Elina Tsvetanova

Encapsulation of resveratrol (RVT), a natural polyphenol, in mixed Pluronic F127/P123 micelles (mRVT) has enhanced its pharmacological efficacy in experimental dementia models. The aim of this study was to evaluate neurochemical and behavioral parameters of mRVT treatment in healthy subjects. For this purpose, pure RVT and mRVT (both at 10 mg/kg i.p.) were applied for 9 consecutive days in healthy male Wistar rats. Memory performance was assessed using the novel object recognition and passive avoidance tests. Neurotransmitter levels, neurotrophic and transcription factors, and oxidative stress markers were quantified in the cortex and hippocampus using enzyme-linked immunosorbent assay kits. Our results showed that neither treatment altered locomotor activity or short-term memory performance. Both RVT and mRVT treatments reduced hippocampal acetylcholinesterase activity to a similar extent and elevated acetylcholine levels in the cortex and hippocampus, with mRVT producing significantly more pronounced effect in the hippocampus. Compared to pure RVT, mRVT elicited a greater increase in noradrenaline and serotonin levels in both brain regions and comparably upregulated BDNF and pCREB protein levels in the cortex. Furthermore, mRVT uniquely reduced cortical lipid peroxidation—an effect absent with pure RVT treatment. These findings demonstrate that micellar encapsulation substantially amplifies the neurochemical efficacy of resveratrol under physiological conditions without adverse behavioral effects.

Microplastic pollution has attracted significant attention in recent years due to evidence that these particles can accumulate in organisms’ tissues and organs and induce adverse health effects, with oxidative stress being a key underlying mechanism of toxicity. The present study investigated the effects of polystyrene microplastics (0.1 μm in diameter) administered at a dose of 0.1 mg/day/animal for 4 weeks, followed by a 2-week recovery period without exposure, on oxidative stress markers in the liver, kidney, and spleen and on hematological and blood biochemical parameters in mice. The results showed a statistically significant increase in white blood cell counts, including lymphocytes, granulocytes, and monocytes, at week 5, indicating the development of an inflammatory response. During the last week of the recovery period (week 6), values returned to levels that approached baseline. Changes in lipid peroxidation demonstrated an induction of oxidative stress, accompanied by alterations in glutathione levels and antioxidant enzyme activities, with a tendency toward recovery after cessation of polystyrene microplastic exposure. In conclusion, these findings demonstrated that even short-term exposure to low doses of polystyrene microplastics could trigger oxidative stress and inflammatory responses, highlighting their potential health risks and the need for further investigation into their long-term biological effects.

Plastic pollution has emerged as one of the most pervasive environmental challenges, with microplastics (MPs) widely distributed across marine ecosystems worldwide. This study aimed to assess the uptake of MPs by key fish and invertebrate species from different locations in the coastal zone of the Bulgarian Black Sea. Fish were collected during routine monitoring surveys in September–November 2024, while invertebrates were obtained via scuba diving. The presence of MPs in fish stomachs and invertebrate soft tissues, and their polymer composition, shape and size were analyzed using an Agilent 8700 LDIR Chemical Imaging System. Potential biological effects of ingested MPs were evaluated by an integrated Specific Oxidative Stress (SOS) index. The results revealed MP uptake levels comparable to those reported globally. Small-sized particles (<50 µm) with rounded shapes were most abundant across studied taxa. Polymer composition varied considerably depending on species and sampling region, indicating differences in exposure sources and environmental conditions. Oxidative stress levels in both fish and invertebrates showed substantial interspecific variation, and clear differences between the northern and southern region of the Bulgarian Black Sea. Overall, elevated uptake of MPs appears to contribute to oxidative stress in marine organisms, potentially affecting their health status, resilience, and adaptive capacity, as reflected by increased SOS index values.

