Dietary Mg2+ Intake and the Na+/Mg2+ Exchanger SLC41A1 Influence Components of Mitochondrial Energetics in Murine Cardiomyocytes

Cardiomyocytes are among the most energy-intensive cell types. Interplay between the components of cellular magnesium (Mg) homeostasis and energy metabolism in cardiomyocytes is poorly understood. We have investigated the effects of dietary Mg content and presence/functionality of the Na+/Mg2+ exchanger SLC41A1 on enzymatic functions of selected constituents of the Krebs cycle and complexes of the electron transport chain (ETC). The activities of aconitate hydratase (ACON), isocitrate dehydrogenase (ICDH), α-ketoglutarate dehydrogenase (KGDH), and ETC complexes CI–CV have been determined in vitro in mitochondria isolated from hearts of wild-type (WT) and Slc41a1−/− mice fed a diet with either normal or low Mg content. Our data demonstrate that both, the type of Mg diet and the Slc41a1 genotype largely impact on the activities of enzymes of the Krebs cycle and ETC. Moreover, a compensatory effect of Slc41a1−/− genotype on the effect of low Mg diet on activities of the tested Krebs cycle enzymes has been identified. A machine-learning analysis identified activities of ICDH, CI, CIV, and CV as common predictors of the type of Mg diet and of CII as suitable predictor of Slc41a1 genotype. Thus, our data delineate the effect of dietary Mg content and of SLC41A1 functionality on the energy-production in cardiac mitochondria

Search for Molecular Biomarkers of Parkinson’s Disease. New Tissues and Methods

Parkinson’s disease (PD) is a chronic neurodegenerative disorder that is clinically manifested by motor and non-motor symptoms. At the early stage of the disease, it can be misdiagnosed with some neurologic disorders due to overlapping or similar clinical features. In addition, the pathogenesis of this disease is initiated several years prior to the appearance of classical motor symptoms. This latent phase of neurodegeneration in PD characterised at cellular level by preservation of significant fraction of dopaminergic neurones is of particular interest with respect to the development of disease-modifying or neuroprotective therapies which would require intervention at the earliest stages of disease with an aim to slow down or reverse the disease progression. Therefore, huge effort was performed in order to find and validate a biomarker that would reliably differentiate PD from other neurologic diseases as well as a biomarker that would reveal preclinical/prodromal stage of PD. This short review summarises a recent progress in validation of molecular biomarkers of PD, distinct from genetic markers of PD, with some focus on new analysed tissues and new methods

Benefits of anticitrullinated peptides examination in rheumatoid arthritis

Background: Anti‑citrullinated peptides antibodies (ACPA) are specific for rheumatoid arthritis and have been implicated in disease pathogenesis. ACPA examination is a new component of ACR/EULAR 2010 classification criteria for rheumatoid arthritis. ACPA positivity predicts a more erosive disease course with severe joint damage and extra‑articular manifestations.Objectives: To evaluate the benefits of ACPA examination in patients with early undifferentiated arthritis and patients with rheumatoid arthritis.Methods: We examined patients with arthritis and tested them for ACPA positivity. In every individual patient we evaluated if ACPA examination was necessary to establish the diagnosis of rheumatoid arthritis, or to change treatment, or if the diagnosis could have been established without ACPA examination (ACR/EULAR 2010 classification criteria was met without ACPA scoring).Results and Conclusions: The study was placed in Slovak Republic. We examined 833 patients with arthritis. There were 43 patients, or 62% of a subgroup of 69 who were ACPA positive whose ACPA examination was not needed—ACR/EULAR criteria was met without ACPA scoring. This number represents 5.1% of the total number examined. There were 15 patients, or 22% of the subgroup and 1.8% of the total whose diagnosis was revised to rheumatoid arthritis due to ACPA positivity—ACR/EULAR criteria were met solely with ACPA scoring. There were 11 patients (16% and 1.3%) whose medication was changed due to ACPA positivity. ACPA examination is useful in 3.1% of all examined patients. When we correlate data on ACPA positive patients, 38% of the patients profit from ACPA examinations. Considering the relatively low price of ACPA testing, this examination should not be excluded.Keywords: ACR/EULAR 2010 classification criteria, anti‑citrullinated peptides antibodies, rheumatoid arthriti

Ectopic parvalbumin expression in mouse forebrain neurons increases excitotoxic injury provoked by ibotenic acid injection into the striatum

