PPARgamma and inflammatory bowel disease: a new therapeutic target for ulcerative colitis and Crohn's disease

Unraveling the mechanism of malancao in treating ulcerative colitis: A multi-omics approach

BACKGROUND

Malancao (MLC) is a traditional Chinese medicine with a long history of utilization in treating ulcerative colitis (UC). Nevertheless, the precise molecular mechanisms underlying its efficacy remain elusive. This study leveraged ultra-high-performance liquid chromatography coupled with exactive mass spectrometry (UHPLC-QE-MS), network pharmacology, molecular docking (MD), and gene microarray analysis to discern the bioactive constituents and the potential mechanism of action of MLC in UC management.

AIM

To determine the ingredients related to MLC for treatment of UC using multiple databases to obtain potential targets for fishing.

METHODS

This research employs UHPLC-QE-MS for the identification of bioactive compounds present in MLC plant samples. Furthermore, the study integrates the identified MLC compound-related targets with publicly available databases to elucidate common drug disease targets. Additionally, the R programming language is utilized to predict the central targets and molecular pathways that MLC may impact in the treatment of UC. Finally, MD are conducted using AutoDock Vina software to assess the affinity of bioactive components to the main targets and confirm their therapeutic potential.

RESULTS

Firstly, through a comprehensive analysis of UHPLC-QE-MS data and public database resources, we identified 146 drug-disease cross targets related to 11 bioactive components. The Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analysis highlighted that common disease drug targets are primarily involved in oxidative stress management, lipid metabolism, atherosclerosis, and other processes. They also affect AGE-RAGE and apoptosis signaling pathways. Secondly, by analyzing the differences in diseases, we identified key research targets. These core targets are related to 11 active substances, including active ingredients such as quercetin and luteolin. Finally, MD analysis revealed the stability of compound-protein binding, particularly between JUN-Luteolin, JUN-Quercetin, HSP90AA1-Wogonin, and HSP90AA1-Rhein. Therefore, this suggests that MLC may help alleviate intestinal inflammation in UC, restore abnormal lipid accumulation, and regulate the expression levels of core proteins in the intestine.

CONCLUSION

The utilization of MLC has demonstrated notable therapeutic efficacy in the management of UC by means of the compound target interaction pathway. The amalgamation of botanical resources, metabolomics, natural products, MD, and gene chip technology presents a propitious methodology for investigating therapeutic targets of herbal medicines and discerning novel bioactive constituents.

Pioglitazone-Mediated Attenuation of Experimental Colitis Relies on Cleaving of Annexin A1 Released by Macrophages

Ulcerative colitis and Crohn's disease are chronic inflammatory bowel diseases (IBDs) which burden health systems worldwide; available pharmacological therapies are limited and cost-intensive. Use of peroxisome proliferator activated-receptor γ (PPARγ) ligands for IBD treatment, while promising, lacks solid evidences to ensure its efficacy. Annexin A1 (AnxA1), a glucocorticoid-modulated anti-inflammatory protein, plays a key role on IBD control and is a potential biomarker of IBD progression. We here investigated whether effects of pioglitazone, a PPARγ ligand, rely on AnxA1 actions to modulate IBD inflammation. Experimental colitis was evoked by 2% dextran sodium sulfate (DSS) in AnxA1 knockout (AnxA1^-/-) or wild type (WT) C57BL/6 mice. Clinical and histological parameters were more severe for AnxA^-/- than WT mice, and 10 mg/kg pioglitazone treatment attenuated disease parameters in WT mice only. AnxA1 expression was increased in tissue sections of diseased WT mice, correlating positively with presence of CD68⁺ macrophages. Metalloproteinase-9 (MMP-9) and inactive 33 kDa AnxA1 levels were increased in the colon of diseased WT mice, which were reduced by pioglitazone treatment. Cytokine secretion, reactive oxygen species generation and MMP-9 expression caused by lipopolysaccharide (LPS) treatment in AnxA1-expressing RAW 264.7 macrophages were reduced by pioglitazone treatment, effects not detected in AnxA1 knockdown macrophages. LPS-mediated increase of AnxA1 cleaving in RAW 264.7 macrophages was also attenuated by pioglitazone treatment. Finally, pioglitazone treatment increased extracellular signal-regulated kinase (ERK) phosphorylation in AnxA1-expressing RAW 264.7 macrophages, but not in AnxA1-knockdown macrophages. Thus, our data highlight AnxA1 as a crucial factor for the therapeutic actions of pioglitazone on IBDs.

Peroxisome Proliferator-Activated Receptors as Molecular Links between Caloric Restriction and Circadian Rhythm

The circadian rhythm plays a chief role in the adaptation of all bodily processes to internal and environmental changes on the daily basis. Next to light/dark phases, feeding patterns constitute the most essential element entraining daily oscillations, and therefore, timely and appropriate restrictive diets have a great capacity to restore the circadian rhythm. One of the restrictive nutritional approaches, caloric restriction (CR) achieves stunning results in extending health span and life span via coordinated changes in multiple biological functions from the molecular, cellular, to the whole-body levels. The main molecular pathways affected by CR include mTOR, insulin signaling, AMPK, and sirtuins. Members of the family of nuclear receptors, the three peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ take part in the modulation of these pathways. In this non-systematic review, we describe the molecular interconnection between circadian rhythm, CR-associated pathways, and PPARs. Further, we identify a link between circadian rhythm and the outcomes of CR on the whole-body level including oxidative stress, inflammation, and aging. Since PPARs contribute to many changes triggered by CR, we discuss the potential involvement of PPARs in bridging CR and circadian rhythm.

Peroxisome Proliferator-Activated Receptors and Caloric Restriction-Common Pathways Affecting Metabolism, Health, and Longevity

Caloric restriction (CR) is a traditional but scientifically verified approach to promoting health and increasing lifespan. CR exerts its effects through multiple molecular pathways that trigger major metabolic adaptations. It influences key nutrient and energy-sensing pathways including mammalian target of rapamycin, Sirtuin 1, AMP-activated protein kinase, and insulin signaling, ultimately resulting in reductions in basic metabolic rate, inflammation, and oxidative stress, as well as increased autophagy and mitochondrial efficiency. CR shares multiple overlapping pathways with peroxisome proliferator-activated receptors (PPARs), particularly in energy metabolism and inflammation. Consequently, several lines of evidence suggest that PPARs might be indispensable for beneficial outcomes related to CR. In this review, we present the available evidence for the interconnection between CR and PPARs, highlighting their shared pathways and analyzing their interaction. We also discuss the possible contributions of PPARs to the effects of CR on whole organism outcomes.

Peroxisome Proliferator-Activated Receptors: Experimental Targeting for the Treatment of Inflammatory Bowel Diseases

The peroxisome proliferator-activated receptors (PPARs) are a group of nuclear receptor proteins that promote ligand-dependent transcription of target genes that regulate energy production, lipid metabolism, and inflammation. The PPAR superfamily comprises three subtypes, PPARα, PPARγ, and PPARβ/δ, with differential tissue distributions. In addition to their different roles in the regulation of energy balance and carbohydrate and lipid metabolism, an emerging function of PPARs includes normal homeostasis of intestinal tissue. PPARα activation represses NF-κB signaling, which decreases the inflammatory cytokine production by different cell types, while PPARγ ligands can inhibit activation of macrophages and the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, and Il-1β. In this regard, the anti-inflammatory responses induced by PPAR activation might restore physiopathological imbalances associated with inflammatory bowel diseases (IBD). Thus, PPARs and their ligands have important therapeutic potential. This review briefly discusses the roles of PPARs in the physiopathology and therapies of the most important IBDs, ulcerative colitis (UC), and Crohn's disease (CD), as well some new experimental compounds with PPAR activity as promising drugs for IBD treatment.

Metabolic cross-talk between skeletal muscle and adipose tissue in high-intensity interval training vs. moderate-intensity continuous training by regulation of PGC-1α

PURPOSE

An imbalance in the production of adipokines and myokines impairs the energy expenditure, increases adipocyte and develops metabolic pathologies. Physical exercise is able to regulate the secretion of myokines and adipokines. The present study considers the metabolic cross talk between skeletal muscle and adipose tissue in high-intensity interval training vs. moderate-intensity continuous training by regulation of PGC-1α.

