Glutathione and K+ channel remodeling in postinfarction rat heart

2002 ◽  
Vol 282 (6) ◽  
pp. H2346-H2355 ◽  
Author(s):  
George J. Rozanski ◽  
Zhi Xu
Keyword(s):  
Oxidative Stress ◽  
Glutathione Reductase ◽  
Ventricular Myocytes ◽  
K Channel ◽  
Glycolytic Flux ◽  
Cell Functions ◽  
Tissue Extracts ◽  
Rat Hearts ◽  
Glutamylcysteine Synthetase ◽  
Pentose Pathway

Electrical remodeling of the diseased ventricle is characterized by downregulation of K+ channels that control action potential repolarization. Recent studies suggest that this shift in electrophysiological phenotype involves oxidative stress and changes in intracellular glutathione (GSH), a key regulator of redox-sensitive cell functions. This study examined the role of GSH in regulating K+ currents in ventricular myocytes from rat hearts 8 wk after myocardial infarction (MI). Colorimetric analysis of tissue extracts showed that endogenous GSH levels were significantly less in post-MI hearts compared with controls, which is indicative of oxidative stress. This change in GSH status correlated with significant decreases in activities of glutathione reductase and γ-glutamylcysteine synthetase. Voltage-clamp studies of isolated myocytes from post-MI hearts demonstrated that downregulation of the transient outward K+ current ( I to) could be reversed by pretreatment with exogenous GSH or N-acetylcysteine, a precursor of GSH. Upregulation of I to was also elicited by dichloroacetate, which increases glycolytic flux through the GSH-related pentose pathway. This metabolic effect was blocked by inhibitors of glutathione reductase and the pentose pathway. These data indicate that oxidative stress-induced alteration in the GSH redox state plays an important role in I to channel remodeling and that GSH homeostasis is influenced by pathways of glucose metabolism.

scholarly journals Adeno-Associated Viral Transfer of Glyoxalase-1 Blunts Carbonyl and Oxidative Stresses in Hearts of Type 1 Diabetic Rats

Antioxidants ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 592
Author(s):  
Fadhel A. Alomar ◽  
Abdullah Al-Rubaish ◽  
Fahad Al-Muhanna ◽  
Amein K. Al-Ali ◽  
JoEllyn McMillan ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Ventricular Myocytes ◽  
Diabetic Rats ◽  
Confocal Imaging ◽  
Glyoxalase 1 ◽  
Microvascular Leakage ◽  
Oxidative Stresses ◽  
Rat Hearts ◽  
Longitudinal Strains

Accumulation of methylglyoxal (MG) arising from downregulation of its primary degrading enzyme glyoxalase-1 (Glo1) is an underlying cause of diabetic cardiomyopathy (DC). This study investigated if expressing Glo1 in rat hearts shortly after the onset of Type 1 diabetes mellitus (T1DM) would blunt the development of DC employing the streptozotocin-induced T1DM rat model, an adeno-associated virus containing Glo1 driven by the endothelin-1 promoter (AAV2/9-Endo-Glo1), echocardiography, video edge, confocal imaging, and biochemical/histopathological assays. After eight weeks of T1DM, rats developed DC characterized by a decreased E:A ratio, fractional shortening, and ejection fraction, and increased isovolumetric relaxation time, E: e’ ratio, and circumferential and longitudinal strains. Evoked Ca2+ transients and contractile kinetics were also impaired in ventricular myocytes. Hearts from eight weeks T1DM rats had lower Glo1 and GSH levels, elevated carbonyl/oxidative stress, microvascular leakage, inflammation, and fibrosis. A single injection of AAV2/9 Endo-Glo1 (1.7 × 1012 viron particles/kg) one week after onset of T1DM, potentiated GSH, and blunted MG accumulation, carbonyl/oxidative stress, microvascular leakage, inflammation, fibrosis, and impairments in cardiac and myocyte functions that develop after eight weeks of T1DM. These new data indicate that preventing Glo1 downregulation by administering AAV2/9-Endo-Glo1 to rats one week after the onset of T1DM, blunted the DC that develops after eight weeks of diabetes by attenuating carbonyl/oxidative stresses, microvascular leakage, inflammation, and fibrosis.

