Brain-derived peptides increase the expression of a blood-brain barrier GLUT1 glucose transporter reporter gene

Enhanced Spontaneous Motor Recovery After Stroke in Mice Treated With Cerebrolysin

BACKGROUND

Motor recovery after stroke in humans and in rodent models is time sensitive. Recovery in patients is a result of biological spontaneous recovery via endogenous repair mechanisms and is likely improved by enhancing the synaptic plasticity required for endogenous repair. Cerebrolysin is a polypeptide preparation known to enhance neuroplasticity and may improve recovery in patients. In mice, we tested the hypothesis that Cerebrolysin can act poststroke to enhance both spontaneous and training-associated motor recovery.

METHODS

Mice were trained to perform a skilled prehension task. We then induced a photothrombotic stroke in the caudal forelimb area, after which we retrained animals on the prehension task in the presence or absence of Cerebrolysin after a 2-day or 8-day delay. Mice received daily intraperitoneal Cerebrolysin or saline injections starting poststroke day 1 or poststroke day 7.

RESULTS

Prior studies showed that poststroke recovery of prehension can occur if animals receive rehabilitative training during an early sensitive period but is incomplete if rehabilitative training is delayed. In contrast, we show complete recovery of prehension, despite a delay in rehabilitative training, when mice receive daily Cerebrolysin administration starting on poststroke day 1 or on poststroke day 8. When Cerebrolysin is given on poststroke day 1, recovery occurred even in the absence of training. Stroke volumes were similar across groups.

CONCLUSIONS

Poststroke Cerebrolysin administration leads to recovery of motor function independent of rehabilitative training without a protective effect on stroke volume. This is one of the first demonstrations of training-independent motor recovery in rodent stroke models.

Brain and behavioral perturbations in rats following Western diet access

Energy dense "Western" diets (WD) are known to cause obesity as well as learning and memory impairments, blood-brain barrier damage, and psychological disturbances. Impaired glucose (GLUT1) and monocarboxylate (MCT1) transport may play a role in diet-induced dementia development. In contrast, ketogenic diets (KD) have been shown to be neuroprotective. We assessed the effect of 10, 40 and 90 days WD, KD and Chow maintenance on spontaneous alternation (SA) and vicarious trial and error (VTE) behaviors in male rats, then analyzed blood glucose, insulin, and ketone levels; and hippocampal GLUT1 and MCT1 mRNA. Compared to Chow and KD, rats fed WD had increased 90 day insulin levels. SA was decreased in WD rats at 10, but not 40 or 90 days. VTE was perturbed in WD-fed rats, particularly at 10 and 90 days, indicating hippocampal deficits. WD rats had lower hippocampal GLUT1 and MCT1 expression compared to Chow and KD, and KD rats had increased 90 day MCT1 expression compared to Chow and WD. These data suggest that WD reduces glucose and monocarboxylate transport at the hippocampus, which may result in learning and memory deficits. Further, KD consumption may be useful for MCT1 transporter recovery, which may benefit cognition.

Delivery of peptide drugs to the brain by adenovirus-mediated heterologous expression of human oligopeptide transporter at the blood-brain barrier

The feasibility of using adenovirus-mediated human oligopeptide transporter (hPEPT1) gene transfer to achieve peptide drug delivery to the brain across the blood-brain barrier was tested by examining the accumulation of model peptides in a rat brain endothelial cell line (RBEC1) and rat brain after transduction with a recombinant adenovirus encoding hPEPT1-enhanced yellow fluorescent protein fusion gene (AdhPEPT1-EYFP). In vitro uptake of [(3)H]GlySar was determined in RBEC1 transduced with AdhPEPT1-EYFP. In vivo, the accumulation of cefadroxil in rat brain was evaluated after transduction of AdhPEPT1-EYFP. At pH 6.0, the uptake of [(3)H]GlySar by RBEC1 transduced with AdhPEPT1-EYFP was increased 4-fold compared with that of nontransduced cells. At pH 7.4, uptake of [(3)H]GlySar in AdhPEPT1-EYFP transduced RBEC1 was 1.5 times higher than that of nontransduced cells. Unlabeled glycylsarcosine (10 mM) reduced the uptake of [(3)H]GlySar to a level comparable with that of nontransduced cells. At 30 min after intravenous administration of cefadroxil to rats transduced with AdhPEPT1-EYFP at 3.2 x 10(9) plaque-forming units/rat by an in situ brain perfusion method, the brain-to-plasma concentration ratio (Kp) of cefadroxil was increased about 2 times compared with that of nontransduced or AdGFP (control vector)-transduced rats, although this was not statistically significant. In contrast, Kp of [(14)C]inulin, a marker for extracellular fluid space, remained unchanged after adenoviral transduction. In conclusion, our results suggest that adenovirus-mediated heterologous expression of hPEPT1 in vivo could be a useful approach to deliver oligopeptides to the brain.

