Protective effect of a new hypothalamic peptide against cobra venom and trauma-induced neuronal injury

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.

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

It is recognized that the main trigger of Alzheimer disease related neurodegeneration is β-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 Aβ25-35 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.

Hypothalamic proline rich polypeptide regulates hematopoiesis

The AGAPEPAEPAQPGVY proline-rich polypeptide (PRP-1) was isolated from neurosecretory granules of the bovine neurohypophysis; it is produced by N. supraopticus and N. paraventricularis. It has been shown that PRP-1 has many potentially beneficial biological effects including immunoregulatory, hematopoietic, antimicrobial and anti-neurodegenerative properties. Here we demonstrated that PRP-1 administration influence on redistribution of monocytes, granulocytes and lymphocytes between bone marrow (BM) and peripheral blood and promotes the influx of granulocytes and monocytes/macrophages from BM into peripheral blood and accumulation of immature granulocyte and monocyte in BM and delayed the maturation of T cells in BM. PRP-1 increased colony-forming cell proliferation in rat cells in vivo. In PRP-treated rat BM, the CFU number at day 4, 7 and 14 was considerably increased in comparison with untreated rats BM and no difference was found at day 21 and day 28. We found that PRP-1 enhances erythroid and myeloid colonies formation in human CD34(+) progenitor cell culture in the presence of different growth factors and down-regulates T cells colony formation and specific surface markers expression during induction of human CD34(+) progenitor cells differentiation into T lymphocytes lineage. We suggested that the hypothalamic PRP-1 possibly represents an endogenous peptide whose primary functions are to regulate neuronal survival and differentiation and hematopoiesis within neurosecretory hypothalamus-bone marrow humoral axis.

Neuroprotection by hypothalamic peptide proline-rich peptide-1 in Abeta25-35 model of Alzheimer's disease

BACKGROUND

This work sought to determine the effects of hypothalamic proline-rich peptide (PRP)-1 in a rat model of Alzheimer's disease.

METHODS

Complex histochemical, electrophysiologic, and behavioral analyses were performed on intact or diseased Wistar rats (n = 28). Pathologic conditions were induced by bilateral intracerebroventricular injection of amyloid peptide Abeta25-35. The diseased rats received systemic administration of PRP-1 or placebo control.

RESULTS

Abeta25-35 caused cellular neurodegeneration with marked glial reaction in the hippocampal complex and almost full destruction of the dentate fascia, which was not observed in conditions of PRP-1 administration after Abeta25-35 injection. Hippocampal neurons of intact animals responded to high-frequency (tetanic) stimulation of entorhinal cortex of ipsilateral cerebral hemisphere by tetanic and posttetanic potentiation of a different intensity and duration, which was accompanied by posttetanic depression. Abeta25-35 led to significant changes in the level and pattern of hippocampal neuronal activity, indicating the absence of both tetanic and posttetanic activity. Poststimulus activity manifestations rarely occurred and rapidly decreased after repeated trials. This indicated the focal character of lesion. Regular administration of PRP-1 for 4 weeks resulted in optimal restoration of electrophysiologic parameters. PRP-1 maintained the initial learning level achieved in a behavioral study in a Morris water maze.

CONCLUSIONS

Systemic administration of PRP-1 possesses neuroprotective effects and can prevent the neurodegeneration in hippocampus induced by Abeta25-35. This suggests that PRP-1 could be a potential therapeutic agent for specific neurodegenerative diseases.

Proline-rich polypeptides in Alzheimer's disease and neurodegenerative disorders -- therapeutic potential or a mirage?

