VIP as a cell-growth and differentiation neuromodulator role in neurodevelopment

Niosomes: a novel targeted drug delivery system for cancer

Recently, nanotechnology is involved in various fields of science, of which medicine is one of the most obvious. The use of nanoparticles in the process of treating and diagnosing diseases has created a novel way of therapeutic strategies with effective mechanisms of action. Also, due to the remarkable progress of personalized medicine, the effort is to reduce the side effects of treatment paths as much as possible and to provide targeted treatments. Therefore, the targeted delivery of drugs is important in different diseases, especially in patients who receive combined drugs, because the delivery of different drug structures requires different systems so that there is no change in the drug and its effectiveness. Niosomes are polymeric nanoparticles that show favorable characteristics in drug delivery. In addition to biocompatibility and high absorption, these nanoparticles also provide the possibility of reducing the drug dosage and targeting the release of drugs, as well as the delivery of both hydrophilic and lipophilic drugs by Niosome vesicles. Since various factors such as components, preparation, and optimization methods are effective in the size and formation of niosomal structures, in this review, the characteristics related to niosome vesicles were first examined and then the in silico tools for designing, prediction, and optimization were explained. Finally, anticancer drugs delivered by niosomes were compared and discussed to be a suitable model for designing therapeutic strategies. In this research, it has been tried to examine all the aspects required for drug delivery engineering using niosomes and finally, by presenting clinical examples of the use of these nanocarriers in cancer, its clinical characteristics were also expressed.

Nanoparticle-Guided Brain Drug Delivery: Expanding the Therapeutic Approach to Neurodegenerative Diseases

Neurodegenerative diseases (NDs) represent a heterogeneous group of aging-related disorders featured by progressive impairment of motor and/or cognitive functions, often accompanied by psychiatric disorders. NDs are denoted as 'protein misfolding' diseases or proteinopathies, and are classified according to their known genetic mechanisms and/or the main protein involved in disease onset and progression. Alzheimer's disease (AD), Parkinson's disease (PD) and Huntington's disease (HD) are included under this nosographic umbrella, sharing histopathologically salient features, including deposition of insoluble proteins, activation of glial cells, loss of neuronal cells and synaptic connectivity. To date, there are no effective cures or disease-modifying therapies for these NDs. Several compounds have not shown efficacy in clinical trials, since they generally fail to cross the blood-brain barrier (BBB), a tightly packed layer of endothelial cells that greatly limits the brain internalization of endogenous substances. By engineering materials of a size usually within 1-100 nm, nanotechnology offers an alternative approach for promising and innovative therapeutic solutions in NDs. Nanoparticles can cross the BBB and release active molecules at target sites in the brain, minimizing side effects. This review focuses on the state-of-the-art of nanoengineered delivery systems for brain targeting in the treatment of AD, PD and HD.

Fluorescein-entrapped magnetosomes for magnetically assisted photodynamic therapy

Aim: We investigated the application of fluorescein (FL)-entrapped magnetosomes, in other words, silica-coated iron oxide nanoparticles entrapped within niosomes (SIO/NIO), in magnetically assisted photodynamic therapy (PDT) in vitro. Methods: Panc-1 cells were treated with the magnetosomes, with and without external magnetic guidance, and irradiated with blue light. Results & conclusion: Upon photoactivation, the FL-entrapped magnetosomes can produce higher singlet oxygen in comparison to FL-entrapped micelles, probably due to the higher release tendency of the photosensitizer from the former. In vitro studies in Panc-1 cells revealed magnetically assisted enhancement in the cellular uptake of the magnetosomes. Magnetic assistance also led to enhancement in PDT efficiency in cells treated with the FL-entrapped magnetosomes and light, thus highlighting their potential in PDT.

PKA at a Cross-Road of Signaling Pathways Involved in the Regulation of Glioblastoma Migration and Invasion by the Neuropeptides VIP and PACAP

Glioblastoma (GBM) remains an incurable disease, mainly due to the high migration and invasion potency of GBM cells inside the brain. PI3K/Akt, Sonic Hedgehog (SHH), and PKA pathways play major regulatory roles in the progression of GBM. The vasoactive intestinal peptide (VIP) family of neuropeptides and their receptors, referred in this article as the “VIP-receptor system”, has been reported to regulate proliferation, differentiation, and migration in a number of tumor cell types and more particularly in GBM cells. These neuropeptides are potent activators of the cAMP/PKA pathway. The present study aimed to investigate the cross-talks between the above cited signaling cascades. Regulation by VIP-related neuropeptides of GBM migration and invasion was evaluated ex vivo in rat brain slices explanted in culture. Effects of different combinations of VIP-related neuropeptides and of pharmacological and siRNA inhibitors of PKA, Akt, and of the SHH/GLI1 pathways were tested on GBM migration rat C6 and human U87 GBM cell lines using the wound-healing technique. Quantification of nuclear GLI1, phospho-Akt, and phospho-PTEN was assessed by western-immunoblotting. The VIP-receptor system agonists VIP and PACAP-38 significantly reduced C6 cells invasion in the rat brain parenchyma ex vivo, and C6 and U87 migration in vitro. A VIP-receptor system antagonist, VIP_10-28 increased C6 cell invasion in the rat brain parenchyma ex vivo, and C6 and migration in vitro. These effects on cell migration were abolished by selective inhibitors of the PI3K/Akt and of the SHH pathways. Furthermore, VIP and PACAP-38 reduced the expression of nuclear GLI1 while VIP_10-28 increased this expression. Selective inhibitors of Akt and PKA abolished VIP, PACAP-38, and VIP_10-28 effects on nuclear GLI1 expression in C6 cells. PACAP-38 induced a time-dependent inhibition of phospho-Akt expression and an increased phosphorylation of PTEN in C6 cells. All together, these data indicate that triggering the VIP-receptor system reduces migration and invasion in GBM cells through a PKA-dependent blockade of the PI3K/Akt and of the SHH/GLI1 pathways. Therefore, the VIP-receptor system displays anti-oncogenic properties in GBM cells and PKA is a central core in this process.

