Vasoactive Intestinal Polypeptide Suppressed Experimental Autoimmune Encephalomyelitis by Inhibiting T Helper 1 Responses

Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors

Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.

Mechanism of Immunoregulatory Properties of Vasoactive Intestinal Peptide in the K/BxN Mice Model of Autoimmune Arthritis

The K/BxN mouse model of rheumatoid arthritis (RA) closely resembles the human disease. In this model, arthritis results from activation of autoreactive KRN T cells recognizing the glycolytic enzyme glucose-6-phosphate isomerase (GPI) autoantigen, which provides help to GPI-specific B cells, resulting in the production of pathogenic anti-GPI antibodies that ultimately leads to arthritis symptoms from 4 weeks of age. Vasoactive intestinal peptide (VIP) is a neuropeptide broadly distributed in the central and peripheral nervous system that is also expressed in lymphocytes and other immune cell types. VIP is a modulator of innate and adaptive immunity, showing anti-inflammatory and immunoregulatory properties. Basically, this neuropeptide promotes a shift in the Th1/Th2 balance and enhances dedifferentiation of T regulatory cells (Treg). It has demonstrated its therapeutic effects on the collagen-induced arthritis (CIA) mouse model of RA. In the present hypothesis and theory article, we propose that the immunoregulatory properties of VIP may be due likely to the inhibition of T cell plasticity toward non-classic Th1 cells and an enhanced follicular regulatory T cells (Tfr) activity. The consequences of these regulatory properties are the reduction of systemic pathogenic antibody titers.

A Clinical Approach for the Use of VIP Axis in Inflammatory and Autoimmune Diseases

The neuroendocrine and immune systems are coordinated to maintain the homeostasis of the organism, generating bidirectional communication through shared mediators and receptors. Vasoactive intestinal peptide (VIP) is the paradigm of an endogenous neuropeptide produced by neurons and endocrine and immune cells, involved in the control of both innate and adaptive immune responses. Exogenous administration of VIP exerts therapeutic effects in models of autoimmune/inflammatory diseases mediated by G-protein-coupled receptors (VPAC1 and VPAC2). Currently, there are no curative therapies for inflammatory and autoimmune diseases, and patients present complex diagnostic, therapeutic, and prognostic problems in daily clinical practice due to their heterogeneous nature. This review focuses on the biology of VIP and VIP receptor signaling, as well as its protective effects as an immunomodulatory factor. Recent progress in improving the stability, selectivity, and effectiveness of VIP/receptors analogues and new routes of administration are highlighted, as well as important advances in their use as biomarkers, contributing to their potential application in precision medicine. On the 50th anniversary of VIP's discovery, this review presents a spectrum of potential clinical benefits applied to inflammatory and autoimmune diseases.

Vasoactive intestinal peptide gene polymorphisms, associated with its serum levels, predict treatment requirements in early rheumatoid arthritis

We previously reported that early arthritis (EA) patients with low vasoactive intestinal peptide (VIP) serum levels demonstrate a worse clinical disease course. In this study, we analysed whether variants in the VIP gene correlated with its serum levels and clinical EA parameters. The VIP gene was sequenced in patients with extremely high/low VIP levels, measured by enzyme immunoassay. Sixteen single nucleotide polymorphisms (SNPs) were differentially distributed between both groups, which were subsequently genotyped in two patients’ sets. We observed that patients with rs688136 CC genotype showed higher VIP levels in both discovery (n = 91; p = 0.033) and validation populations (n = 131; p = 0.007). This effect was attenuated by the presence of minor alleles rs35643203 and rs12201140, which showed a clear trend towards low VIP level association (p = 0.118 and p = 0.049, respectively). Functional studies with miR-205-5p, which has a target site in the 3′ UTR close to rs688136, revealed a miRNA-mediated regulatory mechanism explaining the higher VIP gene expression in homozygous patients. Moreover, patients with an rs688136 CC genotype and no minor alleles of the other polymorphisms required less treatment (p = 0.009). We concluded that the identification of polymorphisms associated with VIP serum levels would complement the clinical assessment of the disease severity in rheumatoid arthritis patients.

