Albena Momchilova

• professor
• Bulgarian Academy of Sciences

European mistletoe extract (Iscador Qu) has been studied for decades, but it has not ceased to arouse scientific interest. The purpose was to investigate the impact of Iscador Qu on the antiproliferative potential of 11 standard chemotherapeutic agents on two breast cancer cell lines: MCF-7 low-metastatic and MDA-MB-231 high-metastatic and control...

This study examined the influence of nanomaterials (NMs) on the organization of membrane lipids and the resulting morphological changes. The cell plasma membrane is heterogeneous, featuring specialized lipid do- mains in the liquid-ordered (Lo) phase surrounded by regions in the liquid-disordered (Ld) phase. We utilized model membranes composed of...

The studies of rejuvenation are important for promoting health and longevity, preventing age-related diseases, reducing economic burdens, improving quality of life and addressing the challenges posed by an aging global population. This review explores the intersection of aging, regeneration and bioelectric fields examining the emerging role of memb...

Resveratrol (Resv) is considered to exert a beneficial impact due to its radical scavenger, anti-microbial and anti-inflammatory properties through several mechanisms that could include its interaction with the cell plasma membrane. To address this issue, we investigated the influence of Resv on membrane lipid order and organization in large unilam...

The pathogenesis of multiple sclerosis (MS) suggests that, in genetically susceptible subjects, T lymphocytes undergo activation in the peripheral compartment, pass through the BBB, and cause damage in the CNS. They produce pro-inflammatory cytokines; induce cytotoxic activities in microglia and astrocytes with the accumulation of reactive oxygen s...

Multiple sclerosis (MS) is predominantly an immune-mediated disease of the central nervous system (CNS) of unknown etiology with a possible genetic predisposition and effect of certain environmental factors. It is generally accepted that the disease begins with an autoimmune inflammatory reaction targeting oligodendrocytes followed by a rapid deple...

The interplay between inflammatory and redox processes is a ubiquitous and critical phenomenon in cell biology that involves numerous biological factors. Among them, secretory phospholipases A2 (sPLA2) that catalyze the hydrolysis of the sn-2 ester bond of phospholipids are key players. They can interact or be modulated by the presence of truncated...

Coronary artery disease (CAD) is a medical condition that is characterized by an inability of the arteries to supply the myocardium of the heart with enough blood, therefore affecting its function and leading to serious pathological changes. CAD development is caused by plaque buildup on the inner walls of the coronary arteries. The plasma and red...

Investigations were carried out on the effect of quercetin on the level of the major sphingolipid metabolites in ras-transformed 3T3 fibroblasts. Quercetin is a polyphenol of a significant biomedical importance, which has been reported to show beneficial effects such as antioxidant, anti-neoplastic, anti-ageing, etc. Sphingolipids are functionally...

Studies were performed for the first time on the effect of Iscador Qu and Iscador M on phototoxicity, cytotoxicity, antiproliferative activity, changes in ξ-potential of cells, membrane lipid order, actin cytoskeleton organization and migration on three breast cancer lines with different metastatic potential: MCF10A (control), MCF-7 (low metastatic...

The effect of quercetin on phospholipase A2 activity and its products has been investigated in A549 adenocarcinoma cells. Quercetin is a polyphenol of medico-biological significance, which has been reported to show antioxidant and anti-tumour beneficial effects. Phospholipids are functionally active molecules, which participate in various cellular...

Combinations of anti-cancer drugs can overcome resistance to therapy and provide new more effective treatments. In this work we have analyzed the effect of the polyphenol quercetin and the anti-cancer sphingosine analog fingolimod on the sphingolipid metabolism in HepG2 cells, since sphingolipids are recognized as mediators of cell proliferation an...

The effect of resveratrol on the sphingolipid metabolism has been investigated in ras-transformed 3T3 fibroblasts. Resveratrol is a phytoalexin of a great medico-biological significance, which has been reported to exhibit significant beneficial effects such as antioxidant, lipid-lowering, anti-neoplastic, etc. Sphingolipids are functionally active...

