Therapeutic effect of urocortin and adrenomedullin in a murine model of Crohn's disease

Vitamin D deficiency in mice impairs colonic antibacterial activity and predisposes to colitis

Vitamin D insufficiency is a global health issue. Although classically associated with rickets, low vitamin D levels have also been linked to aberrant immune function and associated health problems such as inflammatory bowel disease (IBD). To test the hypothesis that impaired vitamin D status predisposes to IBD, 8-wk-old C57BL/6 mice were raised from weaning on vitamin D-deficient or vitamin D-sufficient diets and then treated with dextran sodium sulphate (DSS) to induce colitis. Vitamin D-deficient mice showed decreased serum levels of precursor 25-hydroxyvitamin D(3) (2.5 +/- 0.1 vs. 24.4 +/- 1.8 ng/ml) and active 1,25-dihydroxyvitamin D(3) (28.8 +/- 3.1 vs. 45.6 +/- 4.2 pg/ml), greater DSS-induced weight loss (9 vs. 5%), increased colitis (4.71 +/- 0.85 vs. 1.57 +/- 0.18), and splenomegaly relative to mice on vitamin D-sufficient chow. DNA array analysis of colon tissue (n = 4 mice) identified 27 genes consistently (P < 0.05) up-regulated or down-regulated more than 2-fold in vitamin D-deficient vs. vitamin D-sufficient mice, in the absence of DSS-induced colitis. This included angiogenin-4, an antimicrobial protein involved in host containment of enteric bacteria. Immunohistochemistry confirmed that colonic angiogenin-4 protein was significantly decreased in vitamin D-deficient mice even in the absence of colitis. Moreover, the same animals showed elevated levels (50-fold) of bacteria in colonic tissue. These data show for the first time that simple vitamin D deficiency predisposes mice to colitis via dysregulated colonic antimicrobial activity and impaired homeostasis of enteric bacteria. This may be a pivotal mechanism linking vitamin D status with IBD in humans.

Mechanisms underlying the effects of leukocyte apheresis with a fiber filter in a rat model of dextran sulfate sodium-induced colitis

While several clinical trials have suggested that leukocytapheresis (LCAP) by filtration can benefit patients with active ulcerative colitis, the mechanisms underlying these benefits are largely unknown. The aim of this study was to address the mechanisms that may underlie the therapeutic effects of LCAP using a dextran sulfate sodium-induced colitis model in rats. Treatment with the active column, but not the sham column, improved disease severity by down-regulating pro-inflammatory events, including the cell-proliferative responses and inflammatory cytokine and reactive oxygen production, as well as by up-regulating protective events, including hepatocyte growth factor production, bone marrow-derived endothelial progenitor cell induction, and colonic blood flow levels, which were mediated predominantly by calcitonin gene-related peptide. The improvement was also associated with the increase of Ki-67 labeling in the colonic epithelium. In conclusion, the LCAP procedure was used in a dextran sulfate sodium-induced colitis model in rats under extracorporeal circulation conditions. This approach down-regulated pro-inflammatory events and up-regulated protective events in association with disease improvement. These data suggest that LCAP is feasible in animals and should shed light on the mechanisms of LCAP in clinical settings.

Adrenomedullin treatment reduces intestinal inflammation and maintains epithelial barrier function in mice administered dextran sulphate sodium

Hyperactivation and hyperpermeability of the intestinal epithelium is a hallmark of IBD. AM has been shown to reduce the severity of colitis in the acetic acid and TNBS-induced colitis model, however the mechanism of the therapeutic effect of AM against the colitis has not been clarified. Here, we show that the protective capability of AM is associated with suppression of inflammation and maintenance of the intestinal epithelial barrier function. In the DSS-induced colitis model, intra-rectal AM-treated mice showed a reduction in loss of body weight and severity of colitis. AM-treatment suppressed phosphorylation of STAT1 and STAT3 in the colonic epithelium, and altered the cytokine balance in the intestinal T cells, with lower levels of IFN-gamma and TNF-alpha but higher levels of TGF-beta. Expression of the epithelial intercellular junctions such as tight and adherence junctions were sustained in the AM-treated mice. In contrast, the epithelial junctions were down-regulated in the control mice, leading to loss of epithelial barrier integrity and enhanced permeability. Collectively, these data indicate a broad spectrum of AM-induced effects with respect to protection against DSS-induced colitis, and suggest a potential therapeutic value of this treatment for IBD.

Neuropeptides and inflammatory bowel disease

PURPOSE OF REVIEW

Inflammatory bowel disease (IBD) is a chronic intestinal inflammatory condition, the pathophysiology of which is not well understood. It has, however, become increasingly evident that interactions between the enteric nervous system and the immune system play an important role in the cause of IBD. Both the enteric nervous system and the central nervous system can amplify or modulate the aspects of intestinal inflammation through secretion of neuropeptides or small molecules. The purpose of this study is to present recent data on the role that neuropeptides play in the pathophysiology of IBD.

RECENT FINDINGS

The best studied of the neuropeptides thought to play a role in the pathogenesis of IBD include substance P, corticotropin-releasing hormone, neurotensin, and vasoactive intestinal peptide; small molecules include acetylcholine and serotonin. Recently discovered functions of each of these neuropeptides with a discussion of implications of the data for therapy are reviewed.

