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Biomedical subjects

D E Brenneman

Publications and source records attributed to D E Brenneman.

At least 55 records · Page 3Linked to original sources
PubMed1998

Involvement of pituitary adenylate cyclase-activating polypeptide II vasoactive intestinal peptide 2 receptor in mouse neocortical astrocytogenesis.

At the end of neuronal migration, the neopallial germinative zone produces glial cells destined to colonize the upper layers of neocortex. High densities of binding sites for vasoactive intestinal peptide (VIP) have been found in the rodent germinative zone just after completion of neuronal migration, suggesting a possible role of VIP in neocortical astrocytogenesis. In the present study, administration of a VIP antagonist at embryonic days 17 and 18 to pregnant mice was followed by a dramatic depletion of astrocytes in the upper cortical layer of the offspring. The depletion of astrocytes was dose-dependent, with a 42% reduction in the density of astrocytes observed with 50 microg of antagonist. The antagonist effect was reversed by cotreatment with VIP or pituitary adenylate cyclase-activating polypeptide (PACAP), suggesting the involvement of a receptor common to these two neuropeptides. VIP antagonist-induced inhibition of astrocytogenesis was also blocked by Ro 25-1553, a long-acting cyclic VIP analogue selective for the PACAP II VIP2 receptor subclass. Our results demonstrate that VIP and/or PACAP play a crucial physiological role in neocortical astrocytogenesis, possibly through interaction with PACAP II VIP2 receptors.

Animals↗
PubMed1998

Activity-dependent neurotrophic factor: structure-activity relationships of femtomolar-acting peptides.

Activity-dependent neurotrophic factor (ADNF) is a glia-derived protein that is neuroprotective at femtomolar concentrations. A 14-amino acid peptide of ADNF (ADNF-14) has been reported that protects cultured neurons from multiple neurotoxins. Structure-activity relationships of peptides related to ADNF-14 now have been determined. A 9-amino acid core peptide (ADNF-9) has been identified that has greater potency and a broader effective concentration range (10(-16) to 10(-13) M) than ADNF or ADNF-14 in preventing cell death associated with tetrodotoxin treatment of cerebral cortical cultures. Deletions or conservative amino acid substitutions to ADNF-9 resulted in reduced potency, narrower effective concentration range and/or decreased efficacy. Removal of the N-terminal serine or the COOH-terminal isoleucine-proline-alanine from ADNF-9 produced a significant reduction in survival-promoting activity. Comparative studies of ADNF-9 action in mixed (glia plus neurons) vs. glia-depleted neuronal cultures indicated that ADNF-9 can act directly on neurons, although the potency of the peptide was 10,000-fold greater in mixed cultures. Kinetic studies showed that exposure to ADNF-9 for only 2 hr was sufficient to produce a 4-day protection against the cell-killing action of tetrodotoxin. Treatment with bafilomycin A1 (an inhibitor of receptor-mediated endocytosis) for 2 hr prevented the ADNF- and ADNF-9-mediated neuroprotection. ADNF-9, like ADNF-14, was neuroprotective against N-methyl-D-aspartate and the beta-amyloid peptide (amino acids 25-35), and had a much broader range of effective concentrations than ADNF-14. These studies identify ADNF-9 as an attractive lead compound for the development of therapeutic agents against neurodegenerative diseases.

Animals↗
PubMed1997

Vasoactive intestinal peptide prevents excitotoxic cell death in the murine developing brain.

Excitotoxic damage may be a critical factor in the formation of brain lesions associated with cerebral palsy. When injected at birth, the glutamatergic analog ibotenate induces mouse brain lesions that strikingly mimic human microgyria. When ibotenate is injected at postnatal day 5, it produces transcortical necrosis and white matter cysts that mimic human perinatal hypoxic-like lesions. Vasoactive intestinal peptide (VIP) has potent growth-related actions and neuroprotective properties that influence mitosis and neuronal survival in culture. The goal of this study was to assess the protective role of VIP against excitotoxic lesions induced by ibotenate in developing mouse brain. VIP cotreatment reduced ibotenate-induced microgyric-like cortical lesions and white matter cysts by up to 77 and 85%, respectively. VIP protective effects were reproduced by a peptide derived from activity-dependent neurotrophic factor (ADNF), a trophic factor released by VIP-stimulated astrocytes, and by stearyl norleucine VIP, a specific VIP agonist that does not activate adenylate cyclase. Neither forskolin, an adenylate cyclase activator, nor pituitary adenylate cyclase-activating peptide, provided VIP-like protection. VIP and neurotrophic analogs, acting through a cAMP-independent mechanism and inducing ADNF release, could represent new avenues in the understanding and prevention of human cerebral palsy.

