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

Control of myeloid cell functions by nociceptors

The immune system has evolved to protect the host from infectious agents, parasites, and tumor growth, and to ensure the maintenance of homeostasis. Similarly, the primary function of the somatosensory branch of the peripheral nervous system is to collect and interpret sensory information about the environment, allowing the organism to react to or avoid situations that could otherwise have deleterious effects. Consequently, a teleological argument can be made that it is of advantage for the two systems to cooperate and form an “integrated defense system” that benefits from the unique strengths of both subsystems. Indeed, nociceptors, sensory neurons that detect noxious stimuli and elicit the sensation of pain or itch, exhibit potent immunomodulatory capabilities. Depending on the context and the cellular identity of their communication partners, nociceptors can play both pro- or anti-inflammatory roles, promote tissue repair or aggravate inflammatory damage, improve resistance to pathogens or impair their clearance. In light of such variability, it is not surprising that the full extent of interactions between nociceptors and the immune system remains to be established. Nonetheless, the field of peripheral neuroimmunology is advancing at a rapid pace, and general rules that appear to govern the outcomes of such neuroimmune interactions are beginning to emerge. Thus, in this review, we summarize our current understanding of the interaction between nociceptors and, specifically, the myeloid cells of the innate immune system, while pointing out some of the outstanding questions and unresolved controversies in the field. We focus on such interactions within the densely innervated barrier tissues, which can serve as points of entry for infectious agents and, where known, highlight the molecular mechanisms underlying these interactions.

Adrenomedullin Expression Characterizes Leukemia Stem Cells and Associates With an Inflammatory Signature in Acute Myeloid Leukemia

Adrenomedullin (ADM) is a hypotensive and vasodilator peptide belonging to the calcitonin gene-related peptide family. It is secreted in vitro by endothelial cells and vascular smooth muscle cells, and is significantly upregulated by a number of stimuli. Moreover, ADM participates in the regulation of hematopoietic compartment, solid tumors and leukemias, such as acute myeloid leukemia (AML). To better characterize ADM involvement in AML pathogenesis, we investigated its expression during human hematopoiesis and in leukemic subsets, based on a morphological, cytogenetic and molecular characterization and in T cells from AML patients. In hematopoietic stem/progenitor cells and T lymphocytes from healthy subjects, ADM transcript was barely detectable. It was expressed at low levels by megakaryocytes and erythroblasts, while higher levels were measured in neutrophils, monocytes and plasma cells. Moreover, cells populating the hematopoietic niche, including mesenchymal stem cells, showed to express ADM. ADM was overexpressed in AML cells versus normal CD34+ cells and in the subset of leukemia compared with hematopoietic stem cells. In parallel, we detected a significant variation of ADM expression among cytogenetic subgroups, measuring the highest levels in inv(16)/t(16;16) or complex karyotype AML. According to the mutational status of AML-related genes, the analysis showed a lower expression of ADM in FLT3-ITD, NPM1-mutated AML and FLT3-ITD/NPM1-mutated cases compared with wild-type ones. Moreover, ADM expression had a negative impact on overall survival within the favorable risk class, while showing a potential positive impact within the subgroup receiving a not-intensive treatment. The expression of 135 genes involved in leukemogenesis, regulation of cell proliferation, ferroptosis, protection from apoptosis, HIF-1α signaling, JAK-STAT pathway, immune and inflammatory responses was correlated with ADM levels in the bone marrow cells of at least two AML cohorts. Moreover, ADM was upregulated in CD4+ T and CD8+ T cells from AML patients compared with healthy controls and some ADM co-expressed genes participate in a signature of immune tolerance that characterizes CD4+ T cells from leukemic patients. Overall, our study shows that ADM expression in AML associates with a stem cell phenotype, inflammatory signatures and genes related to immunosuppression, all factors that contribute to therapy resistance and disease relapse.

Triterpene saponins from Guo-gang-long attenuate collagen-induced arthritis via regulating A20 and inhibiting MAPK pathway

ETHNOPHARMACOLOGICAL RELEVANCE

The stems of Entada phaseoloides (L.) Merr commonly named "Guo-gang-long", is a traditional Chinese folk medicine that has been used clinically in China for the treatment of arthritis. Our previous study described that triterpene saponins isolated from "Guo-gang-long" could inhibit the inflammatory response. However, the potential mechanism of "Guo-gang-long" on treatment of arthritis, and whether the triterpene saponins responsible for its anti-arthritic effect are unclear.

AIM

To investigate the function and mechanisms of the triterpene saponins from E. phaseoloides (ES) in collagen-induced arthritis (CIA) rats.

MATERIALS AND METHODS

The chemical components of ES were analyzed by HPLC. Anti-arthritic activity of ES was investigated in CIA rats, which was established by immunization with bovine type II collagen. Three doses of ES (25, 50 and 100 mg/kg) were administrated using oral gavage to CIA rats daily for 3 weeks. The anti-arthritic activity of ES was evaluated by clinical arthritis scoring, paw swelling and mechanical sensitivity, as well as histological changes in CIA rats. The impacts of ES on the regulation of the ubiquintin-editing enzyme A20 and MAPK signaling pathway, and production of pro-inflammatory cytokines in CIA rats were examined by Western blot, quantitative real-time PCR, ELISA, and immunohistochemical staining, respectively.

RESULTS

ES treatment relieved the paw swelling, hyperalgesia and joint destruction, and prevented the progression of arthritis in CIA rats. Meanwhile, ES suppressed the excessive mRNA levels and protein expression of TNF-α and IL-17 in synovial tissues and hind paw joints, and reduced the production of IL-1β, TNF-α and IL-17 in serum. Furthermore, ES up-regulated A20 and suppressed the phosphorylation of p38 and ERK1/2 in hind paw joints, as well as inhibiting the activation of spinal p38 in CIA rats.