Vasoactive Intestinal Peptide in Early Spondyloarthritis: Low Serum Levels as a Potential Biomarker for Disease Severity

Spondyloarthritis (SpA) is a family of inflammatory diseases sharing clinical, genetic, and radiological features. While crucial for tailoring early interventions, validated prognostic biomarkers are scarce in SpA. We analyze the correlation between serum levels of vasoactive intestinal peptide (VIP) and disease activity/severity in patients with early chronic inflammatory back pain. The study population comprised 54 patients enrolled in our early chronic inflammatory back pain register. We collected demographic information, clinical data, laboratory data, and imaging findings. VIP levels were measured by enzyme immunoassay in serum samples from 162 visits. The association between independent variables and VIP levels was analyzed using longitudinal multivariate analysis nested by patient and visit. No significant differences were observed in VIP levels between these two groups. Lower levels of VIP were significantly associated with a higher Bath Ankylosing Spondylitis Disease Activity Index (BASFI) score, presence of bone edema in magnetic resonance imaging (MRI) scan, and lower hemoglobin levels. Coexistence of cutaneous psoriasis was independently associated with lower VIP levels, and similar trend was observed for enthesitis. We conclude that SpA patients with low serum VIP levels had worse 2-year disease outcome, suggesting that serum VIP levels could be a valid prognostic biomarker.

VIP modulates IL-22R1 expression and prevents the contribution of rheumatoid synovial fibroblasts to IL-22-mediated joint destruction

Rheumatoid arthritis (RA) and osteoarthritis are two rheumatic diseases whose progression is associated with a chronic synovitis. Fibroblast-like synoviocytes (FLS) have been shown to play a pivotal role in initiating and perpetuating inflammatory and destructive processes in the rheumatoid joint. Recently, the stimulating role of IL-22 has been reported on RA-FLS contribution to joint destruction by means of the increase of proliferation and matrix-metalloproteinase-1 (MMP-1) and alarmin S100A8/A9 production. Besides, mediators potentially present in inflamed joints have been shown to increase the expression of IL-22/IL-22R1 axis, amplifying the capacity of FLS to respond to IL-22 signalling. Since targeting cytokines that govern FLS activation would allow controlling their contribution to synovial inflammation, the present study was designed to analyze the potential immunoregulatory capacity of vasoactive intestinal peptide (VIP) to counterbalance IL-22 effects on FLS behavior. Our results showed that VIP is able to downregulate the augmented expression of IL-22 specific receptor in FLS subjected to a proinflammatory milieu. Moreover, this study revealed the ability of VIP to inhibit the IL-22 stimulatory effects on proliferation as well as on expression of both MMP-1 and alarmins in RA-FLS. The present findings reinforce the potential of this neuroimmunopeptide as a therapeutic agent in rheumatic diseases.

Protected graft copolymer excipient leads to a higher acute maximum tolerated dose and extends residence time of vasoactive intestinal Peptide significantly better than sterically stabilized micelles

PURPOSE

To determine and compare pharmacokinetics and toxicity of two nanoformulations of Vasoactive Intestinal Peptide (VIP).

METHODS

VIP was formulated using a micellar (Sterically Stabilized Micelles, SSM) and a polymer-based (Protected Graft Copolymer, PGC) nanocarrier at various loading percentages. VIP binding to the nanocarriers, pharmacokinetics, blood pressure, blood chemistry, and acute maximum tolerated dose (MTD) of the formulations after injection into BALB/c mice were determined.

RESULTS

Both formulations significantly extend in vivo residence time compared to unformulated VIP. Formulation toxicity is dependent on loading percentage, showing major differences between the two carrier types. Both formulations increase in vivo potency of unformulated VIP and show acute MTDs at least 140 times lower than unformulated VIP, but still at least 100 times higher than the anticipated highest human dose, 1-5 μg/kg. These nanocarriers prevented a significant drop in arterial blood pressure compared to unformulated VIP.

