Dietary oleuropein and its acyl derivative ameliorate inflammatory response in peritoneal macrophages from pristane-induced SLE mice via canonical and noncanonical NLRP3 inflammasomes pathway.

Systemic lupus erythematosus (SLE) is a multifactorial autoimmune disease without an effective and safe treatment. Besides, macrophages are the major components of the innate immune system and play a critical role in the inflammation process in SLE. Secoiridoids from olive tree are phenolic compounds which have shown important pharmacological effects. Particularly, oleuropein (OL) has shown antioxidant, anti-inflammatory and immunomodulatory properties suggesting a potential application in a large number of inflammatory and reactive oxygen species (ROS)-mediated diseases. In addition, different studies have shown the importance of acyl derivatives of natural phenols due to their better hydrophilic/lipophilic balance.

Dietary oleuropein and its new acyl-derivate attenuate murine lupus nephritis through HO-1/Nrf2 activation and suppressing JAK/STAT, NF-κB, MAPK and NLRP3 inflammasome signaling pathways.

Systemic lupus erythemathosus (SLE) is a chronic inflammatory and autoimmune disease which can affect multiple organ systems, without an effective and safe treatment. Olive leaf extracts are of special interest for their therapeutic effects. Oleuropein (OL) is the most abundant constituents of olive leaf extract and possesses many beneficial properties. In this study, we evaluated the effects of dietary OL and its new derivate, peracetylated oleuropein (Per-OL), in a pristane-induced SLE model. Mice received an injection of pristane or saline solution and were fed with experimental diets: enriched with OL and Per-OL. The levels of proinflammatory cytokines and markers were evaluated by enzyme-linked immunosorbent assay. The protein expressions of inducible nitric oxide synthase, microsomal prostaglandin E synthase 1, heme oxygenase (HO-1), nuclear factor E2-related factor 2 (Nrf2), mitogen-activated protein kinases (MAPKs), Janus kinase/signal transducer and activator of transcription (JAK/STAT), nuclear transcription factor-kappa B (NF-κB) and inflammasome nucleotide-binding domain, leucine-rich repeats-containing family, pyrin domain-containing-3 (NLRP3) pathways activation were determined in kidneys by Western blot. OL and Per-OL significantly reduced renal damage and decreased serum matrix metalloproteinase 3 and prostaglandine E2 kidneys levels. Our findings indicate that Nrf2 and HO-1 antioxidant protein expressions were up-regulated in mice fed with OL and Per-OL diets, whereas the activation of JAK/STAT, MAPK, NF-κB and NLRP3 inflammasome pathways was significantly ameliorated. These results suggest that OL and Per-OL supplementation might provide a new alternative approach as a preventive/palliative treatment of nephritis in SLE management.

The unsaponifiable fraction of extra virgin olive oil promotes apoptosis and attenuates activation and homing properties of T cells from patients with inflammatory bowel disease.

The unsaponifiable fraction (UF) of extra virgin olive oil (EVOO) possesses anti-inflammatory properties and exerts preventative effects in murine models of inflammatory bowel disease (IBD). The present study was designed to determine the in vitro effects of UF on blood and intestinal T cells from IBD patients and healthy subjects. The T cell phenotype was investigated by flow cytometry and cytokine secretion was determined by ELISA. The presence of UF of EVOO promoted apoptosis and attenuated activation of intestinal and blood T cells isolated from IBD patients, decreasing the frequency of CD69(+) and CD25(+) T cells and, also, the secretion of IFN-γ. Moreover, UF reduced the expression of the gut homing receptor integrin ß7 on blood T cells from IBD patients. In conclusion, UF modulates the activity and the gut homing capacity of T cells, and might therefore be considered as a dietary complement with an anti-inflammatory role in IBD patients.

Extra virgin olive oil polyphenolic extracts downregulate inflammatory responses in LPS-activated murine peritoneal macrophages suppressing NFκB and MAPK signalling pathways.

