Urocortin 2 suppresses host resistance to Listeria monocytogenes infection via up-regulation of interleukin-10

Human skin CD141+ dendritic cells regulate cutaneous immunity via the neuropeptide urocortin 2

Skin immune homeostasis is a multi-faceted process where dermal dendritic cells (DDCs) are key in orchestrating responses to environmental stressors. We have previously identified CD141+CD14+ DDCs as a skin-resident immunoregulatory population that is vitamin-D3 (VitD3) inducible from monocyte-derived DCs (moDCs), termed CD141hi VitD3 moDCs. We demonstrate that CD141+ DDCs and CD141hi VitD3 moDCs share key immunological features including cell surface markers, reduced T cell stimulation, IL-10 production, and a common transcriptomic signature. Bioinformatic analysis identified the neuroactive ligand receptor pathway and the neuropeptide, urocortin 2 (UCN2), as a potential immunoregulatory candidate molecule. Incubation with VitD3 upregulated UCN2 in CD141+ DCs and UVB irradiation induced UCN2 in CD141+ DCs in healthy skin in vivo. Notably, CD141+ DDC generation of suppressive Tregs was dependent upon the UCN2 pathway as in vivo administration of UCN2 reversed skin inflammation in humanized mice. We propose the neuropeptide UCN2 as a novel skin DC-derived immunoregulatory mediator with a potential role in UVB and VitD3-dependent skin immune homeostasis.

Hypothalamic Regulation of Corticotropin-Releasing Factor under Stress and Stress Resilience

This review addresses the molecular mechanisms of corticotropin-releasing factor (CRF) regulation in the hypothalamus under stress and stress resilience. CRF in the hypothalamus plays a central role in regulating the stress response. CRF stimulates adrenocorticotropic hormone (ACTH) release from the anterior pituitary. ACTH stimulates glucocorticoid secretion from the adrenal glands. Glucocorticoids are essential for stress coping, stress resilience, and homeostasis. The activated hypothalamic-pituitary-adrenal axis is suppressed by the negative feedback from glucocorticoids. Glucocorticoid-dependent repression of cAMP-stimulated Crf promoter activity is mediated by both the negative glucocorticoid response element and the serum response element. Conversely, the inducible cAMP-early repressor can suppress the stress response via inhibition of the cAMP-dependent Crf gene, as can the suppressor of cytokine signaling-3 in the hypothalamus. CRF receptor type 1 is mainly involved in a stress response, depression, anorexia, and seizure, while CRF receptor type 2 mediates “stress coping” mechanisms such as anxiolysis in the brain. Differential effects of FK506-binding immunophilins, FKBP4 and FKBP5, contribute to the efficiency of glucocorticoids under stress resilience. Together, a variety of factors contribute to stress resilience. All these factors would have the differential roles under stress resilience.

Captopril reduces lung inflammation and accelerated senescence in response to thoracic radiation in mice

The lung is sensitive to radiation and exhibits several phases of injury, with an initial phase of radiation-induced pneumonitis followed by delayed and irreversible fibrosis. The angiotensin-converting enzyme inhibitor captopril has been demonstrated to mitigate radiation lung injury and to improve survival in animal models of thoracic irradiation, but the mechanism remains poorly understood. Here we investigated the effect of captopril on early inflammatory events in the lung in female CBA/J mice exposed to thoracic X-ray irradiation of 17-17.9 Gy (0.5-0.745 Gy min-1). For whole-body + thoracic irradiation, mice were exposed to 7.5 Gy (0.6 Gy min-1) total-body 60Co irradiation and 9.5 Gy thoracic irradiation. Captopril was administered orally (110 mg kg-1 day-1) in the drinking water, initiated 4 h through to150 days post-irradiation. Captopril treatment increased survival from thoracic irradiation to 75% at 150 days compared with 0% survival in vehicle-treated animals. Survival was characterized by a significant decrease in radiation-induced pneumonitis and fibrosis. Investigation of early inflammatory events showed that captopril significantly attenuated macrophage accumulation and decreased the synthesis of radiation-induced interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) pro-inflammatory cytokines in the lungs of irradiated mice. Suppression of IL-1β and TNF-α correlated with an increase of the anti-inflammatory cytokine IL-10 in the spleen with captopril treatment. We also found that captopril decreased markers for radiation-induced accelerated senescence in the lung tissue. Our data suggest that suppression of inflammation and senescence markers, combined with an increase of anti-inflammatory factors, are a part of the mechanism for captopril-induced survival in thoracic irradiated mice.

