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Parallel activation of Ca2+-induced survival and death pathways in cardiomyocytes by sorbitol-induced hyperosmotic stress

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Abstract

Hyperosmotic stress promotes rapid and pronounced apoptosis in cultured cardiomyocytes. Here, we investigated if Ca2+ signals contribute to this response. Exposure of cardiomyocytes to sorbitol [600 mosmol (kg water)−1] elicited large and oscillatory intracellular Ca2+ concentration increases. These Ca2+ signals were inhibited by nifedipine, Cd2+, U73122, xestospongin C and ryanodine, suggesting contributions from both Ca2+ influx through voltage dependent L-type Ca2+ channels plus Ca2+ release from intracellular stores mediated by IP3 receptors and ryanodine receptors. Hyperosmotic stress also increased mitochondrial Ca2+ levels, promoted mitochondrial depolarization, reduced intracellular ATP content, and activated the transcriptional factor cyclic AMP responsive element binding protein (CREB), determined by increased CREB phosphorylation and electrophoretic mobility shift assays. Incubation with 1 mM EGTA to decrease extracellular [Ca2+] prevented cardiomyocyte apoptosis induced by hyperosmotic stress, while overexpression of an adenoviral dominant negative form of CREB abolished the cardioprotection provided by 1 mM EGTA. These results suggest that hyperosmotic stress induced by sorbitol, by increasing Ca2+ influx and raising intracellular Ca2+ concentration, activates Ca2+ release from stores and causes cell death through mitochondrial function collapse. In addition, the present results suggest that the Ca2+ increase induced by hyperosmotic stress promotes cell survival by recruiting CREB-mediated signaling. Thus, the fate of cardiomyocytes under hyperosmotic stress will depend on the balance between Ca2+-induced survival and death pathways.

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Abbreviations

AdLacZ:

Adenovirus β-galactosidase

Ad dnCREB:

Adenovirus dominant negative CREB

AIF:

Apoptosis inducing factor

[Ca2+]i:

Intracellular calcium concentration

CICR:

Ca2+-induced Ca2+ release

CaMK:

Calmodulin kinase

CREB:

Cyclic AMP responsive element binding protein

CsA:

Cyclosporin A

ERK:

Extracellular signal-regulated kinase

fluo3-AM:

Fluo3 acetoximethylester

IP3:

Inositol-1,4,5-trisphosphate

IP3R:

IP3 receptor

LY:

LY294002

MAPK:

Mitogen activated protein kinase

MOI:

Multiplicity of infection

p38:

p38-Mitogen activated protein kinase

PD:

PD98059

PLC:

Phospholipase C

RuRed:

Ruthenium red

SB:

SB203580

SERCA:

Sarco/endoplasmic reticulum Ca2+-ATPase

TMRM:

Tetramethylrhodamine methyl ester

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Acknowledgments

We thank Fidel Albornoz and Ruth Marquez for their technical assistance and Drs Paola Llanos and David Mears (Faculty of Medicine, Universidad de of Chile, Santiago, Chile) for their help with fura2-AM experiments. This work was supported by FONDAP (Fondo de Areas Prioritarias, Fondo Nacional de Desarrollo Cientifico y Tecnologico, CONICYT, Chile) grant 15010006 (to S. L., C. H., E. J.). We also thank the International Collaboration Program ECOS-CONICTY grants C04B03 and C08S01 (to G. K. and S. L.) and FONDECYT Postdoctoral Grant 3070043 (to V. E.). C. M., C. I., V. P., R. B., C. Q., A. C. and J. M. V. are recipients of Ph. D. fellowships from CONICYT, Chile. S. L. is in a sabbatical leave at The University of Texas Southwestern Medical Center, Dallas.

Conflicts of interest statement

The authors declare that they have no conflict of interest.

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Authors and Affiliations

  1. Centro FONDAP Estudios Moleculares de la Célula, Universidad de Chile, Santiago, Chile

    M. Chiong, V. Parra, V. Eisner, C. Ibarra, C. Maldonado, A. Criollo, R. Bravo, C. Quiroga, A. Contreras, J. M. Vicencio, P. Cea, J. L. Bucarey, E. Jaimovich, C. Hidalgo & S. Lavandero

  2. Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Olivos 1007, 8380492, Santiago, Chile

    S. Lavandero

  3. Division of Cardiology, Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, 75235, USA

    S. Lavandero

  4. Instituto de Ciencias Biomédicas, Facultad de Medicina, Universidad de Chile, 8380492, Santiago, Chile

    E. Jaimovich, C. Hidalgo & S. Lavandero

  5. Centre National de la Recherche Scientifique, Institut de Neurobiologie Alfred Fessard, FRC2118, UPR 9040, 91198, Gif-sur-Yvette, France

    J. Molgó

  6. Institut Gustave Roussy, 39 rue Camille Desmoulins, 94805, Villejuif, France

    G. Kroemer

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  1. M. Chiong
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Correspondence to S. Lavandero.

