A femtomolar-acting neuroprotective peptide

Measurement of Vasoactive Intestinal Peptide using a Competitive Fluorescent Microsphere Immunoassay or ELISA in human blood samples

The concentration of Vasoactive Intestinal Peptide (VIP) as measured by recycling immunoaffinity chromatography (RIC) has been reported to be elevated in the blood of patients with autism as compared with normal subjects. In this study, we have developed a "Competitive Fluorescent Microsphere Immunoassay" (cFMI) in which VIP competes with biotinylated VIP in binding to polyclonal antibodies on microspheres. The results were obtained using the Luminex100 system. We measured VIP in serum, plasma, and material eluted from dried blood spots on filter paper with both the cFMI and an ELISA procedure. We found that a purification procedure was necessary for obtaining useful results from plasma and serum, however, a preincubation step was required with the blood eluates. This newly developed cFMI was more sensitive (2.5 vs. 20.0 pg/ml), and more reproducible than the ELISA. To get accurate measurements of VIP in eluted material high sensitivity is especially important. Thus, the cFMI using the Luminex system has definite advantages over a conventional ELISA including the possibility that samples can be assayed at higher dilutions. We have determined that the VIP concentrations of serum, plasma, and dried blood spot eluate specimens as measured with the cFMI assay system were similar to those measured with ELISA. Thus, the new cFMI using Luminex system may be useful for detection of VIP in human blood samples.

Microglial NADPH oxidase is a novel target for femtomolar neuroprotection against oxidative stress

Inflammation has been increasingly recognized to contribute to the pathogenesis of Parkinson's disease. Several compounds are neuroprotective at femtomolar concentrations through the inhibition of inflammation. However, the mechanisms mediating femtomolar-acting compounds are poorly understood. Here we show that both gly-gly-phe (GGF), a tri-peptide contained in the dynorphin opioid peptide, and naloxone are neuroprotective at femtomolar concentrations against LPS-induced dopaminergic neurotoxicity through the reduction of microglial activation. Mechanistic studies demonstrated the critical role of NADPH oxidase in the GGF and naloxone inhibition of microglial activation and associated DA neurotoxicity. Pharmacophore analysis of the neuroprotective dynorphin peptides and naloxone revealed common chemical properties (hydrogen bond acceptor, hydrogen bond donor, positive ionizable, hydrophobic) of these femtomolar-acting compounds. These results support a common high-affinity site of action for several femtomolar-acting compounds, where NADPH oxidase is the critical mechanism governing neuroprotection, suggesting a novel avenue of anti-inflammatory and neuroprotective therapy.

Neuroprotective effect of activity-dependent neurotrophic factor against toxicity from familial amyotrophic lateral sclerosis-linked mutant SOD1 in vitro and in vivo

Amyotrophic lateral sclerosis (ALS) is the most common fatal motor neuron disease, affecting mostly middle-aged people. There are no curative therapies for ALS. Several lines of evidence have supported the notion that the proapoptotic property of familial ALS (FALS)-linked mutant Cu/Zn-superoxide dismutase-1 (SOD1) genes may play an important role in the pathogenesis of some FALS cases. Here we found that activity-dependent neurotrophic factor (ADNF), a neurotrophic factor originally identified to have the anti-Alzheimer's disease (AD) activity, protected against neuronal cell death caused by FALS-linked A4T-, G85R- and G93R-SOD1 in a dose-responsive fashion. Notably, ADNF-mediated complete suppression of SOD1 mutant-induced neuronal cell death occurs at concentrations as low as 100 fM. ADNF maintains the neuroprotective activity even at concentrations of more than 1 nM. This is in clear contrast to the previous finding that ADNF loses its protective activity against neurotoxicity induced by AD-relevant insults, including some familial AD genes and amyloid beta peptide at concentrations of more than 1 nM. Characterization of the neuroprotective activity of ADNF against cell death caused by SOD1 mutants revealed that CaMKIV and certain tyrosine kinases are involved in ADNF-mediated neuroprotection. Moreover, in vivo studies showed that intracerebroventricularly administered ADNF significantly improved motor performance of G93A-SOD1 transgenic mice, a widely used model of FALS, although survival was extended only marginally. Thus, the neuroprotective activity of ADNF provides a novel insight into the development of curative drugs for ALS.

Sexual dimorphism of activity-dependent neuroprotective protein in the mouse arcuate nucleus

Activity-dependent neuroprotective protein (ADNP) is a highly conserved vasoactive intestinal peptide (VIP) responsive gene that is expressed abundantly in the brain and in the body and is essential for brain formation and embryonic development. Since, VIP exhibits sexual dimorphism in the hypothalamus, the potential differential expression of ADNP in male and female mice was investigated. Real-time polymerase chain reaction revealed sexual dimorphism in ADNP mRNA expression as well as fluctuations within the estrus cycle. Immunohistochemistry with an antibody to ADNP showed specific staining in the arcuate nucleus of the hypothalamus. ADNP-like immunoreactivity in the arcuate nucleus also exhibited fluctuations during the estrus cycle. Here, brain sections at proestrus were the most immunoreactive and brain sections at estrus--the least. Furthermore, male arcuate nucleus ADNP-like immunoreactivity was significantly lower than that of the female estrus. Many neuropeptides, neurotransmitters and proteins are localized to the arcuate nucleus where they contribute to the regulation of reproductive cyclicity and energy homeostasis. The results presented here suggest that ADNP has a part in the estrus cycle as an affecter or an effector.

Therapeutic and preventive interventions for postulated vasoactive neuropeptide autoimmune fatigue-related disorders

Major advances have been made in understanding the relatively novel group of vasoactive (vasodilatory) neuropeptides (VNs) in humans. VNs comprise a novel but expanding group of substances having immunoregulation, inflammation modulation, neurotransmitter, neurotrophic, hormonal and metabolic functions. These substances may control gene expression for mRNA for themselves and their receptors. They have complex relationships with gaseous and other neurotransmitters and xenobiotic substances. Theoretical arguments have implicated these substances in autoimmune phenomena resulting in fatigue-related conditions such as chronic fatigue syndrome (CFS), sudden infant death syndrome (SIDS), fibromyalgia (FM) and Gulf War syndrome (GWS) but remain unproven. As well as possibly spontaneous onset, the precipitating causes of VN autoimmune dysfunction are likely to be a combination of genetic predisposition, infection and xenobiotic substances. Therapeutic and preventive possibilities for postulated VN autoimmune conditions will be influenced by the complex patholophysiology underpinning them. Some speculative possibilities are VN substitution/replacement, preservation of biological effect, epigenetic DNA modifications, plasma exchange, anti-cholinesterases, e.g., pyridostigmine, corticosteroids and other drug treatments, thymectomy, intravenous immunoglobulin and anti-idiotype antibodies, and CpG/DNA vaccines. Prevention and treatment of possible VN autoimmune fatigue-related disorders may prove to be important areas for future research and development.

Differential regulation of activity-dependent neuroprotective protein in rat astrocytes by VIP and PACAP

Activity-dependent neuroprotective protein (ADNP) was shown to be a vasoactive intestinal peptide (VIP) responsive gene in astrocytes derived from the cerebral cortex of newborn rats. The present study was set out to identify VIP receptors that are associated with increases in ADNP expression in developing astrocytes. Using VIP analogues specific for the VPAC1 and the VPAC2 receptors, it was discovered that VIP induced changes in ADNP expression in astrocytes via the VPAC2 receptor. The constitutive synthesis of ADNP and VPAC2 was shown to be age-dependent and increased as the astrocyte culture developed. Pituitary adenylate cyclase-activating polypeptide (PACAP) also induced changes in ADNP expression. The apparent changes induced by VIP and PACAP on ADNP expression were developmentally dependent, and while stimulating expression in young astrocytes, an inhibition was demonstrated in older cultures. In conclusion, VIP, PACAP and the VPAC2 receptor may all contribute to the regulation of ADNP gene expression in the developing astrocyte.

