Vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide inhibit nuclear factor-kappa B-dependent gene activation at multiple levels in the human monocytic cell line THP-1

PACAP regulates VPAC1 expression, inflammatory processes and lipid homeostasis in M1- and M2-macrophages

Background

Pituitary adenylate cyclase-activating polypeptide (PACAP) acts as an anti-atherogenic neuropeptide and plays an important role in cytoprotective, as well as inflammatory processes, and cardiovascular regulation. Therefore, the aim of this study is to investigate the regulatory effects of PACAP and its receptor VPAC1 in relation to inflammatory processes and lipid homeostasis in different macrophage (MΦ) subtypes.

Methods

To investigate the role of PACAP deficiency in the pathogenesis of atherosclerosis under standard chow (SC) or cholesterol-enriched diet (CED) in vivo, PACAP-/- mice were crossbred with ApoE-/- to generate PACAP-/-/ApoE-/- mice. Lumen stenosis in the aortic arch and different MΦ-subtypes were analyzed in atherosclerotic plaques by quantitative immunohistochemistry. Undifferentiated bone marrow-derived cells (BMDC) from 30-weeks-old ApoE-/- and PACAP-/-/ApoE-/- mice were isolated, differentiated into BMDM1- and BMDM2-MΦ, and incubated with oxidized low-density lipoprotein (oxLDL). In addition, PMA-differentiated human THP-1 MΦ were further differentiated into M1-/M2-MΦ and subsequently treated with PACAP38, the VPAC1 agonist [(Ala11,22,28)VIP], the antagonist (PG 97-269), and/or oxLDL. Uptake/accumulation of oxLDL was analyzed by oxLDL-DyLight™488 and Bodipy™ 493/503. The mRNA expression was analyzed by qRT-PCR, protein levels by Western blot, and cytokine release by ELISA.

Results

In vivo, after 30 weeks of SC, PACAP-/-/ApoE-/- mice showed increased lumen stenosis compared with ApoE-/- mice. In atherosclerotic plaques of PACAP-/-/ApoE-/- mice under CED, immunoreactive areas of VPAC1, CD86, and CD163 were increased compared with ApoE-/- mice. In vitro, VPAC1 protein levels were increased in PACAP-/-/ApoE-/- BMDM compared with ApoE-/- BMDM, resulting in increased TNF-α mRNA expression in BMDM1-MΦ and decreased TNF-α release in BMDM2-MΦ. Concerning lipid homeostasis, PACAP deficiency decreased the area of lipid droplets in BMDM1-/M2-MΦ with concomitant increasing adipose differentiation-related protein level. In THP-1 M1-/M2-MΦ, the VPAC1 antagonist increased the uptake of oxLDL, whereas the VPAC1 agonist decreased the oxLDL-induced intracellular triglyceride content.

Conclusion

Our data suggest that PACAP via VPAC1 signaling plays an important regulatory role in inflammatory processes in atherosclerotic plaques and in lipid homeostasis in different MΦ-subtypes, thereby affecting foam cell formation. Therefore, VPAC1 agonists or PACAP may represent a new class of anti-atherogenic therapeutics.

Vasoactive Intestinal Peptide (VIP) Protects Nile Tilapia (Oreochromis niloticus) against Streptococcus agalatiae Infection

Vasoactive intestinal peptide (VIP), a member of secretin/glucagon family, is involved in a variety of biological activities such as gut motility, immune responses, and carcinogenesis. In this study, the VIP precursor gene (On-VIP) and its receptor gene VIPR1 (On-VIPR1) were identified from Nile tilapia (Oreochromis niloticus), and the functions of On-VIP in the immunomodulation of Nile tilapia against bacterial infection were investigated and characterized. On-VIP and On-VIPR1 contain a 450 bp and a 1326 bp open reading frame encoding deduced protein of 149 and 441 amino acids, respectively. Simultaneously, the transcript of both On-VIP and On-VIPR1 were highly expressed in the intestine and sharply induced by Streptococcus agalatiae. Moreover, the positive signals of On-VIP and On-VIPR1 were detected in the longitudinal muscle layer and mucosal epithelium of intestine, respectively. Furthermore, both in vitro and in vivo experiments indicated several immune functions of On-VIP, including reduction of P65, P38, MyD88, STAT3, and AP1, upregulation of CREB and CBP, and suppression of inflammation. Additionally, in vivo experiments proved that On-VIP could protect Nile tilapia from bacterial infection and promote apoptosis and pyroptosis. These data lay a theoretical basis for further understanding of the mechanism of VIP guarding bony fish against bacterial infection.

The neuropeptide PACAP alleviates T. gondii infection-induced neuroinflammation and neuronal impairment

Background

Cerebral infection with the protozoan Toxoplasma gondii (T. gondii) is responsible for inflammation of the central nervous system (CNS) contributing to subtle neuronal alterations. Albeit essential for brain parasite control, continuous microglia activation and recruitment of peripheral immune cells entail distinct neuronal impairment upon infection-induced neuroinflammation. PACAP is an endogenous neuropeptide known to inhibit inflammation and promote neuronal survival. Since PACAP is actively transported into the CNS, we aimed to assess the impact of PACAP on the T. gondii-induced neuroinflammation and subsequent effects on neuronal homeostasis.

Methods

Exogenous PACAP was administered intraperitoneally in the chronic stage of T. gondii infection, and brains were isolated for histopathological analysis and determination of pathogen levels. Immune cells from the brain, blood, and spleen were analyzed by flow cytometry, and the further production of inflammatory mediators was investigated by intracellular protein staining as well as expression levels by RT-qPCR. Neuronal and synaptic alterations were assessed on the transcriptional and protein level, focusing on neurotrophins, neurotrophin-receptors and signature synaptic markers.

Results

Here, we reveal that PACAP administration reduced the inflammatory foci and the number of apoptotic cells in the brain parenchyma and restrained the activation of microglia and recruitment of monocytes. The neuropeptide reduced the expression of inflammatory mediators such as IFN-γ, IL-6, iNOS, and IL-1β. Moreover, PACAP diminished IFN-γ production by recruited CD4⁺ T cells in the CNS. Importantly, PACAP promoted neuronal health via increased expression of the neurotrophin BDNF and reduction of p75^NTR, a receptor related to neuronal cell death. In addition, PACAP administration was associated with increased expression of transporters involved in glutamatergic and GABAergic signaling that are particularly affected during cerebral toxoplasmosis.

Conclusions

Together, our findings unravel the beneficial effects of exogenous PACAP treatment upon infection-induced neuroinflammation, highlighting the potential implication of neuropeptides to promote neuronal survival and minimize synaptic prejudice.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02639-z.

The Construction of ITP Diagnostic Modeling Based on the Expressions of Hub Genes Associated with M1 Polarization of Macrophages

Purpose

Primary immune thrombocytopenia (ITP) is an immune disease with a diagnosis of exclusion, since no validated biomarkers have been identified. In this study, we explored biomarkers associated with the development of ITP from an immune perspective to inform the clinical diagnosis.

