Gliotoxin reduces the severity of trinitrobenzene sulfonic acid-induced colitis in mice: evidence of the connection between heme oxygenase-1 and the nuclear factor-kappaB pathway in vitro and in vivo

Targeting Nrf2 signaling pathways in the role of bladder cancer: From signal network to targeted therapy

Bladder cancer (BC) is the most common malignancy of the urinary system and often recurs after tumor removal and/or is resistant to chemotherapy. In cancer cells, the activity of the signaling pathway changes significantly, affecting a wide range of cell activities from growth and proliferation to apoptosis, invasion and metastasis. Nrf2 is a transcription factor that plays an important role in cellular defense responses to a variety of cellular stresses. There is increasing evidence that Nrf2 acts as a tumor driver and that it is involved in the maintenance of malignant cell phenotypes. Abnormal expression of Nrf2 has been found to be common in a variety of tumors, including bladder cancer. Over-activation of Nrf2 can lead to DNA damage and the development of bladder cancer, and is also associated with various pathological phenomena of bladder cancer, such as metastasis, angiogenesis, and reduced toxicity and efficacy of therapeutic anticancer drugs to provide cell protection for cancer cells. However, the above process can be effectively inhibited or reversed by inhibiting Nrf2. Therefore, Nrf2 signaling may be a potential targeting pathway for bladder cancer. In this review, we will characterize this signaling pathway and summarize the effects of Nrf2 and crosstalk with other signaling pathways on bladder cancer progression. The focus will be on the impact of Nrf2 activation on bladder cancer progression and current therapeutic strategies aimed at blocking the effects of Nrf2. To better determine how to promote new chemotherapy agents, develop new therapeutic agents, and potential therapeutic targets.

Xenobiotic metabolites modify immune responses of the cervicovaginal epithelium: potential mechanisms underlying barrier disruption

OBJECTIVE

Xenobiotic metabolites are exogenous biochemicals that can adversely impact reproductive health. We previously identified xenobiotics in cervicovaginal fluid during pregnancy in association with short cervix. In other organ systems, xenobiotics can modify epithelial barrier function. We hypothesise that xenobiotics dysregulate epithelial cell and macrophage immune responses as a mechanism to disrupt the cervicovaginal barrier.

DESIGN

In vitro cell culture system.

SETTING

Laboratory within academic institution.

SAMPLE

Vaginal, ectocervical and endocervical epithelial cell lines and primary macrophages.

METHODS

Cells were treated with diethanolamine (2.5 mM), ethyl glucoside (5 mM) or tartrate (2.5 mM) for 24 h.

MAIN OUTCOME MEASURES

Cytokines and matrix metalloproteinases were measured in cell supernatants (n = 3 per condition). One-way analysis of variance (ANOVA) with Dunnett's test for multiple comparisons was performed.

RESULTS

Diethanolamine induces inflammatory cytokines, whereas ethyl glucoside and tartrate generally exert anti-inflammatory effects across all cells. Diethanolamine increases interleukin 6 (IL-6), IL-8, interferon γ-induced protein 10 kDa (IP-10), growth-regulated oncogene (GRO), fractalkine, matrix metalloproteinase 1 (MMP-1), MMP-9 and MMP-10 (p < 0.05 for all), factors involved in acute inflammation and recruitment of monocytes, neutrophils and lymphocytes. Ethyl glucoside and tartrate decrease multiple cytokines, including RANTES and MCP-1 (p < 0.05 for all), which serve as chemotactic factors. Vaginal cells exhibit heightened inflammatory tone compared with cervical cells and macrophages, with a greater number of differentially expressed analytes after xenobiotic exposure.

CONCLUSIONS

Xenobiotic metabolites present in the cervicovaginal space during pregnancy modify immune responses, unveiling potential pathways through which environmental exposures may contribute to the pathogenesis of cervical remodelling preceding preterm birth. Future work identifying xenobiotic sources and routes of exposure offers the potential to modify environmental risks to improve pregnancy outcomes.

The functional role of sulforaphane in intestinal inflammation: a review

Intestinal inflammation represented by inflammatory bowel disease (IBD) has become a global epidemic disease and the number of patients with IBD continues to increase. This digestive tract disease not only affects the absorption of food components by destroying the intestinal epithelial structure, but also can induce diseases in remote organs via the gut-organ axis, seriously harming human health. Nowadays, increasing attention is being paid to the nutritional and medicinal value of food components with increasing awareness among the general public regarding health. As an important member of the isothiocyanates, sulforaphane (SFN) is abundant in cruciferous plants and is famous for its excellent anti-cancer effects. With the development of clinical research, more physiological activities of SFN, such as antidepressant, hypoglycemic and anti-inflammatory activities, have been discovered, supporting the fact that SFN and SFN-rich sources have great potential to be dietary supplements that are beneficial to health. This review summarizes the characteristics of intestinal inflammation, the anti-inflammatory mechanism of SFN and its various protective effects on intestinal inflammation, and the possible future applications of SFN for promoting intestinal health have also been discussed.