Clinical endocrinology and metabolism. Potential clinical applications of vasoactive intestinal peptide: a selected update

Neuropeptides are expressed in neurons innervating endocrine cells or in endocrine cells and cancer cells, and are released on site to act as hormones and growth factors. Vasoactive intestinal peptide (VIP) was first discovered in the early 1970s and has since become the area of research for many laboratories. VIP has a neuroendocrine role as it is intimately involved with the synthesis, secretion and action of other neuroendocrine hormones as well as cytokines and chemokines. Major outcomes of VIP downregulation encompass developmental and behavioral dysfunctions, including impaired diurnal rhythms. Overexpression of VIP has been associated with diarrhea and cancer, and overexpression of VIP receptors is associated with cancerous growth. This short review outlines some of the recent progress made in VIP research.

Cytotoxic mechanisms by M239V presenilin 2, a little-analyzed Alzheimer's disease-causative mutant

Although neurotoxic functions are well characterized in familial Alzheimer's disease (FAD)-linked N141I mutant of presenilin (PS)2, little has been known about M239V-PS2, another established FAD-causative mutant. We found that expression of M239V-PS2 caused neuronal cytotoxicity. M239V-PS2 exerted three forms of cytotoxicity: one was sensitive to both an antioxidant glutathione-ethyl-ester (GEE) and a caspase inhibitor Ac-DEVD-CHO (DEVD); the second was sensitive to GEE but resistant to DEVD; and the third was resistant to both. The GEE/DEVD-sensitive cytotoxicity by M239V-PS2 was likely through NADPH oxidase and the GEE-sensitive/DEVD-resistant cytotoxicity through xanthine oxidase (XO). Both mechanisms by M239V-PS2 were suppressed by pertussis toxin (PTX) and were mediated by Galpha(o), but not by Galpha(i). Although Abeta1-43 itself induced no cytotoxicity, Abeta1-43 potentiated all three components of M239V-PS2 cytotoxicity. As these cytotoxic mechanisms by M239V-PS2 are fully shared with N141I-PS2, they are most likely implicated in the pathomechanism of FAD by PS2 mutations. Notably, cytotoxicity by M239V-PS2 could be inhibited by the combination of two clinically usable inhibitors of superoxide-generating enzymes, apocynin and oxypurinol.

A Femtomolar Acting Octapeptide Interacts with Tubulin and Protects Astrocytes against Zinc Intoxication

An octapeptide was previously described that protects neurons against a wide variety of insults directly and indirectly as a result of interactions (at femtomolar concentrations) with supporting glial cells. The current study set out to identify the octapeptide binding molecules so as to understand the high affinity mechanisms of cellular protection. Studies utilizing affinity chromatography of brain extracts identified tubulin, the brain major protein, as the octapeptide-binding ligand. Dot blot analysis with pure tubulin and the biotinylated octapeptide verified this finding. When added to cerebral cortical astrocytes, the octapeptide (10(-15)-10(-10) m) induced a rapid microtubule reorganization into distinct microtubular structures that were stained by monoclonal tubulin antibodies and visualized by confocal microscopy. Fluorescein-labeled octapeptide induced a similar change and was detected in the intracellular milieu, even when cells were incubated at 4 degrees C or at low pH. In a cell-free system, the octapeptide stimulated tubulin assembly into microtubules. Furthermore, treatment of astrocytes with zinc chloride resulted in microtubule disassembly and cell death that was protected by the octapeptide. In conclusion, the results suggest that the octapeptide crosses the plasma membrane and interacts directly with tubulin, the microtubule subunit, to induce microtubule reorganization and improved survival. Because microtubules are the key component of the neuronal and glial cytoskeleton that regulates cell division, differentiation, and protection, this finding may explain the breadth and efficiency of the cellular protective capacities of the octapeptide.

Humanin antagonists: mutants that interfere with dimerization inhibit neuroprotection by Humanin

The 24-residue peptide Humanin (HN) protects neuronal cells from insults of various Alzheimer's disease (AD) genes and Abeta by forming a homodimer. We have previously shown that P3A, S7A, C8A, L9A, L12A, T13A, S14A and P19A mutations nullify the neuroprotective function of HN [Yamagishi, Y., Hashimoto, Y., Niikura, T. & Nishimoto, I. (2003) Peptides, 24, 585-595]. Here we examined whether any of these 'null' mutants could function as dominant-negative mutants. Homodimerization-defective mutants, P3A-, L12A-, S14A- and P19A-HN, specifically blocked neuroprotection by HN, but not by activity-dependent neurotrophic factor. Furthermore, insertion of S7A, the mutation that blocks the homodimerization of HN, but not insertion of G5A abolished the antagonizing function of L12A-HN. While L12A-HN and G5A/L12A-HN actually inhibited HN homodimerization, S7A/L12A-HN had no effect. These data indicate that P3A-, L12A-, S14A- and P19A-HN function as HN antagonists by forming an inactive dimer with HN. This study provides a novel insight into the understanding of the in vivo function of HN, as well as into the development of clinically applicable HN neutralizers.

Role of vasoactive intestinal peptide and inflammatory mediators in enteric neuronal plasticity

Complex circuits involving both local intrinsic neurones (i.e. enteric nervous system; ENS) and extrinsic neurones achieve nervous control of digestive functions. The ENS is comprised of many functionally different types of neurons: sensory neurons, interneurons and secreto-motor neurons. Each neuronal population is required to manifest local reflex behavior and is central to the regulation of both motor and secretory activities. It must be emphasized, however, that not only muscle and secretory cells but also other intestinal cells are targeted by enteric neurones, i.e. endocrine cells, interstitial cells of Cajal, immune cells, blood vessels and enteric glia. In addition to the ENS the gastrointestinal tract receives an extrinsic innervation by sympathetic, parasympathetic and sensory fibres. Neuronal projections from the intestine to prevertebral ganglia also exist. Taken together, the picture of a complex nervous regulation of digestive functions highly integrated with the central nervous system and the rest of the autonomic nervous system has emerged. The ENS is adaptive and plastic, but also vulnerable, system and ENS disturbances may be of pathogenic importance in functional bowel disease. In particular the interplay between the enteric neurones and the immune cells is suggested to be of crucial importance. The review discusses possible roles of the mediators vasoactive intestinal peptide (VIP) and prostanoids in ENS plasticity in response to injury and inflammation.

Protective peptides that are orally active and mechanistically nonchiral

Previous reports identified two peptides that mimic the action of neuroprotective proteins derived from astrocytes. These peptides, NAPVSIPQ and SALLRSIPA, prevent neuronal cell death produced by electrical blockade, N-methyl-d-aspartate, and beta-amyloid peptide (25-35). In the present study, all d-amino acid peptides of NAPVSIPQ and SALLRSIPA were synthesized and compared respectively to the corresponding all l-amino acid peptides. In rat cerebral cortical test cultures cotreated with 1 microM tetrodotoxin, the d-amino acid peptides produced similar potency and efficacy for neuroprotection as that observed for their respective l-amino acid peptides. Since all these peptides tested individually exhibited attenuation of efficacy at concentrations of >10 pM, combinations of these peptides were tested for possible synergies. Equimolar d-NAPVSIPQ and d-SALLRSIPA combination treatment produced potent neuroprotection (EC(50), 0.03 fM) that did not attenuate with increasing concentrations. Similarly, the combination of l-NAPVSIPQ and d-SALLRSIPA also had high potency (EC(50), 0.07 fM) without attenuation of efficacy. Combined administration of peptides was tested in a model of fetal alcohol syndrome and in a model of learning impairment: apolipoprotein E knockout mice. Intraperitoneal administration of d-NAPVSIPQ plus d-SALLRSIPA to pregnant mice (embryonic day 8) attenuated fetal demise after treatment with an acute high dose of alcohol. Furthermore, oral administration of d-NAPVSIPQ plus d-SALLRSIPA significantly increased fetal survival after maternal alcohol treatment. Apolipoprotein E knockout mice injected with d-NAPVSIPQ plus d-SALLRSIPA showed improved performance in the Morris water maze. These studies suggest therapeutic potential for the combined administration of neuroprotective peptides that can act through a mechanism independent of chiral recognition.

