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

Design, Synthesis, and Biological Evaluation of Novel Tetramethylpyrazine- nitrone Derivatives as Antioxidants

Background:

Thrombolysis and endovascular thrombectomy are the two main therapeutic strategies for ischemic stroke in clinic. However, reperfusion injury causes oxidative stress leading to overproduction of reactive oxygen species, mitochondrial dysfunction and subsequent cell death.

Methods:

We designed and synthesized two tetramethylpyrazine-nitrone derivatives (T-003 and T- 005) and investigated their abilities for scavenging free radicals and protective effects as well as neurite outgrowth promotion in vitro.

Results:

Both of them showed potent radical-scavenging activity and neuroprotective effects against iodoacetic acid-induced cell injury. Furthermore, T-003 and T-005 significantly promoted neurite outgrowth in PC12 cells.

Conclusion:

Our results suggest that compound T-003 and T-005 could be potent antioxidants for the treatment of neurological disease, particularly ischemic stroke.

Activity-dependent neuroprotective protein (ADNP)-end-binding protein (EB) interactions regulate microtubule dynamics toward protection against tauopathy

The 1102-amino-acid activity-dependent neuroprotective protein (ADNP) was originally discovered by expression cloning through the immunological identification of its 8-amino-acid sequence NAPVSIPQ (NAP), constituting the smallest active neuroprotective fragment of the protein. ADNP expression is essential for brain formation and cognitive function and is dysregulated in a variety of neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, and schizophrenia). ADNP has been found to be mutated in autism, with an estimated prevalence of 0.17% (together, these autism cases now constitute ADNP syndrome cases) and our recent results showed somatic mutations in ADNP in Alzheimer's disease brains correlating with tauopathy. Furthermore, Adnp haploinsufficiency in mice causes an age-dependent reduction in cognitive functions coupled with tauopathy-like features such as an increased formation of tangle-like structures, defective axonal transport, and Tau hyperphosphorylation. ADNP and its derived peptides, NAP and SKIP, directly interact with end-binding proteins (EBs), which decorate plus-tips of the growing axonal cytoskeleton-microtubules (MTs). Functionally, NAP and SKIP are neuroprotective and stimulate axonal transport. Clinical trials have suggested the potential efficacy of NAP (davunetide, CP201) for improving cognitive performance/functional activities of daily living in amnestic mild cognitive impairment (aMCI) and schizophrenia patients, respectively. However, NAP was not found to be an effective treatment (though well-tolerated) for progressive supranuclear palsy (PSP) patients. Here we review the molecular mechanism of NAP activity on MTs and how NAP modulates the MT-Tau-EBs crosstalk. We offer a molecular explanation for the different protective potency of NAP in selected tauopathies (aMCI vs. PSP) expressing different ratios/pathologies of the alternatively spliced Tau mRNA and its resulting protein (aMCI expressing similar quantities of the dynamic Tau 3-MT binding isoform (Tau3R) and the Tau 4-MT binding isoform (Tau4R) and PSP enriched in Tau4R pathology). We reveal the direct effect of truncated ADNPs (resulting from de novo autism and newly discovered Alzheimer's disease-related somatic mutations) on MT dynamics. We show that the peptide SKIP affects MT dynamics and MT-Tau association. Since MT impairment is linked with neurodegenerative and neurodevelopmental conditions, the current study implicates a paucity/dysregulation of MT-interacting endogenous proteins, like ADNP, as a contributing mechanism and provides hope for NAP and SKIP as MT-modulating drug candidates.

ADNP differentially interact with genes/proteins in correlation with aging: a novel marker for muscle aging

Activity-dependent neuroprotective protein (ADNP) is essential for embryonic development with ADNP mutations leading to syndromic autism, coupled with intellectual disabilities and motor developmental delays. Here, mining human muscle gene-expression databases, we have investigated the association of ADNP transcripts with muscle aging. We discovered increased ADNP and its paralogue ADNP2 expression in the vastus lateralis muscle of aged compared to young subjects, as well as altered expression of the ADNP and the ADNP2 genes in bicep brachii muscle of elderly people, in a sex-dependent manner. Prolonged exercise resulted in decreased ADNP expression, and increased ADNP2 expression in an age-dependent manner in the vastus lateralis muscle. ADNP expression level was further correlated with 49 genes showing age-dependent changes in muscle transcript expression. A high degree of correlation with ADNP was discovered for 24 genes with the leading gene/protein being NMNAT1 (nicotinamide nucleotide adenylyl transferase 1). Looking at correlations differentiating the young and the old muscles and comparing protein interactions revealed an association of ADNP with the cell division cycle 5-like protein (CDC5L), and an aging-muscle-related interactive pathway in the vastus lateralis. In the bicep brachii, very high correlation was detected with genes associated with immune functions as well as mitochondrial structure and function among others. Taken together, the results suggest a direct association of ADNP with muscle strength and implicate ADNP fortification in the protection against age-associated muscle wasting.

