Neuropeptides as growth and differentiation factors in general and VIP in particular

Tracing the invisible mutant ADNP protein in Helsmoortel-Van der Aa syndrome patients

Heterozygous de novo mutations in the Activity-Dependent Neuroprotective Homeobox (ADNP) gene underlie Helsmoortel-Van der Aa syndrome (HVDAS). Most of these mutations are situated in the last exon and we previously demonstrated escape from nonsense-mediated decay by detecting mutant ADNP mRNA in patient blood. In this study, wild-type and ADNP mutants are investigated at the protein level and therefore optimal detection of the protein is required. Detection of ADNP by means of western blotting has been ambiguous with reported antibodies resulting in non-specific bands without unique ADNP signal. Validation of an N-terminal ADNP antibody (Aviva Systems) using a blocking peptide competition assay allowed to differentiate between specific and non-specific signals in different sample materials, resulting in a unique band signal around 150 kDa for ADNP, above its theoretical molecular weight of 124 kDa. Detection with different C-terminal antibodies confirmed the signals at an observed molecular weight of 150 kDa. Our antibody panel was subsequently tested by immunoblotting, comparing parental and homozygous CRISPR/Cas9 endonuclease-mediated Adnp knockout cell lines and showed disappearance of the 150 kDa signal, indicative for intact ADNP. By means of both a GFPSpark and Flag-tag N-terminally fused to a human ADNP expression vector, we detected wild-type ADNP together with mutant forms after introduction of patient mutations in E. coli expression systems by site-directed mutagenesis. Furthermore, we were also able to visualize endogenous ADNP with our C-terminal antibody panel in heterozygous cell lines carrying ADNP patient mutations, while the truncated ADNP mutants could only be detected with epitope-tag-specific antibodies, suggesting that addition of an epitope-tag possibly helps stabilizing the protein. However, western blotting of patient-derived hiPSCs, immortalized lymphoblastoid cell lines and post-mortem patient brain material failed to detect a native mutant ADNP protein. In addition, an N-terminal immunoprecipitation-competent ADNP antibody enriched truncating mutants in overexpression lysates, whereas implementation of the same method failed to enrich a possible native mutant protein in immortalized patient-derived lymphoblastoid cell lines. This study aims to shape awareness for critical assessment of mutant ADNP protein analysis in Helsmoortel-Van der Aa syndrome.

mTOR Signaling, Translational Control, and the Circadian Clock

Almost all cellular processes are regulated by the approximately 24 h rhythms that are endogenously driven by the circadian clock. mRNA translation, as the most energy consuming step in gene expression, is temporally controlled by circadian rhythms. Recent research has uncovered key mechanisms of translational control that are orchestrated by circadian rhythmicity and in turn feed back to the clock machinery to maintain robustness and accuracy of circadian timekeeping. Here I review recent progress in our understanding of translation control mechanisms in the circadian clock, focusing on a role for the mammalian/mechanistic target of rapamycin (mTOR) signaling pathway in modulating entrainment, synchronization and autonomous oscillation of circadian clocks. I also discuss the relevance of circadian mTOR functions in disease.

■ REVIEW : LIF, NGF, and the Cell Body Response to Axotomy

Adult peripheral neurons can regenerate after axonal damage. Large changes in gene expression occur in the cell bodies of these axotomized neurons, including decreases in expression of a number of proteins used for synaptic transmission and increases in expression of a number of proteins involved in regeneration. The signals that trigger these changes are just beginning to be elucidated. One characteristic of axotomized sympathetic, sensory, and motor neurons is that they increase expression of two neuropeptides, vasoactive intestinal peptide and galanin. These peptides may play important roles in the survival and regeneration of axotomized neurons deprived of their target-derived trophic factors. Recent studies have demonstrated two important signals in the induction of these peptides in sympathetic neurons: one is the release of leukemia inhibitory factor (LIF) by non-neuronal cells in the vicinity of the injured neurons and the other, the removal of target-derived nerve growth factor (NGF). Furthermore, there is a synergistic interaction between these two events whereby the removal of NGF alters the responsiveness of neurons to LIF. Future efforts will hopefully determine the extent to which LIF and NGF signal other aspects of the cell body response and the mechanisms that underlie these actions. NEUROSCIENTIST 3:176-185, 1997

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.

VIP Immunoreactivity in Human Aqueous Humor

PURPOSE

To demonstrate the presence of vasoactive intestinal pep-tide (VIP)-immunoreactive molecule in the human aqueous humor collected from eyes undergoing either cataract or glaucoma surgeries and to identify them asses of molecules responsible for the VIP immunoreactivity.

METHODS

Aqueous humor specimens were collected by parencentesis from nine cataract patients and also from eight patients undergoing glaucoma surgery following the creation of the limbal based conjunctival flap, partial dissection of the scleral flap, and application of mitomycin-C. The aqueous humor specimens were analyzed by radioimmunoassay to determine the level of VIP immunoreactivity. Specimens from 10 other cataract patients were pooled and analyzed for VIP immunoreactivity by Western blot analysis.

RESULTS

Levels of VIP immunoreactivity in aqueous humor of cataract and glaucoma patients were significantly different and were 610 +/- 160 and 260 +/- 64 pg VIP/ml, respectively (p = 0.03), while there was no correlation between the donor age and the level of VIP immunoreactivity. VIP immunoreactivity was detected as a single molecule with a molecular weight of 9000.

CONCLUSIONS

The disease status and the treatments of the eye that led to surgery and procedures applied to the eye immediately before aqueous humor collection, but not the age of the patients, affected the level of VIP immunoreactivity in the aqueous humor. The relationship between the 9000 Da VIP-immunoreactive molecule and the authentic (3326 Da) VIP remains to be studied.

VIP, from gene to behavior and back: summarizing my 25 years of research

Vasoactive intestinal peptide (VIP) is an interesting example of a 28-amino acid neuropeptide that is abundantly expressed in discrete brain regions/neurons and hence may contribute to brain function. This short review summarizes my own point of view and encompasses 25 years of work and over 100 publications targeting the understanding of VIP production and biological activity. The review starts with our original cloning of the VIP gene, it then continues to discoveries of regulation of VIP synthesis and the establishment of the first VIP transgenic mice. The review ends with the identification of novel VIP analogs that helped decipher VIP's important role during development, in regulation of the biological clock(s) and diurnal rhythms, sexual activity, learning and memory as well as social behavior, and cancer. This review cites only articles that I have coauthored and gives my own perspective of this exciting ever-growing field.

