with PrLP prevented ethanol-induced gastric lesions in mice after single intravenous administration. The gastroprotective mechanism of PrLP was associated with the involvement of prostaglandins and balance of oxidant/antioxidant factors. Secondarily, the NO/cGMP/K_ATP pathway and activation of capsaicin-sensitive primary afferents were also demonstrated as part of the mechanism. This study shows that proteins extracted from the latex of P. rubra prevent gastric lesions induced in experimental animals. Also, the results support the use of the plant in folk medicine.

Protective Factors of the Gastric and Duodenal Mucosa: An Overview

The structural and functional integrity of the gastric and duodenal mucosa represents equilibrium between aggressive factors and protective mechanisms. Mucus-buffers-phospholipid layer as pre-epithelial barrier, enhanced by prostaglandins and epidermal growth factor, remains a vanguard of mucosal protection. It maintains a neutral pH at the surface epithelial luminal interface, facing luminal pH dropping to 1.0, i.e., hydrogen ion concentration gradient equal 1,000,000. The surface epithelial cells, elaborating mucins, buffers, phospholipids, prostaglandins, trefoil peptides, peptide growth factor and their receptors, heat shock proteins, cathelicidins, and β-defensins form the second line of defense. Endothelium exerts mucosal protection through production of potent vasodilators like nitric oxide and prostacyclins and through release of angiogenic growth factors, securing adequate blood flow and representing the third and an ultimate line of mucosal protection. This microcirculation is instrumental for supply of oxygen, nitric oxide, hydrogen sulfide and removal of ad hoc generated toxic substances as well as for continuous mucosal cell renewal from progenitor cells, secured by growth factors accompanied by survivin preventing early apoptosis.

Protective effects of n-6 fatty acids-enriched diet on intestinal ischaemia/reperfusion injury involve lipoxin A4 and its receptor

BACKGROUND AND PURPOSE

Long-term intake of dietary fatty acids is known to predispose to chronic inflammation, but their effects on acute intestinal ischaemia/reperfusion (I/R) injury is unknown. The aim of this study was to determine the consequences of a diet rich in n-3 or n-6 polyunsaturated fatty acids (PUFA) on intestinal I/R-induced damage.

EXPERIMENTAL APPROACH

Mice were fed three different isocaloric diets: a balanced diet used as a control and two different PUFA-enriched diets, providing either high levels of n-3 or of n-6 PUFA. Intestinal injury was evaluated after intestinal I/R. PUFA metabolites were quantitated in intestinal tissues by LC-MS/MS.

KEY RESULTS

In control diet-fed mice, intestinal I/R caused inflammation and increased COX and lipoxygenase-derived metabolites compared with sham-operated animals. Lipoxin A4 (LxA4 ) was significantly and selectively increased after ischaemia. Animals fed a high n-3 diet did not display a different inflammatory profile following intestinal I/R compared with control diet-fed animals. In contrast, intestinal inflammation was decreased in the I/R group fed with high n-6 diet and level of LxA4 was increased post-ischaemia compared with control diet-fed mice. Blockade of the LxA4 receptor (Fpr2), prevented the anti-inflammatory effects associated with the n-6 rich diet.

CONCLUSIONS AND IMPLICATIONS

This study indicates that high levels of dietary n-6, but not n-3, PUFAs provides significant protection against intestinal I/R-induced damage and demonstrates that the endogenous production of LxA4 can be influenced by diet.

Anti-ulcer activity of essential oil constituents

Essential oils have attracted considerable worldwide attention over the last few decades. These natural products have wide-ranging pharmacological activities and biotechnological applications. Faced with the need to find new anti-ulcer agents and the great effort on the development of drugs for the treatment of ulcers, in this review, the anti-ulcer activities of 21 bioactive compounds found in essential oils are discussed.

Gastroprotective activity of Cenostigma macrophyllum Tul. var. acuminata Teles Freire leaves on experimental ulcer models

ETHNOPHARMACOLOGICAL RELEVANCE

Cenostigma macrophyllum Tul. var. acuminata Teles Freire (Leguminosae-Caesalpinioideae), popularly known in Brazil as "caneleiro", is widely used in folk medicine against gastrointestinal diseases. In previous studies, the ethanol extract of leaves from Cenostigma macrophyllum Tul. var. acuminata Teles Freire had shown antinociceptive, anti-inflammatory, antibacterial, antioxidant and antiulcerogenic activities.

