Vasoactive intestinal peptide mediation of development and functions of T lymphocytes

Modified BuShenYiQi formula alleviates experimental allergic asthma in mice by negative regulation of type 2 innate lymphoid cells and CD4+ type 9 helper T cells and the VIP-VPAC2 signalling pathway

CONTEXT

Modified BuShenYiQi formula (M-BYF) is derived from BuShenYiQi formula, used for the treatment of allergic asthma. The exact effect and mechanism of M-BYF on the improvement of asthma remain unclear.

OBJECTIVE

We investigated the mechanism underlying the therapeutic effect of M-BYF on allergic asthma.

MATERIALS AND METHODS

The asthma model was established in female BALB/c mice that were sensitized and challenged with ovalbumin (OVA). Mice in the treated groups were orally treated once a day with M-BYF (7, 14 and 28 g/kg/d) or dexamethasone before OVA challenge. Control and Model group received saline. Pathophysiological abnormalities and percentages of lung type 2 innate lymphoid cells (ILC2s) and Th9 cells were measured. Expression levels of type 2 cytokines and transcription factors required for these cells function and differentiation were analysed. Expression of vasoactive intestinal polypeptide (VIP)-VPAC2 signalling pathway-related proteins, and percentages of VIP expressing (VIP⁺) cells and VPAC2, CD90 co-expressing (VPAC2⁺CD90⁺) cells were detected.

RESULTS

M-BYF alleviated airway hyperresponsiveness, inflammation, mucus hypersecretion and collagen deposition in asthmatic mice. M-BYF down-regulated percentages of ILC2s and Th9 cells with lower expression of GATA3, PU.1 and IRF4, reduced IL-5, IL-13, IL-9 and VIP production. The decrease in the expression of VIP-VPAC2 signalling pathway and percentages of VIP⁺ cells, VPAC2⁺CD90⁺ cells were observed after M-BYF treatment. The LD₅₀ value of M-BYF was higher than 90 g/kg.

DISCUSSION AND CONCLUSIONS

M-BYF alleviated experimental asthma by negatively regulating ILC2s and Th9 cells and the VIP-VPAC2 signalling pathway. These findings provide the theoretical basis for future research of M-BYF in asthma patient population.

The effects of vasoactive intestinal peptide in the rat model of experimental autoimmune neuritis and the implications for treatment of acute inflammatory demyelinating polyradiculoneuropathy or Guillain-Barré syndrome

Background

Guillain-Barré syndrome is an acute inflammatory demyelinating polyneuropathy that is characterized histologically by demyelination of peripheral nerves and nerve roots, infiltrates of T lymphocytes, and an inflammatory response that includes macrophage infiltrates. The aim of this study was to evaluate the effects of vasoactive intestinal peptide (VIP) in a rat model of experimental autoimmune neuritis (EAN).

Methods

Forty male Lewis rats were divided into a control group (N=10), an EAN group (N=10), an EAN group treated with 15 nmol of VIP (N=10), and an EAN group treated with 30 nmol of VIP (N=10). The rat model was created by subcutaneous injection of P2 polypeptide (200 µg P257-81) into the base of the tail. Intraperitoneal injection of VIP was given on day 7. Rats were weighed and functionally evaluated using an EAN score (0-10). On day 16, the rats were euthanized. The sciatic nerve was examined histologically and using immunohistochemistry with antibodies against CD8, CD68, and forkhead box p3 (Foxp3). Serum concentrations of IL-17 and interferon-α (IFN-α) were measured by ELISA on day 16 after creating the EAN model.

Results

The VIP-treated EAN groups had increased body weight and improved EAN scores compared with the untreated EAN group. CD8-positive and CD68-positive cells were significantly reduced in the EAN group treated with 30 nmol of VIP compared with 15 nmol of VIP. Foxp3-positive cells were significantly decreased in both EAN groups treated with VIP, and serum concentrations of IL-17 and IFN-α were significantly lower compared with the untreated EAN group (P<0.05).

Conclusion

In a rat model of EAN, treatment with VIP resulted in functional improvement, reduced nerve inflammation, and decreased serum levels of inflammatory cytokines.

