Use of animal models in elucidating disease pathogenesis in IBD

The role of Raptor in lymphocytes differentiation and function

Raptor, a key component of mTORC1, is required for recruiting substrates to mTORC1 and contributing to its subcellular localization. Raptor has a highly conserved N-terminus domain and seven WD40 repeats, which interact with mTOR and other mTORC1-related proteins. mTORC1 participates in various cellular events and mediates differentiation and metabolism. Directly or indirectly, many factors mediate the differentiation and function of lymphocytes that is essential for immunity. In this review, we summarize the role of Raptor in lymphocytes differentiation and function, whereby Raptor mediates the secretion of cytokines to induce early lymphocyte metabolism, development, proliferation and migration. Additionally, Raptor regulates the function of lymphocytes by regulating their steady-state maintenance and activation.

Exploring the Potential of IL-1β Inhibitor Diacerein and its Combination with 5-Aminosalicylic Acid for the Possible Ameliorating Effect in TNBS-induced Experimental Colitis in Wistar Rats

Background:

Pro-inflammatory mediators such as tumor necrosis factor-alpha (TNF-α), interleukin (IL), and oxidative stress are crucial players in the pathophysiology of inflammatory bowel disease (IBD) that contribute in perpetuating intestinal inflammation. Targeting them presents a novel approach in disease management. In the present study, the potential of an antiosteoarthritic IL-inhibitor drug, diacerein (DIA) was investigated in 2, 4, 6-trinitrobenzene sulfonic acid (TNBS)- instigated ulcerative colitis (UC) in Wistar rats. A comparative study was also undertaken to investigate the potential of combination therapy of DIA with the standard drug 5-aminosalicylic acid (5-ASA) versus monotherapy.

Methods:

Colitis was developed by single intra-colonic administration of TNBS (100mg/kg); whereas drugs 5-ASA (25.5 mg/kg), DIA (100 mg/kg), and DIA+5-ASA (100+ 25.5 mg/kg) were administered orally for five days post-induction to various groups of rats. Parameters like disease activity score, colon/body weight ratio, colon length, diameter, gut pH were assessed, and histopathological analysis was carried out. Biochemical markers of colonic inflammation such as IL-1β, TNF-α, reduced glutathione (GSH), and malondialdehyde (MDA) were also estimated.

Results:

Combination of DIA and 5-ASA demonstrated the most significant reduction of the colon to body weight ratio and disease activity score. It prominently restored the colon length, diameter, and gut pH to normal. It attenuated the biochemical alterations induced by TNBS, indicating a highly significant defensive outcome against colonic inflammation. The histopathological report demonstrated the renovating effect of the combination of disrupted colonic histology with minimally distressing liver, stomach, or pancreas compared to individual drugs.

Conclusion:

The combination remarkably downregulated the level of inflammation by suppressing both provocative cytokines and reactive oxygen species production. It can be evaluated further in a clinical setup as a novel and promising drug therapy for UC.

Protective effect of naringin ameliorates TNBS-induced colitis in rats via improving antioxidant status and pro-inflammatory cytokines

Aim: Ulcerative colitis (UC) is a chronic inflammatory bowel disease that disturbs the colon mucosal lining and is characterized by oxido-nitrosative stress and the release of pro-inflammatory cytokines. Naringin (NG) belongs to a group of chemicals called bioflavonoids derived from grapefruit and related citrus species. NG has been widely used as folk medicine in many countries, due to its several health benefits.Method: This study examined the effect of NG on 2,4,6 trinitrobenzene sulfonic acid (TNBS)-induced colitis in rats. Forty-two male Wistar rats were divided into seven groups like Normal Control (NC), Ethanol Control (EC), Disease Control (DC), NG 20 (20 mg/kg, p.o.), NG 40 (40 mg/kg, p.o.), NG 80 (80 mg/kg, p.o.), and Dexamethasone (DEX) (2 mg/kg, p.o.). Colitis was induced in Wistar albino rats by administering TNBS intra-rectally (in 50% ethanol). The rats were then given 14 days of NG (20, 40, and 80 mg/kg) and DEX (2 mg/kg) treatment. Several behavioral, biochemical, molecular, and histological analyses were performed.Result: The treatment of rats with NG significantly increased the body weight (p < .05, p < .01), hematological parameters like hemoglobin (p < .05, p < .01, p < .001), red blood cells (p < .01, p < .001), and platelets count (p < .01, p < .001) and decreased in spleen weight (p < .01, p < .001), colon weight (p < .01, p < .001), colon weight to length ratio (p < .05, p < .01, p < .001), macroscopic score (p < .01, p < .001), adhesion score (p < .01, p < .001), diarrhea score (p < .05, p < .001), stool consistency (p < .01, p < .001), rectal bleeding score (p < .05, p < .01, p < .001), white blood cells count (p < .01, p < .001). NG significantly (p < .01, p < .001) increased colonic superoxide, glutathione, and catalase levels and decreased malondialdehyde and myeloperoxidase levels. It also significantly (p < .01, p < .001) decreased the biochemical parameters, proinflammatory cytokines and reduced the histological damage in the colon tissue caused by TNBS.Conclusion: Our results demonstrated that NG treatment attenuated pathologic changes of TNBS-induced colitis in rats through restoring colonic damage and reducing inflammatory response in the colon tissue. Thus, NG might be considered as an effective candidate for the treatment of UC patients.