Nervous system development in normal and atresic chick embryo intestine: an immunohistochemical study

Intestinal motility disorders are a common complication after surgery for neonatal intestinal atresia. Although intestinal atresia causes alterations in the enteric nervous system, especially in its inner structures (nervous fibers in the mucosa, submucous and deep muscular plexuses), how these alterations develop is unclear. The chick model is a useful research tool for investigating the ontogenesis of the enteric nervous system and the pathogenesis of congenital bowel diseases. More information is needed on the overlap between the developing enteric nervous system and intestinal atresia. Because vasoactive intestinal polypeptide and substance P are typical intestinal neuropeptides, and vasoactive intestinal polypeptide acts as a modulator in neurodevelopment and an inhibitor of smooth muscle cell proliferation, our aim in this study was to investigate the distribution of their immunoreactivity in the developing enteric nervous system of normal and experimental chick models. We studied gut specimens excised from normal chick embryos (aged 12-20 days) and experimental chick embryos (aged 15-20 days) that underwent surgical intervention on day 12 to induce intestinal atresia (atresic embryos) or simply to grasp the bowel loop (sham-operated embryos). In normal chick embryos we showed vasoactive intestinal polypeptide and substance P immunoreactivity from day 12 in the submucous and myenteric plexuses. The distribution of peptide immunoreactivity differed markedly in atresic and normal or sham-operated gut embryos. These differences especially affected the inner structures of the enteric nervous system of specimens proximal to atresia and were related to the severity of dilation. Because nerve structures in the gut wall mucosa and submucous and deep muscular plexuses play a role in motility control and stretch sensation in the intestinal wall, our findings in the chick embryo may help to explain how gut motility disorders develop after surgery for neonatal intestinal atresia.

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.

Vasoactive intestinal peptide and nitric oxide promote survival of adult rat myenteric neurons in culture

Several motility disorders originate in the enteric nervous system (ENS). Our knowledge of factors governing survival of the ENS is poor. Changes in the expression of vasoactive intestinal peptide (VIP) and nitric oxide synthase (NOS) in enteric neurons occur after neuronal injury and in intestinal adaptation. The aim of this study was to evaluate whether VIP and nitric oxide (NO) influence survival of cultured, dissociated myenteric neurons. Neuronal survival was evaluated after 0, 4, and 8 days in culture. Influence of VIP and NO on neuronal survival was examined after culturing in the presence of VIP, NO donor, VIP antiserum, or NOS inhibitor. A marked loss of neurons was noted during culturing. VIP and NO significantly promoted neuronal survival. Corroborating this was the finding of an enhanced neuronal cell loss when cultures were grown in the presence of VIP antiserum or NOS inhibitor.

The increased proliferation of cultured neuroblastoma cells treated with vasoactive intestinal peptide is enhanced by simultaneous inhibition of neutral endopeptidase

Vasoactive intestinal peptide (VIP) stimulates the neuroblastoma cell line (NMB) to proliferate. Neuropeptide activity can be inhibited by neutral endopeptidases that function intracellularly and in the extracellular milieu. NMB cells express neutral endopeptidase (NEP) activity that can be specifically inhibited by phosphoramidon (PA). Our data now show that phosphoramidon treatment increases the efficacy of VIP-stimulated neuroblastoma proliferation. These results suggest that membrane endopeptidases modulate VIP-associated cell proliferation and enhancement of endopeptidase activity may serve as a target for cancer therapy.

Early and transient ontogenetic expression of the cocaine- and amphetamine-regulated transcript peptide in the rat mesencephalon: correlation with tyrosine hydroxylase expression

The ontogeny of cocaine- and amphetamine-regulated transcript (CART) expression has been analyzed by immunohistochemistry in the mesencephalon of the rat central nervous system, and compared to the pattern of tyrosine hydroxylase- (TH-) expression. CART-producing neurons were first detected on the embryonic day 11 (E11) in the ventral mesencephalic vesicle. These neurons are among the first cells of the mantle layer to differentiate. From E13, a complementary pattern of distribution was observed, dividing the mantle layer into an external TH zone and an internal CART zone. Many TH-positive neurons were found to migrate from the neuroepithelium through the area containing the CART-immunoreactive neurons to settle more laterally. These TH cells exhibited prominent leading and trailing dendrites in the immediate vicinity of CART perikarya. On E16, the number of CART neurons appeared to diminish, and they were confined near the ventricle and around the fasciculus retroflexus. On E18 and E20, only the Edinger-Westphal nucleus exhibited a strong CART staining as described in the adult brain. Thus, the very early detection of CART during prenatal ontogeny led us to speculate that this peptide might have a role in the development of specific regions of the rat brain. In particular, our observations suggest that CART-expressing neurons might help the migration of the dopaminergic neurons of the substantia nigra.

VIP stimulation of cAMP production in corneal endothelial cells in tissue and organ cultures

PURPOSE

To demonstrate that vasoactive intestinal peptide (VIP), an immunosuppressive factor found in the aqueous humor, is a modulator of the corneal endothelium (CE) stimulating its intracellular cAMP production.

METHODS

Rabbit CE cells in cell culture and CE cells in cornea cup organ cultures established from bovine and human donor eyes were treated with VIP at varying concentrations (0, 10(-11)-10(-6) mol/L) for a constant time (4 minutes) or varying times (1, 3.25, 10, 15 minutes) at a constant concentration (1 x 10(-6) mol/L). Intracellular cAMP was extracted and its concentrations were determined by radioimmunoassay. Agonists that are known to modulate the intracellular cAMP concentrations of target cells were allowed to react with cultured rabbit CE cells at 1 x 10(-6) mol/L for 4 minutes.