Single nucleotide polymorphisms in the 3'UTR of VPAC-1 cooperate in modulating gene expression and impact differently on the interaction with miR525-5p

Complex immune and neurodegenerative disorders are the result of multiple interactions between common genetic variations having, individually, a weak effect on the disease susceptibility or resistance. Interestingly, some genes have been found to be associated with more than one disease although not necessarily the same SNPs are involved. In this context, single nucleotide polymorphisms in the 3′UTR region of type 1 receptor (VPAC-1) for vasoactive intestinal peptide (VIP) have been reported to be associated with some immune-mediated as well as with neurodegenerative diseases such as Alzheimer's Disease (AD). Here, we demonstrate that variations at the 3′UTR of the VPAC-1 gene act synergistically to affect the expression of the luciferase as well as of the GFP reporter genes expressed in HEK293T cells. Moreover, the miRNA 525-5p, previously shown by us to target the 3′UTR of VPAC-1, is more efficient in decreasing GFP expression when co-expressed with constructs carrying the allele C at rs896 (p<10^-3) suggesting that this miRNA regulates VPAC-1 expression at different levels depending on rs896 polymorphism and thus adding complexity to the network of disease susceptibility.

Monocytes from Sjögren's syndrome patients display increased vasoactive intestinal peptide receptor 2 expression and impaired apoptotic cell phagocytosis

Sjögren's syndrome (SS) is a chronic autoimmune disease characterized by salivary and lacrimal gland dysfunction. Clinical observations and results from animal models of SS support the role of aberrant epithelial cell apoptosis and immune homeostasis loss in the glands as triggering factors for the autoimmune response. Vasoactive intestinal peptide (VIP) promotes potent anti-inflammatory effects in several inflammatory and autoimmune disease models, including the non-obese diabetic (NOD) mouse model of SS. With the knowledge that VIP modulates monocyte function through vasoactive intestinal peptide receptors (VPAC) and that immune homeostasis maintenance depends strongly upon a rapid and immunosuppressant apoptotic cell clearance by monocytes/macrophages, in this study we explored VPAC expression on monocytes from primary SS (pSS) patients and the ability of VIP to modulate apoptotic cell phagocytic function and cytokine profile. Monocytes isolated from individual pSS patients showed an increased expression of VPAC2 subtype of VIP receptors, absent in monocytes from control subjects, with no changes in VPAC1 expression. VPAC2 receptor expression could be induced further with lipopolysaccharide (LPS) in pSS monocytes and VIP inhibited the effect. Moreover, monocytes from pSS patients showed an impaired phagocytosis of apoptotic epithelial cells, as evidenced by reduced engulfment ability and the failure to promote an immunosuppressant cytokine profile. However, VIP neither modulated monocyte/macrophage phagocytic function nor did it reverse their inflammatory profile. We conclude that monocytes from pSS patients express high levels of VPAC2 and display a deficient clearance of apoptotic cells that is not modulated by VIP.

Novel, biocompatible, and disease modifying VIP nanomedicine for rheumatoid arthritis

Despite advances in rheumatoid arthritis (RA) treatment, efficacious and safe disease-modifying therapy still represents an unmet medical need. Here, we describe an innovative strategy to treat RA by targeting low doses of vasoactive intestinal peptide (VIP) self-associated with sterically stabilized micelles (SSMs). This spontaneous interaction of VIP with SSM protects the peptide from degradation or inactivation in biological fluids and prolongs circulation half-life. Treatment with targeted low doses of nanosized SSM-VIP but not free VIP in buffer significantly reduced the incidence and severity of arthritis in an experimental model, completely abrogating joint swelling and destruction of cartilage and bone. In addition, SSM associated VIP, unlike free VIP, had no side-effects on the systemic functions due to selective targeting to inflamed joints. Finally, low doses of VIP in SSM successfully downregulated both inflammatory and autoimmune components of RA. Collectively, our data clearly indicate that VIP-SSM should be developed to be used as a novel nanomedicine for the treatment of RA.