Effects of pentasa-combined probiotics on the microflora structure and prognosis of patients with inflammatory bowel disease

BACKGROUND/AIMS

The aim of the present study was to investigate the effects of the combination treatment of pentasa and probiotics on the microflora composition and prognosis in patients with inflammatory bowel disease (IBD).

MATERIALS AND METHODS

A total of 40 patients with IBD (19 control group and 21 observation group) were randomized. Patients in the control group were given pentasa, and patients in the observation group were given probiotics along with pentasa. The microflora composition, biochemical indices, inflammatory markers, and activity scores of the two groups were analyzed.

RESULTS

After treatment, the number of enterobacteria, enterococci, saccharomyces, and bacteroides; the levels of fecal lactoferrin, 1-antitrypsin, β2-microglobulin, high-sensitivity C-reactive protein, and interleukin (IL)-6; activity scores; and recurrence rate in the observation group were significantly lower than those in the control group. Bifidobacterium and lactobacillus counts and IL-4 levels were significantly higher in the observation group than in the control group.

CONCLUSION

The combination of probiotics and pentasa can improve microflora composition in patients with IBD and reduce the level of inflammatory cytokines; therefore, it is worthy of further clinical validation.

The role of IL-17A in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies

Although the pathogenic mechanisms underlying axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) are not fully elucidated, several lines of evidence suggest that immune responses mediated by interleukin 17A (IL-17A) play a pivotal role in both diseases. This is best highlighted by the significant clinical efficacy shown with inhibitors of IL-17A in treating axSpA and PsA. Nevertheless, a number of knowledge gaps exist regarding the role of IL-17A in the pathophysiology of spondyloarthritis in man, including its cellular origin, its precise role in discrete disease processes such enthesitis, bone erosion, and bone formation, and the reasons for the discrepant responses to IL-17A inhibition observed in certain other spondyloarthritis manifestations. In this review, we focus on the latest data from studies investigating the role of IL-17A in ankylosing spondylitis (AS) and PsA that build on existing and emerging scientific knowledge in the field. Key remaining research questions are also highlighted to guide future research.

Extracts from Hericium erinaceus relieve inflammatory bowel disease by regulating immunity and gut microbiota

Hericium erinaceus (HE), a traditional edible mushroom, is known as a medicine food homology to ameliorate gastrointestinal diseases. To investigate whether HE is clinically effective in alleviating inflammatory bowel disease (IBD), HE extracts (polysaccharide, alcoholic extracts and whole extracts were prepared using solvent extraction methods) were administrated for 2 weeks in rats with IBD induced by trinitro-benzene-sulfonic acid (TNBS) enema (150 mg/kg). Significant clinical and histological changes in IBD rats were identified, including damage activity, common morphous and tissue damage index scores in colonic mucosa and myeloperoxidase (MPO) activity. The damage activity, common morphous and tissue damage index scores in colonic mucosa (P <0.05) were improved, MPO activities were decreased. Inflammatory factors were also differentially expressed in colonic mucosa in IBD rats, including serum cytokines, Foxp3 and interleukin (IL)-10 were increased while NF-κB p65 and tumor necrosis factor (TNF)-α were decreased (P <0.05), and T cells were activated (P <0.05), especially in the alcohol extracts-treated group. We also found that the structure of gut microbiota of the H. erinaceus extracts-treated groups changed significantly by compared with the model group. Further studies revealed that the polysaccharides in HE extracts may play a prebiotic role, whereas the alcoholic extracts show bactericidin-like and immunomodulatory effects. Taken together, we demonstrated that H. erinaceus extracts could promote the growth of beneficial gut bacteria and improve the host immunity in vivo IBD model, which shows clinical potential in relieving IBD by regulating gut microbiota and immune system.

