The effects of citicoline and/or MK-801 on survival, neurological and behavioral outcome of mice exposed to transient hyperglycemia and oligemic hypoxia

A systematic review of preclinical studies exploring the role of insulin signalling in executive function and memory

Beside its involvement in somatic dysfunctions, altered insulin signalling constitutes a risk factor for the development of mental disorders like Alzheimer's disease and obsessive-compulsive disorder. While insulin-related somatic and mental disorders are often comorbid, the fundamental mechanisms underlying this association are still elusive. Studies conducted in rodent models appear well suited to help decipher these mechanisms. Specifically, these models are apt to prospective studies in which causative mechanisms can be manipulated via multiple tools (e.g., genetically engineered models and environmental interventions), and experimentally dissociated to control for potential confounding factors. Here, we provide a narrative synthesis of preclinical studies investigating the association between hyperglycaemia - as a proxy of insulin-related metabolic dysfunctions - and impairments in working and spatial memory, and attention. Ultimately, this review will advance our knowledge on the role of glucose metabolism in the comorbidity between somatic and mental illnesses.

[Molecular and clinical aspects of the effect of cytidyndiphosphocholine on cognitive functions]

OBJECTIVE

Systematization of the array of publications on cytidyldiphosphocholine (CDP-choline).

MATERIAL AND METHODS

Systematic computer analysis of all currently available publications on CDP-choline (1750 publications in PUBMED) using the topological theory of big data analysis.

RESULTS

CDP-choline is essential for acetylcholine biosynthesis, phospholipid metabolism, and DNA methylation. The article describes the effects of CDP-choline on acetylcholinergic and other types of neurotransmission, anti-inflammatory, neuroprotective and neurotrophic effects of CDP-choline. Also, the paper presents the effects of the molecule on lipid metabolism and gene expression within the post-genomic paradigm (in particular, an increase in the expression of nicotinic and muscarinic acetylcholine receptors). The results of fundamental and clinical studies of CDP-choline in the treatment of cognitive impairments associated with cerebral ischemia and neurodegeneration are presented.

CONCLUSION

The pharmacological effects of CDP-choline are mediated through multiple molecular mechanisms that contribute to the nootropic action of this molecule.

An unmet clinical need: roads to remyelination in MS

Background

In the central nervous system (CNS) myelin sheaths stabilize, protect, and electrically insulate axons. However, in demyelinating autoimmune CNS diseases such as multiple sclerosis (MS) these sheaths are destroyed which ultimately leads to neurodegeneration. The currently available immunomodulatory drugs for MS effectively control the (auto)inflammatory facets of the disease but are unable to regenerate myelin by stimulating remyelination via oligodendroglial precursor cells (OPCs). Accordingly, there is broad consensus that the implementation of new regenerative approaches constitutes the prime goal for future MS pharmacotherapy.

Main text

Of note, recent years have seen several promising clinical studies investigating the potential of substances and monoclonal antibodies such as, for instance, clemastine, opicinumab, biotin, simvastatin, quetiapin and anti-GNbAC1. However, beyond these agents which have often been re-purposed from other medical indications there is a multitude of further molecules influencing OPC homeostasis. Here, we therefore discuss these possibly beneficial regulators of OPC differentiation and assess their potential as new pharmacological targets for myelin repair in MS.

Conclusion

Remyelination remains the most important therapeutic treatment goal in MS in order to improve clinical deficits and to avert neurodegeneration. The promising molecules presented in this review have the potential to promote remyelination and therefore warrant further translational and clinical research.

CDP-choline treatment induces brain plasticity markers expression in experimental animal stroke

We investigated the effect of CDP-choline on brain plasticity markers expression in the acute phase of cerebral infarct in an experimental animal model. Male Sprague-Dawley rats were subjected to permanent middle cerebral artery occlusion (pMCAO) and treated or not with CDP-choline (500 mg/kg) daily for 14 days starting 30 min after pMCAO. Functional status was evaluated with Roger's test; lesion volume with magnetic resonance imaging (MRI) and hematoxylin and eosin staining (H&E); cell death with TUNEL; cellular proliferation with BrdU immunohistochemistry; vascular endothelial growth factor (VEGF), synaptophysin, glial fibrillary acidic protein (GFAP) and low-density lipoprotein receptor-related protein (LRP) by immunofluorescence and Western-blot techniques. CDP-choline significantly improved functional recovery and decreased lesion volume on MRI, TUNEL-positive cell number and LRP levels at 14 days. In addition, CDP-choline significantly increased BrdU, VEGF and synaptophysin values and decreased GFAP levels in the peri-infarct zone compared with the infarct group. In conclusion, our data indicate that CDP-choline improved functional recovery after permanent middle cerebral artery occlusion in association with reductions in lesion volume, cell death and LRP expression. In fact, CDP-choline increased cell proliferation, vasculogenesis and synaptophysin levels and reduced GFAP levels in the peri-infarct area of the ischemic stroke.