Patients and Methods

Differentially expressed genes (DEGs) between normal and ITP samples were analyzed using limma package. Random forest algorithm and LASSO regression were further used to screen for DEGs associated with ITP. The expression of these hub genes was validated by PCR. The relationship between DEGs and immunity was explored by enrichment analysis. Immune cell infiltration in ITP was analyzed by CIBERSORT and ssGSEA, and the relationship between DEGs and infiltrating immune cells was analyzed by Spearman’s rank correlation analysis. Finally, a diagnostic model related to DEGs was constructed by the neural network, and its efficiency was detected by the ROC curve.

Results

After screening the GEO database and validation by PCR analysis, The expression of CTH and TAF8 were higher and while OSBP2 expression was lower in ITP patients compared to normal subjects (P<0.05). GO enrichment analysis showed that these DEGs were associated with inflammatory immune-related diseases, and KEGG analysis showed that they mainly regulated signaling pathways such as JAK-STAT. CIBERSORT and ssGSEA analyses showed that these DEGs were mainly associated with macrophage M1 polarization. The expression of CTH and TAF8 were positively correlated with M1 expression, while OSBP2 was negatively correlated with M1 expression. The ROC curve showed high accuracy of the neural network model [AUC= 0.939, 95% CI (0.8–1)].

Conclusion

Our results suggest that CTH, TAF8, and OSBP2 can be used as effective diagnostic biomarkers of ITP.

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.

Implications of VIP and PACAP in Parkinson's Disease: What do we Know So Far?

BACKGROUND

Parkinson's disease is one of the most common neurodegenerative disorders and although its aetiology is not yet fully understood, neuroinflammation has been identified as a key factor in the progression of the disease. Vasoactive intestinal peptide and pituitary adenylate-cyclase activating polypeptide are two neuropeptides that exhibit anti-inflammatory and neuroprotective properties, modulating the production of cytokines and chemokines and the behaviour of immune cells. However, the role of chemokines and cytokines modulated by the endogenous receptors of the peptides varies according to the stage of the disease.

METHODS

We present an overview of the relationship between some cytokines and chemokines with vasoactive intestinal peptide, pituitary adenylate cyclase activating polypeptide and their endogenous receptors in the context of Parkinson's disease neuroinflammation and oxidative stress, as well as the modulation of microglial cells by the peptides in this context.

RESULTS

The two peptides exhibit neuroprotective and anti-inflammatory properties in models of Parkinson's disease, as they ameliorate cognitive functions, decrease the level of neuroinflammation and promote dopaminergic neuronal survival. The peptides have been tested in a variety of in vivo and in vitro models of Parkinson's disease, demonstrating the potential for therapeutic application.

CONCLUSION

More studies are needed to establish the clinical use of vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide as safe candidates for treating Parkinson's disease, as the use of the peptides in different stages of the disease could produce different results concerning effectiveness.

VIP modulates human macrophages phenotype via FPRL1 via activation of RhoA-GTPase and PLC pathways

OBJECTIVE AND DESIGN

This study is aimed at uncovering the signaling pathways activated by vasoactive intestinal peptide in human macrophages MATERIALS: Human peripheral blood mononuclear cell-derived macrophages were used for the in vitro investigation of the VIP-activated signaling pathways.

METHODS AND TREATMENT

Time-course and dose-response experiments and siRNA were used in human macrophages co-challenged with various concentrations of VIP and different MAPK pharmacologic inhibitors to investigate signaling pathways activated by VIP. Flow analysis was performed to assess the levels of CD11b, CD35 and CD66. Luminescence spectrometry was used to measure the levels of the released hydrogen peroxide and the intracellular calcium levels in the media.

RESULTS

Macrophages incubated with VIP showed increased phospho-AKT and phospho-ERK1/2 levels in a GTP-RhoA-GTPase-dependent manner. Similarly, VIP increased intracellular release of H₂O₂ and calcium via PLC and GTP-RhoA-GTPase, in addition to inducing the expression of CD11b, CD35, CD66 and MMP9. Furthermore, VIP activated P38 MAPK through the cAMP/PKA pathway but was independent of both PLC and RhoA signaling. The above-mentioned VIP effects were mediated via activation of the FPRL1 receptor.

CONCLUSION

VIP/FPRL1/VPAC/GTP-RhoA-GTPase signaling modulated macrophages phenotype through activation of multiple signaling pathways including ERK1/2, AKT, P38, ROS, cAMP and calcium.

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.

The Neuropeptides Vasoactive Intestinal Peptide and Pituitary Adenylate Cyclase-Activating Polypeptide Control HIV-1 Infection in Macrophages Through Activation of Protein Kinases A and C

Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are highly similar neuropeptides present in several tissues, endowed with immunoregulatory functions and other systemic effects. We previously reported that both neuropeptides reduce viral production in HIV-1-infected primary macrophages, with the participation of β-chemokines and IL-10, and now we describe molecular mechanisms engaged in this activity. Macrophages exposed to VIP or PACAP before HIV-1 infection showed resistance to viral replication, comparable to that observed when the cells were treated after infection. Also, multiple treatments with a suboptimal dose of VIP or PACAP after macrophage infection resulted in a decline of virus production similar to the inhibition promoted by a single exposure to the optimal inhibitory concentration. Cellular signaling pathways involving cAMP production and activation of protein kinases A and C were critical components of the VIP and PACAP anti-HIV-1 effects. Analysis of the transcription factors and the transcriptional/cell cycle regulators showed that VIP and PACAP induced cAMP response element-binding protein activation, inhibited NF-kB, and reduced Cyclin D1 levels in HIV-1-infected cells. Remarkably, VIP and PACAP promoted G-to-A mutations in the HIV-1 provirus, matching those derived from the activity of the APOBEC family of viral restriction factors, and reduced viral infectivity. In conclusion, our findings strengthen the antiretroviral potential of VIP and PACAP and point to new therapeutic approaches to control the progression of HIV-1 infection.

LncRNA and mRNA profiling during activation of tilapia macrophages by HSP70 and Streptococcus agalactiae antigen

Objectives

To investigate the lncRNA profiling during tilapia peritoneal macrophages (TPMs) activation and discuss the relationship between lncRNA and mRNA.

Materials and Methods

RNA sequencing was used to investigate the lncRNA and mRNA profiles of TPMs activation following stimulation with Streptococcus agalactiae (Sa) antigen, heat shock protein 70 (HSP70) and HSP70+Sa. The expressions of lncRNA and mRNA were confirmed by qPCR. 356 lncRNA, 10173 mRNA and 1782 transcripts of uncertain coding potential (TUCP) were differentially expressed by pairwise comparison. These lncRNAs were shorter in length, fewer in exon number and higher in expression levels as compared with mRNAs. 683 lncRNAs and 4320 mRNAs were co-located, while 316 lncRNAs and 9997 mRNAs were in co-expression networks. Seven mRNAs (ANKRD34A, FMODA, GJA3, CNTN5, BMP10, BAI2 and HS3ST6) were involved in both networks of LNC_00035 and LNC_000466. Differentially expressed genes were involved in signaling pathways, such as "phosphorylation", "cytokine-cytokine receptor interaction", "endocytosis" and "MHC protein complex". LNC_000792, LNC_000215, LNC_000035 and LNC_000310, with cis and/or trans relationships with mRNAs, were also involved in ceRNA network.