Molecular bionics - engineering biomaterials at the molecular level using biological principles

Life and biological units are the result of the supramolecular arrangement of many different types of molecules, all of them combined with exquisite precision to achieve specific functions. Taking inspiration from the design principles of nature allows engineering more efficient and compatible biomaterials. Indeed, bionic (from bion-, unit of life and -ic, like) materials have gained increasing attention in the last decades due to their ability to mimic some of the characteristics of nature systems, such as dynamism, selectivity, or signalling. However, there are still many challenges when it comes to their interaction with the human body, which hinder their further clinical development. Here we review some of the recent progress in the field of molecular bionics with the final aim of providing with design rules to ensure their stability in biological media as well as to engineer novel functionalities which enable navigating the human body.

VIP and PACAP analogs regulate therapeutic targets in high-risk neuroblastoma cells

Neuroblastoma (NB) is a pediatric cancer. New therapies for high-risk NB aim to induce cell differentiation and to inhibit MYCN and ALK signaling in NB. The vasoactive intestinal peptide (VIP) and the pituitary adenylate cyclase-activating polypeptide (PACAP) are 2 related neuropeptides sharing common receptors. The level of VIP increases with NB differentiation. Here, the effects of VIP and PACAP analogs developed for therapeutic use were studied in MYCN-amplified NB SK-N-DZ and IMR-32 cells and in Kelly cells that in addition present the F1174L ALK mutation. As previously reported by our group in IMR-32 cells, VIP induced neuritogenesis in SK-N-DZ and Kelly cells and reduced MYCN expression in Kelly but not in SK-N-DZ cells. VIP decreased AKT activity in the ALK-mutated Kelly cells. These effects were PKA-dependent. IMR-32, SK-NDZ and Kelly cells expressed the genes encoding the 3 subtypes of VIP and PACAP receptors, VPAC1, VPAC2 and PAC1. In parallel to its effect on MYCN expression, VIP inhibited invasion in IMR-32 and Kelly cells. Among the 3 PACAP analogs tested, [Hyp(2)]PACAP-27 showed higher efficiency than VIP in Kelly cells. These results indicate that VIP and PACAP analogs act on molecular and cellular processes that could reduce aggressiveness of high-risk NB.

GABA networks destabilize genetic oscillations in the circadian pacemaker

Systems of coupled oscillators abound in nature. How they establish stable phase relationships under diverse conditions is fundamentally important. The mammalian suprachiasmatic nucleus (SCN) is a self-sustained, synchronized network of circadian oscillators that coordinates daily rhythms in physiology and behavior. To elucidate the underlying topology and signaling mechanisms that modulate circadian synchrony, we discriminated the firing of hundreds of SCN neurons continuously over days. Using an analysis method to identify functional interactions between neurons based on changes in their firing, we characterized a GABAergic network comprised of fast, excitatory, and inhibitory connections that is both stable over days and changes in strength with time of day. By monitoring PERIOD2 protein expression, we provide the first evidence that these millisecond-level interactions actively oppose circadian synchrony and inject jitter into daily rhythms. These results provide a mechanism by which circadian oscillators can tune their phase relationships under different environmental conditions.

MAPT isoforms: differential transcriptional profiles related to 3R and 4R splice variants

Tau aggregation in neurofibrillary tangles is a pathological hallmark in tauopathies including Alzheimer's disease (AD). The predominant aggregation of certain MAPT (tau gene) isoforms, either the 4-repeat (4R tau) or the 3-repeat (3R tau) isoform has been widely described in tauopathies. Alterations of the 4R tau to 3R tau ratio may be a key for tau-related neurodegeneration. To study the biological consequences in expression between tau splicing isoforms 4R and 3R, we analyzed the main neurobiological effects of inclusion of the repeat region coded by exon 10 in MAPT. We compared the transcriptional profiles of the 4R tau isoforms to 3R tau isoforms using whole-genome gene expression profiling microarrays using human neuroblastoma SH-SY5Y cell lines overexpressing either human 4R tau or 3R tau isoforms. We identified 68 transcripts that differed significantly (at p < 0.001) between 4R and 3R isoforms as conditioned on a second variant, the so-called 2N inclusion. We extended these findings in a 2 × 2 ANOVA to examine interaction effects of these variants. Transcripts involved in embryonic development were downregulated when exon 10 was present, while transcripts related to outgrowth of neurites were generally upregulated. An important pathway implicated in AD also differed between the 3R and 4R cell lines, Wnt signaling. These studies demonstrate expression differences between MAPT isoforms 4R tau and 3R tau due to the inclusion/exclusion of the repeat region coded for by exon 10. Our data add to complex findings on the role of 3R/4R in normal and abnormal neuronal function and highlight several molecular mechanisms that might drive neurodegeneration, or perhaps, set the stage for it.

The vasoactive intestinal peptide-receptor system is involved in human glioblastoma cell migration

Glioblastoma multiforme (GBM) is the most aggressive form of brain tumor in adults. This cancer has an infiltrative nature and the median survival of patients is about one year. Vasoactive intestinal peptide (VIP) belongs to a structurally related family of polypeptides and is a major regulatory factor in the central and peripheral nervous systems. VIP regulates proliferation of astrocytes and of numerous cancer cell lines and modulates migration in prostatic and colonic cancer cell lines. Little is known about the involvement of VIP and its receptors (VIP-receptor system) in proliferation or migration of GBM cells. The effects of VIP, PACAP and of synthetic VIP antagonists were tested in two human GBM cell lines, M059K and M059J, established from two different parts of a single tumor. In these cells, the data revealed that the VIP-receptor system did not affect proliferation but controlled cell migration. Indeed, in M059K cells which express components of the VIP receptor system, the VIP receptor antagonists and a PACAP antibody enhanced migration. The VIP receptor antagonists increased generation of typical migration-associated processes: filopodia and lamellipodia, and activation of Rac1 and Cdc42 GTPases. Reciprocally, in M059J cells which poorly express the VIP-receptor system, treatments with the agonists VIP and PACAP resulted in decreased cell migration. Furthermore, the peptides appeared to act through a subclass of binding sites displaying an uncommon very high affinity for these ligands. Taken together, these observations suggest that components of the VIP-receptor system negatively regulate cell migration, thus showing potential anti-oncogenic properties.

