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Background: Sepsis is a systemic inflammatory response to a local severe infection that can lead to multiple organ failure and ultimately death. Studies have shown that 40%-50% of septic patients have diverse myocardial injuries, with mortality ranging from 70% to 90% in contrast to 20% in septic patients without myocardial injury. Therefore, uncovering the mechanism of myocardial injury induced by sepsis and finding a treatment for the corresponding target are immensely important.Methods: We employed cecal ligation and puncture (CLP) for inducing sepsis in mice, and detect the situation of myocardial injury and cardiac function through serological markers and echocardiography. The cardiomyocytes apoptosis and the ultrastructural of heart tissue detected by TUNEL and transmission electron microscope (TEM) respectively. The Fura-2 AM was used to monitored Ca2+ uptake and efflux of mitochondria. FQ-PCR and Western blot detected the expression of mitochondria Ca2+ distribution regulators and PINK1. JC-1 was used to detected the mitochondrial membrane potential (Δψm) of cardiomyocytes. Results: We found that the expression of PINK1 decreased in mouse hearts during sepsis, which caused cardiomyocyte mitochondrial calcium efflux disorder, mitochondrial calcium overload and cardiomyocyte injury. In contrast, we found that exosomes isolated from huMSCs (huMSCs-exo) carried Pink1 mRNA that could be transferred to recipient cardiomyocytes, increasing PINK1 expression. Then, the reduction in cardiomyocyte mitochondrial calcium efflux was reversed, and cardiomyocytes recovered from their injury. Furthermore, we confirmed the effect of the PINK1-PKA-NCLX axis on mitochondrial calcium homeostasis in cardiomyocytes during sepsis.Conclusion: The PINK1-PKA-NCLX axis play an important role in cardiomyocytes mitochondrial calcium efflux, therefore PINK1 could be a therapeutic target to protect cardiomyocyte mitochondria, and the application of huMSCs-exo is a promising strategy against heart dysfunction induced by sepsis.

Mitochondrial Ca2+ transport is essential for regulating cell bioenergetics, Ca2+ signaling and cell death. Mitochondria accumulate Ca2+ via the mitochondrial Ca2+ uniporter (MCU), whereas Ca2+ is extruded by the mitochondrial Na+/Ca2+ (mtNCX) and H+/Ca2+ exchangers. The balance between these processes is essential for preventing toxic mitochondrial Ca2+ overload. Recent work demonstrated that MCU activity varies significantly among tissues, likely reflecting tissue-specific Ca2+ signaling and energy needs. It is less clear whether this diversity in MCU activity is matched by tissue-specific diversity in mitochondrial Ca2+ extrusion. Here we compared properties of mitochondrial Ca2+ extrusion in three tissues with prominent mitochondria function: brain, heart and liver. At the transcript level, expression of the Na+/Ca2+/Li+ exchanger (NCLX), which has been proposed to mediate mtNCX transport, was significantly greater in liver than in brain or heart. At the functional level, Na+ robustly activated Ca2+ efflux from brain and heart mitochondria, but not from liver mitochondria. The mtNCX inhibitor CGP37157 blocked Ca2+ efflux from brain and heart mitochondria but had no effect in liver mitochondria. Replacement of Na+ with Li+ to test the involvement of NCLX, resulted in a slowing of mitochondrial Ca2+ efflux by ∼70 %. Collectively, our findings suggest that mtNCX is responsible for Ca2+ extrusion from the mitochondria of the brain and heart, but plays only a small, if any, role in mitochondria of the liver. They also reveal that Li+ is significantly less effective than Na+ in driving mitochondrial Ca2+ efflux.

