Excitation–contraction coupling in heart. XIX. Effect of hypoxia on calcium transport by subcellular particles in the isolated perfused rat heart

1976 ◽  
Vol 54 (1) ◽  
pp. 49-58 ◽  
Author(s):  
S. L. Lee ◽  
V. Balasubramanian ◽  
N. S. Dhalla
Keyword(s):  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Microsomal Fraction ◽  
Contractile Force ◽  
Mitochondrial Calcium ◽  
Rat Hearts ◽  
Mitochondrial Calcium Uptake ◽  
Contractile Failure

To examine the role of changes in calcium transport by subcellular particles in the pathogenesis of contractile failure due to oxygen lack, both mitochondrial and microsomal fractions were obtained from the isolated hypoxic rat hearts and their calcium binding and uptake abilities were determined by the Millipore filtration technique. The contractile force decreased by about 40, 60 and 70% of the control within 5, 10 and 30 min respectively, of perfusing the heart with hypoxic medium containing glucose. In hearts perfused for 10 min with hypoxic medium containing glucose, calcium binding and uptake by the microsomal fraction decreased significantly. However, mitochondrial calcium binding, but not uptake, decreased significantly on perfusing the hearts with hypoxic medium containing glucose for 20 to 30 min when the microsomal calcium transport was markedly depressed. Reduction in contractile force, calcium binding and uptake by the microsomal fraction as well as calcium binding by mitochondria of hearts made hypoxic for 30 min recovered towards normal upon reperfusion with control medium for 15 min. On the other hand, omitting glucose from the hypoxic medium significantly decreased calcium binding by mitochondrial and microsomal fractions within 10 min of perfusion in comparison to the control and accelerated the effects of hypoxia upon contractile force and microsomal calcium uptake. In contrast to the hypoxic hearts, the mitochondrial calcium uptake decreased significantly and the magnitude of depression in the microsomal calcium binding was appreciably greater in hearts made to fail to a comparable degree upon perfusion with substrate-free medium. The observed defects in calcium transporting properties of microsomal and mitochondrial membranes appear secondary to the contractile failure in hypoxic hearts.

Subcellular calcium transport in failing hearts due to calcium deficiency and overload

1976 ◽  
Vol 231 (4) ◽  
pp. 1159-1165 ◽  
Author(s):  
SL Lee ◽  
NS Dhalla
Keyword(s):  
Intracellular Calcium ◽  
Calcium Binding ◽  
Calcium Transport ◽  
Calcium Deficiency ◽  
Contractile Force ◽  
Calcium Overload ◽  
Mitochondrial Calcium ◽  
Control Medium ◽  
Free Medium ◽  
Rat Hearts

Mitochondrial and heavy microsomal fractions were isolated from rat hearts perfused for different intervals with Ca2+-free medium, as well as from hearts reperfused with control medium after perfusion with Ca2+-free medium. Contractile failure due to intracellular calcium deficiency produced by perfusing the isolated rat hearts with Ca2+-free medium resulted in a marked decline of calcium binding and uptake activities of the mitochondrial fraction without any effect on the microsomal fraction. On the other hand, inability of the rat hearts to recover their contractile force due to intracellular calcium overload produced by reperfusion for 10 min with control medium after 5-20 min of perfusion with Ca2+-free medium was associated with decreased microsomal calcium-binding and uptake activities and increased mitochondrial calcium-binding and uptake activities. When the hearts perfused with Ca2+-free medium in the presence of low sodium (35 mM) for 5 min were reperfused with control medium, the contractile force recovered completely, and appreciable augmentation in mitochondrial calcium transport or depression in microsomal calcium transport as seen in conditions of intracellular calcium overload did not occur. These results suggest dramatic alterations in calcium-transporting properties of mitochondria and sarcoplasmic reticulum in hearts failing due to intracellular calcium deficiency and calcium overload, respectively.