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.

Unconventional binding sites and receptors for VIP and related peptides PACAP and PHI/PHM: an update

The 28-amino-acid neuropeptide VIP and related peptides PACAP and PHI/PHM modulate virtually all of the vital functions in the body. These peptides are also commonly recognized as major regulators of cell growth and differentiation. Through their trophic and cytoprotective functions, they appear to play major roles in embryonic development, neurogenesis and the progression of a number of cancer types. These peptides bind to three well-characterized subtypes of G-protein coupled receptors: VPAC1 and VPAC2 share a common high affinity in the nanomolar range for VIP and PACAP; a third receptor type, PAC1, has been characterized for its high affinity for PACAP but its low affinity for VIP. Complex effects and pharmacological behaviors of these peptides suggest that multiple subtypes of binding sites may cooperate to mediate their function in target cells and tissues. In this complex response, some of these binding sites correspond to the definition of the conventional receptors cited above, while others display unexpected pharmacological and functional properties. Here we present potential clues that may lead investigators to further characterize the molecular nature and functions of these atypical binding species.

Microarray analyses of pituitary adenylate cyclase activating polypeptide (PACAP)-regulated gene targets in sympathetic neurons

The high and preferential expression of the PAC(1)(short)HOP1 receptor in postganglionic sympathetic neurons facilitates microarray studies for mechanisms underlying PACAP-mediate neurotrophic signaling in a physiological context. Replicate primary sympathetic neuronal cultures were treated with 100 nM PACAP27 either acutely (9 h) or chronically (96 h) before RNA extraction and preparation for Affymetrix microarray analysis. Compared to untreated control cultures, acute PACAP treatment modulated significantly the expression of 147 transcripts of diverse functional groups, including peptides, growth factors/cytokines, transcriptional factors, receptors/signaling effectors and cell cycle regulators, that collectively appeared to facilitate neuronal plasticity, differentiation and/or regeneration processes. Some regulated transcripts, for example, were related to BDNF/TrkB, IL-6/Jak2/Socs2 and TGF/follistatin signaling; many transcripts affected bioactive peptide and polyamine biosynthesis. Although chronic PACAP treatments altered the expression of 109 sympathetic transcripts, only 43 transcripts were shared between the acute and chronic treatment data sets. The PACAP-mediated changes in transcript expression were corroborated independently by quantitative PCR measurement. The PACAP-regulated transcripts in sympathetic neurons did not bear strong resemblance to those in PACAP-treated pheochromocytoma cells. However, many PACAP-targeted sympathetic transcripts, especially those related to peptide plasticity and nerve regeneration processes, coincided significantly with genes altered after peripheral nerve injury. The ability for sympathetic PAC(1)(short)HOP1 receptors to engage multiple downstream signaling cascades appeared to be reflected in the number and diversity of genes targeted in a multifaceted strategy for comprehensive neurotrophic responses.

Brain delivery of vasoactive intestinal peptide enhanced with the nanoparticles conjugated with wheat germ agglutinin following intranasal administration

The development of biotech drugs such as peptides and proteins that act in the central nervous system has been significantly impeded by the difficulty of delivering them across the blood-brain barrier. The surface engineering of nanoparticles with lectins opened a novel pathway to the absorption of drugs loaded by biodegradable poly (ethylene glycol)-poly (lactic acid) nanoparticles in the brain following intranasal administration. In the present study, vasoactive intestinal peptide, a neuroprotective peptide, was efficiently incorporated into the poly (ethylene glycol)-poly (lactic acid) nanoparticles modified with wheat germ agglutinin and the biodistribution, brain uptake and neuroprotective effect of the formulation were assessed. The area under the concentration-time curve of intact 125I-vasoactive intestinal peptide in brain of mice following the intranasal administration of 125I-vasoactive intestinal peptide carried by nanoparticles and wheat germ agglutinin-conjugated ones was significantly enlarged by 3.5 approximately 4.7 folds and 5.6 approximately 7.7 folds, respectively, compared with that after intranasal application of 125I-vasoactive intestinal peptide solution. The same improvements in spatial memory in ethylcholine aziridium-treated rats were observed following intranasal administration of 25 microg/kg and 12.5 microg/kg of vasoactive intestinal peptide loaded by unmodified nanoparticles and wheat germ agglutinin-modified nanoparticles, respectively. Distribution profiles of wheat germ agglutinin-conjugated nanoparticles in the nasal cavity presented their higher affinity to the olfactory mucosa than to the respiratory one. Inhibition experiment with specific sugars suggested that the interaction between the nasal mucosa and the wheat germ agglutinin-functionalized nanoparticles were due to the immobilization of carbohydrate-binding pockets on the surface of the nanoparticles. The results clearly indicated wheat germ agglutinin-modified nanoparticles might serve as promising carriers especially for biotech drugs such as peptides and proteins.

PACAP/PAC1 autocrine system promotes proliferation and astrogenesis in neural progenitor cells

The Pituitary adenylate cyclase-activating peptide (PACAP) ligand/type 1 receptor (PAC1) system regulates neurogenesis and gliogenesis. It has been well established that the PACAP/PAC1 system induces differentiation of neural progenitor cells (NPCs) through the Gs-mediated cAMP-dependent signaling pathway. However, it is unknown whether this ligand/receptor system has a function in proliferation of NPCs. In this study, we identified that PACAP and PAC1 were highly expressed and co-localized in NPCs of mouse cortex at embryonic day 14.5 (E14.5) and found that the PACAP/PAC1 system potentiated growth factor-induced proliferation of mouse cortical NPCs at E14.5 via Gq-, but not Gs-, mediated PLC/IP3-dependent signaling pathway in an autocrine manner. Moreover, PAC1 activation induced elongation of cellular processes and a stellate morphology in astrocytes that had the bromodeoxyuridine (BrdU)-incorporating ability of NPCs. Consistent with this notion, we determined that the most BrdU positive NPCs differentiated to astrocytes through PAC1 signaling. These results suggest that the PACAP/PAC1 system may play a dual role in neural/glial progenitor cells not only differentiation but also proliferation in the cortical astrocyte lineage via Ca2+-dependent signaling pathways through PAC1.

