ERK1/2 modulation in the central nervous system of male and female thiamine-deficient mice with amprolium.

Thiamine deficiency experimental models focus on using the pyrithiamine analog in male rodents, making the thiamine deficiency effects in females and the use of other thiamine antagonists, such as amprolium, unknown. We investigated the impact of thiamine deficiency with amprolium in the cerebral cortex and thalamus of male and female mice by evaluating the modulation of ERK1/2 phosphorylation. The animals were exposed for 20 days to thiamine-deficient chow with different doses of amprolium (20, 40, 60 and 80 mg/kg) and at different treatment periods (five, 10, 15 or 20 days) at a dose of 60 mg/kg. After treatments, ERK1/2 phosphorylation was analyzed by western blot. In male mice, we observed a progressive increase in ERK1/2 phosphorylation in both the cerebral cortex and thalamus in response to the dose of amprolium. In females, ERK1/2 phosphorylation did not progressively increase in response to the amprolium dosage. However, an increase in phosphorylation at the higher doses of 60 and 80 mg/kg was observed. We observed a more intense increase in ERK1/2 phosphorylation in males' cerebral cortex and thalamus from 10 days onwards. In females, the ERK1/2 modulation profiles were similar. The results show that thiamine deficiency induction with amprolium is efficient, compatible with other recognized models that use pyrithiamine, showing changes in cell signaling in the nervous system. The study showed differences in response to thiamine deficiency with amprolium between male and female mice in relation to ERK1/2 phosphorylation and demonstrated that females respond positively to the method and can also be used as model animals.

Protocatechuic Acid Prevents Some of the Memory-Related Behavioural and Neurotransmitter Changes in a Pyrithiamine-Induced Thiamine Deficiency Model of Wernicke-Korsakoff Syndrome in Rats.

The purpose of this research was to investigate the effects of protocatechuic acid (PCA) at doses of 50 and 100 mg/kg on the development of unfavourable changes in cognitive processes in a pyrithiamine-induced thiamine deficiency (PTD) model of the Wernicke-Korsakoff syndrome (WKS) in rats. The effects of PCA were assessed at the behavioural and biochemical levels. Behavioural analysis was conducted using the Foot Fault test (FF), Bar test, Open Field test, Novel Object Recognition test (NOR), Hole-Board test and Morris Water Maze test (MWM). Biochemical analysis consisting of determination of concentration and turnover of neurotransmitters in selected structures of the rat CNS was carried out using high-performance liquid chromatography. PTD caused catalepsy (Bar test) and significantly impaired motor functions, leading to increased ladder crossing time and multiplied errors due to foot misplacement (FF). Rats with experimentally induced WKS showed impaired consolidation and recall of spatial reference memory in the MWM test, while episodic memory related to object recognition in the NOR was unimpaired. Compared to the control group, rats with WKS showed reduced serotonin levels in the prefrontal cortex and changes in dopamine and/or norepinephrine metabolites in the prefrontal cortex, medulla oblongata and spinal cord. PTD was also found to affect alanine, serine, glutamate, and threonine levels in certain areas of the rat brain. PCA alleviated PTD-induced cataleptic symptoms in rats, also improving their performance in the Foot Fault test. In the MWM, PCA at 50 and 100 mg/kg b.w. improved memory consolidation and the ability to retrieve acquired information in rats, thereby preventing unfavourable changes caused by PTD. PCA at both tested doses was also shown to have a beneficial effect on normalising PTD-disrupted alanine and glutamate concentrations in the medulla oblongata. These findings demonstrate that certain cognitive deficits in spatial memory and abnormalities in neurotransmitter levels persist in rats that have experienced an acute episode of PTD, despite restoration of thiamine supply and long-term recovery. PCA supplementation largely had a preventive effect on the development of these deficits, to some extent also normalising neurotransmitter concentrations in the brain.

Sex differences in cholinergic circuits and behavioral disruptions following chronic ethanol exposure with and without thiamine deficiency.

