Receptors and transcriptional factors involved in the anti-inflammatory activity of VIP and PACAP

Increased Expression of the Neuropeptides PACAP/VIP in the Brain of Mice with CNS Targeted Production of IL-6 Is Mediated in Part by Trans-Signalling

Inflammation with expression of interleukin 6 (IL-6) in the central nervous system (CNS) occurs in several neurodegenerative/neuroinflammatory conditions and may cause neurochemical changes to endogenous neuroprotective systems. Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are two neuropeptides with well-established protective and anti-inflammatory properties. Yet, whether PACAP and VIP levels are altered in mice with CNS-restricted, astrocyte-targeted production of IL-6 (GFAP-IL6) remains unknown. In this study, PACAP/VIP levels were assessed in the brain of GFAP-IL6 mice. In addition, we utilised bi-genic GFAP-IL6 mice carrying the human sgp130-Fc transgene (termed GFAP-IL6/sgp130Fc mice) to determine whether trans-signalling inhibition rescued PACAP/VIP changes in the CNS. Transcripts and protein levels of PACAP and VIP, as well as their receptors PAC1, VPAC1 and VPAC2, were significantly increased in the cerebrum and cerebellum of GFAP-IL6 mice vs. wild type (WT) littermates. These results were paralleled by a robust activation of the JAK/STAT3, NF-κB and ERK1/2MAPK pathways in GFAP-IL6 mice. In contrast, co-expression of sgp130Fc in GFAP-IL6/sgp130Fc mice reduced VIP expression and activation of STAT3 and NF-κB pathways, but it failed to rescue PACAP, PACAP/VIP receptors and Erk1/2MAPK phosphorylation. We conclude that forced expression of IL-6 in astrocytes induces the activation of the PACAP/VIP neuropeptide system in the brain, which is only partly modulated upon IL-6 trans-signalling inhibition. Increased expression of PACAP/VIP neuropeptides and receptors may represent a homeostatic response of the CNS to an uncontrolled IL-6 synthesis and its neuroinflammatory consequences.

The role of vasoactive intestinal peptide in pulmonary diseases

Vasoactive intestinal peptide (VIP) is an abundant neurotransmitter in the lungs and other organs. Its discovery dates back to 1970. And VIP gains attention again due to the potential application in COVID-19 after a research wave in the 1980s and 1990s. The diverse biological impacts of VIP extend beyond its usage in COVID-19 treatment, encompassing its involvement in various pulmonary and systemic disorders. This review centers on the function of VIP in various lung diseases, such as pulmonary arterial hypertension, chronic obstructive pulmonary disease, asthma, cystic fibrosis, acute lung injury/acute respiratory distress syndrome, pulmonary fibrosis, and lung tumors. This review also outlines two main limitations of VIP as a potential medication and gathers information on extended-release formulations and VIP analogues.

The role of sensory and sympathetic nerves in craniofacial bone regeneration

Multiple factors regulate the regeneration of craniofacial bone defects. The nervous system is recognized as one of the critical regulators of bone mass, thereby suggesting a role for neuronal pathways in bone regeneration. However, in the context of craniofacial bone regeneration, little is known about the interplay between the nervous system and craniofacial bone. Sensory and sympathetic nerves interact with the bone through their neuropeptides, neurotransmitters, proteins, peptides, and amino acid derivates. The neuron-derived factors, such as semaphorin 3A (SEMA3A), substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP), possess a remarkable role in craniofacial regeneration. This review summarizes the roles of these factors and recently published factors such as secretoneurin (SN) and spexin (SPX) in the osteoblast and osteoclast differentiation, bone metabolism, growth, remodeling and discusses the novel application of nerve-based craniofacial bone regeneration. Moreover, the review will facilitate understanding the mechanism of action and provide potential treatment direction for the craniofacial bone defect.

Design and Synthesis of Brain Penetrant Glycopeptide Analogues of PACAP With Neuroprotective Potential for Traumatic Brain Injury and Parkinsonism

There is an unmet clinical need for curative therapies to treat neurodegenerative disorders. Most mainstay treatments currently on the market only alleviate specific symptoms and do not reverse disease progression. The Pituitary adenylate cyclase-activating polypeptide (PACAP), an endogenous neuropeptide hormone, has been extensively studied as a potential regenerative therapeutic. PACAP is widely distributed in the central nervous system (CNS) and exerts its neuroprotective and neurotrophic effects via the related Class B GPCRs PAC1, VPAC1, and VPAC2, at which the hormone shows roughly equal activity. Vasoactive intestinal peptide (VIP) also activates these receptors, and this close analogue of PACAP has also shown to promote neuronal survival in various animal models of acute and progressive neurodegenerative diseases. However, PACAP's poor pharmacokinetic profile (non-linear PK/PD), and more importantly its limited blood-brain barrier (BBB) permeability has hampered development of this peptide as a therapeutic. We have demonstrated that glycosylation of PACAP and related peptides promotes penetration of the BBB and improves PK properties while retaining efficacy and potency in the low nanomolar range at its target receptors. Furthermore, judicious structure-activity relationship (SAR) studies revealed key motifs that can be modulated to afford compounds with diverse selectivity profiles. Most importantly, we have demonstrated that select PACAP glycopeptide analogues (2LS80Mel and 2LS98Lac) exert potent neuroprotective effects and anti-inflammatory activity in animal models of traumatic brain injury and in a mild-toxin lesion model of Parkinson's disease, highlighting glycosylation as a viable strategy for converting endogenous peptides into robust and efficacious drug candidates.

Macrophage Polarization and Alveolar Bone Healing Outcome: Despite a Significant M2 Polarizing Effect, VIP and PACAP Treatments Present a Minor Impact in Alveolar Bone Healing in Homeostatic Conditions

Host inflammatory immune response comprises an essential element of the bone healing process, where M2 polarization allegedly contributes to a favorable healing outcome. In this context, immunoregulatory molecules that modulate host response, including macrophage polarization, are considered potential targets for improving bone healing. This study aims to evaluate the role of the immunoregulatory molecules VIP (Vasoactive intestinal peptide) and PACAP (Pituitary adenylate cyclase activating polypeptide), which was previously described to favor the development of the M2 phenotype, in the process of alveolar bone healing in C57Bl/6 (WT) mice. Experimental groups were submitted to tooth extraction and maintained under control conditions or treated with VIP or PACAP were evaluated by microtomographic (µCT), histomorphometric, immunohistochemical, and molecular analysis at 0, 3, 7, and 14 days to quantify tissue healing and host response indicators at the healing site. Gene expression analysis demonstrates the effectiveness of VIP or PACAP in modulating host response, evidenced by the early dominance of an M2-type response, which was paralleled by a significant increase in M2 (CD206+) in treated groups. However, despite the marked effect of M1/M2 balance in the healing sites, the histomorphometric analysis does not reveal an equivalent/corresponding modulation of the healing process. µCT reveals a slight increase in bone matrix volume and the trabecular thickness number in the PACAP group, while histomorphometric analyzes reveal a slight increase in the VIP group, both at a 14-d time-point; despite the increased expression of osteogenic factors, osteoblastic differentiation, activity, and maturation markers in both VIP and PACAP groups. Interestingly, a lower number of VIP and PACAP immunolabeled cells were observed in the treated groups, suggesting a reduction in endogenous production. In conclusion, while both VIP and PACAP treatments presented a significant immunomodulatory effect with potential for increased healing, no major changes were observed in bone healing outcome, suggesting that the signals required for bone healing under homeostatic conditions are already optimal, and additional signals do not improve an already optimal process. Further studies are required to elucidate the role of macrophage polarization in the bone healing process.

