| Summary: |
Rational: Doxorubicin (DOX) is a highly effective antibiotic used to treat several types of cancer. Unfortunately, the clinical use of DOX is limited by the occurrence of a dose-related cardiac toxicity that results in life-threatening cardiomyopathy. It has been described that DOX-induced cardiomyocyte dysfunction is associated with increased levels of oxidative damage and apoptosis, with the involvement of mitochondrial alterations. Many preventive and therapeutic strategies have been explored to counteract DOX toxicity and dysfunction, such as the antioxidant supplementation and exercise. Our previous works have demonstrated that exercise prevents DOX-induced mitochondrial alterations and apoptotic signaling in rodent models. However, the mechanisms related to this protection targeting mitochondria remain elusive. In fact, mitochondria have a central role cellular energy production,
regulation of pH, calcium homeostasis and cell signaling. One particular aspect of mitochondrial physiology which is very relevant regulation of pH, calcium homeostasis and cell signaling. One particular aspect of mitochondrial physiology which is very relevant during normal function or during cell death signaling is the mitochondrial permeability transition pore (mtPTP). It has been
described that DOX-treatment leads to augmented mtPTP, which is associated with mitochondrial oxidative stress and calcium overload. Nevertheless, the non-pharmacological modulation afforded by exercise against deleterious mtPTP induction in DOXtreated animals was not studied so far, being the central concern of this innovative project Work hypothesis: The main hypothesis of the present project is that life-span voluntary exercise prevents increased susceptibility of heart mitochondria to mtPTP opening and apoptosis in chronically DOX- treated rats;
Specific aims and methods: Several exercise models have been used with excellent positive outcomes on cardiac hemodynamic parameters, morphological alte  |
Summary
Rational: Doxorubicin (DOX) is a highly effective antibiotic used to treat several types of cancer. Unfortunately, the clinical use of DOX is limited by the occurrence of a dose-related cardiac toxicity that results in life-threatening cardiomyopathy. It has been described that DOX-induced cardiomyocyte dysfunction is associated with increased levels of oxidative damage and apoptosis, with the involvement of mitochondrial alterations. Many preventive and therapeutic strategies have been explored to counteract DOX toxicity and dysfunction, such as the antioxidant supplementation and exercise. Our previous works have demonstrated that exercise prevents DOX-induced mitochondrial alterations and apoptotic signaling in rodent models. However, the mechanisms related to this protection targeting mitochondria remain elusive. In fact, mitochondria have a central role cellular energy production,
regulation of pH, calcium homeostasis and cell signaling. One particular aspect of mitochondrial physiology which is very relevant regulation of pH, calcium homeostasis and cell signaling. One particular aspect of mitochondrial physiology which is very relevant during normal function or during cell death signaling is the mitochondrial permeability transition pore (mtPTP). It has been
described that DOX-treatment leads to augmented mtPTP, which is associated with mitochondrial oxidative stress and calcium overload. Nevertheless, the non-pharmacological modulation afforded by exercise against deleterious mtPTP induction in DOXtreated animals was not studied so far, being the central concern of this innovative project Work hypothesis: The main hypothesis of the present project is that life-span voluntary exercise prevents increased susceptibility of heart mitochondria to mtPTP opening and apoptosis in chronically DOX- treated rats;
Specific aims and methods: Several exercise models have been used with excellent positive outcomes on cardiac hemodynamic parameters, morphological alterations, oxidative damage, apoptosis signaling and mitochondrial function. The explored exercise models include forced acute exercise bout, chronic moderate or low intensity endurance training and life span voluntary running on free wheel. The latter model has more clinical relevance for subjects receiving anti-cancer therapy as it implies low intensity
exercise loads and simulates the voluntary habitual physical activity. Because of this, we will use a rodent model of voluntary free wheel running to investigate the potential protection against a sub-chronic DOX treatment (7 weekly injections of 2mg/kg), which is relevant, as it resembles usual chemotherapy protocols. Male rats will be divided into sedentary, DOX (7 weekly i.p. 2mg/kg DOX-injection), 32wks free wheel and free wheel plus DOX. 24h after the end of physically active period and 1wk after the final injection, animals will be sacrificed and heart mitochondria isolated
for in vitro fresh experiments. Classical bioenergetics endpoints (oxygen consumption and membrane potential) as well as cyclosporine A-sensitive mtPTP induction will be investigated. Markers of oxidative damage, apoptosis and antioxidants, will be measured in mitochondria and/or muscle homogenates from the different treatment groups. Protection afforded by exercise against an in vitro model for induced mitochondrial oxidative stress (by using the pair iron-hydrogen peroxide) will also be investigated;
Significance of the present work: With the present project, an important contribution to understand the mitochondrial mechanisms associated with decreased |