Stroke is a leading cause of disability and death world-wide and nutrition is a modifiable risk factor for stroke. Metheylenetetrahydrofolate reductase (MTHFR) is an enzyme involved in the metabolism ...of folic acid, a B-vitamin. In humans, a polymorphism in MTHFR (677C→T) is linked to increased risk of stroke, but the mechanisms remain unknown. The Mthfr+/− mice mimic a phenotype described in humans at bp677. Using this mouse model, the aim of this study was to investigate the impact of MTHFR deficiency on stroke outcome. Male Mthfr+/− and wildtype littermate control mice were aged (~1.5-year-old) and trained on the single pellet reaching task. After which the sensorimotor cortex was then damaged using photothrombosis (PT), a model for ischemic stroke. Post-operatively, animals were tested for skilled motor function, and brain tissue was processed to assess cell death. Mthfr+/− mice were impaired in skilled reaching 2-weeks after stroke but showed some recovery at 5-weeks compared to wild types after PT damage. Within the ischemic brain, there was increased expression of active caspase-3 and reduced levels of phospho-AKT in neurons of Mthfr+/− mice. Recent data suggests that astrocytes may play a significant role after damage, the impact of MTHFR and ischemic investigated the impact of MTHFR-deficiency on astrocyte function. MTHFR-deficient primary astrocytes showed reduced cell viability after exposure to hypoxia compared to controls. Increased immunofluorescence staining of active caspase-3 and hypoxia-inducible factor 1-alpha were also observed. The data suggest that MTHFR deficiency decreases recovery after stroke by reducing neuronal and astrocyte viability.
•Aged Mthfr+/− mice have impaired skilled reaching after stroke compared to Mthfr+/+.•Daily testing on skilled reaching task improved recovery in Mthfr+/− mice.•Mthfr+/− mice have mildly higher homocysteine, but lesion size does not differ.•There is lower neuronal survival within damage site of Mthfr+/− mice.•MTHFR deficiency results in reduced viability of primary astrocytes after hypoxia.
Stress and stress hormones affect a variety of behaviors and cognitive abilities. The influences of stress and glucocorticoids on motor function, however, have not been characterized although the ...presence of glucocorticoid receptors in the motor system has been documented. Here we demonstrate that stress and the stress hormone corticosterone influence motor system function in rats. Groups of adult female Long‐Evans rats underwent either a daily stress‐inducing procedure (immobilization or swimming in cold water) or oral corticosterone treatment. While these treatments continued, animals were tested in skilled reaching and skilled walking tasks for a period of 2 weeks. Both acute (day 1) and chronic (day 14) stress and corticosterone treatment reduced skilled movement accuracy in reaching and walking and increased performance speed. Furthermore, both chronic stress and chronic corticosterone treatment altered skilled movement patterns in the reaching task. These findings indicate that stress modulates motor system function and that these effects are partially mediated by glucocorticoids. To examine whether stress‐induced changes might also derive from enhanced emotionality, rats were treated with the benzodiazepine diazepam. Based on an inverted U‐shaped dose–response relationship, a moderate dose of diazepam significantly improved reaching success while at the same time reducing corticosterone levels. Thus, stress‐associated emotional responses such as anxiety might account for diminished movement accuracy. These results suggest that stress affects the motor system both directly via hormonal changes and indirectly via changes in emotionality. These findings are discussed with respect to the role of stress in motor system function and movement disorders.