In vitro models of brain ischemia: the peptidergic drug cerebrolysin protects cultured chick cortical neurons from cell death

Glutamate (1 mM), iodoacetate (0.01 mM) and ionomycin (0.25 micro M) are reported to induce several characteristics of ischemia and neuronal degeneration in vitro, e.g. glutamate and ionomycin lesion result in a disturbance of Ca(2+) homeostasis, iodoacetate impairment leads to an inhibition of energy metabolism, suppression of protein synthesis and generation of oxygen free radicals. In this study these three lesion models were used to investigate the effects of the nootropic drug Cerebrolysin (Cere) on the survival of cortical neurons in culture and on the occurrence of apoptosis. The viability of the cells was evaluated with the colorimetric MTT-reduction assay. Apoptosis was detected with Bisbenzimide (Hoechst:33258), a fluorescent DNA stain. Administration of Cere resulted in dose dependent neuroprotection independent from the kind of lesion. In the glutamate model the drug almost doubled neuronal viability compared to lesioned controls. After acute glutamate exposure Cere reduced the number of apoptotic cells significantly. In spite of the protective efficacy after cytotoxic hypoxia induced by iodoacetate, the drug significantly increased the number of apoptotic neurons, indicating a shift from necrosis to apoptosis. In contrast to previous studies investigating acute ionomycin lesions, the chronic Ca(2+)-overload used here did not increase the abundance of apoptosis compared to the unlesioned control. Summarizing the findings it can be suggested that Cere is able to stabilize Ca(2+) homeostasis, to protect protein synthesis and to counteract neuronal death in different in vitro medels of ischemia.

Increased density of glutamate receptor subunit 1 due to Cerebrolysin treatment: an immunohistochemical study on aged rats

Glutamate receptor subunit 1 (GluR1) is one of the four possible subunits of the AMPA-type glutamate receptor. The integrity of this receptor is crucial for learning processes. However, reductions of GluR1 are noticeable in the hippocampal formation of patients suffering from Alzheimer's disease. Such degradations presumably result in an impaired synaptic communication and might be causally linked to the neurodegenerative process in this cognitive disorder. The peptidergic drug Cerebrolysin counteracts cognitive deficits of patients affected by Alzheimer's disease. These findings are supported by experiments revealing neuroprotective and neurotrophic capacities of the drug. In order to examine the effect of the drug on the density of GluR1 in hippocampal formation 24-month-old rats were treated with either Cerebrolysin or its peptide fraction E021, or saline as a control. Spatial navigation of the animals was tested in the Morris water maze. Rat brain slices were stained immunohistochemically with a GluR1-specific antibody. GluR1 immunoreactivity was quantified using light microscopy and a computerised image analysis system. Cerebrolysin and E021 increased GluR1 density in most measured regions of the hippocampal formation in a highly significant way. These results correlate with the behavioural outcome, revealing an improvement in learning and memory of these rats after treatment with Cerebrolysin and E021.

Amplification of blood-brain barrier GLUT1 glucose transporter gene expression by brain-derived peptides

Glucose is a critical nutrient for the brain, and the transport of this hexose from blood to brain is mediated by the blood-brain barrier (BBB) GLUT1 glucose transporter. The expression of the BBB-GLUT1 gene is compromised in different pathological conditions and it is modulated by brain trophic factors. The brain-derived peptide preparation Cerebrolysin (Cl, EBEWE, Austria) increases the expression of the BBB-GLUT1 via mRNA stabilization. In order to gain more insights into the mechanism of BBB-GLUT1 gene regulation, the present investigation studied the effect of Cl on the expression of both the GLUT1 protein and GLUT1 reporter genes in brain endothelial cultured cells (ECL). Cl markedly increased the expression of reporter genes containing GLUT1 translational control elements and cis-acting elements involved in the stabilization of the GLUT1 mRNA transcript in a dose dependent manner. Cl produced only marginal effects on the reporter gene control lacking the GLUT1 regulatory elements. In parallel experiments, Cl markedly increased the uptake of 3H-2-deoxy-D-glucose and the levels of the GLUT1 protein measured by ELISA. Data presented here demonstrate: (i) that Cl increases the expression of BBB-GLUT1 reporter genes containing regulatory cis-elements involved in the stabilization and translation of the GLUT1 transcript; (ii) that the effect on both regulatory elements cooperates to increase gene expression; and (iii) that the increased levels of the BBB-GLUT1 reporter genes in Cl-treated ECL cells are associated with an increase in the glucose uptake and in the expression of the GLUT1 protein.

