Corticotropin-releasing factor regulates TLR4 expression in the colon and protects mice from colitis.

BACKGROUND & AIMS: Defects in the colonic innate immune response have been associated with inflammatory bowel disease (IBD). Corticotropin-releasing hormone (CRH, or corticotropin-releasing factor [CRF]) is a neuropeptide that mediates the stress response in humans, is an immunomodulatory factor with proinflammatory effects, and regulates transcription of Toll-like receptors (TLR)-2 and TLR4. We investigated the role of CRF in an innate immunity-dependent mouse model of IBD. METHODS: Crh(-/-) and wild-type (Crh(+/+)) mice, which are glucocorticoid insufficient, were given dextran sodium sulfate in their drinking water to induce colitis; in some experiments, mice were also given glucocorticoids. Phenotypes of mice were compared; tissues were analyzed by histology and for expression of immune mediators. RESULTS: Crh(-/-) mice had more colonic inflammation than Crh(+/+) mice, characterized by reduced numbers of crypts and severe epithelial damage and ulcerations. Colonic tissue levels of the proinflammatory factors interleukin-12 and prostaglandin E(2) were increased in the Crh(-/-) mice. Colons of Crh(-/-) mice expressed lower levels of Tlr4 than wild-type mice before, but not after, colitis was induced. Administration of glucocorticoid at low levels did not prevent Crh(-/-) mice from developing severe colitis. Crh(-/-) mice were unable to recover from acute colitis, as indicated by their increased death rate. CONCLUSIONS: Mice deficient in CRF down-regulate TLR4 and are more susceptible to dextran sodium sulfate-induced colitis. CRF has anti-inflammatory effects in innate immunity-dependent colitis and its recovery phase; these are independent of glucocorticoid administration. CRF might therefore be developed as a therapeutic target for patients with IBD.

Corticotropin-releasing hormone deficiency is associated with reduced local inflammation in a mouse model of experimental colitis.

CRH, the hypothalamic component of the hypothalamic-pituitary adrenal axis, attenuates inflammation through stimulation of glucocorticoid release, whereas peripherally expressed CRH acts as a proinflammatory mediator. CRH is expressed in the intestine and up-regulated in patients with ulcerative colitis. However, its pathophysiological significance in intestinal inflammatory diseases has just started to emerge. In a mouse model of acute, trinitrobenzene sulfonic acid-induced experimental colitis, we demonstrate that, despite low glucocorticoid levels, CRH-deficient mice develop substantially reduced local inflammatory responses. These effects were shown by histological scoring of tissue damage and neutrophil infiltration. At the same time, CRH deficiency was found to be associated with higher serum leptin and IL-6 levels along with sustained anorexia and weight loss, although central CRH has been reported to be a strong appetite suppressor. Taken together, our results support an important proinflammatory role for CRH during mouse experimental colitis and possibly in inflammatory bowel disease in humans. Moreover, the results suggest that CRH is involved in homeostatic pathways that link inflammation and metabolism.

CCK-induced Fos expression in brain stem is enhanced after intestinal nematode infection in rats.

Intestinal infections often trigger functional bowel disorders. The nematode Nippostrongylus brasiliensis induces post-infective alterations mainly consisting in an intestinal mast cell hyperplasia. Mast cells contact vagal afferent nerve fibres. Therefore, it is possible that the anatomical sequels of intestinal nematode infection induce long term alterations in the mediation of afferent signals from the gut to the brain. To test this hypothesis, we examined hindbrain expression of Fos immunoreactivity following systemic cholecystokinin (CCK) administration in control rats and 35 days after N. brasiliensis infection. In controls, Fos was expressed in the area postrema and the nucleus of solitary tract. After infection, this expression was increased by 262 and 157%, respectively. We conclude that an intestinal infection, at least in this model, is followed by an enhancement of the activation of hindbrain sites by CCK.

micro-Opioid receptor activation prevents acute hepatic inflammation and cell death.

