[Show abstract][Hide abstract] ABSTRACT: Common hop (Humulus lupulus) constitutes a source of numerous prenylated chalcones such as xanthohumol (XH) and flavanones such as 8-prenylnaringenin (8-PN) and isoxanthohumol (IXH). Range of their biological activities includes estrogenic, anti-inflammatory, anti-infective, anti-cancer, and antioxidant activities. Aim of the present work was to characterize the influence of prenylated polyphenols on model 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes by means of differential scanning calorimetry (DSC), fluorescence and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopies. All studied compounds intercalated into DPPC bilayers and decreased is melting temperature as recorded by DSC, Laurdan and Prodan fluorescence, and ATR-FTIR. Polyphenols interacted mainly with glycerol backbone and acyl chain region of membrane. Magnitude of the induced effect correlated both with lipophilicity and molecular shape of the studied compounds. Elbow-shaped 8-PN and IXH were locked at polar-apolar region with their prenyl chains penetrating into hydrophobic part of the bilayer, while relatively planar XH molecule adopted linear shape that resulted in its deeper insertion into hydrophobic region. Additionally, by means of DSC and Laurdan fluorescence IXH was demonstrated to induce lateral phase separation in DPPC bilayers in gel-like state. It was assumed that IXH-rich and IXH-poor microdomains appeared within membrane. Present work constitutes the first experimental report describing interactions of prenylated hop polyphenols with phospholipid model membranes.
[Show abstract][Hide abstract] ABSTRACT: The resistance of cancer cells to multiple chemotherapeutic agents remains a major obstacle in cancer therapy (1). Cancer cell lines developed in vitro have provided significant insights into the mechanisms of multidrug resistance. Cell lines which are highly resistant to a variety of anticancer agents can be obtained by slowly increasing the concentration of cytotoxic agents in the growth medium. The phenomenon of multidrug resistance (MDR) is not restricted to mammalian cells - it occurs from cancer cells to microorganisms. Homologues of mammalian MDR genes have been identified in bacteria, fungi and protozoan parasites (2-4). Most organisms appear to have developed a lot of strategies to protect them from toxic environmental compounds. A variety of these specific genetic changes have been identified in cancer cells and they are capable of protecting these cells from multiple chemotherapeutic agents. Mechanisms of drug resistance in cancer One of the protection mechanisms of cancer cells is an increased efflux of cytotoxic compounds out of the cell due to an increased expression of membrane transport proteins such as P- glycoprotein (MDR1) or multidrug resistance associated protein (MRP) (5). P-glycoprotein (P-gp) is believed to be one of the key molecules which cause multidrug resistance in cancer. Transmembrane glycoprotein Pögp is an ATPödependent extrusion pump which confers cross-resistance to a variety of structurally- unrelated cytotoxic agents, such as anthracyclines, taxanes, vinca alkaloids and other drugs which are widely used in cancer treatment. P-gp is a member of the ATP-binding cassette (ABC) superfamily of proteins (6). A prominent member of the ABC superfamily of transporters is CFTR - cystic fibrosis transmembrane conductance regulator. CFTR is a chloride channel which malfunctions in cystic fibrosis. P-gp consists of four distinct domains. Two of these are highly hydrophobic, integral membrane domains, each of which spans the membrane six times by alfa-helices. The other two are hydrophilic nucleotide-binding domains (NBDs). Recently, a 2 .5 nm resolution structure of P- gp was obtained by electron microscopy and single-particle image analysis (7). In the P-gp molecule there is a large central pore, ~5 nm in diameter, which is closed at the inner (cytoplasmic) side of the plasma membrane. A gap may be present in the
