Kynurenine System and Multiple Sclerosis, Pathomechanism and Drug Targets with An Emphasis on Laquinimod

Multiple sclerosis is a common chronic, disabling autoimmune neurological disease affecting mainly young adults. In its pathomechanism, neurodegenerative and acute inflammatory characteristics are both involved. Disease-modifying therapies aim to reduce relapse-rate and slow down the deterioration in neurological functions. The currently available therapies fail to exert neuroprotective effects and most of them are associated with potentially toxic side-effects, therefore, ongoing research aims to develop novel drug candidates to cover these therapeutic gaps. The kynurenine pathway has been implicated in both the physiological processes of the central nervous system and in the pathomechanism of several neurological disorders as well. Alterations of the kynurenine pathway metabolites have been detected in multiple sclerosis and a number of potential therapeutic targets related to this metabolic route have been already identified. Laquinimod is a quinoline carboxamide showing structural similarities with kynurenic acid, which proved to have beneficial effects on reduction of brain atrophy and disability progression. The kynurenine pathway is therefore a promising target for the development of future drugs for the treatment of autoimmune diseases such as multiple sclerosis.

Clinical Characteristics and Possible Drug Targets in Autosomal Dominant Spinocerebellar Ataxias

Background & Objective:

The autosomal dominant spinocerebellar ataxias (SCAs) belong to a large and expanding group of neurodegenerative disorders. SCAs comprise more than 40 subtypes characterized by progressive ataxia as a common feature. The most prevalent diseases among SCAs are caused by CAG repeat expansions in the coding-region of the causative gene resulting in polyglutamine (polyQ) tract formation in the encoded protein. Unfortunately, there is no approved therapy to treat cerebellar motor dysfunction in SCA patients. In recent years, several studies have been conducted to recognize the clinical and pathophysiological aspects of the polyQ SCAs more accurately. This scientific progress has provided new opportunities to develop promising gene therapies, including RNA interference and antisense oligonucleotides.

Conclusion:

The aim of the current work is to give a brief summary of the clinical features of SCAs and to review the cardinal points of pathomechanisms of the most common polyQ SCAs. In addition, we review the last few year’s promising gene suppression therapies of the most frequent polyQ SCAs in animal models, on the basis of which human trials may be initiated in the near future.

The effect of physical stimuli on the expression level of key elements in mitochondrial biogenesis

Proper mitochondrial function is crucial for intact cellular homeostasis. Mitochondrial dysfunction is clearly involved in the pathogenesis of most neurodegenerative- and age-related chronic disorders. The aim of this study is to stimulate cellular production of important compounds of mitochondrial biogenesis, namely in the peroxisome proliferator-activated receptor-gamma coactivator (PGC)- and Sirtuin (SIRT)-systems. We studied the effect of cold challenge and training on the mRNA expression levels of some compounds of these systems in different brain areas of mice. With regard to the PGC-system, the mRNA levels of the full- and N-truncated isoforms, and those of the two promoters (brain-specific, reference) were measured. In case of Sirtuins, the mRNA levels of SIRT1 and SIRT3-M1/M2/M3 were assessed. We found the following expression level alterations: cooling resulted in the elevation of cortical SIRT3-M1 levels and the decrease of cerebellar SIRT3-M3 levels after 200 min. 900 min of cold exposure resulted in the reduction of cortical SIRT1 and striatal SIRT3-M1 levels. A prominent elevation could be observed in the levels of all PGC-1α isoforms in the cerebellum after 12 days of training. The 12 days of exercise resulted in increased cerebellar SIRT3-M1 and SIRT3-M2 mRNA levels as well. Although the efficacy of cooling core body and brain temperature is questionable, we found that training exerted a clear effect. The cause of the prominent cerebellar elevation of PGC-, and Sirtuin isoforms could be an increase in synaptic plasticity between Purkinje cells, which facilitates better motor coordination and more precise movement integration. We propose that these systems may serve as promising targets for future therapeutic studies in neurodegenerative diseases.