Conclusions

These results might represent the first identified expression profile of lncRNAs and mRNAs in tilapia macrophages activated by HSP70 and Sa.

Neuropeptides and Microglial Activation in Inflammation, Pain, and Neurodegenerative Diseases

Microglial cells are responsible for immune surveillance within the CNS. They respond to noxious stimuli by releasing inflammatory mediators and mounting an effective inflammatory response. This is followed by release of anti-inflammatory mediators and resolution of the inflammatory response. Alterations to this delicate process may lead to tissue damage, neuroinflammation, and neurodegeneration. Chronic pain, such as inflammatory or neuropathic pain, is accompanied by neuroimmune activation, and the role of glial cells in the initiation and maintenance of chronic pain has been the subject of increasing research over the last two decades. Neuropeptides are small amino acidic molecules with the ability to regulate neuronal activity and thereby affect various functions such as thermoregulation, reproductive behavior, food and water intake, and circadian rhythms. Neuropeptides can also affect inflammatory responses and pain sensitivity by modulating the activity of glial cells. The last decade has witnessed growing interest in the study of microglial activation and its modulation by neuropeptides in the hope of developing new therapeutics for treating neurodegenerative diseases and chronic pain. This review summarizes the current literature on the way in which several neuropeptides modulate microglial activity and response to tissue damage and how this modulation may affect pain sensitivity.

Inhibition of histone deacetylation enhances endotoxin-stimulated transcription but does not reverse endotoxin tolerance

Covalent modification of histones and the subsequent remodeling of chromatin have emerged as important mechanisms in regulating gene expression. In particular, recent identification of the enzyme families responsible for the steady-state balance of histone acetylation has served to redefine our understanding of these modifications as fundamental biochemical processes regulating transcription. Current evidence suggests that histone acetylation correlates positively with gene activation, while histone deacetylation acts to repress transcription. In this study, we examined the role of histone modification in the inflammatory response to endotoxin. We focused on the endotoxin-stimulated expression of the interleukin-1β promoter and tested the hypotheses that persistent histone deacetylation was responsible for the decreased expression of this promoter observed after prolonged exposure to endotoxin, a manifestation of a phenomenon known as endotoxin tolerance. We found that histone deacetylase inhibitors enhanced endotoxin-stimulated transcription; however, deacetylation inhibitors could neither block the development of tolerance nor restore endotoxin sensitivity in a tolerant cell. Deacetylase inhibitors could not restore LPS-mediated transcription in tolerant cells. These results show that histone acetylation/deacetylation regulates, at least in part, the endotoxin-induced expression of inflammatory genes and that repressed transcription observed in endotoxin tolerance is not caused by enhanced activity of histone deacetylases.

VIP impairs acquisition of the macrophage proinflammatory polarization profile

This study tested the hypothesis that vasoactive intestinal peptide (VIP) is able to modify the macrophage inflammatory profile, thus supporting its therapeutic role in autoimmune diseases. Macrophages are innate immune cells that display a variety of functions and inflammatory profiles in response to the environment that critically controls their polarization. Deregulation between the pro- and anti-inflammatory phenotypes has been involved in different pathologies. Rheumatoid arthritis (RA) is an autoimmune disease, in which macrophages are considered central effectors of synovial inflammation, displaying a proinflammatory profile. VIP is a pleiotropic neuropeptide with proven anti-inflammatory actions. As modulation of the macrophage phenotype has been implicated in the resolution of inflammatory diseases, we evaluated whether VIP is able to modulate human macrophage polarization. In vitro-polarized macrophages by GM-CSF (GM-MØ), with a proinflammatory profile, expressed higher levels of VIP receptors, vasoactive intestinal polypeptide receptors 1 and 2 (VPAC1 and VPAC2, respectively), than macrophages polarized by M-CSF (M-MØ) with anti-inflammatory activities. RA synovial macrophages, according to their GM-CSF-like polarization state, expressed both VPAC1 and VPAC2. In vitro-generated GM-MØ exposed to VIP exhibited an up-regulation of M-MØ gene marker expression, whereas their proinflammatory cytokine profile was reduced in favor of an anti-inflammatory function. Likewise, in GM-MØ, generated in the presence of VIP, VIP somehow changes the macrophages physiology profile to a less-damaging phenotype. Therefore, these results add new value to VIP as an immunomodulatory agent on inflammatory diseases.

Epigallocatechin gallate stimulates the neuroreactive salivary secretomotor system in autoimmune sialadenitis of MRL-Fas(lpr) mice via activation of cAMP-dependent protein kinase A and inactivation of nuclear factor κB

The water channel aquaporin 5 (AQP5) plays a crucial role in regulating salivary flow rates. Xerostomia is often observed in patients with Sjögren's syndrome, and this is attributed to reduced AQP5 expression in the salivary glands. Recently, anti-type 3 muscarinic cholinergic receptors (M3R) autoantibodies and nuclear factor κB (NF-κB) have been found to be negative regulators of AQP5 expression in the salivary gland. Anti-M3R autoantibodies desensitize M3R to salivary secretagogues in Sjögren's syndrome, while activated NF-κB translocates to nuclei and binds to the AQP5 gene promoter, resulting in the suppression of AQP5 expression. We previously documented that epigallocatechin gallate (EGCG), which is a robust antioxidant contained in green tea, ameliorates oxidative stress-induced tissue damage to the salivary glands of MRL/MpJ-lpr/lpr (MRL-Fas(lpr)) mice, which are widely used as a model of Sjögren's syndrome. Reactive oxygen species (ROS) can activate NF-κB and inactivate protein kinase A (PKA), which is a key driver of AQP5 expression. In this study, we examined the effects of administering EGCG to MRL-Fas(lpr) mice with autoimmune sialadenitis on the levels of AQP5, activated NF-κB p65 subunit, activated PKA, activated c-Jun N-terminal kinase (JNK) (an activator of NF-κB), inhibitor κB (IκB) and histone deacetylase 1 (HDAC1) (an inhibitor of NF-κB). In EGCG-treated mice, intense aster-like immunostaining for AQP5 was observed on the apical plasma membranes (APMs) of submandibular gland acinar cells. Likewise, PKA, IκB and HDAC1 were highly expressed in salivary gland tissues, whereas the expression of JNK and NF-κB p65 was negligible. Rank correlation and partial correlation analyses revealed that treatment with EGCG upregulated AQP5 expression on the APM of acinar cells through activation of PKA and inactivation of NF-κB, while IκB and HDAC1 played a pivotal role in the induction of AQP5 expression by PKA. Our study indicates that EGCG may have therapeutic potential for Sjögren's syndrome patients.

