In vitro effects of the anti-Alzheimer drug memantine on the human erythrocyte membrane and molecular models

Differential scanning calorimetry in drug-membrane interactions

Differential Scanning Calorimetry (DSC) is a central technique in investigating drug - membrane interactions, a critical component of pharmaceutical research. DSC measures the heat difference between a sample of interest and a reference as a function of temperature or time, contributing essential knowledge on the thermally induced phase changes in lipid membranes and how these changes are affected by incorporating pharmacological substances. The manuscript discusses the use of phospholipid bilayers, which can form structures like unilamellar and multilamellar vesicles, providing a simplified yet representative membrane model to investigate the complex dynamics of how drugs interact with and penetrate cellular barriers. The manuscript consolidates data from various studies, providing a comprehensive understanding of the mechanisms underlying drug - membrane interactions, the determinants that influence these interactions, and the crucial role of DSC in elucidating these components. It further explores the interactions of specific classes of drugs with phospholipid membranes, including non-steroidal anti-inflammatory drugs, anticancer agents, natural products with antioxidant properties, and Alzheimer's disease therapeutics. The manuscript underscores the critical importance of DSC in this field and the need for continued research to improve our understanding of these interactions, acting as a valuable resource for researchers.

A rhein-huprine hybrid protects erythrocyte membrane integrity against Alzheimer's disease related Aβ(1-42) peptide

Alzheimer's disease remains largely unknown, and currently there is no complete cure for the disease. New synthetic approaches have been developed to create multi-target agents, such as RHE-HUP, a rhein-huprine hybrid which can modulate several biological targets that are relevant to the development of the disease. While RHE-HUP has shown in vitro and in vivo beneficial effects, the molecular mechanisms by which it exerts its protective effect on cell membranes have not been fully clarified. To better understand RHE-HUP interactions with cell membranes, we used synthetic membrane models and natural models of human membranes. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. X-ray diffraction and differential scanning calorimetry (DSC) results indicated that RHE-HUP was able to interact mainly with DMPC. In addition, scanning electron microscopy (SEM) analysis showed that RHE-HUP modified the normal biconcave shape of erythrocytes inducing the formation of echinocytes. Moreover, the protective effect of RHE-HUP against the disruptive effect of Aβ(1-42) on the studied membrane models was tested. X-ray diffraction experiments showed that RHE-HUP induced a recovery in the ordering of DMPC multilayers after the disruptive effect of Aβ(1-42), confirming the protective role of the hybrid.

Erythrocytes as model cells for biocompatibility assessment, cytotoxicity screening of xenobiotics and drug delivery

Erythrocytes (RBCs) represent the main cell component in circulation and recently have become a topic of intensive scientific interest. The relevance of erythrocytes as a model for cytotoxicity screening of xenobiotics is under the spotlight of this review. Erythrocytes constitute a fundamental cellular model to study potential interactions with blood components of manifold novel polymer or biomaterials. Morphological changes, subsequent disruption of RBC membrane integrity, and hemolysis could be used to determine the cytotoxicity of various compounds. Erythrocytes undergo a programmed death (eryptosis) which could serve as a good model for evaluating certain mechanisms which correspond to apoptosis taking place in nucleated cells. Importantly, erythrocytes can be successfully used as a valuable cellular model in examination of oxidative stress generated by certain diseases or multiple xenobiotics since red cells are subjected to permanent oxidative stress. Additionally, the antioxidant capacity of erythrocytes, and the activity of anti-oxidative enzymes could reflect reactive oxygen species (ROS) generating properties of various substances and allow to determine their effects on tissues. The last part of this review presents the latest findings on the possible application of RBCs as drug delivery systems (DDS). In conclusion, all these findings make erythrocytes highly valuable cells for in vitro biocompatibility assessment, cytotoxicity screening of a wide variety of substances as well as drug delivery.

The acetylcholinesterase (AChE) inhibitor and anti-Alzheimer drug donepezil interacts with human erythrocytes

Donepezil is used to treat symptomatically the Alzheimer's disease (AD). This drug is a specific inhibitor of the enzyme acetylcholinesterase (AChE), whose main physiological function is to hydrolyze the neurotransmitter acetylcholine. The main objective of this work was to study the effect of donepezil on human erythrocytes as AChE is present in its membrane. For this purpose, human erythrocytes and molecular model of its membrane built-up of dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were used. The latter correspond to classes of phospholipids present in the outer and inner monolayers of the human erythrocyte membrane, respectively. Our experimental evidences obtained from X-ray diffraction and differential scanning calorimetry (DSC) analysis indicated that donepezil was capable of interacting with both phospholipids. Fluorescence spectroscopy results showed a moderate increase in the fluidity of the hydrophobic tails of DMPC and isolated unsealed human erythrocyte membranes (IUM). On the other hand, results by scanning electron microscopy (SEM) and optical defocusing microscopy (DM) showed that the drug changed the normal biconcave shape of the erythrocytes inducing the formation of stomatocytes (cup-shaped cells). This effect was explained by the incorporation of donepezil molecules into the erythrocyte membrane and interactions with AChE.

An explanation of the reversal of erythrocyte echinocytosis by incubation and storage by serum albumin

It is proposed that the specific reversal by serum albumin of the erythrocyte echinocytosis in an inorganic phosphate buffer saline or in a saline, either after 24 h in blood or after a storage of 6-7 weeks in SGAM or PAGGSM media, is due to a cell dehydration by a decrease of the total NaCl and KCl concentrations favoring the stomatocytogenic slow outward transport of inorganic phosphate with a hydrogen ion by band 3 anion exchanger, which was previously proposed to control the erythrocyte shape. This proposal would indicate that the opposition of the erythrocyte echinocytosis by serum albumin is not limited to binding to echinocytogenic amphiphiles, supported by the ability of the band 3-based mechanism of control of the erythrocyte shape to explain a variety of observations on the erythrocyte shape. It would also imply that this mechanism is a determinant of the erythrocyte rheological properties since influenced by cell shape and volume. It is shown that the above process of stomatocytosis can explain stomatocytoses by different agents as well as a knizocytosis induced in vitro and occurring in acquired and inherited disorders and other situations. Lastly, it can also explain the opposition of hemolysis by mannitol in SGAM and PAGGSM media.