METHODS

A sample of 32 male Wistar rats (8 weeks old with mean weight 250 ± 55 g) were divided into four groups randomly: control of base (CO), control of 8 weeks (CO8w), moderate-intensity continuous training (MICT), and high-intensity interval training (HIIT). The rats were fed with standard chow diet. The CO group was killed at the start of the study and the CO8w group was kept alive for the same time as the experimental groups, but did not participate in any exercise. MICT and HIIT groups for 8 weeks were placed under the moderate-intensity continuous training (15-60 min, with speed of 15-30 m/min) and high-intensity interval training (8-4 intense period for 1 min, with speed of 28-55 m/min, with 3-7 slow-intensity period for 1 min, with a speed of 12-30 m/min) for 8 weeks, respectively. To measure the levels of serum irisin, nesfatin, and resistin the ELISA method was used and real-time PCR method was used to evaluate the relative expression of soleus PGC-1α gene mRNA.

RESULTS

The levels of irisin and nesfatin significantly increased in the HIIT compared with control groups (p = 0.001). Resistin values in both training groups showed a significant decrease compared to the control groups (p = 0.005). The level of PGC-1α gene expression in both HIIT and MICT groups was significantly increased in comparison with the control groups (p = 0.001).

DISCUSSION

The results showed that HIIT and MICT increase the transcription of the PGC-1α gene and possibly the increased expression of this gene after HIIT and MICT plays a central role in the secretion of skeletal muscle myokines and adipokines of adipose tissue.

LEVEL OF EVIDENCE

No Level of evidence: Animal study.

15-Deoxy-Δ12,14-prostaglandin J2 as a potential regulator of bone metabolism via PPARγ-dependent and independent pathways: a review

Bone metabolism is a complex physiological process that primarily involves osteoblast-mediated bone formation and osteoclast-mediated bone resorption, both of which are regulated by a variety of biological factors. There is increasing evidence that peroxisome proliferator-activated receptor γ (PPARγ) is a member of the nuclear receptor superfamily and plays an important role in lipid metabolism and bone metabolism. Through the PPARγ-dependent pathway, 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) promotes the formation of marrow adipocytes and inhibits the formation of osteoblasts, resulting in bone loss and increasing the risk of fracture and osteoporosis. Recent studies have found that through the PPARγ-independent pathway, 15d-PGJ₂ plays a regulatory role in bone metastasis of breast cancer, which can inhibit osteoclastogenesis and reduce bone destruction. The purpose of our review is to summarize the recent progress in elucidating the mechanisms and effects of 15d-PGJ₂ in bone metabolism, which can serve as a novel therapeutic target for bone tumors, osteoporosis, rheumatoid arthritis (RA), and other bone diseases.

Enteric Microbiota⁻Gut⁻Brain Axis from the Perspective of Nuclear Receptors

Nuclear receptors (NRs) play a key role in regulating virtually all body functions, thus maintaining a healthy operating body with all its complex systems. Recently, gut microbiota emerged as major factor contributing to the health of the whole organism. Enteric bacteria have multiple ways to influence their host and several of them involve communication with the brain. Mounting evidence of cooperation between gut flora and NRs is already available. However, the full potential of the microbiota interconnection with NRs remains to be uncovered. Herewith, we present the current state of knowledge on the multifaceted roles of NRs in the enteric microbiota–gut–brain axis.

Is the Wnt/β-catenin pathway involved in the anti-inflammatory activity of glucocorticoids in spinal cord injury?

The Wnt canonical or the Wnt/β-catenin pathway has been implicated in the regulation of several physiopathological pathways such as inflammation. Glucocorticoids (GCs) are administered widely to treat inflammation in several diseases, including spinal cord injury (SCI). The aim of this study was to evaluate whether the Wnt canonical pathway is involved in experimental SCI and whether it is implicated in the anti-inflammatory activity of two different GCs: the methylprednisolone sodium succinate (MPSS), considered the standard treatment for acute SCI, and mometasone furoate (MF), mainly administered for the treatment of airway and skin diseases. Experimental SCI was induced in mice by surgical spinal cord compression at the T6-T7 level. Then, mice were treated with MPSS (6 mg/kg) or MF (0.1 mg/kg) for 7 days until they were killed. Both GCs were found to modulate the Wnt canonical pathway, but in particular, the MF treatment was shown to restore completely the downregulated pathway in SCI. The MF treatment also significantly increased peroxisome proliferator-activated receptor-γ, a Wnt target gene with anti-inflammatory properties, compared with MPSS, and it also inhibited the levels of the proinflammatory cytokines interleukin 1β and tumor necrosis factor-α. Here, we suggest that MF has more efficacy than MPSS in inhibiting inflammation in an SCI experimental model and we propose the β-catenin/peroxisome proliferator-activated receptor-γ axis as the mechanism by which MF exerts these beneficial effects.

Commensal gut bacteria modulate phosphorylation-dependent PPARγ transcriptional activity in human intestinal epithelial cells

In healthy subjects, the intestinal microbiota interacts with the host’s epithelium, regulating gene expression to the benefit of both, host and microbiota. The underlying mechanisms remain poorly understood, however. Although many gut bacteria are not yet cultured, constantly growing culture collections have been established. We selected 57 representative commensal bacterial strains to study bacteria-host interactions, focusing on PPARγ, a key nuclear receptor in colonocytes linking metabolism and inflammation to the microbiota. Conditioned media (CM) were harvested from anaerobic cultures and assessed for their ability to modulate PPARγ using a reporter cell line. Activation of PPARγ transcriptional activity was linked to the presence of butyrate and propionate, two of the main metabolites of intestinal bacteria. Interestingly, some stimulatory CMs were devoid of these metabolites. A Prevotella and an Atopobium strain were chosen for further study, and shown to up-regulate two PPARγ-target genes, ANGPTL4 and ADRP. The molecular mechanisms of these activations involved the phosphorylation of PPARγ through ERK1/2. The responsible metabolites were shown to be heat sensitive but markedly diverged in size, emphasizing the diversity of bioactive compounds found in the intestine. Here we describe different mechanisms by which single intestinal bacteria can directly impact their host’s health through transcriptional regulation.

Preclinical and clinical development of a YFV 17 D-based chimeric vaccine against West Nile virus

Substantial success has been achieved in the development and implementation of West Nile (WN) vaccines for horses; however, no human WN vaccines are approved. This review focuses on the construction, pre-clinical and clinical characterization of ChimeriVax-WN02 for humans, a live chimeric vaccine composed of a yellow fever (YF) 17D virus in which the prM-E envelope protein genes are replaced with the corresponding genes of the WN NY99 virus. Pre-clinical studies demonstrated that ChimeriVax-WN02 was significantly less neurovirulent than YF 17D in mice and rhesus and cynomolgus monkeys. The vaccine elicited neutralizing antibody titers after inoculation in hamsters and monkeys and protected immunized animals from lethal challenge including intracerebral inoculation of high dose of WN NY99 virus. Safety, viremia and immunogenicity of ChimeriVax-WN02 were assessed in one phase I study and in two phase II clinical trials. No safety signals were detected in the three clinical trials with no remarkable differences in incidence of adverse events (AEs) between vaccine and placebo recipients. Viremia was transient and the mean viremia levels were low. The vaccine elicited strong and durable neutralizing antibody and cytotoxic T cell responses. WN epidemiology impedes a classical licensure pathway; therefore, innovative licensure strategies should be explored.