Vasoactive intestinal peptide signaling axis in human leukemia

The vasoactive intestinal peptide (VIP) signaling axis constitutes a master “communication coordinator” between cells of the nervous and immune systems. To date, VIP and its two main receptors expressed in T lymphocytes, vasoactive intestinal peptide receptor (VPAC)1 and VPAC2, mediate critical cellular functions regulating adaptive immunity, including arresting CD4 T cells in G₁ of the cell cycle, protection from apoptosis and a potent chemotactic recruiter of T cells to the mucosa associated lymphoid compartment of the gastrointestinal tissues. Since the discovery of VIP in 1970, followed by the cloning of VPAC1 and VPAC2 in the early 1990s, this signaling axis has been associated with common human cancers, including leukemia. This review highlights the present day knowledge of the VIP ligand and its receptor expression profile in T cell leukemia and cell lines. Also, there will be a discussion describing how the anti-leukemic DNA binding transcription factor, Ikaros, regulates VIP receptor expression in primary human CD4 T lymphocytes and T cell lymphoblastic cell lines (e.g. Hut-78). Lastly, future goals will be mentioned that are expected to uncover the role of how the VIP signaling axis contributes to human leukemogenesis, and to establish whether the VIP receptor signature expressed by leukemic blasts can provide therapeutic and/or diagnostic information.

VPAC1 (vasoactive intestinal peptide (VIP) receptor type 1) G protein-coupled receptor mediation of VIP enhancement of murine experimental colitis

Distinct roles of the two T cell G protein-coupled receptors for vasoactive intestinal peptide (VIP), termed VPAC1 and VPAC2, in VIP regulation of autoimmune diseases were investigated in the dextran sodium sulfate (DSS)-induced murine acute colitis model for human inflammatory bowel diseases. In mice lacking VPAC2 (VPAC2-KO), DSS-induced colitis appeared more rapidly with greater weight loss and severe histopathology than in wild-type mice. In contrast, DSS-induced colitis in VPAC1-KO mice was milder than in wild-type mice and VPAC2-KO mice. Tissues affected by colitis showed significantly higher levels of myeloperoxidase, IL-6, IL-1β and MMP-9 in VPAC2-KO mice than wild-type mice, but there were no differences for IL-17, IFN-γ, IL-4, or CCR6. Suppression of VPAC1 signals in VPAC2-KO mice by PKA inhibitors reduced the clinical and histological severity of DSS-induced colitis, as well as tissue levels of IL-6, IL-1β and MMP-9. Thus VIP enhancement of the severity of DSS-induced colitis is mediated solely by VPAC1 receptors.

The absence of VPAC2 leads to aberrant antibody production in Aspergillus fumigatus sensitized and challenged mice

Vasoactive intestinal peptide (VIP) facilitates a "pro-allergy" phenotype when signaling through its G protein-coupled receptor, VPAC(2). We have shown that VPAC(2) knock-out (KO) mice developed an allergic phenotype marked by eosinophilia and elevated serum IgE. Therefore, we hypothesized that the humoral response to allergen challenge in these mice was T(H)2 dominant similar to wild-type (WT) C57BL/6 mice. Antibody responses in WT and KO mice were measured after Aspergillus fumigatus conidia inhalation. In contrast to previous reports, basal levels of serum IgG(2a) and IgA were significantly higher in naïve VPAC(2) KO animals. Antibody availability in the serum as well as the bronchoalveolar lavage fluid after fungal challenge was dominated by the pro-inflammatory isotype IgG(2a) and the mucosal isotype, IgA. IgA localizing cells dominated in the peribronchovascular areas of allergic KO mice while IgE immune complexes were found in WT allergic lungs. This research shows for the first time that VPAC(2) has a significant effect on antibody regulation, in the context of allergy.

A transcriptionally permissive epigenetic landscape at the vasoactive intestinal peptide receptor-1 promoter suggests a euchromatin nuclear position in murine CD4 T cells

T cells express receptors for neuropeptides that mediate immunological activities. Vasoactive intestinal peptide receptor-1 (VPAC1), the prototypical group II G protein coupled receptor, binds two neuropeptides with high-affinity, called vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide. During T cell signaling, VPAC1 mRNA expression levels are significantly downregulated through a Src kinase dependent mechanism, thus altering the sensitivity for these neuropeptides during an immune reaction. Presently, it is unknown whether the mechanism that regulates VPAC1 during T cell signaling involves epigenetic changes. Therefore, we hypothesized that the epigenetic landscape consisting of diacetylation at H3K9/14 and trimethylation at H3K4, two transcriptionally permissive histone modifications, would parallel VPAC1 expression showing high enrichment in untreated T cells, but lower enrichment in alpha-CD3 treated T cells. To this end, quantitative chromatin immunoprecipitation (ChIP) analysis of H3K9/14ac and H3K4me3 was conducted using purified CD4(+) T cells, with CD45R(+) B cells as a negative control. Our data revealed that these histone modifications at the VPAC1 promoter did indeed parallel its mRNA levels between T and B lymphocytes, but did not decrease during T cell signaling. Collectively, these data strongly imply a euchromatin nuclear position for the VPAC1 locus irrespective of the activation status of T cells.