AIM OF THE STUDY

The aim of this study was to assess the gastroprotective effect of the hydroalcoholic fraction of leaves of Cenostigma macrophyllum Tul. var. acuminata Teles Freire (Cm-FHA), as well as to elucidate the possible underlying mechanisms of action.

MATERIALS AND METHODS

Mice were used for the evaluation of the acute toxicity, and mice and rats to study the gastroprotective activity. The potential gastroprotective of Cm-FHA was assessed on different gastric ulcer models in rodents, such as absolute ethanol, HCl/ethanol, ischemia-reperfusion, cold restraint stress and indomethacin. The participation of prostaglandins, NO-synthase pathway and ATP-sensitive potassium channels (KATP) in gastroprotective activity of Cm-FHA were evaluated after treatment with a cyclooxygenase inhibitor (indomethacin), a NO-synthase inhibitor (L-NAME) and a KATP channel blocker (glibenclamide 5mg/kg), respectively. Likewise, the catalase activity was determinated in order to assess the possible participation of antioxidant mechanisms.

RESULTS

No signs of acute toxicity was observed after oral acute administration of Cm-FHA, considering the analyzed parameters. Likewise, Cm-FHA promoted a protective effect against gastric ulcers induced by absolute ethanol (lesion inhibition by 40% at both 100 and 200mg/kg), HCl/ethanol (lesion inhibition by 50 or 48% at 100 or 200mg/kg, respectively), ischemia-reperfusion (lesion inhibition by 49 or 90% at 100 or 200mg/kg, respectively) and cold restraint stress (lesion inhibition by 63 or 76% at 100 or 200mg/kg, respectively), as well as a increase of catalase activity was observed. Otherwise, Cm-FHA was not able to protect gastric mucosa against indomethacin-induced lesions. Nitric oxide release, the of KATP channels opening and antioxidant activity are the possibly involved in the Cm-FHA-induced gastroprotective activity.

CONCLUSION

This study corroborates the folk medicine use of Cenostigma macrophyllum for treatment of gastric ulcers, as well as reinforces this species as a valuable source of promising natural drugs with gastroprotective activity.

Control of myeloid cell trafficking in resolution

Following tissue injury or microbial invasion, neutrophils are robustly recruited to inflammatory loci, which is a hallmark of the host inflammatory response. This event initiates a series of processes required to activate resolution, including recruitment of monocytes, clearance of microbes, cellular debris and apoptotic neutrophils, the egress of phagocytes and, ultimately, regain of tissue homeostasis. Substantial evidence now signifies that resolution of inflammation is a highly coordinated, active process dictated by the spatial-temporal generation of proresolving mediators that act on specific receptors to modulate cell and tissue reactivity. This review will focus on the mediators, targets and pathways initiated to orchestrate resolution. Importantly, disruption of the key processes involved in inflammatory resolution could result in delayed restoration of tissue homeostasis, leading to fibrosis and/or persistent inflammation.

Role of gastric mucus secretion, oxinitrergic system and sulfhydryl groups on the gastroprotection elicited by Polygala cyparissias (Polygalaceae) in mice

Objectives

This study has aimed to assess the mechanisms of action for the gastroprotective effect of the acetone extract (PCAE) and methanol fraction (PCMF) of Polygala cyparissias, as well as to evaluate the activity of 1,3,6,8-tetrahydroxy-2,7-dimethoxyxanthone (1), 1,7-dihydroxy-2,3-dimethoxyxanthone (2) and astragalin (3).

Methods

Gastric secretion and mucus content were determined by pylorus ligation in mice. Nitric oxide (NO) and sulfhydryl group participation were observed by the pretreatment of mice with L-NAME or NEM. Acute ulcer was induced by ethanol/HCl and chronic ulcer by acetic acid. Anti-Helicobacter pylori activity was evaluated by the agar solid dilution assay.

Key findings

Neither PCAE nor PCMF had the ability to reduce H+ concentration. However, both of them enhanced mucus secretion. PCAE demonstrated its gastroprotection in a NO-dependent manner, while PCMF exerted the activity depending on the sulfhydryl group. In chronic ulcer, the curative ratios for the PCAE and PCMF were 67.5 and 58.4%, respectively. No effect over H. pylori was detected. Compounds 1, 2 and 3 were able to reduce lesions in the order of 79.6, 73.8 and 67.6%, respectively.