The role of adipose tissue-associated macrophages and T lymphocytes in the pathogenesis of inflammatory bowel disease

Inflammatory bowel diseases (IBDs) are chronic inflammatory disorders of the gastrointestinal tract that affect more than 3 million people worldwide, but the pathological etiology is still unknown. The overall purpose of our investigations was to elucidate the possibility of pathological causes of IBD, and therefore, we determined the difference of inflammatory cytokine profiles in adipose tissue macrophages (ATMs) and T lymphocytes (ATTs) obtained near active lesions of IBD; investigated whether the alteration in ATM activation induces genes involved in collagen formation; and evaluated the effects of fatty acid oxidation inhibitors on factors involved in inflammation and collagen production by ATMs in IBD. Adipose tissues (ATs) were collected near active lesions and also at the margin of resected segments of the bowel from IBD patients with ulcerative colitis (UC) and CD (n=14/group). Normal appearing ATs from control subjects (n=14) who had colon resection for adenocarcinoma were collected as far away from the cancer lesion as possible to rule out possible changes. Compared with inactive disease lesions, ATMs and ATTs from active lesions released more IL-6, IL-4 and IL-13. Treatments of cytokine IL-4 and/or IL-13 to ATMs reduced iNOS expression but increased Arg-I expression which were exacerbated when treated with T cell- and adipocyte-conditioned medium. However, fatty acid oxidation inhibitors prevented the effects of cytokines IL-4 and/or IL-13 on iNOS and Arg-I expressions. This study was the first to show the effect of IL-4 and IL-13 on collagen formation, through iNOS and Arg-I expressions, that was exacerbated in a condition that mimics in vivo condition of active lesions. Moreover, our study was the first to provide potential benefits of fatty acid oxidation inhibitors to ATMs on preventing collagen formation; thus, providing therapeutic implications for individuals with intestinal fibrosis and stricture lesions, although future study should be guaranteed to elucidate the underlying mechanisms.

Infection of specific strains of Streptococcus mutans, oral bacteria, confers a risk of ulcerative colitis

Although oral bacteria-associated systemic diseases have been reported, association between Streptococcus mutans, pathogen of dental caries, and ulcerative colitis (UC) has not been reported. We investigated the effect of various S. mutans strains on dextran sodium sulfate (DSS)-induced mouse colitis. Administration of TW295, the specific strain of S. mutans, caused aggravation of colitis; the standard strain, MT8148 did not. Localization of TW295 in hepatocytes in liver was observed. Increased expression of interferon-γ in liver was also noted, indicating that the liver is target organ for the specific strain of S. mutans-mediated aggravation of colitis. The detection frequency of the specific strains in UC patients was significantly higher than in healthy subjects. Administration of the specific strains of S. mutans isolated from patients caused aggravation of colitis. Infection with highly-virulent specific types of S. mutans might be a potential risk factor in the aggravation of UC.

Role of PPARs in Trypanosoma cruzi Infection: Implications for Chagas Disease Therapy

Chagas disease, which is caused by Trypanosoma cruzi (T. cruzi), remains a substantial public health concern and an important cause of morbidity and mortality in Latin America. T. cruzi infection causes an intense inflammatory response in diverse tissues by triggering local expression of inflammatory mediators, which results in the upregulation of the levels of cytokines and chemokines, and important cardiac alterations in the host, being one of the most characteristic damages of Chagas disease. Therefore, controlling the inflammatory reaction becomes critical for the control of the proliferation of the parasite and of the evolution of Chagas disease. The nuclear receptors known as peroxisome proliferator-activated receptors (PPARs) have emerged as key regulators of lipid metabolism and inflammation. The precise role of PPAR ligands in T. cruzi infection or in Chagas disease is poorly understood. This review summarizes our knowledge about T. cruzi infection as well as about the activation of PPARs and the potential role of their ligands in the resolution of inflammation, with the aim to address a new pharmacological approach to improve the host health.

PPARgamma Agonists: Potential as Therapeutics for Neovascular Retinopathies

The angiogenic, neovascular proliferative retinopathies, proliferative diabetic retinopathy (PDR), and age-dependent macular degeneration (AMD) complicated by choroidal neovascularization (CNV), also termed exudative or “wet” AMD, are common causes of blindness. The antidiabetic thiazolidinediones (TZDs), rosiglitazone, and troglitazone are PPARγ agonists with demonstrable antiproliferative, and anti-inflammatory effects, in vivo, were shown to ameliorate PDR and CNV in rodent models, implying the potential efficacy of TZDs for treating proliferative retinopathies in humans. Activation of the angiotensin II type 1 receptor (AT1-R) propagates proinflammatory and proliferative pathogenic determinants underlying PDR and CNV. The antihypertensive dual AT1-R blocker (ARB), telmisartan, recently was shown to activate PPARγ and improve glucose and lipid metabolism and to clinically improve PDR and CNV in rodent models. Therefore, the TZDs and telmisartan, clinically approved antidiabetic and antihypertensive drugs, respectively, may be efficacious for treating and attenuating PDR and CNV humans. Clinical trials are needed to test these possibilities.

Topical rosiglitazone treatment improves ulcerative colitis by restoring peroxisome proliferator-activated receptor-gamma activity

OBJECTIVES

Impaired epithelial expression of peroxisome proliferator-activated receptor-gamma (PPARgamma) has been described in animal colitis models and briefly in patients with ulcerative colitis, but the functional significance in humans is not well defined. We examined PPARgamma expression and functional activity in human colonic epithelium and explored the potential of topical treatment with rosiglitazone (a PPARgamma ligand) in patients with ulcerative colitis.

METHODS

Spontaneous and rosiglitazone-mediated PPARgamma and adipophillin expression (a gene transcriptionally activated by PPARgamma) were measured by reverse transcriptase PCR in colonic biopsies and isolated epithelial cells from patients with ulcerative colitis and controls. Fourteen patients with active distal ulcerative colitis were randomized to either rosiglitazone (4 mg) or mesalazine (1 g) enema treatment once daily for 14 days.

RESULTS

PPARgamma expression was fourfold reduced in epithelial cells from inflamed compared with uninflamed mucosa and controls. Adipophillin levels were decreased in parallel. Rosiglitazone induced a concentration-dependent increase in adipophillin levels and restored PPARgamma activity in epithelial cells from inflamed mucosa in vitro. Rosiglitazone enema treatment was well tolerated and reduced the Mayo ulcerative colitis score from 8.9 to 4.3 (P<0.01), similar to the effect of mesalazine. Rosiglitazone increased adipophillin levels in the epithelial cells of the patients, indicating PPARgamma activation in vivo.

CONCLUSIONS

Roziglitasone enemas improve impaired PPARgamma activity in inflamed colonic epithelium and have beneficial clinical effect in patients with active distal ulcerative colitis. These findings raise interest in further studies of PPARgamma ligands that exhibit their anti-inflammatory effect locally in the gut to avoid possible systemic side effects.

Genetic polymorphisms differently influencing the emergence of atrophy and fat accumulation in HIV-related lipodystrophy

OBJECTIVE AND DESIGN

The present study aims at evaluating the influence of genetic polymorphisms on antiretroviral therapy (ART)-associated lipodystrophy. We included in the study 255 ICoNA. patients and we assessed the distribution of Fas -670 AG polymorphism, ApoC3 -455 CT and -482 CT polymorphisms, C161T silent substitution in the PPAR gamma gene, the Adrenergic beta3 Receptor (ARbeta3) codon 64 TC variant, and two polymorphisms in the Adrenergic beta2 Receptor (ARbeta2) codon 16 AG and codon 27 CG. Crude rates of lipoatrophy and fat accumulation and adjusted relative rates were calculated using Poisson regression.

RESULTS

In a multivariate model after adjusting for gender, HIV exposure, age, current viral load, hepatitis C virus (HCV) serology, nucleoside reverse-transcriptase inhibitor (NRTI) pair/'third drugs' currently used, months of pre-highly active antiretroviral therapy (HAART) exposures to NRTI, the following genotypes resulted protective against lipoatrophy: ApoC3 -455 CC genotype [adjusted relative risks (ARR) 0.2, 95% confidence interval (CI) 0.046-0.91 vs CT/TT, P = 0.037], ARbeta3 codon 64 TT genotype (ARR 0.39, 95% CI 0.14-1.06 vs TC/CC, P = 0.066), and Fas -670 GG genotype (ARR 0.51, 95% CI 0.26-1.01 vs AG/AA, P = 0.053). With regard to fat accumulation, in the multivariate model, the ARbeta2 codon 27 CC genotype resulted protective (ARR 0.21, 95% CI 0.08-0.51 vs CG/GG, P = 0.0006), whereas the ARbeta2 codon 16 AA genotype resulted associated with higher risk (ARR 3.72, 95% CI 1.58-8.76 vs AG/GG, P = 0.0026).

