Silica nanoparticles induce cardiotoxicity interfering with energetic status and Ca2+ handling in adult rat cardiomyocytes

Recent evidence has shown that nanoparticles that have been used to improve or create new functional properties for common products may pose potential risks to human health. Silicon dioxide (SiO2) has emerged as a promising therapy vector for the heart. However, its potential toxicity and mechanisms of damage remain poorly understood. This study provides the first exploration of SiO2-induced toxicity in cultured cardiomyocytes exposed to 7- or 670-nm SiO2 particles. We evaluated the mechanism of cell death in isolated adult cardiomyocytes exposed to 24-h incubation. The SiO2 cell membrane association and internalization were analyzed. SiO2 showed a dose-dependent cytotoxic effect with a half-maximal inhibitory concentration for the 7 nm (99.5 ± 12.4 µg/ml) and 670 nm (>1,500 µg/ml) particles, which indicates size-dependent toxicity. We evaluated cardiomyocyte shortening and intracellular Ca2+ handling, which showed impaired contractility and intracellular Ca2+ transient amplitude during β-adrenergic stimulation in SiO2 treatment. The time to 50% Ca2+ decay increased 39%, and the Ca2+ spark frequency and amplitude decreased by 35 and 21%, respectively, which suggest a reduction in sarcoplasmic reticulum Ca2+-ATPase (SERCA) activity. Moreover, SiO2 treatment depolarized the mitochondrial membrane potential and decreased ATP production by 55%. Notable glutathione depletion and H2O2 generation were also observed. These data indicate that SiO2 increases oxidative stress, which leads to mitochondrial dysfunction and low energy status; these underlie reduced SERCA activity, shortened Ca2+ release, and reduced cell shortening. This mechanism of SiO2 cardiotoxicity potentially plays an important role in the pathophysiology mechanism of heart failure, arrhythmias, and sudden death. NEW & NOTEWORTHY Silica particles are used as novel nanotechnology-based vehicles for diagnostics and therapeutics for the heart. However, their potential hazardous effects remain unknown. Here, the cardiotoxicity of silica nanoparticles in rat myocytes has been described for the first time, showing an impairment of mitochondrial function that interfered directly with Ca2+ handling.

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Synchronous progression of calcium transient-dependent beating and sarcomere destruction in apoptotic adult cardiomyocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00669.2005 ◽

2006 ◽

Vol 290 (4) ◽

pp. H1493-H1502 ◽

Cited By ~ 15

Author(s):

Rumi Maruyama ◽

Genzou Takemura ◽

Noritsugu Tohse ◽

Tomoko Ohkusa ◽

Yasuhiro Ikeda ◽

...

Keyword(s):

Electron Microscopic Examination ◽

Immunohistochemical Analysis ◽

Calcium Transient ◽

Cytoskeletal Proteins ◽

Adrenergic Stimulation ◽

Electron Microscopic ◽

Rat Cardiomyocytes ◽

Adult Rat ◽

Adult Cardiomyocytes ◽

Intracellular Ca

During early apoptosis, adult cardiomyocytes show unusual beating, suggesting possible participation of abnormal Ca2+ transients in initiation of apoptotic processes in this cell type. Simultaneously with the beating, these cells show dynamic structural alteration resulting from cytoskeletal disintegration that is quite rapid. Because of the specialized structure and extensive cytoskeleton of cardiomyocytes, we hypothesized that its degradation in so short a time would require a particularly efficient mechanism. To better understand this mechanism, we used serial video microscopy to observe β-adrenergic stimulation-induced apoptosis in isolated adult rat cardiomyocytes while simultaneously recording intracellular Ca2+ concentration and cell length. Trains of Ca2+ transients and corresponding rhythmic contractions and relaxations (beating) were observed in apoptotic cells. Frequencies of Ca2+ transients and beating gradually increased with time and were accompanied by cellular shrinkage. As the cells shrank, amplitudes of Ca2+ transients declined and diastolic intracellular Ca2+ concentration increased until the transients were lost. Beating and progression of apoptosis were significantly inhibited by antagonists against the L-type Ca2+ channel (nifedipine), ryanodine receptor (ryanodine), inositol 1,4,5-trisphosphate receptor (heparin), sarco(endo)plasmic Ca2+-ATPase (thapsigargin), and Na+/Ca2+ exchanger (KB-R7943). Electron-microscopic examination of beating cardiomyocytes revealed progressive breakdown of Z disks. Immunohistochemical analysis and Western blot confirmed that disappearance of Z disk constituent proteins (α-actinin, desmin, and tropomyosin) preceded degradation of other cytoskeletal proteins. It thus appears that, in adult cardiomyocyte apoptosis, Ca2+ transients mediate apoptotic beating and efficient sarcomere destruction initiated by Z disk breakdown.

