Doxorubicin in myocardial lysophosphatidic acid signaling

Abstract

Generation of reactive oxygen species has been implicated in the toxicity of nearly 50% of the current FDA approved cancer therapeutic drugs. Mitochondrial respiration is a major source of reactive oxygen species production and that the presence of the mitochondrial antioxidant enzyme, manganese superoxide dismutase, is essential for the survival of all aerobic life. Our studies of animals using the prototype redox‐active anticancer drug, doxorubicin, indicate that overexpression of manganese superoxide dismutase protects the heart against doxorubicin‐induced cardiac injury and reduction of manganese superoxide dismutase by heterozygous knockout mice increases cardiac injury after exposure to doxorubicin. While the bioactive glycerophospholipid lysophosphatidic acid rises by seven‐fold over control subjects, suggesting lysophosphatidic acid may contribute to the doxorubicin‐induced cardiac toxicity. Lysophosphatidic acid production involves hydrolysis of lysophosphatidylcholine by the secreted enzyme autotaxin, whereas lipid phosphate phosphatase‐3 (LPP3) catalyzes lysophosphatidic acid dephosphorylation to generate lipid products that are not receptor active. In this application, we present the first evidence that doxorubicin‐induced cardiac injury enhances myocardial autotaxin levels and decreases myocardial LPP3 expression, and this is associated with increased serum lysophosphatidic acid levels. Reactive oxygen species production arises as a burst of superoxide from mitochondria following doxorubicin‐induced cardiac injury. The redox‐sensitive transcription factor NFAT (a nuclear factor of activated T‐cells) has been shown to bind to the autotaxin promoter and induce its expression. Similarly, oxidant stress may deplete LPP3 levels in the context of cardiac injury through reduced LPP3 expression or enhanced LPP3 degradation. Thus, we hypothesize that doxorubicin‐induced cardiac injury alters autotaxin and LPP3 expression through mitochondrial superoxide production to drive lysophosphatidic acid signaling and cardiomyocyte dysfunction. The following interrelated specific aims are designed to provide step‐wise and in‐depth studies in vitro, in vivo, and in experimental therapeutics settings. Specific aim 1 will assess the role of myocardial superoxide production in autotaxin expression and lysophosphatidic acid production in doxorubicin‐induced cardiac injury. Specific aim 2 will determine the role of mitochondrial superoxide production in LPP3 depletion and lysophosphatidic acid regulation in doxorubicin‐induced cardiac injury. We could identify whether modulation of cellular versus mitochondrial antioxidant status confers a differential protective effect in doxorubicin‐induced cardiac injury models.Support or Funding InformationAAA‐ FGAP Fellow grant funded by the American Association of Anatomists.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.