Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit expression of Fas ligand in activated T lymphocytes by regulating c-Myc, NF-kappa B, NF-AT, and early growth factors 2/3

The mechanism of immune related signal pathway Egr2-FasL-Fas in transcription regulation and methylated modification of Paralichthys olivaceus under acute hypoxia stress

Apoptosis genes Egr2, Fas and FasL are related to immune responses. However, the mechanism of these genes inducing apoptosis in fish are still not very clear. An acute hypoxia treatment (1.73 ± 0.06 mg/L) for 24 h was carried out on Japanese flounder (Paralichthys olivaceus). The increasingly dense apoptotic signals at 3 h, 6 h, 12 h by TUNEL in skeletal muscle indicated that hypoxia could quickly affect muscle growth and development. Furthermore, we concluded that the Egr2-FasL-Fas signal pathway, which was located at the upstream of apoptotic executor protein caspases, was related to the apoptosis by quantitative real-time PCR, protein concentration detection in ELISA and double gene in situ hybridization methods. The mechanism of the pathway was researched in transcription regulation and epigenetic modification by dual-luciferase reporter assay and bisulfite modified method, respectively. Egr2, as a transcription factor, could up-regulate the expression of FasL gene. And its binding site was mainly between -479 to -1 of FasL gene promoter. The 5th CpG dinucleotides (-514) methylation levels in FasL gene were significantly affected by hypoxia, and they were negatively correlated with its expressions. These suggested that the -514 site may be a very important site to regulate the FasL gene expression. Above results, we concluded that hypoxia activated the immune related signal pathway Egr2-FasL-Fas to induced skeletal muscle apoptosis to affect growth and development of Japanese flounder. The study revealed the mechanism of hypoxia induced apoptosis, which could provide a reference for fish immunity and aquaculture management.

PKA and AKIP1 interact to mediate cAMP-driven COX-2 expression: A potentially pivotal interaction in preterm and term labour

Previously, we showed that cAMP increased COX-2 expression in myometrial cells via MAPK. Here, we have extended these observations, using primary myometrial cell cultures to show that the cAMP agonist, forskolin, enhances IL-1β-driven COX-2 expression. We then explored the role of A-kinase interacting protein (AKIP1), which modulates the effect of PKA on p65 activation. AKIP1 knockdown reversed the effect of forskolin, such that its addition inhibited IL-1β-induced COX-2 mRNA expression and reduced the IL-1β-induced increase in nuclear levels of p65 and c-jun. Forskolin alone and with IL-1β increased IκBα mRNA expression suggesting that in the context of inflammation and in the presence of AKIP1, cAMP enhances p65 activation. AKIP1 knockdown reversed these changes. Interestingly, AKIP1 knockdown had minimal effect on the ability of forskolin to repress either basal OTR expression or IL-1β-stimulated OTR mRNA expression. AKIP1 was up-regulated by IL-1β, but not stretch and was repressed by cAMP. The mRNA expression of AKIP1 increased in early labour in tandem with an increase in COX-2 mRNA and protein. AKIP1 protein levels were also increased with inflammation and stretch-induced preterm labour. Our results identify a second important cAMP effector-switch occurring at term in human myometrium and suggest that a hitherto unrecognized interaction may exist between AKIP1, NFκB and AP-1. These data add to the proposition that cAMP acts as a key regulator of human myometrial contractility.

The interaction between protein kinase A and progesterone on basal and inflammation-induced myometrial oxytocin receptor expression

Our previous work has shown myometrial PKA activity declines in term and twin-preterm labour in association with an increase in the expression of the oxytocin receptor (OTR). Here we investigate the action of cAMP/PKA in basal conditions, with the addition of progesterone (P4) and/or IL-1β to understand how cAMP/PKA acts to maintain pregnancy and whether the combination of cAMP and P4 would be a viable therapeutic combination for the prevention of preterm labour (PTL). Further, given that we have previously found that cAMP enhances P4 action we wanted to test the hypothesis that changes in the cAMP effector system are responsible for the functional withdrawal of myometrial P4 action. Myometrial cells were grown from biopsies obtained from women at the time of elective Caesarean section before the onset of labour. The addition of forskolin, an adenylyl cyclase activator, repressed basal OTR mRNA levels at all doses and P4 only enhanced this effect at its highest dose. Forskolin repressed the IL-1β-induced increase in OTR mRNA and protein levels in a PKA-dependent fashion and repressed IL-1β-activation and nuclear transfer of NFκB and AP-1. P4 had similar effects and the combination P4 and forskolin had greater effects on OTR and NFκB than forskolin alone. While PKA knockdown had no effect on the ability of P4 to repress IL-1β-induced OTR expression it reversed the repressive effect of the combination of P4 and forskolin and resulted in a greater increase than observed with IL-1β alone. These studies suggest that cAMP acts via PKA to repress inflammation-driven OTR expression, but that when PKA activity is reduced, the combination of cAMP and P4 actually enhances the OTR response to inflammation, promoting the onset of labour and suggesting that changes in the cAMP effector system can induce a functional P4 withdrawal.

Pituitary adenylate cyclase-activating peptide: Potential roles in the pathophysiology and complications of cirrhosis

Pituitary adenylate cyclase-activating peptide (PACAP) is a ubiquitous neuropeptide with diverse functions throughout the organism. Most abundantly investigated for its role in several neurological disorders as well as in circadian rhythms, other fields of medicine, including cardiology, have recently shown interest in the role of PACAP and its potential as a biomarker. Timely diagnosis and treatment of cirrhosis and its complications is a considerable challenge for health services world-wide and development of new areas of research is warranted. Direct and indirect evidence exists of PACAP involvement in the cascade of pathological events and processes ultimately leading to cirrhosis and its complications, but its exact role remains to be determined. Studies have documented PACAP involvement in immune function, metabolism, local vasoconstriction and dilatation and systemic vascular decompensation and there is ongoing research of a possible role in liver reperfusion injury. Considering these reports, PACAP could theoretically exude influence on the disease course of cirrhosis through the hypothalamus-pituitary-adrenal axis, chronic inflammation, fibrogenesis, vasodilation and reduced vascular resistance. The paucity of literature on the specific topic of PACAP and cirrhosis reflects complex mechanisms and difficulty in accurate measurements and sample taking. This does not detract from the need to further characterize and elucidate the role PACAP plays in the underdiagnosed and undertreated condition of cirrhosis.

Targeting Adenosine in Cancer Immunotherapy to Enhance T-Cell Function

T cells play a critical role in cancer control, but a range of potent immunosuppressive mechanisms can be upregulated in the tumor microenvironment (TME) to abrogate their activity. While various immunotherapies (IMTs) aiming at re-invigorating the T-cell-mediated anti-tumor response, such as immune checkpoint blockade (ICB), and the adoptive cell transfer (ACT) of natural or gene-engineered ex vivo expanded tumor-specific T cells, have led to unprecedented clinical responses, only a small proportion of cancer patients benefit from these treatments. Important research efforts are thus underway to identify biomarkers of response, as well as to develop personalized combinatorial approaches that can target other inhibitory mechanisms at play in the TME. In recent years, adenosinergic signaling has emerged as a powerful immuno-metabolic checkpoint in tumors. Like several other barriers in the TME, such as the PD-1/PDL-1 axis, CTLA-4, and indoleamine 2,3-dioxygenase (IDO-1), adenosine plays important physiologic roles, but has been co-opted by tumors to promote their growth and impair immunity. Several agents counteracting the adenosine axis have been developed, and pre-clinical studies have demonstrated important anti-tumor activity, alone and in combination with other IMTs including ICB and ACT. Here we review the regulation of adenosine levels and mechanisms by which it promotes tumor growth and broadly suppresses protective immunity, with extra focus on the attenuation of T cell function. Finally, we present an overview of promising pre-clinical and clinical approaches being explored for blocking the adenosine axis for enhanced control of solid tumors.