CONCLUSIONS

While both carriers enhance in vivo residence time compared to unformulated VIP and reduce the drop in blood pressure immediately after injection, PGC is the excipient of choice to extend residence time and improve the safety of potent therapeutic peptides such as VIP.

Inflammatory mediators alter interleukin-17 receptor, interleukin-12 and -23 expression in human osteoarthritic and rheumatoid arthritis synovial fibroblasts: immunomodulation by vasoactive intestinal Peptide

AIMS

To assess the contribution of fibroblast-like synoviocytes (FLS) to the inflammatory joint microenvironment under different pathogenic stimuli and their potential to respond to interleukin (IL)-17 and to determine whether the neuroimmunomodulatory vasoactive intestinal peptide (VIP) is able to modulate IL-17 receptor (IL-17R) and related cytokines.

METHODS

The effect of proinflammatory cytokines [tumor necrosis factor α (TNFα) and IL-17] and Toll-like receptor (TLR) ligands [poly(I:C) and lipopolysaccharide (LPS)] on IL-17R expression and IL-12 and IL-23 production was studied in osteoarthritis (OA)- and rheumatoid arthritis (RA)-FLS, involved in Th1/Th17 differentiation. The effect of VIP was also determined. IL-17RA, IL-17RC, IL-12p35 and IL-23p19 expression was measured by real-time polymerase chain reaction. IL-12 and IL-23 protein levels were measured by ELISA in supernatant cultures.

RESULTS

TNFα, LPS and poly(I:C) induced an increase in IL-17RA in RA-FLS, whereas TNFα, TNFα plus IL-17 and poly(I:C) enhanced IL-17RC transcripts in FLS. VIP diminished the upregulated expression of IL-17RA in RA-FLS following TNFα and poly(I:C). TNFα, LPS and poly(I:C) increased IL-12 and IL-23 levels in cells derived from patients presenting both pathologies. However, IL-17A DECREASED IL-12 AND AUGMENTED IL-23. VIP DECREASED IL-12P35 MRNA UPREGULATION BY POLY(I:C) AND IL-23P19 TRANSCRIPTS IN LPS-TREATED FLS.

CONCLUSIONS

Inflammatory cytokines and TLR ligands modulate IL-17R, IL-12 and IL-23 possibly favoring the cross talk between FLS and Th1/Th17 cells. The ability of VIP to counteract the enhancing effect of proinflammatory molecules on IL-17R and the IL-12 family of cytokines corroborates and amplifies the beneficial effect of this endogenous neuroimmunopeptide in rheumatic diseases.

Vasoactive intestinal peptide enhances TNF-α-induced IL-6 and IL-8 synthesis in human proximal renal tubular epithelial cells by NF-κB-dependent mechanism

Vasoactive intestinal polypeptide (VIP) is a 28-amino acid neuropeptide with vasodilator, bronchodilator, and anti-inflammatory effects. But little is known about its pro-inflammatory effects. We investigated the effect of VIP on the secretion of interleukin-6 (IL-6) and interleukin-8 (IL-8), two pro-inflammatory cytokines, in TNF-α-activated proximal renal tubular epithelial cell line (HK-2 cells). Cultured HK-2 cells were treated with TNF-α in the presence or absence of VIP with a dose range from 1 to 100 nM, followed by analysis of pro-inflammatory cytokines (IL-6 and IL-8) induction and their signal events including activation of the NF-κB pathway. We report here that tumor necrosis factor-α (TNF-α) increased IL-6 and IL-8 production, and that these effects were potentiated by VIP at 10 nM in HK-2 cells. However, VIP at 1 and 100 nM did not display this function. Consistent with these observations, we were able to show that VIP at 10 nM upregulated TNF-α-induced phosphorylation of IκB-α, leading to IκB-α degradation and the subsequent nuclear translocation of NF-κB. Furthermore, VIP-enhanced activation of NF-κB transcription activity was demonstrated using a NF-κB reporter construct upon transient transfection into HK-2 cells. These results strongly suggest that VIP synergistically enhances TNF-α-stimulated IL-6 and IL-8 synthesis via activating the NF-κB pathway in HK-2 cells.

