Role of antioxidative activity in the docosahexaenoic acid's enteroprotective effect in the indomethacin-induced small intestinal injury model.

Therapeutic effect of non-steroidal anti-inflammatory drugs (NSAIDs) has been related with gastrointestinal injury. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid (PUFA), can prevent gastric and small intestinal damage. Nonetheless, contribution of antioxidative action in the protective effect of DHA has not been evaluated before in the small intestine injury after indomethacin treatment. Pathogenesis of NSAID-induced small intestinal injury is multifactorial, and reactive oxidative species have been related to indomethacin's small intestinal damage. The present work aimed to evaluate antioxidative activity in the protective action of DHA in the indomethacin-induced small intestinal damage. Female Wistar rats were gavage with DHA (3 mg/kg) or omeprazole (3 mg/kg) for 10 days. Each rat received indomethacin (3 mg/kg, orally) daily to induce small intestinal damage. The total area of intestinal ulcers and histopathological analysis were performed. In DHA-treated rats, myeloperoxidase and superoxide dismutase activity, glutathione, malondialdehyde, leukotriene, and lipopolysaccharide (LPS) levels were measured. Furthermore, the relative abundance of selective bacteria was assessed. DHA administration (3 mg/kg, p.o.) caused a significant decrease in indomethacin-induced small intestinal injury in Wistar rats after 10 days of treatment. DHA's enteroprotection resulted from the prevention of an increase in myeloperoxidase activity, and lipoperoxidation, as well as an improvement in the antioxidant defenses, such as glutathione levels and superoxide dismutase activity in the small intestine. Furthermore, we showed that DHA's enteroprotective effect decreased significantly LPS levels in indomethacin-induced injury in small intestine. Our data suggest that DHA's enteroprotective might be attributed to the prevention of oxidative stress.

Role of LTB4 and nitric oxide in the gastroprotective effect of Prosthechea karwinskii leaves extract in the indomethacin-induced gastric injury in the rat.

Gastric injury is mainly described by inflammation of the gastric epithelium. Recently, our group of work demonstrated that Prosthechea karwinskii leaves extract induces both an in vitro antioxidative action and an in vivo gastroprotective effect in a rat. However, the molecules involved in the gastroprotective action by Prosthechea karwinskii are not known. Thus, the aim of this study is to determine whether Prosthechea karwinskii extract modifies anti-inflammatory and antioxidative biomarkers in an in vivo rat model of indomethacin-induced gastric injury. Rats were orally administered with indomethacin and Prosthechea karwinskii leaf extract. Our results suggest that the gastroprotective effect of Prosthechea karwinskii leaf extract is related to the reduction in leukocyte infiltration and antioxidative action in a model of indomethacin-induced gastric injury. Further studies are warranted to investigate the role of the compounds identified in the gastroprotective action of Prosthechea karwinskii leaves extract.

Gastroprotective effect methanol extract of Caesalpinia coriaria pods against indomethacin- and ethanol-induced gastric lesions in Wistar rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Caesalpinia coriaria (Jacq.) Willd is widely used as a traditional medinal plant in Mexico for protective and healing purposes and the treatment of gastrointestinal diseases. AIM OF THE STUDY: To investigate the gastroprotective effect of extract of Caesalpinia coriaria pods against ethanol-induced and indomethacin-induced gastric lesion models, its anti-inflammatory and antioxidative activities, and its main compounds through LC-MS analysis. MATERIALS AND METHODS: Male Wistar rats were orally administered a methanol extract obtained from the pods of C. coriaria at doses of 10, 30, 100, and 300 mg/kg prior to inducing gastric lesions with ethanol or indomethacin. Gastric mucosal lesions were evaluated by macroscopic and histopathological alterations. Determination of prostaglandin E2 (PGE2), alpha tumor necrosis factor (TNF-α), leukotriene B4 (LTB4), nitrites/nitrates, superoxide dismutase (SOD), and H2S gastric levels were investigated. Its main compounds of the active extract through LC-MS analysis. RESULTS: Phenolic compounds were identified as major components of methanol extract. LC-MS analysis identified 15 constituents, and the significant compounds were gallic acid, 3-O-galloylquinic acid, digalloylglucose, tetragalloylglucose, valoneic acid dilactone, pentagalloylglucose, digalloylshikimic acid, and ellagic acid. Pretreatment with the extract at doses of 100 and 300 mg/kg significantly reduced gastric ulcer lesions in both models. Compared with the reference drugs (omeprazole or ranitidine, respectively), no significant difference was found (p < 0.05). The extract's gastroprotective effect was accompanied by significant decreases in leukocyte recruitment, and gastric levels of TNF-α and LTB4 by two to fourfold (p < 0.05). Also, gastric levels of PGE2 gastric levels were maintained and the antioxidant enzyme activities of SOD and nitrate/nitrite in the gastric tissue were improved (p < 0.05). The LC-MS analysis indicated the presence of hydrolyzable tannins (mainly gallic acid derivatives). CONCLUSION: The results suggest that the gastroprotective effect of the methanol extract of C. coriaria pods occurs through anti-inflammatory, antioxidant, and NO modulation properties, and gallic acid derivatives may be the main possible compounds responsible for its actions.