SUMMARY

Although the available data suggest an important role for neuropeptides in the pathophysiology of intestinal inflammation, there does yet not appear to be a function that can be taken as established for any of these molecules. The complexity of neuroimmune-endocrine systems, conflicting study results and dual mechanisms of action, warrant further research in this field. Clarification of the molecular mechanisms of action of neuropeptides and on immune and inflammatory reactions will likely yield new treatment options in the future.

Adrenomedullin reduces intestinal epithelial permeability in vivo and in vitro

Leakage of the gut mucosal barrier in the critically ill patient may allow translocation of bacteria and their virulence factors, thereby perpetuating sepsis and inflammation. Present evidence suggests that adrenomedullin (AM) improves endothelial barrier function and stabilizes circulatory function in systemic inflammation. We tested the hypothesis that exogenously applied AM stabilizes gut epithelial barrier function. Infusion of Staphylococcus aureus alpha-toxin induced septic shock in rats. AM infusion in a therapeutic setting reduced translocation of labeled dextran from the gut into the systemic circulation in this model. AM also reduced alpha-toxin and hydrogen peroxide (H2O2)-related barrier disruption in Caco-2 cells in vitro and reduced H2O2-related rat colon barrier malfunction in Ussing chamber experiments. AM was shown to protect endothelial barrier function via cAMP elevation, but AM failed to induce cAMP accumulation in Caco-2 cells. cAMP is degraded via phosphodiesterases (PDE), and Caco-2 cells showed high activity of cAMP-degrading PDE3 and 4. However, AM failed to induce cAMP accumulation in Caco-2 cells even in the presence of sufficient PDE3/4 inhibition, whereas adenylyl cyclase activator forskolin induced strong cAMP elevation. Furthermore, PDE3/4 inhibition neither amplified AM-induced epithelial barrier stabilization nor affected AM cAMP-related rat colon short-circuit current, furthermore indicating that AM may act independently of cAMP in Caco-2 cells. Finally, experiments using chemical inhibitors indicated that PKC, phosphatidylinositide 3-kinase, p38, and ERK did not contribute to AM-related stabilization of barrier function in Caco-2 cells. In summary, during severe inflammation, elevated AM levels may substantially contribute to the stabilization of gut barrier function.

Generating tolerogenic dendritic cells with neuropeptides

Induction of antigen-specific tolerance is critical to prevent autoimmunity, to maintain immune homeostasis, and to achieve transplant tolerance. In addition to their classic role as sentinels of the immune response, dendritic cells (DCs) play important roles in maintaining peripheral tolerance through the induction/activation of regulatory T (Treg) cells. The possibility of generating tolerogenic DCs opens new therapeutic perspectives in autoimmune and inflammatory diseases. Characterizing endogenous factors that contribute to the development of tolerogenic DCs is highly relevant. Some neuropeptides that are produced during the ongoing inflammatory response have emerged as endogenous anti-inflammatory agents that participate in the regulation of the processes that ensure self-tolerance. Here, we examine the latest research findings indicating that the role of these neuropeptides in immune tolerance is partially mediated through differential effects on DC functions, which depend on the differentiation and activation states. Importantly, neuropeptides such as vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide, and melanocyte-stimulating hormone have demonstrated an ability to induce tolerogenic DCs with the capacity to generate CD4 and CD8 Treg cells. The possibility of generating or expanding ex vivo tolerogenic DCs with neuropeptides indicates the therapeutic potential for autoimmune diseases and graft-versus-host disease after allogeneic transplantation in humans.

Nociceptin-induced modulation of human T cell function

There is an accumulating evidence for the immunoregulatory role of the neuropeptide, nociceptin/orphanin FQ (N/OFQ) however its role on T cell function requires elucidation. This study has demonstrated an inhibitory role for N/OFQ on SEB-activated T cell function. N/OFQ decreases T cell proliferation, which is abrogated when the costimulatory receptors CD80 and CD86 are blocked. In addition, evidence suggests that the immunoregulatory cytokines TGF-beta, IFN-gamma and nitric oxide (NO) are involved in the N/OFQ effect. N/OFQ also, through involvement of IFN and NO, induces the expression of the immunosuppressive modulator indoleamine 2,3-dioxygenase (IDO), suggesting a central role for IDO in the N/OFQ effect on T cell proliferation. The data presented in this report indicate a multi-faceted mechanism of action used by N/OFQ to modulate T cell function.

Mitomycin C-treated antigen-presenting cells as a tool for control of allograft rejection and autoimmunity: from bench to bedside

Cells have been previously used in experimental models for tolerance induction in organ transplantation and autoimmune diseases. One problem with the therapeutic use of cells is standardization of their preparation. We discuss an immunosuppressive strategy relying on cells irreversibly transformed by a chemotherapeutic drug. Dendritic cells (DCs) of transplant donors pretreated with mitomycin C (MMC) strongly prolonged rat heart allograft survival when injected into recipients before transplantation. Likewise, MMC-DCs loaded with myelin basic protein suppressed autoreactive T cells of MS patients in vitro and prevented experimental autoimmune encephalitis in mice. Comprehensive gene microarray analysis identified genes that possibly make up the suppressive phenotype, comprising glucocorticoid leucine zipper, immunoglobulin-like transcript 3, CD80, CD83, CD86, and apoptotic genes. Based on these findings, a hypothetical model of tolerance induction by MMC-treated DCs is delineated. Finally, we describe the first clinical application of MMC-treated monocyte-enriched donor cells in an attempt to control the rejection of a haploidentical stem cell transplant in a sensitized recipient and discuss the pros and cons of using MMC-treated antigen-presenting cells for tolerance induction. Although many questions remain, MMC-treated cells are a promising clinical tool for controlling allograft rejection and deleterious immune responses in autoimmune diseases.