Extra virgin olive oil (EVOO) is obtained from the fruit of the olive tree Olea europaea L. Phenolic compounds present in EVOO have recognized anti-oxidant and anti-inflammatory properties. However, the activity of the total phenolic fraction extracted from EVOO and the action mechanisms involved are not well defined. The present study was designed to evaluate the potential anti-inflammatory mechanisms of the polyphenolic extract (PE) from EVOO on LPS-stimulated peritoneal murine macrophages. Nitric oxide (NO) production was analyzed by the Griess method and intracellular reactive oxygen species (ROS) by fluorescence analysis. Moreover, changes in the protein expression of the pro-inflammatory enzymes, inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 and microsomal prostaglandin E synthase-1 (mPGES-1), as well as the role of nuclear transcription factor kappa B (NFκB) and mitogen-activated protein kinase (MAPK) signalling pathways, were analyzed by Western blot. PE from EVOO reduced LPS-induced oxidative stress and inflammatory responses through decreasing NO and ROS generation. In addition, PE induced a significant down-regulation of iNOS, COX-2 and mPGES-1 protein expressions, reduced MAPK phosphorylation and prevented the nuclear NFκB translocation. This study establishes that PE from EVOO possesses anti-inflammatory activities on LPS-stimulated murine macrophages.

Melatonin modulates microsomal PGE synthase 1 and NF-E2-related factor-2-regulated antioxidant enzyme expression in LPS-induced murine peritoneal macrophages.

BACKGROUND AND PURPOSE: Increasing evidence demonstrates that melatonin regulates inflammatory and immune processes acting as both an activator and inhibitor of these responses. Nevertheless, the molecular mechanisms of its anti-inflammatory action remain unclear. Here we have characterized the cellular mechanisms underlying the redox modulation of LPS-stimulated inflammatory responses in murine peritoneal macrophages by melatonin to provide insight into its anti-inflammatory effects. EXPERIMENTAL APPROACH: Murine peritoneal macrophages were isolated and treated with melatonin in the presence or absence of LPS (5 µg·mL(-1) ) for 18 h. Cell viability was determined using sulforhodamine B assay and NO production was measured using the Griess reaction. Pro-inflammatory enzymes and transcription factors were detected by Western blotting. KEY RESULTS: Without affecting cell viability, melatonin (12.5, 25, 50 and 100 µM) reduced the level of nitrites, inducible NOS (iNOS), COX-2 and microsomal PGE synthase-1 (mPGES1) protein, and p38 MAPK phosphorylation, and prevented NF-κB translocation. Furthermore, melatonin treatment significantly increased NF-E2-related factor 2 (Nrf2) and haem oxygenase 1 (HO1) protein levels in murine macrophages exposed to LPS. CONCLUSIONS AND IMPLICATIONS: Melatonin reduced pro-inflammatory mediators and enhanced the expression of HO1 via NF-κB, p38 MAPK and Nrf2 cascade signalling pathways in murine macrophages. Thus, melatonin might be a promising target for diseases associated with overactivation of macrophages.

An up-date of olive oil phenols in inflammation and cancer: molecular mechanisms and clinical implications.

Olive oil (OO), the main fatty component of the Mediterranean diet, exhibits numerous biological functions which are beneficial for the state of health. In addition to monounsaturated fatty acid (MUFA) evidences have accumulated on the favorable properties of its minor though highly bioactive components, particularly the phenolic compounds, which have shown a broad spectrum of bioactive properties, including antioxidant and anti-inflammatory effects both associated with the origin of the main chronic diseases. Additional studies have demonstrated that the health effects of olive oil polyphenols have been also associated with their, neuroprotective, antiaging and antiatherogenic effects. On the other hand, because of their ability to modulate cell death, olive polyphenols have been proposed as chemopreventive and therapeutic agents. Thus, the purpose of this article is to review the chemistry, bioavailability and pharmacokinetic characteristics of OO polyphenols, in addition to provide the reader an up-date of their putative antioxidant, anti-inflammatory and anti-cancer activities as well as the plausible action mechanisms involved.

Influence of extra virgin olive oil diet enriched with hydroxytyrosol in a chronic DSS colitis model.

