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Title: Disruption of the intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes

Abstract

Aconitine is an effective ingredient in Aconite tuber, an important traditional Chinese medicine. Aconitine is also known to be a highly toxic diterpenoid alkaloid with arrhythmogenic effects. In the present study, we have characterized the properties of arrhythmic cytotoxicity and explored the possible mechanisms of aconitine-induced cardiomyocytes. Results show that aconitine induces significant abnormity in the spontaneous beating rate, amplitude of spontaneous oscillations and the relative intracellular Ca{sup 2+} concentration. Also, mRNA transcription levels and protein expressions of SR Ca{sup 2+} release channel RyR{sub 2} and sarcolemmal NCX were elevated in aconitine-induced cardiomyocytes. However, co-treatment with ruthenium red (RR), a RyR channel inhibitor, could reverse the aconitine-induced abnormity in intracellular Ca{sup 2+} signals. These results demonstrate that disruption of intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling (EC coupling) is a crucial mechanism of arrhythmic cytotoxicity in aconitine-induced cardiomyocytes. Moreover, certain inhibitors appear to play an important role in the detoxification of aconitine-induced Ca{sup 2+}-dependent arrhythmias.

Authors:
 [1];  [2];  [1];  [3];  [3];  [4]
  1. School of Medicine, Tsinghua University, Beijing 100084 (China)
  2. (China)
  3. Beijing University of Chinese Medicine, Beijing 100029 (China)
  4. School of Medicine, Tsinghua University, Beijing 100084 (China). E-mail: zwang@tsinghua.edu.cn
Publication Date:
OSTI Identifier:
20979843
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biochemical and Biophysical Research Communications; Journal Volume: 354; Journal Issue: 4; Other Information: DOI: 10.1016/j.bbrc.2007.01.082; PII: S0006-291X(07)00113-1; Copyright (c) 2007 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ALKALOIDS; CALCIUM IONS; CHINA; COUPLING; DETOXIFICATION; DRUGS; EXCITATION; HOMEOSTASIS; MEDICINE; PROTEINS; RUTHENIUM; TOXICITY; TRANSCRIPTION