[Show abstract][Hide abstract] ABSTRACT: Multidrug resistance (MDR) of cancer cells constitutes one of the main reasons for chemotherapy failure. The search for nontoxic modulators that reduce MDR is a task of great importance. An ability to enhance apoptosis of resistant cells would also be beneficial. In the present study, the MDR reversal and apoptosis-inducing potency of three flavonoids produced by Citrus plants, namely, naringenin (1a), aromadendrin (2), and tangeretin (3), and the methylated naringenin derivatives (1b, 1c), have been studied in sensitive (LoVo) and multidrug-resistant (LoVo/Dx) human colon adenocarcinoma cells. Cytotoxicity of methoxylated flavonoids was higher as compared to hydroxylated analogues. Only 3 turned out to inhibit P-glycoprotein, as demonstrated by a rhodamine 123 accumulation assay. It also increased doxorubicin accumulation in LoVo/Dx cells and enabled doxorubicin to enter cellular nuclei. In addition, 3 was found to be an effective MDR modulator in resistant cells by sensitizing them to doxorubicin. Tangeretin-induced caspase-3 activation and elevated surface phosphatidylserine exposure demonstrated its apoptosis-inducing activity in LoVo/Dx cells, while the other flavonoids evaluated were not active. Additionally, 3 was more toxic to resistant rather than to sensitive cancer cells. Its apoptosis-inducing activity was also higher in LoVo/Dx than in LoVo cells. It was concluded that the activity of 3 against multidrug-resistant cancer cells may be enhanced by its apoptosis-inducing activity.
Journal of Natural Products 11/2012; · 3.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Multidrug resistance (MDR) of cancer cells poses a serious obstacle to successful chemotherapy. The overexpression of multispecific ATP-binding cassette transporters appears to be the main mechanism of MDR. A search for MDR-reversing agents able to sensitize resistant cells to chemotherapy is ongoing in the hope of their possible clinical use. Studies of MDR modulators, although they have not produced clinically beneficial effects yet, may greatly enrich our knowledge about MDR transporters, their specificity and mechanism of action, especially substrate and/or inhibitor recognition. In the present review, interactions of three groups of modulators: phenothiazines, flavonoids and stilbenes with both P-glycoprotein and MRP1 are discussed. Each group of compounds is likely to interact with the MDR transporters by a different mechanism. Phenothiazines probably interact with drug binding sites, but they also could indirectly affect the transporter's activity by perturbing lipid bilayers. Flavonoids mainly interact with ABC proteins within their nucleotide-binding domains, though the more hydrophobic flavonoids may bind to regions within transmembrane domains. The possible mechanism of MDR reversal by stilbenes may result from their direct interaction with the transporter (possibly within substrate recognition sites) but some indirect effects such as stilbene-induced changes in gene expression pattern and in apoptotic pathways should also be considered. Literature data as well as some of our recent results are discussed. Special emphasis is put on cases when the interactions of a given compound with both P-glycoprotein and MRP1 have been studied simultaneously.
[Show abstract][Hide abstract] ABSTRACT: Genistein (5,7,4'-trihydroxyisoflavone) the common soy beans isoflavone has attracted scientific interest due to its antioxidant, estrogenic, antiangiogenic and aniticancer activities. The aim of the present study was to investigate the interaction of genistein with biological (erythrocyte) and model membranes (dimyristoyl- and dipalmitoylphosphatidylcholine). Using Laurdan and Prodan as fluorescent probes, we demonstrated phase behavior and membrane fluidity changes induced by genistein. ESR spectroscopy revealed alterations caused by genistein in membrane domains structure and mobility of spin probes with free radicals located at different depths of membrane. The method of ESR spectra decomposition and computer simulation of the recorded spectra were used in order to visualize domain coexistence by GHOST condensation method. Fluorescence and ESR spectroscopy experiments performed at different temperatures enabled us to observe the effect of isoflavone on phospholipid bilayers in either gel or liquid crystalline phase. It was concluded that genistein preferentially intercalated into lipid headgroup region, to some extent into polar-apolar interface and only in minimal degree into hydrophobic core of the membrane. According to our best knowledge this is the first study on modification of domain structure of membranes by genistein.
