Hg2+ and Cd2+ interact differently with biomimetic erythrocyte membranes.
In order to characterize the potentially deleterious effects of toxic Hg(2+) and Cd(2+) on lipid membranes, we have studied their binding to liposomes whose composition mimicked erythrocyte membranes. Fluorescence spectroscopy utilizing the concentration dependent quenching of Phen Green SK by Hg(2+) and Cd(2+) was found to be a sensitive tool to probe these interactions at metal concentrations < or =1 microM. We have systematically developed a metal binding affinity assay to screen for the interactions of Hg(2+) or Cd(2+) with certain lipid classes. A biomimetic liposome system was developed that contained four major lipid classes of erythrocyte membranes (zwitterionic lipids: phosphatidylcholine and phosphatidylethanolamine; negatively charged: phosphatidylserine and neutral: cholesterol). In contrast to Hg(2+), which preferentially bound to the negatively charged phosphatidylserine compared to the zwitterionic components, Cd(2+) bound stronger to the two zwitterionic lipids. Thus, the observed distinct differences in the binding affinity of Hg(2+) and Cd(2+) for certain lipid classes together with their known effects on membrane properties represent an important first step toward a better understanding the role of these interactions in the chronic toxicity of these metals.
Department of Biological Sciences, University of Calgary, 2500 University Drive, Calgary, AB, Canada.
Mary Trang
MT
Le
Jürgen
J
Gailer
Elmar J
EJ
Prenner
D002104:Cadmium / Q000633:toxicity*; D002784:Cholesterol / Q000737:chemistry / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000187:drug effects*; D005456:Fluorescent Dyes / Q000494:pharmacology; D006801:Humans; D008055:Lipids / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008563:Membrane Lipids; D008628:Mercury / Q000737:chemistry / Q000633:toxicity*; D008670:Metals / Q000737:chemistry; D009930:Organic Chemicals / Q000494:pharmacology; D010713:Phosphatidylcholines / Q000737:chemistry; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010718:Phosphatidylserines / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
D005456:Fluorescent Dyes; D008055:Lipids; D008081:Liposomes; D008563:Membrane Lipids; D008670:Metals; D009930:Organic Chemicals; C431805:Phen Green SK; D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010718:Phosphatidylserines; D002104:Cadmium; C483858:phosphatidylethanolamine; D002784:Cholesterol; D008628:Mercury