Metformin Treatment Attenuates Brain Inflammation and Rescues PACAP/VIP Neuropeptide Alterations in Mice Fed a High-Fat Diet

High-fat diet (HFD)-induced comorbid cognitive and behavioural impairments are thought to be the result of persistent low-grade neuroinflammation. Metformin, a first-line medication for the treatment of type-2 diabetes, seems to ameliorate these comorbidities, but the underlying mechanism(s) are not clear. Pituitary adenylate cyclase-activating peptide (PACAP) and vasoactive intestinal peptide (VIP) are neuroprotective peptides endowed with anti-inflammatory properties. Alterations to the PACAP/VIP system could be pivotal during the development of HFD-induced neuroinflammation. To unveil the pathogenic mechanisms underlying HFD-induced neuroinflammation and assess metformin’s therapeutic activities, (1) we determined if HFD-induced proinflammatory activity was present in vulnerable brain regions associated with the development of comorbid behaviors, (2) investigated if the PACAP/VIP system is altered by HFD, and (3) assessed if metformin rescues such diet-induced neurochemical alterations. C57BL/6J male mice were divided into two groups to receive either standard chow (SC) or HFD for 16 weeks. A further HFD group received metformin (HFD + M) (300 mg/kg BW daily for 5 weeks) via oral gavage. Body weight, fasting glucose, and insulin levels were measured. After 16 weeks, the proinflammatory profile, glial activation markers, and changes within the PI3K/AKT intracellular pathway and the PACAP/VIP system were evaluated by real-time qPCR and/or Western blot in the hypothalamus, hippocampus, prefrontal cortex, and amygdala. Our data showed that HFD causes widespread low-grade neuroinflammation and gliosis, with regional-specific differences across brain regions. HFD also diminished phospho-AKT^(Ser473) expression and caused significant disruptions to the PACAP/VIP system. Treatment with metformin attenuated these neuroinflammatory signatures and reversed PI3K/AKT and PACAP/VIP alterations caused by HFD. Altogether, our findings demonstrate that metformin treatment rescues HFD-induced neuroinflammation in vulnerable brain regions, most likely by a mechanism involving the reinstatement of PACAP/VIP system homeostasis. Data also suggests that the PI3K/AKT pathway, at least in part, mediates some of metformin’s beneficial effects.

PACAP and VIP Modulate LPS-Induced Microglial Activation and Trigger Distinct Phenotypic Changes in Murine BV2 Microglial Cells

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are two structurally related immunosuppressive peptides. However, the underlying mechanisms through which these peptides regulate microglial activity are not fully understood. Using lipopolysaccharide (LPS) to induce an inflammatory challenge, we tested whether PACAP or VIP differentially affected microglial activation, morphology and cell migration. We found that both peptides attenuated LPS-induced expression of the microglial activation markers Iba1 and iNOS (### p < 0.001), as well as the pro-inflammatory mediators IL-1β, IL-6, Itgam and CD68 (### p < 0.001). In contrast, treatment with PACAP or VIP exerted distinct effects on microglial morphology and migration. PACAP reversed LPS-induced soma enlargement and increased the percentage of small-sized, rounded cells (54.09% vs. 12.05% in LPS-treated cells), whereas VIP promoted a phenotypic shift towards cell subpopulations with mid-sized, spindle-shaped somata (48.41% vs. 31.36% in LPS-treated cells). Additionally, PACAP was more efficient than VIP in restoring LPS-induced impairment of cell migration and the expression of urokinase plasminogen activator (uPA) in BV2 cells compared with VIP. These results suggest that whilst both PACAP and VIP exert similar immunosuppressive effects in activated BV2 microglia, each peptide triggers distinctive shifts towards phenotypes of differing morphologies and with differing migration capacities.

Linarin Protects the Kidney against Ischemia/Reperfusion Injury via the Inhibition of Bioactive ETS2/IL-12

Ischemia/reperfusion injury (IRI), a participant in acute kidney injury (AKI), can occur as a series of pathological processes such as inflammation. Linarin (LIN) has been widely used for different diseases. To confirm the anti-inflammatory value and relevant mechanism of LIN during IRI, in vivo and vitro models were established. LIN or dissolvent was given, and histologic analysis, quantitative (q)RT-PCR, serum creatinine and blood urea nitrogen testing were used to evaluate kidney injury. Microarray analysis, protein-protein interaction (PPI) analysis and molecular docking were used to identify the target protein of LIN, and small interfering RNA (siRNA) transfection was applied to explore the crucial role of identified protein. First, we found that LIN inhibited kidney injury in an in vivo IRI model and decreased the expression of interleukin-12 (IL-12) p40 in vivo and in vitro IRI models. To explore the mechanism of LIN, we collected raw data from a public microarray database and identified E26 oncogene homolog 2 (ETS2) as a crucial protein of LIN according to microarray analysis and PPI. Meanwhile, qRT-PCR indicated that IL-12 p40 showed no significant difference between ETS2 knock down group and LIN treated ETS2 knock down group after hypoxia reoxygenation treatment. In addition, according to molecular docking the contact area is highly conserved and located on a PPI domain of ETS2 which indicates that LIN may alter the interaction with synergistic proteins in the regulation of IL-12 p40 expression. Our study demonstrated the anti-inflammatory effect of LIN during IRI-AKI, broadening the medicinal value of LIN and the therapeutic options for IRI-AKI.

Vasoactive Intestinal Polypeptide (VIP) in the Intestinal Mucosal Nerve Fibers in Dogs with Inflammatory Bowel Disease

Simple Summary

Canine inflammatory bowel disease (IBD)—a group of gastrointestinal disorders—is a serious problem in veterinary medicine. The etiology of IBD remains unknown, and its diagnosis and effective treatment are difficult. One of the less-known aspects of IBD pathology is the influence of this disease on the enteric nervous system, which is located in the intestinal wall and regulates most of the gastrointestinal functions. Therefore, the aim of the present study was to evaluate the influence of IBD on the intramucosal nerve fibers containing vasoactive intestinal polypeptide (VIP). VIP is one of the most important substances produced by the enteric nervous structures that is involved in many regulatory processes in the gastrointestinal tract. The obtained results show that IBD induces changes in the density of intramucosal VIP-positive nerve fibers in the canine gastrointestinal tract. It suggests that VIP is involved in the pathological processes occurring during this disease. Observed changes may be a result of neuroprotective and/or adaptive processes regulated by VIP, aimed at the homeostasis maintenance in the inflamed gastrointestinal (GI) tract and induced by proinflammatory factors.

Abstract

Canine inflammatory bowel disease (IBD) is a group of enteropathies with nonspecific chronic symptoms and poorly understood etiology. Many aspects connected with IBD are not understood. One of them is the participation of the intestinal nervous system in the development of pathological processes. Thus, this study aimed to demonstrate changes in the density of intramucosal nerve fibers containing vasoactive intestinal polypeptide (VIP)—one of the most important intestinal nervous factors caused by the various stages of IBD development. Mucosal biopsy specimens collected from the duodenum, jejunum and descending colon of healthy dogs and dogs with varied severity of IBD were included in the experiment. The density of VIP-like immunoreactive (VIP-LI) nerves was determined by a single immunofluorescence technique and a semi-quantitative method consisting in VIP-LI fiber counts in the field of view (0.1 mm²). The obtained results indicate that IBD induces changes in the density of mucosal VIP-LI nerve fibers in the canine gastrointestinal tract. The initial decrease is followed by an increase in VIP-like immunoreactivity in successive stages of the disease. These observations show that VIP is a neuronal factor that participates in the pathological processes connected with canine IBD. The observed changes probably result from the neuroprotective and/or adaptive properties of VIP. Protective and adaptive reactions induced by inflammation aim to protect the GI tract against damage by proinflammatory factors and ensure the homeostasis in the enteric nervous system (ENS) under the conditions changed by the disease process.