Design, Synthesis, and Biological Evaluation of Novel Tetramethylpyrazine Derivatives as Potential Neuroprotective Agents

Oxidative stress plays a crucial role in neurological diseases, resulting in excessive production of reactive oxygen species, mitochondrial dysfunction and cell death. In this work, we designed and synthesized a series of tetramethylpyrazine (TMP) derivatives and investigated their abilities for scavenging free radicals and preventing against oxidative stress-induced neuronal damage in vitro. Among them, compound 22a, consisted of TMP, caffeic acid and a nitrone group, showed potent radical-scavenging activity. Compound 22a had broad neuroprotective effects, including rescuing iodoacetic acid-induced neuronal loss, preventing from tert-butylhydroperoxide (t-BHP)-induced neuronal injury. Compound 22a exerted its neuroprotective effect against t-BHP injury via activation of the phosphatidyl inositol 3-kinase (PI3K)/Akt signaling pathway. Furthermore, in a rat model of permanent middle cerebral artery occlusion, compound 22a significantly improved neurological deficits, and alleviated the infarct area and brain edema. In conclusion, our results suggest that compound 22a could be a potential neuroprotective agent for the treatment of neurological disease, particularly ischemic stroke.

ADNP: A major autism mutated gene is differentially distributed (age and gender) in the songbird brain

ADNP is a protein necessary for brain development, important for brain plasticity, cognitive and social functioning, characteristics that are all impaired in autism and in the Adnp(+/-) mouse model, in a sex-dependent manner. ADNP was originally discovered as a protein that is secreted from glial cells in response to vasoactive intestinal peptide (VIP). VIP is a major neuroprotective peptide in the CNS and PNS and was also associated with social recognition in rodents and aggression, pair-bonding and parental behaviors in birds. Comparative sequence alignment revealed high evolutionary conservation of ADNP in Chordata. Despite its importance in brain function, ADNP has never been studied in birds. Zebra finches (Taeniopygia guttata) are highly social songbirds that have a sexually dichotomous anatomical brain structure, with males demonstrating a developed song system, presenting a model to study behavior and potential sexually dependent fundamental differences. Here, using quantitative real time polymerase chain reaction (qRT-PCR), we discovered sexually dichotomous and age related differences in ADNP mRNA expression in three different regions of the song bird brain-cerebellum, cerebrum, and brain stem. Higher levels of ADNP mRNA were specifically found in young male compared to the female cerebrum, while aging caused a significant 2 and 3-fold decrease in the female and male cerebrum, respectively. Furthermore, a comparison between the three tested brain regions revealed unique sex-dependent ADNP mRNA distribution patterns, affected by aging. Future studies are aimed at deciphering the function of ADNP in birds, toward a better molecular understanding of sexual dichotomy in singing behavior in birds.

Polyphenol extract from Phellinus igniarius protects against acrolein toxicity in vitro and provides protection in a mouse stroke model

The basidiomycetous mushroom Phellinus igniarius (L.) Quel. has been used as traditional medicine in various Asian countries for many years. Although many reports exist on its anti-oxidative and anti-inflammatory activities and therapeutic effects against various diseases, our current knowledge of its effect on stroke is very limited. Stroke is a neurodegenerative disorder in which oxidative stress is a key hallmark. Following the 2005 discovery by Igarashi's group that acrolein produced from polyamines in vivo is a major cause of cell damage by oxidative stress, we now describe the effects of anti-oxidative extracts from P. igniarius on symptoms of experimentally induced stroke in mice. The toxicity of acrolein was compared with that of hydrogen peroxide in a mouse mammary carcinoma cell line (FM3A). We found that the complete inhibition of FM3A cell growth by 5 μM acrolein could be prevented by crude ethanol extract of P. igniarius at 0.5 μg/ml. Seven polyphenol compounds named 3,4-dihydroxybenzaldehyde, 4-(3,4-dihydroxyphenyl-3-buten-2one, inonoblin C, phelligridin D, inoscavin C, phelligridin C and interfungin B were identified from this ethanolic extract by LCMS and 1H NMR. Polyphenol-containing extracts of P. igniarius were then used to prevent acrolein toxicity in a mouse neuroblastoma (Neuro-2a) cell line. The results suggested that Neuro-2a cells were protected from acrolein toxicity at 2 and 5 μM by this polyphenol extract at 0.5 and 2 μg/ml, respectively. Furthermore, in mice with experimentally induced stroke, intraperitoneal treatment with P. igniarius polyphenol extract at 20 μg/kg caused a reduction of the infarction volume by 62.2% compared to untreated mice. These observations suggest that the polyphenol extract of P. igniarius could serve to prevent ischemic stroke.

