Pharmacologically Replicating Metabolic Protective Mechanisms of Hypothermia in Cardiac Arrest

New therapies are urgently needed for cardiac arrest which carries a high mortality rate due to cardiovascular collapse and neurological injury. Rapid application of therapeutic hypothermia is one of few therapies which consistently improves neurological outcomes in animal models; however, clinical trials have yielded disappointing results which may be explained by inadequate cooling rates provided by currently available technology. Prior work has demonstrated that the Akt pathway is required for the metabolic protective effects of hypothermia. Small molecule inhibition of PTEN or PHLPP leads to enhanced Akt activation and improved metabolic recovery in a manner similar to hypothermia, thus representing an attractive alternative strategy to improve outcomes without the need for cooling. To pharmacologically enhance Akt activation while avoiding off-target toxicity of small molecule inhibitors, two cell-penetrating peptides were developed—TAT-PTEN9c and TAT-PHLPP9c. In the present study, we investigate how hypothermia influences myocardial signaling and metabolism in the setting of ischemia/reperfusion, and then attempt to pharmacologically replicate these effects with cell-penetrating peptides. Then, we investigate how peripheral leukocytes respond to peptide treatment to determine if Akt response in these cells may be used to guide dosing and precision medicine. Finally, we characterize the effect of hypothermia or peptide treatment on ischemic release of amino acids taurine and glutamate, and then evaluate the neuroprognostication potential of these markers in a prospective observational study of cardiac arrest patients. Using an isolated rat heart model, we found that direction cardioprotection by hypothermia was associated with preserved PTEN expression, attenuated taurine release, and no change in PHLPP expression. A cell-penetrating peptide inhibitor of PTEN—but not PHLPP—improved myocardial functional recovery in a manner similar to hypothermia treatment, suggesting that PTEN is a major regulator of protective signaling in this model. Similar to cardiomyocytes, peripheral leukocytes respond to peptide treatment in a dose-dependent manner, which warrants further in vivo validation to determine whether leukocyte signaling events may be used to guide dosing and precision medicine. Furthermore, peptide treatment reduced plasma levels of glutamate and taurine following resuscitation in mouse and swine models of cardiac arrest, suggesting that these amino acids may serve as novel biomarkers of tissue injury. In a human cohort of cardiac arrest patients, post-admission plasma levels of taurine—but not glutamate—were negatively associated with survival. In summary, we demonstrate that the protective effects of hypothermia may be replicated pharmacologically by administration of cell-penetrating peptides targeted to the Akt pathway. It is our ultimate goal to translate these findings to emergency resuscitative care in order to improve outcomes for patients with cardiac arrest.

Author dc:creator

• Cody N Justice (24399056)

• Biology, Animal Physiology
• Biology, Molecular
• Health Sciences, Medicine and Surgery
• Biology, Physiology

Statement dc:rights

• In Copyright

DOI dc:identifier

https://doi.org/10.25417/uic.32991944.v1

OAI identifier oai:identifier

oai:figshare.com:article/32991944