Targeting macrophage polarization by Nrf2 agonists for treating various xenobiotics-induced toxic responses

Macrophages can polarize into different phenotypes in response to different microenvironmental stimuli. Macrophage polarization has been assigned to two extreme states, namely proinflammatory M1 and anti-inflammatory M2. Accumulating evidences have demonstrated that M1 polarized macrophages contribute to various toxicants-induced deleterious effects. Switching macrophages from proinflammatory M1 phenotype toward anti-inflammatory M2 phenotype could be a promising approach for treating various inflammatory diseases. Studies in the past few decades have revealed that nuclear factor erythroid 2-related factor 2 (Nrf2) can modulate the polarization of macrophages. Specifically, activation of Nrf2 could block M1 stimuli-induced production of proinflammatory cytokines and chemokines, and shift the polarization of macrophages toward M2 by cross-talking with nuclear factor kappa-B (NF-κB), mitogen-activated protein kinases (MAPKs), peroxisome proliferator-activated receptor γ (PPARγ), and autophagy. Importantly, a great number of studies have confirmed the beneficial effects of natural and synthesized Nrf2 agonists on various inflammatory diseases; however, most of these compounds are far away from clinical application due to lack of characterization and defects of study designs. Interestingly, some endogenous Nrf2 inducers and compounds with dual activities (such as the Nrf2 inducing and CO releasing effects) exhibit potent anti-inflammatory effects, which points out an important direction for future researches.

Therapeutic potential of sulfur-containing natural products in inflammatory diseases

Owing to the prevalence of chronic inflammation and its related disorders, there is a demand for novel therapeutic agents capable of preventing or suppressing inflammation. Natural products (NPs) are well established as an important resource for drug development and provide an almost infinite array of molecular entities. Sulfur-containing NPs (i.e., NPs containing one or more sulfur atoms) are abundant throughout nature, from bacteria to animals. The aim of this review was to survey the emerging evidence on role of sulfur-containing NPs, such as glutathione, garlic-derived sulfur compounds, Epipolythiodioxopiperazines (EPTs), Isothiocyanates (ITCs), and Ergothioneine (EGT), in the control of inflammation and to determine the possible underlying mechanisms. A discussion of how hydrogen sulfide (H₂S), an endogenous gaseous signaling molecule, links sulfur-containing NPs and their anti-inflammatory action is also performed. This review may help to further the development of sulfur-based compounds by providing a guide for structure-activity relationship-based modification for use in modern medicinal chemistry. However, as this field is still in its infancy, the review is concluded by an overview of the progression of these promising entities as therapeutic agents.

Roles of peroxisome proliferator-activated receptor α in the pathogenesis of ethanol-induced liver disease

Alcoholic liver disease (ALD) is a progressively aggravated liver disease with high incidence in alcoholics. Ethanol-induced fat accumulation and the subsequent lipopolysaccharide (LPS)-driven inflammation bring liver from reversible steatosis, to irreversible hepatitis, fibrosis, cirrhosis, and even hepatocellular carcinoma. Peroxisome proliferator-activated receptor α (PPARα) is a member of the nuclear receptor superfamily of ligand-activated transcription factors and plays pivotal roles in the regulation of fatty acid homeostasis as well as the inflammation control in the liver. It has been well documented that PPARα activity and/or expression are downregulated in liver of mice exposed to ethanol, which is thought to be one of the prime contributors to ethanol-induced steatosis, hepatitis and fibrosis. This article summarizes the current evidences from in vitro and animal models for the critical roles of PPARα in the onset and progression of ALD. Importantly, it should be noted that the expression of PPARα in human liver is reported to be similar to that in mice, and PPARα expression is downregulated in the liver of patients with nonalcoholic fatty liver disease (NAFLD), a disease sharing many similarities with ALD. Therefore, clinical trials investigating the expression of PPARα in the liver of ALD patients and the efficacy of strong PPARα agonists for the prevention and treatment of ALD are warranted.

