metallothionein and Brain-Ischemia

Methallothionein (MT) is a low molecular weight cysteine rich metalloprotein. In mammals, there are four isoforms (MT-1, -2, -3, and -4) and they have multiple roles, such as the detoxification of heavy metals, regulating essential metal homeostasis, and protecting against oxidative stress. Recently, accumulating studies have suggested that MTs (especially MT-1, -2, and -3) are an important neuroprotective substance for cerebral ischemia and retinal diseases, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP), that are characterized by a progressive retinal degeneration. Oxidative stress and/or zinc toxicity has been implicated as part of the common pathway in these diseases. Studying the expression patterns and functions of MTs may broaden our understanding of the endogenous molecular responses that these diseases trigger, and may help us to develop new therapeutic strategies to treat them. However, the precise roles of MTs within the brain and retina are not fully understood in terms of neuropathological conditions. In this review, we discuss the recent findings focusing on MTs' functions following cerebral ischemia, AMD, and RP.

Topics: Animals; Brain; Brain Ischemia; Humans; Macular Degeneration; Metallothionein; Retina; Retinitis Pigmentosa

Metallothionein-II (MT-II) is an ubiquitously expressed small-molecular-weight protein and highly induced in various species and tissues upon stress, inflammation, and ischemia. MT-deficiency exacerbates ischemic injury in rodent stroke models in vitro and in vivo. However, there is conflicting data on the potential neuroprotective effect of exogenously applied metallothionein. Thus, we applied MT-II in an in vitro stroke model and intraperitoneally (i.p.) in two in vivo standard models of transient middle cerebral artery occlusion (MCAO) (a 'stringent' one [60 min MCAO/48 h reperfusion] and a 'mild' one [30 min MCAO/72 h reperfusion]), as well as i.v. together with recombinant tissue plasminogen activator (rtPA) to evaluate if exogenous MT-II-application protects against ischemic stroke. Whereas MT-II did not protect against 60 min MCAO, there was a significant reduction of direct and indirect infarct volumes and neurological deficit in the MT-II (i.p.) treated animals in the 'mild' model at 3d after MCAO. Furthermore, MT-II also improved survival of the mice after MCAO, suppressed TNF-α mRNA induction in ischemic brain tissue, and protected primary neuronal cells against oxygen-glucose-deprivation in vitro. Thus, exogenous application of MT-II protects against ischemic injury in vitro and in vivo. However, long-term studies with different species and larger sampling sizes are required before a clinical use can be envisaged.

Topics: Animals; Brain Ischemia; Cells, Cultured; Cytokines; In Vitro Techniques; Inflammation Mediators; Male; Metallothionein; Mice; Mice, Inbred C57BL; Neurons; Neuroprotective Agents

Free radicals are known to cause secondary neuronal damage in cerebral ischemia/reperfusion (I/R). We investigated here the neuroprotective effect of resveratrol, a potent antioxidant present in grape seed, against cerebral I/R-induced mitochondrial dysfunctions in hippocampus. Transient rat middle cerebral artery occlusion (MCAO) model of brain ischemia was used to induce brain infarction. Resveratrol (10(-7) g/kg) was given twice intravenously: 15 min pre-occlusion and at the time of reperfusion (2 h post-occlusion). Resveratrol significantly restored ATP content and the activity of mitochondrial respiratory complexes in resveratrol treated group which were severely altered in MCAO group. Western blot analysis showed a marked decrease in cytochrome c release as a result of resveratrol treatment. Electrophoretic migration of hippocampal genomic DNA showed a marked decrease in DNA fragmentation after resveratrol treatment. Notably, expression of Hsp70 and metallothionein (MT) was significantly higher in MCAO group but their expression was more significant in resveratrol treated group. The status of mitochondrial glutathione (GSH), glucose 6-phosphate dehydrogenase (G6-PD) and serum lactate dehydrogenase (LDH) was restored by resveratrol treatment with a significant decrease in mitochondrial lipid peroxidation (LPO), protein carbonyl and intracellular H(2)O(2) content. Resveratrol significantly improved neurological deficits assessed by different scoring methods. Also, the brain infarct volume and brain edema were significantly reduced. Histological analysis of CA1 hippocampal region revealed that resveratrol treatment diminished intercellular and pericellular edema and glial cell infiltration. The findings of this study highlight the ability of resveratrol in anatomical and functional preservation of ischemic neurovascular units and its relevance in the treatment of ischemic stroke.

