Exercise intensity and training alter the innate immune cell type and chromosomal origins of circulating cell-free DNA in humans
Rodrigues, Kameron B.; Weng, Ziming; Graham, Zachary A.; Lavin, Kaleen; McAdam, Jeremy; Tuggle, S. Craig; Peoples, Brandon; Seay, Regina; Yang, Sufen; Bamman, Marcas M.; Broderick, Timothy J.; Montgomery, Stephen B.
Exercising regularly promotes health, but these benefits are complicated by acute inflammation induced by exercise. A potential source of inflammation is cell-free DNA (cfDNA), yet the cellular origins, molecular causes, and immune system interactions of exercise-induced cfDNA are unclear.
To study these, 10 healthy individuals were randomized to a 12-wk exercise program of either high-intensity tactical training (HITT) or traditional moderate-intensity training (TRAD). Blood plasma was collected pre- and postexercise at weeks 0 and 12 and after 4 wk of detraining upon program completion. Whole-genome enzymatic methylation sequencing (EM-seq) with cell-type proportion deconvolution was applied to cfDNA obtained from the 50 plasma samples and paired to concentration measurements for 90 circulating cytokines.
Acute exercise increased the release of cfDNA from neutrophils, dendritic cells (DCs), and macrophages proportional to exercise intensity. Exercise training reduced cfDNA released in HITT participants but not TRAD and from DCs and macrophages but not neutrophils. For most participants, training lowered mitochondrial cfDNA at rest, even after detraining. Using a sequencing analysis approach we developed, we concluded that rapid ETosis, a process of cell death where cells release DNA extracellular traps, was the likely source of cfDNA, demonstrated by enrichment of nuclear DNA. Further, several cytokines were induced by acute exercise, such as IL-6, IL-10, and IL-16, and training attenuated the induction of only IL-6 and IL-17F. Cytokine levels were not associated with cfDNA induction, suggesting that these cytokines are not the main cause of exercise-induced cfDNA.
Overall, exercise intensity and training modulated cfDNA release and cytokine responses, contributing to the anti-inflammatory effects of regular exercise.
SIGNIFICANCE
We present a whole-genome view of the cellular origins of cell-free DNA (cfDNA) in humans induced by exercise and how these origins are influenced by exercise intensity and training. We find evidence supporting acute exercise causing rapid, nuclear ETosis in neutrophils, dendritic cells (DCs), and macrophages. By simultaneously analyzing major inflammatory cytokines, we conclude that major cytokines are not the main trigger for cfDNA release during exercise, indicating that other factors may instead induce cfDNA release. Additionally, exercise training decreased cfDNA release in DCs and macrophages, but not neutrophils. This implies that exercise training reduces the inflammatory potential of DCs and macrophages, having significance for inflammation in diverse contexts such as aging, cancer, autoimmunity, and vaccination.
Link | PDF (Proceedings of the National Academy of Sciences)
Rodrigues, Kameron B.; Weng, Ziming; Graham, Zachary A.; Lavin, Kaleen; McAdam, Jeremy; Tuggle, S. Craig; Peoples, Brandon; Seay, Regina; Yang, Sufen; Bamman, Marcas M.; Broderick, Timothy J.; Montgomery, Stephen B.
Exercising regularly promotes health, but these benefits are complicated by acute inflammation induced by exercise. A potential source of inflammation is cell-free DNA (cfDNA), yet the cellular origins, molecular causes, and immune system interactions of exercise-induced cfDNA are unclear.
To study these, 10 healthy individuals were randomized to a 12-wk exercise program of either high-intensity tactical training (HITT) or traditional moderate-intensity training (TRAD). Blood plasma was collected pre- and postexercise at weeks 0 and 12 and after 4 wk of detraining upon program completion. Whole-genome enzymatic methylation sequencing (EM-seq) with cell-type proportion deconvolution was applied to cfDNA obtained from the 50 plasma samples and paired to concentration measurements for 90 circulating cytokines.
Acute exercise increased the release of cfDNA from neutrophils, dendritic cells (DCs), and macrophages proportional to exercise intensity. Exercise training reduced cfDNA released in HITT participants but not TRAD and from DCs and macrophages but not neutrophils. For most participants, training lowered mitochondrial cfDNA at rest, even after detraining. Using a sequencing analysis approach we developed, we concluded that rapid ETosis, a process of cell death where cells release DNA extracellular traps, was the likely source of cfDNA, demonstrated by enrichment of nuclear DNA. Further, several cytokines were induced by acute exercise, such as IL-6, IL-10, and IL-16, and training attenuated the induction of only IL-6 and IL-17F. Cytokine levels were not associated with cfDNA induction, suggesting that these cytokines are not the main cause of exercise-induced cfDNA.
Overall, exercise intensity and training modulated cfDNA release and cytokine responses, contributing to the anti-inflammatory effects of regular exercise.
SIGNIFICANCE
We present a whole-genome view of the cellular origins of cell-free DNA (cfDNA) in humans induced by exercise and how these origins are influenced by exercise intensity and training. We find evidence supporting acute exercise causing rapid, nuclear ETosis in neutrophils, dendritic cells (DCs), and macrophages. By simultaneously analyzing major inflammatory cytokines, we conclude that major cytokines are not the main trigger for cfDNA release during exercise, indicating that other factors may instead induce cfDNA release. Additionally, exercise training decreased cfDNA release in DCs and macrophages, but not neutrophils. This implies that exercise training reduces the inflammatory potential of DCs and macrophages, having significance for inflammation in diverse contexts such as aging, cancer, autoimmunity, and vaccination.
Link | PDF (Proceedings of the National Academy of Sciences)