To elucidate the mechanism for preventing entry into embryonic diapause or breakdown of diapause in Bombyx mori by HCl and dimethyl sulfoxide (DMSO) treatment or a combination of cold and HCl treatment, we performed quantitative analysis of Ca2+ and Mg2+ in the chorion and egg content using inductively coupled plasma atomic emission spectrometry (ICP-AES). When diapause eggs that had been incubated at 25°C for 2 days from oviposition and at 4°C for an additional six days were treated with HCl solution, the amount of Ca2+ in the chorion and egg content after HCl treatment was reduced to one-seventh, as compared with the amount before treatment. In contrast, there was no change in the amount of Mg2+ with HCl treatment. The amount of Ca2+ in the HCl solution after the diapause eggs were treated increased 7.5-fold, as compared with that of eggs treated with water. Even when 17-day-old diapausing eggs were treated with HCl, which did not break diapause, the amount of Ca2+ in the chorion and egg content was reduced to one-fifth, as compared with the control. Meanwhile, changes in Ca2+ and Mg2+ contents were not observed in 12-hr-old diapause-destined eggs before or after treatment with DMSO, which effectively prevents diapause. These data may suggest that Ca2+ efflux from diapause eggs by HCl is not directly associated with preventing entry into diapause or breaking of diapause. In addition, we discovered that the amount of Ca2+ in diapause-destined eggs was more than 2.4-fold larger than in non-diapause-destined eggs.

Because of its outstanding thermochromic characteristics and metal-insulator transition (MIT) property, nano-vanadium dioxide (abbreviated as nano-VO2 or nVO2) has been applied widely in electrical/optical devices and design of intelligent window. However, the biological effect of nVO2 is not well understood, especially when affected by environmental factors or living organisms. For VO2 is an amphoteric oxide, we simulated pH's influence to nVO2’s physicochemical properties by exposure nVO2 in water of different pH values. We found that nVO2 transformed to a new product after exposure in acidic water for two weeks, as revealed by physicochemical characterization such as SEM, TEM, XRD, and DLS. This transformation product formed in acidic water was referred as (acidic) transformed nVO2). Both pristine/untransformed and transformed nVO2 displayed no obvious toxicity to common epithelial cells; however, the acidic transformed nVO2 rapidly induced macrophage cell death. Further investigation demonstrated that transformed nVO2 caused macrophage apoptosis by the induction of Ca2+ efflux and the following mitochondrial membrane permeabilization (MMP) process. And a more detailed time course study indicated that transformed nVO2 caused lysosomal membrane permeabilization (LMP) at the earlier stage, indicating LMP could be chosen as an earlier and sensitive end point for nanotoxicological study. We conclude that although nVO2 displays no acute toxicity, its acidic transformation product induces macrophage apoptosis by the induction of LMP and Ca2+ efflux. This report suggests that the interplay with environmental factors or living organisms can results in physicochemical transformation of nanomaterials and the ensuing distinctive biological effects.

Marine biofouling is a serious environmental problem worldwide. As an effort to find environmental friendly antifoulants, indole derivatives were determined for their activities to inhibit the growth of bacteria and diatom. The minimum inhibitory concentrations (MICs) of indole derivatives against bacteria were very low, especially for 6-chloroindole. It was proved that 6-chloroindole obviously inhibited the growth of bacteria, interfered with the formation of bacterial biofilm, destroyed bacterial cell morphology and also inhibited the growth of diatom Cylindrotheca sp. as well. By using noninvasive micro-test technique (NMT), 6-chloroindole triggered algal cellular Ca2+ efflux. The highest value was 72.03 pmol cm(-2) s(-1), 10.6 times of the control group. The present studies indicated that indole derivatives might have the potential to be new antifouling agents because of their excellent antibacterial and anti-algal activities. At the same time, Ca2+ efflux might be one of the mechanisms that indole derivatives inhibited the growth of diatom. (C) 2014 Elsevier Ltd. All rights reserved.

In many non-excitable eukaryotic cells, including hepatocytes, Ca(2+) oscillations play a key role in intra- and intercellular signalling, thus regulating many cellular processes from fertilisation to death. Therefore, understanding the mechanisms underlying these oscillations, and consequently understanding how they may be regulated, is of great interest. In this paper, we study the influence of reduced Ca(2+) plasma membrane efflux on Ca(2+) oscillations in hepatocytes. Our previous experiments with carboxyeosin show that a reduced plasma membrane Ca(2+) efflux increases the frequency of Ca(2+) oscillations, but does not affect the duration of individual transients. This phenomenon can be best explained by taking into account not only the temporal, but also the spatial dynamics underlying the generation of Ca(2+) oscillations in the cell. Here we divide the cell into a grid of elements and treat the Ca(2+) dynamics as a spatio-temporal phenomenon. By converting an existing temporal model into a spatio-temporal one, we obtain theoretical predictions that are in much better agreement with the experimental observations.