Neurotrophic effects of Cerebrolysin in animal models of excitotoxicity

Excitotoxicity might play an important role in neurodegenerative disorders such as Alzheimer's disease. In the mouse brain, kainic acid (KA) lesioning results in neurodegeneration patterns similar to those found in human disease. For this study, two sets of experiments were performed in order to determine if Cerebrolysin ameliorates the alterations associated with KA administration. In the first set of experiments, mice received intraperitoneal KA injections followed by Cerebrolysin administration, while in the second, mice were pretreated with Cerebrolysin for 4 weeks and then challenged with KA. Behavioral testing in the water maze and assessment of neuronal structure by laser scanning confocal microscopy showed a significant protection against KA lesions in mice pretreated with Cerebrolysin. In contrast, mice that received Cerebrolysin after KA injections did not show significant improvement. This study supports the contention that Cerebrolysin might have a neuroprotective effect in vivo against excitotoxicity.

The drug cerebrolysin and its peptide fraction E021 increase the abundance of the blood-brain barrier GLUT1 glucose transporter in brains of young and old rats

The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. In the present study, we investigated the effects of Cerebrolysin and its peptide preparation E021 on spatial learning and memory, as well as on the abundance of the blood-brain barrier GLUT1 glucose transporter (GLUT1) in 2-month-old and 24-month-old rats. Young rats were treated with the drugs or saline (2.5 ml/kg/day) daily on postnatal days 1-7, and old rats for 19 consecutive days. For behavioural testing the Morris water maze was used. The abundance of GLUT1 was determined in brain slices by immunocytochemistry. Quantification of the density of the GLUT1 immunostaining was performed using light microscopy and a computerised image analysing system. All drug-treated rats, young and old, exhibit shorter escape latencies in the water maze, on all testing days (p < 0.01), indicating improved cognitive performance. Immunohistochemical data show an age-related decrease of the density of GLUTI (p < 0.05). In young animals, the administration of the drugs led to an increase of the abundance of GLUT1 in all experimental groups (p < 0.01). In old rats, the treatment with Cerebrolysin, but not with E021, resulted in an increase in the immunoreactive GLUT1 (p < 0.01). The elevated abundance of GLUT1 after the administration of both peptidergic substances might be supportive for the cognitive effects of this drug, by causing an improved nutritional supply of glucose to the neurons.

Approach towards an integrative drug treatment of Alzheimer's disease

At present pharmacotherapy of Alzheimer's disease (AD) is limited to acetylcholinesterase inhibitors. These drugs produce small, but consistent improvements of memory and global function, some are also positively influencing activities of daily living. This therapeutic approach neglects the complexity of AD and the fact that most of the degenerating neurons are not cholinergic. Acetylcholinesterase inhibitors are symptomatic drugs, with no influence on disease progression. There is a need for disease modifying compounds, or preventive drugs. Data are indicating that vitamin E has some ability to influence the disease progression. The potency of non-steroidal anti-inflammatory drugs (NSAIDs) or estrogen as preventive agents has to be explored further in prospective clinical studies. The initial hope in the use of naturally occurring neurotrophic factors, like nerve growth factor, to rescue cholinergic neurons from degeneration and to restore cognitive function has been disappointed in first, small clinical studies. The peptidergic drug Cerebrolysin exhibiting neurotrophic stimulation, neuroimmunotrophic regulation and induction of BBB glucose transporter expression, might be able to address the pathological changes of AD at different levels simultaneously. In addition to an impressive preclinical database, results from 3 placebo-controlled, double-blind studies demonstrate significant improvements of cognitive performance, global function and activities of daily living in AD patients. In all studies persisting improvements, up to 6 months after drug withdrawal, indicate a powerful disease modifying activity.

