Calbindin D28K gene transfer via herpes simplex virus amplicon vector decreases hippocampal damage in vivo following neurotoxic insults

Entorhinal cortex dysfunction in Alzheimer's disease

The entorhinal cortex (EC) is the brain region that often exhibits the earliest histological alterations in Alzheimer's disease (AD), including the formation of neurofibrillary tangles and cell death. Recently, brain imaging studies from preclinical AD patients and electrophysiological recordings from AD animal models have shown that impaired neuronal activity in the EC precedes neurodegeneration. This implies that memory impairments and spatial navigation deficits at the initial stage of AD are likely caused by activity dysfunction rather than by cell death. This review focuses on recent findings on EC dysfunction in AD, and discusses the potential pathways for mitigating AD progression by protecting the EC.

Calcium Signaling During Brain Aging and Its Influence on the Hippocampal Synaptic Plasticity

Calcium (Ca²⁺) ions are highly versatile intracellular signaling molecules and are universal second messenger for regulating a variety of cellular and physiological functions including synaptic plasticity. Ca²⁺ homeostasis in the central nervous system endures subtle dysregulation with advancing age. Research has provided abundant evidence that brain aging is associated with altered neuronal Ca²⁺ regulation and synaptic plasticity mechanisms. Much of the work has focused on the hippocampus, a brain region critically involved in learning and memory, which is particularly susceptible to dysfunction during aging. The current chapter takes a specific perspective, assessing various Ca²⁺ sources and the influence of aging on Ca²⁺ sources and synaptic plasticity in the hippocampus. Integrating the knowledge of the complexity of age-related alterations in neuronal Ca²⁺ signaling and synaptic plasticity mechanisms will positively shape the development of highly effective therapeutics to treat brain disorders including cognitive impairment associated with aging and neurodegenerative disease.

Calcium-Binding Proteins as Determinants of Central Nervous System Neuronal Vulnerability to Disease

Neuronal subpopulations display differential vulnerabilities to disease, but the factors that determine their susceptibility are poorly understood. Toxic increases in intracellular calcium are a key factor in several neurodegenerative processes, with calcium-binding proteins providing an important first line of defense through their ability to buffer incoming calcium, allowing the neuron to quickly achieve homeostasis. Since neurons expressing different calcium-binding proteins have been reported to be differentially susceptible to degeneration, it can be hypothesized that rather than just serving as markers of different neuronal subpopulations, they might actually be a key determinant of survival. In this review, we will summarize some of the evidence that expression of the EF-hand calcium-binding proteins, calbindin, calretinin and parvalbumin, may influence the susceptibility of distinct neuronal subpopulations to disease processes.

Isx9 Regulates Calbindin D28K Expression in Pancreatic β Cells and Promotes β Cell Survival and Function

Pancreatic β-cell dysfunction and death contribute to the onset of diabetes, and novel strategies of β-cell function and survival under diabetogenic conditions need to be explored. We previously demonstrated that Isx9, a small molecule based on the isoxazole scaffold, drives neuroendocrine phenotypes by increasing the expression of genes required for β-cell function and improves glycemia in a model of β cell regeneration. We further investigated the role of Isx9 in β-cell survival. We find that Isx9 drives the expression of Calbindin-D28K (D28K), a key regulator of calcium homeostasis, and plays a cytoprotective role through its calcium buffering capacity in β cells. Isx9 increased the activity of the calcineurin (CN)/cytoplasmic nuclear factor of the activated T-cells (NFAT) transcription factor, a key regulator of D28K, and improved the recruitment of NFATc1, cAMP response element-binding protein (CREB), and p300 to the D28K promoter. We found that nutrient stimulation increased D28K plasma membrane enrichment and modulated calcium channel activity in order to regulate glucose-induced insulin secretion. Isx9-mediated expression of D28K protected β cells against chronic stress induced by serum withdrawal or chronic inflammation by reducing caspase 3 activity. Consequently, Isx9 improved human islet function after transplantation in NOD-SCID mice in a streptozotocin-induced diabetes model. In summary, Isx9 significantly regulates expression of genes relevant to β cell survival and function, and may be an attractive therapy to treat diabetes and improve islet function post-transplantation.

Overexpression of Human SOD1 Leads to Discrete Defects in the Cerebellar Architecture in the Mouse

The human superoxide dismutase 1 (SOD1) gene is responsible for neutralizing supercharged oxygen radicals within the cell. Mutation in SOD1 gene causes amyotrophic lateral sclerosis (ALS). Recent studies have shown involvement of the cerebellum in ALS, although the cerebellar contribution in SOD1 transgenic mice remains unclear. Using immunohistopathology, we investigated the Purkinje cell phenotype in the vermis of the SOD1 transgenic mice cerebellum. Calbindin 1 (Calb1) and three well-known zone and stripe markers, zebrin II, HSP25, and PLCβ4 have been used to explore possible alteration in zone and stripe. Here we show that Calb1 expression is significantly reduced in a subset of the Purkinje cells that is almost aligned with the cerebellar zones and stripes pattern. The Purkinje cells of SOD1 transgenic mice display a pattern of Calb1 down-regulation, which seems to proceed to Purkinje cell degeneration as the mice age. The onset of Calb1 down-regulation in Purkinje cells begins from the central zone and continues into the nodular zone, however it has not been observed in the anterior and posterior zones. In a subgroup of SOD1 transgenic mice in which gait unsteadiness was apparent, down-regulation of Calb1 is seen in a subset of PLCβ4⁺ Purkinje cells in the anterior zone. These observations suggest that the Calb1^- subset of Purkinje cells in the anterior zone, which receives somatosensory input, causes unsteady gait. Our data suggest that human SOD1 overexpression leads to Calb1 down-regulation in the zone and strip pattern and raise the question of whether SOD1 overexpression leads to Purkinje cells degeneration.

Biological chemistry and functionality of protein sulfenic acids and related thiol modifications

Selective modification of proteins at cysteine residues by reactive oxygen, nitrogen or sulfur species formed under physiological and pathological states is emerging as a critical regulator of protein activity impacting cellular function. This review focuses primarily on protein sulfenylation (-SOH), a metastable reversible modification connecting reduced cysteine thiols to many products of cysteine oxidation. An overview is first provided on the chemistry principles underlining synthesis, stability and reactivity of sulfenic acids in model compounds and proteins, followed by a brief description of analytical methods currently employed to characterize these oxidative species. The following chapters present a selection of redox-regulated proteins for which the -SOH formation was experimentally confirmed and linked to protein function. These chapters are organized based on the participation of these proteins in the regulation of signaling, metabolism and epigenetics. The last chapter discusses the therapeutic implications of altered redox microenvironment and protein oxidation in disease.

Morphological changes in the suprachiasmatic nucleus of aging female marmosets (Callithrix jacchus)

The suprachiasmatic nuclei (SCN) are pointed to as the mammals central circadian pacemaker. Aged animals show internal time disruption possibly caused by morphological and neurochemical changes in SCN components. Some studies reported changes of neuronal cells and neuroglia in the SCN of rats and nonhuman primates during aging. The effects of senescence on morphological aspects in SCN are important for understanding some alterations in biological rhythms expression. Therefore, our aim was to perform a comparative study of the morphological aspects of SCN in adult and aged female marmoset. Morphometric analysis of SCN was performed using Nissl staining, NeuN-IR, GFAP-IR, and CB-IR. A significant decrease in the SCN cells staining with Nissl, NeuN, and CB were observed in aged female marmosets compared to adults, while a significant increase in glial cells was found in aged marmosets, thus suggesting compensatory process due to neuronal loss evoked by aging.

