title: Apoptosis progression studied using parallel dielectrophoresis electrophysiological analysis and flow cytometry.
abstract: Apoptosis is characterised by many cellular events, but the standard Annexin-V assay identifies two; the transfer of the phospholipid phosphatidylserine (PS) from inner to outer leaflets of the plasma membrane, acting as an "eat me" signal to macrophages, and the permeabilisation of the plasma membrane. In this paper we compare the results from the Annexin-V assay with electrophysiology data obtained in parallel using dielectrophoresis, which highlights two changes in cell electrophysiology; a change in cytoplasmic conductivity which correlates with PS expression, and a membrane conductance spike that correlates with permeabilisation. Combining results from both methods shows a strong inverse relationship between conductivity and PS externalisation. One mechanism which may explain this correlation is related to intracellular Ca(2+), which is known to increase early in apoptosis. PS expression occurs when enzymes called scramblases swap external and internal phospholipids, and which are usually activated by Ca(2+), whilst the change in cytoplasmic conductivity may be due to K(+) efflux from intermediate conductance (IK) ion channels that are also activated by Ca(2+).
authors.affiliation: Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK. m.hughes@surrey.ac.uk.
authors.forename: H J
authors.initials: HJ
authors.lastname: Mulhall
authors.affiliation: Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK. m.hughes@surrey.ac.uk.
authors.forename: A
authors.initials: A
authors.lastname: Cardnell
authors.affiliation: Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK. m.hughes@surrey.ac.uk.
authors.forename: K F
authors.initials: KF
authors.lastname: Hoettges
authors.affiliation: Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK. m.hughes@surrey.ac.uk.
authors.forename: F H
authors.initials: FH
authors.lastname: Labeed
authors.affiliation: Centre for Biomedical Engineering, Department of Mechanical Engineering Sciences, University of Surrey, Guildford, Surrey GU2 7XH, UK. m.hughes@surrey.ac.uk.
authors.forename: M P
authors.initials: MP
authors.lastname: Hughes
mesh_terms: D017304:Annexin A5 / Q000737:chemistry; D017209:Apoptosis; D002118:Calcium / Q000737:chemistry; D002462:Cell Membrane / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004586:Electrophoresis; D004594:Electrophysiology / Q000379:methods*; D005434:Flow Cytometry / Q000379:methods*; D006801:Humans; D019169:Jurkat Cells; D010718:Phosphatidylserines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D011419:Propidium / Q000737:chemistry; D019311:Staurosporine / Q000737:chemistry
chemical_list: D017304:Annexin A5; D010718:Phosphatidylserines; D010743:Phospholipids; D011419:Propidium; D019311:Staurosporine; D002118:Calcium