Autophagy has a key role in the pathophysiology of schizophrenia

Autophagy is a process preserving the balance between synthesis, degradation and recycling of cellular components and is therefore essential for neuronal survival and function. Several key proteins govern the autophagy pathway including beclin1 and microtubule associated protein 1 light chain 3 (LC3). Here, we show a brain-specific reduction in beclin1 expression in postmortem hippocampus of schizophrenia patients, not detected in peripheral lymphocytes. This is in contrast with activity-dependent neuroprotective protein (ADNP) and ADNP2, which we have previously found to be deregulated in postmortem hippocampal samples from schizophrenia patients, but that now showed a significantly increased expression in lymphocytes from related patients, similar to increases in the anti-apoptotic, beclin1-interacting, Bcl2. The increase in ADNP was associated with the initial stages of the disease, possibly reflecting a compensatory effect. The increase in ADNP2 might be a consequence of neuroleptic treatment, as seen in rats subjected to clozapine treatment. ADNP haploinsufficiency in mice, which results in age-related neuronal death, cognitive and social dysfunction, exhibited reduced hippocampal beclin1 and increased Bcl2 expression (mimicking schizophrenia and normal human aging). At the protein level, ADNP co-immunoprecipitated with LC3B suggesting a direct association with the autophagy process and paving the path to novel targets for drug design.

Back to the future with phenotypic screening

There are no disease-modifying drugs for any old age associated neurodegenerative disease or stroke. This is at least in part due to the failure of drug developers to recognize that the vast majority of neurodegenerative diseases arise from a confluence of multiple toxic insults that accumulate during normal aging and interact with genetic and environmental risk factors. Thus, it is unlikely that the current single target approach based upon rare dominant mutations or even a few preselected targets is going to yield useful drugs for these conditions. Therefore, the identification of drug candidates for neurodegeneration should be based upon their efficacy in phenotypic screening assays that reflect the biology of the aging brain, not a single, preselected target. It is argued here that this approach to drug discovery is the most likely to produce safe and effective drugs for neurodegenerative diseases.

Neuroprotective actions of methylene blue and its derivatives

Methylene blue (MB), the first lead chemical structure of phenothiazine and other derivatives, is commonly used in diagnostic procedures and as a treatment for methemoglobinemia. We have previously demonstrated that MB could function as an alternative mitochondrial electron transfer carrier, enhance cellular oxygen consumption, and provide protection in vitro and in rodent models of Parkinson's disease and stroke. In the present study, we investigated the structure-activity relationships of MB in vitro using MB and six structurally related compounds. MB reduces mitochondrial superoxide production via alternative electron transfer that bypasses mitochondrial complexes I-III. MB mitigates reactive free radical production and provides neuroprotection in HT-22 cells against glutamate, IAA and rotenone toxicity. Distinctly, MB provides no protection against direct oxidative stress induced by glucose oxidase. Substitution of a side chain at MB's 10-nitrogen rendered a 1000-fold reduction of the protective potency against glutamate neurototoxicity. Compounds without side chains at positions 3 and 7, chlorophenothiazine and phenothiazine, have distinct redox potentials compared to MB and are incapable of enhancing mitochondrial electron transfer, while obtaining direct antioxidant actions against glutamate, IAA, and rotenone insults. Chlorophenothiazine exhibited direct antioxidant actions in mitochondria lysate assay compared to MB, which required reduction by NADH and mitochondria. MB increased complex IV expression and activity, while 2-chlorphenothiazine had no effect. Our study indicated that MB could attenuate superoxide production by functioning as an alternative mitochondrial electron transfer carrier and as a regenerable anti-oxidant in mitochondria.

Subcellular localization and secretion of activity-dependent neuroprotective protein in astrocytes

Activity-dependent neuroprotective protein (ADNP, approximately 123562.8 Da), is synthesized in astrocytes and expression of ADNP mRNA is regulated by the neuroprotective peptide vasoactive intestinal peptide (VIP). The gene that encodes ADNP is conserved in human, rat and mouse, and contains a homeobox domain profile that includes a nuclear-export signal and a nuclear-localization signal. ADNP is essential for embryonic brain development, and NAP, an eight-amino acid peptide that is derived from ADNP, confers potent neuroprotection. Here, we investigate the subcellular localization of ADNP through cell fractionation, gel electrophoresis, immunoblotting and immunocytochemistry using alpha-CNAP, an antibody directed to the neuroprotective NAP fragment that constitutes part of an N-terminal epitope of ADNP. Recombinant ADNP was used as a competitive ligand to measure antibody specificity. ADNP-like immunoreactivity was found in the nuclear cell fraction of astrocytes and in the cytoplasm. In the cytoplasm, ADNP-like immunoreactivity colocalized with tubulin-like immunoreactivity and with microtubular structures, but not with actin microfilaments. Because microtubules are key components of developing neurons and brain, possible interaction between tubulin and ADNP might indicate a functional correlate to the role of ADNP in the brain. In addition, ADNP-like immunoreactivity in the extracellular milieu of astrocytes increased by approximately 1.4 fold after incubation of the astrocytes with VIP. VIP is known to cause astrocytes to secrete neuroprotective/neurotrophic factors, and we suggest that ADNP constitutes part of this VIP-stimulated protective milieu.