Resveratrol is a naturally occurring polyphenol which has various beneficial effects, such as anti-inflammatory, anti-tumor, anti-aging, antioxidant, and neuroprotective effects, among others. The anti-cancer activity of resveratrol has been related to alterations in sphingolipid metabolism. We analyzed the effect of resveratrol on the enzymes resp...

The phenyl glycoside myconoside, extracted from Balkan endemic Haberlea rhodopensis, has a positive effect on human health, but the exact molecular mechanism of its action is still unknown. The cell membrane and its associated junctional complex are the first targets of exogenous compound action. We aimed to study the effect of myconoside on membra...

Multiple sclerosis (MS) is an autoimmune, inflammatory, degenerative disease of the central nervous system. Changes in lipid metabolism have been suggested to play important roles in MS pathophysiology and progression. In this work we analyzed the lipid composition and sphingolipid-catabolizing enzymes in erythrocytes and plasma from MS patients an...

Oxidative stress is an important etiologic factor in the pathogenesis of various diseases. The formation of oxidized phospholipid species in vivo induces membrane remodelling with direct pathological implications with a prominent inflammatory component. Secretory phospholipases A2 (sPLA2) are involved in the regulation of inflammation and immune re...

Nonhealing wounds are a common complication in patients suffering from diabetes with hyperglycemia being the most deteriorating factor for this serious pathological condition. Despite the great body of data, the molecular mechanisms by which high glucose affects cellular physiology are still poorly defined. Here we used primary human foreskin fibro...

Studies have been carried out on the effects of the phenyl glycoside myconoside, extracted from the relict, Balkan endemic resurrection plant Haberlea rhodopensis on the plasma membrane structural organization and the actin cytoskeleton. Because the plasma membrane is the first target of exogenous bioactive compounds, we focused our attention on th...

In response to exogenous stress some plant species synthesize the phytoalexin resveratrol (3, 5, 4′-trihydroxy-trans-stilbene). Found in the skins and seeds of red grapes, red wines, peanuts and other nutrients this polyphenolic compound has been recognized as beneficial in the prevention of oxidative damage in the human organism. The mechanism by...

In the present study, chloroplast ultrastructure, PSII functionality and lipid and fatty acids pattern of isolated chloroplasts have been used in order to characterize structural and functional peculiarities of photosynthetic apparatus in some halophytic and glycophytic Lactuca species. The comparative studies of Lactuca tatarica (L.) C.A. Mey, L....

Chitosan is a natural copolymer derived from the deacetylation of chitin. Because of its specific physicochemical properties, chitosan is a perfect material to be used in bioengineering and biomedicine. In this study, we demonstrated how chitosan is able to affect the lipid order and organisation in biomimetic membranes. We formed large unilamellar...

In this study, we present initial data for the potential anti-cancer effects of standardized Bulgarian Petasites hybridus root extract against breast cancer cells. The results showed that Butterbur extract (BE) caused a dose-dependent selective reduction in viability with concomitant increase of apoptosis in human breast cancer cells after 72 h tre...

The polyphenol quercetin is associated with numerous beneficial health effects in various pathologies such as oxidative stress, neurodegenerative disorders, inflammation, neoplastic processes, age-related diseases, and so on. However, the molecular mechanisms underlying the effects of quercetin and its implication in the pharmaceutical practice req...

Three lactic acid bacteria (LAB) strains identified as Lactobacillus plantarum, Lactobacillus brevis, and Lactobacillus sakei isolated from meat products were tested for their ability to utilize and grow on xylooligosaccharides (XOSs). The extent of carbohydrate utilization by the studied strains was analyzed by HPLC. All three strains showed prefe...

Alkylphospholipids are a novel class of antineoplastic drugs showing remarkable therapeutic potential. Among them, erufosine (EPC3) is a promising drug for the treatment of several types of tumors. While EPC3 is supposed to exert its function by interacting with lipid membranes, the exact molecular mechanisms involved are not known yet. In this wor...

Sphingolipid metabolites are implicated in a wide variety of intracellular and extracellular processes, including neurodegenerative pathologies. Multiple sclerosis is an inflammatory neurodegenerative disease, which is closely related to sphingolipids, especially to sphingosine-1-phosphate. In this work we studied the differences in the sphingolipi...

