The leptin defense against wasting is abolished in the IL-2-deficient mouse model of inflammatory bowel disease

Implications the Role of miR-155 in the Pathogenesis of Autoimmune Diseases

MicroRNAs (miRNAs) are small noncoding conserved RNAs containing 19 to 24 nucleotides that are regulators of post-translational modifications and are involved in the majority of biological processes such as immune homeostasis, T helper cell differentiation, central and peripheral tolerance, and immune cell development. Autoimmune diseases are characterized by immune system dysregulation, which ultimately leads to destructive responses to self-antigens. A large body of literature suggests that autoimmune diseases and immune dysregulation are associated with different miRNA expression changes in the target cells and tissues of adaptive or innate immunity. miR-155 is identified as a critical modulator of immune responses. Recently conducted studies on the expression profile of miR-155 suggest that the altered expression and function of miR-155 can mediate vulnerability to autoimmune diseases and cause significant dysfunction of the immune system.

Corticotropin-Releasing Hormone Receptor Alters the Tumor Development and Growth in Apcmin/+ Mice and in a Chemically-Induced Model of Colon Cancer

The neuroendocrine circuit of the corticotropin-releasing hormone (CRH) family peptides, via their cognate receptors CRHR1 and CRHR2, copes with psychological stress. However, peripheral effects of the CRH system in colon cancer remains elusive. Thus, we investigate the role of CRHR1 and CRHR2 in colon cancer. Human colon cancer biopsies were used to measure the mRNA levels of the CRH family by quantitative real-time PCR. Two animal models of colon cancer were used: Apcmin/+ mice and azoxymethane (AOM)/dextran sulfate sodium (DSS)-treated mice. The mRNA levels of CRHR2 and UCN III are reduced in human colon cancer tissues compared to those of normal tissues. Crhr1 deletion suppresses the tumor development and growth in Apcmin/+ mice, while Crhr2 deficiency exacerbates the tumorigenicity. Crhr1 deficiency not only inhibits the expression of tumor-promoting cyclooxygenase 2, but also upregulates tumor-suppressing phospholipase A2 in Apcmin/+ mice; however, Crhr2 deficiency does not change these expressions. In the AOM/DSS model, Crhr2 deficiency worsens the tumorigenesis. In conclusion, Crhr1 deficiency confers tumor-suppressing effects in Apcmin/+ mice, but Crhr2 deficiency worsens the tumorigenicity in both Apcmin/+ and AOM/DSS-treated mice. Therefore, pharmacological inhibitors of CRHR1 or activators of CRHR2 could be of significance as anti-colon cancer drugs.

Genistein induces macrophage polarization and systemic cytokine to ameliorate experimental colitis

Mucosal changes in Crohn’s disease (CD) and ulcerative colitis (UC), two major forms of inflammatory bowel disease (IBD), are characterized by a prominent infiltration of inflammatory cells including lymphocytes, macrophages, T cells and neutrophils. The precise etiology of IBD is unknown but it involves a complex interplay of factors associated with the immune system, environment, host genotype and enteric commensal bacteria. As there is no known safe cure for IBD, natural alternative therapeutic options without side effects are urgently needed. To this end, Soy-based foods, which have been eaten for centuries in Asian countries, have potential benefits, including lowering the incidence of coronary heart disease, atherosclerosis, type-2 diabetes, allergic response, and autoimmune diseases. This study describes the effect of Soy isoflavons 4', 5, 7 Trihydroxyisoflavone (genistein) on dextran sodium sulphate (DSS) induced experimental colitis. The extent and severity of disease was analyzed through body weight, histopathological analysis, cellular immune response, systemic cytokine levels, and inflammation score using a disease activity index. Genistein treatment significantly attenuated DSS-induced colitis severity and resulted in increase in body weight, colon length and reduction in inflammation score. Genistein also skews M1 macrophages towards the M2 phenotype. Further, gen also reduced the systemic cytokine levels as compared to vehicle control. This serves as the first detailed study towards natural soya based product that shows the polarization of M1 towards M2 macrophages, and reduction of systemic cytokine in part to attenuate the colitis symptoms. Thus, our work demonstrates that genistein, a soya compound, may be useful for the treatment of IBD.

