PSBLAB RESEARCH

Funding
Research in the lab’ is supported by NIH R01 HL-071158 “Acid, Succinate and Glyoxal Metabolism in Ischemia”. 3/1/2022-2/28/2026 (continuously funded since 8/2003 and currently on its 5th funding cycle).

Overview
Our broad research interest is cardiac metabolism and its role in protection of the heart against ischemia-reperfusion (IR) injury. A variety of model systems are used, including: Langendorff perfused mouse hearts, isolated adult mouse cardiomyocytes, isolated heart mitochondria, and H9c2 myocytes in cell culture. We also use many biochemical techniques to investigate metabolism including: mitochondrial respiration & membrane potential assays, fluorescence based measurements of reactive oxygen species (ROS), analysis of protein post-translational modifications by western blotting and protein mass spectrometry, Seahorse XF analysis, chemical synthesis of novel small molecule therapeutics, and LC-MS/MS based metabolomics. We maintain several lines of engineered mice for these studies. The overall goal of the lab’ is to identify novel targets that can be targeted for therapeutic benefit in IR injury (in simple terms – drugs to to improve outcomes of heart-attack).

Current Projects (no particular order of priority)…
Succinate in Ischemia
We have a long-standing interest in the use of mitochondrial respiratory chain inhibitors to protect organs against IR injury. With Mike Murphy’s group (Cambridge UK) succinate accumulation in ischemia was identified as a major driver of ROS generation at reperfusion. We have also probed mechanisms of ischemic succinate accumulation using 13C labeled metabolite tracing, and with Paul Trippier at the University of Nebraska have developed novel mitochondrial complex II inhibitors for IR injury therapy. We are also investigating the role of succinate transport pathways in the heart, in regulating succinate levels during acute IR injury.

ALKBH7 & MGO Metabolism
Our collaborator Dragony Fu in UofR’s Biology Department discovered that the mitochondrial protein ALKBH7 is required for programmed necrosis. Given the importance of necrosis in the post-IR injured heart, we found that Alkbh7-/- mice are protected against IR. Metabolomic and proteomic analysis revealed that these mice have massive up-regulation of GLO-1, the main enzyme responsible for the detoxification of methyglyoxal (MGO), a reportedly toxic by-product of glycolysis. This finding has driven an ongoing interest in the role of MGO in the heart, including the possibility of protective signaling (hormesis) by this metabolite. ALKBH7 is a member of the alpha-ketoglutarate dioxygenase family of proteins, but its function and biochemical substrates are not well understood – it does not have a nucleic acid binding domain like other ALKBHs. As such, an important sub-project is to identify the function and substrate of this mitochondrial enzyme.

Legacy projects that we are no longer funded to work on, but still maintain an interest in and may still have shareable resources related to…
Sirtuins & Cardioprotective Metabolism
Sirtuins (SIRTs) are a family of NAD+ dependent lysine deacylases. Using SIRT1 knockout and overexpressing mice, and pharmacologic agents, we showed that cytosolic SIRT1 is necessary for cardioprotection by ischemic preconditioning (IPC), and for the metabolic remodeling that accompanies it. We are also interested in SIRT3 and its role in cardioprotection & aging. During these studies, we discovered the oncometabolite 2-hydroxyglutarate (2-HG) is elevated in hypoxia, and showed that acidic pH facilitates this (subsequently confirmed by other labs). Current studies are aimed at further understanding the role of acidic pH in metabolic remodeling during ischemia.

Mitochondrial Potassium Channels, Cardioprotection & Metabolism
A multi-PI R01 grant with Keith Nehrke drove an interest in identifying K+ channels in mitochondria that mediate the protective effects of volatile anesthetic preconditioning (APC). The field had focused on SLO1, the channel encoded by Kcnma1, but we showed Kcnma1-/- mice can still be protected by APC, and their mitochondria contain K+ channel activity. Subsequently, we reported that SLO2.1, encoded by Kcnt2, is required for APC.  Since these K+ channels likely did not evolve for the purpose of protecting hearts by volatile anesthetics, we embarked on a study to elucidate their physiologic roles, and found that SLO2.1 is likely a regulator of fatty acid metabolism and mitochondrial uncoupling. Unpublished ongoing studies are testing mito’ K+ channel agonists as potential anti-obesity drugs.

Mitochondrial Unfolded Protein Response (UPRmt) & Cardioprotection
Under normal conditions, the bifunctional transcription factor ATFS-1 (C. elegans) is imported into mitochondria and destroyed by proteases. Under conditions of mitochondrial proteotoxic stress, ATFS-1 import is blocked, sending it to the nucleus to upregulate protective chaperones. The mammalian ortholog of ATFS-1 is ATF5, and using Atf5-/- mice we showed that UPRmt activation is cardioprotective in a manner that depends on ATF5.