Effects of ß-amyloid (1-42) Administration on the Main Neurogenic Niches of the Adult Brain: Amyloid-Induced Neurodegeneration Influences Neurogenesis.

Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and warrants further study as well as timely treatment. Additionally, the mechanisms of the brain's intrinsic defense against chronic injury are not yet fully understood. Herein, we examined the response of the main neurogenic niches to amyloid exposure and the associated changes in structure and synaptic activity. Flow cytometry of Nestin-, Vimentin-, Nestin/Vimentin-, NeuN-, GFAP-, NeuN/GFAP-, NSE-, BrdU-, Wnt-, BrdU/Wnt-, VEGF-, Sox14-, VEGF/Sox14-, Sox10-, Sox2-, Sox10/Sox2-, Bax-, and Bcl-xL-positive cells was performed in the subventricular zone (SVZ), hippocampus, and cerebral cortex of rat brains on 90th day after intracerebroventricular (i.c.v.) single injection of a fraction of ß-amyloid (Aß) (1-42). The relative structural changes in these areas and disruptions to synaptic activity in the entorhinal cortex-hippocampus circuit were also evaluated. Our flow analyses revealed a reduction in the numbers of Nestin-, Vimentin-, and Nestin/Vimentin-positive cells in neurogenic niches and the olfactory bulb. These changes were accompanied by an increased number of BrdU-positive cells in the hippocampus and SVZ. The latter changes were strongly correlated with changes in the numbers of VEGF- and VEGF/Sox14-positive cells. The morphological changes were characterized by significant neural loss, a characteristic shift in entorhinal cortex-hippocampus circuit activity, and decreased spontaneous alternation in a behavioral test. We conclude that although an injection of Aß (1-42) induced stem cell proliferation and triggered neurogenesis at a certain stage, this process was incomplete and led to neural stem cell immaturity. We propose the idea of enhancing adult neurogenesis as a promising strategy for preventing dementia at healthy elderly people andpeople at high risk for developing AD, or treating patients diagnosed with AD.

Plasticity in Motoneurons Following Spinal Cord Injury in Fructose-induced Diabetic Rats.

Spinal cord injury (SCI) causes motor impairment and the proper excitation/inhibition balance in motoneurons is important for recovery. Diabetes mellitus impairs regenerative capacity following SCI. The purpose of this study was to assess the short-term plasticity (STP) of lumbar spinal cord motoneurons in conditions of (1) lateral hemisection (SCI), (2) fructose-induced diabetes (D), and (3) diabetes associated with hemisection (D + SCI). We show that in the cases of SCI, D, and D + SCI, the ratio of percentage share of excitatory and inhibitory combinations of motoneurons responses to high-frequence stimulation of sciatic nerve is multidirectional. In the SCI and D + SCI groups, the cumulative changes in generalized baseline frequencies decreased significantly. When we compared the cumulative changes in the intensity of excitatory and inhibitory responses relative to baseline during high-frequency stimulation (tetanization epoch), we found that there was a significant intensification in tetanic depression in the D + SCI groups versus SCI, as well as an intensification in tetanic potentiation in the D + SCI vs. D and D + SCI vs. SCI groups. Thus, in conditions of traumatic and/or metabolic pathology, the distinct synaptic inputs exhibit opposing plasticity for homeostatic control of neurotransmission and these integral changes most likely shape postsynaptic STP in the spinal motor network.

Diabefit as a Modifier of Fructose-induced Impairment of Cardio-vascular System.

Today, cardiovascular diseases, due to their widespread prevalence, are among the most relevant biomedical problems in the modern world. The development of cardiovascular comorbidity among patients with diabetes mellitus is of high clinical urgency. Therefore, the study of cardiovascular risk modification among patients with diabetes mellitus is of paramount importance. In the context of the above, the data on the cardiotoxicity of fructose look very alarming since these patients usually use fructose as an affordable alternative to glucose. At the same time, it is an independent inducer of destabilization of cardiovascular homeostasis. Sixty rats were used in the experiment to study this problem. Modeling of fructose-induced overload was performed using a diabetic fructose supplement in an aqueous solution. The collection of herbs "Diabefit" was used as an infusion in addition to feeding highly enriched with fructose. The used markers which reflect the state of the heart and the blood vessels were: MDA, SOD, NO, and ET-1. MDA, ET-1, and NO concentrations demonstrated a significant increase in the fructose overload group and a significant decrease in the Diabefit group. At the same time, changes in SOD level as an indicator of the antioxidant reserve, on the contrary, implied a decrease in the group with a high fructose content and increased in the Diabefit group. All detected changes were associated with fructose-induced inhibition of SOD activity and its restoration using the Diabefit phyto-collection.