Differences of calcium binding proteins immunoreactivities in the young hippocampal CA1 region from the adult following transient ischemic damage

It has been reported that the young were much more resistant to transient cerebral ischemia than in the adult. In the present study, we examined that about 90% of CA1 pyramidal cells in the adult gerbil hippocampus died at 4days after ischemia-reperfusion; however, in the young hippocampus, about 56% of them died at 7days after ischemia-reperfusion. We compared immunoreactivities and levels of calcium binding proteins (CBPs), such as calbindin 28k (CB-D28k), calretinin (CR) and parvalbumin (PV). The immunoreactivities and protein levels of all the CBPs in the young sham were higher than those in the adult sham. In the adult, the immunoreactivities and protein levels of all the CBPs were markedly decreased at 4days after ischemia-reperfusion, however, in the young, they were apparently maintained. At 7days after ischemia-reperfusion, they were decreased in the young, however, they were much higher than those in the adult. In brief, the immunoreactivities and levels of CBPs were not decreased in the ischemic CA1 region of the young 4days after transient cerebral ischemia. This finding indicates that the longer maintenance of CBPs may contribute to a less and more delayed neuronal death/damage in the young.

The absence of the calcium-buffering protein calbindin is associated with faster age-related decline in hippocampal metabolism

Although reductions in the expression of the calcium-buffering proteins calbindin D-28K (CB) and parvalbumin (PV) have been observed in the aging brain, it is unknown whether these changes contribute to age-related hippocampal dysfunction. To address this issue, we measured basal hippocampal metabolism and hippocampal structure across the lifespan of C57BL/6J, calbindin D-28k knockout (CBKO) and parvalbumin knockout (PVKO) mice. Basal metabolism was estimated using steady state relative cerebral blood volume (rCBV), which is a variant of fMRI that provides the highest spatial resolution, optimal for the analysis of individual subregions of the hippocampal formation. We found that like primates, normal aging in C57BL/6J mice is characterized by an age-dependent decline in rCBV-estimated dentate gyrus (DG) metabolism. Although abnormal hippocampal fMRI signals were observed in CBKO and PVKO mice, only CBKO mice showed accelerated age-dependent decline of rCBV-estimated metabolism in the DG. We also found age-independent structural changes in CBKO mice, which included an enlarged hippocampus and neocortex as well as global brain hypertrophy. These metabolic and structural changes in CBKO mice correlated with a deficit in hippocampus-dependent learning in the active place avoidance task. Our results suggest that the decrease in CB that occurs during normal aging is involved in age-related hippocampal metabolic decline. Our findings also illustrate the value of using multiple MRI techniques in transgenic mice to investigate mechanisms involved in the functional and structural changes that occur during aging.

Teleost fish as a model system to study successful regeneration of the central nervous system

Traumatic brain injury and spinal cord injury are devastating conditions that may result in death or long-term disability. A promising strategy for the development of effective cell replacement therapies involves the study of regeneration-competent organisms. Among this group, teleost fish are distinguished by their excellent potential to regenerate nervous tissue and to regain function after injury to the central nervous system. In this chapter, we summarize our current understanding of the cellular processes that mediate this regenerative potential, and we show that several of these processes are shared with the normal development of the intact central nervous system; we describe how the spontaneous self-repair of the teleostean central nervous system leads to functional recovery, at physiological and behavioral levels; we discuss the possible function of molecular factors associated with the degenerative and regenerative processes after injury; and, finally, we speculate on evolutionary aspects of adult neurogenesis and neuronal regeneration, and on how a better understanding of these aspects could catalyze the development of therapeutic strategies to overcome the regenerative limits of the mammalian CNS.

Herpes simplex virus type 1-based amplicon vectors for fundamental research in neurosciences and gene therapy of neurological diseases

Somatic manipulation of the nervous system without the involvement of the germinal line appears as a powerful counterpart of the transgenic strategy. The use of viral vectors to produce specific, transient and localized knockout, knockdown, ectopic expression or overexpression of a gene, leads to the possibility of analyzing both in vitro and in vivo molecular basis of neural function. In this approach, viral particles engineered to carry transgenic sequences are delivered into discrete brain regions, to transduce cells that will express the transgenic products. Amplicons are replication-incompetent helper-dependent vectors derived from herpes simplex virus type 1 (HSV-1), with several advantages that potentiate their use in neurosciences: (1) minimal toxicity: amplicons do not encode any virus proteins, are neither toxic for the infected cells nor pathogenic for the inoculated animals and elicit low levels of adaptive immune responses; (2) extensive transgene capacity to carry up to 150-kb of foreign DNA; i.e., entire genes with regulatory sequences could be delivered; (3) widespread cellular tropism: amplicons can experimentally infect several cell types including glial cells, though naturally the virus infects mainly neurons and epithelial cells; (4) since the viral genome does not integrate into cellular chromosomes there is low probability to induce insertional mutagenesis. Recent investigations on gene transfer into the brain using these vectors, have focused on gene therapy of inherited genetic diseases affecting the nervous system, such as ataxias, or on neurodegenerative disorders using experimental models of Parkinson's or Alzheimer's disease. Another group of studies used amplicons to investigate complex neural functions such as neuroplasticity, anxiety, learning and memory. In this short review, we summarize recent data supporting the potential of HSV-1 based amplicon vector model for gene delivery and modulation of gene expression in primary cultures of neuronal cells and into the brain of living animals.

Phenotypic changes in calbindin D28K immunoreactivity in the hippocampus of Fmr1 knockout mice

Fragile X syndrome (FXS), the most prevalent form of inherited mental retardation, is caused by the lack of FMRP (fragile mental retardation protein) as a result of the transcriptional silencing of the FMR1 gene. Here we analyze the immunohistochemical expression of the calbindin D28K protein in the hippocampus of Fmr1 knockout (KO) mice and compare it with that of their wildtype (WT) littermates. The spatial distribution pattern of calbindin-immunoreactive cells in the hippocampus was similar in WT and KO mice but for each age studied (ranging from 3.5-8 months) the dentate gyrus of Fmr1-KO mice showed a significant reduction in calbindin-immunoreactive granule cells. Also, the number of calbindin-immunoreactive cells was reduced in the CA1 pyramidal layer in KO mice compared to their WT littermates. In addition, Frm1-KO mice showed a group of calbindin-immunoreactive cells located only in the left CA3b subregion that was only sometimes observed in WT mice. Overall, the absence of FMRP results in a dysregulation of the calbindin protein expression in the hippocampus. This dysregulation is cell type- and time-dependent and as a consequence key elements of the hippocampal trisynaptic circuitry may lack calbindin in critical periods for normal memory/learning abilities to be achieved and may explain some of the FXS symptoms observed in the Fmr1-KO mouse model.

