Future of IBD pathogenesis: how much work is left to do?

Expression of IL-1 and IL-10 mRNAs in colonic tissue of ulcerative colitis rats with abnormal sapra syndrome

AIM

To investigate the role of interleukin (IL)-1α, IL-1β and IL-10 in the pathogenesis and development of ulcerative colitis in rats with abnormal sapra syndrome.

METHODS

A rat model of abnormal sapra syndrome was used to develop UC using trinitro-benzene-sulfonic acid (TNBS)/ethanol. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was used to detect the differences in IL-1α, IL-1β and IL-10 mRNA expression levels in the colonic tissues between normal rats (control group) and UC rats with abnormal sapra syndrome (model group).

RESULTS

Rat signs, symptoms and colonic mucosa damage suggested that UC with abnormal sapra syndrome was successfully induced. qRT-PCR results showed that compared with the normal group, the expression of IL-1α, IL-1β and IL-10 mRNAs was significantly up-regulated in the model group (P < 0.05).

CONCLUSION

Imbalance of inflammatory factors may occur in colon tissue of UC rats with abnormal sapra syndrome.

Establishment of a rat model of ulcerative colitis with abnormal sapra syndrome of traditional Uyghur medicine and detection of changes in inflammation related factors in colon tissue of this model

AIM

To develop a rat model of ulcerative colitis (UC) with abnormal sapra syndrome and detect the changes in inducible nitric oxide synthase (iNOS) and endothelial nitric oxide synthase (eNOS) hnRNA and mRNA expression in colon tissues of this model.

METHODS

Based on a rat model of abnormal sapra syndrome, trinitrobenzene sulfonic acid/ethanol was used to induce UC in rats with abnormal sapra syndrome. Rats were randomly divided into two groups: normal group and UC with abnormal sapra syndrome model group. Quantitative RT-PCR was used to detect the differences in iNOS and eNOS hnRNA and mRNA expression in colon tissues of rats in the two groups.

RESULTS

UC with abnormal sapra syndrome was successfully induced as evidenced by the presence of anticipated signs, symptoms and colonic mucosa damage. Compared with the normal group, the expression of iNOS hnRNA in colon tissue was significantly upregulated in the model group (P < 0.05), but the expression of eNOS hnRNA in colon tissue showed no statistical difference between the two groups (P > 0.05). The expression of iNOS and eNOS mRNA was significantly upregulated in the model group compared with the normal group (P < 0.05).

CONCLUSION

The inflammatory factors iNOS and eNOS are involved in the development of UC in rats with abnormal sapra syndrome, and changes in inflammation related factors are mediated by a post-transcriptional regulatory mechanism.

CD69 is the crucial regulator of intestinal inflammation: a new target molecule for IBD treatment?

CD69 has been identified as an early activation marker of lymphocytes. However, recent work has indicated that CD69 plays an essential role for the regulation of inflammatory processes. Particularly, CD69 is highly expressed by lymphocytes at mucosal sites being constantly exposed to the intestinal microflora (one of the nature's most complex and most densely populated microbial habitats) and food antigens, while only a small number of circulating leukocytes express this molecule. In this review we will discuss the role of CD69 in mucosal tissue and consider CD69 as a potential target for the development of novel treatments of intestinal inflammation.

Efficacy profiles for different concentrations of Lactobacillus acidophilus in experimental colitis

AIM: To determine the efficacy profiles of different concentrations of Lactobacillus acidophilus (L. acidophilus) for treating colitis using an experimental murine model.

METHODS: Colitis was established in 64 BALB/c mice by adding 5% dextran sodium sulfate (DSS) to the drinking water and allowing ad libitum access for 7 d. The mice were then randomly divided into the following control and experimental model groups (n = 8 each; day 0): untreated model control; negative-treatment model control (administered gavage of 1 mL/10 g normal saline); experimental-treatment models C4-C8 (administered gavage of 10⁴, 10⁵, 10⁶, 10⁷, or 10⁸ CFU/10 g L. acidophilus, respectively); positive-treatment model control (administration of the anti-inflammatory agent prednisone acetate at 45 μg/10 g). Eight mice given regular water (no DSS) and no subsequent treatments served as the normal control group. Body weight, fecal traits, and presence of fecal occult blood were assessed daily. All animals were sacrificed on post-treatment day 7 to measure colonic length, perform histological scoring, and quantify the major bacteria in the proximal and distal colon. Intergroup differences were determined by one-way ANOVA and post-hoc Student-Newman-Keuls comparison.