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IP3R1 regulates Ca2+ transport and pyroptosis through the NLRP3/Caspase-1 pathway in myocardial ischemia/reperfusion injury

Cell Death Discovery ◽

10.1038/s41420-021-00404-4 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Guixi Mo ◽

Xin Liu ◽

Yiyue Zhong ◽

Jian Mo ◽

Zhiyi Li ◽

...

Keyword(s):

Myocardial Ischemia ◽

Ischemia Reperfusion Injury ◽

Cell Model ◽

Ischemia Reperfusion ◽

Inflammatory Factors ◽

Rat Cardiomyocytes ◽

Adult Rat ◽

Caspase 1 ◽

Intracellular Ca ◽

Myocardial Ischemia Reperfusion

AbstractIntracellular ion channel inositol 1,4,5-triphosphate receptor (IP3R1) releases Ca2+ from endoplasmic reticulum. The disturbance of IP3R1 is related to several neurodegenerative diseases. This study investigated the mechanism of IP3R1 in myocardial ischemia/reperfusion (MI/R). After MI/R modeling, IP3R1 expression was silenced in myocardium of MI/R rats to explore its role in the concentration of myocardial enzymes, infarct area, Ca2+ level, NLRP3/Caspase-1, and pyroptosis markers and inflammatory factors. The adult rat cardiomyocytes were isolated and cultured to establish hypoxia/reperfusion (H/R) cell model. The expression of IP3R1 was downregulated or ERP44 was overexpressed in H/R-induced cells. Nifedipine D6 was added to H/R-induced cells to block Ca2+ channel or Nigericin was added to activate NLRP3. IP3R1 was highly expressed in myocardium of MI/R rats, and silencing IP3R1 alleviated MI/R injury, reduced Ca2+ overload, inflammation and pyroptosis in MI/R rats, and H/R-induced cells. The binding of ERP44 to IP3R1 inhibited Ca2+ overload, alleviated cardiomyocyte inflammation, and pyroptosis. The increase of intracellular Ca2+ level caused H/R-induced cardiomyocyte pyroptosis through the NLRP3/Caspase-1 pathway. Activation of NLRP3 pathway reversed the protection of IP3R1 inhibition/ERP44 overexpression/Nifedipine D6 on H/R-induced cells. Overall, ERP44 binding to IP3R1 inhibits Ca2+ overload, thus alleviating pyroptosis and MI/R injury.

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Effects of sprint training on contractility and [Ca2+]i transients in adult rat myocytes

Journal of Applied Physiology ◽

10.1152/japplphysiol.01071.2001 ◽

2002 ◽

Vol 93 (4) ◽

pp. 1310-1317 ◽

Cited By ~ 5

Author(s):

Xue-Qian Zhang ◽

Jianliang Song ◽

Lois L. Carl ◽

Weixing Shi ◽

Anwer Qureshi ◽

...

Keyword(s):

