Cell and tissue research, 2012 Nov;350(2):361-372.

Effects of doxorubicin cancer therapy on autophagy and the ubiquitin-proteasome system in long-term cultured adult rat cardiomyocytes

Polychronis Dimitrakis, Maria-Iris Romay-Ogando, Francesco Timolati, Thomas M. Suter, 
Christian Zuppinger

Cardiology, Swiss Cardiovascular Center Bern, Bern University Hospital and University of Bern, Switzerland.

PMID: 22864983

 

Abstract

Problem:

The clinical use of anthracyclines in cancer therapy is limited by dose-dependent cardiotoxicity that involves cardiomyocyte injury and death. We have tested the hypothesis that anthracyclines affect protein degradation pathways in adult cardiomyocytes. To this aim, we assessed the effects of doxorubicin (Doxo) on apoptosis, autophagy and the proteasome/ubiquitin system in long-term cultured adult rat cardiomyocytes.

Results:

Accumulation of poly-ubiquitinated proteins, increase of cathepsin-D-positive lysosomes and myofibrillar degradation were observed in Doxo-treated cardiomyocytes. Chymotrypsin-like activity of the proteasome was initially increased and then inhibited by Doxo over a time-course of 48 h. Proteasome 20S proteins were down-regulated by higher doses of Doxo. The expression of MURF-1, an ubiquitin-ligase specifically targeting myofibrillar proteins, was suppressed by Doxo at all concentrations measured. Microtubule-associated protein 1 light chain 3B (LC3)-positive punctae and both LC3-I and -II proteins were induced by Doxo in a dose-dependent manner, as confirmed by using lentiviral expression of green fluorescence protein bound to LC3 and live imaging. The lysosomotropic drug chloroquine led to autophagosome accumulation, which increased with concomitant Doxo treatment indicating enhanced autophagic flux.

Conclusions:

We conclude that Doxo causes a downregulation of the protein degradation machinery of cardiomyocytes with a resulting accumulation of poly-ubiquitinated proteins and autophagosomes. Although autophagy is initially stimulated as a compensatory response to cytotoxic stress, it is followed by apoptosis and necrosis at higher doses and longer exposure times. This mechanism might contribute to the late cardiotoxicity of anthracyclines by accelerated aging of the postmitotic adult cardiomyocytes and to the susceptibility of the aging heart to anthracycline cancer therapy.

 

Supplemental picture:

Christian Zuppinger-2

The picture shows a simplified overview of pathways induced by Doxorubicin cancer therapy in cardiomyocytes. The induction of apoptosis and necrosis cell death pathways has been described for many years as being involved in cardiomyocyte loss after Doxorubicin therapy. In the here featured publication we have investigated the role of catabolic pathways in adult rat cardiomyocytes exposed to doses of the cancer therapy that do not lead to cell death, but may affect autophagy and the proteasome pathway and contribute to the late cardiotoxicity of anthracyclines observed in the clinic.

Multiselect Ultimate Query Plugin by InoPlugs Web Design Vienna | Webdesign Wien and Juwelier SchönmannMultiselect Ultimate Query Plugin by InoPlugs Web Design Vienna | Webdesign Wien and Juwelier Schönmann