Adipokines and the role of visceral adipose tissue in inflammatory bowel disease

Recently, adipocytes have been recognized as actively participating in local and systemic immune responses via the secretion of peptides detectable in relevant levels in the systemic circulation, the so-called "adipo(cyto)kines". Multiple studies appearing within the last 10-15 years have focused on the possible impact of adipose tissue depots on inflammatory bowel disease (IBD). Consequently, various hypotheses regarding the role of different adipokines in inflammatory diseases in general and in intestinal inflammatory processes in particular have been developed and have been further refined in recent years. After a focused summary of the data reported concerning the impact of visceral adipose tissue on IBD, such as Crohn's disease and ulcerative colitis, our review focuses on recent developments indicating that adipocytes as part of the innate immune system actively participate in antimicrobial host defenses in the context of intestinal bacterial translocation, which are of utmost importance for the homeostasis of the whole organism. Modulators of adipose tissue function and regulators of adipokine secretion, as well as modifiers of adipocytic pattern recognition molecules, might represent future potential drug targets in IBD.

Chemokine and cytokine levels in inflammatory bowel disease patients

Crohn's disease (CD) and ulcerative colitis (UC), two forms of inflammatory bowel disease (IBD), are chronic, relapsing, and tissue destructive lesions that are accompanied by the uncontrolled activation of effector immune cells in the mucosa. Recent estimates indicate that there are 1.3 million annual cases of IBD in the United States, 50% of which consists of CD and 50% of UC. Chemokines and cytokines play a pivotal role in the regulation of mucosal inflammation by promoting leukocyte migration to sites of inflammation ultimately leading to tissue damage and destruction. In recent years, experimental studies in rodents have led to a better understanding of the role played by these inflammatory mediators in the development and progression of colitis. However, the clinical literature on IBD remains limited. Therefore, the aim of this study was to evaluate systemic concentrations of key chemokines and cytokines in forty-two IBD patients with a range of disease activity compared to levels found in ten healthy donors. We found a significant increase in an array of chemokines including macrophage migration factor (MIF), CCL25, CCL23, CXCL5, CXCL13, CXCL10, CXCL11, MCP1, and CCL21 in IBD patients as compared to normal healthy donors (P<0.05). Further, we also report increases in the inflammatory cytokines IL-16, IFN-γ, IL-1β and TNF-α in IBD patients when compared to healthy donors (P<0.05). These data clearly indicate an increase in circulating levels of specific chemokines and cytokines that are known to modulate systemic level through immune cells results in affecting local intestinal inflammation and tissue damage in IBD patients. Blockade of these inflammatory mediators should be explored as a mechanism to alleviate or even reverse symptoms of IBD.

miR-155 deficiency protects mice from experimental colitis by reducing T helper type 1/type 17 responses

Inflammatory bowel disease (IBD), a chronic intestinal inflammatory condition that affects millions of people worldwide, results in high morbidity and exorbitant health-care costs. The critical features of both innate and adaptive immunity are to control inflammation and dysfunction in this equilibrium is believed to be the reason for the development of IBD. miR-155, a microRNA, is up-regulated in various inflammatory disease states, including IBD, and is a positive regulator of T-cell responses. To date, no reports have defined a function for miR-155 with regard to cellular responses in IBD. Using an acute experimental colitis model, we found that miR-155(-/-) mice, as compared to wild-type control mice, have decreased clinical scores, a reversal of colitis-associated pathogenesis, and reduced systemic and mucosal inflammatory cytokines. The increased frequency of CD4+ lymphocytes in the spleen and lamina propria with dextran sodium sulphate induction was decreased in miR-155(-/-) mice. Similarly, miR-155 deficiency abrogated the increased numbers of interferon-γ expressing CD4+ T cells typically observed in wild-type mice in this model. The frequency of systemic and mucosal T helper type 17-, CCR9-expressing CD4+ T cells was also reduced in miR-155(-/-) mice compared with control mice. These findings strongly support a role for miR-155 in facilitating pro-inflammatory cellular responses in this model of IBD. Loss of miR-155 also results in decreases in T helper type 1/type 17, CD11b+) and CD11c+ cells, which correlated with reduced clinical scores and severity of disease. miR-155 may serve as a potential therapeutic target for the treatment of IBD.