Animals↗
PubMed1997

Inhibition of murine embryonic growth by human immunodeficiency virus envelope protein and its prevention by vasoactive intestinal peptide and activity-dependent neurotrophic factor.

Intrauterine growth retardation and neurodevelopmental handicaps are common among infants born to HIV-positive mothers and may be due to the actions of virions and/or maternally derived viral products. The viral envelope protein, gp120, is toxic to neurons, induces neuronal dystrophy, and retards behavioral development in neonatal rats. Vasoactive intestinal peptide, a neuropeptide regulator of early postimplantation embryonic growth, and the neuroprotective protein, activity-dependent neurotrophic factor, prevent gp120-induced neurotoxicity. Whole embryo culture of gestational day 9.5 mouse embryos was used to assess the effect of gp120 on growth. Embryos treated with gp120 exhibited a dose-dependent inhibition of growth. gp120-treated embryos (10(-8) M) grew 1.2 somites in the 6-h incubation period, compared with 3.9 somites by control embryos. Embryos treated with gp120 were significantly smaller in cross-sectional area and had significantly less DNA and protein than controls. Growth inhibition induced by gp120 was prevented by cotreatment with vasoactive intestinal peptide or activity-dependent neurotrophic factor. gp120 may play a role in the growth retardation and developmental delays experienced by infants born to HIV-positive mothers. Vasoactive intestinal peptide and related factors may provide a therapeutic strategy in preventing developmental deficits.

Animals↗
PubMed1997

Growth factor properties of VIP during early brain development. Whole embryo culture and in vivo studies.

Vasoactive intestinal peptide (VIP), a 28 amino acid neuropeptide widely distributed in the mammalian nervous system, has potent growth-related actions that influence cell division, neuronal survival, and neurodifferentiation. To address the potential effects of VIP on embryonic growth, whole postimplantation embryo cultures were used. After a 4-hour incubation, VIP stimulated growth as assessed by the following increases from control: embryonic volume (63%), DNA (103%), and protein content (63%), as well as the number of cells in S-phase (490%). No apparent histological abnormalities are produced by VIP. To assess the in vivo function of VIP in early CNS growth, a VIP antagonist (VA) was injected i.p. between E9 and E11. VA induced a dose reduction of the DNA (84% of controls) and protein (80% of controls) contents of the E11 head and a decrease of E17 brain weight (87% of controls). In contrast, body growth was less affected by the antagonist. injections of VA for a longer period (E9 to E17) did not increase the severity of the microcephaly. By ex vivo autoradiography, GTP-sensitive VIP binding sites were detected in the germinative neuroepithelium between E9 and E11, but not between E13 and E15, during neuronal migration. These data demonstrate that VIP regulates mitogenic activity in the premigratory neuroepithelium. Although this effect is limited to a short ontogenic period, blockade of VIP by a specific antagonist induces a severe microcephaly.

Amino Acid Sequence↗
PubMed1997

Identity of neurotrophic molecules released from astroglia by vasoactive intestinal peptide.

Subnanomolar concentrations of VIP elicit a survival-producing action in CNS cultures composed of both astroglia and neurons. This neurotrophic action is mediated by a complex array of substances released by VIP from astrocytes. Included in this glial protein mixture is a cytokine (interleukin-1 alpha), a serine protease inhibitor (protease nexin I), and an extracellular stress protein (activity-dependent neurotrophic factor). In dissociated spinal cord cultures, all of these substances exhibit neuroprotection from neuronal cell death produced by electrical blockade with tetrodotoxin. All these substances produce neuronal cell death when test cultures are treated with neutralizing antisera to any one of them. They are all apparently necessary for the survival of a subpopulation of neurons that are dependent on spontaneous, excitatory neurotransmission. Our view is that these substances are components of a glia-derived environment that regulates, together with target-derived growth factors, the survival fate of developing neurons. In addition, it is our belief that some of these glia-derived substances will be found to have active roles in the injury response to the CNS or in the regulation of VIP-mediated growth in other tissues. Drugs based on these substances may provide therapeutic agents for the treatment of neurodegeneration and tumor growth.

Amyloid beta-Protein Precursor↗
PubMed1997

Cholinergic stimulation increases thrombin activity and gene expression in cultured mouse muscle.