BACKGROUND: Few studies have investigated differences in the vulnerabilities of males and females to alcohol use disorder and alcohol-related brain damage (ARBD). According to epidemiological and clinical findings, females appear to be more sensitive to the effects of alcohol and thiamine deficiency and have a worse prognosis in recovery from neurocognitive deficits compared with males. This study aimed to characterize the effects of chronic ethanol (EtOH) toxicity and thiamine deficiency across the sexes using rodent models. METHODS: Male and female Sprague Dawley rats were assigned to chronic forced EtOH treatment (CET), pyrithiamine-induced thiamine deficiency (PTD), combined CET-PTD, or pair-fed (PF) control treatment conditions. Following treatments, spatial working memory was assessed during a spontaneous alternation task while measuring acetylcholine (ACh) in the prefrontal cortex (PFC) and the hippocampus (HPC). The animals also underwent an operant-based attentional set-shifting task (ASST) for the analysis of behavioral flexibility. RESULTS: Female and male rats did not differ in terms of EtOH consumption; however, the CET and CET-PTD-treated female rats had lower BECs than male rats. Compared with the PF group, the CET, PTD, and CET-PTD groups exhibited spatial working memory impairments with corresponding reductions in ACh efflux in the PFC and HPC. The ASST revealed that CET-PTD-treated males and females displayed impairments marked by increased latency to make decisions. Thalamic shrinkage was prominent only in the CET-PTD and PTD treatment conditions, but no sex-specific effects were observed. CONCLUSIONS: Although the CET and CET-PTD-treated females had lower BECs than the males, they demonstrated similar cognitive impairments. These results provide evidence that female rats experience behavioral and neurochemical disruptions at lower levels of alcohol exposure than males and that chronic EtOH and thiamine deficiencies produce a unique behavioral profile.

Identification of a novel pyrithiamine resistance marker gene thiI for genome co-editing in Aspergillus oryzae.

Marker genes are essential for gene modification and genome editing of microorganisms. In Aspergillus oryzae, a widely used host for enzyme production, only a few marker genes can be used for positive selection. One of these genes, the pyrithiamine (PT) resistance marker gene thiA, is not useful for CRISPR/Cas9 genome editing because of its unique resistance-conferring mechanism. In this study, a novel PT resistance marker was investigated considering its potential applications in genome editing. A mutant resistant to PT was selected from UV-mutagenized A. oryzae RIB40. Whole genome analysis was conducted on the mutants, and a novel candidate gene for PT resistance was identified. This candidate gene exhibited similarity to the thiamine transporter gene thi9 of Schizosaccharomyces pombe and was designated as thiI. A thiI loss-of-function mutant was generated using the CRISPR/Cas9 genome editing system to investigate its effect on PT resistance. This mutant showed PT resistance and exhibited no growth defect or auxotrophy. The thiI gene was further investigated for its use as a selection marker in genome co-editing. Ribonucleoprotein complex comprising recombinant Cas9 nuclease and sgRNA targeting thiI or another target gene (wA or sreA) was prepared and simultaneously introduced into A. oryzae RIB40. thiI and target gene double loss-of-function mutants were efficiently selected on PT-containing medium. thiI was shown to be a useful marker gene in A. oryzae for use in genome editing. This study is expected to provide insights, which will promote basic research and industrial applications of A. oryzae.

Thiamine Deficiency Modulates p38MAPK and Heme Oxygenase-1 in Mouse Brain: Association with Early Tissue and Behavioral Changes.