Functional polarization of neuroglia: Implications in neuroinflammation and neurological disorders

Recent neuroscience research has established the adult brain as a dynamic organ having a unique ability to undergo changes with time. Neuroglia, especially microglia and astrocytes, provide dynamicity to the brain. Activation of these glial cells is a major component of the neuroinflammatory responses underlying brain injury and neurodegeneration. Glial cells execute functional reaction programs in response to diverse microenvironmental signals manifested by neuropathological conditions. Activated microglia exist along a continuum of two functional states of polarization namely M1-type (classical/proinflammatory activation) and M2-type (alternative/anti-inflammatory activation) as in macrophages. The balance between classically and alternatively activated microglial phenotypes influences disease progression in the CNS. The classically activated state of microglia drives the neuroinflammatory response and mediates the detrimental effects on neurons, whereas in their alternative activation state, which is apparently a beneficial activation state, the microglia play a crucial role in tissue maintenance and repair. Likewise, in response to immune or inflammatory microenvironments astrocytes also adopt neurotoxic or neuroprotective phenotypes. Reactive astrocytes exhibit two distinctive functional phenotypes defined by pro- or anti-inflammatory gene expression profile. In this review, we have thoroughly covered recent advances in the understanding of the functional polarization of brain and peripheral glia and its implications in neuroinflammation and neurological disorders. The identifiable phenotypes adopted by neuroglia in response to specific insult or injury can be exploited as promising diagnostic markers of neuroinflammatory diseases. Furthermore, harnessing the beneficial effects of the polarized glia could undoubtedly pave the way for the formulation of novel glia-based therapeutic strategies for diverse neurological disorders.

The neuropeptide vasoactive intestinal peptide: direct effects on immune cells and involvement in inflammatory and autoimmune diseases

Neuropeptides represent an important category of endogenous contributors to the establishment and maintenance of immune deviation in the immune-privileged organs such as the CNS and in the control of acute inflammation in the peripheral immune organs. Vasoactive intestinal peptide (VIP) is a major immunoregulatory neuropeptide widely distributed in the central and peripheral nervous system. In addition to neurones, VIP is synthesized by immune cells which also express VIP receptors. Here, we review the current information on VIP production and VIP-receptor-mediated effects in the immune system, the role of endogenous and exogenous VIP in inflammatory and autoimmune disorders and the present and future VIP therapeutic approaches.

Vasoactive intestinal peptide-deficient mice exhibit reduced pathology in trinitrobenzene sulfonic acid-induced colitis

OBJECTIVES

Vasoactive intestinal peptide (VIP) is an immunomodulatory neuropeptide with therapeutic properties in multiple murine models of inflammatory disease including the trinitrobenzene-sulfonic acid (TNBS)-colitis model of Crohn's disease. Understanding the spectrum of biological actions of endogenously produced VIP may help us dissect the complex and multifactorial pathogenesis of such inflammatory diseases. Our goal was to determine the contribution of endogenously produced VIP to TNBS-colitis by using VIP knockout (KO) mice.

METHODS

TNBS was intracolonically administered to wild-type (WT) and VIP KO mice, and weight loss and colitis were assessed over time. Colon histopathological changes and myeloperoxidase activities were analyzed and the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6 in colon and serum quantified. The proliferative response in vitro of splenocytes from TNBS WT and VIP KO administered mice to anti-CD3 and anti-CD28 was determined.

RESULTS

VIP KO mice did not exhibit the predicted exacerbated response to TNBS. Instead, they developed a milder clinical profile than WT mice, with lower TNF-α and IL-6 levels. Such potential defects seem selective, because other parameters such as the histopathological scores and the cytokine levels in the colon did not differ between the two strains of mice. Moreover, splenocytes from TNBS-treated VIP KO mice exhibited an enhanced proliferative response to anti-CD3/CD28 stimulation in vitro.

CONCLUSION

Chronic loss of VIP in mice leads to a disruption of certain but not all immunological compartments, corroborating recent findings that VIP KO mice exhibit reduced mortality in the lipopolysaccharide-induced endotoxemia model and attenuated clinical development of experimental autoimmune encephalomyelitis while developing robust T-cell responses.

Direct and indirect antimicrobial activities of neuropeptides and their therapeutic potential

As global resistance to conventional antibiotics rises we need to develop new strategies to develop future novel therapeutics. In our quest to design novel anti-infectives and antimicrobials it is of interest to investigate host-pathogen interactions and learn from the complexity of host defense strategies that have evolved over millennia. A myriad of host defense molecules are now known to play a role in protection against human infection. However, the interaction between host and pathogen is recognized to be a multifaceted one, involving countless host proteins, including several families of peptides. The regulation of infection and inflammation by multiple peptide families may represent an evolutionary failsafe in terms of functional degeneracy and emphasizes the significance of host defense in survival. One such family is the neuropeptides (NPs), which are conventionally defined as peptide neurotransmitters but have recently been shown to be pleiotropic molecules that are integral components of the nervous and immune systems. In this review we address the antimicrobial and anti-infective effects of NPs both in vitro and in vivo and discuss their potential therapeutic usefulness in overcoming infectious diseases. With improved understanding of the efficacy of NPs, these molecules could become an important part of our arsenal of weapons in the treatment of infection and inflammation. It is envisaged that targeted therapy approaches that selectively exploit the anti-infective, antimicrobial and immunomodulatory properties of NPs could become useful adjuncts to our current therapeutic modalities.

Vasoactive intestinal peptide downregulates proinflammatory TLRs while upregulating anti-inflammatory TLRs in the infected cornea

TLRs recognize microbial pathogens and trigger an immune response, but their regulation by neuropeptides, such as vasoactive intestinal peptide (VIP), during Pseudomonas aeruginosa corneal infection remains unexplored. Therefore, C57BL/6 (B6) mice were injected i.p. with VIP, and mRNA, protein, and immunostaining assays were performed. After VIP treatment, PCR array and real-time RT-PCR demonstrated that proinflammatory TLRs (conserved helix-loop-helix ubiquitous kinase, IRAK1, TLR1, TLR4, TLR6, TLR8, TLR9, and TNFR-associated factor 6) were downregulated, whereas anti-inflammatory TLRs (single Ig IL-1-related receptor [SIGIRR] and ST2) were upregulated. ELISA showed that VIP modestly downregulated phosphorylated inhibitor of NF-κB kinase subunit α but upregulated ST2 ~2-fold. SIGIRR was also upregulated, whereas TLR4 immunostaining was reduced in cornea; all confirmed the mRNA data. To determine whether VIP effects were cAMP dependent, mice were injected with small interfering RNA for type 7 adenylate cyclase (AC7), with or without VIP treatment. After silencing AC7, changes in mRNA levels of TLR1, TNFR-associated factor 6, and ST2 were seen and unchanged with addition of VIP, indicating that their regulation was cAMP dependent. In contrast, changes were seen in mRNA levels of conserved helix-loop-helix ubiquitous kinase, IRAK1, 2, TLR4, 9 and SIGIRR following AC7 silencing alone; these were modified by VIP addition, indicating their cAMP independence. In vitro studies assessed the effects of VIP on TLR regulation in macrophages and Langerhans cells. VIP downregulated mRNA expression of proinflammatory TLRs while upregulating anti-inflammatory TLRs in both cell types. Collectively, the data provide evidence that VIP downregulates proinflammatory TLRs and upregulates anti-inflammatory TLRs and that this regulation is both cAMP dependent and independent and involves immune cell types found in the infected cornea.