Topics: Adenosine Triphosphate; Animals; Antioxidants; Brain Ischemia; Cell Death; Cytochromes c; DNA Fragmentation; Glucosephosphate Dehydrogenase; Glutathione; Hippocampus; HSP70 Heat-Shock Proteins; Hydrogen Peroxide; Infarction, Middle Cerebral Artery; Lactate Dehydrogenases; Lipid Peroxidation; Male; Metallothionein; Mitochondria; Neuroprotective Agents; Protein Carbonylation; Rats; Rats, Wistar; Resveratrol; Stilbenes

Metallothioneins (MTs) are small cysteine-rich proteins found widely throughout the mammalian body, including the CNS. MT-1 and -2 protect against reactive oxygen species and free radicals. We investigated the role of MT-1 and -2 using MT-1,-2 knockout (KO) mice. MT-1,-2 KO mice exhibited greater neuronal damage after permanent middle cerebral artery occlusion (MCAO) than wild-type mice. MT-2 mRNA was significantly increased at 6, 12, and 24 h after MCAO in the wild-type mouse brain [as detected by real-time reverse-transcription polymerase chain reaction (RT-PCR)], while MT-1 and MT-3 were decreased at 12 and 24 h. In an immunohistochemical study, MT expression displayed colocalization with glial fibrillary acidic protein (GFAP)-positive cells (astrocytes) in the penumbra area in wild-type mice. Since erythropoietin (EPO) has been reported to induce MT-1 and -2 gene expression in vitro, we examined its effect after permanent MCAO, and explored the possible underlying mechanism by examining MT-1 and -2 induction in vivo. In wild-type mice, EPO significantly reduced both infarct area and volume at 24 h after the ischemic insult. However, in MT-1,-2 KO mice EPO-treatment did not alter infarct volume (vs. vehicle-treatment). In wild-type mice at 6 h after EPO administration, real-time RT-PCR revealed increased MT-1 and -2 mRNA expression in the cerebral cortex (without MCAO). Further, MT-1 and -2 immunoreactivity was increased in the cortex of EPO-treated mice. These findings indicate that MTs are induced, and may be neuroprotective against neuronal damage, after MCAO. Furthermore, EPO is neuroprotective in vivo during permanent MCAO, and this may be at least partly mediated by MTs.

Topics: Animals; Astrocytes; Brain; Brain Infarction; Brain Ischemia; Cytoprotection; Erythropoietin; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Infarction, Middle Cerebral Artery; Male; Metallothionein; Metallothionein 3; Mice; Mice, Inbred C57BL; Mice, Knockout; Nerve Degeneration; Neuroprotective Agents; RNA, Messenger; Up-Regulation