Involvement of PACAP/ADNP signaling in the resistance to cell death in malignant peripheral nerve sheath tumor (MPNST) cells

Malignant peripheral nerve sheath tumors (MPNSTs) are sarcomas able to grow under conditions of metabolic stress caused by insufficient nutrients or oxygen. Both pituitary adenylate cyclase-activating polypeptide (PACAP) and activity-dependent neuroprotective protein (ADNP) have glioprotective potential. However, whether PACAP/ADNP signaling is involved in the resistance to cell death in MPNST cells remains to be clarified. Here, we investigated the involvement of this signaling system in the survival response of MPNST cells against hydrogen peroxide (H(2)O(2))-evoked death both in the presence of normal serum (NS) and in serum-starved (SS) cells. Results showed that ADNP levels increased time-dependently (6-48 h) in SS cells. Treatment with PACAP38 (10(-9) to 10(-5) M) dose-dependently increased ADNP levels in NS but not in SS cells. PAC(1)/VPAC receptor antagonists completely suppressed PACAP-stimulated ADNP increase and partially reduced ADNP expression in SS cells. NS-cultured cells exposed to H(2)O(2) showed significantly reduced cell viability (~50 %), increased p53 and caspase-3, and DNA fragmentation, without affecting ADNP expression. Serum starvation significantly reduced H(2)O(2)-induced detrimental effects in MPNST cells, which were not further ameliorated by PACAP38. Altogether, these finding provide evidence for the involvement of an endogenous PACAP-mediated ADNP signaling system that increases MPNST cell resistance to H(2)O(2)-induced death upon serum starvation.

Chemical modification of the multitarget neuroprotective compound fisetin

Many factors are implicated in age-related central nervous system (CNS) disorders, making it unlikely that modulating only a single factor will provide effective treatment. Perhaps a better approach is to identify small molecules that have multiple biological activities relevant to the maintenance of brain function. Recently, we identified an orally active, neuroprotective, and cognition-enhancing molecule, the flavonoid fisetin, that is effective in several animal models of CNS disorders. Fisetin has direct antioxidant activity and can also increase the intracellular levels of glutathione (GSH), the major endogenous antioxidant. In addition, fisetin has both neurotrophic and anti-inflammatory activity. However, its relatively high EC(50) in cell based assays, low lipophilicity, high topological polar surface area (tPSA), and poor bioavailability suggest that there is room for medicinal chemical improvement. Here we describe a multitiered approach to screening that has allowed us to identify fisetin derivatives with significantly enhanced activity in an in vitro neuroprotection model while at the same time maintaining other key activities.

Targeting VIP and PACAP receptor signalling: new therapeutic strategies in multiple sclerosis

MS (multiple sclerosis) is a chronic autoimmune and neurodegenerative pathology of the CNS (central nervous system) affecting approx. 2.5 million people worldwide. Current and emerging DMDs (disease-modifying drugs) predominantly target the immune system. These therapeutic agents slow progression and reduce severity at early stages of MS, but show little activity on the neurodegenerative component of the disease. As the latter determines permanent disability, there is a critical need to pursue alternative modalities. VIP (vasoactive intestinal peptide) and PACAP (pituitary adenylate cyclase-activating peptide) have potent anti-inflammatory and neuroprotective actions, and have shown significant activity in animal inflammatory disease models including the EAE (experimental autoimmune encephalomyelitis) MS model. Thus, their receptors have become candidate targets for inflammatory diseases. Here, we will discuss the immunomodulatory and neuroprotective actions of VIP and PACAP and their signalling pathways, and then extensively review the structure–activity relationship data and biophysical interaction studies of these peptides with their cognate receptors.

Delayed treatment with a novel neurotrophic compound reduces behavioral deficits in rabbit ischemic stroke

Acute ischemic stroke is a major risk for morbidity and mortality in our aging population. Currently only one drug, the thrombolytic tissue plasminogen activator, is approved by the US Food and Drug Administration to treat stroke. Therefore, there is a need to develop new drugs that promote neuronal survival following stroke. We have synthesized a novel neuroprotective molecule called CNB-001 (a pyrazole derivative of curcumin) that has neurotrophic activity, enhances memory, and blocks cell death in multiple toxicity assays related to ischemic stroke. In this study, we tested the efficacy of CNB-001 in a rigorous rabbit ischemic stroke model and determined the molecular basis of its in vivo activity. CNB-001 has substantial beneficial properties in an in vitro ischemia assay and improves the behavioral outcome of rabbit ischemic stroke even when administered 1 h after the insult, a therapeutic window in this model comparable to tissue plasminogen activator. In addition, we elucidated the protein kinase pathways involved in neuroprotection. CNB-001 maintains the calcium-calmodulin-dependent kinase signaling pathways associated with neurotrophic growth factors that are critical for the maintenance of neuronal function. On the basis of its in vivo efficacy and novel mode of action, we conclude that CNB-001 has a great potential for the treatment of ischemic stroke as well as other CNS pathologies.