Hypothyroid states mitigate the diabetes-induced reduction of calbindin D-28k, calretinin, and parvalbumin immunoreactivity in type 2 diabetic rats

In this study, we investigated the differences in calbindin D-28k (CB), calretinin, (CR) and parvalbumin (PV) immunoreactivity in the hippocampus of Zucker diabetic fatty (ZDF) rats and Zucker lean control (ZLC) rats. In addition, we observed the effects of hypothyroidism on the levels of immunoreactivity of these proteins in ZDF rats. For this study, 7-week-old ZDF rats were used, and methimazole treatment was continued for 5 weeks to induce hypothyroidism. The animals were sacrificed at 12 weeks of age. ZDF rats showed increased blood glucose levels compared to those in ZLC rats. Methimazole intervention significantly reduced total and free T3 levels, and it ameliorated the increase of blood glucose levels in ZDF rats. In ZLC rats, CB, CR, and PV immunoreactivity was detected in regions of the hippocampus proper. In vehicle-treated ZDF rats, CB, CR, and PV immunoreactivity was significantly decreased in the hippocampus. However, in the methimazole-treated rats, CB, CR, and PV immunoreactivity was significantly increased compared to that in the vehicle-treated rats. These results suggest that hypothyroidism ameliorated the diabetes-induced reduction of CB, CR, and PV immunoreactivity in the hippocampus.

Calbindin-D28K inhibits apoptosis in dopaminergic neurons by activation of the PI3-kinase-Akt signaling pathway

Calbindin-D28k (CaBP) has a neuroprotective effect on dopaminergic (DA) neurons in several models of Parkinson's disease. We used the DA cell line MN9D to explore the mechanisms underlying CaBP-mediated protection against the neurotoxin 6-hydroxydopamine (6-OHDA) of DA neurons. In MN9D cells that were transfected with the expression vector pcDNA3-CB containing CaBP cDNA, the expression level of CaBP was significantly increased. After treating with 6-OHDA, a significant decrease in the apoptosis rate of the transfected MN9D cells was noted, as well as an obvious increase in the expression of phosphorylation of Akt (p-Akt); however, no significant change in the expression of total Akt or phospho-p100 (p-p100) occurred after this treatment. After treatment with wortmannin, an inhibitor of the PI3-kinase-Akt (PI-3K/Akt) signal pathway, an increase in the expression level of CaBP was observed, but there were no other obvious changes of the experimental index mentioned previously in the groups transfected with pcDNA3-CB. These studies suggest that CaBP has a significant role in protecting DA cells against the apoptosis induced by 6-OHDA--through PI-3K/Akt signaling pathway--where the non-canonical nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway might have no relevance.

Of mice and rats: key species variations in the sexual differentiation of brain and behavior

Mice and rats are important mammalian models in biomedical research. In contrast to other biomedical fields, work on sexual differentiation of brain and behavior has traditionally utilized comparative animal models. As mice are gaining in popularity, it is essential to acknowledge the differences between these two rodents. Here we review neural and behavioral sexual dimorphisms in rats and mice, which highlight species differences and experimental gaps in the literature, that are needed for direct species comparisons. Moving forward, investigators must answer fundamental questions about their chosen organism, and attend to both species and strain differences as they select the optimal animal models for their research questions.

Parvalbumin-, calbindin-, and calretinin-immunoreactive hippocampal interneuron density in autism

BACKGROUND

There has been a long-standing interest in the possible role of the hippocampus in autism and both postmortem brain and neuroimaging studies have documented varying abnormalities in this limbic system structure.

AIMS

This study investigates the density of subsets of hippocampal interneurons, immunostained with the calcium binding proteins, calbindin (CB), calretinin (CR) and parvalbumin (PV) to determine whether specific subpopulations of interneurons are impacted in autism.

MATERIALS AND METHODS

Unbiased stereological techniques were used to quantify the neuronal density of these immunoreactive subpopulations of gamma-aminobutyric acid-ergic (GABAergic) interneurons analyzed in the CA and subicular fields in postmortem brain material obtained from five autistic and five age-, gender- and postmortem interval-matched control cases.

RESULTS

Results indicate a selective increase in the density of CB-immunoreactive interneurons in the dentate gyrus, an increase in CR-immunoreactive interneurons in area CA1, and an increase in PV-immunoreactive interneurons in areas CA1 and CA3 in the hippocampus of individuals with autism when compared with controls.

DISCUSSION/CONCLUSIONS

Although our sample size is small, these findings suggest that GABAergic interneurons may represent a vulnerable target in the brains of individuals with autism, potentially impacting upon their key role in learning and information processing. These preliminary findings further suggest the need for future more expanded studies in a larger number of postmortem brain samples from cases of autism and controls.

Hippocampal transcriptome after status epilepticus in mice rendered seizure damage-tolerant by epileptic preconditioning features suppressed calcium and neuronal excitability pathways

Preconditioning brain with a sub-lethal stressor can temporarily generate a damage-refractory state. Microarray analyses have defined the changes in hippocampal gene expression that follow brief preconditioning seizures, but not the transcriptome after a prolonged and otherwise injurious seizure in previously preconditioned brain. Presently, microarray analysis was performed 24 h after status epilepticus in mice that had received previously either seizure preconditioning (tolerance) or sham-preconditioning (injury). Transcriptional changes in the hippocampal CA3 subfield of >or=2 fold were detected for 1357 genes in the tolerance group compared to a non-seizure control group, with 54% up-regulated. Of these regulated genes, 792 were also regulated in the injury group. Among the remaining 565 genes regulated only in tolerance, 73% were down-regulated. Analysis of the genes differentially suppressed in tolerance identified calcium signaling, ion channels and excitatory neurotransmitter receptors, and the synapse as over-represented among pathways, functions and compartments. Finally, 12 days continuous EEG recordings determined mice with induced tolerance had fewer spontaneous electrographic seizures compared to the injury group. Our data suggest the transcriptional phenotype of neuroprotection in tolerance may be dictated by the biology of the preconditioning stressor, functions by transcriptional reduction of vulnerability to excitotoxicity, and has anti-epileptogenic effects.

Crosstalk between calcium and redox signaling: from molecular mechanisms to health implications

Studies done many years ago established unequivocally the key role of calcium as a universal second messenger. In contrast, the second messenger roles of reactive oxygen and nitrogen species have emerged only recently. Therefore, their contributions to physiological cell signaling pathways have not yet become universally accepted, and many biological researchers still regard them only as cellular noxious agents. Furthermore, it is becoming increasingly apparent that there are significant interactions between calcium and redox species, and that these interactions modify a variety of proteins that participate in signaling transduction pathways and in other fundamental cellular functions that determine cell life or death. This review article addresses first the central aspects of calcium and redox signaling pathways in animal cells, and continues with the molecular mechanisms that underlie crosstalk between calcium and redox signals under a number of physiological or pathological conditions. To conclude, the review focuses on conditions that, by promoting cellular oxidative stress, lead to the generation of abnormal calcium signals, and how this calcium imbalance may cause a variety of human diseases including, in particular, degenerative diseases of the central nervous system and cardiac pathologies.