Exploiting the Therapeutic Potential of Endogenous Immunomodulatory Systems in Multiple Sclerosis-Special Focus on the Peroxisome Proliferator-Activated Receptors (PPARs) and the Kynurenines

Multiple sclerosis (MS) is a progressive neurodegenerative disease, characterized by autoimmune central nervous system (CNS) demyelination attributable to a disturbed balance between encephalitic T helper 1 (Th1) and T helper 17 (Th17) and immunomodulatory regulatory T cell (Treg) and T helper 2 (Th2) cells, and an alternatively activated macrophage (M2) excess. Endogenous molecular systems regulating these inflammatory processes have recently been investigated to identify molecules that can potentially influence the course of the disease. These include the peroxisome proliferator-activated receptors (PPARs), PPARγ coactivator-1alpha (PGC-1α), and kynurenine pathway metabolites. Although all PPARs ameliorate experimental autoimmune encephalomyelitis (EAE), recent evidence suggests that PPARα, PPARβ/δ agonists have less pronounced immunomodulatory effects and, along with PGC-1α, are not biomarkers of neuroinflammation in contrast to PPARγ. Small clinical trials with PPARγ agonists have been published with positive results. Proposed as immunomodulatory and neuroprotective, the therapeutic use of PGC-1α activation needs to be assessed in EAE/MS. The activation of indolamine 2,3-dioxygenase (IDO), the rate-limiting step of the kynurenine pathway of tryptophan (Trp) metabolism, plays crucial immunomodulatory roles. Indeed, Trp metabolites have therapeutic relevance in EAE and drugs with structural analogy to kynurenines, such as teriflunomide, are already approved for MS. Further studies are required to gain deeper knowledge of such endogenous immunomodulatory pathways with potential therapeutic implications in MS.

Non-motor Behavioral Alterations of PGC-1α-Deficient Mice - A Peculiar Phenotype With Slight Male Preponderance and No Apparent Progression

Dysfunction of peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1α) has been linked to various neurodegenerative and neuropsychiatric disorders; however, reports on psychic behavioral alterations on PGC-1α-deficient animals are sparse. The present study revisited prior observations of anxiety-related, depression-related, and hippocampal memory-related observations having been made on different PGC-1α-deficient murine strains, in a large-scale analysis on whole-body full-length (FL-)PGC-1α-deficient mice. The examinations were performed on animals covering a wide age range enrolled from both sexes, and included paradigms such as the open-field, elevated plus maze, light-dark box, tail suspension test, and spatial recognition two-trial Y-maze. The findings revealed no signs of previously reported anxiety-like behavior, but revealed an unexpected phenotype with decreased anxiety behavior consistent throughout different paradigms, with slight male preponderance. This was associated with despair-like anhedonic behavior, consistent with that reported previously, but did not associate with either peripheral or brain alterations in kynurenic acid synthesis, which was previously proposed. Though male FL-PGC-1α-deficient mice tended to perform poorer in the hippocampus-based spatial learning paradigm, the genotype overall was not associated with impairment in spatial memory, contradicting with prior observations. None of the observed alterations deteriorated with age, similarly to motor alterations as reported previously. The most likely contributors of this peculiar phenotype are discussed, with clinicopathological correlations drawn. Being the first to address these behavioral domains within the same PGC-1α-deficient strain, our findings extend the knowledge about the complex in vivo effect of PGC-1α dysfunction and add important notes to research in the field of PGC-1α in connection with neuropsychiatric disorders.

Monoamine Oxidase B Inhibitors in Parkinson's Disease

BACKGROUND

Parkinson's disease (PD) is a neurodegenerative disorder with a prevalence increasing with age. Oxidative stress and glutamate toxicity are involved in its pathomechanism. There are still many unmet needs of PD patients, including the alleviation of motor fluctuations and dyskinesias, and the development of therapies with neuroprotective potential.

OBJECTIVE

To give an overview of the pharmacological properties, the efficacy and safety of the monoamine oxidase B (MAO-B) inhibitors in the treatment of PD, with special focus on the results of randomized clinical trials.

METHOD

A literature search was conducted in PubMed for 'PD treatment', 'MAO-B inhibitors', 'selegiline', 'rasagiline', 'safinamide' and 'clinical trials' with 'MAO-B inhibitors' in 'Parkinson' disease'.

RESULTS

MAO-B inhibitors have a favorable pharmacokinetic profile, improve the dopamine deficient state and may have neuroprotective properties. Safinamide exhibits an anti-glutamatergic effect as well. When applied as monotherapy, MAO-B inhibitors provide a modest, but significant improvement of motor function and delay the need for levodopa. Rasagiline and safinamide were proven safe and effective when added to a dopamine agonist in early PD. As add-on to levodopa, MAO-B inhibitors significantly reduced off-time and were comparable in efficacy to COMT inhibitors. Improvements were achieved as regards certain non-motor symptoms as well.

CONCLUSION

Due to the efficacy shown in clinical trials and their favorable side-effect profile, MAO-B inhibitors are valuable drugs in the treatment of PD. They are recommended as monotherapy in the early stages of the disease and as add-on therapy to levodopa in advanced PD.