Abstract 284: Loss of Micu3 Confers Cardioprotection Against Cardiac Injury

2020 ◽  
Vol 127 (Suppl_1) ◽  
Author(s):  
Bao Puente ◽  
Junhui Sun ◽  
Maria Fergusson ◽  
Julia Liu ◽  
Anna Kosmach ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Infarct Size ◽  
Reperfusion Injury ◽  
Calcium Uptake ◽  
Cardiac Injury ◽  
Mitochondrial Calcium ◽  
Wild Type ◽  
Ischemic Reperfusion ◽  
Mitochondrial Calcium Uptake

Background: Mitochondrial calcium flux and signaling is integral to cardiac function and contraction. However, during pathologic conditions such as ischemic/reperfusion injury, mitochondrial calcium overload can induce the opening of the mitochondrial permeability transitioning pore (PTP), resulting in the collapse of mitochondrial membrane potential, ATP depletion, and generation of reactive oxygen species, all together leading to cell death. Hence, modulation of mitochondrial calcium and inhibition of the PTP is a promising target for cardioprotection and prevention of cardiomyocyte death. The mitochondrial calcium uniporter (MCU) complex mediates rapid mitochondrial calcium uptake. MICU3 is a regulator of the MCU complex and has been shown to be a highly potent stimulator of MCU-dependent calcium uptake in neuronal cells. We found that MICU3 is expressed in hearts and we therefore investigated the role of MICU3 in the heart. We examined the role of MICU3 in the development of hypertrophy and in a separate study we examined the response to ischemic-reperfusion (I/R) injury. Given its role in regulating mitochondrial calcium uptake, we hypothesized that loss of MICU3 confers protection against cardiac injury. Methods: Mice with global deletion of Micu3 (Micu3 -/- ) were created utilizing CRISPR-Cas9 technology. Adult knockout and littermate wild type mice were treated with Isoproterenol (15mg/kg/day) for two weeks to induce hypertrophy. Echocardiograms were performed at baseline and after treatment to assess changes in left ventricular size and function. I/R injury was studied using Langendorff ex vivo perfused heart system, exposing knockout and wild type hearts to 20 minutes of ischemia and 90 minutes of reperfusion. Hemodynamic data and infarct size were collected and compared. Student t-test and 2-way ANOVA were used for statistical analysis. Result: Micu3 -/- mice had normal cardiac function at baseline. There was no sex difference in cardiac function. Micu3 -/- mice continued to show normal function after 2 weeks of treatment with Isoproterenol, whereas wild type mice exhibited depressed function (median FS 35% vs. 24% p = 0.0001, EF 64% vs. 50% p = 0.0001). Wild type mice developed LV dilation from baseline (median 4.15mm vs. 4.57mm, p = 0.0014), whereas LV dimension remained stable in Micu3 -/- mice (median 4.12mm vs. 4.18mm, p= 0.9892). Micu3 - /- mice were also protected from I/R injury. Compared to wild types, Micu3 -/- hearts demonstrated less contractile dysfunction at end reperfusion (median rate pressure product 62% vs. 41%, p = 0.002), and significantly smaller infarct size (median 33% vs. 53%, p = 0.0001). Conclusion: Loss of MICU3 confers cardioprotection against ischemic reperfusion injury and Isoproterenol induced cardiac dysfunction.

scholarly journals Role of mitochondrial calcium uptake homeostasis in resting state fMRI brain networks

2015 ◽  
Vol 28 (11) ◽  
pp. 1579-1588 ◽  
Author(s):  
Sridhar S. Kannurpatti ◽  
Basavaraju G. Sanganahalli ◽  
Peter Herman ◽  
Fahmeed Hyder
Keyword(s):  
Resting State ◽  
Calcium Uptake ◽  
Brain Networks ◽  
Resting State Fmri ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uptake

scholarly journals Structure of the MICU1–MICU2 heterodimer provides insights into the gatekeeping threshold shift

IUCrJ ◽  
2020 ◽  
Vol 7 (2) ◽  
pp. 355-365 ◽  
Author(s):  
Jongseo Park ◽  
Youngjin Lee ◽  
Taein Park ◽  
Jung Youn Kang ◽  
Sang A Mun ◽  
...  
Keyword(s):  
Calcium Uptake ◽  
Mitochondrial Calcium ◽  
Salt Bridges ◽  
Face To Face ◽  
Calcium Uniporter ◽  
Molecular Action ◽  
The Face ◽  
Mitochondrial Calcium Uptake ◽  
Apo State