Calcium-sensitive regulation of monoamine oxidase-A contributes to the production of peroxyradicals in hippocampal cultures: implications for Alzheimer disease-related pathology

Background

Calcium (Ca²⁺) has recently been shown to selectively increase the activity of monoamine oxidase-A (MAO-A), a mitochondria-bound enzyme that generates peroxyradicals as a natural by-product of the deamination of neurotransmitters such as serotonin. It has also been suggested that increased intracellular free Ca²⁺ levels as well as MAO-A may be contributing to the oxidative stress associated with Alzheimer disease (AD).

Results

Incubation with Ca²⁺ selectively increases MAO-A enzymatic activity in protein extracts from mouse hippocampal HT-22 cell cultures. Treatment of HT-22 cultures with the Ca²⁺ ionophore A23187 also increases MAO-A activity, whereas overexpression of calbindin-D28K (CB-28K), a Ca²⁺-binding protein in brain that is greatly reduced in AD, decreases MAO-A activity. The effects of A23187 and CB-28K are both independent of any change in MAO-A protein or gene expression. The toxicity (via production of peroxyradicals and/or chromatin condensation) associated with either A23187 or the AD-related β-amyloid peptide, which also increases free intracellular Ca²⁺, is attenuated by MAO-A inhibition in HT-22 cells as well as in primary hippocampal cultures.

Conclusion

These data suggest that increases in intracellular Ca²⁺ availability could contribute to a MAO-A-mediated mechanism with a role in AD-related oxidative stress.

HSV-1 amplicon vectors: a promising and versatile tool for gene delivery

Amplicons are defective and non-integrative vectors derived from herpes simplex virus type 1. They carry no virus genes in the vector genome and are, therefore, not toxic to the infected cells or pathogenic for the transduced organisms, making these vectors safe. In addition, the large transgenic capacity of amplicons, which allow delivery of < or = 150 Kbp of foreign DNA, make these vectors one of the most powerful, interesting and versatile gene delivery platforms. Here, the authors present recent technological developments that have significantly improved and extended the use of amplicons, both in cultured cells and in living organisms. In addition, this review illustrates the many possible applications that are presently being developed with amplicons and discuss the many difficulties still pending to be solved in order to achieve stable and physiologically regulated transgenic expression.

Distribution of calbindin-D28k, neuronal nitric oxide synthase, and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) in the lateral nucleus of the sheep amygdaloid complex

This study describes calbindin-D28k (CB), neuronal nitric oxide synthase (nNOS), and nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) expression in the lateral nucleus of the sheep amygdaloid complex. Double immunofluorescence protocol was used in order to determine whether there is colocalization of CB and nNOS. The CB-immunoreactive (IR) neuronal population was composed especially of non-pyramidal neurons, but a few pyramidal cells were also present. The non-pyramidal neurons showed a multipolar and, occasionally, a fusiform morphology. The comparison between single-labeled CB-IR non-pyramidal neurons and cells belonging to CB-IR neuronal population showed they were identical for morphology, mean size, and distribution. The single-labeled CB-IR non-pyramidal neurons were only the 17.8% of the total non-pyramidal neurons counted. The nNOS-IR neuronal population was represented by non-pyramidal multipolar and fusiform neurons. Single-labeled nNOS-IR non-pyramidal neurons had the same morphology, mean area, and distribution as cells belonging to nNOS-IR neuronal population. Single-labeled nNOS-IR non-pyramidal neurons were more numerous than single-labeled CB-IR, and represented the 73.7% of total non-pyramidal neurons counted. NADPH-d-positive cells had the same morphology and distribution as the nNOS-IR neurons. Double immunolabeling (CB/nNOS) was found mostly in non-pyramidal multipolar neurons and only in a few non-pyramidal fusiform cells. These neurons had a mean perikaryal area significantly higher and significantly smaller than that of single-labeled nNOS and single-labeled CB-IR non-pyramidal neurons, respectively. CB and nNOS coexist only in a minority of non-pyramidal neurons (8.5%). The 32.4% of all CB-IR non-pyramidal neurons were nNOS-positive; only 10.4% of nNOS-IR non-pyramidal neurons were CB-positive. These results indicate that CB and nNOS are expressed by selective neurons and that the majority of nNOS-IR non-pyramidal neurons are lacking in CB.

Upregulation of calbindin-D28k expression during regeneration in the adult fish cerebellum

In contrast to mammals, fish are distinguished by their enormous potential for brain repair after injuries. This phenomenon has been well studied after application of stab-wound lesions to the corpus cerebelli, a cerebellar subdivision, in the teleost fish Apteronotus leptorhynchus. By combining this lesion paradigm with immunohistochemical staining, we examined the potential role of the calcium-binding protein calbindin-D(28k) in the process of regeneration. Calbindin-D(28k)-immunoreactive cell bodies and fibers were evident in the lesion path and the immediate vicinity of the lesion in the period between 16 h and 7 days after the lesion but absent from this region at shorter or longer postlesion survival times and in the intact brain. Both the number of immunolabeled cells and the intensity of the label were most pronounced 1-3 days postlesion. Analysis of the morphology of the immunostained cells by confocal microscopy suggested that most, and perhaps all of them, were granular neurons. Since the transient upregulation of calbindin-D(28k) is paralleled by a decline in the number of cells undergoing apoptotic cell death, we hypothesize that this protein exerts a neuroprotective function, probably by buffering free intracellular Ca(2+), whose concentration is elevated after brain insults.

Calbindin D-28 and microtubule-associated protein-2: their use as sensitive immunohistochemical markers of cerebellar neurotoxicity in a regulatory toxicity study

The aim of this study was to develop an immunohistochemical (IHC) method for calbindin D-28 (CB-28) and microtubule-associated protein-2 (MAP-2) and evaluate their expression as markers in the detection, characterisation and grading of unexpected cerebellar toxicity in the rat. High power examination of H&E-stained brain sections of treated rats 2 days following a single oral dose of a novel compound revealed irregular vacuolation of the molecular layer and Purkinje cell degeneration. Animals killed after 14 days recovery showed Purkinje cell degeneration but vacuolation of the molecular layer was absent. In control animals, CB-28 and MAP-2 expression was high in Purkinje cell dendrites and cell bodies in the molecular layer. In treated animals, low power examination revealed loss of CB-28 and MAP-2 expression in degenerating neurons arranged in parasagittal stripes within the vermis. This is the first description of successful use of these two markers in a regulatory toxicity study using FFPE brain. In particular, CB-28 provides a sensitive method for characterising CNS toxicity which can be detected at low power enabling easier detection, screening and grading of neurotoxicity.