BACKGROUND AND AIMS: The detrimental impact of opioid agonist on the clinical management of inflammatory diseases remains elusive. Given the anti-inflammatory properties of the mu-opioid receptor (MOR) agonists at the intestinal barrier, we hypothesised that MOR activation might also dampen acute hepatic inflammation and cell death-major determinants in the pathogenesis of liver diseases. PATIENTS AND METHODS: The expression of MOR in liver biopsy specimens and peripheral blood mononuclear cells of untreated patients with chronic hepatitis C virus infection and controls, primary hepatocytes and cell lines was determined by quantitative PCR, immunoblotting and/or immunohistochemistry. The effects of peripheral MOR agonist (d-Ala2,NMe-Phe4,Gly5-ol (DAMGO)) and/or antagonist (naloxone methiodide) were explored in two models of acute hepatitis in mice. MOR-deficient mice were used to evaluate the essential regulatory role of MOR during carbon tetrachloride (CCl(4))-induced hepatitis. The role of DAMGO in cell death was investigated using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) analysis and quantification of lactate dehydrogenase release. RESULTS: The key role of MOR in the prevention of acute hepatic inflammation and cell death in vivo and in vitro is reported. Whereas MOR gene expression increased transiently in the model of acute liver injury and TNFalpha-treated HepG2 cells, an impaired expression of MOR mRNA in human chronic hepatitis C samples was found. Furthermore, preventive administration of the selective MOR agonist DAMGO enhanced hepatoprotective-signalling pathways in vivo that were blocked by using naloxone methiodide. Consistently, genetic and pharmacological inhibition of MOR enhanced the severity associated with experimental hepatotoxin-induced hepatitis. Finally, treatment with DAMGO was shown to prevent cell death in vitro in HepG2 cells in a MOR-dependent manner and to prevent concanavalin A- and CCl(4)-induced cell death in vivo, providing a possible explanation for the anti-inflammatory role of MOR activation in the liver. CONCLUSIONS: The results indicate that MOR agonists may prevent acute hepatitis and hold promising therapeutic use to maintain remission in both chronic inflammatory bowel and liver diseases.

Urocortin II mediates pro-inflammatory effects in human colonocytes via corticotropin-releasing hormone receptor 2alpha.

BACKGROUND/AIMS: Urocortin II (UcnII) is a neuropeptide that binds with high affinity to the corticotropin-releasing hormone receptor 2 (CRHR2) in peripheral tissues. UcnII is synthesised in the intestine, but its role in human intestinal inflammation is largely unknown. METHODS: Responses of human colonic epithelial cells expressing CRHR2 to stimulation by UcnII were measured using ELISA, western blot analysis, real-time reverse transcription-PCR (RT-PCR) and interleukin (IL)8 promoter activity. Expression levels of CRHR2 and UcnII in human colitis were determined by immunofluorescence and real-time RT-PCR in mucosal biopsies from patients with Crohn's and ulcerative colitis, and in human intestinal xenografts after exposure to Clostridium difficile toxin A. RESULTS: It is reported here that expression of CRHR2 mRNA and protein in human colonic epithelial cells (HT-29) are increased by exposure to C difficile toxin A or tumour necrosis factor (TNF)alpha. Stimulation of non-transformed NCM460 colonocytes overexpressing CRHR2alpha receptor with UcnII resulted in a time- and concentration-dependent increase in IL8 production. UcnII stimulation also led to activation of nuclear factor-kappaB (NF-kappaB) and mitogen-acivated protein (MAP) kinase in these cells, as evidenced by degradation of IkappaBalpha and phosphorylation of the p65 subunit of NF-kappaB and extracellularly regulated kinase (ERK) 1/2. Furthermore, expression of UcnII and CRHR2 mRNA was increased in mucosal samples of patients with inflammatory bowel disease, and after exposure of human intestinal xenografts to C difficile toxin A. CONCLUSIONS: These results suggest that UcnII has pro-inflammatory effects in human intestinal cells via the CRHR2alpha receptor and may play an important role in the pathophysiology of colitis in humans.

Interleukin-6 genetic ablation protects from trinitrobenzene sulfonic acid-induced colitis in mice. Putative effect of antiinflammatory cytokines.

BACKGROUND: Interleukin (IL)-6 is a proinflammatory cytokine implicated in the pathogenesis of inflammatory bowel disease. IL-6 is locally upregulated in inflammatory bowel disease patients and in murine models of experimental colitis. Treatment with anti-IL-6 receptor antibody ameliorates intestinal inflammation. OBJECTIVE: It was the aim of this study to investigate the role of genetic IL-6 deficiency in trinitrobenzene sulfonic acid (TNBS)-mediated colitis, an experimental model inflammation that shares several features with Crohn's disease in humans. METHODS: Acute colitis was induced in wild-type and IL-6-deficient (Il-6(-/-)) mice by intracolonic administration of TNBS. Forty-eight hours after treatment, the local and systemic features of inflammation, i.e. food intake, weight loss, histological markers of colitis, cytokine expression by real-time PCR, food intake and body weight changes, were assessed. RESULTS: In wild-type mice, TNBS administration increased both IL-6 serum levels and local expression of IL-6 by 36 and 9 fold, respectively, compared with control, vehicle-injected mice. Compared with the wild-type mice, the Il-6(-/-) mice had significantly reduced intestinal inflammation as evidenced by epithelial damage, neutrophil infiltration, colon thickness and proinflammatory cytokine expression, following treatment with TNBS. Moreover, baseline levels of the antiinflammatory cytokines IL-10 and tumor growth factor-beta were significantly elevated in Il-6(-/-)compared with the wild-type mice. CONCLUSIONS: Our results demonstrate that Il-6(-/-)are partially protected from the development of TNBS-induced acute experimental colitis, most likely via their significantly elevated baseline levels of antiinflammatory cytokines.