Neuroimmune Communication in Health and Disease

The immune and nervous systems are tightly integrated, with each system capable of influencing the other to respond to infectious or inflammatory perturbations of homeostasis. Recent studies demonstrating the ability of neural stimulation to significantly reduce the severity of immunopathology and consequently reduce mortality have led to a resurgence in the field of neuroimmunology. Highlighting the tight integration of the nervous and immune systems, afferent neurons can be activated by a diverse range of substances from bacterial-derived products to cytokines released by host cells. While activation of vagal afferents by these substances dominates the literature, additional sensory neurons are responsive as well. It is becoming increasingly clear that although the cholinergic anti-inflammatory pathway has become the predominant model, a multitude of functional circuits exist through which neuronal messengers can influence immunological outcomes. These include pathways whereby efferent signaling occurs independent of the vagus nerve through sympathetic neurons. To receive input from the nervous system, immune cells including B and T cells, macrophages, and professional antigen presenting cells express specific neurotransmitter receptors that affect immune cell function. Specialized immune cell populations not only express neurotransmitter receptors, but express the enzymatic machinery required to produce neurotransmitters, such as acetylcholine, allowing them to act as signaling intermediaries. Although elegant experiments have begun to decipher some of these interactions, integration of these molecules, cells, and anatomy into defined neuroimmune circuits in health and disease is in its infancy. This review describes these circuits and highlights continued challenges and opportunities for the field.

Neuroendocrine cells derived chemokine vasoactive intestinal polypeptide (VIP) in allergic diseases

Worldwide increase incidences of allergic diseases have heightened the interest of clinicians and researchers to understand the role of neuroendocrine cells in the recruitment and activation of inflammatory cells. Several pieces of evidence revealed the association of neuropeptides in the pathogenesis of allergic diseases. Importantly, one such peptide that is secreted by neuronal cells and immune cells exerts a wide spectrum of immunological functions as cytokine/chemokine is termed as Vasoactive Intestinal Peptide (VIP). VIP mediates immunological function through interaction with specific receptors namely VPAC-1, VPAC-2, CRTH2 and PAC1 that are expressed on several immune cells such as eosinophils, mast cells, neutrophils, and lymphocytes; therefore, provide the basis for the action of VIP on the immune system. Additionally, VIP mediated action varies according to target organ depending upon the presence of specific VIP associated receptor, involved immune cells and the microenvironment of the organ. Herein, we present an integrative review of the current understanding on the role of VIP and associated receptors in allergic diseases, the presence of VIP receptors on various immune cells with particular emphasis on the role of VIP in the pathogenesis of allergic diseases such as asthma, allergic rhinitis, and atopic dermatitis. Being crucial signal molecule of the neuroendocrine-immune network, the development of stable VIP analogue and/or antagonist may provide the future therapeutic drug alternative for the better treatment of these allergic diseases. Taken together, our current review summarizes the current understandings of VIP biology and further explore the significance of neuroendocrine cells derived VIP in the recruitment of inflammatory cells in allergic diseases that may be helpful to the investigators for planning the experiments and accordingly predicting new therapeutic strategies for combating allergic diseases. Summarized graphical abstract will help the readers to understand the significance of VIP in allergic diseases.

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.

PACAP immunoreactivity in human malignant tumor samples and cardiac diseases

Pituitary adenylate cyclase activating polypeptide (PACAP) is a pleiotropic and multifunctional neuropeptide having important roles in various physiological processes. Recent trends in PACAP research point to the clinical introduction of PACAP or its analogs/fragments possibly in the near future. Recently, we have shown the presence of PACAP in human plasma, milk, placenta, and follicular fluid samples. However, relatively few data are available on PACAP in human tissues from patients with different disorders. The aim of the present study was to determine, by radioimmunoassay, the tissue level of PACAP38-like immunoreactivity (LI) and PACAP27-LI in different primary non-small cell lung cancer, colon tumor samples, and in cardiac muscle samples from patients suffering from ischemic heart disease and valvular disorders. We also labeled the PAC1 receptors in human cardiac cells. All samples showed significantly higher PACAP38-LI compared with PACAP27-LI. We found significantly lower levels of PACAP38-LI and PACAP27-LI in tumoral and peripheral samples compared with normal healthy tissue in both lung and colon cancers. Further investigations are necessary to describe the exact function of PACAP in oncogenesis. We showed that PACAP38-LI and PACAP27-LI are significantly higher in ischemic heart diseases compared with valvular abnormalities, suggesting that PACAP might play a role in ischemic heart disorders.

Effects of PACAP on intracellular signaling pathways in human retinal pigment epithelial cells exposed to oxidative stress

The integrity of retinal pigment epithelial cells is critical for photoreceptor survival and vision. Pituitary adenylate cyclase activating polypeptide (PACAP) exerts retinoprotective effects against several types of injuries in vivo, including optic nerve transection, retinal ischemia, excitotoxic injuries, UVA-induced lesion, and diabetic retinopathy. In a recent study, we have proven that PACAP is also protective in oxidative stress-induced injury in human pigment epithelial cells (ARPE-19 cells). The aim of the present study was to investigate the possible mechanisms of this protection. ARPE cells were exposed to a 24-h hydrogen peroxide treatment. Expressions of kinases and apoptotic markers were studied by complex array kits and Western blot. Oxidative stress induced the activation of several apoptotic markers, including Bad, Bax, HIF-1α, several heat shock proteins, TNF-related apoptosis-inducing ligand, and Fas-associated protein with death domain, while PACAP treatment decreased them. The changes in the expression of MAP kinases showed that PACAP activated the protective ERK1/2 and downstream CREB, and decreased the activation of the pro-apoptotic p38MAPK and c-Jun N-terminal kinase, an effect opposite to that observed with only oxidative stress. Furthermore, PACAP increased the activation of the protective Akt pathway. In addition, the effects of oxidative stress on several other signaling molecules were counteracted by PACAP treatment (Chk2, Yes, Lyn, paxillin, p53, PLC, STAT4, RSK). These play a role in cell death, cell cycle, inflammation, adhesion, differentiation and proliferation. In summary, PACAP, acting at several levels, influences the balance between pro- and anti-apoptotic factors in favor of anti-apoptosis, thereby providing protection in oxidative stress-induced injury of human retinal pigment epithelial cells.

Underlying mechanisms of cAMP- and glucocorticoid-mediated inhibition of FasL expression in activation-induced cell death

Glucocorticoids (GCs) and cAMP-dependent signaling pathways exert diverse and relevant immune regulatory functions, including a tight control of T cell death and homeostasis. Both of these signaling molecules inhibit TCR-induced cell death and FasL expression, but the underlying mechanisms are still poorly understood. Therefore, to address this question, we performed a comprehensive screening of signaling pathways downstream of the TCR, in order to define which of them are targets of cAMP- and GC-mediated inhibition. We found that cAMP inhibited NF-κB and ERK pathways through a PKA-dependent mechanism, while Dexamethasone blocked TCR-induced NF-κB signaling. Although GCs and cAMP inhibited the induction of endogenous FasL mRNA expression triggered by TCR activation, they potentiated TCR-mediated induction of FasL promoter activity in transient transfection assays. However, when the same FasL promoter was stably transfected, the facilitatory effect of GCs and cAMP became inhibitory, thus resembling the effects on endogenous FasL mRNA expression. Hence, the endogenous chromatinization status known to occur in integrated or genomic vs. episomic DNA might be critical for proper regulation of FasL expression by cAMP and GCs. Our results suggest that the chromatinization status of the FasL promoter may function as a molecular switch, controlling cAMP and GC responsiveness and explaining why these agents inhibit FasL expression in T cells but induce FasL in other cell types.

Cyclic AMP: a selective modulator of NF-κB action

It has been known for several decades that cyclic AMP (cAMP), a prototypical second messenger, transducing the action of a variety of G-protein-coupled receptor ligands, has potent immunosuppressive and anti-inflammatory actions. These actions have been attributed in part to the ability of cAMP-induced signals to interfere with the function of the proinflammatory transcription factor Nuclear Factor-kappaB (NF-κB). NF-κB plays a crucial role in switching on the gene expression of a plethora of inflammatory and immune mediators, and as such is one of the master regulators of the immune response and a key target for anti-inflammatory drug design. A number of fundamental molecular mechanisms, contributing to the overall inhibitory actions of cAMP on NF-κB function, are well established. Paradoxically, recent reports indicate that cAMP, via its main effector, the protein kinase A (PKA), also promotes NF-κB activity. Indeed, cAMP actions appear to be highly cell type- and context-dependent. Importantly, several novel players in the cAMP/NF-κB connection, which selectively direct cAMP action, have been recently identified. These findings not only open up exciting new research avenues but also reveal novel opportunities for the design of more selective, NF-κB-targeting, anti-inflammatory drugs.

