Activated and inactivated PPARs-γ modulate experimentally induced colitis in rats

Peroxisome proliferator-activated receptor γ plays dual roles on experimental periodontitis in rats

AIM

To investigate the effects of peroxisome proliferator-activated receptor γ (PPARγ) on inflammation control and bone remodelling in experimental periodontitis in rats.

MATERIALS AND METHODS

Experimental periodontitis was induced in rats by thread ligation around cervixes of mandibular first molars. PPARγ agonist, antagonist and vehicle were intraperitoneally administrated, respectively, into rats. Ninety-six male SD rats were randomly divided into control, ligation + vehicle, ligation + agonist and ligation + antagonist groups. After 1, 4 and 8 weeks, alveolar bone loss was assessed by Micro-CT and HE staining. Inflammation and bone metabolism factors were evaluated by ELISA and immunohistochemical examination. Osteoclasts were quantified by tartrate-resistant acid phosphatase (TRAP) staining.

RESULTS

Alveolar bone loss was significantly reduced after 1 week, while significantly increased after 8 weeks in agonist group, but antagonist group showed the opposite trend. Agonist decreased some inflammatory cytokines expression after 1 and 4 weeks, downregulated OPG, RUNX2, BMP-2 and upregulated RANKL after 8 weeks, but antagonist brought the opposite effect. PPARγ agonist significantly reduced osteoclast counting after 1 week, while increased it after 8 weeks.

CONCLUSIONS

During periodontitis progression, PPARγ could inhibit inflammation, prevent bone resorption within a short time, while the long-term PPARγ activation would lead to increased bone resorption, and PPARγ repression by antagonist would enhance alveolar bone formation.

Stricture of ileo-anal J pouch anastomosis increased the intensity of pouchitis in an experimental rat model

Background

Pouchitis appears to be the most common complication after restorative proctocolectomy.

Material/Methods

In experimental models we investigated the correlation between the width of anastomosis and the frequency of pouchitis. Twenty-three Wistar rats underwent restorative proctocolectomy under pentobarbital anesthesia. Normal width anastomosis was performed in 11 animals (Group I). In the remaining 12 animals (Group II) the diameter of anastomosis was reduced by 50%. All animals were sacrificed and the pouch mucosa was histologically (Moskowitz score) and immunohistochemically (IL-1, IL-6, IL-10, IL-12 expression) examined.

Results

Morphological assessment of pouchitis symptoms based on Moskowitz scale revealed considerably more severe inflammation (p=0.0079) in the animals from Group II than in the rats from Group I. The expressions of investigated cytokines, assessed qualitatively in histopathological examination, were higher in rats with narrow anastomosis in comparison with animals with normal anastomosis.

Conclusions

The stricture of anastomosis increases the intensity of pouchitis and stimulates the production of interleukins. It seems that anastomotic stricture plays an important role in the development of pouchitis.

Relevance of TNBS-colitis in rats: a methodological study with endoscopic, histologic and Transcriptomic [corrected] characterization and correlation to IBD

Background

Rectal instillation of trinitrobenzene sulphonic acid (TNBS) in ethanol is an established model for inflammatory bowel disease (IBD). We aimed to 1) set up a TNBS-colitis protocol resulting in an endoscopic and histologic picture resembling IBD, 2) study the correlation between endoscopic, histologic and gene expression alterations at different time points after colitis induction, and 3) compare rat and human IBD mucosal transcriptomic data to evaluate whether TNBS-colitis is an appropriate model of IBD.

Methodology/Principal Findings

Five female Sprague Daley rats received TNBS diluted in 50% ethanol (18 mg/0.6 ml) rectally. The rats underwent colonoscopy with biopsy at different time points. RNA was extracted from rat biopsies and microarray was performed. PCR and in situ hybridization (ISH) were done for validation of microarray results. Rat microarray profiles were compared to human IBD expression profiles (25 ulcerative colitis Endoscopic score demonstrated mild to moderate colitis after three and seven days, but declined after twelve days. Histologic changes corresponded with the endoscopic appearance. Over-represented Gene Ontology Biological Processes included: Cell Adhesion, Immune Response, Lipid Metabolic Process, and Tissue Regeneration. IL-1α, IL-1β, TLR2, TLR4, PRNP were all significantly up-regulated, while PPARγ was significantly down-regulated. Among genes with highest fold change (FC) were SPINK4, LBP, ADA, RETNLB and IL-1α. The highest concordance in differential expression between TNBS and IBD transcriptomes was three days after colitis induction. ISH and PCR results corresponded with the microarray data. The most concordantly expressed biologically relevant pathways included TNF signaling, Cell junction organization, and Interleukin-1 processing.

Conclusions/Significance

Endoscopy with biopsies in TNBS-colitis is useful to follow temporal changes of inflammation visually and histologically, and to acquire tissue for gene expression analyses. TNBS-colitis is an appropriate model to study specific biological processes in IBD.

Association between the Pro12Ala polymorphism of peroxisome proliferator-activated receptor gamma 2 and inflammatory bowel disease: a meta-analysis

Background

Peroxisome proliferator-activated receptor gamma (PPARγ), a nuclear receptor, has been implicated playing a role in the development of inflammatory bowel disease (IBD). However, previous studies evaluating the association between the PPARγ2 Pro12Ala polymorphism and IBD are inconsistent. We performed a meta-analysis to determine whether the PPARγ2 Pro12Ala mutation was associated with the presence of IBD.

Methods and Findings

Electronic databases were searched for case-control studies evaluating the association between the Pro12Ala mutation and the presence of IBD. Effects were summarized with the methods recommended by the Cochrane Collaboration. A total of 7 studies including 1002 ulcerative colitis (UC) cases, 1090 Crohǹs disease (CD) cases and 1983 controls were involved in this meta-analysis. In the overall analysis, no significant association of this polymorphism with UC or CD was found. In the subgroup analyses in different populations, AlaAla genotype seemed to protect the European Caucasian population against the development of CD (Pro vs Ala: OR = 1.135, 95%CI = 0.951–1.354, P = 0.162, Bon = 1.000; ProPro vs ProAla: OR = 1.042, 95%CI = 0.852–1.273, P = 0.690, Bon = 1.000; ProPro vs AlaAla: OR = 2.379, 95%CI = 1.110–5.100, P = 0.026, Bon = 0.156; ProAla vs AlaAla: OR = 2.315, 95%CI = 1.064–5.037, P = 0.034, Bon = 0.204; Pro homozygotes vs Ala positives: OR = 1.094, 95%CI = 0.899–1.330, P = 0.371, Bon = 1.000; Pro positives vs Ala homozygotes: OR = 2.360, 95%CI = 1.103–5.053, P = 0.027, Bon = 0.162; heterozygotes vs all homozygotes: OR = 0.976, 95%CI = 0.799–1.192, P = 0.809, Bon = 1.000). There was no significant association of this polymorphism with UC or CD in the East Asian population and the Turkish population.

Conclusion

AlaAla genotype may be a protective factor in the European Caucasian population against the development of CD in a recessive way.