Ellagic acid reduces methotrexate-induced apoptosis and mitochondrial dysfunction via up-regulating Nrf2 expression and inhibiting the IĸBα/NFĸB in rats

BACKGROUND

The clinical application of methotrexate (MTX), an efficacious cytotoxic drug, is restricted due to its associated liver toxicity. Ellagic acid (EA), a natural polyphenol, possesses hepatoprotective, antioxidant and anti-inflammatory properties.

OBJECTIVES

The present study seeks to address the hepatoprotective effects of Ellagic acid (EA) against MTX-mediated oxidative stress (OS) and widen our current knowledge of the underlying molecular mechanisms of MTX toxicity.

METHODS

Wistar rats were orally given EA (5 mg/kg and 10 mg/kg) for 10 successive days and at the end of the third day they were administered a single dose of MTX (20 mg/kg i.p).

RESULTS

After performing biochemical analysis, liver enzymes and malondialdehyde were significantly higher in the MTX group, indicating hepatic oxidative damage. MTX-induced OS was further confirmed with observation of events such as reactive oxygen species (ROS) overproduction, mitochondrial outer membrane potential decrease, mitochondrial swelling, cytochrome c release and caspase-3/9 increase, resulting in apoptosis. Furthermore, overexpression of pro-inflammatory factors such as nuclear factor kappa B (NF-ĸB) and interleukin 6 (IL-6) indicated the MTX-induced inflammation in MTX-treated group. Interestingly, EA was able to significantly prevent OS, mitochondrial dysfunction, apoptosis and inflammation induced by MTX. Also, EA-treated rats demonstrated significant upregulation of both nuclear factor erythroid 2-related factor 2 (Nrf2) and hemoxygenase-1 (HO-1), which were considerably downregulated in MTX-treated rats.

CONCLUSIONS

EA protects rats against MTX-induced apoptosis and mitochondrial dysfunction via up-Regulating Nrf2 and HO-1 expression and inhibiting the NF-κB signaling pathway. Therefore, EA may protect patients against MTX-induced hepatotoxicity and encourage its clinical application. Graphical abstract Beneficial effect of Ellagic acid (EA) on Methotrexate (MTX)-induced liver injury: molecular mechanism.

Preparations for Invasion: Modulation of Host Lung Immunity During Pulmonary Aspergillosis by Gliotoxin and Other Fungal Secondary Metabolites

Pulmonary aspergillosis is a severe infectious disease caused by some members of the Aspergillus genus, that affects immunocompetent as well as immunocompromised patients. Among the different disease forms, Invasive Aspergillosis is the one causing the highest mortality, mainly, although not exclusively, affecting neutropenic patients. This genus is very well known by humans, since different sectors like pharmaceutical or food industry have taken advantage of the biological activity of some molecules synthetized by the fungus, known as secondary metabolites, including statins, antibiotics, fermentative compounds or colorants among others. However, during infection, in response to a hostile host environment, the fungal secondary metabolism is activated, producing different virulence factors to increase its survival chances. Some of these factors also contribute to fungal dissemination and invasion of adjacent and distant organs. Among the different secondary metabolites produced by Aspergillus spp. Gliotoxin (GT) is the best known and better characterized virulence factor. It is able to generate reactive oxygen species (ROS) due to the disulfide bridge present in its structure. It also presents immunosuppressive activity related with its ability to kill mammalian cells and/or inactivate critical immune signaling pathways like NFkB. In this comprehensive review, we will briefly give an overview of the lung immune response against Aspergillus as a preface to analyse the effect of different secondary metabolites on the host immune response, with a special attention to GT. We will discuss the results reported in the literature on the context of the animal models employed to analyse the role of GT as virulence factor, which is expected to greatly depend on the immune status of the host: why should you hide when nobody is seeking for you? Finally, GT immunosuppressive activity will be related with different human diseases predisposing to invasive aspergillosis in order to have a global view on the potential of GT to be used as a target to treat IA.

Hemin reduces inflammation associated with TNBS-induced colitis

Purpose

Hemin is a heme-oxygenase inducer, which can confer anti-inflammatory, cytoprotective, and antiapoptotic effects. These properties are beneficial therapeutical effects to inflammatory bowel disease (IBD). IBD is a worldwide health problem characterized by chronic inflammation of intestinal epithelium, which promotes intestinal and extraintestinal symptomatology. Current treatment only induces and maintains the patient in remission and results in many side effects. The research of other pharmacologic approaches is crucial to the treatment of IBD. The aim of this study is to evaluate the effect of hemin in the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis model.