The CRF-like peptide urocortin greatly attenuates loss of extracellular striatal dopamine in rat models of Parkinson's disease by activating CRF(1) receptors

We have recently observed that the corticotrophin releasing factor (CRF) related peptide urocortin reverses key features of nigrostriatal damage in two paradigms of Parkinson's disease. Here we have studied whether these effects are supported by a retention of striatal basal and evoked extracellular dopamine and the receptor(s) that may mediate this effect. Fourteen days following stereotaxic injections of 6-hydroxydopamine (6-OHDA) or lipopolysaccharide (LPS) and urocortin, extracellular dopamine levels in striata ipsilateral to injection sites of 6-OHDA/LPS and urocortin treated rats were comparable with sham injected rats, whilst rats given 6-OHDA/LPS and vehicle had considerably lower dopamine levels. Striatal dopamine levels in animals where urocortin injection was delayed by seven days were only modestly decreased compared to animals receiving 6-OHDA/LPS and urocortin concomitantly. Additionally, the dopamine metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) were also preserved in dialysates from urocortin treated rats. The effects of urocortin were entirely blocked by the non-selective CRF receptor antagonist alpha-helical CRF as well as the selective CRF(1) antagonist NBI 27914 and were not replicated by the selective CRF(2) ligand urocortin III. In the substantia nigra tissue dopamine changes mirrored those seen in striatal extracellular dopamine. Our data strongly suggest that urocortin is capable of maintaining adequate nigrostriatal function in vivo via CRF(1) receptors following. neurotoxic challenge.

Therapeutic efficacy of intra-articular adrenomedullin injection in antigen-induced arthritis in rabbits

Introduction

Adrenomedullin is a potent vasodilatory and hypotensive peptide as well as an endogenous immunomodulatory factor with predominantly anti-inflammatory effects. The purpose of the present study was to evaluate the therapeutic effects of adrenomedullin in rabbits with antigen-induced arthritis, an experimental model of rheumatoid arthritis.

Methods

Following the induction of arthritis in both knee joints by ovalbumin injection into the joint spaces of pre-immunized rabbits, increasing daily doses of adrenomedullin were injected into the knee joint spaces or saline was injected into the contralateral knee joint spaces as the control. For time-course experiments, adrenomedullin and saline were injected into the knee joint spaces daily for 7 days and 20 days. The degree of joint swelling and the histological change in the knee joints injected with adrenomedullin were compared with the control knee joints. Histological evaluation of the infrapatellar fat pads and synovial tissue was performed. TNFα, IL-6, vascular endothelial growth factor and transforming growth factor-beta mRNA levels in the synovial tissue were measured using real-time quantitative PCR.

Results

Daily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis decreased joint swelling. Histological examination revealed that adrenomedullin reduced edematous changes and the infiltration of inflammatory cells in the synovial tissues. Analysis of mRNA levels showed that adrenomedullin significantly reduced TNFα mRNA expression by 21% to 49% in a dose-dependent manner, and dose-dependently increased IL-6 mRNA expression by 45% to 121%.

Conclusions

These results suggest that daily injections of adrenomedullin into the knee joint spaces of rabbits with antigen-induced arthritis ameliorated the inflammatory response in arthritic joints. Adrenomedullin may thus be useful as a treatment for rheumatoid arthritis; however, the effect of adrenomedullin on IL-6 production in the synovial tissue may be an undesirable adverse effect in rheumatoid arthritis therapy.

Acute and chronic responses associated with adrenomedullin administration in experimental colitis

Adrenomedullin (AM) is a 52 amino acid peptide and member of the calcitonin gene-related peptide (CGRP) super family. Given that AM has emerged as a potential immuno-regulatory and anti-inflammatory agent in various experimental models, this study has deepened into its possible therapeutic effect in intestinal inflammation analyzing the responses in both acute and chronic (14 and 21 days) phases of TNBS-induced colitis in rats. In the acute model, AM treatment reduced the incidence of diarrhea and the severity of colonic damage, and improved the survival rate at the three doses assayed (50, 100, and 200ng/kg animal). AM administration was able to reduce the early production of TNF-alpha and collaborated to maintaining basal levels of IFN-gamma and IL-10. In the chronic studies the peptide attenuated the extent of the damage with lesser incidence of weight loss and diarrhea (50 and 100ng/kg animal). Cellular neutrophil infiltration, with the subsequent increase in myeloperoxidase (MPO) levels caused by TNBS, was reduced after chronic AM administration. The peptide played a role in the evolution of Th1/Th2 cytokines balance and chronic disease recuperation: levels of proinflammatory TNF-alpha and IFN-gamma decreased and anti-inflammatory IL-10 increased significantly. Cyclooxygenase-2 (COX-2) and nitric oxide synthase (iNOS) protein expression were not modified by AM administration, although a reduction of nitric oxide (NO) production could be detected in the chronic model. These results support a role of AM as an anti-inflammatory factor with beneficial effects in intestinal inflammatory colitis.