Vasoactive intestinal peptide: a neuropeptide with pleiotropic immune functions

Vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide/neurotransmitter, is widely distributed in both the central and peripheral nervous system. VIP is released by both neurons and immune cells. Various cell types, including immune cells, express VIP receptors. VIP has pleiotropic effects as a neurotransmitter, immune regulator, vasodilator and secretagogue. This review is focused on VIP production and effects on immune cells, VIP receptor signaling as related to immune functions, and the involvement of VIP in inflammatory and autoimmune disorders. The review addresses present clinical use of VIP and future therapeutic directions.

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.

Vasoactive intestinal peptide promotes gut barrier function against severe acute pancreatitis

To explore the influence of vasoactive intestinal peptide (VIP) on the gut barrier function in severe acute pancreatitis (SAP). Fifty four SD rats were randomly divided into three groups: sham operated (SO) group, SAP group and VIP intervention group. Each group was further divided into three time points: 1, 6 and 12 h after operation with 6 rats for each treatment point. SAP models were induced by retrograde injection of 4% sodium taurocholate into the bili-pancreatic duct. VIP intervention group was made by 5 nmol VIP intraperitoneal injection within 5 min after SAP model successfully obtained. The VIP in plasma and intestinal homogenate were detected with ELISA. The endotoxin in plasma of all groups was also tested. The expression levels of TLR4, TNF-α, IL-6, and IL-10 in gut mucosa were measured by RT-PCR. Meanwhile intestinal samples were harvested for pathological examination. Compared to SO group, the VIP in plasma and intestinal homogenate of SAP group were significantly decreased at 1 h after induction, and then gradually increased to beyond the level of SO group at 12 h. The endotoxin of SAP group was continually increased. The mRNA levels of TLR4, TNF-α, IL-6, and IL-10 were also increased with obvious pathological injuries in the intestine. In the VIP group, endotoxin in plasma was obviously decreased compared to SAP group. The expressions of TNF-α, IL-6 mRNA were suppressed while IL-10mRNA was increased. The intestinal pathological injuries were also markedly alleviated. These results suggested that VIP had protective effects on SAP gut barrier function through inhibiting intestinal mucosal inflammatory responses.

Neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) slows down Alzheimer's disease-like pathology in amyloid precursor protein-transgenic mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) has neuroprotective and neurotrophic properties and is a potent α-secretase activator. As PACAP peptides and their specific receptor PAC1 are localized in central nervous system areas affected by Alzheimer's disease (AD), this study aims to examine the role of the natural peptide PACAP as a valuable approach in AD therapy. We investigated the effect of PACAP in the brain of an AD transgenic mouse model. The long-term intranasal daily PACAP application stimulated the nonamyloidogenic processing of amyloid precursor protein (APP) and increased expression of the brain-derived neurotrophic factor and of the antiapoptotic Bcl-2 protein. In addition, it caused a strong reduction of the amyloid β-peptide (Aβ) transporter receptor for advanced glycation end products (RAGE) mRNA level. PACAP, by activation of the somatostatin-neprilysin cascade, also enhanced expression of the Aβ-degrading enzyme neprilysin in the mouse brain. Furthermore, daily PAC1-receptor activation via PACAP resulted in an increased mRNA level of both the PAC1 receptor and its ligand PACAP. Our behavioral studies showed that long-term PACAP treatment of APP[V717I]-transgenic mice improved cognitive function in animals. Thus, nasal application of PACAP was effective, and our results indicate that PACAP could be of therapeutic value in treating AD.—Rat, D., Schmitt, U., Tippmann, F., Dewachter, I., Theunis, C., Wieczerzak, E, Postina, R., van Leuven, F., Fahrenholz, F., Kojro, E. Neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) slows down Alzheimer's disease-like pathology in amyloid precursor protein-transgenic mice.

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.

Actively targeted low-dose camptothecin as a safe, long-acting, disease-modifying nanomedicine for rheumatoid arthritis

PURPOSE

Camptothecin (CPT), a potent topoisomerase I inhibitor, was originally discovered as an anticancer agent to induce programmed cell death of cancer cells. Recent evidence suggests that, similar to cancer, alterations in apoptosis and over-proliferation of key effector cells in the arthritic joint result in rheumatoid arthritis (RA) pathogenesis. Initial in vitro studies have suggested that camptothecin inhibits synoviocyte proliferation, matrix metalloproteinases expression in chrondrocytes and angiogenesis. This study is one of the first to test, in vivo, RA as a new indication for CPT.

METHODS

To circumvent insolubility, instability and toxicity of CPT, we used biocompatible, biodegradable and targeted sterically stabilized micelles (SSM) as nanocarriers for CPT (CPT-SSM). We also surface-modified CPT-SSM with vasoactive intestinal peptide (VIP) for active targeting. We then determined whether this nanomedicine abrogated collagen-induced arthritis (CIA) in mice.

RESULTS

Based on our findings, this is the first study to report that CPT was found to be efficacious against CIA at concentrations significantly lower than usual anti-cancer dose. Furthermore, a single subcutaneous injection of CPT-SSM-VIP (0.1 mg/kg) administered to CIA mice mitigated joint inflammation for at least 32 days thereafter without systemic toxicity. CPT alone needed at least 10-fold higher dose to achieve the same effect, albeit with some vacuolization in liver histology.

CONCLUSION

We propose that CPT-SSM-VIP is a promising targeted nanomedicine and should be further developed as a safe, long-acting, disease-modifying pharmaceutical product for RA.

Vasoactive intestinal peptide increases hepatic transduction and reduces innate immune response following administration of helper-dependent Ad

Helper-dependent adenoviral vectors (HDAd) are effective tools for liver-directed gene therapy because they can mediate long-term transgene expression in the absence of chronic toxicity. However, high vector doses required for efficient hepatocyte transduction by intravascular delivery result in systemic vector dissemination and dose-dependent activation of the innate immunity. Therefore, strategies to achieve high-efficiency hepatocyte transduction using low vector doses and/or to reduce the acute elevations of proinflammatory cytokines and chemokines may have significant clinical potential. Vasoactive intestinal peptide (VIP) is an endogenous neuropeptide involved in the regulation of hepatic blood flow and plays an important role as modulator of immune functions. Here, we show that VIP pretreatment in mice is able to increase hepatocyte transduction by HDAd, decrease vector uptake by the spleen, reduce elevation of proinflammatory serum cytokines interleukin (IL)-6 and IL-12, and reduce serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) following intravenous HDAd injection. VIP pretreatment also resulted in a reduction in the expression of the chemokines macrophage-inflammatory protein 2 (MIP-2), monocyte chemotactic protein 1 (MCP-1), and regulated on activation normal T-cell expressed and secreted (RANTES) in the livers of mice injected with HDAd. These results suggest that VIP can improve the therapeutic index of HDAd by increasing hepatocyte transduction efficiency while reducing cytokine and chemokine expression following intravascular delivery of HDAd.