Synergistic protective effects between docosahexaenoic acid and omeprazole on the gastrointestinal tract in the indomethacin-induced injury model.

Nonsteroidal anti-inflammatory drugs (NSAIDs) are the most commonly used drugs due to their antipyretic, anti-inflammatory, and analgesic properties. However, NSAIDs can cause adverse reactions, mainly gastrointestinal damage. Omeprazole (OMP) exhibits gastroprotective activity, but its protection is limited at the intestinal level. For this reason, it is essential to utilize a combination of therapies that provide fewer adverse effects, such as the combined treatment of OMP and docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid with anti-inflammatory, analgesic, and gastroprotective activities. The objective of this study was to evaluate the pharmacological interaction between DHA and OMP in a murine model of indomethacin-induced gastrointestinal damage. The gastroprotective and enteroprotective effects of DHA (0.3-10 mg/kg, p.o.), OMP (1-30 mg/kg, p.o.), or the combination treatment of both compounds (3-56.23 mg/kg, p.o.) were evaluated in the indomethacin-induced gastrointestinal damage model (30 mg/kg, p.o.). Since DHA and OMP exhibited a protective effect in a dose-responsive fashion, the ED30 for each individual compound was determined and a 1:1 combination of DHA and OMP was tested. Isobolographic analysis was used to determine any pharmacodynamic interactions. Since the effective experimental dose ED30 (Zexp) of the combined treatment of DHA and OMP was lower than the theoretical additive dose (Zadd; p < .05) in both the stomach and small intestine their protective effects were considered synergistic. These results indicate that the synergistic protective effects from combined treatment of DHA and OMP could be ideal for mitigating damage generated by NSAIDs at the gastrointestinal level.

Anti-inflammatory, antioxidant, and gaso-protective mechanism of 3α-hydroxymasticadienoic acid and diligustilide combination on indomethacin gastric damage.

The co-administration of 3α-hydroxymasticadienoic acid (3α-OH MDA) and diligustilide (DLG) generates a synergist gastroprotective effect on indomethacin-induced gastric damage. However, the related protective activities of the compounds alone (or in combination) remain unclear. In the present study, we evaluated the anti-inflammatory and antioxidative activities, as well as the potential modulation of important gasotransmitters of each compound individually and in combination using the indomethacin-induced gastric damage model. Male Wistar rats were treated orally with the 3α-OH MDA, DLG, or their combination (at a fixed ratio of 1:1, 1:3, and 3:1) 30 min before the generation of gastric mucosal lesions with indomethacin (30 mg/kg, p.o.). Three hours later, the gastric injury (mm2) was determined. Results from these experiments indicate, in addition to maintaining basal levels of PGE2, the gastroprotective effect of the pre-treatment with 3α-OH MDA (70%), DLG (81%), and their combination (72%) which was accompanied by significant decreases in leukocyte recruitment, as well as decreases in TNF-α and LTB4 gastric levels (p < 0.05). We also found that the pre-treatment maintains the basal antioxidant enzyme activities (SOD) and gastric NO and H2S production even in the presence of indomethacin (p < 0.05). In conclusion, when 3α-OH MDA-DLG is given at a 1:1 combination ratio, the gastroprotective effect and the inflammatory, antioxidant, and gaso-modulation properties are not different from those of treatments using the maximum doses of each compound, revealing that this combination produces promising results for the treatment of gastric ulcers.