Neurochemistry of Enteric Neurons Following Prolonged Indomethacin Administration in the Porcine Duodenum

Gastrointestinal inflammation resulting from prolonged NSAID drugs treatment constitutes a worldwide medical problem. The role of enteric neuroactive substances involved in this process has recently gained attention and neuropeptides produced by the enteric nervous system may play an important role in the modulation of gastrointestinal inflammation. Therefore, the aim of this study was to determine the effect of inflammation caused by indomethacin supplementation on vasoactive intestinal polypeptide (VIP), substance P (SP), neuronal nitric oxide synthase (nNOS), galanin (GAL), pituitary adenylate cyclase-activating polypeptide (PACAP), and cocaine- and amphetamine-regulated transcript peptide (CART) expression in enteric duodenal neurons in domestic pigs. Eight immature pigs of the Pietrain × Duroc race (20 kg of body weight) were used. Control animals (n=4) received empty gelatine capsules. Experimental pigs (n=4) were given indomethacin for 4 weeks, orally 10 mg/kg daily, approximately 1 h before feeding. The animals from both groups were then euthanized. Frozen sections were prepared from the collected duodenum and subjected to double immunofluorescence staining. Primary antibodies against neuronal marker PGP 9.5 and VIP, nNOS, SP, GAL, CART, and PACAP were visualized with Alexa Fluor 488 and 546. Sections were analyzed under an Olympus BX51 fluorescence microscope. Microscopic analysis showed significant increases in the number of nNOS-, VIP-, SP-, GAL-, PACAP-, and CART-immunoreactive ganglionic neurons, in both the myenteric and submucous plexuses of the porcine duodenum. The obtained results show the participation of enteric neurotransmitters in the neuronal duodenal response to indomethacin-induced inflammation.

Inhibition of IRF4 in dendritic cells by PRR-independent and -dependent signals inhibit Th2 and promote Th17 responses

Cyclic AMP (cAMP) is involved in many biological processes but little is known regarding its role in shaping immunity. Here we show that cAMP-PKA-CREB signaling (a pattern recognition receptor [PRR]-independent mechanism) regulates conventional type-2 Dendritic Cells (cDC2s) in mice and reprograms their Th17-inducing properties via repression of IRF4 and KLF4, transcription factors essential for cDC2-mediated Th2 induction. In mice, genetic loss of IRF4 phenocopies the effects of cAMP on Th17 induction and restoration of IRF4 prevents the cAMP effect. Moreover, curdlan, a PRR-dependent microbial product, activates CREB and represses IRF4 and KLF4, resulting in a pro-Th17 phenotype of cDC2s. These in vitro and in vivo results define a novel signaling pathway by which cDC2s display plasticity and provide a new molecular basis for the classification of novel cDC2 and cDC17 subsets. The findings also reveal that repressing IRF4 and KLF4 pathway can be harnessed for immuno-regulation.

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

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

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.

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) plays an inhibitory role against inflammation induced by chemical damage to zebrafish hair cells

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) is a common neuropeptide exerting a wide spectrum of functions in many fields, including immunology. In the present study, 5-day post-fertilization (dpf) zebrafish larvae of three diverse genetic lines [transgenic lines Tg(MPX:GFP) with GFP-labelled neutrophils and Tg(pou4f3:GAP-GFP) with GFP-labelled hair cells and the wild-type Tuebingen] were used to investigate an inhibitory role of PACAP-38 in inflammation associated with damaged hair cells of the lateral line. Individuals of each genetic line were assigned to four groups: (1) control, and those consisting of larvae exposed to (2) 10 µM CuSO4, (3) 10 µM CuSO4+100 nM PACAP-38 and (4) 100 nM PACAP-38, respectively. Forty-minute exposure to CuSO4 solution was applied to evoke necrosis of hair cells and consequent inflammation. The inhibitory role of PACAP-38 was investigated in vivo under a confocal microscope by counting neutrophils migrating towards damaged hair cells in Tg(MPX:GFP) larvae. In CuSO4-treated individuals, the number of neutrophils associated with hair cells was dramatically increased, while PACAP-38 co-treatment resulted in its over 2-fold decrease. However, co-treatment with PACAP-38 did not prevent hair cells from extensive necrosis, which was found in Tg(pou4f3:GAP-GFP) individuals. Real-Time PCR analysis performed in wild-type larvae demonstrated differential expression pattern of stress and inflammation inducible markers. The most significant findings showed that CuSO4 exposure up-regulated the expression of IL-8, IL-1β, IL-6 and ATF3, while after PACAP-38 co-treatment expression levels of these genes were significantly decreased. The presence of transcripts for all PACAP receptors in neutrophils was also revealed. Adcyap1r1a and vipr1b appeared to be predominant forms. The present results suggest that PACAP-38 should be considered as a factor playing an important regulatory role in inflammatory response associated with pathological processes affecting zebrafish hair cells and it cannot be excluded that this interesting property has more universal significance.

Crotamine stimulates phagocytic activity by inducing nitric oxide and TNF-α via p38 and NFκ-B signaling in RAW 264.7 macrophages

Crotamine is a peptide toxin found in the venom of the rattlesnake Crotalus durissus terrificus and has antiproliferative, antimicrobial, and antifungal activities. Herein, we show that crotamine dose-dependently induced macrophage phagocytic and cytostatic activity by the induction of nitric oxide (NO) and tumor necrosis factor-alpha (TNF-α). Moreover, the crotamineinduced expression of iNOS and TNF-α is mediated through the phosphorylation of p38 and the NF-κB signaling cascade in macrophages. Notably, pretreatment with SB203580 (a p38-specific inhibitor) or BAY 11-7082 (an NF-κB inhibitor) inhibited crotamine-induced NO production and macrophage phagocytic and cytotoxic activity. Our results show for the first time that crotamine stimulates macrophage phagocytic and cytostatic activity by induction of NO and TNF-α via the p38 and NF-κB signaling pathways and suggest that crotamine may be a useful therapeutic agent for the treatment of inflammatory disease. [BMB Reports 2016; 49(3): 185-190].

Parasympathetic innervation of vertebrobasilar arteries: is this a potential clinical target?

This review aims to summarise the contemporary evidence for the presence and function of the parasympathetic innervation of the cerebral circulation with emphasis on the vertebral and basilar arteries (the posterior cerebral circulation). We consider whether the parasympathetic innervation of blood vessels could be used as a means to increase cerebral blood flow. This may have clinical implications for pathologies associated with cerebral hypoperfusion such as stroke, dementia and hypertension. Relative to the anterior cerebral circulation little is known of the origins and neurochemical phenotypes of the parasympathetic innervation of the vertebrobasilar arteries. These vessels normally provide blood flow to the brainstem and cerebellum but can, via the Circle of Willis upon stenosis of the internal carotid arteries, supply blood to the anterior cerebral circulation too. We review the multiple types of parasympathetic fibres and their distinct transmitter mechanisms and how these vary with age, disease and species. We highlight the importance of parasympathetic fibres for mediating the vasodilatory response to sympathetic activation. Current trials are investigating the possibility of electrically stimulating the postganglionic parasympathetic ganglia to improve cerebal blood flow to reduce the penumbra following stroke. We conclude that although there are substantial gaps in our understanding of the origins of parasympathetic innervation of the vertebrobasilar arteries, activation of this system under some conditions might bring therapeutic benefits.

PDE4B as a microglia target to reduce neuroinflammation

The importance of microglia in immune homeostasis within the brain is undisputed. Their role in a diversity of neurological and psychiatric diseases as well as CNS injury is the subject of much investigation. Cyclic adenosine monophosphate (AMP) is a critical regulator of microglia homeostasis; as the predominant negative modulator of cyclic AMP signaling within microglia, phosphodiesterase 4 (PDE4) represents a promising target for modulating immune function. PDE4 expression is regulated by inflammation, and in turn, PDE4 inhibition can alter microglia reactivity. As the prototypic PDE4 inhibitor, rolipram, was tested clinically in the 1980s, drug discovery and clinical development of PDE4 inhibitors have been severely hampered by tolerability issues involving nausea and emesis. The two PDE4 inhibitors approved for peripheral inflammatory disorders (roflumilast and apremilast) lack brain penetration and are dose-limited by side effects making them unsuitable for modulating microglial function. Subtype selective inhibitors targeting PDE4B are of high interest given the critical role PDE4B plays in immune function versus the association of PDE4D with nausea and emesis. The challenges and requirements for successful development of a novel brain-penetrant PDE4B inhibitor are discussed in the context of early clinical development strategies. Furthermore, the challenges of monitoring the state of microglia in vivo are highlighted, including a description of the currently available tools and their limitations. Continued drug discovery efforts to identify safe and well-tolerated, brain-penetrant PDE4 inhibitors are a reflection of the confidence in the rationale for modulation of this target to produce meaningful therapeutic benefit in a wide range of neurological conditions and injury. GLIA 2016;64:1698-1709.