Glucose-targeted niosomes deliver vasoactive intestinal peptide (VIP) to the brain

The aim of this study was to evaluate glucose-bearing niosomes as a brain targeted delivery system for the vasoactive intestinal peptide (VIP). To this end, VIP/125I-VIP-loaded glucose-bearing niosomes were intravenously injected to mice. Brain uptake was determined by measuring the radioactivity of 125I-labeled VIP using gamma-counting, after intravenous administration of VIP in solution or encapsulated in glucose-bearing niosomes or in control niosomes. VIP integrity was assessed by reversed-phase HPLC analysis of brain extracts. Distribution of 125I-VIP derived radioactivity was examined from serial brain slices. HPLC analysis confirmed the presence of intact VIP in brain after administration of VIP-loaded niosomes, but not after administration of VIP solution. Encapsulation within glucose-bearing niosomes mainly allowed a significantly higher VIP brain uptake compared to control niosomes (up to 86%, 5min after treatment). Brain distribution of intact VIP after injection of glucose-bearing niosomes, indicated that radioactivity was preferentially located in the posterior and the anterior parts of the brain, whereas it was homogeneously distributed in the whole brain after the administration of control vesicles. In conclusion, this novel vesicular formulation of VIP delivers intact VIP to particular brain regions in mice. Glucose-bearing vesicles might be therefore a novel tool to deliver drugs across the blood-brain barrier (BBB).

Suramin disrupts receptor-G protein coupling by blocking association of G protein alpha and betagamma subunits

Most drugs target a receptor for a hormone or neurotransmitter. A newer strategy for drug development is to target a downstream signaling element, such as the G protein associated with a receptor. Suramin is considered a lead compound targeting this moiety. It inhibits binding of guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS) to G proteins and reduces agonist binding to G protein-coupled receptors. Suramin is thought to uncouple the G protein from its associated receptor, although there is no direct evidence for this mechanism. We have now examined the effect of suramin on G protein signaling for the vasoactive intestinal peptide (VIP) receptor in lung. The primary experimental strategy was a two-step cross-linking reaction that covalently captures the VIP-receptor-G protein ternary complex. Such cross-linking provided the first direct evidence that suramin physically disrupts receptor-G protein coupling. We investigated how this uncoupling relates to the inhibition of GTPgammaS binding. Suramin indiscriminately hindered the dissociation of various guanine nucleotides from the G protein, implying that its action is not allosteric. Further cross-linking studies suggested that suramin does not obstruct the receptor docking site directly but appears to block the interface between G protein alpha and betagamma subunits. Observations with a purified system of recombinant G protein subunits without a receptor yielded direct evidence that suramin suppresses the association between these subunits. This action can explain how it both disrupts receptor-G protein coupling and inhibits guanine nucleotide release. The improved understanding of suramin's action advances the development of selective inhibitors of G protein signaling.

Vasoactive intestinal peptide-induced neurite remodeling in human neuroblastoma SH-SY5Y cells implicates the Cdc42 GTPase and is independent of Ras-ERK pathway

Vasoactive intestinal peptide (VIP) is known to regulate proliferation or differentiation in normal and tumoral cells. SH-SY5Y is a differentiated cell subclone derived from the SK-N-SH human neuroblastoma cell line and possess all the components for an autocrine action of VIP. In the present study, we investigated the morphological changes and intracellular signaling pathways occurring upon VIP treatment of SH-SY5Y cells. VIP induced an early remodeling of cell projections: a branched neurite network spread out and prominent varicosities developed along neurites. Although activated by VIP, the Ras/ERK pathway was not required for the remodeling process. In contrast, pull-down experiments revealed a strong Cdc42 activation by VIP while expression of a dominant-negative Cdc42 prevented the VIP-induced neurite changes, suggesting an important role for this small GTPase in the process. These data provide the first evidence for a regulation of the activity of Rho family GTPases by VIP and bring new insights in the signaling pathways implicated in neurite remodeling process induced by VIP in neuroblastoma cells.

Neuritogenesis induced by vasoactive intestinal peptide, pituitary adenylate cyclase-activating polypeptide, and peptide histidine methionine in SH-SY5y cells is associated with regulated expression of cytoskeleton mRNAs and proteins

Vasoactive intestinal peptide (VIP) and the related peptides pituitary adenylate cyclase-activating polypeptide (PACAP) and peptide histidine methionine (PHM) are known to regulate proliferation and/or differentiation in normal and tumoral cells. In this study, neuritogenesis in human neuroblastoma SH-SY5Y cells cultured in serum-free medium was induced by VIP, PACAP, and PHM. The establishment of this process was followed by the quantification of neurite length and branching and the expression of neurofilament mRNAs, neurofilament proteins, and other cytoskeletal protein markers of neuronal differentiation: neuron-specific MAPs and beta-tubulin III. Neurite length and branching and the expression of most markers tested were increased by VIP and PACAP in a similar, although slightly different, fashion. In contrast, neuritic elongation induced by PHM was correlated with neither an increase in branching or neurofilament mRNAs nor a clear change in the expression of cytoskeleton proteins, with the exception of the stimulation by PHM of doublecortin, a microtubule-associated marker of migrating neuroblasts. These findings are the first evidence from a human neuron-like cell line for 1) a direct regulation of the metabolism of neurofilaments by VIP and PACAP and 2) the induction by PHM of neuritic processes of an apparent immature character.

