Expression of the Na(+)/Ca(2+) exchanger ameliorates ionomycin-induced cell death

In Vivo Immune Adjuvant Effects of CaCO3 Nanoparticles through Intracellular Ca2+ Concentration Regulation

Calcium (Ca) is a vital component of the human body and plays a crucial role in intracellular signaling and regulation as a second messenger. Recent studies have shown that changes in intracellular Ca2+ concentration can influence immune cell function. In this study, we developed calcium carbonate nanoparticles (CaNPs) of various sizes using a Nanosystem Platform to modulate intracellular Ca2+ concentration in vitro and in vivo. Our findings demonstrate that intravenous administration of CaNPs led to changes in the number and ratio of immune cells in the spleen and stimulated the activation of dendritic cells (DCs) and macrophages. Notably, CaNPs exhibited strong adjuvant properties in the absence of antigenic stimuli. These results indicate that CaNPs have the potential to regulate immune cell function by modulating Ca2+ concentrations, offering a novel approach for disease prevention and treatment in combination with antigens or drugs. Overall, our study emphasizes the importance of modulating intracellular Ca2+ concentration as a means of regulating immune cell function.

Protein kinase Calpha modulates depolarizaton-evoked changes of intracellular Ca2+ concentration in a rat pheochromocytoma cell line

Conventional protein kinase C (cPKC) isoforms are activated by a coincident rise in cytosolic Ca(2+) and membrane-bound diacylglycerol. In excitable cells, cPKC may be activated by Ca(2+) influx through voltage-gated Ca(2+) channels (VGCC). cPKCs, in turn, are known to modulate the activity of VGCC. We examined whether PKCalpha, a cPKC, could be activated by depolarization in a neuroendocrine cell line and whether activation occurred on a time scale that modulated the depolarization-evoked intracellular Ca(2+) concentration ([Ca(2+)](i)) signal. Pheochromocytoma cells (PC12 cells) were transfected with wild-type and mutant forms of PKCalpha labeled with yellow fluorescent protein to monitor kinase translocation. Simultaneously, [Ca(2+)](i) changes were monitored with fura-2. Two point mutations that render PKCalpha inactive, D187A in the Ca(2+) binding site and K368R in the ATP binding site, significantly prolonged the time-to-peak of the depolarization-evoked [Ca(2+)](i) signal. A mutation that modulates membrane insertion (W58G) and two mutations of an autophosphorylation site (S657A, S657E) had no effect on the kinetics of the [Ca(2+)](i) signal. We conclude that in PC12 cells, Ca(2+) entry through VGCC rapidly activates PKCalpha, and that PKCalpha can modulate the Ca(2+) signal on a physiologically relevant time scale. Point mutations of PKCalpha can be used as specific and potent modulators of the PKC signaling pathway.

Down regulation of sodium channel Na(v)1.1 expression by veratridine and its reversal by a novel sodium channel blocker, RS100642, in primary neuronal cultures

This study investigated the effects of veratridine-induced neuronal toxicity on sodium channel gene (NaCh) expression in primary forebrain cultures enriched in neurons, and its reversal by a novel sodium channel blocker, RS100642. Using quantitative RT-PCR, our findings demonstrated the expression ratio of NaCh genes in normal fetal rat forebrain neurons to be Na(v)1.2 > Na(v)1.3 > Na(v)1.8 > Na(v)1.1 > Na(v)1.7 (rBII > rBIII > PN3 > rBI > PN1). Veratridine treatment of neuronal cells produced neurotoxicity in a dose-dependent manner (0.25-20 micro M). Neuronal injury caused by a dose of veratridine producing 80% cell death (2.5 micro M) significantly, and exclusively down-regulated the Na(v)1.1 gene. However, treatment of neurons with RS100642 (200 micro M) reversed the down-regulation of the Na(v)1.1 gene expression caused by veratridine. Our findings document for the first time quantitative and relative changes in the expression of various NaCh genes in neurons following injury produced by selective activation of voltage-gated sodium channels, and suggest that the Na(v)1.1 sodium channel gene may play a key role in the neuronal injury/recovery process.

Differential pattern of expression of voltage-gated sodium channel genes following ischemic brain injury in rats

This study investigated the effects of brain ischemia on sodium channel gene (NaCh) expression in rats. Using quantitative RT-PCR, our findings demonstrated the expression ratio of NaCh genes in normal rat brain to be Na(v)1.1 > Na(v)1.8 > Na(v)1.3 > Na(v)1.7 (rBI > PN3 > rBIII > PN1). In contrast, brain injury caused by middle cerebral artery occlusion (MCAo) for 2 h followed by reperfusion significantly down-regulated Na(v)1.3 and Na(v)1.7 genes in both injured and contralateral hemispheres; whereas the Na(v)1.8 gene was down regulated in only the injured hemisphere (though only acutely at 2 or 2-6 h post-MCAo). However, the time-course of NaCh gene expression revealed a significant down-regulation of Na(v)1.1 only in the ischemic hemisphere beginning 6 h post-MCAo and measured out to 48 h post-MCAo. In a separate preliminary study Na(v)1.2 (rBII) gene was found to be expressed at levels greater than that of Na(v)1.1 in normal rats and was significantly down regulated at 24 h post-MCAo). Our findings document, for the first time, quantitative and relative changes in the expression of various NaCh genes following ischemic brain injury and suggest that the Na(v)1.1 sodium channel gene may play a key role in ischemic injury/recovery.