Evaluation of iNOS Expression in Esophageal Cancer Patients

BACKGROUND

Esophageal cancer is a public health concern around the world; this cancer is the sixth leading cause of death of cancer in the world with about 386,000 deaths per year. Its risk factors include environmental factors such as tobacco smoke, gastroesophageal reflux and genetic changes. iNOS is stated by the effect of various inflammatory factors and is thus called inducible NOS. Investigating iNOS expression is a powerful tool for understanding effective molecular parameters at tissue and cellular responses to external factors. In this research work, iNOS expression in patients with esophageal cancer was studied in Iran.

MATERIALS AND METHODS

15 formalin-fixed and paraffin-embedded (FFPE) esophageal cancer tissue samples and 15 normal FFPE samples were collected from various medical centers (Zabol, Zahedan, Kashan) to measure iNOS expression by real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR). All PCR reactions were conducted by three replicates for iNOS and internal control (β-actin) by 2^-ΔΔCT (Livak) method. Differences were measured in target gene expression in patients and control group using the t test. All statistical analyses were done using the SPSS software.

RESULTS

The results showed that there was no significant difference between iNOS expression in the case and control groups (p > 0.05); however, there was an increase in iNOS expression in the case group. On the other hand, there was a significant difference between iNOS expression in males and females in the two groups of healthy subjects and patients, and it was higher in women than in men.

CONCLUSION

Further studies need to be conducted with larger sample sizes and in other populations to validate these findings.

Microglial VPAC1R mediates a novel mechanism of neuroimmune-modulation of hippocampal precursor cells via IL-4 release

Neurogenesis, the production of new neurons from neural stem/progenitor cells (NSPCs), occurs throughout adulthood in the dentate gyrus of the hippocampus, where it supports learning and memory. The innate and adaptive immune systems are increasingly recognized as important modulators of hippocampal neurogenesis under both physiological and pathological conditions. However, the mechanisms by which the immune system regulates hippocampal neurogenesis are incompletely understood. In particular, the role of microglia, the brains resident immune cell is complex, as they have been reported to both positively and negatively regulate neurogenesis. Interestingly, neuronal activity can also regulate the function of the immune system. Here, we show that depleting microglia from hippocampal cultures reduces NSPC survival and proliferation. Furthermore, addition of purified hippocampal microglia, or their conditioned media, is trophic and proliferative to NSPCs. VIP, a neuropeptide released by dentate gyrus interneurons, enhances the proliferative and pro-neurogenic effect of microglia via the VPAC1 receptor. This VIP-induced enhancement is mediated by IL-4 release, which directly targets NSPCs. This demonstrates a potential neuro-immuno-neurogenic pathway, disruption of which may have significant implications in conditions where combined cognitive impairments, interneuron loss, and immune system activation occurs, such as temporal lobe epilepsy and Alzheimer's disease.

Molecular mechanisms underlying the Nephroprotective effects of PACAP in diabetes

Diabetic nephropathy is the leading cause of end-stage renal failure and accounts for 30-40 % of patients entering renal transplant programmes. The nephroprotective effects of the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP38) against diabetes have been shown previously, but the molecular mechanisms responsible for these effects remain unknown. In the present study, we showed that PACAP treatment counteracted the diabetes-induced increase in the level of the proapoptotic pp38MAPK and cleaved caspase-3 and also decreased the p60 subunit of NFκB. The examined antiapoptotic factors, including pAkt and pERK1/2, showed a slight increase in the diabetic kidneys, while PACAP treatment resulted in a notable elevation of these proteins. PCR and Western blot revealed the downregulation of fibrotic markers, like collagen IV and TGF-β1 in the kidney. PACAP treatment resulted in increased expression of the antioxidant glutathione. We conclude that the nephroprotective effect of PACAP in diabetes is, at least partly, due to its antiapoptotic, antifibrotic and antioxidative effect in addition to the previously described antiinflammatory effect.

Emerging neuropeptide targets in inflammation: NPY and VIP

The enteric nervous system (ENS), referred to as the "second brain," comprises a vast number of neurons that form an elegant network throughout the gastrointestinal tract. Neuropeptides produced by the ENS play a crucial role in the regulation of inflammatory processes via cross talk with the enteric immune system. In addition, neuropeptides have paracrine effects on epithelial secretion, thus regulating epithelial barrier functions and thereby susceptibility to inflammation. Ultimately the inflammatory response damages the enteric neurons themselves, resulting in deregulations in circuitry and gut motility. In this review, we have emphasized the concept of neurogenic inflammation and the interaction between the enteric immune system and enteric nervous system, focusing on neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP). The alterations in the expression of NPY and VIP in inflammation and their significant roles in immunomodulation are discussed. We highlight the mechanism of action of these neuropeptides on immune cells, focusing on the key receptors as well as the intracellular signaling pathways that are activated to regulate the release of cytokines. In addition, we also examine the direct and indirect mechanisms of neuropeptide regulation of epithelial tight junctions and permeability, which are a crucial determinant of susceptibility to inflammation. Finally, we also discuss the potential of emerging neuropeptide-based therapies that utilize peptide agonists, antagonists, siRNA, oligonucleotides, and lentiviral vectors.

VPAC1 receptor expression in peripheral blood mononuclear cells in a human endotoxemia model

Background

Vasoactive intestinal peptide (VIP) exerts immune-modulatory actions mainly via VPAC1 receptor stimulation. VPAC1 may be a treatment target of inflammatory diseases, but little is known about the receptor expression profile in immune-competent cells in vivo.

Material and methods

20 male healthy subjects received a single intravenous bolus of 2ng/kg body weight Escherichia coli endotoxin (LPS). Receptor status was evaluated in peripherial blood cells before and 3, 6 and 24 h after LPS by FACS analysis and q-PCR. VIP plasma concentrations were measured by ELISA.

Results

Granulocytes accounted for 51% of leukocytes at baseline and 58 ± 37% were positive for VPAC1. The granulocyte population increased 2.6 fold after LPS, and a transient down-regulation of VPAC1 to 28 ± 23% was noted at 3 h (p < 0.001), which returned to baseline at 24 hours. Baseline VPAC1 expression was low in lymphocytes (6.3 ± 3.2%) and monocytes (11 ± 9.6%). In these cells, LPS up-regulated VPAC1 at 6 h (13.2 ± 4.9%, p < 0.001) and 24 h (31.6 ± 20.5%, p = 0.001), respectively. Consistent changes were noted for the VIP-receptors VPAC2 and PAC1. VPAC1, VPAC2 and PAC1 mRNA levels were unchanged in peripheral blood mononuclear cells (PBMC). VIP plasma concentration increased from 0.5 ± 0.3 ng/ml to 0.7 ± 0.4 ng/ml at 6 h after LPS (p < 0.05) and returned to baseline within 24 h.

Conclusion

The time profile of VPAC receptor expression differs in granulocytes, monocytes and lymphocytes after LPS challenge in humans. Changes in circulating VIP concentrations may reflect innate immune responses.

Liver kinase B1 is required for thromboxane receptor-dependent nuclear factor-κB activation and inflammatory responses

OBJECTIVE

Thromboxane A2 receptor (TPr) has been reported to trigger vascular inflammation. Nuclear factor κ B (NF-κB) is a known transcription factor. The aims of the present study were to determine the contributions of NF-κB activation to TPr-triggered vascular inflammation and elucidate the mechanism(s) underlying TPr activation of NF-κB.