Thiamine deficiency (TD) produces severe neurodegenerative lesions. Studies have suggested that primary neurodegenerative events are associated with both oxidative stress and inflammation. Very little is known about the downstream effects on intracellular signaling pathways involved in neuronal death. The primary aim of this work was to evaluate the modulation of p38MAPK and the expression of heme oxygenase 1 (HO-1) in the central nervous system (CNS). Behavioral, metabolic, and morphological parameters were assessed. Mice were separated into six groups: control (Cont), TD with pyrithiamine (Ptd), TD with pyrithiamine and Trolox (Ptd + Tr), TD with pyrithiamine and dimethyl sulfoxide (Ptd + Dmso), Trolox (Tr) and DMSO (Dmso) control groups and treated for 9 days. Control groups received standard feed (AIN-93M), while TD groups received thiamine deficient feed (AIN-93DT). All the groups were subjected to behavioral tests, and CNS samples were collected for cell viability, histopathology and western blot analyses. The Ptd group showed a reduction in weight gain and feed intake, as well as a reduction in locomotor, grooming, and motor coordination activities. Also, Ptd group showed a robust increase in p38MAPK phosphorylation and mild HO-1 expression in the cerebral cortex and thalamus. The Ptd group showed a decreased cell viability, hemorrhage, spongiosis, and astrocytic swelling in the thalamus. Groups treated with Trolox and DMSO displayed diminished p38MAPK phosphorylation in both the structures, as well as attenuated thalamic lesions and behavioral activities. These data suggest that p38MAPK and HO-1 are involved in the TD-induced neurodegeneration in vivo, possibly modulated by oxidative stress and neuroinflammation.

Thiamin transport in Helicobacter pylori lacking the de novo synthesis of thiamin.

Helicobacter pylori lacks the genes involved in the de novo synthesis of thiamin, and is therefore a thiamin auxotroph. The PnuT transporter, a member of the Pnu transporter family, mediates the uptake of thiamin across the membrane. In the genome of H. pylori, the pnuT gene is clustered with the thiamin pyrophosphokinase gene thi80. In this study, we found that [3H]thiamin is incorporated into the H. pylori SS1 strain via facilitated diffusion with a Km value of 28 µM. The incorporation of radioactive thiamin was inhibited to some extent by 2-methyl-4-amino-5-hydroxymethylpyrimidine or pyrithiamine, but was largely unaffected by thiamin phosphate or thiamin pyrophosphate. RT-PCR analysis demonstrated that the pnuT and thi80 genes are cotranscribed as a single transcript. The estimated Km value for thiamin in the thiamin pyrophosphokinase activity exerted by the recombinant Thi80 protein was 0.40 µM, which is much lower than the Km value of thiamin transport in H. pylori cells. These findings suggested that the incorporated thiamin from the environment is efficiently trapped by pyrophosphorylation to make the transport directional. In addition, the thiamin transport activity in the pnuT-deficient H. pylori strain was less than 20 % of that in the wild-type strain at extracellular thiamin concentration of 1 µM, but the incorporated scintillation signals of the pnuT-deficient strain with 100 nM [3H]thiamin were nearly at the background level. We also found that the pnuT-deficient strain required 100-times more thiamin to achieve growth equal to that of the wild-type. These findings reflect the presence of multiple routes for entry of thiamin into H. pylori, and PnuT is likely responsible for the high-affinity thiamin transport and serves as a target for antimicrobial agents against H. pylori.

A Dual Selection Marker Transformation System Using Agrobacterium tumefaciens for the Industrial Aspergillus oryzae 3.042.

Currently, the genetic modification of Aspergillus oryzae is mainly dependent on protoplastmediated transformation (PMT). In this study, we established a dual selection marker system in an industrial A. oryzae 3.042 strain by using Agrobacterium tumefaciens-mediated transformation (ATMT). We first constructed a uridine/uracil auxotrophic A. oryzae 3.042 strain and a pyrithiamine (PT)-resistance binary vector. Then, we established the ATMT system by using uridine/uracil auxotrophy and PT-resistance genes as selection markers. Finally, a dual selection marker ATMT system was developed. This study demonstrates a useful dual selection marker transformation system for genetic manipulations of A. oryzae 3.042.