Conclusions

The data suggested that PCAE and PCMF displayed antiulcer activity due to different mechanisms and with the participation of phenolic compounds obtained from the plant.

Reciprocal regulation of the nitric oxide and cyclooxygenase pathway in pathophysiology: relevance and clinical implications

The nitric oxide (NO) and cyclooxygenase (COX) pathways share a number of similarities. Nitric oxide is the mediator generated from the NO synthase (NOS) pathway, and COX converts arachidonic acid to prostaglandins, prostacyclin, and thromboxane A(2). Two major forms of NOS and COX have been identified to date. The constitutive isoforms critically regulate several physiological states. The inducible isoforms are overexpressed during inflammation in a variety of cells, producing large amounts of NO and prostaglandins, which may underlie pathological processes. The cross-talk between the COX and NOS pathways was initially reported by Salvemini and colleagues in 1993, when they demonstrated in a series of in vitro and in vivo studies that NO activates the COX enzymes to produce increased amounts of prostaglandins. Those studies led to the concept that COX enzymes represent important endogenous "receptor" targets for amplifying or modulating the multifaceted roles of NO in physiology and pathology. Since then, numerous studies have furthered our mechanistic understanding of these interactions in pathophysiological settings and delineated potential clinical outcomes. In addition, emerging evidence suggests that the canonical nitroxidative species (NO, superoxide, and/or peroxynitrite) modulate biosynthesis of prostaglandins through non-COX-related pathways. This article provides a comprehensive state-of-the art overview in this area.

A double-blind controlled trial of a single dose naproxen and an amino acid medical food theramine for the treatment of low back pain

To study the safety and efficacy of a new medical food (Theramine) in the treatment of low back pain, we performed a 28-day double-blind randomized controlled trial in 129 patients. Back pain was present for at least 6 weeks and was not mild. Patients were randomly assigned to receive medical food alone (n = 43), naproxen alone (250 mg/d, n = 42), or both medical food and naproxen (n = 44). All patients were assessed by using Roland-Morris Disability Questionnaire, Oswestry Low Back Pain Scale, Visual Analog Scale Evaluation and laboratory analysis performed at baseline and at 28 days for assessing the safety and impact on inflammatory markers, which included complete blood counts, C-Reactive protein (CRP), and liver function (alkaline phosphatase, aspartate transaminase, and alanine transaminase). At baseline, there were no statistically significant differences in low back pain when assessed by Roland-Morris function or Oswestry assessments nor were there differences in the blood indices of inflammation. At day 28, both the medical food group and combined therapy group (medical food with naproxen) were statistically significantly superior to the naproxen-alone group (P < 0.05). The medical food and naproxen group showed functional improvement when compared to the naproxen-alone group. The naproxen-alone group showed significant elevations in CRP, alanine transaminase, and aspartate transaminase when compared with the other groups. Medical food alone or with naproxen showed no significant change in liver function tests or CRP, with medical food potentially mitigating the effects seen with naproxen alone. The medical food (Theramine) appeared to be effective in relieving back pain without causing any significant side effects and may provide a safe alternative to presently available therapies.

Protective effect of Chresta martii extract on ethanol-induced gastropathy depends on alpha-2 adrenoceptors pathways but not on nitric oxide, prostaglandins or opioids

ETHNOPHARMACOLOGICAL RELEVANCE

Species of Chresta genus- are recognized by the population of northeastern Brazil as traditional herbs used to treat gastric diseases and other disorders.

AIM OF THE STUDY

This work aimed to find out the action mechanism of Chresta martii hydro alcoholic extract gastro protective effect in the model of ethanol-induced gastropathy.

MATERIAL AND METHODS

Gastropathy was assessed by percentual damaged area determination in photographs of mice opened stomachs. Fasted mice treated with ethanol 99.9% (0.2 ml/animal, p.o.) were pre-treated with Chresta martii hydro alcoholic extract (HAE) (50, 100 or 200 mg/kg, p.o.), ranitidine (80 mg/kg, p.o.) or saline (5 ml/kg; p.o.) in different experimental sets, in which pharmacological tools (naloxone, indomethacin, N(ω)-Nitro-L-arginine methyl ester hydrochloride (L-NAME) or yohimbine) were added in order to clarify a possible action mechanism. Animals were sacrificed 30 min after ethanol challenge to stomach analysis. Determination of non-protein sulfhydryl groups and tissue hemoglobin, besides histological assessment (H&E) were taken to fully characterize the HAE gastro protective effect.