PURPOSE: Recent epidemiological studies have shown that habitual consumption of extra virgin olive oil (EVOO), the characteristic culinary fat of the Mediterranean area, is effective in the prevention of diverse types of digestive disorders such as inflammatory bowel disease. Many of these benefits are, in addition to its high proportion of oleic acid, due to the high content of phenolic compounds. METHODS: Six-week-old mice were randomized into three dietary groups: standard, EVOO and hydroxytyrosol-enriched EVOO. After 30 days, mice that were exposed to 3% DSS for 5 days developed acute colitis that progressed to severe chronic inflammation during a regime of 21 days of water. RESULTS: Diets enriched with EVOO significantly attenuated the clinical and histological signs of damage, improving results from disease activity index and reducing about 50% the mortality caused by DSS. Moreover, hydroxytyrosol supplement showed better results. Cytokines study showed that TNF-α was maintained near to sham control and IL-10 levels were significantly improved in EVOO and EVOO plus hydroxytyrosol diet-DSS groups. In the same way, COX-2 and iNOS were downregulated, and the activation of p38 MAPK was reduced. We also observed a higher significant reduction in iNOS in hydroxytyrosol-enriched EVOO compared with EVOO alone. CONCLUSIONS: EVOO diets exerted a noteworthy beneficial effect in chronic DSS-induced colitis by cytokine modulation and COX-2 and iNOS reduction via downregulation of p38 MAPK. In addition to the beneficial effect by EVOO, supplementation of the diet with hydroxytyrosol may improve chronic colitis through iNOS downregulation plus its antioxidant capacity.

Extra-virgin olive oil-enriched diet modulates DSS-colitis-associated colon carcinogenesis in mice.

BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) are at increased risk for developing ulcerative colitis (UC)-associated colorectal cancer (CRC). Several studies have shown that extra virgin olive oil (EVOO) might possess anti-inflammatory, antiproliferative and antiapoptotic effects. We have evaluated EVOO diet effects on the severity of repeated colitis-associated CRC. METHODS: Six-week-old C57BL/6 mice were randomized into two dietary groups: sunflower oil (SFO) and EVOO diets, both at 10%. Mice were exposed to 15 cycles of 0.7% dextran sodium sulphate (DSS) for 1 week followed by distilled water for 10 days. After, the rats were sacrificed and colonic damage was both histologically and biochemically assessed. RESULTS: Disease activity index (DAI) was significantly higher on SFO vs. EVOO diet at the end of the experimental period. EVOO-fed mice showed less incidence and multiplicity of tumors than in those SFO-fed mice. ß-catenin immunostaining was limited to cell membranes in control groups, whereas translocation from the cell membrane to the cytoplasm and/or nucleus was showed in DSS-treated groups and its expression was higher in SFO-fed animals. Cytokine production was significantly enhanced in SFO-fed mice, while this increase was not significant in EVOO-fed mice. Conversely, cyclooxygenase-2 (COX-2) and inducible nitric oxidase synthase (iNOS) expression were significantly lower in the animal group fed with EVOO than in the SFO group. CONCLUSIONS: These results confirm that EVOO diet has protective/preventive effect in the UC-associated CRC. This beneficial effect was correlated with a better DAI, a minor number of dysplastic lesions, a lower ß-catenin immunoreactivity, a proinflammatory cytokine levels reduction, a non modification of p53 expression and, COX-2 and iNOS reduction in the colonic tissue.

Intestinal immunomodulation. Role of regulative peptides and promising pharmacological activities.