A Pivotal Role for Thiamine Deficiency in the Expression of Neuroinflammation Markers in Models of Alcohol-Related Brain Damage.

BACKGROUND: Alcohol-related brain damage (ARBD) is associated with neurotoxic effects of heavy alcohol use and nutritional deficiency, in particular thiamine deficiency (TD), both of which induce inflammatory responses in brain. Although neuroinflammation is a critical factor in the induction of ARBD, few studies have addressed the specific contribution(s) of ethanol (EtOH) versus TD. METHODS: Adult rats were randomly divided into 6 conditions: chronic EtOH treatment (CET) where rats consumed a 20% v/v solution of EtOH for 6 months; CET with injections of thiamine (CET + T); severe pyrithiamine-induced TD (PTD); moderate PTD; moderate PTD during CET; and pair-fed controls. After the treatments, the rats were split into 3 recovery phase time points: the last day of treatment (time point 1), acute recovery (time point 2: 24 hours posttreatment), and delayed recovery (time point 3: 3 weeks posttreatment). At these time points, vulnerable brain regions (thalamus, hippocampus, frontal cortex) were collected and changes in neuroimmune markers were assessed using a combination of reverse transcription polymerase chain reaction and protein analysis. RESULTS: CET led to minor fluctuations in neuroimmune genes, regardless of the structure being examined. In contrast, PTD treatment led to a profound increase in neuroimmune genes and proteins within the thalamus. Cytokine changes in the thalamus ranged in magnitude from moderate (3-fold and 4-fold increase in interleukin-1ß [IL-1ß] and IκBα) to severe (8-fold and 26-fold increase in tumor necrosis factor-α and IL-6, respectively). Though a similar pattern was observed in the hippocampus and frontal cortex, overall fold increases were moderate relative to the thalamus. Importantly, neuroimmune gene induction varied significantly as a function of severity of TD, and most genes displayed a gradual recovery across time. CONCLUSIONS: These data suggest an overt brain inflammatory response by TD and a subtle change by CET alone. Also, the prominent role of TD in the immune-related signaling pathways leads to unique regional and temporal profiles of induction of neuroimmune genes.

Microglial activation and vascular responses that are associated with early thalamic neurodegeneration resulting from thiamine deficiency.

Thiamine/vitamin B1 deficiency can lead to behavioral changes and neurotoxicity in humans. This may due in part to vascular damage, neuroinflammation and neuronal degeneration in the diencephalon, which is seen in animal models of pyrithiamine-enhanced thiamine deficiency. However, the time course of the progression of these changes in the animal models has been poorly characterized. Therefore, in this study, the progression of: 1) activated microglial association with vasculature; 2) neurodegeneration; and 3) any vascular leakage in the forebrain during the progress of thiamine deficiency were determined. A thiamine deficient diet along with 0.25 mg/kg/d of pyrithiamine was used as the mouse model. Vasculature was identified with Cd31 and microglia with Cd11b and Iba1 immunoreactivity. Neurodegeneration was determined by FJc labeling. The first sign of activated microglia within the thalamic nuclei were detected after 8 d of thiamine deficiency, and by 9 d activated microglia associated primarily with vasculature were clearly present but only in thalamus. At the 8 d time point neurodegeneration was not present in thalamus. However at 9 d, the first signs of neurodegeneration (FJc + neurons) were seen in most animals. Over 80% of the microglia were activated at 10 d but almost exclusively in the thalamus and the number of degenerating neurons was less than 10% of the activated microglia. At 10 d, there were sporadic minor changes in IgG presence in thalamus indicating minor vascular leakage. Dizocilpine (0.2-0.4 mg/kg) or phenobarbital (10-20 mg/kg) was administered to groups of mice from day 8 through day 10 to block neurodegeneration but neither did. In summary, activated microglia start to surround vasculature 1-2 d prior to the start of neurodegeneration. This response may be a means of controlling or repairing vascular damage and leakage. Glutamate excitotoxicity and vascular leakage likely only play a minor role in the early neurodegeneration resulting from thiamine deficiency. However, failure of dysfunctional vasculature endothelium to supply sufficient nutrients to neurons could be contributing to the neurodegeneration.