RESULTS

HAE (100 and 200 mg/kg) was able to protect mucosa against ethanol gastropathy in presence of three (naloxone, indomethacin and L-NAME) of four antagonist/inhibitor tools. The HAE effect was reversed only by yohimbine, showing the alpha-2 adrenoceptors participation on gastro protective effect of this extract. HAE histological characteristics, NP-SH and Hb were compatible with the protective effects.

CONCLUSIONS

HAE possesses gastroprotective effects in an ethanol-induced gastropathy model in mice, corroborating the traditional use of this family of plants to treat gastric disorders. This activity is mediated by alpha-2 adrenoceptors activation, but not by nitric oxide release, opioid receptor activation or prostaglandin synthesis. HAE also has antioxidant activity that is thought to either play a role in this biological activity or to be a byproduct of alpha-2 adrenergic complex activation.

Aspirin and immune system

The time-tested gradual exploration of aspirin's diverse pharmacological properties has made it the most reliable therapeutic agent worldwide. In addition to its well-argued anti-inflammatory effects, many new and exciting data have emerged regarding the role of aspirin in cells of the immune system and certain immunopathological states. For instance, aspirin induces tolerogenic activity in dendritic cells and determines the fate of naive T cells to regulatory phenotypes, which suggests its immunoregulatory potential in relevance to immune tolerance. It also displays some intriguing traits to modulate the innate and adaptive immune responses. In this article, the immunomodulatory relation of aspirin to different immune cells, such as neutrophils, macrophages, dendritic cells (DCs), natural killer (NK) cells, and the T and B lymphocytes has been highlighted. Moreover, the clinical prospects of aspirin in terms of autoimmunity, allograft rejection and immune tolerance have also been outlined.

Nuclear factor-kappa B mediates TRPV4-NO pathway involved in thermal hyperalgesia following chronic compression of the dorsal root ganglion in rats

The aim of this study was to test the hypothesis that nuclear factor-kappa B (NF-κB) is involved in TRPV4-NO pathway in thermal hyperalgesia following chronic compression of the dorsal root ganglion (DRG) (the procedure hereafter termed CCD) in rat. Intrathecal administration of two NF-κB inhibitors, pyrrolidine dithiocarbamate (PDTC; 10(-1) to 10(-2)M) and BAY (100-50 μM), both induced significantly dose-dependent increase in the paw withdrawal latency (PWL) and decrease in nitric oxide (NO) content in DRG when compared with control rats. Pretreatment with 4α-phorbol 12,13-didecanoate (4α-PDD, transient receptor potential vanilloid 4 (TRPV4) synthetic activator, 1 nm) attenuated the suppressive effects of PDTC (10(-1)M) and BAY (100 μM) on CCD-induced thermal hyperalgesia and NO production. In addition, Western blot analysis indicated that CCD rats exhibited nuclear NF-κB protein expression and low levels of cytoplasmic inhibitory-kappa B (I-κB) expression; the increase in NF-κB expression and decrease in I-κB expression were reversed after intrathecal injection of PDTC. In conclusion, our data suggested that NF-κB could be involved in TRPV4-NO pathway in CCD-induced thermal hyperalgesia.

The role of the DDAH-ADMA pathway in the protective effect of resveratrol analog BTM-0512 on gastric mucosal injury

A recent study showed that resveratrol, a polyphenol found in many plant species, exerts dual effects on gastric mucosal injury. By using the model of ethanol-induced gastric mucosal injury in the present study, we explored the effect of trans-3,5,4'-trimethoxystilbene (BTM-0512), a novel analog of resveratrol, on gastric mucosal injury and the possible underlying mechanisms. Gastric mucosal injury in the rat was induced by oral administration of acidified ethanol. The gastric tissues were collected for determination of the gastric ulcer index, asymmetric dimethylarginine (ADMA) and nitric oxide (NO) contents, the activity of dimethylarginine dimethylaminohydrolase (DDAH) and superoxide anion (O2(-)) or hydroxyl radical (OH*) formation. The results showed that acute administration of ethanol significantly increased the gastric ulcer index concomitantly with the decrease in DDAH activity and NO content as well as the increase in ADMA content, effects that were reversed by pretreatment with BTM-0512 (100 mg/kg) or L-arginine (300 mg/kg). Administration of BTM-0512 did not show a significant effect on O2(-) or OH. formation. The results suggest that BTM-0512 could protect the gastric mucosa against ethanol-induced injury, which is mainly related to an increase in DDAH activity and subsequent decrease in ADMA content.