CONCLUSION

Our study suggests that genetic polymorphisms of genes involved in apoptosis and adipocyte metabolism are significantly related to ART associated lipodystrophy. Particularly, we evidenced a role for ApoC3 -455 in lipoatrophy and for the two variants of ARbeta2 in fat accumulation.

Rosiglitazone ameliorates diabetic nephropathy by inhibiting reactive oxygen species and its downstream-signaling pathways

AIM

To study whether rosiglitazone prevents the development of diabetic nephropathy through reduction of reactive oxygen species and its downstream signal transduction pathways.

METHODS

The rats were intraperitoneally injected with streptozotocin to induce diabetes, meanwhile the rats in the therapeutic groups were given rosiglitazone (5 or 20 mg/kg/day) for 4 weeks by intragastric administration. Blood glucose, serum lipid and creatinine, urinary albumin excretion were measured. Malondialdehyde content, the activities of nuclear factor-kappaB (NF-kappaB), antioxidant enzymes including Cu-Zn SOD and GSH-Px in kidney were also measured. In addition, the mRNA and protein expression of MCP-1 were semiquantitatively determined with PT-PCR and immunohistochemical staining respectively.

RESULTS

No significant difference of blood glucose and lipid were found between diabetic rats and rosiglitazone treatment groups. The renal histopathology was improved significantly. The expressions of MCP-1 mRNA and protein, malondialdehyde level and the activity of NF-kappaB were decreased markedly in rats treated with high-dose rosiglitazone, but the activities of renal Cu-Zn SOD and GSH-Px increased significantly.

CONCLUSIONS

Rosiglitazone treatment prevented glomerular injury in diabetic rats, which was closely related with its roles of reducing reactive oxygen species, NF-kappaB activation and MCP-1 expression in the early phase of diabetic nephropathy.

Effect of pioglitazone treatment on behavioral symptoms in autistic children

Introduction

Autism is complex neuro-developmental disorder which has a symptomatic diagnosis in patients characterized by disorders in language/communication, behavior, and social interactions. The exact causes for autism are largely unknown, but is has been speculated that immune and inflammatory responses, particularly those of Th2 type, may be involved. Thiazolidinediones (TZDs) are agonists of the peroxisome proliferator activated receptor gamma (PPARγ), a nuclear hormone receptor which modulates insulin sensitivity, and have been shown to induce apoptosis in activated T-lymphocytes and exert anti-inflammatory effects in glial cells. The TZD pioglitazone (Actos) is an FDA-approved PPARγ agonist used to treat type 2 diabetes, with a good safety profile, currently being tested in clinical trials of other neurological diseases including AD and MS. We therefore tested the safety and therapeutic potential of oral pioglitazone in a small cohort of children with diagnosed autism.

Case description

The rationale and risks of taking pioglitazone were explained to the parents, consent was obtained, and treatment was initiated at either 30 or 60 mg per day p.o. A total of 25 children (average age 7.9 ± 0.7 year old) were enrolled. Safety was assessed by measurements of metabolic profiles and blood pressure; effects on behavioral symptoms were assessed by the Aberrant Behavior Checklist (ABC), which measures hyperactivity, inappropriate speech, irritability, lethargy, and stereotypy, done at baseline and after 3–4 months of treatment.

Discussion and evaluation

In a small cohort of autistic children, daily treatment with 30 or 60 mg p.o. pioglitazone for 3–4 months induced apparent clinical improvement without adverse events. There were no adverse effects noted and behavioral measurements revealed a significant decrease in 4 out of 5 subcategories (irritability, lethargy, stereotypy, and hyperactivity). Improved behaviors were inversely correlated with patient age, indicating stronger effects on the younger patients.

Conclusion

Pioglitazone should be considered for further testing of therapeutic potential in autistic patients.

Vanin-1 licenses inflammatory mediator production by gut epithelial cells and controls colitis by antagonizing peroxisome proliferator-activated receptor gamma activity

Colitis involves immune cell–mediated tissue injuries, but the contribution of epithelial cells remains largely unclear. Vanin-1 is an epithelial ectoenzyme with a pantetheinase activity that provides cysteamine/cystamine to tissue. Using the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-colitis model we show here that Vanin-1 deficiency protects from colitis. This protection is reversible by administration of cystamine or bisphenol A diglycidyl ether, a peroxisome proliferator-activated receptor (PPAR)γ antagonist. We further demonstrate that Vanin-1, by antagonizing PPARγ, licenses the production of inflammatory mediators by intestinal epithelial cells. We propose that Vanin-1 is an epithelial sensor of stress that exerts a dominant control over innate immune responses in tissue. Thus, the Vanin-1/pantetheinase activity might be a new target for therapeutic intervention in inflammatory bowel disease.

Intestinal-specific PPARgamma deficiency enhances tumorigenesis in ApcMin/+ mice

Multiple investigations of the effects of peroxisome proliferator-activated receptor gamma (PPARgamma) ligands on colon cancer have produced contradictory results. While some studies demonstrated increased numbers of colonic polyps in Apc(Min/+) mice treated with various thiazolidinedione (TZD) PPARgamma ligands, others reported amelioration of tumor multiplicity and progression in both Apc(Min/+) mice and in mice with chemically-induced colon cancer. Here, we addressed the role of PPARgamma in murine intestinal tumorigenesis using gene knockout methodology. We found that either heterozygous or homozygous intestinal-specific PPARgamma deficiency enhanced the number of Apc(Min/+) tumors in both the small intestine and colon, especially in the colon, where PPARgamma deficiency also modulated tumor incidence. Gender significantly affected tumor multiplicity independent of PPARgamma genotype. Female Apc(Min/+) mice developed more tumors in the small intestine and more tumors overall, whereas male Apc(Min/+) mice developed more tumors in the colon. Nevertheless, intestinal PPARgamma deficiency enhanced tumorigenesis irrespective of gender. Our results suggest that PPARgamma functions as a tumor resistance factor in the mouse intestine and warrant further investigation of the PPARgamma-dependent and independent actions of TZDs in cancer.

Inflammation-related gene polymorphisms and colorectal adenoma

Chronic inflammation has been reported to be a risk factor for colorectal neoplasia. The propensity to mount an inflammatory response is modified by germ line variation in cytokine and other inflammation-related genes. We hypothesized that a proinflammatory genotype would be positively associated with colorectal adenoma, a precursor of colorectal cancer. We investigated the association of colorectal adenoma with 19 single nucleotide polymorphisms in a range of important proinflammatory (IL1B, IL6, IL8, TNF, and LTA) and anti-inflammatory (IL4, IL10, and IL13) cytokines and other inflammation-related genes (PTGS2 and PPARG) in a case-control study of risk factors for colorectal polyps in which all participants (ages 18-74 years) had undergone colonoscopy or sigmoidoscopy. The study sample comprised 244 cases of colorectal adenoma and 231 polyp-free controls. Compared with being homozygous for the common allele, heterozygosity at the IL1B -31 (C>T) locus was associated with an odds ratio (OR) for colorectal adenoma of 1.8 [95% confidence interval (95% CI), 1.2-2.9]. Homozygous carriers of the IL8 -251-A allele were at 2.7-fold increased risk of adenoma (95% CI, 1.5-4.9) compared with homozygosity for the common T allele, whereas carriage of at least one IL8 -251-A allele conferred a 1.5 increased odds of disease (95% CI, 1.0-2.4). Among non-nonsteroidal anti-inflammatory drug users, there was a statistically significant association between the IL10 -819-T/T genotype and adenoma compared with the common IL10 -819-C/C genotype (OR, 3.9; 95% CI, 1.1-13.6), which was not evident among nonsteroidal anti-inflammatory drug users (OR, 0.7; 95% CI, 0.3-1.5; P(interaction) = 0.01). These exploratory data provide evidence that polymorphic variation in genes that regulate inflammation could alter risk for colorectal adenoma.