Activity-dependent synapse reduction is a major determinant of neuromuscular innervation. Previous research has shown that nanomolar concentrations of hirudin, a specific thrombin antagonist, significantly attenuates this reduction, and protease nexin 1 (PN1), an endogenous thrombin inhibitor closely localized to the neuromuscular synapse, can inhibit synapse reduction at similar concentrations. Protease inhibitors which do not inhibit thrombin, including cystatin and aprotinin, had no effect on synapse reduction. We present a series of experiments examining whether prothrombin and/or PN1 gene expression, as well as thrombin activity, are regulated in muscle cultures by acetylcholine (ACh) receptor activation. We also studied the effect of exogenous thrombin on synapse elimination in co-cultures of muscle and cholinergic neurons. Cultured muscle cells were electrically blocked with tetrodotoxin (TTX), or co-treated with ACh in order to isolate ACh receptor activation. Electrical blockade resulted in a decrease in thrombin release to about two-thirds of control values. The application of ACh to electrically blocked muscle cultures resulted in a 2.5-fold increase in thrombin activity released into the medium and a 2-fold increase in prothrombin gene expression. In contrast, ACh treatment in the presence of TTX had no effect on PN1 gene expression compared to treatment with TTX alone. In addition, exogenous thrombin significantly increased synapse elimination in unstimulated muscle/cholinergic neuron co-cultures. These results suggest that thrombin or a thrombin-like molecule released from muscle is required for activity-dependent synapse elimination and is regulated by neuromuscular activity.

Acetylcholine↗
PubMed1997

Antiserum to activity-dependent neurotrophic factor produces neuronal cell death in CNS cultures: immunological and biological specificity.

Activity-dependent neurotrophic factor (ADNF) is a glia-derived protein that is neuroprotective at femtomolar concentrations. ADNF is released from astroglia after treatment with 0.1 nM vasoactive intestinal peptide (VIP). To further assess the biological role of ADNF, antiserum was produced following sequential injections of purified ADNF into mice. Anti-ADNF ascites fluid (1:10,000) decreased neuronal survival by 45-55% in comparison to untreated cultures or those treated with control ascites. The neuronal death after anti-ADNF treatment was observed in cultures derived from the spinal cord, hippocampus or cerebral cortex at similar IC50's. Using a terminal deoxynucleotidyl transferase in situ assay to estimate apoptosis in cerebral cortical cultures, anti-ADNF was shown to produce a 70% increase in the number of labeled cells in comparison to controls. In spinal cord cultures, anti-ADNF treatment produced a 20% decrease in choline acetyltransferase activity in comparison to controls. Neuronal cell death produced by the antiserum to ADNF was prevented in cultures co-treated with purified ADNF or ADNF-15, an active peptide derived from the parent ADNF. In vitro binding between the anti-ADNF and ADNF-15 was demonstrated with size exclusion chromatography. Comparative studies with other growth factors (insulin-like growth factor-1, platelet-derived growth factor, nerve growth factor, epidermal growth factor, ciliary neurotrophic growth factor, and neurotrophin-3) demonstrated that only ADNF prevented neuronal cell death associated with electrical blockade. These investigations indicated that an ADNF-like substance was present in cultures derived from multiple locations in the central nervous system and that ADNF-15 exhibited both neuroprotection and immunogenicity. ADNF appears to be both a regulator of activity-dependent neuronal survival and a neuroprotectant.

Amino Acid Sequence↗
PubMed1997

Identification of VIP/PACAP receptors on rat astrocytes using antisense oligodeoxynucleotides.

Vasoactive intestinal peptide (VIP) has been shown to be a potent promoter of neuronal survival. Pituitary adenylate cyclase-activating peptide (PACAP), a homologous peptide, shares activity and receptor molecules with VIP. The neuroprotective effects of VIP have been shown to be mediated via astroglial-derived molecules. Utilizing a battery of antisense oligodeoxynucleotides directed against the multiple cloned VIP-preferring (VIP receptors 1 and 2) or PACAP-preferring receptors (six splice variants derived from the same gene transcript), the authors have demonstrated the existence of a specific PACAP receptor splice variant (PACAP4 or hop2) on astrocytes as well as a VIP type2 receptor. The identification of the receptors was achieved by incubation of the cells in the presence of the specific antisense oligodeoxynucleotide followed by radiolabeled VIP binding and displacement. Polymerase chain reaction (PCR) coupled to direct sequencing identified the expression of the PACAP4-hop2 receptor splice variant in astrocytes. Neuronal survival assays were conducted in mixed neuronal-glial cultures derived from newborn rat cerebral cortex. When these cultures were exposed to the battery of the antisense oligodeoxynucleotides, in serum-free media, only the PACAP-specific ones (e.g., hop2-specific) had an effect in decreasing neuronal cell counts. Thus, the VIP neuronal survival effect is mediated, at least in part, via a specific PACAP receptor (containing a unique insertion of 27 amino acids--the hop2 cassette). These data indicate that a hop2-like PACAP/VIP receptor is the receptor that mediates neurotropism.

Alternative Splicing↗
PubMed1997

Neurobehavioral development of neonatal mice following blockade of VIP during the early embryonic period.