About 50 peptides, and a similar number of peptide receptors, are known to be present in the gut and this amount is likely to rise significantly over the next few years. While there has been a massive research effort to define their functions and their anatomical distribution in the central nervous system (CNS), the understanding of their roles in the gut is far more limited. Classically, the physiological functions include the control of motility, fluids, electrolytes, and digestive enzymes secretion, or vascular and visceral pain function, and more recently, the role-played in cell proliferation and survival, and in immune-inflammatory responses. The term inflammatory bowel disease (IBD) that encompasses Crohn's disease and ulcerative colitis, is clearly an inflammatory disease where several mediators such as cytokines, chemokines, prostanoids, nitric oxide or free radicals, produced by infiltrating cells, play a critical role in intestine tissue alteration. Some peptides, initially known for their neuroregulative properties, have been suggested to act as endogenous immune factors, with predominant antiinflammatory effects. Based on these actions, these molecules are proposed as potential agents for the treatment of IBD and selective peptide analogs are being developed as novel therapeutic strategies for IBD patients. Patients with IBD have an increased risk for developing colorectal cancer (CRC). Up to the present time, no known genetic basis has been identified to explain CRC predisposition in these IBD. Instead, it is assumed that chronic inflammation is what causes cancer. This is supported by the fact that colon cancer risk increases with longer duration of colitis, greater anatomic extent of colitis, the concomitant presence of other inflammatory manifestations, and the fact that certain drugs used to treat inflammation, may prevent the development of CRC. However, though different regulative peptides play a beneficial role in experimental IBD, an increasing number of articles about cancer pathology are starting to implicate different peptides in tumor initiation and progression. The complexities of cancer could be described in terms of a small number of underlying principles and the malignant growth is dependent upon a multi-step process including different basic essential alterations. The activities of many peptides that are overexpressed in cancer cells help them to develop several of the molecular and physiological features that are now considered the basis of malignant growth. These collective findings implicate regulative peptides, receptors, or peptide-levels modulators, as important biological targets for developing intervention strategies against intestinal immunological disorders and cancers.

The COX-2 inhibitor, rofecoxib, ameliorates dextran sulphate sodium induced colitis in mice.

OBJECTIVE: We have evaluated the efficacy of the selective cyclo-oxygenase (COX)-2 inhibitor, rofecoxib, for the prevention of experimental colitis. MATERIAL AND METHODS: To induce colitis BALB/c mice received 5% dextran sulphate sodium (DSS) in their drinking water continuously for 7 days. Rofecoxib (2.5-10 mg/kg body weight, p.o.) was administered throughout the treatment period with DSS. Colitis was quantified by a clinical damage score, colon length, weight loss, stool consistency and rectal bleeding. Inflammatory response was assessed by neutrophil infiltration, determined by histology and myeloperoxidase (MPO) activity. Interleukin (IL)-1beta, prostaglandin (PG)E2 and PGD2 levels in colon mucosa and the immunohistochemical expression of COX-1 and -2 were also studied. RESULTS: The COX-2 inhibitor ameliorated severe colitis, reduced the degree of inflammation through reduction of neutrophil infiltration and IL-1beta levels. PGE2, and PGD2 synthesis were significantly reduced in DSS-treated groups. Indeed, treatment with rofecoxib diminished the lost of COX-1 caused by DSS in the crypt epithelium whereas expression of COX-2 remained unaffected. CONCLUSIONS: Rofecoxib is protective in acute DSS-induced colitis, probably by reducing neutrophil infiltration, inhibiting up-regulation of IL-1beta and returning to normal COX-1 expression in the inflamed colonic mucosa.

Rosiglitazone, an agonist of peroxisome proliferator-activated receptor gamma, reduces chronic colonic inflammation in rats.

Recent studies have shown the implication of the peroxisome proliferator-activated receptor gamma (PPARgamma) in control of inflammation, immune and apoptotic responses during early experimental colitis. However, there is little information about the effects of these agents on colonic mucosa under chronic inflammatory conditions. In this study, we have evaluated the effects of rosiglitazone, a PPAR-gamma agonist, on the chronic injury caused by intra-colonic administration of trinitrobenzensulfonic acid (TNBS) in rats. Rosiglitazone (1 and 5mg/kg p.o.) was administered by oral gavage, 24h after TNBS instillation and daily during 2 weeks before killing the rats. Colons were removed for histological and biochemical analysis. Administration of rosiglitazone corrected the disorders in morphology associated to lesions, significantly reduced the ulceration index, the rise of myeloperoxidase (MPO) and the levels of tumour necrosis factor alpha (TNF-alpha). In addition, rosiglitazone treatment increased prostaglandin (PG)E(2) production and returned PGD(2) to basal levels. Also, reduced cyclooxygenase (COX)-2 and nuclear transcription factor NF-kappa B (NF-kappaB) p65 proteins expression. Furthermore, treatment of rats with rosiglitazone caused a significant increase of TNBS-induced apoptosis. In summary, rosiglitazone exerts protective effects in chronic experimental colitis. The anti-inflammatory effects seem to be related to impairment of neutrophil function, absence of up-regulation of TNF-alpha and decrease of nuclear NF-kappaB p65 expression. Our results also suggest that the activation of the PPARgamma pathway reduces COX-2 overexpression, returns the increased PGD(2) values to basal levels and induces a significant increase of TNBS-induced apoptosis. We conclude that rosiglitazone represents a novel approach to the treatment of ulcerative colitis.

