Morphofunctional effects of moderate forebrain ischemia combined with short-term hypoxia in rats--protective effects of Cerebrolysin

Neuroprotective strategies of cerebrolysin for the treatment of infants with neonatal hypoxic-ischemic encephalopathy

BACKGROUND

Perinatal asphyxia (PA) is a devastating neonatal condition characterized by a lack of oxygen supporting the organ systems. PA can lead to hypoxic-ischemic encephalopathy (HIE), a brain dysfunction due to oxygen deprivation with a complex neurological sequela. The pathophysiology of HIE and PA is not entirely understood, with therapeutic hypothermia being the standard treatment with only limited value. However, alternative neuroprotective therapies can be a potential treatment modality.

METHODS

In this review, we will characterize the biochemical mechanisms of PA and HIE, while also giving insight into cerebrolysin, a neuroprotective treatment used for HIE and PA.

RESULTS

We found that cerebrolysin has up to 6-month treatment window post-ischemic insult. Cerebrolysin injections of 0.1 ml/kg of body weight twice per week were found to provide gross motor and speech deficit improvement.

CONCLUSION

Our literature search emphasizes the positive effects of cerebrolysin for general improvement outcomes. Nevertheless, biomarker establishment is warranted to improve patient outcomes.

Cerebrolysin administration reduces oxidative stress-induced apoptosis in lymphocytes from healthy individuals

Cerebrolysin is the only drug available for clinical use containing active fragments of some important neurotrophic factors obtained from purified porcine brain proteins, which has long been used for the treatment of dementia and stroke sequels. Cerebrolysin has growth factor-like activities and promotes neuronal survival and sprouting, however, its molecular mechanism still needs to be determined. It has been shown that Cerebrolysin may interact with proteolytic pathways linked to apoptosis. Administration of Cerebrolysin significantly reduces the number of apoptotic neurons after glutamate exposure. Furthermore, it has been reported that Cerebrolysin inhibits free radicals formation and lipid peroxidation. In vitro we evaluated the protective effects of Cerebrolysin towards spontaneous and induced apoptotic death in cells from healthy individuals. Peripheral blood lymphocytes (PBLs) from 10 individuals were used as cell model; 2-deoxy-D-ribose (dRib), a highly reducing sugar, was used as paradigm pro-apoptotic stimulus. Apoptosis was analysed using flow cytometry and fluorescence microscopy. Our results showed that Cerebrolysin significantly reduced the number of apoptotic PBLs after dRib treatment, although it had no significative effects on cells cultured in standard conditions. Our work showed a protective effect of Cerebrolysin on oxidative stress-induced apoptosis and suggested that PBLs can be used as an easy obtainable and handy cell model to verify Cerebrolysin effects in neurodegenerative pathologies.

Label-free detection of neuron–drug interactions using acoustic and Kelvin vibrational fields

Kelvin and acoustic fields of high-frequency have been employed in the non-invasive investigation of immortalized hypothalamic neurons, in order to assess their response to different concentrations of specific drugs, toxins, a stress-reducing hormone and neurotrophic factors. In an analytical systems biology approach, this work constitutes a first study of living neuron cultures by scanning Kelvin nanoprobe (SKN) and thickness shear mode (TSM) acoustic wave techniques. N-38 hypothalamic mouse neurons were immobilized on the gold electrode of 9 MHz TSM acoustic wave devices and gold-coated slides for study by SKN. The neurons were exposed to the neurochemicals betaseron, forskolin, TCAP, and cerebrolysin. Signals were collected with the TSM in real-time mode, and with the SKN in scanning and real-time modes, as the drugs were applied at biologically significant concentrations. With the TSM, for all drugs, some frequency and resistance shifts were in the same direction, contrary to normal functioning for this type of instrument. Possible mechanisms are presented to explain this behaviour. An oscillatory signal with periodicity of approximately 2 min was observed for some neuron-coated surfaces, where the amplitude of these oscillations was altered upon application of certain neurotrophic factors. These two new techniques present novel and non-invasive electrodeless methods for detecting changes at the cellular level caused by a variety of neuroactive compounds, without killing or destroying the neurons.

Neuroprotection of Cerebrolysin in tissue culture models of brain ischemia: post lesion application indicates a wide therapeutic window

All attempts to reduce neuronal damage after acute brain ischemia by the use of neuroprotective compounds have failed to prove efficacy in clinical trials so far. One of the main reasons might be the relatively narrow time window for intervention. In this study 2 different tissue culture models of ischemia, excitotoxic lesion by the use of glutamate and oxygen-glucose deprivation (OGD), were used to investigate the effects of delayed application of Cerebrolysin (Cere) on neuronal survival. This drug consists of low molecular weight peptides with neuroprotective and neurotrophic properties similar to naturally occurring growth factors. After both types of lesion, acute as well as delayed treatment with Cere resulted in a dose dependent and significant rescue of neurons. In the model of excitotoxic cell death significant drug effects were found even when the treatment started with a delay of 96 hours after addition of glutamate. In the OGD model pronounced effects were found after 48 hours delay of treatment, and even after 72 hours a small but significant rescue of neurons was detected. The neuroprotective effects of a single addition of Cerebrolysin to the culture medium resulted in significant protection until end of the experiments which was up to 2 weeks after the initial lesion. A shift of the efficacious dosages from low to high concentrations indicates that most likely active compounds are used up, indicating that multiple dosing might even increase the effect size. In conclusion the results indicate that Cere displays a relatively wide therapeutic time window which might be explained by a combination of acute neuroprotective properties and neurotrophic efficacy.

