Quantification of VGF- and pro-SAAS-derived peptides in endocrine tissues and the brain, and their regulation by diet and cold stress

Two novel granin-like polypeptides, VGF and pro-SAAS, which are stored in and released from secretory vesicles and are expressed widely in nervous, endocrine, and neuroendocrine tissues, play roles in the regulation of body weight, feeding, and energy expenditure. Both VGF and pro-SAAS are cleaved into peptide fragments, several of which are biologically active. We utilized a highly sensitive and specific radioimmunoassay (RIA) to immunoreactive, pro-SAAS-derived PEN peptides, developed another against immunoreactive, VGF-derived AQEE30 peptides, and quantified these peptides in various mouse tissues and brain regions. Immunoreactive AQEE30 was most abundant in the pituitary, while brain levels were highest in hypothalamus, striatum, and frontal cortex. Immunoreactive PEN levels were highest in the pancreas and spinal cord, and in brain, PEN was most abundant in striatum, hippocampus, pons and medulla, and cortex. Since both peptides were expressed in hypothalamus, a region of the brain that controls feeding and energy expenditure, double label immunofluorescence studies were employed. These demonstrated that 42% of hypothalamic arcuate neurons coexpress VGF and SAAS peptides, and that the intracellular distributions of these peptides in arcuate neurons differed. By RIA, cold stress increased immunoreactive AQEE30 and PEN peptide levels in female but not male hypothalamus, while a high fat diet increased AQEE30 and PEN peptide levels in female but not male hippocampus. VGF and SAAS-derived peptides are therefore widely expressed in endocrine, neuroendocrine, and neural tissues, can be accurately quantified by RIA, and are differentially regulated in the brain by diet and cold stress.     

T cells promote the regeneration of neural precursor cells in the hippocampus of Alzheimer＇s disease mice

Alzheimer's disease is closely associated with disorders of neurogenesis in the brain, and growing evidence supports the involvement of immunological mechanisms in the development of the disease. However, at present, the role of T cells in neuronal regeneration in the brain is unknown. We injected amyloid-beta 1–42 peptide into the hippocampus of six BALB/c wild-type mice and six BALB/c-nude mice with T-cell immunodeficiency to establish an animal model of Alzheimer's disease. A further six mice of each genotype were injected with same volume of normal saline. Immunohistochemistry revealed that the number of regenerated neural progenitor cells in the hippocampus of BALB/c wild-type mice was significantly higher than that in BALB/c-nude mice. Quantitative fluorescence PCR assay showed that the expression levels of peripheral T cell-associated cytokines(interleukin-2, interferon-γ) and hippocampal microglia-related cytokines(interleukin-1β, tumor necrosis factor-α) correlated with the number of regenerated neural progenitor cells in the hippocampus. These results indicate that T cells promote hippocampal neurogenesis in Alzheimer's disease and T-cell immunodeficiency restricts neuronal regeneration in the hippocampus. The mechanism underlying the promotion of neuronal regeneration by T cells is mediated by an increased expression of peripheral T cells and central microglial cytokines in Alzheimer's disease mice. Our findings provide an experimental basis for understanding the role of T cells in Alzheimer's disease.     

Neurodegenerative diseases: basic and clinical research Abstracts

Posrischemic changes in hippocampal non-principal cells Neuronal activity in rat hippocampus slices following in vivo brain ischemia Sulphur amino acids — endogenous ligands for glutamate receptors? Novel NMDA receptor agonists structurally related to ibotenic acid and aspartic acid HIV- 1 nef protein exhibits structural and functional similarity to Neurotoxins Glial reactions to ischemic lesions of the rat hippocampus Microglial and astroglial reactions to perforant path axonal degeneration Unbiased stereological estimation of the total number of neurons in the aging human hippocampus Macroscopic volume measurements on brains from senile demented patients and age-matched controls Cerebral atrophy in 18 males with aids. Stereologic estimate on formalin-fixed brains Absolute number of neurons in substantia nigra in Parkinson's disease The rat nigrostriatal, dopaminergic system studied in organotypic slice cultures of ventral mesencephalon and striatum Basal forebrain neurons in adult rats can reinnervate fetal frontal cortex grafted to frontal cortex lesions. A double-fluorescent tracing study Neuronal plasticity and astrocytic reaction in Alzheimer's disease Problems concerning the use of rating scales and psychometric tests in the study of dementia [^99mTc]-HMPA0 and SPECT of the brain in normal aging SPECT in Alzheimer's disease     

Distribution of neuropeptide S receptor mRNA and neurochemical characteristics of neuropeptide S-expressing neurons in the rat brain

