131 Increased Na+/Ca2+-exchanger activity protects against inhibition of SERCA2a in adult rat myocytes

2003 ◽  
Vol 2 (1) ◽  
pp. 20-21
Author(s):  
M SATO ◽  
H RANU ◽  
S HARDING
Keyword(s):  
Adult Rat ◽  
Rat Myocytes

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

2002 ◽  
Vol 93 (4) ◽  
pp. 1310-1317 ◽  
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.

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

2017 ◽  
Vol 312 (4) ◽  
pp. H645-H661 ◽  
Author(s):  
Carlos Enrique Guerrero-Beltrán ◽  
Judith Bernal-Ramírez ◽  
Omar Lozano ◽  
Yuriana Oropeza-Almazán ◽  
Elena Cristina Castillo ◽  
...  
Keyword(s):  
Silica Nanoparticles ◽  
Glutathione Depletion ◽  
Energy Status ◽  
Adrenergic Stimulation ◽  
Rat Cardiomyocytes ◽  
Atp Production ◽  
Adult Rat ◽  
Intracellular Ca ◽  
Rat Myocytes ◽  
Potential Risks

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.

scholarly journals Phospholemman overexpression inhibits Na+-K+-ATPase in adult rat cardiac myocytes: relevance to decreased Na+ pump activity in postinfarction myocytes

2006 ◽  
Vol 100 (1) ◽  
pp. 212-220 ◽  
Author(s):  
Xue-Qian Zhang ◽  
J. Randall Moorman ◽  
Belinda A. Ahlers ◽  
Lois L. Carl ◽  
Douglas E. Lake ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Cardiac Myocytes ◽  
Messenger Rna ◽  
Fluorescent Protein ◽  
Pump Current ◽  
Relative Level ◽  
Adult Rat ◽  
Rat Myocytes ◽  
Rat Cardiac Myocytes ◽  
Rna Levels

Messenger RNA levels of phospholemman (PLM), a member of the FXYD family of small single-span membrane proteins with putative ion-transport regulatory properties, were increased in postmyocardial infarction (MI) rat myocytes. We tested the hypothesis that the previously observed reduction in Na+-K+-ATPase activity in MI rat myocytes was due to PLM overexpression. In rat hearts harvested 3 and 7 days post-MI, PLM protein expression was increased by two- and fourfold, respectively. To simulate increased PLM expression post-MI, PLM was overexpressed in normal adult rat myocytes by adenovirus-mediated gene transfer. PLM overexpression did not affect the relative level of phosphorylation on serine68 of PLM. Na+-K+-ATPase activity was measured as ouabain-sensitive Na+-K+ pump current (Ip). Compared with control myocytes overexpressing green fluorescent protein alone, Ip measured in myocytes overexpressing PLM was significantly ( P < 0.0001) lower at similar membrane voltages, pipette Na+ ([Na+]pip) and extracellular K+ ([K+]o) concentrations. From −70 to +60 mV, neither [Na+]pip nor [K+]o required to attain half-maximal Ip was significantly different between control and PLM myocytes. This phenotype of decreased Vmax without appreciable changes in Km for Na+ and K+ in PLM-overexpressed myocytes was similar to that observed in MI rat myocytes. Inhibition of Ip by PLM overexpression was not due to decreased Na+-K+-ATPase expression because there were no changes in either protein or messenger RNA levels of either α1- or α2-isoforms of Na+-K+-ATPase. In native rat cardiac myocytes, PLM coimmunoprecipitated with α-subunits of Na+-K+-ATPase. Inhibition of Na+-K+-ATPase by PLM overexpression, in addition to previously reported decrease in Na+-K+-ATPase expression, may explain altered Vmax but not Km of Na+-K+-ATPase in postinfarction rat myocytes.

Overexpression of phospholemman alters contractility and [Ca2+]i transients in adult rat myocytes

2002 ◽  
Vol 283 (2) ◽  
pp. H576-H583 ◽  
Author(s):  
Jianliang Song ◽  
Xue-Qian Zhang ◽  
Lois L. Carl ◽  
Anwer Qureshi ◽  
Lawrence I. Rothblum ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Contractile Function ◽  
Maximal Contraction ◽  
Western Blots ◽  
Adult Rat ◽  
Rat Myocytes ◽  
Green Fluorescent ◽  
Rat Cardiac Myocytes

Previous studies showed increased phospholemman (PLM) mRNA after myocardial infarction (MI) in rats (Sehl PD, Tai JTN, Hillan KJ, Brown LA, Goddard A, Yang R, Jin H, and Lowe DG. Circulation 101: 1990–1999, 2000). We tested the hypothesis that, in normal adult rat cardiac myocytes, PLM overexpression alters contractile function and cytosolic Ca2+ concentration ([Ca2+]i) homeostasis in a manner similar to that observed in post-MI myocytes. Compared with myocytes infected by control adenovirus expressing green fluorescent protein (GFP) alone, Western blots indicated a 41% increase in PLM expression after 72 h ( P < 0.001) but no changes in Na+/Ca2+ exchanger, SERCA2, and calsequestrin levels in myocytes infected by adenovirus expressing GFP and PLM. At 5 mM extracellular [Ca2+] ([Ca2+]o), maximal contraction amplitudes in PLM-overexpressed myocytes were 24% ( P < 0.005) and [Ca2+]i transient amplitudes were 18% ( P < 0.05) lower than control myocytes. At 0.6 mM [Ca2+]o, however, contraction and [Ca2+]i transient amplitudes were significantly ( P < 0.05) higher in PLM-overexpressed than control myocytes (18% and 42%, respectively); at 1.8 mM [Ca2+]o, the differences in contraction and [Ca2+]i transient amplitudes were narrowed. This pattern of contractile and [Ca2+]itransient abnormalities in PLM-overexpressed myocytes mimics that observed in post-MI rat myocytes. We suggest that PLM overexpression observed in post-MI myocytes may partly account for contractile abnormalities by perturbing Ca2+ fluxes during excitation-contraction.