Transcriptional modulation by VIP: a rational target against inflammatory disease

Vasoactive intestinal peptide (VIP) is a pleiotropic, highly conserved, peptide found in many different biological systems throughout invertebrate phyla. VIP is produced by cells of the immune system but also inhibits many different inflammatory products produced by these immune cells, including cytokines and chemokines. VIP inhibits these immune mediators by affecting transcriptional regulators such as NFκB and activator protein 1 which transcribes genes responsible for the production of inflammatory mediators in response to pathogens or cytokines. In this review, the therapeutic potential of VIP will be discussed in the context of transcriptional regulation of immune cells in in vitro and in vivo animal models.

Adenosine A2A receptor activation protects CD4+ T lymphocytes against activation-induced cell death

Activation-induced cell death (AICD) is initiated by T-cell receptor (TCR) restimulation of already activated and expanded peripheral T cells and is mediated through Fas/Fas ligand (FasL) interactions. Adenosine is a purine nucleoside signaling molecule, and its immunomodulatory effects are mediated by 4 G-protein-coupled receptors: A(1), A(2A), A(2B), and A(3). In this study, we investigated the role of A(2A) receptors in regulating CD4(+) T lymphocyte AICD. Our results showed that the selective A(2A) receptor agonist CGS21680 (EC(50)=15.2-32.6 nM) rescued mouse CD4(+) hybridomas and human Jurkat cells from AICD and that this effect was reversed by the selective A(2A) receptor antagonist ZM241385 (EC(50)=2.3 nM). CGS21680 decreased phosphatidylserine exposure on the membrane, as well as the cleavage of caspase-3, caspase-8 and poly(ADP-ribose) polymerase indicating that A(2A) receptor stimulation blocks the extrinsic apoptotic pathway. In addition, CGS21680 attenuated both Fas and FasL mRNA expression. This decrease in FasL expression was associated with decreased activation of the transcription factor systems NF-kappaB, NF-ATp, early growth response (Egr)-1, and Egr-3. The antiapoptotic effect of A(2A) receptor stimulation was mediated by protein kinase A. Together, these results demonstrate that A(2A) receptor activation suppresses the AICD of peripheral T cells.

The absence of the VPAC(2) receptor does not protect mice from Aspergillus induced allergic asthma

Allergic asthma is a T(H)2-mediated disease marked by airway inflammation, increased mucus production, and elevated serum IgE in response to allergen provocation. Among its ascribed functions, the neuropeptide vasoactive intestinal peptide (VIP) is believed to promote a T(H)2 phenotype when signaling through its VPAC(2) receptor. In this study, we assessed the requirement for the VIP/VPAC(2) axis in initiating the allergic pulmonary phenotype in a murine model of fungal allergic asthma. C57BL/6 wild-type (WT) and VPAC(2) knock-out (KO) mice were sensitized with Aspergillus fumigatus antigen and challenged with an aerosol of live conidia to induce allergic airways disease. WT and KO mice exhibited similar peribronchovascular inflammation, increased number of goblet cells, and elevated serum IgE. However, the absence of VPAC(2) receptor resulted in a marked enhancement of MUC5AC mRNA with an associated increase in goblet cells and a reduction in eosinophils in the airway lumen at day 3 when VIP mRNA was undetectable in the KO lung. Sustained elevation of serum IgE was noted in KO mice at day 14, while the level in WT mice declined at this time point. These data suggest that the absence of VPAC(2) does not protect mice from developing the signs and symptoms of allergic asthma.

Vasoactive intestinal peptide induces cell cycle arrest and regulatory functions in human T cells at multiple levels

Vasoactive intestinal peptide (VIP) is a potent anti-inflammatory neuropeptide that, by inhibiting Th1-driven responses and inducing the emergence of regulatory T cells (T(reg)), has been proven successful in the induction of tolerance in various experimental models of autoimmune disorders. Here, we investigate the molecular mechanisms involved in VIP-induced tolerance. VIP treatment in the presence of T-cell receptor (TCR) signaling and CD28 costimulation induced cell cycle arrest in human T cells. VIP blocked G(1)/S transition and inhibited the synthesis of cyclins D3 and E and the activation of the cyclin-dependent kinases (CDKs) cdk2 and cdk4. This effect was accompanied by maintenance of threshold levels of the CDK inhibitor p27(kip1) and impairment of phosphatidylinositol 3-kinase (PI3K)-Akt signaling. Inhibition of interleukin 2 (IL-2) transcription and downregulation of signaling through NFAT, AP-1, and Ras-Raf paralleled the VIP-induced cell cycle arrest. Noteworthy from a functional point of view is the fact that VIP-treated T cells show a regulatory phenotype characterized by high expression of CD25, cytotoxic-T-lymphocyte-associated protein 4 (CTLA4), and Forkhead box protein 3 (FoxP3) and potent suppressive activities against effector T cells. CTLA4 appears to be critically involved in the generation and suppressive activities of VIP-induced T(reg). Finally, cyclic AMP (cAMP) and protein kinase A (PKA) activation seems to mediate the VIP-induced cell cycle arrest and T(reg) generation.

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.

Transcriptional regulation of bone and joint remodeling by NFAT

Osteoporosis and arthritis are highly prevalent diseases and a significant cause of morbidity and mortality worldwide. These diseases result from aberrant tissue remodeling leading to weak, fracture-prone bones or painful, dysfunctional joints. The nuclear factor of activated T cells (NFAT) transcription factor family controls diverse biologic processes in vertebrates. Here, we review the scientific evidence that links NFAT-regulated gene transcription to bone and joint pathology. A particular emphasis is placed on the role of NFATs in bone resorption and formation by osteoclasts and osteoblasts, respectively. In addition, emerging data that connect NFATs with cartilage biology, angiogenesis, nociception, and neurogenic inflammation are explored. The goal of this article is to highlight the importance of tissue remodeling in musculoskeletal disease and situate NFAT-driven cellular responses within this context to inspire future research endeavors.

Immunomodulation of innate immune responses by vasoactive intestinal peptide (VIP): its therapeutic potential in inflammatory disease

Since the late 1970s a number of laboratories have studied the role of vasoactive intestinal peptide (VIP) in inflammation and immunity. These studies have highlighted the dramatic effect of VIP on immune cell activation and function, and studies using animal models of disease have indicated that VIP has significant therapeutic and prophylactic potential. This review will focus on the effects of VIP on innate immune cell function and discuss the therapeutic potential for VIP in inflammatory diseases of humans.

Pituitary adenylate cyclase-activating polypeptide and its receptors: 20 years after the discovery

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a 38-amino acid C-terminally alpha-amidated peptide that was first isolated 20 years ago from an ovine hypothalamic extract on the basis of its ability to stimulate cAMP formation in anterior pituitary cells (Miyata et al., 1989. PACAP belongs to the vasoactive intestinal polypeptide (VIP)-secretin-growth hormone-releasing hormone-glucagon superfamily. The sequence of PACAP has been remarkably well conserved during evolution from protochordates to mammals, suggesting that PACAP is involved in the regulation of important biological functions. PACAP is widely distributed in the brain and peripheral organs, notably in the endocrine pancreas, gonads, respiratory and urogenital tracts. Characterization of the PACAP precursor has revealed the existence of a PACAP-related peptide, the activity of which remains unknown. Two types of PACAP binding sites have been characterized: type I binding sites exhibit a high affinity for PACAP and a much lower affinity for VIP, whereas type II binding sites have similar affinity for PACAP and VIP. Molecular cloning of PACAP receptors has shown the existence of three distinct receptor subtypes: the PACAP-specific PAC1-R, which is coupled to several transduction systems, and the PACAP/VIP-indifferent VPAC1-R and VPAC2-R, which are primarily coupled to adenylyl cyclase. PAC1-Rs are particularly abundant in the brain, the pituitary and the adrenal gland, whereas VPAC receptors are expressed mainly in lung, liver, and testis. The development of transgenic animal models and specific PACAP receptor ligands has strongly contributed to deciphering the various actions of PACAP. Consistent with the wide distribution of PACAP and its receptors, the peptide has now been shown to exert a large array of pharmacological effects and biological functions. The present report reviews the current knowledge concerning the pleiotropic actions of PACAP and discusses its possible use for future therapeutic applications.

