Circulating Cell-Free DNA in Physical Activities

Effect of a 12-Week Walking Program Monitored by Global Physical Capacity Score (GPCS) on Circulating Cell-Free mtDNA and DNase Activity in Patients with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) involves low-grade mucosal inflammation. Among the various approaches capable of managing the symptoms, physical activity is still under investigation. Despite its benefits, it promotes oxidative stress and inflammation. Mitochondria impacts gut disorders by releasing damage-associated molecular patterns, such as cell-free mtDNA (cf-mtDNA), which support inflammation. This study evaluated the effects of a 12-week walking program on the cf-mtDNA and DNase in 26 IBS and 17 non-IBS subjects. Pro- and anti-inflammatory cytokines were evaluated by ELISA. Digital droplet PCR was used to quantify cf-mtDNA; DNase activity was assessed using a single radial enzyme diffusion assay. PCR-RFLP was used to genotype DNASE1 rs1053874 SNP. Significantly lower IL-10 levels were found in IBS than in non-IBS individuals. Exercise reduced cf-mtDNA in non-IBS subjects but not in IBS patients. DNase activity did not correlate with the cf-mtDNA levels in IBS patients post-exercise, indicating imbalanced cf-mtDNA clearance. Different rs1053874 SNP frequencies were not found between groups. The study confirms the positive effects of regular moderate-intensity physical activity in healthy subjects and its role in cf-mtDNA release and clearance. Walking alone might not sufficiently reduce subclinical inflammation in IBS, based on imbalanced pro- and anti-inflammatory molecules. Prolonged programs are necessary to investigate their effects on inflammatory markers in IBS.

Three-week sprint interval training (SIT) reduces cell-free DNA and low-frequency fatigue but does not induce VO2max improvement in older men

PURPOSE

This study aimed to investigate the impact of sprint interval training (SIT) on both the acute and 3-week modulations of cell-free DNA (cfDNA), as well as its association with neuromuscular fatigue and physical performance in healthy young and old men.

METHODS

Ten young (20-25 year old) and nine elderly (63-72 year old) healthy men performed nine SIT sessions consisting of 4-to-6-all-out cycling repetitions of 30 s interspaced with 4-min rest intervals. We compared the maximal voluntary contractions torque, central activation ratio, low-frequency fatigue (LFF), and cfDNA concentrations between the groups before, immediately after, 1 h after, and 24 h after the first and ninth SIT sessions.

RESULTS

The plasma cfDNA levels were increased post-exercise (from 1.4 ± 0.258 to 1.91 ± 0.278 ng/ml (P < 0.01) on a log10 scale), without significant differences between the groups. However, older individuals showed a slight decrease in the baseline cfDNA values, from 1.39 ± 0.176 to 1.29 ± 0.085 ng/ml on a log10 scale, after 3 weeks (P = 0.043). Importantly, the elevation of the post-exercise cfDNA values was correlated with an increase in LFF in both groups. Three weeks of SIT induced an improvement in the recovery of LFF (main session effect, P = 0.0029); however, only the young group showed an increase in aerobic capacity (VO2max) (from 40.8 ± 6.74 to 43.0 ± 5.80 ml/kg/min, P = 0.0039).

CONCLUSION

Three weeks of SIT diminished the baseline cfDNA values in the old group, together with an improvement in the recovery of LFF. However, VO2max was increased only in the young group.

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

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, cardiomyocyte cfDNA concentration 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 neutrophil cfDNA release, while muscle contraction, increased heart rate, β-adrenergic signaling, or steroid treatment fail to cause elevation of cfDNA. Physical training reduces neutrophil cfDNA release 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.

Circulating cell-free endometrial DNA level is unaltered during menstruation and in endometriosis

STUDY QUESTION

Is circulating cell-free DNA (cirDNA) from the endometrium elevated during menstruation and in endometriosis?

SUMMARY ANSWER

Endometrial cirDNA does not increase during menstruation and is not elevated in endometriosis.