Prosthechea karwinskii, an orchid used as traditional medicine, exerts anti-inflammatory activity and inhibits ROS.

ETHNOPHARMACOLOGICAL RELEVANCE: Prosthechea karwinskii (Mart.) J.M.H. Shaw is a Mexican orchid used in traditional medicine by some indigenous communities to treat issues related to inflammation (cough, wounds, burns, and diabetes). Pharmacological research of this orchid could validate its therapeutic uses and demonstrate its potential for treating other health conditions of high prevalence in Mexico, including those associated with oxidative stress such as diabetes, cancer, atherosclerosis, and hypertension as well as inflammation. AIM OF THE STUDY: The leaf extract from P. karwinskii was examined to identify its compounds and elucidate its inhibitory effect on reactive oxygen species as well as its anti-inflammatory activity and gastroprotective effects in an animal model. MATERIALS AND METHODS: Compounds were identified via ultra-high-performance liquid chromatography coupled with electrospray ionization with quadrupole time of flight-mass spectrometry. Inhibition of reactive oxygen species was determined ex vivo in peripheral blood mononuclear cells with 2',7'-dichlorodihydrofluorescein diacetate. The anti-inflammatory activity was assessed using a carrageenan-induced paw edema model in Wistar rats; nitric oxide and tumor necrosis factor alpha levels were quantified. The gastroprotective effect was evaluated in Wistar rats with indomethacin-induced gastric injury. RESULTS: Nine compounds were identified in the P. karwinskii leaf extract. Most compounds, such as quinic acid, malic acid, neochlorogenic acid, chlorogenic acid, rutin, embelin, pinellic acid, and azelaic acid, were reported to exhibit antioxidant and/or anti-inflammatory activity. The extract was also found to inhibit reactive oxygen species in the ex vivo model. Unlike other anti-inflammatory drugs, the extract exerted a dual effect: anti-inflammatory activity and protection of the gastric mucosa. The results showed that the extract could significantly inhibit the release of nitric oxide without a dose-response relationship. CONCLUSION: P. karwinskii leaf extract inhibited reactive oxygen species and exerted an anti-inflammatory effect. Moreover, this extract did not induce gastric damage in the animals. The bioactivity of the species was found to support its use in traditional medicine. This orchid could be used to treat inflammatory diseases without causing the side effects associated with nonsteroidal anti-inflammatory drugs. It can also be employed to treat other pathological conditions associated with oxidative stress. The findings herein form the basis for the future discovery of natural products that may serve as safe alternative therapies for inflammatory disorders.

The antihyperalgesic effect of docosahexaenoic acid in streptozotocin-induced neuropathic pain in the rat involves the opioidergic system.

Docosahexaenoic acid (DHA) is a polyunsaturated fatty acid that has shown an antinociceptive effect in multiple pain models, such as inflammatory and neuropathic pain by chronic constriction injury in rats; however, its mechanism of action is still not well-understood. Reports suggest that DHA activates opioid signaling, but there is no information on this from a model of neuropathic pain. As a result, the aims of this study were (1) to determine the antihyperalgesic and antiallodynic effect of peripheral DHA administration, and (2) to evaluate the participation of the opioid receptors in the antihyperalgesic effect of DHA on streptozotocin-induced neuropathic pain in the rat. Female Wistar rats were injected with streptozotocin (50 mg/kg, i.p.) to induce hyperglycemia. The formalin, Hargreaves, and von Frey filaments tests were used to assess the nociceptive activity. Intraplantar administration of DHA (100-1000 µg/paw) or gabapentin (562-1778 µg/paw) decreased formalin-evoked hyperalgesia in diabetic rats, in a dose-dependent manner. Furthermore, DHA (562 µg/paw) and gabapentin (1000 µg/paw) reduced thermal hyperalgesia and allodynia. Local peripheral administration of naloxone (non-selective opioid receptor antagonist; 100 µg/paw), naltrindole (selective δ receptor antagonist; 1 µg/paw), and CTOP (D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2, µ receptor antagonist; 20 µg/paw) prevented formalin-evoked hyperalgesia in diabetic rats but not by GNTI (guanidinonaltrindole, κ receptor antagonist;1 µg/paw). It is suggested that peripheral DHA shows an antihyperalgesic effect in neuropathic pain in the rat. Furthermore, δ and µ receptors are involved in the antihyperalgesic peripheral effect of DHA in diabetic rats.

