Date Published: April 29, 2019
Publisher: Public Library of Science
Author(s): Henrike Tscheschner, Eric Meinhardt, Philipp Schlegel, Andreas Jungmann, Lorenz H. Lehmann, Oliver J. Müller, Patrick Most, Hugo A. Katus, Philip W. Raake, Ferenc Gallyas.
The clinical use of the chemotherapeutic doxorubicin (Dox) is limited by cardiotoxic side-effects. One of the early Dox effects is induction of a sarcoplasmic reticulum (SR) Ca2+ leak. The chaperone Glucose regulated protein 78 (GRP78) is important for Ca2+ homeostasis in the endoplasmic reticulum (ER)—the organelle corresponding to the SR in non-cardiomyocytes—and has been shown to convey resistance to Dox in certain tumors. Our aim was to investigate the effect of cardiac GRP78 gene transfer on Ca2+ dependent signaling, cell death, cardiac function and survival in clinically relevant in vitro and in vivo models for Dox cardiotoxicity.By using neonatal cardiomyocytes we could demonstrate that Dox induced Ca2+ dependent Ca2+ /calmodulin-dependent protein kinase II (CaMKII) activation is one of the factors involved in Dox cardiotoxicity by promoting apoptosis. Furthermore, we found that adeno-associated virus (AAV) mediated GRP78 overexpression partly protects neonatal cardiomyocytes from Dox induced cell death by modulating Ca2+ dependent pathways like the activation of CaMKII, phospholamban (PLN) and p53 accumulation. Most importantly, cardiac GRP78 gene therapy in mice treated with Dox revealed improved diastolic function (dP/dtmin) and survival after Dox treatment. In conclusion, our results demonstrate for the first time that Ca2+ dependent CaMKII activation fosters Dox cardiomyopathy and provide additional insight into possible mechanisms by which GRP78 overexpression protects cardiomyocytes from Doxorubicin toxicity.
The anthracycline doxorubicin (Dox) is an effective and thus frequently applied anticancer treatment. However, Dox treatment comes with severe adverse effects substantially limiting its use as chemotherapeutic. The risk of developing cardiomyopathy increases with the cumulative dose . Molecular mechanisms are still controversial and therapeutic options are still limited and mainly restricted to symptomatic approaches.
Anticancer treatment has made considerable progress over the last 20 years. Prolonged survival now poses new challenges, as many chemotherapeutics–Dox being one of the most prominent–impose cardiotoxic side-effects. Still the underlying mechanisms for Dox cardiotoxicity are not fully understood and current therapeutic recommendations are mainly symptomatic. Our results shed new light on Dox induced alterations in Ca2+ handling for the induction of cardiomyocyte apoptosis. To our knowledge this is the first time apoptotic effects of Ca2+ induced CaMKII activity have been explored as a consequence of Dox treatment. Furthermore, we have direct evidence that therapeutic overexpression of the ER chaperone GRP78 partly protects from Dox induced cardiotoxicity by reducing Dox induced CaMKII activation.
In conclusion, we could provide first evidence that Dox induced Ca2+ dependent CaMKII activation directly contributes to Dox cardiotoxicity. Furthermore, we found that GRP78 overexpression reduces the activation of CaMKII and thereby influences proapoptotic and Ca2+ dependent pathways involved in Dox cardiotoxicity. GRP78 treatment translates into prolonged survival as well as improved diastolic and to a certain extent systolic cardiac function in our mouse model of Dox cardiotoxicity. As such GRP78 gene therapy holds potential for prophylactic protection from cardiotoxic effects of Dox.