CONCLUSION

ES could relieve rheumatic symptoms and prevent the development of rheumatoid arthritis. The effects of ES may be mediated by reducing proinflammatory cytokine levels, up-regulating A20 expression, reducing p38 and ERK1/2 activation in periphery, and inhibiting of phospho-p38 in spinal cord.

Prevalence, risk factors and proteomic bioprofiles associated with heart failure in rheumatoid arthritis: The RA-HF study

BACKGROUND

Rheumatoid arthritis (RA) patients have high risk of heart failure (HF).

AIMS

Identifying the risk factors and mechanistic pathways associated with HF in patients with RA.

METHODS

Cohort study enrolling 355 RA patients. HF was defined according to the ESC criteria. 93 circulating protein-biomarkers (91CVDIIOlink®+troponin-T+c-reactive protein) were measured. Regression modeling (multivariate and multivariable) were built and network analyses were performed - based on the identified relevant protein biomarkers.

RESULTS

115 (32.4%) patients fulfilled the ESC criteria for HF, but only 24 (6.8%) had a prior HF diagnosis. Patients with HF were older (67 vs. 55yr), had a longer RA duration (10 vs. 14yr), had more frequently diabetes, hypertension, obesity, dyslipidemia, atrial fibrillation, and ischemic arterial disease. Several protein-biomarkers remained independently associated with HF, the top (FDR1%) were adrenomedullin, placenta-growth-factor, TNF-receptor-11A, and angiotensin-converting-enzyme-2. The networks underlying the expression of these biomarkers pointed towards congestion, apoptosis, inflammation, immune system signaling and RAAS activation as central determinants of HF in RA. Similar HF-associated biomarker-pathways were externally found in patients without RA. Having RA plus HF increased the risk of cardiovascular events compared to RA patients without RF; adjusted-HR (95%CI)=2.37 (1.07-5.30), p=0.034 CONCLUSION: Age, cardiovascular risk factors, and RA duration increase the HF odds in patients with RA. Few RA patients had a correct prior HF diagnosis, but the presence of HF increased the patients` risk. RA patients with HF largely share the mechanistic pathways of HF patients without RA. Randomized HF trials should include patients with RA. CLINICALTRIALS.

GOV ID

NCT03960515.

Adrenomedullin and truncated peptide adrenomedullin(22-52) affect chondrocyte response to apoptotis in vitro: downregulation of FAS protects chondrocyte from cell death

Chondrocyte apoptosis may have a pivotal role in the development of osteoarthritis. Interest has increased in the use of anti-apoptotic compounds to protect against osteoarthritis development. In this work, we investigated the effect of adrenomedullin (AM), a 52 amino-acid hormone peptide, and a 31 amino-acid truncated form, AM(22-52), on chondrocyte apoptosis. Bovine articular chondrocytes (BACs) were cultured under hypoxic conditions to mimic cartilage environment and then treated with Fas ligand (Fas-L) to induce apoptosis. The expression of AM and its calcitonin receptor-like receptor (CLR)/receptor activity-modifying protein (RAMP) (receptor/co-receptor) was assessed by immunostaining. We evaluated the effect of AM and AM(22-52) on Fas-L-induced chondrocyte apoptosis. FAS expression was appreciated by RT-qPCR and immunostainings. The expression of hypoxia-inducible factor 1α (HIF-1α), CLR and one co-receptor (RAMP2) was evidenced. With BACs under hypoxia, cyclic adenosine monophosphate production increased dose-dependently with AM stimulation. AM significantly decreased caspase-3 activity (mean 35% decrease; p = 0.03) as a marker of Fas-L-induced apoptosis. Articular chondrocytes treated with AM showed significantly reduced cell death, along with downregulated Fas expression and production, as compared with AM(22-52). AM decreased articular chondrocyte apoptosis by downregulating a Fas receptor. These findings may pave the way for novel therapeutic approaches in osteoarthritis.

Adrenomedullin, a Novel Target for Neurodegenerative Diseases

Neurodegenerative diseases represent a heterogeneous group of disorders whose common characteristic is the progressive degeneration of neuronal structure and function. Although much knowledge has been accumulated on the pathophysiology of neurodegenerative diseases over the years, more efforts are needed to understand the processes that underlie these diseases and hence to propose new treatments. Adrenomedullin (AM) is a multifunctional peptide involved in vasodilation, hormone secretion, antimicrobial defense, cellular growth, and angiogenesis. In neurons, AM and related peptides are associated with some structural and functional cytoskeletal proteins that interfere with microtubule dynamics. Furthermore, AM may intervene in neuronal dysfunction through other mechanisms such as immune and inflammatory response, apoptosis, or calcium dyshomeostasis. Alterations in AM expression have been described in neurodegenerative processes such as Alzheimer's disease or vascular dementia. This review addresses the current state of knowledge on AM and its possible implication in neurodegenerative diseases.

Peptide Receptor-Targeted Fluorescent Probe: Visualization and Discrimination between Chronic and Acute Ulcerative Colitis