The HECT-type E3 ubiquitin ligase AIP2 inhibits activation-induced T-cell death by catalyzing EGR2 ubiquitination

E3 ubiquitin ligases, which target specific molecules for proteolytic destruction, have emerged as key regulators of immune functions. Several E3 ubiquitin ligases, including c-Cbl, Cbl-b, GRAIL, Itch, and Nedd4, have been shown to negatively regulate T-cell activation. Here, we report that the HECT-type E3 ligase AIP2 positively regulates T-cell activation. Ectopic expression of AIP2 in mouse primary T cells enhances their proliferation and interleukin-2 production by suppressing the apoptosis of T cells. AIP2 interacts with and promotes ubiquitin-mediated degradation of EGR2, a zinc finger transcription factor that has been found to regulate Fas ligand (FasL) expression during activation-induced T-cell death. Suppression of AIP2 expression by small RNA interference upregulates EGR2, inhibits EGR2 ubiquitination and FasL expression, and enhances the apoptosis of T cells. Therefore, AIP2 regulates activation-induced T-cell death by suppressing EGR2-mediated FasL expression via the ubiquitin pathway.

Vasoactive intestinal peptide inhibits TNF-alpha-induced apoptotic events in acinar cells from nonobese diabetic mice submandibular glands

Introduction

The role of apoptotic secretory epithelium as a pro-inflammatory triggering factor of exocrine dysfunction is currently explored in Sjogren's syndrome patients and in the nonobese diabetic (NOD) mouse model. Vasoactive intestinal peptide (VIP) has anti-inflammatory effects in various models of chronic inflammation. Our goal was to analyse the effect of TNF-α on apoptotic mediators in isolated acinar cells from NOD submandibular gland and their modulation by VIP.

Methods

Acinar cells were isolated from submandibular glands of 16-week-old NOD females with salivary flow decline. Age-matched BALB/c females or eight-week-old NOD females were used as controls. Apoptotic mediators and TNF-α receptor expression were assessed by immunoblotting and RT-PCR, caspase 3 activity was assessed by optical density at 405 nm with Ac-DEVD-pNA as a substrate and chromatin condensation by Hoechst stain. They were evaluated in resting conditions and after a 3.5 or 6 hours of culture with TNF-α. VIP effects in acinar cells were assessed at 100 nM in TNF-α-treated cultures and VIP receptor functional assays by radio immunoassay (cAMP) or enzymatic detection (amylase).

Results

NOD acinar cells at 16 weeks present an increased expression of TNF-α receptor1 together with increased Bax, tumour protein 53-induced nuclear protein1α (TP53INP1α), caspase 3 activity and chromatin condensation. Acini from NOD mice were more sensitive to TNF-α-induced increases of apoptotic mediators than control cells. VIP inhibited TNF-α-induced apoptotic events through functional VPAC1 receptors coupled to the protein kinase A (PKA) signalling pathway.

Conclusions

Our results indicate that acinar cells isolated from submandibular glands of NOD mice with salivary dysfunction are more sensitive to apoptosis induced by TNF-α which could be prevented by VIP through a PKA-mediated pathway.

Role of PACAP in ischemic neural death

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide that was first isolated from an ovine hypothalamus in 1989. Since its discovery, more than 2,000 papers have reported on the tissue and cellular distribution and functional significance of PACAP. A number of papers have reported that PACAP but not the vasoactive intestinal peptide suppressed neuronal cell death or decreased infarct volume after global and focal ischemia in rodents, even if PACAP was administered several hours after ischemia induction. In addition, recent studies using PACAP gene-deficient mice demonstrated that endogenous PACAP also contributes greatly to neuroprotection similarly to exogenously administered PACAP. The studies suggest that neuroprotection by PACAP might extend the therapeutic time window for treatment of ischemia-related conditions, such as stroke. This review summarizes the effects of PACAP on ischemic neuronal cell death, and the mechanism clarified in vivo ischemic studies. In addition, the prospective mechanism of PACAP on ischemic neuroprotection from in vitro neuronal and neuronal-like cell cultures with injured stress model is reviewed. Finally, the development of PACAP and/or receptor agonists for human therapy is discussed.

PACAP has anti-apoptotic effect in the salivary gland of an invertebrate species, Helix pomatia

Pituitary adenylate cyclase activating polypeptide (PACAP) shows a remarkable sequence similarity among species and several studies provide evidence that the functions of PACAP have also been conserved among vertebrate species. Relatively little is known about its presence and functions in invertebrates. The aim of the present study was to investigate whether the well-known anti-apoptotic effect of PACAP can also be demonstrated in invertebrates. This effect was studied in the salivary gland of a molluscan species, Helix pomatia. In this work, we first showed the presence of PACAP-like immunoreactivity in the Helix salivary gland by means of immunohistochemistry. Radioimmunoassay measurements showed that PACAP38-like immunoreactivity dominated in the salivary gland of both active and inactive snails and its concentration was higher in active than in inactive animals in contrast to PACAP27-like immunoreactivity, which did not show activity-dependent changes. PACAP induced a significant elevation of cAMP level in salivary gland extracts. Application of apoptosis-inducing agents, dopamine and colchicine, led to a marked increase in the number of terminal uridine deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive apoptotic cells in the salivary gland, which was significantly attenuated by PACAP treatment. In a similar manner, the number of caspase-positive cells was reduced after co-application of dopamine and PACAP. Taken together, the data indicate that PACAP activates cAMP in a molluscan species and we show, for the first time, that PACAP is anti-apoptotic in the invertebrate Helix pomatia.

Stimulatory heterotrimeric GTP-binding protein inhibits hydrogen peroxide-induced apoptosis by repressing BAK induction in SH-SY5Y human neuroblastoma cells

Heterotrimeric stimulatory GTP-binding protein (G(s)) stimulates adenylate cyclases to activate the cAMP signaling pathway. Although the cAMP pathway has been reported to be involved in apoptosis, the role of the G(s)-cAMP signaling pathway during reactive oxygen species (ROS)-mediated apoptosis, which is involved in the resistance of cancer cells to chemotherapy and radiation, is not clearly understood. Thus, in this study we aimed to investigate the role of the alpha subunit of G(s) (Galpha(s)) in the ROS-induced apoptosis of cancer cells. The stable expression of constitutively active Galpha(s) (Galpha(s)QL) inhibited the hydrogen peroxide-induced apoptosis of SH-SY5Y human neuroblastoma cells and reduced the hydrogen peroxide-induced increase in Bak and the decrease in Bcl-x(L) protein expression. Exogenous Bak expression abolished these inhibitory effects of Galpha(s)QL, but Bak small interfering RNA decreased hydrogen peroxide-induced apoptosis. Galpha(s) repressed hydrogen peroxide-induced Bak expression by inhibiting the transcription of Bak mRNA, which resulted from the inhibition of the hydrogen peroxide-induced activation of transcription factors such as AP1, NF-kappaB, and NFAT. Moreover, Galpha(s) also inhibited the hydrogen peroxide-induced binding of AP1, NF-kappaB, and NFAT to the Bak promoter. Furthermore, hydrogen peroxide-induced apoptosis was reduced by treating cells with prostaglandin E(2), which activates Galpha(s), but this was augmented by CCPA, which activates Galpha(i) causing a decrease in cAMP levels. From the results, we conclude that Galpha(s) protects neuroblastoma cells from hydrogen peroxide-induced apoptosis by repressing Bak induction, which is mediated by the inhibition of the hydrogen peroxide-induced activations of AP1, NF-kappaB, and NFAT through cAMP-PKA-CREB signaling system.

