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The remodelling of neuronal ionic homeostasis by altered channels and transporters is a critical feature of the Alzheimer's disease (AD) pathogenesis. Different reports converge on the concept that the Na+/Ca2+ exchanger (NCX), as one of the main regulators of Na+ and Ca2+ concentrations and signalling, could exert a neuroprotective role in AD. The activity of NCX has been found to be increased in AD brains, where it seemed to correlate with an increased neuronal survival. Moreover, the enhancement of the NCX3 currents (INCX) in primary neurons treated with the neurotoxic amyloid β 1–42 (Aβ1–42) oligomers prevented the endoplasmic reticulum (ER) stress and neuronal death. The present study has been designed to investigate any possible modulation of the INCX, the functional interaction between NCX and the NaV1.6 channel, and their impact on the Ca2+ homeostasis in a transgenic in vitro model of AD, the primary hippocampal neurons from the Tg2576 mouse, which overproduce the Aβ1–42 peptide. Electrophysiological studies, carried in the presence of siRNA and the isoform-selective NCX inhibitor KB-R7943, showed that the activity of a specific NCX isoform, NCX3, was upregulated in its reverse, Ca2+ influx mode of operation in the Tg2576 neurons. The enhanced NCX activity contributed, in turn, to increase the ER Ca2+ content, without affecting the cytosolic Ca2+ concentrations of the Tg2576 neurons. Interestingly, our experiments have also uncovered a functional coupling between NCX3 and the voltage-gated NaV1.6 channels. In particular, the increased NaV1.6 currents appeared to be responsible for the upregulation of the reverse mode of NCX3, since both TTX and the Streptomyces griseolus antibiotic anisomycin, by reducing the NaV1.6 currents, counteracted the increase of the INCX in the Tg2576 neurons. In agreement, our immunofluorescence analyses revealed that the NCX3/NaV1.6 co-expression was increased in the Tg2576 hippocampal neurons in comparison with the WT neurons. Collectively, these findings indicate that NCX3 might intervene in the Ca2+ remodelling occurring in the Tg2576 primary neurons thus emerging as a molecular target with a neuroprotective potential, and provide a new outcome of the NaV1.6 upregulation related to the modulation of the intracellular Ca2+ concentrations in AD neurons. [ABSTRACT FROM AUTHOR]

Introduction: Addressing the formidable therapeutic hurdles posed by Alzheimer's disease (AD), our study delves into the central role of amyloid β 1-42 (Aβ1-42) protein aggregation in its onset. Aim: Our investigation aims to assess the therapeutic potential of the isoindolinone derivative 3-(3-oxoisoindolin-1-yl)pentane-2,4-dione (ISOAC1) against the Aβ1-42-induced toxicity. Material and methods: Employing a combination of thioflavin T fluorescence assay and biological and cellular approaches, alongside other experimental methods, we explored ISOAC1's ability to mitigate Aβ1-42 aggregation and toxicity. Results and conclusions: Our study unveils ISOAC1's capacity to disrupt Aβ1-42 aggregation and impede its transition towards β-sheet structures. Furthermore, our findings shed light on ISOAC1's binding mechanisms with Aβ1-42, indicating its promise as a therapeutic agent. ISOAC1 emerges as a compelling neuroprotective compound, offering novel avenues for AD treatment. [ABSTRACT FROM AUTHOR]

Introduction: Alzheimer's disease (AD) presents significant therapeutic challenges, with amyloid β1-42 (Aβ1-42) protein aggregation playing a central role in its pathogenesis. Aim: Our study investigates the potential therapeutic efficacy of the isoindolinone derivative 3-(3-oxoisoindolin-1-yl)pentane-2,4-dione (ISOAC1) against Aβ1-42-induced toxicity. Material and methods: We employed spectroscopic and computational approaches to explore ISOAC1's ability to mitigate Aβ1-42 aggregation and its consequent toxicity. Other experimental analyses included Thioflavin T fluorescence assay, and Western blotting. Results: Our findings reveal ISOAC1's capacity to disrupt Aβ1-42 aggregation and hinder its transition towards β-sheet structures. Computational investigations elucidate ISOAC1's binding mechanisms with Aβ1-42, highlighting its potential as a therapeutic agent. Conclusions: ISOAC1 emerges as a promising neuroprotective compound, offering insights into novel therapeutic strategies for AD treatment. The combined spectroscopic and computational approach herein presented provides a comprehensive understanding of ISOAC1's mechanism of action against Aβ1-42-induced toxicity. [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) is a neurodegenerative disorder leading to cognitive deficits and cognitive decline. Since no cure or preventing therapy is currently available to counteract AD, natural‐derived compounds are investigated to find new potential neuroprotective agents for its treatment. In the present study, we tested the neuroprotective effect of lavender and coriander essential oils (EOs) and their main active constituent linalool, against the neurotoxicity elicited by Aβ1‐42 oligomers, a key molecular factor in the neurodegeneration of AD. Importantly, our findings on neuronally differentiated PC12 cells exposed to Aβ1‐42 oligomers are in accordance with previous in vivo studies reporting the neuroprotective potential of lavender and coriander EOs and linalool. We found that lavender and coriander EOs at the concentration of 10 μg/mL as well as linalool at the same concentration were able to improve viability and to reduce nuclear morphological abnormalities in cells treated with Aβ1‐42 oligomers for 24 hours. Lavender and coriander EOs and linalool also showed to counteract the increase of intracellular reactive oxygen species production and the activation of the pro‐apoptotic enzyme caspase‐3 induced by Aβ1‐42 oligomers. Our findings provide further evidence that these EOs and their main constituent linalool could be natural agents of therapeutic interest against Aβ1‐42‐induced neurotoxicity. [ABSTRACT FROM AUTHOR]