Thiamine and selected thiamine antivitamins - biological activity and methods of synthesis.

Thiamine plays a very important coenzymatic and non-coenzymatic role in the regulation of basic metabolism. Thiamine diphosphate is a coenzyme of many enzymes, most of which occur in prokaryotes. Pyruvate dehydrogenase and 2-oxoglutarate dehydrogenase complexes as well as transketolase are the examples of thiamine-dependent enzymes present in eukaryotes, including human. Therefore, thiamine is considered as drug or diet supplement which can support the treatment of many pathologies including neurodegenerative and vascular system diseases. On the other hand, thiamine antivitamins, which can interact with thiamine-dependent enzymes impeding their native functions, thiamine transport into the cells or a thiamine diphosphate synthesis, are good propose to drug design. The development of organic chemistry in the last century allowed the synthesis of various thiamine antimetabolites such as amprolium, pyrithiamine, oxythiamine, or 3-deazathiamine. Results of biochemical and theoretical chemistry research show that affinity to thiamine diphosphate-dependent enzymes of these synthetic molecules exceeds the affinity of native coenzyme. Therefore, some of them have already been used in the treatment of coccidiosis (amprolium), other are extensively studied as cytostatics in the treatment of cancer or fungal infections (oxythiamine and pyrithiamine). This review summarizes the current knowledge concerning the synthesis and mechanisms of action of selected thiamine antivitamins and indicates the potential of their practical use.

BDNF regains function in hippocampal long-term potentiation deficits caused by diencephalic damage.

Thiamine deficiency (TD), commonly associated with chronic alcoholism, leads to diencephalic damage, hippocampal dysfunction, and spatial learning and memory deficits. We show a decrease in the magnitude of long-term potentiation (LTP) and paired-pulse facilitation (PPF) at CA3-CA1 synapses, independent of sex, following diencephalic damage induced by TD in rats. Thus, despite a lack of extensive hippocampal cell loss, diencephalic brain damage down-regulates plastic processes within the hippocampus, likely contributing to impaired hippocampal-dependent behaviors. However, both measures of hippocampal plasticity (LTP, PPF) were restored with brain-derived neurotrophic factor (BDNF), revealing an avenue for neural and behavioral recovery following diencephalic damage.

Brain endothelial dysfunction following pyrithiamine induced thiamine deficiency in the rat.

Prolonged vitamin B1 (thiamine) deficiency can lead to neurological disorders such as Wernicke's encephalopathy and Wernicke-Korsakoff Syndrome (WKS) in humans. These thiamine deficiency disorders have been attributed to vascular leakage, blood-brain barrier breakdown and neuronal loss in the diencephalon and brain stem. However, endothelial dysfunction following thiamine deficiency and its relationship to the phenomenon of neurodegeneration has not been clearly elucidated. The present study sought to begin to address this issue by evaluating vascular morphology and integrity in a pyrithiamine (PT)-induced rat model of thiamine deficiency. Adjacent brain sections were used to either assess vascular integrity through immunohistochemical localization of rat endothelial cell antigen (RECA-1) and endothelial brain barrier antigen (EBA-1) or neurodegeneration using the de Olmos cupric silver method. GFAP and CD11b immunolabeling was used to evaluate astrocytic and microglial/macrophagic changes. Extensive neurodegeneration occurred concomitant with both vascular damage (thinning and breakage) and microglial activation in the inferior olive, medial thalamic area, and medial geniculate nuclei of pyrithiamine treated rats. Likewise, glucose transporter-1 (Glut-1), which is mostly expressed in endothelial cells, was also severely decreased in this pyrithiamine induced thiamine deficient rat model. MRI scans of these animals prior to sacrifice show that the pyrithiamine induced thiamine deficient animals have abnormal T2 relaxation values, which are commensurate with, and possibly predictive of, the neurodegeneration and/or endothelial dysfunction subsequently observed histologically in these same animals.

