Metallothionein expression and roles in the central nervous system

Metallothioneins (MTs) are low-molecular-weight (6-7kD) nonenzymatic proteins (60-68 amino acid residues, 25-30% being cysteine) ubiquitously expressed in the animal kingdom. In the central nervous system (CNS), three MT isoforms are known, namely MT-I, MT-II, andMT-III. MT-I andMT-II (MT-I+II) are regulated and expressed coordinately and are currently the best characterized MT isoforms. This review will focus on the expression and roles of MT-I+II in the CNS. MT-I+II are implicated in diverse physiological and pathophysiological functions, such as metal ion metabolism, regulation of the CNS inflammatory response, protection against reactive oxygen species and oxidative stress, reduction of apoptotic cell death, and stimulation of neuroregeneration and brain tissue repair in vivo. Accordingly, brain tissue damage and neuro degeneration during pathological conditions and the accompanying mortality and clinical symptoms are altogether significantly increased in MT-I+II deficient mice, while the opposite is observed after medical MT-II treatment and in MT-I overexpressing mice. Consequently, MT-I+II are likely essential factors in CNS disorders, which suggests a potential therapeutic use of these proteins.Biomedical Reviews 2002; 13: 1-15

From bone marrow to brain: stem cells in neuroprotection, plasticity, and neuroregeneration

At present, curative therapies for neurological diseases are limited, even though they are prevalent worldwide. So far, molecular strategies developed for brain disorders act through one single molecular mechanism, yet, these diseases are multifactorial and highly complex, as to why a successful therapy likely calls for a more multifaceted and cell-based approach. The bone marrow contains a mixed stem and progenitor cell population including hematopoietic stem cells (HSC) and mesenchymal stromal stem cells (MSC), which are potential endogenous candidates for cell-based therapy in various brain disorders like stroke, trauma, and neurodegeneration. Unlike the neural stem cells (NSC), bone marrow HSC are readily isolated, mobilized and expanded by means of treatment with granulocyte-colony stimulating factor (G-CSF) and CXCR4-antagonist plerixafor. Once in the blood circulation, the cells preferentially home to injured tissues including the brain. Bone marrow cells may convey neuroprotection, plasticity, and neuroregeneration by different mechanisms of action, which include either transdifferentiation or cell-cell fusion with resident brain cells. Bone marrow cells also benefit the injured brain by secreting bioactive factors, which in a paracrine manner convey intrinsic repair and enhance neurogenesis. Furthermore, transplanted MSC may activate the astrocytes leading to increased glial secretion of neurotrophic growth factors and enhanced proliferation and migration of the resident NSC. These neuroregenerative mechanisms of action are not mutually exclusive, in fact they may provide a multifaceted therapeutic approach, which is requested in order to move neurorestorative and protective strategies into the clinic.Biomedical Reviews 2011; 22: 1-6

The Balance between Life and Death of Cells: Roles of Metallothioneins

Metallothionein (MT) is a highly conserved, low-molecular-weight, cysteine-rich protein that occurs in 4 isoforms (MT-I to MT-IV), of which MT-I+II are the major and best characterized proteins

Chemical Blocking of Zinc Ions in CNS Increases Neuronal Damage Following Traumatic Brain Injury (TBI) in Mice

Traumatic brain injury (TBI) is one of the leading causes of disability and death among young people. Although much is already known about secondary brain damage the full range of brain tissue responses to TBI remains to be elucidated. A population of neurons located in cerebral areas associated with higher cognitive functions harbours a vesicular zinc pool co-localized with glutamate. This zinc enriched pool of synaptic vesicles has been hypothesized to take part in the injurious signalling cascade that follows pathological conditions such as seizures, ischemia and traumatic brain injury. Pathological release of excess zinc ions from pre-synaptic vesicles has been suggested to mediate cell damage/death to postsynaptic neurons.In order to substantiate the influence of vesicular zinc ions on TBI, we designed a study in which damage and zinc movements were analysed in several different ways. Twenty-four hours after TBI ZnT3-KO mice (mice without vesicular zinc) were compared to littermate Wild Type (WT) mice (mice with vesicular zinc) with regard to histopathology. Furthermore, in order to evaluate a possible neuro-protective dimension of chemical blocking of vesicular zinc, we treated lesioned mice with either DEDTC or selenite. Our study revealed that chemical blocking of vesicular zinc ions, either by chelation with DEDTC or accumulation in zinc-selenium nanocrystals, worsened the effects on the aftermath of TBI in the WT mice by increasing the number of necrotic and apoptotic cells within the first 24 hours after TBI, when compared to those of chemically untreated WT mice.ZnT3-KO mice revealed more damage after TBI compared to WT controls. Following treatment with DEDTC or selenium an increase in the number of both dead and apoptotic cells were seen in the controls within the first 24 hours after TBI while the degree of damage in the ZnT3-KO mice remained largely unchanged. Further analyses revealed that the damage development in the two mouse strains was almost identical after either zinc chelation or zinc complexion therapy

Generalization of DNA microarray dispersion properties: microarray equivalent of t-distribution