RESULTS

Vasoactive intestinal peptide stimulated the intracellular cAMP production in CE cells in a dose- and time-dependent manner. At concentrations lower than 10(-9) mol/L, VIP showed little effect. Treatment with 10(-8), 10(-7), and 10(-6) mol/L VIP for 4 minutes, however, increased the intracellular cAMP by 5.7-, 12.3-, and 9.5-fold, respectively, compared with the basal level in rabbit CE cell cultures, and by 19.5-, 38.7-, and 23.3-fold, respectively, in CE cells in bovine cornea cups. The effect of VIP was confirmed in two pairs of donor human corneas in which an average of 2.7-fold stimulation by 5 x 10(-7) mol/L was observed. Treatment of rabbit CE cells with 1 x 10(-6) mol//L VIP for 1 to 15 minutes elevated the intracellular cAMP level by six- to 69-fold. Among the agonists tested, alpha-melanocyte-stimulating hormone and glucagon were not effective, whereas l-isoproterenol and prostaglandin E1 were capable of stimulating the intracellular cAMP levels in rabbit CE cells.

CONCLUSIONS

The current study demonstrated that VIP stimulated cAMP production in CE cells, similar to that shown previously in trabecular meshwork and nonpigmented ciliary epithelial cells. Tissues bathed in the aqueous humor are thus responsive to VIP modulation.

Activin type II receptors in embryonic dorsal root ganglion neurons of the chicken

Activin induces neuropeptide expression in chicken ciliary ganglion neurons. To determine if activin might also influence neuropeptide expression in developing sensory neurons, we examined whether type II activin receptors are expressed during embryonic development of the chicken dorsal root ganglia (DRG), and also examined the effects of activin on neuropeptide expression in cultured DRG neurons. Using reverse transcription polymerase chain reaction (rtPCR), we detected mRNAs for both the activin receptors type IIA (ActRIIA) and type IIB (ActRIIB) in DRG from embryonic day 7 through posthatch day 1. With in situ hybridization, we found that morphologically identifiable neurons express mRNAs for both ActRIIA and ActRIIB. With developmental age, a subset of neurons that hybridizes more intensely with riboprobes to these receptor mRNAs becomes evident. A similar pattern of expression is observed with immunocytochemical staining using antisera against activin type II receptors. To examine whether embryonic DRG cells respond to activin we treated dissociated cultures of DRG with activin A and assessed the expression of vasoactive intestinal peptide (VIP) and calcitonin gene related peptide (CGRP) mRNAs using semiquantitative rtPCR. Activin treatment results in an increase in VIP mRNA, but does not affect CGRP mRNA levels. These observations indicate that neurons in the embryonic chicken DRG can respond to activin and suggest that activin has the potential to play a role in the development and function of DRG sensory neurons.

VIP enhances the differentiation of retinal pigment epithelium in culture: from cAMP and pp60(c-src) to melanogenesis and development of fluid transport capacity

The retinal pigment epithelium (RPE) is a single cell layer juxtaposed between the neural retina and the choroid and functions as a blood-retina barrier. The RPE performs functions essential for photoreceptor (PR) survival. Although the regulation of these functions has remained unknown, it is a distinct possibility that the RPE is under constant regulation by signaling molecules coming from the choroid and the retina. Vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide present in the retina and in the choroid, has been shown to promote the growth and differentiation of a variety of cells in tissue and organ cultures. In cultured RPE cells, VIP is the one most effective stimulator of the cAMP signaling pathway among a long list of neurotransmitters and modulators tested. For example, VIP, at 1 microM, stimulates the intracellular cAMP to 80-100- and 20-fold in 3 min in RPE cells cultured from chick embryos and adult human donor eyes, respectively. In cultured chick embryonic RPE, VIP is also shown to be a potent and effective modulator of pp60(c-src), the non-receptor tyrosine kinase present in differentiating and terminally differentiated cells. VIP stimulates both overall phosphorylation at unknown sites and phosphotyrosine dephosphorylation in pp60(c-src). A 190-kDa microtubule-associated protein is known to be one of the downstream targets in VIP-modulated signaling pathways. At the cellular level, VIP stimulates cell proliferation modestly and melanogenesis pronouncedly in growing chick embryonic RPE cultures. Ultimately, the differentiation goal of RPE cells in vivo is to perform functions that are essential for photoreceptor survival. On bare permeable supports (that is, without biological material coating), the chick embryonic RPE cells grow to become RPE sheets with a cytoarchitecture that allows the display of two of the RPE functions. These cultures demonstrate structural polarity and are functionally polarized, allowing for proper macromolecule secretion and fluid transport. VIP is shown to stimulate macromolecule secretion at the apical surface (retina facing) and the development of the capacity for fluid transport from the apical to the basal surface of the RPE sheet. In conclusion, studies in our laboratory indicate that VIP is a differentiation promotor during the development of a functional RPE. Recent advances in the molecular biology of melanogenesis and the fluid transport-linked Na-K-2Cl cotransporter in other cells will allow future studies of VIP modulated events in the RPE at the molecular level. Finally, identification of RPE differentiation factors may prove essential for the ultimate success of RPE transplantation, thus promoting the rescue of photoreceptor cells in retinal degeneration.

CREB contributes to the increased neurite outgrowth of sensory neurons induced by vasoactive intestinal polypeptide and activity-dependent neurotrophic factor

Our recent experiments suggest that vasoactive intestinal polypeptide (VIP) enhances neurite outgrowth of dissociated rat dorsal root ganglion cells, indirectly, via the release of a trophic factor from the spinal cord. In this study, we have examined the possible contribution of activity-dependent neurotrophic factor (ADNF) to the trophic actions of VIP. In addition, as we have shown that the factor mediating the trophic actions of VIP acts via protein kinase A we have also examined the contribution of CREB, which is a transcription factor activated by protein kinase A. As previously shown, supernatant taken from spinal cord incubated with VIP, significantly increased the percentage of sensory neurons with neurites. Antiserum against ADNF attenuated the trophic effect of the VIP-conditioned supernatant. Consistently, the ADNF agonist, ADNF(14) (0.001-0.1 fM), significantly enhanced the percentage of cells with neurite outgrowth. Furthermore, the trophic action of ADNF(14) was attenuated by a protein kinase A inhibitor, Rp-cAMPS, whereas the inactive isomer, Sp-cAMPS, had no effect. Preincubation of cells with 5 mcM CREB antisense oligonucleotides, attenuated the increase in neurite outgrowth induced by either the supernatant or ADNF(14). The sense oligonucleotide had no influence on the enhanced neurite outgrowth. We also found that both the supernatant and ADNF(14) induced an increase in the percentage of cells expressing phosphorylated CREB. The data suggests that VIP induces a release of neurotrophic factors, such as ADNF, which enhance neurite outgrowth. In addition, protein kinase A and CREB appear to contribute to the neurotrophic actions of VIP and ADNF. The mechanisms underlying the neurotrophic action of VIP, may have important implications for sprouting and/or synaptic reorganization of central terminals of sensory neurons, which may contribute to neuropathic pain that commonly occurs following peripheral nerve damage.

