Modifications of erythrocyte membrane hydration induced by organic tin compounds

Determination of organotin compounds in marine sediments from Arctic Svalbard and West Antarctic Fildes Peninsula

This study investigated the contamination levels of five typical organotin compounds in Arctic and Antarctic marine sediments. Organotin total concentrations ranged from not detected (ND) to 37.9 ng Sn/g dw and from ND to 34.0 ng Sn/g dw in surface sediments of Svalbard and Fildes Peninsula, respectively. Dibutyltin accounted for 11.3 %-100 % of butyltins in Arctic sediments, whilst diphenyltin was the predominant phenyltin species in both Arctic and Antarctic. However, the concentrations of tributyltin and triphenyltin were lower than low-substituted organotins in the study areas, indicating the effectiveness of international ban on the use of triorganotin-based antifouling paints. No significant difference in organotin contamination was found between Arctic and Antarctic, although the time suffered from human interference was shorter in the Antarctic. Overall, these data can provide a diagnosis of recent organotin inputs in polar regions and serve as a baseline for future study assessing their local applications.

Changes in lipid membrane mechanics induced by di- and tri-phenyltins

Organotin compounds, being biologically active, affect a variety of cellular functions due to their ability to accumulate in and penetrate biological membranes. These compounds influence the distribution of electrostatic charges, alter organization, disrupt molecular dynamics and change mechanical properties of biological membranes. It was found that the membrane/water partition coefficient equals 4, a value significantly higher than octanol/water partition coefficient. In addition, the effect of di- and tri-phenyltin chlorides on the mechanics of model lipid membranes was measured for the first time. It has been determined that phenyltins affect the global model lipid bilayer properties by reducing the membrane expansion modulus, when measured using micromanipulation technique, and elevating the bending rigidity coefficient of the lipid bilayer, as determined with the flickering noise spectroscopy. In addition, the elevated water permeability shows that phenyltins also cause the local defects formation in the lipid bilayer, i.e. lipid pores. These data shows that phenyltins may interfere indirectly with variety cellular processes by altering non-specifically the entire cellular membrane system. Accordingly, when phenyltins are added to macrophages in culture, they inflict massive alterations of cell morphology and interfere with membrane-associated processes, as visualized using fluorescence labelling of selected subcellular compartments.

Physical Effects of Buckwheat Extract on Biological Membrane In Vitro and Its Protective Properties

Buckwheat is a valuable source of many biologically active compounds and nutrients. It has properties that reduce blood cholesterol levels, and so reduces the risk of atherosclerosis, seals the capillaries, and lowers blood pressure. The aim of the study was to determine quantitative and qualitative characteristics of polyphenols contained in extracts from buckwheat husks and stalks, the biological activity of the extracts, and biophysical effects of their interaction with the erythrocyte membrane, treated as a model of the cell. An analysis of the extract’s composition has shown that buckwheat husk and stalk extracts are a rich source of polyphenolic compounds, the stalk extracts showing more compounds than the husk extract. The study allowed to determine the location which incorporated polyphenols occupy in the erythrocyte membrane and changes in the membrane properties caused by them. It was found that the extracts do not induce hemolysis of red blood cells, causing an increase in osmotic resistance of erythrocytes. They affect mainly the hydrophilic region by changing the degree of order of the polar heads of lipids, but do little to change the fluidity of the membrane and its hydration. The results showed also that polyphenolic substances included in the extracts well protect the membranes of red blood cells against oxidation and exhibit anti-inflammatory effect.

Effect of Trimethyltin Chloride on Slow Vacuolar (SV) Channels in Vacuoles from Red Beet (Beta vulgaris L.) Taproots

