Isabel Villegas

Evidence for protective and antioxidant properties of rutin, a natural flavone, against ethanol induced gastric lesions.

This study was designed to determine the ulcer-protecting effects of rutin, a natural flavone, against gastric lesions induced by 50% ethanol, the experimental model related to lesion pathogenesis with production of reactive species. The possible involvement of sulphydryl compounds (SH), neutrophil infiltration, and the capacity of this flavone to restrain the oxidative process produced in the gastric tissue were also investigated. The levels of thiobarbituric acid (TBA, as index of lipid peroxidation), the myeloperoxidase activity (MPO, as a marker of neutrophil infiltration), the content of mucosal sulphydryls (SH) groups and the activity of glutathione peroxidase (GSH-Px, an important antioxidant enzyme) were determined. Pretreatment with the highest dose of rutin (200 mg/kg), 120 min before 50% ethanol, resulted in the most effective necrosis prevention. TBA reactive substances in the gastric mucosa, were increased by ethanol injury, and this increase was inhibited by the administration of 200 mg/kg of rutin. However, the flavonoid was not able to modify the ethanol-induced neutrophil infiltrate expressed as myeloperoxidase activity. Exposure of the gastric mucosa to 50% ethanol induced a significant diminution in gastric non-protein SH content; this parameter also was not modified by the treatment with rutin. GSH-Px activity decreased in the gastric mucosa after ethanol-treatment. In contrast, rutin at all tested doses induced a significant increase in this enzymatic activity, higher than in control group. These results suggest that the gastroprotective effect of rutin in this experimental model appears through an anti-lipoperoxidant effect, and also by enhancement of the anti-oxidant enzymatic (GSH-Px) activity.

The effects of resveratrol, a phytoalexin derived from red wines, on chronic inflammation induced in an experimentally induced colitis model

Neutrophil infiltration, proinflammatory cytokines, eicosanoid generation and oxidative stress have been implicated in colitis. Resveratrol is a polyphenolic compound found in grapes and wine, with multiple pharmacological actions, including anti‐inflammatory, antioxidant, antitumour and immunomodulatory activities. In a previous report, we documented that resveratrol decreases the degree of inflammation associated with acute experimental colonic inflammation, but its effects on chronic experimental colitis remain undetermined. The aim of this research was to investigate the effects of resveratrol on the chronic colonic injury caused by intracolonic instillation of trinitrobenzenesulphonic acid (TNBS) in rats. The inflammatory response was assessed by histology and myeloperoxidase activity. Tumour necrosis factor alpha (TNF‐α) production, histological and histochemical analysis of the lesions were also carried out. We determined the production of prostaglandin (PG) E2 and D2 in colon mucosa, as well as cyclooxygenase (COX)‐1 and ‐2 and nuclear transcription factor NF‐kappa B (NF‐κB) p65 protein expression. Finally, since resveratrol has been found to modulate apoptosis, we intended to elucidate its effects on colonic mucosa under chronic inflammatory conditions. Resveratrol (10 mg kg−1 day−1) significantly attenuated the damage score and corrected the disturbances in morphology associated to injury. In addition, the degree of neutrophil infiltration and the levels of TNF‐α were significantly ameliorated. Resveratrol did not modify PGD2 levels but returned the decreased PGE2 values to basal levels and also reduced COX‐2 and the NF‐κB p65 protein expression. Furthermore, treatment of rats with resveratrol caused a significant increase of TNBS‐induced apoptosis in colonic cells. In conclusion, resveratrol reduces the damage in chronic experimentally induced colitis, alleviates the oxidative events, returns PGE2 production to basal levels and stimulates apoptosis in colonic cells.

Dietary supplementation of resveratrol attenuates chronic colonic inflammation in mice.

Ulcerative colitis is a nonspecific inflammatory disorder characterized by oxidative and nitrosative stress, leucocyte infiltration and upregulation of inflammatory mediators. Resveratrol is a polyphenolic compound found in grapes and wine, with multiple pharmacological actions, mainly anti-inflammatory, antioxidant, antitumour and immunomodulatory activities. The aim of this study was to investigate the effect of dietary resveratrol on chronic dextran sulphate sodium (DSS)-induced colitis. Six-week-old mice were randomized into two dietary groups: one standard diet and the other enriched with resveratrol at 20mg/kg of diet. After 30days, mice were exposed to 3% DSS for 5days developing acute colitis that progressed to severe chronic inflammation after 21days of water. Our results demonstrated that resveratrol group significantly attenuated the clinical signs such as loss of body weight, diarrhea and rectal bleeding improving results from disease activity index and inflammatory score. Moreover, the totality of resveratrol-fed animals survived and finished the treatment while animals fed with standard diet showed a mortality of 40%. Three weeks after DSS removal, the polyphenol caused substantial reductions of the rise of pro-inflammatory cytokines, TNF-alpha and IL-1beta and an increase of the anti-inflammatory cytokine IL-10. Also resveratrol reduced prostaglandin E synthase-1 (PGES-1), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proteins expression, via downregulation of p38, a mitogen-activated protein kinases (MAPK) signal pathway. We conclude that resveratrol diet represents a novel approach to the treatment of chronic intestinal inflammation.