Insulin regulation of glutathione and contractile phenotype in diabetic rat ventricular myocytes

2007 ◽  
Vol 292 (3) ◽  
pp. H1619-H1629 ◽  
Author(s):  
Shumin Li ◽  
Xun Li ◽  
Yu-Long Li ◽  
Chun-Hong Shao ◽  
Keshore R. Bidasee ◽  
...  
Keyword(s):  
De Novo ◽  
Ventricular Myocytes ◽  
Cardiovascular Complications ◽  
Diabetic Rat ◽  
Sprague Dawley ◽  
Cell Functions ◽  
Glutamylcysteine Synthetase ◽  
Rat Myocytes ◽  
Glucose 6 Phosphate Dehydrogenase

Cardiovascular complications of diabetes mellitus involve oxidative stress and profound changes in reduced glutathione (GSH), an essential tripeptide that controls many redox-sensitive cell functions. This study examined regulation of GSH by insulin to identify mechanisms controlling cardiac redox state and to define the functional impact of GSH depletion. GSH was measured by fluorescence microscopy in ventricular myocytes isolated from Sprague-Dawley rats made diabetic by streptozotocin, and video and confocal microscopy were used to measure mechanical properties and Ca2+ transients, respectively. Spectrophotometric assays of tissue extracts were also done to measure the activities of enzymes that control GSH levels. Four weeks after injection of streptozotocin, mean GSH concentration ([GSH]) in isolated diabetic rat myocytes was ∼36% less than in control, correlating with decreased activities of two major enzymes regulating GSH levels: glutathione reductase and γ-glutamylcysteine synthetase. Treatment of diabetic rat myocytes with insulin normalized [GSH] after a delay of 3–4 h. A more rapid but transient upregulation of [GSH] occurred in myocytes treated with dichloroacetate, an activator of pyruvate dehydrogenase. Inhibitor experiments indicated that insulin normalized [GSH] via the pentose pathway and γ-glutamylcysteine synthetase, although the basal activity of glucose-6-phosphate dehydrogenase was not different between diabetic and control hearts. Diabetic rat myocytes were characterized by significant mechanical dysfunction that correlated with diminished and prolonged Ca2+ transients. This phenotype was reversed by in vitro treatment with insulin and also by exogenous GSH or N-acetylcysteine, a precursor of GSH. Our data suggest that insulin regulates GSH through pathways involving de novo GSH synthesis and reduction of its oxidized form. It is proposed that a key function of glucose metabolism in heart is to supply reducing equivalents required to maintain adequate GSH levels for the redox control of Ca2+ handling proteins and contraction.

scholarly journals Increased susceptibility of aged hearts to ventricular fibrillation during oxidative stress

2009 ◽  
Vol 297 (5) ◽  
pp. H1594-H1605 ◽  
Author(s):  
Norishige Morita ◽  
Ali A. Sovari ◽  
Yuanfang Xie ◽  
Michael C. Fishbein ◽  
William J. Mandel ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Young Adult ◽  
Ventricular Myocytes ◽  
Tissue Level ◽  
Left Ventricular ◽  
Middle Aged ◽  
Aged Rat ◽  
Adult Rat ◽  
Inactive Form ◽  
Rat Hearts

Oxidative stress with hydrogen peroxide (H2O2) readily promotes early afterdepolarizations (EADs) and triggered activity (TA) in isolated rat and rabbit ventricular myocytes. Here we examined the effects of H2O2 on arrhythmias in intact Langendorff rat and rabbit hearts using dual-membrane voltage and intracellular calcium optical mapping and glass microelectrode recordings. Young adult rat (3–5 mo, N = 25) and rabbit (3–5 mo, N = 6) hearts exhibited no arrhythmias when perfused with H2O2 (0.1–2 mM) for up to 3 h. However, in 33 out of 35 (94%) aged (24–26 mo) rat hearts, 0.1 mM H2O2 caused EAD-mediated TA, leading to ventricular tachycardia (VT) and fibrillation (VF). Aged rabbits (life span, 8–12 yr) were not available, but 4 of 10 middle-aged rabbits (3–5 yr) developed EADs, TA, VT, and VF. These arrhythmias were suppressed by the reducing agent N-acetylcysteine (2 mM) and CaMKII inhibitor KN-93 (1 μM) but not by its inactive form (KN-92, 1 μM). There were no significant differences between action potential duration (APD) or APD restitution slope before or after H2O2 in aged or young adult rat hearts. In histological sections, however, trichrome staining revealed that aged rat hearts exhibited extensive fibrosis, ranging from 10–90%; middle-aged rabbit hearts had less fibrosis (5–35%), whereas young adult rat and rabbit hearts had <4% fibrosis. In aged rat hearts, EADs and TA arose most frequently (70%) from the left ventricular base where fibrosis was intermediate (∼30%). Computer simulations in two-dimensional tissue incorporating variable degrees of fibrosis showed that intermediate (but not mild or severe) fibrosis promoted EADs and TA. We conclude that in aged ventricles exposed to oxidative stress, fibrosis facilitates the ability of cellular EADs to emerge and generate TA, VT, and VF at the tissue level.