Vasoactive intestinal peptide inhibits cytokine production in T lymphocytes through cAMP-dependent and cAMP-independent mechanisms

Previous reports indicate that VIP and the structurally related peptide PACAP, inhibit IL-2 and IL-10 production in antigen-stimulated T lymphocytes. Intracellular cAMP elevation appears to be the primary transduction pathway involved. However, in the lower concentration range, an additional, cAMP-independent transduction pathway appears to mediate the VIP inhibition of cytokine production. Here, we address this question by using VIP agonists and antagonists which act through cAMP-dependent and -independent pathways. The antagonists based on the neurotensin-VIP hybrid molecule did not affect the inhibitory effect of VIP/PACAP on IL-2 and IL-10 production, confirming that astrocytes and T lymphocytes express different receptors. A lipophilic antagonist with increased membrane permeability, partially reversed the inhibitory effect of VIP/PACAP, forskolin, prostaglandin E2, and 8-bromo-cAMP without significantly affecting cAMP levels, suggesting that it acts downstream of cAMP. Two VIP agonists inhibit IL-2 and IL-10 production. One of the agonists increases cAMP, whereas the second one does not induce cAMP/cGMP. Our results indicate that VIP inhibits cytokine production in stimulated CD4+ T cells through two separate mechanisms, which involve both cAMP-dependent and cAMP-independent transduction pathways.

Mapping the active site in vasoactive intestinal peptide to a core of four amino acids: neuroprotective drug design

The understanding of the molecular mechanisms leading to peptide action entails the identification of a core active site. The major 28-aa neuropeptide, vasoactive intestinal peptide (VIP), provides neuroprotection. A lipophilic derivative with a stearyl moiety at the N-terminal and norleucine residue replacing the Met-17 was 100-fold more potent than VIP in promoting neuronal survival, acting at femtomolar-picomolar concentration. To identify the active site in VIP, over 50 related fragments containing an N-terminal stearic acid attachment and an amidated C terminus were designed, synthesized, and tested for neuroprotective properties. Stearyl-Lys-Lys-Tyr-Leu-NH2 (derived from the C terminus of VIP and the related peptide, pituitary adenylate cyclase activating peptide) captured the neurotrophic effects offered by the entire 28-aa parent lipophilic derivative and protected against beta-amyloid toxicity in vitro. Furthermore, the 4-aa lipophilic peptide recognized VIP-binding sites and enhanced choline acetyltransferase activity as well as cognitive functions in Alzheimer's disease-related in vivo models. Biodistribution studies following intranasal administration of radiolabeled peptide demonstrated intact peptide in the brain 30 min after administration. Thus, lipophilic peptide fragments offer bioavailability and stability, providing lead compounds for drug design against neurodegenerative diseases.

Complete sequence of a novel protein containing a femtomolar-activity-dependent neuroprotective peptide

The vulnerability of neurons and the irreversibility of loss make discoveries of neuroprotective compounds fundamentally important. Here, the complete coding sequence of a novel protein (828 amino acids, pI 5.99), derived from mouse neuroglial cells, is revealed. The sequence contained (1) a neuroprotective peptide, NAPVSIPQ, sharing structural and immunological homologies with the previously reported, activity-dependent neurotrophic factor; (2) a glutaredoxin active site; and (3) a zinc binding domain. Gene expression was enriched in the mouse hippocampus and cerebellum and augmented in the presence of the neuropeptide vasoactive intestinal peptide, in cerebral cortical astrocytes. In mixed neuron-astrocyte cultures, NAPVSIPQ provided neuroprotection at subfemtomolar concentrations against toxicity associated with tetrodotoxin (electrical blockade), the beta-amyloid peptide (the Alzheimer's disease neurotoxin), N-methyl-D-aspartate (excitotoxicity), and the human immunodeficiency virus envelope protein. Daily NAPVSIPQ injections to newborn apolipoprotein E-deficient mice accelerated the acquisition of developmental reflexes and prevented short-term memory deficits. Comparative studies suggested that NAPVSIPQ was more efficacious than other neuroprotective peptides in the apolipoprotein E-deficiency model. A potential basis for rational drug design against neurodegeneration is suggested with NAPVSIPQ as a lead compound. The relative enrichment of the novel mRNA transcripts in the brain and the increases found in the presence of vasoactive intestinal peptide, an established neuroprotective substance, imply a role for the cloned protein in neuronal function.

Galanin induced in sympathetic neurons after axotomy is anterogradely transported toward regenerating nerve endings

Peripheral neurons begin to express galanin after axotomy. When neurons in the superior cervical ganglion were axotomized near (about 2 mm) from the ganglion, galanin-like immunoreactivity (IR) was maximal within 72 h. Axotomy of neurons in the middle and inferior cervical ganglion complex (MICG), which could be performed 2 cm from the ganglia, led to an additional galanin increase 7 and 14 days later. This second increase was not accompanied by changes in galanin mRNA or the number of galanin-immunostained neurons. Galanin-IR was detectable in a postganglionic trunk of the MICG 2 days after axotomy. At this time, immunoreactive fibers were only seen near the lesion site, while later they were found throughout the trunk. The data suggest that galanin is actively transported toward the site of nerve crush/transection and that the second increase in galanin-IR found in the MICG may be due to a saturation of the axonal transport system.