Effects of the vasoactive intestinal peptide (VIP) and related peptides on glioblastoma cell growth in vitro

The growth rate of numerous cancer cell lines is regulated in part by actions of neuropeptides of the vasoactive intestinal peptide (VIP) family, which also includes pituitary adenylate cyclase-activating peptide (PACAP), glucagon, and peptide histidine/isoleucine (PHI). The aim of this work was to investigate the effect of these peptides on the growth of the rat glioblastoma cell line C6 in vitro. We also sought to determine which binding sites were correlated with the effects observed. Proliferation studies performed by means of a CyQuant trade mark assay showed that VIP and PACAP strongly stimulated C6 cell proliferation at most of the concentrations tested, whereas PHI increased cell proliferation only when associated with VIP. Two growth hormone-releasing factor (GRF) derivatives and the VIP antagonist hybrid peptide neurotensin-VIP were able to inhibit VIP-induced cell growth stimulation, even at very low concentrations. Binding experiments carried out on intact cultured C6 cells, using 125I-labeled VIP and PACAP as tracers, revealed that the effects of the peptides on cell growth were correlated with the expression on C6 cells of polyvalent high-affinity VIP-PACAP binding sites and of a second subtype corresponding to very high-affinity VIP-selective binding species. The latter subtype, which interacted poorly with PACAP with a 10,000-fold lower affinity than VIP, might mediate the antagonist effects of neurotensin- VIP and of both GRF derivatives on VIP-induced cell growth stimulation.

Peptides and hormesis

The article provides a broad assessment of the occurrence of hormetic-like biphasic dose-response relationships by over 30 peptides representing many major peptide classes. These peptide-induced biphasic dose responses were observed to occur in a extensive range of tissues, affecting an diverse range of biological endpoints. Despite diversity of peptides, models and endpoints, the quantitative features of the biphasic dose responses are remarkably similar with respect to the amplitude and width of the stimulatory response. These findings strongly suggest that hormetic-like biphasic dose responses represent a broadly generalizable biological phenomenon.

Brain delivery of vasoactive intestinal peptide (VIP) following nasal administration to rats

The aim of this work was to study in rats the nasal route for the brain delivery of the vasoactive intestinal peptide (VIP) neuropeptide. After evaluating VIP stability in solutions obtained from nasal washes, the effect of formulation parameters (pH 4-9, 0-1% (w/v) lauroylcarnitine (LC), hypo- or isoosmolality) on the brain uptake of intranasally administered VIP (10(-8)M)/125I-VIP (300,000 cpm/ml) was studied, using an in situ perfusion technique. Brain radioactivity distribution was assessed by quantitative autoradiographic analysis. Results were compared to intravenously administered VIP. With a hypotonic formulation at pH 4 containing 0.1% LC and 1% bovine serum albumin, VIP stability was satisfactory and loss by adsorption was minimal. Using this formulation, around 0.11% of initial radioactivity was found in the brain after 30 min perfusion and was located in the olfactory bulbs, the midbrain and the cerebellum. HPLC analysis of brain and blood extracts demonstrated the presence of intact VIP in brain and its complete degradation in the blood compartment. By intravenous administration, no intact VIP was found either in brain or in blood. In conclusion, intact VIP could be delivered successfully to the brain using the intranasal route for administration.

Antagonism of VIP-stimulated cyclic AMP formation in chick brain

Of eight peptides tested (0.01-5 microM), only two, that is, pituitary adenylate cyclase-activating polypeptide (PACAP27) and chicken vasoactive intestinal peptide (cVIP), potently stimulated cyclic AMP (cAMP) production in cerebral cortical slices of the chick. Mammalian VIP (mVIP) showed some activity only at the highest dose tested, whereas truncated forms of PACAP or VIP, that is, PACAP6-27, cVIP6-28, and mVIP6-28, or hybrid compounds, that is, neurotensin6-11-cVIP7-28 (NT-cVIP) and neurotensin6-11-mVIP7-28 (NT-mVIP), were inactive. Thirty-minute preincubation of chick cortical slices with 5 microM PACAP6-27, NT-cVIP, or NT-mVIP competitively antagonized the cAMP effects of cVIP (0.03-1 microM), with the truncated form of PACAP being the best antagonist. Preincubation of slices with 5 microM mVIP6-28 also produced a significant inhibition of the cVIP (0.1-1 microM)-induced increase in cAMP production; however its action was independent of the concentration of cVIP. In contrast to mVIP6-28, cVIP6-28 showed no antagonistic activity against the full-length peptide. In parallel experiments, 30-min pretreatment of cortical slices with 5 microM PACAP6-27 significantly antagonized the PACAP38-evoked increase in cAMP formation, whereas mVIP6-28 or the NT-mVIP hybrid was ineffective. It has been concluded that in the chick brain, PACAP and cVIP stimulate cAMP biosynthesis via PAC1 and VPAC-type receptors, respectively, and PACAP6-27 seems to be the most potent, yet PACAP/VIP receptor-nonselective antagonist. Unlike truncated PACAP, the NT-VIP hybrid peptides tested may represent VPACtype receptor-selective blocking activity.

Vasoactive intestinal peptide stimulates proliferation in HT29 human colonic adenocarcinoma cells: concomitant activation of Ras/Rap1-B-Raf-ERK signalling pathway

The vasoactive intestinal peptide (VIP) has been shown to regulate cell proliferation and differentiation in many cell types. We previously reported that this neuropeptide inhibited proliferation in HT29 adenocarcinoma cells cultured in serum-containing medium. In addition, it has been demonstrated that VIP induced a potent stimulation of intracellular cAMP production in these cells cultured either in the absence or in the presence of serum. We also demonstrated that VIP induced phosphorylation of the small GTPase Rap1 in these cancerogenous cells. In the present study, the effects of VIP on the proliferation of HT29 cells cultured in the absence of growth factors and various concomitant signalling events were investigated. Under serum-free conditions VIP stimulates HT29 cell proliferation and induced a time- and concentration-dependent ERK activation. Furthermore, VIP induced the activation of the small GTPase Rap1 and of a 95 kDa isoform of the serine/threonine kinase B-Raf. Ras GTPase is also activated in VIP-stimulated cells. We hypothesize that VIP-induced proliferation in HT29 adenocarcinoma cells may involve a cAMP-Rap1/Ras-B-Raf-ERK signalling pathway.