Protective effects of pituitary adenylate cyclase activating polypeptide in endothelial cells against oxidative stress-induced apoptosis

Pituitary adenylate cyclase activating polypeptide (PACAP) is a widely distributed neuropeptide that has various different functions in the nervous system and in non-neural tissues. Little is known about the effects of PACAP in endothelial cells. The aim of the present study was to investigate the effects of PACAP on endothelial cell survival and apoptotic signaling pathways under oxidative stress. Mouse hemangioendothelioma (EOMA) cells were exposed to 0.5mM H(2)O(2) which resulted in a marked reduction of cell viability and a parallel increase of apoptotic cells assessed by MTT test and flow cytometry. Co-incubation with 20nM PACAP1-38 increased cell viability and reduced the percentage of apoptotic cells. Flow cytometry analysis showed that oxidative stress reduced the phosphorylation of the anti-apoptotic ERK and increased the phosphorylation of the pro-apoptotic JNK and p38 MAP kinases. PACAP1-38 treatment ameliorated these changes: levels of phospho-ERK were elevated and those of phospho-JNK and p38 were decreased. All these effects were abolished by simultaneous treatment with the PACAP antagonist PACAP6-38. In summary, our results show that PACAP effectively protects endothelial cells against the apoptosis-inducing effects of oxidative stress.

Effect of vasoactive intestinal peptide on gastric adenocarcinoma

BACKGROUND AND AIM

Vasoactive intestinal peptide (VIP) is a gastrointestinal hormone in the secretin-VIP family. It has been reported that VIP affects some tumor growth, and there is a VIP autocrine regulation in some cancers. However, the effect of VIP on gastric adenocarcinoma is not clear yet. The aim of the present study was to investigate the effect of VIP on gastric adenocarcinoma, especially autocrine regulation of VIP on gastric adenocarcinoma.

METHODS

VIP mRNA and protein, and its receptor mRNA (VIPR(1) and VIPR(2)) were measured in 15 normal antrum mucosa, 20 gastric adenocarcinoma tissues, and the SGC7901 gastric adenocarcinoma cell line by using reverse transcription polymerase chain reaction (RT-PCR), immunohistochemistry, or radioimmunoassay methods. The effect of the VIP protein and its antagonist (D-p-Cl-Phe6, Leu17)-VIP on SGC7901 cell growth was detected by methylthiazolyldiphenyl-tetrazolium bromide (MTT) method. The expressions of c-myc mRNA and ornithine decarboxylase (ODC) mRNA in SGC7901 cells before and after the incubated VIP protein and/or its antagonist were also measured by RT-PCR method.

RESULTS

The VIP mRNA expression in gastric adenocarcinoma tissues was significantly higher than that in normal antrum mucosa (P < 0.01). The VIP-positive immunoreactivity cells existed in 40% of gastric adenocarcinoma tissues, but not in normal tissues (P < 0.01). The VIP-positive immunoreactivity nerve fibers were observed in normal tissues, but not in adenocarcinoma tissues (P < 0.01). The expression rate of VIPR(1) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues, but that of VIPR(2) mRNA in the two kinds of tissues were similar (P > 0.05). In addition, the expression quantity of VIPR(1) mRNA and VIPR(2) mRNA in adenocarcinoma tissues was significantly lower than that in normal tissues (P < 0.05). SGC7901 cells expressed not only VIP mRNA and the VIP protein, but also VIPR(1) and VIPR(2) mRNA. 10(6) SGC7901 cells secreted 13.15 +/- 8.54 pg VIP on average. VIP did not affect the proliferation of SGC7901 cells, but the antagonist stimulated the proliferation of SGC7901 cells from 10(-5) to 10(-8) mol/L concentration incubated for 24-96 h. VIP downregulated the expressions of c-myc and ODC mRNA, but its antagonist upregulated their expressions.

CONCLUSIONS

The expression of VIP mRNA upregulates, but the expressions of VIPR mRNA downregulates in gastric adenocarcinoma tissues. The gastric adenocarcinoma tissues contain endocrine cells to secrete VIP, which show malignant specialities. The VIP autocrine regulation exists in SGC7901 cells, and potentially inhibits the proliferation of the cells by downregulating the expressions of c-myc and ODC mRNA. It suggests that VIP may play an important role in the regulation of the growth of gastric cancer cells.

Inhibition of T-cell proliferation by Helicobacter pylori gamma-glutamyl transpeptidase

BACKGROUND & AIMS

Helicobacter pylori colonizes the human gastric mucosa of >50% of the world's population. Most of the patients have no overt clinical symptoms. However, the infection is invariably associated with the development of active chronic gastritis, leading in some cases to the development of peptic ulcer disease, distal gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. In contrast to most other pathogens, infection with H pylori persists lifelong, but reasons for the persistence remain obscure. CD4-positive T cells are crucial for bacterial elimination but are inhibited by H pylori. We aimed to identify the factor responsible for suppression of T-cell response and characterize this inhibitory effect on a cellular and molecular level.

METHODS

Using size-exclusion chromatography, sodium dodecyl sulfate/polyacrylamide gel electrophoresis, and a spectrophotometric enzyme assay, we identified the secreted gamma-glutamyl transpeptidase of H pylori (HPGGT) as the factor responsible for inhibition of T-cell proliferation.

RESULTS

Mutagenesis of HPGGT in different H pylori strains completely abrogated this inhibitory effect. Recombinantly expressed HPGGT protein showed full antiproliferative activity. Site-directed mutagenesis and application of the GGT inhibitor acivicin revealed that inhibition of T cells depends on catalytic activity of HPGGT. Cell cycle analysis of human T cells indicated that HPGGT was necessary and sufficient to induce G(1) arrest. Reduced levels of c-Myc and phosphorylated c-Raf protein suggest the disruption of Ras-dependent signaling by HPGGT.

CONCLUSIONS

GGT is a novel immunosuppressive factor of H pylori inhibiting T-cell proliferation by induction of a cell cycle arrest in the G(1) phase.

Tumor immune escape mechanisms: impact of the neuroendocrine system

Tumor cells act upon, and react to both their proximate and more distant environment, the mechanisms by which this is achieved being both autocrine and paracrine in nature. This interaction, however, takes place not only between adjacent malignant cells, but also non-malignant cells such as those of the immune system, the latter also partaking in the modeling of the tumor environment. Although tumor cells descend from normal tissue cells and thus bear in classical immunological terms 'self signals', it is evident that the immune system is able to recognize tumor cells as a harassment for the body and in consequence tries to eliminate these cells. On the counterpart, tumor cells acquire various characteristics which allow them to evade this immunological surveillance, and have been collectively coined with the term "tumor escape mechanisms". This review will describe and summarize current understanding of tumor escape strategies, and also more closely elaborate on the modulatory role of the neuroendocrine system in the immune system-tumor cell interaction.

Pharmacological properties of Chinese hamster ovary cells coexpressing two vasoactive intestinal peptide receptors (hVPAC1 and hVPAC2)

1. In the light of recent findings that VPAC1 and VPAC2 receptors form homodimers and heterodimers, we have evaluated the function of these receptors coexpressed in the same cells, using whole-cell and membrane preparations. Cells expressing each receptor alone were used for comparison. 2. The study was performed on Chinese hamster ovary cells stably transfected with both human recombinant receptors and we compared receptor occupancy and adenylate cyclase activation by VIP, Ro 25-1553 - a VPAC2 selective agonist - and [K(15),R(16),L(27)]VIP(1-7)/GRF(8-27) - a VPAC1 selective agonist - on membranes prepared from each cell line and on a mixture of membranes from cells expressing each receptor individually. We also studied receptor internalization induced by the three agonists on intact cells expressing both receptors alone or together by fluorescence-activated cell sorting using monoclonal antibodies and demonstrated by using co-immunoprecipitation that the two receptors did interact.3. The results indicated that coexpression of the receptors did not modify the recognition of ligands, nor the capacity of the agonists to stimulate adenylate cyclase activity and, in intact cells, to induce internalization of the receptors.4. As a consequence, the properties of the selective ligands that were established on cell lines expressing a single population of VIP receptors were valid on cells expressing both receptors. Furthermore, the recently demonstrated VPAC1/VPAC2 receptor heterodimerization did not affect the function of either receptor.