Simultaneous glutamate and GABA(A) receptor agonist administration increases calbindin levels and prevents hippocampal damage induced by either agent alone in a model of perinatal brain injury

Perinatal brain injury is associated with the release of amino acids, principally glutamate and GABA, resulting in massive increases in intracellular calcium and eventual cell death. We have previously demonstrated that independent administration of kainic acid (KA), an AMPA/kainate receptor agonist, or muscimol, a GABA(A) receptor agonist, to newborn rats results in hippocampal damage [Hilton, G.D., Ndubuizu, A., and McCarthy, M.M., 2004. Neuroprotective effects of estradiol in newborn female rat hippocampus. Dev. Brain Res. 150, 191-198; Hilton, G. D., Nunez, J.L. and McCarthy, M.M., 2003. Sex differences in response to kainic acid and estradiol in the hippocampus of newborn rats. Neuroscience. 116, 383-391; Nunez, J.L. and McCarthy, M.M., 2003. Estradiol exacerbates hippocampal damage in a model of preterm infant brain injury. Endocrinology. 144, 2350-2359; Nunez, J.L., Alt, J.J. and McCarthy, M.M., 2003. A new model for prenatal brain damage. I. GABA(A) receptor activation induces cell death in developing rat hippocampus. Exp. Neurol. 181, 258-269]. We now report that KA or muscimol alone administered to immature hippocampal neurons in culture induces significant cell death as evidenced by TUNEL assay. Surprisingly, simultaneous administration of equimolar quantities of these two agonists blocks the effect of either one alone. Moreover, treatment of newborn pups results in less damage compared to either muscimol or KA alone. We further observed that immunoreactivity for the calcium-binding protein, calbindin D(28K), is increased in the brains of pups simultaneously administered KA and muscimol as compared to either alone.

Ketogenic diet increases calbindin-D28k in the hippocampi of male ICR mice with kainic acid seizures

The ketogenic diet (KD) increased the expression of calbindin-D(28k) (CB) in the interneurons of the hippocampus compared with the normal diet (ND)-fed mice. Also, 2 days after kainic acid (KA) administration, numerous CB-expressing astrocytes were found in the KD-fed mice compared with those of the ND-fed mice. These results suggest that the neuroprotective effect of the KD on the KA-induced toxicity may be, in part, mediated via an increased expression of CB.

Increased calbindin-D28k immunoreactivity in striatal projection neurons of R6/2 Huntington's disease transgenic mice

Striatal degeneration in Huntington's disease (HD) is associated with increases in perikaryal calbindin immunolabeling in yet-surviving striatal projection neurons. Since similar increases have also been observed in surviving striatal projection neurons after intrastriatal injection of the excitotoxin quinolinic acid, the increased calbindin in HD striatum has been interpreted to suggest an excitotoxic process in HD. We used immunolabeling to assess if calbindin is elevated in striatal projection neurons of R6/2 HD transgenic mice. These mice bear exon 1 of the human huntingtin gene with 144 CAG repeats and show some of the neuropathological signs (e.g., neuronal intranuclear inclusions) and clinical traits (e.g., wasting prior to early death) of HD. We found an increased frequency of calbindin-immunoreactive neuronal perikarya in the striatum of 6- and 12-week-old R6/2 mice compared to wild-type controls. This increase was most notable in the normally calbindin-poor dorsolateral striatum. We found no significant changes in the total area of striatum occupied by the calbindin-negative striosomes and no consistent changes in striatal calbindin mRNA. The increase in calbindin in R6/2 striatal neurons was thus limited to the matrix compartment, and it may be triggered by increased Ca2+ entry due to the demonstrated heightened NMDA sensitivity of these neurons. The data further support the similarity of R6/2 mice to HD, and are consistent with the occurrence of an excitotoxic process in striatum in both.

Quantitative neuropathologic correlates of changes in ratio of N-acetylaspartate to creatine in macaque brain

PURPOSE

To elucidate the neuropathologic basis of transient changes in the ratio of N-acetylaspartate (NAA) to creatine (Cr) in the primate brain by using a simian immunodeficiency virus (SIV)-infected macaque model of the neurologic manifestation of acquired immune deficiency syndrome.

MATERIALS AND METHODS

This study was approved by the Massachusetts General Hospital Subcommittee on Research and Animal Care and the Institutional Animal Care and Use Committee of Harvard University. Rhesus macaques infected with SIV were evaluated during the 1st month of infection. A total of 11 animals were studied, including four control animals, three animals sacrificed 12 days after infection, three animals sacrificed 14 days after infection, and one animal sacrificed 28 days after infection. All animals underwent in vivo proton ((1)H) magnetic resonance (MR) spectroscopy, and postmortem frontal lobe tissue was investigated by using high-spectral-resolution (1)H MR spectroscopy of brain extracts. In addition, quantitative neuropathologic analyses were performed. Stereologic analysis was performed to determine neuronal counts, and immunohistochemical analysis was performed to analyze three neuronal markers: synaptophysin, microtubule-associated protein 2 (MAP2), and calbindin. Analysis of variance (ANOVA) was used to determine substantial changes in neuropathologic and MR spectroscopic markers. Spearman rank correlations were calculated between plasma viral load and neuropathologic and spectroscopic markers.

RESULTS

During acute infection with SIV, the macaque brain exhibited significant changes in NAA/Cr (P < .02, ANOVA) and synaptophysin (P < .013, ANOVA). There was no significant change in the concentration of Cr. No significant changes were found in neuronal counts or other immunohistochemical neuronal markers. With the Spearman rank test, a significant direct correlation was detected between synaptophysin and ex vivo NAA/Cr (r(s) = 0.72, P < .013). No correlation between NAA/Cr and neuronal counts, calbindin, or MAP2 was found.

CONCLUSION

NAA/Cr is a sensitive marker of neuronal injury, not necessarily neuronal loss, and best correlates with synaptophysin, a marker of synaptodendritic dysfunction.

Gene expression profiles associated with survival of individual rat dentate cells after endogenous corticosteroid deprivation

Removal of circulating corticosterone by adrenalectomy (ADX) leads to apoptosis after 3 days in a small population of rat dentate granule neurons, whereas most surrounding cells remain viable. Interestingly, a specific expression profile is triggered in surviving granule cells that may enhance their survival. Hippocampal slices prepared 1, 2 or 3 days after ADX or sham operation were stained ex vivo with Hoechst 33258, which serves to identify apoptotic neurons. After electrophysiological analysis, multiple gene expression in surviving individual granule cells was assessed by linear antisense RNA amplification and hybridization to slot blots containing various neuronal cDNAs. Hierarchical clustering and principal component analysis was performed on two physiological variables and 14 mRNA ratios from ADX cells from every time point. Our results indicate that surviving 3-day ADX granule cells display lower membrane capacitance, lower relative N-methyl-d-aspartate (NMDA) R1 mRNA expression and higher relative mineralocorticoid receptor (MR), alpha1A voltage-gated Ca-channel, Bcl-2 and NMDA R2C mRNA expression. Some 1- and 2-day ADX cells cluster with these 3-day survivors; therefore, one or more components of their mRNA expression profile may represent predictive markers for apoptosis resistance. The functional relevance of two candidate genes was tested by in vivo local over-expression in the same model system; of these, Bcl-2 conferred partial protection when induced shortly before ADX. Therefore, removal of corticosteroids triggers a specific gene expression profile in surviving dentate granule cells; key components of this profile may be associated with their survival.

Calbindin-D28K, parvalbumin and calretinin in primate lower motor neurons

It has been suggested that lower motor neurons containing calcium-binding proteins (CBP) may be resistant to degeneration in motor neuron disease. The testing of this hypothesis is hampered by lack of comprehensive information regarding the presence of CBPs in motor neurons. To address this shortcoming, we investigated the distribution of the CBPs calbindin-D28K (CB), parvalbumin (PV) and calretinin (CRT) in lower motor neurons in the normal human and two non-human primates (rhesus monkey and common marmoset) using immunohistochemistry. A variable proportion of motor neurons in cranial nerve motor nuclei contained immunoreactivity for one or more CBPs. A subpopulation of spinal cord alpha-motor neurons was also CBP-positive. Comparison of staining for choline acetyltransferase (ChAT) and CBPs in the human spinal cord demonstrated that approximately 63% of ventral horn motor neurons contained PV, 53% contained CRT and 56% contained CB. CBP immunoreactivity within motor neurons was of variable staining intensity. It remains to be established whether the presence of these CBPs confers protection against the pathogenic mechanisms of motor neuron disease.