Nutrition is a modifiable risk factor for ischemic stroke. As people age their ability to absorb some nutrients decreases, a primary example is vitamin B12. Older individuals with a vitamin B12 ...deficiency are at a higher risk for ischemic stroke and have worse stroke outcome. However, the mechanisms through which these occur remain unknown. The aim of the study was to investigate the role of vitamin B12 deficiency in ischemic stroke outcome and mechanistic changes in a mouse model. Ten-month-old male and female mice were put on control or vitamin B12 deficient diets for 4 weeks prior to and after ischemic stroke to the sensorimotor cortex. Motor function was measured, and tissues were collected to assess potential mechanisms. All deficient mice had increased levels of total homocysteine in plasma and liver tissues. After ischemic stroke, deficient mice had impaired motor function compared to control mice. There was no difference between groups in ischemic damage volume. However, within the ischemic damage region, there was an increase in total apoptosis of male deficient mice compared to controls. Furthermore, there was an increase in neuronal survival in ischemic brain tissue of the vitamin B12 deficient mice compared to controls. Additionally, there were changes in choline metabolites in ischemic brain tissue because of a vitamin B12 deficiency. The data presented in this study confirms that a vitamin B12 deficiency worsens stroke outcome in male and female mice. The mechanisms driving this change may be a result of neuronal survival and compensation in choline metabolism within the damaged brain tissue.
Hyperhomocysteinaemia can contribute to cognitive impairment and brain atrophy. MTRR (methionine synthase reductase) activates methionine synthase, which catalyses homocysteine remethylation to ...methionine. Severe MTRR deficiency results in homocystinuria with cognitive and motor impairments. An MTRR polymorphism may influence homocysteine levels and reproductive outcomes. The goal of the present study was to determine whether mild hyperhomocysteinaemia affects neurological function in a mouse model with Mtrr deficiency. Mtrr+/+, Mtrr+/gt and Mtrrgt/gt mice (3 months old) were assessed for short-term memory, brain volumes and hippocampal morphology. We also measured DNA methylation, apoptosis, neurogenesis, choline metabolites and expression of ChAT (choline acetyltransferase) and AChE (acetylcholinesterase) in the hippocampus. Mtrrgt/gt mice exhibited short-term memory impairment on two tasks. They had global DNA hypomethylation and decreased choline, betaine and acetylcholine levels. Expression of ChAT and AChE was increased and decreased respectively. At 3 weeks of age, they showed increased neurogenesis. In the cerebellum, mutant mice had DNA hypomethylation, decreased choline and increased expression of ChAT. Our work demonstrates that mild hyperhomocysteinaemia is associated with memory impairment. We propose a mechanism whereby a deficiency in methionine synthesis leads to hypomethylation and compensatory disturbances in choline metabolism in the hippocampus. This disturbance affects the levels of acetylcholine, a critical neurotransmitter in learning and memory.
Clinical stroke usually results from a cerebral ischaemic event, and is frequently a debilitating condition with limited treatment options. A significant proportion of clinical strokes result from ...specific damage to the subcortical white matter (SWM), but currently there are few animal models available to investigate the pathogenesis and potential therapeutic strategies to promote recovery. Granulocyte macrophage colony‐stimulating factor (GM‐CSF) is a cytokine that has been previously shown to promote neuroprotective effects after brain damage; however, the mechanisms mediating this effect are not known. Here, it is reported that GM‐CSF treatment results in dramatic functional improvement in a white matter model of stroke in mice. SWM stroke was induced in mice by unilateral injections of the vasoconstrictor, endothelin‐1 (ET‐1). The results reveal that ET‐1‐induced stroke impairs skilled motor function on the single pellet‐reaching task and results in forelimb asymmetry, in adult mice. Treatment with GM‐CSF, after stroke, restores motor function and abolishes forelimb asymmetry. The results also indicate that GM‐CSF promotes its effects by activating mammalian target of rapamycin signalling mechanisms in the brain following stroke injury. Additionally, a significant increase in GM‐CSF receptor expression was found in the ipsilateral hemisphere of the ET‐1‐injected brain. Taken together, the present study highlights the use of an under‐utilized mouse model of stroke (using ET‐1) and suggests that GM‐CSF treatment can attenuate ET‐1‐induced functional deficits.
GM‐CSF treatment promotes recovery from stroke‐induced white matter damage. Endothelin‐1 induced subcortical white matter (SWM) stroke enhances GM‐CSF receptor expression in the mouse brain. GM‐CSF treatment, following SWM stroke, promotes functional recovery via an mTOR‐dependent mechanism.