New mechanisms and therapeutic potential of curcumin for colorectal cancer

Curcumin is a polyphenol derived from Curcuma longa. Over the last few years, a number of studies have provided evidence of its main pharmacological properties including chemosensitizing, radiosensitizing, wound healing activities, antimicrobial, antiviral, antifungical, immunomodulatory, antioxidant and anti-inflammatory. More recent data provide interesting insights into the effect of this compound on cancer chemoprevention and chemotherapy. In fact, preclinical studies have shown its ability to inhibit carcinogenesis in various types of cancer including colorectal cancer (CRC). Curcumin has the capacity of interact with multiple molecular targets affecting the multistep process of carcinogenesis. Also, curcumin is able to arrest the cell cycle, to inhibit the inflammatory response and the oxidative stress and to induce apoptosis in cancer cells. Likewise, it has been shown to possess marked antiangiogenic properties. Furthermore, curcumin potentiates the growth inhibitory effect of cyclo-oxygenase (COX)-2 inhibitors and traditional chemotherapy agents implicating another promising therapy regimen in the future treatment of CRC. However, its clinical advance has been hindered by its short biological half-life and low bioavailability after oral administration. This review is intended to provide the reader an update of the bioavailability and pharmacokinetics of curcumin and describes the recently identified molecular pathways responsible of its anticancer potential in CRC.

Dietary supplementation of an ellagic acid-enriched pomegranate extract attenuates chronic colonic inflammation in rats

Dietary polyphenols present in Punica granatum (pomegranate), such as ellagitannins and ellagic acid (EA) have shown to exert anti-inflammatory and antioxidant properties. This study was designed to evaluate the effects of a dietary EA-enriched pomegranate extract (PE) in a murine chronic model of Cronhs disease (CD). Colonic injury was induced by intracolonic instillation of trinitrobenzensulfonic acid (TNBS). Rats were fed with different diets during 30 days before TNBS instillation and 2 weeks before killing: (i) standard, (ii) PE 250 mg/kg/day, (iii) PE 500 mg/kg/day, (iv) EA 10 mg/kg/day and (v) EA 10 mg/kg/day enriched-PE 250 mg/kg/day. Inflammation response was assessed by histology and MPO activity and TNF-α production. Besides, colonic expressions of iNOS, COX-2, p38, JNK, pERK1/2 MAPKs, IKBα and nuclear p65 NF-κB were studied by western blotting. MPO activity and the TNF-α levels were significantly reduced in dietary fed rats when compared with TNBS group. Similarly, PE and an EA-enriched PE diets drastically decreased COX-2 and iNOS overexpression, reduced MAPKs phosporylation and prevented the nuclear NF-κB translocation. Dietary supplementation of EA contributes in the beneficial effect of PE in this experimental colitis model and may be a novel therapeutic strategy to manage inflammatory bowel disease (IBD).

Poly(ADP-Ribose) Polymerase Inhibitors: New Pharmacological Functions and Potential Clinical Implications

Poly(ADP-ribose) polymerase (PARP) comprise of a family of enzymes which catalyses poly(ADP-ribosyl)ation of DNA-binding proteins. To date, seven isoforms have been identified: PARP-1, PARP-2, PARP-3, PARP-4 (Vault-PARP), PARP-5 (Tankyrases), PARP-7 and PARP-10 with structural domains and different functions. PARP-1, the best characterised member, works as a DNA damage nick-sensor protein that uses beta-NAD(+) to form polymers of ADP-ribose and has been implicated in DNA repair, maintenance of genomic integrity and mammalian longevity. The generation of free radicals, reactive oxygen species, and peroxynitrite causes overactivation of PARP resulting in the depletion of NAD(+) and ATP and consequently in necrotic cell death and organ dysfunction. PARP has also been involved in the up-regulation of numerous pro-inflammatory genes through the activation of several transcription nuclear factors. Thus, PARP plays an important role in the pathogenesis of several diseases, such as, stroke, myocardial infarction, circulatory shock, diabetes, neurodegenerative disorders, including Parkinson and Alzheimer diseases, allergy, colitis and other inflammatory disorders. Pharmacological modulation of PARP activity may constitute a suitable target to enhance the cytotoxicity of certain DNA-damaging anticancer drugs. Also, PARP inhibition may be a viable strategy to control viral infections. This review is intended to provide an appreciation of new pharmacological perspectives of these remarkable drugs, summarize novel underlying mechanisms and discuss their potential clinical implications.