Expression of synovial fluid and articular cartilage VIP in human osteoarthritic knee: a new indicator of disease severity?

OBJECTIVES

Vasoactive intestinal peptide (VIP) is a molecule shared by the neuroendocrine immune network and is considered to be a potential candidate for treatment of inflammatory and autoimmune diseases. Although some recent studies demonstrate that VIP has a protective role in animal RA models, its variant in different disease grade of OA remains uncertain.

DESIGN AND METHODS

Fifty patients with primary knee OA and ten controls with severe trauma were enrolled. Synovial fluid and articular cartilage samples were collected from specimens of total knee arthroplasty (TKA) or knee above amputation. VIP levels in these samples were assessed by ELISA and immunohistochemistry. Kellgren-Lawrence criteria and Mankin score were taken to determine the disease severity.

RESULTS

Compared to the controls, OA patients have lower VIP concentration in synovial fluid (659.70±112.79, 95%CI 579.01-740.38 vs 470.83±156.40, 95%CI 426.38-515.28 pg/mL, P<0.001) and articular cartilage (0.26±0.02, 95%CI 0.24-0.28 vs 0.20±0.04, 95%CI 0.18-0.21, P<0.001). Subsequent analysis show that the VIP expression in synovial fluid is markedly correlated with its OD in articular cartilage (Pearson's r=0.580, P<0.001). Furthermore, the synovial fluid and articular cartilage levels of VIP both demonstrated to be negatively correlated with severity of disease (Spearman's ρ=0.838, P<0.001; Spearman's ρ=0.814, P<0.001).

CONCLUSIONS

VIP in synovial fluid and articular cartilage is negatively associated with progressive joint damage in OA and is a potential indictor of disease severity.

RNA sensors in human osteoarthritis and rheumatoid arthritis synovial fibroblasts: immune regulation by vasoactive intestinal peptide

OBJECTIVE

The aim of this study was to analyze both the constitutive and induced expression and function of double-stranded RNA (dsRNA; Toll-like receptor 3 [TLR-3], retinoic acid-inducible gene I [RIG-I], and melanoma differentiation-associated gene 5 [MDA5]) and single-stranded RNA (ssRNA; TLR-7) receptors in osteoarthritis (OA) and rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS), by studying the transcription factors involved and the subsequent effects on antiviral interferon-β (IFNβ), the proinflammatory CXCL8 chemokine, and matrix metalloproteinase 3 (MMP-3). An additional goal was to study the effect of vasoactive intestinal peptide (VIP).

METHODS

The expression of TLR-3, TLR-7, RIG-I, and MDA5 in cultured FLS was studied by reverse transcription-polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA), immunofluorescence, and Western blotting. Transcription factors were studied using the ELISA-based TransAM transcription factor kit. The expression of IFNβ, CXCL8 (interleukin-8), and MMP-3 was analyzed by RT-PCR and ELISA.

RESULTS

FLS expressed TLR-3, TLR-7, RIG-I, and MDA5. The expression of TLR-3 and RIG-I was higher in RA FLS, while the expression of TLR-7 and MDA5 was higher in OA FLS. Stimulation with poly(I-C) induced the activation of IFN regulatory factor 3 (IRF-3), NF-κB, and activator protein 1 (AP-1) c-Jun as well as the subsequent production of IFNβ, CXCL8, and MMP-3. VIP reduced the activation of IRF-3 and the production of IFNβ in both OA and RA FLS. Imiquimod induced the activation of NF-κB, AP-1 c-Fos, and AP-1 c-Jun and the synthesis of CXCL8 and MMP-3. VIP significantly diminished MMP-3 production only in imiquimod-treated RA FLS.