Alkylphospholipids are a novel class of antineoplastic drugs showing remarkable therapeutic potential. Among them, Erufosine (EPC3) is a promising drug for the treatment of several types of tumors which has not been sufficiently characterized. While EPC3 is supposed to exert its function by interacting with lipid membranes, the exact molecular mech...

The effect of genistein on the lipid compositions and sphingolipid metabolism has been investigated in A549 adenocarcinoma cells. The obtained results showed that sphingomyelin, phosphatidylserine and phosphatidylethanol-amine were augmented, whereas phosphatidylcholine was reduced as a result of genistein treatment. In order to reveal the mechanis...

Fibronectin is a multifunctional, extracellular matrix glycoprotein that exists either as an insoluble multimeric fibrillar component of the extracellular matrix or as a soluble monomer. Cells attach to fibronectin through transmembrane integrin receptors and form a variety of cell-matrix contacts. Here we show that primary fibroblasts can use fibr...

The effect of resveratrol on the lipid compositions and sphingolipid metabolism has been investigated in fibroblast three-dimensional cultures. The obtained results demonstrated that almost all tested membrane lipids remained unchanged except sphingomyelin which was augmented, and phosphatidylcholine, which was reduced as a result of resveratrol tr...

The aim of this study was to investigate the structural-functional peculiarities of chloroplast membranes of halophytic species with different adaptive strategy against soil salinity. Materials and Methods: Leaves of the euhalophyte Eryngium maritimum L. (Apiaceae) and glycohalophyte Polygonum maritimum L. (Polygonaceae) were collected in August 20...

Multiple sclerosis (MS), a leading cause of physical disability in young adults, is a chronic autoimmune neuroinflammatory disease characterized by axonal injury and demyelination. In this study, denaturational heat capacity profiles of blood plasma from MS patients were recorded by DSC and used to monitor the effect of therapeutic plasma exchange....

Purpose: Activation of CB1 receptors, produces anticonvulsant effect accompanied by memory disturbance both in animal seizure tests and in patients with epilepsy. Few reports considered the role of CB2 receptor on seizure susceptibility and cognitive functions. The aim of the present study was to explore the effect of a selective CB2 receptor agon...

For the purpose of revealing the impact of specific environmental conditions on photosynthetic process of medicinal plant Petasites hybridus, chlorophyll thermoluminescence, as indicator of energy balance and functioning of PSII reaction centres, chlorophyll content and fatty acid composition of chloro-plast membrane lipids in plants from different...

Halophyte plants possess a variety of adaptive strategies to deal with the extreme saline environments, including changes in the chloroplasts photosystem II activity and alterations in plant membrane lipids and their fatty acids composition. In this study extreme halophyte plant from Bulgarian Black sea coast, Lactuca tatarica, is selected as model...

The present study describes a live-cell biosensor, suitable for general evaluation of adhesion qualities of different substrates. It is based on NIH/3T3 fibroblast cell line stably expressing fusion fluorescently tagged proteins mCherry-vinculin and GFP-tensin as quantifiable markers for assessment not only of focal but also of fibrillar contacts....

The partial efficacy and high toxicity of the current anticancer chemotherapeutics as well as the development of multiple drug resistance are major problems in cancer therapy. Therefore, there is an emergency need for the development of novel well-tolerated anticancer agents with different mode of action that could be successfully used in combinati...

Vesicle cycling, an important biological event, involves the interplay between membrane lipids and proteins, among which the enzyme phospholipase A2 (PLA2) plays a critical role. The PLA2 capacity to trigger budding and fission of liquid-ordered (Lo) domains has been examined in palmitoyl-docosahexaenoyl phosphatidylcholine (PDPC) and palmitoyl-ole...

A number of neurological diseases are related to autoimmune pathogenesis. These are multiple sclerosis, Guillain–Barre syndrome, chronic inflammatory demyelinating polyneuropathy, monoclonal gammopathy, myasthenia, polymyositis, and others. The mentioned diseases are characterized by autoantibodies from immunocompetent cells connected to myelin of...