Stimulatory and suppressive signal transduction regulates vasoactive intestinal peptide receptor-1 (VPAC-1) in primary mouse CD4 T cells

Vasoactive intestinal peptide receptor-1 (VPAC-1) is an anti-proliferative, G-protein coupled receptor that is highly expressed on naïve T cells, and has been reported to be downregulated upon T cell activation. The T cell signaling molecules involved in mediating low VPAC-1 levels have not been identified. Therefore, to gain a greater understanding into this regulation, this study investigated the signaling pathways that regulate (VPAC-1) in murine, primary CD4 T cells. To this end, murine, splenic CD4 T cells were pretreated separately with 10 different pharmacological inhibitors and incubated +/- anti-CD3 for 24h. Total RNA was isolated, and VPAC-1 mRNA levels were measured by qPCR. Our results support that JNK kinases, downstream from the protein kinase, Zap70, are involved in suppressive regulation of VPAC-1 steady-state mRNA levels after anti-CD3 treatment. In contrast, inhibitors against PKC, ERK, p38, Zap70 and Rac1 supported a stimulatory influence in VPAC-1 regulation in the absence of T cell signaling. By studying the signaling pathways that regulate VPAC-1 in T cells, we can gain greater insight into the role of this anti-inflammatory receptor in autoimmunity and infectious diseases.

TCR signaling and environment affect vasoactive intestinal peptide receptor-1 (VPAC-1) expression in primary mouse CD4 T cells

Strict regulation of T cell function is imperative to control adaptive immunity, and dysregulation of T cell activation can contribute to infectious and autoimmune diseases. Vasoactive intestinal peptide receptor-1 (VPAC-1), an anti-inflammatory G-protein coupled receptor, has been reported to be downregulated during T cell activation. However, the regulatory mechanisms controlling the expression of VPAC-1 in T cells are not well understood. Therefore, mouse splenic CD4 T cells were treated in complete media+/-anti-CD3 for 24h, total RNA isolated and VPAC-1 levels measured by qPCR. Surprisingly, we discovered that T cells incubated in complete media steadily upregulated VPAC-1 mRNA levels over time (24h). Importantly, CD4 T cells isolated from blood also showed elevated VPAC-1 expression compared to splenic T cells. Collectively, these data support that the vascular environment positively influences VPAC-1 mRNA expression that is negatively regulated by TCR signaling. This research was supported by a national service award (1KO1 DK064828) to G.D., the Center for Protease Research (2P20RR015566), and INBRE (P20 RR016741).

Functional splice variants of the type II G protein-coupled receptor (VPAC2) for vasoactive intestinal peptide in mouse and human lymphocytes

A PCR-based search for splice variants of the VPAC2 G protein-coupled receptor for vasoactive intestinal peptide (VIP) revealed: (a) a short-deletion variant in mouse lymphocytes termed VPAC2de367-380, that lacks 14 amino acids in the seventh transmembrane domain, and (b) a long-deletion variant in human lymphocytes termed VPAC2de325-438(i325-334), that lacks 114 amino acids beginning with the carboxyl-terminal end of the third cytoplasmic loop and has 10 new carboxy-terminal amino acids. VPAC2de367-380 binds VIP normally, but shows reduced VIP-evoked signaling and effects on immune functions, whereas VPAC2de325-438(i325-334) shows reduced binding affinity for VIP and a complex pattern of functional differences. These splice variants may modify the immunoregulatory contributions of the VIP-VPAC2 axis.