Early growth response-1 is required for CD154 transcription

CD154 (CD40 ligand) expression on CD4 T cells is normally tightly controlled, but abnormal or dysregulated expression of CD154 has been well documented in autoimmune diseases, such as systemic lupus erythematosus. Beyond regulation by NFAT proteins, little is known about the transcriptional activation of the CD154 promoter. We identified a species-conserved purine-rich sequence located adjacent to the CD154 transcriptional promoter proximal NFAT site, which binds early growth response (Egr) transcription factors. Gel shift assays and chromatin immunoprecipitation assays reveal that Egr-1, Egr-3, and NFAT1 present in primary human CD4 T cells are capable of binding this combinatorial site in vitro and in vivo, respectively. Multimerization of this NFAT/Egr sequence in the context of a reporter gene demonstrates this sequence is transcriptionally active upon T cell activation in primary human CD4 T cells. Overexpression of Egr-1, but not Egr-3, is capable of augmenting transcription of this reporter gene as well as that of an intact CD154 promoter. Conversely, overexpression of small interfering RNA specific for Egr-1 in primary human CD4 T cells inhibits CD154 expression. Similarly, upon activation, CD154 message is notably decreased in splenic CD4 T cells from Egr-1-deficient mice compared with wild-type controls. Our data demonstrate that Egr-1 is required for CD154 transcription in primary CD4 T cells. This has implications for selective targeting of Egr family members to control abnormal expression of CD154 in autoimmune diseases such as systemic lupus erythematosus.

Granzyme B, a new player in activation-induced cell death, is down-regulated by vasoactive intestinal peptide in Th2 but not Th1 effectors

Following antigenic stimulation and differentiation, Th1 and Th2 effector cells contribute differently to cellular and humoral immunity. Vasoactive intestinal peptide (VIP) induces Th2 responses by promoting Th2 differentiation and survival. In this study, we investigate the mechanisms for the protective effect of VIP against activation-induced cell death (AICD) of Th2 effectors. Surprisingly, microarray and protein data indicate that VIP prevents the up-regulation of granzyme B (GrB) in Th2 but not Th1 effectors. This is the first report of GrB expression in Th cells and of its involvement in activation-induced apoptosis. The enhanced responsiveness of Th2 cells to VIP is probably due to the higher expression of VIP receptors. The effect of VIP on Th2 survival and GrB expression is mediated through the VIP receptors 1 and 2 and cAMP signaling through exchange protein activated by cAMP and, to a lesser degree, protein kinase A. In addition to effects on GrB, VIP also down-regulates Fas ligand (FasL) and perforin (Pfr) expression. The extrinsic Fas/FasL pathway and the intrinsic GrB-dependent pathway act independently in inducing AICD. The mechanisms by which GrB induces cell death in Th1/Th2 effectors include both fratricide and suicide. Fratricide killing, prevalent in wild-type cells, is calcium and Pfr dependent, whereas the cell death of Pfr-deficient Th cells involves Fas and GrB but is calcium independent. This study identifies GrB as a new significant player in Th1/Th2 AICD and characterizes two mechanisms for the protective effect of VIP on Th2 survival, i.e., the down-regulation of GrB and FasL expression.

Fusokine Interleukin-2/Interleukin-18, a Novel Potent Innate and Adaptive Immune Stimulator with Decreased Toxicity

To redress the immune imbalances created by pathologies such as cancer, it would be beneficial to create novel cytokine molecules, which combine desired cytokine activities with reduced toxicities. Due to their divergent but complementary activities, it is of interest to combine interleukin-2 (IL-2) and IL-18 into one recombinant molecule for immunotherapy. Evaluation of a fusokine protein that combines murine IL-2/IL-18 shows that it is stable, maintains IL-2 and IL-18 bioactivities, has notably reduced IL-2 associated toxicities, and has a novel lymphocyte-stimulating activity. An adeno-viral expression system was used to explore the biology of this "fusokine". Inclusion of the IL-18 prosequence (proIL-18) increases the expression, secretion, and potency of this fusokine. In vivo gene transfer experiments show that Ad-IL-2/proIL-18 dramatically outdoes Ad-IL-2, Ad-proIL-18, or the combination of both, by inducing high rates of tumor rejection in several murine models. Both innate and adaptive effector mechanisms are required for this antitumor activity.

Increased expression of interleukin-6 by vasoactive intestinal peptide is associated with regulation of CREB, AP-1 and C/EBP, but not NF-kappaB, in mouse calvarial osteoblasts

Interleukin-6 (IL-6), and the related cytokines IL-11, leukemia inhibitory factor (LIF) and oncostatin M (OSM), are potent stimulators of osteoclastic bone resorption. In the present study, we have addressed the possibility that the neuropeptide vasoactive intestinal peptide (VIP) may regulate the production of and/or sensitivity to the IL-6 family of cytokines in mouse calvarial osteoblasts. VIP stimulated IL-6 mRNA expression and protein release in a time- and concentration-dependent manner, whereas mRNA expression of the IL-6 receptor, as well as mRNA expressions of IL-11, LIF, OSM and their cognate receptors, were unaffected by VIP. In cells transfected with the IL-6 promoter coupled to luciferase, VIP increased transcriptional activity. The effects of VIP were shared by the related neuropeptide PACAP-38, belonging to the same superfamily of neuropeptides, whereas secretin did not have any effect, indicating that the effects were mediated by VPAC2 receptors. The effects of VIP were potentiated by the cyclic AMP phosphodiesterase inhibitor rolipram and mimicked by forskolin, indicating the involvement of the cyclic AMP/protein kinase A pathway. This was further demonstrated by the facts that the stimulatory effect of VIP on luciferase activity could be reversed by the PKA inhibitors H-89 and KT5720 and was mimicked by cyclic AMP analogues selective for PKA, but not by those selective for Epac. In addition, VIP enhanced the phosphorylation of CREB, as assessed by both immunocytochemical analysis and Western blot. The DNA binding activity of nuclear extracts to C/EBP was increased by VIP, whereas binding to AP-1 was decreased. In contrast, DNA binding to NF-kappaB, as well as nuclear translocation of NF-kappaB and C/EBP, were unaffected by VIP. The mRNA expressions of C/EBPbeta, C/EBPdelta, C/EBPgamma, c-Jun, JunB, c-Fos, Fra-1 and IkappaBalpha and protein level of IkappaBalpha were all unaffected by VIP. These observations, together, demonstrate that VIP stimulates IL-6 production in osteoblasts by a mechanism likely to be mediated by VPAC2 receptors and dependent on cyclic AMP/protein kinase A/CREB activation and also involving the transcription factors C/EBP and AP-1.

The beneficial helminth parasite?

There is unequivocal evidence that parasites influence the immune activity of their hosts, and many of the classical examples of this are drawn from assessment of helminth infections of their mammalian hosts. Thus, helminth infections can impact on the induction or course of other diseases that the host might be subjected to. Epidemiological studies demonstrate that world regions with high rates of helminth infections consistently have reduced incidences of autoimmune and other allergic/inflammatory-type conditions. Here I review and assess the possible ways by which helminth infections can block or modulate concomitant disease processes. There is much to be learned from careful analysis of immuno-regulation in helminth-infected rodents and from an understanding of the immune status of acutely and chronically infected humans. The ultimate reward from this type of investigation will likely be a more comprehensive knowledge of immunity, novel ways to intervene in the immune response to alleviate autoimmune and allergic diseases (growing concerns in economically developed areas), and perhaps the development of helminth therapy for patients suffering from specific inflammatory, autoimmune or allergic disorders.

Is fibromyalgia an autoimmune disorder of endogenous vasoactive neuropeptides?