Migraine, Neurogenic Inflammation, Drug Development - Pharmacochemical Aspects

BACKGROUND

Migraine is a primary headache disorder. Despite numerous studies conducted with the aim to understand the pathophysiology of migraine, several aspects are still unclear. The trigeminovascular system plays a key role. Neurogenic inflammation is presumed to be an important factor in migraine pathophysiology, mediated by the activation of primary neurons, leading to the release of various pro-inflammatory neuropeptides and neurotransmitters such as Calcitonin Gene-Related Peptide (CGRP), substance P (SP), and vasoactive intestinal peptide (VIP). Nitric oxide (NO), Pituitary adenylate cyclase-activating polypeptide (PACAP) and Glutamate (Glu) also play an important role in the modulation of inflammatory mechanisms.

OBJECTIVE

To review the literature focusing on novel therapeutic targets in migraine, related to neurogenic inflammation.

METHOD

A systematic literature search in the database of PUBMED was conducted regarding therapeutic strategies in migraine, focusing on substances and cytokines released during neurogenic inflammation, published until January 2017.

RESULTS

Ongoing phase III clinical studies with monoclonal antibodies against CGRP and CGRP receptors offer promising novel aspects for migraine treatment. Preclinical and clinical studies targeting SP and nitric oxide synthase (NOS) were all terminated with no significant results compared to placebo. New promising therapeutic goal could be PACAP and its receptor (PAC1), and kynurenic acid (KYNA) analogues.

CONCLUSION

Current migraine treatment offers pain relief only for a small proportion of migraine patients and might not be adequate for patients with cardiovascular comorbidity due to side effects. Better understanding of migraine pathophysiology might, therefore, lead to novel therapeutic lines both in migraine attack treatment and prophylaxis.

Kynurenines and PACAP in Migraine: Medicinal Chemistry and Pathogenetic Aspects

BACKGROUND

Migraine is a highly disabling neurovascular primary headache disorder, with its exact pathomechanism being still unrevealed. The current leading hypotheses are based on the sensitization and activation of the trigeminovascular system.

OBJECTIVE

To review the literature with focus on the effects of kynurenines (L-kynurenine and kynurenic acid) and pituitary adenylate cyclase-activating polypeptide on the regulation of the trigeminovascular system.

METHOD

A literature search was conducted to identify preclinical and clinical publications (198 references) by using the keywords 'kynurenines', 'pituitary adenylate cyclase-activating polypeptide', and 'migraine' in the database of MEDLINE/PubMed up to 10 September 2016 for topical review. Additional filters used included 'review', 'systematic review', 'original article', and 'English language'.

RESULTS

L-kynurenine and kynurenic acid act on the glutamatergic system at the level of the second-order nociceptive neurons in the trigeminal nucleus caudalis. Pituitary adenylate cyclase- activating polypeptide is released from the peripheral nerve endings of the trigeminal pseudounipolar neurons and causes vasodilation and mast cell degranulation, leading to consequent peripheral sensitization of the dural nociceptors. Centrally released pituitary adenylate cyclase-activating polypeptide in the trigeminal nucleus caudalis results in the central sensitization of the second-order neurons. The sensitization process leads to the characteristic features of migraine.

CONCLUSION

L-kynurenine, kynurenic acid, and pituitary adenylate cyclase-activating polypeptide may have fundamental roles in the initiation of migraine headache attacks.

Unlike PPARgamma, neither other PPARs nor PGC-1alpha is elevated in the cerebrospinal fluid of patients with multiple sclerosis

Corroborating with prior experimental findings, we recently reported the pronounced elevation of peroxisome proliferator-activated receptor gamma (PPARγ) protein concentration in the cerebrospinal fluid (CSF) of patients with multiple sclerosis (MS), in association with neuroinflammatory markers and clinical severity. Based on subsequent reports on the possible involvement of other PPARs and PPARγ coactivator-1alpha (PGC-1α) in neuroinflammation in MS, we analyzed the protein levels of PPARα, PPARβ/δ, and PGC-1α in a subset of CSF samples from the same cohort of relapsing-remitting MS patients. Unlike PPARγ, none of these proteins were found elevated in MS patients (n=25) compared to non-inflammatory controls (n=16), with the levels of PPARα and PPARβ/δ found generally below the limit of detection, and that of PGC-1α being detectable but comparable in both groups. The clinical and laboratory associations previously reported with PPARγ were however significant even in this smaller subset. The potential underlying causes of these differential alterations are discussed. The findings suggest that despite their proposed involvement in the regulation of inflammatory processes in MS, PPARα, PPARβ/δ, and PGC-1α proteins are not potential biomarkers of neuroinflammation in MS, and indicate a preferential role of PPARγ in the endogenous regulation of autoimmune response in the human CNS within its receptor family.