Assessment of behavioral, morphological and electrophysiological changes in prenatal and postnatal valproate induced rat models of autism spectrum disorder.

Autism spectrum disorders (ASD) are neurodevelopmental disorders, that are characterized by core symptoms, such as alterations of social communication and restrictive or repetitive behavior. The etiology and pathophysiology of disease is still unknown, however, there is a strong interaction between genetic and environmental factors. An intriguing point in autism research is identification the vulnerable time periods of brain development that lack compensatory homeostatic corrections. Valproic acid (VPA) is an antiepileptic drug with a pronounced teratogenic effect associated with a high risk of ASD, and its administration to rats during the gestation is used for autism modeling. It has been hypothesized that valproate induced damage and functional alterations of autism target structures may occur and evolve during early postnatal life. Here, we used prenatal and postnatal administrations of VPA to investigate the main behavioral features which are associated with autism spectrum disorders core symptoms were tested in early juvenile and adult rats. Neuroanatomical lesion of autism target structures and electrophysiological studies in specific neural circuits. Our results showed that prenatal and early postnatal administration of valproate led to the behavioral alterations that were similar to ASD. Postnatally treated group showed tendency to normalize in adulthood. We found pronounced structural changes in the brain target regions of prenatally VPA-treated groups, and an absence of abnormalities in postnatally VPA-treated groups, which confirmed the different severity of VPA across different stages of brain development. The results of this study clearly show time dependent effect of VPA on neurodevelopment, which might be explained by temporal differences of brain regions' development process. Presumably, postnatal administration of valproate leads to the dysfunction of synaptic networks that is recovered during the lifespan, due to the brain plasticity and compensatory ability of circuit refinement. Therefore, investigations of compensatory homeostatic mechanisms activated after VPA administration and directed to eliminate the defects in postnatal brain, may elucidate strategies to improve the course of disease.

The Involvement of Insulin-Like Growth Factor 1 and Nerve Growth Factor in Alzheimer's Disease-Like Pathology and Survival Role of the Mix of Embryonic Proteoglycans: Electrophysiological Fingerprint, Structural Changes and Regulatory Effects on Neurotrophins.

Alzheimer's disease (AD)-associated neurodegeneration is triggered by different fragments of amyloid beta (Aß). Among them, Aß (25-35) fragment plays a critical role in the development of neurodegeneration-it reduces synaptic integrity by disruption of excitatory/inhibitory ratio across networks and alters the growth factors synthesis. Thus, in this study, we aimed to identify the involvement of neurotrophic factors-the insulin-like growth factor 1 (IGF-1) and nerve growth factor (NGF)-of AD-like neurodegeneration induced by Aß (25-35). Taking into account our previous findings on the neuroprotective effects of the mix of proteoglycans of embryonic genesis (PEG), it was suggested to test its regulatory effect on IGF-1 and NGF levels. To evaluate the progress of neurodegeneration, in vivo electrophysiological investigation of synaptic activity disruption of the entorhinal cortex-hippocampus circuit at AD was performed and the potential recovery effects of PEG with relative structural changes were provided. To reveal the direct effects of PEG on brain functional activity, the electrophysiological pattern of the single cells from nucleus supraopticus, sensomotor cortex and hippocampus after acute injection of PEG was examined. Our results demonstrated that after i.c.v. injection of Aß (25-35), the level of NGF decreased in cerebral cortex and hypothalamus, and, in contrast, increased in hippocampus, prompting its multidirectional role in case of brain damage. The concentration of IGF-1 significantly increased in all investigated brain structures. The administration of PEG balanced the growth factor levels accompanied by substantial restoration of neural tissue architecture and synaptic activity. Acute injection of PEG activated the hypothalamic nucleus supraopticus and hippocampal neurons. IGF-1 and NGF levels were found to be elevated in animals receiving PEG in an absence of amyloid exposure. We suggest that IGF-1 and NGF play a critical role in the development of AD. At the same time, it becomes clear that the neuroprotective effects of PEG are likely mediated via the regulation of neurotrophins.

Disruption of Cholinergic Circuits as an Area for Targeted Drug Treatment of Alzheimer's Disease: In Vivo Assessment of Short-Term Plasticity in Rat Brain.