Postnatal physiological development of rats after acute prenatal hypoxia

The aim of the present work was to identify the characteristics of the physiological development of the brain and the formation of behavior in rats subjected to hypoxia on day 13.5 of embryogenesis. These animals showed delayed development and changes in nerve tissue structure in the sensorimotor cortex, along with disturbances to the processes forming normal movement responses during the first month after birth. These changes were partially compensated with age, though adult animals subjected to acute prenatal hypoxia were less able to learn new complex manipulatory movements. Alterations in nerve tissue structure and changes in the neuronal composition of the sensorimotor cortex correlated with the times of appearance of behavioral impairments at different stages of ontogenesis. Thus, changes in the conditions in which the body is formed during a defined period of embryogenesis lead to abnormalities in the process of ontogenetic development and the ability to learn new movements.

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.

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.

Two peptidergic drugs increase the synaptophysin immunoreactivity in brains of 6-week-old rats

An increase of synaptic density has been found in the hippocampus, the dendate gyrus and in the entorhinal cortex of 6-week-old rats after 7 days of treatment with the peptidergic drug Cerebrolysin, its peptide preparation E021 and the diluted peptide preparation E021dil. Rats received drugs on postnatal days 1-7 (2.5 ml/kg, each day). Controls received saline. The animals were sacrificed on days 42-48 of their life, after they had undergone behavioural testing in a Morris water maze. Slices of brain were stained immunohistochemically with anti-synaptophysin, a specific marker of presynaptic terminals. The synaptophysin-immunoreactivity of presynaptic terminals was quantified using light microscopy and a computerised image analysis system. Our results showed that rats benefit from the treatment with both drugs. A significant increase in the number of synaptophysin-immunoreactive presynaptic terminals was found in the entorhinal cortex and the hippocampal subfields CA1, CA2, CA3 stratum radiatum and CA3 stratum lucidum. The increased immunoreactive presynaptic terminals found in the present study are in accordance with the positive effects of the drugs on spatial learning and memory in young rats (Gschanes & Windisch 1999).

In vivo upregulation of the blood-brain barrier GLUT1 glucose transporter by brain-derived peptides

Glucose is the critical 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 expression of the BBB-GLUT1 gene is augmented in brain endothelial cultured cells incubated with brain-derived trophic factors and the brain-derived peptide preparation Cerebrolysin (C1, EBEWE, Austria). The aim of the present investigation was to determine if C1 induces similar changes in the expression of the BBB-GLUT1 gene following its administration to rats in vivo. The BBB glucose transporter activity was investigated with the intracarotid artery perfusion technique using [3H]diazepam as cerebral blood flow marker. The acute or chronic administration of C1 markedly increased the brain permeability surface area of D-[14C]glucose compared to controls (D-[14C]glucose/[3H]diazepam ratio, 1.6- to 1.9-fold increase in frontal cortex, P < 0.05). Increased activity of the BBB glucose transporter was correlated with a significant rise in the abundance of the BBB-GLUT1 protein measured by both Western blot analysis and immunocytochemistry, and with a decrease in the transcript levels of this transporter. Data presented here demonstrate that the in vivo administration of Cl increases the transport of glucose from blood to brain via BBB-GLUT1 gene expression.

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.

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.

Brain-derived peptides reduce the size of cerebral infarction and loss of MAP2 immunoreactivity after focal ischemia in rats

The effects of brain-derived peptides (BDP; Cerebrolysin) upon the amount of brain injury due to focal brain ischemia were assessed. Male Thomae rats were divided randomly into a sham-operated group (n = 5), an ischemic control (untreated) group (n = 7) and an ischemic BDP-treated group (n = 6) and subjected to reversible middle cerebral artery occlusion (MCAO) for 2h followed by 90min of reperfusion. Local cortical blood flow (LCBF) was monitored by Laser-Doppler flowmetry to assess the MCAO and to measure the blood flow in regions peripheral to the infarction. Infarcted areas of the hippocampus and subcortical structures were quantified in hematoxylin and eosin (H&E) stainings. Functional disturbances of the neurons were detected by immunohistochemical staining of the microtubule associated protein MAP2. Moreover, brain edema was estimated morphometrically. LCBF was estimated from the periphery of infarcted areas and was reduced to 55 to 65% of baseline values (p < 0.05). Reperfusion led to LCBF being increased again to baseline values. No differences in LCBF between the control and the BDP-treated animals were found. In the hippocampus, BDP-treated animals showed a significant reduction of loss of MAP2 immunoreactivity in the subiculum and CA1 region by 59% and 64%, respectively, in comparison to control animals (p < 0.05). The amount of irreversibly damaged neurons in these regions was decreased in tendency. However, the inner blade of the dentate gyrus in BDP-treated animals showed a significant reduction of neuronal injury by 98% (p < 0.05). Likewise, BDP treatment reduced the size of the areas showing a loss of MAP2 immunoreactivity in the thalamic and hypothalamic structures by 51% and in the mesencephalon by 81% (p < 0.05). The size of the infarcted areas in these regions (H&E) was reduced in tendency. In the caudate putamen, no protective effect of BDP-treatment could be proven. Cerebral infarction was accompanied by an increase in the volume of the ischemic hemisphere by 10 +/- 1% in the control and 8 +/- 1% in the BDP-treated animals. These findings indicate a beneficial effect for BDP treatment in ameliorating the early effects of focal brain ischemia.