Fibromyalgia (FM) is a disorder characterised by soft tissue pain, disturbance of function an often prolonged course and variable fatigue and debility. A clearly defined aetiology has not been described. This paper proposes that immunological aberration is likely and this may prove to be associated with an expanding group of novel vasoactive neuropeptides. Vasoactive neuropeptides act as hormones, neurotransmitters, immune modulators and neurotrophes. They are readily catalysed to small peptide fragments. They and their binding sites are immunogenic and are known to be associated with a range of autoimmune conditions. They have a vital role in maintaining vascular flow in organs, and in thermoregulation, memory and concentration. They are co-transmitters for acetylcholine, are potent immune regulators with primarily anti-inflammatory activity, and have a significant role in protection of the nervous system to toxic assault and the maintenance of homeostasis. Failure of these substances has adverse consequences for homeostasis. This paper describes a biologically plausible mechanism for the development of FM based on loss of immunological tolerance to the vasoactive neuropeptides. The proposed mechanism of action is that inflammatory cytokines are provoked by tissue injury from unaccustomed exercise or physical injury. This may trigger a response by certain vasoactive neuropeptides which then undergo autoimmune dysfunction as well as affecting their receptor binding sites. The condition may potentially arise de novo perhaps in genetically susceptible individuals. FM is postulated to be an autoimmune disorder and may include dysfunction of purine nucleotide metabolism and nociception.

c-Maf and JunB mediation of Th2 differentiation induced by the type 2 G protein-coupled receptor (VPAC2) for vasoactive intestinal peptide

Vasoactive intestinal peptide and its G protein-coupled receptors, VPAC(1) and VPAC(2), regulate critical aspects of innate and adaptive immunity. T cell VPAC(2)Rs mediate changes in cytokine generation, which potently increase the Th2/Th1 ratio and consequently shift the effector responses toward allergy and inflammation. To examine mechanisms of VPAC(2) promotion of the Th2 phenotype, we analyzed controls of IL-4 transcription in CD4 T cells from T cell-targeted VPAC(2) transgenic (Tg), VPAC(2) knockout, and wild-type (WT) mice. c-maf and junB mRNA, protein, and activity were significantly up-regulated to a higher level in TCR-stimulated CD4 T cells from Tg mice compared with those from knockout and WT C57BL/6 mice. In contrast, GATA3, T-bet, and NFATc levels were identical in WT and Tg CD4 T cells. Vasoactive intestinal peptide binding to VPAC(2) on CD4 T cells specifically induces an up-regulation of the Th2-type transcription factors c-Maf and JunB, which consequently enhances IL-4 and IL-5 production, leading to a Th2-type phenotype.

Inhibition of microglial inflammatory responses by norepinephrine: effects on nitric oxide and interleukin-1beta production

BACKGROUND: Under pathological conditions, microglia produce proinflammatory mediators which contribute to neurologic damage, and whose levels can be modulated by endogenous factors including neurotransmitters such as norepinephrine (NE). We investigated the ability of NE to suppress microglial activation, in particular its effects on induction and activity of the inducible form of nitric oxide synthase (NOS2) and the possible role that IL-1beta plays in that response. METHODS: Rat cortical microglia were stimulated with bacterial lipopolysaccharide (LPS) to induce NOS2 expression (assessed by nitrite and nitrate accumulation, NO production, and NOS2 mRNA levels) and IL-1beta release (assessed by ELISA). Effects of NE were examined by co-incubating cells with different concentrations of NE, adrenergic receptor agonists and antagonists, cAMP analogs, and protein kinase (PK) A and adenylate cyclase (AC) inhibitors. Effects on the NFkappaB:IkappaB pathway were examined by using selective a NFkappaB inhibitor and measuring IkappaBalpha protein levels by western blots. A role for IL-1beta in NOS2 induction was tested by examining effects of caspase-1 inhibitors and using caspase-1 deficient cells. RESULTS: LPS caused a time-dependent increase in NOS2 mRNA levels and NO production; which was blocked by a selective NFkappaB inhibitor. NE dose-dependently reduced NOS2 expression and NO generation, via activation of beta2-adrenergic receptors (beta2-ARs), and reduced loss of inhibitory IkBalpha protein. NE effects were replicated by dibutyryl-cyclic AMP. However, co-incubation with either PKA or AC inhibitors did not reverse suppressive effects of NE, but instead reduced nitrite production. A role for IL-1beta was suggested since NE potently blocked microglial IL-1beta production. However, incubation with a caspase-1 inhibitor, which reduced IL-1beta levels, had no effect on NO production; incubation with IL-receptor antagonist had biphasic effects on nitrite production; and NE inhibited nitrite production in caspase-1 deficient microglia. CONCLUSIONS: NE reduces microglial NOS2 expression and IL-1beta production, however IL-1beta does not play a critical role in NOS2 induction nor in mediating NE suppressive effects. Changes in magnitude or kinetics of cAMP may modulate NOS2 induction as well as suppression by NE. These results suggest that dysregulation of the central cathecolaminergic system may contribute to detrimental inflammatory responses and brain damage in neurological disease or trauma.

The significance of vasoactive intestinal peptide in immunomodulation

First identified by Said and Mutt some 30 years ago, the vasoactive intestinal peptide (VIP) was originally isolated as a vasodilator peptide. Subsequently, its biochemistry was elucidated, and within the 1st decade, their signature features as a neuropeptide became consolidated. It did not take long for these insights to permeate the field of immunology, out of which surprising new attributes for VIP were found in the last years. VIP is rapidly transforming into something more than a mere hormone. In evolving scientifically from a hormone to a novel agent for modifying immune function and possibly a cytokine-like molecule, VIP research has engaged many physiologists, molecular biologists, biochemists, endocrinologists, and pharmacologists and it is a paradigm to explore mutual interactions between neural and neuroendocrine links in health and disease. The aim of this review is firstly to update our knowledge of the cellular and molecular events relevant to VIP function on the immune system and secondly to gather together recent data that support its role as a type 2 cytokine. Recognition of the central functions VIP plays in cellular processes is focusing our attention on this "very important peptide" as exciting new candidates for therapeutic intervention and drug development.

Is chronic fatigue syndrome an autoimmune disorder of endogenous neuropeptides, exogenous infection and molecular mimicry?

Chronic fatigue syndrome is a disorder characterised by prolonged fatigue and debility and is mostly associated with post-infection sequelae although ongoing infection is unproven. Immunological aberration is likely and this may prove to be associated with an expanding group of vasoactive neuropeptides in the context of molecular mimicry and inappropriate immunological memory. Vasoactive neuropeptides including vasoactive intestinal peptide (VIP) and pituitary adenylate activating polypeptide (PACAP) belong to the secretin/glucagon superfamily and act as hormones, neurotransmitters, immune modulators and neurotrophes. They are readily catalysed to smaller peptide fragments by antibody hydrolysis. They and their binding sites are immunogenic and are known to be associated with a range of autoimmune conditions. Vasoactive neuropeptides are widely distributed in the body particularly in the central, autonomic and peripheral nervous systems and have been identified in the gut, adrenal gland, reproductive organs, vasculature, blood cells and other tissues. They have a vital role in maintaining vascular flow in organs, and in thermoregulation, memory and concentration. They are co-transmitters for acetylcholine, nitric oxide, endogenous opioids and insulin, are potent immune regulators with primarily anti-inflammatory activity, and have a significant role in protection of the nervous system to toxic assault, promotion of neural development and the maintenance of homeostasis. This paper describes a biologically plausible mechanism for the development of CFS based on loss of immunological tolerance to the vasoactive neuropeptides following infection, significant physical exercise or de novo. It is proposed that release of these substances is accompanied by a loss of tolerance either to them or their receptor binding sites in CFS. Such an occurrence would have predictably serious consequences resulting from compromised function of the key roles these substances perform. All documented symptoms of CFS are explained by vasoactive neuropeptide compromise, namely fatigue and nervous system dysfunction through impaired acetylcholine activity, myalgia through nitric oxide and endogenous opioid dysfunction, chemical sensitivity through peroxynitrite and adenosine dysfunction, and immunological disturbance through changes in immune modulation. Perverse immunological memory established against these substances or their receptors may be the reason for the protracted nature of this condition. The novel status of these substances together with their extremely small concentrations in blood and tissues means that clinical research into them is still in its infancy. A biologically plausible theory of CFS causation associated with vasoactive neuropeptide dysfunction would promote a coherent and systematic approach to research into this and other possibly associated disabling conditions.

Is gulf war syndrome an autoimmune disorder of endogenous neuropeptides, exogenous sandfly maxadilan and molecular mimicry?

