Preventive effect of bergenin against the development of TNBS-induced acute colitis in rats is associated with inflammatory mediators inhibition and NLRP3/ASC inflammasome signaling pathways

Ulcerative colitis is an idiopathic inflammatory bowel disease characterized by intestinal inflammation; blocking this inflammatory process may be the key to the development of new naturally occurring anti-inflammatory drugs, with greater efficiency and lower side effects. The objective of this study is to explore the effects of bergenin (BG) in TNBS (2,4,6-trinitrobenzenesulfonic acid)-induced acute colitis model in rats in order to assist in the studies for the development of novel natural product therapies for inflammatory bowel disease. 48 Wistar rats were randomized into six groups: (i) Control and (ii) TNBS control; (iii) 5-ASA 100 mg/kg/day (iv) BG 12 mg/kg/day (v) BG 25 mg/kg/day and (vi) BG 50 mg/kg/day. Colitis was induced by instillation of TNBS. Colitis was evaluated by an independent observer who was blinded to the treatment. Our results revealed that bergenin decreased the macroscopic and microscopic damage signs of colitis, and reduced the degree of neutrophilic infiltration in the colon tissue; also, it was capable to down-regulate COX-2, iNOS, IkB-α, and pSTAT3 protein expression. Similarly, using a protocol for indirect ELISA quantification of cytokines, bergenin treatment reduced IL-1β, IFN-γ and IL-10 levels, and inhibited both canonical (IL-1) and non-canonical (IL-11) NLRP3/ASC inflammasome signaling pathways in TNBS-induced acute colitis. Conclusion: Our study has provided evidence that administration of bergenin reduced the damage caused by TNBS in an experimental model of acute colitis in rats, reduced levels of pro-inflammatory proteins and cytokines probably by modulation of pSTAT3 and NF-κB signaling and blocking canonical and non-canonical NLRP3/ASC inflammasome pathways.

Effects of dietary virgin olive oil polyphenols: hydroxytyrosyl acetate and 3, 4-dihydroxyphenylglycol on DSS-induced acute colitis in mice

Hydroxytyrosol, a polyphenolic compound from extra virgin olive oil (EVOO) has exhibited an improvement in a model of DSS-induced colitis. However, other phenolic compounds present such as hydroxytyrosyl acetate (HTy-Ac) and 3,4-dihydroxyphenylglycol (DHPG) need to be explored to complete the understanding of the overall effects of EVOO on inflammatory colon mucosa. This study was designed to evaluate the effect of both HTy-Ac and DHPG dietary supplementation in the inflammatory response associated to colitis model. Six-week-old mice were randomized in four dietary groups: sham and control groups received standard diet, and other two groups were fed with HTy-Ac and DHPG, respectively, at 0.1%. After 30 days, all groups except sham received 3% DSS in drinking water for 5 days followed by a regime of 5 days of water. Acute inflammation was evaluated by Disease Activity Index (DAI), histology and myeloperoxidase (MPO) activity. Colonic expression of iNOS, COX-2, MAPKs, NF-kB and FOXP3 were determined by western blotting. Only HTy-Ac-supplemented group showed a significant DAI reduction as well as an improvement of histological damage and MPO. COX-2 and iNOS protein expression were also significantly reduced. In addition, this dietary group down-regulated JNK phosphorylation and prevented the DSS-induced nuclear translocation level of p65. However, no significant differences were observed in the FOXP3 expression. These results demonstrated, for the first time, that HTy-Ac exerts an antiinflammatory effect on acute ulcerative colitis. We concluded that HTy-Ac supplement might provide a basis for developing a new dietary strategy for the prevention of ulcerative colitis.

Dietary squalene supplementation improves DSS-induced acute colitis by downregulating p38 MAPK and NFkB signaling pathways

SCOPE

Squalene is a polyunsaturated triterpene, which has exhibited anticancer and antioxidant activities among others. We investigated dietary squalene supplementation effect on an acute colitis model induced by dextran sulfate sodium (DSS) in C57BL/6 mice.

METHODS AND RESULTS

Mice were fed from weaning with squalene at 0.02% and 0.1%. After 4 weeks, mice were exposed to 3% DSS for 5 days developing acute colitis. After DSS removal (5 days), colons were histological and biochemically processed. Our results showed that dietary squalene treatment exerts anti-inflammatory action in DSS-induced acute colitis. Western blot revealed that squalene downregulated COX-2 (where COX is cyclooxygenase) and inducible nitric oxide synthase system by inhibition of mitogen-activated protein kinase p38 and the nuclear factor-kappa B signaling pathways, preventing an increase in the cytokines levels. Under our experimental conditions, STAT3 and FOXP3 (where FOXP3 is forkhead box P3) were not modified and the transcriptional regulation of antioxidant and/or detoxifying enzymes, Nrf2 (where Nrf2 is nuclear factor (erythroid-derived 2)-like 2), was reduced in DSS-induced colitis. However, any change could be observed after squalene supplementation.