Neuroprotective protein and carboxypeptidase E

This review outlines the neuroprotective activities and structural specificities of two distinct proteins, activity-dependent neuroprotective protein, a protein assigned transcription factor/chromatin remodeling activity, and carboxypeptidase E, a classic exopeptidase. Future studies will elucidate how these two versatile proteins converge onto a similar endpoint: neuroprotection.

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.

ADNP differential nucleus/cytoplasm localization in neurons suggests multiple roles in neuronal differentiation and maintenance

Complete deficiency in activity-dependent neuroprotective protein (ADNP) results in neural tube closure defects and death at gestation day 9 in mice. ADNP-deficient embryos exhibit dramatic increases in gene transcripts associated with lipid metabolism coupled to reduction in organogenesis/neurogenesis-related transcripts. In the pluripotent teratocarcinoma cell line P19, ADNP was shown to interact with specific chromatin regions in the neurodifferentiated state, which was associated with binding to the heterochromatin protein 1 alpha. In this study, using P19 cells as a differentiation model, we showed that ADNP expression and cytoplasm/nucleus distribution is unique in neuronal-differentiated cells compared to cardiovascular and nondifferentiated pluripotent cells. ADNP-like immunohistochemical localization to the neuronal cytoplasm and neurites was shown in this study not only in the cellular model but also in the brain cerebral cortex and olfactory bulb. Small hairpin RNA ADNP downregulation was used to further investigate ADNP involvement in p19 neurodifferentiation. An approximately 80% robust reduction in ADNP led to a substantial reduction in embryoid body formation and a significant reduction (approximately 50%) in neurite numbers. These results position ADNP in direct association with neuronal cell differentiation and maturation.

Blockage of VIP during mouse embryogenesis modifies adult behavior and results in permanent changes in brain chemistry

Vasoactive intestinal peptide (VIP) regulates growth and development during the early postimplantation period of mouse embryogenesis. Blockage of VIP with a VIP antagonist during this period results in growth restriction, microcephaly, and developmental delays. Similar treatment of neonatal rodents also causes developmental delays and impaired diurnal rhythms, and the adult brains of these animals exhibit neuronal dystrophy and increased VIP binding. These data suggest that blockage of VIP during the development of the nervous system can result in permanent changes to the brain. In the current study, pregnant mice were treated with a VIP antagonist during embryonic days 8 through 10. The adult male offspring were examined in tests of novelty, paired activity, and social recognition. Brain tissue was examined for several measures of chemistry and gene expression of VIP and related compounds. Glial cells from the cortex of treated newborn mice were plated with neurons and examined for VIP binding and their ability to enhance neuronal survival. Treated adult male mice exhibited increased anxiety-like behavior and deficits in social behavior. Brain tissue exhibited regionally specific changes in VIP chemistry and a trend toward increased gene expression of VIP and related compounds that reached statistical significance in the VIP receptor, VPAC-1, in the female cortex. When compared to control astrocytes, astrocytes from treated cerebral cortex produced further increases in neuronal survival with excess synaptic connections and reduced VIP binding. In conclusion, impaired VIP activity during mouse embryogenesis resulted in permanent changes to both adult brain chemistry/cell biology and behavior with aspects of autism-like social deficits.

Baicalein, an antioxidant 12/15-lipoxygenase inhibitor improves clinical rating scores following multiple infarct embolic strokes

The present study assessed whether baicalein (5,6,7-trihydroxyflavone), a polyphenolic antioxidant 12/15-lipoxygenase inhibitor would attenuate oxidative cell death in vitro using a mouse hippocampal HT22 cell assay. Moreover, we determined if baicalein would be useful to attenuate behavioral deficits associated with multiple infarct ischemic events in vivo using a rabbit small clot embolic stroke model (RSCEM). Using HT22 cell in vitro, baicalein was shown to significantly promote cell survival with an estimated dose for 50% cell survival of 2 muM following incubation in the presence of iodoacetic acid (20 muM), an irreversible inhibitor of the glycolytic pathway that results in the free radical production, lipid peroxidation and cell death. Since baicalein was neuroprotective and attenuated iodoacetic acid (IAA) toxicity in vitro, we studied its effects in vivo in an embolic stroke model using behavioral measures as the endpoint. Quantal analysis for each treatment in the embolism model identifies the quantity of microclots (mg) that produce neurologic dysfunction in 50% of a group of animals (P(50)), with intervention considered neuroprotective if it increases the P(50) compared with controls. Baicalein (100 mg/kg, s.c.) injected 5 and 60 min post-embolization significantly (P<0.05) improved behavioral function. The calculated P(50) values were 2.85+/-0.64 mg (n=21) and 2.15+/-0.12 mg (n=14), respectively compared with 1.37+/-0.20 mg (n=23) for the control group. In conclusion, we have shown that baicalein effectively attenuated cell death in vitro using HT22 cells and also significantly reduced behavioral deficits in rabbits when given up to 1 h following an embolic stroke. The results suggest that baicalein, or derivatives of baicalein with multiple pharmacological activities may be useful to develop as novel treatments for acute ischemic stroke.