VIP as a trophic factor in the CNS and cancer cells

The effects of vasoactive intestinal peptide (VIP) on the proliferation of central nervous system (CNS) and cancer cells were investigated. VIP has important actions during CNS development. During neurogenesis, VIP stimulates the proliferation and differentiation of brain neurons. Addition of VIP to embryonic mouse spinal cord cultures increases neuronal survival and activity dependent neurotrophic factor (ADNF) secretion from astroglial cells. VIP is an integrative regulator of brain growth and development during neurogenesis and embryogenesis. Also, VIP causes increased proliferation of human breast and lung cancer cells in vitro. VIP binds with high affinity to cancer cells, elevates the cAMP and increases gene expression of c-fos, c-jun, c-myc and vascular endothelial cell growth factor. The effects of VIP on cancer cells are reversed by VIPhybrid, a synthetic VPAC(1) receptor antagonist. VIPhyb inhibits the basal growth of lung cancer cells in vitro and tumors in vivo and potentiates the ability of chemotherapeutic drugs to kill cancer cells. Due to the high density of VPAC(1) receptors in cancer cells, VIP has been radiolabeled with 123I, 18F and 99mTc to image tumors. It remains to be determined if radiolabeled VIP analogs will be useful agents for early detection of cancer in patients.

Elucidation of vasoactive intestinal peptide pharmacophore for VPAC(1) receptors in human, rat, and guinea pig

Vasoactive intestinal peptide (VIP) is a neurotransmitter involved in a number of pathological and physiological processes. VIP is rapidly degraded and simplified stable analogs are needed. VIP's action was extensively studied in rat and guinea pig. However, it is largely unknown whether its pharmacophore in these species resembles human. To address this issue we investigated the VIP pharmacophore for VPAC(1) (the predominant receptor subtype in cancers and widely distributed in normal tissues) by using alanine and D-amino acid scanning. Interaction with rat, guinea pig, and human VPAC(1) was assessed using transfected Chinese hamster ovary (CHO) and PANC1 cells and cells possessing native VPAC(1). Important species differences existed in the VIP pharmacophore. The human VPAC(1) expressed in CHO cells, which were used almost exclusively in previous studies, differed markedly from the native VPAC(1) in T47D cells. The most important amino acids for determining affinity are His(1), Asp(3), Phe(6), Arg(12), Arg(14), and Leu(23). Ser(2), Asp(8), Asn(9), Thr(11), Val(19), Asn(24), Ser(25), Leu(27), and Asn(28) are not essential for high-affinity interaction/activation. [Ala(2,8,9,11,19,24,25,27,28)]VIP, which contained 11 alanines, was synthesized and it was equipotent to VIP at VPAC(1) receptors in all species and was metabolically stable. Our results show in any design of simplified VIP analogs for VPAC(1) it will be important to consider species differences and it is essential to use transfected systems that reflect the native receptor's pharmacophore. Last, with our results a simplified, metabolically stable VIP analog was identified that should be useful as a prototype for design of selective agonists/antagonists that could be useful therapeutically.

Involvement of VIP on BDNF-induced somatostatin gene expression in cultured fetal rat cerebral cortical cells

Previous studies have shown that BDNF promotes expression of SS. In earlier studies we demonstrated the stimulatory effect of locally produced VIP upon SS secretion. These facts led us to explore the peptidergic action of BDNF on VIP, and to determine if BDNF-induced SS might be mediated by the induction of VIP. Cultured fetal rat cerebrocortical cells were incubated with BDNF (50 ng/ml) and/or VIP (10(-11) M) for 2 and 5 days. In other experiments IgGs from BDNF or VIP antisera were also added. BDNF increased VIP and SS gene expression and peptide production. After 2 days of incubation with both BDNF and VIP the induction of SS mRNA was similar to that obtained with BDNF alone. However when the treatment was extended to 5 days the increase in SS mRNA was higher than that obtained with BDNF alone. This finding suggests the possibility that both factors acted synergistically. To define the potential role of VIP in the response of SS gene expression to BDNF, endogenous VIP was blocked with IgGs from VIP antiserum. Under these experimental conditions BDNF-induced SS decreased. Our study provides the first evidence that BDNF up-regulates VIP gene expression and concentration of the peptide. The involvement of VIP on BDNF-induced SS gene expression is also demonstrated.

Vasoactive intestinal peptide (VIP) stimulates rat prostatic epithelial cell proliferation

BACKGROUND

Androgens play a major role in supporting normal growth and functional maintenance in the prostate. However, this gland contains an array of neuroendocrine peptides that can play a regulatory role in its physiopathology. Among these peptides, one of the best studied is vasoactive intestinal peptide (VIP), which is abundant in autonomic nerves surrounding both human and rat prostatic acini. This neuropeptide may act through interaction with two types of high-affinity receptors, named VPAC(1) and VPAC(2) receptors. Another regulatory peptide, the pituitary adenylate cyclase-activating peptide (PACAP), interacts with these receptors with the same affinity as VIP, but binds with higher affinity to PAC(1) receptors. Human prostate tumors and rat prostate show a major presence of VPAC(1) receptors, whereas various findings suggest a role for VIP in prostatic development. Here we studied the effects of VIP on the proliferation of rat prostatic epithelial cells in culture.

METHODS

We studied the [(3)H]-thymidine uptake by rat prostatic epithelial cells in culture, characterized previously by using biomarkers such as cytokeratin and vimentin. In these cells we tested the effect of VIP and PACAP-27 on two different signaling pathways, the cyclic AMP (cAMP) and the inositol phosphate (IPs).

RESULTS

The rat prostatic cells in culture were cytokeratin (5,6,8) and vimentin positive, indicating that the culture was predominantly epithelial. The proliferation curves showed that the cells followed different states of growth: a quiescent, an exponential proliferative, and a steady state. Cyclic AMP production, but not inositol phosphate production, was increased in the presence of VIP and PACAP-27, which suggests the expression of VPAC(1) and/or VPAC(2) receptors primarily. VIP significantly increased prostatic cell proliferation in a bimodal manner, as shown for dibutyryl cyclic AMP (dbcAMP), which suggests that the effect of VIP upon prostatic proliferation is cAMP-dependent.