CONCLUSION

Squalene was able to improve the oxidative events and returned proinflammatory proteins expression to basal levels probably through p38 mitogen-activated protein kinase and nuclear factor-kappa B signaling pathways. However, supplementary studies are needed in order to provide a basis for developing a new dietary supplementation strategy.

Mechanisms involved in the antiproliferative and proapoptotic effects of unsaponifiable fraction of extra virgin olive oil on HT-29 cancer cells

Extra virgin olive oil (EVOO) has demonstrated great oncostatic and antiinflammatory properties. Nowadays, it is clear that unsaponifiable fraction (UF) as well as other minor EVOO components have a key role in these beneficial effects. The present study was designed to evaluate UF effect in HT-29 human colon adenocarcinoma cells. Cell growth and viability assays were determined by sulphorhodamine B test at different time points (24, 48, and 72 h). The proapoptotic effect was evaluated by flow cytometric studies and different protein expression were determined by immunoblotting. UF μg/mL concentrations' range significantly reduced the growth of HT-29 cell line. Moreover UF induced intrinsic apoptotic pathway in HT-29 human colon adenocarcinoma cells through PPARγ and NFκB signaling pathways coming up to COX-2 downregulation and modulating p53 suppressor protein levels. The results suggest that UF of EVOO may exert an important role in the anticancer effect of EVOO and provide a natural resource for the prevention or treatment of human colon cancer.

Oleuropein, a secoiridoid derived from olive tree, inhibits the proliferation of human colorectal cancer cell through downregulation of HIF-1α

Oleuropein (OL) is the most prominent phenolic compound in the fruit of olive tree. Although OL has shown powerful anticancer activity the underlying action mechanism remains largely unknown. The present study evaluated the effects of OL on hydroxityrosol (HT)-29 human colon adenocarcinoma cells in comparison to hydroxytyrosol, its hydrolysis product, and to elucidate the underlying anticancer molecular mechanisms involved. Cell proliferation was determined using SRB assay. Cell cycle and apoptosis were assessed by flow cytometry and changes in MAPK cascade protein expression, HIF-1α, p53, PPARγ, and NFKβ signaling pathways by Western blot. Although OL showed less potency than HT, in terms of cell growth inhibition, induced significant changes in cell cycle analysis and caused a significant increase in the apoptotic population. Both compounds produced a remarkable decrease in HIF-1α protein and an upregulation of p53 protein expression. However, no significant changes in IkB-α and MAPK cascade protein expressions were observed. HT produced a significant upregulation in peroxisome proliferator-activated receptor gamma (PPARγ) expression whereas OL failed. PPARγ upregulation may be one of the principal mechanisms of the tumor shrinkage by HT. Our novel findings demonstrate that OL limits the growth and induces apoptosis in HT-29 cells via p53 pathway activation adapting the HIF-1α response to hypoxia.

Anti-inflammatory intestinal activity of Arctium lappa L. (Asteraceae) in TNBS colitis model

ETHNOPHARMACOLOGICAL RELEVANCE

In Brazilian traditional medicine, Arctium lappa (Asteraceae), has been reported to relieve gastrointestinal symptoms.

AIM OF THE STUDY

In the present study, we investigated the effects of the lactone sesquiterpene onopordopicrin enriched fraction (ONP fraction) from Arctium lappa in an experimental colitis model induced by 2,4,6 trinitrobenzene sulfonic acid and performed experiments to elucidate the underlying action mechanisms involved in that effect.

MATERIALS AND METHODS

ONP fraction (25 and 50 mg/kg/day) was orally administered 48, 24 and 1 h prior to the induction of colitis and 24 h after. The inflammatory response was assessed by gross appearance, myeloperoxidase (MPO) activity, tumor necrosis factor alpha (TNF-α) levels and a histological study of the lesions. We determined cyclooxygenase (COX)-1 and -2 protein expressions by western blotting and immunohistochemistry assays.

RESULTS

TNBS group was characterized by increased colonic wall thickness, edema, diffuse inflammatory cell infiltration, increased MPO activity and TNF-α levels. On the contrary, ONP fraction (25 and 50 mg/kg) treatment significantly reduced the macroscopic inflammation scores (p<0.05 and p<0.01, respectively) and morphological alterations associated with an increase in the mucus secretion. Similarly, the degree of neutrophil infiltration and the cytokine levels were significantly ameliorated. Moreover, COX-2 expression was up regulated in TNBS-treated rats. In contrast, ONP fraction (50 mg/kg) administration reduced COX-2 overexpression.

CONCLUSIONS

We have shown that the ONP fraction obtained from Arctium lappa exert marked protective effects in acute experimental colitis, confirming and justifying, at least in part, the popular use of this plant to treat gastrointestinal diseases.