New pharmacological perspectives and therapeutic potential of PPAR-gamma agonists.

The peroxisome proliferator-activated receptor gamma (PPARgamma), a member of the nuclear hormone receptor superfamily has classically been characterized for its implications in adipocyte differentiation and fat metabolism. Recently, PPARgamma has been implicated in the pathophysiology of inflammatory and immune responses possibly through inhibition of the mitogen-activated protein kinase (MAPK) pathways or the activation of the transcription nuclear factor kappa B (NF-kappaB). Thus, these agents might also have therapeutic potential in the treatment of gastrointestinal inflammatory disorders, such as ulcerative colitis and Crohn's disease. The synthetic thiazolidinediones (TZDs), a novel class of insulin-sensitizing drugs, were the first class of compounds identified as PPARgamma ligands, and represent a significant advance in anti-diabetic therapy. However, there is less information about endogenous ligands, although the prostaglandin (PG)J(2) and the oxidized phosphatidylcholine have been suggested. Furthermore, PPARgamma ligands have been shown to be potent inhibitors of angiogenesis, a process necessary for tumor growth and metastasis, and protect against cellular transformation. Further work is needed to establish in detail the anti-proliferative and pro-differentiation mechanisms of PPARgamma activators and their efficacy in certain cancers.

Role of L-arginine in ibuprofen-induced oxidative stress and neutrophil infiltration in gastric mucosa.

It has been proposed that neutrophil and oxygen dependent microvascular injuries may be important prime events in gastrointestinal (GI) toxicity of non-steroidal antiinflammatory drugs (NSAIDs). L-arginine (L-ARG) is an essential amino acid which participates in many important biochemical reactions associated to the normal physiology of the organism. In these experimentations, we studied the role of L-ARG, aminoacid precursor of NO synthesis, on ibuprofen (IB) induced gastric lesions, and also on the inflammatory and oxidative mechanisms related to mucosal damage. Oral administration of IB (100 mg kg(-1)), produced severe damage on gastric mucosa, which was more important after 6 h test-period, and was accompanied by a significant increment in myeloperoxidase (MPO) activity, as index of neutrophil activation, as well as lipid peroxidation (LP) levels and xanthine oxidase (XO) activity. However, no changes were observed in total mucosal glutathione (tGSH), nor glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activity. Simultaneous treatment with equimolar doses of L-ARG (oral and i.p.), considerably reduced the number and intensity of lesions, and at the same time (6 h) the maximum protection was also observed. In addition, L-ARG inhibited the IB-induced LP and XO enhancement, but did not produce changes in leukocyte infiltration, tGSH, GSH-Px and SOD activity. These findings suggest that (1) L-ARG protective effect on gastric mucosa against IB-induced mucosal lesions could be explained by a local effect and also might be due to the systemic action of the aminoacid; (2) the active oxygen species, derived both from XO and activated neutrophils, could play a role in the pathogenesis of gastric injury induced by IB, (3) L-ARG exhibit a protective effect against IB-induced mucosal damage, probably through the inhibition of oxidative stress derived via xanthine-XO, but it does not block the oxygen free radical production through polymorphe nuclear leukocytes.

Extra-virgin olive oil-enriched diets reduce indomethacin-induced gastric oxidative damage in rats.