Endogenous anti-inflammatory neuropeptides and pro-resolving lipid mediators: a new therapeutic approach for immune disorders

Identification of the factors that regulate the immune tolerance and control the appearance of exacerbated inflammatory conditions is crucial for the development of new therapies of inflammatory and autoimmune diseases. Although much is known about the molecular basis of initiating signals and pro-inflammatory chemical mediators in inflammation, it has only recently become apparent that endogenous stop signals are critical at early checkpoints within the temporal events of inflammation. Some neuropeptides and lipid mediators that are produced during the ongoing inflammatory response have emerged as endogenous anti-inflammatory agents that participate in the regulation of the processes that ensure self-tolerance and/or inflammation resolution. Here we examine the latest research findings, which indicate that neuropeptides participate in maintaining immune tolerance in two distinct ways: by regulating the balance between pro-inflammatory and anti-inflammatory factors, and by inducing the emergence of regulatory T cells with suppressive activity against autoreactive T-cell effectors. On the other hand, we also focus on lipid mediators biosynthesized from omega-3 and omega-6 polyunsaturated fatty-acids in inflammatory exudates that promote the resolution phase of acute inflammation by regulating leucocyte influx to and efflux from local inflamed sites. Both anti-inflammatory neuropeptides and pro-resolving lipid mediators have shown therapeutic potential for a variety of inflammatory and autoimmune disorders and could be used as biotemplates for the development of novel pharmacologic agents.

The CRF-like peptide urocortin produces a long-lasting recovery in rats made hemiparkinsonian by 6-hydroxydopamine or lipopolysaccharide

We have recently observed that the corticotropin releasing factor related peptide urocortin (UCN) reverses key features of nigrostriatal neurodegeneration following intracerebral injection of either 6-hydroxydopamine (6-OHDA) or lipopolysaccharide (LPS). To determine the potential therapeutic utility of UCN here we have studied whether these effects are sustained for several weeks following peptide injection. In addition we have studied whether UCN still shows efficacy in rats with more pronounced nigrostriatal lesions. Rats were lesioned using 6-OHDA or LPS and injected with UCN either 7 or 14 days later. At different time points animals were tested for rotational behaviour (apomorphine, 0.5 mg/kg) and subsequently implanted with bilateral dialysis probes into the striata. The following day rats were dialysed to estimate extracellular striatal dopamine (DA) and then sacrificed for estimation of striatal tissue DA and subsequent immunohistochemistry of TH(+) cells in the substantia nigra (SN). Toxin treated rats given UCN 7 days later showed clear evidence of reduced nigrostriatal damage both 28 and 84 days following UCN compared with saline injection. In rats given UCN 14 days after toxin injection, by which time deficits were maximal, a restoration of nigrostriatal damage was observed. This suggests that UCN is able to elicit a sustained restoration of functional nigrostriatal integrity and has the ability to produce a recovery in severely lesioned rats. These findings suggest that stimulation of CRF (probably CRF(1)) receptors could have therapeutic utility in PD.

Glucagon-like peptide 1 receptor stimulation reverses key deficits in distinct rodent models of Parkinson's disease

Background

It has recently become apparent that neuroinflammation may play a significant role in Parkinson's disease (PD). This is also the case in animal paradigms of the disease. The potential neuroprotective action of the glucagon-like peptide 1 receptor (GLP-1R) agonist exendin-4 (EX-4), which is protective against cytokine mediated apoptosis and may stimulate neurogenesis, was investigated In paradigms of PD.

Methods

Two rodent 'models' of PD, 6-hydroxydopamine (6-OHDA) and lipopolysaccaride (LPS), were used to test the effects of EX-4. Rats were then investigated in vivo and ex vivo with a wide range of behavioural, neurochemical and histological tests to measure integrity of the nigrostriatal system.

Results

EX-4 (0.1 and 0.5 μg/kg) was given seven days after intracerebral toxin injection. Seven days later circling behaviour was measured following apomorphine challenge. Circling was significantly lower in rats given EX-4 at both doses compared to animals given 6-OHDA/LPS and vehicle. Consistent with these observations, striatal tissue DA concentrations were markedly higher in 6-OHDA/LPS + EX-4 treated rats versus 6-OHDA/LPS + vehicle groups, whilst assay of L-DOPA production by tyrosine hydroxylase was greatly reduced in the striata of 6-OHDA/LPS + vehicle rats, but this was not the case in rats co-administered EX-4. Furthermore nigral TH staining recorded in 6-OHDA/LPS + vehicle treated animals was markedly lower than in sham-operated or EX-4 treated rats. Finally, EX-4 clearly reversed the loss of extracellular DA in the striata of toxin lesioned freely moving rats.

Conclusion

The apparent ability of EX-4 to arrest progression of, or even reverse nigral lesions once established, suggests that pharmacological manipulation of the GLP-1 receptor system could have substantial therapeutic utility in PD. Critically, in contrast to other peptide agents that have been demonstrated to possess neuroprotective properties in pre-clinical models of PD, EX-4 is in current clinical use in the management of type-II diabetes and freely crosses the blood brain barrier; hence, assessment of the clinical efficacy of EX-4 in patients with PD could be pursued without delay.