Protection against developmental deficiencies by a lipophilic VIP analogue

Stearyl-Nle-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, the developmental and protective effects of SNV were investigated in vivo using two models of developmental retardation, hypoxia and cholinergic blockade. In both cases chronic administration of SNV during development provided protective effects. Water maze experiments on the weaned animals have demonstrated a prophylactic action for SNV and enhancement of spatial memory in animals exposed to a cholinotoxin. SNV may act by providing neuroprotection, thereby improving cognitive functions. This work is dedicated to Prof. R.J. Wurtman whose inspiration and leadership in the field of neuroscience and cognition is beyond comparison.

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.

Pituitary adenylate cyclase-activating peptide (PACAP) and PACAP type 1 receptor expression in regenerating adult mouse and rat superior cervical ganglia in vitro

Pituitary adenylate cyclase-activating polypeptide (PACAP), a regulatory peptide belonging to the vasoactive intestinal peptide (VIP) family, is widely distributed in the central and peripheral nervous system. Recent studies have shown that PACAP expression is upregulated in sensory neurons in response to axonal injury. Here we report that PACAP and PACAP type 1 receptors are located in rat and mouse superior cervical ganglia (SCG). PACAP-immunoreactivity (-IR) was demonstrated in preganglionic fibers, whereas only occasional PACAP-IR cell bodies could be observed. In situ hybridization histochemistry using 35S-labeled deoxyribonucleotide probes confirmed that PACAP mRNA was present only in occasional cell bodies. In contrast, PACAP type 1 receptor mRNA was expressed in virtually all cell bodies within the ganglia. After removal and culturing of the SCG for 24 h, there was a marked increase in PACAP mRNA, whilst PACAP type 1 receptor mRNA expression appeared to be downregulated in most nerve cell bodies except for a few scattered neurons displaying a strong upregulation. The total specific binding of PACAP to isolated SCG membranes as assayed by [125I]PACAP-27 binding showed an increase in SCG cultured for 48 h. PACAP-27 neither affected axonal outgrowth from the cultured SCG nor the survival of cells within the SCG. We conclude that PACAP and PACAP receptors are rapidly upregulated in sympathetic ganglia in response to axonal injury and that PACAP may play a role during nerve regeneration.

Neuronal protection from apoptosis by pituitary adenylate cyclase-activating polypeptide

Pituitary adenylate cyclase-activating polypeptide (PACAP) is known to have trophic effects on neurons. Apoptosis of PC12 cells was induced by depletion of serum and nerve growth factor (NGF) from culture medium. Not only high potassium-induced Ca2+ channel activation but PACAP-38 at physiological concentrations (10[-10] to 10[-8] M) protected PC12 cells from apoptosis. PACAP-38 increased Ca2+ uptake and intracellular Ca2+ concentrations in PC12 cells. The effects of PACAP-38 on cell survival and Ca2+ channels were eliminated by inhibitors for Ca2+ channels and protein kinase A, and mimicked by 8-bromo-cAMP. Mitogen-activated protein (MAP) kinase activity was stimulated by PACAP-38. These findings implicate that PACAP protects PC12 cells from apoptosis by activating Ca2+ channels via the cAMP-protein kinase A pathway to stimulate MAP kinase cascade.

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.

Age-related changes of VIP, NPY and somatostatin-immunoreactive neurons in the cerebral cortex of aged rats

Recent studies have explored certain changes with aging of neurons containing neuropeptides. The degree of loss of vasoactive intestinal polypeptide (VIP)-, neuropeptide Y (NPY)- and somatostatin-containing neurons in the aged CNS has not yet been established with certainty however, and available data is often contradictory. Changes with aging of VIP- and NPY-containing neurons were demonstrated by immunocytochemistry in this study. A major loss of VIP-immunoreactive (ir) neurons in aged rat brain was observed in the frontal cortex area 3, parietal cortex area 1, hindlimb area, temporal cortex area 1 and 2, monocular part of occipital cortex area 1, occipital cortex area 2, and retrosplenial cortex. VIP-ir cells in the frontal cortex areas 1 and 2, parietal cortex area 2, forelimb area, binocular part of the occipital cortex area 1, and the dentate gyrus were moderately decreased. The axis of VIP neurons in the aged group showed an irregular orientation tendency, especially in layers II and III. Major loss of NPY-ir neurons in aged rat brain were observed in the retrosplenial cortex, frontal cortex areas 1 and 2, parietal cortex areas 1 and 2, occipital cortex areas 1 and 2, the temporal cortex, hippocampus proper and cingulate cortex. Loss of NPY-ir neurons was observed mostly in layers V and VI. The number and length of dendritic branches also appeared to have decreased and shortened in the aged group. There were only slight decreases of somatostatin-ir cell numbers in the parietal and occipital cortex of the aged group. These results indicate the involvement of VIP and NPY-ir neurons in the aging process of cerebral cortex, and provide the morphological evidence for the decreased number of VIP and NPY neurons by immunocytochemistry in each area of cerebral cortex of aged rats.

VIP in the rat parotid gland in response to irradiation

In the present study, the immunohistochemical expression of vasoactive intestinal polypeptide (VIP) in the parotid gland of rats exposed to fractionated irradiation was examined. VIP concentration was analyzed by radioimmunoassay (RIA). Irradiation lead to a marked increase in the immunohistochemical expression of VIP in the innervation of the gland parenchyme. VIP-like immunoreactivity (LI) frequently coexisted with SP (substance P)-LI in these nerve fibers. The pattern of VIP-innervation in association with large ducts and blood vessel walls was unchanged. RIA analysis revealed a more than three-fold elevation in VIP content in the gland in response to irradiation. The increase in VIP immunoreaction and VIP content was seen at examination ten days after cessation of a five-day treatment with a total dose of 30-40 Gray. The upregulation of VIP may be related to changes in the production of neurotrophic factors and to an increased demand for a potentiation of secretagogue effects of SP.

Activity-dependent neurotrophic factor (ADNF). An extracellular neuroprotective chaperonin?