One-carbon (1C) metabolism is a metabolic network that is centered on folate, a B vitamin; it integrates nutritional signals with biosynthesis, redox homeostasis, and epigenetics. This metabolic ...pathway also reduces levels of homocysteine, a non-protein amino acid. High levels of homocysteine are linked to increased risk of hypoxic events, such as stroke. Several preclinical studies have suggested that 1C metabolism can impact stroke outcome, but the clinical data are unclear. The objective of this paper was to review preclinical and clinical research to determine whether 1C metabolism has an antioxidant role on stroke. To accomplish the objective, we searched for publications using the following medical subject headings (MeSH) keywords: antioxidants, hypoxia, stroke, homocysteine, one-carbon metabolism, folate, methionine, and dietary supplementation of one-carbon metabolism. Both pre-clinical and clinical studies were retrieved and reviewed. Our review of the literature suggests that deficiencies in 1C play an important role in the onset and outcome of stroke. Dietary supplementation of 1C provides beneficial effects on stroke outcome. For stroke-affected patients or individuals at high risk for stroke, the data suggest that nutritional modifications in addition to other therapies could be incorporated into a treatment plan.
Tissue plasminogen activator (tPA) is a thrombolytic agent commonly used in the treatment of ischemic stroke. While the thrombolytic effects of tPA have been well established, the impact of this ...blood–brain barrier (BBB) crossing drug on neurons is not known. Given the widespread use of tPA in the clinical setting and the strict therapeutic window established for effective use of the drug, we examined the molecular mechanisms mediating the impact of tPA on postnatal cortical neurons isolated from the mouse brain. Dissociated postnatal primary cortical neurons were treated with tPA and the effects on neuron survival were evaluated. Pharmacological inhibitors of several signaling pathways previously implicated in neuroprotection (mTOR, JAK/STAT, MAPK and PKA-dependent mechanisms) were used to pinpoint the mechanistic effectors of tPA on neuron survival in vitro. We report here that tPA treatment results in a time-dependent neuroprotective effect on postnatal cortical neurons that relies predominantly on Janus kinase (JAK) and mammalian target of rapamycin (mTOR) signaling mechanisms. Taken together, these data suggest that tPA promotes neuroprotection in a temporally-regulated manner and that both JAK and mTOR signaling effectors are critical mediators of this neuroprotective effect. The results suggest the possibility of targeting these defined mechanisms to potentially expand the therapeutic window for tPA.
•The thrombolytic agent, tPA has a significant beneficial impact on postnatal cortical neuron viability in vitro•Neuroprotective effect of tPA treatment on postnatal primary cortical neurons in vitro•tPA-mediated cell survival requires mTOR and JAK/STAT pathway activation•Increase in p-S6 expression following tPA treatment in postnatal cortical neurons
Abstract
Paraquat is an herbicide that is commonly used worldwide. Exposure to paraquat results in Parkinson's disease (PD)-like symptoms including dopaminergic cell loss. Nutrition has also been ...linked in the pathogenesis of PD, such as reduced levels of folic acid, a B-vitamin, and component of one-carbon metabolism. Within one-carbon metabolism, methylenetetrahydrofolate reductase (MTHFR) catalyzes the irreversible conversion of 5, 10-methylenetetrahydrofolate to 5-methyltetrahydrofolate. A polymorphism in MTHFR (677 C&→T) has been reported in 5%-15% of North American and European human populations. The MTHFR polymorphism is also prevalent in PD patients. The goal of this study was to investigate the impact of paraquat-induced PD-like pathology in the context of reduced levels of MTHFR. Three-month-old male Mthfr+/− mice, which model the MTHFR polymorphism observed in humans, were administered intraperitoneal injections of paraquat (10 mg/kg) or saline 6 times over 3 weeks. At the end of paraquat treatment, motor and memory function were assessed followed by collection of brain tissue for biochemical analysis. Mthfr+/- mice treated with paraquat showed impaired motor function. There was increased microglial activation within the substantia nigra (SN) of Mthfr+/− mice treated with paraquat. Additionally, all Mthfr+/− mice that were treated with paraquat showed increased oxidative stress within the dorsal striatum, but not the SN. The present results show that paraquat exposure increases PD-like pathology in mice deficient in one-carbon metabolism.