Chemistry and Physics of Lipids 03/2011; 164(4):283-91. · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Lipid rafts constitute dynamic assemblies within a bilayer, engaged in, e.g., signal transduction, membrane trafficking and cell polarization. Despite wide interest in the process of domain formation in binary or ternary lipid model systems, only a limited number of papers are devoted to the influence of different additives on this process. In particular, works devoted to the role of drugs in raft formation are missing. In the present study, the influence of trifluoperazine, thioridazine and chlorpromazine on domain organization in raft-mimicking model membranes was investigated. Using giant unilamellar vesicles formed from an equimolar DOPC:sphingomyelin:cholesterol mixture, we found that phenothiazines elevated the number of domains, decreased their area and markedly increased the total length of the domain border. The impact of studied drugs on phase separation in the raft lipid mixture was also confirmed by Laurdan generalized polarization measurements. Alteration of domain organization induced by antipsychotic drugs was very likely to arise from selective accumulation of phenothiazines in interfacial regions between liquid ordered and liquid disordered domains. Interpretation of the results allowed us to demonstrate new aspects underlaying mechanisms of action of phenothiazine-type antipsychotic drugs. To the best of our knowledge, this is the first report demonstrating the influence of drugs on domain morphology directly visualized in giant unilamellar vesicles.
[Show abstract][Hide abstract] ABSTRACT: Flavonoids with hydrophobic e.g. prenyl substituents might constitute the promising candidates for multidrug resistance (MDR) reversal agents. The interaction of 8-prenylnaringenin (8-isopentenylnaringenin), a potent phytoestrogen isolated from common hop (Humulus lupulus), with two multidrug resistance-associated ABC transporters of cancer cells, P-glycoprotein and MRP1, has been studied for the first time. Functional test based on the transport of fluorescent substrate BCECF revealed that the flavonoid strongly inhibited MRP1 transport activity in human erythrocytes (IC(50)=5.76+/-1.80muM). Expression of MDR-related transporters in drug-sensitive (LoVo) and doxorubicin-resistant (LoVo/Dx) human colon adenocarcinoma cell lines was characterized by RT-PCR and immunochemical methods and elevated expression of P-glycoprotein in resistant cells was found to be the main difference between these two cell lines. By means of flow cytometry it was shown that 8-prenylnaringenin significantly increased the accumulation of rhodamine 123 in LoVo/Dx cells. Doxorubicin accumulation in both LoVo and LoVo/Dx cells observed by confocal microscopy was also altered in the presence of 8-prenylnaringenin. However, the presence of the studied compound did not increase doxorubicin cytotoxicity to LoVo/Dx cells. It was concluded that 8-prenylnaringenin was not able to modulate MDR in human adenocarcinoma cell line in spite of the ability to inhibit both P-glycoprotein and MRP1 activities. To our best knowledge, this is the first report of 8-prenylnaringenin interaction with clinically important ABC transporters.
European journal of pharmacology 10/2010; 644(1-3):32-40. · 2.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Resveratrol and piceatannol are plant-derived polyphenols possessing extremely wide range of biological activities such as cancer chemopreventive, cardio- and neuroprotective, antioxidant, anti-inflammatory, anticancer and lifespan extending properties. Despite great interest in these stilbenes, their interactions with lipid bilayers have not been extensively studied. In the present work, the interaction of both resveratrol and piceatannol with model membranes composed of phosphatidylcholine (DMPC and DPPC) was investigated by means of fluorescence spectroscopy, differential scanning calorimetry (DSC) and electron spin resonance spectroscopy (ESR). Generalized polarization of two fluorescent probes Laurdan and Prodan measured in pure lipid and lipid:stilbene mixtures revealed that resveratrol and piceatannol changed bilayer properties in both gel-like and liquid crystalline phase and interacted with lipid headgroup region of the membrane. These findings were corroborated by DSC experiments in which the stilbene-induced decrease of lipid melting temperature and transition cooperativity were recorded. Resveratrol and piceatannol restricted also the ESR-measured mobility of spin probes GluSIN18, 5DSA and 16DSA with nitroxide group localized at different depths. Since the most pronounced effect was exerted on the spin probe located near membrane surface, we concluded that also ESR results pointed to the preferential interaction of resveratrol and piceatannol with headgroup region of lipid bilayer.