Catalytic hydrolysis of VIP in pregnant women with asthma

RATIONALE

The neuropeptide vasoactive intestinal peptide (VIP) is one of the physiologic mediators of non-adrenergic, non-cholinergic smooth muscle relaxation of the airway and an important modulator of innate and adaptive immune responses. VIP catalytic autoantibodies are increased in asthma and serum VIP level is decreased during acute exacerbation of asthma. The effect of pregnancy on asthma is variable and depends in part on the severity of pre-existing asthma, along with other physiological and pathophysiological changes. We hypothesized that hydrolysis of VIP by circulating catalytic VIP antibodies will be increased in pregnancy in patients with asthma.

STUDY OBJECTIVE

To determine the level of catalytic autoantibodies to VIP in pregnant asthmatics compared to non-pregnant asthmatics and control pregnant women without asthma.

METHODS

We prospectively enrolled eight pregnant asthmatics (age, 26.5 +/- 2.6 years; mean +/- SEM), nine pregnant women without asthma (32.0 +/- 3.0 years), seven non-pregnant women with asthma (25.0 +/-1.9 years), and seven non-pregnant women without asthma (34.4 +/- 2 years) into the study. VIP hydrolysis was performed in all subjects.

RESULTS

Immunoglobulin G (IgG) autoantibodies that catalyze the hydrolysis of vasoactive intestinal peptide (VIP) were present at greater levels in the blood of pregnant women with asthma (7.6 +/- 1.1 pM VIP/6 h) compared to pregnant women without asthma (4.0 +/- 0.5; p < 0.001), non-pregnant asthmatics (4.9 +/- 0.9; p < 0.05) or non-pregnant women without asthma (1.9 +/- 0.7; p < 0.05).

CONCLUSION

An increase in the VIP hydrolyzing activity of IgG is independently associated with asthma and pregnancy. The autoantibodies hold the potential of affecting the pathophysiology of the airways in pregnant asthmatics.

Differential signaling of T cell generation of IL-4 by wild-type and short-deletion variant of type 2 G protein-coupled receptor for vasoactive intestinal peptide (VPAC2)

Vasoactive intestinal peptide (VIP) released from some neurons and T cells affects T cell migration, cytokine generation, and other functions by binding to constitutively expressed type 1 G protein-coupled receptor (VPAC1) or activation-induced type 2 G protein-coupled receptor (VPAC2). Recently, a short-deletion (SD) splice variant of mouse VPAC2 that lacks 14 amino acids at the end of the last transmembrane domain has been identified in T cells and shown to resemble wild-type (WT) VPAC2 in affinity of VIP binding but to differ by lack of signaling of T cell adenylyl cyclase, migration, and IL-2 secretion. As Th2 cells are the principal source of immune VIP and have the greatest functional responses to VIP, the differences in signals transduced by WT and SD VPAC2 were studied in VPAC2-low D10G4.1 model Th2 cell transfectants individually expressing the respective types of VPAC2 equally. WT and SD VPAC2 Th2 cell transfectants secreted equal amounts of VIP. WT VPAC2 transfectants generated more IL-4 than did SD VPAC2 transfectants, and this increment was dependent on endogenous VIP. Exogenous VIP further increased IL-4 production by WT VPAC2 transfectants but decreased IL-4 production by SD VPAC2 transfectants. Cotransfection of the two constructs diminished VIP enhancement of IL-4 production seen with WT VPAC2 alone by preventing increases in nuclear levels of the requisite transcription factors c-Maf and Jun B. Thus the ratio of two forms of T cell VPAC2 determines the net effect of VIP on IL-4 generation by activated Th2 cells.

Neural immune pathways and their connection to inflammatory diseases

Inflammation and inflammatory responses are modulated by a bidirectional communication between the neuroendocrine and immune system. Many lines of research have established the numerous routes by which the immune system and the central nervous system (CNS) communicate. The CNS signals the immune system through hormonal pathways, including the hypothalamic-pituitary-adrenal axis and the hormones of the neuroendocrine stress response, and through neuronal pathways, including the autonomic nervous system. The hypothalamic-pituitary-gonadal axis and sex hormones also have an important immunoregulatory role. The immune system signals the CNS through immune mediators and cytokines that can cross the blood-brain barrier, or signal indirectly through the vagus nerve or second messengers. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. This review discusses neuroimmune interactions and evidence for the role of such neural immune regulation of inflammation, rather than a discussion of the individual inflammatory mediators, in rheumatoid arthritis.

