Environmental enrichment rescues DYRK1A activity and hippocampal adult neurogenesis in TgDyrk1A

Molecular rescue of DYRK1A overexpression in cystathionine beta synthase-deficient mouse brain by enriched environment combined with voluntary exercise

Hyperhomocysteinemia resulting from cystathionine beta synthase (CBS) deficiency can produce cognitive dysfunction. We recently found that CBS-deficient mice exhibit increased expression of the serine/threonine kinase dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 1A (DYRK1A) in the brain. When dysregulated, DYRK1A contributes to the neurodegeneration, neuronal death, and loss of function observed in neurodegenerative diseases. However, brain plasticity can be improved by interventions like enriched environment combined with voluntary exercise (EE/VE). The present study sought to assess the effects of EE/VE on molecular mechanisms linked to DYRK1A overexpression in the brain of CBS-deficient mice. EE/VE was applied to 3-month-old female CBS-deficient mice for 1 month. Without intervention, CBS-deficient mice exhibited increased DYRK1A and decreased brain-derived neurotrophic factor (BDNF) levels in the cortex and hippocampus. However, EE/VE rescued these altered DYRK1A and BDNF levels in the hippocampus of CBS-deficient mice. We conclude that exercise combined with enriched environment can restore the altered molecular mechanisms in the brain of CBS-deficient mice.

Prestroke living situation and depression contribute to initial stroke severity and stroke recovery

Substantial evidence from both experimental and clinical studies has demonstrated that social isolation can increase stroke incidence and impair recovery. Social isolation leads to higher rates of recurrent stroke but is often not reported as a risk factor. We examined prospectively collected stroke center database variables, which included prestroke living situation, to determine if social isolation could be determined from existing data using living arrangement as a proxy. Patients were categorized into 4 groups hypothesized to represent increasing levels of social isolation: living with spouse, living with family, living alone with visiting services, and living alone. Initial stroke severity and recovery were measured using the National Institutes of Health Stroke Scale and Barthel Index, respectively. A multivariate model was used to determine the relationship among prestroke living situation, stroke severity, and functional outcome. Patients living alone had less severe strokes on admission and better recovery at 3 months compared with the other cohorts. Patients living alone or those who lived with a spouse had less severe strokes on presentation and better recovery at both 3 and 12 months after stroke compared with the other cohorts. However, on detailed examination, it was found that these patients also had significantly higher prestroke function. Pre-existing depression was significantly higher in women, and depressed patients had poorer outcomes 3 months after stroke. Information regarding isolation is notably absent from most large stroke databases. A more comprehensive evaluation of social interaction should be obtained to more accurately measure social isolation.

Oxidative stress and Down syndrome. Do antioxidants play a role in therapy?

Oxidative stress is a phenomenon associated with imbalance between production of free radicals and reactive metabolites (e.g. superoxide and hydrogen peroxide) and the antioxidant defences. Oxidative stress in individuals with Down syndrome (DS) has been associated with trisomy of the 21st chromosome resulting in DS phenotype as well as with various morphological abnormalities, immune disorders, intellectual disability, premature aging and other biochemical abnormalities. Trisomy 21 in patients with DS results in increased activity of an important antioxidant enzyme Cu/Zn superoxide dismutase (SOD) which gene is located on the 21st chromosome along with other proteins such as transcription factor Ets-2, stress inducing factors (DSCR1) and precursor of beta-amyloid protein responsible for the formation of amyloid plaques in Alzheimer disease. Mentioned proteins are involved in the management of mitochondrial function, thereby promoting mitochondrial theory of aging also in people with DS. In defence against toxic effects of free radicals and their metabolites organism has built antioxidant defence systems. Their lack and reduced function increases oxidative stress resulting in disruption of the structure of important biomolecules, such as proteins, lipids and nucleic acids. This leads to their dysfunctions affecting pathophysiology of organs and the whole organism. This paper examines the impact of antioxidant interventions as well as positive effect of physical exercise on cognitive and learning disabilities of individuals with DS. Potential therapeutic targets on the molecular level (oxidative stress markers, gene for DYRK1A, neutrophic factor BDNF) after intervention of natural polyphenols are also discussed.

Neuroepigenetics of memory formation and impairment: the role of microRNAs

MicroRNAs (miRNAs) are a class of short non-coding RNAs that primarily regulate protein synthesis through reversible translational repression or mRNA degradation. MiRNAs can act by translational control of transcription factors or via direct action on the chromatin, and thereby contribute to the non-genetic control of gene-environment interactions. MiRNAs that regulate components of pathways required for learning and memory further modulate the influence of epigenetics on cognition in the normal and diseased brain. This review summarizes recent data exemplifying the known roles of miRNAs in memory formation in different model organisms, and describes how neuronal plasticity regulates miRNA biogenesis, activity and degradation. It also examines the relevance of miRNAs for memory impairment in human, using recent clinical observations related to neurodevelopmental and neurodegenerative diseases, and discusses the potential mechanisms by which these miRNAs may contribute to memory disorders.