BACKGROUND: DNA microarrays are a powerful technology that can provide a wealth of gene expression data for disease studies, drug development, and a wide scope of other investigations. Because of the large volume and inherent variability of DNA microarray data, many new statistical methods have been developed for evaluating the significance of the observed differences in gene expression. However, until now little attention has been given to the characterization of dispersion of DNA microarray data. RESULTS: Here we examine the expression data obtained from 682 Affymetrix GeneChips(® )with 22 different types and we demonstrate that the Gaussian (normal) frequency distribution is characteristic for the variability of gene expression values. However, typically 5 to 15% of the samples deviate from normality. Furthermore, it is shown that the frequency distributions of the difference of expression in subsets of ordered, consecutive pairs of genes (consecutive samples) in pair-wise comparisons of replicate experiments are also normal. We describe a consecutive sampling method, which is employed to calculate the characteristic function approximating standard deviation and show that the standard deviation derived from the consecutive samples is equivalent to the standard deviation obtained from individual genes. Finally, we determine the boundaries of probability intervals and demonstrate that the coefficients defining the intervals are independent of sample characteristics, variability of data, laboratory conditions and type of chips. These coefficients are very closely correlated with Student's t-distribution. CONCLUSION: In this study we ascertained that the non-systematic variations possess Gaussian distribution, determined the probability intervals and demonstrated that the K(α )coefficients defining these intervals are invariant; these coefficients offer a convenient universal measure of dispersion of data. The fact that the K(α )distributions are so close to t-distribution and independent of conditions and type of arrays suggests that the quantitative data provided by Affymetrix technology give "true" representation of physical processes, involved in measurement of RNA abundance. REVIEWERS: This article was reviewed by Yoav Gilad (nominated by Doron Lancet), Sach Mukherjee (nominated by Sandrine Dudoit) and Amir Niknejad and Shmuel Friedland (nominated by Neil Smalheiser)

Recombinant human erythropoietin increases survival and reduces neuronal apoptosis in a murine model of cerebral malaria

<p>Abstract</p> <p>Background</p> <p>Cerebral malaria (CM) is an acute encephalopathy with increased pro-inflammatory cytokines, sequestration of parasitized erythrocytes and localized ischaemia. In children CM induces cognitive impairment in about 10% of the survivors. Erythropoietin (Epo) has – besides of its well known haematopoietic properties – significant anti-inflammatory, antioxidant and anti-apoptotic effects in various brain disorders. The neurobiological responses to exogenously injected Epo during murine CM were examined.</p> <p>Methods</p> <p>Female C57BL/6j mice (4–6 weeks), infected with <it>Plasmodium berghei </it>ANKA, were treated with recombinant human Epo (rhEpo; 50–5000 U/kg/OD, i.p.) at different time points. The effect on survival was measured. Brain pathology was investigated by TUNEL (Terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP)-digoxigenin nick end labelling), as a marker of apoptosis. Gene expression in brain tissue was measured by real time PCR.</p> <p>Results</p> <p>Treatment with rhEpo increased survival in mice with CM in a dose- and time-dependent manner and reduced apoptotic cell death of neurons as well as the expression of pro-inflammatory cytokines in the brain. This neuroprotective effect appeared to be independent of the haematopoietic effect.</p> <p>Conclusion</p> <p>These results and its excellent safety profile in humans makes rhEpo a potential candidate for adjunct treatment of CM.</p

Hydrocephalus induces dynamic spatiotemporal regulation of aquaporin-4 expression in the rat brain

<p>Abstract</p> <p>Background</p> <p>The water channel protein aquaporin-4 (AQP4) is reported to be of possible major importance for accessory cerebrospinal fluid (CSF) circulation pathways. We hypothesized that changes in AQP4 expression in specific brain regions correspond to the severity and duration of hydrocephalus.</p> <p>Methods</p> <p>Hydrocephalus was induced in adult rats (~8 weeks) by intracisternal kaolin injection and evaluated after two days, one week and two weeks. Using magnetic resonance imaging (MRI) we quantified lateral ventricular volume, water diffusion and blood-brain barrier properties in hydrocephalic and control animals. The brains were analysed for AQP4 density by western blotting and localisation by immunohistochemistry. Double fluorescence labelling was used to study cell specific origin of AQP4.</p> <p>Results</p> <p>Lateral ventricular volume was significantly increased over control at all time points after induction and the periventricular apparent diffusion coefficient (ADC) value significantly increased after one and two weeks of hydrocephalus. Relative AQP4 density was significantly decreased in both cortex and periventricular region after two days and normalized after one week. After two weeks, periventricular AQP4 expression was significantly increased. Relative periventricular AQP4 density was significantly correlated to lateral ventricular volume. AQP4 immunohistochemical analysis demonstrated the morphological expression pattern of AQP4 in hydrocephalus in astrocytes and ventricular ependyma. AQP4 co-localized with astrocytic glial fibrillary acidic protein (GFAP) in glia limitans. In vascular structures, AQP4 co-localized to astroglia but not to microglia or endothelial cells.</p> <p>Conclusions</p> <p>AQP4 levels are significantly altered in a time and region dependent manner in kaolin-induced hydrocephalus. The presented data suggest that AQP4 could play an important neurodefensive role, and may be a promising future pharmaceutical target in hydrocephalus and CSF disorders.</p