Metabolomics and metabolites in ischemic stroke.

Stroke is a major reason for disability and the second highest cause of death in the world. When a patient is admitted to a hospital, it is necessary to identify the type of stroke, and the likelihood for development of a recurrent stroke, vascular dementia, and depression. These factors could be determined using different biomarkers.

Disabling phosphorylation at the homer ligand of the metabotropic glutamate receptor 5 alleviates complete Freund's adjuvant-induced inflammatory pain.

Metabotropic glutamate receptor 5 (mGluR5) has been reported to contribute to inflammatory pain. The intracellular C-terminal domain has a Homer-binding motif that can form an mGluR5/Homer complex. Phosphorylation of mGluR5 at the Homer binding domain enhances the mGluR5/Homer interaction and modulates intracellular signal transduction.

High Concentration of Ketone Body β-Hydroxybutyrate Modifies Synaptic Vesicle Cycle and Depolarizes Plasma Membrane of Rat Brain Synaptosomes.

Ketoacidosis is a dangerous complication of diabetes mellitus in which plasma levels of ketone bodies can reach 20-25 mM. This condition is life-threatening. In contrast, a ketogenic diet, achieving plasma levels of ketone bodies of about 4-5 mM, can be used for treating different brain diseases.

Calcium release from intracellular stores is involved in mitochondria depolarization after lowering extracellular pH in rat brain synaptosomes.

In the brain, pH can be lowered in both healthy and disease states. Previously, we showed that moderate extracellular acidification (down to pHo 7.0), but not intracellular acidification, leads to mitochondrial depolarization in synaptosomes.

Ketogenic diet ketoacidosis: what determines the influence of ketone bodies on neurons?

Glucose is the main energy substrate for neurons, however, at certain conditions, e.g. in starvation, these cells could also use ketone bodies.

Metabolic regulation of synaptic activity.

Brain tissue is bioenergetically expensive. In humans, it composes approximately 2% of body weight and accounts for approximately 20% of calorie consumption. The brain consumes energy mostly for ion and neurotransmitter transport, a process that occurs primarily in synapses.

Reduced Synaptic Vesicle Recycling during Hypoxia in Cultured Cortical Neurons.

Improvement of neuronal recovery in the ischemic penumbra, an area around the core of a brain infarct with some remaining perfusion, has a large potential for the development of therapy against acute ischemic stroke. However, mechanisms that lead to either recovery or secondary damage in the penumbra largely remain unclear. Recent studies in cultured networks of cortical neurons showed that failure of synaptic transmission (referred to as synaptic failure) is a critical factor in the penumbral area, but the mechanisms that lead to synaptic failure are still under investigation.

Biogenetic and morphofunctional heterogeneity of mitochondria: the case of synaptic mitochondria.

The mitochondria of different cells are different in their morphological and biochemical properties. These organelles generate free radicals during activity, leading inevitably to mitochondrial DNA damage. It is not clear how this problem is addressed in long-lived cells, such as neurons.

β-Hydroxybutyrate supports synaptic vesicle cycling but reduces endocytosis and exocytosis in rat brain synaptosomes.

The ketogenic diet is used as a prophylactic treatment for different types of brain diseases, such as epilepsy or Alzheimer's disease. In such a diet, carbohydrates are replaced by fats in everyday food, resulting in an elevation of blood-borne ketone bodies levels. Despite clinical applications of this treatment, the molecular mechanisms by which the ketogenic diet exerts its beneficial effects are still uncertain.

Influence of Glucose Deprivation on Membrane Potentials of Plasma Membranes, Mitochondria and Synaptic Vesicles in Rat Brain Synaptosomes.

Hypoglycemia can cause neuronal cell death similar to that of glutamate-induced cell death. In the present paper, we investigated the effect of glucose removal from incubation medium on changes of mitochondrial and plasma membrane potentials in rat brain synaptosomes using the fluorescent dyes DiSC3(5) and JC-1. We also monitored pH gradients in synaptic vesicles and their recycling by the fluorescent dye acridine orange.

Role of iron, zinc and reduced glutathione in oxidative stress induction by low pH in rat brain synaptosomes.

Brain ischemia leads to a decrease in pHo. We have shown previously in synaptosomes that the extracellular acidification induces depolarization of mitochondria followed by synthesis of superoxide anions and oxidative stress. Here, we investigated the effects of lowered pHo on oxidative stress and membrane potentials in synaptosomes treated by the iron chelator deferoxamine and zinc chelator TPEN.

Piracetam induces plasma membrane depolarization in rat brain synaptosomes.

Piracetam is a cyclic derivative of γ-aminobutyric acid (GABA). It was the first nootropic drug approved for clinical use. However, mechanism of its action is still not clear.

Influence of intra- and extracellular acidification on free radical formation and mitochondria membrane potential in rat brain synaptosomes.

