Circulating cell-free DNA in schizophrenia patients is considerably enriched with fragments of ribosomal repeats that stimulate TLR9 – MyD88 – NF-kB signaling pathway - 11th International Symposium on Circulating Nucleic Acids in Plasma and Serum (CNAPS)

Lidiia Bravve ² Elizaveta Ershova ^1,3 Natalia Veiko ¹ Georgy Kostyuk ² Natalia Zakharova ² Andrei Martynov ¹ Galina Shmarina ^1,3 Elena Malinovskaya ¹ Marina Konkova ¹ Svetlana Kostyuk ^1,3

¹Science, Research Centre for Medical Genetics (RCMG), Moscow, Russia
²Healthcare, Clinical Psychiatric Hospital №1 n.a. N. A. Alexeev, Moscow, Russia
³Healthcare, I.M. Sechenov First Moscow State Medical University, Moscow, Russia

Background. Cell free ribosomal DNA (cf-rDNA) is known to stimulate expression of genes for the TLR9-MyD88-NF-kB signaling in human peripheral blood mononuclear cells; this leads to a significant increase in concentrations of the proinflammatory cytokines IL-6 and TNF-a (Speranskii et al., 2016). The number of rDNA copies (rDNA CN) in the genomes of SZ patients is increased (Chestkov et al., 2018). We hypothesized that the concentration of cf-rDNA in the plasma of the SZ patients also increases and this may be one of the explanations of proinflammatory cytokines increase that is often observed in SZ.

Methods. We determined rDNA CN in the leukocyte DNA and plasma DNA with nonradioactive quantitative hybridization in the untreated male SZ-group (N=100) and in the

male healthy control (HC, N=100). Total cfDNA was determined with PicoGreen in the isolated cfDNA samples (RNase A/proteinase K/solvent extraction/ ethanol DNA precipitation). The level of TLR9 was determined with flow cytometry using TLR9(FITC)-antibody.

Results. In the SZ- and HC-groups rDNA CN in the plasma cfDNA was higher than in the leukocyte DNA. In the SZ-group rDNA CN in the plasma cfDNA was significantly higher than in the HC (median 1452 vs 717 copies; p=10-12). Plasma cf-rDNA concentration was three-fold higher in the SZ-group (4.8 vs 1.3 ng/mL; p=10-13). The level of TLR9 expression in SZ lymphocytes was also significantly increased (p=10-9).

Conclusion: Fragments of cf-rDNA accumulate in the blood plasma of SZ patients. Expression of the activator TLR9 of the TLR9 – MyD88 – NF-kB signaling is increased in the SZ

lymphocytes. Potentially, SZ patients` cfDNA should be a strong stimulating factor for the TLR9 – MyD88 – NF-kB signaling pathway. Blocking cf-rDNA activity can potentially reduce the inflammation that is often observed in SZ patients.

Russian Science Foundation (Grant No.18-15-00437) supportedI the study