Circulating adrenomedullin levels in ankylosing spondylitis and Familial Mediterranean Fever

INTRODUCTION

Adrenomedullin (AM) is a 52-amino acid peptide with vasorelaxant properties. Apart from its roles on vascular tonus, AM can also contribute to inflammatory events. Plasma AM levels were elevated in connective tissue diseases and vasculitic disorders. Ankylosing spondylitis (AS) is a chronic inflammatory disease of the spine initiating in the sacroiliac joints. Familial Mediterranean Fever (FMF) is a hereditary disorder characterized by self-limiting acute attacks of fever and the presence of sustained subclinical inflammation in the attack-free periods. In this study, we investigated plasma AM levels in patients with AS and patients with FMF.

METHODS

Twenty AS patients with active disease manifestations (mean age: 41.6+/-10.9 years, female/male: 7/13), 28 FMF patients with acute attack (mean age: 27.4+/-10.7 years, female/male: 17/11), and 26 healthy controls (mean age: 39.9+/-5.5 years, female/male: 16/10) were enrolled in this study. AM levels were also measured in 11 FMF patients 2 months after the cessation of their attacks. AM levels of those 11 patients during their FMF attacks and attack-free periods were also compared.

RESULTS

Median plasma AM levels were 23.86 (17.24-40.09) pmol/mL, 27.33 (17.24-38.52) pmol/mL, and 26.11 (17.05-37.42) pmol/mL in AS patients, FMF patients with acute attack, and healthy controls, respectively (p>0.05). AM levels were also similar in the attack-free periods of FMF patients [26.35 (24.35-34.14) pmol/mL]. There was no correlation between plasma AM levels and C-reactive protein, or between plasma AM levels and erythrocyte sedimentation rate.

CONCLUSIONS

AM does not seem to have any role in the pathogenesis of AS and FMF. Previous reports of elevated levels of AM in connective tissue disorders and vasculitic diseases are probably disease specific, and AM does not seem to be a common component of inflammatory rheumatic disorders.

Adrenomedullin reduces the severity of cerulein-induced acute pancreatitis

We investigated the effect of Adrenomedullin (AM) on cerulein-induced acute pancreatitis in rats. AM treatment (100 ng/kg per rat, subcutaneous) after one hour of cerulein injection reduced the plasma amylase levels, pancreatic weight, pancreatic malondialdehyde (MDA) levels, and the severity of the lesions microscopically. These data suggest that AM has a protective effect on cerulein-induced acute pancreatitis. These could be due to anti-inflammatory properties of AM, inhibition of proinflammatory cytokine secretion, reducing the endothelial permeability increased by reactive oxygen species, endotoxins or cytokines.

The corticotrophin-releasing factor-like peptide urocortin reverses key deficits in two rodent models of Parkinson's disease

The potential neuroprotective action of the corticotrophin-releasing factor-related peptide urocortin (UCN) was investigated in the rat 6-hydroxydopamine (6-OHDA) and lipopolysaccharide (LPS) paradigms of Parkinson's disease. UCN (20 fmol) was either given at the same time as (T = 0) or 7 days after (T = +7) intracerebral 6-OHDA or LPS injection. At 14 days after 6-OHDA or LPS injection, circling behaviour was measured following apomorphine challenge. Circling was significantly lower in rats given UCN at either T = 0 or T = +7 compared with animals given 6-OHDA or LPS and vehicle. Sham-treated rats showed no circling. Consistent with these observations, striatal dopamine concentrations were markedly higher in 6-OHDA/LPS + UCN rats vs. 6-OHDA/LPS + vehicle groups. Additionally, L-dihydroxyphenylalanine production by tyrosine hydroxylase was greatly reduced in the striata of 6-OHDA/LPS + vehicle rats, whereas this was not the case in rats coadministered UCN. Finally, the numbers of tyrosine hydroxylase-positive cells recorded in the substantia nigra of 6-OHDA/LPS + vehicle-treated animals were markedly lower than those of sham-operated or 6-OHDA/LPS + UCN rats. Critically, UCN was effective in reversing lesion-induced deficits when given either at the same time as or 7 days after the neurotoxic insult. To our knowledge, this is the first time that such an effect has been demonstrated in vivo. The apparent ability of UCN to arrest the progression of or even reverse nigral lesions once established suggests that pharmacological manipulation of this system could have substantial therapeutic utility.

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.

Alleviation of experimental ulcerative colitis with the synthetic peptide, F2A4-K-NS (Fibratide)

Recombinant fibroblast growth factors (FGFs) maintain the integrity of the gut epithelium and reduce mucosal injury in experimental inflammatory bowel disease (IBD). Chemically synthesized FGF mimetics could potentially extend the utility of FGFs by tailoring them for optimal bioactivity and oral administration, for example. Here, F2A4-K-NS (Fibratide), a synthetic FGF mimetic peptide, alleviated dextran sulfate sodium (DSS)-induced ulcerative colitis in mice when delivered systemically and, to a lesser extent, orally. Intraperitoneal injection of Fibratide (1 or 5 mg/kg/day) ameliorated DSS-induced ulcerative colitis, resulting in reduced weight loss, decreased colon wall thickening, and increased colon length. Fibratide also improved epithelial integrity by reducing histological-detectable crypt damage and inflammation. Orally administered Fibratide (1 mg/kg/day) was also effective in ameliorating symptoms with effects generally similar to those of intraperitoneal injection. In vitro studies were conducted to help clarify how Fibratide might act in vivo. Fibratide exhibited a modest enhancement of epithelial cell proliferation. On the other hand, Fibratide doubled the rate of epithelial cells migration and restitution in a cell culture model of wound repair. Collectively, the results indicate that Fibratide reduced the severity of experimental ulcerative colitis and may be potentially useful in the treatment of IBD.