15-Deoxy-Δ12,14-prostaglandin J2 as a potential endogenous regulator of redox-sensitive transcription factors

15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) has been known to display multifaceted cellular functions, including anti-inflammatory and cytoprotective effects. However, depending on the concentrations and intracellular microenvironment, this cyclopentenone prostaglandin can exert opposite effects. Because of the alpha,beta-unsaturated carbonyl moiety present in its cyclopentenone ring structure, 15d-PGJ(2) can act as a Michael reaction acceptor and readily interacts with critical cellular nucleophiles, such as cysteine thiol groups in proteins. Many of the biological effects induced by 15d-PGJ(2) involve redox-transcription factors as the potential targets. Thus, 15d-PGJ(2) can modulate the transcriptional activities of nuclear factor-kappaB (NF-kappaB), activator protein-1 (AP-1), nuclear factor-erythroid 2p45 (NF-E2)-related factors (Nrf2), hypoxia inducible factor (HIF), etc. 15d-PGJ(2) is also well known as an endogenous ligand of peroxisome proliferator-activated receptor gamma (PPARgamma). However, the regulation of the aforementioned redox-sensitive transcription factors by 15d-PGJ(2) is not necessarily mediated via PPARgamma activation, but rather involves covalent modification or oxidation of their critical cysteine residues acting as a redox-sensor. This commentary describes the biological and physiological functions of 15d-PGJ(2) and underlying biochemical and molecular mechanisms with emphasis on the modulation of redox-sensitive transcription factors and their regulators.

Secretion of RANTES (CCL5) and interleukin-10 from mesenteric adipose tissue and from creeping fat in Crohn's disease: regulation by steroid treatment

BACKGROUND

Creeping fat represents a characteristic feature of Crohn's disease (CD) and adipose tissue is currently being recognized as a complex compartment secreting highly active molecules. Pro- or anti-inflammatory adipose tissue-derived secretory products (adipocytokines) might play a role in the pathogenesis of CD.

METHODS

Adipose tissue specimens were obtained from creeping fat contiguous to the involved intestine of 10 patients with CD. Mesenteric adipose tissue specimens resected in 13 patients with colon cancer (CC) and in seven patients with diverticulitis (DIV) served as controls. Three fat tissue specimens per well and n = 6-8 wells per patient were incubated ex vivo for 24 h. The release of regulated on activation, T-cell expressed and secreted (RANTES) and interleukin (IL)-10 into the supernatant was measured by ELISA.

RESULTS

Both RANTES and IL-10 secretion could be demonstrated from total adipose tissue explants. The RANTES secretion is increased from creeping fat in CD (3691 +/- 597 pg/g fat per 24 h) when compared to mesenteric adipose tissue from patients with CC (1690 +/- 191 pg/g fat per 24 h; P < 0.0001) or DIV (1672 +/- 336 pg/g fat per 24 h; P < 0.0001). In contrast, IL-10 secretion is downregulated significantly only in patients with DIV (1418 +/- 180 pg/g fat per 24 h; P = 0.016) when compared to CC patients (2368 +/- 259 pg/g fat per 24 h). Crohn's disease patients receiving steroids had a higher secretion rate of RANTES and IL-10.

CONCLUSIONS

Both RANTES and IL-10 secretion can be detected from mesenteric adipose tissue and from creeping fat. The elevated RANTES and IL-10 secretion from creeping fat in CD is not due to a CD-specific effect but caused by steroid treatment.

Relation between common polymorphisms in genes related to inflammatory response and colorectal cancer

AIM: To investigate the association between common single nucleotide polymorphisms (SNPs) in inflammatory response-related genes such as interleukin (IL)-6, IL-8, tumor necrosis factor α (TNFα), peroxisome proliferators-activated receptor γ (PPARγ), intercellular adhesion molecule-1 (ICAM-1) and the risk of colorectal cancer (CRC) in a group of Greek patients.

METHODS: The study group consisted of 222 CRC patients and 200 healthy controls. Genotyping was performed using allele-specific PCR of PRC-RFLP and the results were confirmed by sequencing. We studied the association of SNPs in the IL-6 (-174G > C), IL-8 (-251T > A), TNFα (-308G > A), ICAM-1 (R241G and K469E), and PPARγ (Pro12Ala) genes and the risk of CRC.

RESULTS: The IL-6 -174G, R241 and K469 alleles of ICAM-1 were associated with increased risk of CRC (OR = 1.77, 95% CI: 1.34-2.34; OR = 1.83, 95% CI: 1.23-2.72; and OR = 1.35, 95% CI: 1.03-1.77 respectively). The IL-8 and TNFα polymorphisms had no effect. Whereas the PPARγ Pro12 genotype was associated with increased risk of disease (OR = 1.78, 95% CI: 1.25-2.49).

CONCLUSION: The association between common SNPs in immunologic response-related genes and CRC is reported in the present study. Apart from shedding light on the mechanisms of malignancy initiation and progression, SNPs may improve appropriate screening for sub-populations at risk.

Role of CEACAM1 as a Regulator of T Cells

A major immunological attribute of inflammatory bowel disease (IBD) is the presence of unrestrained activation of T cells that produce a variety of inflammatory cytokines and other mediators. Gaining an understanding of T cell regulation is therefore of major importance to IBD. Carcinoembryonic antigen-related cell adhesion molecule 1 CEACAM1) is a novel protein that has been recently recognized as being expressed by immune cells and T lymphocytes, in particular; this protein appears to function as a coinhibitory receptor after T cell activation. Ligation of CEACAM1 on T cells induces a signal cascade that leads inhibition of T cell cytokine production and IBD. CEACAM1 is thus a novel potential therapeutic target in the treatment of IBD.

Role of adipose tissue as an inflammatory organ in human diseases

Reviews on the inflammatory role of adipose tissue outside the field of metabolism are rare. There is increasing evidence provided by numerous basic research studies from nearly all internal medicine subspecializations that adipocytes and adipocytokines are involved in primary inflammatory processes and diseases. Therefore, it is the aim of the present review to discuss and to summarize the current knowledge on the inflammatory role of adipocytokines and special types of regional adipocytes such as retroorbital, synovial, visceral, subdermal, peritoneal, and bone marrow adipocytes in internal medicine diseases. Future clinical and therapeutic implications are discussed.

Systematic review: adipose tissue, obesity and gastrointestinal diseases

BACKGROUND

Obesity is increasingly being recognized as a risk factor for a number of benign and malignant gastrointestinal conditions. However, literature on the underlying pathophysiological mechanisms is sparse and ambiguous. Insulin resistance is the most widely accepted link between obesity and disease, particularly colorectal cancer. The recognition that intra-abdominal fat is immunologically active sheds new light not only on the pathogenesis of obesity-related gastrointestinal conditions, but also on inflammatory conditions such as Crohn's disease.

AIM

To describe the biology of adipose tissue, its impact on the immune system and explores the possible underlying mechanisms linking obesity to gastrointestinal diseases. It also looks at the role of mesenteric fat in determining severity and course of Crohn's disease.

METHODS

Relevant English-language literature and abstracts cited on MEDLINE database were reviewed.

RESULTS

Our recent finding of an association between obesity and subclinical bowel inflammation suggests that, apart from promoting generalized immune activation, fat also evokes local immune responses. We propose that the proinflammatory milieu promoted by obesity could underlie many of these associations and that the mechanism implicating insulin resistance may merely represent an epiphenomenon. In Crohn's disease, on the other hand, intra-abdominal fat may provide a protective mechanism.

CONCLUSION

The potential of adipose tissue as a therapeutic target is vast and needs exploration.

Mechanisms of disease: adipocytokines and visceral adipose tissue--emerging role in intestinal and mesenteric diseases

Adipose tissue has long been regarded as a passive type of connective tissue that stores energy as triglycerides and releases energy as free fatty acids, however, this point of view has now changed. The wide variety of products expressed and secreted by adipose tissue, such as adiponectin, leptin, and resistin, mean that the total adipose tissue mass can be defined as a real endocrine organ. The anatomic, metabolic and biochemical characteristics of visceral adipose tissue make it interesting in the context of intestinal and mesenteric diseases. These characteristics include increased lipolysis, venous drainage via the portal vein and local glucocorticoid excess owing to the specific expression of 11-beta-hydroxysteroid-dehydrogenase type 1. In this review, the role of the visceral adipose tissue and its secretory products in intestinal and mesenteric diseases is systematically reviewed, with special focus on 'creeping fat' in Crohn's disease and mesenteric panniculitis.