Catalase over-expression protects striatal neurons from transient focal cerebral ischemia

Reactive oxygen species (ROS) play key roles in the cascade of brain injury after stroke, and strategies to increase the antioxidant defenses of neurons after stroke hold great promise. In this study we evaluate the neuroprotective potential of using a herpes simplex viral vector to over-express catalase in rats. Vector was microinfused into the striatum either prior to or after middle cerebral artery occlusion (MCAO). Catalase over-expression was protective (relative to control vector) when the vector was delivered 14-16 h prior to ischemia, but not when delivered after ischemia. Thus, the timing of catalase over-expression relative to ischemia is a critical variable determining its potential therapeutic value.

Overexpression of calbindin D28k in dentate gyrus granule cells alters mossy fiber presynaptic function and impairs hippocampal-dependent memory

Calcium is a key signaling ion for induction of synaptic plasticity processes that are believed to influence cognition. Mechanisms regulating activity-induced increases in neuronal calcium and related synaptic modifications are not fully understood. Moreover, involvement of specific synapses in discrete aspects of spatial learning remains to be elucidated. We used herpes simplex amplicons to overexpress calbindin D(28k) (CaBP) selectively in dentate gyrus (DG) granule cells. We then examined the effects on hippocampal network activity by recording evoked synaptic responses in vivo and in vitro and analyzing hippocampal-dependent behavior. Relative to Lac-Z- and sham-infected controls, CaBP overexpression increased mossy fiber (MF-CA3) excitatory postsynaptic potentials and reduced paired-pulse facilitation (PPF), suggesting an increase in presynaptic strength. Additionally, CaBP overexpression reduced long-term potentiation (LTP), caused a frequency-dependent inhibition of post-tetanic potentiation (PTP), and impaired spatial navigation. Thus, increasing CaBP levels selectively in the DG disrupts MF-CA3 presynaptic function and impairs spatial cognition. The results demonstrate the power of gene delivery in the study of the neural substrates of learning and memory and suggest that mossy fiber synaptic plasticity is critical for long-term spatial memory.

Selective age-related loss of calbindin-D28k from basal forebrain cholinergic neurons in the common marmoset (Callithrix jacchus)

A significant number of the cholinergic neurons in the basal forebrain of the primate, but not the rodent brain contain the calcium binding protein calbindin-D28k (CB). Previous experiments in our laboratory have demonstrated a substantial age-related loss of CB from the human basal forebrain cholinergic neurons (BFCN). The present study investigated the possible age-related loss of CB from the BFCN in a non-human primate species, the common marmoset (Callithrix jacchus). Quantitative analysis of matching sections as well as unbiased stereological determination of neuronal number were used in 16 adult marmosets ranging in age between 2 and 15 years. No significant changes were observed in the number of choline acetyltransferase-positive BFCN when a group of young animals (< or =4 years) was compared with a 6-8-year-old group and a 9-15-year-old group. Similarly, no age-related changes were observed in Nissl-stained magnocellular basal forebrain (putatively cholinergic) neurons. In contrast, the BFCN of the two older groups of animals displayed a significant loss of CB. The age-related loss of CB occurred in all sectors of the BFCN, but was greatest in the anterior sector of this cell group. The CB loss was neurochemically specific since the BFCN in the older groups of animals continued to express other markers such as high and low affinity neurotrophin receptors. The age-related loss of CB from the marmoset BFCN was also regionally selective as CB positive neurons in other structures, such as the cerebral cortex and the striatum displayed no apparent age-related changes. These results indicate that the marmoset BFCN display a significant and selective age-related loss of CB reminiscent of that observed in the human. Therefore, the common marmoset represents an appropriate animal model in which the consequences of BFCN CB loss can be investigated in depth. Loss of CB from the aged BFCN is likely to reduce the capacity of these neurons to buffer intracellular calcium and to leave them vulnerable to insults which can result in increased calcium levels. The vulnerability of the CB-negative BFCN in the aged marmoset to various insults which disturb calcium homeostasis remains to be investigated.

Potassium channel gene therapy can prevent neuron death resulting from necrotic and apoptotic insults

Necrotic insults such as seizure are excitotoxic. Logically, membrane hyperpolarization by increasing outwardly conducting potassium channel currents should attenuate hyperexcitation and enhance neuron survival. Therefore, we overexpressed a small-conductance calcium-activated (SK2) or voltage-gated (Kv1.1) channel via viral vectors in cultured hippocampal neurons. We found that SK2 or Kv1.1 protected not only against kainate or glutamate excitotoxicity but also increased survival after sodium cyanide or staurosporine. In vivo overexpression of either channel in dentate gyrus reduced kainate-induced CA3 lesions. In hippocampal slices, the kainate-induced increase in granule cell excitability was reduced by overexpression of either channel, suggesting that these channels exert their protective effects during hyperexcitation. It is also important to understand any functional disturbances created by transgene overexpression alone. In the absence of insult, overexpression of Kv1.1, but not SK2, reduced baseline excitability in dentate gyrus granule cells. Furthermore, while no behavioral disturbances during spatial acquisition in the Morris water maze were observed with overexpression of either channel, animals overexpressing SK2, but not Kv1.1, exhibited a memory deficit post-training. This difference raises the possibility that the means by which these channel subtypes protect may differ. With further development, potassium channel vectors may be an effective pre-emptive strategy against necrotic insults.

Opposing effects of ethanol and nicotine on hippocampal calbindin-D28k expression

Long-term ethanol exposure produces multiple neuroadaptations that likely contribute to dysregulation of Ca(2+) balance and neurotoxicity during ethanol withdrawal. Conversely, nicotine exposure may reduce the neurotoxic consequences of Ca(2+) dysregulation, putatively through up-regulation of the Ca(2+)-buffering protein calbindin-D(28k). The current studies were designed to examine the extent to which 10-day ethanol exposure and withdrawal altered calbindin-D(28k) expression in rat hippocampus. Further, in these studies, we examined the ability of nicotine, through action at alpha(7)(*)-bearing nicotinic acetylcholine receptors (nAChRs), to antagonize the effects of ethanol exposure on calbindin-D(28k) expression. Organotypic cultures of rat hippocampus were exposed to ethanol (50-100 mM) for 10 days. Additional cultures were exposed to 500 nM (-)-nicotine with or without the addition of 50 mM ethanol, 100 nM methyllycaconitine (an alpha(7)*-bearing nAChR antagonist), or both. Prolonged exposure to ethanol (>/=50 mM) produced significant reductions of calbindin-D(28k) immunolabeling in all regions of the hippocampal formation, even at nontoxic concentrations of ethanol. Calbindin-D(28k) expression levels returned to near-control levels after 72 h of withdrawal from 10-day ethanol exposure. Extended (-)-nicotine exposure produced significant elevations in calbindin-D(28k) expression levels that were prevented by methyllycaconitine co-exposure. Co-exposure of cultures to (-)-nicotine with ethanol resulted in an attenuation of ethanol-induced reductions in calbindin-D(28k) expression levels. These findings support the suggestion that long-term ethanol exposure reduces the neuronal capacity to buffer accumulated Ca(2+) in a reversible manner, an effect that likely contributes to withdrawal-induced neurotoxicity. Further, long-term exposure to (-)-nicotine enhances calbindin-D(28k) expression in an alpha(7)* nAChR-dependent manner and antagonizes the effects of ethanol on calbindin-D(28k) expression.