The Effect of Emotion and Reward Contingencies on Relational Memory in Major Depression: An Eye-Movement Study with Follow-Up

Background: Episodic memory disturbances were found to constitute a potential trait marker for major depression (MD). The recall of positive or rewarding information in a relational context is specifically impaired. Eye-movement recording constitutes a novel, direct approach to examine implicit memory performance. Here we aimed to assess the effect of emotional context and implicit virtual monetary reward or loss on viewing patterns in association with relational memory in a 6-months follow-up study in MD.

Materials and Methods: Twenty-eight patients with MD and 30 healthy participants were trained to associate a face (happy/sad/neutral) with a background scene. After each pair a virtual monetary reward or loss appeared briefly. During testing, scenes were presented as a cue and then overlaid with three previously studied faces. Participants were asked to recall the matching face if present (Match trials), with eye-movements and subsequent forced-choice recognition being recorded.

Results: Explicit recognition of the matching face was impaired in the MD group as compared to controls. In correlation with this, viewing of the matching face was significantly reduced in the MD group. We found a significant interaction of group (MD vs HC) with the relational memory condition (Match and Non-match), facial emotion and monetary reward and loss. MD patients attended longer to previously rewarded stimuli, but significantly less to sad faces in the Match condition. The relational memory impairment persisted at follow-up and correlated with symptom severity both at baseline and follow-up. Viewing patterns associated with previous virtual reward were associated with clinical symptoms at follow-up.

Conclusion: Our current results provide novel evidence for a specific relational memory impairment in MD as supported by abnormal eye-movement behavior and a deficit in explicit recognition. MD patients showed an attentional bias to rewarded stimuli and decreased viewing of sad faces when relational memory information was present.

Novel AARS2 gene mutation producing leukodystrophy: a case report

AARS2 gene (NM_020745.3) mutations result in two different phenotypic diseases: infantile mitochondrial cardiomyopathy and late-onset leukoencephalopathy. The patient's first symptoms appeared at the age of 18 years with behavioral changes and psychiatric problems. Some years later, extrapyramidal symptoms, cognitive impairment, nystagmus, dysarthria and pyramidal symptoms also developed. The brain magnetic resonance imaging (MRI) indicated extensive white matter abnormalities. The diagnosis of AARS2 gene mutations causing leukodystrophy was confirmed by genetic testing. Segregation analysis confirmed the compound heterozygous state of the patient. Histological examination of the biopsy did not prove specific pathological alterations. The clinical phenotype of our patient was compared with seven previously described patients suffering from leukoencephalopathy caused by AARS2 mutations. We have documented a new, nonsense AARS2 gene mutation (c.578T>G, p.Leu193*) and a known missense mutation (c.595C>T, p.Arg199Cys) associated with leukoencephalopathy in a male patient. Clinical features, imaging characteristics and genetic testing are presented, and histological data from an AARS2-related leukodystrophy patient are described for the first time.

Treatment Possibilities for Psychosis in Parkinson's Disease with An Emphasis on the Newly Approved Drug: Pimavanserin

Parkinson's disease (PD) is a progressive neurodegenerative disorder with prominent motor and non-motor symptoms. Psychosis develops in over 40% of PD patients and it is one of the most distressing symptoms for patients and caregivers alike. Until recently, atypical antipsychotics, clozapine and quetiapine were used to treat psychotic symptoms, but treatment was associated with substantial concerns for side-effects of clozapine and unfounded efficacy for quetiapine. Extensive research has shown that the antipsychotic effect of these drugs could be attributed to serotonin 2a receptor (5-HT2A) triggered mechanisms. A selective 5-HT2A inverse agonist, pimavanserin, has been developed, investigated and has gained approval in April 2016 in the US for the treatment of hallucinations and delusions in PD. In this review we primarily focus on psychosis in PD, the current treatment possibilities and the new, emerging therapy, pimavanserin, a selective 5-HT2A inverse agonist. All articles were reviewed in this topic and indexed in PubMed with keywords: Parkinson's disease psychosis, serotonin 2a receptor inverse agonist, clozapine, quetiapine, pimavanserin.