Influence of the C161T but not Pro12Ala polymorphism in the peroxisome proliferator-activated receptor-gamma on colorectal cancer in an Indian population

The aim of the present study was to investigate associations between Pro12Ala and C161T polymorphisms in the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) gene and colorectal cancer (CRC) risk. We recruited 301 newly diagnosed CRC patients and 291 healthy control subjects at the Madras Cancer Institute in Chennai, India, from 1999 to 2001. Genotypes of the Pro12Ala and C161T polymorphisms were determined using the PCR-RFLP method. After adjustment for age, sex, smoking habit, family history and family income, an increased risk of CRC was observed for the C/T + T/T genotype compared to the C/C genotype of the C161T polymorphism (odds ratio = 1.61, 95% confidence interval: 1.10-2.36), whereas no significant association was found for Pro12Ala (odds ratio = 1.06, 95% confidence interval: 0.70-1.61). Analysis with estimated haplotypes showed a significant difference in haplotype frequencies between cases and controls (chi(2) = 11.62, P = 0.009, d.f. = 3). The relationship between the two polymorphisms and CRC risk was not significantly modified by dietary intake of fish. Although the biological mechanisms of the observed association remain to be elucidated, our findings suggest that the C161T polymorphism of the PPAR-gamma gene is related to risk of CRC. Further research is needed to investigate functional implications of polymorphisms of the PPAR-gamma gene in CRC development.

Inhibition of corneal neovascularization by a peroxisome proliferator-activated receptor-gamma ligand

PURPOSE

To determine the efficacy of the peroxisome proliferator-activated receptor gamma agonist, pioglitazone, in inhibiting corneal neovascularization.

METHODS

Twenty-six adult male Sprague-Dawley rats were randomly divided into three groups. Each group received intrastromal polymer micropellets containing one of the following: Group 1, no active ingredient (n=10); Group 2, vascular endothelial growth factor (VEGF) (n=7); Group 3, VEGF and pioglitazone (n=9). Neovascularization was evaluated 7 days after pellet implantation. After systemic India ink injection, digital photographs of the eyes were taken. The area and density of neovascularization were measured using imaging software.

RESULTS

Mean area of neovascularization was 0.43+/-0.18 mm2 for Group 1, 2.87+/-0.48 mm2 for Group 2 and 2.10+/-0.22 mm2 for Group 3. Statistical analysis showed significant differences between Groups 1 and 2 and Groups 1 and 3. There was no significant difference between Groups 2 and 3. Mean density of neovascularization was 2.16+/-0.66 for Group 1, 27.14+/-2.93 for Group 2 and 12.02+/-2.24 for Group 3. All comparisons between groups were statistically significant (P<0.01).

CONCLUSIONS

Pioglitazone is effective in decreasing the density of angiogenesis in a VEGF-induced neovascular rat cornea model. There is possibility of even greater effect with higher doses of the drug. Pioglitazone is a promising drug for the treatment of ocular neovascularization.

15d-PGJ2: the anti-inflammatory prostaglandin?

15-Deoxy-Delta-12,14-prostaglandin J2 (15d-PGJ2) is the most recently discovered prostaglandin. This cyclopentanone, the dehydration end product of PGD2, differs from other prostaglandins in several respects. There is no specific prostaglandin synthase (PGS) leading to 15d-PGJ2 production and no specific 15d-PGJ2 receptor has been identified to date. Instead, 15d-PGJ2 has been shown to act via PGD2 receptors (DP1 and DP2) and through interaction with intracellular targets. In particular, 15d-PGJ2 is recognized as the endogenous ligand for the intranuclear receptor PPARgamma. This property is responsible for many of the 15d-PGJ2 anti-inflammatory functions. In this review, we summarize the current understanding of 15d-PGJ2 synthesis, biology and main effects both in molecular physiology and pathological states.

Rosiglitazone combined with insulin preserves islet beta cell function in adult-onset latent autoimmune diabetes (LADA)

BACKGROUND

LADA is thought to result from the chronic autoimmune destruction of the insulin-producing pancreatic beta cells. In addition to antidiabetic effects, the newly developed insulin sensitizer-thiazolidinediones have the potential to increase the insulin content of islet cells by downregulating local inflammation and autoimmune response. Therefore, we hypothesized that LADA patients might benefit from thiazolidinediones treatment.

METHODS

LADA patients, with a fasting C-peptide (FCP) of 0.3 nmol/L or more, were enrolled and randomly assigned to receive subcutaneous insulin alone (insulin group, n = 12) or rosiglitazone plus insulin (insulin + RSG group, n = 11) to compare the impacts on islet beta cell function. Plasma glucose, HbA 1c, fasting C-peptide (FCP) and C-peptide after 2 h 75-g glucose load (PCP) were determined every 6 months. GAD-Ab and C-peptide were measured with radioimmune assays. Islet beta cell function was evaluated by PCP and DeltaCP(DeltaCP = PCP-FCP).

RESULTS

All of the 23 patients have been followed up for 6 months, 17 cases for 12 months and 14 for 18 months. (1) During 6 months' follow-up, there were no significant changes for DeltaCP and PCP levels in both groups. (2) PCP and DeltaCP levels in insulin + RSG group patients stayed steady during the 12 months' observation (P = 0.161 for both PCP and DeltaCP), while in the insulin alone group, both FCP (P = 0.021) and PCP (P = 0.028) levels decreased significantly. Furthermore, PCP (P = 0.004) and DeltaCP(P = 0.015) differences between 12th month and baseline were higher in insulin + RSG group than those in the insulin group. (3) When observed up to 18 months, PCP and DeltaCP levels in insulin + RSG group patients still stayed steady, while PCP and DeltaCP levels decreased more in the insulin alone group.

CONCLUSIONS

This pilot study suggests that rosiglitazone combined with insulin may preserve islet beta cell function in LADA patients.

Nuclear receptors as targets for drug development: the role of nuclear receptors during neural stem cell proliferation and differentiation

The fate of stem cells, such as neural stem cells and hematopoietic stem cells, depends on strictly regulated signaling events including activation of nuclear receptors, resulting in subsequent gene induction. Recently, we demonstrated that PPARgamma, a ligand-activated nuclear receptor, plays an important role in regulating the proliferation and differentiation of murine neural stem cell (NSC). NSC prepared from heterozygous PPARgamma-deficient mouse exhibited a slower growth rate compared with that of wild-type mouse, which was also demonstrated in PPARgamma-knockdown NSC that was generated by the lentiviral-vector-mediated RNA interference approach. These studies have important implications for understanding central nervous system functions and developing a therapy for neurodegenerative disorders. In this review, recent findings on stem cell biology, especially focusing on nuclear receptors in NSCs, including our current study, will be discussed.

Role of PPARgamma in macrophage biology and atherosclerosis

Macrophages carry out key functions by defending a host from microbial invaders and by clearing endogenous cellular debris. Molecules that are essential for the recognition, phagocytosis and clearance of pathogens also mediate the uptake and degradation of pathogenic lipoproteins. During atherogenesis, for example, scavenging trapped lipoproteins leads to the formation of foam cells and subsequently the activation of these lipid-laden macrophages. Although they are initially clinically silent, these fatty streaks evolve into complex inflammatory plaques that cause significant morbidity and mortality. Thus, interventions that decrease foam cell formation and reduce the inflammatory response of macrophages could become effective therapies for coronary artery disease. Thiazolidinediones (TZDs) might be developed as anti-atherogenic agents on the basis of their actions as ligands for peroxisome proliferator-activated receptor-gamma (PPARgamma).

