V práci sumarizujeme výsledky našich štúdií zameraných na objasnenie patofyziologických mechanizmov zmenenej homeostázy vápnika v neexcitabilných bunkách pacientov v skorých štádiách chronickej choroby obličiek (CKD) a zistenie vplyvu suplementácie vitamínu D3 na tieto mechanizmy. Základné mechanizmy vstupu vápnika, ako aj jeho odčerpávania z bunky sú už v skorých štádiách CKD zmenené. Tieto poruchy spôsobujú zvýšenie koncentrácie voľného cytosolového vápnika ([Ca2+]i), čo môže viesť k zmene mnohých bunkových procesov a expresii rôznych signálnych molekúl. Suplementácia vitamínu D je štandardný postup korekcie nedostatku/deficitu vitamínu D u pacientov v skorých štádiách CKD, pričom pleiotropné účinky vitamínu D sa môžu podieľať na modulácii bunkovej homeostázy vápnika. Suplementácia vitamínu D3 mala za následok zníženie [Ca2+]i ovplyvnením niektorých transportných systémov vstupu katiónov vápnika do bunky a jeho odčerpávania z bunky. Normalizácia [Ca2+]i môže mať priaznivý účinok na intracelulárnu signalizáciu, a tým pozitívne ovplyvňovať funkčnosť buniek, tkanív, resp. orgánov.
Mini review summarizes the results of our studies focused on elucidation of the pathophysiological mechanisms of altered calcium homeostasis in nonexcitable cells from patients with early stages of chronic kidney disease (CKD), as well as on determining the effect of vitamin D3 supplementation on these mechanisms. The basic mechanisms of calcium entry to and removal of the cell are already changed in early stages of CKD. These disturbances cause an increased the concentration of cytosolic free calcium ([Ca2+]i), which may change a number of cellular processes, and the expression of various signaling molecules. Vitamin D3 supplementation is a standard procedure of vitamin D insufficiency/ deficiency correction in these patients. The pleiotropic effects of vitamin D may be involved in the modulation of cellular calcium homeostasis. Vitamin D3 supplementation resulted in a reduction in [Ca2+]i by affecting of specific transport systems of calcium cations entry to and removal of the cell. The normalization [Ca2+]i can have a beneficial effect on intracellular signalling, and thus positively influence the functioning of cells, tissues or organs.
- MeSH
- Cholecalciferol deficiency MeSH
- Renal Insufficiency, Chronic * drug therapy physiopathology MeSH
- Homeostasis * physiology MeSH
- Intracellular Membranes MeSH
- Intracellular Space MeSH
- Clinical Trials as Topic MeSH
- Humans MeSH
- Calcium adverse effects MeSH
- Calcium Channels, L-Type MeSH
- Check Tag
- Humans MeSH
Koncentrácia voľného cytosolového vápnika ([Ca2+]i) je veľmi dôležitým signálnym mediátorom pre množstvo biologických systémov. Katióny vápnika (Ca2+) sú významnými ubikvitárnymi poslami, ktoré kontrolujú široké spektrum bunkových procesov. [Ca2+]i je kontrolovaná mechanizmami, ktoré regulujú vstup vápnika z extracelulárneho priestoru a jeho uvoľnenie z intracelulárnych priestorov. Aktivitou ATP-dependentných Ca2+ púmp a výmenníkových systémov sa vápnik vracia do intracelulárnych zásobníkov alebo sa odčerpáva z bunky. Chronické ochorenie obličiek je spojené so signifikantným zvýšením [Ca2+]i, ktoré je pre bunky toxické a môže byť zodpovedné za mnohé orgánové poruchy. Za zmeny vápnikovej homeostázy buniek u pacientov s chronickým ochorením obličiek zodpovedá navzájom prepojený komplex procesov. Naše štúdie objasňujú patofyziologické mechanizmy, podieľajúce sa na zmenenej homeostáze vápnika v periférnych mononukleárnych bunkách, ktoré sú modelom neexcitabilných buniek. [Ca2+]i je signifikantne zvýšená už v skorých štádiách chronického ochorenia obličiek. Koncentrácia intracelulárnych vápnikových rezerv a kapacitný vstup vápnika sú v porovnaní so zdravými dobrovoľníkmi významne zvýšené. Na tomto zvýšení sa podieľajú aj „pore-forming“ P2X7 receptory, ktoré majú u pacientov s chronickým ochorením obličiek zmenenú funkciu a vo zvýšenej miere sa exprimujú. Na druhej strane je aktivita plazmatických Ca2+-ATPáz zodpovedných za odstraňovanie nadbytočného vápnika z bunky znížená o 25 %. To znamená, že pri chronickom ochoreniu obličiek sú porušené ako mechanizmy vstupu, tak aj výstupu vápnika z bunky. Všetky tieto poruchy sa v signalizácii vápnika podieľajú na zvýšenej [Ca2+]i už v skorých štádiách renálneho ochorenia.