Urocortin, a CRF-like peptide, restores key indicators of damage in the substantia nigra in a neuroinflammatory model of Parkinson's disease

We have recently observed that the corticotrophin releasing hormone (CRF) related peptide urocortin (UCN) reverses key features of nigrostriatal damage in the hemiparkinsonian 6-hydroxydopamine lesioned rat. Here we have studied whether similar effects are also evident in the lipopolysaccaride (LPS) neuroinflammatory paradigm of Parkinson's disease (PD). To do this we have measured restoration of normal motor behaviour, retention of nigral dopamine (DA) and also tyrosine hydroxylase (TH) activity. Fourteen days following intranigral injections of LPS and UCN, rats showed only modest circling after DA receptor stimulation with apomorphine, in contrast to those given LPS and vehicle where circling was pronounced. In separate experiments, rats received UCN seven days following LPS, and here apomorphine challenge caused near identical circling intensity to those that received LPS and UCN concomitantly. In a similar and consistent manner with the preservation of motor function, UCN 'protected' the nigra from both DA depletion and loss of TH activity, indicating preservation of DA cells. The effects of UCN were antagonised by the non-selective CRF receptor antagonist α-helical CRF and were not replicated by the selective CRF₂ ligand UCN III. This suggests that UCN is acting via CRF₁ receptors, which have been shown to be anti-inflammatory in the periphery. Our data therefore indicate that UCN is capable of maintaining adequate nigrostriatal function in vivo, via CRF₁ receptors following a neuro-inflammatory challenge. This has potential therapeutic implications in PD.

Urocortin 2 expression in the rat gastrointestinal tract under basal conditions and in chemical colitis

It is becoming increasingly evident that the urocortins (Ucns) and their receptors are involved in the initiation and development of inflammation in the gastrointestinal (GI) tract. There has not been a systematic study of the basal expression of Ucns or their receptors in the GI tract. Here, we examined basal expression of Ucn 2 and its high-affinity receptor, CRF-R2 in the rat GI tract. Ucn 2 mRNA was expressed throughout the small and large intestine. Surprisingly, CRF-R2 mRNA expression was detected in only a subset of GI regions that expressed Ucn 2. Immunohistochemical study showed that both Ucn 2 immuno-reactivity (Ucn 2-IR) and CRF-R2-IR were consistently seen in the neurons of the myenteric plexus and the nerve fibers innervating the circular muscle. By and large, Ucn 2-IR was detected in all layers, including the mucosal and the submucosal layers throughout the GI regions. In contrast, CRF-R2-IR was very low or undetectable in the mucosal layers of all regions examined. The role of Ucn 2 and CRF-R2 was then examined in a rat model of chemically-induced colitis. In the early phase of colitis, Ucn 2 mRNA levels peaked, whereas, in striking contrast, CRF-R2 mRNA expression decreased approximately 2.5-fold below control levels. At the peptide level, Ucn 2-IR was specifically induced in a large population of immune cells that infiltrated the lamina propria and submucosa of the distal colon, whereas CRFR2-IR was detected in only a small fraction of infiltrated immune cells. CRF-R2-IR was dramatically reduced in the neurons of the myenteric plexus. Thus, we show, for the first time, that in the acute phase of inflammation, Ucn 2 levels are increased whereas expression levels of its only identified receptor, CRF-R2, are decreased. This suggests that Ucn 2 exerts its effects only in part via CRF-R2.

Role of neuropeptides in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic, relapsing condition involving complex interactions between genes and the environment. The mechanisms triggering the initial attack and relapses, however, are not well understood. In the past several years the enteric nervous system (ENS) has been implicated in the pathophysiology of IBD. Both the ENS and the central nervous system (CNS) can amplify or modulate aspects of intestinal inflammation through secretion of neuropeptides that serve as a link between the ENS and CNS. Neuropeptides are defined as any peptide released from the nervous system that serves as an intercellular signaling molecule. Neuropeptides thought to play a potentially key role in IBD include substance P, corticotropin-releasing hormone, neurotensin, vasoactive intestinal peptide, mu-opioid receptor agonists, and galanin. This review focuses on the role of these neuropeptides in the pathophysiology of IBD and discusses the cell types and mechanisms involved in this process. The available evidence that neuropeptide blockade may be considered a therapeutic approach in both Crohn's disease and ulcerative colitis will also be discussed.

Vasoactive intestinal peptide and regulatory T-cell induction: a new mechanism and therapeutic potential for immune homeostasis

The identification of regulatory T (Treg) cells as important regulators of self-tolerance has opened up new therapeutic avenues for the treatment of several human diseases associated with Treg dysfunction, including autoimmune diseases and transplantation. Recent evidence indicates that vasoactive intestinal peptide (VIP), an anti-inflammatory neuropeptide with therapeutic potential in various immune disorders, participates in maintaining immune tolerance by a novel mechanism of inducing the generation of Treg cells. We propose a Treg-cell-based immunotherapy approach for resetting the balance of immune homeostasis, which takes advantage of novel functions of VIP in immunoregulation.