The inflammatory activity of ulcerative colitis plays an important role in the medical treatment. However, accurate and real-time monitoring of the colitis activity with noninvasive bioimaging method is still challenging, especially in distinguishing between chronic and acute colitis. As a good receptor, the oligopeptide transporter (PepT1) is overexpressed in the colonic epithelial cells of chronic ulcerative colitis, which can deliver tripeptide KPV (Lys-Pro-Val, the C-terminal sequence of α-MSH) into cytosol in the intestine. Herein, we report a PepT1 peptide receptor-targeted fluorescent probe, dicyanomethylene-4H-pyran (DCM)-KPV, with the strategy of conjugating the KPV into the DCM chromophore. The diagnostic fluorescent probe bestows a specific receptor-targeted interaction with PepT1 through the KPV moiety, possessing several beneficial characteristics, such as efficient long emission, low photobleaching, negligible cytotoxicity, and high cytocompatibility in living cells. We build the overexpressed PepT1 on the cytomembrane of ulcerative colitis model Caco-2 cell as the efficient receptor to accumulate the targeted tripeptide KPV in the cytoplasm and nucleus. With the co-localization of DCM-KPV and the DNA-specific fluorophore, DAPI, the specifically long emission from chromophore DCM and efficient receptor-targeted peptide KPV, the fluorescent probe of DCM-KPV makes a breakthrough to the direct noninvasive observation of the accumulation in colon inflammation regions via intestinal mucosa, even successfully distinguishing the chronic, acute ulcerative colitis and normal groups. Compared with the traditional unenhanced magnetic resonance imaging and hematoxylin and eosin (H&E) staining, we make full use of exploiting the specific target-receptor interaction between the tripeptide unit, KPV, and the oligopeptide transporter, PepT1, for sensing selectivity. The desirable diagnostic ability of DCM-KPV can guarantee the real-time tracking and visualization of the role of intracellular KPV on ulcerative colitis, which provides an alternative to replace the time-consuming and tissue sampling-invasive H&E staining diagnosis.

Adrenomedullin Regulates IL-1β Gene Expression in F4/80+ Macrophages during Synovial Inflammation

Adrenomedullin (AM) plays an important role in the regulation of inflammatory processes; however, the role and expression of AM in synovial inflammation have not been determined. To investigate the expression and role of AM in inflamed synovial tissue (ST), the gene expression profiles of AM in the ST, including synovial macrophages and fibroblasts, of a murine patellar surgical dislocation model were characterized. In addition, the effects of interleukin- (IL-) 1β and AM in cultured synovial cells were also examined. CD11c⁺ macrophages were found to be elevated in ST of the surgically dislocated patella. Higher gene expression of CD11c, IL-1β, AM, receptor activity-modifying proteins 2 (RAMP2), and 3 (RAMP3) was also observed in ST obtained from the dislocated side. AM expression was also significantly increased in synovial fibroblasts and macrophages in response to IL-1β treatment. Synovial macrophages also highly expressed RAMP3 compared to fibroblasts and this expression was further stimulated by exogenously added IL-1β. Further, the treatment of the F4/80-positive cell fraction obtained from ST with AM inhibited IL-1β expression. Taken together, these findings demonstrated that AM was produced by synovial fibroblasts and macrophages in inflamed ST and that increased levels of AM may exert anti-inflammatory effects on synovial macrophages.

An intracellular adrenomedullin system reduces IL-6 release via a NF-kB-mediated, cAMP-independent transcriptional mechanism in rat thymic epithelial cells

Thymic epithelial cells (TECs) play a key role in the regulation of central immune tolerance by expressing autoantigens and eliminating self-reactive T cells. In a previous paper we reported that adrenomedullin (ADM) and its co-receptor protein RAMP2 are located intracellularly in newborn human thymic epithelial cells (TECs). This work has two main aims: (1) to examine the cellular localization of ADM and its receptor in TECs of adult Wistar rats to validate this animal model for the study of the ADM system and its function(s) in thymus; (2) to investigate the potential modulating effect of ADM on the NF-kB pathway, which is involved through the production of cytokines such as IL-6, in the maturation of T-lymphocytes and immunological tolerance. Our results show that, similarly to human newborn TECs, ADM is localized to the cytoplasm of adult rat TECs, and RAMP2 is expressed in the nucleus but not in the plasma membrane. Pretreatment of TECs for 4h with ADM significantly reduced lipopolysaccharide (LPS)-induced release of IL-6 (P<0.001) and expression of the p65 subunit of NF-kB, while doubled the expression of IkBα (P<0.001), the physiological inhibitor of NF-kB nuclear translocation. These effects were not mediated by activation of the cAMP pathway, a signalling cascade that is rapidly activated by ADM in cells that express plasma membrane RAMP2, but were the consequence of a reduction in the transcription of p65 (P<0.001) and an increase in the transcription of IkBα (P<0.05). On the basis of these findings we propose that in rat TECs ADM reduces IL-6 secretion by modulating NF-kB genes transcription through an interaction with a receptor localized to the nucleus. This may partly explain the protective effects of ADM in autoimmune diseases and points to the ADM system of TECs as a novel potential target for immunomodulating drugs.

Osteoarticular Expression of Musashi-1 in an Experimental Model of Arthritis

Background. Collagen-induced arthritis (CIA), a murine experimental disease model induced by immunization with type II collagen (CII), is used to evaluate novel therapeutic strategies for rheumatoid arthritis. Adult stem cell marker Musashi-1 (Msi1) plays an important role in regulating the maintenance and differentiation of stem/precursor cells. The objectives of this investigation were to perform a morphological study of the experimental CIA model, evaluate the effect of TNFα-blocker (etanercept) treatment, and determine the immunohistochemical expression of Msi1 protein. Methods. CIA was induced in 50 male DBA1/J mice for analyses of tissue and serum cytokine; clinical and morphological lesions in limbs; and immunohistochemical expression of Msi1. Results. Clinically, TNFα-blocker treatment attenuated CIA on day 32 after immunization (P < 0.001). Msi1 protein expression was significantly higher in joints damaged by CIA than in those with no lesions (P < 0.0001) and was related to the severity of the lesions (Spearman's rho = 0.775, P = 0.0001). Conclusions. Treatment with etanercept attenuates osteoarticular lesions in the murine CIA model. Osteoarticular expression of Msi1 protein is increased in joints with CIA-induced lesion and absent in nonlesioned joints, suggesting that this protein is expressed when the lesion is produced in order to favor tissue repair.