Discovering novel phenotype-selective neurotrophic factors to treat neurodegenerative diseases

Astrocytes and neurons in the central nervous system (CNS) interact functionally to mediate processes as diverse as neuroprotection, neurogenesis and synaptogenesis. Moreover, the interaction can be homotypic, implying that astrocyte-derived secreted molecules affect their adjacent neurons optimally vs remote neurons. Astrocytes produce neurotrophic and extracellular matrix molecules that affect neuronal growth, development and survival, synaptic development, stabilization and functioning, and neurogenesis. This new knowledge offers the opportunity of developing astrocyte-derived, secreted proteins as a new class of therapeutics specifically to treat diseases of the CNS. However, primary astrocytes proliferate slowly in vitro, and when induced to immortalize by genetic manipulation, tend to lose their phenotype. These problems have limited the development of astrocytes as sources of potential drug candidates. We have successfully developed a method to induce spontaneous immortalization of astrocytes. Gene expression analysis, karyotyping and activity profiling data show that these spontaneously immortalized type-1 astrocyte cell lines retain the properties of their primary parents. The method is generic, such that cell lines can be prepared from any region of the CNS. To date, a library of 70 cell lines from four regions of the CNS: ventral mesencephalon, striatum, cerebral cortex and hippocampus, has been created. A phenotype-selective neurotrophic factor for dopaminergic neurons has been discovered from one of the cell lines (VMCL1). This mesencephalic astrocyte-derived neurotrophic factor (MANF) is a 20 kD, glycosylated, human secreted protein. Homologs of this protein have been identified in 16 other species including C. elegans. These new developments offer the opportunity of creating a library of astrocyte-derived molecules, and developing the ones with the best therapeutic indices for clinical use.

Ethanol Antagonist Peptides: Structural Specificity without Stereospecificity

Increasing evidence suggests that ethanol damages the developing nervous system partly by disrupting the L1 cell adhesion molecule. Ethanol inhibits L1-mediated cell adhesion, and compounds that antagonize this action also prevent ethanol-induced embryotoxicity. Two such compounds are the small peptides NAPVSIPQ (NAP) and SALLRSIPA (SAL). We showed previously that NAP and SAL antagonize ethanol inhibition of L1 adhesion at femtomolar to picomolar concentrations. Here we demonstrate that, despite this extraordinary potency, both NAP and SAL lack stereospecificity. d-NAP, a peptide composed entirely of d-amino acids, was an effective ethanol antagonist in NIH/3T3 cells transfected with human L1 and in the NG108-15 neural cell line. Interestingly, Ala-substituted derivatives of d-NAP demonstrate the same structure-activity relation as the corresponding derivatives of l-NAP. The Ser-Ile-Pro motif was important for the ethanol antagonist activity of d-NAP, l-NAP, and l-SAL, with Ile being the most critical element in all three. Like l-NAP, d-NAP effectively reduced ethanol-induced growth retardation in mouse whole embryo culture. The potential resistance of d-peptides to proteases makes d-NAP a potentially attractive agent for the prevention of fetal alcohol syndrome.

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.

A three amino acid peptide, Gly-Pro-Arg, protects and rescues cell death induced by amyloid β-peptide

Amyloid beta-peptide (Abeta) contributes to the pathogenesis of Alzheimer's disease (AD), causing neuronal death through apoptosis. In this study, the neuroprotective role of small peptides, Gly-Pro-Glu (GPE), Gly-Glu (GE), Gly-Pro-Asp (GPD), and Gly-Pro-Arg (GPR) were examined against Abeta-induced toxicity in cultured rat hippocampal neurons. We report here that GPR (10-100 microM) prevented Abeta-mediated increase in lactate dehydrogenase (LDH) release and Abeta inhibition of MTT reduction, even in neurons that were pre-exposed to Abeta for 24 or 48 h. Since GPR prevented Abeta inhibition of MTT reduction, the anti-apoptotic effect of GPR was studied by examining activation of caspase-3 and expression of p53 protein. Caspase-3 was significantly activated by 20 microM Abeta25-35 and 5 microM Abeta1-40, but GPR effectively prevented the Abeta-mediated activation of caspase-3. Similarly, Abeta increased numbers of p53-positive cells, but GPR prevented this Abeta effect. Our findings suggest that GPR can rescue cultured rat hippocampal neurons from Abeta-induced neuronal death by inhibiting caspase-3/p53-dependent apoptosis.

Vasoactive intestinal peptide in the brain of a mouse model for Down syndrome

The most common genetic cause of mental retardation is Down syndrome, trisomy of chromosome 21, which is accompanied by small stature, developmental delays, and mental retardation. In the Ts65Dn segmental trisomy mouse model of Down syndrome, the section of mouse chromosome 16 most homologous to human chromosome 21 is trisomic. This model exhibits aspects of Down syndrome including growth restriction, delay in achieving developmental milestones, and cognitive dysfunction. Recent data link vasoactive intestinal peptide malfunction with developmental delays and cognitive deficits. Blockage of vasoactive intestinal peptide during rodent development results in growth and developmental delays, neuronal dystrophy, and, in adults, cognitive dysfunction. Also, vasoactive intestinal peptide is elevated in the blood of newborn children with autism and Down syndrome. In the current experiments, vasoactive intestinal peptide binding sites were significantly increased in several brain areas of the segmental trisomy mouse, including the olfactory bulb, hippocampus, cortex, caudate/putamen, and cerebellum, compared with wild-type littermates. In situ hybridization for VIP mRNA revealed significantly more dense vasoactive intestinal peptide mRNA in the hippocampus, cortex, raphe nuclei, and vestibular nuclei in the segmental trisomy mouse compared with wild-type littermates. In the segmental trisomy mouse cortex and hippocampus, over three times as many vasoactive intestinal peptide-immunopositive cells were visible than in wild-type mouse cortex. These abnormalities in vasoactive intestinal peptide parameters in the segmental trisomy model of Down syndrome suggest that vasoactive intestinal peptide may have a role in the neuropathology of Down-like cognitive dysfunction.

Characterization of the toxic mechanism triggered by Alzheimer's amyloid-beta peptides via p75 neurotrophin receptor in neuronal hybrid cells

Neuronal pathology of the brain with Alzheimer's disease (AD) is characterized by numerous depositions of amyloid-beta peptides (Abeta). Abeta binding to the 75-kDa neurotrophin receptor (p75NTR) causes neuronal cell death. Here we report that Abeta causes cell death in neuronal hybrid cells transfected with p75NTR, but not in nontransfected cells, and that p75NTR(L401K) cannot mediate Abeta neurotoxicity. We analyzed the cytotoxic pathway by transfecting pertussis toxin (PTX)-resistant G protein alpha subunits in the presence of PTX and identified that Galpha(o), but not Galpha(i), proteins are involved in p75NTR-mediated Abeta neurotoxicity. Further investigation suggested that Abeta neurotoxicity via p75NTR involved JNK, NADPH oxidase, and caspases-9/3 and was inhibited by activity-dependent neurotrophic factor, insulin-like growth factor-I, basic fibroblast growth factor, and Humanin, as observed in primary neuron cultures. Understanding the Abeta neurotoxic mechanism would contribute significantly to the development of anti-AD therapies.