Gastroprotective effect of a flavone from Lonchocarpus araripensis Benth. (Leguminosae) and the possible mechanism

The gastroprotective effect of DDF (3,6-dimethoxy-6“, 6”-dimethyl-[2“, 3”: 7,8]-chromeneflavone) from Lonchocarpus araripensis Benth. (Leguminosae) on gastric damage induced by absolute ethanol (96%, 0.2 mL/mouse) and indometacin (30 mg kg−1, p.o.) in mice was investigated. Intraperitoneally administered DDF at dose levels of 50, 100 and 200 mg kg−1 markedly reduced the gastric lesions in the ethanol model by 62, 72 and 96%, and in the indometacin model by 34, 70 and 75%, respectively, as compared with misoprostol (50 μg kg−1, p.o.), the reference compound that caused lesion suppression by 67% in ethanol model and by 72% against indometacin-induced ulceration. The ED50 of DDF in reducing gastric lesions induced by ethanol and indometacin (dose of the DDF that reduced the gastric lesion area by 50% in relation to the control value) was 50.87 and 61.56 mg kg−1, respectively. Mechanistic studies were carried out at 100 mg kg−1 DDF using the ethanol model. Compared with N-acetylcysteine (750 mg kg−1, p.o.), a donor of sulfhydryls, DDF only partially replenished the ethanol-induced depletion of gastric mucosal NP-SH. Pretreatment with TRPV1 antagonist capsazepine (5 mg kg−1, i.p.) or the non-selective cyclooxygenase inhibitor indometacin (10 mg kg−1, p.o.) effectively blocked the gastroprotective effect of DDF (100 mg kg−1) against ethanol damage. Furthermore, the effect of DDF was significantly reduced in mice pretreated with L-NAME, or glibenclamide, the respective inhibitors of nitric oxide synthase and K+ATP channel activation. These data provide evidence to show that DDF affords gastroprotection against gastric damage induced by ethanol and indometacin by different and complementary mechanisms, which include involvement of endogenous prostaglandins, nitric oxide release, the activation of TRPV1 receptor or K+ATP channels, besides a sparing effect on NP-SH reserve.

Protective effect of anacardic acids from cashew (Anacardium occidentale) on ethanol-induced gastric damage in mice

Cashew nut-shell liquid and the contained anacardic acids (AAs) have been shown to possess antioxidant, lipoxygenase inhibitory, anti-Helicobacter pylori and antitumor properties. Despite these known effects, hitherto there were no published reports on their likely gastroprotective effects. The present study was designed to verify whether AAs afford gastroprotection against the ethanol-induced gastric damage and to examine the underlying mechanism(s). Gastric damage was induced by intragastric administration of 0.2mL of ethanol (96%). Mice in groups were pretreated orally with AAs (10, 30 and 100mg/kg), misoprostol (50 microg/kg), or vehicle (2% Tween 80 in saline, 10mL/kg), 45min before ethanol administration. They were sacrificed 30min later, the stomachs excised, and the mucosal lesion area (mm(2)) measured by planimetry. Gastroprotection was assessed in relation to inhibition of gastric lesion area. To study the gastroprotective mechanism(s), its relations to capsaicin-sensitive fibers, endogenous prostaglandins, nitric oxide and ATP-sensitive potassium channels were analysed. Treatments effects on ethanol-associated oxidative stress markers GSH, MDA, catalase, SOD, and total nitrate/nitrite levels as an index of NO were measured in gastric tissue. Besides, the effects of AAs on gastric secretory volume and total acidity were analysed in 4-h pylorus-ligated rat. AAs afforded a dose-related gastroprotection against the ethanol damage and further prevented the ethanol-induced changes in the levels of GSH, MDA, catalase, SOD and nitrate/nitrite. However, they failed to modify the gastric secretion or the total acidity. It was observed that the gastroprotection by AAs was greatly reduced in animals pretreated with capsazepine, indomethacin, l-NAME or glibenclamide. These results suggest that AAs afford gastroprotection principally through an antioxidant mechanism. Other complementary mechanisms include the activation of capsaicin-sensitive gastric afferents, stimulation of endogenous prostaglandins and nitric oxide, and opening of K(+)(ATP) channels. These combined effects are likely to be accompanied by an increase in gastric microcirculation.