Protective effect of endogenous PPARgamma against acute gastric mucosal lesions associated with ischemia-reperfusion

Acute gastric mucosal lesions (AGMLs) are an important cause of gastrointestinal bleeding. Herein, we demonstrate that peroxisome proliferator-activated receptor-gamma (PPARgamma), a member of a nuclear receptor family, functions as an endogenous anti-inflammatory pathway in a murine model of AGML induced by ischemia-reperfusion (I/R). Treatment with specific PPARgamma ligands such as BRL-49653, pioglitazone, or troglitazone was examined in a model of AGML induced by I/R. PPARgamma-deficient and wild-type mice were also examined for their response to I/R in stomach. Specific PPARgamma ligands exhibited dramatic and rapid protection against AGML formation associated with I/R in mice in a dose-dependent manner. In contrast, the AGML induced by I/R in PPARgamma-deficient mice was more severe than that observed in wild-type mice. Administration of the PPARgamma ligand significantly inhibited the upregulation of TNF-alpha, ICAM-1, inducible nitric oxide synthase, apoptosis, and nitrotyrosine formation induced by I/R in the stomach. These data indicate that an endogenous pathway associated with PPARgamma plays an important role in the pathogenesis of I/R-associated injury in the stomach.

Role of peroxisome proliferator-activated receptor-gamma in the protection afforded by 15-deoxydelta12,14 prostaglandin J2 against the multiple organ failure caused by endotoxin

OBJECTIVE

The cyclopentenone prostaglandin 15-deoxydelta-prostaglandin J2 (15 d-PGJ2) exerts potent anti-inflammatory effects in vivo, which are in part due to the activation of peroxisome proliferator-activated receptor (PPAR)-gamma. Here we investigate the effects of 15 d-PGJ2 on the multiple organ injury/dysfunction associated with severe endotoxemia.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Seventy anesthetized male Wistar rats.

INTERVENTIONS

Rats received either Escherichia coli lipopolysaccharide (endotoxin, 6 mg/kg intravenously) or vehicle (saline, 1 mL/kg intravenously). 15 d-PGJ2 (0.3 mg/kg intravenously) or vehicle (10% dimethyl sulfoxide) was administered 30 mins before endotoxin. The selective PPAR-gamma antagonist GW9662 (0.3 mg/kg intravenously) or its vehicle (10% dimethyl sulfoxide) was given 45 mins before endotoxin.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia for 6 hrs increased serum concentrations of creatinine (indicator of renal dysfunction), aspartate aminotransferase, alanine aminotransferase, gamma-glutamyl transferase, bilirubin (markers for hepatic injury and dysfunction), lipase (indicator of pancreatic injury), and creatine kinase (an indicator of neuromuscular skeletal muscle or cardiac injury). The potent PPAR-gamma agonist 15 d-PGJ2 attenuated the increases in the serum concentrations of these variables, indicating a protective effect of 15 d-PGJ2 against the multiple organ injury/dysfunction caused by endotoxin. The specific PPAR-gamma antagonist GW9662 reduced the protective effects afforded by 15 d-PGJ2. 15 d-PGJ2 did not affect the biphasic decrease in blood pressure or the increase in heart rate caused by endotoxemia.

CONCLUSIONS

The potent PPAR-gamma agonist 15 d-PGJ2 reduces the multiple organ injury and dysfunction, but not the hypotension, caused by endotoxin in the rat. The mechanisms of the protective effect of this cyclopentenone prostaglandin are--at least in part--PPAR-gamma dependent, as the protection afforded by 15 d-PGJ2 was reduced by the PPAR-gamma antagonist GW9662. We propose that 15 d-PGJ2 or other ligands for PPAR-gamma may be useful in treating organ injury associated with endotoxic shock.

[PPARgamma-gene therapy using an adenovirus vector for inflammatory bowel disease]

Peroxisome proliferator-activated receptor gamma (PPARgamma) is one of the nuclear receptors that plays a central role in adipocyte differentiation and insulin sensitivity. Recently, PPARgamma has also been recognized as a suppressive regulator of inflammation in the gastrointestinal tract. We summarize here the therapeutic benefits of PPARgamma-gene therapy using a replication-deficient adenovirus vector expressing PPARgamma (AdRGD-PPARgamma). We demonstrate that PPARgamma- protein levels are decreased in dextran sodium sulfate-induced colitis and restored in this model by intraperitoneal administration of the AdRGD-PPARgamma. Treatment with AdRGD-PPARgamma and PPARgamma-specific ligands resulted in a marked amelioration of tissue inflammation associated with the colitis, including reduction in intercellular adhesion molecule-1, cyclooxygenase-2, and tumor necrosis factor-alpha expression. Our results suggest that gene delivery of PPARgamma may open up a novel therapeutic approach for inflammatory bowel diseases such as Crohn's disease and ulcerative colitis.

Rosiglitazone and 15-deoxy-Delta12,14-prostaglandin J2, ligands of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), reduce ischaemia/reperfusion injury of the gut

1. The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the nuclear receptor superfamily of ligand-dependent transcription factors related to retinoid, steroid and thyroid hormone receptors. The thiazolidinedione rosiglitazone and the endogenous cyclopentenone prostaglandin (PG)D2 metabolite, 15-deoxy-Delta12,14-PGJ2 (15d-PGJ2), are two PPAR-gamma ligands, which modulate the transcription of target genes. 2. The aim of this study was to investigate the effect of rosiglitazone and 15d-PGJ2 on the tissue injury caused by ischaemia/reperfusion (I/R) of the gut. 3. I/R injury of the intestine was caused by clamping both the superior mesenteric artery and the coeliac trunk for 45 min, followed by release of the clamp allowing reperfusion for 2 or 4 h. This procedure results in splanchnic artery occlusion (SAO) shock. 4. Rats subjected to SAO developed a significant fall in mean arterial blood pressure, and only 10% of the animals survived for the entire 4 h reperfusion period. Surviving animals were killed for histological examination and biochemical studies. Rats subjected to SAO displayed a significant increase in tissue myeloperoxidase (MPO) activity and malondialdehyde (MDA) levels, significant increases in plasma tumour necrosis factor (TNF)-alpha and interleukin (IL)-1beta levels and marked injury to the distal ileum. 5. Increased immunoreactivity to nitrotyrosine was observed in the ileum of rats subjected to SAO. Staining of sections of the ileum obtained from SAO rats with anti-intercellular adhesion molecule (ICAM-1) antibody resulted in diffuse staining. 6. Administration at 30 min prior to the onset of gut ischaemia of the two PPAR-gamma agonists (rosiglitazone (0.3 mg kg-1 i.v.) and 15d-PGJ2 (0.3 mg kg-1 i.v.)) significantly reduced the (i) fall in mean arterial blood pressure, (ii) mortality rate, (iii) infiltration of the reperfused intestine with polymorphonuclear neutrophils (MPO activity), (iv) lipid peroxidation (MDA levels), (v) production of proinflammatory cytokines (TNF-alpha and IL-1beta) and (vi) histological evidence of gut injury. Administration of rosiglitazone and 15d-PGJ2 also markedly reduced the nitrotyrosine formation and the upregulation of ICAM-1 during reperfusion. 7. In order to elucidate whether the protective effects of rosiglitazone and 15d-PGJ2 are related to the activation of the PPAR-gamma receptor, we also investigated the effect of a PPAR-gamma antagonist, bisphenol A diglycidyl ether (BADGE), on the protective effects of rosiglitazone and 15d-PGJ2. BADGE (1 mg kg-1 administered i.v. 30 min prior to the treatment of rosiglitazone or 15d-PGJ2) significantly antagonised the effect of the two PPAR-gamma agonists and thus abolished the protective effect against gut I/R. 8. These results demonstrate that the two PPAR-gamma agonists, rosiglitazone and 15d-PGJ2, significantly reduce I/R injury of the intestine.

A novel PPAR gamma gene therapy to control inflammation associated with inflammatory bowel disease in a murine model

BACKGROUND & AIMS

Peroxisome proliferator-activated receptor gamma (PPAR gamma) is one of the nuclear receptors that plays a central role in adipocyte differentiation and insulin sensitivity. PPAR gamma has also recently been recognized as an endogenous regulator of intestinal inflammation. However, its levels are decreased during chronic inflammation in human and mice, thus limiting PPAR gamma ligand therapy during established disease. We sought to determine whether this decrease in PPAR gamma could be counteracted by a gene therapy approach.

