metallothionein and Hypoxia-Ischemia--Brain

We investigated the effects of the neuroprotective drug cerebrolysin on the autoimmune parameters (FasL, Fas and metallotionein-1) in 20 newborns with perinatal ischemic CNS damage and 20 healthy newborns. The treatment with cerebrolysin in dosage of 0,1 ml per 1 kg of body mass, 10 injections every other day, resulted in the normalization (p<0,001) of the T-lymphocyte apoptosis (the increase of Fas and decrease of FasL) and activation of antioxidant protection through the increase of metallotionein-1 expression. The normalization of the autoimmunity was found to reduce edema and improve the circulation of the brain sites affected with ischemia.

Topics: Amino Acids; Antioxidants; Apoptosis; Autoantibodies; Fas Ligand Protein; Humans; Hypertension; Hypoxia-Ischemia, Brain; Infant, Newborn; Metallothionein; Nootropic Agents; Reverse Transcriptase Polymerase Chain Reaction; T-Lymphocytes

Sub-lethal activation of cell death processes initiate pro-survival signaling cascades. As intracellular Zn(2+) liberation mediates neuronal death pathways, we tested whether a sub-lethal increase in free Zn(2+) could also trigger neuroprotection. Neuronal free Zn(2+) transiently increased following preconditioning, and was both necessary and sufficient for conferring excitotoxic tolerance. Lethal exposure to NMDA led to a delayed increase in Zn(2+) that contributed significantly to excitotoxicity in non-preconditioned neurons, but not in tolerant neurons, unless preconditioning-induced free Zn(2+) was chelated. Thus, preconditioning may trigger the expression of Zn(2+)-regulating processes, which, in turn, prevent subsequent Zn(2+)-mediated toxicity. Indeed, preconditioning increased Zn(2+)-regulated gene expression in neurons. Examination of the molecular signaling mechanism leading to this early Zn(2+) signal revealed a critical role for protein kinase C (PKC) activity, suggesting that PKC may act directly on the intracellular source of Zn(2+). We identified a conserved PKC phosphorylation site at serine-32 (S32) of metallothionein (MT) that was important in modulating Zn(2+)-regulated gene expression and conferring excitotoxic tolerance. Importantly, we observed increased PKC-induced serine phosphorylation in immunopurified MT1, but not in mutant MT1(S32A). These results indicate that neuronal Zn(2+) serves as an important, highly regulated signaling component responsible for the initiation of a neuroprotective pathway.

Topics: Amino Acid Sequence; Animals; Brain Infarction; Cell Death; Cell Survival; Cells, Cultured; Cytoprotection; Gene Expression Regulation; Hypoxia-Ischemia, Brain; Intracellular Fluid; Ischemic Preconditioning; Metallothionein; Nerve Degeneration; Neurons; Phosphorylation; Protein Kinase C; Rats; Serine; Signal Transduction; Zinc

Metallothionein I and II are small metal binding proteins with a high affinity for zinc. They are found in the CNS and are thought to play a role in modulating the effects of free zinc. We hypothesized that MT-I,II deficient mice would have more neurological deficits both functionally and anatomically following a neonatal hypoxic-ischemic (HI) insult than wild-type mice subjected to the same insult. Forty wild-type and 40 MT-I,II deficient C57 X 129T2 F1 P10 mice were randomized to either 45 min of HI or sham HI. Beginning on P50, the mice were given a series of behavioral tests including locomotor activity, novel object recognition, Morris water maze (cued, hidden platform, reduced platform), a 2-week-delayed probe trial and an apomorphine-induced rotation test. At the conclusion of testing, the brains were removed for histological analysis including staining with NeuN and GFAP to assess neuronal loss and reactive gliosis. There were no significant differences in functional or anatomic measures between the wild-type HI mice and the MT-I,II deficient HI mice. The MT-I,II deficient mice exhibited an impaired rate of learning in the spatially oriented mazes but once learned retained the information as well as the wild-type mice. The absence of functional MT-I,II proteins does not result in significantly worse injury following 45 min of HI on P10. The MT-I,II deficient mice have baseline impairments in spatial learning but not retention.

Topics: Analysis of Variance; Animals; Animals, Newborn; Exploratory Behavior; Functional Laterality; Hippocampus; Hypoxia-Ischemia, Brain; Isoenzymes; Maze Learning; Metallothionein; Mice; Mice, Inbred C57BL; Mice, Knockout; Mice, Mutant Strains; Motor Activity; Organ Size; Random Allocation; Retention, Psychology; Single-Blind Method; Zinc