Citation Formats

Fu Min, Beijing University of Chinese Medicine, Beijing 100029, Wu Meng, Wang Jifeng, Qiao Yanjiang, and Wang Zhao. Disruption of the intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes. United States: N. p., 2007. Web.
Fu Min, Beijing University of Chinese Medicine, Beijing 100029, Wu Meng, Wang Jifeng, Qiao Yanjiang, & Wang Zhao. Disruption of the intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes. United States.
Fu Min, Beijing University of Chinese Medicine, Beijing 100029, Wu Meng, Wang Jifeng, Qiao Yanjiang, and Wang Zhao. Fri . "Disruption of the intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes". United States. doi:.
@article{osti_20979843,
title = {Disruption of the intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling is a crucial mechanism of arrhythmic toxicity in aconitine-induced cardiomyocytes},
author = {Fu Min and Beijing University of Chinese Medicine, Beijing 100029 and Wu Meng and Wang Jifeng and Qiao Yanjiang and Wang Zhao},
abstractNote = {Aconitine is an effective ingredient in Aconite tuber, an important traditional Chinese medicine. Aconitine is also known to be a highly toxic diterpenoid alkaloid with arrhythmogenic effects. In the present study, we have characterized the properties of arrhythmic cytotoxicity and explored the possible mechanisms of aconitine-induced cardiomyocytes. Results show that aconitine induces significant abnormity in the spontaneous beating rate, amplitude of spontaneous oscillations and the relative intracellular Ca{sup 2+} concentration. Also, mRNA transcription levels and protein expressions of SR Ca{sup 2+} release channel RyR{sub 2} and sarcolemmal NCX were elevated in aconitine-induced cardiomyocytes. However, co-treatment with ruthenium red (RR), a RyR channel inhibitor, could reverse the aconitine-induced abnormity in intracellular Ca{sup 2+} signals. These results demonstrate that disruption of intracellular Ca{sup 2+} homeostasis in the cardiac excitation-contraction coupling (EC coupling) is a crucial mechanism of arrhythmic cytotoxicity in aconitine-induced cardiomyocytes. Moreover, certain inhibitors appear to play an important role in the detoxification of aconitine-induced Ca{sup 2+}-dependent arrhythmias.},
doi = {},
journal = {Biochemical and Biophysical Research Communications},
number = 4,
volume = 354,
place = {United States},
year = {Fri Mar 23 00:00:00 EDT 2007},
month = {Fri Mar 23 00:00:00 EDT 2007}
}
  • We have recently shown that stimulation of cultured neonatal cardiomyocytes with endothelin-1 (ET-1) first produces conformational disorder within the ryanodine receptor (RyR2) and diastolic Ca{sup 2+} leak from the sarcoplasmic reticulum (SR), then develops hypertrophy (HT) in the cardiomyocytes (Hamada et al., 2009 ). The present paper addresses the following question. By what mechanism does crosstalk between defective operation of RyR2 and activation of the HT gene program occur? Here we show that the immuno-stain of calmodulin (CaM) is localized chiefly in the cytoplasmic area in the control cells; whereas, in the ET-1-treated/hypertrophied cells, major immuno-staining is localized in themore » nuclear region. In addition, fluorescently labeled CaM that has been introduced into the cardiomyocytes using the BioPORTER system moves from the cytoplasm to the nucleus with the development of HT. The immuno-confocal imaging of Ca{sup 2+}/CaM-dependent protein kinase II (CaMKII) also shows cytoplasm-to-nucleus shift of the immuno-staining pattern in the hypertrophied cells. In an early phase of hypertrophic growth, the frequency of spontaneous Ca{sup 2+} transients increases, which accompanies with cytoplasm-to-nucleus translocation of CaM. In a later phase of hypertrophic growth, further increase in the frequency of spontaneous Ca{sup 2+} transients results in the appearance of trains of Ca{sup 2+} spikes, which accompanies with nuclear translocation of CaMKII. The cardio-protective reagent dantrolene (the reagent that corrects the de-stabilized inter-domain interaction within the RyR2 to a normal mode) ameliorates aberrant intracellular Ca{sup 2+} events and prevents nuclear translocation of both CaM and CaMKII, then prevents the development of HT. These results suggest that translocation of CaM and CaMKII from the cytoplasm to the nucleus serves as messengers to transmit the pathogenic signal elicited in the surface membrane and in the RyR2 to the nuclear transcriptional sites to activate HT program.« less