Review article: cellular and molecular mechanisms of NSAID-induced peptic ulcers

BACKGROUND

Nonsteroidal anti-inflammatory drugs (NSAIDs) are some of the most prescribed drugs worldwide and have now probably overtaken Helicobacter pylori as the most common cause of gastrointestinal injury in Western countries. Further understanding of the pathogenesis of NSAID-induced ulcers is important to enable the development of novel and effective preventive strategies.

AIMS

To provide an update on recent advances in our understanding of the cellular and molecular mechanisms involved in the development of NSAID-induced ulcers.

METHODS

A Medline search was performed to identify relevant literature using search terms including 'nonsteroidal anti-inflammatory drugs, aspirin, gastric ulcer, duodenal ulcer, pathogenesis, pharmacogenetics'.

RESULTS

The mechanisms of NSAID-induced ulcers can be divided into topical and systemic effects and the latter may be prostaglandin-dependent (through COX inhibition) or prostaglandin-independent. Genetic factors may play an important role in determining individual predisposition.

CONCLUSIONS

The pathogenesis of NSAID-induced peptic ulcers is complex and multifactorial. Recent advances in cellular and molecular biology have highlighted the importance of various prostaglandin-independent mechanisms. Pharmacogenetic studies may provide further insights into the pathogenetic mechanisms of NSAID-induced ulcers and help identify patients at increased risk.

Role of nitric oxide in the gastrointestinal tract

Worldwide osteoarthritis (OA) affects more than 9.6% of men and 18% of women older that 60 years. Treatment for OA often requires chronic use of selective or nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), which have been associated with gastrointestinal and cardiovascular complications. An increased risk for upper gastrointestinal bleeding with NSAIDs alone and when combined with low-dose aspirin has been described in numerous studies. Although cyclo-oxygenase-2 inhibitors have been shown to carry a lower risk for gastrointestinal injury than nonselective NSAIDs, research continues to identify new treatments that not only are effective but also provide an improved benefit/risk profile, including better gastrointestinal tolerability. Nitric oxide (NO) is known to have a protective effect on the gastrointestinal tract. In preclinical studies NO was shown to help maintain gastric mucosal integrity, to inhibit leukocyte adherence to the endothelium, and to repair NSAID-induced damage. In addition, epidemiologic studies have shown that the use of NO-donating agents with NSAIDs or aspirin resulted in reduced risk for gastrointestinal bleeding. Recent studies have shown that cyclo-oxygenase inhibiting NO-donating drugs (CINODs), in which a NO molecule is chemically linked to an NSAID, are effective anti-inflammatory agents and may result in less gastrointestinal damage than is associated with NSAID use. Therefore, these agents provide a potential therapeutic option for patients with arthritis who require long-term NSAID therapy.

Nitric oxide as a target of complementary and alternative medicines to prevent and treat inflammation and cancer

Nitric oxide (NO) and associated reactive nitrogen species (RNS) are involved in many physiological functions. There has been an ongoing debate to whether RNS can inhibit or perpetuate chronic inflammation and associated carcinogenesis. Although the final outcome depends on the genetic make-up of its target, the surrounding microenvironment, the activity and localization of nitric oxide synthase (NOS) isoforms, and overall levels of NO/RNS, evidence is accumulating that in general, RNS drive inflammation and cancers associated with inflammation. To this end, many complementary and alternative medicines (CAMs) that work in chemoprevention associated with chronic inflammation, are inhibitors of excessive NO observed in inflammatory conditions. Here, we review recent literature outlining a role of NO/RNS in chronic inflammation and cancer, and point toward NO as one of several targets for the success of CAMs in treating chronic inflammation and cancer associated with this inflammation.