GLUT1: a newly discovered immunohistochemical marker for juvenile hemangiomas

Juvenile hemangiomas are common, benign vascular tumors of infancy. These lesions enlarge rapidly through cellular hyperplasia during the first year of life and then involute over several years. Distinctive histopathologic features of hemangiomas diminish during this evolution, and differentiation from vascular malformations becomes increasingly difficult. This distinction has important therapeutic implications, as juvenile hemangiomas differ from malformations in natural history and in potential for recurrence. We report here that high endothelial immunoreactivity for the erythrocyte-type glucose transporter protein GLUT1 is a specific feature of juvenile hemangiomas during all phases of these lesions. In a retrospective study, we found intense endothelial GLUT1 immunoreactivity, involving more than 50% of lesional microvessels, in 97% (139 of 143) of juvenile hemangiomas from patients aged 1 month to 11 years. No endothelial GLUT1 immunoreactivity was found in any of 66 vascular malformations (17 arteriovenous, 33 venous, 11 lymphatic, and 5 port-wine) from patients aged 5 days to 75 years, or in any of 20 pyogenic granulomas or 7 granulation tissue specimens. Abundant Ki-67 positivity in these latter lesions established that GLUT1 expression does not simply reflect mitotically active endothelium. Focal GLUT1 immunoreactivity was found in 3 of 12 angiosarcomas, but not in any of 5 hemangioendotheliomas (epithelioid or infantile kaposiform). These findings establish GLUT1 immunoreactivity as a highly selective and diagnostically useful marker for juvenile hemangiomas. Because high levels of endothelial GLUT1 expression in normal tissue are restricted to microvessels with blood-tissue barrier function, these findings also have implications for the molecular and developmental pathogenic mechanisms of juvenile hemangiomas.

The influence of mRNA stability on glucose transporter (GLUT1) gene expression

One mechanism for modification of glucose transport activity occurs through regulation of the cellular content of transporter protein by alteration of transcript stability. Regulated mRNA decay has been shown to play an important role in control of posttranscriptional gene expression. Implicated, as a pivotal element in this regulation is the 3'-untranslated region (UTR) of the message. Recent work from several labs has focused on sequence motifs within the 3'-UTR of glucose transporter (GLUT1) mRNA that serve as destabilizing or stabilizing elements and recognition of these elements by specific proteins. In this review, we address several critical studies each of which has identified elements in the GLUT1 3'-UTR that are involved in the control of transcript stability and demonstrated that these sequence motifs are recognized by specific binding proteins.

Changes in the constant potential in brain structures in rats during focal ischemia and systemic hypoxia

The functional consequences of spreading depression (SD) during the evolution of ischemic damage was studied in two models: focal cortical ischemia induced by photothrombosis of the middle cerebral artery (MCA) and systemic hypoxia induced by 0.8% carbon monoxide (CO). These studies showed that cortical waves of SD, arising spontaneously during MCA thrombosis and after arterial occlusion delayed thrombus formation and promoted the establishment of a collateral blood supply in the perifocal zone of ischemic lesions. The underlying mechanism consisted of episodes of intense vasodilation at the decay phase of every wave of SD. Respiration of 0.8% CO increased the blood carboxyhemoglobin level to 50-60%. In lightly anesthetized rats (pentobarbital 20 mg/kg), cortical and subcortical spontaneous waves of SD were transformed into stable hypoxic depolarization, leading to death of 60% of the animals or severe lesions of the central nervous system, in 20% of animals. Increases in the level of anesthesia (50 mg/kg anesthetic) prevented the spontaneous appearance of SD during long-lasting exposure to CO. In these conditions, experimentally induced waves of SD demonstrated that the hippocampus has a high sensitivity to moderate levels of hypoxia. The duration of hypoxic depolarization of the hippocampus, provoking a single SD wave, reached 30-60 min. Selective neuron damage in field CA1 was seen 30 days after hypoxia. Additionally, the left hippocampus of rats frequently showed profound morphological lesions in the form of "granules." Cerebrolysine (2.5 ml/kg daily for 10 days) completely prevented the formation of these lesions.

Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 24-month-old rats

The brain-derived peptidergic drug Cerebrolysin has been found to support the survival of neurones in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trails. In the present study, the effects of Cerebrolysin and its peptide preparation E021 on the synapse density in the hippocampus, the dentate gyrus and in the entorhinal cortex of 24-month-old rats were investigated. Rats received the drugs or saline for control for 19 consecutive days (2.5 ml/kg per day). Slices of the brains were immunohistochemically stained with anti-synaptophysin, which is a specific marker of presynaptic terminals. Quantification of the synapse density was done by using light microscopy and a computerised image analysing system. Our results clearly showed that the rats benefit from the administration of both drugs, showing an enhancement in the number of synaptophysin-immunostained presynaptic terminals in the entorhinal cortex, the dentate gyrus, and also in the hippocampal subfields CA1, CA2, CA3 stratum lucidum and CA3 stratum radiatum. It can be assumed that these effects are the reason for improved cognitive performances of rats treated with Cerebrolysin and E021.

The pecten oculi of the chicken: a model system for vascular differentiation and barrier maturation

The pecten oculi is a convolute of blood vessels in the vitreous body of the avian eye. This structure is well known for more than a century, but its functions are still a matter of controversies. One of these functions must be the formation of a blood-retina barrier because there is no diffusion barrier for blood-borne compounds available between the pecten and the retina. Surprisingly, the blood-retina barrier characteristics of this organ have not been studied so far, although the pecten oculi may constitute a fascinating model of vascular differentiation and barrier maturation: Pectinate endothelial cells grow by angiogenesis from the ophthalmotemporal artery into the pecten primordium and consecutively gain barrier properties. The pectinate pigmented cells arise during development from retinal pigment epithelial cells and subsequently lose barrier properties. These inverse transdifferentiation processes may be triggered by the peculiar microenvironment in the vitreous body. In addition, the question is discussed whether the avascularity of the avian retina may be due to the specific metabolic activity of the pecten.

Protein kinase inhibitor H7 blocks the induction of immediate-early genes zif268 and c-fos by a mechanism unrelated to inhibition of protein kinase C but possibly related to inhibition of phosphorylation of RNA polymerase II

1-(5-Isoquinolinesulfonyl)-2-methylpiperazine (H7) has often been used in combination with protein kinase inhibitor (N-(2-guanidinoethyl)-5-isoquinolinesulfonamide) (HA1004) to assess the contribution of protein kinase C (PKC) to cellular processes, including the induction of gene expression. This use of H7 and HA1004 is based upon the fact that H7 inhibits PKC more potently than HA1004 in in vitro assays. Thus, although both compounds are broad spectrum protein kinase inhibitors, inhibition by H7, but not by HA1004, has often been interpreted as evidence for the involvement of PKC in the cellular process under study. Here we describe experiments that show that this interpretation is not correct with regard to the induction of two immediate-early genes, zif268 and c-fos, in PC12D cells. In these studies we confirmed that H7, but not HA1004, potently blocks the induction of zif268 and c-fos mRNA by nerve growth factor, carbachol, phorbol ester, Ca2+ ionophore, or forskolin. Surprisingly, however, H7 has no effect on the ability of these agents to activate mitogen-activated protein kinase (MAPK), an upstream activator of zif268 and c-fos gene expression. H7 also does not inhibit preactivated MAPK in vitro. Taken together, these results suggest that H7 blocks gene expression by acting at a site downstream from MAPK. H7 has previously been shown to block transcription in vitro by blocking the phosphorylation of the carboxyl-terminal domain of RNA polymerase II (Yankulov, K., Yamashita, K., Roy, R., Egly, J.-M., and Bentley, D. L.(1995) J. Biol. Chem. 270, 23922-23925). In this study, we show that pretreating PC12D cells with H7, but not with HA1004, significantly reduces levels of phosphorylated RNA polymerase II in vivo. These results suggest that H7 blocks gene expression by inhibiting the phosphorylation of RNA polymerase II, a step required for progression from transcription initiation to mRNA chain elongation.