Passive immunization with anti-ActA and anti-listeriolysin O antibodies protects against Listeria monocytogenes infection in mice

Listeria monocytogenes is an intracellular pathogen that causes listeriosis. Due to its intracellular niche, L. monocytogenes has evolved to limit immune recognition and response to infection. Antibodies that are slightly induced by listerial infection are completely unable to protect re-infection of L. monocytogenes. Thus, a role of antibody on the protective effect against L. monocytogenes infection has been neglected for a long time. In the present study, we reported that passive immunization with an excessive amount of antibodies against ActA and listeriolysin O (LLO) attenuates severity of L. monocytogenes infection. Combination of these antibodies improved survival of L. monocytogenes infected mice. Bacterial load in spleen and liver of listerial infected mice and infected RAW264.7 cells were significantly reduced by administration of anti-ActA and anti-LLO antibodies. In addition, anti-LLO antibody neutralized LLO activity and inhibited the bacterial escape from the lysosomal compartments. Moreover, anti-ActA antibody neutralized ActA activity and suppressed actin tail formation and cell-to-cell spread. Thus, our studies reveal that passive immunization with the excessive amount of anti-ActA and -LLO antibodies has potential to provide the protective effect against listerial infection.

Corticotropin-Releasing Hormone Receptor 2 Signaling Promotes Mucosal Repair Responses after Colitis

The corticotropin-releasing hormone family mediates functional responses in many organs, including the intestine. Activation of corticotropin-releasing hormone receptor 2 (CRHR2) in the colonic mucosa promotes inflammation during acute colitis but inhibits inflammation during chronic colitis. We hypothesized that specific modulation of CRHR2 signaling in the colonic mucosa can promote restoration of the epithelium through stimulation of cell proliferative, migratory, and wound healing responses. Mucosal repair was assessed after dextran sodium sulfate (DSS)-induced colitis in mice receiving intracolonic injections of a CRHR2 antagonist or vehicle and in Crhr2(-/-) mice. Histologic damage, cytokine expression, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling, and Ki-67 immunoreactivity were evaluated. Cell viability, proliferation, and migration were compared between parental and CRHR2-overexpressing colonic epithelial cells. Protein lysates were processed for phosphoprotein assays and a wound healing assay performed in vitro. Administration of a CRHR2 antagonist after DSS-induced colitis increased disease activity, delayed healing, and decreased epithelial cell proliferation in vivo. Colons from these mice also showed increased apoptosis and proinflammatory cytokine expression. Compared with controls, Crhr2(-/-) mice showed increased mortality in the DSS healing protocol. CRHR2-overexpressing cells had increased proliferation and migration compared with parental cells. Wound healing and signal transducer and activator of transcription 3 activity were elevated in CRHR2-overexpressing cells after urocortin 2 and IL-6 treatment, suggesting advanced healing progression. Our results suggest that selective CRHR2 activation may provide a targeted approach to enhance mucosal repair pathways after colitis.

[Host responses to bacterial infections]

Pathogenic bacteria and host defense system have been evolved by their offense and defense. In vivo research is crucial for elucidation of interactions between them. I have investigated their offence and defense by various standpoints using mouse models of Listeria monocytogenes and Staphylococcus aureus infections. Herein, the results of my research including the roles of endogenous cytokines in host defense, the attenuation of host defense mechanism in obesity and diabetes, the development of vaccines against S. aureus infection by staphylococcal enterotoxin (SE) family molecules, and the emesis-inducing mechanism of SEA are described.

