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Intracellular Ca 2+ ions as second messenger played key role in cell behaviour, which was often overlooked in traditional antitumor treatment. Disrupting Ca 2+ ion homeostasis by Ca 2+ overload might switch ions signal from 'regulating' to 'destroying'. Inspired by this, a biomimetic Ca 2+ nanogenerator was constructed. Briefly, the curcumin (CUR) was loaded into mesoporous calcium carbonate nanoparticles (MCC NPs), and then coated with platelet (PLT) membrane. Upon reaching tumour cells by PLT membrane-mediated tumour targeting effect, PLT@MCC/CUR would instantaneously decompose in acidic lysosomes, concurrently accompanying with Ca 2+ generation and CUR release. The CUR could further facilitate Ca 2+ release from endoplasmic reticulum (ER) and inhibit Ca 2+ efflux, aggravating Ca 2+ overload to disrupt mitochondrial Ca 2+ homeostasis for mitochondria apoptosis signalling pathway activation. Interestingly, such effect was ineffective in normal cells, realising the tumour-specific therapeutic therapy. Based on ions interference strategy, PLT@MCC/CUR herein offered synergistic combination of Ca 2+ overload therapy and chemotherapy, which would pave the way towards more effective nanotherapeutics.

Heart failure (HF), the leading cause of death among men and women world-wide, causes great health and economic burdens. HF can be triggered by many factors, such as coronary artery disease, heart attack, cardiomyopathy, hypertension, obesity, etc., all of which have close relations with calcium signal and the level of reactive oxygen species (ROS). Calcium is an essential second messenger in signaling pathways, playing a pivotal role in regulating the life and death of cardiomyocytes via the calcium-apoptosis link mediated by the cellular level of calcium. Meanwhile, calcium can also control the rate of energy production in mitochondria that are the major resources of ROS whose overproduction can lead to cell death. More importantly, there are bidirectional interactions between calcium and ROS, and such interactions may have therapeutic implications in treating HF through finely tuning the balance between these two by certain drugs. Many naturally derived products, e.g., flavones and isoflavones, have been shown to possess activities in regulating calcium and ROS simultaneously, thereby leading to a balanced microenvironment in heart tissues to exert therapeutic efficacies in HF. In this mini review, we aimed to provide an updated knowledge of the interplay between calcium and ROS in the development of HF. In addition, we summarized the recent studies ( in vitro , in vivo and in clinical trials) using natural isolated flavones and isoflavones in treating HF. Critical challenges are also discussed. The information collected may help to evoke multidisciplinary efforts in developing novel agents for the potential prevention and treatment of HF., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Yu, Huang, Wu, Chen, Chen and Cui.)

We studied the role of acetylcholine (ACh) and calcium overload in the induction of atrial flutter or atrial fibrillation (AF) in right atria from 34 normal male Syrian hamsters (F1B) and 33 cardiomyopathic Syrian hamsters (BIO 14.6) associated with focal myocardial necrosis. Action potential (AP) was recorded with conventional microelectrode techniques and twitch force by a transducer. ACh (0.1, 1 and 10 μM) induced high-frequency AF (around 33 Hz) along with tension oscillations and contracture in 7 of 12 normal hamster atria. These effects of ACh were abolished by tetrodotoxin or quinidine as well as by atropine. In contrast, ACh induced AF only in 1 of 12 myopathic atria. In both normal and myopathic atria, ACh induced similar changes in AP duration, spontaneous rate and force. The effects of calcium overload were tested by means of a high [Ca[sup 2+] ][sub o] (8.1 mM) low [K[sup +] ][sub o] (1 mM) solution in another series of experiments. This solution also induced incidence of AF higher in normal (10/12) than in myopathic atria (4/12). The calcium load was also increased by high-frequency pacing (32 Hz for 3 or 30 s): AF occurred in normal atria (5/8), but not in myopathic atria (0/8). Measurement of the refractory period revealed a longer refractory period in myopathic than in control atria. We concluded that the lower incidence of AF in myopathic atria was probably due to their longer refractory period and the associated focal myocardial necrosis which then hindered the establishment of such a reentrant rhythm. [ABSTRACT FROM AUTHOR]

Although early reperfusion of cardiac tissue is now considered to be the only intervention capable of restoring the various cellular functions altered by ischaemia and preventing progression towards necrosis of myocardial cells, reperfusion is frequently accompanied by various manifestations grouped under the heading of reperfusion syndrome or reperfusion injury. Functional recovery is therefore not immediate, but usually appears after a certain delay following a period of contractile dysfunction (myocardial stunning) lasting for several hours or even days after the start of reperfusion. Characteristic reperfusion-induced arrhythmias are also observed. The cellular mechanisms underlying the reperfusion syndrome may involve cellular calcium overload, over-production of oxygen-derived free radicals, acidosis and/or development of an inflammatory reaction. Numerous pharmacological studies have been conducted over several years designed to limit such reperfusion injury and, consequently, prevent stunning and/or reperfusion-inducedarrhythmias. A number of experimental studies in this field have demonstrated that trimetazidine exerts direct anti-ischaemic effects, limiting calcium accumulation and acidosis, inflammation and oxygen-derived free radical production following reperfusion. This agent therefore appears to be particularly promising clinically in the treatment of reperfusion lesions, for example in combination with thrombolysis during the acute phase of myocardial infarction. [ABSTRACT FROM PUBLISHER]

We recently described autoantibodies to the ADP/ATP carrier of the inner mitochondrial membrane as an organ specific autoantigen found in high frequencies in sera of patients with myocarditis and dilated cardiomyopathy. These antibodies not only showed an intracellular binding at the mitochondrial membrane, but also crossreact with antigenic determinants at the cardiac myocyte plasma membrane. They therefore may account, at least in part, for the so-called sarcolemmal-bound IgG of heart-reactive autoantibodies found to be associated with these diseases. Heart muscle diseases are associated with electrocardiographic abnormalities such as complex ventricular arrhythmias and disturbed ventricular function. Our data indicate that abnormalities in current spread and impaired heart contractility might also be caused by an antibody mediated disturbance of calcium channel gating leading to prolongation of the action potential and potentiation of tension. The enhanced calcium permeability of the cell may moreover cause calcium overload and cell death. The calcium channel complex plays a central role in cardiac contractility. Disturbing calcium channel gating by antibodies might therefore contribute to the pathogenesis of these diseases. [ABSTRACT FROM PUBLISHER]