Early postnatal treatment with peptide preparations influences spatial navigation of young and adult rats

The brain derived peptidergic drug Cerebrolysin has been found to support the survival of neurons in vitro and in vivo. Positive effects on learning and memory have been demonstrated in various animal models and also in clinical trials. In the present study the effects of early postnatal administration of Cerebrolysin (Cere, 10 mg/ml peptides) or an enriched peptide fraction of Cere (E021, 80.6 mg/ml peptides) were investigated in young, young adult, and old adult rats. Rat pups received the drugs or saline for control on postnatal days 1-7. The animals were tested in the Morris water maze (MWM) either in the 5th week, in the 3rd or the 16th month of life for 6 consecutive days (test days 1-6), eight trials per day. In order to prevent the chance finding of the hidden platform, the rigid underwater platform was replaced by a collapsible island, resting at the bottom of the pool. The platform was raised when the animal stayed in the target area for 2 s. In the young and young adult rats both Cere and E021 treated rats showed shorter escape latencies than saline treated controls on all 6 test days. No significant differences in the swimming speed were evaluated for the young rats, although in 3-month-old drug-tested animals a moderate increase of the swimming speed was investigated. For 16-month-old animals no significant differences in either escape latencies or swimming speed was found. Summarizing, early postnatal application of Cere or E021 improved the spatial learning and memory of young rats and led to long-lasting behavioural effects at least up to 3 months after treatment.

Cerebrolysin ameliorates performance deficits, and neuronal damage in apolipoprotein E-deficient mice

Recent studies suggest that Cerebrolysin improves behavioral performance by affecting synaptic transmission in the hippocampus. The main objective of this study was to determine if Cerebrolysin administration ameliorates the neurodegenerative and performance deficits in aged apolipoprotein E (apoE)-deficient mice. ApoE-deficient mice treated with Cerebrolysin showed a significant improved performance in the Morris water maze, compared to saline-treated apoE-deficient mice. Although the improved performance in the Cerebrolysin-treated apoE-deficient mice was associated with restoration of the neuronal structure, the poor learning ability of saline-treated apoE-deficient mice was related to the a disrupted synaptodendritic structure. This study supports the contention that Cerebrolysin might have a neurotrophic effect in vivo.

Hippocampal damage induced by carbon monoxide poisoning and spreading depression is alleviated by chronic treatment with brain derived polypeptides

A model of acute carbon monoxide poisoning combined with spreading depression (SD) induced metabolic stress was used to examine the protective effects of cerebrolysin (CL) on the development of electrophysiological, behavioral and morphological signs of hypoxic damage. Capillary electrodes were implanted into the neocortex and hippocampus of anesthetized rats which were then exposed for 90 min to breathing of 0.8% to 0.5% CO, while 3 to 4 waves of cortical and hippocampal SD were elicited by microinjections of 5% KCl. Duration of SD-provoked depolarization of cerebral cortex and hippocampus was noted. Nine and 18 to 19 days later propagation of SD waves was recorded with the same electrodes and decrease of their amplitude was used as an index of brain damage which was significant in the hippocampus but not in the cortex. CL-treatment (2.5 ml/kg per day) started after CO administration and continued for 14 days significantly improved hippocampal recovery manifested by increased amplitude of SD waves. Behavioral tests performed 10 and 20 days after CO poisoning in the Morris water maze revealed better performance (escape latency 7 s) in the CL-treated than in untreated animals (14 s). Morphological analysis showed marked damage in the hippocampus consonant with electrophysiological and behavioral findings in the same animals. No apparent histological damage was found in rats exposed to CO inhalation alone without the additional SD-provoked depolarization. It is concluded that chronic CL-treatment enhances recovery of hippocampal tissue after hypoxic damage of intermediate severity.

Amplification of gene expression using both 5'- and 3'-untranslated regions of GLUT1 glucose transporter mRNA

Cis-regulatory elements located at either the 5'- or 3'-untranslated region (UTR) of the GLUT1 glucose transporter mRNA increase the expression of luciferase reporter genes. The aim of the present study was to investigate the possible cooperative effects of 5'- and 3'-UTRs of the GLUT1 mRNA on the expression of a luciferase reporter gene in cultured brain endothelial cells. Luciferase reporter genes containing control elements in nucleotides (nt) 1-171 of GLUT1 5'-UTR, or nt 2100-2300 of GLUT1 3'-UTR produced a 10- and 6-fold increase in the expression of the luciferase reporter gene compared to the control vector containing no GLUT1 regulatory sequences, respectively. The insertion of both GLUT1 mRNA cis-regulatory elements increased 59-fold the activity of luciferase compared to controls. Data presented here demonstrate that cis-regulatory elements located at both the 5'- and 3'-UTR of GLUT1 mRNA increase expression of a reporter gene in an independent manner.