Waves of calcium-induced calcium release occur in a variety of cell types and have been implicated in the origin of cardiac arrhythmias. We have investigated the effects of inhibiting the SR Ca2+-ATPase (SERCA) with the reversible inhibitor 2′,5′-di(tert-butyl)-1,4-benzohydroquinone (TBQ) on the properties of these waves. Cardiac myocytes were voltage clamped at a constant potential between −65 and −40 mV and spontaneous waves evoked by increasing external Ca2+ concentration to 4 mm. Application of 100 μm TBQ decreased the frequency of waves. This was associated with increases of resting [Ca2+]i, the time constant of decay of [Ca2+]i and the integral of the accompanying Na+–Ca2+ exchange current. There was also a decrease in propagation velocity of the waves. There was an increase of the calculated Ca2+ efflux per wave. The SR Ca2+ content when a wave was about to propagate decreased to 91.7 ± 3.2%. The period between waves increased in direct proportion to the Ca2+ efflux per wave meaning that TBQ had no effect on the Ca2+ efflux per unit time. We conclude that (i) decreased wave frequency is not a direct consequence of decreased Ca2+ pumping by SERCA between waves but, rather, to more Ca2+ loss on each wave; (ii) inhibiting SERCA increases the chance of spontaneous Ca2+ release propagating at a given SR content.

The G protein-coupled estrogen receptor 1 (GPER) has been demonstrated to have a vast array of cardiovascular effects. Ca2+ extrusion via the plasma membrane Ca2+-ATPase (PMCA) plays important role...

The effects of Pion sarcoplasmic reticulum (SR) Ca2+regulation were studied in mechanically skinned rat skeletal muscle fibers. Brief application of caffeine was used to assess the SR Ca2+content, and changes in concentration of Ca2+([Ca2+]) within the cytosol were detected with fura 2 fluorescence. Introduction of Pi(1–40 mM) induced a concentration-dependent Ca2+efflux from the SR. In solutions lacking creatine phosphate (CP), the amplitude of the Pi-induced Ca2+transient approximately doubled. A similar potentiation of Pi-induced Ca2+release occurred after inhibition of creatine kinase (CK) with 2,4-dinitrofluorobenzene. In the presence of ruthenium red or ryanodine, caffeine-induced Ca2+release was almost abolished, whereas Pi-induced Ca2+release was unaffected. However, introduction of the SR Ca2+ATPase inhibitor cyclopiazonic acid effectively abolished Pi-induced Ca2+release. These data suggest that Piinduces Ca2+release from the SR by reversal of the SR Ca2+pump but not via the SR Ca2+channel under these conditions. If this occurs in intact skeletal muscle during fatigue, activation of a Ca2+efflux pathway by Pimay contribute to the reported decrease in net Ca2+uptake and increase in resting [Ca2+].

The effect of extracellular adenosine 5′-triphosphate (ATP) on Ca 2+ efflux from freshly isolated adult rat cardiomyocytes was examined. ATP stimulated the efflux of 45 Ca 2+ from the cells in a concentration-dependent manner (0.01–1 mM). The 45 Ca 2+ efflux from the cells was also stimulated by adenosine-5′-O-(3-thiotriphosphate) (ATP-γs) and α,β-methylene-ATP and adenosine 5′-diphosphate, but not by adenosine 5′-monophosphate and adenosine. The ATP-stimulated 45 Ca 2+ efflux was not affected by deprivation of the extracellular Ca 2+ , but was dependent on the presence of extracellular Na + . These results indicate that ATP stimulates extracellular Na + -dependent 45 Ca 2+ efflux from freshly isolated adult rat cardiomyocytes, probably through its stimulatory effect on the plasma membrane P 2 purinoceptors which may couple to Na + /Ca 2+ exchange.