Hybrid materials based on tetraethylorthosilicate (TEOS), hydroxypropyl cellulose (HPC) or hydroxypropyl methyl cellulose (HPMC) with silver nanoparticles were synthesized. They were analyzed and characterized using differential thermal analysis and thermo gravimetry (DTA/TG), atomic force microscopy (AFM) and static contact angle (CA) measurements...

Hybrid materials based on tetraethyl orthosilicate (TEOS), hydroxypropyl cellulose (HPC), or hydroxypropyl methyl cellulose (HPMC) with silver nanoparticles were synthesized. They were analyzed and characterized using differential thermal analysis and thermogravimetry, atomic force microscopy, and static contact angle measurements. It was experimen...

Cell proliferation and metastasis are considered hallmarks of tumor progression. Therefore, efforts have been made to develop novel anticancer drugs that inhibit both the proliferation and the motility of tumor cells. Synthetic antitumor lipids (ATLs), which are chemically divided into two main classes, comprise (i) alkylphospholipids (APLs) and (i...

The phase separation of aminophospholipids in glycerophospholipid matrix and the effect of cholesterol were studied by means of fluorescence microscopy of giant unilamellar vesicles (GUV). GUVs were composed of binary mixtures, egg yolk phosphatidylcholine (eggPC)/egg yolk phosphatidylethanolamine (eggPE) and egg yolk phosphatidylcholine (eggPC)/br...

The understanding of the functional role of the lipid diversity in biological membranes is a major challenge. Lipid models have been developed to address this issue by using lipid mixtures generating liquid-ordered (Lo)/liquid-disordered (Ld) immiscibility. The present study examined mixtures comprising Egg sphingomyelin (SM), cholesterol (chol) an...

Objectives: Regulatory mechanisms of cell proliferation have been extensively studied as they represent major challenges when dealing with pathologies such as fibrosis, tumourigenesis or tissue regeneration. Numerous in vitro studies still exploit conventional, two-dimensional cell cultures where cells are forced to adhere to unnaturally stiff and...

Investigations were performed on the effect of xylooligosaccharide (XOS) intake on the phospholipid and fatty acid composition of rat liver plasma membranes. The results showed that phosphatidylcholine was elevated and lysophosphatidylcholine was reduced in liver plasma membranes of XOS-fed rats and these alterations were due to decrease of phospho...

Investigations were carried out on the changes in the alveolar surfactant lipids induced by administration of the antioxidant ascorbic acid in patients with adult respiratory distress syndrome (ARDS). The pulmonary surfactant phospholipids play an essential role in the maintenance of the alveolar surface activity and in the general physiological fu...

The effect of beta-glucan intake on cholesterol content and susceptibility to oxidative damage has been investigated in rat liver plasma membranes. The obtained results demonstrated that all tested membrane lipids remained almost unchanged except cholesterol, which was reduced as a result of beta-glucan intake. Since cholesterol (CH) is the only ma...

The antioxidant n-propyl gallate (nPG) is widely used in the food industry, pharmaceutics and cosmetics. Therefore, we should be well acquainted with its exact mechanism of action and its effects on the human organism, especially at the molecular level. Because of its slight solubility in water, it could be expected that, in cells, nPG would enter...

Xylooligosaccharides (XOS) are non-digestible carbohydrate prebiotics that beneficially affect the host by selective stimulation of specific bacteria in the gastro-intestinal tract. The impact of XOS on gastrointestinal microflora and blood lipids is well known but the exact mechanism of action on liver membranes is still unclear. The organization...

A study on the production of soluble and cell wall-bound glucansucrases (GS) and fructansucrases (FS) by Leuconostoc mesenteroides URE13 and L. mesenteroides Lm17 during their growth on media containing sucrose, glucose or fructose as a main carbon source was carried out. The changes in the enzyme activity, the assimilation of sugars and the format...

The influence of the prebiotic inulin on the level and sensitivity to oxida- tive attack has been investigated in rat liver plasma membranes. The obtained results showed that the oral administration of inulin in experimental animals induced a slight decrease of the content of cholesterol in liver plasma mem- branes. In addition, the susceptibility...