Quebrachitol-induced gastroprotection against acute gastric lesions: role of prostaglandins, nitric oxide and K+ ATP channels

The effect of Quebrachitol (2-O-methyl-L-inositol), a bioactive component from Magonia glabrata fruit extract was investigated against gastric damage induced by absolute ethanol (96%, 0.2 ml/animal) and indomethacin (30 mg/kg, p.o.), in mice. Quebrachitol at oral doses of 12.5, 25, and 50mg/kg markedly attenuated the gastric lesions induced by ethanol to the extent of 69%, 64%, and 53% and against indomethacin by 55%, 59%, and 26%, respectively. While pretreatment with TRPV1 antagonist capsazepine (5mg/kg, i.p.) failed to block effectively the gastroprotective effect of quebrachitol (25mg/kg) against ethanol damage, the non-selective cyclooxygenase inhibitor indomethacin (10mg/kg, p.o.), almost abolished it. Furthermore, quebrachitol effect was significantly reduced in mice pretreated with L-NAME, or glibenclamide, the respective inhibitors of nitric oxide synthase and K(+)(ATP) channel activation. Thus we provide the first evidence that quebrachitol reduces the gastric damage induced by ethanol and indomethacin, at least in part, by mechanisms that involve endogenous prostaglandins, nitric oxide release, and or the activation of K(+)(ATP) channels.

NO-donating NSAIDs and cancer: an overview with a note on whether NO is required for their action

Nitric oxide-donating nonsteroidal anti-inflammatory drugs (NO-NSAIDs) consist of a conventional NSAID to which an NO-releasing moiety is attached covalently, often via a spacer molecule. NO-NSAIDs represent an emerging class of compounds with chemopreventive properties against a variety of cancers, demonstrated in preclinical models including cell culture systems and animal tumor models; their potential efficacy in humans has not been assessed. Their mechanism of action appears complex and involves the generation of reactive oxygen species, suppression of microsatellite instability in mismatch repair-deficient cells, and modulation of several signaling cascades that culminate in inhibited cell renewal and enhanced apoptosis. NO, long appreciated to be able to protect from and also promote cancer, is released form NO-NSAIDs and constitutes their defining property. Existing data are consistent with the notion that NO may mediate their anticancer effect. In addition there is evidence that long-term administration of NO-donating compounds is not associated with increased incidence of colon cancer. Whether NO release is required for the anticancer effect of NO-NSAIDs has being questioned by recent data indicating that, at least in the case of NO-aspirin, the NO-releasing moiety may serve as a leaving group while the spacer actually being the moiety responsible for its pharmacological action. Regardless of mechanistic issues, these compounds promise to contribute to the control of cancer.

Biochemical aspects of inflammation

This review considers biochemical aspects of inflammation. The international literature until December 2006 has been analyzed, with the principal attention paid to the most dynamic problems: enzymology of inflammation, its regulation by hormones and signal transducers, and negative feedbacks, which underlie intensive current studies on pathogenesis, diagnostics, and therapy of inflammation. Such achievements as discoveries of defensins, toll-like receptors, interconnections of inflammation and iron metabolism, the roles of oxidative stress and antioxidant defense, lipoxins, inflammatory components of "non-inflammatory" diseases, and action mechanisms of effective drugs are discussed.

Roles of platelet and endothelial cell COX-1 in hypercholesterolemia-induced microvascular dysfunction

Aspirin is a common preventative therapy in patients at risk for cardiovascular diseases, yet little is known about how aspirin protects the vasculature in hypercholesterolemia. The present study determines whether aspirin, nitric oxide-releasing aspirin (NCX-4016), a selective cyclooxygenase (COX)-1 inhibitor (SC560), or genetic deficiency of COX-1 prevents the inflammatory and prothrombogenic phenotype assumed by hypercholesterolemic (HC) venules. Aspirin or NCX-4016 (60 mg/kg) was administered orally for the last week of a 2-wk HC diet. COX-1-deficient (COX-1(-/-)) and wild-type (WT) mice were transplanted with WT (WT/COX-1(-/-)) or COX-1(-/-) (COX-1(-/-)/WT) bone marrow, respectively. HC-induced adhesion of platelets and leukocytes in murine intestinal venules, observed with intravital fluorescence microscopy, was greatly attenuated in aspirin-treated mice. Adhesion of aspirin-treated platelets in HC venules was comparable to untreated platelets, whereas adhesion of SC560-treated platelets was significantly attenuated. HC-induced leukocyte and platelet adhesion in COX-1(-/-)/WT chimeras was comparable to that in SC560-treated mice, whereas the largest reductions in blood cell adhesion were in WT/COX-1(-/-) chimeras. NCX-4016 treatment of platelet recipients or donors attenuated leukocyte and platelet adhesion independent of platelet COX-1 inhibition. Platelet- and endothelial cell-associated COX-1 promote microvascular inflammation and thrombogenesis during hypercholesterolemia, yet nitric oxide-releasing aspirin directly inhibits platelets independent of COX-1.