Synergistic interaction between docosahexaenoic acid and diclofenac on inflammation, nociception, and gastric security models in rats.

Preclinical Research & Development The addition of polyunsaturated fatty acids to nonsteroidal anti-inflammatory drugs can increase their antinociceptive activity and produce a gastroprotective effect. The aim of the present study was to examine the effects of the interaction between docosahexaenoic acid (DHA) and diclofenac on inflammation (fixed ratios 1:1, 1:3, and 3:1), nociception (fixed ratio 1:3), and gastric injury in rats. DHA, diclofenac, or combinations of DHA and diclofenac produced anti-inflammatory and antinociceptive effects in rat. The administration of diclofenac produced significant gastric damage, but this effect was not observed with either DHA or the DHA-diclofenac combinations. Effective dose (ED30 ) values were estimated for each individual drug and analyzed isobolographically. The anti-inflammatory experimental ED30 values were 6.97 mg/kg (1:1 fixed ratio), 1.1 mg/kg (1:3 fixed ratio), and 11.34 mg/kg (3:1 fixed ratio). These values were significantly lower (p < .05) than the theoretical ED30 values: 67.94 mg/kg (1:1), 35.37 mg/kg (1:3), and 100.51 mg/kg (3:1). The antinociceptive experimental value was 1.25 mg/kg (1:3 fixed ratio). This value was lower (p < .05) than the theoretical ED30 , which was predicted to be 15.92 mg/kg. These data indicate that the DHA-diclofenac combinations interact at the systemic level, produce minor gastric damage, and potentially have therapeutic advantages for the clinical treatment of inflammatory pain.

Pharmacological interaction of α-bisabolol and diclofenac on nociception, inflammation, and gastric integrity in rats.

Preclinical Research & Development The combination of nonsteroidal anti-inflammatory drugs (NSAIDs) with herbal products having analgesic and anti-inflammatory effects may increase their beneficial effects and limit their side effects. In this study, the effects of an interaction between α-bisabolol and the NSAID, diclofenac on nociception (formalin test), inflammation (paw inflammation produced by carrageenan) and gastric injury in rat was assessed. Diclofenac, α-bisabolol, or diclofenac-α-bisabolol combinations produced antinociceptive and anti-inflammatory effects in rat (p < .05). The systemic administration of diclofenac, but not α-bisabolol, produced gastric damage while the diclofenac-α-bisabolol combinations produced limited gastric damage. Effective dose (ED40 ) values were determined for each individual drug and analyzed isobolographically. The theoretical ED40 values for the antinociceptive (98.89 mg/kg) and the anti-inflammatory (41.2 mg/kg) effects differed from the experimental ED40 values (antinociception: 38.7 mg/kg and anti-inflammation: 13.4 mg/kg). We concluded that the interactions between diclofenac and α-bisabolol are synergistic. These data suggest that the diclofenac-α-bisabolol combinations can interact to produce minor gastric damage, thereby offering a safer therapeutic alternative for the clinical management of inflammation and/or inflammatory pain.

Participation of the anti-inflammatory and antioxidative activity of docosahexaenoic acid on indomethacin-induced gastric injury model.