Olive oil, the main fat component of the Mediterranean diet, has been found to be protective against oxidative stress and could be beneficial in inflammatory and gastrointestinal disorders. First-pressed, extra-virgin olive oil (EVOO) has appreciable amounts of powerful antioxidants such as polyphenolic compounds that prevent its autoxidation and are responsible for its high stability. The aim of the present study was to determine whether diets supplemented with EVOO could reduce the severity of indomethacin-induced gastric oxidative damage and also to study changes in the activities of certain oxidative stress-related enzymes such as xanthine oxidase, myeloperoxidase as a marker of neutrophil infiltration, and the antioxidant enzyme superoxide dismutase. Lipid peroxidation and possible modifications in gluthatione metabolism were also studied. Weanling rats were maintained on semisynthetic diet for 6 weeks; a standard diet containing 5% (w/w) of fat as control or EVOO supplemented diets (5% and 20% w/w). Gastric lesions were induced on the last day by oral administration of indomethacin (60 mg/kg body wt). In animals fed EVOO diets, gastric lesions were decreased significantly and in parallel with dietary fat, when compared to animals consuming a standard diet. These protective effects were related to a reduction of lipid peroxides generation, neutrophil infiltration, and xanthine oxidase activity. Superoxide dismutase, an important enzyme to scavenger of lipid peroxides, was unaffected by feeding conditions. On the other hand, dietary supplementation with EVOO significantly increased both glutathione peroxidase activity and total glutathione content. In conclusion, this study provides evidence that fat diets containing EVOO reduces indomethacin-induced gastric damage in rats. This effect may be partly due not only to reducing oxidative stress and neutrophil-induced toxicity but also to enhancing the glutathione antioxidant defense system.

Role of prostaglandins and nitric oxide in gastric damage induced by metamizol in rats.

OBJECTIVE AND DESIGN: In addition to the depletion of prostaglandins (PGs), oxygen free radicals generation and nitrogen species haven been implicated in non-steroidal anti-inflammatory drugs (NSAIDs)-induced gastric injury. The aim of the present study was to examine changes in PGE2 generation and its relationship with proinflammatory parameters and nitric oxide (NO) production in the comparative pathogenesis of gastric injury induced by metamizol vs. diclofenac, NSAIDs that present different gastric tolerability and cyclooxygenase (COX) inhibition profiles. MATERIAL: Studies were performed in Wistar-Han rats. TREATMENTS: Metamizol (120, 500 and 1,000 mg/kg body weight) and diclofenac (50 mg/kg body weight) were given by oral administration. METHODS: Determinations were made of macroscopic and histological evaluation of gastric mucosal injury, gastric prostaglandin synthesis (PGE2 levels), myeloperoxidase activity (MPO), tumor necrosis factor-alpha levels (TNF-a), cyclic guanosine monophosphate (cGMP), nitric oxide synthase activity (NOS) and NOS mRNA expression. RESULTS: Metamizol, only at the highest doses assayed, provoked weak lesions in the gastric mucosa. To the contrary, diclofenac treatment presented the highest grade of lesion. All treatments decreased PGE2 gastric generation. Treatment of the animals with metamizol neither modified the MPO activity nor TNF-alpha levels. In contrast, statistically significant increases in both parameters were observed after diclofenac administration. cGMP levels were not influenced with diclofenac treatment, nevertheless metamizol reduced the nucleotide levels, which was accompanied by an inhibition of constitutive NOS (cNOS) activity without modifying the mRNA expression of the enzyme. CONCLUSIONS: In addition to inhibition of PG synthesis, damage induced by metamizol was associated with an inhibition of the NO/cGMP pathway and cNOS activity. In contrast, diclofenac-induced gastric damage was associated with an increase of the inflammatory response.

Gastric toxicity of racemic ketoprofen and its enantiomers in rat: oxygen radical generation and COX-expression.