Hyperglycaemia and infarct size in animal models of middle cerebral artery occlusion: systematic review and meta-analysis

Poststroke hyperglycaemia (PSH) is common, has an unclear pathophysiology, and is associated with poor outcomes. Animal studies report conflicting findings. We systematically reviewed the effects of hyperglycaemia on infarct volume in middle cerebral artery occlusion (MCAO) models, generating weighted mean differences between groups using random effects models summarised as effect size (normalised to control group infarct volume as 100%) and 95% confidence interval. Of 72 relevant papers, 23 reported infarct volume. Studies involved 664 animals and 35 distinct comparisons. Hyperglycaemia was induced by either streptozotocin (STZ, 17 comparisons, n=303) or dextrose (18 comparisons, n=356). Hyperglycaemic animals had infarcts that were 94% larger, but STZ was associated with significantly greater increase in infarct volumes than dextrose infusion (140% larger versus 48% larger). In seven studies, insulin did not significantly reduce infarct size and results were heterogeneous. Although hyperglycaemia exacerbates infarct volume in MCAO models, studies are heterogeneous, and do not address the common clinical problem of PSH because they have used either the STZ model of type I diabetes or extremely high glucose loads. Insulin had a nonsignificant and significantly heterogeneous effect. Further studies with relevant models may inform clinical trial design.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.

Neuroprotection during cardiac surgery

Cerebral injury following cardiac surgery continues to be a significant source of morbidity and mortality after cardiac surgery. A spectrum of injuries ranging from subtle neurocognitive dysfunction to fatal strokes are caused by a complex series of multifactorial mechanisms. Protecting the brain from these injuries has focused on intervening on each of the various etiologic factors. Although numerous studies have focused on a pharmacologic solution, more success has been found with nonpharmacologic strategies, including optimal temperature management and reducing emboli generation.

A chronic treatment with CDP-choline improves functional recovery and increases neuronal plasticity after experimental stroke

Chronic impairment of forelimb and digit movement is a common problem after stroke that is resistant to therapy. Although in the last years some studies have been performed to increase the efficacy of rehabilitative experience and training, the pharmacological approaches in this context remain poorly developed. We decided to study the effect of a chronic treatment with CDP-choline, a safe and well-tolerated drug that is known to stabilize membranes, on functional outcome and neuromorphological changes after stroke. To assess the functional recovery we have performed the staircase reaching test and the elevated body swing test (EBST), for studying sensorimotor integration and asymmetrical motor function respectively. The treatment with CDP-choline, initiated 24 h after the middle cerebral artery occlusion (MCAO) and maintained during 28 days, improved the functional outcome in both the staircase test (MCAO+CDP=87.0+/-6.6% pellets eaten vs. MCAO+SAL=40.0+/-4.5%; p<0.05) and the EBST (MCAO+CDP=70.0+/-6.8% vs. MCAO+SAL=88.0+/-5.4%; contralateral swing p<0.05). In addition, to study potential neuronal substrates of the improved function, we examined the dendritic morphology of layer V pyramidal cells in the undamaged motor cortex using a Golgi-Cox procedure. The animals treated with CDP-choline showed enhanced dendritic complexity and spine density compared with saline group. Our results suggest that a chronic treatment with CDP-choline initiated 24 h after the insult is able to increase the neuronal plasticity within noninjured and functionally connected brain regions as well as to promote functional recovery.

Xenon and the inflammatory response to cardiopulmonary bypass in the rat

OBJECTIVE

The purpose of this study was to investigate the effect of xenon on the inflammatory response to cardiopulmonary bypass.

DESIGN

Prospective, randomized experimental study.

SETTING

University research laboratory.

PARTICIPANTS

Sprague-Dawley rats.

INTERVENTIONS

After surgical preparation, rats were randomly divided into 4 groups: (1) SHAM rats were cannulated but did not undergo cardiopulmonary bypass; (2) cardiopulmonary bypass rats were subjected to 60 minutes of cardiopulmonary bypass using an oxygenator receiving a 30% O(2), 65% N(2), and 5% CO(2) gas mixture; (3) MK801 rats received MK801 (0.15 mg/kg intravenous) 15 minutes before 60 minutes of cardiopulmonary bypass with the same gas mixture; and (4) xenon rats underwent 60 minutes of cardiopulmonary bypass receiving a 30% O(2), 60% xenon, 5% N(2), and 5% CO(2) gas mixture.