TNFα deficiency results in increased IL-1β in an early onset of spontaneous murine colitis

Inflammatory bowel disease (Crohn's disease (CD) and ulcerative colitis (UC)) is a multifactorial disease resulting from immune dysregulation in the gut. The underlying colitis is characterized by high levels of inflammatory cytokines, including TNFα. Biological intervention for IBD patients using anti-TNFα antibodies is often an effective therapeutic solution. However, TNFα neutralization fails to induce remission in a subgroup of IBD patients, primarily in UC patients. There is a dearth of suitable animal models representing TNFα non-responders. Here we have combined one of the best UC models currently available, namely Winnie and the TNFαKO mouse to generate a TNFα-deficient Winnie to study early onset colitis. The induced TNFα deficiency with underlying colitis does not influence general health (viability and body weight) or clinical parameters (colon weight, colon length and histological colitis) when compared with the Winnie genotype alone. The molecular characterization resulted in identification of Il1β as the major elevated cytokine during early phases of colitis. Further, in vitro functional assay using bone marrow-derived dendritic cells confirmed IL-1β as the major cytokine released in the absence of TNFα. This study has generated a successful model of colitis that remains TNFα non-responsive and has demonstrated that IL-1β expression is a major pathway for the progression of colitis in this system. These data also suggest that IL-1β can be a potential target for clinical intervention of UC patients who fail to respond to TNFα neutralization.

A vitamin D receptor agonist converts CD4+ T cells to Foxp3+ regulatory T cells in patients with ulcerative colitis

One of the pathological features of ulcerative colitis (UC) is the dysfunction of immune regulatory T cells (Treg cells); the pathogenesis is unclear and needs to be further investigated. Vitamin D has immune regulatory functions. This study tests a hypothesis that vitamin D receptor (VDR) regulates Treg cell differentiation. Peripheral blood samples were collected from UC patients and healthy subjects. The correlation between VDR expression and T helper (Th)2 cell differentiation in peripheral CD4⁺ T cells was analyzed. We observed that the expression of VDR was lower, the expression of interleukin (IL)-4 was higher, in peripheral CD4⁺ T cells of UC patients than that in healthy controls. Naive CD4⁺ T cells from VDR deficient mice were prone to differentiating into Th2 cells, which could be adjusted by the presence of VDR agonists. The Th2 polarization status in the peripheral CD4⁺ T cells of UC patients could be converted to regulatory T cells in the culture in the presence of VDR agonists. In conclusion, the peripheral Th2 cells in UC patients can be converted to regulatory T cells by VDR agonists in the culture. The results suggest that administration of VDR agonists at proper dosages may improve the immunity of UC patients.

Anti-inflammatory effect of Chang-An-Shuan on TNBS-induced experimental colitis in rats

Background

Inflammatory bowel disease (IBD), denominated by Crohn’s disease and ulcerative colitis, is often associated with abdominal pain, diarrhea and bloody stool. The standard protocols for treating colitis conditions are not satisfactory; thus, complementary and alternative medicines have been increasingly accepted by IBD sufferers worldwide. In this study, we aimed to elucidate the anti-inflammatory effect of Chang-An-Shuan (CAS), a 6-herb Chinese medicinal formula, on 2, 4, 6-trinitrobenzenesulfonic acid (TNBS)-induced colitis in rats and the underlying mechanisms.

Methods

Sprague-Dawley rats were administered with rectal gavage of 2.5% TNBS in 50% ethanol for the induction of experimental colitis which is considered as a model for Crohn’s disease. Upon the TNBS induction, rats were given CAS at 0.5 g/kg/day or 5 g/kg/day for 10 days. The application of salicylazosulfapyridine (0.5 g/kg/day) was served as a positive reference drug for the colitis condition. The efficacy and mechanistic action of CAS were evaluated by means of histopathological and biochemical approaches such as histological staining, real-time polymerase chain reaction, Western blotting analysis and enzyme-linked immunosorbent assay.

Results

Oral administration of CAS at 5 g/kg/day, but not 0.5 g/kg/day, significantly ameliorated the severity of TNBS-induced colitis as evidenced by the reduced loss of body weight, alleviated diarrhea and decreased bloody stool. While lowering the disease activity index, the administration of CAS lessened mucosal lesions thus mucosal integrity of the colitis rats was notably improved. Further, the CAS treatment also significantly suppressed the mRNA and protein levels of pro-inflammatory cytokines, namely interleukin-1β and tumor necrosis factor-α while enhancing the level of anti-inflammatory cytokine IL-10 in the TNBS-treated rats. Importantly, the ameliorative effect of CAS was related to an inhibition of the nuclear factor-κB (NF-κB) signaling pathway by downregulating the expression levels of NF-κBp-65, p-38 and p-AKT.