Contractile Function ◽

Sprint Training ◽

Cell Width ◽

Western Blots ◽

Adult Rat ◽

Protein Levels ◽

Intracellular Ca ◽

Uptake Activity ◽

Rat Myocytes ◽

Myocyte Contractility

The effects of 6–8 wk of high-intensity sprint training (HIST) on rat myocyte contractility and intracellular Ca2+ concentration ([Ca2+]i) transients were investigated. Compared with sedentary (Sed) myocytes, HIST induced a modest (5%) but significant ( P < 0.0005) increase in cell length with no changes in cell width. In addition, the percentage of myosin heavy chain α-isoenzyme increased significantly ( P < 0.02) from 0.566 ± 0.077% in Sed rats to 0.871 ± 0.006% in HIST rats. At all three (0.6, 1.8, and 5 mM) extracellular Ca2+concentrations ([Ca2+]o) examined, maximal shortening amplitudes and maximal shortening velocities were significantly ( P < 0.0001) lower and half-times of relaxation were significantly ( P < 0.005) longer in HIST myocytes. HIST myocytes had significantly ( P < 0.0001) higher diastolic [Ca2+]i levels. Compared with Sed myocytes, systolic [Ca2+]ilevels in HIST myocytes were higher at 0.6 mM [Ca2+]o, similar at 1.8 mM [Ca2+]o, and lower at 5 mM [Ca2+]o. The amplitudes of [Ca2+]i transients were significantly ( P < 0.0001) lower in HIST myocytes. Half-times of [Ca2+]i transient decline, an estimate of sarcoplasmic reticulum (SR) Ca2+ uptake activity, were not different between Sed and HIST myocytes. Compared with Sed hearts, Western blots demonstrated a significant ( P < 0.03) threefold decrease in Na+/Ca2+ exchanger, but SR Ca2+-ATPase and calsequestrin protein levels were unchanged in HIST hearts. We conclude that HIST effected diminished myocyte contractile function and [Ca2+]itransient amplitudes under the conditions studied. We speculate that downregulation of Na+/Ca2+ exchanger may partly account for the decreased contractility in HIST myocytes.

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Short-term hibernation in adult cardiomyocytes is Po 2 dependent and Ca2+mediated

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.280.1.h42 ◽

2001 ◽

Vol 280 (1) ◽

pp. H42-H50 ◽

Cited By ~ 5

Author(s):

Thomas Stumpe ◽

Jürgen Schrader

Keyword(s):

Contractile Activity ◽

Substantial Reduction ◽

Observation Time ◽

Energy Status ◽

Short Term ◽

Rat Cardiomyocytes ◽

Lactate Release ◽

State Observation ◽

Myocardial Hibernation ◽

Intracellular Ca

The mechanism of myocardial hibernation, the reversible downregulation of contractile activity on reduction of coronary flow with unchanged cardiac energetics, is presently not understood. The oxygen consumption (V˙o 2), shortening fraction (Δ L), energy status [phosphocreatine (PCr), ATP, and adenosine and lactate release], and free intracellular Ca2+ concentration ([Ca2+]i) were measured in isolated rat cardiomyocytes at precisely controlled ambient Po 2 (Oxystat). When Po 2was reduced from 25 to 6 mmHg, V˙o 2decreased by 50%, while Δ L was downregulated from 11.2 ± 4.1 to 7.6 ± 4.0%, and energy status was unchanged in the steady state (observation time 12 min). Only transiently PCr decreased, and lactate and adenosine release increased. Further reduction of Po 2 (to 3 mmHg) reducedV˙o 2 by 80%, decreased PCr by 35%, moderately increased adenosine and lactate release, and progressively reduced Δ L by 50% (to 5.6 ± 3.3%). All parameters fully recovered during reoxygenation. Po 2-dependent downregulation of Δ Lwas accompanied by a progressive reduction in systolic [Ca2+]i (from 512 ± 110 to 357 ± 91 nmol/l at 6 mmHg and to 251 ± 69 nmol/l at 3 mmHg), whereas diastolic free [Ca2+]i remained unchanged. Therefore, the mechanism of the reversible, Po 2-dependent downregulation of contractile activity (myocardial hibernation) involves a substantial reduction of systolic calcium.

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Different Densities of Na-Ca Exchange Current in T-Tubular and Surface Membranes and Their Impact on Cellular Activity in a Model of Rat Ventricular Cardiomyocyte

BioMed Research International ◽

10.1155/2017/6343821 ◽

2017 ◽

Vol 2017 ◽

pp. 1-9 ◽

Cited By ~ 4

Author(s):

M. Pásek ◽

J. Šimurda ◽

G. Christé

Keyword(s):