Biochimica et Biophysica Acta 07/2009; 1788(9):1851-60. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Model systems such as black lipid membranes or conventional uni- or multilamellar liposomes are commonly used to study membrane properties and structure. However, the construction and dimensions of these models excluded their direct optical microscopic observation. Since the introduction of the simple method of liposome electroformation in alternating electric field giant unilamellar vesicles (GUVs) have become an important model imitating biological membranes. Due to the average diameter of GUVs reaching up to 100 microm, they can be easily observed under a fluorescent or confocal microscope provided that the appropriate fluorescent probe was incorporated into the lipid phase during vesicle formation. GUVs can be formed from different lipid mixtures and they are stable in a wide range of physical conditions such as pH, pressure or temperature. This mini-review presents information about the methods of GUV production and their usage. Particularly, the use of GUVs in studying lipid phase separation and the appearance and behavior of lipid domains (rafts) in membranes is discussed but also other examples of GUVs use in membrane research are given. The experience of the authors in setting up the GUV-forming equipment and production of GUVs is also presented.
[Show abstract][Hide abstract] ABSTRACT: The expression of transmembrane transporter multidrug resistance-associated protein 1 (MRP1) confers the multidrug-resistant
phenotype (MDR) on cancer cells. Since the activity of the other MDR transporter, P-glycoprotein, is sensitive to membrane
perturbation, we aimed to check whether the changes in lipid bilayer properties induced by flavones (apigenin, acacetin) and
flavonols (morin, myricetin) were related to their MRP1 inhibitory activity. All the flavonoids inhibited the efflux of MRP1
fluorescent substrate from human erythrocytes and breast cancer cells. Morin was also found to stimulate the ATPase activity
of erythrocyte ghosts. All flavonoids intercalated into phosphatidylcholine bilayers as judged by differential scanning calorimetry
and fluorescence spectroscopy with the use of two carbocyanine dyes. The model of an intramembrane localization for flavones
and flavonols was proposed. No clear relationship was found between the membrane-perturbing activity of flavonoids and their
potency to inhibit MRP1. We concluded that mechanisms other than perturbation of the lipid phase of membranes were responsible
for inhibition of MRP1 by the flavonoids.
[Show abstract][Hide abstract] ABSTRACT: Lipid rafts are membrane structures enriched in cholesterol, sphingomyelin and glycolipids. In majority raft-mimicking model systems high contents of cholesterol and sphingomyelin (approximately 30 mol%) are used. Existence of raft-like structures was, however, reported also in model and natural membranes containing low levels of cholesterol and sphingomyelin. In the present work differential scanning calorimetry and fluorescence spectroscopy with the use of Laurdan probe was employed to demonstrate the existence of phase separation in model systems containing DPPC with addition of 5 mol% or 10 mol% of both cholesterol and sphingomyelin. Additionally, the influence of three phenothiazine derivatives on phase separation in mixed DPPC/cholesterol/sphingomyelin bilayers was investigated. Chlorpromazine, thioridazine and trifluoperazine were able to induce phase separation in DPPC and DPPC/cholesterol/sphingomyelin bilayers in temperatures below lipid main phase transition. However, only trifluoperazine induced phase separation in temperatures close to or above main phase transition. Trifluoperazine also induced phase separation in bilayers composed of egg yolk PC or DOPC mixed with cholesterol and sphingomyelin. We concluded that presence of lipid domains can be observed in model membranes containing low levels of cholesterol and sphingomyelin. Among three phenothiazine derivatives studied, only trifluoperazine was able to induce a permanent phase separation in phosphatidylcholine/cholesterol/sphingomyelin systems.
