Developing and validating a model of oxidative stress for PET probe development: SI:Abstracts ISHR-ES Amsterdam

Background: The non-invasive detection of tissue redox status by PET imaging of ROS could be used to gain invaluable insight into numerous disease processes, exploitable for early diagnosis, patient staging and stratification, gauging response to therapy, or identifying drug toxicity. We are developing, screening and validating ROS-sensing PET probes for this purpose.

Methods and results: To screen our radiotracer candidates, we constructed a triple γ-detector to characterise their cardiac retention and pharmacokinetics in isolated perfused hearts. We then performed a dose-response study with Antimycin A to invoke titratable ROS generation, validated using invasive biomarkers of oxidative stress. At our highest examined dose (100nM), total glutathione fell to 66% of control, PKG1α dimerization increased 3-fold, and aconitase activity decreased 4-fold. We are now ready to evaluate our ROS probes in this model. In parallel, we are developing a clinically relevant rodent model of anthracycline cardiotoxicity using chronic doxorubicin delivery via osmotic minipumps. We are characterising this model in terms of iron overload, mitochondrial dysfunction, contractile dysfunction (by echocardiography), and the oxidative stress biomarkers described above.

Conclusion: Our preliminary data indicate that our model (10 mg.kg-1 total delivered over 4 weeks, then 4 weeks to allow injury to develop) invokes a 36% increase in mitochondrial iron content and a 40% increase in p38 phosphorylation, before cardiotoxicity is demonstrable by echocardiography. Once validated, we will use this model to screen and characterise the radiotracer candidates identified by the Langendorff screen to identify ROS-sensing imaging agents capable of detecting evolving cardiotoxicity earlier than is currently possible clinically.