Dietary extra virgin olive oil polyphenols supplementation modulates DSS-induced chronic colitis in mice

We evaluated the protective effect of dietary extra virgin olive oil (EVOO) polyphenol extract (PE) supplementation in the inflammatory response associated to chronic colitis model. Six-week-old mice were randomized in four dietary groups: standard diet (SD), EVOO diet and both enriched with PE (850 ppm) (SD+PE and EVOO+PE). After 30 days, animals that were exposed to dextran sodium sulfate (DSS) (3%) followed by 3 weeks of drinking water developed chronic colitis, which was evaluated by disease activity index (DAI) and histology. Cell proliferation was analyzed by immunohistochemical and changes in monocyte chemotactic protein (MCP)-1 and tumor necrosis factor (TNF)-α mRNA expression by quantitative real-time polymerase chain reaction. Colonic expression of inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2, mitogen-activated protein kinases (MAPKs), IκBα inhibitory and peroxisome proliferator-activated receptor gamma (PPARγ) were determined by western blotting. SD-DSS group showed a significant increase of DAI, histological damage and cell proliferation, as well as an up-regulation of TNF-α, MCP-1, COX-2 and iNOS proteins. p38 and JNK MAPKs phosphorylation, IκBα degradation and PPARγ deactivation were also observed. However, in DSS-treated and EVOO+PE-fed mice, DAI and cell proliferation were significantly reduced, as well as MCP-1, TNF-α, COX-2 and iNOS expression levels. In addition, this dietary group, notably down-regulated JNK phosphorylation, prevented IκBα degradation and PPARγ deactivation. These results demonstrated, for the first time, that EVOO-PE supplementation possessed marked protective effects on experimental colitis through PPARγ up-regulation and nuclear transcription factor-kappa B and MAPK signaling pathway inhibition, decreasing the inflammatory cascade. We concluded that PE-enriched EVOO diet could be a beneficial functional food on ulcerative colitis.

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 Cronh's 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).

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 Cronh's 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).

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.

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.

PARP inhibition reduces acute colonic inflammation in rats

Poly(ADP-ribose) polymerases (PARP) comprise a family of enzymes which catalyse poly(ADP-ribosyl)ation of DNA-binding proteins. Multiple researches indicate the importance of PARP in promoting cell recruitment and thereby inducing organ injury in various forms of inflammation, such as colitis. We have evaluated the effects of two PARP inhibitors, nicotinamide and 1,5-dihydroxyisoquinoline, in acute colitis induced by trinitrobenzensulfonic acid (TNBS) in rats. Nicotinamide (20-40 mg/kg) and 1,5-dihydroxyisoquinoline (4-8 mg/kg) were administered 48, 24 and 1 h prior to the induction of colitis as well as 24 h later. 48 h after colitis induction the lesions were blindly scored and quantified as ulcer index. Histological study and colonic inflammation were assessed by gross appearance and myeloperoxidase (MPO) activity. Prostaglandin E2 (PGE2) synthesis and, cyclooxygenase-1 and cyclooxygenase-2 expressions by Western blotting and immunohistochemistry were also performed. Inflammation following TNBS induction was characterized by increased colonic wall thickness, oedema, diffuse inflammatory cells infiltration in the mucosa and necrosis. Furthermore, increased MPO activity, cyclooxygenase-2 expression and PGE2 synthesis were significantly augmented after TNBS instillation. On the contrary, treatment with 1,5-dihydroxyisoquinoline significantly reduced the degree of colon injury and also caused a substantial reduction in the rise in MPO activity, in the increase of staining for cyclooxygenase-2, as well as in the up-regulation of PGE2 caused by TNBS in the colon. Although nicotinamide significantly did not reduce macroscopic damage, it decreased both MPO activity and PGE2 colonic levels. In conclusion, we demonstrated that PARP inhibition can exert beneficial effects in experimental colitis and may, therefore, be useful in the treatment of ulcerative colitis.

Rosiglitazone, a PPARgamma ligand, modulates signal transduction pathways during the development of acute TNBS-induced colitis in rats