The search for new therapeutics for the treatment of Alzheimer's disease (AD) is still in progress. Aberrant pathways of synaptic transmission in basal forebrain cholinergic neural circuits are thought to be associated with the progression of AD. However, the effect of amyloid-beta (Aß) on short-term plasticity (STP) of cholinergic circuits in the nucleus basalis magnocellularis (NBM) is largely unknown. STP assessment in rat brain cholinergic circuitry may indicate a new target for AD cholinergic therapeutics. Thus, we aimed to study in vivo electrophysiological patterns of synaptic activity in NBM-hippocampus and NBM-basolateral amygdala circuits associated with AD-like neurodegeneration. The extracellular single-unit recordings of responses from the hippocampal and basolateral amygdala neurons to high-frequency stimulation (HFS) of the NBM were performed after intracerebroventricular injection of Aß 25-35. We found that after Aß 25-35 exposure the number of hippocampal neurons exhibiting inhibitory responses to HFS of NBM is decreased. The reverse tendency was seen in the basolateral amygdala inhibitory neural populations, whereas the number of amygdala neurons with excitatory responses decreased. The low intensity of inhibitory and excitatory responses during HFS and post-stimulus period is probably due to the anomalous basal synaptic transmission and excitability of hippocampal and amygdala neurons. These functional changes were accompanied by structural alteration of hippocampal, amygdala, and NBM neurons. We have thus demonstrated that Aß 25-35 induces STP disruption in NBM-hippocampus and NBM-basolateral amygdala circuits as manifested by unbalanced excitatory/inhibitory responses and their frequency. The results of this study may contribute to a better understanding of synaptic integrity. We believe that advancing our understanding of in vivo mechanisms of synaptic plasticity disruption in specific neural circuits could lead to effective drug searches for AD treatment.

Embryonic proteoglycans regulate monoamines in the rat frontal cortex and hippocampus in Alzheimer's disease-like pathology.

Using the rat Alzheimer's disease (AD)-like model we have analyzed the hippocampal short-term potentiation, levels of monoamines, and morphological changes in the hippocampal and cortical neurons after the administration of proteoglycans of embryonic origin (PEG). Results showed that the levels of monoamines and especially norepinephrine in the target AD brain structures were found elevated, except serotonin, which was unaffected in the hippocampus, but decreased in the frontal cortex. These changes were accompanied by the substantial structural damage of cortical and hippocampal neurons. PEG was able to reverse most of these changes. In addition, PEG administration had regime-dependent effects on a short-term potentiation pattern of hippocampal neurons. The elevated levels of key elements of brain monoaminergic system in the model of AD support the hypothesis of the important role of monoamines in the excessive synaptic excitation resulting in cognitive dysfunction in AD brain. The neuroprotective effect of PEG, as manifested by the recovery of the monoaminergic system, suggests this bioactive substance as a perspective therapeutic agent for the treatment of AD.

Alzheimer's disease-like pathology-triggered oxidative stress, alterations in monoamines levels, and structural damage of locus coeruleus neurons are partially recovered by a mix of proteoglycans of embryonic genesis.

Alzheimer's disease (AD) pathogenesis includes oxidative damage and perturbations of monoamines. However, as many details of these alterations are not known, we have investigated the changes in monoamine levels as well as the free radical oxidation processes (FRO) in the brainstem of rats that were administered i.c.v. Aß (25-35) (rat model of AD-like pathology). The level of oxidative stress was found elevated in the brainstem along with the increased concentrations of monoamines, especially norepinephrine in the locus coeruleus (LC) area of the brainstem. This was accompanied by the substantial structural damage of monoaminergic neurons of LC. In addition, we have tested the ability of proteoglycans of embryonic genesis (PEG) that were shown previously to act as neuroprotectors, to restore the AD-triggered alterations in monoaminergic system and FRO. Indeed, PEG reduced the increased FRO and upregulated monoamines in the brainstem of Aß (25-35) treated animals. Administration of PEG to control animals led to the increase of the antioxidant capacity as well as the intensity of free radical oxidation processes. Our study confirms the important role of the brainstem FRO and monoamine shifts in AD development along with the known aggregation of Ab peptide and Tau hyperphosphorylation. We suggest that at the early stages of AD development, with still functional neurons, regulation of monoamine levels via stabilizing FRO processes can be beneficial. Our data demonstrate the regulatory action of PEG on the monoamine disturbances and the level of oxidative stress in the AD damaged structures, suggesting its possible therapeutic application in AD.

The role of monoamines in the development of Alzheimer's disease and neuroprotective effect of a proline rich polypeptide.