CONCLUSION

The results of this study revealed a prominent function of FLS in the recognition of both dsRNA and ssRNA, which may be present in the joint microenvironment. This study also advances the healing function of the endogenous neuroimmune peptide VIP, which inhibited TLR-3-, RIG-I-, MDA5-, and TLR-7-mediated stimulation of antiviral, proinflammatory, and joint destruction mediators.

Effect of VIP on the balance between cytokines and master regulators of activated helper T cells

CD4T helper cells are decisive in the struggle against pathogens and in maintaining immune homeostasis. Nevertheless, they also drive immune-mediated disease. Recently, emerging evidence suggests that seemingly committed Th cells possess plasticity and may convert into other types of effector cells. Vasoactive Intestinal Peptide (VIP) is an immunomodulator neuropeptide, which is able to promote or inhibit individually the differentiation or function of some T-helper subsets. We conducted ex vivo study with erythrocyte-depleted spleen cells from healthy mice to check the balance between cytokines and master regulators of different T-helper subsets. This neuropeptide adversely affected the differentiation and functionality phases of Th17 cells and had a negative influence on cytokines related to Th1 function, increasing Th17 cells over those of the Th1 cell subset. With respect to Th2 subsets, VIP augmented the interleukin (IL)-4/IL-9 mRNA ratio, and a negative correlation between IL-4 and IL-9 was observed in culture supernatants. VIP augmented Th2 relative to Th1 in cell subsets. VIP decreased the iTreg/Th17 balance. Regarding the induced T-regulatory (iTreg)/Th1 balance, VIP increased the presence of immunoregulatory cytokines in relation to IFNγ. Although additional studies are needed to clarify the role of VIP on the balance between cytokines and master regulators during T-helper differentiation, our data show that VIP reduces Th17/Th1 and Th1/Th2 ratios. However, the iTreg/Th17 ratio was differently counterbalanced, probably because of culture conditions. Finally, this is the first study showing that VIP also modulates Th2/Th9 and iTreg/Th1 ratios.

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.

New insights into the role of VIP on the ratio of T-cell subsets during the development of autoimmune diabetes

Type I diabetes is an autoimmune T-cell-mediated disease associated with overexpression of inflammatory mediators and the disturbance of different T-cell subsets. Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory agent with regulatory effects on activated T cells. As the equilibrium between different T-cell subsets is involved in the final outcome, leading to tolerance or autoimmunity, we studied the evolution of markers for T cells in nonobese diabetic (NOD) mice. The study of different transcription factors, cytokines or cytokine receptors, shows that VIP interferes with functional phase of T helper 17 (Th17) cells and prevents the increase in the proportion of Th1 to Th17 cells. On the other hand, VIP-treated NOD mice show an increase in the proportion of CD4(+)CD25(+) cells in the spleen. Thus, VIP switches the Tregs/Th17 ratio leading to tolerance in NOD mice. Similarly, VIP reverses the ratio of Th1-/Th2-cell subsets associated with autoimmune pathology. All these effects on the ratio of T-cell subsets and the anti-inflammatory effect of VIP in decreasing proinflammatory mediators result in a reduction of β-cell destruction in pancreas. Taken together, these results show that VIP provides significant protection against spontaneous diabetes by modulating T-cell subsets and counterbalancing tolerance and immunity.

Identification of the early VIP-regulated transcriptome and its associated, interactome in resting and activated murine CD4 T cells

More than 40 years after the discovery of vasoactive intestinal peptide (VIP), its transcriptome in the immune system has still not been completely elucidated. In an attempt to understand the biological role of this neuropeptide in immunity, we chose CD4 T cells as a cellular system. Agilent Mouse Whole Genome microarrays were hybridized with fluorescently labeled total RNA isolated from resting CD4 T cells cultured +/-10(-7)M VIP for 5h or PMA/ionomycin activated CD4 T cells cultured +/-10(-7)M VIP for 5h. These VIP-regulated transcriptomes were analyzed by Significance Analysis of Microarrays (SAM) and Ingenuity Pathway Analysis (IPA) software to identify relevant signaling pathways modulated by VIP in the absence and presence of T cell activation. In resting CD4 T cells, VIP-modulated 368 genes, ranging from 3.49 to -4.78-fold. In the PMA/ionomycin activated CD4 T cells, 326 gene expression levels were changed by VIP, ranging from 2.94 to -1.66-fold. IPA analysis revealed that VIP exposure alters cellular function through EGFR signaling in resting CD4 T cells, and modulates immediate early genes, Fos and CREM/ICER, in activated CD4 T cells. These gene expression changes are suggested to explain at a molecular level how VIP can regulate T cell homing to the gut and induce regulatory T cell generation.