Complex array of cytokines released by vasoactive intestinal peptide

A complex mixture of five cytokines has been shown to be released by vasoactive intestinal peptide (VIP). Cytokines were measured in paired samples of culture medium and astroglial cytosol by capillary electrophoresis. This is the first description of VIP-mediated release for TNF-alpha, IL-3, G-CSF and M-CSF from astrocyte cultures. Kinetic studies after VIP treatment demonstrated a gradual but incomplete depletion of cytosolic cytokine levels, with differences observed among the cytokines. Significant increases in release were apparent within 15-30 min for all cytokines. As the recognized VIP receptors (VPAC1 and VPAC2) are linked to adenylate cyclase and also interact with pituitary adenylate cyclase activating polypeptide-38 (PACAP-38), both this homologous peptide and 8-bromo cAMP were investigated and compared to VIP-mediated release. Treatment with 1 mM 8-bromo cAMP produced cytokine release similar in amount to 0.1 nM PACAP-38, but significantly less (<50%) in comparison to 0.1 nM VIP. PACAP-38 and VIP exhibited similar EC(50)'s for the release of G-CSF and TNF-alpha; however, the maximal release was 4-6 times greater for VIP than for PACAP-38. This similarity in potency suggested a VPAC-like receptor; however, the greater efficacy for VIP in comparison to PACAP-38, combined with a lack of cAMP production at subnanomolar concentrations of VIP, suggested a mechanism not currently associated with VPAC receptors. For M-CSF, IL-3 and IL-6, the EC(50)'s of VIP were 3-30 times more potent than those of PACAP-38 in producing release. These studies suggested that multiple mechanisms mediate cytokine release in astrocytes: (1) a low efficacy release produced by PACAP-38 that is cAMP-mediated and (2) a high efficacy, VIP-preferring mechanism that was not linked to cAMP. In summary, subnanomolar concentrations of VIP released a complex array of cytokines from astrocytes that may contribute to the mitogenic and neurotrophic properties of this neuropeptide in the central nervous system.

VIPase autoantibodies in Fas-defective mice and patients with autoimmune disease

The immunoregulatory neuropeptide vasoactive intestinal peptide (VIP) was cleaved by purified IgG from Fas-defective C3H/gld mice, lupus patients, and autoimmune thyroiditis patients. No VIPase activity was detected in IgG from control mice and humans. Kinetic analyses of VIPase IgG preparations suggested low-affinity recognition of VIP. Yet the VIPase activity was VIP selective, judged by lack of correlation with other protease activities expressed by the IgG and by noninterference of unrelated peptides in the activity. Recombinant Fv constructs selected from a human lupus phage show library displayed VIPase activity, confirming that the active site is located in the V domains. Inhibition of the VIPase activity by di-isopropylfluorophosphate suggested a serine protease-like mechanism of catalysis. Irreversible binding of a biotinyated phosphonate diester by the IgG and Fv preparations was observed, consistent with the presence of activated nucleophiles similar to those in enzymes capable of covalent catalysis. These observations show that VIP is a target for specific catalytic autoantibodies in autoimmune disease.

Blood genomic expression profile for neuronal injury

This study determined whether stroke and other types of insults produced a gene expression profile in blood that correlated with the presence of neuronal injury. Adult rats were subjected to ischemic stroke, intracerebral hemorrhage, status epilepticus, and insulin-induced hypoglycemia and compared with untouched, sham surgery, and hypoxia animals that had no brain injury. One day later, microarray analyses showed that 117 genes were upregulated and 80 genes were downregulated in mononuclear blood cells of the "injury" (n = 12) compared with the "no injury" (n = 9) animals. A second experiment examined the whole blood genomic response of adult rats after global ischemia and kainate seizures. Animals with no brain injury were compared with those with brain injury documented by TUNEL and PANT staining. One day later, microarray analyses showed that 37 genes were upregulated and 67 genes were downregulated in whole blood of the injury (n = 4) animals compared with the no-injury (n = 4) animals. Quantitative reverse transcription-polymerase chain reaction confirmed that the vesicular monoamine transporter-2 increased 2.3- and 1.6-fold in animals with severe and mild brain injury, respectively, compared with no-injury animals. Vascular tyrosine phosphatase-1 increased 2.0-fold after severe injury compared with no injury. The data support the hypothesis that there is a peripheral blood genomic response to neuronal injury, and that this blood response is associated with a specific blood mRNA gene expression profile that can be used as a marker of the neuronal damage.