During hibernation animals decrease their body temperature down to a few degrees above 0 °C. This means that when entering into and arousing from hibernation their body temperature passes through the critical level of 20 °C, a temperature region where nonhibernating mammals develop circulatory arrest, usually ventricular fibrillation (VF). The hibernator heart is resistant to VF, not only induced by hypothermia, but also when induced by local application of aconitine on the epicardium, and other ways of inducing VF in nonhibernators. Several mechanisms may explain this resistance to VF of the hibernator heart. The factors of greatest importance seem to be the different adrenergic innervation pattern, the different physico-chemical properties with a lower melting point of the lipids in the hibernator, the different enzyme temperature activity curves in the hibernator and the different handling of intracellular calcium, which results in protection against calcium overload in the hibernator heart, when compared with the nonhibernator heart. [ABSTRACT FROM PUBLISHER]

Objectives Calcium overload induces spontaneous cyclic calcium release from the sarcoplasmic reticulum, leading to spontaneous myocardial oscillation. This study was designed to elucidate (1) the effect of the myocardial oscillation on changes in ventricular performance and (2) how these changes relate to the strength of the diastolic spontaneous myocardial oscillation and the spatial extent—that is, in how extensive an area of the epicardium it occurred. Methods the isovolumic pressure of the left ventricle and epicardial fura 2 fluorescence in isolated hamster hearts were simultaneously observed at various calcium concentrations ([Ca2+]o). Endothelial cells and pericytes of the capillaries, preferentially stained by fura 2, were passively oscillated by surrounding myocytes during diastole at concentrations greater than 1 mmol/1 of [Ca2+]o. The strength of the myocardial oscillation was evaluated as the root mean square (RMS) of fluctuation in the distance between endothelial cells or pericytes. The spatial extent of the myocardial oscillation was estimated as the appearance rate, defined as the ratio of the number of microscopic fields showing the capillary oscillation, to the total number of examined fields. Results Up to 4 mmol/l of [Ca2+]o, developed pressure and maximum rate of pressure rise significantly increased in a manner dependent on [Ca2+]o, but a further increase in [Ca2+]o significantly decreased these parameters. In the presence of ryanodine (2.5 μmol/l), developed pressure and maximum rate of pressure rise monotonously increased in a manner dependent on [Ca2+]o. Although the oscillation was never observed at 1 mmol/l of [Ca2+]o (appearance rate = 0%), it occurred in some of the microscopic fields at 2 and 4 mmol/l (appearance rate = 19.5 and 56.3%, respectively) and occurred in all microscopic fields at concentrations greater than 4 mmol/l (appearance rate = 100%). Ryanodine, which completely eliminated the capillary oscillation, inhibited the increase of both RMS and end-diastolic pressure by an increase in [Ca2+]o. Conclusions Our data suggest that the myocardial oscillation impairs systolic and diastolic function in intact ventricle, and that these effects are associated with the spatial extent and the strength of the myocardial oscillation. [ABSTRACT FROM PUBLISHER]

Objectives: The purpose of this study was to investigate the effects of prolonged arachidonic acid (AA) exposure on electrically induced fluctuations of cytosolic free Ca2+ concentration ([Ca2+]i) in cardiac myocytes and to identify intracellular biochemical events that may play a role in the actions of AA on [Ca2+]i dynamics. Methods: Electrically induced [Ca2+]i transients were investigated in cultured single neonatal rat ventricular myocytes using spectrofluorometric analysis of fura-2-[Ca2+]i binding. KCl-induced depolarization, caffeine and ryanodine were used to assess the effects of AA on Ca2+ handling by the sarcolemma and the sarcoplasmic reticulum. Prostanoid formation was measured with an ELISA technique. α-Tocopherol was used to determine if free radical formation was a factor in the AA effects on [Ca2+]i. Results: Exposure to 10–30 μM AA produced a concentration-dependent and reversible configuration change and eventually a cessation of [Ca2+]i transients. Continued exposure resulted in a Ca2+ overload (tonic [Ca2+]i greater than peak systolic [Ca2+]i). AA did not influence KCl-induced [Ca2+]i increase but did eliminate caffeine-induced [Ca2+]i transients. AA exposure stimulated the formation of 6-oxo-prostaglandin F1α in a concentration-dependent manner, but thromboxane B2 formation was not influenced. α-Tocopherol pretreatment significantly delayed times till cessation of [Ca2+]i transients and Ca2+ overload, whereas ryanodine and cyclo-oxygenase inhibitors were without effect. Conclusions: The present data provide evidence that the initial action of AA on [Ca2+]i transients during excitation-contraction coupling involves an effect of AA on sarcolemmal Ca2+ influx and sarcoplasmic reticulum Ca2+ handling. AA-induced cessation of electrically induced [Ca2+]i transients and Ca2+ overload may involve the formation of free radicals. [ABSTRACT FROM PUBLISHER]

Objective: As a result of oxidative stress to membrane lipid matrix, the peroxidation of polyunsaturated fatty acids induced the transient formation of lipid hydroperoxides (ROOM). The aim of this study was to evaluate the damaging effects of ROOH on the cardiac cell and the link between the alterations observed and intracellular calcium overload. Methods: Necrosis of cultured rat cardiac cells was determined by measuring the release of lactate dehydrogenase (LDH). In guinea-pig papillary muscles, action potential (AP) and isometric tension were recorded with standard microelectrodes and a transducer, respectively. The reactive oxygen species (ROS) scavenging properties of tested compounds were determined using a cell-free model of lipid photoperoxidation. Results: 15(S)-HpETE (15(S)-hydroperoxyeicosatetraenoic acid), an arachidonic acid hydroperoxide, induced a concentration-dependent loss of cardiomyocytes membrane integrity. The release of LDH induced by 15(S)-HpETE (30 μM) was prevented by a ROS scavenger, BW755C (10 μM), but not by a sarcolemmal calcium channel blocker, Amlodipine (10 μM), or a calcium overload protective agent, R56865 (10 μM). Cardiomyocytes necrosis induced by calcium paradox was prevented by Amlodipine (10 μM) and R56865 (10 μM), but not by BW755C (10 μM). Superfusion of papillary muscles with 15(S)-HpETE (20 μM) induced a membrane depolarization and a marked reduction in the AP amplitude and duration. Concomitantly, a transient positive inotropic effect and a progressive rise in diastolic tension were observed. These alterations were maximal after 15 min and associated with delayed after-depolarizations (DADs) and after-contractions. Every alteration was inhibited by BW755C (10 μM) and R56865 (30 μM), but not by Amlodipine (1 μM). Ryanodine (1 μM), a blocker of sarcoplasmic reticulum calcium channel, only prevented the appearance of DADs and after-contractions. Only BW755C exibited ROS scavenging properties. Conclusions: ROOH induced enzyme leakage and electromechanical alterations in cardiac cells. These effects of ROOH implicated oxidative mechanisms and resulted in an intracellular calcium overload. [ABSTRACT FROM PUBLISHER]