Inactivation of the Ca2+extrusion mode of the retinal rod Na- Ca + K exchanger is suggested to be the mechanism that prevents lowering of cytosolic free Ca2+to < 1 nM when rod cells are saturated for a prolonged time under bright light conditions. Under these conditions, Ca2+fluxes across disk membranes can contribute significantly to Ca2+homeostasis in rods.

Tetraphenylphosphonium (TPP + ) inhibits Na + -stimulated Ca 2+ efflux from brain mitochondria. Half inhibition is observed when 1·10 −8 M TPP + is present in the medium. Some other lipophylic cations show similar effect. TPP + must be used carefully for measuring transmembrane potential because of its effects on the system studied. TPP + will be a useful tool to study Ca-transport system in mitochondria.

Bongkrekic acid and atractyloside, inhibitors of adenine nucleotide translocase, do not inhibit Ca2+ uptake and H+ production by pig heart mitochondria. However, bongkrekic acid, but not atractyloside, inhibits dinitrophenol-induced Ca2+ efflux and H+ uptake. Conversely, ruthenium red blocks Ca2+ uptake and H+ production but does not prevent dinitrophenol-induced Ca2+ efflux and H+ uptake by mitochondria. These results suggest that mitochondrial Ca2+ uptake and release exist as two independent pathways. The efflux of Ca2+ from mitochondria is mediated by a bongkrekic acid sensitive component which is apparently not identical to the ruthenium red sensitive Ca2+ uptake carrier.

IT was reported by Mela1,2 that local anaesthetics stimulate Ca2+ uptake by rat liver mitochondria. This has been attributed to the protective action of these compounds on mitochondrial structure3,4, particularly with regard to inhibition of phospholipase A (refs 5, 6). However, another possibility is that local anaesthetics affect differentially, and more directly, the uptake and efflux of Ca2+. Recent evidence suggests that mammalian mitochondria, in addition to the well documented route for Ca2+ accumulation, have a different mechanism for Ca2+ release7–9. In the case of rat liver mitochondria, inhibition of Ca2+ uptake by the addition of ruthenium red causes a slow release of Ca2+ from the mitochondrial matrix7,8 which is enhanced by substrates such as acetoacetate, which cause oxidation of intra-mitochondrial NADH (ref. 10). In mitochondria from other tissues, such as heart and brain8,9, the ruthenium red-insensitive release is dependent on Na+ ions. We report here, using mitochondria from both rat liver and brain, that nupercaine and tetracaine, at concentrations which do not inhibit Ca2+ uptake, cause considerable inhibition of the ruthenium red-insensitive Ca2+ efflux observed in energised conditions.

During the 1970’s it was established that the inner membrane of isolated mitochondria from adrenal cortex, heart, and liver can display an unusually high permeability to small molecules and ions following the imposition of certain metabolic conditions (1–10). Generally, what is required to produce the permeable inner membrane state is energy-dependent Ca2+ accumulation preceding or following the administration of another agent which is often referred to as a “Ca2+ -releasing agent” (11–14). Substances possessing “Ca2+-releasing agent” activity normally lack detergent properties and are diverse with respect to their chemical properties and biological activities. The “Ca2+-releasing agents” investigated by our group include N-ethylmaleimide (5, 6, 11, 13, 15), t-butylhydroperoxide (14–16), oxalacetate, (11), inorganic phosphate (11, 13), rhein (16), and hypolipidemic drugs such as WY-14643 and dofibric acid (17).

The effects of fatty acids and monovalent cations on the Ca2+ efflux from isolated liver and kidney mitochondria were investigated by means of electrode techniques. It was shown that unsaturated fatty acids and saturated fatty acids of medium chain length (C12 and C14) induced a Ca2+ efflux from mitochondria which was not inhibited by ruthenium red, but was specifically inhibited by Na+ and Li+. The Ca2+-releasing activity of unsaturated fatty acids did not correlate with their uncoupling activity. In kidney mitochondria a spontaneous, temperature-dependent Ca2+ efflux was observed which was inhibited either by albumin or by Na+. It is suggested that the net Ca2+ accumulation by mitochondria depends on the operation of independent pump and leak pathways. The pump is driven by the membrane potential and can be inhibited by ruthenium red, the leak depends on the presence of unsaturated fatty acids and is inhibited by Na+ and Li+. It is suggested that the unsaturated fatty acids produced by mitochondrial phospholipase A2 can be essential in the regulation of the Ca2+ retention in and the Ca2+ release from the mitochondria.