Inhibition of monocyte adhesion to endothelial cells and attenuation of atherosclerotic lesion by a glucagon-like peptide-1 receptor agonist, exendin-4

OBJECTIVE

Exogenous administration of glucagon-like peptide-1 (GLP-1) or GLP-1 receptor agonists such as an exendin-4 has direct beneficial effects on the cardiovascular system. However, their effects on atherosclerogenesis have not been elucidated. The aim of this study was to investigate the effects of GLP-1 on accumulation of monocytes/macrophages on the vascular wall, one of the earliest steps in atherosclerogenesis.

RESEARCH DESIGN AND METHODS

After continuous infusion of low (300 pmol . kg(-1) . day(-1)) or high (24 nmol . kg(-1) . day(-1)) dose of exendin-4 in C57BL/6 or apolipoprotein E-deficient mice (apoE(-/-)), we evaluated monocyte adhesion to the endothelia of thoracic aorta and arteriosclerotic lesions around the aortic valve. The effects of exendin-4 were investigated in mouse macrophages and human monocytes.

RESULTS

Treatment with exendin-4 significantly inhibited monocytic adhesion in the aortas of C57BL/6 mice without affecting metabolic parameters. In apoE(-/-) mice, the same treatment reduced monocyte adhesion to the endothelium and suppressed atherosclerogenesis. In vitro treatment of mouse macrophages with exendin-4 suppressed lipopolysaccharide-induced mRNA expression of tumor necrosis factor-alpha and monocyte chemoattractant protein-1, and suppressed nuclear translocation of p65, a component of nuclear factor-kappaB. This effect was reversed by either MDL-12330A, a cAMP inhibitor or PKI(14-22), a protein kinase A-specific inhibitor. In human monocytes, exendin-4 reduced the expression of CD11b.

CONCLUSIONS

Our data suggested that GLP-1 receptor agonists reduced monocyte/macrophage accumulation in the arterial wall by inhibiting the inflammatory response in macrophages, and that this effect may contribute to the attenuation of atherosclerotic lesion by exendin-4.

Homeostatic and therapeutic roles of VIP in smooth muscle function: myo-neuroimmune interactions

We tested the hypothesis that spontaneous release of vasoactive intestinal peptide (VIP) from enteric neurons maintains homeostasis in smooth muscle function in mild inflammatory insults and that infusion of exogenous VIP has therapeutic effects on colonic smooth muscle dysfunction in inflammation. In vitro experiments were performed on human colonic circular smooth muscle tissues and in vivo on rats. The incubation of human colonic circular smooth muscle strips with TNF-alpha suppressed their contractile response to ACh and the expression of the pore-forming alpha(1C) subunit of Ca(v)1.2 channels. VIP reversed both effects by blocking the translocation of NF-kappaB to the nucleus and its binding to the kappaB recognition sites on halpha(1C)1b promoter. The translocation of NF-kappaB was inhibited by blocking the degradation of IkappaBbeta. Induction of inflammation by a subthreshold dose of 17 mg/kg trinitrobenzene sulfonic acid (TNBS) in rats moderately decreased muscularis externa concentration of VIP, and it had little effect on the contractile response of circular smooth muscle strips to ACh. The blockade of VIP and pituitary adenylate cyclase-activating peptide receptors 1/2 during mild inflammatory insult significantly worsened the suppression of contractility and the inflammatory response. The induction of more severe inflammation by 68 mg/kg TNBS induced marked suppression of colonic circular muscle contractility and decrease in serum VIP. Exogenous infusion of VIP by an osmotic pump reversed these effects. We conclude that the spontaneous release of VIP from the enteric motor neurons maintains homeostasis in smooth muscle function in mild inflammation by blocking the activation of NF-kappaB. The infusion of exogenous VIP mitigates colonic inflammatory response and smooth muscle dysfunction.

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.

Effect of Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) on IL-6, IL-8, and MCP-1 Expression in Human Retinal Pigment Epithelial Cell Line

PURPOSE

To examine pituitary adenylate cyclase-activating polypeptide (PACAP) receptors (PAC1, VPAC1, and VPAC2) mRNA and the effect of PACAP on interleukin-6 (IL-6), interleukin-8 (IL-8), and monocyte chemotactic protein-1 (MCP-1) expression in human retinal pigment epithelial cell line (ARPE-19) stimulated with interleukin-1beta (IL-1beta).

METHODS

Expression of PACAP receptor mRNA was examined by reverse transcription polymerase chain reaction (RT-PCR). PACAP and IL-1beta were added to serum-free medium. IL-6, IL-8, and MCP-1 mRNA were measured by real-time PCR. IL-6, IL-8, and MCP-1 protein concentrations were measured using enzyme-linked immunosorbent assay. Nuclear factor kappaB (NF-kappaB) translocation was examined by immunofluorescence.

RESULTS

PAC1 and VCAP1 receptors mRNA were expressed in unstimulated cells. VCAP2 mRNA was expressed in cells stimulated with IL-1beta. IL-1beta stimulated IL-6, IL-8, and MCP-1 mRNA expression and protein levels. PACAP (10(- 7) to 10(- 6) M) inhibited IL-1beta -stimulated IL-6, IL-8, and MCP-1 mRNA and protein levels. Immunofluorescence of NF-kappaB in the nucleus was dense 30 min after stimulation with IL-1beta, and it was decreased by PACAP.

CONCLUSIONS

ARPE-19 cells had PACAP receptors mRNA. PACAP inhibited IL-6, IL-8, and MCP-1 expression and protein secretion. Possibly, the effect on cytokines may be via suppression of NF-kappaB translocation.

Suppression of LPS-induced TNF-alpha production in macrophages by cAMP is mediated by PKA-AKAP95-p105

The activation of macrophages through Toll-like receptor (TLR) pathways leads to the production of a broad array of cytokines and mediators that coordinate the immune response. The inflammatory potential of this response can be reduced by compounds, such as prostaglandin E(2), that induce the production of cyclic adenosine monophosphate (cAMP). Through experiments with cAMP analogs and multigene RNA interference (RNAi), we showed that key anti-inflammatory effects of cAMP were mediated specifically by cAMP-dependent protein kinase (PKA). Selective inhibitors of PKA anchoring, time-lapse microscopy, and RNAi screening suggested that differential mechanisms of PKA action existed. We showed a specific role for A kinase-anchoring protein 95 in suppressing the expression of the gene encoding tumor necrosis factor-alpha, which involved phosphorylation of p105 (also known as Nfkb1) by PKA at a site adjacent to the region targeted by inhibitor of nuclear factor kappaB kinases. These data suggest that crosstalk between the TLR4 and cAMP pathways in macrophages can be coordinated through PKA-dependent scaffolds that localize specific pools of the kinase to distinct substrates.