To understand and intervene in neuronal cell death, intensive investigations have been directed at the discovery of intracellular and extracellular factors that provide natural neuroprotection. This goal has fundamental importance for both rational strategies for the treatment of neurodegenerative diseases and also the delineation of molecular mechanisms that regulate nervous system differentiation and growth. We have discovered a potential interface among these fields of research with activity-dependent neurotrophic factor (ADNF), a protein containing sequence homologies to intracellular stress proteins that is found in the extracellular milieu of astroglial cells incubated with the neuropeptide vasoactive intestinal peptide (VIP). Femtomolar concentrations of ADNF and a short peptide sequence derived from it (a peptidergic active site) protected neurons from death associated with a broad range of toxins, including those related to Alzheimer's disease, the human immunodeficiency virus, excito-toxicity, and electrical blockade. Because the activity of the protein was mimicked by a short peptide fragment, this peptide is now proposed as a lead compound for drug development against neurodegeneration.

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 expression in enteric neurons is upregulated by both colchicine and axotomy

Axotomy is known to induce changes in neuropeptide expression in several types of neurons. Colchicine blocks the axonal transport and may mimic axotomy. The effects of colchicine-treatment and axotomy (local nerve crush by clamping of the gut) on enteric neurons expressing vasoactive intestinal peptide, neuropeptide Y and nitric oxide synthase were studied in rat small intestine by immunocytochemistry and in situ hybridization. Colchicine treatment significantly increased the number of submucous and myenteric neurons expressing vasoactive intestinal peptide and its mRNA. In contrast, an increase in the number of neuropeptide Y or nitric oxide synthase expressing neurons could not be detected. Axotomy markedly increased the number of myenteric vasoactive intestinal peptide-immunoreactive neurons in the segment located orally to the lesion, but not in the segment anally to the lesion, whereas that of nitric oxide synthase and neuropeptide Y expressing neurons was not affected. Double immunostaining revealed that the myenteric neurons containing nitric oxide synthase were induced by colchicine and axotomy to express vasoactive intestinal peptide. The present data indicate that colchicine and axotomy may induce marked changes in the neuropeptide expression of enteric neurons.

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.

Peptidergic transmission: from morphological correlates to functional implications

Like non-peptidergic transmitters, neuropeptides and their receptors display a wide distribution in specific cell types of the nervous system. The peptides are synthesized, typically as part of a larger precursor molecule, on the rough endoplasmic reticulum in the cell body. In the trans-Golgi network, they are sorted to the regulated secretory pathway, packaged into so-called large dense-core vesicles, and concentrated. Large dense-core vesicles are preferentially located at sites distant from active zones of synapses. Exocytosis may occur not only at synaptic specializations in axonal terminals but frequently also at nonsynaptic release sites throughout the neuron. Large dense-core vesicles are distinguished from small, clear synaptic vesicles, which contain "classical' transmitters, by their morphological appearance and, partially, their biochemical composition, the mode of stimulation required for release, the type of calcium channels involved in the exocytotic process, and the time course of recovery after stimulation. The frequently observed "diffuse' release of neuropeptides and their occurrence also in areas distant to release sites is paralleled by the existence of pronounced peptide-peptide receptor mismatches found at the light microscopic and ultrastructural level. Coexistence of neuropeptides with other peptidergic and non-peptidergic substances within the same neuron or even within the same vesicle has been established for numerous neuronal systems. In addition to exerting excitatory and inhibitory transmitter-like effects and modulating the release of other neuroactive substances in the nervous system, several neuropeptides are involved in the regulation of neuronal development.

Neuroprotective strategy for Alzheimer disease: intranasal administration of a fatty neuropeptide

Neurodegenerative diseases, in which neuronal cell disintegrate, bring about deteriorations in cognitive functions as is evidenced in millions of Alzheimer patients. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective and to play an important role in the acquisition of learning and memory. A potent lipophilic analogue to VIP now has been synthesized, [stearyl-norleucine17]VIP ([St-Nle17]VIP), that exhibited neuroprotection in model systems related to Alzheimer disease. The beta-amyloid peptide is a major component of the cerebral amyloid plaque in Alzheimer disease and has been shown to be neurotoxic. We have found a 70% loss in the number of neurons in rat cerebral cortical cultures treated with the beta-amyloid peptide (amino acids 25-35) in comparison to controls. This cell death was completely prevented by cotreatment with 0.1 pM [St-Nle17]VIP. Furthermore, characteristic deficiencies in Alzheimer disease result from death of cholinergic neurons. Rats treated with a cholinergic blocker (ethylcholine aziridium) have been used as a model for cholinergic deficits. St-Nle-VIP injected intracerebroventricularly or delivered intranasally prevented impairments in spatial learning and memory associated with cholinergic blockade. These studies suggest both an unusual therapeutic strategy for treatment of Alzheimer deficiencies and a means for noninvasive peptide administration to the brain.

A VIP hybrid antagonist: from developmental neurobiology to clinical applications

1. The 28 amino acid vasoactive intestinal peptide, VIP, was originally isolated from the intestine, following a bioassay measuring vasodilating properties. Immunocytochemistry, receptor binding assays and in situ hybridizations have demonstrated VIP abundance in the nervous system, suggesting multiple bioactivities. 2. A pharmacological approach was chosen to dissect VIP activities and a prototype VIP antagonist (Met-Hybrid) consisting of a carboxyl fragment of VIP7-28 and a six amino acid fragment of neurotensin, neurotensin6-11-VIP7-28 was synthesized. 3. This hybrid peptide was designed to maintain the binding capacity of one parent molecule (VIP), while loosing the agonistic properties, representing a classical competitive receptor antagonist. Furthermore, the new molecule exhibited increased specificity to central nervous system VIP receptors. 4. The Met-Hybrid was originally discovered as a potent inhibitor of VIP function in vivo. In the adult rodent, acute administration of the antagonist resulted in blockade of VIP-mediated potentiation of sexual behavior and chronic intracerebroventricular application impaired VIP-associated learning abilities. During ontogeny, chronic injections of the molecule resulted in neuronal damage, disruption of the diurnal rhythmicity of motor behavior, and retardation in the acquisition of neonatal reflexes in the rat. 5. During gestation, severe microcephaly was induced by acute administration of the Met-Hybrid to pregnant mice. The hybrid antagonist inhibited VIP-stimulated mitosis in whole embryo cultures and in a variety of cancer cell lines in vitro and in vivo, suggesting therapeutical potential.