Adverse gastrointestinal (GI) effects caused by nonsteroidal anti-inflammatory drugs (NSAIDs), including indomethacin, are recognized as the major limitation to their clinical use. NSAID-induced gastric damage is generated by cyclooxygenase inhibition, activation of inflammatory processes, and oxidative stress. Docosahexaenoic acid (DHA), an omega-3 polyunsaturated fatty acid, has shown gastroprotective effects; however, the molecular mechanisms underlying these effects have not been fully explained. As a result, the aim of this study was to examine DHA's anti-inflammatory and antioxidative actions in a mouse model of indomethacin-induced gastric injury. Oral administration of DHA (3, 10, 30, and 100mg/kg) caused a reduction in indomethacin-induced gastric hemorrhagic lesions. We found that the gastroprotective effects of DHA treatment (100mg/kg) were accompanied by decreases in several parameters: in leukocyte recruitment; gastric levels of myeloperoxidase; leukotriene B4; intercellular adhesion molecule-1; tumor necrosis factor alpha; and nuclear translocation of nuclear factor-кB. Concurrently, we observed an improvement in antioxidant defenses produced by the increase in superoxide dismutase and glutathione activities but not catalase; in addition, a decrease in some oxidative damage markers such as malondialdehyde and carbonyl proteins in lipids and proteins was observed. Furthermore, resolvin D1 production and expression of free fatty acid receptor 4 were stimulated by DHA. Therefore, this study identified the antioxidant and anti-inflammatory actions of DHA as the main mechanisms involved in DHA's gastroprotective effects against indomethacin-induced gastric damage.

Supra-Additive Interaction of Docosahexaenoic Acid and Naproxen and Gastric Safety on the Formalin Test in Rats.

Preclinical Research The aim of this work was to evaluate the effect of docosahexaenoic acid (DHA) on the pharmacokinetics and pharmacodynamics-nociception-of naproxen in rats, as well as to determine the gastric safety resulting from this combination versus naproxen alone. Female Wistar rats were orally administered DHA, naproxen or the DHA-naproxen mixture at fixed-ratio combination of 1:3. The antinociceptive effect was evaluated using the formalin test. The gastric injury was determined 3 h after naproxen administration. An isobolographic analysis was performed to characterize the antinociceptive interaction between DHA and naproxen. To determine the possibility of pharmacokinetic interactions, the oral bioavailability of naproxen was evaluated in presence and absence of oral DHA. The experimental effective dose ED30 values (Zexp) were decreased from theoretical additive dose values (Zadd; P < 0.05). The isobolographic analysis showed that the combination exhibited supra-additive interaction. The oral administration of DHA increased the pharmacokinetic parameter AUC0-t of naproxen (P < 0.05). Furthermore, the gastric damage induced by naproxen was abolished when this drug was combined with DHA. These data suggest that oral administration of DHA-naproxen combination induces gastric safety and supra-additive antinociceptive effect in the formalin test so that this combination could be useful to management of inflammatory pain. Drug Dev Res 78 : 332-339, 2017. © 2017 Wiley Periodicals, Inc.

Evidence against the participation of a pharmacokinetic interaction in the protective effect of single-dose curcumin against gastrointestinal damage induced by indomethacin in rats.

OBJECTIVE: To determine the role of a pharmacokinetic interaction in the protective effect of curcumin against the gastric damage induced by indomethacin administration as such or as its prodrug acemetacin. METHODS: Wistar rats orally received single dose of indomethacin (30 mg/kg) with and without curcumin (30 mg/kg); gastric injury was evaluated by determining the total damaged area. Additional groups of rats received an oral single dose of indomethacin (30 mg/kg) or its prodrug acemetacin (34.86 mg/kg) in the presence or absence of curcumin (30 mg/kg). Indomethacin and acemetacin concentrations in plasma from blood draws were determined by high-performance liquid chromatography.Plasma concentration-against-time curves were constructed, and bioavailability parameters, maximal concentration (Cmax) and area under the curve to the last sampling time (AUC0-t) were estimated. RESULTS: Concomitant administration of indomethacin and curcumin resulted in a significantly reduced gastric damage compared to indomethacin alone. However, co-administration of curcumin did not produce any significant alteration in the bioavailability parameters of indomethacin and acemetacin after administration of either the active compound or the prodrug. CONCLUSION: Curcumin exhibits a protective effect against indomethacin-induced gastric damage, but does not produce a reduction of the bioavailability of this nonsteroidal anti-inflammatory drug, indomethacin. Data thus suggest that a pharmacokinetic mechanism of action is not involved in curcumin gastroprotection.