The neuropeptides GnRH-II and GnRH-I are produced by human T cells and trigger laminin receptor gene expression, adhesion, chemotaxis and homing to specific organs

Can T cells be directly activated to de novo gene expression by gonadotropin-releasing hormone-II (GnRH-II), a unique 10-amino-acid neuropeptide conserved through 500 million years of evolution? GnRH-II, which has been identified in mammals, shares 70% homology with the mammalian hypothalamic neurohormone GnRH (GnRH-I), the primary regulator of reproduction, but is encoded by a different gene. Although both neuropeptides are produced mainly in brain, their localization and promoter regulation differ, suggestive of distinct functions. Indeed, GnRH-II barely affects reproduction and its role in mammalian physiology is unknown. We find here that human normal and leukemic T cells produce GnRH-II and GnRH-I. Further, exposure of normal or cancerous human or mouse T cells to GnRH-II or GnRH-I triggered de novo gene transcription and cell-surface expression of a 67-kD non-integrin laminin receptor that is involved in cellular adhesion and migration and in tumor invasion and metastasis. GnRH-II or GnRH-I also induced adhesion to laminin and chemotaxis toward SDF-1alpha, and augmented entry in vivo of metastatic T-lymphoma into the spleen and bone marrow. Homing of normal T cells into specific organs was reduced in mice lacking GnRH-I. A specific GnRH-I-receptor antagonist blocked GnRH-I- but not GnRH-II-induced effects, which is suggestive of signaling through distinct receptors. We suggest that GnRH-II and GnRH-I, secreted from nerves or autocrine or paracrine sources, interact directly with T cells and trigger gene transcription, adhesion, chemotaxis and homing to specific organs, which may be of clinical relevance.

Vasoactive intestinal peptide binding autoantibodies in autoimmune humans and mice

Autoantibodies capable of binding the immunoregulatory neuropeptide vasoactive intestinal peptide (VIP) were detected in the sera of a mouse strain prone to autoimmune disease due to the lpr mutation (MRL/lpr). The autoantibodies were not present in control wildtype MRL/lpr mice, but they were readily detected in humans without autoimmune disease. The binding was due to low affinity VIP recognition. Increased VIP binding activity was evident in patients with systemic lupus erythematosus but not systemic sclerosis, Sjögren's syndrome (SS), rheumatoid arthritis or autoimmune thyroiditis. Recombinant VIP binding Fv clones (fragment variable; the variable domains of the light and heavy chains antibody subunits joined with a peptide linker) were isolated from a phage display library prepared from lupus patients. One Fv clone displaying VIP-selective binding and several clones displaying cross-reactivity with unrelated peptides were identified. Replacement mutations in the VIP-selective clone were preferentially localized in the regions known to make contacts with the antigen, i.e. the complementarity determining regions, suggesting that the selective binding activity is due to immunological maturation of the antibodies. Frequent occurrences of autoantibody responses to VIP indicate that immunological tolerance to this neuropeptide can be readily broken. The depletion of VIP by specific antibodies in autoimmune disease may interfere with VIP regulation of T cells and inflammatory cells and result in further amplification of autoreactive immunological responses.

Immunoeffector and immunoregulatory activities of vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP) and its two G protein-coupled receptors, VPAC1R and VPAC2R, are prominent in the immune system and potently affect T cells and macrophages. VPAC1Rs are expressed constitutively by blood and tissue T cells, with an order of prevalence of Th2>Th1>>Ts, and transmit signals suppressive for migration, proliferation and cytokine production. Immune activation of T cells downregulates VPAC1Rs and upregulates VPAC2Rs. VPAC2Rs mediate T cell chemotaxis, stimulation of some Th2-type cytokines, and inhibition of some Th1-type cytokines. A tentative hypothesis that the VIP-VPAC2R axis is the major neuroregulator of Th2/Th1 balance has been confirmed by finding an increased ratio in CD4 T cells of transgenic (TG) mice, expressing high levels of VPAC2Rs, and a decreased ratio in CD4 T cells of VPAC2R-null (K/O) mice. VPAC2R TG mice exhibit an allergic phenotype, whereas the K/O mice are hypoallergic and have heightened delayed-type hypersensitivity. The mechanisms of VIP-VPAC2R effects include decreased Th2 apoptosis, increased Th2-type cytokine production, and greater generation of Th2 memory cells. VPAC2R antagonists are being developed to alleviate allergic diseases and strengthen effector Th1 cell-mediated immunoprotection.