In the present study, patch-clamp techniques have been used to investigate the effect of trimethyltin chloride (Met3SnCl) on the slow vacuolar (SV) channels in vacuoles from red beet (Beta vulgaris L.) taproots. Activity of SV channels has been measured in whole-vacuole and cytosolic side-out patch configurations. It was found that addition of trimethyltin chloride to the bath solution suppressed, in a concentration-dependent manner, SV currents in red beet vacuoles. The time constant, τ, increased significantly in the presence of the organotin. When single channel activity was analyzed, only little channel activity could be recorded at 100 μM Met3SnCl. Trimethyltin chloride added to the bath medium significantly decreased (by ca. threefold at 100 μM Met3SnCl and at 100 mV voltage, as compared to the control medium) the open probability of single channels. Single channel recordings obtained in the presence and absence of trimethyltin chloride showed that the organotin only slightly (by <10%) decreased the unitary conductance of single channels. It was also found that Met3SnCl significantly diminished the number of SV channel openings, whereas it did not change the opening times of the channels. Taking into account the above and the fact that under the here applied experimental conditions (pH = 7.5) Met3SnCl is a non-dissociated (more lipophilic) compound, we suggest that the suppression of SV currents observed in the presence of the organotin results probably from its hydrophobic properties allowing this compound to translocate near the selectivity filter of the channel.

Triphenyltin biodegradation and intracellular material release by Brevibacillus brevis

Triphenyltin (TPT) is an endocrine disruptor that has polluted the global environment, and thus far, information regarding the mechanisms of TPT biodegradation and intracellular material release is limited. Here, TPT biodegradation was conducted by using Brevibacillus brevis. Degradation affecting factors, metabolite formation, ion and protein release, membrane permeability, and cell viability after degradation were investigated to reveal the biodegradation mechanisms. The results showed that TPT could be degraded simultaneously to diphenyltin and monophenyltin, with diphenyltin further degraded to monophenyltin, and ultimately to inorganic tin. During degradation process, B. brevis metabolically released Cl(-) and Na(+), and passively diffused Ca(2+). Protein release and membrane permeability were also enhanced by TPT exposure. pH ranging from 6.0 to 7.5 and relatively high biomass dosage in mineral salt medium improved TPT degradation. Biodegradation efficiency of 0.5 mg L(-1) TPT by 0.3 g L(-1)B. brevis at 25 °C for 5d was up to 80%.

Biological activity of blackcurrant Extracts (Ribes nigrum L.) in relation to erythrocyte membranes

Compounds contained in fruits and leaves of blackcurrant (Ribes nigrum L.) are known as agents acting preventively and therapeutically on the organism. The HPLC analysis showed they are rich in polyphenol anthocyanins in fruits and flavonoids in leaves, that have antioxidant activity and are beneficial for health. The aim of the research was to determine the effect of blackcurrant fruit and leaf extracts on the physical properties of the erythrocyte membranes and assess their antioxidant properties. The effect of the extracts on osmotic resistance, shape of erythrocytes and hemolytic and antioxidant activity of the extracts were examined with spectrophotometric methods. The FTIR investigation showed that extracts modify the erythrocyte membrane and protect it against free radicals induced by UV radiation. The results show that the extracts do not induce hemolysis and even protect erythrocytes against the harmful action of UVC radiation, while slightly strengthening the membrane and inducing echinocytes. The compounds contained in the extracts do not penetrate into the hydrophobic region, but bind to the membrane surface inducing small changes in the packing arrangement of the polar head groups of membrane lipids. The extracts have a high antioxidant activity. Their presence on the surface of the erythrocyte membrane entails protection against free radicals.

The obesogen tributyltin

The obesogen hypothesis postulates the role of environmental chemical pollutants that disrupt homeostatic controls and adaptive mechanisms to promote adipose-dependent weight gain leading to obesity and metabolic syndrome complications. One of the most direct molecular mechanisms for coupling environmental chemical exposures to perturbed physiology invokes pollutants mimicking endogenous endocrine hormones or bioactive dietary signaling metabolites that serve as nuclear receptor ligands. The organotin pollutant tributyltin can exert toxicity through multiple mechanisms but most recently has been shown to bind, activate, and mediate RXR-PPARγ transcriptional regulation central to lipid metabolism and adipocyte biology. Data in support of long-term obesogenic effects on whole body adipose tissue are also reported. Organotins represent an important model test system for evaluating the impact and epidemiological significance of chemical insults as contributing factors for obesity and human metabolic health.