A neuroprotective role for Ca²⁺-binding proteins in neurodegenerative conditions ranging from ischemia to Alzheimer's disease has been suggested in several studies. A key phenomenon in neurodegeneration is the Ca²⁺-mediated excitotoxicity brought about by the neurotransmitter glutamate. To evaluate the relative ability to resist excitotoxicity of neurons containing the slow-onset Ca²⁺-binding protein parvalbumin (PV), we injected the glutamate agonist ibotenic acid (IBO) into the striatum of adult mice ectopically expressing PV in neurons. Striatal ibotenic acid injection results in local nerve cell loss and reactive astrogliosis. Light microscopic evaluation, carried out after a delay of 2 and 4 weeks, reveals an enlarged and accelerated neurodegenerative process in mice ectopically expressing neuronal PV. Thus, PV is not neuroprotective, it rather enhances nerve cell death. This result implicates that the increase in cytosolic Ca²⁺-buffering capacity in the transgenic mice impairs other systems involved in Ca²⁺ sequestration. In addition, ultrastructural morphometric analysis shows that in neurons the mitochondrial volume is reduced in mice ectopically expressing neuronal PV. This is paralleled by a reduction in the amount of the mitochondrial marker enzyme cytochrome c oxidase subunit I (COXI). We conclude that alterations in the Ca²⁺ homeostasis present in mice ectopically expressing neuronal PV are more deleterious under excitotoxic stress and largely outweigh the potential benefits of an increased Ca²⁺-buffering capacity resulting from PV

The Involvement of Mg 2+

Mg2+ is an essential mineral with pleotropic impacts on cellular physiology and functions. It acts as a cofactor of several important enzymes, as a regulator of ion channels such as voltage-dependent Ca2+ channels and K+ channels and on Ca2+-binding proteins. In general, Mg2+ is considered as the main intracellular antagonist of Ca2+, which is an essential secondary messenger initiating or regulating a great number of cellular functions. This review examines the effects of Mg2+ on mitochondrial functions with a particular focus on energy metabolism, mitochondrial Ca2+ handling, and apoptosis

Mutational analysis of dendritic Ca2+ kinetics in rodent Purkinje cells: role of parvalbumin and calbindin D28k

The mechanisms governing the kinetics of climbing fibre-mediated Ca2+ transients in spiny dendrites of cerebellar Purkinje cells (PCs) were quantified with high-resolution confocal Ca2+ imaging. Ca2+ dynamics in parvalbumin (PV−/−) and parvalbumin/calbindin D28k null-mutant (PV/CB−/−) mice were compared with responses in wild-type (WT) animals. In the WT, Ca2+ transients in dendritic shafts were characterised by double exponential decay kinetics that were not due to buffered Ca2+ diffusion or saturation of the indicator dye. Ca2+ transients in PV−/− PCs reached the same peak amplitude as in the WT but the biphasic nature of the decay was less pronounced, an effect that could be attributed to PV's slow binding kinetics. In contrast, peak amplitudes in PV/CB−/− PCs were about two times higher than in the WT and the decay became nearly monophasic. Numerical simulations indicate that the residual deviation from a single exponential decay in PV/CB−/− is due to saturation of the Ca2+ indicator dye. Furthermore, the simulations imply that the effect of uncharacterised endogenous Ca2+ binding proteins is negligible, that buffered diffusion and dye saturation significantly affects spineous Ca2+ transients but not those in the dendritic shafts, and that neither CB nor PV undergoes saturation in spines or dendrites during climbing fibre-evoked Ca2+ transients. Calbindin's medium-affinity binding sites are fast enough to reduce the peak amplitude of the Ca2+ signal. However, similar to PV, delayed binding by CB leads to biphasic Ca2+ decay kinetics. Our results suggest that the distinct kinetics of PV and CB underlie the biphasic kinetics of synaptically evoked Ca2+ transients in dendritic shafts of PCs

Deficiency in parvalbumin, but not in calbindin D-28k upregulates mitochondrial volume and decreases smooth endoplasmic reticulum surface selectively in a peripheral, subplasmalemmal region in the soma of Purkinje cells

The Ca²⁺-binding proteins parvalbumin (PV) and calbindin D-28k (CB) are key players in the intracellular Ca²⁺-buffering in specific cells including neurons and have profound effects on spatiotemporal aspects of Ca²⁺ transients. The previously observed increase in mitochondrial volume density in fast-twitch muscle of PV−/− mice is viewed as a specific compensation mechanism to maintain Ca²⁺ homeostasis. Since cerebellar Purkinje cells (PC) are characterized by high expression levels of the Ca²⁺ buffers PV and CB, the question was raised, whether homeostatic mechanisms are induced in PC lacking these buffers. Mitochondrial volume density, i.e. relative mitochondrial mass was increased by 40% in the soma of PV−/− PC. Upregulation of mitochondrial volume density was not homogenous throughout the soma, but was selectively restricted to a peripheral region of 1.5 μm width underneath the plasma membrane. Accompanied was a decreased surface of subplasmalemmal smooth endoplasmic reticulum (sPL-sER) in a shell of 0.5 μm thickness underneath the plasma membrane. These alterations were specific for the absence of the “slow-onset” buffer PV, since in CB−/− mice neither changes in peripheral mitochondria nor in sPL-sER were observed. This implicates that the morphological alterations are aimed to specifically substitute the function of the slow buffer PV. We propose a novel concept that homeostatic mechanisms of components involved in Ca²⁺ homeostasis do not always occur at the level of similar or closely related molecules. Rather the cell attempts to restore spatiotemporal aspects of Ca²⁺ signals prevailing in the undisturbed (wildtype) situation by subtly fine tuning existing components involved in the regulation of Ca²⁺ fluxes