Doxorubicin-induced markers of myocardial autophagic signaling in sedentary and exercise trained animals

The role of autophagy in doxorubicin-induced cardiotoxicity

Doxorubicin (Dox) is an effective chemotherapeutic agent, however, its use is limited by cardiotoxicity. The mechanisms causing cardiotoxicity have not been clearly elucidated, but known to involve, at least in part, oxidative stress, mitochondrial dysfunction and apoptosis. More recently, it has been suggested that dysregulation of autophagy may also play an important role in Dox-induced cardiotoxicity. Autophagy has dual functions. Under physiological conditions, autophagy is essential for optimal cellular function and survival by ridding the cell of damaged or unwanted proteins and organelles. Under pathological conditions, autophagy may be stimulated in order to protect the cell from stress stimuli or, alternatively, to contribute to cell death. Thus, appropriate regulation of autophagy can be a matter of life or death. The role of autophagy in Dox-induced cardiotoxicity has recently been explored, however, conflicting reports on the effects of Dox on autophagy and its role in cardiotoxicity exist. Most, but not all, of the studies conclude that Dox upregulates cardiac autophagy and contributes to the pathogenesis of Dox-induced toxicity. Dox may induce autophagy by suppressing the expression of GATA4 and/or S6K1, which may directly or indirectly regulate expression of essential autophagy genes such as Atg12, Atg5, Beclin1 and Bcl-2. Interestingly, the Dox-induced autophagic response may be species specific as Dox treatment has been shown to stimulate autophagy in rat models, but suppress autophagy in mouse models. Additional studies will elucidate this possibility.

A biodegradable microvessel scaffold as a framework to enable vascular support of engineered tissues

A biodegradable microvessel scaffold comprised of distinct parenchymal and vascular compartments separated by a permeable membrane interface was conceptualized, fabricated, cellularized, and implanted. The device was designed with perfusable microfluidic channels on the order of 100 μm to mimic small blood vessels, and high interfacial area to an adjacent parenchymal space to enable transport between the compartments. Poly(glycerol sebacate) (PGS) elastomer was used to construct the microvessel framework, and various assembly methods were evaluated to ensure robust mechanical integrity. In vitro studies demonstrated the differentiation of human skeletal muscle cells cultured in the parenchymal space, a 90% reduction in muscle cell viability due to trans-membrane transport of a myotoxic drug from the perfusate, and microvessel seeding with human endothelial cells. In vivo studies of scaffolds implanted subcutaneously and intraperitoneally, without or with exogenous cells, into nude rats demonstrated biodegradation of the membrane interface and host blood cell infiltration of the microvessels. This modular, implantable scaffold could serve as a basis for building tissue constructs of increasing scale and clinical relevance.

Complications of chemotherapy, a basic science update

Anthracyclines, discovered 50 years ago, are antibiotics widely used as antineoplastic agents and are among the most successful anticancer therapies ever developed to treat a wide range of cancers, including hematological malignancies, soft tissue sarcomas and solid tumors. However, some anthracyclines, including doxorubicin, exhibit major signs of cardiotoxicity that may ultimately lead to heart failure (HF). Despite intensive research on doxorubicine-induced cardiotoxicity, the underlying mechanisms responsible for doxorubicin-induced cardiotoxicity have not been fully elucidated yet. Published literature so far has focused mostly on mitochondria dysfunction with consequent oxidative stress, Ca(2+) overload, and cardiomyocyte death as doxorubicin side effects, leading to heart dysfunction. This review focuses on the current understanding of the molecular mechanisms underlying doxorubicin-induced cardiomyocyte death (i.e.: cardiomyocyte death, mitochondria metabolism and bioenergetic alteration), but we will also point to new directions of possible mechanisms, suggesting potent prior or concomitant alterations of specific signaling pathways with molecular actors directly targeted by the anticancer drugs itself (i.e. calcium homeostasis or cAMP signaling cascade). The mechanisms of anticancer cardiac toxicity may be more complex than just mitochondria dysfunction. Partnership of both basic and clinical research is needed to promote new strategies in diagnosis, therapies with concomitant cardioprotection in order to achieve cancer treatment with acceptable cardiotoxicity along life span.