Microplastics are emerging environmental contaminants capable of crossing epithelial barriers and circulating systemically, potentially affecting organisms, including humans. This study investigated the hematological and biochemical effects of sub-chronic oral exposure to polystyrene microplastics (PS-MPs) in male Swiss albino mice. Animals received 1 μm PS-MPs in drinking water at 0.01 mg/day for four weeks, followed by a two-week recovery period. Blood samples were collected weekly for hematological and biochemical analysis. PS-MP exposure resulted in an increased number of certain immunocytes after the first week of treatment. The highest values compared with the control group were observed in Week 2, reaching 18.5 ± 4.61 vs. 7.2 ± 1.14; 10.9 ± 2.58 vs. 5.1 ± 1.20; and 5.8 ± 2.35 vs. 2.2 ± 0.69 × 10⁹ cells/L for white blood cells, lymphocytes, and granulocytes, respectively (p < 0.001). A significant increase in platelet count was also observed, becoming evident by Week 6 (725.8 ± 307.96 vs. 470.1 ± 121.87 × 10⁹ cells/L, p < 0.05). The elevated alanine aminotransferase and aspartate aminotransferase activities observed after PS-MP exposure were potentially associated with hepatic pathology, erythrocyte damage, and inflammatory responses. No significant recovery was observed during the period after exposure. These findings demonstrate that sub-chronic oral PS-MP exposure induces inflammatory responses and may disrupt organ function.

Increasing environmental contamination with microplastics (MPs) raises significant concerns regarding their potential impact on reproductive health. This study evaluated the effects of prolonged oral exposure to fluorescent polystyrene microplastics (FPS-MPs) of different sizes on the male reproductive system in Wistar rats. Juvenile male rats at 21 days of age were exposed to FPS-MPs of 1 µm and 5 µm for 52 days, covering the period of sexual maturation and a complete spermatogenesis cycle. Body weight, reproductive organ indices, serum levels of testosterone (T), estradiol (E2), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), as well as sperm motility and morphology, were assessed. Reproductive potential and accumulation of microplastics in reproductive tissues were also evaluated. No significant differences were observed in body weight or most reproductive organ indices, except for a slight reduction in the left epididymis index in the group exposed to 5 µm particles. FPS-MPs induced size-dependent changes in the hormonal profile, including decreases in T and E2 and compensatory increases in FSH and LH, as well as impairments in sperm quality, which were more pronounced in rats exposed to smaller particles. In conclusion, fertility potential remained preserved, while FPS-MPs accumulated in the testes and epididymides, demonstrating subclinical, size-dependent effects on the male reproductive system.

The Black Sea waters and sediments accumulate a wide range of pollutants, which, together with natural factors, can have diverse and combined effects on marine organisms. Cellular oxidative stress (OS) is a common response to environmental stressors and thus an indicator of the physiological resilience of organisms. The present study analyzed OS in fish species from the Bulgarian part of the Black Sea. Samples of 18 fish species were obtained during monitoring trawling in the northern and southern regions of the Bulgarian Black Sea and were analyzed. The OS-specific biomarkers (lipid peroxidation, glutathione, and antioxidant enzymes) were spectrophotometrically measured in the liver and gills. The obtained results revealed pronounced variability in pro- and antioxidant responses, shaped by sampling location, species identity, and tissue type. In fish sampled from the northern part, the liver showed stronger antioxidant activation, while the gills exhibited higher lipid peroxidation. Benthic fish exhibited pronounced hepatic antioxidant responses. Pelagic species had higher gill lipid peroxidation. Generalist feeders displayed variable stress responses associated with a diverse diet and the presence of multiple contaminants in it. In conclusion, OS was most pronounced in benthopelagic and pelagic species, which were more stressed in the northern Bulgarian part of the Black Sea, while benthic or coastal fish species experienced greater environmental pressure in the southern part.

Microplastics are emerging environmental contaminants capable of crossing epithelial barriers and circulating systemically, potentially affecting organisms, including humans. This study investigated the hematological and biochemical effects of subchronic oral exposure to polystyrene microplastics (PS-MPs) in male Swiss albino mice. Animals received 1 μm PS-MPs in drinking water at 0.01 mg/day for four weeks, followed by a two-week recovery period. Blood samples were collected weekly for analysis. PS-MP exposure increased white blood cell, lymphocyte, and granulocyte counts, with a reduced monocyte percentage after the first week, and a significant rise in platelet count by week six. Elevated alanine and aspartate aminotransferase activities indicated hepatic injury, while altered urea and creatinine levels suggested renal impairment. No significant recovery was observed after PS-MP withdrawal. These findings demonstrate that subchronic oral PS-MP exposure induces inflammatory responses and disrupts liver and kidney function.