Participation of potassium channels in the antinociceptive effect of docosahexaenoic acid in the rat formalin test.

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid (PUFA) that has shown gastroprotective, cardioprotective, neuroprotective, anti-inflammatory and antinociceptive effects in different models. However, its action mechanism is still not well-defined. Reports indicate that some PUFAs regulate potassium (K+) channels in ventricular myocytes of rodents. As a result, the aim of this study was to evaluate the probable participation of K+ channels in the antinociceptive effect of DHA. The rat paw 1% formalin test was used to assess nociception and antinociception. Fifty microliters of formalin solution were administered subcutaneously in the paw, and the number of flinches were quantified. Rats were treated with local peripheral administration of DHA (100-1778µg/paw) or diclofenac (10-300µg/paw). The antinociception of DHA was evaluated with and without the local pretreatment of K+ channel blockers. DHA and diclofenac produced dose-dependent antinociceptive effects during the second phase (P<0.05). Local peripheral administration of tolbutamide and glibenclamide (Kir6.1-2; ATP-sensitive K+ channel blockers); iberiotoxin and charybdotoxin (KCa1.1; big conductance calcium-activated K+ channel blockers); apamin and dequalinium (KCa2.1-3; small conductance Ca2+-activated K+ channel blockers); but not by 4-aminopyridine and tetraethylammonium (KV; voltage-gated K+ channel blockers) reverted the DHA-induced antinociceptive effect. It is concluded that big- and small-conductance Ca2+-activated K+ channels and ATP-sensitive K+ channels are activated by DHA to produce local antinociception on the rat formalin test.

Synergistic antinociceptive effect and gastric safety of the combination of docosahexaenoic acid and indomethacin in rats.

The use of analgesics is limited by the presence of significant adverse side effects. Thus, combinations of non-steroidal anti-inflammatory drugs (NSAIDs) with other antinociceptive agents are frequently used to decrease these adverse reactions. The aims of this work were to evaluate the antinociceptive interaction of the systemic administration of the combination of DHA and indomethacin through an isobolographic analysis of the theoretical and experimental antinociceptive effect and to demonstrate the gastric safety of the mixture compared with indomethacin alone. Female Wistar rats were orally administered indomethacin (1-10 mg/kg), DHA (100-300 mg/kg), or the DHA-indomethacin mixture at a fixed-ratio combination (1:1, 1:3, 3:1), and the antinociceptive effects of these treatments were evaluated through the formalin (1%) test. An isobolographic analysis was performed to characterize the antinociceptive interaction between DHA and indomethacin. The degree of gastric injury in all of the rats was determined 1 h after the formalin test. The theoretical ED30 values (Zadd) for the 1:1, 1:3, and 3:1 combinations were 73.48 ± 8.96, 37.75 ± 4.50, and 109.2 ± 13.43 mg/kg, p.o., respectively, and the experimental ED30 values (Zexp) were 43.63 ± 5.18, 13.13 ± 1.61, and 54.20 ± 6.53, respectively. The isobolographic analysis showed that the three fixed-ratio combinations studied exhibited a synergistic interaction. Furthermore, the gastric damage induced by indomethacin was abolished when this drug was combined with DHA. These data suggest that the systemic administration of the DHA-indomethacin combination induces a synergistic and gastric safety effect.

Pharmacological evidence for the participation of NO-cGMP-KATP pathway in the gastric protective effect of curcumin against indomethacin-induced gastric injury in the rat.