The development of effective and safe drugs for a growing Alzheimer disease population is an increasing need at present. Both experimental and clinical evidence support a beneficial effect of proline-rich polypeptides in a number of neurodegenerative diseases, including Alzheimer disease. Experimental data have shown that proline-rich polypeptides isolated from bovine neurohypophisis possess neuroprotective and neuromodulatory properties in mice with aluminum neurotoxicosis or neuronal damage caused by venoms and toxins. Proline-rich polypeptides from ovine colostrums, so called Colostrinin, have been shown to produce cognitive improvement in an experimental model and in patients with Alzheimer disease. However, the precise mechanism underlying the neuroprotective action of proline-rich polypeptides is not very well established. Moreover, studies pointing at a neuroprotective effect of proline-rich polypeptides from bovine neurohypophisis in humans have not been reported thus far. The authors conclude that more detailed information on the mode of action of proline-rich polypeptides is needed as well as confirmation of their efficacy in broad clinical trials before this approach can really show its potential in the treatment of neurodegenerative disorders.

Effect of Hypothalamic Proline-Rich Peptide (PRP-1) on Neuronal and Bone Marrow Cell Apoptosis

The AGAPEPAEPAQPGVY proline-rich peptide (PRP-1) was isolated from neurosecretory granules of the bovine neurohypophysis; it is produced by N. supraopticus and N. paraventricularis. It has been shown that PRP-1 has many potentially beneficial biological effects including immunoregulatory, hematopoietic, antimicrobial and anti-neurodegenerative properties. Here we investigated the influence of PRP-1 on staurosporine-induced apoptosis of postnatal hippocampal cells and on doxorubicin-induced bone marrow granulocyte- and monocyte apoptosis. The intention was to further characterize the effect of PRP-1 on the survival rate of neurons and in context with myelopoiesis. We demonstrate that PRP-1 significantly reduced apoptosis of postnatal hippocampal cells induced by staurosporine. The protective effect of PRP-1 against apoptotic cell death was shown to be both time- and dose-dependent. Neuroprotection was more pronounced after prolonged pretreatment of the cells with PRP-1 before the induction of apoptosis with staurosporine. The related peptide [arg(8)]vasopressin did not reveal neuroprotection. PRP-1 also significantly reduced apoptosis of bone marrow monocytes and granulocytes induced by doxorubicin. This protective effect lasted for 2-4 h and was not detectable anymore after 24 h when PRP-1 and doxorubicin were added simultaneously. Previously obtained data and results of the current studies suggested that the hypothalamic PRP-1 possibly represents an endogenous peptide whose primary functions are to regulate myelopoiesis and neuron survival as we provide evidence that PRP can differentially reduce both staurosporine- and doxorubicin-induced hippocampal and bone marrow cell apoptosis.

The Protective Effect of Vipera Raddei Venom on Peripheral Nerve Damage

Acute experiments were performed on spinal rats to study the protective actions of Vipera raddei venom after section of the sciatic nerve. Individual spike activity was recorded from interneurons and motoneurons in the lumbar segment of the spinal cord, induced by stimulation of the sciatic nerve and the extensor (gastrocnemius) and flexor (peroneus communis) nerves on the lesioned and symmetrical intact sides in controls and after daily injections of venom for four weeks. In animals not treated with Vipera raddei venom, the lesioned side lacked interneuron and motoneuron responses to stimulation of the extensor and flexor nerves of the distal stump, though these were present on stimulation of the contralateral side; responses were the inverse of this on the intact side, due to the failure of the proximal and distal stumps to fuse, as also demonstrated by atrophy of the distal stump of the sciatic nerve and the absence of movement activity in the lesioned limb. Treatment with Vipera raddei venom led to restoration, by four weeks, of interneuron and motoneuron responses on the lesioned side on stimulation of the ipsilateral nerves and on the intact side by stimulation of the contralateral nerves; this is the result of apparent fusion of the proximal and distal stumps of the lesioned nerve. Further evidence for this was hypertrophy of the distal stump and restoration of movement activity in the lesioned limb. These results show that Vipera raddei venom has potential for use in regenerating damaged peripheral nerves.

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.

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.