CONCLUSIONS

Here, we demonstrate that VIP increased [(3)H]thymidine uptake by rat prostatic epithelial cells in culture, conceivably by the activation of the adenylate cyclase.

Epidermal growth factor as a local mediator of the neurotrophic action of vitamin B(12) (cobalamin) in the rat central nervous system

We have recently demonstrated that the myelinolytic lesions in the spinal cord (SC) of rats made deficient in vitamin B(12) (cobalamin) (Cbl) through total gastrectomy (TG) are tumor necrosis factor-alpha (TNF-alpha)-mediated. We investigate whether or not permanent Cbl deficiency, induced in the rat either through TG or by chronic feeding of a Cbl-deficient diet, might modify the levels of three physiological neurotrophic factors-epidermal growth factor (EGF), vasoactive intestinal peptide (VIP), and somatostatin (SS)-in the cerebrospinal fluid (CSF) of these rats. We also investigated the ability of the central nervous system (CNS) in these Cbl-deficient rats to synthesize EGF mRNA and of the SC to take up labeled Cbl in vivo. Cbl-deficient rats, however the vitamin deficiency is induced, show a selective decrease in EGF CSF levels and an absence of EGF mRNA in neurons and glia in various CNS areas. In contrast, radiolabeled Cbl is almost exclusively taken up by the SC white matter, but to a much higher degree in totally gastrectomized (TGX) rats. Chronic administration of Cbl to TGX rats restores to normal both the EGF CSF level and EGF mRNA expression in the various CNS areas examined. This in vivo study presents the first evidence that the neurotrophic action of Cbl in the CNS of TGX rats is mediated by stimulation of the EGF synthesis in the CNS itself. It thus appears that Cbl inversely regulates the expression of EGF and TNF-alpha genes in the CNS of TGX rats.

Pituitary adenylate cyclase-activating polypeptide regulation of vasoactive intestinal polypeptide transcription requires Ca2+ influx and activation of the serine/threonine phosphatase calcineurin

A >15-fold increase in vasoactive intestinal polypeptide (VIP) mRNA and VIP peptide levels occurred in primary chromaffin cells following exposure to the neurotrophic neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP)-27 with an EC50 of approximately 2 nM. PACAP induction of VIP expression was blocked by methoxyverapamil or by a combination of nimodipine and omega-conotoxin MVIIC, indicating a requirement for PACAP-initiated calcium entry through voltage-dependent calcium channels for regulation of VIP biosynthesis. Ascomycin, which inhibits calcineurin through formation of an ascomycin/FKBP12/calcineurin ternary complex, abolished the PACAP-evoked increase in VIP expression, whereas rapamycin, which also binds to FKBP12 but does not cause inhibition of calcineurin, did not. Cyclosporin A, which inhibits calcineurin through formation of a cyclosporin A/cyclophilin/calcineurin complex, also abolished PACAP-evoked VIP biosynthesis. These data indicate that PACAP regulates the expression of VIP via a signaling pathway that requires calcium influx and activation of calcineurin.

The small G-proteins Rap 1 as potential targets of vasoactive intestinal peptide effects in the human clonic cancer cells HT29

We recently reported that the vasoactive intestinal peptide (VIP) potently inhibited proliferation and induced in parallel a strong cAMP rise, in the human colonic cancer cell line HT29. In this study, we investigated whether Rap 1 proteins could be potential targets of VIP effects in HT29 cells. These Ras-related proteins in which activity was demonstrated to be regulated by PKA phosphorylation, are considered as potential modulators of the Ras / Raf / MAP kinases cascade that governs cell growth control. Our data revealed that the Rap 1a isoform is highly expressed in HT29 cells and mainly localized in a late endosomal compartment. In these cells, VIP induces Rap 1 phosphorylation and a yet unidentified modification that leads to their acidification. This latter Rap 1 acidification seems to be, at least partially, cAMP-dependent. It is concluded that in HT29 cells, Rap 1 proteins may be part of a VIP-induced signaling cascade.

Differential effects of peptide histidine isoleucine (PHI) and related peptides on stimulation and suppression of neuroblastoma cell proliferation. A novel VIP-independent action of PHI via MAP kinase

The growth rate of rodent embryonic neuroblasts and human neuroblastoma cell lines is regulated in part by autocrine or paracrine actions of neuropeptides of the family that includes vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), and pituitary adenylate cyclase-activating peptide (PACAP). These peptides act via seven transmembrane G-protein-linked receptors coupled to cAMP elevation, phospholipase C activation, intracellular Ca2+ release, and/or of mitogen-activated protein (MAP) kinase activation. Here we investigated the action of these peptides on the mouse neuroblastoma cell line Neuro2a. PHI and VIP inhibited proliferation at concentrations as low as 10(-13) M and 10(-10) M, respectively. In contrast, PACAP action was biphasic, with stimulation occurring at subnanomolar doses and inhibition at higher doses. Peptide actions were studied further by measuring cAMP and ERK1/2 MAP kinase activity and by assessing 3H-thymidine incorporation in conjunction with a panel of signal transduction pathways inhibitors. The data obtained indicated that the PHI-inhibitory and PACAP-stimulatory activities were mediated by corresponding changes in activity of the MAP kinase pathway and independent of protein kinase A (PKA) or protein kinase C (PKC). In contrast, the inhibitory actions of VIP and PACAP were specifically blocked by antagonists of PKA. Northern blot analysis revealed gene expression for only the PACAP-preferring (PAC1) receptor. However, binding experiments using 125I-labeled PACAP27, PHI, and VIP, demonstrated the presence of PACAP-preferring sites, bivalent VIP/PACAP sites, and PHI-binding sites that did not interact with VIP. The studies demonstrate potent regulatory actions of PACAP, PHI, and VIP on neuroblastoma cell proliferation which appear to be mediated by multiple subsets of receptors which differentially couple to MAP kinase and PKA signaling pathways.