Dynamic Frequency of Blood CD4+CD25+ Regulatory T Cells in Rats with Collagen-induced Arthritis

CD4+CD25+ regulatory T cells (CD4+CD25+ Tregs) have been shown to play a regulatory or suppressive role in the immune response and are possibly relevant to the pathogenesis of autoimmune diseases. In the present study, we attempted to investigate the frequency of CD4+CD25+ Tregs in peripheral blood (PB) of collagen-induced arthritis (CIA) rats during the development of arthritis, to determine whether their frequency is involved in the immunoregulation of this disease. The results showed that normal rats had similar frequencies of CD4+CD25+ Tregs in PB during the experiment time, expressed as a percentage of CD4+CD25+Foxp3+ T cells among the CD4+ T lymphocyte population. In contrast, the frequency of CD4+CD25+Foxp3+ T cells in CIA rats was found to change during the development of arthritis. In CIA rats, there is a significant negative correlation between the frequency of CD4+CD25+Foxp3+ T cells and paw swelling (r=-0.786, p< 0.01). The relationship between the frequency of CD4+CD25+Foxp3+ T and immune activation was not found in normal rats. During the time course, the frequency of CD4+CD25+Foxp3+ T was lower in CIA rats than in normal ones. The data suggest that the frequency of PB CD4+CD25+ Tregs may be a promising marker for arthritis activity.

Involvement of calcitonin gene-related peptide and receptor component protein in experimental autoimmune encephalomyelitis

Calcitonin Gene-Related Peptide (CGRP) inhibits microglia inflammatory activation in vitro. We here analyzed the involvement of CGRP and Receptor Component Protein (RCP) in experimental autoimmune encephalomyelitis (EAE). Alpha-CGRP deficiency increased EAE scores which followed the scale alpha-CGRP null>heterozygote>wild type. In wild type mice, CGRP delivery into the cerebrospinal fluid (CSF) 1) reduced chronic EAE (C-EAE) signs, 2) inhibited microglia activation (revealed by quantitative shape analysis), and 3) did not alter GFAP expression, cell density, lymphocyte infiltration, and peripheral lymphocyte production of IFN-gamma, TNF-alpha, IL-17, IL-2, and IL-4. RCP (probe for receptor involvement) was expressed in white matter microglia, astrocytes, oligodendrocytes, and vascular-endothelial cells: in EAE, also in infiltrating lymphocytes. In relapsing-remitting EAE (R-EAE) RCP increased during relapse, without correlation with lymphocyte density. RCP nuclear localization (stimulated by CGRP in vitro) was I) increased in microglia and decreased in astrocytes (R-EAE), and II) increased in microglia by CGRP CSF delivery (C-EAE). Calcitonin like receptor was rarely localized in nuclei of control and relapse mice. CGRP increased in motoneurons. In conclusion, CGRP can inhibit microglia activation in vivo in EAE. CGRP and its receptor may represent novel protective factors in EAE, apparently acting through the differential cell-specific intracellular translocation of RCP.

Adrenomedullin protects from experimental autoimmune encephalomyelitis at multiple levels

Adrenomedullin is a neuropeptide known for its cardiovascular activities and anti-inflammatory effects. Here, we investigated the effect of adrenomedullin in a model of experimental autoimmune encephalomyelitis (EAE) that mirrors chronic progressive multiple sclerosis. A short-term systemic treatment with adrenomedullin reduced clinical severity and incidence of EAE, the appearance of inflammatory infiltrates in spinal cord and the subsequent demyelination and axonal damage. This effect was exerted at multiple levels affecting both early and late events of the disease. Adrenomedullin decreased the presence/activation of encephalitogenic Th1 and Th17 cells and down-regulated several inflammatory mediators in peripheral lymphoid organs and central nervous system. Noteworthy, adrenomedullin inhibited the production by encephalitogenic cells of osteopontin and of Granulocyte Macrophage Colony-Stimulating Factor (GM-CSF), two critical cytokines in the development of EAE. At the same time, adrenomedullin increased the number of IL-10-producing regulatory T cells with suppressive effects on the progression of EAE. Furthermore, adrenomedullin generated dendritic cells with a semi-mature phenotype that impaired encephalitogenic responses in vitro and in vivo. Finally, adrenomedullin regulated glial activity and favored an active program of neuroprotection/regeneration. Therefore, the use of adrenomedullin emerges as a novel multimodal therapeutic approach to treat chronic progressive multiple sclerosis.

Adrenomedullin and adrenotensin regulate collagen synthesis and proliferation in pulmonary arterial smooth muscle cells

To understand the pathophysiological mechanisms of pulmonary arterial smooth muscle cell (PASMC) proliferation and extracellular-matrix accumulation in the development of pulmonary hypertension and remodeling, this study determined the effects of different doses of adrenomedullin (ADM) and adrenotensin (ADT) on PASMC proliferation and collagen synthesis. The objective was to investigate whether extracellular signal-regulated kinase (ERK1/2) signaling was involved in ADM- and ADT-stimulated proliferation of PASMCs in 4-week-old male Wistar rats (body weight: 100-150 g, n=10). The proliferation of PASMCs was examined by 5-bromo-2-deoxyuridine incorporation. A cell growth curve was generated by the Cell Counting Kit-8 method. Expression of collagen I, collagen III, and phosphorylated ERK1/2 (p-ERK1/2) was evaluated by immunofluorescence. The effects of different concentrations of ADM and ADT on collagen I, collagen III, and p-ERK1/2 protein expression were determined by immunoblotting. We also investigated the effect of PD98059 inhibition on the expression of p-ERK1/2 protein by immunoblotting. ADM dose-dependently decreased cell proliferation, whereas ADT dose-dependently increased it; and ADM and ADT inhibited each other with respect to their effects on the proliferation of PASMCs. Consistent with these results, the expression of collagen I, collagen III, and p-ERK1/2 in rat PASMCs decreased after exposure to ADM but was upregulated after exposure to ADT. PD98059 significantly inhibited the downregulation by ADM and the upregulation by ADT of p-ERK1/2 expression. We conclude that ADM inhibited, and ADT stimulated, ERK1/2 signaling in rat PASMCs to regulate cell proliferation and collagen expression.