The Ca2+ efflux from smooth muscle into a Ca2+-free physiological solution was continuously monitored by using a Radiometer Ca2+-selective electrode and examined for its availability for determination of Ca2+ effluxed from the smooth muscle. The results show that the Ca2+ electrode used here is sufficiently sensitive to investigate Ca2+ efflux from the smooth muscle into the Ca2+-free solution. Further, this method is suitable for the continuous recording of free ionized Ca2+ effluxed from the smooth muscle into the Ca2+-free physiological solution.

The pyridine nucleotide specificity, the participation of Δψ, and the energy-linked transhydrogenase in the process of Ca2+ efflux stimulated by the oxidized state of NAD(P) were examined in rat liver mitochondria energized by ascorbate + TMPD. The following observations were made: (i) The Ca2+ efflux rate is independent of the redox state of mitochondrial NAD, but is at a minimum when mitochondrial NADP is in the reduced state and accelerated several-fold when it is in the oxidized state, (ii) When the redox state of NADP is shifted to a more oxidized state, the steady-state level of Ca2+ in the medium increased and Δψ decreased in proportion to the mitochondrial NADP+ level, (iii) The activity of the energy-linked NAD(P) transhydrogenase seems to be a key element in determining the redox state of NADP and thus of Ca2+ retention and efflux from mitochondria.

The Ca2+ with the calmodulin system plays a major role in the receptor-induced intracellular biochemical events. Thus, as in our previous studies, we found an altered postreceptorial coupling in the case of elderly, we were interested to elucidate the Ca2+ transport in the case of healthy young (less than 25 years) and aged (greater than 65 years) subjects. The chemotactic peptide FMLP was used for receptor stimulation. Our data show that both spontaneous and FMLP-triggered Ca2+ extrusion measured on monocyte monolayers is decreased with aging. The FMLP-triggered Ca2+ extrusion nevertheless did not occur through the TFP-sensitive pathway. These alterations of Ca2+ transport seem to indicate an impaired Ca2+-calmodulin function in monocytes with aging.

1. Two processes of Ruthenium Red-insensitive Ca2+ efflux exist in liver and in heart mitochondria: one Na+-independent, and another Na+-dependent. The processes attain maximal rates of 1.4 and 3.0 nmol of Ca2+.min-1.mg-1 for the Na+-dependent and 1.2 and 2.0 nmol of Ca2+.min-1.mg-1 for the Na+-independent, in liver and heart mitochondria, respectively. 2. The Na+-dependent pathway is inhibited, both in heart and in liver mitochondria, by the Ca2+ antagonist diltiazem with a Ki of 4 microM. The Na+-independent pathway is inhibited by diltiazem with a Ki of 250 microM in liver mitochondria, while it behaves as almost insensitive to diltiazem in heart mitochondria. 3. Stretching of the mitochondrial inner membrane in hypo-osmotic media results in activation of the Na+-independent pathway both in liver and in heart mitochondria. 4. Both in heart and liver mitochondria the Na+-independent pathway is insensitive to variations of medium pH around physiological values, while the Na+-dependent pathway is markedly stimulated parallel with acidification of the medium. The pH-activated, Na+-dependent pathway maintains the diltiazem sensitivity. 5. In heart mitochondria, the Na+-dependent pathway is non-competitively inhibited by Mg2+ with a Ki of 0.27 mM, while the Na+-independent pathway is less affected; similarly, in liver mitochondria Mg2+ inhibits the Na+-dependent pathway more than it does the Na+-independent pathway. In the presence of physiological concentrations of Na+, Ca2+ and Mg2+, the Na+-independent and the Na+-dependent pathways operate at rates, respectively, of 0.5 and 1.0 nmol of Ca2+.min-1.mg-1 in heart mitochondria and 0.9 and 0.2 nmol of Ca2+.min-1.mg-1 in liver mitochondria. It is concluded that both heart and liver mitochondria possess two independent pathways for Ca2+ efflux operating at comparable rates.