A novel approach to screening for new neuroprotective compounds for the treatment of stroke

Despite the significant advances that have been made in understanding the pathophysiology of cerebral ischemia on the cellular and molecular level, only one drug, the thrombolytic tissue plasminogen activator (rt-PA), is approved by the FDA for use in patients with acute ischemic stroke. Therefore, there is a critical need for additional safe and effective treatments for stroke. In order to identify novel compounds that might be effective, we have developed a cell culture-based assay with death being an endpoint as a screening tool. We have performed an initial screening for potential neuroprotective drugs among a group of flavonoids by using the mouse hippocampal cell line, HT22, in combination with chemical ischemia. Further screens were provided by biochemical assays for ATP and glutathione, the major intracellular antioxidant, as well as for long-term induction of antioxidant proteins. Based upon the results of these screens, we tested the best flavonoid, fisetin, in the small clot embolism model of cerebral ischemia in rabbits. Fisetin significantly reduced the behavioral deficits following a stroke, providing proof of principle for this novel approach to identifying new compounds for the treatment of stroke.

Neonatal mice of the Down syndrome model, Ts65Dn, exhibit upregulated VIP measures and reduced responsiveness of cortical astrocytes to VIP stimulation

The Ts65Dn segmental mouse model of Down syndrome (DS) possesses a triplication of the section of chromosome 16 that is most homologous to the human chromosome 21 that is trisomic in DS. This model exhibits many of the characteristics of DS including small size, developmental delays, and a decline of cholinergic systems and cognitive function with age. Recent studies have shown that vasoactive intestinal peptide (VIP) systems are upregulated in aged Ts65Dn mice and that VIP dysregulation during embryogenesis is followed by the hypotonia and developmental delays as seen in both DS and in Ts65Dn mice. Additionally, astrocytes from aged Ts65Dn brains do not respond to VIP stimulation to release survival-promoting substances. To determine if VIP dysregulation is age-related in Ts65Dn mice, the current study examined VIP and VIP receptors (VPAC-1 and VPAC-2) in postnatal day 8 Ts65Dn mice. VIP and VPAC-1 expression was significantly increased in the brains of trisomic mice compared with wild-type mice. VIP-binding sites were also significantly increased in several brain areas of young Ts65Dn mice, especially in the cortex, caudate/putamen, and hippocampus. Further, in vitro treatment of normal neurons with conditioned medium from VIP-stimulated Ts65Dn astrocytes from neonatal mice did not enhance neuronal survival. This study indicates that VIP anomalies are present in neonatal Ts65Dn mice, a defect occurs in the signal transduction mechanism of the VPAC-1 VIP receptor, cortical astrocytes from neonatal brains are dysfunctional, and further, that VIP dysregulation may play a significant role in DS.

Vasoactive intestinal peptide antagonist treatment during mouse embryogenesis impairs social behavior and cognitive function of adult male offspring

Vasoactive intestinal peptide (VIP) is a regulator of rodent embryogenesis during the period of neural tube closure. VIP enhanced growth in whole cultured mouse embryos; treatment with a VIP antagonist during embryogenesis inhibited growth and development. VIP antagonist treatment during embryogenesis also had permanent effects on adult brain chemistry and impaired social recognition behavior in adult male mice. The neurological deficits of autism appear to be initiated during neural tube closure and social behavior deficits are among the key characteristics of this disorder that is more common in males and is frequently accompanied by mental retardation. The current study examined the blockage of VIP during embryogenesis as a model for the behavioral deficits of autism. Treatment of pregnant mice with a VIP antagonist during embryonic days 8 through 10 had no apparent effect on the general health or sensory or motor capabilities of adult offspring. However, male offspring exhibited reduced sociability in the social approach task and deficits in cognitive function, as assessed through cued and contextual fear conditioning. Female offspring did not show these deficiencies. These results suggest that this paradigm has usefulness as a mouse model for aspects of autism as it selectively impairs male offspring who exhibit the reduced social behavior and cognitive dysfunction seen in autism. Furthermore, the study indicates that the foundations of some aspects of social behavior are laid down early in mouse embryogenesis, are regulated in a sex specific manner and that interference with embryonic regulators such as VIP can have permanent effects on adult social behavior.

