Autukaitė, Gintarė

Selenium is an essential microelement involved in antioxidant defence, redox regulation, and cellular signalling. Both its inorganic form, sodium selenite (Na₂SeO₃), and organic form, selenomethionine (SeMet), influence gene expression related to oxidative stress, apoptosis, and cell survival. The brain and liver, being highly vulnerable to oxidative stress, are critical tissues in understanding selenium’s biological effects. This study evaluates the impact of sodium selenite and selenomethionine on gene expression in these tissues, focusing on genes involved in redox regulation (MsrB1), apoptosis (Caspase-3), and cell cycle control (GADD45). The study was performed on 4-6-week-old BALB/c mice, which were divided into 4 experimental groups, that were given solutions of different concentrations of SeMet or Na₂SeO₃ (0.2 and 0.4 mg Se/kg body weight) for 8 weeks, and a control group that had free access to tap water. Then, mRNA was extracted from mouse liver and brain tissues and used to synthesize cDNA for RT-PCR analysis. The results show that MsrB1 expression in both brain and liver was higher in mice receiving 0.2 mg Se/kg of either SeMet or Na₂SeO₃ compared to the control group and those receiving 0.4 mg Se/kg. Caspase-3 expression in brain and liver was increased in mice receiving 0.2 mg Se/kg of Na₂SeO₃, but lower in those receiving 0.2 mg Se/kg of SeMet compared to the control group and those given 0.4 mg Se/kg of either selenium form. GADD45 expression in the brain and liver was elevated in mice given 0.2 mg Se/kg of Na₂SeO₃, while in SeMet-treated mice, GADD45 expression in the liver increased with higher concentrations, whereas in the brain, it decreased with increasing SeMet dosage. Overall, Na₂SeO₃ may promote stronger oxidative stress defence and apoptosis regulation, while SeMet could be more selective in its influence on apoptosis and cell cycle control, depending on tissue type.

Parkinson's disease (PD) is a neurodegenerative disorder that results in tremor and bradykinesia due to the death of dopaminergic neurons. PD is difficult to diagnose, it progresses for several years before a clinical diagnosis is made and its treatment isn‘t curative (1). Recently, miRNA interference has been extensively studied due to it’s affects in many biological processes including neurodegenerative diseases (2). MiRNA molecules formed in various body cells can be packed into extracellular vesicles (EV), then infiltrate the extracellular space and travel through biological fluids providing long lasting effects of disease related genes. EV associated miRNA‘s are expected to useful in clinical practice to facilitate diagnosis, prognosis and treatment (3). The aim of this study was to evaluate EV miR-16-5p, miR-103a-3p, miR-497-3p, miR-22-3p expression levels in the serum of patients with PD and check for relations with patient’s age, sex, the onset of the disease, its duration, severity of symptoms and selected method of treatment. EV miRNA’s were isolated from blood serum, transcribed into cDNA and its expression was measured by RT-PCR. Statistical analysis was performed using Student's t test, ANOVA criteria and Pearson’s correlation coefficient in GraphPad Software Inc. Prism 8. 3 groups of PD patients were tested. 36 control group patients received medicamental treatment, 39 underwent deep brain stimulation and 13 had gamma knife surgery. miR-126 expression was evaluated before and after the surgical treatment. The results reveled, that miR-16, miR-103a and miR-22 expression was higher in patients receiving medicamental treatment when comparing patients between different treatment groups (p < 0,05; p < 0,01; p < 0,001). Statistical analysis showed that miR-16, miR-22 and miR-103a levels were down regulated (p < 0,05; p < 0,01) and miR-497 was upregulated as intensity of bradykinesia increases. As symptoms of tremor become more intense miR-16 levels decrease and miR-497 expression increases. No statistically relevant changes in miRNA expression were observed after assigned treatment, but it seemed, that patients had lower miR103a and miR-497 expression levels after receiving gamma knife surgery. However, more patient samples are needed to confirm this pattern. Association between miRNA expression levels were observed regarding gender of the patients. Men had higher miR-103a and miR-22 levels in their blood (p < 0,05). Also, no statistically relevant correlation was found between miRNA expression and patients age, duration of the disease and age of diagnosis. Primary data suggest that patient groups with downregulated EV miR-16, miR-22, miR-103a expression levels and elevated miR-497 experience stronger PD related symptoms and require surgical treatment. However miRNA profile did not change significantly after treatment.

Selenomethionine (SeMet) is an organic form of selenium, an essential trace element that plays an important role in reproduction, thyroid hormone metabolism, DNA synthesis, immune response regulation. This study aimed to evaluate the effects of SeMet concentration on genes responsible for redox regulation (MsrB1), regulation of protein folding, immune and inflammatory processes (SELENOS) as well as genes related to apoptosis and cell cycle control (Caspase-3 and GADD45) in mice liver and brain. The study was performed on 4‒6 week old BALB/c mice, which were divided into a control group that had free access to tap water, and groups that were given ad libitum tap water supplemented with different concentrations of selenomethionine (0.2 and 0.4 mg SeMet/kg of body weight) for the period of 8 weeks. After extracting mRNA from mouse liver and brain samples and performing complementary DNA synthesis, gene expression changes in the samples were determined by Real-time polymerase chain reaction. The obtained results showed that the expression of the Caspase-3 gene in both liver and brain samples was the highest among the control group, while the lowest expression was found among the mice that received 0.2 mg SeMet/kg. The expression of MsrB1 and SELENOS genes in the control groups of both samples is the lowest, while the expression of the mice exposed to 0.2 mg SeMet/kg is the highest. It was also found that with increasing SeMet concentration, GADD45 gene expression increased in liver samples and decreased in brain samples. According to the results, in mice treated with Selenomethionine, an increase in MsrB1 and SELENOS gene expression and a decrease in Caspase-3 gene expression in liver and brain samples, and an increase in GADD45 gene expression in liver samples lead to better cell survival associated with the crucial protection of these genes against inflammation, oxidative stress, DNA damage and apoptosis. However, as the concentration of SeMet increases, the decrease in GADD45 gene expression in brain samples may have a negative impact on cell functions, causing DNA damage.