The emerging role of leptin antagonist as potential therapeutic option for inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic relapsing immune-mediated inflammatory disorder that affects millions of people around the world. Leptin is a satiety hormone produced primarily by adipose tissue and acts both centrally and peripherally. Leptin has been shown to play a major role in regulating metabolism, which increases during IBD progression. Leptin mediates several physiological functions including elevated blood pressure, tumorogenesis, cardiovascular pathologies and enhanced immune response in many autoimmune diseases. Recent development of a leptin mutant antagonist that blocks leptin activity raises great hope and opens up new possibilities for therapy in many autoimmune diseases including IBD. To this end, preliminary data from an ongoing study in our laboratory on pegylated leptin antagonist mutant L39A/D40A/F41A (PEG-MLA) treatment shows an inhibition of chronic colitis in IL-10-/- mice. PEG-MLA effectively attenuates the overall clinical scores, reverses colitis-associated pathogenesis including a decrease in body weight, and decreases systemic leptin level. PEG-MLA induces both central and peripheral leptin deficiency by mediating the cellular immune response. In summary, after blocking leptin activity, the correlative outcome between leptin-mediated cellular immune response, systemic leptin levels, and amount of adipose tissue together may provide new strategies for therapeutic intervention in autoimmune diseases, especially for intestinal inflammation.

Leptin antagonist ameliorates chronic colitis in IL-10⁻/⁻ mice

BACKGROUND

Although the etiology of two major forms of inflammatory bowel disease (IBD), Crohn's disease (CD) and ulcerative colitis (UC) are unknown and evidence suggests that chronic intestinal inflammation is caused by an excessive immune response to mucosal antigens. Previous studies support the role for TGF-β1 through 3 in the initiation and maintenance of tolerance via the induction of regulatory T cells (Tregs) to control intestinal inflammation. Leptin, a satiety hormone produced primarily by adipose tissue, has been shown to increase during colitis progression and is believed to contribute to disease genesis and/or progression.

AIM

We investigated the ability of a pegylated leptin antagonist (PG-MLA) to ameliorate the development of chronic experimental colitis.

RESULTS

Compared to vehicle control animals, PG-MLA treatment of mice resulted in an (1) attenuated clinical score; (2) reversed colitis-associated pathogenesis including a decrease in body weight; (3) reduced systemic and mucosal inflammatory cytokine expression; (4) increased insulin levels and (5) enhanced systemic and mucosal Tregs and CD39⁺ Tregs in mice with chronic colitis. The percentage of systemic and mucosal TGF-β1, -β2 and -β3 expressing CD4⁺ T cells were augmented after PG-MLA treatment. The activation of STAT1 and STAT3 and the expression of Smad7 were also reduced after PG-MLA treatment in the colitic mice. These findings clearly suggest that PG-MLA treatment reduces intestinal Smad7 expression, restores TGF-β1-3 signaling and reduces STAT1/STAT3 activation that may increase the number of Tregs to ameliorate chronic colitis.

CONCLUSION

This study clearly links inflammation with the metabolic hormone leptin suggesting that nutritional status influences immune tolerance through the induction of functional Tregs. Inhibiting leptin activity through PG-MLA might provide a new and novel therapeutic strategy for the treatment of IBD.

Green Tea Polyphenols and Sulfasalazine have Parallel Anti-Inflammatory Properties in Colitis Models

Background: There is no cure for autoimmune chronic inflammatory bowel disease (IBD). IBD patients commonly use complementary and alternative medications of which the safety, efficacy, and interaction with standard-of-care therapies are not fully known. Thus the consequences can become life-threatening. Sulfasalazine commonly used in IBD, potentially has severe adverse effects, including infertility, pulmonary fibrosis, lack of response, and ultimately patients may require intestinal resection. We hypothesized that green tea polyphenols (GrTP, EGCG) and sulfasalazine have similar anti-inflammatory properties.

Methods: BALB/c mice received Dextran sodium sulfate (DSS) to induce colitis (ulcerative colitis model). Exposure of IL-10 deficient mice (BALB/c-background) to normal microbiota provoked enterocolitis (mimics Crohn’s disease). Animals were treated with agents incorporated into daily diets. Control animals received sham treatment.

Results: DSS-treated animals developed severe bloody diarrhea and colitis (score 0–4, 3.2 ± 0.27). IL-10 deficient mice developed severe enterocolitis as manifested by diarrhea, rectal prolapse, and colonic lesions. Animals tolerated regimens (GrTP, EGCG, sulfasalazine) with no major side effects, and further developed less severe colitis. IL-10 deficient animals became moribund on high dose, while tolerated low and Mid doses with significant improved symptoms of enterocolitis. GrTP, EGCG, and sulfasalazine significantly ameliorated colonic damage and histological scores in treated animals in a similar manner (GrTP vs. DSS p < 0.05; EGCG, sulfasalazine vs. DSS p < 0.01). The inflammatory markers TNFα (3-fold), IL-6 (14-fold), and serum amyloid A (40-fold) increased in colitic animals and significantly decreased with treatment regiments. In contrast, circulatory leptin levels decreased in colitic animals (twofold). EGCG additionally reduced leptin levels (p < 0.01) while GrTP and sulfasalazine had no effect on leptin levels (p < 0.05). Hepatic and colonic antioxidants were significantly depleted in colitic animals and treatment regiments significantly restored antioxidants levels.