Objectives: The relative contribution of oxygen free radicals, disturbances in calcium homeostasis and Na+/H+ exchange in the development of injury in the ischemic/reperfused bean was investigated. The study was designed to assess whether these factors initiate independent mechanisms of injury or, alternatively, they share a common mechanism of toxicity. Methods: Isolated working rat hearts were subjected to different periods (30–55 min) of global ischemia and then were reperfused for 30 min. We compared the effects of oxygen radical scavengers (10 mM dimethylthiourea, DMTU and 0.6 mM desferrioxamine), inhibitors of Na+/H+ exchange (0.15 mM amiloride and 15 μM dimethylamiloride, DMA) and of 0.1 μM diltiazem, which was used to limit calcium overload, given alone or in combination, on the rate of myocardial injury development (recovery of hemodynamic function, LDH release, incidence of severe arrhythmias and structural integrity of cardiomyocytes were estimated at reperfusion following different periods of ischemia). Results: All interventions studied, when given alone, provided nearly equivalent cardioprotection. DMTU or desferrioxamine when applied in combination with diltiazem provided additive cardioprotection, relatively limited, however, as compared to the remarkable cardioprotection achieved by DMTU or desferrioxamine in combination with amiloride. Conclusions: All mechanisms studied may contribute in an equal manner to the rate of injury development in the ischemic/reperfused heart. The oxygen free radicals-induced myocardial injury may be partially attributed to some disturbance in intracellular calcium homeostasis, possibly calcium overload, whereas the damaging effect of the Na+/H+ exchange activated upon reperfusion is probably largely related to some other mechanism. [ABSTRACT FROM PUBLISHER]

Objective: The aim was to answer the following questions: (1) Does treatment with calcium antagonists have to be begun before ischaemia or is postischaemic application also protective? (2) When applied before ischaemia, do calcium antagonists have to depress preischaemic cardiac function in order to elicit protection? (3) Is cardioprotection a matter of improved reflow or do the agents influence the degree of oxidative injury during reperfusion? Methods: Isolated working guinea pig hearts underwent ischaemia (15 min) and reperfusion (15 min). The calcium antagonist gallopamil was given either before (0.1 nM and 1 nM) or after ischaemia (0.1 nM) during early reperfusion (first 5 min). Recovery was defined as postischaemic compared to preischaemic external heart work, expressed in percent. Oxidative stress was assessed by the release of glutathione (GSH). Lactate release served as a measure of the ischaemic challenge. The ability of gallopamil to scavenge oxygen radicals directly was investigated in an in vitro chemiluminescence assay. Results: Pump function of control hearts recovered to only 28% after reperfusion. Pretreatment with 0.1 and 1 nM gallopamil improved recovery to the same extent (48.7% and 43.4%, respectively); however, postischaemic application of 0.1 nM gallopamil afforded equal protection (45.4% recovery). Only the higher concentration of 1 nM gallopamil depressed preischaemic external heart work (by 11%). During earliest reperfusion (1–5 min), release of GSH only tended to be lower in treated hearts. During the subsequent minutes of reperfusion (5–15 min), release of GSH was significantly less in hearts postischaemically treated with 0.1 nM gallopamil (40 pmol·min−1v 940 pmol·min−1 for controls). In contrast, ischaemia-induced lactate release did not differ between the groups. Gallopamil did not scavenge reactive oxygen species in vitro. Conclusions: Short term postischaemic application of the calcium antagonist gallopamil is almost as effective at restoring pump function as preischaemic application which, in turn, does not have to depress preischaemic cardiac function in order to elicit protection. A reduction of oxidative stress during reperfusion seems to contribute to the beneficial effects of postischaemic application of gallopamil, but a direct oxygen radical scavenging activity of gallopamil is not involved. [ABSTRACT FROM PUBLISHER]

Objective: Both inhibition of glycolysis and enhancement of the H+ buffering capacity of the perfusate during ischaemia reduce myocardial reperfusion injury. The aim of the study was to investigate whether these manoeuvres, performed separately or together, could reduce myocardial stunning after brief global ischaemia. Methods: The hearts of male Sprague-Dawley rats were preperfused for 10 min with oxygenated or hypoxic buffer (pH 7.4) containing 100 mM sucrose, 100 mM HEPES, or 5 mM 2-deoxyglucose plus 100 mM sucrose, followed by 15 min of total ischaemia and 30 min of reperfusion. In some hearts, 5 mM 2-deoxyglucose was combined with 100 mM HEPES during the 10 min preperfusion period. Results: Brief hypoxic preperfusion, 2-deoxyglucose, or HEPES reduced myocardial stunning as well as improving the metabolic recovery and reducing Ca2+ overload after reperfusion. These changes were associated with a smaller increase in intracellular Na+ and a smaller decrease of coronary effluent pH at the end of ischaemia. In contrast, the combination of HEPES with hypoxic preperfusion or 2-deoxyglucose depressed functional recovery and increased the intracellular Na+ level at the end of ischaemia as well as increasing Ca2+ overload after reperfusion. This happened even though the decrease in coronary effluent pH was attenuated to the same extent as before. Conclusions: Both inhibition of glycolysis and enhancement of the perfusate H+ buffering capacity before ischaemia attenuated myocardial stunning, but the protective effect of each manoeuvre was lost when they were combined.Cardiovascular Research 1993;27:1645-1650 [ABSTRACT FROM PUBLISHER]

Objective: The relationship between oxidative stress induced cell necrosis and perturbation of intracellular calcium homeostasis was investigated in cultured myocytes. Methods: Cultured neonatal rat heart cells were loaded with fura-2 AM to measure cytosolic free calcium ([Ca2+]i). Probenecid, an inhibitor of organic anion transport, was present during the experiment to reduce efflux of fura-2 from the cytoplasm. Cells were exposed to cumene hydroperoxide, a toxic organic hydroperoxide that is known to induce oxidative stress in myocytes. The efficacy of the protective agents Trolox C (a vitamin E analogue) and chlorpromazine (a phospholipase inhibitor) on cumene hydroperoxide induced cell injury was determined. Results: [Ca2+]i in control cells was constant (60 nM) during an incubation time of 45 min. Probenecid did not affect [Ca2+]i levels or cell viability under the experimental conditions. Cumene hydroperoxide caused a sustained rise in [Ca +]i starting after 5-10 min, to a level of 1300 nM at 45 min. After 20-25 min the viability of the heart cells started to decline and after 45 min 44% of the cells were irreversibly injured. The loss of cell viability was expressed as percentage decrease of the fluorescence at 360 nm (the calcium independent wavelength), since the percent release of cellular α-hydroxybutyrate dehydrogenase (α-HBDH) activity equalled the percent decrease of the fluorescence at 360 nm. Trolox C and chlorpromazine almost completely prevented the cumene hydroperoxide induced α-HBDH release. The [Ca2+]i of myocytes incubated with cumene hydroperoxide in combination with Trolox C rose to 1000 nM without affecting cell viability. The cumene hydroperoxide induced rise in [Ca2+]i was markedly reduced by chlorpromazine (at t=45 min, [Ca2+]i=360 nM). Addition of Trolox C to untreated cells did not influence [Ca2+]i, whereas chlorpromazine alone induced a slight increase of [Ca2+]i up to 360 nM with complete preservation of cell viability. Conclusions: Trolox C and chlorpromazine are very effective inhibitors of cumene hydroperoxide induced perturbation of calcium homeostasis and subsequent cell death. A role for peroxidation of membrane phospholipids and activation of calcium dependent phospholipase in the cascade of events leading to irreversible injury is suggested. [ABSTRACT FROM PUBLISHER]