The location of organotins within the erythrocyte membrane in relation to their toxicity

The aim of the present study on organotin compounds, which are toxic to biological systems, was to determine the relationship between the compounds' toxicity and their location in the lipid bilayer of the biological membrane. It was assumed that the degree of disturbance caused within the lipid bilayer of the membrane, which in turn depends on the depth of incorporation, was an appropriate measure of toxicity. Previous results from our studies on the effect of organotin chlorides on membranes, made by using infrared radiation and hemolysis of erythrocytes, indicated that tributyltin (TBT) is the most active in terms of its interaction with the erythrocyte membrane. This compound causes the most severe hemolysis of erythrocytes and dehydration of membrane constituents. In order to connect the changes induced within the membrane structure with the compounds' location, we have investigated erythrocyte shape changes using both microscopic and fluorimetric methods. The microscopic results show that organotin compounds accumulate in the outer monolayer of the membrane. The fluorimetric studies indicate that all the compounds are present in the hydrophilic part of the outer lipid monolayer, and change the order parameter of the layer. However, only tributyltin, by being incorporated into the hydrophobic region of the monolayer, changes the fluidity in the alkyl chain region of the erythrocyte membrane. Furthermore, only TBT is present in both the hydrophilic and hydrophobic regions, as evidenced by the changed order parameter of the polar groups and fluorescence anisotropy of DPH probe in the hydrophobic region, these being connected with its high toxicity.

Structural and functional changes in gill mitochondrial membranes from the Mediterranean mussel Mytilus galloprovincialis exposed to tri-n-butyltin

The use of tributyltin (TBT) as a biocide in antifouling paints leads to a ruinous input of this contaminant in the aquatic environment. Human exposure to TBT mainly occurs through ingestion of contaminated seafood such as filter-feeding mollusks. Tributyltin is known to act as a membrane-active toxicant on several targets, but especially on the mitochondria, and by several mechanisms. The effects of tributyltin on fatty acid composition, on Mg-adenosine triphosphatase (ATPase) activities, and on the membrane physical state were investigated in gill mitochondrial membranes from cultivated mussels Mytilus galloprovincialis exposed to 0.5 µg/L and 1.0 µg/L TBT and unexposed for 120 h. The higher TBT exposure dose induced a decrease in the total and n-3 polyunsaturated fatty acids (PUFAs), especially 22:6 n-3, and an activation of the oligomycin-sensitive Mg-ATPase. Both TBT concentrations decreased mitochondrial membrane polarity detected by Laurdan steady-state fluorescence spectroscopy. These findings may help cast light on the multiple modes of action of this toxicant.

Interaction between plant polyphenols and the erythrocyte membrane

The purpose of these studies was to determine the effect of polyphenols contained in extracts from apple, strawberry and blackcurrant on the properties of the erythrocyte membrane, treated as a model of the biological membrane. To this end, the effect of the substances used on hemolysis, osmotic resistance and shape of erythrocytes, and on packing order in the hydrophilic region of the erythrocyte membrane was studied. The investigation was performed with spectrophotometric and fluorimetric methods, and using the optical microscope. The hemolytic studies have shown that the extracts do not induce hemolysis at the concentrations used. The results obtained from the spectrophotometric measurements of osmotic resistance of erythrocytes showed that the polyphenols contained in the extracts cause an increase in the resistance, rendering them less prone to hemolysis in hypotonic solutions of sodium chloride. The fluorimetric studies indicate that the used substances cause a decrease of packing order in the hydrophilic area of membrane lipids. The observations of erythrocyte shapes in a biological optical microscope have shown that, as a result of the substances' action, the erythrocytes become mostly echinocytes, which means that the polyphenols of the extracts localize in the outer lipid monolayer of the erythrocyte membrane. The results obtained indicate that, in the concentration range used, the plant extracts are incorporated into the hydrophilic area of the membrane, modifying its properties.

Vibrational spectroscopy of biomembranes

Vibrational spectroscopy, commonly associated with IR absorption and Raman scattering, has provided a powerful approach for investigating interactions between biomolecules that make up cellular membranes. Because the IR and Raman signals arise from the intrinsic properties of these molecules, vibrational spectroscopy probes the delicate interactions that regulate biomembranes with minimal perturbation. Numerous innovative measurements, including nonlinear optical processes and confined bilayer assemblies, have provided new insights into membrane behavior. In this review, we highlight the use of vibrational spectroscopy to study lipid-lipid interactions. We also examine recent work in which vibrational measurements have been used to investigate the incorporation of peptides and proteins into lipid bilayers, and we discuss the interactions of small molecules and drugs with membrane structures. Emerging techniques and measurements on intact cellular membranes provide a prospective on the future of vibrational spectroscopic studies of biomembranes.