Conclusions

We suggest that CAS is a potential alternative remedial approach for treating IBD conditions, and the anti-inflammatory effect of CAS is associated with the down-regulation of the NF-κB signaling pathway and the balanced production of pro- and anti-inflammatory cytokines.

Mouse Model of Reversible Intestinal Inflammation

Current therapies to treat inflammatory bowel disease by dampening excessive inflammatory immune responses have had limited success ( Reinisch et al., 2011 ; Rutgeerts et al., 2005 ; Sandborn et al., 2012 ). To develop new therapeutic interventions, there is a need for better understanding of the mechanisms that are operative during mucosal healing (Pineton de Chambrun et al., 2010 ). To this end, a reversible model of colitis was developed in which colitis induced by adoptive transfer of naïve CD4⁺ CD45RB^hi T cells in lymphopenic mice can be reversed through depletion of colitogenic CD4⁺ T cells ( Brasseit et al., 2016 ).

Validation and Optimization of an Ex Vivo Assay of Intestinal Mucosal Biopsies in Crohn's Disease: Reflects Inflammation and Drug Effects

Crohn’s disease (CD) is a chronic illness demanding better therapeutics. The marketed biologics only benefit some patients or elicit diminishing effect over time. To complement the known methods in drug development and to obtain patient specific drug responses, we optimized and validated a known human explant method to test drug candidates and pathophysiological conditions in CD intestinal biopsies. Mucosal biopsies from 27 CD patients and 6 healthy individuals were collected to validate an explant assay test where the polarized tissue was cultured on a novel metal mesh disk, slightly immersed in medium imitating an air-liquid interphase. After culture in high oxygen for 24 hours with or without biological treatment in the medium, biopsy integrity and penetration of antibodies was measured by immunohistochemistry (IHC). Nine cytokines were quantified in the conditioned medium as a read-out for degree of inflammation in individual biopsies and used to evaluate treatment efficacy. The biopsies were well-preserved, showing few structural changes. IHC revealed tissue penetration of antibodies demonstrating ability to test therapeutic antibodies. The cytokine release to the medium showed that the assay can distinguish between inflammation states and then validate the known effect of two treatment biologics confirmed by a detection panel of five specific cytokines. Our data also suggest that the assay would be able to indicate which patients are responders to anti-TNF-α therapeutics, and which are non-responders. This study demonstrates this version of an ex vivo culture as a valid and robust assay to assess inflammation in mucosal biopsies and test of the efficacy of novel drug candidates and current treatments on individual patients–potentially for a personalized medicine approach.

Cytokine and anti-cytokine therapies in prevention or treatment of fibrosis in IBD

The frequency of fibrosing Crohn's disease (CD) is significant, with approximately 40% of CD patients with ileal disease developing clinically apparent strictures throughout their lifetime. Although strictures may be subdivided into fibrotic, inflammatory, or mixed forms, despite immunosuppressive therapy in CD patients in the form of steroids or immunomodulators, the frequency of fibrostenosing complications has still remained significant. A vast number of genetic and epigenetic variables are thought to contribute to fibrostenosing disease, including those that affect cytokine biology, and therefore highlight the complexity of disease, but also shed light on targetable pathways. Exclusively targeting fibrosis may be difficult, however, because of the relatively slow evolution of fibrosis in CD, and the potential adverse effects of inhibiting pathways involved in tissue repair and mucosal healing. Acknowledging these caveats, cytokine-targeted therapy has become the mainstay of treatment for many inflammatory conditions and is being evaluated for fibrotic disorders. The question of whether anti-cytokine therapy will prove useful for intestinal fibrosis is, therefore, acutely relevant. This review will highlight some of the current therapeutics targeting cytokines involved in fibrosis.