Extracellular Ca2+-influx induced by trivalent metal ions (Fe3+, Al3+, Cr3+, In3+, Ga3+, and La3+) in Ehrlich carcinoma cells is enhanced by ATP. This action seems to be related to the high coordination capacity of the ATP ligand that inhibits the polymerization of the solvated cations taking place at physiological pH, and consequently permits their biological activity. A general relationship between induced lipid peroxidation and increased calcium uptake was not found. These results emphasize the ATP role in the toxicity of trivalent metals, and its possible involvement, via cellular calcium overload, in a neurodegenerative process, such as Alzheimer's and Parkinson's diseases, in whose etiology the implication of aluminum and iron has been suggested. [ABSTRACT FROM AUTHOR]

The number of putative calcium channels in cardiac muscle from young adult hamsters (60 days old) was compared in normal (F1B) hamsters and two different mutant strains (CHF 146 and Bio 14.6) which express cardiomyopathy and muscular dystrophy. Equilibrium binding assays of high affinity sites for [3H]-nitrendipine in ventricular homogenate preparations showed that the maximum number of [3H]-nitrendipine binding sites (Bmax), which corresponds to the number of putative calcium channels, was not significantly different in normal and cardiomyopathic hearts: 79(SEM9), 64(14) and 69(10) fmol·mg−1 protein in 4-6 hearts from F1B, Bio 14.6 and CHF 146 hamster strains, respectively. Similar results were obtained with binding data after partial purification of the preparation. These data are in agreement with earlier studies comparing two normal strains (CHF 148 and random bred Syrian hamsters) with cardiomyopathic (CHF 146) hamsters, and conflict with other studies comparing normal and cardiomyopathic hamsters. Comparisons with the conflicting data suggest (a) that change in the number of high affinity [3H]-nitrendipine binding sites is not responsible for calcium overload and cell necrosis in cardiomyopathy, and (b) that increased numbers of low affinity [3H]-nitrendipine binding sites may emerge in cardiomyopathic hearts. [ABSTRACT FROM PUBLISHER]

The hypothesis that in the presence of acetylcholine overdrive may induce spontaneous repetitive activity (overdrive excitation) was tested by recording the transmembrane potentials and contractile force in sheep cardiac Purkinje fibres perfused in vitro. The results were: (a) acetylcholine 10−8 to 10−4 mol·litre−1 increased the action potential duration, the diastolic depolarisation slope and amplitude, and the twitch amplitude in a dose dependent manner; (b) at concentrations of 10−5 to 10−4 mol·litre−1 the interruption of a 60 beat·min−1 drive often induced repetitive spontaneous activity which was fastest immediately after the drive, slowed gradually, and ceased abruptly when an oscillatory potential failed to attain the threshold; (c) in the presence of acetylcholine, in quiescent preparations, applying drives of different durations and at different frequencies resulted in a steeper and larger diastolic depolarisation, oscillatory potentials, and a prolonged afterdepolarisation; (d) when overdrive excitation was induced it was faster and longer after faster or longer overdrives; (e) the cessation of overdrive was often associated with an aftercontraction; (f) in me presence of acetylcholine and a high extracellular calcium concentration (10.8 mmol·litre−1) overdrive excitation was preceded by a short period of inhibition; (g) strophanthidin (5 × 10−8 mol·litre−1) facilitated acetylcholine induced overdrive excitation (wimout an initial inhibition); (h) lowering the extracellular sodium concentration (-50% NaCl) antagonised overdrive excitation; and (i) atropine 10−5 mol·litre−1 prevented acetylcholine induced overdrive excitation.It is concluded that acetylcholine induces overdrive excitation by causing a larger diastolic depolarisation, oscillatory potentials, and a transient prolonged afterdepolarisation; that overdrive excitation requires sodium as a charge carrier underlying the electrical events leading to the attainment of the threshold; and that acetylcholine induces excitation by acting on a muscarinic receptor. [ABSTRACT FROM PUBLISHER]

The Ca2+ paradox is characterized by a rapid and uncontrolled entry of ca2+ Whilst the consequence of the resultant gain in Ca2+ are relatively well defined, uncertainty exists concerning the route of entry. Possible routes include passive diffusion across damaged sarcolemma and intercalated discs, active transport in exchange for K+ or Na+ and entry through the voltage-activated, Ca2+ slow channels. The following experiments were designed to differentiate between these possibilities.Isolated spontaneously beating Sprague-Dawley rat hearts were perfused at 37ΰC with Ca2+ perfusion buffer for >1 min before starting Ca2+ repletion. Adding 2–4 m mol l−1 Co2+ or Mn2+ before, during but not coincident with Ca2+ repletion protected against the paradox as indicated by an absence of myoglobin release and Ca2+ overload. Despite this protection marked distortion of the glycocalyx occurred, with splitting of the basement coat and blebbing. The intercalated discs, however, remained intact. It seems unlikely therefore that splitting of the basement coat necessarily results in an uncontrolled entry of Ca2+Since Mn2+ and Co2+ block Ca2+ entry through the slow channels their failure to prevent the uncontrolled entry of Ca2+ when added at the time of Ca2+ repletion favours the view that Ca2+ entry during the paradox does not depend upon entry of Ca2+ through the slow channels.In other experiments hearts were preloaded with Na2+ to alter intracellular Na2+ before Ca2+ repletion. This procedure did not markedly affect the gain in Ca2+These findings will be discussed in terms of the route(s) and consequence(s) of the uncontrolled entry of Ca2+ that occurs when Ca2+ is reintroduced after a period of Ca2+-free perfusion. [ABSTRACT FROM PUBLISHER]

