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eBook details
- Title: Studies of the Change of Intracellular Zinc Triggered by Exogenous NO and the Induction of Tolerance to OGD by Exogenous NO and Lipophilic Metal Chelators in Cultured Cortical Neurons
- Author : Wei Lin
- Release Date : January 18, 2013
- Genre: Medical,Books,Professional & Technical,
- Pages : * pages
- Size : 12527 KB
Description
Intracellular Zn2+ release and concomitant cell death after prolonged exposure to NO was demonstrated by different studies. In this study, cortical neurons were loaded with the Zn2+ selective fluorophore FluoZin-3 and treated with NO generator, spermine NONOate. Microfluorimetry was used to detect intracellular Zn2+ change. N,N,N',N'-Tetrakis-(2-pyridylmethyl)-Ethylenediamine (TPEN) was applied to eliminate Zn2+ signals. A significant increase of intracellular fluorescence was detected during a 5 min perfusion with NO. The increased intracellular Zn2+ appeared to peak at 1 ΞM. The NO scavenger hemoglobin blocked the effects and the inactive analog of the spermine NONOate, spermine, was without effect. These data indicate that in vivo release of NO may elevate intracellular Zn2+ in neurons that may have physiological significance.Neurons exposed to oxygen glucose deprivation (OGD) were used as an in vitro model to study ischemic injury. After a 5 min pretreatment with spermine NONOate 24 hrs prior to OGD, neurons exhibited tolerance. Coincubation of NO with TPEN prevented the development of tolerance. The effect of TPEN could be blocked by coadministration with Zn2+ but not Cu2+ or Fe2+. Increased intracellular Zn2+ alone was not sufficient to induce tolerance. Cycloheximide (CHX) blocked the induction of 4 tolerance suggesting that de novo protein synthesis is necessary for development of tolerance. Using S35 incorporation assay, TPEN was shown to inhibit new protein synthesis and addition of Zn2+ reversed the effect by TPEN. ERK1/2 and RSK inhibitors blocked the induction of tolerance indicating that ERK1/2-RSK pathway was involved.Clioquinol (Cq), a metal chelator with neuroprotective effects in Alzheimer's disease, was shown to induced tolerance. TPEN prevented the induction of tolerance by Cq. DP-b99 is a lipophilic metal chelator shown to be effective in the treatment of stroke. A 5 min pretreatment with DP-b99 induced a robust tolerance. TPEN or CHX blocked tolerance indicating that DP-b99 shares similar mechanisms with NO. ERK1/2 and RSK inhibitors blocked the induction of tolerance by DP-b99 indicating that ERK1/2-RSK pathway is also involved. Incubation with DP-b99 caused an increase in cellular Ca2+ content detected by ICP-OES. The presence of extracellular Ca2+ was shown to be necessary for the induction of tolerance. The NOS inhibitor, L-NAME was able to prevent the induction of tolerance by DP-b99 suggesting that the production of NO is the downstream effecter.This study suggests that Zn2+ action is involved in the neuroprotection mechanism against ischemic cell death.
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