METHODS

We characterized PPAR gamma levels in experimental colitis associated with dextran sodium sulfate administration to mice. In this model, the therapeutic benefits of PPAR gamma gene therapy using a replication-deficient adenovirus vector expressing PPAR gamma (Ad-PPAR gamma) was assessed.

RESULTS

PPAR gamma protein levels were decreased in whole colonic tissue, lamina propria lymphocytes, and peritoneal exudate cells during the course of colitis. PPAR gamma gene delivery using Ad-PPAR gamma restored responsiveness to a PPAR gamma ligand, resulting in marked amelioration of tissue inflammation associated with the colitis, which included attenuation of intercellular adhesion molecule-1, cyclooxygenase-2 and tumor necrosis factor-alpha expression.

CONCLUSIONS

Our results suggest that gene delivery of PPAR gamma can be used to restore and/or enhance endogenous anti-inflammatory processes that are normally operative in mammalian tissues such as in the colon.

Role of PPAR.GAMMA. in the development of the central nervous system

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor that plays a central role in adipocyte differentiation and insulin sensitivity. Recently, a diversity of the action of PPARgamma on many other cell types or organs is indicated. We summarize here the possible role of PPARgamma in the development of the murine central nervous system. Expressions of PPARgamma in newborn or adult mouse brain are extremely low, but high in embryo or fetal mouse brain. Furthermore, we investigated the role of PPARgamma in proliferation or differentiation of neural stem cells (NSCs) isolated from murine embryonic brains, because NSCs are considered to be a major source of neurons in developmental brains. Administrations of PPARgamma-specific ligands on the NSCs from wild-type mice resulted in the stimulation of cell growth. On the other hand, administration of PPARgamma-antagonist showed the cell death and apoptosis of NSCs. These results may indicate that PPARgamma plays an important role during the early stage of the development of the central nervous system.

Inflammatory status and insulin resistance

PURPOSE OF REVIEW

The inflammatory response is essential in the response to pathogens. TNF-alpha, IL-1 and IL-6 are key mediators of the response. They initiate metabolic changes to provide nutrients for the immune system, from host tissues. These changes include hyperlipidemia and increased gluconeogenesis. Insulin resistance and disordering of lipid metabolism occur in obesity, diabetes mellitus, atherosclerosis. This review examines recent research that links inflammation to insulin insensitivity.

RECENT FINDINGS

Population studies show a strong association between indices of inflammation, and abnormal lipid and carbohydrate metabolism, obesity and atherosclerosis. TNF-alpha is produced, by cells of the immune system and by adipocytes. It may provide the link between inflammation and insulin sensitivity. TNF-alpha results in insulin insensitivity, indirectly by stimulating stress hormone production and directly by sustained induction of SOCS-3 which decreases insulin-induced insulin receptor substrate 1 (IRS1) tyrosine phosphorylation and its association with the p85, regulatory subunit of phosphatidylinositol-3 kinase; and by negative regulation of PPAR gamma. Adipose tissue produces both TNF-alpha and leptin. Production of the latter relates positively to adipose tissue mass and through its actions on immune function exerts a pro-inflammatory influence.

SUMMARY

Recent studies on diseases which involve insulin insensitivity (e.g. obesity, type 2 diabetes and atherosclerosis) also show increased cytokine production and markers of inflammation. Evidence at present favours chronic inflammation as a trigger for chronic insulin insensitivity, rather than the reverse situation.

Human apical sodium-dependent bile salt transporter gene (SLC10A2) is regulated by the peroxisome proliferator-activated receptor alpha

The apical sodium-dependent bile salt transporter (ASBT/SLC10A2), also called the ileal bile acid transporter, mediates the intestinal absorption of bile salts. The efficiency of this transport process is a determinant of hepatic bile salt synthesis from cholesterol and of serum triglyceride levels. Our aim was to characterize the human ASBT gene promoter with respect to regulatory mechanisms that coordinately affect ASBT expression and hepatic lipid and bile salt metabolism. The minimal construct that confers full promoter activity contains three functional hepatocyte nuclear factor 1alpha (HNF1alpha) recognition sites, explaining the dependence of ASBT gene expression upon HNF1alpha. A nuclear receptor binding site arranged as a direct hexanucleotide repeat (DR1 motif) is localized approximately 1.6 kb upstream of the transcription initiation site. Constructs containing this element were transactivated by WY14643 and ciprofibrate, ligands of the peroxisome proliferator-activated receptor alpha (PPARalpha), in Caco2 cells. The DR1 element was shown to bind the PPARalpha/9-cis-retinoic acid receptor heterodimer, and targeted mutagenesis of the DR1 motif abolished PPARalpha responsiveness. Ciprofibrate treatment of SK-ChA cholangiocytes increased ASBT mRNA levels, suggesting a physiologic role for PPARalpha-mediated ASBT gene regulation. This study identifies PPARalpha as a novel link between ileal bile salt absorption and hepatic lipid metabolism.

Nitration of PPARgamma inhibits ligand-dependent translocation into the nucleus in a macrophage-like cell line, RAW 264

Nitration of tyrosine residues in proteins has been observed in many inflammatory tissues of arthritis, ulcerative colitis, septic shock and ischemia-reperfusion injury. Although several studies have been carried out, it is still unclear what type of protein is nitrated and whether tyrosine nitration interferes with protein function. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor whose activation is linked to several physiological pathways including regulation of insulin sensitivity and control of inflammation. PPARgamma possesses several tyrosine residues, which might be potential targets for nitration by peroxynitrite during inflammatory responses. Here we have investigated whether PPARgamma is nitrated in macrophage-like RAW 264 cells and the effect of nitration on the translocation of PPARgamma into the nucleus. Western blot analysis showed that tumor necrosis factor-alpha, lipopolysaccharide or peroxynitrite treatment significantly increases the nitration of PPARgamma. Cell fractionation analysis and immunofluorescence coupled with confocal laser microscopy revealed that nitration of PPARgamma inhibits its ligand-dependent translocation from the cytosol into the nucleus. Together, these results indicate that nitration of PPARgamma during inflammation may be involved in a reduction in the control of inflammatory responses and also in the development of resistance to PPARgamma ligand-based therapies against inflammation.

PPAR gamma ligands inhibit nitrotyrosine formation and inflammatory mediator expressions in adjuvant-induced rheumatoid arthritis mice

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a nuclear receptor, whose activation has been linked to several physiologic pathways including those related to the regulation of insulin sensitivity. Here, we investigate effects of PPARgamma specific ligands, rosiglitazone and pioglitazone, on formation of nitrotyrosine and increased expression of inflammatory mediators such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 and intercellular adhesion molecule-1 (ICAM-1) in adjuvant-induced murine arthritis. Administration of rosiglitazone or pioglitazone (30 mg/kg, p.o.) significantly inhibited the adjuvant-induced increase in formation of nitrotyrosine and expression of iNOS on both ankle and temporomandibular joints. Rosiglitazone also inhibited the adjuvant-induced expression of M30 positive cells, as a marker of apoptosis, in the joint tissues. In addition, treatment with rosiglitazone or pioglitazone (30 microM) inhibited lipopolysaccharide plus tumor necrosis factor (TNF)-alpha-induced protein expression of iNOS, cyclooxygenase-2, ICAM-1 and nitrotyrosine formation in RAW 264 cells, a murine macrophage-like cell line. Rosiglitazone or pioglitazone inhibited increase in phosphorylated I-kappaB (pI-kappaB) expression, as an index of activation of nuclear factor (NF)-kappaB, in both joint tissues and RAW264 cells. Furthermore, in PPARgamma-transfected HEK293 cells, rosiglitazone inhibited the TNF-alpha-stimulated response using NF-kappaB-mediated transcription reporter assay. These results indicate that PPARgamma ligands may possess anti-inflammatory activity against adjuvant-induced arthritis via the inhibition of NF-kappaB pathway.