Lack of age-related clinical progression in PGC-1α-deficient mice - implications for mitochondrial encephalopathies

Impaired peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) function has been demonstrated in several neurodegenerative diseases, and murine whole-body knockouts of PGC-1α have been considered as models for Huntington's disease. Recent neuropathological studies, however, rather propose these animals to be morphological models of mitochondrial encephalopathies, with special reminiscence of Kearns-Sayre syndrome. PGC-1α-deficient animals have already been subjected to behavioral assessments; however, the contradictory findings and the paucity of data assessing long-term progression necessitated further examinations. This study provides a comprehensive neurological phenotypic profiling of full-length-(FL-)PGC-1α-deficient mice in a broad age spectrum, with special focus on previously controversial findings, the issue of long-term phenotypic progression, the histopathological assessment of previously non-characterized tissues of potential clinicopathological relevance, and the gene expression profile of novel brain-specific isoforms of PGC-1α. Our findings demonstrate moderate hypomotility with signs of gait and trunk ataxia in addition to severe impairments in coordination and muscle strength in FL-PGC-1α-deficient mice, phenotypic features consistent of a mitochondrial disease. Intriguingly, however, these early alterations did not progress with age, the understanding of which may unveil mechanisms of potential therapeutic relevance, as discussed. The observed phenotype did not associate with retinal or spinal cord alterations, and was accompanied by mild myopathic changes. Based on these, FL-PGC-1α-deficient mice can be regarded not only as morphological but behavioral models of mitochondrial encephalopathies, with an important temporal limitation that has now been clarified. The mechanisms capable of halting a potentially lethal phenotype are to be unveiled, as they may hold therapeutic value for mitochondrial diseases.

Nitroglycerin-Induced nNOS Increase in Rat Trigeminal Nucleus Caudalis is Inhibited by Systemic Administration of Lysine Acetylsalicylate but not of Sumatriptan

Systemic administration of nitroglycerin (NTG), a nitric oxide (NO) donor, in migraineurs triggers after several hours an attack of which the precise mechanisms are unknown. We found previously in rats that nitroglycerin (10 mg/kg s.c.) is able to increase significantly after 4 h the number of neuronal nitric oxide synthase (nNOS)-immunoreactive neurones in the cervical part of trigeminal nucleus caudalis. In the present experiments, we demonstrate that the 5-HT1B/D agonist sumatriptan (0.6 mg/kg s.c.) does not alter this phenomenon when given before NTG. By contrast, pretreatment with lysine acetylsalicylate (50 mg/kg i.m.) attenuates the NTG-induced nNOS expression in the superficial laminae of trigeminal nucleus caudalis. These findings suggest that effect of NTG on nNOS at a high dosage may involve the cycloxygenase pathway and that activation of the peripheral 5-HT1B/D receptors is not able to modify this effect. These data could help to better understand the role of NO in the pathogenesis of headaches and the action of antimigraine drugs.

Oestrogen-Modulated Increase of Calmodulin-Dependent Protein Kinase II (CamKII) in Rat Spinal Trigeminal Nucleus After Systemic Nitroglycerin

Migraine can be triggered by systemic administration of the nitric oxide (NO) donor nitroglycerin (NTG) and by abrupt falls in plasma oestradiol. Calmodulin-dependent protein kinase II (CamKII) present in superficial dorsal horns is thought to play a role in sensitization of central nociceptors, a phenomen present in migraineurs. We therefore examined in rats the expression of CamKII in the caudal trigeminal nucleus (TNC) after subcutaneous NTG (10 mg/kg) and its modulation by oestrogen. In male rats and in ovariectomized females, after 4 h NTG increased significantly CamKII expression in the superficial layers of TNC, but not in the upper thoracic spinal cord. NTG had no effect on CamKII expression in oestradiol-treated ovariectomized animals. Thus NTG, i.e. NO, selectively enhances CamKII in the rat TNC and oestradiol blocks this effect. These data may help to understand the mechanisms by which NO triggers migraine attacks and oestrogens influence migraine severity.

Novel kynurenic acid analogues in the treatment of migraine and neurodegenerative disorders: preclinical studies and pharmaceutical design

Though migraine and neurodegenerative disorders have a high socioeconomic impact, their therapeutic management has not been fully addressed. Their pathomechanisms are not completely understood, but glutamateinduced excitotoxicity, mitochondrial disturbances and oxidative stress all seem to play crucial roles. The overactivation of glutamate receptors contributes to the hyperexcitability observed in migraine and also to the neurodegenerative process. The kynurenine pathway of the tryptophan metabolism produces the only known endogenous Nmethyl- D-aspartate receptor antagonist, kynurenic acid, which has been proven in different preclinical studies to exert a neuroprotective effect. Influencing the kynurenine pathway might be beneficial in migraine and neurodegenerative diseases, and in the normalization of glutamatergic neurotransmission and the prevention of excitotoxic neuronal damage. The synthesis of kynurenic acid analogues may offer a valuable tool for drug development.