INTRODUCTION: We have analyzed the alterations in the brain monoaminergic system using the rat model of AD-like pathology. In addition, we have investigated potential neuroprotective effects of the hypothalamic proline-rich polypeptide (PRP-1). METHODS: Histochemical staining, HPLC, chemiluminescent and bioluminescence assays. RESULTS: The levels of monoamines in the target AD brain structures were found elevated, except serotonin, which was unaffected in both hippocampus and brainstem and decreased in frontal cortex. This was accompanied by the substantial structural damage of cortical, hippocampal, as well as the monoaminergic neurons of locus coeruleus and oxidative stress. PRP-1 was able to reverse most of these changes. DISCUSSION: The increased levels of major brain monoamines in the model of AD supports the hypothesis of the important role of monoamines in the excessive synaptic excitation resulting in cognitive dysfunction in AD brain. The neuroprotective effect of PRP-1 as manifested by the recovery of monoaminergic system suggests this bioactive compound as a perspective therapeutic agent for the treatment of AD.

Protective Effects of Proline-Rich Peptide in a Rat Model of Alzheimer Disease: An Electrophysiological Study.

INTRODUCTION: Alzheimer disease (AD) is the most common form of dementia in the elderly that slowly destroys memory and cognitive functions. The disease has no cure and leads to significant structural and functional brain abnormalities. To facilitate the treatment of this disease, we aimed to investigate proline-rich peptide (PRP-1) action of hypothalamus on hippocampal (HP) neurons and dynamics of their recovery, after intracerebroventricular (ICV) injection of amyloid-ß (Aß). METHODS: Experiments were carried out on 24 adult, male Albino rats (average weight: 230±30 g). The animals were randomly divided into 3 groups (control, Aß, and Aß plus PRP-1). Electrophysiological patterns of hippocampal neurons in response to stimulation of entorhinal cortex (EC) with high frequency stimulation (50 Hz) were studied. RESULTS: It was found that Aß (25-35) suppresses the electrical activity of hippocampal neurons. The PRP-1 would return this activity to normal levels. CONCLUSION: In general, PRP-1 has protective effect against AD-related alterations induced by amyloid peptides. This protective effect is probably due to stimulation of the immune and glia system.

Neuroprotective action of proline-rich polypeptide-1 in ß-amyloid induced neurodegeneration in rats.

It is recognized that the main trigger of Alzheimer disease related neurodegeneration is ß-amyloid peptide, which subsequently generates different metabolic disorders in neuron and finally leads to neuronal death. Several biologically active products were tested as neuroprotectors, but only few of them demonstrated any efficiency. Proline-rich polypeptide-1 was tested as a neuroprotective agent on Aß25-35 animal model of Alzheimer disease. Biochemical analysis (determination of spectrum of neuroactive amino acids, such as glutamate, gamma-aminobutyric acid, glycine, aspartate and taurine), as well as behavioral, electrophysiological and morphological studies were performed to reveal the neuroprotective potential of proline-rich polypeptide in rats. Based on the results of our study it can be concluded that proline-rich polypeptide-1 has a potential to be one of the effective preventive or therapeutic agents against neurodegenerative disorders, such as Alzheimer disease.

Protective effects of hypothalamic proline-rich peptide and cobra venom Naja Naja Oxiana on dynamics of vestibular compensation following unilateral labyrinthectomy.

We tested the action of proline-rich peptide (PRP-1) and cobra venom Naja Naja Oxiana (NOX) on Deiters' nucleus neurons at 3rd, 15th and 35th days after unilateral labyrinthectomy (UL). Early and late tetanic, post-tetanic potentiation and depression of Deiters'neurons to bilateral high frequency stimulation of hypothalamic supraoptic and paraventricualar nuclei was studied. The analysis of spike activity was carried out by mean of on-line selection and special program. The complex averaged peri-event time and frequency histograms shows the increase of inhibitory and excitatory reactions of Deiters' neurons at early stage of vestibular compensation following PRP-1 and NOX injection, reaching the norm at the end of tests. In histochemical study the changes in Ca(2+)-dependent acidic phosphatase (AP) activity in neurons was discovered. It was shown that in UL animals the total disappearance or delay of decolorizing of Deiters' neurons lead to neurodegenerative pattern as cellular "shade". AP activity after UL and PRP-1 injection exerts more effective recovery of neurons in comparison with events, observed after the administration of NOX. The data of this study indicate that PRP-1 and NOX are protectors, which may successfully recover the disturbed vestibular functions.

Protective action of snake venom Naja naja oxiana at spinal cord hemisection.