Curcumin, main compound obtained from rizhoma of Curcuma longa, shows antitumoral, antioxidant, anticarcinogenic and gastric protective properties. Recently, it has been demonstrated that curcumin exerts its gastric protective action due to an increase in gastric nitric oxide (NO) levels. However, it is unknown whether these increased NO levels are associated with activation of intracellular signaling pathways. Thus, the purpose of this study was to investigate the role of NO-cGMP-KATP pathway in the gastric protective effect of curcumin during indomethacin-induced gastric injury in the rat. Adult female Wistar rats were gavaged with curcumin (3-300mg/kg, p.o.) or omeprazole (30mg/kg, p.o.) 30min before indomethacin insult (30mg/kg, p.o.). Other groups of rats were administered L-NAME (70mg/kg, i.p.; inhibitor of nitric oxide synthase), ODQ (10mg/kg, i.p.; inhibitor of soluble guanylate cyclase) or glibenclamide (1mg/kg, i.p.; blocker of ATP-sensitive potassium (KATP) channels) 30min before curcumin (30mg/kg, p.o.). 3h after indomethacin administration, rats were sacrificed and gastric injury was evaluated by determining total damaged area. A sample of gastric tissue was harvested and processed to quantify organic nitrite levels. Curcumin significantly protected against indomethacin-induced gastric injury and this effect was comparable to gastroprotective effect by omeprazole. L-NAME, ODQ and glibenclamide significantly prevented the curcumin-mediated gastric protective effect in the indomethacin-induced gastric injury model. Furthermore, curcumin administration induced a significant increase in gastric nitric oxide levels as compared to vehicle administration. Our results show for the first time that curcumin activates NO/cGMP/KATP pathway during its gastro protective action.

Evidence for the Participation of ATP-sensitive Potassium Channels in the Antinociceptive Effect of Curcumin.

BACKGROUND: It has been reported that curcumin, the main active compound of Curcuma longa, also known as turmeric, exhibits antinociceptive properties. The aim of this study was to examine the participation of ATP-sensitive potassium channels (K(ATP) channels) and, in particular, that of the L-arginine-nitric oxide-cyclic GMP-K(ATP) channel pathway, in the antinociceptive effect of curcumin. METHODS: Pain was induced by the intraplantar injection of 1% formalin in the right hind paw of Wistar rats. Formalin-induced flinching behavior was interpreted as an expression of nociception. The antinociceptive effect of oral curcumin was explored in the presence and absence of local pretreatment with L-NAME, an inhibitor of nitric oxide synthase, ODQ, an inhibitor of soluble guanylyl cyclase, and glibenclamide, a blocker of K(ATP) channels. RESULTS: Oral curcumin produced a dose-dependent antinociceptive effect in the 1% formalin test. Curcumin-induced antinociception was not altered by local L-NAME or ODQ, but was significantly impaired by glibenclamide. CONCLUSIONS: Our results confirm that curcumin is an effective antinociceptive agent. Curcumin-induced antinociception appears to involve the participation of K(ATP) channels at the peripheral level, as local injection of glibenclamide prevented its effect. Activation of K(ATP) channels, however, does not occur by activation of the L-arginine-nitric oxide-cGMP-K(ATP) channel pathway.

Docosahexaenoic acid, an omega-3 polyunsaturated acid protects against indomethacin-induced gastric injury.

Previous studies have shown gastroprotective effect of fish oil in several experimental models. However, the mechanisms and active compounds underlying this effect are not fully understood. Fish oil has several components; among them, one of the most studied is docosahexaenoic acid (DHA), which is an omega-3 long-chain polyunsaturated fatty acid. The aim of this study was to examine the gastroprotective effect of DHA as a pure compound in a rat model of indomethacin-induced gastric injury as well as elucidate some of the mechanism(s) behind DHA's gastroprotective effect. Indomethacin was orally administered to induce an acute gastric injury (3, 10 and 30mg/kg). Omeprazol (a proton pump inhibitor, 30mg/kg, p.o.) and DHA (3, 10, 30mg/kg, p.o.) were gavaged 30 and 120min, respectively, before indomethacin insult (30mg/kg p.o.). Three hours after indomethacin administration, rats were sacrificed, gastric injury was evaluated by determining the total damaged area. A sample of gastric tissue was harvested and processed to quantify prostaglandin E(2) (PGE(2)) and leukotriene B(4) (LTB(4)) levels by enzyme-linked immunosorbent assay. Indomethacin produced gastric injury in dose-dependent manner. DHA protected against indomethacin-induced gastric damage, and this effect was comparable with omeprazol's gastroprotective effect. DHA did not reverse the indomethacin-induced reduction of PGE(2) gastric levels. In contrast, DHA partially prevented the indomethacin-induced increase in LTB(4) gastric levels. This is the first report demonstrating DHA's gastroprotective effect as a pure compound. Furthermore, the results reveal that the gastroprotective effect is mediated by a decrease in gastric LTB(4) levels in indomethacin-induced gastric damage.