Tuning inflammation with anti-inflammatory neuropeptides

The immune system is confronted with the daunting task of defending the organism against invading pathogens while at the same time remaining self-tolerant to the body's own constituents and preserving its integrity. The loss of immune tolerance stemming from an unbalance in pro-inflammatory factors versus anti-inflammatory cytokines, or of autoreactive/inflammatory T helper 1 cells versus regulatory/suppressive T cells, results in the breakdown of immune homeostasis and the subsidiary appearance of exacerbated inflammatory and autoimmune diseases. Some neuropeptides have been shown to have anti-inflammatory properties and to participate in maintaining immune tolerance. Here the authors examine the most recent developments in this field and highlight the effectiveness of using neuropeptides in treating several inflammatory and autoimmune disorders.

Therapeutic effect of urocortin on collagen-induced arthritis by down-regulation of inflammatory and Th1 responses and induction of regulatory T cells

OBJECTIVE

To investigate the potential therapeutic action of the immunomodulatory neuropeptide urocortin (UCN) in an experimental model of rheumatoid arthritis (RA).

METHODS

After disease onset, DBA/1J mice with collagen-induced arthritis (CIA) were treated with UCN, and the incidence, severity (clinical score), and joint histopathology were evaluated. The inflammatory response was determined by measuring the levels of different mediators of inflammation (cytokines and chemokines) in the joints and sera. The Th1-mediated autoreactive response was evaluated by determining the proliferative response and cytokine profile of draining lymph node cells stimulated with the autoantigen and by assaying the content of serum autoantibodies. The number of regulatory CD4+,CD25+ T cells and their capacity to suppress self-reactive Th1 cells were determined in joints and lymph nodes.

RESULTS

UCN treatment significantly reduced the incidence and severity of CIA, completely abrogating joint swelling and cartilage and bone destruction. The therapeutic effect of UCN was associated with a striking reduction of the 2 deleterious components of the disease: the Th1-driven autoimmune response and the inflammatory response. UCN also induced the generation and/or activation of efficient interleukin-10/transforming growth factor beta1-producing Treg cells in arthritis with the capacity to suppress the autoreactive response and to restore immune tolerance, thus playing a pivotal role in the therapeutic effect of UCN.

CONCLUSION

Our findings provide a powerful rationale for assessing the efficacy of UCN as a novel multistep therapeutic approach to the treatment of RA in humans.

Adrenomedullin protects from experimental arthritis by down-regulating inflammation and Th1 response and inducing regulatory T cells

Rheumatoid arthritis is a chronic autoimmune disease of unknown etiology characterized by chronic inflammation in the joints and subsequent destruction of the cartilage and bone. The present study proposes a new strategy for the treatment of arthritis: the administration of the immunomodulatory neuropeptide adrenomedullin. Treatment with adrenomedullin significantly reduced incidence and severity of collagen-induced arthritis, an experimental model of rheumatoid arthritis, completely abrogating joint swelling and destruction of cartilage and bone. The therapeutic effect of adrenomedullin was associated with a striking reduction of the two deleterious components of the disease, ie, the Th1-driven autoimmune and inflammatory responses. Adrenomedullin also induced the generation and/or activation of efficient CD4+ CD25+ regulatory T cells in arthritis with capacity to suppress autoreactive response and restore immune tolerance, which could play a pivotal role in the therapeutic effect of adrenomedullin on experimental arthritis contributing to the restoration of immune tolerance.

Regulation of immune tolerance by anti-inflammatory neuropeptides

The induction of antigen-specific tolerance is essential to maintain immune homeostasis, control autoreactive T cells, prevent the onset of autoimmune diseases and achieve tolerance of transplants. Inflammation is a necessary process for eliminating pathogens, but can lead to serious deleterious effects in the host if left unchecked. Identifying the endogenous factors that control immune tolerance and inflammation is a key goal in the field of immunology. In the last decade, various neuropeptides that are produced by immune cells with potent anti-inflammatory actions were found to participate in the maintenance of tolerance in different immunological disorders.

New evidence for a role of allograft accommodation in long-term tolerance

BACKGROUND

Progressively better therapies have largely prevented or at least effectively treated acute allograft rejection. Consequently, the long-term survival of solid organ transplants has increasingly become limited primarily by the development of chronic allograft rejection. The mechanisms of chronic rejection remain largely unknown and the induction of specific tolerance would be the ultimate achievement in transplant immunology. We previously demonstrated, in a fully major histocompatibility complex (MHC)-mismatched rat cardiac allograft combination, that a 20-day treatment with a deoxyspergualin (DSG) analogue, LF15-0195, induces allograft tolerance with the development of potent CD4CD25 regulatory T cells. In order to better characterize the mechanisms involved in allograft tolerance, we compared long-term tolerated allografts with allografts exhibiting signs of chronic rejection induced by donor-specific blood transfusion.

METHODS

We analyzed both types of allografts for infiltration, alloantibody production and gene expression by histology, exhaustive microarray and quantitative reverse-transcriptase polymerase chain reaction.