Vitamin B1-deficient mice show impairment of hippocampus-dependent memory formation and loss of hippocampal neurons and dendritic spines: potential microendophenotypes of Wernicke-Korsakoff syndrome.

Patients with severe Wernicke-Korsakoff syndrome (WKS) associated with vitamin B1 (thiamine) deficiency (TD) show enduring impairment of memory formation. The mechanisms of memory impairment induced by TD remain unknown. Here, we show that hippocampal degeneration is a potential microendophenotype (an endophenotype of brain disease at the cellular and synaptic levels) of WKS in pyrithiamine-induced thiamine deficiency (PTD) mice, a rodent model of WKS. PTD mice show deficits in the hippocampus-dependent memory formation, although they show normal hippocampus-independent memory. Similarly with WKS, impairments in memory formation did not recover even at 6 months after treatment with PTD. Importantly, PTD mice exhibit a decrease in neurons in the CA1, CA3, and dentate gyrus (DG) regions of the hippocampus and reduced density of wide dendritic spines in the DG. Our findings suggest that TD induces hippocampal degeneration, including the loss of neurons and spines, thereby leading to enduring impairment of hippocampus-dependent memory formation.

Exercise leads to the re-emergence of the cholinergic/nestin neuronal phenotype within the medial septum/diagonal band and subsequent rescue of both hippocampal ACh efflux and spatial behavior.

Exercise has been shown to improve cognitive functioning in a range of species, presumably through an increase in neurotrophins throughout the brain, but in particular the hippocampus. The current study assessed the ability of exercise to restore septohippocampal cholinergic functioning in the pyrithiamine-induced thiamine deficiency (PTD) rat model of the amnestic disorder Korsakoff Syndrome. After voluntary wheel running or sedentary control conditions (stationary wheel attached to the home cage), PTD and control rats were behaviorally tested with concurrent in vivo microdialysis, at one of two time points: 24-h or 2-weeks post-exercise. It was found that only after the 2-week adaption period did exercise lead to an interrelated sequence of events in PTD rats that included: (1) restored spatial working memory; (2) rescued behaviorally-stimulated hippocampal acetylcholine efflux; and (3) within the medial septum/diagonal band, the re-emergence of the cholinergic (choline acetyltransferase [ChAT+]) phenotype, with the greatest change occurring in the ChAT+/nestin+ neurons. Furthermore, in control rats, exercise followed by a 2-week adaption period improved hippocampal acetylcholine efflux and increased the number of neurons co-expressing the ChAT and nestin phenotype. These findings demonstrate a novel mechanism by which exercise can modulate the mature cholinergic/nestin neuronal phenotype leading to improved neurotransmitter function as well as enhanced learning and memory.

Identification of vitamin B1 metabolism as a tumor-specific radiosensitizing pathway using a high-throughput colony formation screen.

Colony formation is the gold standard assay for determining reproductive cell death after radiation treatment, since effects on proliferation often do not reflect survival. We have developed a high-throughput radiosensitivity screening method based on clonogenicity and screened a siRNA library against kinases. Thiamine pyrophosphokinase-1 (TPK1), a key component of Vitamin B1/thiamine metabolism, was identified as a target for radiosensitization. TPK1 knockdown caused significant radiosensitization in cancer but not normal tissue cell lines. Other means of blocking this pathway, knockdown of thiamine transporter-1 (THTR1) or treatment with the thiamine analogue pyrithiamine hydrobromide (PyrH) caused significant tumor specific radiosensitization. There was persistent DNA damage in cells irradiated after TPK1 and THTR1 knockdown or PyrH treatment. Thus this screen allowed the identification of thiamine metabolism as a novel radiosensitization target that affects DNA repair. Short-term modulation of thiamine metabolism could be a clinically exploitable strategy to achieve tumor specific radiosensitization.