Carbenoxolone gastroprotective mechanism: participation of nitric oxide/(c) GMP/K(ATP) pathway in ethanol-induced gastric injury in the rat.

Carbenoxolone, a semi-synthetic triterpenoid, exhibits gastroprotective activity related to the participation of nitric oxide (NO); however, the complete NO/(c) GMP/K(ATP) channels pathway for carbenoxolone is unknown. Therefore the aim of this study was to examine the NO/(c) GMP/K(ATP) channels pathway as the gastroprotective mechanism of carbenoxolone in the ethanol-induced gastric injury model in the rat. Oral administration of carbenoxolone (30 mg/kg, p.o.) exhibited gastroprotective effect against ethanol-induced gastric injury in rats. Pretreatment with N(G) -nitro-l-arginine methyl ester (L-NAME, 70 mg/kg, i.p.); 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ, guanylate cyclase inhibitor, 10 mg/kg, i.p.); or glibenclamide (K(ATP) channels inhibitor, 1 mg/kg, i.p.) reversed the gastroprotective effect of carbenoxolone for ethanol-induced gastric injury. Furthermore, gastric prostaglandins and NO levels increased after carbenoxolone administration in ethanol-induced gastric injury in rats. In conclusion, our results suggest that the increase of NO levels in gastric tissue after pretreatment with carbenoxolone activates the NO/(c)GMP/K(ATP) channels pathway, the principal gastroprotective mechanism of carbenoxolone.

Inhibition of endogenous hydrogen sulfide synthesis by PAG protects against ethanol-induced gastric damage in the rat.

Hydrogen sulfide (H(2)S) is a gaseous mediator involved in a multitude of physiological functions; however the role of H(2)S in the gut is far from being understood completely. The aim of this study was to determine the effect of d-l-propargylglycine (PAG), an inhibitor of H(2)S synthesis, on ethanol-induced gastric injury in rat and to examine the role of l-cysteine, exogenous H(2)S, prostaglandins, non-protein sulphydryls groups, nitric oxide and K(ATP) channels in the gastroprotective effect of PAG. Administration of PAG (3.12 to 75mg/kg i.p.) or l-cysteine (0.3 to 300mg/kg, p.o.) exhibited a dose-dependent protective effect after intragastric administration of 1ml of ethanol to induce gastric injury. The gastroprotective effect of PAG (25mg/kg i.p.) was maintained after post-treatment with l-cysteine (10mg/kg p.o.), while NaHS (8.4mg/kg p.o.) inhibited this effect. The levels of gastric hydrogen sulfide were increased after ethanol-induced gastric damage and they were reverted by PAG while prostaglandin E(2) levels in gastric tissue were decreased by ethanol and PAG did not revert to this effect. Pretreatment with indomethacin (10mg/kg i.p.) and N-ethylmaleimide (NEM, 10mg/kg s.c.) resulted in a reversion of the gastroprotective effect of PAG while N(G)-nitro-l-arginine methyl ester (L-NAME, 70mg/kg s.c.), glibenclamide (1mg/kg i.p.) or diazoxide (3mg/kg i.p.) did not induce any changes. These results suggest that ethanol-induced gastric injury is related with an increment of endogenous H(2)S levels, and therefore a decrement of H(2)S levels by PAG is a benefit to protect gastric injury caused by ethanol.