Mitochondrial calcium uptake proteins 1 and 2 (MICU1 and MICU2) mediate mitochondrial Ca2+ influx via the mitochondrial calcium uniporter (MCU). Its molecular action for Ca2+ uptake is tightly controlled by the MICU1–MICU2 heterodimer, which comprises Ca2+ sensing proteins which act as gatekeepers at low [Ca2+] or facilitators at high [Ca2+]. However, the mechanism underlying the regulation of the Ca2+ gatekeeping threshold for mitochondrial Ca2+ uptake through the MCU by the MICU1–MICU2 heterodimer remains unclear. In this study, we determined the crystal structure of the apo form of the human MICU1–MICU2 heterodimer that functions as the MCU gatekeeper. MICU1 and MICU2 assemble in the face-to-face heterodimer with salt bridges and methionine knobs stabilizing the heterodimer in an apo state. Structural analysis suggests how the heterodimer sets a higher Ca2+ threshold than the MICU1 homodimer. The structure of the heterodimer in the apo state provides a framework for understanding the gatekeeping role of the MICU1–MICU2 heterodimer.

scholarly journals Increased mitochondrial calcium uniporter in adipocytes underlies mitochondrial alterations associated with insulin resistance

2017 ◽  
Vol 313 (6) ◽  
pp. E641-E650 ◽  
Author(s):  
Lauren E. Wright ◽  
Denis Vecellio Reane ◽  
Gabriella Milan ◽  
Anna Terrin ◽  
Giorgia Di Bello ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Calcium Uptake ◽  
Genetic Manipulation ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uniporter ◽  
Insulin Resistant ◽  
Calcium Uniporter ◽  
Obesity And Diabetes ◽  
Mitochondrial Calcium Uptake

Intracellular calcium influences an array of pathways and affects cellular processes. With the rapidly progressing research investigating the molecular identity and the physiological roles of the mitochondrial calcium uniporter (MCU) complex, we now have the tools to understand the functions of mitochondrial Ca2+ in the regulation of pathophysiological processes. Herein, we describe the role of key MCU complex components in insulin resistance in mouse and human adipose tissue. Adipose tissue gene expression was analyzed from several models of obese and diabetic rodents and in 72 patients with obesity as well as in vitro insulin-resistant adipocytes. Genetic manipulation of MCU activity in 3T3-L1 adipocytes allowed the investigation of the role of mitochondrial calcium uptake. In insulin-resistant adipocytes, mitochondrial calcium uptake increased and several MCU components were upregulated. Similar results were observed in mouse and human visceral adipose tissue (VAT) during the progression of obesity and diabetes. Intriguingly, subcutaneous adipose tissue (SAT) was spared from overt MCU fluctuations. Furthermore, MCU expression returned to physiological levels in VAT of patients after weight loss by bariatric surgery. Genetic manipulation of mitochondrial calcium uptake in 3T3-L1 adipocytes demonstrated that changes in mitochondrial calcium concentration ([Ca2+]mt) can affect mitochondrial metabolism, including oxidative enzyme activity, mitochondrial respiration, membrane potential, and reactive oxygen species formation. Finally, our data suggest a strong relationship between [Ca2+]mt and the release of IL-6 and TNFα in adipocytes. Altered mitochondrial calcium flux in fat cells may play a role in obesity and diabetes and may be associated with the differential metabolic profiles of VAT and SAT.

scholarly journals Role of polyhydroxybutyrate in mitochondrial calcium uptake

Cell Calcium ◽  
2013 ◽  
Vol 54 (2) ◽  
pp. 86-94 ◽  
Author(s):  
Matthew Smithen ◽  
Pia A. Elustondo ◽  
Robert Winkfein ◽  
Eleonora Zakharian ◽  
Andrey Y. Abramov ◽  
...  
Keyword(s):  
Calcium Uptake ◽  
Mitochondrial Calcium ◽  
Mitochondrial Calcium Uptake
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