APPROACH AND RESULTS

The effects of TPr activators, [1S-[1 alpha,2 alpha(Z),3beta(1E,3S*), 4 alpha]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) and U46619, on NF-κB activation, phosphorylation of rhoA/rho-associated kinases and liver kinase B1, cell adhesion and migration, proliferation, and endothelium-dependent vasorelaxation were assayed in cultured human umbilical vein endothelial cells, human monocytes, or isolated mouse aortas. Exposure of human umbilical vein endothelial cells to TPr agonists I-BOP and U46619 induced dose-dependent and time-dependent phosphorylation of inhibitor of κB α in parallel with aberrant expression of inflammatory markers cyclooxygenase-2, inducible nitric oxide synthase, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1. Inhibition of NF-κB by pharmacological or genetic means abolished TPr-triggered expression of inflammatory markers. Consistently, exposure of human umbilical vein endothelial cells to either I-BOP or U46619 significantly increased phosphorylation of inhibitor of κB α, I kappaB kinase, rhoA, rho-associated kinases, and liver kinase B1. Pretreatment of human umbilical vein endothelial cells with the TPr antagonist SQ29548 or rho-associated kinases inhibitor Y27632 or silencing of the LKB1 blocked TPr-enhanced phosphorylation of inhibitor of κB α and its upstream kinase, I kappaB kinase. Finally, exposure of isolated mouse aortas to either U46619 or I-BOP enhanced NF-κB activation and vascular inflammation in parallel with reduced endothelium-dependent relaxation in intact vessels.

CONCLUSIONS

TPr stimulation instigates aberrant inflammation and endothelial dysfunction via rho-associated kinases/liver kinase B1/I kappaB kinase-dependent NF-κB activation in vascular endothelial cells.

PACAP signaling exerts opposing effects on neuroprotection and neuroinflammation during disease progression in the SOD1(G93A) mouse model of amyotrophic lateral sclerosis

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a pleiotropic peptide with autocrine neuroprotective and paracrine anti-inflammatory properties in various models of acute neuronal damage and neurodegenerative diseases. Therefore, we examined a possible beneficial role of endogenous PACAP in the superoxide dismutase 1, SOD1(G93A), mouse model of amyotrophic lateral sclerosis (ALS), a lethal neurodegenerative disease particularly affecting somatomotor neurons. In wild-type mice, somatomotor and visceromotor neurons in brain stem and spinal cord were found to express the PACAP specific receptor PAC1, but only visceromotor neurons expressed PACAP as a potential autocrine source of regulation of these receptors. In SOD1(G93A) mice, only a small subset of the surviving somatomotor neurons showed induction of PACAP mRNA, and somatomotor neuron degeneration was unchanged in PACAP-deficient SOD1(G93A) mice. Pre-ganglionic sympathetic visceromotor neurons were found to be resistant in SOD1(G93A) mice, while pre-ganglionic parasympathetic neurons degenerated during ALS disease progression in this mouse model. PACAP-deficient SOD1(G93A) mice showed even greater pre-ganglionic parasympathetic neuron loss compared to SOD1(G93A) mice, and additional degeneration of pre-ganglionic sympathetic neurons. Thus, constitutive expression of PACAP and PAC1 may confer neuroprotection to central visceromotor neurons in SOD1(G93A) mice via autocrine pathways. Regarding the progression of neuroinflammation, the switch from amoeboid to hypertrophic microglial phenotype observed in SOD1(G93A) mice was absent in PACAP-deficient SOD1(G93A) mice. Thus, endogenous PACAP may promote microglial cytodestructive functions thought to drive ALS disease progression. This hypothesis was consistent with prolongation of life expectancy and preserved tongue motor function in PACAP-deficient SOD1(G93A) mice, compared to SOD1(G93A) mice. Given the protective role of PACAP expression in visceromotor neurons and the opposing effect on microglial function in SOD1(G93A) mice, both PACAP agonism and antagonism may be promising therapeutic tools for ALS treatment, if stage of disease progression and targeting the specific auto- and paracrine signaling pathways are carefully considered.

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

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

Effects of VIP on corneal reconstitution and homeostasis following Pseudomonas aeruginosa induced keratitis

PURPOSE

Studies from our laboratory have demonstrated that vasoactive intestinal peptide (VIP) directly converts the normally susceptible C57BL/6J (B6) mouse to resistant after ocular infection through modulation of the inflammatory response. This study examines mechanisms by which VIP influences the healing phase following infection--specifically reconstitution of the extracellular matrix (ECM).

METHODS

B6 mice received daily intraperitoneal (IP) injections of VIP, while control mice were similarly injected with sterile phosphate buffered saline (PBS). Real-time RT-PCR, ELISA, and immunofluorescent staining were used to assess the effects of VIP treatment on ECM molecule expression after Pseudomonas aeruginosa-induced keratitis. We also compared the effect of VIP treatment on lipopolysaccharide (LPS)-stimulated B6- and BALB/c-derived fibroblasts.

RESULTS

In vivo analyses revealed that VIP treatment of P. aeruginosa-infected B6 corneas led to a significant increase in ECM molecules associated with healing/homeostasis, while those associated with ECM degradation were significantly down-regulated when compared to wild-type (WT) controls. In vitro studies revealed that VIP treatment of lipopolysaccharide-stimulated fibroblasts derived from susceptible B6 and resistant BALB/c mice expressed distinct differences in ECM molecule expression, whereby the latter expressed higher levels of ECM molecules aimed at reconstitution. Furthermore, differential expression of VIP receptor-1/VIP receptor-2 (VIPR1/VIPR2) was observed between B6 and BALB/c after VIP treatment of LPS-stimulated fibroblasts.

CONCLUSIONS

VIP treatment functions to enhance ECM reconstitution, which appears to be carried out in large part by fibroblasts via VIPR2. Overall, the data from this study suggest that VIP not only regulates disease pathogenesis, but also functions to restore integrity of the corneal stroma.

Systems Biological Approaches Reveal Non-additive Responses and Multiple Crosstalk Mechanisms between TLR and GPCR Signaling

A variety of ligands differ in their capacity to bind the receptor, elicit gene expression, and modulate physiological responses. Such receptors include Toll-like receptors (TLRs), which recognize various patterns of pathogens and lead to primary innate immune activation against invaders, and G-protein coupled receptors (GPCRs), whose interaction with their cognate ligands activates heterotrimeric G proteins and regulates specific downstream effectors, including immuno-stimulating molecules. Once TLRs are activated, they lead to the expression of hundreds of genes together and bridge the arm of innate and adaptive immune responses. We characterized the gene expression profile of Toll-like receptor 4 (TLR4) in RAW 264.7 cells when it bound with its ligand, 2-keto-3-deoxyoctonate (KDO), the active part of lipopolysaccharide. In addition, to determine the network communications among the TLR, Janus kinase (JAK)/signal transducer and activator of transcription (STAT), and GPCR, we tested RAW 264.7 cells with KDO, interferon-β, or cAMP analog 8-Br. The ligands were also administered as a pair of double and triple combinations.

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

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

Prospect of vasoactive intestinal peptide therapy for COPD/PAH and asthma: a review

There is mounting evidence that pulmonary arterial hypertension (PAH), asthma and chronic obstructive pulmonary disease (COPD) share important pathological features, including inflammation, smooth muscle contraction and remodeling. No existing drug provides the combined potential advantages of reducing vascular- and bronchial-constriction, and anti-inflammation. Vasoactive intestinal peptide (VIP) is widely expressed throughout the cardiopulmonary system and exerts a variety of biological actions, including potent vascular and airway dilatory actions, potent anti-inflammatory actions, improving blood circulation to the heart and lung, and modulation of airway secretions. VIP has emerged as a promising drug candidate for the treatment of cardiopulmonary disorders such as PAH, asthma, and COPD. Clinical application of VIP has been limited in the past for a number of reasons, including its short plasma half-life and difficulty in administration routes. The development of long-acting VIP analogues, in combination with appropriate drug delivery systems, may provide clinically useful agents for the treatment of PAH, asthma, and COPD. This article reviews the physiological significance of VIP in cardiopulmonary system and the therapeutic potential of VIP-based agents in the treatment of pulmonary diseases.