Conclusion: GrTP and EGCG improved antioxidants levels and attenuated severity of colitis analogous to sulfasalazine. Future studies will reveal whether polyphenols can become an alternative/additive therapy for IBD therapy in humans.

Lactobacillus plantarum consumption increases PepT1-mediated amino acid absorption by enhancing protein kinase C activity in spontaneously colitic mice

Although probiotic consumption has generally been shown to have many beneficial effects for the prevention and treatment of inflammatory bowel disease, the effects of Lactobacillus plantarum (LP) on intestinal nutrient absorption, particularly oligopeptide transporter 1 (PepT1)-mediated absorption of dietary protein under inflammatory conditions, has not yet been characterized. In this study, we first investigated the effects of LP consumption on plasma amino acid concentrations and PepT1-mediated absorption of cephalexin in the small intestine of wild-type (WT) mice and interleukin-10 knockout (IL-10(-/-)) mice, a model of spontaneous colitis. We then analyzed expression and distribution of PepT1 and protein kinase C (PKC) activity in the jejunum of these mice. LP consumption (10(9) colony-forming units/0.5 mL) delivered by gavage once per day for 4 wk increased the total plasma amino acid concentration and the concentration of plasma cephalexin through enhancement of PepT1-mediated uptake in LP treated IL-10(-/-) mice compared with IL-10(-/-) mice. However, Western blotting and quantitative PCR analysis revealed no significant differences in PepT1 protein and mRNA expression between LP-treated and untreated mice. Additionally, immunofluorescence analysis showed that PepT1 did not appear to be mislocalized in IL-10(-/-) mice. Interestingly, IL-10(-/-) mice had significantly lower PKC activity and expression of phosphorylated PKC compared with WT mice, and these decreases could be prevented by LP treatment. These data suggest that consumption of LP enhances PepT1-mediated amino acid absorption, likely through alterations in PKC activity, as opposed to changes in expression or distribution of PepT1 in the small intestine of IL-10(-/-) mice.

Bacillus polyfermenticus ameliorates colonic inflammation by promoting cytoprotective effects in colitic mice

Although human consumption of Bacillus polyfermenticus provides several health benefits, the probiotic effect of this bacterium against colonic inflammation has not yet, to our knowledge, been studied. Therefore, we induced colitis in mice by oral or intrarectal administration of dextran sodium sulfate (DSS) or trinitrobenzenosulfonic acid (TNBS), respectively, and investigated the effect of B. polyfermenticus on colitis. We found that mice treated with DSS or TNBS along with B. polyfermenticus had reduced mortality and severity of colitis (weight loss, diarrhea, and mucosal damages) than mice treated with DSS or TNBS alone. B. polyfermenticus also reduced the expression of inflammatory molecules, including chemokine (C-X-C motif) ligand 1, intercellular adhesion molecule, and tumor necrosis factor-alpha, but enhanced the expression of the antiinflammatory cytokine interleukin-10 in the inflamed mouse colon. Moreover, B. polyfermenticus suppressed apoptosis both in vivo in inflamed colonic mucosa and in vitro in colonic epithelial cells stimulated with apoptosis-inducing agents (FasL or Clostridium difficile Toxin A) when the apoptotic response was determined by a terminal deoxynucleotidyl transferase dUTP nick end labeling assay and cleavage of poly(ADP-ribose) polymerase or caspase-3, respectively. Treating colonic epithelial cells with B. polyfermenticus-conditioned medium (BPCM) enhanced cell proliferation and induced the phosphoinositide 3-kinases/Akt signaling pathway, suggesting that this bacterium can promote epithelial cell proliferation. BPCM also promoted the migration of colonic epithelial cells. These data suggest that B. polyfermenticus ameliorates colonic inflammation by suppressing apoptosis and promoting epithelial cell proliferation and migration.