Recent studies have shown that peroxisome proliferator-activated receptor gamma (PPARgamma), a highly nuclear receptor expressed in the colon, may participate in the control of inflammation, especially in regulating the production of immunomodulatory and inflammatory mediators, cellular proliferation and apoptosis. In order to delve into the anti-inflammatory mechanisms and signalling pathways of PPARgamma agonists, we have studied the effects of rosiglitazone, a PPARgamma agonist on the extent and severity of acute ulcerative colitis caused by intracolonic administration of 2,4,6-trinitribenzene sulfonic acid (TNBS) in rats. The inflammatory response was assessed by gross appearance, myeloperoxidase (MPO) activity, tumour necrosis factor alpha (TNF-alpha) levels and a histological study of the lesions. We determined prostaglandin E2 production as well as the cyclooxygenases (COX)-1 and -2 expressions by immunohistochemistry and Western blotting. The nuclear factor kappa (NF-kappaB) p65 and p38 mitogen-activated protein kinase (MAPK) expression levels were also measured by Western blotting. Finally, since PPARgamma agonists modulate apoptosis, we tried to clarify its effects under early acute inflammatory conditions. Inflammation following TNBS induction was characterized by increased colonic wall thickness, edema, diffuse inflammatory cells infiltration, necrosis reaching an ulcer index (UI) of 9.66+/-0.66 cm(2) and increased MPO activity and TNF-alpha colonic levels. Rosiglitazone treatment significantly reduced the morphological alteration associated with TNBS administration and the UI with the highest dose. In addition, the degree of neutrophil infiltration and the cytokine levels were significantly ameliorated. Rosiglitazone significantly reduced the rise in the prostaglandin (PG) E(2) generation compared with TNBS group. The COX-1 levels remained stable throughout the treatment in all groups. The COX-2 expression was elevated in TNBS group; however rosiglitazone administration reduced the COX-2 overexpression. A high expression of NF-kappaB p65 and p38 MAPK proteins appeared in colon mucosa from control TNBS-treated rats; nevertheless, PPARgamma agonist treatment drastically decreased them. There were no significant changes in apoptosis after rosiglitazone treatment when compared to TNBS group. In conclusion, rosiglitazone seems to modulate the acute colitis through NF-kappaB p65 and p38 MAPK signalling pathways.

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-alpha) 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-kappaB) 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-alpha 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-kappaB 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.

Curcumin, a Curcuma longa constituent, acts on MAPK p38 pathway modulating COX-2 and iNOS expression in chronic experimental colitis

Ulcerative colitis (UC) is a nonspecific inflammatory disorder characterized by oxidative and nitrosative stress, leucocyte infiltration and up-regulation of pro-inflammatory cytokines. Mitogen-activated protein kinases (MAPKs), such as the p38 and the c-Jun N-terminal kinase (JNK) modulate the transcription of many genes involved in the inflammatory process. Curcumin is a polyphenol derived from Curcuma longa, which is known to have anti-inflammatory activity. The aim of this study was to study the effects and mechanisms of action of curcumin, on chronic colitis in rats. Inflammation response was assessed by histology and myeloperoxidase activity (MPO). We determined the production of Th1 and Th2 cytokines and nitrites in colon mucosa, as well as the expression of inducible nitric oxide synthase (iNOS), cyclo-oxygenase(COX)-1 and-2 by western blotting and inmmunohistochemistry. Finally, we studied the involvement of MAPKs signaling in the protective effect of curcumin in chronic colonic inflammation. Curcumin (50-100 mg/kg/day) were administered by oral gavage 24 h after trinitrobenzensulfonic acid (TNBS) instillation, and daily during 2 weeks before sacrifice. Curcumin significantly attenuated the damage and caused substantial reductions of the rise in MPO activity and tumour necrosis factor alpha (TNF)-alpha. Also curcumine was able to reduce nitrites colonic levels and induced down-regulation of COX-2 and iNOS expression, and a reduction in the activation of p38 MAPK; however, no changes in the activation of JNK could be observed. In conclusion, we suggest that inhibition of p38 MAPK signaling by curcumin could explain the reduced COX-2 and iNOS immunosignals and the nitrite production in colonic mucosa reducing the development of chronic experimental colitis.

Resveratrol as an anti-inflammatory and anti-aging agent: mechanisms and clinical implications

Resveratrol is a phytoalexin polyphenolic compound found in various plants, including grapes, berries, and peanuts. Multiple lines of compelling evidence indicate its beneficial effects on neurological, hepatic, and cardiovascular systems. Also one of the most striking biological activities of resveratrol soundly investigated during the late years has been its cancer-chemopreventive potential. In fact, recently it has been demonstrated that this stilbene blocks the multistep process of carcinogenesis at various stages: tumor initiation, promotion, and progression. One of the possible mechanisms for its biological activities involves downregulation of the inflammatory response through inhibition of synthesis and release of pro-inflammatory mediators, modification of eicosanoid synthesis, inhibition of activated immune cells, or inhibiting such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) via its inhibitory effects on nuclear factor (kappa)B (NF-(kappa)B) or the activator protein-1 (AP-1). More recent data provide interesting insights into the effect of this compound on the lifespan of yeast and flies, implicating the potential of resveratrol as an anti-aging agent in treating age-related human diseases. It is worthy to note that the phenolic compound possesses a low bioavailability and rapid clearance from the plasma. As the positive effects of resveratrol on inflammatory response regulation may comprise relevant clinical implications, the purpose of this article is to review its strong anti-inflammatory activity and the plausible mechanisms of these effects. Also, this review is intended to provide the reader an up-date of the bioavailability and pharmacokinetics of resveratrol and its impact on lifespan.