RESULTS: All treatments (L. acidophilus and prednisone acetate) protected against colitis-induced weight loss (P < 0.05 vs model and normal control groups). The extent of colitis-induced colonic shortening was significantly reduced by all treatments (prednisone acetate > C4 > C5 > C7 > C8 > C6; P < 0.05 vs untreated model group), and the C6 group showed colonic length similar to that of the normal control group (P > 0.05). The C6 group also had the lowest disease activity index scores among the model groups. The bacterial profiles in the proximal colon were similar between all of the experimental-treatment model groups (all P > 0.05). In contrast, the bacterial profile in the distal colon of the C6 group showed the distinctive features (P < 0.05 vs all other experimental-treatment model groups) of Lactobacillus sp. and Bifidobacterium sp. being the most abundant bacteria and Staphylococcus aureus being the least abundant bacteria.

CONCLUSION: The most therapeutically efficacious concentration of L. acidophilus (10⁶ CFU/10 g) may exert its effects by modulating the bacterial profile in the distal colon.

Expression of PPAR γ in intestinal epithelial cells is dispensable for the prevention of colitis by dietary abscisic acid

BACKGROUND & AIMS

Dietary abscisic acid (ABA) has shown efficacy in ameliorating experimental IBD in mice through mechanisms requiring expression of peroxisome proliferator activated-receptor γ (PPAR γ) in immune cells. The goal of this study was to determine whether PPAR γ expression in colonic epithelial cells is required for the anti-inflammatory actions of ABA.

METHODS

Conditional knockout mice expressing a transgenic recombinase in intestinal epithelial cells under the control of a villin promoter (PPAR γ flfl; Villin Cre+ or VC+) with defective expression of PPAR γ in intestinal cells (IEC) and PPAR γ-expressing wild type (PPAR γ flfl; Villin Cre- or VC-) mice in a C57BL/6 background were fed diets with and without ABA (0.1 g/kg) for 35 days and challenged with 2.5% dextran sodium sulfate (DSS) in the drinking water for 7 days. Clinical disease severity was assessed daily and colonic lesions on day 7 through macroscopic and histopathological examination. Immune cell phenotypes were examined systemically and at the mesenteric lymph nodes (MLN). Epithelial gene expression was assayed in the colon.

RESULTS

Dietary ABA-supplementation prevented colitis, reduced disease severity, improved colonic histopathology, and upregulated epithelial lanthionine synthetase C-like protein 2 (LANCL2) expression in VC+ mice. Dietary ABA significantly increased the percentages of MLN CD4+IL-10+ T cells, and blood CD4+CD25+FoxP3+ T cells and CD8+IL-10+ T cells.

CONCLUSION

Expression of PPAR γ in IECs was not required for the anti-inflammatory efficacy of ABA in IBD. LANCL2 in IECs and T cell-derived IL-10 may be implicated in the mechanism underlying ABA's immune modulatory activity in IBD.

Etiology of inflammatory bowel disease: a unified hypothesis

Inflammatory bowel disease (IBD), including both ulcerative colitis (UC) and Crohn's disease (CD), emerged and dramatically increased for about a century. Despite extensive research, its cause remains regarded as unknown. About a decade ago, a series of findings made me suspect that saccharin may be a key causative factor for IBD, through its inhibition on gut bacteria and the resultant impaired inactivation of digestive proteases and over digestion of the mucus layer and gut barrier (the Bacteria-Protease-Mucus-Barrier hypothesis). It explained many puzzles in IBD such as its emergence and temporal changes in last century. Recently I further found evidence suggesting sucralose may be also linked to IBD through a similar mechanism as saccharin and have contributed to the recent worldwide increase of IBD. This new hypothesis suggests that UC and CD are just two symptoms of the same morbidity, rather than two different diseases. They are both caused by a weakening in gut barrier and only differ in that UC is mainly due to increased infiltration of gut bacteria and the resultant recruitment of neutrophils and formation of crypt abscess, while CD is mainly due to increased infiltration of antigens and particles from gut lumen and the resultant recruitment of macrophages and formation of granulomas. It explained the delayed appearance but accelerated increase of CD over UC and many other phenomena. This paper aims to provide a detailed description of a unified hypothesis regarding the etiology of IBD, including the cause and mechanism of IBD, as well as the relationship between UC and CD.