Targeted Disruption of Na⁺/Ca²⁺Exchanger 3 (NCX3) Gene Leads to a Worsening of Ischemic Brain Damage

Abstract

Naϩ /Ca 2ϩ exchanger 3 (NCX3), one of the three isoforms of the NCX family, is highly expressed in the brain and is involved in the maintenance of intracellular Na ϩ and Ca 2ϩ homeostasis. Interestingly, whereas the function of NCX3 under physiological conditions has been determined, its role under anoxia is still unknown. To assess NCX3 role in cerebral ischemia, we exposed ncx3Ϫ/Ϫ mice to transient middle cerebral artery occlusion followed by reperfusion. In addition, to evaluate the effect of ncx3 ablation on neuronal survival, organotypic hippocampal cultures and primary cortical neurons from ncx3Ϫ/Ϫ mice were subjected to oxygen glucose deprivation (OGD) plus reoxygenation. Here we report that ncx3 gene suppression leads to a worsening of brain damage after focal ischemia and to a massive neuronal death in all the hippocampal fields of organotypic cultures as well as in cortical neurons from ncx3Ϫ/Ϫ mice exposed to OGD plus reoxygenation. In addition, in ncx3Ϫ/Ϫ cortical neurons exposed to hypoxia, NCX currents, recorded in the reverse mode of operation, were significantly lower than those detected in ncx3ϩ/ϩ. From these results, NCX3 protein emerges as a new molecular target that may have a potential therapeutic value in modulating cerebral ischemia.

Silencing or knocking out the Na+/Ca2+ exchanger-3 (NCX3) impairs oligodendrocyte differentiation

“…To assess whether NCX3 might have a role in CNS myelination, we analyzed the expression of myelin markers in the oligodendrocytes of mice lacking NCX3, an animal model that has been extensively characterized in our laboratory as well as in others. 22,14,23 For instance, our previous western blot analyses in brain tissue homogenates from ncx3 þ / þ and ncx3 À/À mice have revealed no detectable NCX3 protein levels in ncx3-null mice. 14,23 Colocalization experiments, performed using the neuronal marker NeuN or the oligodendrocyte marker MBP in the presence of the NCX3 antibody, revealed that the NCX3 protein was expressed both in the gray and the white matter of the spinal cord of congenic, wild-type, ncx3 þ / þ mice ( Figure 8A).…”

“…22,14,23 For instance, our previous western blot analyses in brain tissue homogenates from ncx3 þ / þ and ncx3 À/À mice have revealed no detectable NCX3 protein levels in ncx3-null mice. 14,23 Colocalization experiments, performed using the neuronal marker NeuN or the oligodendrocyte marker MBP in the presence of the NCX3 antibody, revealed that the NCX3 protein was expressed both in the gray and the white matter of the spinal cord of congenic, wild-type, ncx3 þ / þ mice ( Figure 8A). Interestingly, spinal cords isolated from ncx3 À/À mice were smaller than those isolated from wild-type, congenic, ncx3 þ / þ mice ( Figure 8B).…”

“…[5][6][7] The Na þ /Ca 2 þ exchanger (NCX), 8 a transmembrane domain protein, which, by operating in a bidirectional way, couples the efflux of Ca 2 þ to the influx of Na þ into the cell or, vice versa, the influx of Ca 2 þ to the efflux of Na þ , is involved in the regulation of diverse neuronal and glial cell functions. 8,9 Furthermore, NCX is involved in regulating intracellular Ca 2 þ concentration under pathological conditions and has been proposed as a potential therapeutic target in different disorders of the nervous system, including de-myelinating conditions such as MS, 10,11 ischemia-reperfusion injury, [12][13][14] and spinal cord injury. 15,16 Three different ncx1, ncx2, and ncx3 genes have been identified in mammals.…”

Dofetilide as Activator of Na/Ca Exchange: New Perspectives on an ‘Old’ Drug

“…In the brain, activation of NCX is apparently part of a protective pathway during ischemia [28,29] and pharmacological activators of NCX would be an interesting tool to further test this pathway. With dofetilide, in the correct experimental circumstances, we could have such a tool.…”

Plasma Calcium Concentration Modifies the Blood Sodium During Hemodialysis: Lessons from Hard Water Syndrome

“…Clearly, since the extracellular proteins can bind both calcium and Na + , some extrarenal form of interaction between the two ions might exist. For instance, it is well known that Unauthenticated Download Date | 5/11/18 1:00 PM many cells express a Na + -Ca +2 Exchanger (NCX), and that there is a perfect coupling between Na + and calcium transcellular fluxes based on their extracellular concentrations [6,7]. The exact knowledge of this interplay is important because it may provide an additional mechanism of sodium regulation, independent of the kidney function; in addition, this regulation might have clinical impact particularly in patients undergoing dialysis (who lack kidney regulation for extracellular sodium and rely on the dialysis system).…”