Rosiglitazone, an agonist of peroxisome proliferator-activated receptor gamma, protects against gastric ischemia-reperfusion damage in rats: role of oxygen free radicals generation

Peroxisome proliferator-activated receptor gamma (PPAR-gamma) is a nuclear hormone receptor super family that has recently been implicated in atherosclerosis, inflammation, cancer, infertility, and demyelination. Oxidative stress, neutrophil infiltration, proinflammatory cytokines, and the exhibition of luminal acid play a role in the pathogenesis of gastric injury induced by ischemia-reperfusion. Rosiglitazone, a specific PPAR-gamma ligand, has been shown to have antiinflammatory activity, but its effects on experimental ischemia-reperfusion gastric injury remain unknown. We have investigated the effects of the rosiglitazone on gastric injury caused by ischemia following reperfusion in rats. Tumour necrosis factor-alpha (TNF-alpha) levels and changes in enzymatic activities of myeloperoxidase, as a marker of neutrophils infiltration, xanthine oxidase, superoxide dismutase, and glutathione peroxidase, were determined. Histological analysis of the lesions was also carried out. Pretreatment with 1 or 4 mg/kg of rosiglitazone ameliorated the gastric damage induced by clamping the celiac artery for 30 min followed by 60 min of reperfusion. It significantly (P<0.05) reduced the index of neutrophil infiltration and the levels of the cytokine. Rosiglitazone did not revert the reduced glutathione peroxidase activity but enhanced significantly (P<0.01) the decreased xanthine oxidase and superoxide dismutase activities in gastric mucosa of ischemic rats. In conclusion, rosiglitazone reduces the damage in ischemia-reperfusion gastric injury and alleviates the inflammatory response and the oxidative events.

COX expression and PGE2 and PGD2 production in experimental acute and chronic gastric lesions

Prostaglandin E(2) and D(2) (PGE(2) and PGD(2)) production and cyclooxygenase-2 (COX-2) expression during the resolution of acute and chronic gastric inflammatory lesions in Wistar rats have been investigated. Differences between ibuprofen, nonselective COX inhibitor, and rofecoxib, specific COX-2 inhibitor, on the development of the induced responses were also analysed. In an acute model, by instillation of HCL, the greatest injury was observed early with a rapid and progressive restoration. Maximal up-regulation of COX-2 protein was detected at 6 h and was accompanied by increase of PGE(2) synthesis but not PGD(2). Both drugs stimulated COX-2 expression in accordance to their capacity of inhibiting this enzymatic activity, driving to delay in the healing. In a chronic model, by acetic acid-induced gastric ulcers, COX-2 was expressed at 7 days and was also associated with PGE(2) increase. Ibuprofen and rofecoxib also augmented COX-2 protein and inhibited PGE(2) levels. However, PGD(2) production was augmented when none signal of COX-2 protein could be detected. Together, this study confirms the role played by COX-2 enzyme in the resolution of acute and chronic gastric inflammatory process, PGE(2) being the principal product. The antiinflammatory effect of nonsteroidal antiinflammatory drugs (NSAIDs) could be mediated not only through the inhibition of COX activity but also through the induction of antiinflammatory PGs production-such as PGD(2)-although further studies would be needed to clarify the mechanisms of this activity and the possible implicated processes.

A new flavonoid derivative, dosmalfate, attenuates the development of dextran sulphate sodium-induced colitis in mice

In this study, we have evaluated the efficacy of dosmalfate, a new flavonoid derivative compound, for the prevention and treatment of experimental colitis. To induce colitis, BALB/c mice received 5% dextran sulphate sodium (DSS) in their drinking water continuously for 7 days. 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)-1 beta, prostaglandins (PG)E(2) and (PG)D(2) concentrations in colonic tissue, histological and histochemical analysis of the lesions were also measured. Dosmalfate (400-800 mg/kg body weight, p.o.) ameliorated severe colitis reduced the degree of inflammation through reduction of neutrophil infiltration and IL-1 beta levels. (PG)E(2) and (PG)D(2) synthesis were significantly reduced in colitis control group and treatment with dosmalfate abolished the decrease in PG synthesis in colon mucosa. We conclude that dosmalfate is protective in acute DSS-induced colitis. The beneficial effects seem to be related to a decrease of neutrophil infiltration, absence of up-regulation of IL-1 beta and increase of PG production in colon mucosa.

The cyclo-oxygenase-2 inhibitor, rofecoxib, attenuates mucosal damage due to colitis induced by trinitrobenzene sulphonic acid in rats

