Changes in specific characteristics of extracellular DNA in inflammatory processes in patients with bronchial asthma and rheumatoid arthritis

BACKGROUND: The search for additional diagnostic markers that reflect the dynamics of disease progression remains a necessary and relevant task. Inflammation, as a key component of the pathogenesis of many diseases, is one of the main factors contributing to an increased level of extracellular DNA (ecDNA) in the blood plasma of affected patients. AIM: To determine the fragmentation index of ecDNA, the quantitative content of mitochondrial ecDNA (mt-ecDNA) within the total ecDNA pool, and the level of membrane-bound ecDNA in the blood of patients with rheumatoid arthritis and bronchial asthma to assess the potential diagnostic value of these parameters in evaluating inflammatory activity and therapeutic effectiveness. METHODS: The total ecDNA pool was measured using the Quant-IT™ PicoGreen reagent for double-stranded DNA. The amount of mt-ecDNA and the ratio of long to short ecDNA fragments in blood plasma were assessed by real-time quantitative polymerase chain reaction. RESULTS: The ecDNA fragmentation index was significantly lower in both patients with bronchial asthma (Me=0.42; p 0.001) and rheumatoid arthritis (Me=0.34; p 0.001) compared to the donor group (Me=0.81). The prescribed therapy had no substantial effect on the fragmentation index, which remained nearly unchanged from the time of admission: Me=0.49 in the bronchial asthma group and Me=0.35 in the rheumatoid arthritis group. In patients with bronchial asthma, a moderate correlation was observed between mt-ecDNA levels and C-reactive protein (ρ=0.34; p 0.05). In patients with rheumatoid arthritis, similar correlations were found between mt-ecDNA and DAS-28 (ρ=0.36; p 0.05), as well as C-reactive protein (ρ=0.28; p 0.05). The membrane-bound ecDNA fraction was significantly lower in patients with rheumatoid arthritis compared to healthy donors (18.7 ng/mL vs. 55.6 ng/mL; p 0.01). A decrease in membrane-bound ecDNA fraction was also observed in patients with bronchial asthma compared to the donor group (19.4 ng/mL; p 0.01). CONCLUSION: The ecDNA fragmentation index and mt-ecDNA levels cannot serve as markers of inflammatory activity or indicators of the pathological shift in the Th1/Th2 balance in various immune system disorders. This is supported by the fact that diseases with differing levels of inflammatory activity, such as rheumatoid arthritis and bronchial asthma, result in a similar reduction in the ecDNA fragmentation index relative to healthy donors and do not lead to any significant difference in mean mt-ecDNA levels between these patient groups.