Adrenomedullin delivery in microsphere-scaffold composite for remodeling of the alveolar bone following tooth extraction: an experimental study in the rat

Background

Alveolar ridge resorption, as a significant problem in implant and restorative dentistry, has long been considered as an inevitable outcome following tooth extraction. Recently, adrenomedullin (ADM) is reported to be able to stimulate the proliferation and migration of various cells including osteoblasts. The purpose of this study was to investigate the influence of local ADM application in the tooth extraction socket in vivo.

Methods

Chitosan micropheres were developed by an emulsion-ionic cross-linking method for ADM delivery. Poly (L -lactic-co-glycolic) acid (PLGA) and nano-hydroxyapatite (nHA) were used to prepare scaffolds to contain the micrspheres with ADM. In vivo experiment was evaluated by transplanting the composite into the rat socket right after the incisor extraction. After 4, 8, 12 weeks implantation, radiographic and histological tests were carried out to evaluate the effect of released ADM on the alveolar bone.

Results

The microspheres had a spherical structure and a relative rough and uniform surface, and the particle size was under a normal distribution, with the average diameter of 38.59 μm. The scaffolds had open and interconnected pores. In addition, the high porosity of the composite was 88.93%. Radiographic and histological examination revealed that the PLGA/nHA/CMs/ADM composite could accelerate the alveolar bone remodeling and reduce the residual ridge resorption compared with the PLGA/nHA/CMs scaffold.

Conclusions

The results of this study suggest that local application of ADM has the potential to preserve the residual alveolar ridge and accelerate the alveolar bone remodeling.

Regulation of myofibroblast differentiation and bleomycin-induced pulmonary fibrosis by adrenomedullin

Myofibroblast differentiation induced by transforming growth factor-β (TGF-β) is characterized by the expression of smooth muscle α-actin (SMA) and extracellular matrix proteins. We and others have previously shown that these changes are regulated by protein kinase A (PKA). Adrenomedullin (ADM) is a vasodilator peptide that activates cAMP/PKA signaling through the calcitonin-receptor-like receptor (CRLR) and receptor-activity-modifying proteins (RAMP). In this study, we found that recombinant ADM had little effect on cAMP/PKA in quiescent human pulmonary fibroblasts, whereas it induced a profound activation of cAMP/PKA signaling in differentiated (by TGF-β) myofibroblasts. In contrast, the prostacyclin agonist iloprost was equally effective at activating PKA in both quiescent fibroblasts and differentiated myofibroblasts. TGF-β stimulated a profound expression of CRLR with a time course that mirrored the increased PKA responses to ADM. The TGF-β receptor kinase inhibitor SB431542 abolished expression of CRLR and attenuated the PKA responses of cells to ADM but not to iloprost. CRLR expression was also dramatically increased in lungs from bleomycin-treated mice. Functionally, ADM did not affect initial differentiation of quiescent fibroblasts in response to TGF-β but significantly attenuated the expression of SMA, collagen-1, and fibronectin in pre-differentiated myofibroblasts, which was accompanied by decreased contractility of myofibroblasts. Finally, sensitization of ADM signaling by transgenic overexpression of RAMP2 in myofibroblasts resulted in enhanced survival and reduced pulmonary fibrosis in the bleomycin model of the disease. In conclusion, differentiated pulmonary myofibroblasts gain responsiveness to ADM via increased CRLR expression, suggesting the possibility of using ADM for targeting pathological myofibroblasts without affecting normal fibroblasts.

Adrenomedullin, a neuropeptide with immunoregulatory properties induces semi-mature tolerogenic dendritic cells

Dendritic cells (DC) play a pivotal role in tolerance. Adrenomedullin (AM), a neuropeptide with anti-apoptotic and anti-inflammatory effects, may decrease T helper type 1 effector cells and induce regulatory T (Treg) cells. The aim of this study was to evaluate AM effects on murine dendritic cell (DC) maturation and functions. Bone marrow-derived DC were produced and stimulated with CpG motifs, lipopolysaccharide or AM for 24 hr. Then, DC maturation and expression of AM and AM receptors were evaluated. Compared with lipopolysaccharide-stimulated or CpG-stimulated DC, AM-stimulated DC had lower levels of co-stimulatory molecule expression and pro-inflammatory cytokine release. The AM induced high levels of interferon-γ but not of interleukin-10. Importantly, AM inhibited lipopolysaccharide-induced maturation of DC. However, allogeneic T-cell stimulation and endocytic capacity of AM-stimulated DC were comparable to those of semi-mature and mature DC. Moreover, DC expressed AM and its receptors at a basal level, and AM receptor expression increased with DC maturation. The AM stimulation induced indoleamine 2,3-dioxygenase (IDO) expression, promoting Treg cell expansion. For the first time, we describe the DC maturation phenotype by a neuropeptide (AM). We have demonstrated that AM and its receptors are expressed in DC and that exogenous AM can modify the DC phenotype and functions and can induce a semi-mature DC phenotype with IDO expression. These results indicate close interactions among immune system regulation mechanisms and calcitonin-like peptides.