[Show abstract][Hide abstract] ABSTRACT: Phenothiazine derivatives as well as flavonoids belong to heterocyclic compounds that exert numerous
effects on biological systems. The structure of these compounds enables their specific interactions with
different membrane proteins and also nonspecific interactions with the lipid phase of membranes. In the
present review we focus on the influence of phenothiazines and flavonoids on lipid bilayers and other model
systems, and on two groups of membrane proteins: transporters involved in the phenomenon of multidrug resistance
and ion channels. Most of the compounds described in this paper interact with membranes and affect different
properties of lipid bilayers. Modification of membrane properties should contribute to mechanisms underlying
certain types of biological activity of the discussed molecules. Structural features essential for the
modulatory effects exerted by phenothiazines and flavonoids on multidrug transporters are presented. Also
various types of response of voltage-gated and chemically activated ion channels to the presence of heterocyclic
compounds are reviewed.
[Show abstract][Hide abstract] ABSTRACT: AIM: Silybin (silibinin) is major biologically active flavonolignan extracted from milk thistle (Sylibum marianum). Its biological activities include hepato-protection, anticancer properties, and antioxidant- and membrane-stabilizing functions. Although membranes are postulated to be one of the cellular targets for silybin, little is known about its interaction with phospholipid bilayers. METHODS: In the present work, the interactions of silybin with phosphatidylcholine bilayers were studied in detail using fluorescence spectroscopy, microcalorimetry and electron spin resonance techniques. RESULTS: The results showed that silybin interacted with the surface of lipid bilayers. It affected the generalized polarization of the fluorescent probe Prodan, while not influencing the more deeply located Laurdan. Silybin lowered the main phospholipid phase transition temperature as judged by microcalorimetry, and caused the immobilization of spin probe Tempo-palmitate located on the surface of membranes. The mobility of spin probes 5- and 16-doxyl stearic acid was not affected by silybin. Silybin-induced quenching of 1,6-diphenyl-1,3,5-hexatriene fluorescence indicated that some flavonoid molecules partitioned into the hydrophobic region of membranes, which did not change significantly the biophysical properties of the deeper membrane regions. CONCLUSION: Such a behavior of silybin in membranes is in accordance with its postulated biological functions and neglectable side effects of therapies using silybin.
[Show abstract][Hide abstract] ABSTRACT: The expression of multidrug resistance-associated protein (MRP1) results in ATP-dependent reduction of drugs' concentration in cancer cells, i.e., multidrug resistance (MDR). Since the majority of projects are concentrated on the search of the new MDR modulators, there are very few reports on drug-induced stimulation of MDR transporters activity. In the present work, by means of functional fluorescence assay we have shown that MRP1-mediated efflux of 2',7'-bis-(3-carboxypropyl)-5-(and-6)-carboxyfluorescein (BCPCF) out of human erythrocytes is stimulated by phenothiazine maleates that have been already identified as P-glycoprotein inhibitors. Phenothiazine maleates-induced stimulation of ATP-dependent uptake of 2',7'-bis-(3-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) into inside-out membrane vesicles prepared from erythrocyte membranes has been also demonstrated. Moreover, it was shown that phenothiazine maleates exerted stimulating effect on ATPase activity measured in erythrocyte membranes. To our best knowledge, this report is the first one demonstrating that compounds able to inhibit transport activity of P-glycoprotein can stimulate MRP1 transporter. We conclude that phenothiazine maleates probably exert their stimulatory effect on MRP1 by direct interaction with the protein at the site different from the substrate binding site.
Biochimica et Biophysica Acta 01/2006; 1720(1-2):52-8. · 4.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Substances able to modulate multidrug resistance (MDR), including antipsychotic phenothiazine derivatives, are mainly cationic amphiphiles. The molecular mechanism of their action can involve interactions with transporter proteins as well as with membrane lipids. The interactions between anionic phospholipids and MDR modulators can be crucial for their action. In present work we study interactions of 2-trifluoromethyl-10-(4-[methanesulfonylamid]buthyl)-phenothiazine (FPhMS) with neutral (PC) and anionic lipids (PG and PS). Using microcalorimetry, steady-state and time-resolved fluorescence spectroscopy we show that FPhMS interacts with all lipids studied and drug location in membrane depends on lipid type. The electrostatic attraction between drug and lipid headgroups presumably keeps phenothiazine derivative molecules closer to surface of negatively charged membranes with respect to neutral ones. FPhMS effects on bilayer properties are not proportional to phosphatidylserine content in lipid mixtures. Behavior of equimolar PC:PS mixtures is similar to pure PS bilayers, while 2:1 or 1:2 (mole:mole) PC:PS mixtures resemble pure PC ones.