Brain-derived peptides increase blood-brain barrier GLUT1 glucose transporter gene expression via mRNA stabilization

The present investigation studied the effect of the brain-derived peptide preparation Cerebrolysin (CI, EBEWE, Austria) on the turnover rate and gene expression of the blood-brain barrier (BBB) GLUT1 glucose transporter mRNA. Studies were performed in brain endothelial cultured cells transfected with the human (h) GLUT1 transcript. In control cells, the full length 2.8 Kb hGLUT1 mRNA was rapidly degraded following transfection, and the abundance of this transcript at 4 and 6 h was comparable to background mRNA levels seen in cells transfected without hGLUT1 mRNA. On the contrary, the decay of the hGLUT1 mRNA was stabilized in CI-treated cells resulting in a marked reduction in the fractional turnover rate (72.4 and 4.0%/h, control and CI, respectively). In parallel experiments, CI induced a significant increase in the levels of immunoreactive GLUT1 protein measured by enzyme-linked immunosorbent assay (ELISA). In conclusion, data presented here demonstrate that factors in CI increase BBB-GLUT1 transcript stability, and that this is associated with an induction of BBB-GLUT1 gene expression in brain endothelial cultured cells.

Ten nucleotide cis element in the 3'-untranslated region of the GLUT1 glucose transporter mRNA increases gene expression via mRNA stabilization

The GLUT1 glucose transporter gene is regulated at the post-transcriptional level, and a 10 nucleotide (nt) cis-acting element located at nt 2181-2190 of the GLUT1 3'-untranslated region (3'-UTR) increases the transient expression of a luciferase reporter gene. To investigate the role of this mRNA cis-element, stable transfectants expressing luciferase reporter genes were established in rat C6 glioma cells. Insertion of nt 2100-2300 of GLUT1 3'-UTR resulted in a marked increase in the abundance of both reporter gene mRNA and protein compared to the control, in parallel with a 228% increase in the mRNA t1/2 determined with actinomycin D. Deletion of the 10 nt cis-acting element in the GLUT1 3'-UTR reduced the abundance of reporter gene products and the mRNA t1/2 to levels similar to the control clone. Data suggest that the cis-acting element located at nt 2181-2190 of bovine GLUT1 mRNA 3'-UTR is responsible for increased GLUT1 gene expression via enhanced GLUT1 mRNA stabilization.

Neurotrophic activities and therapeutic experience with a brain derived peptide preparation

In spite that the use of naturally occurring neurotrophic factors like NGF, BDNF, CNTF, GDNF and others for treatment of neurodegenerative disorders seems promising because of their pharmacological properties, until now no large scale clinical trials have been published. One of the reasons is that these molecules are unable to penetrate through the blood brain barrier, making invasive application strategies like intracerebroventricular infusion necessary. Another one is the fact that in first clinical studies, several undesirable side-effects like hyperalgesia or weight loss have been reported. Major efforts are now put into development of improved application procedures and in treatment protocols for avoiding the known side-effects. Already 7 years ago it has been demonstrated that Cerebrolysin, a peptidergic drug, produced from purified brain proteins by standardized enzymatic breakdown, containing biologically active peptides, is exerting nerve growth factor like activity on neurons from dorsal root ganglia. Still ongoing investigations are showing growth promoting efficacy of this drug in different neuronal populations from peripheral and central nervous system. The current findings are in accordance with several older publications, enabling now a more clear interpretation of these findings. In addition to the direct neurotrophic effect, the drug also shows clear neuroprotective properties after different types of lesion in vitro and in vivo, resembling the pharmacological activities of naturally occurring nerve growth factors. Neurotrophic and neuroprotective efficacy has been shown with a broad variety of methods in different models and it is remarkable that all biochemical and morphological drug dependent alterations are resulting in improvements of learning and memory. Because of these experimental results, clinical trials using cerebrolysin in Alzheimer's patients have been performed, demonstrating a quick improvement in the overall state of the patients, particularly enhancing the cognitive performance. It is remarkable that these effects are long lasting after cessation of the active treatment procedure. Even 6 months after stop of drug application improvements in AD-patients are detectable. Therefore it is concluded that cerebrolysin is able to induce repair phenomena, resulting in long term stabilization. In contrast to the naturally occurring growth factors, tolerability of this drug is extremely high, without any reports about serious side-effects in these clinical studies.