Inflammation-induced functional connectivity of melanin-concentrating hormone and IL-10

Melanin-concentrating hormone (MCH) was identified in mammals as a hypothalamic neuropeptide regulating appetite and energy balance. However, similarly to most of the brain peptides, MCH is also produced in the gastrointestinal system and can act locally as an immunomodulator. We have previously reported high expression of MCH and its receptor MCHR1 in the affected mucosa of patients with inflammatory bowel disease. Furthermore, MCH deficiency in mice attenuated experimental colitis, pointing to MCH as a mediator of intestinal inflammation. In the present study, in order to gain further insights into the underlying mechanisms of such effects of MCH, we treated mice with established experimental colitis due to IL-10 deficiency with a MCHR1 antagonist (DABA-822). While treatment with the same drug was successful in attenuating TNBS-induced colitis in previous studies, it offered no benefit to the IL-10 knockout mouse model, suggesting that perhaps IL-10 is a downstream target of MCH. Indeed, in experiments focusing on monocytes, we found that treatment with MCH inhibited LPS-mediated IL-10 upregulation. Conversely, in the same cells, exogenous IL-10 prevented LPS-induced MCHR1 expression. Taken together, these findings indicate a functional cross-talk between MCH and IL-10 which prevents resolution of inflammation.

Targeting urocortin signaling pathways to enhance cardioprotection: is it time to move from bench to bedside?

Despite the exponential growth in medical knowledge, cardiovascular diseases (CVDs) contribute to more than one-third of worldwide morbidity and mortality. A range of therapies already exist for established CVDs, although there is significant interest in further understanding their pathogenesis. The urocortins (Ucns) are peptide members of the corticotrophin-releasing factor family, a group of evolutionary conserved peptides with homologues in fish, amphibians and mammals and considered to play a pivotal role in energy homeostasis and local tissue repair. A number of preclinical studies in vitro, in-vivo and ex-vivo have defined a multifaceted effect of Ucns on the cardiovascular system. Different G-protein coupled signaling and protein-kinase pathways have been shown to be activated by Ucns, together with different transcriptional and translational effects, all of which preferentially converge on the mitochondria, where the modulation of apoptosis is considered their principal action. It has been demonstrated in experimental models, and consequentially suggested in human diseases, that Ucn-mediated inhibition of apoptosis can be exploited for the improvement of both therapeutic and preventative strategies against CVDs. Specifically, some unavoidable iatrogenic ischemia/reperfusion (I/R) injuries, e.g. during cardiac surgery or percutaneous coronary angioplasty, may greatly benefit from the anti-apoptotic effect of Ucns. However, few studies on the topic have been employed in humans to date. Therefore, this review will focus on the different intra-cellular mechanisms of action of Urocortins, and detail the different Ucn-mediated pathways identified so far. It will also highlight the limited evidence already existing in human clinical and surgical settings, as well as emphasize the potential uses of Ucns in human cardiac pathology.

Listeria monocytogenesInduces the Expression of Retinoic Acid-Inducible Gene-I

Retinoic acid-inducible gene-I (RIG-I) is considered to play a role in innate immunity against virus infections. We showed by immunohistochemical study that RIG-I expression is upregulated in vivo in hepatic Kupffer cells and in splenic reticular cells of mice infected with Listeria monocytogenes. Both heat-killed L. monocytogenes and live L. monocytogenes induced the expression of RIG-I in cultured RAW264.7 murine macrophage-like cells in vitro. RIG-I may also be involved in innate immunity against Listeria infection.