Adrenomedullin receptors on human T cells are glucocorticoid-sensitive

Adrenomedullin (AM) is a novel vasodilatatory peptide which acts primarily through the calcitonin receptor-like receptor (CLR) in combination with either receptor-activity-modifying-protein (RAMP) 2 or 3 (forming receptors, AM(1) and AM(2) respectively). AM plays an important role during inflammation, with its expression increasing following cytokine treatment, promoting macrophage action in situ and high expression by T cells during hypoxic conditions. Examination of T cell AM receptor expression has previously been incomplete, hence we here consider the presentation of AM receptors and their responsiveness to AM and glucocorticoids (GC). AM receptor expression was examined by PCR and flow cytometry in primary human T cells, revealing that RAMP2, 3 and CLR are physiologically expressed in unstimulated T cells, both intracellularly and on the cell surface. PHA stimulation decreased receptor proteins, significantly so for CLR and RAMP3. Incubation with AM elicited limited receptor alterations however, GC treatment (10(-6) M; 24 h) markedly affected cell surface expression, significantly increasing receptor components in unstimulated cells and significantly decreasing the same in stimulated T cells. Our findings indicate that human T cells utilize both AM(1) and AM(2) receptors, which are GC-sensitive in an activation-state dependent manner.

Anti-inflammatory effects of adrenomedullin on acute lung injury induced by Carrageenan in mice

Adrenomedullin (AM) is a 52 amino acid peptide that has shown predominant anti-inflammatory activities. In the present study, we evaluated the possible therapeutic effect of this peptide in an experimental model of acute inflammation, the carrageenan- (CAR-) induced pleurisy. Pleurisy was induced by injection of CAR into the pleural cavity of mice. AM (200 ng/kg) was administered by intraperitoneal route 1 h after CAR, and the animals were sacrificed 4 h after that. AM treatment attenuated the recruitment of leucocytes in the lung tissue and the generation and/or the expression of the proinflammatory cytokines as well as the expression of the intercellular cell adhesion molecules. Moreover, AM inhibited the induction of inducible nitric oxide synthase (iNOS), thereby abating the generation of nitric oxide (NO) and prevented the oxidative and nitroxidative lung tissue injury, as shown by the reduction of nitrotyrosine, malondialdehyde (MDA), and poly (ADP-ribose) polymerase (PARP) levels. Finally, we demonstrated that these anti-inflammatory effects of AM were associated with the inhibition of nuclear factor-κB (NF-κB) activation. All these parameters were markedly increased by intrapleural CAR in the absence of any treatment. We report that treatment with AM significantly reduces the development of acute lung injury by downregulating a broad spectrum of inflammatory factors.

Adrenomedullin(22-52) combats inflammation and prevents systemic bone loss in murine collagen-induced arthritis

OBJECTIVE

Adrenomedullin(22-52) is a truncated peptide derived from adrenomedullin, a growth factor with antiapoptotic and immunoregulatory properties. It can act as an agonist or an antagonist depending on cell type. Its in vivo effects are unknown, but adrenomedullin(22-52) could possess immunomodulatory properties. This study was undertaken to evaluate the effect of adrenomedullin(22-52) in a mouse model of arthritis.

METHODS

DBA/1 mice with collagen-induced arthritis (CIA) were treated with 1.2 μg/gm adrenomedullin(22-52) , adrenomedullin, or saline at arthritis onset. Bone mineral density was measured at the beginning of the experiment and when mice were killed. Mouse joints were processed for histologic analysis and protein studies, and spleens were examined for Treg cell expression. Cytokine expression was studied in mouse joint tissue and serum.

RESULTS

In mice with CIA, adrenomedullin and adrenomedullin(22-52) reduced clinical and histologic arthritis scores and shifted the pattern of articular and systemic cytokine expression from Th1 to Th2, as compared to untreated mice with CIA (controls). Tumor necrosis factor α, interleukin-6 (IL-6), and IL-17A levels were significantly decreased in the joints of mice with CIA treated with adrenomedullin or adrenomedullin(22-52) as compared to controls, whereas IL-4 and IL-10 levels were increased. Adrenomedullin(22-52) was more effective than adrenomedullin in modulating cytokine content and enhanced Treg cell function without changing Treg cell expression compared to controls. Adrenomedullin receptor binding and transcriptional adrenomedullin receptor expression were markedly increased in joints from controls, whereas adrenomedullin receptor binding was considerably decreased in treated animals. Mice with CIA treated with adrenomedullin or adrenomedullin(22-52) had considerably fewer apoptotic chondrocytes and diminished cartilage degradation. Adrenomedullin(22-52) completely prevented systemic bone loss by preserving osteoblastic activity, but without changes in osteoclastic activity.

CONCLUSION

Our findings indicate that adrenomedullin(22-52) , which has no vasoactive or tumor-inducing effects, is a potent antiinflammatory and bone-protective agent in this arthritis model.

Cholecystokinin octapeptide significantly suppresses collagen-induced arthritis in mice by inhibiting Th17 polarization primed by dendritic cells

Cholecystokinin octapeptide (CCK-8) is a neuropeptide, and is shown to be a potent immunomodulator with predominant anti-inflammatory effects. Although the regulatory effect of CCK-8 on macrophages and B cells has been defined, the effect of CCK-8 on dendritic cells (DCs) and T cells is not well understood. In this study, we showed that CCK-8 reduced the expression of CD80, CD86, and MHCII on DCs. Moreover, CCK-8 promoted Th1 and inhibited Th17 polarization by increasing the production of IL-12 and decreasing the production of IL-6 and IL-23 on DCs in vitro and in vivo. In addition, intraperitoneal administration of CCK-8 to mice with collagen-induced arthritis (CIA) was found to effectively reduce the incidence of arthritis, delay its onset and prevent the occurrence of joint damage. Collectively, these results suggest that CCK-8 significantly suppresses the incidence and severity of CIA in mice, through the inhibition of DC mediated Th17 polarization.