Involvement of proton-sensing TDAG8 in extracellular acidification-induced inhibition of proinflammatory cytokine production in peritoneal macrophages

Extracellular acidification inhibited LPS-induced TNF-alpha protein production, which was associated with an inhibition of TNF-alpha mRNA expression, in mouse peritoneal macrophages. The LPS-induced cytokine production was also inhibited by G(s) protein-coupled receptor agonists prostaglandin E(1) and isoproterenol. Among OGR1 family proton-sensing GTP-binding regulatory protein-coupled receptors, TDAG8, OGR1, and G2A are expressed in the cells. The inhibitory action by acidic pH on TNF-alpha production was significantly attenuated in macrophages from TDAG8(Tp/Tp) mice but not in those from OGR1(geo/geo) mice. Moreover, small interfering RNA specific to TDAG8, but not to G2A, clearly attenuated the acidification-induced inhibition of TNF-alpha production. On the other hand, the down-regulation or deficiency of TDAG8 hardly affected prostaglandin E(1)- or isoproterenol-induced actions. LPS-induced IL-6 production was also inhibited by extracellular acidification in a manner that was sensitive to TDAG8 expression. The acidic pH-induced inhibitory action on the cytokine production was significantly reversed either by a small interfering RNA specific to G(s) proteins or by a protein kinase A (PKA)-specific inhibitor H89. Indeed, a PKA-specific cAMP derivative inhibited LPS-induced cytokine production. Moreover, acidification induced cAMP accumulation in a TDAG8-specific way. We conclude that TDAG8, at least partly, mediates the extracellular acidification-induced inhibition of proinflammatory cytokine production through the G(s) protein/cAMP/PKA signaling pathway in mouse macrophages.

Controversies in the management of colorectal liver metastases: role of PET and PET/CT

Positron emission tomography (PET) using [F-18]-2-deoxy-2-fluoro-D-glucose (FDG) has emerged as a promising diagnostic modality in recurrent colorectal cancer. Data in the literature show that the addition of FDG-PET changes patient management in up to 30% of patients with potentially resectable liver metastases, mainly by detecting previously unknown extrahepatic disease. Furthermore, FDG-PET is useful in the follow-up of patients who underwent surgical procedures of the liver, since it is sensitive in detecting residual or relapse malignancy in scarred liver tissue following both resection and local ablative techniques. For follow-up during systemic therapy, early FDG-PET appears predictive for response to therapy. FDG-PET, computerized tomography and magnetic resonance imaging are complementary techniques in staging and restaging patients with advanced colorectal cancer. A combination of FDG-PET and CT scanning characteristics seems promising, and integrated PET/ CT is becoming more widely available, although the exact clinical value and efficacy is not yet fully established. In addition, assessment of these modalities in joint reading sessions with radiologist, nuclear medicine physician, medical and surgical oncologists significantly impacts upon patient management. This review evaluates the potential of FDG-PET and combined PET/CT in patients with colorectal liver metastases and discusses potential future possibilities.

Vasoactive intestinal peptide-induced neuritogenesis in neuroblastoma SH-SY5Y cells involves SNAP-25

Vasoactive intestinal peptide (VIP) is a neuropeptide known to regulate proliferation and differentiation in normal and tumoral cells. We previously reported that VIP induced neuritogenesis in human neuroblastoma SH-SY5Y cells cultured in serum-free medium. This neuritogenesis was associated with a regulated expression of neuronal cytoskeleton markers. To further characterize the neuroblastic cell differentiation induced by VIP in human SH-SY5Y cells, we investigated expression of synaptosomal-associated protein of 25 kDa (SNAP-25), a protein implicated in exocytosis associated with different processes, including neurite outgrowth. Western immunoblotting and real-time RT-PCR analyses revealed that VIP increased expression of the SNAP-25 protein and the level of both SNAP-25a and SNAP-25b mRNA isoforms. Immunofluorescence experiments indicated that SNAP-25 was mainly located in neurites and at the plasma membrane in SH-SY5Y cells treated with VIP. RNA interference experiments demonstrated that SNAP-25 was involved in VIP-induced neuritogenesis. In conclusion, SNAP-25 is up-regulated and implicated in neuritogenesis in human neuroblastoma SH-SY5Y cells treated with the neuropeptide VIP.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Vasoactive intestinal peptide inhibits cyclooxygenase-2 expression in activated macrophages, microglia, and dendritic cells

Prostaglandin E2 (PGE2) is a potent lipid mediator produced by the inducible form of the enzyme cyclooxygenase (COX-2) in inflammatory cells. PGE2 and COX-2 are critical mediators in the pathogenesis of several inflammatory and degenerative diseases, and have therefore emerged as therapeutic targets for the treatment of such disorders. Vasoactive intestinal peptide (VIP) is a well-known anti-inflammatory neuropeptide that protects against several immune disorders by regulating a wide panel of inflammatory mediators. In this work we show the inhibitory effect of VIP on COX-2 expression and subsequent production of PGE2 by macrophages, dendritic cells, and microglia activated with different inflammatory stimuli. This inhibitory effect is exerted at the transcriptional level and mediated through the VIP receptor VPAC1. VIP downregulates NFkappaB-dependent gene activation of the COX-2 promoter. These findings demonstrate a novel property of VIP that might contribute to their anti-inflammatory effects in vivo, i.e., the inhibition of the inducible COX-2/PGE2 system.

VIP inhibits human HepG2 cell proliferation in vitro

Hepatocellular carcinoma (HCC) is an aggressive and often fatal neoplasm. HepG2 cells are a cell line derived from HCC. This investigation shows that vasoactive intestinal peptide (VIP) inhibits HepG2 cell proliferation in vitro. In addition, VIP decreases the expression of signal transducers and activators of transcription-3 (STAT-3) and phosphorylated STAT-3 (pSTAT-3). Transfection of HepG2 cells with STAT-3 siRNA also dose-dependently inhibits proliferation. These findings suggest that VIP-mediated inhibition of HepG2 proliferation may be mediated by STAT-3. Further studies demonstrate that VIP increases HepG2 cAMP levels and 8-cl-cAMP inhibits HepG2 proliferation as well as pSTAT-3 and STAT-3 levels, suggesting that cAMP is also involved in the inhibition of HepG2 proliferation. VIP also attenuates the proliferative effects of hepatocyte growth factor (HGF) and interleukin-6 (IL-6) on HepG2 cells. These preliminary studies suggest that the antiproliferative actions of VIP may offer a new and promising means of suppressing HCC.