Neural-immune interactions in health and disease

Many lines of research have established the numerous routes by which the immune and central nervous systems (CNS) communicate. The CNS signals the immune system via hormonal and neuronal pathways and the immune system signals the CNS through similar routes via immune mediators and cytokines. The primary hormonal pathway by which the CNS regulates the immune system is the hypothalamic-pituitary-adrenal (HPA) axis, through the hormones of the neuroendocrine stress response. The sympathetic nervous system regulates immune system function primarily via adrenergic neurotransmitters released through neuronal routes. Neuroendocrine regulation of immune function is essential for survival during stress or infection and to modulate immune responses in inflammatory disease. Glucocorticoids are the main effector endpoint of the neuroendocrine response system.

Vasoactive intestinal peptide receptor-1 (VPAC-1) is a novel gene target of the hemolymphopoietic transcription factor Ikaros

Vasoactive intestinal peptide and its G-protein-coupled receptors, VPAC-1 and VPAC-2, are highly expressed in the immune system and modulate diverse T cell functions. The human VPAC-1 5'-flanking region (1.4 kb) contains four high affinity Ikaros (IK) consensus sequences. Ikaros native protein from T cell nuclear extracts and IK-1 and IK-2 recombinant proteins recognized an IK high affinity binding motif in the VPAC-1 promoter in electrophoretic mobility shift assays by a sequence-specific mechanism, and anti-IK antibodies supershifted this complex. Stable NIH-3T3 clones overexpressing IK-1 or IK-2 isoforms were generated to investigate Ikaros regulation of endogenous VPAC-1 expression as assessed by quantifying VPAC-1 mRNA and protein. By traditional and fluorometric-based kinetic reverse transcription-PCR and (125)I-labeled vasoactive intestinal peptide binding, both IK-1 and IK-2 suppressed endogenous VPAC-1 expression in NIH-3T3 clones by a range of 50-93%. When a series of nested deletions of the VPAC-1 luciferase reporter construct were transiently transfected into IK-2 clones there was up to a 41% decrease in transcriptional activity compared with vector control. Two major IK-2 binding domains also were identified at -1076 to -623 bp and at -222 to -35 bp, respectively. As both Ikaros and its novel target VPAC-1 are highly expressed in T cells, this system may be a dominant determinant of the VPAC-1 expression in immune responses.

Enhanced delayed-type hypersensitivity and diminished immediate-type hypersensitivity in mice lacking the inducible VPAC(2) receptor for vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP) and its G protein-coupled receptors, VPAC(1)R and VPAC(2)R, are prominent in the immune system and regulate many aspects of T cell-dependent immunity. In mouse T cells, VPAC(1)R is expressed constitutively, whereas VPAC(2)R is induced by immune stimuli. VPAC(2)R-null (VPAC(2)R(-/-)) mice on a C57BL/6 background are shown here to have normal basic immune characteristics, including serum Ig concentrations, blood levels of all leukocytes, and spleen number of total T cells (CD3(+)) and T cells bearing CD4, CD8, and CD28. Hapten-evoked cutaneous delayed-type hypersensitivity (DTH) was significantly enhanced in VPAC(2)R-null mice compared with age- and sex-matched wild-type mice. In contrast, generation of IgE anti-hapten antibodies and active cutaneous anaphylaxis were > or =70% lower in VPAC(2)R-null mice than in wild-type controls. Cytokine production by splenic CD4(+) T cells, stimulated with adherent anti-CD3 plus anti-CD28 antibodies, revealed higher levels of IL-2 (mean = 3-fold) and IFN-gamma (mean = 3-fold), and lower levels of IL-4 (mean = one-fifth) in VPAC(2)R-null mice than wild-type controls. Loss of VIP-VPAC(2)R maintenance of the normal ratio of Th2/Th1 cytokines thus leads to a state of enhanced DTH and depressed immediate-type hypersensitivity, which may alter both host defense and susceptibility to immune-mediated diseases.