Sequential perfusion of the heart with Ca2+-free and Ca2+ containing solutions leads to defects in myocytal surface membranes through which excess Ca2+ enters and cytosolic constituents leave the cells.During Ca2+-free perfusion the glycocalyx of the cells is damaged Lipoprotein lipase, bound to mucopolysaccharides on the outside of cells, is released during Ca2+-free perfusion. This enzyme, involved in lipoprotein triglyceride uptake into the cells, is an α-lipase. which also hydrolyzes phospholipids In addition to this phospholipase A1 activity some phospholipase A2 activity, due to another enzyme, is partially lost during Ca2+-free perfusion. The partial loss of this enzyme might be a reflection of the known increase of motional freedom of membrane phospholipids in the absence of Ca2+. The reintroduction of Ca2+ might rearrange phospholipids and activate residual phospholipase A2 so that pores arise that allow the passage of excess amounts of Ca2+ There is no reason to believe that the membranes of the organelles beyond the plasmalemma contribute to the early phenomena of the calcium paradox, as no soluble enzymes, contained within these organelles, are initially released from the heart. However, the calcium overload may stimulate Ca2+-dependent (phospho)lipases and proteases to contribute to the irreversible loss of structure and function. [ABSTRACT FROM PUBLISHER]

The effect of 7-oxo PGI on function and metabolism of postischemic reperfused (30-min ischemia and 30-min reperfusion) rat hearts was studied with special regard to calcium overload as one of the main factors of the postischemic reperfusion damage to the heart. The drug (50 μg/kg i.p.) was applied 48 h prior to starting the experiments on isolated rat hearts (Langendorff preparation at 37 °C and constant perfusion pressure of 65 mm Hg). A late protective effect of 7-oxo PGI was manifested by an improved recovery of heart function during reperfusion and calcium overload, better preservation of myocardial ATP contents during ischemia and also after calcium overload, as well as by a normalization of the lactate content, otherwise extremely increased during ischemia. Electron microscopic data also supported the above results. The beneficial effect of pretreatment with PGI may be explained not only by its vasodilating action, but more by its membrane stabilizing effect with a consequently decreased sodium accumulation, potassium loss, as well as intracellular calcium overload. [ABSTRACT FROM AUTHOR]

The protective effects of lidoflazine and mioflazine against shape changes in isolated rat cardiac myocytes induced by depolarizing concentrations of potassium and veratrine have been examined. Myocardial cells, isolated from adult rat hearts and plated in Petri-dishes, yielded a population of nearly 100% rod-shaped calcium-tolerant myocytes. Addition of veratrine or potassium resulted in a calcium-dependent cell shortening and finally rounding up of nearly all cells. Ultrastructurally, the shape changes were accompanied by a complete loss of calcium associated with the sarcolemmal and T-tubular bilayer. Calcium deposits accumulated in the mitochondria, indicating intracellular calcium overload. Pretreatment of the myocytes with lidoflazine or mioflazine (10-10 M) dose-dependently increased the number of remanining rod-shaped cells after potassium or veratrine addition. Such rod-shaped cells retained a normal pattern of calcium distribution along the sarcolemma and T-tubuli with no evidence of mitochondrial calcium overload. The protective effects of lidoflazine and mioflazine are explained in terms of preserving sarcolemmal integrity, whereby excessive calcium influx and subsequent cytosolic calcium overload could be prevented. [ABSTRACT FROM AUTHOR]

The role of extracellular calcium in the process of oxidative stress-induced calcium overload and cell death was investigated in cultured neonatal rat myocytes. Oxidative stress was induced by addition of cumene hydroperoxide (CHPO), a toxic organic hydroperoxide, in combination with varying extracellular calcium concentrations (1. normal calcium buffer: 2.5 mM Ca, 2. low calcium buffer: 5 μM Ca, 3. zero calcium buffer: 2.5 mM EGTA, no CaCl). Intracellular free calcium ion concentration ([Ca]) was measured with fura-2 using a spectrofluorometer. To study the toxicant-induced changes in [Ca] in more detail, single cell imaging was performed using digital imaging fluorescence microscopy (DIFM). In control experiments (in the absence of CHPO, but under different extracellular Ca conditions) the [Ca] remained at the basal level and cell viability was preserved. Administration of CHPO (50 μM) to the myocyte cultures generated a sustained increase in [Ca] followed by loss of cell in the rise in [Ca] but was not able to prevent the CHPO-induced calcium overload and cell necrosis. Addition of EGTA (2.5 mM) to the low calcium buffer resulted also in CHPO-induced cell death, although no increase in [Ca] was observed. In normal and low calcium buffers, DIFM revealed that CHPO produced a temporally and spatially heterogeneous distribution of [Ca] in a group of myocytes. So in the presence of normal or low extracellular Ca, CHPO intoxication of cultured myocytes leads to an increase of [Ca] prior to the onset of cell death. If extracellular Ca is chelated by EGTA, CHPO also induces cell death which is not preceded by cellular calcium overload. Apparently a disturbance in the calcium homeostasis is not causally related with oxidative stress-induced myocardial cell death. [ABSTRACT FROM AUTHOR]

We investigated the effect of Ca overload on the phospholipase C-catalyzed hydrolysis of phosphoinositides in the rat left ventricular papillary muscle. Ca overload on the papillary muscle was induced by treatment with 0.3 mM ouabain in Ca-containing medium following either Ca-containing or Ca-free superfusion. The phosphoinositide breakdown was evaluated by determining accumulations of [H]inositol phosphates ([H]IPs) in the tissues prelabeled with [H]inositol. Ca repletion following Ca-free superfusion resulted in a rapid but small increase in resting tension that was not followed by contracture, nor was it associated with a significant increase in [H]IPs accumulations. Treatment with ouabain following Ca-containing superfusion increased resting tension after a lag period of several minutes and produced contracture associated with an increase in [H]IPs accumulations. The ouabain induced increases in resting tension, and accumulations of [H]IPs were significantly potentiated by prior Ca-free superfusion instead of Ca-containing superfusion. There was a significant positive correlation between increases in resting tension and the phosphoinositide breakdown. The increased resting tension and the accumulations of [H]IPs were not antagonized by treatments with prazosin plus atropine or indomethacin, but were abolished by superfusion with Ca-free buffer solution. Although the enhanced phospholipase C-catalyzed hydrolysis of phosphoinositides appears to be a consequence rather than a cause of increased intracellular Ca, such a biochemical change may provoke a positive feedback mechanism to develop the muscle contracture through the putative intracellular messenger action of inositol triphosphate and diacylglycerol. [ABSTRACT FROM AUTHOR]