The ceramide-1-phosphate analogue PCERA-1 modulates tumour necrosis factor-alpha and interleukin-10 production in macrophages via the cAMP-PKA-CREB pathway in a GTP-dependent manner

The synthetic phospho-ceramide analogue-1 (PCERA-1) down-regulates production of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) and up-regulates production of the anti-inflammatory cytokine interleukin-10 (IL-10) in lipopolysaccharide (LPS) -stimulated macrophages. We have previously reported that PCERA-1 increases cyclic adenosine monophosphate (cAMP) levels. The objective of this study was to delineate the signalling pathway leading from PCERA-1 via cAMP to modulation of TNF-alpha and IL-10 production. We show here that PCERA-1 elevates intra-cellular cAMP level in a guanosine triphosphate-dependent manner in RAW264.7 macrophages. The cell-permeable dibutyryl cAMP was able to mimic the effects of PCERA-1 on cytokine production, whereas 8-chloro-phenylthio-methyladenosine-cAMP, which specifically activates the exchange protein directly activated by cAMP (EPAC) but not protein kinase A (PKA), failed to mimic PCERA-1 activities. Consistently, the PKA inhibitor H89 efficiently blocked PCERA-1-driven cytokine modulation as well as PCERA-1-stimulated phosphorylation of cAMP response element binding protein (CREB) on Ser-133. Finally, PCERA-1 activated cAMP-responsive transcription of a luciferase reporter, in synergism with the phosphodiesterase (PDE)-4 inhibitor rolipram. Our results suggest that PCERA-1 activates a G(s) protein-coupled receptor, leading to elevation of cAMP, which acts via the PKA-CREB pathway to promote TNF-alpha suppression and IL-10 induction in LPS-stimulated macrophages. Identification of the PCERA-1 receptor is expected to set up a new target for development of novel anti-inflammatory drugs.

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.

Vasoactive intestinal peptide inhibits toll-like receptor 3-induced nitric oxide production in Schwann cells and subsequent sensory neuronal cell death in vitro

We have previously reported that polyinosinic-polycytidylic acids [poly(I:C)], a synthetic toll-like receptor 3 (TLR3) agonist, induce Schwann cell activation, which exerts neurotoxic effects on sensory neurons. In this study, we investigated the effects of vasoactive intestinal peptide (VIP), a neuropeptide implicated in nerve regeneration, on TLR3-induced Schwann cell activation. VIP receptors VPAC1 and VPAC2 were constitutively expressed in rat Schwann cells. VIP pretreatment inhibited TLR3-induced inducible nitric oxide synthase (iNOS) gene expression and NO production in Schwann cells. Studies on the intracellular signal transduction pathways indicate that the VIP effect is mediated by protein kinase A activation. VIP also inhibited the poly(I:C)-induced p38 activation that is responsible for the iNOS gene expression in Schwann cells. Finally, VIP inhibited dorsal rooyt ganglion neuronal cell death caused by NO produced in activated Schwann cells. Taken together, our data suggest that VIP exerts a neuroprotective effect by inhibiting neurotoxic Schwann cell activation.

Vasoactive Intestinal Peptide Causes Marked Cephalic Vasodilation, but does not Induce Migraine

We hypothesized that intravenous infusion of the parasympathetic transmitter, vasoactive intestinal peptide (VIP), might induce migraine attacks in migraineurs. Twelve patients with migraine without aura were allocated to receive 8 pmol kg-1 min-1 VIP or placebo in a randomized, double-blind crossover study. Headache was scored on a verbal rating scale (VRS), mean blood flow velocity in the middle cerebral artery ( Vmean mca) was measured by transcranial Doppler ultrasonography, and diameter of the superficial temporal artery (STA) by high-frequency ultrasound. None of the subjects reported a migraine attack after VIP infusion. VIP induced a mild immediate headache (maximum 2 on VRS) compared with placebo ( P = 0.005). Three patients reported delayed headache (3-11 h after infusion) after VIP and two after placebo ( P = 0.89). Vmean mca decreased (16.3 ± 5.9%) and diameter of STA increased significantly after VIP (45.9 ± 13.9%). VIP mediates a marked dilation of cranial arteries, but does not trigger migraine attacks in migraineurs. These data provide further evidence against a purely vascular origin of migraine.

Altered anti-inflammatory response of mononuclear cells to neuropeptide PACAP is associated with deregulation of NF-{kappa}B in chronic pancreatitis

Although it is recognized that neurogenic influences contribute to progression of chronic inflammatory diseases, the molecular basis of neuroimmune interactions in the pathogenesis of chronic pancreatitis (CP) is not well defined. Here we report that responsiveness of peripheral blood mononuclear cells (PBMC) to the neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) is altered in CP. Expression of PACAP and its receptors in human CP was analyzed with quantitative RT-PCR, laser-capture microdissection, and immunohistochemistry. Regulation of PACAP expression was studied in coculture systems using macrophages and acinar cells. Responsiveness of donor and CP PBMC to PACAP was determined based on cytokine profiles and NF-kappaB activation of LPS- or LPS+PACAP-exposed cells. Although donor and CP PBMC responded equally to LPS, PACAP-mediated counteraction of LPS-induced cytokine response was switched from inhibiting TNF-alpha to decreasing IL-1beta and increasing IL-10 secretion. The change of PACAP-mediated anti-inflammatory pattern was associated with altered activation of NF-kappaB: compared with LPS alone, a combination of LPS and PACAP had no effect on NF-kappaB p65 nuclear translocation in CP PBMC, whereas NF-kappaB was significantly decreased in donor PBMC. According to laser-capture microdissection and coculture experiments, PBMC also contributed to generation of a PACAP-rich intrapancreatic environment by upregulating PACAP expression in macrophages encountering apoptotic pancreatic acini. The nociceptive status of CP patients correlated with pancreatic PACAP levels and with IL-10 bias of PACAP-exposed CP PBMC. Thus the ability of PBMC to produce and to respond to PACAP might influence neuroimmune interactions that regulate pain and inflammation in CP.

Experimental study on vasoactive intestinal peptide (VIP) and its diaminopropane bound (VIP-DAP) analog in solution

Bioactive peptides represent an exciting area of research in the fields of biochemistry and medicine and in particular the VIP/PACAP network appears to be of interest. Vasoactive intestinal peptide (VIP) is a pleiotropic factor that exerts a physiological regulatory influence and is involved in the pathogenesis of several human disorders. In this paper we have reported structural characterization of VIP by experimental and computational methods as well as a comparative analysis of the peptide with its transglutaminase catalyzed analog VIP-Diaminopropane (VIP-DAP).

Vasoactive Intestinal Peptide Inhibits Adhesion Molecule Expression in Activated Human Colon Serosal Fibroblasts by Preventing NF-κB Activation

BACKGROUND

Stricture formation in Crohn's disease (CD) occurs as a result of persistent intestinal inflammatory activation, which leads to enhanced adhesion molecule expression in serosal fibroblasts (SFs). Vasoactive intestinal peptide (VIP) has anti-inflammatory and immunoregulatory properties. Treatment with VIP prevents experimental CD in animal models at the clinical and pathologic levels. The present study reports the effect of VIP on the expression of intracellular adhesion molecule-1 (ICAM-1) in IL-1beta-stimulated human colon SFs.

MATERIALS AND METHODS

Primary human colon SFs were incubated with or without IL-1beta (10 ng/mL) in the presence or absence of VIP at various concentrations (0.1 to 100 nM) for designated time. Cell surface and cytosolic ICAM-1 expression were evaluated by flow cytometry and Western blot analysis, respectively. The DNA binding capacity of NF-kappaB was analyzed by electrophoretic mobility shift assay. The phosphorylation of IkappaB-alpha was examined by Western blot analysis.

RESULTS

VIP inhibited IL-1beta-induced expression of ICAM-1 in a dose-dependent manner. The IL-1beta-induced ICAM-1 was also inhibited by a potent inhibitor of NF-kappaB, MG132. VIP also decreased IL-1beta-induced NF-kappaB DNA binding capacity and phosphorylation of IkappaB-alpha.

CONCLUSION

VIP has an inhibitory effect on IL-1beta-induced ICAM-1 expression in SFs, which may be associated with NF-kappaB activity. This may make VIP potentially a novel therapeutic agent for preventing stricture formation in Crohn's disease.