Inhibition of opioid receptor mediated G-protein activity after chronic administration of kynurenic acid and its derivative without direct binding to opioid receptors

There is an increasing number of evidence showing analgesic properties of the kynurenic acid (KYNA), and also some studies demonstrate that kynurenine might interact with the opioid system. Therefore in this study, for the first time we investigated the direct binding affinity of KYNA and its structural analog KYNA-1 towards mu, kappa and delta opioid receptor in competition binding experiments applying opioid receptor specific radioligands. The binding affinity measurements were performed in Chinese hamster ovary cell lines overexpressing the corresponding opioid receptor (mu and kappa opioid receptor were rat, delta opioid receptor were mouse sequence). Additionally we also examined the chronic effect of these compounds on mu, kappa and delta opioid receptor and also nociceptin peptide receptor mediated G-protein activity in [(35)S]GTPγS binding assays performed in mouse cortex and striatum membranes. Our results showed that KYNA and KYNA-1 had no affinity towards any of the three classic opioid receptors. On the other hand the compounds significantly decreased opioid and nociceptin receptor mediated G-protein activity or in some cases enhanced the potency of the activating ligand. Moreover, the alterations were receptor and brain region specific. Accordingly, we conclude that KYNA and KYNA-1 do not interact directly with the opioid receptors, but more likely alter the receptor functions intracellularly.

Recommendations for the use of prolonged-release fampridine in patients with multiple sclerosis (MS)

Prolonged-release fampridine (fampridine PR) is a potassium channel blocker that improves conductivity of signal on demyelinated axons in central nervous system. Fampridine PR has been approved to improve speed of walking in patients with multiple sclerosis. This statement provides a brief summary of data on fampridine PR and recommendations on practical use of the medication in clinical practice, prediction, and evaluation of response to treatment and patient management.

Elevated levels of PPAR-gamma in the cerebrospinal fluid of patients with multiple sclerosis

Peroxisome proliferator-activated receptor gamma (PPARγ), a ligand-activated transcriptional factor involved in the regulation of glucose and lipid metabolism, has gained interest as a potential therapeutic target in multiple sclerosis (MS) due to its potent immunoregulatory properties and the therapeutic efficacy of its ligands in experimental autoimmune encephalitis (EAE). Elevated expression of PPARγ has been observed in the spinal cord of EAE mice and in an in vitro model of antigen-induced demyelination; however, no reports have yet been available on the PPARγ status in the central nervous system of human individuals with MS. Aiming to identify a possible alteration, the present study assessed the levels of PPARγ protein in the cerebrospinal fluid (CSF) of MS patients via ELISA technique. We report a pronounced elevation in the CSF levels of PPARγ in MS patients (n=35) compared to non-inflammatory controls (n=22). This elevation was independent of blood-CSF barrier integrity, but correlated with CSF white blood cell count and IgG index, associating the observed elevation with neuroinflammation. Controlling for potential confounders, the CSF levels of PPARγ further displayed a moderate but significant association with clinical severity. Corroborating with prior experimental findings, these results may contribute to our understanding about the role of PPARγ in MS, and may implicate this protein as a potential CSF biomarker of the disease.

Neuropathology of partial PGC-1α deficiency recapitulates features of mitochondrial encephalopathies but not of neurodegenerative diseases

BACKGROUND

Deficient peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) function is one component of mitochondrial dysfunction in neurodegenerative diseases. Current molecular classification of such diseases is based on the predominant protein accumulating as intra- or extracellular aggregates. Experimental evidence suggests that mitochondrial dysfunction and impaired protein processing are closely interrelated. In vitro findings further indicate that PGC-1α dysfunction may contribute to protein misfolding in neurodegeneration.

OBJECTIVE

To systematically evaluate the neuropathological alterations of mice lacking the expression of the full-length PGC-1α protein (FL-PGC-1α) but expressing an N-truncated fragment.

METHODS

To assess the pattern of neurodegeneration-related proteins, we performed immunostaining for Tau, pTau, α-synuclein, amyloid-β, amyloid precursor protein, prion protein, FUS, TDP-43 and ubiquitin. Using hematoxylin and eosin, Klüver-Barrera and Bielschowsky silver stainings and anti-GFAP immunohistochemistry, we performed an anatomical mapping to provide a lesion profile.

RESULTS

The immunohistochemical pattern of neurodegeneration-related proteins did not differ between FL-PGC-1α knockout and wild-type animals, and there was a complete lack of protein deposits or ubiquitin-positive inclusions. The analysis of neuropathological alterations revealed widespread vacuolation predominating in the cerebral white matter, caudate-putamen, thalamus and brainstem, and reactive astrogliosis in the brainstem and cerebellar nuclei. This morphological phenotype was thus reminiscent of human mitochondrial encephalopathies, especially the Kearns-Sayre syndrome.