The effects of several calcium antagonists on cell death induced by A23187 were studied. Furthermore, R71811,1-[Bis(4-fluorophenyl)methyl-4-(4-methoxyphenyl)-carbamoylmethyl-trans-2,5-dimethyl-piperazine has been evaluated as a calcium overload blocker and compared to flunarizine. The viability of cultured glial cells was decreased by incubation with the calcium ionophore, A23187. The cytotoxicity of A23187 was reduced by flunarizine and cinnarizine at 10 μmol/l; nicardipine, nifedipine, and verapamil, but not diltiazem, reduced cytotoxicity at 100 μmol/l. N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) and trifluoperazine did not reduce cytotoxicity and trifluoperazine enhanced cytotoxicity at 100 μmol/l. Leupeptin reduced cytotoxicity at 100 μmol/1. [8-(N,N-dimethylamino)octyl-3,4,5-trimethoxybenzoate] (TMB-8) showed no effect. The results indicate that flunarizine, a recognized calcium overload blocker, was most effective in inhibiting the A23187-induced cytotoxicity and that calcium entry blockade does not appear to be implicated in the cytoprotective effect. R71811 inhibited A23187 cytotoxicity at similar concentrations to flunarizine. R71811, as well as flunarizine, also inhibited erythrocyte crenation induced by A23187. Although R71811 showed a relaxant effect in isolated rat aorta contracted by high potassium, its activity was less than that of flunarizine (IC values, 4.1 and 0.045 μmol/l, respectively). On the other hand, R71811 and flunarizine showed similar inhibitory effects on A23187-induced contractions (IC values, 14 and 11 μmol/l, respectively). The results indicate that R71811 has a similar protective effect against A23187-induced cytotoxicity but only weak calcium entry blocking action in comparison to flunarizine. [ABSTRACT FROM AUTHOR]

Effects of phorbol esters on spontaneously beating rabbit sino-atrial (SA) node cells were investigated by means of voltage clamp technique. In a small SA node specimen, 12-O-tetradecanoylphorbol-13-acetate (TPA) 10 mol/l lengthened the cycle length (CL) and at over 3 × 10 mol/l prolonged the action potential duration (APD). Action potential amplitude (APA), maximum diastolic potential (MDP) and maximum rate of rise ( V) were unaffected. Amiloride 10 mol/1, an inhibitor of Na-H exchange, did not reverse the phorbol ester-induced effects. In voltage-clamp experiments, TPA 1-10 × 10 mol/l slightly increased the slow inward current ( I) and the time-dependent inward current ( I) which activates during hyperpolarization. The outward current and the tail current were reduced, although the activation curve was not shifted along the voltage axis. In the presence of 10 mol/l isoprenaline, TPA produced dysrhythmia and a transient inward current in voltage-clamp experiments. In the presence of 5 × 10 mol/l phenylephrine or 2 × 10 mol/l acetylcholine, TPA also elicited dysrhythmia. 4-betaphorbol-12,13-dibutyrate (PBD) induced similar electrophysiological effects as TPA, but 4-alpha-phorbol-12,13-didecanoate (PDD) never did so even in the presence of isoprenaline. These results suggest that TPA and PDB might mobilize intracellular Ca via protein kinase C activation in the presence of isoprenaline, phenylephrine or acetylcholine, resulting in dysrhythmia due to delayed afterdepolarization. [ABSTRACT FROM AUTHOR]

The actions of low concentrations of caffeine (0.5-2 mmol/1) on the transient inward oscillatory current (I) and the inward tail current (I) were studied in sheep cardiac Purkinje fibres by means of a two microelectrode voltage clamp method. The following results were obtained. Caffeine: 1. induced an I when this current was not already present; 2. increased the amplitude (within limits) and consistently decreased the time to peak of an already present I; 3. increased I upon which I may be superimposed; 4. shifted the depolarizing threshold for the appearance of I to more negative and the repolarizing threshold to less negative values; 5. increased the effects of strophanthidin of I and I; 6. exaggerated the effects of high [Ca] which by itself mimicked some of the actions of caffeine; 7. had a small effect of I and I in low [Ca]; 8. reversed the effect of norepinephrine on I; 9. enhanced the effects of trains of clamps and of longer clamp steps on I and I. It is concluded that low concentrations of caffeine facilitate the manifestations of calcium overload thereby inducing or exaggerating the oscillatory and tail currents and that these effects are modulated by the cellular calcium load but are not mediated through adrenergic mechanisms. [ABSTRACT FROM AUTHOR]

The effect of perfusion temperature and duration of calcium deprivation on the occurrence of the calcium paradox was studied in the isolated frog heart. Loss of electrical and mechanical activity, ion fluxes, creatine kinase and protein release were used to define cell damage. Perfusion was performed at 22, 27, 32, and 37°C, and calcium deprivation lasted 10, 20, 30, or 40 min. At 22°C and 27°C even a prolonged calcium-free perfusion failed to induce a calcium paradox. After 30 min of calcium-free perfusion at 37°C ventricular activity ceased and a major contraction occurred followed by an increase in resting tension. During the 15-min re-perfusion period the release of creatine kinase was 158.24±2.49 IU·g dry wt, and the total amount of protein lost was 70.37±0.73 mg·g dry wt, while lower perfusion temperatures resulted in a decreased loss of protein and creatine kinase. Ion fluxes in the perfusion effluent indicate that during re-perfusion a massive calcium influx accompanied by a potassium and a magnesium efflux, and an apparent sodium efflux, occur at a perfusion temperature of 37°C after 30 min of calcium deprivation. The results suggest that the basic principles and damaging effects of calcium overloading are common to both mammalian and frog hearts. [ABSTRACT FROM AUTHOR]

A number of clinical cardiac disorders may be associated with a rise of the intracellular Na concentration (Nai) in heart muscle. A clear example is digitalis toxicity, in which excessive inhibition of the Na/K pump causes the Nai concentration to become raised above the normal level. Especially in digitalis toxicity, but also in many other situations, the rise of Nai may be an important (or contributory) cause of increased cardiac arrhythmias. In this review, we consider the mechanisms by which a raised Nai may cause cardiac arrhythmias. First, we describe the factors that regulate Nai, and we demonstrate that the equilibrium level of Nai is determined by a balance between Na entry into the cell, and Na extrusion from the cell. A number of mechanisms are responsible for Na entry into the cell, whereas the Na/K pump appears to be the main mechanism for Na extrusion. We then consider the processes by which an increased level of Nai might contribute to cardiac arrhythmias. A rise of Nai is well known to result in an Increase of intracellular Ca, via the important and influential Na/Ca exchange mechanism in the cell membrane of cardiac muscle cells. A rise of intracellular Ca modulates the activity of a number of sarcolemmal ion channels and affects release of intracellular Ca from the sarcoplasmic reticulum, all of which might be involved in causing arrhythmia. It is possible that the increase in contractile force that results from the rise of intracellular Ca may initiate or exacerbate arrhythmia, since this will increase wall stress and energy demands in the ventricle, and an increase in wall stress may be arrhythmogenic. In addition, the rise of Nai is anticipated to modulate directly a number of ion channels and to affect the regulation of intracellular pH, which also may be involved in causing arrhythmia. We also present experiments in this review, carded out on the working rat heart preparation, which suggest that a rise of Nai causes an increase of wall stress-induced arrhythmia in this model. In addition, we have investigated the effect on wall stress-induced arrhythmia of maneuvers that might be anticipated to change intracellular Ca, and this has allowed identification of some of the factors involved in causing arrhythmia in the working rat heart. [ABSTRACT FROM AUTHOR]