J. Neurochem. (2012) 122, 911-922. Abstract We evaluated whether changes in expression and activity of the three sodium/calcium exchanger isoforms, NCX1, NCX2, and NCX3 occurred in PC12 cells when the extracellular-signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK), and p38 mitogen-activated protein kinases (MAPKs) were silenced, pharmacologically blocked, or activated with nerve growth factor (NGF). Several findings suggesting that MAPKs control NCX emerged: (1) A decrease in NCX1 and NCX3 basal expression occurred when JNK or MEK1, the extracellular-signal-regulated kinases 1/2 upstream activator, were pharmacologically blocked, respectively; (2) NGF increased cAMP response element-binding 1 (CREB1) and Specificity Protein 1 (Sp1) binding to ncx1 promoter and CREB1 binding to two different sequences close to ncx2 transcription start site on genomic DNA; (3) An up-regulation of NCX1 and NCX3, abrogated upon either MEK1 or p38 blockade, and a down-regulation of NCX2, abolished upon p38 blockade, occurred upon NGF-induced MAPK activation. The NCX1 up-regulation was abolished upon either CREB1 or Sp1 silencing, whereas NCX2 down-regulation was abrogated only by CREB1 silencing. The NCX3 up-regulation was unaffected by CREB1 or Sp1 silencing and abolished upon proteasomal inhibition; (4) Whole-cell Na+/Ca2+ exchange decreased when MEK1 and JNK were blocked and increased when MAPKs were activated by NGF. Collectively, these results demonstrate a MAPK-dependent regulation of NCX expression and activity which could be relevant in mediating some of the effects of MAPKs in neurons. [ABSTRACT FROM AUTHOR]

Although the amyloid-ß1-42 (Aß1-42) peptide involved in Alzheimer's disease is known to cause a dysregulation of intracellular Ca2+ homeostasis, its molecular mechanisms still remain unclear. We report that the extracellular-dependent early increase (30 min) in intracellular calcium concentration ([Ca2+]i), following Aß1-42 exposure, caused the activation of calpain that in turn elicited a cleavage of the Na+/Ca2+ exchanger isoform NCX3. This cleavage generated a hyperfunctional form of the antiporter and increased NCX currents (INCX) in the reverse mode of operation. Interestingly, this NCX3 calpain-dependent cleavage was essential for the Aß1-42-dependent INCX increase. Indeed, the calpain inhibitor calpeptin and the removal of the calpain-cleavage recognition sequence, via site-directed mutagenesis, abolished this effect. Moreover, the enhanced NCX3 activity was paralleled by an increased Ca2+ content in the endoplasmic reticulum (ER) stores. Remarkably, the silencing in PC-12 cells or the knocking-out in mice of the ncx3 gene prevented the enhancement of both INCX and Ca2+ content in ER stores, suggesting that NCX3 was involved in the increase of ER Ca2+ content stimulated by Aß1-42. By contrast, in the late phase (72 h), when the NCX3 proteolytic cleavage abruptly ceased, the occurrence of a parallel reduction in ER Ca2+ content triggered ER stress, as revealed by caspase-12 activation. Concomitantly, the late increase in [Ca2+]i coincided with neuronal death. Interestingly, NCX3 silencing caused an earlier activation of Aß1-42-induced caspase-12. Indeed, in NCX3-silenced neurons, Aß1-42 exposure hastened caspase-dependent apoptosis, thus reinforcing neuronal cell death. These results suggest that Aß1-42, through Ca2+-dependent calpain activation, generates a hyperfunctional form of NCX3 that, by increasing Ca2+ content into ER, delays caspase-12 activation and thus neuronal death. [ABSTRACT FROM AUTHOR]

Long-term potentiation (LTP) depends on the coordinated regulation of an ensemble of proteins related to Ca2+homeostasis, including Ca2+ transporters. One of the major players in the regulation of intracellular Ca2+ ([Ca2+]i ) homeostasis in neurons is the sodium/ calcium exchanger (NCX), which represents the principal mechanism of Ca2+ clearance in the synaptic sites of hippocampal neurons. Because NCX3, one of the three brain isoforms of the NCX family, is highly expressed in the hippocampal subfields involved in LTP, we hypothesized that it might represent a potential candidate forLTPmodulation. To test this hypothesis,wefirst examined the effect of ncx3 gene ablation on NCX currents (INCX) and Ca2+ homeostasis in hippocampal neurons. ncx3-/- neurons displayed a reduced INCX, a higher basal level of [Ca2+]i , and a significantly delayed clearance of [Ca2+]i following depolarization. Furthermore, measurement of field EPSPs, recorded from the CA1 area, revealed that ncx3-/-mice had an impaired basal synaptic transmission. Moreover, hippocampal slices from ncx3-/- mice exhibited a worsening in LTP compared with congenic ncx3-/-. Consistently, immunohistochemical and immunoblot analysis indicated that in the hippocampus of ncx3-/- mice both Ca2+/calmodulin-dependent protein kinase IIα (CaMKIIα) expression and the phospho CaMKIIα/CaMKIIα ratio were significantly reduced compared with ncx3-/-. Interestingly, ncx3-/- mice displayed a reduced spatial learning and memory performance, as revealed by the novel object recognition, Barnes maze, and context-dependent fear conditioning assays. Collectively, our findings demonstrate that the deletion of the ncx3 gene in mice has detrimental consequences on basal synaptic transmission, LTP regulation, spatial learning, and memory performance. [ABSTRACT FROM AUTHOR]