Neuropeptide S (NPS) and its receptor (NPSR) constitute a novel neuropeptide system that is involved in regulating arousal and anxiety. The NPS precursor mRNA is highly expressed in a previously undescribed group of neurons located between the locus coeruleus (LC) and Barrington's nucleus. We report here that the majority of NPS-expressing neurons in the LC area and the principal sensory trigeminal nucleus are glutamatergic neurons, whereas many NPS-positive neurons in the lateral parabrachial nucleus coexpress corticotropin-releasing factor (CRF). In addition, we describe a comprehensive map of NPSR mRNA expression in the rat brain. High levels of expression are found in areas involved in olfactory processing, including the anterior olfactory nucleus, the endopiriform nucleus, and the piriform cortex. NPSR mRNA is expressed in several regions mediating anxiety responses, including the amygdaloid complex and the paraventricular hypothalamic nucleus. NPSR mRNA is also found in multiple key regions of sleep neurocircuitries, such as the thalamus, the hypothalamus, and the preoptic region. In addition, NPSR mRNA is strongly expressed in major output and input regions of hippocampus, including the parahippocampal regions, the lateral entorhinal cortex, and the retrosplenial agranular cortex. Multiple hypothalamic nuclei, including the dorsomedial and the ventromedial hypothalamic nucleus and the posterior arcuate nucleus, express high levels of NPSR mRNA, indicating that NPS may regulate energy homeostasis. These data suggest that the NPS system may play a key role in modulating a variety of physiological functions, especially arousal, anxiety, learning and memory, and energy balance.     

Developmental expression of somatostatin in mouse brain. II. In situ hybridization

The distribution and the levels of expression of preprosomatostatin (PPSOM) mRNA were examined during pre- and postnatal development of the mouse brain using the in situ hybridization technique. The signal obtained by in situ hybridization of embryonic tissues at day 14 and day 17 of gestation was highest over the neurons of the pyriform cortex, amygdala, and entopeduncular nucleus. The signal was very low over cells of the neocortex and the developing hippocampal formation. The density of grains overlying the neurons of the amygdala and pyriform cortex continued to be high during early postnatal life, but decreased as the animals became adults. A progressive increase of PPSOM mRNA expression was observed in postnatal animals in the stratum oriens and dentate gyrus of the hippocampal formation. In the cerebral cortex and striatum, the number of these neurons became maximal between postnatal weeks 1 and 3. In the diencephalon, the highest densities of grains were found over neurons in the nucleus reticularis thalami and zona incerta at postnatal day 21; these levels declined slightly thereafter. The cells of the periventricular nucleus of the hypothalamus had high densities of grains as early as postnatal week 1 and continued to have high densities of grains in adult animals. These patterns of hybridization density parallelled the distribution of SOM-like immunoreactivity in the mouse brain. When PPSOM mRNA expression was examined in the cerebral cortices of mice that received lesions of the nucleus basalis of Meynert as neonates, a transient increase in the number of cells expressing PPSOM mRNA was observed in the frontoparietal cortex ipsilateral to the lesion at postnatal day 10, but not at postnatal day 30. Importantly, the density of grains over the individual cells was not altered in lesioned animals at these two ages.     

Neuroanatomical characterization of a growth hormone secretagogue receptor‐green fluorescent protein reporter mouse

Growth hormone secretagogue receptor (GHSR) 1a is the only molecularly identified receptor for ghrelin, mediating ghrelin‐related effects on eating, body weight, and blood glucose control, among others. The expression pattern of GHSR within the brain has been assessed previously by several neuroanatomical techniques. However, inherent limitations to these techniques and the lack of reliable anti‐GHSR antibodies and reporter rodent models that identify GHSR‐containing neurons have prevented a more comprehensive functional characterization of ghrelin‐responsive neurons. Here we have systematically characterized the brain expression of an enhanced green fluorescence protein (eGFP) transgene controlled by the Ghsr promoter in a recently reported GHSR reporter mouse. Expression of eGFP in coronal brain sections was compared with GHSR mRNA expression detected in the same sections by in situ hybridization histochemistry. eGFP immunoreactivity was detected in several areas, including the prefrontal cortex, insular cortex, olfactory bulb, amygdala, and hippocampus, which showed no or low GHSR mRNA expression. In contrast, eGFP expression was low in several midbrain regions and in several hypothalamic nuclei, particularly the arcuate nucleus, where robust GHSR mRNA expression has been well‐characterized. eGFP expression in several brainstem nuclei showed high to moderate degrees of colocalization with GHSR mRNA labeling. Further quantitative PCR and electrophysiological analyses of eGFP‐labeled hippocampal cells confirmed faithful expression of eGFP within GHSR‐containing, ghrelin‐responsive neurons. In summary, the GHSR‐eGFP reporter mouse model may be a useful tool for studying GHSR function, particularly within the brainstem and hippocampus; however, it underrepresents GHSR expression in nuclei within the hypothalamus and midbrain. J. Comp. Neurol. 522:3644–3666, 2014. © 2014 Wiley Periodicals, Inc.     