Based on data accumulated regarding the neuroprotective action of Proline-Rich-Peptide-1 (PRP-1, a fragment of neurophysin vasopressin associated hypothalamic glycoprotein consisting of 15 amino acid residues) on neurons survival and axons regeneration and taking into the account that LVV-Hemorphin-7 (LVV-H7, an opioid peptide, widely distributed in different cell types of various tissues of intact rats, including those of the nervous and immune systems) derived from the proteolytic processing of hemoglobin in response to adverse environmental and physiological conditions, possesses the anti-stressor properties, we used histochemistry, immunohistochemistry and electrophysiology to investigate the putative neuroprotective action of Central Asian Cobra Naja naja oxiana snake venom (NOX) on trauma-injured rats. ABC immunohistochemical method and histochemical method on detection of Ca2+-dependent acid phosphatase activity were used for the morpho-functional study. By recording the electrical activity of the signals from the single neurons in and below the SC injury place, NOX venom has been shown to result in the complete restoration of hypothalamic-spinal projections originated from ipsi- and contra-lateral PVN and SON to neurons of SC lumbar part. NOX prevented the scar formation, well observed two months after SC injury in the control rats, resulted in the regeneration of nerve fibers growing through the trauma region, survival of the PRP-1- and LVV-H7-immunoreactive (Ir) neurons, and increase of the PRP-1 - and LVV-H7-Ir nerve fibers and astrocytes in the SC lesion region. NOX was suggested to exert the neuroprotective effect, involving the PRP-1 and LVV-H7 in the underlying mechanism of neuronal recovery.

PRP-1 protective effect against central and peripheral neurodegeneration following n. ischiadicus transection.

We investigated the action of the new hypothalamic proline-rich peptide (PRP-1), normally produced by neurosecretory cells of hypothalamic nuclei (NPV and NSO), 3 and 4 weeks following rat sciatic nerve transection. The impulse activity flow of interneurons (IN) and motoneurons (MN) on stimulation of mixed (n. ischiadicus), flexor (n. gastrocnemius--G) and extensor (n. peroneus communis--P) nerves of both injured and symmetric intact sides of spinal cord (SC) was recorded in rats with daily administration of PRP-1 (for a period of 3 weeks) and without it (control). On the injured side of SC in control, there were no responses of IN and MN on ipsilateral G and P stimulation, while responses were elicited on contralateral nerve stimulation. The neuron responses on the intact side of SC were revealed in a reverse ratio. Thus, there were no effects upon stimulation of the injured nerve distal stump in the control because of the absence of fusion between transected nerve stumps. This was also testified by the atrophy of the distal stump and the absence of motor activity of the affected limb. In PRP-1-treated animals, the responses of SC IN and MN in postaxotomy 3 weeks on the injured side of SC at ipsilateral nerve stimulation and on the intact side at contralateral nerve stimulation were recorded because of the obvious fusion of the severed nerve stumps. The histochemical data confirmed the electrophysiological findings. Complete coalescence of transected fibers together with restoration of the motor activity of the affected limb provided evidence for reinnervation on the injured side. Thus, it may be concluded that PRP-1 promotes nerve regeneration and may be used clinically to improve the outcome of peripheral nerve primary repair.

Neuroprotective action of hypothalamic peptide PRP-1 at various time survivals following spinal cord hemisection.

The purpose of the present study was to evaluate the neuroprotective action of proline-rich peptide-1 (PRP-1) produced by hypothalamic nuclei cells (nuclei paraventricularis and supraopticus) following lateral hemisection of spinal cord (SC). The dynamics of rehabilitative shifts were investigated at various periods of postoperative survival (1-2, 3, and 4 weeks), both with administration of PRP-1 and without it (control). We registered evoked spike flow activity in both interneurons and motoneurons of the same segment of transected and symmetric intact sides of SC and below it on the stimulation of mixed (n. ischiadicus), flexor (n. gastrocnemius) and extensor (n. peroneus communis) nerves. In the control group (administration of 0.9% saline as placebo), no significant decrease of post-stimulus activity of neurons was observed on the transected side by the 2nd week. This activity strongly decreased by week 3 postaxotomy, with some increase on the intact side, possibly of compensatory origin. No shifts occurred by the 4th week. Regardless of the period of administration, PRP-1 increased neuronal activity on the transected side, with the same activation levels on both SC sides. These data were confirmed by histochemical investigation. PRP-1 administration, both daily and every other day, for a period of 2-3 weeks led to prevention of scar formation and promotion of the re-growth of white matter nerve fibers in the damaged area. It also resulted in prevention of neuroglial elements degeneration and reduction in gliosis expression in the lesion supporting neuronal survival. Thus, PRP-1 achieved protection against "tissue stress", which was also confirmed by the registration of activity on the level of transection and restoration of the motor activity on the injured side. The obtained data propose the possibility of PRP-1 application in clinical practice for prevention of neurodegeneration of traumatic origin.