CD4 T cells are required for both development and maintenance of disease in a new mouse model of reversible colitis

Current therapies to treat inflammatory bowel diseases have limited efficacy, significant side effects, and often wane over time. Little is known about the cellular and molecular mechanisms operative in the process of mucosal healing from colitis. To study such events, we developed a new model of reversible colitis in which adoptive transfer of CD4(+)CD45RB(hi) T cells into Helicobacter typhlonius-colonized lymphopenic mice resulted in a rapid onset of colonic inflammation that was reversible through depletion of colitogenic T cells. Remission was associated with an improved clinical and histopathological score, reduced immune cell infiltration to the intestinal mucosa, altered intestinal gene expression profiles, regeneration of the colonic mucus layer, and the restoration of epithelial barrier integrity. Notably, colitogenic T cells were not only critical for induction of colitis but also for maintenance of disease. Depletion of colitogenic T cells resulted in a rapid drop in tumor necrosis factor α (TNFα) levels associated with reduced infiltration of inflammatory immune cells to sites of inflammation. Although neutralization of TNFα prevented the onset of colitis, anti-TNFα treatment of mice with established disease failed to resolve colonic inflammation. Collectively, this new model of reversible colitis provides an important research tool to study the dynamics of mucosal healing in chronic intestinal remitting-relapsing disorders.

Polysaccharide-based micro/nanocarriers for oral colon-targeted drug delivery

Oral colon-targeted drug delivery has attracted many researchers because of its distinct advantages of increasing the bioavailability of the drug at the target site and reducing the side effects. Polysaccharides that are precisely activated by the physiological environment of the colon hold greater promise for colon targeting. Considerable research efforts have been directed towards developing polysaccharide-based micro/nanocarriers. Types of polysaccharides for colon targeting and in vitro/in vivo assessments of polysaccharide-based carriers for oral colon-targeted drug delivery are summarised. Polysaccharide-based microspheres have gained increased importance not just for the delivery of the drugs for the treatment of local diseases associated with the colon (colon cancer, inflammatory bowel disease (IBD), amoebiasis and irritable bowel syndrome (IBS)), but also for it's potential for the delivery of anti-rheumatoid arthritis and anti-chronic stable angina drugs. Besides, Polysaccharide-based micro/nanocarriers such as microbeads, microcapsules, microparticles, nanoparticles, nanogels and nanospheres are also introduced in this review.

Differential Roles for Interleukin-23 and Interleukin-17 in Intestinal Immunoregulation

Interleukin-23 (IL-23) and IL-17 are cytokines currently being targeted in clinical trials. Although inhibition of both of these cytokines is effective for treating psoriasis, IL-12 and IL-23 p40 inhibition attenuates Crohn's disease, whereas IL-17A or IL-17 receptor A (IL-17RA) inhibition exacerbates Crohn's disease. This dichotomy between IL-23 and IL-17 was effectively modeled in the multidrug resistance-1a-ablated (Abcb1a(-/-)) mouse model of colitis. IL-23 inhibition attenuated disease by decreasing colonic inflammation while enhancing regulatory T (Treg) cell accumulation. Exacerbation of colitis by IL-17A or IL-17RA inhibition was associated with severe weakening of the intestinal epithelial barrier, culminating in increased colonic inflammation and accelerated mortality. These data show that IL-17A acts on intestinal epithelium to promote barrier function and provide insight into mechanisms underlying exacerbation of Crohn's disease when IL-17A or IL-17RA is inhibited.

Spontaneous and transgenic rodent models of inflammatory bowel disease

Inflammatory Bowel Disease (IBD) is a multifactorial disorder with many different putative influences mediating disease onset, severity, progression and diminution. Spontaneous natural IBD is classically expressed as Crohn's Disease (CD) and Ulcerative Colitis (UC) commonly found in primates; lymphoplasmocytic enteritis, eosinophilic gastritis and colitis, and ulcerative colitis with neuronal hyperplasia in dogs; and colitis in horses. Spontaneous inflammatory bowel disease has been noted in a number of rodent models which differ in genetic strain background, induced mutation, microbiota influences and immunopathogenic pathways. Histological lesions in Crohn's Disease feature noncaseating granulomatous inflammation while UC lesions typically exhibit ulceration, lamina propria inflammatory infiltrates and lack of granuloma development. Intestinal inflammation caused by CD and UC is also associated with increased incidence of intestinal neoplasia. Transgenic murine models have determined underlying etiological influences and appropriate therapeutic targets in IBD. This literature review will discuss current opinion and findings in spontaneous IBD, highlight selected transgenic rodent models of IBD and discuss their respective pathogenic mechanisms. It is very important to provide accommodation of induced putative deficits in activities of daily living and to assess discomfort and pain levels in the face of significant morbidity and/or mortality in these models. Epigenetic, environmental (microbiome, metabolome) and nutritional factors are important in IBD pathogenesis, and evaluating ways in which they influence disease expression represent potential investigative approaches with the greatest potential for new discoveries.