Action Potential ◽

Transport Systems ◽

Duration Of Action ◽

Rat Cardiomyocytes ◽

Adult Rat ◽

Before And After ◽

Action Potential Waveform ◽

Intracellular Ca ◽

Tubular Membranes ◽

Potential Waveform

The ratio of densities of Na-Ca exchanger current (INaCa) in the t-tubular and surface membranes (INaCa-ratio) computed from the values ofINaCaand membrane capacitances (Cm) measured in adult rat ventricular cardiomyocytes before and after detubulation ranges between 1.7 and 25 (potentially even 40). Variations of action potential waveform and of calcium turnover within this span of theINaCa-ratio were simulated employing previously developed model of rat ventricular cell incorporating separate description of ion transport systems in the t-tubular and surface membranes. The increase ofINaCa-ratio from 1.7 to 25 caused a prolongation of APD (duration of action potential at 90% repolarisation) by 12, 9, and 6% and an increase of peak intracellular Ca2+transient by 45, 19, and 6% at 0.1, 1, and 5 Hz, respectively. The prolonged APD resulted from the increase ofINaCadue to the exposure of a larger fraction of Na-Ca exchangers to higher Ca2+transients under the t-tubular membrane. The accompanying rise of Ca2+transient was a consequence of a higher Ca2+load in sarcoplasmic reticulum induced by the increased Ca2+cycling between the surface and t-tubular membranes. However, the reason for large differences in theINaCa-ratio assessed from measurements in adult rat cardiomyocytes remains to be explained.

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Ca+2/Calmodulin-Dependent Protein Kinase Mediates Glucose Toxicity-Induced Cardiomyocyte Contractile Dysfunction

Experimental Diabetes Research ◽

10.1155/2012/829758 ◽

2012 ◽

Vol 2012 ◽

pp. 1-11 ◽

Cited By ~ 4

Author(s):

Rong-Huai Zhang ◽

Haitao Guo ◽

Machender R. Kandadi ◽

Xiao-Ming Wang ◽

Jun Ren

Keyword(s):

Kinase Inhibitor ◽

Maximal Velocity ◽

Cam Kinase ◽

Glucose Toxicity ◽

Rat Cardiomyocytes ◽

Adult Rat ◽

Cardiac Contractile ◽

Intracellular Ca ◽

Dependent Protein ◽

The Impact

(1) Hyperglycemia leads to cytotoxicity in the heart. Although several theories are postulated for glucose toxicity-induced cardiomyocyte dysfunction, the precise mechanism still remains unclear. (2) This study was designed to evaluate the impact of elevated extracellular Ca2+on glucose toxicity-induced cardiac contractile and intracellular Ca2+anomalies as well as the mechanism(s) involved with a focus on Ca2+/calmodulin (CaM)-dependent kinase. Isolated adult rat cardiomyocytes were maintained in normal (NG, 5.5 mM) or high glucose (HG, 25.5 mM) media for 6-12 hours. Contractile indices were measured including peak shortening (PS), maximal velocity of shortening/relengthening (±dL/dt), time-to-PS (TPS), and time-to-90% relengthening (TR90). (3) Cardiomyocytes maintained with HG displayed abnormal mechanical function including reduced PS, ±dL/dt, and prolonged TPS, TR90and intracellular Ca2+clearance. Expression of intracellular Ca2+regulatory proteins including SERCA2a, phospholamban and Na+-Ca2+exchanger were unaffected whereas SERCA activity was inhibited by HG. Interestingly, the HG-induced mechanical anomalies were abolished by elevated extracellular Ca2+(from 1.0 to 2.7 mM). Interestingly, the high extracellular Ca2+-induced beneficial effect against HG was abolished by the CaM kinase inhibitor KN93. (4) These data suggest that elevated extracellular Ca2+protects against glucose toxicity-induced cardiomyocyte contractile defects through a mechanism associated with CaM kinase.

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Effect of alpha adrenergic stimulation and carnitine palmitoyl transferase I inhibition on hypertrophying adult rat cardiomyocytes in culture

Molecular and Cellular Biochemistry ◽

10.1007/bf00928910 ◽

1995 ◽

Vol 142 (1) ◽

pp. 25-34 ◽

Cited By ~ 8

Author(s):

Wieslawa Lesniak ◽

Christoph Schaefer ◽

Stephan Grueninger ◽

Michele Chiesi

Keyword(s):

Adrenergic Stimulation ◽

Carnitine Palmitoyl Transferase ◽

Rat Cardiomyocytes ◽

Adult Rat ◽

Carnitine Palmitoyl Transferase I

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Overexpression of Na+/Ca2+ exchanger alters contractility and SR Ca2+ content in adult rat myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2001.281.5.h2079 ◽

2001 ◽

Vol 281 (5) ◽

pp. H2079-H2088 ◽

Cited By ~ 30

Author(s):

Xue-Qian Zhang ◽

Jianliang Song ◽

Lawrence I. Rothblum ◽

Mingyue Lun ◽

Xujun Wang ◽

...