  • Energy metabolism and Ca{sup 2+} handling serve critical roles in cardiac physiology and pathophysiology. Peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1{alpha}) is a multi-functional coactivator that is involved in the regulation of cardiac mitochondrial functional capacity and cellular energy metabolism. However, the regulation of PGC-1{alpha} in cardiac Ca{sup 2+} signaling has not been fully elucidated. To address this issue, we combined confocal line-scan imaging with off-line imaging processing to characterize calcium signaling in cultured adult rat ventricular myocytes expressing PGC-1{alpha} via adenoviral transduction. Our data shows that overexpressing PGC-1{alpha} improved myocyte contractility without increasing the amplitude of Ca{sup 2+}more » transients, suggesting that myofilament sensitivity to Ca{sup 2+} increased. Interestingly, the decay kinetics of global Ca{sup 2+} transients and Ca{sup 2+} waves accelerated in PGC-1{alpha}-expressing cells, but the decay rate of caffeine-elicited Ca{sup 2+} transients showed no significant change. This suggests that sarcoplasmic reticulum (SR) Ca{sup 2+}-ATPase (SERCA2a), but not Na{sup +}/Ca{sup 2+} exchange (NCX) contribute to PGC-1{alpha}-induced cytosolic Ca{sup 2+} clearance. Furthermore, PGC-1{alpha} induced the expression of SERCA2a in cultured cardiac myocytes. Importantly, overexpressing PGC-1{alpha} did not disturb cardiac Ca{sup 2+} homeostasis, because SR Ca{sup 2+} load and the propensity for Ca{sup 2+} waves remained unchanged. These data suggest that PGC-1{alpha} can ameliorate cardiac Ca{sup 2+} cycling and improve cardiac work output in response to physiological stress. Unraveling the PGC-1{alpha}-calcium handing pathway sheds new light on the role of PGC-1{alpha} in the therapy of cardiac diseases.« less
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  • The global distribution of perfluorinated acids (PFAs) in industry and in household is well known. Their increasing environmental occurrence and biomagnification in the living organisms have drawn growing interests in efforts to describe precisely the mechanisms of action in vitro and in vivo. Our previous investigations widely described lipophilicity-dependent cytotoxicity of PFAs as well as the effect of perfluorination of carbon chain on depolarization of plasma membrane potential, acidification or mitochondrial dysfunctions. In this study we presented in dose- and time-dependent manner the impact of PFAs on calcium homeostasis in HCT116 cells. Comparative analysis of cytosolic [Ca{sup 2+}]{sub c} andmore » mitochondrial calcium [Ca{sup 2+}]{sub m} carried out by flow cytometry revealed distinct uptake of calcium into mitochondria in correlation to increasing lipophilicity of PFAs. Massive accumulation of [Ca{sup 2+}]{sub m} was not accompanied by equivalent loss of [Ca{sup 2+}]{sub c}. Indeed, moderate changes of [Ca{sup 2+}]{sub c} were observed after incubation with 400 {mu}M PFDoDA reaching 29.83% and 49.17% decrease at 4th and 72nd hour, respectively. At the same time, mitochondrial calcium uptake increased from 2- to more than 4-fold comparing with non-treated cells. Incubation with non-fluorinated decanoic acid (DA) did not cause any changes in calcium homeostasis. Presented data show that PFAs-induced perturbations in calcium distribution seem to be a missing link related to mitochondria dysfunction playing a crucial role in determination of apoptotic cell death. Complete scheme for the mechanism of cytotoxic action of PFAs has been included.« less
  • We had earlier shown that exposure to arsenic (0.50 {mu}M) caused caspase-3 mediated head kidney macrophage (HKM) apoptosis involving the p38-JNK pathway in Clarias batrachus. Here we examined the roles of calcium (Ca{sup 2+}) and extra-cellular signal-regulated protein kinase (ERK), the other member of MAPK-pathway on arsenic-induced HKM apoptosis. Arsenic-induced HKM apoptosis involved increased expression of ERK and calpain-2. Nifedipine, verapamil and EGTA pre-treatment inhibited the activation of calpain-2, ERK and reduced arsenic-induced HKM apoptosis as evidenced from reduced caspase-3 activity, Annexin V-FITC-propidium iodide and Hoechst 33342 staining. Pre-incubation with ERK inhibitor U 0126 inhibited the activation of calpain-2 andmore » interfered with arsenic-induced HKM apoptosis. Additionally, pre-incubation with calpain-2 inhibitor also interfered with the activation of ERK and inhibited arsenic-induced HKM apoptosis. The NADPH oxidase inhibitor apocynin and diphenyleneiodonium chloride also inhibited ERK activation indicating activation of ERK in arsenic-exposed HKM also depends on signals from NADPH oxidase pathway. Our study demonstrates the critical role of Ca{sup 2+} homeostasis on arsenic-induced HKM apoptosis. We suggest that arsenic-induced alteration in intracellular Ca{sup 2+} levels initiates pro-apoptotic ERK and calpain-2; the two pathways influence each other positively and induce caspase-3 mediated HKM apoptosis. Besides, our study also indicates the role of ROS in the activation of ERK pathway in arsenic-induced HKM apoptosis in C. batrachus. - Highlights: > Altered Ca{sup 2+} homeostasis leads to arsenic-induced HKM apoptosis. > Calpain-2 plays a critical role in the process. > ERK is pro-apoptotic in arsenic-induced HKM apoptosis. > Arsenic-induced HKM apoptosis involves cross talk between calpain-2 and ERK.« less