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Elevated cfDNA after exercise is derived primarily from mature polymorphonuclear neutrophils, with a minor contribution of cardiomyocytes

ABSTRACT: Strenuous physical exercise causes a massive elevation in the concentration of circulating cell-free DNA (cfDNA), which correlates with effort intensity and duration. The cellular sources and physiological drivers of this phenomenon are unknown. Using methylation patterns of cfDNA and associated histones, we show that cfDNA in exercise originates mostly in extramedullary polymorphonuclear neutrophils. Strikingly, the concentration of cardiomyocyte cfDNA increases after a marathon, consistent with elevated troponin levels and indicating low-level, delayed cardiac cell death. Physical impact, low oxygen levels and elevated core body temperature contribute to the release of neutrophil cfDNA, while muscle contraction, increased heart rate, beta-adrenergic signaling or steroid treatment fail to cause elevation of cfDNA. Physical training reduces the release of neutrophil cfDNA after a standard exercise, revealing an inverse relationship between exercise-induced cfDNA release and training level. We speculate that the release of cfDNA from neutrophils in exercise relates to the activation of neutrophils in the context of exercise-induced muscle damage.

PROVIDER: EGAS00001007157 | EGA |

REPOSITORIES: EGA

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Project description:Relatively brief bouts of exercise alter gene expression in peripheral blood mononuclear cells (PBMCs), but whether or not exercise changes gene expression in circulating neutrophils (whose numbers, like PBMCs, increase) is not known. We hypothesized that exercise would activate neutrophil genes involved in apoptosis, inflammation, and cell growth and repair, since these functions in leukocytes are known to be influenced by exercise. Blood was sampled before and immediately after 30-min of constant, heavy (about 80% peak O2 uptake) cycle-ergometer exercise in 12 healthy men (19-29 yr old) of average fitness. Neutrophils were isolated using density gradients; RNA was hybridized to Affymetrix U133+2 Genechip arrays. Using FDR<0.05 with 95% confidence a total of 526 genes were differentially expressed between before and after exercise. 316 genes had higher expression after exercise. The Jak/STAT pathway, known to inhibit apoptosis, was significantly activated (EASE score, p<0.005), but 14 genes were altered in a way likely to accelerate apoptosis as well. Similarly, both proinflammatory (e.g., IL32, TNFSF8 and CCR5) and anti-inflammatory (e.g., ANXA1) were affected. Growth and repair genes like AREG and FGF2 receptor genes (involved in angiogenesis) were also activated. Finally, a number of neutrophil genes known to be involved in pathological conditions like asthma and arthritis were altered by exercise, suggesting novel links between physical activity and disease or its prevention. In summary, brief heavy exercise leads to a previously unknown substantial and significant alteration in neutrophil gene expression. Experiment Overall Design: Twelve healthy men (19-29 yr old) participated in this study. A baseline blood sample was taken before the onset of exercise and immediately after 30-min exercise bout. Neutrophils were isolated using OptiPrep Density Gradient Medium (SIGMA). Total RNA was extracted using TRIzol. cRNA was hybridized onto Affymetrix U133+2 arrays (total of 24 chips).

Project description:Systemic juvenile idiopathic arthritis (SJIA) is a chronic childhood arthropathy with features of autoinflammation. Early inflammatory SJIA is associated with expansion and activation of neutrophils with a sepsis-like phenotype, but neutrophil phenotypes present in longstanding and clinically inactive disease (CID) are unknown. The objective of this study was to examine activated neutrophil subsets, S100 alarmin release, and gene expression signatures in children with a spectrum of SJIA disease activity. Methods: Highly-purified neutrophils were isolated using a two-step procedure of density-gradient centrifugation followed by magnetic-bead based negative selection prior to flow cytometry or cell culture to quantify S100 protein release. Whole transcriptome gene expression profiles were compared in neutrophils from children with both active SJIA and CID. Results: Patients with SJIA and active systemic features demonstrated a higher number of CD16+CD62Llo neutrophil population compared to controls. This neutrophil subset was not seen in patients with CID or patients with active arthritis not exhibiting systemic features. Using imaging flow cytometry, CD16+CD62Llo neutrophils from patients with active SJIA and features of macrophage activation syndrome (MAS) had increased nuclear hypersegmentation compared to CD16+CD62L+ neutrophils. Serum levels of S100A8/A9 and S100A12 were strongly correlated with peripheral blood neutrophil counts. Neutrophils from active SJIA patients did not show enhanced resting S100 protein release; however, regardless of disease activity, neutrophils from SJIA patients did show enhanced S100A8/A9 release upon PMA stimulation compared to control neutrophils. Furthermore, whole transcriptome analysis of highly purified neutrophils from children with active SJIA identified 214 differentially expressed genes compared to neutrophils from healthy controls. The most significantly upregulated gene pathway was Immune System Process, including AIM2, IL18RAP, and NLRC4. Interestingly, this gene set showed intermediate levels of expression in neutrophils from patients with long-standing CID yet persistent serum IL-18 elevation. Indeed, all patient samples regardless of disease activity demonstrated elevated inflammatory gene expression, including inflammasome components and S100A8. Conclusion: We identify features of neutrophil activation in SJIA patients with active disease and CID, including a proinflammatory gene expression signature, reflecting persistent innate immune activation. Taken together, these studies expand understanding of neutrophil function in chronic autoinflammatory disorders such as SJIA.

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Elevated cfDNA after exercise is derived primarily from mature polymorphonuclear neutrophils, with a minor contribution of cardiomyocytes

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