Intracellular Ca2+ handling

Intracellular Ca2+ is regulated within three major compartments: the cytosol, the endoplasmic reticulum and mitochondria. This Chapter reviews the mechanisms involved in handling of Ca2+ within these compartments with reference to potential strategies for neuroprotection. In the cytosol, Ca2+ buffering has a major influence on Ca2+ signals. Cytosolic Ca(2+)-binding proteins such as CB28 participate in Ca2+ buffering and may have a role in resistance to neurotoxicity. In the endoplasmic reticulum, a number of proteins are involved in Ca2+ uptake, lumenal buffering or release, and these may be of value as potential targets for therapeutic intervention. Mitochondria are receiving increasing attention for their role in Ca2+ storage and signaling, and as key players in the processes leading to cell death following Ca2+ overload. An improved understanding of how Ca2+ is controlled within these intracellular compartments, and how these compartments interact, will be important for neuroprotective strategies.

Loss of calbindin-D28K from aging human cholinergic basal forebrain: relation to plaques and tangles

Reports from our laboratory have indicated a substantial and specific loss of the calcium binding protein calbindin-D28K (CB) from the human basal forebrain cholinergic neurons (BFCN) in the course of normal aging. In the present set of experiments we determined the relationship between the age-related loss of CB and the presence and density of plaques and tangles in the brains of normal elderly. In 23 cases ranging in age from 20 to 93 years of age we observed plaques and tangles in the BFCN region and the cerebral cortex in a subset of cases. Plaques were seen in the basal forebrain in very few cases above 65 years. Plaque density in the basal forebrain and cortex displayed a significant negative correlation with the proportion of the BFCN, which contained CB immunoreactivity. However, the brains of 2 elderly cases that displayed a substantial loss of CB from the BFCN did not contain any plaques. Tangles were observed in the BFCN as early as 26 years of age. Only tangles in the entorhinal cortex showed a significant negative correlation with the loss of CB from the BFCN. It is likely that loss of CB from the BFCN and formation of plaques and tangles are part of general age-related processes that occur in parallel rather than being causally related.

Heat shock protein 27 delivered via a herpes simplex virus vector can protect neurons of the hippocampus against kainic-acid-induced cell loss

Heat shock proteins are expressed in response to cellular stress and can protect cells from further stress and facilitate recovery. Heat shock protein 27 is of particular interest because it has been implicated in a range of protective roles including protein chaperoning, stabilising elements of the cytoskeleton and as an active inhibitor of apoptosis. In the present study, we have examined the potential of administration of exogenous HSP27 to confer protection against KA-induced neuronal cell death in vivo. We aimed to exploit the neurotropic specificity of herpes simplex virus-1 based virus vectors, which have been rendered replication-incompetent, to infect neurons of the hippocampus. The systemic administration of kainic acid, an analogue of glutamate, causes seizures resulting in neuronal damage and is an established animal model of epilepsy. Neuron loss is particularly prominent in the hippocampus and the mode of death is at least partly apoptotic in nature. We show that the overexpression of HSP27 in these neurons can significantly augment their survival following kainic acid administration. In contrast, injection of a control virus expressing beta-galactosidase does not confer protection. This is the first time that protection by exogenously expressed HSP27 has been demonstrated in an in vivo model of neuronal cell death.

Loss of calbindin-D28k from aging human cholinergic basal forebrain: relation to neuronal loss

Cholinergic neurons of the basal forebrain (BFCN) are selectively vulnerable in neurodegenerative disorders of the elderly, particularly in Alzheimer's disease (AD). We investigated age-related changes in the BFCN that may serve as a substrate for this vulnerability. We report a substantial and selective age-related loss of the calcium binding protein calbindin-D(28K) (CB) from the human BFCN. Unbiased stereological estimation indicated that, in individuals under age 65 years, 72% of the choline acetyltransferase (ChAT)-positive BFCN contained CB immunoreactivity. In individuals over age 65 years, only 28% of the BFCN contained CB immunoreactivity, a dramatic loss of 61%. Similar results were obtained using neuronal counts from matching single- or double-stained sections in a larger cohort. The loss of CB immunoreactivity was neurochemically specific. No age-related changes were observed in the number of ChAT- or low-affinity nerve growth factor receptor (p75(NTR))-immunoreactive profiles. The loss of CB was greatest in very old individuals, in whom a small loss of BFCN was observed. Furthermore, the loss of CB displayed the same pattern as the loss of BFCN in AD and was more substantial in the posterior compared with the anterior BFCN sector, suggesting a role for CB in the selective vulnerability of BFCN in AD. The depletion of CB from the BFCN is likely to deprive these neurons of the capacity to buffer high levels of intracellular Ca(2+) and thus to leave them vulnerable to pathological processes, such as those in neurodegenerative disorders, which can cause increased intracellular Ca(2+), thus leading to their degeneration.

Differential changes of calcium binding proteins in the rat striatum after kainic acid-induced seizure

It has been suggested that calcium binding proteins protect against Ca2+ overload, thus rendering neurons more resistant against excitotoxicity. The influence of kainic acid, which induces status epilepticus, on the expressions of calbindin D28k, parvalbumin and calretinin was examined in the rat striatum by immunohistochemistry and microdensitometry. At 1, 3 and 6 days after kainic acid-induced seizure, the number of calretinin-positive neurons in the striatum was significantly lower than in control rats. However, no significant difference was observed in the number of calbindin D28k- and parvalbumin-positive neurons in control and seizure rats. At 1, 3 and 6 days after seizure the optical densities of calretinin- and parvalbumin-positive neurons in the striatum were significantly lower than in control rats. Our finding concerning the selective loss of calretinin-positive neurons in seizure groups suggests that calcium binding proteins in the striatum have differential vulnerabilities to kainic acid-induced seizure.