Giant unilamellar vesicles have become a versatile tool to mimic lateral membrane organization and membrane-associated processes in cells. The interest in sphingolipids has grown rapidly since the establishment of their role in cell signaling. This review summarizes our results on the impact of sphingolipids (sphingomyelin (SM), ceramide (CER), and...

Investigations were carried out on the applicability of L-buthionine-S, R-sulfoximine (BSO) for experimental development of a model of senescent cells in laboratory conditions. The obtained results showed that some of the typical alterations of the membrane lipids such as decrease of sphingomyelin and reduced glutathione, as well as elevation of ce...

The persistence of the defining characteristics of undifferentiated cells in vivo and in vitro is maintained via a complex interplay of several mechanisms, employing molecular events internal to the cell as well as signals originating outside the cell. The exogenous and the endogenous mechanisms maintaining stemness qualities of the cell are intric...

The aim of this study was to investigate the effects of testosterone replacement therapy (TRT) on erythrocyte membrane (EM) lipid composition and physico-chemical properties in hypogonadal men. EM isolated from three patients before and after TRT with injectable testosterone undecanoate or testosterone gel were used for analysis of the phospholipid...

Investigations were carried out on the effect of cholesterol reduction on the antioxidant potential of the avonoid quercetin in rat liver plasma membranes. The results showed that the accumulation of reactive oxygen species in intact membranes was significantly lower, compared to membranes with reduced content of cholesterol in the presence of quer...

Prebiotic intake is generally associated with alterations in the gastrointestinal microflora and blood serum lipids. However, less attention has been paid to the effect of prebiotics on the liver membrane lipids. We hypothesized that the reported alterations in the serum lipids might be related to changes in the liver membrane phospholipids in anim...

The influence of the oxidized phospholipid palmitoyl-oxovaleroyl-phosphocholine (POVPC) on membrane lateral organization was investigated using fluorescence microscopy. Giant unilamellar vesicles (GUVs) composed of palmitoyldocosahexaenoyl-phosphocholine (PDPC)/egg sphingomyelin (eggSM)/cholesterol (CHOL) mixtures were used as a model system mimick...

Sphingosine is a bioactive molecule which is known to participate in the regulation of a number of cellular processes such as apoptosis, cell differentiation, growth, etc. Sphingosine was observed to exhibit different domain morphology depending on the surrounding lipid matrix in biomimetic systems such as giant vesicles. Our current results showed...

The enormous potential of human embryonic stem cells is fueling continuous research aimed at establishment of new lines of these cells. Currently research groups from 24 countries have reported derivation of over 1000 human embryonic stem cell lines. Because of the controversy surrounding the derivation of these cells from human embryos it is impor...

The effect oftumor necrosis factor-α (TNF-α) on sphingomyelin (SM) turnover in human skin fibroblasts (HFS) was investigated. The activation of SM hydrolysis was observed to follow two different pathways depending on the concentration of TNF-α. Treatment of cells with 2 nM TNF-α induced the activation of phospholipase A3 with subsequent stimulation...

The three-dimensional (3D) cell culture approach offers a means to study cells under conditions that mimic an in vivo environment, thus avoiding the limitations imposed by the conventional two-dimensional (2D) monolayer cell cultures. By using this approach we demonstrated significant differences in the plasma membrane phospholipid composition and...

Interactions between cells and extracellular environment are mediated through specific cell adhesion sites. These structures are responsible for transmitting environmental signals, which affect essentially all aspects of a cell’s life, including proliferation, differentiation and death. The morphology, organization and type of signaling transmitted...

Investigations were carried out on the alterations in the lipid peroxide level in control and ras-transformed fibroblasts enriched with two polyunsaturated fatty acids with different degree of unsaturation (linoleic acid (LA) and eicosaheptoenoic acid (EPA)) before and after exposure to oxidative stress induced by hydrogen peroxide. The obtained re...

Here we report the derivation and characterization of a new human embryonic stem cell (hESC) line - BAM1. The line was established from morula stage discarded in vitro fertilization (IVF) embryos using an STO feeder layer. The cells expressed typical markers for undifferentiated hESCs including cell surface markers SSEA-4, TRA-1-60, transcription f...