7.0T nuclear magnetic resonance evaluation of the amyloid beta(1–40) animal model of Alzheimer's disease: comparison of cytology verification

3.0T magnetic resonance spectroscopic imaging is a commonly used method in the research of brain function in Alzheimer's disease.However,the role of 7.0T high-field magnetic resonance spectroscopic imaging in brain function of Alzheimer's disease remains unclear.In this study,7.0T magnetic resonance spectroscopy showed that in the hippocampus of Alzheimer's disease rats,the N-acetylaspartate wave crest was reduced,and the creatine and choline wave crest was elevated.This finding was further supported by hematoxylin-eosin staining,which showed a loss of hippocampal neurons and more glial cells.Moreover,electron microscopy showed neuronal shrinkage and mitochondrial rupture,and scanning electron microscopy revealed small size hippocampal synaptic vesicles,incomplete synaptic structure,and reduced number.Overall,the results revealed that 7.0T high-field nuclear magnetic resonance spectroscopy detected the lesions and functional changes in hippocampal neurons of Alzheimer's disease rats in vivo,allowing the possibility for assessing the success rate and grading of the amyloid beta(1–40) animal model of Alzheimer's disease.     

Postnatal effect of embryonic neurogenesis disturbance on reelin level in organotypic cultures of rat hippocampus

Despite a delayed emergence of the symptoms, schizophrenia is thought to be a late consequence of early disturbances during development. Several reports have found decreased levels of reelin in the cortex and the hippocampus of postmortem brains of schizophrenic patients. In the rat, intraperitoneal injection of the anti-mitotic agent methylazoxymethanol (MAM) during intra-uterine development (embryonic day 17) induces cytoarchitectural abnormalities in the hippocampus and the cortex and behavioural changes reminiscent of positive, negative and cognitive symptoms of schizophrenia. We aimed to examine whether a transient prenatal disturbance of neurogenesis induces postnatal changes in the expression of reelin in the hippocampus. Cellular modifications were explored using hippocampal organotypic slice cultures, which allow for conservation of the in vivo cytoarchitecture. MAM effect on hippocampal neurogenesis was confirmed by birthdating experiments. After 3 weeks in vitro, reelin was expressed by calretinin-negative cells. The number of reelin-positive neurons was increased whereas the total neuron number was decreased in the stratum oriens in the E17 MAM-exposed animals as compared to the control group. Not only an increase in the number of cells expressing reelin was observed, but there was also a slight increase in reelin mRNA levels in hippocampal pyramidal cells of MAM-exposed animals. In contrast, there was no significant change in the dentate gyrus. These results show that transient prenatal disturbance of neurogenesis induces long-term modifications in specific areas of the hippocampus and in particular in the number of neurons expressing reelin. They also confirm the value of organotypic slices to study postnatal maturation in the hippocampus.     

Postnatal expression of H1‐receptor mRNA in the rat brain: correlation to l‐histidine decarboxylase expression and local upregulation in limbic seizures

Histamine is implicated in the regulation of brain functions through three distinct receptors. Endogenous histamine in the brain is derived from mast cells and neurons, but the importance of these two pools during early postnatal development is still unknown. The expression of histamine H₁-receptor in the rat brain was examined using in situ hybridization during postnatal development and in adults. For comparison, the expression of l -histidine decarboxylase (HDC) in the two pools was revealed. H₁-receptor was evenly expressed throughout the brain on the first postnatal days, but resembled the adult, uneven pattern already on postnatal day 5 (P5). HDC was expressed in both mast cells and tuberomammillary neurons from birth until P5, after which the mast cell expression was no more detectable. In adult rat brain, high or moderate levels of H₁-receptor expression were found in the hippocampus, zona incerta, medial amygdaloid nucleus and reticular thalamic nucleus. In most areas of the adult brain the expression of H₁-receptor mRNA correlates well with binding data and histaminergic innervation. A notable exception is the hypothalamus, with high fibre density but moderate or low H₁-receptor expression. Systemic kainic acid administration induced increased expression of H₁-receptor mRNA in the caudate-putamen and dentate gyrus, whereas no change was seen in the hippocampal subfields CA1–CA3 or in the entorhinal cortex 6 h after kainic acid injections. This significant increase supports the concept that histaminergic transmission, through H₁-receptor, is involved in the regulation of seizure activity in the brain.