CONCLUSION

We conclude that the lack of FL-PGC-1α per se is insufficient to recapitulate major features of neurodegenerative diseases, but evokes a pathology seen in mitochondrial encephalopathies, which makes PGC-1α-deficient mice a valuable model for this yet incurable group of diseases.

Kynurenines in cognitive functions: their possible role in depression

Depression can originate from changes in tryptophan availability, caused by activation of the kynurenine pathway (KP) as a result of inflammation. Alterations in the KP and the changing levels of its metabolites have recently been considered to be factors contributing to the pathogenesis of depression. The key molecular mediator which induces the conversion of tryptophan into kynurenine is indoleamine-2,3-dioxygenase. Following its activation, both the production of neurotoxic compounds and the diminished peripheral accessibility of tryptophan are regarded as essential steps in the pathophysiological processes. The aim of this review is to survey the role of the KP in depression and its relationships with cognitive functions.

Cognitive functions in ataxia with oculomotor apraxia type 2

Background: Ataxia with oculomotor apraxia type 2 (AOA2) is characterized by cerebellar atrophy, peripheral neuropathy, oculomotor apraxia, and elevated serum alpha-fetoprotein (AFP) levels. The disease is caused by a recessive mutation in the senataxin gene. Since it is a very rare cerebellar disorder, no detailed examination of cognitive functions in AOA2 has been published to date. The aim of the present study was to investigate the neuropsychological profile of a 54-year-old patient with AOA2. Methods: A broad range of neuropsychological examination protocol was administered including the following domains: short-term, working- and episodic-memories, executive functions, implicit sequence learning, and the temporal parameters of speech. Results: The performance on the Listening Span, Letter Fluency, Serial Reaction Time Task, and pause ratio in speech was 2 or more standard deviations (SD) lower compared to controls, and 1 SD lower on Backward Digit Span, Semantic Fluency, articulation rate, and speech tempo. Conclusion: These findings indicate that the pathogenesis of the cerebrocerebellar circuit in AOA2 is responsible for the weaker coordination of complex cognitive functions such as working memory, executive functions, speech, and sequence learning.

Mild traumatic brain injury

Traumatic Brain Injury (TBI) is among the most frequent neurological disorders. Of all TBIs 90% are considered mild with an annual incidence of 100–300/100.000. Intracranial complications of Mild Traumatic Brain Injury (MTBI) are infrequent (10%), requiring neurosurgical intervention in a minority of cases (1%), but potentially life-threatening (case fatality rate 0,1%). Hence, a true health management problem exists because of the need to exclude the small chance of a life threatening complication in large numbers of individual patients. The 2002 EFNS guidelines used a best evidence approach based on the literature until 2001 to guide initial management with respect to indications for CT, hospital admission, observation and follow up of MTBI patients. This updated EFNS guideline version for initial management inMTBI proposes a more selectively strategy for CT when major (dangerous mechanism, GCS<15, 2 points deterioration on the GCS, clinical signs of (basal) skull fracture, vomiting, anticoagulation therapy, post traumatic seizure) or minor (age, loss of consciousness, persistent anterograde amnesia, focal deficit, skull contusion, deterioration on the GCS) risk factors are present based on published decision rules with a high level of evidence. In addition clinical decision rules for CT now exist for children as well. Since 2001 recommendations, although with a lower level of evidence, have been published for clinical in hospital observation to prevent and treat other potential threads to the patient including behavioral disturbances (amnesia, confusion and agitation) and infection.

Manipulating kynurenic acid levels in the brain - on the edge between neuroprotection and cognitive dysfunction

A number of neurodegenerative diseases have been associated with potentially neurotoxic alterations in the kynurenine pathway. Due to the potent inhibitory effect of kynurenic acid on glutamate receptor function, the potential use of the elevation of its concentrations in the brain in the protection against excitotoxic injury has earned an ever greater interest. The first strong preclinical achievements of protection in transgenic murine models of chronic neurodegenerative diseases by kynurenergic approaches have recently been published. Despite the remarkable neuroprotection provided by these molecules, the potential risk of interfering with cognitive functions when dealing with molecules capable of impairing glutamatergic and cholinergic transmission should always be considered. This issue is of particular interest in light of the high affinity of kynurenic acid towards the glycine site of NMDA receptors, the antagonism of which is known to recapitulate key behavioral features of schizophrenia. In the past decade, however, a number of other sites of action have been revealed, most of them being possible contributors of either the neuroprotective or the cognitive deteriorating effects of kynurenic acid. This paper reviews the current understanding about how kynurenic acid can influence cognitive functions in experimental animals, and discusses the possibility of exploiting the neuroprotective potential of kynurenic acid without impairing cognitive functions.

