Introduction: It was shown that copy number variations (CNVs) of human satellite III (1q12) fragment (f-SatIII) reflects the human cells response to stress of different nature and intensity. Patients with schizophrenia (SZ) experience chronic stress. The major research question: What is the f-SatIII CNVs in human leukocyte as a function of SZ? Materials and Methods: Biotinylated pUC1.77 probe was used for f-SatIII quantitation in leukocyte DNA by the non-radioactive quantitative hybridization for SZ patients (N = 840) and healthy control (HC, N = 401). SZ-sample included four groups. Two groups: first-episode drug-naïve patients [SZ (M-)] and medicated patients [SZ (M+)]. The medical history of these patients did not contain reliable confirmed information about fetal hypoxia and obstetric complications (H/OCs). Two other groups: medicated patients with documented H/OCs [hypoxia group (H-SZ (M+)] and medicated patients with documented absence of H/OCs [non-hypoxia group (NH-SZ (M+)]. The content of f-SatIII was also determined in eight post-mortem brain tissues of one SZ patient. Results: f-SatIII in human leukocyte varies between 5.7 to 44 pg/ng DNA. f-SatIII CNVs in SZ patients depends on the patient’s history of H/OCs. f-SatIII CN in NH-SZ (M+)-group was significantly reduced compared to H-SZ (M+)-group and HC-group (p < 10-30). f-SatIII CN in SZ patients negatively correlated with the index reflecting the seriousness of the disease (Positive and Negative Syndrome Scale). Antipsychotic therapy increases f-SatIII CN in the untreated SZ patients with a low content of the repeat and reduces the f-SatIII CN in SZ patients with high content of the repeat. In general, the SZ (M+) and SZ (M-) groups do not differ in the content of f-SatIII, but significantly differ from the HC-group by lower values of the repeat content. f-SatIII CN in the eight regions of the brain of the SZ patient varies significantly. Conclusion: The content of f-SatIII repeat in leukocytes of the most patients with SZ is significantly reduced compared to the HC. Two hypotheses were put forward: (1) the low content of the repeat is a genetic feature of SZ; and/or (2) the genomes of the SZ patients respond to chronic oxidative stress reducing the repeats copies number.

INTRODUCTION. As shown earlier, copy number variations (CNV) in the human satellite III (1q12) fragment (f-SatIII) and the telomere repeat (TR) reflects the cell’s response to oxidative stress. The contents of f-SatIII and TR in schizophrenic (SZ) patients were found to be lower than in healthy controls (HC) in previous studies. The major question of this study was: ‘What are the f-SatIII and TR CNV dynamic changes in human leukocytes, depending on psychoemotional stress?’ MATERIALS AND METHODS. We chose a model of psychoemotional stress experienced by second-year medical students during their exams. Blood samples were taken in stressful conditions (exams) and in a control non-stressful period. Biotinylated probes were used for f-SatIII, rDNA, and TR quantitation in leukocyte DNA by non-radioactive quantitative hybridization in SZ patients (n = 97), HC (n = 97), and medical students (n = 17, n = 42). A flow cytometry analysis was used for the oxidative stress marker (NOX4, 8-oxodG, and γH2AX) detection in the lymphocytes of the three groups. RESULTS. Oxidative stress markers increased significantly in the students’ lymphocytes during psychoemotional stress. The TR and f-SatIII, but not the rDNA, contents significantly changed in the DNA isolated from human blood leukocytes. After a restoration period (post-examinational vacations), the f-SatIII content decreased, and the TR content increased. Changes in the blood cells of students during examinational stress were similar to those in SZ patients during an exacerbation of the disease. CONCLUSIONS. Psychoemotional stress in students during exams triggers a universal mechanism of oxidative stress. The oxidative stress causes significant changes in the f-SatIII and TR contents, while the ribosomal repeat content remains stable. A hypothesis is proposed to explain the quantitative polymorphisms of f-SatIII and TR contents under transient (e.g., students’ exams) or chronic (in SZ patients) stress. The changes in the f-SatIII and TR copy numbers are non-specific events, irrespective of the source of stress. Thus, our findings suggest that the psychoemotional stress, common in SZ patients and healthy students during exams, but not in a schizophrenia-specific event, was responsible for the changes in the repeat contents that we observed earlier in SZ patients.

Исследованы характеристики вкДНК в плазмах крови подвыборок больных кататонической (КШ, N=46) и параноидной формой (ПШ, N=54) шизофрении в сравнении с выборкой психически здоровых людей соответствующего возраста. Обнаружено, что независимо от типа шизофрении, концентрация вкДНК возрастает почти в 2 раза по сравнению с контролем, и нуклеазная активность плазм крови больных также повышена. Мы определили, что уровень 8-oxodG в мононуклеарах больных КШ и ПШ не различается и значительно выше контроля, и содержание гистонов Н2АХ в двух подвыборках больных шизофренией также значительно выше, чем в лимфоцитах здоровых людей, при этом уровень двунитевых разрывов в подгруппе КШ выше, чем в ПШ. Клетки с двунитевыми разрывами гибнут, пополняя пул вкДНК. Повышенная нуклеазная активность способствует выведению быстро расщепляемых АТ-богатых фрагментов и накоплению GC-богатых фрагментов в составе вкДНК. ВкДНК больных шизофренией обогащена ГЦ-богатыми фрагментами теломерного повтора по сравнению с вкДНК здоровых доноров. В составе вкДНК больных КШ число копий ГЦ-богатого рибосомного повтора увеличено по сравнению с выборкой ПШ и контрольной выборкой. Все исследованные показатели в большей степени изменены в группе пациентов с кататонической формой шизофрении, что может свидетельствовать о более выраженном воспалительном процессе при кататонии. CfDNA parameters of SZ patients with paranoid (N=54) and catatonic SZ (N=46) forms have been analyzed and compared with those of healthy controls. In the subjects from the both SZ forms, the mean cfDNA plasma concentration was twofold higher and NA of the plasma was higher than those in the healthy controls. In addition, peripheral blood lymphocytes of both SZ forms showed elevated levels of oxidized dna (8-OHDG) as well as increased number of double-stranded DNA breaks (flow Cytometry), and the ds-breaks level is higher in catatonic SZ. The cells with genomic DNA damages can undergo to unprogrammed cell death and contribute to circulating cfDNA. Increased DNase I activity in patients with schizophrenia promotes to cleave primarily AT-rich DNA-fragments and the accumulation of GC-rich fragments. Compared to those of healthy controls, plasma cfDNA samples of both SZ forms patients contained increased copy numbers of telomere DNA, as well as ribosomal RNA genes, and cf-rDNA concentration is higher in catatonic SZ group. Changes in cfDNA parameters was significantly higher in the catatonic SZ group, which may indicate a more pronounced inflammatory process.

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