Free intracellular calcium represents a critical signaling mediator in a number of biological systems. Calcium cations (Ca2+) are an important ubiquitous messenger, controlling a broad range of cellular processes. Free cytosolic calcium concentration ([Ca2+]i) is controlled by mechanisms that regulate Ca2+ entry from the extracellular space and Ca2+ release from intracellular stores, and by the activity of ATP-dependent Ca2+ pumps and antiporters that move Ca2+ back into stores or out of cells. Chronic kidney disease is associated with a significant elevation in [Ca2+]i which is toxic to the cells and may be responsible for a multiple organ dysfunction. Disturbances in cellular calcium homeostasis in patients with chronic kidney disease represent a complex process. Our studies elucidate pathophysiological mechanisms of altered cellular calcium homeostasis in the peripheral blood mononuclear cells which represent the model of nonexcitable cells in patients with chronic kidney disease. The results demonstrate that [Ca2+]i is significantly increased in peripheral blood mononuclear cells already in early stages of chronic kidney disease. The calcium concentration of intracellular stores and the capacitative calcium entry into the cells of these patients are significantly higher in comparison with healthy volunteers. Also the pore-forming P2X7 receptors participate in increased [Ca2+]i in peripheral blood mononuclear cells of patients with chronic kidney disease. An altered P2X7 receptor function and increased P2X7 receptor expression may contribute to the complex disturbances in intracellular calcium homeostasis in chronic kidney disease. On the other hand, the activity of plasmatic membrane Ca2+-ATPases which is responsible for removing excessive calcium out of the cell, was found to be decreased by 25 % when compared to healthy subjects. It means that not only the mechanisms of entry, but also of the removal are impaired by the disease. All these alterations in calcium signaling are contributing very likely to the elevated [Ca2+]i from early stages of chronic kidney disease.
- MeSH
- Plasma Membrane Calcium-Transporting ATPases * diagnostic use metabolism deficiency MeSH
- Kidney Failure, Chronic * metabolism MeSH
- Child MeSH
- Adult MeSH
- Homeostasis physiology MeSH
- Intracellular Membranes metabolism MeSH
- Intracellular Space * metabolism MeSH
- Humans MeSH
- Calcium * metabolism MeSH
- Calcium Signaling * physiology MeSH
- Check Tag
- Child MeSH
- Adult MeSH
- Humans MeSH
Introduction. Chronic kidney disease (CKD) has been referred to as a state of cellular calcium toxicity. The aim of this study was to investigate the status of free cytosolic calcium ([Ca 2+ ] i ) and intracellular calcium reserves and the capacitative calcium entry in peripheral blood mononuclear cells (PBMCs) of CKD patients, and to determine the effect of vitamin D3 supplementation on these parameters. Methods. The study involved 44 patients with CKD sta- ges 2-3 and 70 healthy volunteers. 27 were treated with cholecalciferol (5000 IU/week) for 12 months. [Ca 2+ ] i was measured using Fluo-3 AM fluorimetry. Intracellular calci- um reserves were emptied by the application of thapsigar- gin (Tg), a specific inhibitor of endoplasmic reticulum Ca 2+ - ATPase. 2-Aminoethyl-diphenyl borate (2APB) was used to examine the capacitative calcium entry. Results. [Ca 2+ ] i of CKD patients was substantially higher in comparison with healthy subjects: 123 (115-127) vs 102 (98-103) nmol/l; p<0.001. The calcium concentration of Tg-sensitive stores and the capacitative calcium entry were also significantly increased in CKD patients. After the 12- month vitamin D3 supplementation, there was a marked decrease in [Ca 2+ ] i [105 (103-112) nmol/l; p<0.001 vs. baseline], independently of the increase in 25(OH)D 3 or the decrease in PTH levels. No significant changes in intracel- lular calcium reserves and the capacitative calcium entry were found. Conclusions. Our results demonstrate that: (1) [Ca 2+ ] i , intracellular calcium stores and the capacitative calcium entry were significantly increased already in early stages of CKD; (2) long-term vitamin D3 supplementation normalized [Ca 2+ ] i without any effect on intracellular calcium reserves or the capacitative calcium entry.