OBJECTIVE AND DESIGN: The gastric toxicity of racemic-ketoprofen and its enantiomers (S(+)- and R(-)-ketoprofen), oxygen free radical generation and neutrophil infiltration in response to damage were evaluated in rats. Changes in prostaglandin synthesis, cyclooxygenase expression and glutathione metabolism were also studied. MATERIALS AND METHODS: Studies were performed in Wistar rats. Drugs were given by oral administration: racemic-ketoprofen (100, 50 and 25 mg/kg body weight); S(+) and R(-)-ketoprofen (50, 25 and 12.5 mg/kg body weight). Determinations were made of gastric mucosal injury, lipid peroxidation, xanthine oxidase, myeloperoxidase and superoxide dismutase activities, glutathione levels, glutathione peroxidase and glutathione reductase activities, gastric prostaglandin synthesis (PGE2 levels) and COX-expression. RESULTS: Racemic-ketoprofen dose-dependently exhibited the highest toxicity. In contrast, S(+)-ketoprofen at half the dose of the racemic compound proved to be less ulcerogenic. R(-)-ketoprofen was also less ulcerogenic, but when administered as the racemate exacerbated gastric ulceration caused by S(+)-ketoprofen. Drug administration produced significant increases in lipid peroxidation levels and xanthine-oxidase and a decrease in superoxide dismutase activity. Nevertheless the racemate induced the highest disturbances in oxidative metabolism. No changes in myeloperoxidase values and glutathione metabolism were found. Cyclooxygenase-1 immunoreactivity was observed and did not differ from that in control rats. Cyclooxygenase-2 could also be expressed after treatments. CONCLUSIONS: R(-)-ketoprofen and S(+)-ketoprofen have a comparable gastric toxicity and they both have a better gastric toxicity profile as compared to the racemate. In addition to inhibition of prostaglandin synthesis, damage resulted in an increase of cyclooxygenase-2 protein expression. Oxygen radicals, including superoxide anions, could also be implicated.

New issues about melatonin and its effects on the digestive system.

In human beings, melatonin is secreted in a cyclic way by the pineal gland, although it has been detected in other tissues. Synthesis of melatonin takes place in the pinealocyte. It depends on adrenergic stimulation, and its secretion is related to the photoperiod in a circadian model of low activity during light phase and high activity at night time. Former studies aimed to establish the mechanisms by which melatonin carries out its biological function, proved the existance of high affinity binding sites. However, melatonin can pass through the plasmatic membrane; this property suggested a possible activity of the hormone inside the cell trough activation of nuclear receptors. Moreover, melatonin can act by itself as a potent oxygen-free-radical scavenger, which renders it a very strong antioxidant. It is currently accepted that melatonin plays an important role in numerous physiological processes. The gastrointestinal tract of numerous animal species contains melatonin, which is synthesized essentially by intestinal enterochrommaffin cells. Some investigations have revealed that its liberation follows also a circadian rhythm, although its secretion pattern might be influenced by nutritional factors. Receptors for melatonin have been identified in the digestive system, therefore the indolamine might play a leading role in different aspects of the vast digestive physiopathology. The hormone may interact with receptors and subsequently stimulate the synthesis of gastroprotective hormones and also exerts a direct defense on the epithelium, enhances submucosal blood flow and prevents the damage induced by ischemia followed by reperfusion. Moreover, studies have shown that treatment with melatonin reduces the severity of the lesions induced by NSAIDs on gastric mucosa suggesting a beneficial role of melatonin in preventing this gastropathy related to antiinflammatories.

Mediterranean diet and health: biological importance of olive oil.

Olive oil, the main fatty component of the Mediterranean diet, is characterized by consisting of monounsaturated fatty acids as well as by its elevated content in antioxidant agents. This oil exhibits numerous biological functions which are beneficial for the state of health. A diet rich in monounsaturated fatty acids provides an adequate fluidity to the biological membranes, diminishing the hazard of lipid peroxidation which affects polyunsaturated fatty acids. Moreover, the antioxidants present in olive oil are able to scavenge free radicals and afford an adequate protection against peroxidation. Regarding the heart, olive oil decreases the plasmatic levels of LDL-cholesterol and increases those of HDL-cholesterol, hence diminishing the risk of suffering from heart complaints. In this context, it has been suggested that increased consumption of monounsaturated fatty acids in place of polyunsaturated fatty acids will render circulating lipoproteins less sensitive to peroxidation and thereby diminish the development of atherosclerosis. Olive oil has also been proven to contribute to a better control of the hypertriglyceridemia accompanying diabetes and may reduce the risk of breast cancer and colorectum. On the other hand, several investigations have suggested that olive oil can be beneficial in inflammatory and autoimmune diseases, such as rheumatoid arthritis. In this sense, some reports have indicated that olive oil modifies inflammatory cytokines production. As for the digestive system, olive oil enhances gallbladder emptying consequently reducing cholelithiasis risk, decreases the pancreatic exocrine secretion and gastric secretory function in response to food. Finally, it has been demonstrated that a diet rich in olive oil is associated with a high percentage of gastric ulcer healing and affords a higher resistance against non steroidal antiinflammatory drugs-induced gastric ulcerogenesis.