The influence of Cerebrolysin and E021 on spatial navigation of 24-month-old rats

In the present study the behavioural effects of Cerebrolysin (Cere), a peptidergic nootropic drug, and E021, the concentrated peptide fraction of Cere, were investigated in 24-month-old rats. Rats passing a pretest to exclude motor- and eye-deficits were treated with either drugs or saline as control (2.5 ml/kg, intraperitoneally i.p.) for 19 days. Animals were tested in a standard Morris water maze on day 16 after pretest for 4 consecutive days (test days 1-4), eight trials per day. No significant differences of escape latency between males and females were found, therefore, results were pooled. Both Cere and E021 treated rats showed significant lower escape latencies than saline treated controls on all four test days (p < 0.01). More pronounced effects of both drugs were found for female rats. Female rats showed no significant differences in motor activity whereas drug treated males swam quicker on test day 1 (Cere p < 0.01: E021 p < 0.05) and day 2 (Cere p < 0.01). In the present experiments it was demonstrated that i.p. administration of both Cere and E021 improves the spatial learning and memory of 24 month-old male and female rats.

Molecular regulation of the blood-brain barrier GLUT1 glucose transporter by brain-derived factors

Glucose is the crucial metabolic fluid for the brain, and the transport of this nutrient from blood to brain is limited by the blood-brain barrier (BBB) GLUT1 glucose transporter. The activity of this transporter is altered in different pathophysiological conditions including Alzheimer's disease. The expression of the BBB-GLUT1 gene is directed by brain trophic factors, and the brain-derived peptide preparation Cerebrolysin (Cl, EBEWE, Austria), used in the treatment of Alzheimer's disease, increases the BBB-GLUT1 mRNA stability and the expression of the BBB-GLUT1 gene. In the present investigation, Cl markedly increased (p < 0.001) the expression of a BBB-GLUT1 reporter gene, named clone 753, that contains an important regulatory cis-acting element involved in the stabilization of this transcript in brain endothelial cultured cells (ECL). In experiments with a reporter gene lacking this regulatory element, Cl produced only a minimal fraction of the effect observed with clone 753. UV-cross linking/PAGE experiments showed that the GLUT1 transcript reacts with ECL cytosolic proteins to form a RNA/protein complex of approximately 80 kDa. The abundance of this cis/trans acting complex was found to be increased in Cl-treated cells. Overall, data presented here demonstrate that i) Cl increases the expression of a BBB-GLUT1-luciferase reporter gene containing a region of the 3'-untranslated region of BBB-GLUT1 mRNA with important regulatory cis-acting elements involved in the stabilization of this transcript, and ii) the increased expression of this BBB-GLUT1 reporter gene was associated with augmented abundance of a transacting factor that binds to the cis-acting element described in (i), suggesting that this association may be involved in the stabilization of GLUT1 mRNA induced by Cl.

The effect of MK-801 and of brain-derived polypeptides on the development of ischemic lesion induced by photothrombotic occlusion of the distal middle cerebral artery in rats

The effect of neuroprotective drugs on the early and late electrophysiological manifestations of photothrombotic occlusion of distal branches of middle cerebral artery was studied in rats treated with MK-801 and Cerebrolysin (CL). DC potentials were recorded from the irradiated cortex (ischemic core), from the adjacent penumbra zone and from remote intact cortex. Irradiation elicited after a few minutes of spontaneous spreading depression (SD) waves followed during 10-15 min by focal ischemic depolarization (FID) developing in the irradiated cortex and spreading into the perifocal areas. While the core FID amplitude reached about 30 mV and decayed during subsequent 2 h to 10-13 mV, FID in the penumbra zone was broken by periods of partial repolarization and returned during 30-90 min almost to baseline. At the same time, generation of spontaneous SD waves almost stopped. MK-801 (0.5 mg/kg, i.p., 45 min after ischemia) blocked SD waves, but did not shorten penumbra FID, the decay of which was slowed down to the rate found in the ischemic core. CL treatment (2.5 ml/kg, i.p. , 1 h after ischemia) did not influence FID in the acute phase of the experiment, but its 10-day administration facilitated post-ischemic recovery indicated by higher amplitude of evoked SD waves penetrating into the former penumbra zone. Morphological examination showed that the volume of total and partial necrosis was increased in the MK-801 group and marginally reduced in the CL group. It is suggested that the absence of the SD-induced hyperperfusion episodes in MK-801-treated rats may accelerate perifocal thrombotization in this model of focal ischemia.