WHAT IS KNOWN ALREADY

Changes in cirDNA associated with common benign conditions are a potential source of false positives in cancer diagnostic applications, but also present an opportunity for biomarker development for diseases such as endometriosis. Elevated cirDNA has been reported in endometriosis patients compared to healthy community controls, but no difference in total or endometrial cirDNA has been found between patients with endometriosis and patients with other gynaecological conditions. Likewise, menstruation is a potential driver of changes in cirDNA levels and tissue profile, but total and endothelial cirDNA do not increase during menstruation.

STUDY DESIGN, SIZE, DURATION

For endometriosis comparisons, 59 participants with surgically confirmed endometriosis and 27 laparoscopic patients without endometriosis (hospital controls) were prospectively recruited, while 25 healthy community participants (healthy controls) were recruited in a university setting. Total and endometrial cirDNA and cirDNA fragmentation were measured across the three groups. For menstrual comparisons, 36 matched non-menstruating and menstruating samples were collected from healthy women recruited within a university setting, and the endometrial cirDNA was compared between the two groups.

PARTICIPANTS/MATERIALS, SETTING, METHODS

cirDNA was extracted from venous blood plasma then quantitated by quantitative PCR of ALU repetitive element (115 bp) and TP53 gene sequence (105 bp) for total concentration. cirDNA derived from the endometrium was quantitated by methylation-specific droplet digital PCR of a FAM101A region (69 bp) after bisulfite conversion of the DNA. A cirDNA size fragmentation ratio was obtained by quantifying a long segment of ALU repetitive element (247 bp) and expressing the amount relative to the 115 bp ALU target.

MAIN RESULTS AND THE ROLE OF CHANCE

No differences in cirDNA level were found in any comparison populations in this study. Mean total cirDNA was unchanged between healthy controls (ALU-115-3.31 ng/ml; TP53-2.73 ng/ml), hospital controls (ALU-115-3.47 ng/ml; TP53-2.83 ng/ml) and endometriosis patients (ALU-115-3.35 ng/ml; TP53-2.66 ng/ml). Likewise, endometrial cirDNA was unchanged between healthy controls (18.3 copies/ml), hospital controls (20.6 copies/ml) and endometriosis patients (22 copies/ml). Endometrial cirDNA did not change during menstruation (non-menstruating: 38 copies/ml; menstruating: 33 copies/ml). Irrespective of endometriosis diagnosis, blood from patients undergoing laparoscopy (hospital controls: 0.77; endometriosis patients: 0.79), had a significantly higher cirDNA size ratio than community-recruited healthy controls (0.64), indicating increased abundance of long cirDNA fragments.

LIMITATIONS, REASONS FOR CAUTION

It was not possible to completely match the age, BMI and parity between the three cohorts investigated, however of these, only age has been shown to influence circulating DNA levels and not within the age range of our cohort. Blood from community-recruited healthy women and women undergoing laparoscopy was collected via antecubital vein venepuncture (processed within 3 h) and with either peripheral cannula or venepuncture (processed within 6 h), respectively, which could potentially impact the size distribution of circulating DNA fragments. For the collection of non-menstruating phase blood samples, we did not differentiate between follicular phase, ovulation and luteal phase. Thus, only the mensturating samples were collected at a consistent phase, and any fluctuations in cirDNA that occur at the other phases may have obscured small changes during menstruation.

WIDER IMPLICATIONS OF THE FINDINGS

There is no evidence that cirDNA has potential as a diagnostic biomarker for endometriosis. Endometriosis, representing a common benign gynaecological condition, and menstruation, representing a normal physiological occurrence in women, should not affect methylation-based diagnostics in other disease areas, including oncology.

STUDY FUNDING/COMPETING INTEREST(S)

N.L.Y.: Australian Government Research Training Program (RTP) Stipend through The University of New South Wales, Translational Cancer Research Network PhD Scholarship Top-Up Award via the Cancer Institute NSW, Beth Yarrow Memorial Award in Medical Science, UNSW Completion Scholarship; C.E.H.: Gynaecological Oncology Fund of the Royal Hospital for Women; K.W.: Ovarian Cancer Research Foundation and CAMILLA AND MARC. C.E.F.: UNSW Women's Wellbeing Academy and the Australian Human Rights Institute. We declare the following competing interest: K.W. holds stock in Guardant Health, Exact Sciences and Epigenomics AG. No other authors have competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Changes in Specific Biomarkers Indicate Cardiac Adaptive and Anti-inflammatory Response of Repeated Recreational SCUBA Diving

