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

Abstract

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, I229/97) 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 I229/97 and rLBCL (ƍ = –0.37), and I229/97 and fMLP-LBCL (ƍ = –0.40) – analysis of pooled pre- and post-exercise data (n = 66). cf mt- DNA integrity (I218/78) 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.

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

“…Calculations were performed in absolute numbers. * This research is a continuation of the previously published articles [11,16] which allows us to study the correlation with any previously investigated and published data; ns-non significant.…”

“…The studied group involved eleven, non-smoking healthy men. All their characteristics as well as the inclusion/exclusion criteria were the same as in our previous articles [ 11 , 16 ]. Briefly, all volunteers who met inclusion criteria were members of the Medical University of Lodz, mean age was 34.0 ± 5.2 years, mean body weight 87.4 ± 13.8 kg, mean body mass index 26.2 ± 3.1 kg/m 2 , maximal oxygen consumption 49.6 ± 4.5 mL/kg*min, forced vital capacity (FVC) 6.09 ± 0.41 L, 106.4 ± 6.4% of predicted, forced exhaled volume in the first second (FEV 1 ) 4.93 ± 0.45 L, FEV1/FVC 80.9 ± 5.6%.…”

“…The study design was the same as in our previous reports [ 11 , 16 ]. Figure 1 shows point by point: Those male volunteers who fulfilled the inclusion/exclusion criteria underwent a treadmill VO 2 max test at the first visit (day 1st).…”

“…Hence, the plasma concentration of cf nDNA seems to be an efficient marker of exercise load and its persistent elevation could be associated with the increased risk of occurrence of overtraining syndrome in athletes [ 15 ]. In our previous studies, we found that three repeated bouts of exhaustive treadmill exercise caused the increase in cf nDNA without development of tolerance and decreased the integrity of post-exercise cf nDNA correlated with increased post-exercise whole blood chemiluminescence [ 11 , 16 ]. Because nDNA is wrapped around an octamer of (two H2A, two H2B, two H3, and two H4) histones, it may be expected that exercise would result in an increase in plasma histones concentrations.…”

Increased Cell-Free DNA Plasma Concentration Following Liver Transplantation Is Linked to Portal Hepatitis and Inferior Survival

“…The immunostimulatory effect of cfDNA has been demonstrated before. In human studies, cfDNA activates TNF-α mRNA expression and IL-6 production [24,25]. Moreover, nuclear but not mitochondrial cfDNA has been linked to reactive oxygen species ROS [26], and systemic ROS production appears to be caused by circulating phagocytes.…”