scholarly journals Suppression of ventricular arrhythmias by targeting late L-type Ca2+ current

2021 ◽  
Vol 153 (12) ◽  
Author(s):  
Marina Angelini ◽  
Arash Pezhouman ◽  
Nicoletta Savalli ◽  
Marvin G. Chang ◽  
Federica Steccanella ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Ventricular Arrhythmias ◽  
Ventricular Myocytes ◽  
Ex Vivo ◽  
Selective Reduction ◽  
Antiarrhythmic Action ◽  
Early Afterdepolarizations ◽  
Rat Hearts ◽  
New Strategy ◽  
Early Peak

Ventricular arrhythmias, a leading cause of sudden cardiac death, can be triggered by cardiomyocyte early afterdepolarizations (EADs). EADs can result from an abnormal late activation of L-type Ca2+ channels (LTCCs). Current LTCC blockers (class IV antiarrhythmics), while effective at suppressing EADs, block both early and late components of ICa,L, compromising inotropy. However, computational studies have recently demonstrated that selective reduction of late ICa,L (Ca2+ influx during late phases of the action potential) is sufficient to potently suppress EADs, suggesting that effective antiarrhythmic action can be achieved without blocking the early peak ICa,L, which is essential for proper excitation–contraction coupling. We tested this new strategy using a purine analogue, roscovitine, which reduces late ICa,L with minimal effect on peak current. Scaling our investigation from a human CaV1.2 channel clone to rabbit ventricular myocytes and rat and rabbit perfused hearts, we demonstrate that (1) roscovitine selectively reduces ICa,L noninactivating component in a human CaV1.2 channel clone and in ventricular myocytes native current, (2) the pharmacological reduction of late ICa,L suppresses EADs and EATs (early after Ca2+ transients) induced by oxidative stress and hypokalemia in isolated myocytes, largely preserving cell shortening and normal Ca2+ transient, and (3) late ICa,L reduction prevents/suppresses ventricular tachycardia/fibrillation in ex vivo rabbit and rat hearts subjected to hypokalemia and/or oxidative stress. These results support the value of an antiarrhythmic strategy based on the selective reduction of late ICa,L to suppress EAD-mediated arrhythmias. Antiarrhythmic therapies based on this idea would modify the gating properties of CaV1.2 channels rather than blocking their pore, largely preserving contractility.

Effects of Genipin at NO synthesis and Ischemia-Reperfusion Induced Oxidative Stress in Old Rat Hearts

2010 ◽  
Vol 1 (4) ◽  
pp. 335-344 ◽  
Author(s):  
Yulia V. Goshovska ◽  
Yulia P. Korkach ◽  
Tatiana V. Shimanskaya ◽  
Anatolii V. Kotsuruba ◽  
Vadym F. Sagach
Keyword(s):  
Oxidative Stress ◽  
Ischemia Reperfusion ◽  
Rat Hearts

scholarly journals Altered Na/Ca exchange distribution in ventricular myocytes from failing hearts

2016 ◽  
Vol 310 (2) ◽  
pp. H262-H268 ◽  
Author(s):  
Hanne C. Gadeberg ◽  
Simon M. Bryant ◽  
Andrew F. James ◽  
Clive H. Orchard
Keyword(s):  
Heart Failure ◽  
Ventricular Myocytes ◽  
Cell Voltage ◽  
Coronary Artery Ligation ◽  
Sham Operation ◽  
Ca Current ◽  
Artery Ligation ◽  
Whole Cell ◽  
Rat Hearts ◽  
T Tubules