The alterations in the lipid composition and the raft microdomain content in plasma membranes of fibroblasts exposed to oxidative attack have been investigated. The results show that treatment of cells with hydrogen peroxide induces reduction of the raft microdomain lipid components, sphingomyelin and cholesterol, as well as of some of the most uns...

Investigations were performed on the alterations of membrane-bound phospholipase A2 in plasma membranes of fibroblasts cultured as a monolayer (2D) and in three-dimensional (3D) environment. Since previous studies have shown that 2D and 3D cells exhibit different susceptibility to oxidative damage and also have different phospholipid acyl chains, w...

Most in vitro studies use 2-dimensional (2D) monolayer cultures, where cells are forced to adjust to unnatural substrates that differ significantly from the natural 3-dimensional (3D) extracellular matrix that surrounds cells in living organisms. Our analysis demonstrates significant differences in the cholesterol and sphingomyelin content, structu...

Fibronectin fibrillogenesis is a cell-mediated, step-wise process that converts soluble fibronectin into insoluble fibronectin matrix. The deposition of fibronectin fibrils occurs at specific sites on the cell surface and depends on the unfolding of the fibronectin dimer. Fibronectin matrix provides positional information for cell migration during...

The differences in the surface active properties of native lipids extracted from plasma membranes of cells cultured as a monolayer and in three-dimensional (3D) matrix were investigated. This experimental model was chosen because most of the current knowledge on cellular physiological processes is based on studies performed with conventional monola...

The dependence of membrane-bound alkaline phosphatase on the content of membrane sphingomyelin has been investigated. The level of membrane sphingomyelin has been manipulated by means of exogenous sphingomyelinase, which hydrolysed sphingomyelin molecules, yielding ceramide as a product. The results showed that the reduction of the level of membran...

Free-standing giant unilamellar vesicles were used to visualize the complex lateral heterogeneity, induced by ceramide in the membrane bilayer at micron scale using C(12)-NBD-PC probe partitioning under the fluorescence microscope. Ceramide gel domains exist as leaf-like structures in glycerophospholipid/ceramide mixtures. Cholesterol readily incre...

Research in cell signaling often depends on tissue culture, but the artificial substrates used to grow cells in vitro are likely to distort the conclusions, particularly when adhesion-mediated signaling events are investigated. Studies of signal transduction pathways operating in cells grown in three-dimensional (3D) matrices provide a better syste...

Pulmonary complications often accompany the development of acute peritonitis. In this study, we analyzed the alterations of alveolar surfactant phospholipids in rats with experimentally induced peritonitis. The results showed a reduction of almost all phospholipid fractions in pulmonary surfactant of experimental animals. The most abundant alveolar...

Halothane is a volatile anaesthetic, which is known to induce alterations in cellular plasma membranes, modulating the physical state of the membrane lipids and/or interacting directly with membrane-bound proteins, such as integrin receptors. Integrin-mediated cell adhesion is a general property of eukaryotic cells, which is closely related to cell...

Investigations were carried out on the effect of plasma membrane lipid modifications on the fusogenic capacity of control and ras-transformed fibroblasts. The plasma membrane lipid composition was modified by treatment of cells with exogenous phospholipases C and D, sphingomyelinase and cyclodextrin. The used enzymes hydrolyzed definite membrane li...

Investigations were carried out on the influence of phospholipid composition of model membranes on the processes of spontaneous lipid transfer between membranes. Acceptor vesicles were prepared from phospholipids extracted from plasma membranes of control and ras-transformed fibroblasts. Acceptor model membranes with manipulated levels of phosphati...

The effect of integrin receptors on the level and transmembrane localization of cholesterol molecules was investigated in beta1 integrin-expressing (beta1) and beta1 integrin-deficient (beta1 null) cells. We found that the content of specific raft components-cholesterol, sphingomyelin, and caveolin-was increased in integrin-expressing cells. Integr...

The lipid composition and structure of detergent-resistant membrane rafts from human, goat, and sheep erythrocytes is investigated. While the sphingomyelin:cholesterol ratio varied from about 1:5 in human to 1:1 in sheep erythrocytes a ratio of 1:1 was found in all raft preparations insoluble in Triton X-100 at 4 degrees C. Excess cholesterol is ex...