Linkage of β1-adrenergic stimulation to apoptotic heart cell death through protein kinase A–independent activation of Ca2+/calmodulin kinase II
Wei-Zhong Zhu, … , Heping Cheng, Rui-Ping Xiao
Wei-Zhong Zhu, … , Heping Cheng, Rui-Ping Xiao
Published March 1, 2003
Citation Information: J Clin Invest. 2003;111(5):617-625. https://doi.org/10.1172/JCI16326.
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Article

Linkage of β1-adrenergic stimulation to apoptotic heart cell death through protein kinase A–independent activation of Ca2+/calmodulin kinase II

Abstract

β1-adrenergic receptor (β1AR) stimulation activates the classic cAMP/protein kinase A (PKA) pathway to regulate vital cellular processes from the change of gene expression to the control of metabolism, muscle contraction, and cell apoptosis. Here we show that sustained β1AR stimulation promotes cardiac myocyte apoptosis by activation of Ca2+/calmodulin kinase II (CaMKII), independently of PKA signaling. β1AR-induced apoptosis is resistant to inhibition of PKA by a specific peptide inhibitor, PKI14-22, or an inactive cAMP analogue, Rp-8-CPT-cAMPS. In contrast, the β1AR proapoptotic effect is associated with non–PKA-dependent increases in intracellular Ca2+ and CaMKII activity. Blocking the L-type Ca2+ channel, buffering intracellular Ca2+, or inhibiting CaMKII activity fully protects cardiac myocytes against β1AR-induced apoptosis, and overexpressing a cardiac CaMKII isoform, CaMKII-δC, markedly exaggerates the β1AR apoptotic effect. These findings indicate that CaMKII constitutes a novel PKA-independent linkage of β1AR stimulation to cardiomyocyte apoptosis that has been implicated in the overall process of chronic heart failure.

Authors

Wei-Zhong Zhu, Shi-Qiang Wang, Khalid Chakir, Dongmei Yang, Tong Zhang, Joan Heller Brown, Eric Devic, Brian K. Kobilka, Heping Cheng, Rui-Ping Xiao

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PKA-independent increase in intracellular Ca2+ is essential for the β1AR...
PKA-independent increase in intracellular Ca2+ is essential for the β1AR apoptotic effect. After β1β2 DKO myocytes were infected by Adv-β1AR, cells were incubated with designated reagents for 1 hour, then ISO (1 μM) was added and cells were incubated for another 3–6 hours (a, b, d, and e) or 24 hours (c). (a) Prolonged β1AR stimulation elevated basal intracellular free Ca2+ in unpaced cardiac myocytes. This effect was blocked by the L-type Ca2+ channel antagonist nifedipine (1 μM), but not the PKA inhibitor PKI (5 μM). *P < 0.01 vs. ISO-untreated groups and those pretreated by nifedipine (n = 20–35 cells from six hearts). (b) Intracellular Ca2+ transients were measured in a subset of cells electrically paced at 0.5 Hz for at least 10 minutes in the absence (n = 29 cells from four hearts) and presence (n = 22 cells from four hearts) of sustained β1AR stimulation by ISO. *P < 0.05 vs. ISO-untreated myocytes. (c) Effects of nifedipine, EGTA-AM (1 μM), or the SR ATPase inhibitor thapsigargin (1 μM) on β1AR-induced increase in TUNEL-positive cells. *P < 0.01 vs. ISO-untreated myocytes and those pretreated with EGTA-AM, nifedipine, or thapsigargin (n = 4–8). (d) Representative confocal linescan images of caffeine-elicited SR Ca2+ release in ISO-treated (1 μM, 3 hours, bottom) and untreated cells (top). The x axis shows the time courses for caffeine treatment, and the y axis shows the spatial profiles of Ca2+ transients along a scan line inside the cell. (e) Average amplitude of caffeine-elicited Ca2+ transients in ISO-treated or untreated group. *P < 0.01 vs. ISO-untreated myocytes. n = 25–30 cells from six hearts in each group. Nif, nifedipine; TG, thapsigargin.