Mice with experimental colitis show an altered metabolism with decreased metabolic rate

Patients with inflammatory bowel disease (IBD) suffer from body weight loss, malnutrition, and several other metabolic alterations affecting their quality of life. The aim of this study was to investigate the metabolic changes that may occur during acute and chronic colonic inflammation induced by dextran sulfate sodium (DSS) in mice. Clinical symptoms and inflammatory markers revealed the presence of an ongoing inflammatory response in the DSS-treated mice. Mice with acute inflammation had decreased body weight, respiratory exchange ratios (RER), food intake, and body fat content. Mice with chronic inflammation had decreased nutrient uptake, body fat content, locomotor activity, metabolic rates, and bone mineral density. Despite this, the body weight, food and water intake, lean mass, and RER of these mice returned to values similar to those in healthy controls. Thus, murine experimental colitis is associated with significant metabolic alterations similar to IBD patients. Our data show that the metabolic responses during acute and chronic inflammation are different, although the metabolic rate is reduced in both phases. These observations suggest compensatory metabolic alterations in chronic colitis resulting in a healthy appearance despite gross colon pathology.

Leptin in immunology

Leptin is an adipokine which conveys information on energy availability. In humans, leptin influences energy homeostasis and regulates neuroendocrine function primarily in states of energy deficiency. As a cytokine, leptin also affects thymic homeostasis and, similar to other proinflammatory cytokines, leptin promotes Th1 cell differentiation and cytokine production. We review herein recent advances on the role of leptin in the pathophysiology of immune responses.

Leptin increase in multiple sclerosis associates with reduced number of CD4(+)CD25+ regulatory T cells

We analyzed the serum and cerebrospinal fluid (CSF) leptin secretion and the interaction between serum leptin and CD4(+)CD25+ regulatory T cells (T(Regs)) in naive-to-therapy relapsing-remitting multiple sclerosis (RRMS) patients. Leptin production was significantly increased in both serum and CSF of RRMS patients and correlated with IFN-gamma secretion in the CSF. T cell lines against human myelin basic protein (hMBP) produced immunoreactive leptin and up-regulated the expression of the leptin receptor (ObR) after activation with hMBP. Treatment with either anti-leptin or anti-leptin-receptor neutralizing antibodies inhibited in vitro proliferation in response to hMBP. Interestingly, in the RRMS patients, an inverse correlation between serum leptin and percentage of circulating T(Regs) was also observed. To better analyze the finding, we enumerated T(Regs) in leptin-deficient (ob/ob) and leptin-receptor-deficient (db/db) mice and observed the significant increase in T(Regs). Moreover, treatment of WT mice with soluble ObR fusion protein (ObR:Fc) increased the percentage of T(Regs) and ameliorated the clinical course and progression of disease in proteolipid protein peptide (PLP(139-151))-induced relapsing-experimental autoimmune encephalomyelitis (R-EAE), an animal model of RRMS. These findings show an inverse relationship between leptin secretion and the frequency of T(Regs) in RRMS and may have implications for the pathogenesis of and therapy for multiple sclerosis.

Anti-TNF-alpha antibody normalizes serum leptin in IL-2 deficient mice

OBJECTIVE

A recent study reports that the interleukin-2 deficient (IL-2(-/-)) mouse model of autoimmune and inflammatory bowel disease (IBD) with elevated pro-inflammatory cytokine production has elevated leptin concentrations during food deprivation. The objective of this study was to examine whether increased tumor necrosis factor-alpha (TNF-alpha), a pro-inflammatory cytokine, contributes to the abnormally elevated leptin in IL-2(-/-) mice.

METHODS

Eight week old, IL-2(-/-) and wild-type control (IL-2(+/+)), male mice were fed regular laboratory mouse food for two weeks. At the end of the study, blood was collected in the fed state, IL-2(-/-) and IL-2(+/+) mice were injected with either anti-TNF-alpha monoclonal antibody or normal saline, and blood was collected in the starved state.

RESULTS

The IL-2(-/-) mice consumed less food and lost weight. Administration of anti-TNF-alpha antibody markedly reduced serum leptin concentrations in IL-2(-/-) and control mice after food deprivation. Serum leptin in the IL-2(-/-) mice not receiving anti-TNF-alpha antibody increased significantly in the starved state. Serum concentrations of TNF-alpha were higher in IL-2(-/-) mice compared to controls in both the fed and starved state.

CONCLUSIONS

These results suggest that elevated TNF-alpha may be one mechanism for the sustained elevated leptin observed in IL-2(-/-) mice during food deprivation.