Feral individuals of Pacific oysters ( Magallana gigas Thunberg, 1793) in natural habitats are increasingly being reported from the Bulgarian coast. Studies on the interactions of the Pacific oyster with native species in local ecosystems are contradictory and it is not yet definitely established to what extent ecological conditions in the Black Sea are favourable for the Pacific oyster growth and reproduction. For the first time in this study, an assessment has been made of the adaptive capacity and resilience of the alien Pacific oyster allowing its development in the ecological conditions of the Bulgarian Black Sea ecosystems and the risk of a future mass invasion. Oysters were gathered manually by SCUBA diving from natural habitats or obtained from shellfish farms. A set of major oxidative stress (OS) indicators: lipid peroxidation, protein oxidation, glutathione level and activity of anti-oxidant enzymes: superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase, were measured spectrophotometrically, using commercially available kits. The adaptive capacity and resilience of the Pacific oysters were assessed by the integral Specific Oxidative Stress (SOS) index. The results indicate that M. gigas from more polluted localities have higher OS, but it was effectively compensated by their anti-oxidant system. A comparison was also made between M. gigas OS and that of the native species Mytilus galloprovincialis Lamarck, 1819, using the SOS index. In some localities, Pacific oysters had an even lower SOS index than the native black mussels. The level of adaptive capacity of the oysters, as indicated by the SOS index, was compared to the phases of Holling’s adaptive cycle theoretical model and showed that the Bulgarian Black Sea oyster population is in an initial growth stage (resource exploitation), which confirms its high adaptive potential and resilience. In conclusion, this study confirms that the Pacific oyster possesses the capacity to cope with the marine environment and the native species, which allows further expansion of the oyster population in the Bulgarian Black Sea. More research and monitoring of the M. gigas population, along with assessment of their impact on biodiversity and the local ecosystems, are urgently needed for taking adequate management decisions.

Neurodegenerative diseases, including Alzheimer’s disease, are marked by cholinergic dysfunction, oxidative stress, and reduced neurotrophic support, which drives the quest for multifunctional therapeutic agents. This pilot study presents four novel monoterpene–aminoadamantane conjugates (MACs 1–4) designed to combine the antioxidant and neuromodulatory characteristics of monoterpenes with the neuroprotective properties of aminoadamantane derivatives. Their physicochemical characteristics, blood–brain barrier permeability, and binding affinity to human acetylcholinesterase (AChE) were evaluated using molecular docking and in silico descriptor analysis. In vivo, the neuroprotective efficacy of the MACs was investigated in a scopolamine-induced dementia model in rats, employing behavioral tests. Biochemical assays conducted in the hippocampus and prefrontal cortex assessed AChE activity, antioxidant enzyme performance, lipid peroxidation levels, total glutathione content, and BDNF concentrations. The findings indicate that MAC1, MAC3, and MAC4 demonstrate favorable calculated blood–brain barrier permeability, strong predicted affinity for AChE, and significant in vivo alleviation of scopolamine-induced memory deficits, in conjunction with improvement of key markers of oxidative stress and cholinergic function. These results show that the structural hybridization of myrtenal with aminoadamantane frameworks produces promising multifunctional ligands that are relevant for Alzheimer’s-type neurodegeneration.

Cotinus coggygria Scop., a member of the Anacardiaceae family, is known for its antiseptic, anti-inflammatory, and antitumor properties. In the present study, the ethyl acetate/water leaf extract of C. coggygria was evaluated for antioxidant and anticancer activities. The extract exhibited strong radical-scavenging potential, effectively neutralizing DPPH, ABTS^•+, and superoxide radicals in a concentration-dependent manner. The cytotoxic effects of the extract on human hepatocellular carcinoma HepG2 cells were also investigated. Flow cytometry revealed significant S-phase cell cycle arrest, while fluorescent microscopy and annexin V-FITC/PI staining demonstrated induction of apoptosis. DNA damage was confirmed by alkaline comet assay. Molecular docking was used to evaluate the binding affinity and inhibitory potential of penta-O-galloyl-β-D-glucose, a representative of gallotannins found in C. coggygria extracts, towards cyclin-dependent kinase 2 and checkpoint kinase 1. A high inhibition ability was demonstrated, which could explain the observed cell cycle block. Collectively, these findings suggest that C. coggygria extract exerts strong antioxidant capacity and selective antiproliferative activity in HepG2 cells. The anticancer effects of C. coggygria extract were associated with DNA damage, cell cycle arrest, disruption of mitochondrial membrane potential, and apoptosis induction. The results show the potential of the herb as a natural therapeutic agent for hepatocellular carcinoma.