Activity-dependent neuroprotective protein: from gene to drug candidate

Activity-dependent neuroprotective protein (ADNP) is essential for brain formation. The gene encoding ADNP is highly conserved and abundantly expressed in the brain. ADNP contains a homeobox profile and a peptide motif providing neuroprotection against a variety of cytotoxic insults. ADNP mRNA and protein expression responds to brain injury and oscillates as a function of the estrus cycle. The plastic nature of ADNP expression is correlated with brain protection and an association between neuroendocrine regulation and neuroprotection is put forth with ADNP as a focal point. Further understanding of neuroprotective molecules should pave the path to better diagnostics and therapies. In this respect, structure-activity studies have identified a short 8 amino acid peptide in ADNP/NAPVSIPQ (NAP) that provides potent neuroprotection. NAP is currently in clinical development for neuroprotection.

Activity-dependent neuroprotective protein (ADNP) differentially interacts with chromatin to regulate genes essential for embryogenesis

Complete deficiency in activity-dependent neuroprotective protein (ADNP) results in neural tube closure defects and death at days 8.5-9.5 of gestation in the mouse (E8.5-9.5). To elucidate ADNP associated pathways, Affymetrix 22,690-oligonucleotide-based microarrays were used on ADNP knockout and control mouse embryos (E9) separated completely from extra embryonic tissue. Marked differences in expression profiles between ADNP-deficient embryos and ADNP-expressing embryos were discovered. Specifically, a group of dramatically up-regulated gene transcripts in the ADNP-deficient embryos were clustered into a family encoding for proteins enriched in the visceral endoderm such as apolipoproteins, cathepsins and methallotionins. In contrast, a down regulated gene cluster associated with ADNP-deficiency in the developing embryo consisted of organogenesis markers including neurogenesis (Ngfr, neurogenin1, neurod1) and heart development (Myl2). The pluripotent P19 cells were used for ADNP-chromatin-immunoprecipitation, showing direct interactions with multiple relevant gene promoters including members of the up-regulated as well as the down-regulated gene clusters. A comparison between non-differentiated and neuro-differentiated P19 cells revealed increased chromatin interaction of ADNP with chromatin from differentiated cells. These results place ADNP at a crucial point of gene regulation, repressing potential endoderm genes and enhancing genes associated with organogenesis/neurogenesis.

Brain deficits associated with fetal alcohol exposure may be protected, in part, by peptides derived from activity-dependent neurotrophic factor and activity-dependent neuroprotective protein

This review discusses the effects of prenatal alcohol exposure on the developing brain and the potential use of derived peptides from activity-dependent neurotrophic factor (ADNF) and activity-dependent neuroprotective protein (ADNP) in neuroprotection against the insults of alcohol. Alcohol is known to impede the growth of the central nervous system and to induce neurodegeneration through cellular apoptosis. Sari et al. have shown that prenatal alcohol exposure reduced the fetal brain weight, the size of the brain regions and the number of serotonin (5-HT) neurons. Prenatal alcohol exposure compromises neural tube midline development. Sari et al. further suggested that the timing of alcohol exposure during pregnancy is critical to the induction of deficits in 5-HT neurons, as well as other types of neurons and consequently results in deficits in neural tube development. ADNF and ADNP are glial-derived proteins discovered to be induced by vasoactive intestinal peptide (VIP). These proteins are expressed during embryonic development. Functional assays and genetic manipulations have identified these proteins as highly important for neural tube closure and brain formation/development. The peptide derivatives of ADNF, ADNF-14 (VLGGGSALLRSIPA), ADNF-9 (or SALLRSIPA = SAL) and of ADNP, NAPVSIPQ = NAP have shown neuroprotective effects and have been proven to prevent brain damage associated with prenatal alcohol exposure in animals. Here, we discuss the many aspects of alcohol-associated growth restriction in the developing brain and the potential inhibition of this severe phenotype through the use of neuroprotective peptides.

Neuroprotection of Cerebrolysin in tissue culture models of brain ischemia: post lesion application indicates a wide therapeutic window

All attempts to reduce neuronal damage after acute brain ischemia by the use of neuroprotective compounds have failed to prove efficacy in clinical trials so far. One of the main reasons might be the relatively narrow time window for intervention. In this study 2 different tissue culture models of ischemia, excitotoxic lesion by the use of glutamate and oxygen-glucose deprivation (OGD), were used to investigate the effects of delayed application of Cerebrolysin (Cere) on neuronal survival. This drug consists of low molecular weight peptides with neuroprotective and neurotrophic properties similar to naturally occurring growth factors. After both types of lesion, acute as well as delayed treatment with Cere resulted in a dose dependent and significant rescue of neurons. In the model of excitotoxic cell death significant drug effects were found even when the treatment started with a delay of 96 hours after addition of glutamate. In the OGD model pronounced effects were found after 48 hours delay of treatment, and even after 72 hours a small but significant rescue of neurons was detected. The neuroprotective effects of a single addition of Cerebrolysin to the culture medium resulted in significant protection until end of the experiments which was up to 2 weeks after the initial lesion. A shift of the efficacious dosages from low to high concentrations indicates that most likely active compounds are used up, indicating that multiple dosing might even increase the effect size. In conclusion the results indicate that Cere displays a relatively wide therapeutic time window which might be explained by a combination of acute neuroprotective properties and neurotrophic efficacy.