Objective

Recreational SCUBA (rSCUBA) diving has become a highly popular and widespread sport. Yet, information on molecular events underlying (patho)physiological events that follow exposure to the specific environmental conditions (hyperbaric conditions, coldness, immersion, and elevated breathing pressure), in which rSCUBA diving is performed, remain largely unknown. Our previous study suggested that repeated rSCUBA diving triggers an adaptive response of cardiovascular and immune system. To elucidate further molecular events underlying cardiac and immune system adaptation and to exclude possible adverse effects we measured blood levels of specific cardiac and inflammation markers.

Methods

This longitudinal intervention study included fourteen recreational divers who performed five dives, one per week, on the depth 20–30 m that lasted 30 min, after the non-dive period of 5 months. Blood samples were taken immediately before and after the first, third, and fifth dives. Copeptin, immunoglobulins A, G and M, complement components C3 and C4, and differential blood count parameters, including neutrophil-to-lymphocyte ratio (NLR) were determined using standard laboratory methods. Cell-free DNA was measured by qPCR analysis and N-glycans released from IgG and total plasma proteins (TPP), were analyzed by hydrophilic interaction ultra-performance liquid chromatography.

Results

Copeptin level increased after the first dive but decreased after the third and fifth dive. Increases in immunoglobulins level after every dive and during whole studied period were observed, but no changes in C3, C4, and cfDNA level were detected. NLR increased only after the first dive. IgG and TPP N-glycosylation alterations toward anti-inflammatory status over whole studied period were manifested as an increase in monogalyctosylated and core-fucosylated IgG N-glycans and decrease in agalactosylated TPP N-glycans.

Conclusion

rSCUBA diving practiced on a regular basis promotes anti-inflammatory status thus contributing cardioprotection and conferring multiple health benefits.

Detecting Liquid Remnants of Solid Tumors: Circulating Tumor DNA Minimal Residual Disease

Growing evidence demonstrates that circulating tumor DNA (ctDNA) minimal residual disease (MRD) following treatment for solid tumors predicts relapse. These results suggest that ctDNA MRD could identify candidates for adjuvant therapy and measure response to such treatment. Importantly, factors such as assay type, amount of ctDNA release, and technical and biological background can affect ctDNA MRD results. Furthermore, the clinical utility of ctDNA MRD for treatment personalization remains to be fully established. Here, we review the evidence supporting the value of ctDNA MRD in solid cancers and highlight key considerations in the application of this potentially transformative biomarker.

SIGNIFICANCE

ctDNA analysis enables detection of MRD and predicts relapse after definitive treatment for solid cancers, thereby promising to revolutionize personalization of adjuvant and consolidation therapies.

Liquid Biopsies for Molecular Biology-Based Radiotherapy

Molecular alterations drive cancer initiation and evolution during development and in response to therapy. Radiotherapy is one of the most commonly employed cancer treatment modalities, but radiobiologic approaches for personalizing therapy based on tumor biology and individual risks remain to be defined. In recent years, analysis of circulating nucleic acids has emerged as a non-invasive approach to leverage tumor molecular abnormalities as biomarkers of prognosis and treatment response. Here, we evaluate the roles of circulating tumor DNA and related analyses as powerful tools for precision radiotherapy. We highlight emerging work advancing liquid biopsies beyond biomarker studies into translational research investigating tumor clonal evolution and acquired resistance.

cfDNA Changes in Maximal Exercises as a Sport Adaptation Predictor

Changes of circulating free plasma DNA (cfDNA) are associated with different types of tissue injury, including those induced by intensive aerobic and anaerobic exercises. Observed changes are dependent from induced inflammation, and thus it may be a potential marker for athletic overtraining. We aimed to identify the response of cfDNA to different types of exercise, with association to exercise intensity as a potential marker of exercise load. Fifty volunteers (25 athletes and 25 physically active men) were assigned to the study and performed maximal aerobic (Bruce test) and anaerobic (Wingate Anaerobic Test) test. Blood samples for cfDNA analysis were collected at four time-points: before, 2-5 min after, 30 min after and 60 min after each type of maximal physical activity. The two-way ANOVA revealed a significant effect of group factor on serum cfDNA concentrations (32.15% higher concentration of cfDNA in the athletes). In turn the results of the post hoc test for the interaction of the repeated measures factor and the group showed that while the concentration of cfDNA decreased by 40.10% in the period from 30 min to 60 min after exercise in the control group, the concentration of cfDNA in the group of athletes remained at a similar level. Our analysis presents different responses depending on the intensity and duration of exercise. Our observations imply that formation of cfDNA is associated with response to physical activity but only during maximal effort.