Keyword(s):

Fluorescent Protein ◽

Contractile Function ◽

Electrical Field Stimulation ◽

Western Blots ◽

Adult Rat ◽

Gfp Fluorescence ◽

Intracellular Ca ◽

Functional Consequences ◽

Rat Myocytes ◽

Green Fluorescent

The functional consequences of overexpression of rat heart Na+/Ca2+ exchanger (NCX1) were investigated in adult rat myocytes in primary culture. When maintained under continued electrical field stimulation conditions, cultured adult rat myocytes retained normal contractile function compared with freshly isolated myocytes for at least 48 h. Infection of myocytes by adenovirus expressing green fluorescent protein (GFP) resulted in >95% infection as ascertained by GFP fluorescence, but contraction amplitude at 6-, 24-, and 48-h postinfection was not affected. When they were examined 48 h after infection, myocytes infected by adenovirus expressing both GFP and NCX1 had similar cell sizes but exhibited significantly altered contraction amplitudes and intracellular Ca2+ concentration ([Ca2+]i) transients, and lower resting and diastolic [Ca2+]i when compared with myocytes infected by the adenovirus expressing GFP alone. The effects of NCX1 overexpression on sarcoplasmic reticulum (SR) Ca2+ content depended on extracellular Ca2+ concentration ([Ca2+]o), with a decrease at low [Ca2+]o and an increase at high [Ca2+]o. The half-times for [Ca2+]i transient decline were similar, suggesting little to no changes in SR Ca2+-ATPase activity. Western blots demonstrated a significant ( P ≤ 0.02) threefold increase in NCX1 but no changes in SR Ca2+-ATPase and calsequestrin abundance in myocytes 48 h after infection by adenovirus expressing both GFP and NCX1 compared with those infected by adenovirus expressing GFP alone. We conclude that overexpression of NCX1 in adult rat myocytes incubated at high [Ca2+]o resulted in enhanced Ca2+influx via reverse NCX1 function, as evidenced by greater SR Ca2+ content, larger twitch, and [Ca2+]i transient amplitudes. Forward NCX1 function was also increased, as indicated by lower resting and diastolic [Ca2+]i.

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Effects of Na+/Ca2+ exchanger downregulation on contractility and [Ca2+]i transients in adult rat myocytes

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00186.2002 ◽

2002 ◽

Vol 283 (4) ◽

pp. H1616-H1626 ◽

Cited By ~ 36

Author(s):

George M. Tadros ◽

Xue-Qian Zhang ◽

Jianliang Song ◽

Lois L. Carl ◽

Lawrence I. Rothblum ◽

...

Keyword(s):

Membrane Potential ◽

Sarcoplasmic Reticulum ◽

Current Density ◽

Resting Membrane Potential ◽

Action Potential Amplitude ◽

Half Time ◽

Adult Rat ◽

Postmyocardial Infarction ◽

Intracellular Ca ◽

Rat Myocytes

Postmyocardial infarction (MI) rat myocytes demonstrated depressed Na+/Ca2+exchange (NCX1) activity, altered contractility, and intracellular Ca2+ concentration ([Ca2+]i) transients. We investigated whether NCX1 downregulation in normal myocytes resulted in contractility changes observed in MI myocytes. Myocytes infected with adenovirus expressing antisense (AS) oligonucleotides to NCX1 had 30% less NCX1 at 3 days and 66% less NCX1 at 6 days. The half-time of relaxation from caffeine-induced contracture was twice as long in ASNCX1 myocytes. Sarcoplasmic reticulum (SR) Ca2+-ATPase abundance, SR Ca2+uptake, resting membrane potential, action potential amplitude and duration, L-type Ca2+ current density and cell size were not affected by ASNCX1 treatment. At extracellular Ca2+ concentration ([Ca2+]o) of 5 mM, ASNCX1 myocytes had significantly lower contraction and [Ca2+]i transient amplitudes and SR Ca2+ contents than control myocytes. At 0.6 mM [Ca2+]o, contraction and [Ca2+]i transient amplitudes and SR Ca2+ contents were significantly higher in ASNCX1 myocytes. At 1.8 mM [Ca2+]o, contraction and [Ca2+]i transient amplitudes were not different between control and ASNCX1 myocytes. This pattern of contractile and [Ca2+]i transient abnormalities in ASNCX1 myocytes mimics that observed in rat MI myocytes. We conclude that downregulation of NCX1 in adult rat myocytes resulted in decreases in both Ca2+ influx and efflux during a twitch. We suggest that depressed NCX1 activity may partly account for the contractile abnormalities after MI.

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