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Aim: The Na+/Ca2+ exchanger (NCX) is a major Ca2+ extrusion system in the plasma membrane of cardiomyocytes and an important component participating on the excitation–contraction coupling process in muscle cells. NCX1 isoform is the most abundant in the heart and is known to be changed after development of ischaemia or myocardial infarction. Objective of this study was to investigate the effect of stress factors (immobilization, cold and short-term hypoxia) on the expression of NCX1, in vivo, in the heart of rat and mouse. Methods: We compared gene expression and protein levels of control and stressed animals. The activity of NCX was measured by the whole cell configuration using the patch clamp. We also measured physiological parameters of the heart in physiological conditions and under ischaemia-reperfusion to compare response of control and stressed hearts. Results: We have found that only strong stress stimulus (hypoxia, immobilization) applied repeatedly for several days elevated the NCX1 mRNA level. Cold, which is a weaker stressor that activates mainly sympathoneural, and only marginally adrenomedullary system did not affect the gene expression of NCX1. Thus, from these results it appears that hormones produced by the adrenal medulla (mainly adrenaline) might be involved in this process. To study possible mechanism of the NCX1 regulation by stress, we focused on the possible role of the hypothalamo–pituitary–adrenocortical pathway in the activation of catecholamine synthesis in the adrenal medulla. We have already published that cortisol affects activity, but not the gene expression of NCX1. In this work, we used corticotropin-releasing hormone (CRH) knockout mice, where secretion of corticosterone and subsequently adrenaline is significantly suppressed. As no increase in NCX1 mRNA was observed in CRH knockout mice due to immobilization stress, we proposed that adrenaline (probably regulated via corticosterone) is involved in the regulation of NCX1 gene expression during stress. Conclusions: The gene expression and protein levels of the NCX1 are increased by the strong stress stimuli, e.g. hypoxia, or immobilization stress. The activity of NCX1 is decreased. Based on these results, we assume that the gene expression of NCX is increased as a consequence of suppressed activity of this transport system. [ABSTRACT FROM AUTHOR]

Abstract The auxiliary calcium channel α2δ subunit comprises a family of three genes, α2δ-1 to 3, which are expressed in a tissue-specific manner. α2δ-2 mRNA is found in the heart, skeletal muscle, brain, kidney, liver and pancreas. We report here for the first time the identification and functional characterization of α2δ-2 splice variants and their mRNA distribution in the mouse brain. The splice variants differ in the α2 and δ protein by eight and three amino acid residues, respectively, and are differentially expressed in cardiac tissue and human medullary thyroid carcinoma (hMTC) cells. In situ hybridization of mouse brain sections revealed the highest expression of α2δ-2 mRNA in the Purkinje cell layer of the cerebellum, habenulae and septal nuclei, and a lower expression in the cerebral cortex, olfactory bulb, thalamic and hypothalamic nuclei, as well as the inferior and superior colliculus. As the in situ data did not suggest a specific colocalization with any α1 subunit, coexpression studies of α2δ-2 were carried out either with the high-voltage-gated calcium channels, α1C, α1E or α1A, or with the low-voltage-gated calcium channel, α1G. Coexpression of α2δ-2 increased the current density, shifted the voltage dependence of channel activation and inactivation of α1C, α1E and α1A subunits in a hyperpolarizing direction, and accelerated the decay and shifted the steady-state inactivation of the α1G current. [ABSTRACT FROM AUTHOR]

Traumatic injury of the central nervous system is accompanied by various functional and morphological changes. Animal models of traumatic brain injury are commonly used to investigate changes in behaviour, morphology, in the expression of various proteins around the site of the injury, or the expression of diagnostically important biomarkers. Excitability of a single neuron at, or close to, the site of injury was rarely investigated. Several in vitro models were developed which allow such investigation. In the present work, we employed a fibrotic scar model according to Kimura-Kuroda and coauthors to analyse altered excitability of rat hippocampal neurons under the conditions mimicking traumatic brain injury. Hippocampal neurons from newborn rats were cultured either on a fibrotic scar model or in the presence of TGF-β1, a cytokine secreted at a brain injury site that may have both neuroprotective and neurodegenerative function. Fibrotic scar facilitated ability of neonatal hippocampal neurons to fire action potential series by increasing the density of voltage activated sodium and potassium currents. Chondroitin sulphate proteoglycans played substantial role in these effects, as proven by their full reversion after administration of Chondroitinase ABC. In contrast, TGF-β1 did not contribute to them. An application of TGF-β1 itself attenuated generation of action potentials, inhibited sodium current and potentiated potassium currents. Main alteration of electrophysiological parameters of neonatal hippocampal neurons caused by a fibrotic scar model is enhanced excitability. TGF-β1 may have predominantly neuroprotective role in injured rat hippocampus., (© 2017 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.)