Excellence in Research: Mitochondrial Damage-Associated Molecular Patterns (mtDAMPs) as Immunostimulants

This Excellence in Research (EiR) project aspires to enhance STEM research by tackling the central research question, “Why did our immune systems evolve to treat both microbial danger and cellular damage with inflammation?”. Inflammation follows penetrative trauma, in non-sterile settings, when potentially harmful bacteria are present. Similarly, when an organism’s cells/tissues are injured/damaged, perhaps due to non-penetrative trauma, sterile inflammation follows. Despite the very different circumstances, the inflammatory phenomena following these examples of trauma are surprisingly similar. This project will focus on mitochondria, specifically, mitochondrial peptides and nucleic acids, as mediators of sterile inflammation. The mechanisms of sterile inflammation following muscle contraction-induced injury (CII) that will be studied in this project will fulfill a knowledge gap in exercise physiology. The research may offer further insight into the consequences of mitochondria evolving to be endosymbionts as well as immune/ inflammatory implications of CII. Another objective is to fully leverage the project to enhance research capacity. Students and a postdoctoral fellow will be trained and mentored during this project, increasing retention of the next generation of talent in the STEM pipeline. Meanwhile, pursuit of this research will enhance institutional research capacity at a Historically Black College & University (HBCU). Immune systems treat both microbial danger and cellular damage with inflammation. Inflammation follows penetrative trauma in non-sterile settings, when potentially harmful bacteria are present, and inflammation may follow when an organism’s cells/tissues are injured/damaged due to non-penetrative trauma in sterile conditions. Presently, scientists understand that damage-associated molecular patterns emanating from mitochondria (mtDAMPs) are elevated in trauma patients, and that mtDAMPs play a causal role in sterile inflammation. However, the mechanism underlying this increase and its relevance to exercise physiology is unknown. Specific molecular signatures, such as N-formyl peptides (mtFPs), have been implicated, but other possibilities exist, including the pattern of unmethylated cytosine-phosphate-guanine (CpG) DNA repeats in, and circular nature of, mitochondrial DNA. The investigators hypothesize that muscle contraction-induced injury during exercise causes the release of mtDAMPs, which activate innate immunity, leading to sterile inflammation in athletes. In particular, the investigators will measure the levels of mitochondrial proteins and nucleic acids in exercise-induced sterile inflammation. The investigators will also develop cell culture infrastructure to query in vitro interactions of skeletal muscle cells and innate immune cells, such as monocytes and neutrophils. Structural and thermodynamic properties of the human mtDAMP, nicotinamide adenine dinucleotide dehydrogenase subunit 6 (ND6) will be investigated. The investigators will use a variety of methods, such as ELISA to investigate mitochondrial proteins, PCR to investigate mitochondrial nucleic acids, and x-ray crystallography to elucidate the structure of ND6. This research will shed light on similarities between clinical noninfective trauma and the trauma elicited simply by strenuous exercise. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.