Expression of activity-dependent neuroprotective protein in the immune system: possible functions and relevance to multiple sclerosis

BACKGROUND

Activity-dependent neuroprotector (ADNP) is a neuroprotective molecule containing an 8-amino acid peptide, NAPVSIPQ (NAP), that is sufficient for its neuroprotective effects.

OBJECTIVE

To assess the expression of ADNP in the human immune system in normal subjects and multiple sclerosis patients. MaterialsandMethods: ADNP expression was assessed in peripheral blood mononuclear cells (PBMCs) from healthy donors and multiple sclerosis (MS) patients using staining with anti-ADNP (NAP) antibodies and markers for T cells, B cells, monocytes and natural killer cells. ADNP mRNA was determined in peripheral blood from MS patients (n = 24) and matched controls (n = 21). Expression of activation markers CD69 and CD154 and of IFN-gamma was assessed by flow cytometry in stimulated PBMCs. Effects of NAP on immune cell proliferation was assessed by tritiated thymidine incorporation.

RESULTS

Monocytes, B cells and T cells, but not regulatory (CD4+CD25+) T cells expressed ADNP. NAP peptide decreased the expression of CD69, CD154 and IFN-gamma in PBMC and caused suppressed anti-CD3-/anti-CD28-stimulated PBMC proliferation. ADNP mRNA was reduced in MS compared to control peripheral blood.

CONCLUSION

ADNP is expressed in many immune system cells. ADNP mRNA is reduced in PBMCs in MS. The peptide NAP, which plays an important role in neuroprotection, has potential immunomodulatory properties.

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.

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.

Differential expression of vasoactive intestinal peptide and its functional receptors in human osteoarthritic and rheumatoid synovial fibroblasts

OBJECTIVE

Vasoactive intestinal peptide (VIP) has shown potent antiinflammatory effects in murine arthritis and ex vivo in human rheumatoid arthritis (RA) synovial cells. To investigate the potential endogenous participation of this system in the pathogenesis of RA, we analyzed the expression and regulation of VIP and its functional receptors in human fibroblast-like synoviocytes (FLS) from patients with osteoarthritis (OA) and patients with RA.

METHODS

The expression of VIP was studied by reverse transcription-polymerase chain reaction (RT-PCR), enzyme immunoassay, and immunofluorescence in cultured FLS, and by immunohistochemical analysis in synovial tissue. The expression and function of the potential VIP receptors in FLS were studied by RT-PCR, determination of intracellular cAMP production, cell membrane adenylate cyclase (AC) activity, and interleukin-6, CCL2, and CXCL8 production in response to VIP or specific agonists and antagonists.

RESULTS

VIP expression was detected in human FLS at the messenger RNA and protein levels, and it was significantly decreased in RA FLS compared with OA FLS. VIP receptor type 1 (VPAC1) was the dominant AC-coupled receptor in OA FLS, in contrast with RA FLS, in which VPAC2 was dominant. Tumor necrosis factor alpha-treated OA FLS reproduced the VIP and VPAC receptor expression pattern of RA FLS. The antagonistic effects of VIP on FLS proinflammatory factor production were reproduced by VPAC1- and VPAC2-specific agonists in OA FLS and RA FLS, respectively.

CONCLUSION

VIP expression is down-regulated in RA and in tumor necrosis factor alpha-treated FLS, suggesting that down-regulation of this endogenous antiinflammatory factor may contribute to the pathogenesis of RA. In RA FLS, VPAC2 mediates the antiinflammatory effects of VIP, suggesting that VPAC2 agonists may be an alternative to VIP as antiinflammatory agents.