Therapeutic approaches to inflammation in neurodegenerative disease

PURPOSE OF REVIEW

According to the neuroinflammatory hypothesis of neurodegenerative diseases, drugs with an anti-inflammatory mode of action should slow the disease progression. Here we review recent advances in our understanding of one such disorder, Parkinson's disease, in which anti-inflammatory drugs are now becoming a new therapeutic focus.

RECENT FINDINGS

The involvement of inflammatory mechanisms in Parkinson's disease has been revealed through in-vitro and in-vivo experimental studies supported by pathological and epidemiological findings. Several of the demonstrated inflammatory mechanisms are shared by other neurodegenerative disorders but some Parkinson's disease-specific mechanisms have also emerged. These include inflammatory stimulation by interaction of alpha-synuclein with microglia and astrocytes and a suppressive action by nonsteroidal anti-inflammatory drugs on dopamine quinone formation.

SUMMARY

It can be anticipated that a more detailed understanding of neuroinflammatory mechanisms in Parkinson's disease will lead to new cellular and molecular targets, which may, in turn, permit design of Parkinson's disease modifying drugs. Future treatment may involve combination therapies with drugs directed at both inflammatory and non-inflammatory mechanisms.

Evaluation of nitrate-substituted pseudocholine esters of aspirin as potential nitro-aspirins

Herein we explore some designs for nitro-aspirins, compounds potentially capable of releasing both aspirin and nitric oxide in vivo. A series of nitrate-bearing alkyl esters of aspirin were prepared based on the choline ester template preferred by human plasma butyrylcholinesterase. The degradation kinetics of the compounds were followed in human plasma solution. All compounds underwent hydrolysis rapidly (t(1/2) approximately 1min) but generating exclusively the corresponding nitro-salicylate. The one exception, an N-propyl, N-nitroxyethyl aminoethanol ester produced 9.2% aspirin in molar terms indicating that the nitro-aspirin objective is probably achievable if due cognisance can be paid to the demands of the activating enzyme. Even at this low level of aspirin release, this compound is the most successful nitro-aspirin reported to date in the key human plasma model.

Nitrosative stress inhibits the aminophospholipid translocase resulting in phosphatidylserine externalization and macrophage engulfment: implications for the resolution of inflammation

Macrophage recognition of apoptotic cells depends on externalization of phosphatidylserine (PS), which is normally maintained within the cytosolic leaflet of the plasma membrane by aminophospholipid translocase (APLT). APLT is sensitive to redox modifications of its -SH groups. Because activated macrophages produce reactive oxygen and nitrogen species, we hypothesized that macrophages can directly participate in apoptotic cell clearance by S-nitrosylation/oxidation and inhibition of APLT causing PS externalization. Here we report that exposure of target HL-60 cells to nitrosative stress inhibited APLT, induced PS externalization, and enhanced recognition and elimination of "nitrosatively" modified cells by RAW 264.7 macrophages. Using S-nitroso-L-cysteine-ethyl ester (SNCEE) and S-nitrosoglutathione (GSNO) that cause intracellular and extracellular trans-nitrosylation of proteins, respectively, we found that SNCEE (but not GSNO) caused significant S-nitrosylation/oxidation of thiols in HL-60 cells. SNCEE also strongly inhibited APLT, activated scramblase, and caused PS externalization. However, SNCEE did not induce caspase activation or nuclear condensation/fragmentation suggesting that PS externalization was dissociated from the common apoptotic pathway. Dithiothreitol reversed SNCEE-induced S-nitrosylation, APLT inhibition, and PS externalization. SNCEE but not GSNO stimulated phagocytosis of HL-60 cells. Moreover, phagocytosis of target cells by lipopolysaccharide-stimulated macrophages was significantly suppressed by an NO. scavenger, DAF-2. Thus, macrophage-induced nitrosylation/oxidation plays an important role in cell clearance, and hence in the resolution of inflammation.