Materials and methods

Male CD-1 mice with TNBS-induced colitis were treated with a daily dose of hemin 5 mg/kg body weight/day and 10 mg/kg body weight/day intraperitoneal, during 4 days. The evaluated parameters were fecal hemoglobin, alkaline phosphatase (ALP), myeloperoxidase, tumor necrosis factor-α, interleukin (IL)-1β, IL-10, histopathologic analysis, urea, creatinine, and alanine aminotransferase.

Results

The hemin-treated mice presented a decrease in fecal hemoglobin, ALP, and proinflammatory cytokine concentrations compared to the TNBS group. Histopathology analysis confirmed the decrease in lesion extension produced by hemin.

Conclusion

These findings suggest that hemin treatment reduces hemorrhagic focus, intestinal damage, tissue inflammation, and lesion extension associated with experimental colitis.

The complexity of the Nrf2 pathway: beyond the antioxidant response

The NF-E2-related factor 2 (Nrf2)-mediated signalling pathway provides living organisms an efficient and pivotal line of defensive to counteract environmental insults and endogenous stressors. Nrf2 coordinates the basal and inducible expression of antioxidant and Phase II detoxification enzymes to adapt to different stress conditions. The stability and cellular distribution of Nrf2 is tightly controlled by its inhibitory binding protein Kelch-like ECH-associated protein 1. Nrf2 signalling is also regulated by posttranslational, transcriptional, translational and epigenetic mechanisms, as well as by other protein partners, including p62, p21 and IQ motif-containing GTPase activating protein 1. Many studies have demonstrated that Nrf2 is a promising target for preventing carcinogenesis and other chronic diseases, including cardiovascular diseases, neurodegenerative diseases and pulmonary injury. However, constitutive activation of Nrf2 in advanced cancer cells may confer drug resistance. Here, we review the molecular mechanisms of Nrf2 signalling, the diverse classes of Nrf2 activators, including bioactive nutrients and other chemicals, and the cellular functions and disease relevance of Nrf2 and discuss the dual role of Nrf2 in different contexts.

Epigallocatechin-3-Gallate Attenuates Oxidative Stress and Inflammation in Obstructive Nephropathy via NF-κB and Nrf2/HO-1 Signalling Pathway Regulation

Oxidative stress and inflammation contribute importantly to the pathogenesis of chronic kidney disease (CKD). Epigallocatechin-3-gallate (EGCG), which is the most abundant and most active catechin polyphenol extracted from green tea, has been proved to have many bioactivities. In this study, the renoprotective effect of EGCG was evaluated in a widely used kidney disease model, the unilateral ureteral obstruction (UUO) mice model. After 14 days of EGCG administration, mean arterial blood pressure, body-weight and obstructed kidney weight were measured. Levels of blood urea nitrogen (BUN) and creatinine (CR) and activities of glutamic-pyruvic transaminase (GPT) and lactate dehydrogenase (LDH) in serum were estimated as indicators of renal function. Periodic acid-Schiff (PAS) staining was performed to observe the pathological changes of the obstructed kidney. Antioxidant enzymes and pro-inflammatory cytokine production were estimated to reflect the oxidative stress and inflammatory state in the obstructed kidney. Finally, the main proteins in the NF-κB and Nrf2 signalling pathway and DNA binding activity of NF-κB and Nrf2 were measured to investigate the effect of EGCG on these two pathways. The results demonstrated that EGCG could restore UUO-induced kidney weight loss and renal dysfunction. In addition, UUO-induced oxidative stress and inflammatory responses in the obstructed kidney were also prevented by EGCG. Furthermore, EGCG could induce both NF-κB and Nrf2 nuclear translocation in the UUO kidney and promote heme oxygenase-1 (HO-1) production. These results indicated that the renoprotective effect of EGCG might be through its NF-κB and Nrf2 signalling pathway regulations.

Effect of redox modulating NRF2 activators on chronic kidney disease

Chronic kidney disease (CKD) is featured by a progressive decline of kidney function and is mainly caused by chronic diseases such as diabetes mellitus and hypertension. CKD is a complex disease due to cardiovascular complications and high morbidity; however, there is no single treatment to improve kidney function in CKD patients. Since biological markers representing oxidative stress are significantly elevated in CKD patients, oxidative stress is receiving attention as a contributing factor to CKD pathology. Nuclear factor erythroid-2 related factor 2 (NRF2) is a predominant transcription factor that regulates the expression of a wide array of genes encoding antioxidant proteins, thiol molecules and their generating enzymes, detoxifying enzymes, and stress response proteins, all of which can counteract inflammatory and oxidative damages. There is considerable experimental evidence suggesting that NRF2 signaling plays a protective role in renal injuries that are caused by various pathologic conditions. In addition, impaired NRF2 activity and consequent target gene repression have been observed in CKD animals. Therefore, a pharmacological intervention activating NRF2 signaling can be beneficial in protecting against kidney dysfunction in CKD. This review article provides an overview of the role of NRF2 in experimental CKD models and describes current findings on the renoprotective effects of naturally occurring NRF2 activators, including sulforaphane, resveratrol, curcumin, and cinnamic aldehyde. These experimental results, coupled with recent clinical experiences with a synthetic triterpenoid, bardoxolone methyl, have brought a light of hope for ameliorating CKD progression by preventing oxidative stress and maintaining cellular redox homeostasis.