Liquid Biopsy in the Clinical Management of High-Grade Serous Epithelial Ovarian Cancer-Current Use and Future Opportunities

The lack of a sensitive and specific biomarker and the limits relating to the single primary tumor sampling make it difficult to monitor high-grade serous epithelial ovarian cancer (HGS-EOC) over time and to capture those alterations that are potentially useful in guiding clinical decisions. To overcome these issues, liquid biopsy has emerged as a very promising tool for HGS-EOC. The analysis of circulating tumor DNA appears to be feasible and studies assessing specific pathogenic mutations (i.e., TP53) or copy number alterations have shown a sufficient degree of sensitivity and specificity to be realistically used to monitor the effectiveness of antitumor therapy. Liquid biopsy can also provide potential important information on the mechanisms of sensitivity and resistance, e.g., by the determination of the reversion of BRCA mutations. Perspective studies are needed to test whether the application of liquid biopsy will significantly improve HGS-EOC management and patients' survival.

Total and endothelial cell-derived cell-free DNA in blood plasma does not change during menstruation

Assays measuring cell-free DNA (cfDNA) in blood have widespread potential in modern medicine. However, a comprehensive understanding of cfDNA dynamics in healthy individuals is required to assist in the design of assays that maximise the signal driven by pathological changes, while excluding fluctuations that are part of healthy physiological processes. The menstrual cycle involves major remodelling of endometrial tissue and associated apoptosis, yet there has been little investigation of the impact of the menstrual cycle on cfDNA levels. Paired plasma samples were collected from 40 healthy women on menstruating (M) and non-menstruating (NM) days of their cycle. We measured total cfDNA by targeting ALU repetitive sequences and measured endothelial-derived cfDNA by methylation-specific qPCR targeting an endothelium-unique unmethylated CDH5 DNA region. CfDNA integrity and endothelial cfDNA concentration, but not total cfDNA, are consistent across time between NM and M. No significant changes in total (ALU-115 p = 0.273; ALU-247 p = 0.385) or endothelial cell specific (p = 0.301) cfDNA were observed, leading to the conclusion that menstrual status at the time of diagnostic blood collection should not have a significant impact on the quantitation of total cfDNA and methylation-based cancer assays.

Increased Circulating H3 Histone in Response to Repeated Bouts of Exercise Does Not Associate with Parallel Alterations of Cell-Free DNA

Numerous studies have shown that cf nDNA significantly rises in stress caused by exercise. However, during nuclear decondensation, released DNA is followed by histones. Histones are also a common disease marker. After PAD4 mediated hypercitrullination extracellular H3Cit exhibits high toxicity contributing to tissue damage which, in cases of systemic inflammation, may lead to multiorgan failure and finally to death. We tested whether circulating histones rise in response to strenuous exercise. Eleven average-trained men performed three treadmill exercise tests to exhaustion at speed corresponding to 70% VO2max separated by 72 h of resting. Blood was collected before and just after each bout of exercise and plasma proteins were measured using enzyme-linked immunosorbent assay, whereas platelet activity was estimated with Light Transmission Aggregometry. Both, circulating histones and PAD4 raised in response to exercise. Plasma citrullinated histones increased from 3.1 ng/mL to 5.96 ng/mL (p = 0.0059), from 3.65 ng/mL to 6.37 ng/mL (p = 0.02), and from 3.86 ng/mL to 4.75 ng/mL (p = 0.033) after the first, second, and third treadmill run, respectively. However despite the parallel increase, no significant correlation between citrullinated histone and aggregation or cell-free nDNA was found. Furthermore, positive correlations of cf nDNA with aggregation and PAD4, lactate with aggregation, and lactate with citrullinated histone have been observed.