N-PEP-12 – a novel peptide compound that protects cortical neurons in culture against different age and disease associated lesions

The neuroprotective potency of N-PEP-12, a novel, proprietary compound consisting of biopeptides and amino acids was investigated. Lesion models have been applied in neuronal cultures of embryonic chicken cortex, pre-treated with N-PEP-12 from the first day onwards. On day 8 in vitro neurons were lesioned and cell viability was measured 24 and 48 hours later. To simulate acute brain ischemia, cytotoxic hypoxia was induced by sodium cyanide or by iodoacetate and excitotoxicity by L-glutamate. Ionomycin for up to 48 hours induced calcium overload. The cytoskeleton was disrupted by addition of colchicine. N-PEP-12 shows dose-dependent neuroprotection in all different models. The effect size depends on the recovery time but also on the extent of the lesion. In cases of mild to moderate lesion pronounced dose-dependent effects could be demonstrated. This indicates that chronic exposure to N-PEP-12 is able to prevent neuronal cell death associated to conditions occurring during normal aging and neurological disorders like ischemic stroke, hypoxia, brain trauma, or AD.

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.

NAP mechanisms of neuroprotection

An 8-amino-acid peptide, NAPVSIPQ (NAP), was identified as the smallest active element of activity-dependent neuroprotective protein that exhibits potent neuroprotective action. Potential signal transduction pathways include cGMP production and interference with inflammatory mechanisms, tumor necrosis factor-alpha, and MAC1-related changes. Because of its intrinsic structure, NAP might interact with extracellular proteins and also transverse membranes. NAP-associated protection against oxidative stress, glucose deprivation, and apoptotic mechanisms suggests interference with fundamental processes. This paper identifies p53, a key regulator of cellular apoptosis, as an intracellular target for NAP's activity.

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.

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.

From vasoactive intestinal peptide (VIP) through activity-dependent neuroprotective protein (ADNP) to NAP: a view of neuroprotection and cell division

Accelerated neuronal death brings about cognitive as well as motor and other dysfunctions. A major neuropeptide, vasoactive intestinal peptide (VIP), has been shown to be neuroprotective. However, VIP-based drug design is hampered by the instability of the peptide and its limited bioavailability. Two independent approaches were thus taken to exploit VIP as a lead drug candidate: (1) Potent neuroprotective lipophilic analogs of VIP were synthesized, e.g. [stearyl-norleucine-17] VIP (SNV); and (2) potent neuroprotective peptide derivatives were identified that mimic the activity of VIP-responsive neuroprotective glial proteins. VIP provides neuronal defense by inducing the synthesis and secretion of neuroprotective proteins from astrocytes; activity-dependent neuroprotective protein (ADNP) was discovered as such glial cell mediator of VIP- and SNV-induced neuroprotection. In subsequent studies, an eight-amino-acid peptide, NAP, was identified as the smallest active element of ADNP exhibiting potent neuroprotective activities. This paper summarizes the biological effects of SNV and NAP and further reports advances in NAP studies toward clinical development. An original finding described here shows that NAP, while protecting neurons, demonstrated no apparent effect on cell division in a multiplicity of cell lines, strengthening the notion that NAP is a specific neuroprotective drug candidate.

Activity-dependent neuroprotective protein: a novel gene essential for brain formation

We have recently cloned the novel homeobox-containing activity-dependent neuroprotective protein (ADNP). In the current study, mouse ADNP was shown to be expressed at the time of neural tube closure, detected at E7.5 and increased on E9.5. Expression was augmented in the brain (E12.5), sustained throughout embryogenesis and regulated by VIP. To assess the function of ADNP, knockout mice were established. Detailed analysis revealed cranial neural tube closure failure and death on E8.5-9.0 of the ADNP-knockout embryos. The expression of Oct4, a gene associated with germ-line maintenance was markedly augmented in the knockout embryos. In contrast, the expression of Pax6, a gene crucial for cerebral cortex formation, was abolished in the brain primordial tissue of the knockout embryos. Thus, Pax6 and Oct4 constitute a part of the mechanism of action of ADNP on brain formation, inhibiting germ-line division while activating morphogenesis. In conclusion, ADNP is identified here as a new key gene essential for organogenesis in the developing embryo and may be implicated as a clinical target associated with proper neurodevelopment.