Anti-inflammatory actions of adrenomedullin through fine tuning of HIF stabilization

In intact mucosal tissues, epithelial cells are anatomically positioned in proximity to a number of subepithelial cell types, including endothelia. A number of recent studies have suggested that imbalances between energy supply and demand can result in "inflammatory hypoxia." Given these associations, we hypothesized that endothelial-derived, hypoxia-inducible mediators might influence epithelial function. Guided by cDNA microarray analysis of human microvascular endothelial cells (HMEC-1 line) subjected to hypoxia (pO(2) 20 torr, 8 h), we identified adrenomedullin (ADM) as a prominent hypoxia-inducible factor (HIF) that acts on epithelial cells through cell surface receptors. We assessed the functional ability for exogenous ADM to signal in human intestinal Caco2 cells in vitro by demonstrating a dose-dependent induction of Erk1/2phosphorylation. Further analysis revealed that ADM deneddylates cullin-2 (Cul2), whose action has been demonstrated to control the activity of HIF. Caco2 cells stably expressing a hypoxic response element (HRE)-driven luciferase promoter confirmed that ADM activates the HIF signaling pathway. Extensions of these studies revealed an increase in canonical HIF-1-dependent genes following stimulation with ADM. To define physiological relevance, we investigated the effect of ADM in a DSS model of murine colitis. Administration of ADM resulted in reduced inflammatory indices and less severe histological inflammation compared to vehicle controls. Analysis of tissue and serum cytokines showed a marked and significant inhibition of colitis-associated TNF-α, IL-1β, and KC. Analysis of circulating ADM demonstrated an increase in serum ADM in murine models of colitis. Taken together, these results identify ADM as an endogenously generated vascular mediator that functions as a mucosal protective factor through fine tuning of HIF activity.

Neuropeptides as pleiotropic modulators of the immune response

Although necessary to eliminate pathogens, inflammation can lead to serious deleterious effects in the host if left unchecked. During the inflammatory response, further damage may arise from potential autoimmune responses occurring when the immune cells and molecules that respond to pathogen-derived antigens also react to self-antigens. In this sense, the identification of endogenous factors that control exacerbated immune responses is a key goal for the development of new therapeutic approaches for inflammatory and autoimmune diseases. Some neuropeptides that are produced during the ongoing inflammatory response have emerged as endogenous anti-inflammatory agents that could collaborate in tuning the balanced steady state of the immune system. These neuropeptides participate in maintaining immune tolerance through two distinct mechanisms: 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. Indeed, a functioning neuropeptide system contributes to general health, and alterations in the levels of these neuropeptides and/or their receptors lead to changes in susceptibility to inflammatory and autoimmune diseases. Recently, we found that some neuropeptides also have antimicrobial and antiparasitic actions, suggesting that they could act as primary mediators of innate defense, even in the most primitive organisms. In this review, we use the vasoactive intestinal peptide as example of an immunomodulatory neuropeptide to summarize the most relevant data found for other neuropeptides with similar characteristics, including adrenomedullin, urocortin, cortistatin and ghrelin.

Neuropeptides: keeping the balance between pathogen immunity and immune tolerance

Various neuropeptides have emerged recently as potent immunomodulatory factors with potential for their therapeutic use in immune disorders. Here we highlight the most recent data relevant in the field and we offer our opinion on how neuropeptide therapy might impact clinical immune diseases, and the challenges in this field that must be overcome before achieving medical progress. We also review recent reports describing the antimicrobial effects showed by some neuropeptides and the therapeutic, physiological, and evolutionary consequences of this new finding. Finally, we discuss how a physiologically functional neuropeptide system contributes to general health and how neuropeptides educate our immune system to be tolerant.

Role of adrenomedullin in Lyme disease

Borrelia burgdorferi stimulates a strong inflammatory response during infection of a mammalian host. To understand the mechanisms of immune regulation employed by the host to control this inflammatory response, we focused our studies on adrenomedullin, a peptide produced in response to bacterial stimuli that exhibits antimicrobial activity and regulates inflammatory responses by modulating the expression of inflammatory cytokines. Specifically, we investigated the effect of B. burgdorferi on the expression of adrenomedullin as well as the ability of adrenomedullin to dampen host inflammatory responses to the spirochete. The concentration of adrenomedullin in the synovial fluid of untreated Lyme arthritis patients was elevated compared with that in control osteoarthritis patient samples. In addition, coculture with B. burgdorferi significantly increased the expression of adrenomedullin in RAW264.7 macrophages through MyD88-, phosphatidylinositol 3-kinase (PI3-K)-, and p38-dependent signaling cascades. Furthermore, the addition of exogenous adrenomedullin to B. burgdorferi-stimulated RAW264.7 macrophages resulted in a significant decrease in the induction of proinflammatory cytokines. Taken together, these results suggest that B. burgdorferi increases the production of adrenomedullin, which in turn negatively regulates the B. burgdorferi-stimulated inflammatory response.

Adrenomedullin in sinusoidal endothelial cells play protective roles against cold injury of liver

Donor organ damage caused by cold preservation is a major problem affecting liver transplantation. Cold preservation most easily damages liver sinusoidal endothelial cells (LSECs), and information about the molecules modulating LSECs function can provide the basis for new therapeutic strategies. Adrenomedullin (AM) is a peptide known to possess anti-apoptotic and anti-inflammatory properties. AM is abundant in vascular endothelial cells, but levels are comparatively low in liver, and little is known about its function there. In this study, we demonstrated both AM and its receptors are expressed in LSECs. AM treatment reduced LSECs loss and apoptosis under cold treatment. AM also downregulated cold-induced expression of TNFalpha, IL1beta, IL6, ICAM1 and VCAM1. AM reduced apoptosis and expression of ICAM1 and VCAM1 in an in vivo liver model subjected to cold storage. Conversely, apoptosis was exacerbated in livers from AM and RAMP2 (AM receptor activity-modifying protein) knockout mice. These results suggest that AM expressed in LSECs exerts a protective effect against cold-organ damage through modulation of apoptosis and inflammation.