MANF: a new mesencephalic, astrocyte-derived neurotrophic factor with selectivity for dopaminergic neurons

We describe the discovery of a novel, 20 kDa, secreted human protein named mesencephalic astrocyte-derived neurotrophic factor, or MANF. The homologous, native molecule was initially derived from a rat mesencephalic type-1 astrocyte cell line and recombinant MANF subcloned from a cDNA encoding human arginine-rich protein. MANF selectively protects nigral dopaminergic neurons, versus GABAergic or serotonergic neurons. The discovery of MANF marks a more systematic approach in the search for astrocyte-derived, secreted proteins that selectively protect specific neuronal phenotypes. Compared to glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), MANF was more selective in the protection of dopaminergic neurons at lower (0.05-0.25 ng/mL) and middle (0.5-2.5 ng/mL) concentrations: MANF>GDNF>BDNF. GDNF was more selective at higher concentrations (25-50 ng/ml): GDNF>MANF>BDNF. Two domains in MANF of 39-AA and 109-AA respectively, and eight cysteines are conserved from C. elegans to man. MANF is encoded by a 4.3 Kb gene with 4 exons, and is located on the short arm of human chromosome 3. The secondary structure is dominated by alpha-helices (47%) and random coils (37%). Studies to determine the localization of MANF in the brains of rat, monkey, and man, as well as the receptor, signaling pathways, and biologically active peptide mimetics are in progress. The selective, neuroprotective effect of MANF for dopaminergic neurons suggests that it may be indicated for the treatment of Parkinson's disease.

MANF: a new mesencephalic, astrocyte-derived neurotrophic factor with selectivity for dopaminergic neurons

We describe the discovery of a novel, 20 kDa, secreted human protein named mesencephalic astrocyte-derived neurotrophic factor, or MANF. The homologous, native molecule was initially derived from a rat mesencephalic type-1 astrocyte cell line and recombinant MANF subcloned from a cDNA encoding human arginine-rich protein. MANF selectively protects nigral dopaminergic neurons, versus GABAergic or serotonergic neurons. The discovery of MANF marks a more systematic approach in the search for astrocyte-derived, secreted proteins that selectively protect specific neuronal phenotypes. Compared to glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), MANF was more selective in the protection of dopaminergic neurons at lower (0.05-0.25 ng/mL) and middle (0.5-2.5 ng/mL) concentrations: MANF>GDNF>BDNF. GDNF was more selective at higher concentrations (25-50 ng/ml): GDNF>MANF>BDNF. Two domains in MANF of 39-AA and 109-AA respectively, and eight cysteines are conserved from C. elegans to man. MANF is encoded by a 4.3 Kb gene with 4 exons, and is located on the short arm of human chromosome 3. The secondary structure is dominated by alpha-helices (47%) and random coils (37%). Studies to determine the localization of MANF in the brains of rat, monkey, and man, as well as the receptor, signaling pathways, and biologically active peptide mimetics are in progress. The selective, neuroprotective effect of MANF for dopaminergic neurons suggests that it may be indicated for the treatment of Parkinson's disease.

Differential effects of ethanol antagonism and neuroprotection in peptide fragment NAPVSIPQ prevention of ethanol-induced developmental toxicity

NAPVSIPQ (NAP), an active fragment of the glial-derived activity-dependent neuroprotective protein, is protective at femtomolar concentrations against a wide array of neural insults and prevents ethanol-induced fetal wastage and growth retardation in mice. NAP also antagonizes ethanol inhibition of L1-mediated cell adhesion (ethanol antagonism). We performed an Ala scanning substitution of NAP to determine the role of ethanol antagonism and neuroprotection in NAP prevention of ethanol embryotoxicity. The Ser-Ile-Pro region of NAP was crucial for both ethanol antagonism and protection of cortical neurons from tetrodotoxin toxicity (neuroprotection). Ala replacement of either Ser-5 or Pro-7 (P7A-NAP) abolished NAP neuroprotection but minimally changed the efficacy of NAP ethanol antagonism. In contrast, Ala replacement of Ile-6 (I6A-NAP) caused a decrease in potency (>2 logarithmic orders) with only a small reduction (<10%) in the efficacy of NAP neuroprotection but markedly reduced the efficacy (50%) and the potency (5 logarithmic orders) of NAP ethanol antagonism. Ethanol significantly reduced the number of paired somites in mouse whole-embryo culture; this effect was prevented significantly by 100 pM NAP or by 100 pM P7A-NAP, but not by 100 pM I6A-NAP. The structure-activity relation for NAP prevention of ethanol embryotoxicity was similar to that for NAP ethanol antagonism and different from that for NAP neuroprotection. These findings support the hypothesis that NAP antagonism of ethanol inhibition of L1 adhesion plays a central role in NAP prevention of ethanol embryotoxicity and highlight the potential importance of ethanol effects on L1 in the pathophysiology of fetal alcohol syndrome.

Complex array of cytokines released by vasoactive intestinal peptide

A complex mixture of five cytokines has been shown to be released by vasoactive intestinal peptide (VIP). Cytokines were measured in paired samples of culture medium and astroglial cytosol by capillary electrophoresis. This is the first description of VIP-mediated release for TNF-alpha, IL-3, G-CSF and M-CSF from astrocyte cultures. Kinetic studies after VIP treatment demonstrated a gradual but incomplete depletion of cytosolic cytokine levels, with differences observed among the cytokines. Significant increases in release were apparent within 15-30 min for all cytokines. As the recognized VIP receptors (VPAC1 and VPAC2) are linked to adenylate cyclase and also interact with pituitary adenylate cyclase activating polypeptide-38 (PACAP-38), both this homologous peptide and 8-bromo cAMP were investigated and compared to VIP-mediated release. Treatment with 1 mM 8-bromo cAMP produced cytokine release similar in amount to 0.1 nM PACAP-38, but significantly less (<50%) in comparison to 0.1 nM VIP. PACAP-38 and VIP exhibited similar EC(50)'s for the release of G-CSF and TNF-alpha; however, the maximal release was 4-6 times greater for VIP than for PACAP-38. This similarity in potency suggested a VPAC-like receptor; however, the greater efficacy for VIP in comparison to PACAP-38, combined with a lack of cAMP production at subnanomolar concentrations of VIP, suggested a mechanism not currently associated with VPAC receptors. For M-CSF, IL-3 and IL-6, the EC(50)'s of VIP were 3-30 times more potent than those of PACAP-38 in producing release. These studies suggested that multiple mechanisms mediate cytokine release in astrocytes: (1) a low efficacy release produced by PACAP-38 that is cAMP-mediated and (2) a high efficacy, VIP-preferring mechanism that was not linked to cAMP. In summary, subnanomolar concentrations of VIP released a complex array of cytokines from astrocytes that may contribute to the mitogenic and neurotrophic properties of this neuropeptide in the central nervous system.

MANF: a new mesencephalic, astrocyte-derived neurotrophic factor with selectivity for dopaminergic neurons

We describe the discovery of a novel, 20 kDa, secreted human protein named mesencephalic astrocyte-derived neurotrophic factor, or MANF. The homologous, native molecule was initially derived from a rat mesencephalic type-1 astrocyte cell line and recombinant MANF subcloned from a cDNA encoding human arginine-rich protein. MANF selectively protects nigral dopaminergic neurons, versus GABAergic or serotonergic neurons. The discovery of MANF marks a more systematic approach in the search for astrocyte-derived, secreted proteins that selectively protect specific neuronal phenotypes. Compared to glial cell line-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF), MANF was more selective in the protection of dopaminergic neurons at lower (0.05-0.25 ng/mL) and middle (0.5-2.5 ng/mL) concentrations: MANF>GDNF>BDNF. GDNF was more selective at higher concentrations (25-50 ng/ml): GDNF>MANF>BDNF. Two domains in MANF of 39-AA and 109-AA respectively, and eight cysteines are conserved from C. elegans to man. MANF is encoded by a 4.3 Kb gene with 4 exons, and is located on the short arm of human chromosome 3. The secondary structure is dominated by alpha-helices (47%) and random coils (37%). Studies to determine the localization of MANF in the brains of rat, monkey, and man, as well as the receptor, signaling pathways, and biologically active peptide mimetics are in progress. The selective, neuroprotective effect of MANF for dopaminergic neurons suggests that it may be indicated for the treatment of Parkinson's disease.