Effects of food intake and oxidative stress on intestinal lesions caused by meloxicam and piroxicam in rats.

Large intestinal ulcers, bleeding and perforation are occasionally due to non-steroidal anti-inflammatory drugs (NSAID). In addition to suppression of prostaglandins synthesis, a number of factors have been implicated, including enterohepatic recirculation, food intake and vascular injury with oxygen free-radical generation. The present study aimed to determine the effect of food intake and the role of oxidative stress in the pathogenesis of intestinal injury induced by oral administration of meloxicam (preferential cyclooxygenase-2 inhibitor) vs. piroxicam (preferential cyclooxygenase-1 inhibitor). Therefore, the activity of oxidative stress-related enzymes such as myeloperoxidase, xanthine oxidase and superoxide dismutase, as well as levels of lipid peroxides and glutathione homeostasis were studied in an experimental model using re-fed rats. The animals treated with piroxicam (10-20 mg/kg) had a dose-dependent increase in the severity of intestinal lesions, but only the highest dose of meloxicam (15 mg/kg) caused macroscopic damage. The severity of piroxicam and meloxicam-induced damage was correlated with a significant increase of xantine oxidase activity and a decrease of superoxide dismutase activity and glutathione levels (P<0.05 and P<0.001 vs. control). In contrast, there was no significant neutrophil infiltration of the intestine after dosing. Our results support the hypothesis that oxygen free radicals, probably derived via the action of xantine oxidase, the decrease in superoxide dismutase activity, and depletion of mucosal glutathione contribute to the pathogenesis of meloxicam and piroxicam-induced intestinal ulceration in re-fed rats.

Effects of meloxicam on oxygen radical generation in rat gastric mucosa.

AIM AND DESIGN: In addition to a deficiency of endogenous prostaglandins due to inhibition of cyclo-oxygenase and a host of prostaglandin-mediated effects on mucosal protection, it has recently been proposed that neutrophil- and oxygen radical - dependent microvascular injuries may be important prime events that lead to mucosal injury induced by non-steroidal anti-inflammatory drugs. Therefore, we evaluated the role of oxygen free radicals in the pathogenesis of acute gastric ulceration induced by meloxicam, a preferential COX-2 inhibitor. MATERIAL: Studies were performed in Wistar rats. TREATMENT: Meloxicam was given by oral administration (3.75-30 mg/kg body weight). METHODS: Determinations were made of gastric mucosal injury, xanthine-oxidase, myeloperoxidase and superoxide dismutase activities, as well as the effect of meloxicam on gastric prostaglandin synthesis (PGE2 levels) and glutathione homeostasis. RESULTS: Oral administration of meloxicam dose-dependently (3.75-30 mg/kg) caused acute gastric haemorrhage erosions. The total area of gastric lesions increased with time until 24 hours after dosing. Xanthine-oxidase activity increased significantly after administration of the drug. Myeloperoxidase activity, as an index of neutrophil infiltration, as well as glutathione peroxidase, an important enzyme that scavenges lipid peroxides, were unaffected by meloxicam administration. In addition, superoxide dismutase activity, PGE2 and glutathione levels were significantly reduced. CONCLUSION: These results support the hypothesis that in addition to suppression of prostaglandin synthesis, oxygen free radicals, probably derived via the action of xanthine oxidase, the decrease in superoxide dismutase activity, and the depletion of mucosal glutathione contribute to the pathogenesis of meloxicam-induced ulceration.