Additional information

M. Chiong, V. Parra and V. Eisner contributed equally to this work.

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Supplementary Fig. 1

Hyperosmotic stress increases intracellular Ca2+ concentration in cultured cardiomyocytes. Cells preloaded with or fura2-AM were perfused with Ca2+-containing (black circles) or Ca2+-free (white circles) Krebs buffer and at the time indicated with an arrow cells were supplemented with sorbitol (Sor) (600 mosmol (kg water)−1). Using an inverted microscope equipped with a Xenon lamp, fura2-AM preloaded cells were excited at 340 nm and 380 nm, and monitored at 510 nm. The corresponding 340/380 fluorescence ratios were calculated. In the inset a more detailed fura2 340/380 fluorescence ratio in the first 75 s is depicted (TIFF 555 kb)

Supplementary Fig. 2

Hyperosmotic stress induces strong depolarization of cultured cardiomyocytes. The effect of hyperosmotic solutions on the membrane potential of cardiomyocytes was evaluated with the voltage-sensitive dye bis-(1,3-dibutylbarbituric acid)pentamethine oxonol (DiBAC4(3)) (Molecular Probes), an anionic dye that enters depolarized cells and exhibits enhanced fluorescence and green spectral shifts, so that increased fluorescence reflects increased membrane depolarization. Cardiac myocytes were incubated in Krebs buffer (145 mM NaCl, 5 mM KCl, 1 mM MgCl2, 2.6 mM CaCl2, 5.6 mM glucose, 10 mM HEPES, pH 7.4) for 10 min at 37°C; DiBAC4(3) dissolved in 0.2% DMSO was added to a final concentration of 300 nM and cells were further incubated for 10 min at 37°C. Cells preloaded with DiBAC4(3) were excited at 488 nm and monitored at 510 nm; fluorescence images were collected every 5 s in a confocal laser scanning inverted microscope (Zeiss LSM510). At the time indicated with an arrow, cells were perfused with Ca2+-containing Krebs buffer supplemented with sorbitol (Sor, 600 mosmol (kg water)−1). As control, DiBAC4(3) preloaded cardiomyocytes were depolarized by perfusion with Krebs buffer containing 20 mM, 50 mM or 80 mM KCl. Images were analyzed with ImageJ software and relative fluorescence (ΔF/Fo) values were determined. Values are the average ± S. E. M. of 4 independent experiments (TIFF 492 kb)

Supplementary Fig. 3

Effect of the pan caspase inhibitor Z-VAD-fmk on caspase 3 induction triggered by hyperosmotic stress. Cultured cardiomyocytes were exposed to sorbitol (600 mosmol (kg water)−1) or sorbitol supplemented with the pan-caspase inhibitor Z-VAD-fmk (10 μM). At different times, total protein extracts were prepared. Pro-caspase and caspase 3 were detected by Western blot analysis. Gels are representative of 3 different experiments. Results are given as mean ± SEM for 3 independent experiments. * P < 0.05 vs respective control 0 h, # P <0.05 vs 2 h sorbitol (TIFF 871 kb)

Supplementary Fig. 4

Cyclosporin A does not protect cardiomyocytes from cell death induced by hyperosmotic stress. Cardiomyocytes were preincubated 30 min with 0.5 μM cyclosporin A (CsA) and were then stimulated with culture media supplemented with sorbitol (600 mosmol (kg water)−1) for 24 h. Panel A. Cell viability was determined by the trypan blue exclusion method. Results are given as mean ± S. E. M. of 6 independent experiments. * P <0.05 vs control. Panel B. DNA laddering analysis was performed in DNA extracted using the chloroform:phenol method, fractionated by electrophoresis in 2% agarose gels and visualized by ethidium bromide/UV. The standard corresponds to 100 bp DNA ladder. Results are given as mean ± S. E. M. of 3 independent experiments. * P < 0.05 vs control (TIFF 1163 kb)

Supplementary Fig. 5

Effect of the expression of a dominant negative CREB on cardiac myocyte viability. Panel A: Cultured cardiomyocytes were transduced with an adenovirus overexpressing dominant negative CREB (Ad dnCREB) at a different multiplicity of infection (MOI). A LacZ adenovirus (Ad LacZ) was used as control. Cells were transduced for 48 h in DME:199 (4:1) and cell viability was determined as indicated in Materials and methods. Panel B: Cultured cardiomyocytes were transduced for 48 h with Ad dnCREB or Ad LacZ at MOI = 300. Total protein extracts were obtained and CREB and β-actin protein levels were determined by Western blot analysis using anti CREB or anti β-actin polyclonal antibody, respectively. CREB/β-actin levels were 2.0 ± 0.3 and 1.0 ± 0.2 in cardiomyocytes transduced with Ad dnCREB or Ad LacZ, respectively (TIFF 1806 kb)

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Chiong, M., Parra, V., Eisner, V. et al. Parallel activation of Ca2+-induced survival and death pathways in cardiomyocytes by sorbitol-induced hyperosmotic stress. Apoptosis 15, 887–903 (2010). https://doi.org/10.1007/s10495-010-0505-9

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