Glial neuronal signaling in the central nervous system

Glial cells are known to interact extensively with neuronal elements in the brain, influencing their activity. Astrocytes associated with synapses integrate neuronal inputs and release transmitters that modulate synaptic sensitivity. Glial cells participate in formation and rebuilding of synapses and play a prominent role in protection and repair of nervous tissue after damage. For glial cells to take an active part in plastic alterations under physiological conditions and pathological disturbances, extensive specific signaling, both within single cells and between cells, is required. In recent years, intensive research has led to our first insight into this signaling. We know there are active connections between astrocytes in the form of networks promoting Ca2+ and ATP signaling; we also know there is intense signaling between astrocytes, microglia, oligodendrocytes, and neurons, with an array of molecules acting as signaling substances. The cells must be functionally integrated to facilitate the enormous dynamics of and capacity for reconstruction within the nervous system. In this paper, we summarize some basic data on glial neuronal signaling to provide insight into synaptic modulation and reconstruction in physiology and protection and repair after damage.

Proteomics as a tool for discovery: proteins implicated in Alzheimer's disease are highly expressed in normal pancreatic islets

A proteomic analysis of islets was undertaken to determine the protein constituents of normal adult mouse islets. Unexpectedly, we identified several islet proteins that are associated with the pathogenesis of Alzheimer's disease. Some of these proteins had chaperone activity that is integral to proper protein folding. This group includes GRP78, valosin-containing protein, calreticulin, protein disulfide isomerase, DnaK, HSP70, HSP60, and TCP-1. Additionally, neuronal proteins key to coordinated neuronal guidance and survival were also identified in islets. This group includes proprotein convertase subtilisin, collapsin response mediator protein 2, ubiquinol-cytochrome c reductase core protein, L-3-hydroxyacyl-Coenzyme A dehydrogenase, glutamine synthetase, peroxiredoxin, and secretogogin. An important subset of the proteins identified here has not been reported previously in pancreatic islets. Abnormal activity of these proteins in brain may contribute to the pathogenesis of Alzheimer's disease, a neurodegenerative condition characterized by focal amyloid deposits with neurofibrillary tangles. The putative role of these proteins in Alzheimer's pathogenesis is intriguing given the possible clinical relationship and pathological similarity of Alzheimer's disease to type 2 diabetes. These findings have therefore led to the hypothesis that these proteins may also play a role in type 2 diabetes.

Neuroprotective effects of a new synthetic peptide, CMX-9236, in in vitro and in vivo models of cerebral ischemia

NGF (nerve growth factor) and BDNF (brain-derived neurotrophic factor) are protein molecules (MW 26 and 13.6 kDa, respectively) that are neuroprotective in the middle cerebral artery occlusion (MCAO) rat stroke model. Their mechanism of action involves the activation of transcription factor AP-1 that turns on neuronal growth genes. In our ongoing studies we are designing short peptides that mimic some of the properties of full-length neurotrophic factors. We have synthesized a neuroprotective 14-amino acid peptide (CMX-9236) with an N-terminal docosahexaenoic acid (DHA). DHA enhances entry through the blood-brain barrier. Using primary rat brain cortical cultures and a fluorescent assay we found that CMX-9236 can counteract the excitotoxic effects of glutamate or kainate, reversing the intracellular accumulation of Ca(2+) to normal levels. Administration (i.v.) of CMX-9236 post initiation of ischemia reduced the lesion volumes from 178+/-50 to 117+/-55 mm(3) in the temporary rat MCAO model (90 min), and from 216+/-58 to 127+/-57 mm(3) in the permanent (24 h) model for stroke, corresponding to 34+/-28% (P=0.01) and 41+/-19% (P=0.038) reductions of the infarct volumes. Neurological behavior scores showed 57 and 47% improvements for treated temporary and permanent models, respectively. Dose-response studies indicated a 60-fold activation of AP-1 transcription factor in cells treated with 100 ng/ml of the peptide. These studies illustrate that a small peptide can function as a neuroprotective agent and an activator of a beneficial signal transduction 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.

Humanin rescues human cerebrovascular smooth muscle cells from Abeta-induced toxicity

Cerebral amyloid beta-protein (Abeta) angiopathy (CAA) is a key pathological feature of Alzheimer's disease (AD) and related disorders. We have used human cerebrovascular smooth muscle (HCSM) cells as an in vitro model system to investigate the pathogenic mechanisms of the pathology of CAA. It was previously demonstrated that certain pathogenic forms of Abeta induce several pathologic responses in these cells, including fibril assembly at the cell surface, increased levels of Abeta precursor, degradation of HCSM cell alpha-actin and cell death. The recently discovered novel rescue factor humanin (HN) was shown to protect neuronal cells in culture from various AD-relevant insults including treatment with Abeta. In this report we investigated whether the HN peptide could rescue HCSM cells from Abeta-induced toxicity. We found that treatment of HCSM cells with 10 microm HN prevented pathogenic Abeta-induced HCSM cell death using a fluorescent cell viability assay, and degradation of HCSM alpha-actin was diminished shown by quantitative immunoblotting. However, Abeta deposition and fibril formation at the cell surface and increased levels of cell-associated AbetaPP were not affected by treatment with HN as demonstrated by a thioflavin T fluorescence assay and immunochemical methods, respectively. These results suggest that the protective effects of HN occur downstream of these cell surface molecular events. This is the first demonstration of a rescue factor for HCSM cells from Abeta-mediated cell death as well as being the first report to show that neuronal cells and HCSM cells may share a common downstream mechanism in the Abeta-induced cell death pathway.

Death and survival of neuronal cells exposed to Alzheimer's insults

Neuronal cell death is the central abnormality occurring in brains suffering from Alzheimer's disease (AD). The notion that AD is a disease caused by loss of neurons points toward suppression of neuronal death as the most important therapeutic target. Nevertheless, the mechanisms for neuronal death in AD are still relatively unclear. Three known mutant genes cause familial AD (FAD): amyloid precursor protein, presenilin 1, and presenilin 2. Detailed analysis of cytotoxic mechanisms of the FAD-linked mutant genes reveals that they cause neuronal cell death at physiologically low expression levels. Unexpectedly, cytotoxic mechanisms vary depending on the type of mutations and genes, suggesting that various mechanisms for neuronal cell death are involved in AD patients. In support of this, activity-dependent neurotrophic factor, basic fibroblast growth factor, and insulin-like growth factor-I can completely protect neurons from beta-amyloid (A beta) cytotoxicity but exhibit incomplete or little effect on cytotoxicity by FAD mutant genes. By contrast, Humanin, a newly identified 24-residue peptide, suppresses neuronal cell death by various FAD mutants and A beta, whereas this factor has no effect on cytotoxicity from AD-irrelevant insults. Studies investigating death and survival of neuronal cells exposed to AD insults will open a new horizon in developing therapy aimed at neuroprotection.