Cyclo-oxygenase-2 overexpression has been described in experimental colitis. However, there are controversial findings suggesting that its inhibition by selective cyclo-oxygenase-2 inhibitors not only may have a beneficial effect on experimental colitis, but also exacerbate the inflammation-associated colonic injury. Thus, the role of cyclo-oxygenase-2 inhibitors in the possible modulation of colon inflammation is controversial and remains uncertain. In this study, we evaluated the effects of the selective cyclo-oxygenase-2 inhibitor, rofecoxib, on the extent and severity of ulcerative colitis caused by intracolonic administration of 2,4,6-trinitrobenzene sulphonic acid (TNBS) in rats. The lesions and the inflammatory response were assessed by histology and measurement of myeloperoxidase activity. Interleukin-1 beta, prostaglandin E(2) and D(2) levels in colon mucosa and the immunohistochemical expression of the cyclo-oxygenases-1 and -2 were also studied. Finally, we investigated the effects of rofecoxib on apoptosis of colonocytes by the appearance of DNA fragmentation. Inflammation following TNBS was characterized by increased colonic wall thickness, oedema, diffuse inflammatory cell infiltration in the mucosa, and necrosis. Increased myeloperoxidase activity, as an index of neutrophil infiltration in the mucosa, and interleukin-1 beta levels were also measured in the colon. Administration of rofecoxib significantly (P<0.05) reduced the colonic damage, the degree of neutrophil infiltration, and interleukin-1 beta levels. In addition, apoptosis was significantly increased in TNBS-treated rats, but not in rofecoxib plus TNBS-treated rats. We concluded that rofecoxib seems to have beneficial effects in TNBS-induced colitis by diminishing the initial stage of inflammation, probably by a mechanism related to inhibition of prostaglandin E(2) by the cyclo-oxygenase-2 pathway. The data suggest that cyclo-oxygenase-2-selective inhibitors may have a therapeutic role in ulcerative colitis.

Resveratrol, a polyphenol found in grapes, suppresses oxidative damage and stimulates apoptosis during early colonic inflammation in rats

Oxidative stress, neutrophil infiltration, proinflammatory cytokines and eicosanoid generation are clearly involved in the pathogenesis of intestinal bowel disease. Resveratrol, a polyphenolic compound found in grapes and wine, has been shown to have anti-inflammatory, antioxidant, antitumour and immunomodulatory activities, however, its effects on experimental colitis remain unknown. We have investigated the effects of resveratrol on the colon injury caused by intracolonic instillation of trinitrobenzenesulphonic acid (TNBS) in rats. We determined the production of prostaglandin (PG)E(2) and PGD(2) in colon mucosa and the expression of cyclo-oxygenases (COX)-1 and -2 immunohistochemically. The inflammatory response was assessed by histology and myeloperoxidase activity, as an index of neutrophil infiltration. Interleukin-1 beta production, histological and histochemical analysis of the lesions were also carried out. Finally, since resveratrol has been found to modulate apoptosis we intended to elucidate its effects on colonic mucosa under early acute inflammatory conditions. Resveratrol (5-10mg/kg/day) significantly reduced the degree of colonic injury, the index of neutrophil infiltration and the levels of the cytokine. Resveratrol did not revert the increased PGE(2) levels but produced a significant fall in the PGD(2) concentration. Compared with inflamed colon, no changes in staining for COX-1 were observed in colon of resveratrol and TNBS-treated rats. In contrast, COX-2 expression was decreased. Furthermore, resveratrol enhanced apoptosis compared with already high level induced by TNBS. In conclusion, resveratrol reduces the damage in experimentally induced colitis, alleviates the oxidative events and stimulates apoptosis.

Mucosal damage induced by preferential COX-1 and COX-2 inhibitors: role of prostaglandins and inflammatory response

Nonsteroidal anti-inflammatory drugs (NSAID) are well known to induce gastric mucosal damage including bleeding, ulceration and perforation in humans and animals too. These effects are related with the inhibition of the enzyme cyclooxygenase, which is the main established mechanism of action for these drugs. Fasted rats were given piroxicam, preferential COX-1 inhibitor (10-20 mg/kg) or meloxicam, preferential COX-2 inhibitor (7.5-15 mg/kg) orally. Six or nine hours (h) later, respectively, the stomach was excised, the severity of the damage assessed and myeloperoxidase (MPO) activity measured, as well as prostaglandin PGE(2) content. Furthermore, in order to assess the effects of these oxicams over previously damaged gastric mucosa, 1 ml of 0.6 N HCl was administered p.o. followed, 1 h after, of the correspondent dose of each NSAID, and the same parameters were determined. Oral administration of both drugs dose-dependently caused acute gastric haemorrhage erosions. Myeloperoxidase activity was significantly increased by piroxicam administration. In addition, PGE(2) content was significantly reduced. The association between the administration of the acid and NSAID caused a worsening of the damage and, while myeloperoxidase activity did not modify by both piroxicam and meloxicam, PGE(2) levels were reduced. These results suggest that the PG derived from both COX-1 and COX-2 pathway plays a beneficial role in the gastroprotection, and thus caution should be exercise in the clinical use of preferential COX-2 inhibitors.