Indirect evidences in reviews and case reports on Takotsubo syndrome (TTS) support the fact that the existence of oxidative stress (OS) might be its common feature in the pre-acute stage. The sources of OS are exogenous (environmental factors including pharmacological and toxic influences) and endogenous, the combination of both may be present, and they are being discussed in detail. OS is associated with several pathological conditions representing TTS comorbidities and triggers. The dominant source of OS electrones are mitochondria. Our analysis of drug therapy related to acute TTS shows many interactions, e.g., cytostatics and glucocorticoids with mitochondrial cytochrome P450 and other enzymes important for OS. One of the most frequently discussed mechanisms in TTS is the effect of catecholamines on myocardium. Yet, their metabolic influence is neglected. OS is associated with the oxidation of catecholamines leading to the synthesis of their oxidized forms - aminochromes. Under pathological conditions, this pathway may dominate. There are evidences of interference between OS, catecholamine/aminochrome effects, their metabolism and antioxidant protection. The OS offensive may cause fast depletion of antioxidant protection including the homocystein-methionine system, whose activity decreases with age. The alteration of effector subcellular structures (mitochondria, sarco/endoplasmic reticulum) and subsequent changes in cellular energetics and calcium turnover may also occur and lead to the disruption of cellular function, including neurons and cardiomyocytes. On the organ level (nervous system and heart), neurocardiogenic stunning may occur. The effects of OS correspond to the effect of high doses of catecholamines in the experiment. Intensive OS might represent " conditio sine qua non" for this acute clinical condition. TTS might be significantly more complex pathology than currently perceived so far., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Manousek, Kala, Lokaj, Ondrus, Helanova, Miklikova, Brazdil, Tomandlova, Parenica, Pavkova Goldbergova and Hlasensky.)

Myocardial ischemia/reperfusion (MI/R) may impair cardiac functions. Dexmedetomidine (DEX) is protective in various clinical cases. Therefore, this study investigated the role and mechanism of DEX in MI/R. The myocardial infarct size, apoptosis, and levels of myocardial enzymes, SOD, ROS, Ca 2+ , and inflammatory factors in DEX-treated MI/R rats were measured. Differentially expressed microRNAs (miRs) in DEX-treated MI/R rats were detected. miR-346-3p was intervened to assess the effects of DEX on MI/R rats. The targeted binding relationship between miR-346-3p and CaMKIId was predicted and verified. DEX effect on hypoxia/reoxygenation (H/R)-induced cell model was evaluated. The role of CaMKIId in DEX protection was assessed after CaMKIId overexpression in H/R cells. NF-κB pathway and NLRP3 inflammasome-related protein levels were detected. DEX alleviated the myocardial injury and Ca 2+ overload in MI/R rats, as evidenced by reduced infarct size, apoptosis and levels of myocardial enzymes, ROS, Ca 2+ , and inflammatory factors. DEX promoted miR-346-3p expression in MI/R rats, and miR-346-3p knockdown reversed DEX protection on MI/R rats. miR-346-3p targeted CaMKIId. DEX improved H/R-induced cell injury and Ca 2+ overload and inhibited NF-κB/NLRP3 inflammasome-related protein levels, which were all reversed by CaMKIId overexpression. DEX alleviated injury and Ca 2+ overload in MI/R via regulating the miR-346-3p/CaMKIId axis and inhibiting the NF-κB/NLRP3 inflammasome pathway., Competing Interests: Declaration of Competing Interest The authors declared that they have no competing interests., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Downregulation of inward rectifier potassium (I K1 ) channel is a hallmark in cardiac hypertrophy and failure. The cardioprotection of zacopride (a selective I K1 agonist) and underlying mechanisms were investigated in L-thyroxine (T4) or Triiodothyronine (T3)-induced cardiac remodeling. In the in vivo study, adult male Sprague-Dawley (SD) rats were randomly divided into control, L-thyroxine, L-thy+zacopride, and L-thy+zacopride+chloroquine (an I K1 antagonist) groups. Echocardiography, histopathology, TUNEL assay, western blotting and confocal imaging for intracellular Ca 2+ fluorescence were performed. In the in vitro study, zacopride and nifedipine (a LTCC blocker) were used to compare their effects on Kir2.1, SAP97, autophagy, and [Ca 2+ ] i in H9C2 (2-1) cardiomyocytes. Zacopride treatment attenuated L-thyroxine- or T3 induced cardiac remodeling and dysfunction which manifested as cardiac hypertrophy and collagen deposition, dilated ventricle, decreased ejection fraction (EF), increased cardiomyocytes apoptosis, hyper-activation of CaMKII and PI3K/Akt/mTOR signaling, decreased cardiac autophagy, and increased expression of integrin β3. The cardioprotection of zacopride is strongly associated with the upregulation of I K1 , SAP97, and [Ca 2+ ] i homeostasis in cardiomyocytes. I K1 antagonist chloroquine or BaCl 2 reversed these effects. Nifedipine could attenuate intracellular Ca 2+ overload with no significant effects on I K1 , SAP97, and autophagy. This study showed that zacopride could improve cardiac remodeling via facilitating Kir2.1 forward trafficking, and negatively regulating calcium-activated and PI3K/Akt/mTOR signalings, in an I K1 -dependent manner., Competing Interests: None., (AJTR Copyright © 2021.)

Cardiac tissue ischemia/hypoxia increases glycolysis and lactic acid accumulation in cardiomyocytes, leading to intracellular metabolic acidosis. Sodium bicarbonate cotransporters (NBCs) play a vital role in modulating intracellular pH and maintaining sodium ion concentrations in cardiomyocytes. Cardiomyocytes mainly express electrogenic sodium bicarbonate cotransporter (NBCe1), which has been demonstrated to participate in myocardial ischemia/reperfusion (I/R) injury. This review outlines the structural and functional properties of NBCe1, summarizes the signaling pathways and factors that may regulate the activity of NBCe1, and reviews the roles of NBCe1 in the pathogenesis of I/R-induced cardiac diseases. Further studies revealing the regulatory mechanisms of NBCe1 activity should provide novel therapeutic targets for preventing I/R-induced cardiac diseases. Myocardial ischemia leads to accumulation of lactic acid in cardiomyocytes. During reperfusion, the electrogenic sodium bicarbonate cotransporter 1 (NBCe1) is activated to release intracellular acid load. However, the simultaneously increased Na+ influx reverses the action of Na+-Ca2+ exchanger and causes intracellular Ca2+ overload, which ultimately leads to the possibility of electrical arrhythmia and myocardial injury. As shown in the figure, the regulatory signal pathways of NBCe1 were reviewed in this article to unveil the molecular pathogenesis of myocardial ischemia/reperfusion (I/R) injury, which may provide potential therapeutic targets of I/R-induced cardiac diseases. Unlabelled Image • The classification and function of NBCs, especially the stoichiometry and function of NBCe1 variants • NBCe1 regulatory signal pathways and factors • The roles of NBCe1 in the pathogenesis of I/R induced cardiac diseases. • NBCe1 is a new target for preventing I/R induced cardiac diseases. [ABSTRACT FROM AUTHOR]