Live and heat-killed Lactobacillus rhamnosus GG upregulate gene expression of pro-inflammatory cytokines in 5-fluorouracil-pretreated Caco-2 cells

PURPOSE

This study investigates whether post-chemotherapeutic use of live and heat-killed Lactobacillus rhamnosus GG can modulate the expression of three pro-inflammatory cytokines in 5-fluorouracil (5-FU)-induced intestinal mucositis in vitro.

METHODS

Live L. rhamnosus GG and heat-killed L. rhamnosus GG were observed using scanning electron microscopy. To establish the duration required for optimal expression of tumor necrosis factor-α (TNF-α), monocyte chemotactic protein-1 (MCP-1), and interleukin-12 (IL-12), 5 μM of 5-FU was selected to treat 10-day-old Caco-2 cells for 4, 6, 8, and 24 h. Caco-2 cells were treated with 5-FU (5 μM) for 4 h, followed by the administration of live L. rhamnosus GG (multiplicity of infection = 25), and heat-killed L. rhamnosus GG for 2 and 4 h. Finally, total cellular RNA was isolated to quantify mRNA expression of TNF-α, MCP-1, and IL-12 using real-time PCR.

RESULTS

The results demonstrated that heat-killed L. rhamnosus GG remained structurally intact with elongation. A biphasic upregulated expression of TNF-α, MCP-1, and IL-12 was observed in 5-FU-treated Caco-2 cells at 4 and 24 h. Compared to non-L. rhamnosus GG controls in 5-FU-pretreated Caco-2 cells, a 2-h treatment of heat-killed L. rhamnosus GG significantly upregulated the MCP-1 expression (p < 0.05), and both live and heat-killed L. rhamnosus GG treatments lasting 4 h upregulated the TNF-α and MCP-1 expression (p < 0.05). Only live L. rhamnosus GG upregulated the IL-12 expression (p < 0.05).

CONCLUSIONS

Post-chemotherapeutic use of live or heat-killed L. rhamnosus GG can upregulate the gene expression of 5-FU-induced pro-inflammatory cytokines in Caco-2 cells. Human intestinal epithelium may be vulnerable to the post-chemotherapeutic use of L. rhamnosus GG in 5-FU-induced mucositis that requires further in vivo studies for clarification.

Effects of modified Sanhuang decoction () enema on serum tumor necrosis factor-α and colonic mucosa interleukin-1β, interleukin-6 levels in ulcerative colitis rats

OBJECTIVE

To investigate the effects of Modified Sanhuang Decoction (, MSD) enema on the serum tumor necrosis factor alpha (TNF-α) and colonic mucosa interleukin-1β (IL-1β), interleukin-6 (IL-6) levels in experimental ulcerative colitis (UC) rats.

METHODS

Forty-five male Wistar rats were randomly divided into 4 groups: normal group (n=12), model group (n=11), salazosulfapyridine (SASP) group (n=11) and MSD group (n=11). The UC model was induced by 2,4,6-trinitrobenzene sulfonic acid (TNBS)/ethanol solution. Rats in the normal group and model group were clystered with 0.9% normal saline, while in the SASP group and MSD group were clystered with SASP and MSD enema, respectively. After drug administration (10 mL/kg body weight, for 7 days), colonic gross changes and colonic mucosa histology were observed, serum TNF-α and colonic mucosa IL-1β, IL-6 levels were tested by enzyme linked immunosorbent assay and radioimmunoassay, respectively.

RESULTS

As compared with the normal group, the experimental UC rats, the colonic mucosal damage index scores (CMDIs), histopathological scores (HS) and the serum TNF-α and colonic mucosa IL-1β, IL-6 levels significantly increased (P<0.05 or P<0.01). In the MSD and SASP groups, the ulcer area significantly reduced, and edema disappeared. The CMDIs, HS, the serum TNF-α and colonic mucosa IL-1β, IL-6 levels in the MSD and SASP groups significantly decreased (P<0.05 or P<0.01) compared with the model group. The CMDIs in the MSD group were lower than that in the SASP group (P<0.05), but there were no significant differences in HS, serum TNF-α or colonic mucosa IL-1β, IL-6 levels between the MSD and SASP groups.