The neuroprotective effect of cilostazol, an antiplatelet drug, was examined after 24 h permanent middle cerebral artery (MCA) occlusion in mice, and explored the possible underlying mechanism by examining metallothionein (MT)-1 and -2 induction in vivo. Cilostazol (30 mg/kg) was intraperitoneally administered at 12 h before, 1 h before, and just after MCA occlusion. Mice were euthanized at 24 h after the occlusion, and the neuronal damage was evaluated using 2,3,5-triphenyltetrazolium chloride (TTC) staining. Cilostazol significantly reduced the infarct area and volume, especially in the cortex. Real-time RT-PCR revealed increased mRNA expressions for MT-1 and -2 in the cortex of normal brains at 6 h after cilostazol treatment without MCA occlusion. MT-1 and -2 immunoreactivity was also increased in the cortex of such mice, and this immunoreactivity was observed in the ischemic hemisphere at 24 h after MCA occlusion (without cilostazol treatment). The strongest MT-1 and -2 immunoreactivity was detected in MCA-occlused mice treated with cilostazol [in the peri-infarct zone of the cortex (penumbral zone)]. These findings indicate that cilostazol has neuroprotective effects in vivo against permanent focal cerebral ischemia, especially in the penumbral zone in the cortex, and that MT-1 and -2 may be partly responsible for these neuroprotective effects.

Topics: Animals; Brain Ischemia; Cerebral Cortex; Cilostazol; Enzyme Induction; Immunohistochemistry; Infarction, Anterior Cerebral Artery; Male; Metallothionein; Mice; Mice, Inbred C57BL; Middle Cerebral Artery; Neuroprotective Agents; Reverse Transcriptase Polymerase Chain Reaction; Tetrazoles

Topics: Animals; Brain Ischemia; Male; Metallothionein; Metallothionein 3; Nerve Tissue Proteins; Neurons; Rats; Rats, Wistar; Reperfusion Injury; RNA, Messenger

We applied serial analysis of gene expression (SAGE) to study differentially expressed genes in mouse brain 14 hr after the induction of focal cerebral ischemia. Analysis of >60,000 transcripts revealed 83 upregulated and 94 downregulated transcripts (more than or equal to eightfold). Reproducibility was demonstrated by performing SAGE in duplicate on the same starting material. Metallothionein-II (MT-II) was the most significantly upregulated transcript in the ischemic hemisphere. MT-I and MT-II are assumed to be induced by metals, glucocorticoids, and inflammatory signals in a coordinated manner, yet their function remains elusive. Upregulation of both MT-I and MT-II was confirmed by Northern blotting. MT-I and MT-II mRNA expression increased as early as 2 hr after 2 hr of transient ischemia, with a maximum after 16 hr. Western blotting and immunohistochemistry revealed MT-I/-II upregulation in the ischemic hemisphere, whereas double labeling demonstrated the colocalization of MT with markers for astrocytes as well as for monocytes/macrophages. MT-I- and MT-II-deficient mice developed approximately threefold larger infarcts than wild-type mice and a significantly worse neurological outcome. For the first time we make available a comprehensive data set on brain ischemic gene expression and underscore the important protective role of metallothioneins in ischemic damage of the brain. Our results demonstrate the usefulness of SAGE to screen functionally relevant genes and the power of knock-out models in linking function to expression data generated by high throughput techniques.

Topics: Animals; Blotting, Northern; Blotting, Western; Brain; Brain Ischemia; Disease Models, Animal; Gene Expression Profiling; Male; Metallothionein; Mice; Mice, Inbred C57BL; Mice, Knockout; Microcirculation; Monte Carlo Method; Neuroprotective Agents; Reproducibility of Results; RNA, Messenger; Time Factors; Up-Regulation

Metallothioneins (MTs) are cysteine-rich metal-binding proteins that are potentially involved in zinc homeostasis and free radical scavenging. The expression pattern of MT-1 and the binding activity of various MT-1 promoter elements were investigated after mild focal cerebral ischemia in the rat. Transient focal ischemia was induced by occluding both common carotid arteries and the right middle cerebral artery for 30 min. By the use of real-time quantitative PCR, a 10-fold increase in MT-1 and -2 mRNA levels was found in the cortex 24 hr after reperfusion. In situ hybridization and immunocytochemistry showed a rapid increase in MT-1 and -2 mRNA and MT protein in endothelial cells of microvessels at 6 hr after reperfusion, followed by an increased expression in astrocytes of the infarcted cortex at 24 hr after reperfusion. The early increase in MT expression preceded an increase in cerebral edema measured with T2-weighted magnetic resonance imaging. Gel shift assays were performed on nuclear extracts prepared from cortices before and at 6 and 24 hr after reperfusion. Increased binding activity was found at an antioxidant/electrophilic response element (ARE) sequence in the MT-1 promoter at 6 hr with a lower and variable binding activity at 24 hr after reperfusion. Constitutive binding activity was found for Sp1 and a metal response element in the MT-1 promoter that did not increase after ischemia and reperfusion. This study suggests a role of ARE-binding proteins in inducing cerebral MT-1 expression and implicates MT-1 as one of the early detoxifying genes in an endogenous defense response to cerebral ischemia and reperfusion.