Impaired hypothalamic insulin signaling in CUMS rats: restored by icariin and fluoxetine through inhibiting CRF system

Epidemiological evidence demonstrates the neuroendocrine link between stress, depression and diabetes. This study observed glucose intolerance of rats exposed to chronic unpredictable mild stress (CUMS) in oral glucose tolerance test (OGTT). CUMS procedure significantly up-regulated corticotropin-releasing factor (CRF)-related peptide urocortin 2 expression and elevated cAMP production, resulting in over-expression of suppressor of cytokine signaling 3 (SOCS3) in hypothalamic arcuate nucleus (ARC) of rats. Furthermore, SOCS3 activation blocked insulin signaling pathway through the suppression of insulin receptor substrate 2 (IRS2) phosphotyrosine and phosphatidylinositol-3-kinase (PI3-K) activation in hypothalamic ARC of CUMS rats after high-level of insulin stimulation. These data indicated that CUMS procedure induced the hyperactivity of CRF system, and subsequently produced conditional loss of insulin signaling in hypothalamic ARC of rats. More importantly, icariin and fluoxetine with the ability to restrain CRF system hyperactivity improved insulin signaling in hypothalamic ARC of CUMS rats, which were consistent with the enhancement of glucose tolerance in OGTT, showing anti-diabetic efficacy. Although effective in OGTT, anti-diabetic drug pioglitazone failed to restore hypothalamic ARC CRF system hyperactivity, paralleling with its inability to ameliorate the loss of insulin signaling and depression-like behavior in CUMS rats. These observations support the hypothesis that signal cross-talk between hypothalamic CRF system and insulin may be impaired in depression with glucose intolerance and suggest that icarrin and fluoxetine aiming at CRF system may have great potential in the prevention and treatment of depression with comorbid diabetes.

Autolysin amidase of Listeria monocytogenes promotes efficient colonization of mouse hepatocytes and enhances host immune response

Listeria monocytogenes is an intracellularly growing pathogen which is able to infect and to spread from cells to cells. It produces several virulence factors required for invasion and intracellular niche colonization. Endogenous peptidoglycan hydrolases which are important for survival of bacteria have been shown to be involved in pathogenesis. An autolysin amidase (Ami)-deficient mutant of L. monocytogenes (Δami) is attenuated in virulence as evidenced by a reduction in mortality of infected mice. We showed that Ami is not essential for bacterial growth and protein secretion. Histopathological analysis suggests that Ami promotes bacterial colonization of hepatocytes. By using cultured eukaryotic cells, we present evidence that a critical function of Ami in pathogenesis is to promote an efficient listerial adherence and internalization into mouse hepatocytes. Simultaneously, the peptidoglycan hydrolase activity of Ami linked to the release of immunologically active cell wall components enhances production of tumor necrosis factor (TNF)-α and interleukin 6. In the early phase of infection, interferon-γ and TNF-α production of Δami-infected mice is significantly less than that of wild-type controls, suggesting a contribution of Ami to enhance the host innate immune response to listerial infection.

Oncolytic targeting of androgen-sensitive prostate tumor by the respiratory syncytial virus (RSV): consequences of deficient interferon-dependent antiviral defense

Background

Oncolytic virotherapy for cancer treatment utilizes viruses for selective infection and death of cancer cells without any adverse effect on normal cells. We previously reported that the human respiratory syncytial virus (RSV) is a novel oncolytic virus against androgen-independent PC-3 human prostate cancer cells. The present study extends the result to androgen-dependent prostate cancer, and explores the underlying mechanism that triggers RSV-induced oncolysis of prostate cancer cells.

Methods

The oncolytic effect of RSV on androgen-sensitive LNCaP human prostate cancer cells and on androgen-independent RM1 murine prostate cancer cells was studied in vitro in culture and in vivo in a xenograft or allograft tumor model. In vitro, cell viability, infectivity and apoptosis were monitored by MTT assay, viral plaque assay and annexin V staining, respectively. In vivo studies involved virus administration to prostate tumors grown in immune compromised nude mice and in syngeneic immune competent C57BL/6J mice. Anti-tumorogenic oncolytic activity was monitored by measuring tumor volume, imaging bioluminescent tumors in live animals and performing histopathological analysis and TUNEL assay with tumors

Results

We show that RSV imposes a potent oncolytic effect on LNCaP prostate cancer cells. RSV infectivity was markedly higher in LNCaP cells compared to the non-tumorigenic RWPE-1 human prostate cells. The enhanced viral burden led to LNCaP cell apoptosis and growth inhibition of LNCaP xenograft tumors in nude mice. A functional host immune response did not interfere with RSV-induced oncolysis, since growth of xenograft tumors in syngeneic C57BL/6J mice from murine RM1 cells was inhibited upon RSV administration. LNCaP cells failed to activate the type-I interferon (IFNα/β)-induced transcription factor STAT-1, which is required for antiviral gene expression, although these cells could produce IFN in response to RSV infection. The essential role of IFN in restricting infection was further borne out by our finding that neutralizing IFN activity resulted in enhanced RSV infection in non-tumorigenic RWPE-1 prostate cells.