Previous work has shown that blockade of VIP function in the early postimplantation embryo results in growth retardation and microcephaly. In the present work, the neurobehavioral development of neonatal mice was examined following treatment of dams with a VIP antagonist during this period. Inhibition of VIP functions during early embryogenesis impaired the performance of 5 of 10 developmental behaviors. These behaviors included developmental milestones (first appearance of ear twitch and eye opening) and complex motor behaviors (negative geotaxis, surface righting, and air righting). The retardation of neurobehavioral development produced by inhibition of VIP action indicates that this peptide is important to the progression of embryonic development.

Animals↗
PubMed1997

Vasoactive intestinal peptide stimulation of human trabecular meshwork cell growth.

PURPOSE: To demonstrate that vasoactive intestinal peptide (VIP), a 28-amino acid neuropeptide, is a growth factor of human trabecular meshwork (TM) cells in culture and in a corneoscleral explant organ culture treated with laser trabeculoplasty (LTP). METHODS: Proliferating human TM cells in cell cultures were incubated with VIP for 20 hours, followed by total cell number determination, using a Coulter counter. The percentage of proliferating TM cells was assessed, using an antibody against the proliferating cell nuclear antigen (PCNA). To test the growth effect of VIP on TM cells in situ, corneoscleral explants in organ cultures were first treated with argon LTP to initiate TM-cell proliferation and then were exposed to VIP for 48 hours. The mitotic TM cells were demonstrated immunocytochemically, using anti-PCNA in paraffin sections of the explants; and the total number of TM cells was determined after paraffin sections were counterstained by hematoxylin. RESULTS: Vasoactive intestinal peptide dose-dependently stimulated the proliferation of TM cells in cell culture. Treatment with 5 x 10(-10) M VIP resulted in a maximal increase of 40% in cell number. The effect of VIP was blocked by a VIP antagonist. The number of PCNA-stained TM cells and the total cell number in the TM in LTP-treated corneoscleral explants were increased by VIP. CONCLUSIONS: Exogenously applied VIP stimulated the proliferation of human TM cells in subconfluent cultures and in LTP-treated corneoscleral explants. In that LTP has been shown to increase the number of TM cells in situ, the growth stimulatory effect of VIP may help enhance this therapy.

Adolescent↗
PubMed1996

VIP regulation of embryonic growth.

Vasoactive intestinal peptide (VIP) plays a regulatory role in the growth of early postimplantation rodent embryos through its action on receptors localized to the central nervous system (CNS). However, the origin of the VIP influencing embryonic growth is unknown. VIP binding sites have been found prenatally; however, VIP mRNA was not detected in the rat CNS before birth and has been detected in peripheral organs only during the final third of gestation. Recent studies have revealed that VIP receptors were limited to the CNS in the embryonic day 11 (E11) rat embryo/trophoblast, which, in addition, had almost four times the VIP concentration of the E17 fetus. However, neither in situ hybridization or reverse transcriptase-polymerase chain reaction methods detected VIP mRNA in the E11 rat embryo or embryonic membranes. Rat maternal serum revealed a peak in VIP concentration at days E10-E12 of pregnancy, with VIP levels 6- to 10-fold higher than later during pregnancy. Radiolabeled VIP, administered intravenously to pregnant female mice, was found in the E10 embryo. These results suggest that VIP produced by extraembryonic tissues may regulate embryonic growth during the early postimplantation stage of development in the rodent.

Animals↗
PubMed1996

A femtomolar-acting neuroprotective peptide.

A novel 14-amino acid peptide, with stress-protein-like sequences, exhibiting neuroprotection at unprecedented concentrations, is revealed. This peptide prevented neuronal cell death associated with the envelope protein (GP 120) from HIV, with excitotoxicity (N-methyl d-aspartate), with the beta amyloid peptide (putative cytotoxin in Alzheimer's disease), and with tetrodotoxin (electrical blockade). The peptide was designed to contain a sequence derived from a new neuroprotective protein secreted by astroglial cells in the presence of vasoactive intestinal peptide. The neurotrophic protein was isolated by sequential chromatographic methods combining ion exchange, size separation, and hydrophobic interaction. The protein (mol mass, 14 kD and pI, 8.3 +/- 0.25) was named activity-dependent neurotrophic factor, as it protected neurons from death associated with electrical blockade. Peptide sequencing led to the synthesis of the novel 14-amino acid peptide that was homologous, but not identical, to an intracellular stress protein, heat shock protein 60. Neutralizing antiserum to heat shock protein 60 produced neuronal cell death that could be prevented by cotreatment with the novel protein, suggesting the existence of extracellular stress-like proteins with neuroprotective properties. These studies identify a potent neuroprotective glial protein and an active peptide that provide a basis for developing treatments of currently intractable neurodegenerative diseases.

Amino Acid Sequence↗
PubMed1996

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

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

Administration, Intranasal↗