A synthetic human proline-rich-polypeptide enhances hydroxyl radical generation and fails to protect dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced toxicity in mice

Some of the proline-rich-polypeptides (PRPs) are shown to afford protection against spinal cord transection or crush syndrome-induced neurodegeneration in the brain. In the present study a synthetic proline-rich-polypeptide of human hypothalamus origin (h-PRP) has been examined for its potency to protect against dopaminergic neuronal damage caused by the parkinsonian neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Effect of h-PRP on hydroxyl radical (*OH) generation in a Fenton-like reaction was monitored, employing a sensitive salicylate hydroxylation procedure. Balb/c mice treated twice with MPTP (30 mg/kg. i.p., twice, 16 h apart) or h-PRP (20 microg/animal, twice, 16 h apart) showed significant loss of striatal dopamine as assayed by HPLC with electrochemical detection. h-PRP pretreatment failed to attenuate MPTP-induced striatal dopamine depletion. A dose-dependent increase in the generation of *OH by h-PRP suggests its pro-oxidant action, and explains its failure to protect against MPTP-induced parkinsonism in mice.

Hypothalamic proline-rich polypeptide protects brain neurons in aluminum neurotoxicosis

The damaging effect of aluminum ions (Al3+) on the organism is widely investigated in clinics and experiments that indicate its role as a participant in the synthesis of precursors for amyloid proteins and as a potential agent in the ethiology of Alzheimer's disease. It has been shown that Al produces neurotoxic effects. We established that AlCl3 produces degenerative changes in the ultrastructure of Hasserian neurinoma cells in vitro and in L929 fibroblast cells. Proline-rich peptide-1 (PRP-1) isolated from neurosecretory granules of bovine neurohypophysis is a potent antineurodegenerative agent against spinal cord hemisection and crush syndrome-induced neurodegeneration of brain and spinal cord neurons. PRP-1 is one of the neurotrophic brain factors. By electron microscopic study of the rat hippocampus and other tissues, we succeeded in visualizing the epithelioprotectory effect of PRP-1, contributing as a powerful agent in removal of aluminum accumulation in different tissues in experimental aluminum neurotoxicosis.

Survival of trauma-injured neurons in rat brain by treatment with proline-rich peptide (PRP-1): an immunohistochemical study

The objective of this immunohistochemical research was to reveal the distribution of a proline-rich peptide-1 (PRP-1) in various brain structures of intact and trauma-injured rats and to identify the mechanisms of promotion of neuronal recovery processes following PRP-1 treatment. PRP-1, produced by bovine hypothalamic magnocellular cells and consisting of 15 amino acid residues, is a fragment of neurophysin vasopressin associated glycoprotein isolated from bovine neurohypophysis neurosecretory granules. PRP-1-immunoreactivity (PRP-1-IR) was detected in the brain of intact rats in the neurons of paraventricular (PVN) and supraoptic (SON) nuclei in the hypothalamus, in almost all cell groups in the medulla oblongata, in Purkinje and some cerebellar nuclei cells, and in nerve fibers. At 3 weeks after hemisection of the spinal cord (SC) an asymmetry of PRP-1 localization in the PVN and SON was observed: no PRP-1-IR was exhibited at the affected sides of both nuclei. Daily intramuscular administration of PRP-1 for 3 weeks significantly increased the number of PRP-1-immunoreactive (PRP-1-Ir) varicose nerve fibers, and cells in PVN and SON and in cell groups of the limbic system and brain stem. Tanycytes in the median eminence and covering ependyma also demonstrated strong PRP-1-IR. PRP-1 treatment also activated neuropeptide Y-IR (NPY-IR) in nerve fibers and immunophilin fragment-IR (IphF-IR) in lymphocytes and nerve cells. A strong increase of PRP-1-IR was observed in the PVN and SON of SC-injured rats following the treatment with another PRP (PRP-3). Preliminary physiological data demonstrate that PRP-3 is more "aggressive" in the recovery processes than PRP-1. Based on the findings regarding PRP action on neurons survival, axons regeneration, and the number of IphF-Ir lymphocytes and NPY-Ir nerve fibers, PRP is suggested to act as a neuroprotector, functioning as a putative neurotransmitter and immunomodulator.