Conclusions

We demonstrated that RSV is potentially a useful therapeutic tool in the treatment of androgen-sensitive and androgen-independent prostate cancer. Moreover, impaired IFN-mediated antiviral response is the likely cause of higher viral burden and resulting oncolysis of androgen-sensitive prostate cancer cells.

Urocortin prevents indomethacin-induced small intestinal lesions in rats through activation of CRF2 receptors

PURPOSE

The role of corticotropin-releasing factor (CRF) in the pathogenesis of indomethacin-induced small intestinal lesions was examined in rats.

METHODS

Animals were given indomethacin (10 mg/kg) subcutaneously and killed 24 h later. Urocortin I [a nonselective CRF receptor (CRFR) agonist], astressin (a nonselective CRFR antagonist), NBI-27914 (a CRFR1 antagonist), or astressin-2B (a CRFR2 antagonist) was given intravenously 10 min before the administration of indomethacin.

RESULTS

Indomethacin caused hemorrhagic lesions in the small intestine, accompanied by intestinal hypermotility, mucosal invasion of enterobacteria, up-regulation of inducible nitric oxide synthase (iNOS) expression, and an increase of mucosal myeloperoxidase (MPO) activity. Pretreatment of the animals with astressin, a non-selective CRFR antagonist, aggravated the lesions in a dose-dependent manner. Likewise, astressin-2B also exacerbated the intestinal ulcerogenic response induced by indomethacin, while NBI-27914 did not. Urocortin I prevented indomethacin-induced intestinal lesions, together with the suppression of bacterial invasion and an increase in mucosal MPO activity and iNOS expression; these effects were significantly reversed by co-administration of astressin-2B but not NBI-27914. Urocortin I suppressed the hypermotility response to indomethacin, and this effect was also abrogated by astressin-2B but not NBI-27914.

CONCLUSIONS

These results suggest that urocortin 1 prevents indomethacin-induced small intestinal lesions, and that this action is mediated by the activation of CRFR2 and is functionally associated with the suppression of the intestinal hypermotility response caused by indomethacin. It is assumed that endogenous CRF contributes to the maintenance of the mucosal defensive ability of the small intestine against indomethacin through the activation of CRFR2.

Virulence factor p60 of Listeria monocytogenes modulates innate immunity by inducing tumor necrosis factor alpha

We investigated the effect of p60, a virulence factor of Listeria monocytogenes, on host immune response in vitro and in vivo. Administration of p60 before a sublethal infection with L. monocytogenes enhanced innate host resistance in naïve mice. Mouse macrophage RAW264.7 cells produced tumor necrosis factor (TNF)-alpha in response to stimulation with recombinant p60. Toll-like receptor 4 may be involved in TNF-alpha production from RAW264.7 cells and enhanced host resistance induced by p60 administration. Our findings demonstrated that p60 modulates innate immune responses against L. monocytogenes infection.

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.

Activation of phosphatidylinositol 3-kinase/protein kinase B by corticotropin-releasing factor in human monocytes