Effects of dosmalfate, a new cytoprotective agent, on acute and chronic trinitrobenzene sulphonic acid-induced colitis in rats

Activated neutrophils and proinflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha) are clearly involved in the pathogenesis of bowel disease. Increased expression of epidermal growth factor-receptor (EGF receptor) has been reported for the colon mucosa surrounding areas of ulceration, suggesting a pivotal role in mucosal defence and repair. In this study, we examined the effects of dosmalfate, a new flavonoid derivative compound (diosmin heptakis) with antioxidant and cytoprotective properties, on acute and chronic experimental trinitrobenzene sulphonic acid (TNBS)-induced colitis in rats. The inflammation response was assessed by neutrophil infiltration as evaluated by histology and myeloperoxidase activity. Mucosal TNF-alpha production and histological analysis of the lesions was also carried out. In addition, we studied the expression of the EGF receptor inmunohistochemically during the healing of TNBS-induced chronic colitis. A 2-day treatment with 400 or 800 mg/kg of dosmalfate ameliorated the colon damage score and the incidence of adhesions. It also significantly (P<0.05) decreased myeloperoxidase activity and colonic mucosal production of TNF-alpha. Chronic treatment (14 days) with 800 mg/kg/day of dosmalfate also had significant protective effects on TNBS-induced colitis which were reflected by significant attenuation (P<0.05) of the damage score while the inflammatory indicators were not improved. The chronic beneficial effect of dosmalfate was apparently related to the enhancement of EGF receptor expression. These findings confirm the protective effects of dosmalfate in acute and chronic experimental colitis.

Gastrointestinal tolerability of metamizol, acetaminophen, and diclofenac in subchronic treatment in rats

The gastrointestinal tolerability of metamizol and acetaminophen [weak cyclooxygenase (COX) inhibitors] in comparison with diclofenac (nonselective cyclooxygenase inhibitor) was evaluated in subchronic treatments in rats. Wistar rats received 60 mg/kg body weight of metamizol and acetaminophen, and 3 mg/kg body weight of diclofenac by oral route twice daily for 14 days. Myeloperoxidase activity, an index of neutrophil infiltration, COX expression and the effects on blood parameters used as indicators of liver and renal functions were also studied. Metamizol and acetaminophen did not cause apparent gastrointestinal lesions; in contrast diclofenac showed swelling and an increased thickness on the distal intestinal mucosa. Myeloperoxidase activity was significantly increased in the small bowel with diclofenac treatment. In gastric mucosa the expression of the cyclooxygenase-1 was not affected and the expression of cyclooxygenase-2 was not observed. Diclofenac treatment significantly diminished hematocrit, hemoglobin, and corpuscular volume and increased the number of platelets. Aspartate aminotransferase and gamma-glutamyltransferase activity were also altered and, regarding the renal biochemical parameters, the animals treated with diclofenac had increased urea values. In contrast, acetaminophen treatment did not affect either of these parameters and metamizol increased only the alanine aminotransferase activity. Under our experimental conditions, metamizol and acetaminophen seem to be safe drugs. In contrast, with diclofenac treatment blood loss and anemia are observed which could stem from the small intestinal injury. Moreover, this drug could to impair kidney function.

Gastric damage induced by subchronic administration of preferential cyclooxygenase-1 and cyclooxygenase-2 inhibitors in rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) are well known to induce gastrointestinal damage including bleeding, ulceration and perforation in humans and animals. The aim of this study was to compare the effects of two oxicams, preferential cyclooxygenase (COX)-1 or COX-2 inhibitors, on both gastric mucosa and some biological parameters (hematological, hepatic and renal) after subchronic administration (14 and 28 days) in rats. Neutrophil infiltration was also assessed. Equipotent doses of meloxicam (3.75 and 7.5 mg/kg) and piroxicam (5 and 10 mg/kg) were administered. Both drugs dose-dependently caused multiple gastric erosions and hemorrhage in rats after 14 and 28 days of administration. Treatment with meloxicam led to a higher gastric damage than with piroxicam on day 14 although these results were not significant. The levels of myeloperoxidase activity (as an index of neutrophil infiltration) were not changed compared with control after drug treatment. All the hematological parameters obtained after drugs administration for 14 and 28 days were in the range of normal values, and a significant increase in platelet levels could be observed in the group treated with 5 mg/kg of piroxicam for 14 days. Aspartate aminotransferase (AST or GOT) increased significantly after 14 days, but after 28 days the values returned to normality. Creatinine and urea did not undergo significant changes except for the piroxicam 14-day 5 mg/kg group, in which uremia increased significantly over normal values. In conclusion, our results show that meloxicam, a preferential COX-2 inhibitor, causes rates of gastric lesion comparable to those seen with traditional NSAIDs, without inducing important changes in biological parameters.