Vasoactive intestinal peptide mRNA and immunoreactivity are decreased in fetal alcohol syndrome model

Vasoactive intestinal peptide (VIP) regulates growth in the early post-implantation embryo. Previous work has demonstrated that peptide agonists (SALLRSIPA and NAPVSIPQ) from downstream mediators that are regulated by VIP were able to prevent the alcohol-induced fetal death, growth restriction and microcephaly associated with fetal alcohol syndrome. Here we evaluated the role of VIP in this mouse model of fetal alcohol syndrome, to determine if fetal or maternal levels of VIP are altered. In addition, we evaluated whether peptide treatment would alter the effects of alcohol on VIP levels. Treatment groups included control, alcohol, and alcohol+peptides. VIP levels were measured with enzyme immunoassay [EIA] (Peninsula Laboratories, Belmont, CA). Quantitation of VIP expression was measured with rt-PCR using mimic cDNA primers. Embryo/decidual VIP levels were similar in control and alcohol-treated groups 6 h after treatment. However, in the embryo/deciduas at 12 and 24 h, VIP levels were below the EIA's detection limit in the alcohol-treated groups, and significantly lower than the control or peptide-pretreated groups (p<0.05). Maternal cortex VIP levels were undetectable and significantly lower in the alcohol-treated group than control or peptide+alcohol group at 6 and 12 h (p<0.001). VIP mRNA expression was quantitated in the embryo and deciduas, with a significant decline noted at 6 h to 58% of control levels (p=0.02). Pretreatment with the peptides attenuated the alcohol-induced decrease in VIP mRNA. These studies demonstrate that treatment with alcohol can decrease the expression and immunoreactivity of VIP in both maternal and fetal tissues. This alcohol-induced loss of a recognized regulator of embryonic growth and differentiation may contribute to the sequelae of toxicity observed in fetal alcohol syndrome.

Peptide antagonists of ethanol inhibition of l1-mediated cell-cell adhesion

Ethanol inhibits cell-cell adhesion mediated by the L1 cell adhesion molecule. 1-Octanol potently antagonizes this cellular action of ethanol and also prevents ethanol-induced dysmorphology and cell death in mouse whole embryo culture. NAPVSIPQ (NAP) and SALLRSIPA (SAL) are active peptide fragments of two neuroprotective proteins: activity-dependent neuroprotective protein and activity-dependent neurotrophic factor. NAP and SAL are neuroprotective at femtomolar concentrations against a variety of neurotoxins and also prevent ethanol teratogenesis in mice. To explore the cellular basis for this action, we asked whether NAP and SAL antagonize ethanol inhibition of L1 adhesion. Aggregation assays were carried out in ethanol-sensitive, human L1-transfected NIH/3T3 cells in the absence and presence of NAP and SAL. Neither NAP nor SAL altered L1 adhesion or L1 expression; however, both peptides potently and completely antagonized the inhibition of L1 adhesion by 100 mM ethanol (EC(50): NAP, 6 x 10(-14) M; SAL, 4 x 10(-11) M). NAP also antagonized ethanol inhibition of cell-cell adhesion in bone morphogenetic protein-7-treated NG108-15 cells. In L1-expressing NIH/3T3 cells, SAL antagonism was reversible and could be overcome by increasing concentrations of ethanol. In contrast, NAP antagonism was irreversible and could not be overcome by increasing agonist concentration. Two scrambled NAP peptides (ASPNQPIV and PNIQVASP) were not antagonists at concentrations as high as 10(-7) M. Thus, two structurally unrelated classes of compounds, alcohols and small polypeptides, share two common actions: antagonism of ethanol inhibition of L1-mediated cell adhesion and prevention of ethanol teratogenesis. These findings support the hypothesis that ethanol inhibition of L1 adhesion contributes to ethanol teratogenesis.

Vasoactive intestinal peptide regulation of nerve growth factor in the embryonic mouse

Vasoactive intestinal peptide (VIP), a regulator of embryonic growth, increased the concentration of nerve growth factor (NGF)-like immunoreactivity in the conditioned medium of cultured explanted embryonic day (E) 9.5 neural tube preparations compared to control preparations. VIP treatment also induced an increase of NGF-like immunoreactivity (NGF-IR) within the neural tube preparation tissue. A 60 kDa isoform was the primary form of NGF detected. VIP is shown to be a regulator of NGF in the E9.5 embryonic mouse and stimulates the release of a high molecular weight isoform of NGF.

Delivery of neurotrophic factors to the central nervous system: pharmacokinetic considerations

Neurotrophic factors are proteins with considerable potential in the treatment of central nervous system (CNS) diseases and traumatic injuries. However, a significant challenge to their clinical use is the difficulty associated with delivering these proteins to the CNS. Neurotrophic factors are hydrophilic, typically basic, monomeric or dimeric proteins, mostly in the size range of 5 to 30 kDa. Neurotrophic factors potently support the development, growth and survival of neurons, eliciting biological effects at concentrations in the nanomolar to femtomolar range. They are not orally bioavailable and the blood-brain and blood-cerebrospinal fluid barriers severely limit their ability to enter into and act on sites in the CNS following parenteral systemic routes of administration. Most neurotrophic factors have short in vivo half-lives and poor pharmacokinetic profiles. Their access to the CNS is restricted by rapid enzymatic inactivation, multiple clearance processes, potential immunogenicity and sequestration by binding proteins and other components of the blood and peripheral tissues. The development of targeted drug delivery strategies for neurotrophic factors will probably determine their clinical effectiveness for CNS conditions. Achieving significant CNS target site concentrations while limiting systemic exposure and distribution to peripheral sites of action will lessen unwanted pleiotropic effects and toxicity. Local introduction of neurotrophic factors into the CNS intraparenchymally by direct injection/infusion or by implantation of delivery vectors such as polymer matrices or genetically modified cells yields the highest degree of targeting, but is limited by diffusion restrictions and invasiveness. Delivery of neurotrophic factors into the cerebrospinal fluid (CSF) following intracerebroventricular or intrathecal administration is less invasive and allows access to a much wider area of the CNS through CSF circulation pathways. However, diffusional and cellular barriers to penetration into surrounding CNS tissue and significant clearance of CSF into the venous and lymphatic circulation are also limiting. Unconventional delivery strategies such as intranasal administration may offer some degree of CNS targeting with minimal invasiveness. This review presents a summary of the neurotrophic factors and their indications for CNS disorders, their physicochemical characteristics and the different approaches that have been attempted or suggested for their delivery to the CNS. Future directions for further research such as the potential for CNS disease treatment utilising combinations of neurotrophic factors, displacement strategies, small molecule mimetics, chimaeric molecules and gene therapy are also discussed.

Detailed characterization of neuroprotection by a rescue factor humanin against various Alzheimer's disease-relevant insults

A novel factor, termed Humanin (HN), antagonizes against neurotoxicity by various types of familial Alzheimer's disease (AD) genes [V642I and K595N/M596L (NL) mutants of amyloid precursor protein (APP), M146L-presenilin (PS) 1, and N141I-PS2] and by Abeta1-43 with clear action specificity ineffective on neurotoxicity by polyglutamine repeat Q79 or superoxide dismutase 1 mutants. Here we report that HN can also inhibit neurotoxicity by other AD-relevant insults: other familial AD genes (A617G-APP, L648P-APP, A246E-PS1, L286V-PS1, C410Y-PS1, and H163R-PS1), APP stimulation by anti-APP antibody, and other Abeta peptides (Abeta1-42 and Abeta25-35). The action specificity was further indicated by the finding that HN could not suppress neurotoxicity by glutamate or prion fragment. Against the AD-relevant insults, essential roles of Cys(8) and Ser(14) were commonly indicated, and the domain from Pro(3) to Pro(19) was responsible for the rescue action of HN, in which seven residues turned out to be essential. We also compared the neuroprotective action of S14G HN (HNG) with that of activity-dependent neurotrophic factor, IGF-I, or basic FGF for the antagonism against various AD-relevant insults (V642I-APP, NL-APP, M146L-PS1, N141I-PS2, and Abeta1-43). Although all of these factors could abolish neurotoxicity by Abeta1-43, only HNG could abolish cytotoxicities by all of them. HN and HN derivative peptides may provide a new insight into the study of AD pathophysiology and allow new avenues for the development of therapeutic interventions for various forms of AD.