The Alzheimer's Association external quality control program for cerebrospinal fluid biomarkers

BACKGROUND

The cerebrospinal fluid (CSF) biomarkers amyloid β (Aβ)-42, total-tau (T-tau), and phosphorylated-tau (P-tau) demonstrate good diagnostic accuracy for Alzheimer's disease (AD). However, there are large variations in biomarker measurements between studies, and between and within laboratories. The Alzheimer's Association has initiated a global quality control program to estimate and monitor variability of measurements, quantify batch-to-batch assay variations, and identify sources of variability. In this article, we present the results from the first two rounds of the program.

METHODS

The program is open for laboratories using commercially available kits for Aβ, T-tau, or P-tau. CSF samples (aliquots of pooled CSF) are sent for analysis several times a year from the Clinical Neurochemistry Laboratory at the Mölndal campus of the University of Gothenburg, Sweden. Each round consists of three quality control samples.

RESULTS

Forty laboratories participated. Twenty-six used INNOTEST enzyme-linked immunosorbent assay kits, 14 used Luminex xMAP with the INNO-BIA AlzBio3 kit (both measure Aβ-(1-42), P-tau(181P), and T-tau), and 5 used Meso Scale Discovery with the Aβ triplex (AβN-42, AβN-40, and AβN-38) or T-tau kits. The total coefficients of variation between the laboratories were 13% to 36%. Five laboratories analyzed the samples six times on different occasions. Within-laboratory precisions differed considerably between biomarkers within individual laboratories.

CONCLUSIONS

Measurements of CSF AD biomarkers show large between-laboratory variability, likely caused by factors related to analytical procedures and the analytical kits. Standardization of laboratory procedures and efforts by kit vendors to increase kit performance might lower variability, and will likely increase the usefulness of CSF AD biomarkers.

The L-kynurenine signalling pathway in trigeminal pain processing: A potential therapeutic target in migraine?

Introduction: In recent years the kynurenine family of compounds, metabolites of tryptophan, has become an area of intensive research because of its neuroactive properties. Two metabolites of this family have become of interest in relation to migraine and pain processing.

Discussion: Experimental studies have shown that kynurenic acid (KYNA) plays an important role in the transmission of sensory impulses in the trigeminovascular system and that increased levels of KYNA decrease the sensitivity of the cerebral cortex to cortical spreading depression. Furthermore, another metabolite of the kynurenine family, L-kynurenine, exerts vasodilating effects similar to nitric oxide by increasing cyclic guanosine monophosphate.

Conclusion: This review summarizes current knowledge of the role of kynurenine signalling in trigeminal and central pain processing, including its therapeutic prospects in migraine treatment.

Pharmacological models of Parkinson's disease in rodents

Parkinson's disease (PD) is one of the most common neurodegenerative disorders. Despite the substantial progress that has been achieved, the precise mechanisms involved in the development of this disease are still not fully understood. The most common concepts relate to the genetic background and environmental/toxic effects. A number of model systems have been introduced, which mimic the human disease to varying extents. In this chapter, we introduce some of the most widely accepted protocols of the pharmacological models of Parkinson's disease.

cNEUPRO: Novel Biomarkers for Neurodegenerative Diseases

“clinical NEUroPROteomics of neurodegenerative diseases” (cNEUPRO) is a Specific Targeted Research Project (STREP) within the sixth framework program of the European Commission dedicated to the search for novel biomarker candidates for Alzheimer's disease and other neurodegenerative diseases. The ultimate goal of cNEUPRO is to identify one or more valid biomarker(s) in blood and CSF applicable to support the early and differential diagnosis of dementia disorders. The consortium covers all steps required for the discovery of novel biomarker candidates such as acquisition of high quality CSF and blood samples from relevant patient groups and controls, analysis of body fluids by various methods, and finally assay development and assay validation. Here we report the standardized procedures for diagnosis and preanalytical sample-handling within the project, as well as the status of the ongoing research activities and some first results.

Pharmacological therapy in Parkinson's disease: focus on neuroprotection

Although the number of available therapeutic approaches in Parkinson's disease (PD) is steadily increasing the search for effective neuroprotective agent is continuing. Such research is directed at influencing the key steps in the pathomechanism: the mitochondrial dysfunction, the oxidative stress, the neuroinflammatory processes and the final common apoptotic pathway. Earlier-developed symptomatic therapies were implicated to be neuroprotective, and promising novel disease modifying approaches were brought into the focus of interest. The current review presents a survey of our current knowledge relating to the pathomechanism of PD and discusses the putative neuroprotective therapy.