CONCLUSION

MSD enema can improve colonic mucosa impairment and decrease serum TNF-α and colonic mucosa IL-1β, IL-6 levels in experimental UC.

Treatment with diammonium glycyrrhizinate down-regulates M30 expression in ulcerative colitis in rats

AIM: To assess the therapeutic effect of diammonium glycyrrhizinate (DG) on 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis in rats and to explore the underlying mechanisms by detecting the expression of M30 and Fas/FasL.

METHODS: Thirty Wistar rats were equally randomized into a normal control group, a model group and a DG group. Ulcerative colitis was induced in the DG group and model group with TNBS by enema. After ten days, all rats were killed. Disease activity index (DAI), colon macroscopic damage score (CMDS) and histological damage score were calculated, and the expression of M30 and Fas/FasL in the colonic mucosa was detected by immunohistochemistry.

RESULTS: Compared to normal controls, the DAI, CMDS and histological damage score significantly increased in model rats (7.06 ± 0.80 vs 0.32 ± 0.14; 6.03 ± 0.61 vs 0.19 ± 0.16; 5.84 ± 0.53 vs 0.22 ± 0.11, P < 0.01). Compared to the model group, the above parameters were significantly improved in the DG group (3.33 ± 0.27 vs 7.06 ± 0.80; 3.29 ± 0.36 vs 6.03 ± 0.61; 2.98 ± 0.24 vs 5.84 ± 0.53, P < 0.05). Compared to the normal control group, the expression of M30 and Fas/FasL was up-regulated in the model group and DG group (5.76 ± 0.66 vs 0.42 ± 0.18; 26.62 ± 4.20 vs 10.81 ± 2.20; 17.11 ± 3.12 vs 6.02 ± 1.02, P < 0.01). Compared to the model group, the expression of M30 and Fas/FasL was remarkably decreased in the DG group (2.24 ± 0.48 vs 5.76 ± 0.66; 17.23 ± 3.20 vs 26.62 ± 4.20; 11.02 ± 2.12 vs 17.11 ± 3.12, P < 0.05).

CONCLUSION: Treatment with DG could reduce inflammatory injury in rats with experimental ulcerative colitis possibly by reducing the expression Fas/FasL and inhibiting apoptosis of cells in the colonic mucosa.

Heme oxygenase-1 system and gastrointestinal inflammation: A short review

Heme oxygenase-1 (HO-1) system catalyzes heme to biologically active products: carbon monoxide, biliverdin/bilirubin and free iron. It is involved in maintaining cellular homeostasis and many physiological and pathophysiological processes. A growing body of evidence indicates that HO-1 activation may play an important protective role in acute and chronic inflammation of gastrointestinal tract. This review focuses on the current understanding of the physiological significance of HO-1 induction and its possible roles in the gastrointestinal inflammation studied to date. The ability to upregulate HO-1 by pharmacological means or using gene therapy may offer therapeutic strategies for gastrointestinal inflammation in the future.

Iridoid glycosides fraction of Folium syringae leaves modulates NF-κB signal pathway and intestinal epithelial cells apoptosis in experimental colitis

BACKGROUND AND AIMS

Iridoid glycosides (IG), the major active fraction of F. syringae leaves has been demonstrated to have strong anti-inflammatory properties to ulcerative colitis (UC) in our previous study. The aim of this study was to investigate whether IG modulates the inflammatory response in experimental colitis at the level of NF-κB signal pathway and epithelial cell apoptosis.

METHODS

UC in rats was induced by administration with dextran sulfate sodium (DSS) in drinking water. The inflammatory damage was assessed by disease activity index (DAI), macroscopic findings, histology and myeloperoxidase (MPO) activity. The effect of IG on pro-inflammatory cytokines TNF-α, IL-8, COX-2 and regulatory peptide TGF-β1 was measured. Epithelial cell apoptosis and the protein and mRNA expressions of Fas/FasL, Bcl-2/Bax, caspase-3, NF-κB p65, IκBα, p-IκBα and IKKβ were detected by TUNEL method, immunohistochemistry, Western blotting and real-time quantitative PCR, respectively.