A vasoactive intestinal peptide antagonist inhibits the growth of glioblastoma cells

The effects of a vasoactive intestinal peptide (VIP) receptor antagonist (VIPhyb) on human glioblastoma cells were characterized. Pituitary adenylate cyclase activating polypeptide (125I-PACAP-27) bound with high affinity to U87, U118, and U373 cells. Specific 125I-PACAP-27 binding to U87 cells was inhibited, with high affinity, by PACAP but not VIP or VIPhyb (IC50 = 10, 1500, and 500 nM, respectively). By reverse transcriptase-polymerase chain reaction (RT-PCR), a major 305 bp band was observed indicative of PAC1 receptors. PACAP-27 caused cAMP elevation and the increase in cAMP caused by PACAP-27, was inhibited by the VIPhyb. Also, PACAP-27 caused cytosolic Ca2+ elevation in Fura-2AM loaded U87 cells and the VIPhyb inhibited this increase. Using the MTT growth assay, the VIPhyb was shown to inhibit glioblastoma growth in a concentration-dependent manner. Using a clonogenic assay in vitro, 10 microM VIPhyb significantly inhibited proliferation of U87, U118, and U373 cells. In vivo, 0.4 microg/kg VIPhyb inhibited U87 xenograft proliferation in nude mice. These results suggest that the VIPhyb antagonizes PAC1 receptors on glioblastoma cells and inhibits their proliferation.

Neuroprotective peptide drug delivery and development: potential new therapeutics

Alzheimer's disease and related neurodegenerative disorders are prevalent among the elderly and might be considered as the plague of the 21st century. It is thus imperative to find cures for these conditions. The use of nerve growth factor proteins as neuroprotective therapeutics is limited by their hindered mobility through the blood-brain barrier. Peptides provide an attractive alternative. However, do peptide derivatives retain the activity of the entire protein? Are they stable? Would peptides cross the blood-brain barrier and what are the potential side effects? Examples are put forth to strengthen our opinion that peptides are important candidates for future drug development.

Detailed characterization of neuroprotection by a rescue factor humanin against various Alzheimer's disease-relevant insults

A novel factor, termed Humanin (HN), antagonizes against neurotoxicity by various types of familial Alzheimer's disease (AD) genes [V642I and K595N/M596L (NL) mutants of amyloid precursor protein (APP), M146L-presenilin (PS) 1, and N141I-PS2] and by Abeta1-43 with clear action specificity ineffective on neurotoxicity by polyglutamine repeat Q79 or superoxide dismutase 1 mutants. Here we report that HN can also inhibit neurotoxicity by other AD-relevant insults: other familial AD genes (A617G-APP, L648P-APP, A246E-PS1, L286V-PS1, C410Y-PS1, and H163R-PS1), APP stimulation by anti-APP antibody, and other Abeta peptides (Abeta1-42 and Abeta25-35). The action specificity was further indicated by the finding that HN could not suppress neurotoxicity by glutamate or prion fragment. Against the AD-relevant insults, essential roles of Cys(8) and Ser(14) were commonly indicated, and the domain from Pro(3) to Pro(19) was responsible for the rescue action of HN, in which seven residues turned out to be essential. We also compared the neuroprotective action of S14G HN (HNG) with that of activity-dependent neurotrophic factor, IGF-I, or basic FGF for the antagonism against various AD-relevant insults (V642I-APP, NL-APP, M146L-PS1, N141I-PS2, and Abeta1-43). Although all of these factors could abolish neurotoxicity by Abeta1-43, only HNG could abolish cytotoxicities by all of them. HN and HN derivative peptides may provide a new insight into the study of AD pathophysiology and allow new avenues for the development of therapeutic interventions for various forms of AD.

IGF-I as a mediator of VIP/activity-dependent neurotrophic factor-stimulated embryonic growth

IGF-I and the IGF-I receptor are necessary for normal embryonic growth. VIP is an important regulator of early postimplantation growth and acts indirectly through the release of other factors, including activity-dependent neurotrophic factor. The relationship of IGF-I growth regulation to VIP/activity-dependent neurotrophic factor-stimulated growth was examined with whole cultured embryonic d 9.5 mouse embryos. Somite numbers and DNA and protein contents were measured in embryos treated with IGF-I, anti-IGF-I, VIP, activity-dependent neurotrophic factor, and anti-activity-dependent neurotrophic factor-14 (antiserum to an activity-dependent neurotrophic factor agonist). IGF-I mRNA content was measured after incubation with and without VIP for 30 and 60 min using competitive RT-PCR. IGF-I induced a significant, dose-dependent increase in growth as measured by somite number, DNA levels, and protein content. Furthermore, anti-IGF-I inhibited embryonic growth and also prevented exogenous IGF-mediated growth. Both VIP- and activity-dependent neurotrophic factor-stimulated growth were blocked by anti-IGF-I, whereas anti-activity-dependent neurotrophic factor-14 had no detectable effect on IGF-I-induced growth. Treatment with VIP resulted in a 2-fold increase in embryonic IGF-I mRNA. These data suggest that IGF-I is a downstream mediator of VIP and activity-dependent neurotrophic factor in a regulatory pathway coordinating embryonic growth and that VIP may function as a regulator of IGF-I gene expression in the embryo.

Vasoactive intestinal peptide and related molecules induce nitrite accumulation in the extracellular milieu of rat cerebral cortical cultures

Nanomolar concentrations of vasoactive intestinal peptide (VIP), picomolar concentrations of stearyl-norleucine17-VIP (SNV) and femtomolar concentrations of NAPVSIPQ (NAP), an 8-amino-acid peptide derived from the VIP-responsive activity-dependent neuroprotective protein, provide broad neuroprotection. In rat cerebral cortical cultures, 10(-16)-10(-7) M NAP increased intracellular cyclic guanosine monophosphate (cGMP) (2.5-4-fold) and 10(-10) M NAP increased extracellular nitric oxide (NO) by 60%. In the same culture system, VIP and SNV (at micromolar concentrations) increased extracellular NO by 45-55%. The NAP dose required for cGMP increases correlated with the dose providing neuroprotection. However, the concentrations of NAP, SNV and VIP affecting NO production did not match the neuro-protective doses. Thus, NO may mediate part of the cell-cell interaction and natural maintenance activity of VIP/SNV/NAP, while cGMP may mediate neuroprotection.

Pharmacologically distinct vasoactive intestinal peptide binding sites: CNS localization and role in embryonic growth

In vitro autoradiography with [125I]vasoactive intestinal peptide revealed that the vasoactive intestinal peptide analogue, stearyl-norleucine17 vasoactive intestinal peptide, reported to be inactive at adenylyl cyclase-linked receptors in astrocytes, displaced a subset of vasoactive intestinal peptide binding sites on rat brain sections. These sites were widespread in adult rat brains and enriched in the olfactory bulb and thalamus, and corresponded to previously demonstrated GTP-insensitive vasoactive intestinal peptide binding sites. Stearyl-norleucine17 vasoactive intestinal peptide also identified receptors in rat lung and liver. In the adult brain, the stearyl-norleucine analog displaced only GTP-insensitive vasoactive intestinal peptide binding sites. In contrast, stearyl-norleucine17 vasoactive intestinal peptide-displaceable sites in the embryonic day 9 mouse appeared to include both GTP-sensitive and GTP-insensitive binding sites. This observation suggested the presence of an embryonic vasoactive intestinal peptide receptor with distinct pharmacological properties. Treatment of whole cultured mouse embryos with stearyl-norleucine17 vasoactive intestinal peptide resulted in stimulation of embryonic growth, with the stearyl-norleucine analog equipotent to vasoactive intestinal peptide, but less efficacious at higher concentrations (10(-7) M). Embryonic growth was inhibited by pituitary adenylyl cyclase-activating peptide and 8-bromoadenosine 3',5'-cyclic monophosphate. In addition, 8-bromoadenosine 3',5'-cyclic monophosphate inhibited stearyl-norleucine17 vasoactive intestinal peptide-stimulated growth. The results of the current study support the hypothesis that vasoactive intestinal peptide regulation of early postimplantation embryonic growth occurs, at least in part, independently of adenylyl cyclase stimulation.

