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. 2017 Dec 25;9(6):192-201.
eCollection 2017.

Condition-specific transcriptional regulation of neuronal ion channel genes in brain ischemia

Affiliations

Condition-specific transcriptional regulation of neuronal ion channel genes in brain ischemia

Luisa Hernandez-Encarnacion et al. Int J Physiol Pathophysiol Pharmacol. .

Abstract

In the context of seeking novel therapeutic targets for treating ischemic stroke, the preconditioning ischemia-induced brain ischemic tolerance has been used as a model of endogenously operative, broad-based neuroprotective mechanisms. Targeting such mechanisms is considered potentially less prone to adverse side effects, as those seen in many failed clinical trials that focus on single targets using exogenous compounds. Results from previous studies have revealed an overall decrease in potassium channel activity in tolerance development. The objective of this study is to identify ion channel genes that are differentially regulated under different brain ischemic conditions, as a mean to identify those ion channels that are associated with ischemic brain injury and ischemic tolerance. In mice in vivo, transient focal cerebral ischemia was induced by middle cerebral artery occlusion. In cultured neuronal cells in vitro, simulated ischemia was modeled by oxygen-glucose deprivation. For both in vivo and in vitro studies, three principal ischemic conditions were included: ischemic-preconditioned, injured and tolerant, respectively, plus appropriate controls. In these model systems, transcript levels of a panel of 84 neuronal ion channels genes were analyzed with a quantitative real-time PCR mini-array. The results showed that, both in vivo and in vitro, there was a predominant down regulation in neuronal ion channel genes under ischemic-tolerant conditions, and an up regulation in ischemic injury. Similar changes were observed among potassium, sodium and calcium channel genes. A number of regulated genes exhibited opposing changes under ischemic-injured and ischemic-tolerant conditions. This subset of ion channel genes exemplifies potentially novel leads for developing multi-factorial therapeutic targets for treating ischemic stroke.

Keywords: Ischemic stroke; ion channels; neuronal excitability; neuroprotection.

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Figures

Figure 1
Figure 1
Experimental paradigm. The figure illustrates the experimental paradigm by which three principal ischemic conditions were modeled: Ischemic-preconditioned (PC), Ischemic-injured (INJ), and Ischemic-tolerant (TOL). In mice, the preconditioning or injurious ischemia was induced by 15 min or 60 min MCAO, respectively, followed by reperfusions for the numbers of hours noted in the figure (recovery), whereas ischemic tolerance was achieved by 15 min preconditioning MCAO followed by 72 h reperfusion, prior to the 60 min MCAO. In differentiated NS20Y cell cultures, the conditions of preconditioned, injured and tolerant were modeled by subjecting cells to OGD and subsequent recovery incubations for the noted periods of time, respectively. Controls (sham-operated animals or normoxic cell cultures) followed the time regimes of that of injurious groups, respectively.
Figure 2
Figure 2
Heatmaps of expressional changes in neuronal ion channel genes under the three principal ischemic conditions. The heatmaps were generated using the fold regulations listed in Table 1 and arranged according to the tightest clustering. The scale bar indicates the direction of changes (+ and -, an increase or decrease, respectively, when ischemic groups were compared with the appropriate controls). A. Mouse brains; B. Cultured neuronal NS20Y cells. PC, INJ, and TOL: Same as in Figure 1.
Figure 3
Figure 3
Numbers of regulated ion channel genes and directions of their changes. The bars represent numbers of regulated genes under different ischemic conditions (A), or average fold regulations for each of the noted ion channel types under different ischemic conditions (B. mouse brains; C. NS20Y cells). Positive (open bars) and negative (filled bars) values indicate up and down regulations, respectively. PC, INJ, and TOL: Same as in Figure 1.

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