Oxidative Stress Elevated oxidative stress is known to cause global cellular damage by creating reactive oxygen species (ROS) that cause damage to proteins, lipids, and DNA (15, 82). Oxidative stress increases protein phosphorylation, causing changes in signaling pathways. For example, several phosphatases involved in cancer, apoptosis, and aging are inactivated under conditions of high oxidative stress (26). ROS is a known contributing factor to several diseases including Alzheimer's, Parkinson's, Huntington's, kidney disease, and T2DM ( 25 , 27 , 105 ). Known mediators of oxidative stress include transition metals and mitochondrial dysfunction (15, 27). In this project I will study how regulation of cellular iron causes increased oxidative stress, contributing to cellular damage and disease. Aconitase is an important mediator of oxidative stress, metabolism and iron regulation. Aconitase is an enzyme in the TCA cycle that is found in both the cytosol and mitochondria. It is a widely used indicator of oxidative stress and is an important iron regulating point (fig. 3). Aconitase is sensitive to oxidative stress because it contains clusters of iron and sulfur that are released under conditions of low iron or high oxidative stress. After aconitase releases its Fe-S clusters, it undergoes a conformational change and becomes iron regulatory protein 1 (IRP-1). This increases cellular iron uptake and decreases iron storage by regulating iron transport and storage proteins. Aconitase catalyzes the conversion of citrate to isocitrate in the mitochondria and cytosol. In mitochondria, aconitase is required for the TCA cycle to continue. In the case of high mitochondrial ROS production, aconitase becomes oxidized and no longer functions… half of the article… and is the most likely candidate for the increase in ROS observed with doxorubicin administration. Through these mechanisms, doxorubicin works well in slowing the progression of cancer. However, the side effects of this drug limit the total dosage a patient can receive. Four therapies have been described to reduce the muscle toxicity of doxorubicin. First, use of the iron chelator dexrazoxane decreases muscle toxicity (36, 89). Second, aerobic exercise has been shown to protect against doxorubicin-induced skeletal muscle apoptosis through decreasing autophagy signaling (50, 84, 85). Third, the mitochondrial antioxidant SS31 protects against doxorubicin-induced apoptosis (32). Fourth, pretreatment with metformin, an antidiabetic drug, reduces cardiomyocyte apoptosis ( 7 , 8 ). The interaction between doxorubicin and metformin will be discussed in more detail in the next sections.