α1-Antitrypsin regulates CD14 expression and soluble CD14 levels in human monocytes in vitro

The recognition of bacterial lipopolysaccharide (LPS) is principally mediated by either membrane-bound or soluble form of the glycoprotein CD14 and CD14-associated signal transducer, toll-like receptor 4 (TLR4). Recent findings indicate that the serine protease inhibitor, alpha1-antitrypsin (AAT), may not only afford protection against proteolytic injury, but may also neutralize microbial activities and affect regulation of innate immunity. We postulated that AAT affects monocyte responses to LPS by regulating CD14 expression and soluble CD14 release. Here we show that a short-term (up to 2h) monocyte exposure to AAT alone or in combination with LPS leads to a remarkable induction of CD14 levels. In parallel, a short-term (2h) cell exposure to AAT/LPS significantly enhances LPS-induced NF kappaB (p50 and p65) activation in conjunction with increased TNFalpha, IL-1 beta and IL-8 release. In contrast, longer term incubation (18 h) of monocytes with combined AAT/LPS results in a significant reduction in expression of both CD14 and TLR4, inhibition of LPS-induced TNFalpha, IL-1 beta and IL-8 mRNA and protein expression. These findings provide evidence that AAT is an important regulator of CD14 expression and release in monocytes and suggest that AAT may be involved in LPS neutralization and prevention of over-activation of monocytes in vivo.

Neuronal Control of Skin Function: The Skin as a Neuroimmunoendocrine Organ

This review focuses on the role of the peripheral nervous system in cutaneous biology and disease. During the last few years, a modern concept of an interactive network between cutaneous nerves, the neuroendocrine axis, and the immune system has been established. We learned that neurocutaneous interactions influence a variety of physiological and pathophysiological functions, including cell growth, immunity, inflammation, pruritus, and wound healing. This interaction is mediated by primary afferent as well as autonomic nerves, which release neuromediators and activate specific receptors on many target cells in the skin. A dense network of sensory nerves releases neuropeptides, thereby modulating inflammation, cell growth, and the immune responses in the skin. Neurotrophic factors, in addition to regulating nerve growth, participate in many properties of skin function. The skin expresses a variety of neurohormone receptors coupled to heterotrimeric G proteins that are tightly involved in skin homeostasis and inflammation. This neurohormone-receptor interaction is modulated by endopeptidases, which are able to terminate neuropeptide-induced inflammatory or immune responses. Neuronal proteinase-activated receptors or transient receptor potential ion channels are recently described receptors that may have been important in regulating neurogenic inflammation, pain, and pruritus. Together, a close multidirectional interaction between neuromediators, high-affinity receptors, and regulatory proteases is critically involved to maintain tissue integrity and regulate inflammatory responses in the skin. A deeper understanding of cutaneous neuroimmunoendocrinology may help to develop new strategies for the treatment of several skin diseases.

The physiology and pathophysiology of nitric oxide in the brain

Nitric oxide (NO) is a molecule with pleiotropic effects in different tissues. NO is synthesized by NO synthases (NOS), a family with four major types: endothelial, neuronal, inducible and mitochondrial. They can be found in almost all the tissues and they can even co-exist in the same tissue. NO is a well-known vasorelaxant agent, but it works as a neurotransmitter when produced by neurons and is also involved in defense functions when it is produced by immune and glial cells. NO is thermodynamically unstable and tends to react with other molecules, resulting in the oxidation, nitrosylation or nitration of proteins, with the concomitant effects on many cellular mechanisms. NO intracellular signaling involves the activation of guanylate cyclase but it also interacts with MAPKs, apoptosis-related proteins, and mitochondrial respiratory chain or anti-proliferative molecules. It also plays a role in post-translational modification of proteins and protein degradation by the proteasome. However, under pathophysiological conditions NO has damaging effects. In disorders involving oxidative stress, such as Alzheimer's disease, stroke and Parkinson's disease, NO increases cell damage through the formation of highly reactive peroxynitrite. The paradox of beneficial and damaging effects of NO will be discussed in this review.

Protective effect of vasoactive intestinal peptide on bone destruction in the collagen-induced arthritis model of rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune disease of unknown etiology, characterized by the presence of inflammatory synovitis accompanied by destruction of joint cartilage and bone. Treatment with vasoactive intestinal peptide (VIP) prevents experimental arthritis in animal models by downregulation of both autoimmune and inflammatory components of the disease. The aim of this study was to characterize the protective effect of VIP on bone erosion in collagen-induced arthritis (CIA) in mice. We have studied the expression of different mediators implicated in bone homeostasis, such as inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), receptor activator of nuclear factor-κB (RANK), receptor activator of nuclear factor-κB ligand (RANKL), osteoprotegerin (OPG), IL-1, IL-4, IL-6, IL-10, IL-11 and IL-17. Circulating cytokine levels were assessed by ELISA and the local expression of mediators were determined by RT-PCR in mRNA extracts from joints. VIP treatment resulted in decreased levels of circulating IL-6, IL-1β and TNFα, and increased levels of IL-4 and IL-10. CIA-mice treated with VIP presented a decrease in mRNA expression of IL-17, IL-11 in the joints. The ratio of RANKL to OPG decreased drastically in the joint after VIP treatment, which correlated with an increase in levels of circulating OPG in CIA mice treated with VIP. In addition, VIP treatment decreased the expression of mRNA for RANK, iNOS and COX-2. To investigate the molecular mechanisms involved, we tested the activity of NFκB and AP-1, two transcriptional factors closely related to joint erosion, by EMSA in synovial cells from CIA mice. VIP treatment in vivo was able to affect the transcriptional activity of both factors. Our data indicate that VIP is a viable candidate for the development of treatments for RA.

Disruption of MAP kinase activation and nuclear factor binding to the IL-12 p40 promoter in HIV-infected myeloid cells

Progressive immunodeficiency in HIV infection is paralleled by a decrease in IL-12 production, a cytokine crucial for cellular immune function. Here we examine the molecular mechanisms by which HIV infection suppresses IL-12 p40 expression. HIV infection of THP-1 myeloid cells resulted in decreased LPS-induced nuclear factor binding to the NF-kappaB, AP-1, and Sp1 sites of the IL-12 p40 promoter. By site-directed mutagenesis we determined that each of these sites was necessary for transcriptional activation of the IL-12 p40 promoter. Binding of NF-kappaB p50, c-Rel, p65, Sp1, Sp3, c-Fos, and c-Jun proteins to their cognate nuclear factor binding sites was somewhat impaired by HV infection, although a role for other as yet unidentified factors cannot be dismissed. The cellular levels of these transcription factors were unaffected by HIV infection, with the exception of a decrease in expression of NF-kappaB p65, consistent with the observed decrease in its binding to the IL-12 p40 promoter following HIV infection. Analysis of regulation of upstream LPS-induced MAP kinases demonstrated impaired phosphorylation of JNK and p38 MAPK, and suppressed phosphorylation and degradation of IkappaBalpha following HIV infection. These results suggest that alterations in nuclear factor binding to numerous sites in the IL-12 p40 promoter, together may contribute to the suppression in IL-12 p40 transcription previously reported. These effects on nuclear factor binding may be a direct effect of HIV infection on the IL-12 p40 promoter, or may occur indirectly as a consequence of altered MAP kinase activation.

iNOS-mediated nitric oxide production and its regulation

This review focuses on the production of nitric oxide (NO) by inducible nitric oxide synthase (iNOS) and its regulation under physiological and pathophysiological conditions. NO is an important biological mediator in the living organism that is synthesized from L-arginine using NADPH and molecular oxygen. However, the overproduction of NO which is catalyzed by iNOS, a soluble enzyme and active in its dimeric form, is cytotoxic. Immunostimulating cytokines or bacterial pathogens activate iNOS and generate high concentrations of NO through the activation of inducible nuclear factors, including NFkB. iNOS activation is regulated mainly at the transcriptional level, but also at posttranscriptional, translational and postranslational levels through effects on protein stability, dimerization, phosphorylation, cofactor binding and availability of oxygen and L-arginine as substrates. The prevention of the overproduction of NO in the living organism through control of regulatory pathways may assist in the treatment of high NO-mediated disorders without changing physiological levels of NO.