No evidence for an involvement of the p38 and JNK mitogen-activated protein in inflammatory bowel diseases.

Involvement of mitogen-activated protein (MAPK) in inflammatory bowel disease (IBD) remains enigmatic. We sought to evaluate the expression and activity of p38 and JNK MAPK in IBD and 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis; and the effects of a p38 inhibitor, SB203580, in TNBS colitis. P38 and JNK were quantified in colonic mucosa of 28 IBD patients and 19 controls and in 77 TNBS or control mice treated or not with SB203580. Colitis severity was assessed by survival, macroscopic and microscopic scoring, and molecular markers. Expression and activity of p38 and JNK were similar in IBD patients and controls and not modified by inflammation. In mice, p38 and JNK expression or activity did not increase following the induction of colitis. SB203580 decreased the p38 activity but displayed no clinical nor biological therapeutic effect. In conclusion, these results minimize the role of p38 and JNK in inflammatory colitis and the interest of p38 as a therapeutic target in IBD.

Alteration of CCK-induced satiety in post-Nippostrongylus brasiliensis-infected rats.

In rats, the nematode Nippostrongylus brasiliensis induces an intestinal inflammation, but after the inflammation had resolved and the worm burden eliminated, morphological alterations of the intestinal wall, mainly consisting of mast cell hyperplasia and enteric nerve remodeling, persist for several weeks. Intestinal signals reaching the brain through the vagus nerve and involving neuropeptides such as CCK, play a role in the control of food intake. Our hypothesis was that neuroimmune alterations of the intestine may alter this control. This work was aimed to evaluate whether post-infection alterations of the intestinal wall may affect the satiety effects of CCK and further, the role of mast cells and their mediators, histamine and serotonin, in post-N. brasiliensis-infected rats. In basal conditions, food intake was not different in control and post-infected groups of rats. Post-infected rats were characterized by prolonged satiety effects of both CCK and histamine but not serotonin. The prolonged effect of CCK was reduced when mast cells were previously stabilized by ketotifen, which had no effect per se on food intake. No difference was observed in the increase of food intake induced by CCK-A and CCK-B receptor antagonists in both control and post-infected rats. Mast cell degranulation with compound 48/80 induced severe anorectic effects that lasted for less than 24h in post-infected rats and as long as 6 days in controls. Thus, in our experimental conditions, i.e., within 30-50 days post-N. brasiliensis infection, we observed an enhancement of the anorectic effect of exogenous CCK involving mast cell degranulation and histamine.

Corticotropin-releasing hormone (CRH) requirement in Clostridium difficile toxin A-mediated intestinal inflammation.

Clostridium difficile, the causative agent of antibiotic-associated colitis, mediates inflammatory diarrhea by releasing toxin A, a potent 308-kDa enterotoxin. Toxin A-induced inflammatory diarrhea involves many steps, including mucosal release of substance P (SP) corticotropin-releasing hormone (CRH) and neutrophil transmigration. Here we demonstrate that, compared with wild type, mice genetically deficient in CRH (Crh(-/-)) have dramatically reduced ileal fluid secretion, epithelial cell damage, and neutrophil transmigration 4 h after intraluminal toxin A administration. This response is associated with diminished mucosal activity of the neutrophil enzyme myeloperoxidase compared with that of wildtype mice. In wild-type mice, toxin A stimulates an increase in intestinal SP content compared with buffer administration. In contrast, toxin A administration in Crh(-/-) mice fails to result in an increased SP content. Moreover, immunohistochemical experiments showed that CRH and SP are colocalized in some enteric nerves of wild-type mice, and this colocalization is more evident after toxin A administration. These results provide direct evidence for a major proinflammatory role for CRH in the pathophysiology of enterotoxin-mediated inflammatory diarrhea and indicate a SP-linked pathway.