Cholecystokinin octapeptide exerts its therapeutic effects on collagen-induced arthritis by suppressing both inflammatory and Th17 responses

The purpose of this study was to evaluate the potential therapeutic effect of cholecystokinin octapeptide (CCK-8) on collagen-induced arthritis (CIA), an accepted murine experimental disease model with diverse histopathological features similar to human rheumatoid arthritis (RA). CIA was induced in DBA/1J mice by immunization with chicken collagen type II (CII). CCK-8 at different doses was intraperitoneally administered daily for 1 week. Mice treated with CCK-8 at doses of 5 and 10 nmol but not 1 nmol displayed much delayed onset of CIA and significantly lower incidence and decreased severity of arthritis. CCK-8 treatment significantly reduced the production of cytokines (IL-17, IL-23, IL-6 and TNF-α) and chemokines monocyte chemoattractant protein 1 in the joints of arthritic mice or in synovial cell culture supernatant, and increased the levels of IFN-γ and TGF-β. T cells from CCK-8 treated mice proliferated much less, produced low level of IL-17 and high levels of IFN-γ and TGF-β. Moreover, CCK-8 treated mice showed lower levels of CII-specific IgG, particularly that of IgG2a, in sera than those from control mice. These results indicate that CCK-8 is effective in suppressing both inflammatory and Th17 responses in CIA. CCK-8 may represent a new therapeutic modality for rheumatoid arthritis.

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.

Adrenomedullin inhibits MAPK pathway-dependent rheumatoid synovial fibroblast-mediated osteoclastogenesis by IL-1 and TNF-alpha

The objective of this study is to determine the effects of adrenomedullin (AM) on IL-1- and TNF-alpha-induced rheumatoid synovial fibroblasts (RASFs)-mediated osteoclastogenesis. The formation of osteoclasts in co-cultures of RASFs and peripheral blood mononuclear cells was evaluated by tartrate-resistant acid phosphatase and resorption pit formation assay. The expression of RANKL, OPG, p-ERK, p-p38, and p-JNK was examined by immunoblotting and quantitative reverse transcription-polymerase chain reaction. AM (1-52) inhibits IL-1- and TNF-alpha-induced RASFs-mediated osteoclastogenesis. AM affected IL-1-, TNF-alpha-induced RANKL and OPG expression in RASFs. AM also inhibits IL-1 and TNF-alpha-induced phosphorylation of ERK-1/2, p38 MAPK, and JNK. Inhibitor of AM (AM 22-52) inhibits the effects of AM on the osteoclastogenesis. These results suggest that AM might be involved in the inflammatory cytokines-mediated osteoclastogenesis and thus bone damage, and indicate that it can be a new therapeutic strategy against joint destruction in RA.

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.

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.

Adrenomedullin suppresses tumour necrosis factor alpha-induced CXC chemokine ligand 10 production by human gingival fibroblasts

Periodontal disease is an inflammatory disorder characterized by the involvement of chemokines that are important for the recruitment of leucocytes. Several cytokines, including tumour necrosis factor alpha (TNF-alpha), are involved in regulating levels of chemokines in periodontal disease. CXC chemokine ligand 10 (CXCL10) is a chemokine related to the migration of T helper 1 cells. In this study, we examined CXCL10 expression in human gingival fibroblasts (HGFs). Moreover, we investigated the effects of adrenomedullin (AM), which is a multi-functional regulatory peptide, on the production of CXCL10 by HGFs. We revealed that TNF-alpha stimulation induced CXCL10 production by HGFs. HGFs expressed AM and AM receptors, calcitonin-receptor-like receptor (CRLR) and receptor-activity-modifying protein (RAMP) 2, mRNAs constitutively. AM treatment supressed CXCL10 production by TNF-alpha-stimulated HGFs. Moreover, we elucidated that AM produced by HGFs inhibited CXCL10 production by HGFs, because AM antagonist enhanced CXCL10 production by HGFs. TNF-alpha treatment enhanced CRLR and RAMP2 mRNA expression in HGFs. Furthermore, AM is expressed in human periodontal tissues, including both inflamed and clinically healthy tissues. These results suggest that the CXCL10 produced by HGFs may be involved in the migration of leucocytes into inflamed tissues and related to exacerbation of periodontal disease. AM might be a therapeutic target of periodontal disease, because AM can inhibit CXCL10 production by HGFs.

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.

Mice heterozygous for adrenomedullin exhibit a more extreme inflammatory response to endotoxin-induced septic shock

Adrenomedullin (AM) is a highly conserved peptide that can act as a potent vasodilator, anti-microbial factor and anti-inflammatory factor. Several studies have implicated diverse roles for AM in regulating the inflammatory and hemodynamic responses to septic shock. Moreover, during sepsis the receptors that mediate AM signaling [calcitonin receptor-like receptor (calcrl) and receptor activity modifying proteins (RAMP) 2 and 3] undergo dynamic and robust changes in their expression. Although numerous studies have used animal models to study the role of administered or increased AM in septic animals, genetic studies to determine the consequences of reduced AM during septic shock have not yet been performed. Here, we used a murine model of lipopolysaccharide (LPS)-induced septic shock to assess the inflammatory response in mice heterozygous for the AM gene. Following LPS challenge, AM(+/-) mice had higher expression of TNF-alpha and IL-1beta than LPS-treated wild-type (WT) controls. Consequently, serum TNF-alpha was also significantly elevated in LPS-treated AM(+/-) mice compared to WT LPS-treated mice. We also observed higher serum levels of liver enzymes, suggesting more advanced end-organ damage in mice with genetically reduced AM. Finally, we found that RAMP2 and calcrl expression levels were markedly reduced in LPS-treated mice, whereas RAMP3 expression was significantly elevated. Importantly, these changes in receptor gene expression were conserved in AM(+/-) mice, demonstrating that AM peptide itself does not impact directly on the expression of the genes encoding its receptors. We, therefore, conclude that during septic shock the dynamic modulation of AM and its receptors primarily functions to dampen the inflammatory response.

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.