The role of ventral midline thalamus in cholinergic-based recovery in the amnestic rat.

The thalamus is a critical node for several pathways involved in learning and memory. Damage to the thalamus by trauma, disease or malnourishment can impact the effectiveness of the prefrontal cortex (PFC) and hippocampus (HPC) and lead to a profound amnesia state. Using the pyrithiamine-induced thiamine deficiency (PTD) rat model of human Wernicke-Korsakoff syndrome, we tested the hypothesis that co-infusion of the acetylcholinesterase inhibitor physostigmine across the PFC and HPC would recover spatial alternation performance in PTD rats. When cholinergic tone was increased by dual injections across the PFC-HPC, spontaneous alternation performance in PTD rats was recovered. In addition, we tested a second hypothesis that two ventral midline thalamic nuclei, the rhomboid nucleus and nucleus reuniens (Rh-Re), form a critical node needed for the recovery of function observed when cholinergic tone was increased across the PFC and HPC. By using the GABAA agonist muscimol to temporarily deactivate the Rh-Re the recovery of alternation behavior obtained in the PTD model by cholinergic stimulation across the PFC-HPC was blocked. In control pair-fed (PF) rats, inactivation of the Rh-Re impaired spontaneous alternation. However, when inactivation of the Rh-Re co-occurred with physostigmine infusions across the PFC-HPC, PF rats had normal performance. These results further demonstrate that the Rh-Re is critical in facilitating interactions between the HPC and PFC, but other redundant pathways also exist.

Role of astrocytes in thiamine deficiency.

Thiamine deficiency (TD) is the underlying cause of Wernicke's encephalopathy (WE), an acute neurological disorder characterized by structural damage to key periventricular structures in the brain. Increasing evidence suggests these focal histological lesions may be representative of a gliopathy in which astrocyte-related changes are a major feature of the disorder. These changes include a loss of the glutamate transporters GLT-1 and GLAST concomitant with elevated interstitial glutamate levels, lowered brain pH associated with increased lactate production, decreased levels of GFAP, reduction in the levels of glutamine synthetase, swelling, alterations in levels of aquaporin-4, and disruption of the blood-brain barrier. This review focusses on how these manifestations contribute to the pathophysiology of TD and possibly WE.

Rasagiline prevents neurodegeneration in thiamine deficient rats-a longitudinal MRI study.

Neuroprotection is a therapeutic approach for the management of neurodegenerative diseases. Experimental thiamine deficiency (TD) in rats provides a model for selective neurodegeneration accompanied by chronic oxidative deficits. Rats exhibit neurological and cognitive impairments, which can be partially reversed by thiamine administration, enabling the study of mechanisms of neurodegeneration as well as neuroprotection. In this magnetic resonance (MR) study we used various techniques to characterize the neuroprotective effects of rasagiline, a selective MAO-B inhibitor. TD was induced by a thiamine-deficient diet and daily injections of the central thiamine antagonist, pyrithiamine. Daily injections of either saline or rasagiline (3mg/kg) were also administered to untreated-TD rats and rasagiline-treated TD rats respectively. With the appearance of neurological symptoms, all injections were terminated and thiamine was restored. MRI scans were performed before induction of TD (control values), on days 10, 12 (before symptoms appear), 14 (symptomatic stage) and during the recuperation period. Both groups were assessed using in-vivo serial T2-weighted imaging and diffusion tensor imaging (DTI), from which apparent diffusion coefficient (ADC) and fractional anisotropy (FA) maps were calculated. A histopathological evaluation was correlated with the MRI analysis. Thalamic hyperintensities were significantly smaller and less severe in the rasagiline-treated TD rats. Enlargement of the lateral ventricles was significantly less pronounced in the rasagiline-treated TD group. FA values of the untreated-TD group decreased significantly in the thalamic on days 12 and 14 and in the corpus callosum on day 14. These results demonstrate significant neuroprotection by rasagiline which could have implications for clinical neurodegenerative disorders.