Effects of dipyrone on inflammatory infiltration and oxidative metabolism in gastric mucosa: comparison with acetaminophen and diclofenac

In the last several years, it has been proposed that neutrophil- and oxygen-dependent microvascular injuries may be important factors in the gastrointestinal toxicity of nonsteroidal antiinflammatory drugs (NSAIDs). In addition, after oral administration, reduced levels of gastric mucosal adenosine triphosphate in response to mitochondrial damage constitute the earliest event on topical mucosal erosions. In these experiments, we compared the implication of active oxygen, lipid peroxidation levels and neutrophil infiltration in gastric mucosal injury induced by the analgesic-antipyretic drugs, dipyrone (pyrazolone derivative) and acetaminophen (nonacidic drug), both with relatively weak antiinflammatory effects, with diclofenac (an acidic NSAID). After 6 hr of oral administration, dipyrone (120 and 500 mg/kg) did not provoke macroscopic lesions on rat gastric mucosa. Only the highest dose (1000 mg/kg) induced slight erosions similar to the same dose of acetaminophen without modifications in lipid peroxidation levels or myeloperoxidase activity. The area of mucosa with lesions, the increase in neutrophil infiltration, and concentration of TBA-reactive substances was significantly higher with diclofenac (50 mg/kg). By contrast, inhibition in superoxide dismutase activity was observed. In a dose-dependent manner, dipyrone and diclofenac decreased the levels of endogenous gluthatione, and the highest dose (1000 mg/kg) also inhibited glutathione peroxidase activity. None of treatments induced changes in xanthine oxidase activity, an index of ischemic condition. These findings confirm the favorable gastric tolerability of dipyrone, since only the highest dose produced weak mucosal lesions similar to that obtained with acetaminophen, and this effect only could be related to a diminished glutathione metabolism. In contrast, diclofenac induced significant erosions, and the data obtained indicate that the enhancement of oxidative stress plays an important role in the pathogenesis of damage.

Chronic gastric ulcer healing in rats subjected to selective and non-selective cyclooxygenase-2 inhibitors

The influence of different nonsteroidal anti-inflammatory drugs (NSAIDs) and of a proton pump inhibitor on the healing parameters of a chronic gastric ulcer was evaluated. Wistar rats were used after the induction of a chronic acetic acid ulcer. The animals were treated orally for 8 and 15 days, twice daily, with the conventional NSAID, piroxicam (0.35 mg/kg), the non-narcotic analgesic, metamizol (33 mg/kg), the selective cyclooxygenase-2 inhibitor, celecoxib (1.8 mg/kg) and the proton pump inhibitor, omeprazole (0.35 mg/kg). Macroscopic ulcer index, myeloperoxidase activity and prostaglandin E(2) content (both biochemical parameters were evaluated in ulcerated and in intact tissue) as well as histological and immunohistochemical evaluations were carried out at 8 and 15 days. Omeprazole accelerated ulcer healing at 8 and 15 days (P<0.05), while celecoxib delayed healing significantly at 15 days (P<0.01). At 8 days, the prostaglandin E2 content decreased with all NSAIDs at the ulcer site as well as in intact tissue. The same happened at 15 days except for celecoxib, which only diminished prostaglandins in intact mucosa. Immunohistochemistry showed differences in the location of cyclooxygenase-2 and -1. The highest cyclooxygenase-2 expression was found with piroxicam and the lowest expression was with celecoxib.

CONCLUSIONS

Down-regulation of cyclooxygenase-2 expression as well as a possible involvement of the chemical structure of celecoxib, a 1,5-dirarylpirazole with a sulphonamide moiety, may account for the delay in ulcer healing.

Mechanisms involved in the attenuation of intestinal toxicity induced by (S)-(+)-ketoprofen in re-fed rats

In addition to suppression of prostaglandins synthesis a number of factors have been implicated in nonsteroidal antiinflammatory drugs (NSAIDs) enteropathy, including oxygen radical-dependent microvascular injuries, depletion of glutathione, and food. Inflammatory cytokines such as tumor necrosis factor-alpha regulate endothelial adhesion molecules expression and promote vascular neutrophil adherence. Racemic ketoprofen is a potent NSAID with a chiral structure existing in two enantiomeric forms. Its therapeutic effects reside almost exclusively in the (S)-(+) isomer nevertheless the potential contribution to side effects of the (R)-(-) isomer cannot be ignored. The aims of this study were to explore the role of prostaglandins depletion, tumor necrosis factor-alpha production, and glutathione homeostasis in the comparative pathogenesis of intestinal injury induced by racemic-ketoprofen and its enantiomers in re-fed rats. Racemic ketoprofen and (R)-(-)-ketoprofen dose-dependently caused similar and multiple lesions in the mid-jejunum significantly higher than those observed with (S)-(+)-ketoprofen. All the treatments significantly decreased prostaglandins content. A significant increase of tumor necrosis factor-alpha production and decreases in glutathione levels and glutathione reductase activity after treatment of the racemate and (R)-(-)-ketoprofen, were observed whereas the (S)-(+)-isomer did not change these parameters. In conclusion, (S)-(+)-ketoprofen possesses a better intestinal toxicity profile than the racemate and its (R)-(-)-isomer. Despite inhibiting cyclooxygenase activity, the attenuation of (S)-(+)-ketoprofen-induced intestinal toxicity could be correlated with a reduced oxidative damage characterized not only by a lack of changes in glutathione reductase activity and glutathione levels but also by an absence of up-regulation of tumor necrosis factor-alpha production in intestinal mucosa.