In mammalian cardiac ventricular myocytes, Ca efflux via Na/Ca exchange (NCX) occurs predominantly at T tubules. Heart failure is associated with disrupted t-tubular structure, but its effect on t-tubular function is less clear. We therefore investigated t-tubular NCX activity in ventricular myocytes isolated from rat hearts ∼18 wk after coronary artery ligation (CAL) or corresponding sham operation (Sham). NCX current ( INCX) and l-type Ca current ( ICa) were recorded using the whole cell, voltage-clamp technique in intact and detubulated (DT) myocytes; intracellular free Ca concentration ([Ca]i) was monitored simultaneously using fluo-4. INCX was activated and measured during application of caffeine to release Ca from sarcoplasmic reticulum (SR). Whole cell INCX was not significantly different in Sham and CAL myocytes and occurred predominantly in the T tubules in Sham myocytes. CAL was associated with redistribution of INCX and ICa away from the T tubules to the cell surface and an increase in t-tubular INCX/ ICa density from 0.12 in Sham to 0.30 in CAL myocytes. The decrease in t-tubular INCX in CAL myocytes was accompanied by an increase in the fraction of Ca sequestered by SR. However, SR Ca content was not significantly different in Sham, Sham DT, and CAL myocytes but was significantly increased by DT of CAL myocytes. In Sham myocytes, there was hysteresis between INCX and [Ca]i, which was absent in DT Sham but present in CAL and DT CAL myocytes. These data suggest altered distribution of NCX in CAL myocytes.

scholarly journals Regulation of intracellular glutathione levels in erythrocytes infected with chloroquine-sensitive and chloroquine-resistant Plasmodium falciparum

2002 ◽  
Vol 368 (3) ◽  
pp. 761-768 ◽  
Author(s):  
Svenja MEIERJOHANN ◽  
Rolf D. WALTER ◽  
Sylke MÜLLER
Keyword(s):  
Oxidative Stress ◽  
Red Blood Cells ◽  
Blood Cells ◽  
Differential Susceptibility ◽  
Protozoan Parasite ◽  
Chloroquine Resistance ◽  
Glutathione Metabolism ◽  
Glutathione Synthesis ◽  
Intracellular Glutathione ◽  
Glutamylcysteine Synthetase

Malaria is one of the most devastating tropical diseases despite the availability of numerous drugs acting against the protozoan parasite Plasmodium in its human host. However, the development of drug resistance renders most of the existing drugs useless. In the malaria parasite the tripeptide glutathione is not only involved in maintaining an adequate intracellular redox environment and protecting the cell against oxidative stress, but it has also been shown that it degrades non-polymerized ferriprotoporphyrin IX (FP IX) and is thus implicated in the development of chloroquine resistance. Glutathione levels in Plasmodium-infected red blood cells are regulated by glutathione synthesis, glutathione reduction and glutathione efflux. Therefore the effects of drugs that interfere with these metabolic processes were studied to establish possible differences in the regulation of the glutathione metabolism of a chloroquine-sensitive and a chloroquine-resistant strain of Plasmodiumfalciparum. Growth inhibition of P. falciparum 3D7 by d,l-buthionine-(S,R)sulphoximine (BSO), an inhibitor of γ-glutamylcysteine synthetase (γ-GCS), and by Methylene Blue (MB), an inhibitor of gluta thione reductase (GR), was significantly more pronounced than inhibition of P.falciparum Dd2 growth by these drugs. These results correlate with the higher levels of total glutathione in P. falciparum Dd2. Short-term incubations of Percoll-enriched trophozoite-infected red blood cells in the presence of BSO, MB and N,N1-bis(2-chloroethyl)-N-nitrosourea and subsequent determinations of γ-GCS activities, GR activities and glutathione disulphide efflux revealed that maintenance of intracellular glutathione in P. falciparum Dd2 is mainly dependent on glutathione synthesis whereas in P. falciparum 3D7 it is regulated via GR. Generally, P. falciparum Dd2 appears to be able to sustain its intracellular glutathione more efficiently than P. falciparum 3D7. In agreement with these findings is the differential susceptibility to oxidative stress of both parasite strains elicited by the glucose/glucose oxidase system.

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