Evidence of a functional VIP receptor in cultured human retinal pigment epithelium

The effect of VIP on the intracellular cyclic AMP of human retinal pigment epithelium cultures has been studied. Functional VIP receptor has been demonstrated in cultures from eyes given by five normal donors (age 16-64) (N-HRPE). But it has been found to be absent from high passage number cultures obtained from a retinitis pigmentosa eye of an 84-year-old patient (RP-HRPE). After 3 min of reaction with 1 x 10(-6) M VIP, the intracellular cyclic AMP level has increased to 5-15-fold over the basal level. The maximal effect of VIP (20-fold over the basal level) has been observed at 1 x 10(-7) M VIP. The half maximal activity of VIP is 3-5 x 10(-8) M. The present study also demonstrates the inducibility of the VIP responsiveness in RP-HRPE cultures after they have been treated with butyrate. Curr. Eye Res. 14: 1009-1014, 1995.

Attenuation of vasoactive intestinal peptide enhancement of colon carcinogenesis by ornithine decarboxylase inhibitor

The effects of combined administration of vasoactive intestinal peptide (VIP) and the ornithine decarboxylase (ODC) inhibitor, 1,3-diaminopropane (DAP), on development of colon tumors induced by azoxymethane (AOM), on ODC activity of the colon wall, and on the labelling index of colon epithelial cells were investigated in inbred Wistar rats. Rats received weekly subcutaneous injections of AOM for 10 weeks and subcutaneous injections of VIP every other day and drinking water containing DAP (2.5 milligrams) ad libitum until the end of the experiment at week 45. Administration of VIP significantly increased the incidence of colon tumors at week 45. It also resulted in significant increases in colon ODC activity and in the labelling index during administration of AOM, but not after its cessation. Administration of both DAP and VIP significantly reduced the enhanced colon carcinogenesis by VIP. The DAP significantly attenuated the VIP enhancement of colon ODC activity and of the labelling index during AOM administration. These findings indicate that ODC inhibition attenuated enhancement of colon carcinogenesis, and suggest that enhancement of colon carcinogenesis by VIP may be mediated through its polyamine biosynthesis.

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

In addition to its commonly recognized status as a neuromodulator of virtually all vital functions, including neurobiological, the neuropeptide VIP plays a role in the control of cell growth and differentiation and of neuronal survival. Through these actions, VIP, whose impact appears early in ontogeny, may possess developmental functions. VIP can be stimulatory or inhibitory on cell growth in function of the model considered. The growth regulatory actions of VIP, which are often independent of cAMP, are most likely significant when mitogenic or trophic factors, eventually released by nontarget cells, are simultaneously present in the extracellular medium. The intracellular mechanisms that mediate these actions of VIP may involve different transduction cascades triggered by subsets of VIP binding sites that may coexist in the same tissue.

Distribution and origin of the peripheral innervation of rat cervical esophagus

Several neurotransmitters, neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), galanin, enkephalin, calcitonin-gene related peptide (GGRP), substance P, as well as nitric oxide synthase (NOS), and the noradrenergic marker tyrosine-hydroxylase (TH) were localized by immunocytochemistry in the cervical esophagus of rat. Nerve fibers containing the neuropeptides, NOS, and TH were distributed in the myenteric plexus, around muscle bundles and small blood vessels. Injection of the retrograde tracer True Blue (TB) into the cervical esophagus resulted in the appearance of labeled nerve cell bodies in the superior cervical, the stellate, the nodose, the sphenopalatine, the dorsal root ganglia at levels C2-C7, and in local ganglia close to the thyroid. Most of the TB-labeled nerve cell bodies in the superior cervical ganglia contained NPY. In the stellate ganglion, a few labeled nerve cell bodies contained VIP whereas an additional few cell bodies stored VIP. In local ganglia, the majority of labeled cell bodies contained VIP. In the nodose ganglion and cervical dorsal root ganglia, the majority of the labeled nerve cell bodies stored CGRP. The results indicate that the cervical esophagus has a dense innervation with multiple neurotransmitters emanating from several ganglia. As judged by the pattern of nerve fiber distribution, they may regulate esophageal peristalsis and blood flow, some of them possibly in a cooperative manner.

Somatostatin and vasoactive intestinal peptide (VIP) in neuroblastoma and ganglioneuroma: chromatographic characterisation and release during surgery

Neuroblastomas and ganglioneuromas frequently produce somatostatin (SOM) and vasoactive intestinal peptide (VIP), and elevated concentrations in tumour tissue are associated with favourable outcome. Both somatostatin and VIP have been shown to have an autocrine effect on tumour growth and differentiation in vitro, and VIP may cause clinical symptoms when released systemically. Using gel-permeation chromatography and specific radioimmunoassays, we further characterised somatostatin-like immunoreactivity (SOM-LI) and VIP-like immunoreactivity (VIP-LI) in neuroblastoma and ganglioneuroma tumour tissue. The major part of SOM-LI and VIP-LI in both neuroblastoma and ganglioneuroma represents the biologically active forms SOM-28, SOM-14 and VIP-2, respectively. 21 children with neuroblastoma and ganglioneuroma were monitored with serial plasma samples during surgery. In 8 children with measurable concentrations of SOM-LI, all showed increased concentrations during tumour manipulation (P = 0.004) that subsequently decreased below preoperative levels in all but one case (P = 0.06). The only child presenting with diarrhoea showed the highest preoperative plasma VIP-LI in the study (54 pmol/l). 2 children with increased concentrations of VIP-LI preoperatively showed a rapid decrease after surgical tumour removal. These findings indicate a systemic release from the tumours. It is concluded that plasma and tumour tissue from children with neuroblastoma and ganglioneuroma contain biologically active molecular forms of somatostatin and vasoactive intestinal peptide. These peptides may bear significance both for specific symptoms in certain patients as well as influencing tumour growth and differentiation in vivo.