Circulating cell free DNA response to exhaustive exercise in average trained men with type I diabetes mellitus

It is believed that neutrophils extracellular traps (NETs) formation is responsible for the increase in cf DNA after exercise. Since T1DM is accompanied by enhanced NETs generation, we compared exercise-induced increase in cf DNA in 14 men with T1DM and 11 healthy controls and analyzed its association with exercise load. Subjects performed a treadmill run to exhaustion at speed corresponding to 70% of their personal VO2max. Blood was collected before and just after exercise for determination of plasma cf nuclear and mitochondrial DNA (cf n-DNA, cf mt-DNA) by real-time PCR, blood cell count and metabolic markers. Exercise resulted in the increase in median cf n-DNA from 3.9 ng/mL to 21.0 ng/mL in T1DM group and from 3.3 ng/mL to 28.9 ng/mL in controls. Median exercise-induced increment (∆) in cf n-DNA did not differ significantly in both groups (17.8 ng/mL vs. 22.1 ng/mL, p = 0.23), but this variable correlated with run distance (r = 0.66), Δ neutrophils (r = 0.86), Δ creatinine (r = 0.65) and Δ creatine kinase (r = 0.77) only in controls. Pre- and post-exercise cf mt-DNA were not significantly different within and between groups. These suggest low usefulness of Δ cf n-DNA as a marker of exercise intensity in T1DM men.

Circulating Free DNA and Its Emerging Role in Autoimmune Diseases

Liquid biopsies can be used to analyse tissue-derived information, including cell-free DNA (cfDNA), circulating rare cells, and circulating extracellular vesicles in the blood or other bodily fluids, representing a new way to guide therapeutic decisions in cancer. Among the new challenges of liquid biopsy, we found clinical application in nontumour pathologies, including autoimmune diseases. Since the discovery of the presence of high levels of cfDNA in patients with systemic lupus erythaematosus (SLE) in the 1960s, cfDNA research in autoimmune diseases has mainly focused on the overall quantification of cfDNA and its association with disease activity. However, with technological advancements and the increasing understanding of the role of DNA sensing receptors in inflammation and autoimmunity, interest in cfDNA and autoimmune diseases has not expanded until recently. In this review, we provide an overview of the basic biology of cfDNA in the context of autoimmune diseases as a biomarker of disease activity, progression, and prediction of the treatment response. We discuss and integrate available information about these important aspects.

Urinary Catecholamines as Markers in Overtraining Syndrome

In this study, potential urinary markers that show the presence of overtraining syndrome (OTS) were investigated. After a hard training period without an optimal recovery, OTS could appear in athletes. This syndrome could result in a decreasing of performance, a state of chronic fatigue and a not well-being state. The search for markers that demonstrate the presence of OTS could prevent the physiological and psychological health of the athletes, improving the performance.In this chapter, we will analyze some studies that have examined biochemical, physiological, and immunological markers of overtraining in urine and the variation of the catecholamines in a situation of stressed training.

Concentration of cell-free DNA in different tumor types

Introduction: Cell-free DNA (cfDNA) circulates in the blood for a long time. The levels of cfDNA in the blood are assayed in cancer diagnostics because they are closely related to the tumor burden of patients.Areas covered: cfDNA escapes the action of DNA-hydrolyzing enzymes, being a part of supramolecular complexes or interacting with the plasma membrane of blood cells. cfDNA has heterogeneous size and composition, which impose various restrictions on both isolation methods and subsequent analysis. cfDNA concentration and structural changes with the development of diseases highlight the high potential of cfDNA as a diagnostic and prognostic marker. The concentration of cfDNA released in the blood by tumor cells determines the specificity of such diagnostics and the required blood volume. The present review aimed to synthesize the available data on cfDNA concentration in the cancer patient's blood as well as pre-analytical, analytical, and biological factors, which interfere with cfDNA concentration.Expert opinion: The concentration of cfDNA and tumor cell DNA (ctDNA), and the over-presentation of DNA loci in cfDNA must be considered when looking for tumor markers. Some inconsistent data on cfDNA concentrations (like those obtained by different methods) suggest that the study of cfDNA should be continued.

Cell-free nucleic acid patterns in disease prediction and monitoring-hype or hope?