VIP reverses the expression profiling of TLR4-stimulated signaling pathway in rheumatoid arthritis synovial fibroblasts

Since recent evidences point out the potential involvement of Toll-like receptors (TLRs) in the therapeutic effect of vasoactive intestinal peptide (VIP), the purpose of this study is to elucidate the role of VIP as a negative regulator of TLR-signaling. To this aim, we analyzed in fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) or osteoarthritis (OA), the expression profile of TLR-pathway related molecules, as well as the alterations induced by LPS stimulation in RA-FLS and the effect of VIP treatment. Cultured FLS were obtained from patients with RA or OA. RA-FLS were next stimulated with lipopolysaccharide (LPS) in presence or absence of VIP. The gene expression profiling of molecules involved in LPS-mediated TLR4-signaling was studied by cRNA microarray analysis. Twenty three molecules involved in TLR signaling resulted over-expressed at mRNA level in basal RA-FLS compared to OA-FLS. Moreover, in RA-FLS, 23 of the analyzed genes were found to be up-regulated by LPS stimulation whereas 30 were not affected. VIP down-regulated the LPS-induced RNA expression of molecules involved in TLR signaling pathway. Up-regulation of RNA expression of CD14, MD2, TRAM, TRIF, IRAK4, TAB2, TRAF6 and TBK1 was corroborated by RT-PCR as well as the VIP regulatory effect. Increased protein levels of TRAF6, TBK1 and pIRAK1 after exposure to LPS, and the inhibitory effect of VIP, were described by Western blotting. As functional consequences, it was observed the VIP-induced impaired production of IL-6 and RANTES/CCL5 after LPS stimulation. In conclusion, VIP acts as a negative modulator of the TLR4-signaling by overturning the production of several checkpoints molecules of the cascade and thus, widening its potential therapeutic effects.

Emerging roles of vasoactive intestinal peptide: a new approach for autoimmune therapy

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 autoimmune diseases. Some neuropeptides and hormones have emerged as endogenous agents that participate in the regulation of the processes that ensure self-tolerance. Among them, the vasoactive intestinal peptide (VIP), a well-characterised endogenous anti-inflammatory neuropeptide, has shown therapeutic potential for a variety of immune disorders. Here we examine the latest research findings, which indicate that VIP participates 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.

Tuning immune tolerance with vasoactive intestinal peptide: a new therapeutic approach for immune disorders

The induction of immune tolerance is essential for the maintenance of immune homeostasis and to limit the occurrence of exacerbated inflammatory and autoimmune conditions. Multiple mechanisms act together to ensure self-tolerance, including central clonal deletion, cytokine deviation and induction of regulatory T cells. Identifying the factors that regulate these processes is crucial for the development of new therapies of autoimmune diseases and transplantation. The vasoactive intestinal peptide (VIP) is a well-characterized endogenous anti-inflammatory neuropeptide with therapeutic potential for a variety of immune disorders. Here, we examine the latest research findings, which indicate that VIP participates 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.

A novel VIP signaling pathway in T cells cAMP-->protein tyrosine phosphatase (SHP-2?)-->JAK2/STAT4-->Th1 differentiation

Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory agent. In addition to the deactivation of macrophages, dendritic cells, and microglia, VIP shifts the Th1/Th2 balance, promoting the preferential differentiation and survival of Th2 cells, to the detriment of the proinflammatory Th1 effectors. Several mechanisms operate in the Th1/Th2 shift induced by VIP. Here we report on a novel mechanism for the effect of VIP on T cell differentiation, and show that VIP inhibits Th1 differentiation by interfering directly with the IL-12Jak2/STAT4 signaling pathway in T cells. The effect of VIP is cAMP-dependent, and appears to be mediated through the activation of protein tyrosine phosphatases (PTP), with SHP-2 as a potential target. The activation of PTPs represents a novel cAMP-downstream target for the immunomodulatory effects of VIP.

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.