Topics: Animals; Antioxidants; Brain Edema; Brain Ischemia; Cerebral Cortex; DNA-Binding Proteins; Endothelium, Vascular; Gene Expression Regulation; Magnetic Resonance Imaging; Metallothionein; Neuroglia; Promoter Regions, Genetic; Rats; Rats, Long-Evans; Reperfusion; Response Elements; RNA, Messenger; Sp1 Transcription Factor; Transcription Factors

Metallothioneins (MTs) are a family of metal binding proteins that have been proposed to participate in a cellular defense against zinc toxicity and free radicals. In the present study, we investigated whether increased expression of MT in MT-1 isoform-overexpressing transgenic mice (MT-TG) affords protection against mild focal cerebral ischemia and reperfusion. Transient focal ischemia was induced in control (wild type) and MT-TG mice by occluding the right middle cerebral artery for 45 min. Upon reperfusion, cerebral edema slowly developed and peaked at 24 hr as shown by T2-weighted MRI. The volume of affected tissue was on the average 42% smaller in MT-TG mice compared with control mice at 6, 9, 24, and 72 hr and 14 days postreperfusion (P < 0.01). In addition, functional studies showed that 3 weeks after reperfusion MT-TG mice showed a significantly better motor performance compared with control mice (P = 0.011). Although cortical baseline levels of MT-1 mRNA were similar in control and MT-TG mice, there was an increase in MT-1 mRNA levels in the ischemic cortex of MT-TG mice to 7.5 times baseline levels compared with an increase to 2.3 times baseline levels in control mice 24 hr after reperfusion. In addition, MT-TG mice showed an increased MT immunoreactivity in astrocytes, vascular endothelial cells, and neurons 24 hr after reperfusion whereas in control mice MT immunoreactivity was restricted mainly to astrocytes and decreased in the infarcted tissue. These results provide evidence that increased expression of MT-1 protects against focal cerebral ischemia and reperfusion.

Topics: Animals; Behavior, Animal; Brain Ischemia; Immunohistochemistry; Metallothionein; Mice; Reperfusion; RNA, Messenger

The metallothioneins in vitro are both effective free radical and transitional metal ion scavengers. For this reason we investigated the expression of this protein in the normal CNS and after ischaemia using a monoclonal anti-metallothionein antibody to metallothionein isoforms I and II. Using immunohistochemistry and confocal laser scanning microscopy, we found anti-GFAP and anti-metallothionein were co-localized in astrocytes at the edges of infarcts. Energy dispersive X-ray microanalysis demonstrated high levels of copper and iron in the metallothionein positive reactive astrocytes. On the basis of the in vitro properties of these proteins, the functional importance of metallothionein in reactive astrocytes could be as a free radical scavenger and metal ion chelator.

Topics: Aged; Aged, 80 and over; Antibodies, Monoclonal; Astrocytes; Brain Ischemia; Cerebral Infarction; Electron Probe Microanalysis; Fluorescent Antibody Technique, Direct; Glial Fibrillary Acidic Protein; Humans; Immunoenzyme Techniques; Immunohistochemistry; Isomerism; Metallothionein; Microscopy, Confocal; Middle Aged