Corticotropin-releasing factor (CRF) exerts proinflammatory effects in peripheral tissues, whereas the intracellular pathways mediating these effects have not been completely characterized yet. We have previously shown that CRF induces nuclear factor-kappaB DNA-binding activity in mouse and human leukocytes. Here we demonstrate that in the human monocytic THP-1 cells, CRF activates the phosphatidylinositol 3-kinase (PI3K)/Akt and ERK1/2 pathways. These effects of CRF are mediated by corticotropin-releasing factor receptor 2 (CRF2), as suggested by their abolishment after treatment with the specific CRF2 antagonist, astressin 2B. The CRF-mediated PI3K/Akt activation induces cell survival as suggested by the stimulation of the antiapoptotic factor Bcl-2. ERK1/2 activation results in up-regulation of IL-8 expression, an effect inhibited by the CRF-induced activation of PI3K/Akt. These studies demonstrate novel effects of CRF in human monocytes mediated by the activation of PI3K/Akt. Moreover, they reveal pathway-specific effects of the CRF/CRF2 system in chemokine activation and cell survival that may be of importance for the development of novel therapeutics for inflammatory diseases.

Corticotropin Releasing Factor promotes breast cancer cell motility and invasiveness

INTRODUCTION

Cancer cells secrete bioactive peptides that act in an autocrine or paracrine fashion affecting tumor growth and metastasis. Corticotropin-releasing factor (CRF), a hypothalamic neuropeptide that controls the response to stress, has been detected in breast cancer tissues and cell lines. CRF can affect breast cancer cells in an autocrine or paracrine manner via its production from innervating sympathetic neurons or immune cells.

METHODS

In the present study we report our findings regarding the impact of CRF on breast cancer cell motility and invasiveness. For this purpose we used the MCF7 breast cancer cell line and evaluated the effect of CRF on motility and invasiveness using the wound-healing and boyden-chamber assays. In addition, we measured the effect of CRF on molecules that mediate motility by western blot, immunofluorescence, ELISA and RT-PCR.

RESULTS

Our findings show that: 1. CRF transiently inhibited the apoptosis of MCF7 cells. 2. CRF enhanced MCF7 cell motility in a wound healing assay and their invasiveness through extracellular matrix. 3. CRF increased actin polymerization, phosphorylation of Focal Adhesion Kinase (FAK), providing a potential mechanism for the observed induction of MCF7 motility. 4. CRF induced the expression of Cox-1 but not Cox-2 in MCF7 cells as well as the production of prostaglandins, factors known to promote invasiveness and metastasis.

CONCLUSION

Overall, our data suggest that CRF stimulates cell motility and invasiveness of MCF7 cells most probably via induction of FAK phosphorylation and actin filament reorganization and production of prostaglandins via Cox1. Based on these findings we postulate that the stress neuropeptide CRF present in the vicinity of tumors (either produced locally by the tumor cells themselves or by nearby normal cells or secreted from the innervations of surrounding tissues) may play an important role on breast tumor growth and metastatic capacity, providing a potential link between stress and tumor progression.

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.

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.

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.

Activation of corticotropin-releasing factor receptor-2 causes bronchorelaxation and inhibits pulmonary inflammation in mice

Urocortins are members of the corticotropin-releasing factor (CRF) family of peptides that bind to two receptors, CRF(1) and CRF(2). While CRF(1) is a high-affinity receptor for CRF, urocortin III binds with much greater affinity to CRF(2). In the present study we investigated the effect of CRF(2) receptor activation with urocortin III on airway smooth muscle tone in vitro and in an acute model of airway inflammation in mice. Urocortin III caused relaxation of methacholine-precontracted mouse tracheal segments. CRF caused similar relaxation, but with reduced potency compared to urocortin III, consistent with the CRF(2) receptor subtype. Relaxation induced by urocortin III was concentration-dependently inhibited by the CRF(2) antagonist, astressin 2B, with an IC(50) in the nanomolar range. These relaxations were potentiated by inhibition of phosphodiesterases but unaffected by inhibition of cyclooxygenase and NO or by removal of the epithelium. Finally, the number of neutrophils retrieved by bronchoalveolar lavage after administration of bacterial LPS (LPS) was reduced by prior intraperitoneal (i.p.) injection of urocortin III. This effect was also suppressed by astressin 2B, implicating CRF(2) receptors. Therefore, CRF(2) agonists appear to have both bronchorelaxant and anti-inflammatory activities and might represent an interesting therapeutic approach to the treatment of inflammatory lung diseases.