RESULTS

IG significantly ameliorated macroscopic damage and histological changes, reduced the activity of MPO, and strongly inhibited epithelial cell apoptosis. Moreover, IG markedly depressed TNF-α, IL-8, COX-2 and TGF-β1 levels in the colon tissues in a dose-dependent manner. Furthermore, IG significantly blocked of NF-κB signaling by inhibiting IκBα phosphorylation/degradation and IKKβ activity, down-regulated the protein and mRNA expressions of Fas/FasL, Bax and caspase-3, and activated Bcl-2 in intestinal epithelial cells.

CONCLUSIONS

These results demonstrated for the first time that IG possessed marked protective effects on experimental colitis through inhibition of epithelial cell apoptosis and blockade of NF-κB signal pathway.

Heme oxygenase-1: a novel therapeutic target for gastrointestinal diseases

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in the catabolism of heme, followed by production of biliverdin, free iron and carbon monoxide (CO). HO-1 is a stress-responsive protein induced by various oxidative agents. Recent studies demonstrate that the expression of HO-1 in response to different inflammatory mediators may contribute to the resolution of inflammation and has protective effects in several organs against oxidative injury. Although the mechanism underlying the anti-inflammatory actions of HO-1 remains poorly defined, both CO and biliverdin/bilirubin have been implicated in this response. In the gastrointestinal tract, HO-1 is shown to be transcriptionally induced in response to oxidative stress, preconditioning and acute inflammation. Recent studies suggest that the induction of HO-1 expression plays a critical protective role in intestinal damage models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid, and dextran sulfate sodium, indicating that activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in the gastrointestinal tract. In addition, CO derived from HO-1 is shown to be involved in the regulation in gastro-intestinal motility. These in vitro and in vivo data suggest that HO-1 may be a novel therapeutic target in patients with gastrointestinal diseases.

The role of heme oxygenase and carbon monoxide in inflammatory bowel disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease, is a chronic and recurrent inflammatory disorder of the intestinal tract. Since the precise pathogenesis of IBD remains unclear, it is important to investigate the pathogenesis of IBD and to evaluate new anti-inflammatory strategies. Recent evidence suggests that heme oxygenase-1 (HO-1) plays a critical protective role during the development of intestinal inflammation. In fact, it has been demonstrated that the activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in various animal intestinal injury models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid or dextran sulfate sodium. In addition, carbon monoxide (CO) derived from HO-1 has been shown to be involved in the regulation of intestinal inflammation. Furthermore, administration of a low concentration of exogenous CO has a protective effect against intestinal inflammation. These data suggest that HO-1 and CO may be novel therapeutic molecules for patients with gastrointestinal inflammatory diseases. In this review, we present what is currently known regarding the role of HO-1 and CO in intestinal inflammation.

When NRF2 talks, who's listening?

Activation of the KEAP1-NRF2 signaling pathway is an adaptive response to environmental and endogenous stresses and serves to render animals resistant to chemical carcinogenesis and other forms of toxicity, whereas disruption of the pathway exacerbates these outcomes. This pathway, which can be activated by sulfhydryl-reactive, small-molecule pharmacologic agents, regulates the inducible expression of an extended battery of cytoprotective genes, often by direct binding of the transcription factor to antioxidant response elements in the promoter regions of target genes. However, it is becoming evident that some of the protective effects may be mediated indirectly through cross talk with additional pathways affecting cell survival and other aspects of cell fate. These interactions provide a multi-tiered, integrated response to chemical stresses. This review highlights recent observations on the molecular interactions and their functional consequences between NRF2 and the arylhydrocarbon receptor (AhR), NF-κB, p53, and Notch1 signaling pathways.

New light on the anti-colitic actions of therapeutic aminosalicylates: the role of heme oxygenase

Although a variety of pharmaceutical preparations of aminosalicylate are commonly used in the clinic for the control of inflammatory bowel disease, the mechanisms underlying their therapeutic actions remain unclear. Recent in vivo and in vitro studies have demonstrated that 5-aminosalicylic acid (5-ASA), regarded as the active moiety in aminosalicylate preparations such as sulfasalazine, can induce the heat shock protein, heme oxygenase-1 (HO-1) and up-regulate HO enzyme activity in the colon. As HO-1 can produce endogenous anti-oxidant and anti-inflammatory moieties such as bilirubin and carbon monoxide (CO), these findings suggest a novel mechanism of action for aminosalicylates, acting as anti-colitic agents through the up-regulation of HO-1 enzyme expression and activity.