[Show abstract][Hide abstract] ABSTRACT: The phenothiazine multidrug resistance (MDR) modulators are chemically diversified but share the common feature to be hydrophobic cationic molecules. Molecular mechanisms of their action may involve interactions with either P-glycoprotein or membrane lipid matrix. In the present work we study the anti-MDR and biophysical membrane effects of new phenothiazine derivatives differing in the type of group substituting phenothiazine ring at position 2 (H-, Cl-, CF(3)-) and in the side chain group (NHCO(2)CH(3) or NHSO(2)CH(3)). Within each phenothiazine subset we found that anti-MDR activity (determined by P-glycoprotein inhibition assessed by flow cytometry) correlates with the theoretically calculated hydrophobicity value (logP) and experimental parameters (determined by calorimetry and fluorescence spectroscopy) of lipid bilayers. It is concluded that the biological and biophysical activity of phenothiazine derivatives depends more on the type of ring substitution than on the nature of the side chain group.
Biochemical and Biophysical Research Communications 06/2003; 304(2):260-5. · 2.28 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Although phenothiazines are known as multidrug resistance modifiers, the molecular mechanism of their activity remains unclear. Since phenothiazine molecules are amphiphilic, the interactions with membrane lipids may be related, at least partially, to their biological effects. Using the set of phenothiazine maleates differing in the type of phenothiazine ring substitution at position 2 and/or in the length of the alkyl bridge-connecting ring system and side chain group, we investigated if their ability to modulate the multidrug resistance of cancer cells correlated with model membrane perturbing potency. The influence exerted on lipid bilayers was determined by liposome/buffer partition coefficient measurements (using the absorption spectra second-derivative method), fluorescence spectroscopy and calorimetry. Biological effects were assessed by a flow cytometric functional test based on differential accumulation of fluorescent probe DiOC(2)(3) by parental and drug-resistant cells. We found that all phenothiazine maleates were incorporated into lipid bilayers and altered their biophysical properties. With only few exceptions, the extent of membrane perturbation induced by phenothiazine maleates correlated with their lipophilicity. Within the group of studied derivatives, the compounds substituted with CF(3)- at position 2 of phenothiazine ring were the most active membrane perturbants. No clear relation was found between effects exerted by phenothiazine maleates on model membranes and their ability to modulate P-glycoprotein transport activity.
[Show abstract][Hide abstract] ABSTRACT: Using fluorescence spectroscopy, calorimetry and ESR the interactions of the phenothiazine derivative 2-trifluoromethyl-10-(4-[methylsulfonylamid]buthyl)-phenothiazine (FPhMS) with lipids were studied. Calorimetry showed biphasic effect of FPhMS on main phase transition of DPPC. At molar ratios up to 0.06 drug induced decrease of transition temperature and enthalpy, while at higher concentrations it caused subsequent increase of these parameters. For all concentrations studied we observed gradual broadening of transition peaks. Fluorescence polarization revealed that in FPhMS/lipid mixtures, order in bilayers is decreased in the gel state and increased in the liquid crystalline state. ESR experiment showed that at molar ratio of 0.06, FPhMS reduces the mobility of spin probes located in both polar and hydrophobic regions. Comparing observed effects with those reported for cholesterol/lipid mixtures, we conclude that at higher concentrations FPhMS presumably induces a new mode of bilayer packing. This structure is less co-operative than an unperturbed bilayer, but locally the mobility of lipid molecules is decreased.