Cardiomyocyte Derived Extracellular Mitochondria in Inflammatory Response During Oxidative Stress

Increased production of reactive oxygen species (ROS) occurs in a variety of disease states. Elevated oxidative stress often co-exists with inflammatory response. A burst of ROS production due to myocardial ischemia or infarction causes damage to the mitochondria, tissue injury and inflammation. The mitochondria have evolved with quality control mechanisms to maintain the homeostasis for energy metabolism, and to control cell death. We have found secretion of mitochondria as a novel mechanism of mitochondrial quality control and for cell-cell communication. Sublethal doses of H2O2 cause an increased release of mitochondria from cardiomyocytes to the extracellular space. Extracellular mitochondria (EM) appear to be smaller with an average diameter of 524.67±54.69nm (control) and 563.27±41.82nm (H2O2 treated cells), compared to the corresponding intracellular mitochondria (IM) having an average diameter of 1192±256.50nm and 818.37±62.74 nm. LC-MS/MS based proteomics showed an increased levels of peroxiredoxins and several respiratory chain proteins in the EM from stressed cells. However, metabolomics did not reveal significant changes in the EM metabolites collected from control or stressed cells. Both have reduced NAD, ATP, ADP, or AMP but increased nicotinamide, lactate, and a number of amino acids compared to the IM. Inhibiting ceramide synthesis, a sphingolipid derivative, reduced the number of EM released from oxidatively stressed cardiomyocytes, indicating a role of lipids in regulating mitochondrial release. Functionally, EM from oxidatively stressed cardiomyocytes caused activation of M1 and M2 macrophages, as measured by cytokine markers TNFα and CD163. Our data have unveiled a novel mechanism of oxidative stress response and secretion of the extracellular mitochondria as a vehicle for initiation of inflammatory response. NIH R01 GM125212, R01 GM126165, Holsclaw Endowment and the University of Arizona College of Pharmacy start-up fund. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.