Cerebrolysin protects isolated cortical neurons from neurodegeneration after brief histotoxic hypoxia

A brief period of histotoxic hypoxia exhibits certain metabolic features resembling the in vivo situation of ischemia. In this study the neuroprotective effects of the peptidergic nootropic drug Cerebrolysin (Cere) against iodoacetate induced histotoxic hypoxia were investigated. For that purpose isolated cortical neurons from 9 day chicken embryos were precultured with 0 to 6.4 mg.Cere/ml medium. At the 8th day in vitro histotoxic hypoxia was induced by incubation with 0.01 or 0.1 mM iodoacetate. Cells were allowed to recover from toxic stress for 3, 6, 24 or 48 hours. Cere protected neurons dose dependently from delayed neuronal cell death due to 0.01 mM iodoacetate even after a recovery period of 48h. After induction of histotoxic hypoxia by 0.1 mM iodoacetate high concentrations of Cere again led to neuronal protection after the 3 and 6 h recovery period. Moreover the influence of Cere on the cytoskeletal protein MAP2 in neurons submitted to 0.01 mM iodoacetate was investigated. With Western blotting and immunohistochemical techniques it has been demonstrated that the drug clearly increased MAP2 abundance after histotoxic hypoxia. The present study points out that after severe damage of cortical neurons with iodoacetate Cere is able to protect neurons from delayed neuronal cell death maybe by maintaining neuronal plasticity due to avoidance of the cytoskeletal breakdown.

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.

Physiological effects and brain protection by hypothermia and cerebrolysin after moderate forebrain ischemia in rats

The "therapeutic window" of neuroprotective intervention due to hypoxic-ischemic brain injuries are initial disturbances of the neuronal function in regions of only moderate decrease of local cerebral blood flow (ICBF). Because of limited effects of single therapeutic principles therapeutic combinations should be tested. Neuroprotective effects of mild hypothermia and the nootropic drug Cerebrolysin (Cerebrolysin, EBEWE, Austria) on ICBF and development of brain edema were used. Four groups of adult Wistar rats (untreated and Cerebrolysin treated animals with 35 degrees C and 37 degrees C rectal temperature) were subjected to moderate forebrain ischemia by permanent bilateral carotid artery ligation for 6 h. The ICBF was measured continuously in the frontal and the occipital cortex by a 2-channel Laser Doppler flowmeter. The ECoG was derived from 4 ECoG leads above the frontal and occipital cortex and quantified by spectral analysis. Six hours after the onset of ischemia, the function of the blood-brain barrier to proteins was determined by staining with Evans Blue, the animals were sacrificed and the brain water content was estimated by gravimetry. Permanent bilateral carotid artery ligation led to an abrupt ICBF reduction to between 40-50% of baseline levels. Within a few minutes, however, the ICBF increased again to 50-80% of the baseline. The reduced spectral band power of the ECoG was correlated with the decreased ICBF values (p < 0.05) that indirectly indicated changes in the energy state of the neurons (p < 0.05). Changes in the ECoG appeared only with a delay of approximately 4 sec after the onset of ICBF reduction. Six hours after the onset of ischemia, a cytotoxic brain edema was shown in the frontoparietal cortex and hippocampus. Reducing the temperature by 2 degrees C diminished the decrease in ICBF between 10 min and 2 h after the onset of ischemia (p < 0.05). This effect was noted in the frontal but not in the occipital cortex. Furthermore, mild hypothermia prevented the loss of ECoG spectral power in the beta, alpha and theta bands (p < 0.05) as well as the development of cytotoxic brain edema. Cerebrolysin prevented the development of brain edema, too, both under normo- and hypothermic conditions. The ICBF was restored to higher levels in the occipital cortex in comparison both to the normothermic Cerebrolysin treated and hypothermic untreated rats (p < 0.05). This effect of Cerebrolysin was associated with only slight changes in ECoG, indicating that the neuronal activity state and the energy supply was obviously not decisively influenced. In conclusion, moderate ICBF reduction in rats to about 50-80% of baseline values was detectable in the ECoG by using spectral analysis. This reduction led to the development of cytotoxic brain edema in rats within 6 h. Thus, hypothermia prevents the development of cytotoxic brain edema. Cerebrolysin enhanced the effects of hypothermia on ICBF reduction and on the development of brain edema.