The causes of most cases of Parkinson's disease (PD) are still poorly understood. Here we show that chronic stress and elevated corticosterone levels exaggerate motor deficits and neurodegenerative ...events in a Parkinson's disease rat model. Animals were tested in skilled and non‐skilled movement while being exposed to daily restraint stress or oral corticosterone treatment. Stress and corticosterone compromised normal motor function and exaggerated motor deficits caused by unilateral 6‐hydroxydopamine lesion of the nigrostriatal bundle. Moreover, stress and corticosterone treatments diminished the ability to acquire compensatory strategies in limb use during skilled reaching and skilled walking. In contrast, lesion control animals were able to significantly improve in the ability of skilled limb use during the repeated test sessions. The exaggerated motor impairments in stress‐treated animals were related to accelerated loss of midbrain dopamine‐producing neurons during the first week postlesion. Correlation analysis revealed a significant connection between loss of tyrosine hydroxylase‐positive cells and increase in Fluoro‐Jade‐positive cells only in stress‐ and corticosterone‐treated animals. Furthermore, stress and elevated corticosterone levels caused greater permanent loss of midbrain neurons than found in non‐treated lesion animals. These findings demonstrate that stress and elevated corticosterone levels can exaggerate nigral neuronal loss and motor symptoms in a rat analogue of PD. It is therefore possible that stress represents a key factor in the pathogenesis of human PD by impeding functional and structural compensation and exaggerating neurodegenerative processes.
After emerging in China in late 2019, the novel coronavirus severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spread worldwide, and as of mid-2021, it remains a significant threat ...globally. Only a few coronaviruses are known to infect humans, and only two cause infections similar in severity to SARS-CoV-2:
, a species closely related to SARS-CoV-2 that emerged in 2002, and
, which emerged in 2012. Unlike the current pandemic, previous epidemics were controlled rapidly through public health measures, but the body of research investigating severe acute respiratory syndrome and Middle East respiratory syndrome has proven valuable for identifying approaches to treating and preventing novel coronavirus disease 2019 (COVID-19). Building on this research, the medical and scientific communities have responded rapidly to the COVID-19 crisis and identified many candidate therapeutics. The approaches used to identify candidates fall into four main categories: adaptation of clinical approaches to diseases with related pathologies, adaptation based on virological properties, adaptation based on host response, and data-driven identification (ID) of candidates based on physical properties or on pharmacological compendia. To date, a small number of therapeutics have already been authorized by regulatory agencies such as the Food and Drug Administration (FDA), while most remain under investigation. The scale of the COVID-19 crisis offers a rare opportunity to collect data on the effects of candidate therapeutics. This information provides insight not only into the management of coronavirus diseases but also into the relative success of different approaches to identifying candidate therapeutics against an emerging disease.
The COVID-19 pandemic is a rapidly evolving crisis. With the worldwide scientific community shifting focus onto the SARS-CoV-2 virus and COVID-19, a large number of possible pharmaceutical approaches for treatment and prevention have been proposed. What was known about each of these potential interventions evolved rapidly throughout 2020 and 2021. This fast-paced area of research provides important insight into how the ongoing pandemic can be managed and also demonstrates the power of interdisciplinary collaboration to rapidly understand a virus and match its characteristics with existing or novel pharmaceuticals. As illustrated by the continued threat of viral epidemics during the current millennium, a rapid and strategic response to emerging viral threats can save lives. In this review, we explore how different modes of identifying candidate therapeutics have borne out during COVID-19.
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