MEASUREMENTS AND MAIN RESULTS

All bypass groups showed elevations in both cytokines compared with the SHAM-operated group. However, the inflammatory response to cardiopulmonary bypass in the group receiving xenon was no different from the other bypass groups.

CONCLUSIONS

Xenon appears to have no effect on the inflammatory response to cardiopulmonary bypass, making its previously described neuroprotective effect during cardiopulmonary bypass likely independent of any inflammation modulation.

Characterization of cellular and neurological damage following unilateral hypoxia/ischemia

Rodent models of stroke are often used to investigate the mechanisms that lead to ischemic neuronal damage. In this study, we used a model of cerebral hypoxia with ischemia to produce unilateral damage in C57Bl/6 mice. Lesion volume, ascertained by TTC staining, increased with longer durations of hypoxia. Additionally, cresyl violet, TUNEL, and FluoroJade staining showed a statistically significant increase in cellular damage in the ipsilateral cortex, CA1 pyramidal layer, and dentate gyrus of the hippocampus of ipsilateral hypoxic/ischemic tissue versus sham tissue. Astrocyte reactivity, determined by GFAP staining, was significantly higher in the ipsilateral H/I cortex and contralateral hippocampus compared to sham cortex and hippocampus, respectively. Increased microglia activation was evident in the H/I-treated cortex and hippocampus versus sham cortex and hippocampus, particularly within areas undergoing degeneration. To examine whether this model produces motor deficits, a battery of tests were administered before and after hypoxia. Following 45 min H/I, locomotor activity, rotarod performance and performance on an inverted wire hang test were all significantly decreased. These data indicate that the histological evidence of neuronal damage is consistent with functional deficits and suggest that this model may be useful for investigating strategies designed to protect neurons from hypoxia/ischemia-induced damage.

Histopathological and behavioral characterization of a novel model of cardiac arrest and cardiopulmonary resuscitation in mice

Cardiac arrest is associated with high mortality and poor neurological outcome. We characterized functional and histological outcome in a novel mouse model of cardiac arrest and cardiopulmonary resuscitation (CPR) in order to study neuroprotective mechanisms. Cardiac arrest was induced in male C57Bl/6 and 129SVEV mice by i.v. injection of KCl. After 10 min cardiac standstill, CPR was initiated by administration of epinephrine, ventilation with 100% oxygen and chest compressions. Twenty-four hours before and 3 or 7 days after CPR, mice were subjected to behavioral testing using a passive avoidance task, locomotor activity in an open field, and spontaneous alternation in a T-maze. Hippocampal and caudoputamen injury was quantified 3 or 7 days after CPR. At both time points, caudoputamen injury was worse in 129SVEV mice. Post-ischemic mice of both strains showed a reduced number of correct choices in the T-maze up to 7 days after CPR, and were temporarily impaired in learning the passive avoidance task with a retention deficit on day 3 but not on day 7. Locomotor activity showed strain differences with C57Bl/6 mice being more active, but little ischemia-related effects. A dissociation between functional and histological outcome was found emphasizing the importance of combining both outcome measures for evaluation of neuroprotective strategies.

Pharmacodynamics of citicoline relevant to the treatment of glaucoma

Citicoline (exogenous CDP-choline) is a nontoxic and well-tolerated drug used in pharmacotherapy of brain insufficiency and some other neurological disorders, such as stroke, brain trauma, and Parkinson's disease. A few reports indicate that citicoline treatment may also be beneficial in glaucoma. Currently glaucoma is considered a neurodegenerative disease in which retinal ganglion cells (RGC) slowly die, likely in the apoptotic mechanism. Endogenous CDP-choline is a natural precursor of cellular synthesis of phospholipids, mainly phosphatydylcholine (PtdCho). Enhancement of PtdCho synthesis may counteract neuronal apoptosis and provide neuroprotection. Citicoline, when administered, undergoes a quick transformation to cytidine and choline, which are believed to enter brain cells separately and provide neuroprotection by enhancing PtdCho synthesis; similar effect may be expected to occur in glaucomatous RGC. Furthermore, citicoline stimulates some brain neurotransmitter systems, including the dopaminergic system, and dopamine is known as a major neurotransmitter in retina and postretinal visual pathways. In a double-blind, placebo-controlled study, treatment of glaucoma resulted in functional improvement in the visual system noted with electrophysiological methods. Development of citicoline as a treatment for glaucoma is indicated.