Anti-oxidant mechanisms involved in gastroprotective effects of quercetin.

Abstract The anti-ulcerogenic and anti-oxidant effects of various flavonoids have been frequently reported. We investigated the cytoprotective properties of quercetin, a natural flavone, in gastric mucosal injury induced by 50% ethanol, since in this experimental model the pathogenesis of the lesions has been related with production of reactive oxygen species. The involvement of neutrophil infiltration and the capacity of this flavonoid to restrain the oxidative process produced in the gastric tissue after ethanol administration were also investigated. Oral pretreatment with the highest dose of quercetin (200 mg/kg), 120 min before absolute ethanol was the most effective anti-ulcer treatment. Thiobarbituric acid reactive substances in the gastric mucosa, an index of lipid peroxidation, were increased by ethanol injury, but the increase was inhibited by the administration of 200 mg/kg of quercetin. This dose also induced a significant enhancement in the levels of mucosal non-protein SH compounds (important anti-oxidant agents) and in glutathione peroxidase activity. Exposure of the gastric mucosa to 50% ethanol induced a significant increase in myeloperoxidase activity, an index of neutrophil infiltration. Flowever, quercetin was not able to modify the increase in enzymatic activity generated by the necrotizing agent. The activity of superoxide dismutase enzyme involved in several antioxidant processes was also not significantly modified after quercetin treatment. These results suggest that the anti-ulcer activity of quercetin in this experimental model could be partly explained by the inhibition of lipid peroxidation, through decrease of reactive oxygen metabolites. However, the inhibition of neutrophil infiltration or the increase of superoxide dismutase activity does not appear to be involved in gastroprotective effect of this flavonoid.

New Pharmacological Perspectives and Therapeutic Potential of PPAR-γ Agonists

The peroxisome proliferator-activated receptor gamma (PPARγ), a member of the nuclear hormone receptor superfamily has classically been characterized for its implications in adipocyte differentiation and fat metabolism. Recently, PPARg 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-κB). Thus, these agents might also have therapeutic potential in the treatment of gastrointestinal inflammatory disorders, such as ulcerative colitis and Crohns disease. The synthetic thiazolidinediones (TZDs), a novel class of insulin-sensitizing drugs, were the first class of compounds identified as PPARγ ligands, and represent a significant advance in anti-diabetic therapy. However, there is less information about endogenous ligands, although the prostaglandin (PG)J2 and the oxidized phosphatidylcholine have been suggested. Furthermore, PPARg 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 PPARγ activators and their efficacy in certain cancers.

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. β-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 β-catenin immunoreactivity, a proinflammatory cytokine levels reduction, a non modification of p53 expression and, COX-2 and iNOS reduction in the colonic tissue.

Chemopreventive effect of dietary curcumin on inflammation-induced colorectal carcinogenesis in mice

SCOPE Curcumin is a polyphenol with a variety of pharmacologic effects. We evaluate the effect of dietary curcumin on the severity of repeated colitis-associated colorectal cancer. METHODS AND RESULTS Six-week-old C57BL/6 mice were randomized into two dietary groups: standard diet and curcumin at 0.6% diet. The mice were exposed to 15 cycles of 0.7% dextran sodium sulphate for 1 week followed by distilled water for 10 days. After curcumin diet, the disease activity index presented a statistical reduction in the last cycles, macroscopic tumors were not seen and the microscopic study showed minor neoplasic lesions with respect to standard diet-group. β-Catenin translocation to the cytoplasm and/or nucleus was observed in the tumor tissue, but this translocation and its intensity were significantly minor in the curcumin diet-DSS animals. Cytokines as tumor necrosis factor-α and IFN-γ were significantly diminished in DSS-animals fed with curcumin. Conversely, non-modification of p53 expression was observed and cyclo-oxygenase-2 and inducible nitric oxide synthase were significantly reduced in the curcumin diet-DSS group. CONCLUSION We demonstrate the protective/preventive effect of curcumin in the progression of colorectal cancer associated to colitis, which was correlated with a lowered immunoreactivity of ß-catenin, a non-modification of p53 expression, a reduction of proinflammatory cytokine levels and a decrease of inflammatory protein overexpression.