A novel VIP responsive gene. Activity dependent neuroprotective protein

Activity dependent neuroprotective protein (ADNP, 828 amino acids, pI 5.99) is a glial-derived protein that contains a femtomolar active neuroprotective peptide, NAPVSIPQ (NAP). VIP induces a two- to threefold increase in ADNP mRNA in astrocytes, suggesting that ADNP is a VIP-responsive gene. ADNP is widely distributed in the mouse hippocampus, cerebellum, and cerebral cortex. VIP has been shown to possess neuroprotective activity that may be exerted through the activation of glial proteins. We suggest that ADNP may be part of the VIP protection pathway through the femtomolar-acting NAP and through putative interaction with other macromolecules.

A glia-derived signal regulating neuronal differentiation

Astrocytes are present in large numbers in the nervous system, are associated with synapses, and propagate ionic signals. Astrocytes influence neuronal physiology by responding to and releasing neurotransmitters, but the mechanisms that establish the close interaction between these cells are not defined. Here we use hippocampal neurons in culture to demonstrate that vasoactive intestinal polypeptide (VIP) promotes neuronal differentiation through activity-dependent neurotrophic factor (ADNF), a protein secreted by VIP-stimulated astroglia. ADNF is produced by glial cells and acts directly on neurons to promote glutamate responses and morphological development. ADNF causes secretion of neurotrophin 3 (NT-3), and both proteins regulate NMDA receptor subunit 2A (NR2A) and NR2B. These data suggest that the VIP-ADNF-NT-3 neuronal-glial pathway regulates glutamate responses from an early stage in the synaptic development of excitatory neurons and may also contribute to the known effects of VIP on learning and behavior in the adult nervous system.

A novel peptide prevents death in enriched neuronal cultures

We have recently cloned a novel protein (activity-dependent neuroprotective protein, ADNP) containing an 8-amino-acid, femtomolar-acting peptide, NAPVSIPQ (NAP). Here we show, for the first time, that NAP exerted a protective effect on glia-depleted neurons in culture. The number of surviving neurons was assessed in cerebral cortical cultures derived from newborn rats. In these cultures, a 24-h treatment with the beta-amyloid peptide (the Alzheimer's disease associated toxin) induced a 30-40% reduction in neuronal survival that was prevented by NAP (10(-13)-10(-11) M). Maximal survival was achieved at NAP concentrations of 10(-12) M. In a second set of experiments, a 5-day incubation period, with NAP added once (at the beginning of the incubation period) exhibited maximal protection at 10(-10) M NAP. In a third set of experiments, a 10-min period of glucose deprivation resulted in a 30-40% neuronal death that was prevented by a 24-h incubation with NAP. Glucose deprivation coupled with beta-amyloid treatment did not increase neuronal death, suggesting a common pathway. We thus conclude, that NAP can prevent neurotoxicity associated with direct action of the beta-amyloid peptide on neurons, perhaps through protection against impaired glucose metabolism.

VIP and peptides related to activity-dependent neurotrophic factor protect PC12 cells against oxidative stress

Oxidative stress is a common associative mechanism that is part of the pathogenesis of many neurodegenerative diseases. Vasoactive intestinal peptide (VIP) is a principal neuropeptide associated with normal development and aging. We have previously reported that VIP induced the secretion of proteins from glial cells, including the novel survival-promoter: activity-dependent neurotrophic factor (ADNF). ADNF-9, a nine amino acid peptide derived from ADNF, protects neurons from death caused by various toxins. In the present study, we examined the neuroprotective effect of VIP against oxidative stress in a pheochromocytoma cell line (PC12). In addition, a lipophilic derivative of VIP, Stearyl-Nle17-VIP (SNV), and two femtomolar-acting peptides: ADNF-9 and a 70% homologous peptide to ADNF-9, NAP were tested as well. PC12 cells were treated with 100 microM H2O2 for 24 h resulting in a reduction in cell survival to 35-50% as compared to controls. Addition of VIP or SNV prior and during the exposure to100 microM H2O2 increased cell survival to 80-90% of control values. Culture treatment with ADNF-9 or NAP in the presence of 100 microM H2O2 increased cell survival to 75-80% of control values. Messenger RNA expression analysis revealed that incubation with VIP resulted in a twofold increase in VIP mRNA, whereas NAP treatment did not cause any change in VIP expression, implicating different mechanisms of action. Furthermore, addition of an ADNF-9 antibody prevented the ability of VIP to protect against oxidative stress, suggesting that VIP protection is partially mediated via an ADNF-like protein.

VIP-Related protection against lodoacetate toxicity in pheochromocytoma (PC12) cells: a model for ischemic/hypoxic injury

To evaluate the protective properties of peptides related functionally and/or structurally to vasoactive intestinal peptide (VIP), PC12 cultures were treated with iodoacetate as a model for neuronal ischemic/hypoxic injury. Brain tissue can be pre-conditioned against lethal ischemia by several mechanisms including sub-lethal ischemia, moderate hypoglycemia, heat shock, and growth factors. In the present study, a superactive VIP lipophilic analog (Stearyl-Norleucine17-VIP; SNV) was used to pre-condition media of PC12 cells. After removal of the conditioned media, the cultures were exposed to iodoaceate, which inhibits glycolysis. Protective efficacy against iodoacetate-induced injury was assessed by the measurements of lactate dehydrogenase (LDH) activity in the media. Treatment with iodoacetate for 2.5 h produced a twofold increase in LDH activity in the media. The protective effect of SNV had an EC50 of 1 pM. Comparison of the preconditioning time required for full protection by SNV showed no apparent difference between a 15 min and a 2 h incubation period prior to the addition of iodoacetate. Iodoacetate treatment produced a 20% decrease in the RNA transcripts encoding activity-dependent neuroprotective protein (ADNP), a novel glia-derived protein that is regulated by VIP. The iodoacetate-associated reduction in ADNP mRNA was prevented by pre-treatment with SNV. These effects imply that SNV provides a regulatory mechanism for ADNP synthesis during glycolytic stress. Furthermore, a short exposure to SNV provided potent protection from iodoacetate-induced toxicity suggesting that SNV may have therapeutic value in the treatment of ischemic/hypoxic injury.

A glia-derived signal regulating neuronal differentiation

Astrocytes are present in large numbers in the nervous system, are associated with synapses, and propagate ionic signals. Astrocytes influence neuronal physiology by responding to and releasing neurotransmitters, but the mechanisms that establish the close interaction between these cells are not defined. Here we use hippocampal neurons in culture to demonstrate that vasoactive intestinal polypeptide (VIP) promotes neuronal differentiation through activity-dependent neurotrophic factor (ADNF), a protein secreted by VIP-stimulated astroglia. ADNF is produced by glial cells and acts directly on neurons to promote glutamate responses and morphological development. ADNF causes secretion of neurotrophin 3 (NT-3), and both proteins regulate NMDA receptor subunit 2A (NR2A) and NR2B. These data suggest that the VIP-ADNF-NT-3 neuronal-glial pathway regulates glutamate responses from an early stage in the synaptic development of excitatory neurons and may also contribute to the known effects of VIP on learning and behavior in the adult nervous system.

Prosaposin-derived peptides enhanced sprouting of sensory neurons in vitro and induced sprouting at motor endplates in vivo

Prosaposin exhibits neurotrophic factor properties that are localized to a 12-amino acid sequence located in the amino terminal portion of the saposin C domain. Prosaptides are peptides derived from the neurotrophic portion of prosaposin; these have been previously reported to be bioactive in neuroblastoma cell lines in vitro. We report that prosaptides were also bioactive in explants of adult primary sensory neurons by dose-dependently increasing both the number (3- to 4-fold) and elongation of these neurites by 50%. Local injection of prosaptides into the gluteus muscle of adult mice also induced sprouting at the motor endplate. Our results indicate that prosaptides are potent neuritogenic factors for both sensory and motor neurons of adult peripheral nerve.