Intravenous infusion of pituitary adenylate cyclase-activating polypeptide (PACAP) in a patient with multiple myeloma and myeloma kidney: a case study

We have recently shown significant renoprotective effects with the administration of pituitary adenylate cyclase-activating polypeptide (PACAP) in models of myeloma kidney. PACAP markedly inhibited the production of proinflammatory cytokines stimulated by immunoglobulin light chains in human renal proximal tubule epithelial cells and in the kidneys of rats infused with myeloma light chains. PACAP was also shown to suppress the proliferation of human kappa and lambda light chain-secreting multiple myeloma-derived cells. In this case study, an 81-year-old male patient with active multiple myeloma and myeloma kidney was infused intravenously with synthetic human PACAP38 at a rate of 4 pmol/kg/min for 120 min. The continuous infusion increased the level of PACAP38 in blood, with a plateau at about 0.2 nM during the infusion. The level of PACAP in the blood rapidly declined after the cessation of administration with a half-life of about 5-10 min. The continuous infusion did not significantly alter the basal glucose level, blood gases or blood pressure. There was a large reduction in free lambda light chains in urine after the start of the treatment with PACAP. These studies show that PACAP can be safely used in humans and suggest that it could be used as a novel therapeutic agent for the treatment of multiple myeloma and myeloma kidney.

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

The induction of immune tolerance is essential for the maintenance of immune homeostasis and to limit the occurrence of exacerbated inflammatory and autoimmune conditions. Multiple mechanisms act together to ensure self-tolerance, including central clonal deletion, cytokine deviation and induction of regulatory T cells. Identifying the factors that regulate these processes is crucial for the development of new therapies of autoimmune diseases and transplantation. The vasoactive intestinal peptide (VIP) is a well-characterized endogenous anti-inflammatory neuropeptide with therapeutic potential for a variety of immune disorders. Here, we examine the latest research findings, which indicate that VIP participates in maintaining immune tolerance in two distinct ways: by regulating the balance between pro-inflammatory and anti-inflammatory factors, and by inducing the emergence of regulatory T cells with suppressive activity against autoreactive T-cell effectors.

Tuning inflammation with anti-inflammatory neuropeptides

The immune system is confronted with the daunting task of defending the organism against invading pathogens while at the same time remaining self-tolerant to the body's own constituents and preserving its integrity. The loss of immune tolerance stemming from an unbalance in pro-inflammatory factors versus anti-inflammatory cytokines, or of autoreactive/inflammatory T helper 1 cells versus regulatory/suppressive T cells, results in the breakdown of immune homeostasis and the subsidiary appearance of exacerbated inflammatory and autoimmune diseases. Some neuropeptides have been shown to have anti-inflammatory properties and to participate in maintaining immune tolerance. Here the authors examine the most recent developments in this field and highlight the effectiveness of using neuropeptides in treating several inflammatory and autoimmune disorders.

Regulation of immune tolerance by anti-inflammatory neuropeptides

The induction of antigen-specific tolerance is essential to maintain immune homeostasis, control autoreactive T cells, prevent the onset of autoimmune diseases and achieve tolerance of transplants. Inflammation is a necessary process for eliminating pathogens, but can lead to serious deleterious effects in the host if left unchecked. Identifying the endogenous factors that control immune tolerance and inflammation is a key goal in the field of immunology. In the last decade, various neuropeptides that are produced by immune cells with potent anti-inflammatory actions were found to participate in the maintenance of tolerance in different immunological disorders.

Pituitary adenylate cyclase-activating polypeptide: a novel peptide with protean implications

PURPOSE OF REVIEW

The purpose of this review is to highlight the importance of pituitary adenylate cyclase-activating polypeptide in physiological processes and to describe how this peptide is becoming increasingly recognized as having a major role in the body. Since its discovery in 1989, investigators have sought to determine the site of biological activity and the function of pituitary adenylate cyclase-activating polypeptide in maintaining homeostasis.

RECENT FINDINGS

Since its discovery, pituitary adenylate cyclase-activating polypeptide appears to play an important role in the regulation of processes within the central nervous system and gastrointestinal tract, as well in reproductive biology. Pituitary adenylate cyclase-activating polypeptide has been shown to regulate tumor cell growth and to regulate immune function through its effects on T lympocytes. These discoveries suggest the importance of pituitary adenylate cyclase-activating polypeptide in neuronal development, neuronal function, gastrointestinal tract function and reproduction.

SUMMARY

Future studies will examine more closely the role of pituitary adenylate cyclase-activating polypeptide in regulation of malignantly transformed cells, as well as in regulation of immune function.

Expression of pituitary adenylate cyclase-activating polypeptide in the primary lymphoid organs of the duck Anas platyrhynchos

The expression of pituitary adenylate cyclase-activating polypeptide (PACAP) was studied in the thymus and bursa of Fabricius of the duck Anas platyrhynchos, at different ages, using immunohistochemistry, Western blotting, RT-PCR and sequencing. In the thymus, PACAP immunoreactivity (-ir) was found in lymphoid cells. CD68/ and PGP 9.5/PACAP38 double labelling showed that PACAP was not expressed either in macrophages or in epithelial cells, suggesting that the PACAP-positive cells observed were lymphoid cells. Immunoreactive lymphocytes were observed in the interlobular septa. They increased in number with ageing. In the bursa, PACAP-ir was found in nerve fibres and in a few lymphoid cells. RT-PCR revealed PACAP mRNA expression in the thymus but not in the bursa. These results suggest that PACAP plays a role in the functions of the immune system in birds.

The neuropeptide pituitary adenylate cyclase activating protein stimulates human monocytes by transactivation of the Trk/NGF pathway

Transactivation is a process whereby stimulation of G-protein-coupled receptors (GPCR) activates signaling from receptors tyrosine kinase (RTK). In neuronal cells, the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) acting through the GPCR VPAC-1 exerts trophic effects by transactivating the RTK TrkA receptor for the nerve growth factor (NGF). Both PACAP and NGF have pro-inflammatory activities on monocytes. We have tested the possibility that in monocytes, PACAP, as reported in neuronal cells, uses NGF/TrkA signaling pathway. In these cells, PACAP increases TrkA tyrosine phosphorylations through a PI-3kinase dependent but phospholipase C independent pathway. K252a, an inhibitor of TrkA decreases PACAP-induced Akt and ERK phosphorylation and calcium mobilisation resulting in decreases in intracellular H2O2 production and membrane upregulation of CD11b expression, both functions being inhibited after anti-NGF or anti-TrkA antibody treatment. K252a also inhibits PACAP-associated NF-KB activity. Monocytes increase in NGF production is seen after micromolar PACAP exposure while nanomolar treatment which desensitizes cells to high dose of PACAP prevents PACAP-induced TrkA phosphorylation, H2O2 production and CD11b expression. Finally, NGF-dependent ERK activation and H2O2 production is pertussis toxin sensitive. Altogether these data indicate that in PACAP-activated monocytes some pro-inflammatory activities occur through transactivation mechanisms involving VPAC-1, NGF and TrkA-associated tyrosine kinase activity.