Calretinin and calbindin D-28k, but not parvalbumin protect against glutamate-induced delayed excitotoxicity in transfected N18-RE 105 neuroblastoma-retina hybrid cells

Excitotoxic effects leading to neuronal cell degeneration are often accompanied by a prolonged increase in the intracellular level of Ca(2+) ions and L-glutamate-induced toxicity is assumed to be mediated via a Ca(2+)-dependent mechanism. Due to their buffering properties, EF-hand Ca(2+)-binding proteins (CaBPs) can affect intracellular Ca(2+) homeostasis and a neuroprotective role has been attributed to some of the family members including calretinin, calbindin D-28k and parvalbumin. We have stably transfected N18-RE 105 neuroblastoma-retina hybrid cells with the cDNAs for the three CaBPs and investigated the effect of these proteins on the L-glutamate-induced, Ca(2+)-dependent cytotoxicity. Several clones for each CaBP were selected according to immunocytochemical staining and characterization of the overexpressed proteins by Western blot analysis. In calretinin- and parvalbumin-expressing clones, expression levels were quantitatively determined by ELISA techniques. Cytotoxicity of transfected clones was quantified by measurement of the activity of lactate dehydrogenase (LDH) that was released into the medium after L-glutamate (10 mM) exposure as a result of necrotic cell death. In untransfected and parvalbumin-transfected cells, LDH released into the medium progressively increased (starting from the 20th hour) reaching maximum levels after 28-30 h of glutamate application. In contrast, LDH release in both, calretinin and calbindin D-28k-transfected clones, was not significantly different from unstimulated transfected or untransfected cells over the same period of time. The results indicate that the 'fast' Ca(2+)-buffers calretinin and calbindin D-28k, but not the 'slow' buffer parvalbumin can protect N18-RE 105 cells from this type of Ca(2+)-dependent L-glutamate-induced delayed cytotoxicity.

Stress and depression: possible links to neuron death in the hippocampus

Recent intriguing reports have shown an association between major depression and selective and persistent loss of hippocampal volume, prompting considerable speculation as to its underlying causes. In this paper we focus on the hypothesis that overt hippocampal neuron death could cause this loss and review current knowledge about how hippocampal neurons die during insults. We discuss (a) the trafficking of glutamate and calcium during insults; (b) oxygen radical generation and programmed cell death occurring during insults; (c) neuronal defenses against insults; (d) the role of energy availability in modulating the extent of neuron loss following such insults. The subtypes of depression associated with hippocampal atrophy typically involve significant hypersecretion of glucocorticoids, the adrenal steroids secreted during stress. These steroids have a variety of adverse affects, direct and indirect, in the hippocampus. Thus glucocorticoids may play a contributing role toward neuron death. We further discuss how glucocorticoids cause or exacerbate cellular changes associated with hippocampal neuron loss in the context of the events listed above.

Protective effect of parvalbumin on excitotoxic motor neuron death

The mechanism responsible for the selective vulnerability of motor neurons in amyotrophic lateral sclerosis (ALS) is poorly understood. Several lines of evidence indicate that susceptibility of motor neurons to Ca(2+) overload induced by excitotoxic stimuli is involved. In this study, we investigated whether the high density of Ca(2+)-permeable AMPA receptors on motor neurons gives rise to higher Ca(2+) transients in motor neurons compared to dorsal horn neurons. Dorsal horn neurons were chosen as controls as these cells do not degenerate in ALS. In cultured spinal motor neurons, the rise of the cytosolic Ca(2+) concentration induced by kainic acid (KA) and mediated by the AMPA receptor was almost twice as high as in spinal neurons from the dorsal horn. Furthermore, we investigated whether increasing the motor neuron's cytosolic Ca(2+)-buffering capacity protects them from excitotoxic death. To obtain motor neurons with increased Ca(2+) buffering capacity, we generated transgenic mice overexpressing parvalbumin (PV). These mice have no apparent phenotype. PV overexpression was present in the central nervous system, kidney, thymus, and spleen. Motor neurons from these transgenic mice expressed PV in culture and were partially protected from KA-induced death as compared to those isolated from nontransgenic littermates. PV overexpression also attenuated KA-induced Ca(2+) transients, but not those induced by depolarization. We conclude that the high density of Ca(2+)-permeable AMPA receptors on the motor neuron's surface results in high Ca(2+) transients upon stimulation and that the low cytosolic Ca(2+)-buffering capacity of motor neurons may contribute to the selective vulnerability of these cells in ALS. Overexpression of a high-affinity Ca(2+) buffer such as PV protects the motor neuron from excitotoxicity and this protective effect depends upon the mode of Ca(2+) entry into the cell.

HSV-1 helper virus 5dl1.2 suppresses sodium currents in amplicon-transduced neurons

The Herpes Simplex Virus-1 (HSV-1) amplicon system is one of several viral-based strategies currently being developed for gene delivery into mammalian neurons for experimental or therapeutic purposes. Amplicon-containing viruses contain no HSV-1 genes and are amplified in titer relative to the helper viruses used to package them. In this way, they are designed to have a minimal impact on the physiology of transduced neurons. We show here, however, that amplicon preparations made using the 5dl1.2 helper virus selectively suppress sodium currents in cultured neurons by approximately 80% within 2 days of transduction and reduce average spike frequency in response to depolarization from 23 +/- 4 to 0.4 +/- 0.4 Hz. We observe similar suppression of Na(+) currents in cells treated with the 5dl1.2 helper virus alone, indicating that the helper virus retains the ability of wild-type HSV-1 to inhibit these currents potently. Staining amplicon-transduced neurons with anti-HSV antibodies, we find that 80% of the neurons express viral proteins, indicating that helper virus typically co-infects these cells. We conclude that Na(+) current suppression by the amplicon preparation results from the preferential coinfection of transduced neurons by the 5dl1.2 helper virus.

HSV-mediated delivery of virally derived anti-apoptotic genes protects the rat hippocampus from damage following excitotoxicity, but not metabolic disruption

Studies utilizing gene delivery to the nervous system indicate that various strategies are protective following acute neurological insults such as seizure and stroke. We have found that inhibitors of apoptosis are protective against excitotoxicity and heat stress but not energetic impairment in vitro. Here we studied the neuroprotective efficacy in vivo of these mediators: viral genes (crmA, p35, gamma34.5 KsBcl-2) that have evolved to suppress suicidal host responses to infection, by inhibiting apoptosis. We investigated these effects by utilizing modified herpes vectors to deliver the anti-apoptotic agents intracerebrally and examined them in the face of excitotoxic and metabolic insults. We found that p35 and gamma34.5 reduced by 45% a hippocampal CA3 lesion caused by kainic acid, while crmA and KsBcl-2 did not. None of the inhibitors protected the dentate gyrus of the hippocampus following 3-acetylpyridine, a hypoglycemia model, but we found crmA to worsen the damage. These data are similar to our results in neuronal cultures where the inhibitors protected against the excitotoxin domoic acid, but not against the metabolic poison, cyanide. Together, the results suggest that inhibitors of various apoptotic elements are capable of protecting under acute insult conditions both in vitro and in vivo, suggesting possible future therapeutic applications.

Gene therapy for acute diseases

The use of gene transfer systems to study cell function makes it apparent that overexpression of a transgene can restore or improve the function of a protein and positively influence cell function in a predetermined manner for purposes of counterbalancing cellular pathophysiology. The ability of some gene transfer vehicles to produce transgene product within hours of delivery positions gene transfer as a unique pharmaceutical administration system that can quickly affect production of biologic response modifiers in a highly compartmentalized fashion. This approach can be expected to overcome many of the adverse effects and high costs of systemic delivery of recombinant pharmaceuticals. This review highlights recent advances toward development of gene therapies for acute illnesses with particular emphasis on preclinical models of disease. In this context, a growing body of data suggests that gene therapies for polygenic and non-genetic diseases such as asthma, cardiogenic and non-cardiogenic pulmonary edema, stroke, subarachnoid hemorrhage, seizures, acute myocardial infarction, endovascular thrombosis, and infections may someday be options for the treatment of patients.