Differential expression and function of PACAP and VIP receptors in four human colonic adenocarcinoma cell lines

Human colonic adenocarcinoma cell lines have conserved several features of the native tissue. Among these is the expression of cell surface receptors for hormones and neurotransmitters that may be involved in the regulation of proliferation and differentiation processes in these cancer cells. Here, we confirm that high-affinity binding sites for the Vasoactive Intestinal Polypeptide (VIP) and for the VIP analogue Pituitary Adenylate-Cyclase Activating Polypeptide (PACAP), were expressed in 4 human colonic adenocarcinoma cell lines, HT29, SW403, DLD-1 and Caco-2, that spontaneously displayed variable phenotypic properties in culture. We demonstrated that after long-term treatments, VIP and PACAP significantly reduced cell proliferation in the 4 cell lines and modulated intracellular cAMP and cGMP levels. Furthermore, conspicuous differences were observed from one cell type to another concerning expression of the receptor subsets or the effects of the neuropeptides on cell growth and on cyclic nucleotides production.

Protection against developmental retardation in apolipoprotein E-deficient mice by a fatty neuropeptide: implications for early treatment of Alzheimer's disease

Stearyl-Nle17-VIP (SNV) is a novel agonist of vasoactive intestinal peptide (VIP) exhibiting a 100-fold greater potency than the parent molecule and specificity for a receptor associated with neuronal survival. Here, mice deficient in apolipoprotein E (ApoE), a molecule associated with the etiology of Alzheimer's disease, served as a model to investigate the developmental and protective effects of SNV. In comparison to control animals, the deficient mice exhibited (a) reduced amounts of VIP messenger RNA; (b) decreased cholinergic activity (c) significant retardation in the acquisition of developmental milestones: forelimb placing behavior and cliff avoidance behavior; and (d) learning and memory impairments. Daily injections of SNV to ApoE-deficient newborn pups resulted in increased cholinergic activity and marked improvements in the time of acquisition of behavioral milestones, with peptide-treated animals developing as fast as control animals and exhibiting improved cognitive functions after cessation of peptide treatment. Specificity was demonstrated in that treatment with a related peptide (PACAP), pituitary adenylate cyclase-activating peptide, produced only limited amelioration. As certain genotypes of ApoE increase the probability of Alzheimer's disease, early counseling and preventive treatments may now offer an important route for therapeutics design.

Retinoic acid regulation of the VIP and PACAP autocrine ligand and receptor system in human neuroblastoma cell lines

Neuroendocrine tumors, neuroblastoma in particular, commonly express the neuropeptides vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating peptide (PACAP) and their receptors. Retinoic acid (RA) has been shown to induce differentiation of neuroblastoma cell lines, possibly by augmenting or interfering with neuropeptide autocrine loops. We sought to determine which receptor gene subtypes are expressed in selected human neuroblastoma cell lines (SH-SY5Y, IMR-32, and LA-N-5), and the effect of RA on the VIP/PACAP ligand/receptor system. Expression of both PACAP1 and VIP1/PACAP2 receptor genes was detected by Northern analysis, which characteristically encode Type I (PACAP-preferring), and Type II (bivalent VIP/PACAP) receptors, respectively. Binding experiments carried out on IMR-32 cells, using 125I VIP and 125I PACAP-27 as tracers, corroborated that both receptor subtypes were expressed. In contrast to RA upregulation of VIP binding (confirmed here in IMR-32 cells), levels of both receptor mRNAs were reduced after RA treatment. VIP mRNA in each cell line was increased by RA, whereas PACAP mRNA, detected in IMR-32 cells only, was reduced. The studies indicate that several components of the VIP/PACAP autocrine system are regulated in neuroblastoma cell lines during RA differentiation.

Switches in the expression and function of PACAP and VIP receptors during phenotypic interconversion in human neuroblastoma cells

Clonal human neuroblastoma cells SH-IN undergo a very conspicuous phenotypic change in culture. Large substrate-adherent cells with a slow growth rate give rise to small cells emerging in focal aggregates and growing to high cell densities. This is accompanied by a dramatic switch in the expression of receptors for the structurally related neuropeptides VIP (vasoactive intestinal polypeptide) and PACAP (pituitary adenylate cyclase activating polypeptide). Large cells expressed mainly PACAP-specific receptors that triggered stimulation of intracellular cGMP production. On the other hand, polyvalent VIP/PACAP receptors positively coupled to adenylate cyclase were mostly observed in the small cells. Both neuropeptides stimulated cell proliferation in large and small cells. These data, together with the previous demonstration of autocrine/paracrine actions of VIP and PACAP in human neuroblastomas, support the idea that these neuropeptides may participate in the establishment of the apparent phenotype in these cancer cells.

Vasoactive intestinal peptide: mediator of laminin synthesis in cultured Schwann cells

To learn more about neuropeptide-induced glial responses which accompany axon regeneration, we studied effects of VIP on laminin production by cultured Schwann cells. Schwann cells were isolated from sciatic nerves of neonatal mice, purified, and incubated for 5 days in either control medium (DMEM + 15% FCS) or control medium containing 10-7 -10-11 M VIP. At 10-7 and 10-8 M VIP, laminin levels measured by enzyme-linked immunosorbent assay were significantly higher (55% and 35%) than those in control cultures. Lower VIP concentrations (10-9 -10-11 M) produced smaller increases which were not significant. Low-affinity VIP receptors which mediated this effect were demonstrated on Schwann cells by radioligand binding studies. The increased Schwann cell synthesis of laminin induced by VIP was blocked when either a VIP antagonist or a VIP receptor antagonist was added to the VIP-containing incubation medium. In contrast to astrocytes, when Schwann cells were loaded with fura-2, VIP did not increase cytosolic Ca2+. This indicates that Schwann cells and astrocytes may have different intracellular transduction pathways; their receptor subtypes also may differ. We suggest that the VIP-induced increase in laminin synthesis which we have observed in cultured Schwann cells may also occur in vivo and might be an important component of axon-Schwann cell interactions during nerve regeneration.