Brain ischemia is accompanied by lowering of intra- and extracellular pH. Stroke often leads to irreversible damage of synaptic transmission by unknown mechanism. We investigated an influence of lowering of pH(i) and pH(o) on free radical formation in synaptosomes.

Glutamate-induced free radical formation in rat brain synaptosomes is not dependent on intrasynaptosomal mitochondria membrane potential.

Glutamate induces reactive oxygen species formation (ROS) in neurons. Free radicals can potentially be synthesized by NADPH oxidase or mitochondria. The primary source of ROS origin has yet to be identified.

Ca2+ nanodomain-mediated component of swelling-induced volume-sensitive outwardly rectifying anion current triggered by autocrine action of ATP in mouse astrocytes.

The volume-sensitive outwardly rectifying (VSOR) anion channel provides a major pathway for anion transport during cell volume regulation. It is typically activated in response to cell swelling, but how the channel senses the swelling remains unclear. Meanwhile, we recently found that in mouse astrocytes the channel is activated by an inflammatory chemical mediator, bradykinin, without cell swelling and that the activation is regulated via high concentration regions of intracellular Ca(2+) ([Ca(2+)](i)) in the immediate vicinity of open Ca(2+)-permeable channels, so-called Ca(2+) nanodomains.

Presynaptic glycine receptors influence plasma membrane potential and glutamate release.

Glycine is a classical inhibitory neurotransmitter however presynaptic glycine receptors have rather depolarizing action. Reasons for latter phenomenon are unknown. In the present paper we have investigated how glycine influences cytosolic chloride level monitored by fluorescent dye SPQ, membrane potential monitored by fluorescent dye DiSC3(5) and [(14)C]-glutamate release in synaptosomes.

Are synapses targets of nanoparticles?

The last few years have been marked by real breakthroughs in the field of nanotechnology. Application of nanoparticles was proposed for diagnosis and treatment of different central nervous system diseases. Exposure to nanoparticles in vivo increases the risk of onset of neurodegenerative diseases and nanoparticles are apparently able to kill neurons in vitro.

Ferritin, a protein containing iron nanoparticles, induces reactive oxygen species formation and inhibits glutamate uptake in rat brain synaptosomes.

Nanoparticles are currently used in medicine as agents for targeted drug delivery and imaging. However it has been demonstrated that nanoparticles induce neurodegeneration in vivo and kill neurons in vitro. The cellular and molecular bases of this phenomenon are still unclear.

Influence of integrin-blocking peptide on gadolinium- and hypertonic shrinking-induced neurotransmitter release in rat brain synaptosomes.

Polyvalent cations and hypertonic shrinking of presynaptic endings lead to calcium-independent exocytosis in various synapses. In the present study we have investigated the contribution of integrins to this phenomenon. It was found that hypertonic shrinking, polyvalent cations ruthenium red and gadolinium results in dose-dependent calcium-independent neurotransmitter release in rat brain synaptosomes.

Hypertonic shrinking but not hypotonic swelling increases sodium concentration in rat brain synaptosomes.

Neurotransmitter release is dependent on both calcium and sodium influx. Hypotonic swelling and hypertonic shrinking of neurons evokes calcium-independent exocytosis of neurotransmitters into the synaptic cleft. To date, there are not too much data available on relationship between extracellular osmolarity and sodium concentration in presynaptic endings.

Influence of cholesterol depletion in plasma membrane of rat brain synaptosomes on calcium-dependent and calcium-independent exocytosis.

It is well established that calcium-dependent neurotransmitter release and exocytosis can be regulated by altering the cholesterol content of the plasma membrane. We have compared the influence of cholesterol depletion of synaptosomal plasma membrane by 15 mM methyl-beta-cyclodextrin (MCD) treatment on calcium-dependent release of D-[(3)H]aspartate induced by the calcium ionophore A23187 and on calcium-independent release induced by hypertonic shrinking or polyvalent cations. We found that decrease of cholesterol concentration by 9.

Role of calcium in exocytosis induced by hypotonic swelling.

We studied the influence of Ca(2+) on exocytosis induced by hypotonic shock using the fluorescent dyes acridine orange FM1-43 and FM2-10. It was shown using acridine orange that lowering osmolarity to 230 mOsm/L induces exocytosis both in calcium-containing and calcium-free media. By contrast, we were able to demonstrate calcium dependence of exocytosis using styryl dyes.

Calcium regulates the mode of exocytosis induced by hypotonic shock in isolated neuronal presynaptic endings.

A decrease in the osmolarity of incubation medium is accompanied by calcium influx in neuronal presynaptic endings. We studied the influence of Ca2+ on exocytosis induced by hypotonic shock using the hydrophilic fluorescent dye acridine orange and the hydrophobic fluorescent dye FM2-10. It was shown using acridine orange that lowering of osmolarity to 230 mOsm/l induces exocytosis both in calcium-containing and calcium-free medium.