Heme oxygenase-1 as a therapeutic target in inflammatory disorders of the gastrointestinal tract

Heme oxygenase (HO)-1 is the inducible isoform of the first and rate-limiting enzyme of heme degradation. HO-1 not only protects against oxidative stress and apoptosis, but has received a great deal of attention in recent years because of its potent anti-inflammatory functions. Studies with HO-1 knockout animal models have led to major advances in the understanding of how HO-1 might regulate inflammatory immune responses, although little is known on the underlying mechanisms. Due to its beneficial effects the targeted induction of this enzyme is considered to have major therapeutic potential for the treatment of inflammatory disorders. This review discusses current knowledge on the mechanisms that mediate anti-inflammatory protection by HO-1. More specifically, the article deals with the role of HO-1 in the pathophysiology of viral hepatitis, inflammatory bowel disease, and pancreatitis. The effects of specific HO-1 modulation as a potential therapeutic strategy in experimental cell culture and animal models of these gastrointestinal disorders are summarized. In conclusion, targeted regulation of HO-1 holds major promise for future clinical interventions in inflammatory diseases of the gastrointestinal tract.

2',4',6'-tris(methoxymethoxy) chalcone protects against trinitrobenzene sulfonic acid-induced colitis and blocks tumor necrosis factor-alpha-induced intestinal epithelial inflammation via heme oxygenase 1-dependent and independent pathways

2',4',6'-Tris(methoxymethoxy) chalcone (TMMC), a synthesized chalcone derivative, displays potent antiproliferative and anti-inflammatory effects in rat hepatic stellate cells and murine macrophages, respectively. Here we tested the hypothesis that TMMC could ameliorate diseases characterized by mucosal inflammation. Treatment of mice with TMMC significantly protected against trinitrobenzene sulfonic acid (TNBS)-induced colitis, as assessed by reductions in the weight loss, colonic damage and mucosal ulceration that together characterize this symptom. Moreover, TMMC suppressed the expression of intercellular adhesion molecule-1, interleukin 1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) in the mice treated with TNBS. Pretreatment of human intestinal epithelial HT-29 cells with TMMC also significantly inhibited the IL-8 and extracellular matrix metalloproteinase-7 levels induced by TNF-alpha. TMMC induced the expression of heme oxygenase 1 (HO-1) in HT-29 cells. TMMC increased extracellular signal-regulated kinase1/2 and p38 kinase phosphorylation levels, which led to the nuclear translocation of nuclear factor-erythroid 2-related factor 2 (Nrf2) and consequently to HO-1 expression. TMMC inhibited TNF-alpha-induced nuclear factor kappaB (NF-kappaB) activation directly and indirectly. Interestingly, the latter is mediated by HO-1, which presumably blocks the TNF-alpha-induced nuclear translocation of NF-kappaB p65 without affecting I-kappaBalpha degradation. Moreover, we found that the different products of HO-1, carbon monoxide and bilirubin, exerted anti-inflammatory effects that were additive or synergistic in HT-29 cells stimulated with TNF-alpha. Thus, TMMC might serve to protect against intestinal inflammatory diseases.

Nrf2-deficient mice have an increased susceptibility to dextran sulfate sodium-induced colitis

Inflammatory bowel diseases, chronic inflammatory disorders, have been strongly linked with an increased risk of the development of colorectal cancer. Understanding the etiology of these diseases is pivotal for the improvement of currently available strategies to fight against inflammatory bowel disease, and more importantly, to prevent colorectal cancer. Nuclear factor-erythroid 2-related factor 2 (Nrf2) has been known to be a transcriptional factor which plays a crucial role in cytoprotection against inflammation, as well as oxidative and electrophilic stresses. The aim of this study is to investigate the role of Nrf2 in the regulation of dextran sulfate sodium (DSS)-induced experimental colitis in mice. Nrf2-deficient mice were found to be more susceptible to DSS-induced colitis as shown by the increased severity of colitis following 1 week of oral administration of 1% DSS. The increased severity of colitis in Nrf2(-/-) mice was found to be associated with decreased expression of antioxidant/phase II detoxifying enzymes including heme-oxygenase-1, NAD(P)H-quinone reductase-1, UDP-glucurosyltransferase 1A1, and glutathione S-transferase Mu-1. In addition, proinflammatory mediators/cytokines such as COX-2, inducible nitric oxide, interleukin 1beta, interleukin 6, and tumor necrosis factor alpha were significantly increased in the colonic tissues of Nrf2(-/-) mice compared with their wild-type (Nrf2+/+) counterparts. In summary, we show for the first time that mice lacking Nrf2 are more susceptible to DSS-induced colitis. Our data suggests that Nrf2 could play an important role in protecting intestinal integrity, through regulation of proinflammatory cytokines and induction of phase II detoxifying enzymes.