A comparison of the changes in the non-neuronal cell populations of the superior cervical ganglia following decentralization and axotomy

Transecting the axons of neurons in the adult superior cervical ganglion (SCG; axotomy) results in the survival of most postganglionic neurons, the influx of circulating monocytes, proliferation of satellite cells, and changes in neuronal gene expression. In contrast, transecting the afferent input to the SCG (decentralization) results in nerve terminal degeneration and elicits a different pattern of gene expression. We examined the effects of decentralization on macrophages in the SCG and compared the results to those previously obtained after axotomy. Monoclonal antibodies were used to identify infiltrating (ED1+) and resident (ED2+) macrophages, as well as macrophages expressing MHC class II molecules (OX6+). Normal ganglia contained ED2+ cells and OX6+ cells, but few infiltrating macrophages. After decentralization, the number of infiltrating ED1+ cells increased in the SCG to a density about twofold greater than that previously seen after axotomy. Both the densities of ED2+ and OX6+ cells were essentially unchanged after decentralization, though a large increase in OX6+ cells occurred after axotomy. Proliferation among the ganglion's total non-neuronal cell population was examined and found to increase about twofold after decentralization and about fourfold after axotomy. Double-labeling experiments indicated that some of these proliferating cells were macrophages. After both surgical procedures, the percentage of proliferating ED2+ macrophages increased, while neither procedure altered the proliferation of ED1+ macrophages. Axotomy, though not decentralization, increased the proliferation of OX6+ cells. Future studies must address what role(s) infiltrating and/or resident macrophages play in regions of decentralized and axotomized neurons and, if both are involved, whether they play distinct roles.

Effect of cholecystokinin octapeptide on tumor necrosis factor α transcription and nuclear factor-κB activity induced by lipopolysaccharide in rat pulmonary interstitial macrophages

AIM: To elucidate the anti-inflammatory mechanism of an intestinal neuropeptide, sulfated cholecystokinin octapeptide (sCCK-8), the effects of sCCK-8 on lipopolysaccharide (LPS)-induced tumor necrosis factor α (TNF-α) mRNA expression and NF-κB activity in pulmonary interstitial macrophages (PIMs) were studied.

METHODS: PIMs from rat were stimulated with LPS (1 mg·L^-1) in the presence or absence of sCCK-8 (10^-8 - 10^-6 mol·L^-1) or/and CCK receptor antagonist proglumide (2 mg·L^-1). The expression of TNF-α mRNA was assayed by reverse transcription polymerase chain reaction (RT-PCR) at 3 h of the stimulation, and nuclear factor-κB (NF-κB) binding activity was analyzed by electrophoretic mobility shift assay (EMSA) at 1 h of stimulation. The IκB-α protein level in the cytoplasma at 30 min of the stimulation was detected by Western blot.

RESULTS: sCCK-8, at concentrations from 10^-8 mol·L^-1 to 10^-6 mol·L^-1 obviously inhibited LPS-induced TNF-α mRNA expression and NF-κB binding activity in a dose-dependent manner, P < 0.05, P < 0.01. Stimulation PIMs with LPS resulted in a reduction of IκB-α protein level, P < 0.01, which was elevated by sCCK-8, P < 0.05. The effects of sCCK-8 on NF-κB activity and IκB protein level were attenuated by CCK receptor antagonist proglumide, P < 0.01.

CONCLUSION: sCCK-8 inhibits LPS-induced TNF-α mRNA expression by regulating NF-κB activity in rat PIMs, which is mediated through CCK receptors and inhibiting IκB-α degradation. This represents one of the anti-inflammatory mechanisms of sCCK-8.

Transglutaminase-mediated polyamination of vasoactive intestinal peptide (VIP) Gln16 residue modulates VIP/PACAP receptor activity

Previous data showing an increase of receptor binding activity of [R16]VIP, a vasoactive intestinal peptide (VIP) structural analogue containing arginine at the position 16 of its amino acid sequence, have pointed out the importance of a positive charge at this site. Here, the functional characterization of three VIP polyaminated adducts (VIPDap, VIPSpd, and VIPSpm), obtained by a transglutaminase-catalysed reaction between the VIP Gln16 residue and 1,3-diaminopropane (Dap), spermidine (Spd), or spermine (Spm), is reported. Appropriate binding assays and adenylate cyclase enzymatic determinations have shown that these VIP adducts act as structural VIP agonists, both in vitro and in vivo. In particular, their IC50 and EC50 values of human and rat VIP/pituitary adenylate cyclase activating peptide (PACAP)1 and VIP/PACAP2 receptors indicate that VIPDap is a VIP agonist, with an affinity and a potency higher than that of VIP, while VIPSpd and VIPSpm are also agonists but with affinities lower than that of VIP. These findings suggest that the difference in adduct agonist activity reflects the differences in the positive charge and carbon chain length of the polyamine covalently linked with the VIP Gln16 residue. In addition, the data obtained strongly suggest that the length of polyamine carbon chain could be critical for the interaction of the agonist with its receptor, even though possible hydrophobic interaction cannot be ruled out. In vivo experiments on murine J774 macrophage cell cultures have shown the ability of these compounds to stimulate the inducible nitric oxide synthase activity at the transcriptional level.

Vasoactive intestinal polypeptide as mediator of asthma

Vasoactive intestinal polypeptide (VIP) is one of the most abundant, biologically active peptides found in the human lung. VIP is a likely neurotransmitter or neuromodulator of the inhibitory non-adrenergic non-cholinergic airway nervous system and influences many aspects of pulmonary biology. In human airways VIP-immunoreactive nerve fibres are present in the tracheobronchial airway smooth muscle layer, the walls of pulmonary and bronchial vessels and around submucosal glands. Next to its prominent bronchodilatory effects, VIP potently relaxes pulmonary vessels. The precise role of VIP in the pathogenesis of asthma is still uncertain. Although a therapy using the strong bronchodilatory effects of VIP would offer potential benefits, the rapid inactivation of the peptide by airway peptidases has prevented effective VIP-based drugs so far and non-peptide VIP-agonists did not reach clinical use.

Chondrocytes respond to adenosine via A(2)receptors and activity is potentiated by an adenosine deaminase inhibitor and a phosphodiesterase inhibitor

OBJECTIVE

To test the mechanisms by which adenosine and adenosine analogues stimulate adenylate cyclase and suppress lipopolysaccharide (LPS)-induced production of nitric oxide (NO) by chondrocytes.

METHODS

Primary chondrocytes isolated from equine articular cartilage were plated in monolayer. Intracellular cyclic-AMP (cAMP) accumulation was measured following exposure to medium containing adenosine, the non-hydrolyzable adenosine analogue N(6)-methyladenosine, the A(2A)specific agonist N(6)-(dimethoxyphenyl)-ethyl]adenosine (DPMA), the adenosine deaminase inhibitor erythro-9-(2-Hydroxy-3-nonyl)adenine hydrochloride (EHNA), or forskolin, a potent stimulator of adenylate cyclase. Regulation of NO production by LPS-stimulated chondrocytes, as determined by nitrite concentration, was assessed in the presence of adenosine, N(6)-methyladenosine, DPMA, the broad agonist 5'-N-ethylcarboxamidoadenosine (NECA), or forskolin. Alternatively, LPS-stimulated chondrocytes were exposed to EHNA or the phosphodiesterase inhibitor rolipram in the presence or absence of supplemental adenosine.

RESULTS

Adenosine, N(6)-methyladenosine, DPMA, and forskolin each increased intracellular cAMP accumulation in a concentration-dependent manner and suppressed NO production by LPS-stimulated chondrocytes. NECA also decreased NO production by chondrocytes stimulated with LPS. Incubation with EHNA, to protect endogenously produced adenosine, or rolipram, which prevents the degradation of cAMP, similarly suppressed LPS-stimulated NO production. The addition of exogenous adenosine with EHNA or rolipram further suppressed NO production.

CONCLUSIONS

This study documents functional responses to adenosine by articular chondrocytes. These responses are mimicked by the A(2A)receptor agonist, DPMA. Effects were enhanced by protecting adenosine using an adenosine deaminase inhibitor or by potentiating the cAMP response with rolipram. These experiments suggest that adenosine may play a physiological role in regulation of chondrocytes and that adenosine pathways could represent a novel target for therapeutic intervention.