Background: Aconitine-induced cardiotoxicity limits the clinical treatment of cardiotonic, cancers and immune-related diseases. Ginsenoside Rb1 (Rb1) is an active ingredient of traditional Chinese medicine with cardioprotective effect.Purpose: This study aims to study the mechanism of aconitine cardiotoxicity and the detoxification mechanism of Rb1.Study Design: METHODS: The regulatory effect of Rb1 on aconitine was evaluated in vitro and in vivo by myocardial enzyme indicators, pathological analysis, CardioECR detection, calcium transient analysis, western blotting and immunohistochemistry.Results: Rb1 (10, 20, 40 mg/kg) alleviated apoptotic myocardial damage caused by aconitine in rats. Furthermore, Rb1 (25, 50, 100 μM) restored the contractile function and field potential of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) by regulating calcium channels and reduced myocardial cell damage by inhibiting the calcium transients of adult rat ventricular myocytes (ARVMs). Rb1 significantly reduced calcium levels in hiPSC-CMs, directly indicating that aconitine-induced calcium overload was alleviated by Rb1. Further, aconitine caused calcium overload by changing the expression of calcium pathway proteins, while Rb1 effectively restored calcium homeostasis. In addition, Rb1 also had a cardioprotective role by inhibiting cell pyroptosis. These results suggested that the maintenance of calcium homeostasis helped to suppress the inflammatory response related to pyroptosis of the heart.Conclusion: Aconitine-induced cardiotoxicity can be alleviated by Rb1 via restoring calcium homeostasis and inhibiting apoptosis and pyroptosis. [ABSTRACT FROM AUTHOR]

This study investigates the role of ranolazine in contrast-associated acute kidney injury (CA-AKI) and potential mechanisms. For in vivo studies, mouse models of CA-AKI and control mice were treated with ranolazine or vehicle. Blood urea nitrogen (BUN) and serum creatinine were detected by spectrophotometry. Anti-T-cell immunoglobulin and mucin domain 1 (TIM 1) and anti-lipocalin 2 antibody (LCN2) were detected by immunofluorescence. Hemodynamic parameters were detected via invasive blood pressure measurement and renal artery color doppler ultrasound, capillary density was measured by CD31 immunofluorescence, vascular permeability assay was performed by Evans blue dye. The expressions of oxidative stress and apoptotic markers were measured and analyzed by immunofluorescence and western blotting. For in vitro studies, intracellular calcium concentration of HUVECs was measured with Fluo 3-AM under confocal microscopy. Results show that compared with control mice, serum BUN, creatinine, TIM 1 and LCN2 levels were elevated in CA-AKI mice, but this effect was alleviated by ranolazine-pretreatment. Safe doses of ranolazine (less than 64 mg/kg) had no significant effect on overall blood pressure, but substantially improved renal perfusion, reduced contrast-induced microcirculation disturbance, improved renal capillary density and attenuated renal vascular permeability in ranolazine-pretreated CA-AKI mice. Mechanistically, ranolazine markedly down-regulated oxidative stress and apoptosis markers compared to CA-AKI mice. Intracellularly, ranolazine attenuated calcium overload in HUVECs. These results indicate that ranolazine alleviates CA-AKI through modulation of calcium independent oxidative stress and apoptosis. [ABSTRACT FROM AUTHOR]

Ventricular arrhythmia induced by ischemia/reperfusion (I/R) injury is a clinical problem in reperfusion therapies for acute myocardial infarction. Ca2+ overload through reactive oxygen species (ROS) production is a major cause for I/R-induced arrhythmia. We previously demonstrated that canstatin, a C-terminal fragment of type IV collagen α2 chain, regulated Ca2+ handling in rat heart. In this study, we aimed to clarify the effects of canstatin on I/R-induced ventricular arrhythmia in rats. Male Wistar rats were subjected to I/R injury by ligating the left anterior descending artery followed by reperfusion. Ventricular arrhythmia (ventricular tachycardia and ventricular fibrillation) was recorded by electrocardiogram. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) activity and ROS production in neonatal rat cardiomyocytes (NRCMs) stimulated with oxygen glucose deprivation/reperfusion (OGD/R) were measured by lucigenin assay and 2′,7′-dichlorodihydrofluorescein diacetate staining, respectively. The H2O2-induced intracellular Ca2+ ([Ca2+]i) rise in NRCMs was measured by a fluorescent Ca2+ indicator. Canstatin (20 µg/kg) inhibited I/R-induced ventricular arrhythmia in rats. Canstatin (250 ng/mL) inhibited OGD/R-induced NOX activation and ROS production and suppressed the H2O2-induced [Ca2+]i rise in NRCMs. We for the first time demonstrated that canstatin exerts a preventive effect against I/R-induced ventricular arrhythmia, perhaps in part through the suppression of ROS production and the subsequent [Ca2+]i rise. [ABSTRACT FROM AUTHOR]

Synovial sarcoma is a rare but aggressive soft-tissue sarcoma associated with translocation t(X;18). Metastasis occurs in approximately 50% of all patients, and curative outcomes are difficult to achieve in this group. Since the efficacies of current therapeutic approaches for metastatic synovial sarcoma remain limited, new therapeutic agents are urgently needed. Tilapia piscidin 4 (TP4), a marine antimicrobial peptide, is known to exhibit multiple biological functions, including anti-bacterial, wound-healing, immunomodulatory, and anticancer activities. In the present study, we assessed the anticancer activity of TP4 in human synovial sarcoma cells and determined the underlying mechanisms. We first demonstrated that TP4 can induce necrotic cell death in human synovial sarcoma AsKa-SS and SW982 cells lines. In addition, we saw that TP4 initiates reactive oxygen species (ROS) production and downregulates antioxidant proteins, such as uncoupling protein-2, superoxide dismutase (SOD)-1, and SOD-2. Moreover, TP4-induced mitochondrial hyperpolarization is followed by elevation of mitochondrial ROS. Calcium overload is also triggered by TP4, and cell death can be attenuated by a necrosis inhibitor, ROS scavenger or calcium chelator. In our experiments, TP4 displayed strong anticancer activity in human synovial sarcoma cells by disrupting oxidative status, promoting mitochondrial hyperpolarization and causing calcium overload. [ABSTRACT FROM AUTHOR]