RESULTS

Interestingly, we observed in tolerated allografts an infiltrate as dense as the one observed in chronically rejected allografts and alloantibody deposits on graft endothelial cells. Prominent gene expression of many putative proinflammatory cytokines and genes related to cell activation or cytotoxicity were observed in tolerated allografts. However, we observed a specific upregulation of cytoprotective genes such as nitric oxide synthase, BclXL, and indoleamine 2,3 dioxygenase, and a poor in situ expression of immunoglobulin chain gene.

CONCLUSIONS

This study demonstrates a state of accommodation of tolerated allografts and suggests the importance of early control of humoral immunity for the prevention of chronic rejection and the maintenance of long-term tolerance.

Corticotropin-Releasing Hormone Receptor 2-Deficient Mice Have Reduced Intestinal Inflammatory Responses

Corticotropin-releasing hormone (CRH) and urocortins (Ucn) bind with various affinities to two G-protein-coupled receptors, CRHR1 and CRHR2, which are expressed in brain and in peripheral tissues, including immune cells. CRHR2-deficient mice display anxiety-like behavior, hypersensitivity to stress, altered feeding behavior and metabolism, and cardiovascular abnormalities. However, the phenotype of these mice in inflammatory responses has not been determined. In the present study we found that compared with wild-type CRHR2-null mice developed substantially reduced intestinal inflammation and had lower intestinal mRNA expression of the potent chemoattractants keratinocyte chemokine and monocyte chemoattractant protein 1 following intraluminal exposure to Clostridium difficile toxin A, a potent enterotoxin that mediates antibiotic-associated diarrhea and colitis in humans. This effect was recapitulated by administration of astressin 2B, a selective CRHR2 antagonist, before toxin A exposure. Moreover, Ab array analysis revealed reduced expression of several inflammatory chemokines, including keratinocyte chemokine and monocyte chemoattractant protein 1 in toxin A-exposed mice pretreated with astressin 2B. Real-time RT-PCR of wild-type mouse intestine showed that only UcnII, but not other Ucn, was significantly up-regulated by ileal administration of toxin A at 4 h compared with buffer exposure. We also found that human colonic epithelial HT-29 cells express CRHR2alpha mRNA, whereas expression of beta and gamma spliced variants was minimal. Moreover, treatment of HT-29 cells with UcnII, which binds exclusively to CRHR2, stimulated expression of IL-8 and monocyte chemoattractant protein 1. Taken together, these results provide direct evidence that CRHR2 mediates intestinal inflammatory responses via release of proinflammatory mediators at the colonocyte level.

Urocortin and adrenomedullin prevent lethal endotoxemia by down-regulating the inflammatory response

Urocortin 1 (UCN) and adrenomedullin (AM) are two neuropeptides that have emerged as potential endogenous anti-inflammatory factors based on their production by and binding to immune cells. Because human septic shock involves excessive inflammatory cytokine production, we investigated the effect of UCN and AM in the production of inflammatory mediators and their therapeutic actions in two models of septic shock. Both peptides down-regulated the production of inflammatory mediators by endotoxin-activated macrophages. The administration of UCN or AM protected against lethality after cecal ligation and puncture or after injection of bacterial endotoxin and prevented septic shock-associated histopathology, such as infiltration of inflammatory cells and intravascularly disseminated coagulation in various target organs. The therapeutic effect of UCN and AM was mediated by decreasing the local and systemic levels of a wide spectrum of inflammatory mediators, including cytokines, chemokines, and the acute phase protein serum amyloid A. Importantly, UCN or AM treatment was therapeutically effective in established endotoxemia. In conclusion, UCN and AM could represent two multistep therapeutic agents for human septic shock to be used in combination with other immunomodulatory agents or complementary as anti-inflammatory factors to other therapies.

Expression of corticotropin-releasing factor and CRF receptors in micturition pathways after cyclophosphamide-induced cystitis

Corticotropin-releasing factor (CRF) is a prominent neuropeptide involved in micturition reflexes, and different roles in these reflexes have been suggested. These studies examined the expression of CRF in the urinary bladder and lumbosacral sacral parasympathetic nucleus (SPN) in response to cyclophosphamide (CYP)-induced cystitis (4 h, 48 h, or chronic) in rats. The expression of CRF receptors, CRF(1) and CRF(2), was examined in urinary bladder from control and CYP-treated rats. Urinary bladder and lumbosacral spinal cord were harvested from rats killed by isoflurane (4%) and thoracotomy. CRF protein expression in whole urinary bladders significantly (P < or = 0.01) increased with 48 h or chronic CYP treatment. CRF immunoreactivity (IR) was increased significantly (P < or = 0.01) in the urothelium and SPN after CYP treatment. CRF IR nerve fibers increased in density in the suburothelial plexus and detrusor smooth muscle whole mounts with CYP-induced cystitis. CRF(2) receptor transcript was expressed in the urothelium or detrusor smooth muscle, and CRF(2) receptor expression increased in whole bladder with CYP-treatment, whereas no CRF(1) receptor transcript was expressed in either urothelium or detrusor. Immunohistochemical studies demonstrated CRF(2) IR in urinary bladder nerve fibers and urothelial cells from control animals, whereas no CRF(1) IR was observed. These studies demonstrated changes in the expression of CRF in urinary bladder and SPN region with CYP-induced cystitis and CRF receptor (CRF(2)) expression in nerve fibers and urothelium in control rats. CRF may contribute to urinary bladder overactivity and altered sensory processing with CYP-induced cystitis.