Gulf War Syndrome (GWS) remains a contentious diagnosis with conflicting laboratory investigation and lack of a biologically plausible aetiology. This paper discusses the potential role of maxadilan, a potent sandfly vasoactive peptide, in causing autoimmune responses in susceptible individuals through possible molecular mimicry with pituitary adenylate cyclase activating polypeptide (PACAP) and the PAC1R receptor. Gulf War Syndrome may share some causative pathology with Chronic Fatigue Syndrome (CFS), a disorder characterised by prolonged fatigue and debility mostly associated with post-infection sequelae although ongoing infection is unproven. Immunological aberration associated with an expanding group of vasoactive neuropeptides in the context of molecular mimicry and inappropriate immunological memory has been recently raised as possible cause of CFS. Vasoactive neuropeptides act as hormones, neurotransmitters, immune modulators and neurotrophes. They are readily catalysed to small peptide fragments. They and their binding sites are immunogenic and are known to be associated with a range of autoimmune conditions. Maxadilan, while not sharing substantial sequence homology with PACAP is a known agonist of the PACAP specific receptor (PAC1R) and therefore emulates these functions. Moreover a specific amino acid sequence peptide deletion within maxadilan converts it to a PACAP receptor antagonist raising the possibility of this substance provoking a CFS like response in humans exposed to it. This paper describes a biologically plausible mechanism for the development of a GWS-like chronic fatigue state based on loss of immunological tolerance to the vasoactive neuropeptide PACAP or its receptor following bites of the sandfly Phlebotomus papatasi and injection of the vasodilator peptide maxadilan. Exacerbation of this autoimmune response as a consequence of recent or simultaneous multiple vaccination exposures deserves further investigation. While the possible association between the relatively recently discovered vasoactive neuropeptides and chronic fatigue conditions has only recently been reported in the literature, this paper explores links for further research into GWS and CFS.

Function and regulation of the CD95 (APO-1/Fas) ligand in the immune system

CD95/CD95L mediated apoptosis is an important mechanism of immune homeostasis. It is instrumental for termination of an immune response and mainly be involved in peripheral tolerance. Dysregulation of the CD95/CD95L system leads to severe diseases. In this review, we present a survey of the role of the CD95/CD95L system in the immune system and, particularly, focus on the signals and transcription factors (NF-AT, Egr, NF-kappaB, AP-1, c-Myc, Nur77, IRFs, SP-1, ALG-4, ROR(gamma)t, and CIITA) involved in CD95L expression. It should also be evident from this review that a profound insight into the molecular mechanisms of CD95L activation should allow to explore potential therapeutic means to treat CD95/CD95L-dependent diseases.

Plasma pituitary adenylate cyclase activating polypeptide (PACAP) levels in chronic hepatitis B patients under lamivudine treatment

OBJECTIVE

Lamivudine is a nucleoside analogue with potent antiviral activity against hepatitis B virus (HBV). Plasma pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide that is produced within the lymphoid microenvironment and induces the production of Th2-type cytokines. The aim of our study was to investigate the possible alterations of plasma PACAP-38 levels in chronic hepatitis B (CHB) patients during lamivudine treatment and to compare them with biochemical, virological and histological data.

METHODS

Plasma PACAP-38 levels were measured using competitive radio-immune analysis (RIA) in 25 CHB patients before and after completion of a 52-week lamivudine treatment period and in 22 healthy blood donors. Biochemical evaluation was done at baseline and every three months during treatment. Virological evaluation (HBV-DNA) was performed at baseline and at weeks 24 and 52 of treatment. Baseline liver histology was assessed for all patients at the beginning and at week 52 of the study for histological comparison with the pretreatment biopsy, according to the Ishak scoring system. Statistical evaluation of data was done using analysis of variance and Student's t-test.

RESULTS

Virological breakthrough was observed in seven (28%) patients at week 52 of treatment. Histological improvement was observed in 21 (84%) CHB patients, despite the emergence of tyrosine-methionine-aspartate-aspartate (YMDD) mutations. Plasma PACAP-38 levels were significantly lower in CHB patients at baseline than in healthy blood donors. Significant elevation of plasma peptide levels was observed in CHB patients after the completion of lamivudine treatment period, even in the subgroup of those who exhibited YMDD variants.

CONCLUSION

The elevation of plasma PACAP-38 levels in treated CHB patients following lamivudine-induced elimination of viraemia suggests a possible alteration of T-cellular immune response, resulting in biochemical and histological remission of liver disease, even in patients who exhibited virological breakthrough.

Activation-induced cell death in T cells

A properly functioning immune system is dependent on programmed cell death at virtually every stage of lymphocyte development and activity. This review addresses the phenomenon of activation-induced cell death (AICD) in T lymphocytes, in which activation through the T-cell receptor results in apoptosis. AICD can occur in a cell-autonomous manner and is influenced by the nature of the initial T-cell activation events. It plays essential roles in both central and peripheral deletion events involved in tolerance and homeostasis, although it is likely that different forms of AICD proceed via different mechanisms. For example, while AICD in peripheral T cells is often caused by the induction of expression of the death ligand, Fas ligand (CD95 ligand, FasL), it does not appear to be involved in AICD in thymocytes. This and other mechanisms of AICD are discussed. One emerging model that may complement other forms of AICD involves the inducible expression of FasL by nonlymphoid tissues in response to activated T lymphocytes. Induction of nonlymphoid FasL in this manner may serve as a sensing mechanism for immune cell infiltration, which contributes to peripheral deletion.

PACAP in immunity and inflammation

The pituitary adenylate cyclase-activating polypeptide (PACAP) is a neuropeptide belonging to the VIP/secretin/glucagon family of peptides, produced by the lymphoid cells, which exerts a wide spectrum of immunological functions controlling the homeostasis of immune system through different receptors expressed in various immunocompetent cells. In the last decade, PACAP has been clearly identified as a potent anti-inflammatory factor that exerts its function by regulating the production of both anti- and proinflammatory mediators. In this sense, PACAP prevents death by septic shock, an acute inflammatory disease with a high mortality. In addition, PACAP regulates the expression of costimulatory molecules, inasmuch as this related to the modulation in the shift from Th1 towards Th2 differentiation. We recently reported that PACAP prevents the deleterious effects of arthritis by downregulating both inflammatory and autoimmune components of the disease. Therefore, PACAP and analogs have been proposed as very promising candidates, alternative to other existing treatments, for treating acute and chronic inflammatory and autoimmune diseases, such as septic shock, arthritis, multiple sclerosis, Crohn's disease, or autoimmune diabetes.

Noradrenergic depletion increases inflammatory responses in brain: effects on IkappaB and HSP70 expression

The inflammatory responses in many cell types are reduced by noradrenaline (NA) binding to beta-adrenergic receptors. We previously demonstrated that cortical inflammatory responses to aggregated amyloid beta (Abeta) are increased if NA levels were first depleted by lesioning locus ceruleus (LC) noradrenergic neurons, which replicates the loss of LC occurring in Alzheimer's disease. To examine the molecular basis for increased responses, we used the selective neurotoxin DSP4 to lesion the LC, and then examined levels of putative anti-inflammatory molecules. Inflammatory responses were achieved by injection of aggregated Abeta1-42 peptide and IL-1beta into frontal cortex, which induced neuronal inducible nitric oxide synthase (iNOS) and microglial IL-1beta expression. DSP4-treatment reduced basal levels of nuclear factor kappa B (NF-kappaB) inhibitory IkappaB proteins, and of heat shock protein (HSP)70. Inflammatory responses were prevented by co-injection (ibuprofen or ciglitzaone) or oral administration (pioglitazone) of peroxisome proliferator-activated receptor gamma (PPARgamma) agonists. Treatment with PPARgamma agonists restored IkappaBalpha, IkappaBbeta, and HSP70 levels to values equal or above those observed in control animals, and reduced activation of cortical NF-kappaB. These results suggest that noradrenergic depletion reduces levels of anti-inflammatory molecules which normally limit cortical responses to Abeta, and that PPARgamma agonists can reverse that effect. These findings suggest one mechanism by which PPARgamma agonists could provide benefit in neurological diseases having an inflammatory component.