Ontogeny of pituitary adenylate cyclase-activating polypeptide (PACAP) receptors in the rat cerebellum: a quantitative autoradiographic study

Pituitary adenylate cyclase-activating polypeptide and PACAP receptors are both present in the rat cerebellar cortex, suggesting that PACAP may play an important role in the cerebellum. In the present study, the variation of the concentration of PACAP binding sites in the rat cerebellum was investigated during postnatal development by means of quantitative autoradiography, using [125I]PACAP27 as a radioligand. In the external granule cell layer and the medulla, the density of PACAP binding sites was high at birth, markedly decreased from postnatal day 8 (P8) to P25 and finally vanished at the end of the third postnatal week. In the internal granule cell layer and molecular layer, PACAP binding sites were first detected at P8. In the internal granule cell layer, the density of binding sites slightly decreased during development but remained elevated in adults. Conversely, in the molecular layer, PACAP binding sites rapidly decreased during the second and third postnatal weeks and virtually disappeared after P25. In all four layers of the cerebellar cortex, the autoradiographic labeling was displaced by PACAP27 (IC50 close to 10(-8) M), but was not affected by VIP. No significant changes in IC50 and Hill coefficient were noticed in the various layers throughout development. The present study shows that all four layers of the cerebellar cortex express PACAP binding sites during development. The evolution of the receptor concentration exhibited differential profiles in the various layers but the specificity characteristics of the recognition sites were identical in all four structures.(ABSTRACT TRUNCATED AT 250 WORDS)

Neurotrophins and ciliary neurotrophic factor: their biology and pathology

Neurotrophins (NTFs) and ciliary neurotrophic factor (CNTF) induce the differentiation of neuronal cells, rescue them from naturally occurring death, and trigger neuronal regeneration. The NTFs bind to two classes of cell surface receptors, whereas CNTF receptor is composed of three subunits. The functions of these polypeptide survival factors with trophic action on nerve cells have recently been approached by the targeted disruption of the CNTF, NTF and their receptor genes by the homologous recombination technique. The embryonic growth and morphogenesis of these gene 'knock-out' mice is normal, but they develop with defects in various subsets of the peripheral nervous system, and the homozygous mutant mice often die during the early postnatal period. Disturbances in the biology of NTFs and CNTF have recently been implicated in the pathogenesis of certain common neurodegenerative disorders, such as Parkinson's disease, motor neurone diseases, and Alzheimer's disease. Intensive research on their pharmaceutical perspective has, therefore, been provoked. All neurotrophins and CNTF can now be synthesized on a large scale as biologically active recombinant proteins, and several alternatives for their local applications to the target tissue have been presented. Their therapeutic potential is discussed.

Peptide-containing nerve fibers in the parathyroid glands of different species

Several neuropeptides, calcitonin gene-related peptide (CGRP), galanin, neuropeptide Y (NPY), pituitary adenylate cyclase activating peptide (PACAP), substance P (SP), vasoactive intestinal polypeptide (VIP), the noradrenergic marker dopamine beta-hydroxylase (DBH) and the general neuroendocrine marker PGP 9.5 were localized by immunocytochemistry in the parathyroid glands of chicken, rat, guinea-pig, cat, dog and sheep. The general density of innervation varied markedly among the species. Nerve fibers storing CGRP, NPY, PACAP, SP and VIP were present in all species examined. Galanin-containing fibers occurred in all species except guinea-pig and adrenergic (DBH-containing) fibers in all species except chicken and guinea-pig. Generally, the nerve fibers were distributed around blood vessels, in the parenchyma as single scattered fibers, and often also within the capsule. Coexistence studies were performed in cat and sheep. CGRP and SP invariably coexisted in the same nerve fibers. Further, CGRP partially coexisted with PACAP, NPY was observed in the same nerve fibers as DBH. A small population of NPY-containing fibers also seemed to contain galanin (cat only). VIP and NPY coexisted in a population of nerve fibers in the parenchyma. A population of VIP-containing fibers also seemed to contain PACAP. The results indicate the presence of several neuropeptides in the parathyroid glands. As judged by their distribution patterns they may regulate both secretory activity and blood flow, some of them possibly in a cooperative manner.

Inhibition of human neuroblastoma growth by a specific VIP antagonist

The 28-amino-acid neuropeptide, vasoactive intestinal peptide (VIP), is a potent mitogen during embryonic development and plays a vital role in brain growth. VIP is also mitogenic for tumor cells, including the human neuroblastoma (NMB). Northern blot analysis has revealed VIP mRNA transcripts in NMB. We now report VIP-like immunoreactivity within these neuroblastoma cells that increased during logarithmic growth and decreased after attaining confluency. About 10(6) seeded cells secreted 5-40 pg of VIP-like immunoreactivity into the medium. These results suggest an autocrine role for VIP in the regulation of neuroblastoma growth. A VIP hybrid antagonist (neurotensin6-11 VIP7-28) that has been shown to inhibit lung cancer proliferation was now tested for inhibition of neuroblastoma growth. Receptor binding studies indicated that the hybrid antagonist displaced [125I]-VIP binding in the neuroblastoma cells (EC50 = 5 x 10(-6)M). Furthermore, as measured by thymidine incorporation and by cell counts, the potent VIP hybrid antagonist inhibited neuroblastoma multiplication in a dose-dependent manner. In conclusion, VIP may be an important regulator of growth of nerve cell progenitors and of tumors derived from neuronal origin and intervening with VIP function may lead to improved treatment of cancer.

Learning and sexual deficiencies in transgenic mice carrying a chimeric vasoactive intestinal peptide gene

The molecular mechanisms responsible for behavior are largely unknown. A state of the art model, paving the path from genes to behavior, is offered by transgenic animals. Candidate molecules are classic neuropeptides, such as vasoactive intestinal peptide (VIP). Transgenic mice harboring a chimeric VIP gene driven by the polyoma promoter were produced. Behavioral studies revealed learning impairment and prolonged retardation in memory acquisition in the genetically altered animals. Furthermore, reduced performance was observed when the male transgenic mice were tested for sexual activity in the presence of receptive females. Surprisingly, radioimmunoassays showed an approx 20% decrease in the VIP content of the transgenic mice brains. To directly assess genetically reduced VIP content as a cause for learning impairment, transgenic mice carrying diphtheria toxin-encoding sequences driven by the rat VIP promoter were created. These animals had reduced brain VIP and exhibited deficiencies in learning abilities, strongly supporting an important neurobiological function for VIP in vivo.