Phospholemman modulates Na+/Ca2+exchange in adult rat cardiac myocytes

2003 ◽  
Vol 284 (1) ◽  
pp. H225-H233 ◽  
Author(s):  
Xue-Qian Zhang ◽  
Anwer Qureshi ◽  
Jianliang Song ◽  
Lois L. Carl ◽  
Qiang Tian ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Contractile Function ◽  
Resting Membrane Potential ◽  
Adult Rat ◽  
Protein Levels ◽  
Rat Myocytes ◽  
T Tubules ◽  
Green Fluorescent ◽  
Myocyte Contractility ◽  
Rat Cardiac Myocytes

Previous studies have shown that overexpression of phospholemman (PLM) affected contractile function and Ca2+ homeostasis in adult rat myocytes. We tested the hypothesis that PLM modulated Na+/Ca2+exchanger (NCX1) activity. PLM was overexpressed in adult rat myocytes by adenovirus-mediated gene transfer. After 72 h, the half-time of relaxation from caffeine-induced contracture, an estimate of forward NCX1 activity, was prolonged 1.8-fold ( P < 0.003) in myocytes overexpressing PLM compared with control myocytes overexpressing green fluorescent protein alone. Reverse NCX1 current (3 Na+ out:1 Ca2+ in) was significantly ( P < 0.0001) lower in PLM myocytes, especially at more positive voltages. Immunofluorescence demonstrated colocalization of PLM and NCX1 to the plasma membrane and t-tubules. Resting membrane potential, action potential amplitude and duration, myocyte size, and NCX1 and calsequestrin protein levels were not affected by PLM overexpression. At 5 mM extracellular [Ca2+] ([Ca2+]o), the depressed contraction amplitudes in PLM myocytes were increased towards normal by cooverexpression with NCX1. At 0.6 mM [Ca2+]o, the supranormal contraction amplitudes in PLM myocytes were reduced by cooverexpression with NCX1. We conclude that PLM modulated myocyte contractility partly by inhibiting Na+/Ca2+ exchange.

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

2001 ◽  
Vol 281 (5) ◽  
pp. H2079-H2088 ◽  
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.

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

2002 ◽  
Vol 283 (4) ◽  
pp. H1616-H1626 ◽  
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.

Functional alterations in adult rat myocytes after overexpression of phospholamban with use of adenovirus

1999 ◽  
Vol 1 (2) ◽  
pp. 41-50 ◽  
Author(s):  
KERRY DAVIA ◽  
ROGER J. HAJJAR ◽  
CESARE M. N. TERRACCIANO ◽  
NATASHA SINGH KENT ◽  
HARDEEP K. RANU ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Human Heart ◽  
Ventricular Myocytes ◽  
Adenoviral Vectors ◽  
Functional Changes ◽  
Adult Rat ◽  
Plasmic Reticulum ◽  
Adult Cardiac Myocytes ◽  
Functional Consequences ◽  
Rat Myocytes

Davia, Kerry, Roger J. Hajjar, Cesare M. N. Terracciano, Natasha Singh Kent, Hardeep K. Ranu, Peter O'Gara, Anthony Rosenzweig, and Sian E. Harding. Functional alterations in adult rat myocytes after overexpression of phospholamban with use of adenovirus. Physiol. Genomics 1: 41–50, 1999.—An increased phospholamban (PLB)-to-sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) ratio has been suggested to contribute to the slowing of relaxation in failing human ventricle. We have used an adenoviral vector carrying the sequence for PLB to increase this ratio in isolated adult rat ventricular myocytes, and we have examined the functional consequences. With use of adenoviral vectors, the PLB content of adult rat myocytes was increased 2.73-fold, with SERCA2a levels unchanged. Maximum contraction amplitude of PLB-overexpressing myocytes was decreased to 6.9 ± 0.3% shortening compared with 11.2 ± 0.8% for 24-h controls (Con; P < 0.001, 5 preparations, 103 myocytes). Maximum rates of shortening and relengthening were also significantly decreased. Ca2+ transient amplitudes were slightly depressed, and time to 50% decay of the transients was significantly increased: 237 ± 18 ( n = 14 myocytes) and 432 ± 32 ms in Con and PLB ( n = 15) myocytes, respectively ( P < 0.001). The amount of Ca2+ in the sarcoplasmic reticulum stores was reduced by 21% ( P < 0.05). Relaxation was significantly slower in PLB than in Con myocytes when the Na+/Ca2+ exchanger was blocked but not when sarcoplasmic reticulum Ca2+ uptake was inhibited. Adenovirus infection with Ad.RSV.PLB was therefore able to produce functional changes in adult cardiac myocytes within 24 h, consistent with overexpression of PLB and similar to those seen in failing human heart.

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