Interest in the use of cell-free nucleic acids (CFNAs) as clinical non-invasive biomarker panels for prediction and prevention of multiple diseases has greatly increased over the last decade. Indeed, circulating CFNAs are attributable to many physiological and pathological processes such as imbalanced stress conditions, physical activities, extensive apoptosis of different origin, systemic hypoxic-ischemic events and tumour progression, amongst others. This article highlights the involvement of circulating CFNAs in local and systemic processes dealing with the question, whether specific patterns of CFNAs in blood, their detection, quantity and quality (such as their methylation status) might be instrumental to predict a disease development/progression and could be further utilised for accompanying diagnostics, targeted prevention, creation of individualised therapy algorithms, therapy monitoring and prognosis. Presented considerations conform with principles of 3P medicine and serve for improving individual outcomes and cost efficacy of medical services provided to the population.

Comparison of paired cerebrospinal fluid and serum cell-free mitochondrial and nuclear DNA with copy number and fragment length

Background

Most studies on cell‐free DNA (cfDNA) were only for single body fluids; however, the differences in cfDNA distribution between two body fluids are rarely reported. Hence, in this work, we compared the differences in cfDNA distribution between cerebrospinal fluid (CSF) and serum of patients with brain‐related diseases.

Methods

The fragment length of cfDNA was determined by using Agilent 2100 Bioanalyzer. The copy numbers of cell‐free mitochondrial DNA (cf‐mtDNA) and cell‐free nuclear DNA (cf‐nDNA) were determined by using real‐time quantitative PCR (qPCR) and droplet digital PCR (ddPCR) with three pairs of mitochondrial ND1 and nuclear GAPDH primers, respectively.

Results

There were short (~60 bp), medium (~167 bp), and long (>250 bp) cfDNA fragment length distributions totally obtained from CSF and serum using Agilent 2100 Bioanalyzer. The results of both qPCR and ddPCR confirmed the existence of these three cfDNA fragment ranges in CSF and serum. According to qPCR, the copy numbers of long cf‐mtDNA, medium, and long cf‐nDNA in CSF were significantly higher than in paired serum. In CSF, only long cf‐mtDNA's copy numbers were higher than long cf‐nDNA. But in serum, the copy numbers of medium and long cf‐mtDNA were higher than the corresponding cf‐nDNA.

Conclusion

The cf‐nDNA and cf‐mtDNA with different fragment lengths differentially distributed in the CSF and serum of patients with brain disorders, which might serve as a biomarker of human brain diseases.

Decreased integrity of exercise-induced plasma cell free nuclear DNA - negative association with the increased oxidants production by circulating phagocytes

Strenuous exercise increases circulating cell free DNA (cfDNA) and stimulates blood phagocytes to generate reactive oxygen species (ROS) which may induce DNA strand breaks. We tested whether: (A) elevated cfDNA in response to three repeated bouts of exhaustive exercise has decreased integrity; (B) each bout of exercise increases luminol enhanced whole blood chemiluminescence (LBCL) as a measure of ROS production by polymorphonuclear leukocytes. Eleven men performed three treadmill exercise tests to exhaustion separated by 72 hours of resting. Pre- and post-exercise concentrations and integrity of cf nuclear and mitochondrial DNA (cf n-DNA, cf mt-DNA) and resting (r) and fMLP (n-formyl-methionyl-leucyl-phenylalanine)-stimulated LBCL were determined. Each bout increased concentrations of cf n-DNA by more than 10-times which was accompanied by about 2-times elevated post-exercise rLBCL and fMLP-LBCL. Post-exercise cf n-DNA integrity (integrity index, I_229/97) decreased after the first (0.59 ± 0.19 vs. 0.48 ± 0.18) and second (0.53 ± 0.14 vs. 0.44 ± 0.17) bout of exercise. There were negative correlations between I_229/97 and rLBCL (ƍ = –0.37), and I_229/97 and fMLP-LBCL (ƍ = –0.40) – analysis of pooled pre- and post-exercise data (n = 66). cf mt- DNA integrity (I_218/78) did not alter in response to exercise. This suggests an involvement of phagocyte ROS in cf n-DNA strand breaks in response to exhaustive exercise.