Pyrithiamine-induced thiamine deficiency alters proliferation and neurogenesis in both neurogenic and vulnerable areas of the rat brain.

Thiamine deficiency (TD) leads to Wernicke's encephalopathy (WE), in which focal histological lesions occur in periventricular areas of the brain. Recently, impaired neurogenesis has been reported in the hippocampus during the dietary form of TD, and in pyrithiamine-induced TD (PTD), a well-characterized model of WE. To further characterize the consequences of PTD on neural stem/progenitor cell (NSPC) activity, we have examined the effect of this treatment in the rat on both the subventricular zone (SVZ) of the rostral lateral ventricle and subgranular layer (SGL) of the hippocampus, and in the thalamus and inferior colliculus, two vulnerable brain regions in this disorder. In both the SVZ and SGL, PTD led to a decrease in the numbers of bromodeoxyuridine-stained cells, indicating that proliferation of NSPCs destined for neurogenesis in these areas was reduced. Doublecortin (DCX) immunostaining in the SGL was decreased, indicating a reduction in neuroblast formation, consistent with impaired NSPC activity. DCX labeling was not apparent in focal areas of vulnerability. In the thalamus, proliferation of cells was absent while in the inferior colliculus, numerous actively dividing cells were apparent, indicative of a differential response between these two brain regions. Exposure of cultured neurospheres to PTD resulted in decreased proliferation of NSPCs, consistent with our in vivo findings. Together, these results indicate that PTD considerably affects cell proliferation and neurogenesis activity in both neurogenic areas and parts of the brain known to display structural and functional vulnerability, confirming and extending recent findings on the effects of TD on neurogenesis. Future use of NSPCs in vitro may allow a closer and more detailed examination of the mechanism(s) underlying inhibition of these cells during TD.

Differential cortical neurotrophin and cytogenetic adaptation after voluntary exercise in normal and amnestic rats.

Voluntary exercise (VEx) has profound effects on neural and behavioral plasticity, including recovery of CNS trauma and disease. However, the unique regional cortical adaption to VEx has not been elucidated. In a series of experiments, we first examined whether VEx would restore and retain neurotrophin levels in several cortical regions (frontal cortex [FC], retrosplenial cortex [RSC], occipital cortex [OC]) in an animal model (pyrithiamine-induced thiamine deficiency [PTD]) of the amnestic disorder Wernicke-Korsakoff syndrome. In addition, we assessed the time-dependent effect of VEx to rescue performance on a spontaneous alternation task. Following 2-weeks of VEx or stationary housing conditions (Stat), rats were behaviorally tested and brains were harvested either the day after VEx (24-h) or after an additional 2-week period (2-wk). In both control pair-fed (PF) rats and PTD rats, all neurotrophin levels (brain-derived neurotrophic factor [BDNF], nerve growth factor [NGF], and vascular endothelial growth factor) increased at the 24-h period after VEx in the FC and RSC, but not OC. Two-weeks following VEx, BDNF remained elevated in both FC and RSC, whereas NGF remained elevated in only the FC. Interestingly, VEx only recovered cognitive performance in amnestic rats when there was an additional 2-wk adaptation period after VEx. Given this unique temporal profile, Experiment 2 examined the cortical cytogenetic responses in all three cortical regions following a 2-wk adaptation period after VEx. In healthy (PF) rats, VEx increased the survival of progenitor cells in both the FC and RSC, but only increased oligodendrocyte precursor cells (OLPs) in the FC. Furthermore, VEx had a selective effect of only recovering OLPs in the FC in PTD rats. These data reveal the therapeutic potential of exercise to restore cortical plasticity in the amnestic brain, and that the FC is one of the most responsive cortical regions to VEx.