title: Polyethylenimine-mediated impairment of mitochondrial membrane potential, respiration and membrane integrity: implications for nucleic acid delivery and gene therapy.
abstract: The 25 kDa branched polyethylenimine (PEI) is a highly efficient synthetic polycation used in transfection protocols, but also triggers mitochondrial-mediated apoptotic cell death processes where the mechanistic issues are poorly understood. We now demonstrate that PEI in a concentration- and time-dependent manner can affect functions (membrane potential, swelling and respiration) and ultrastructural integrity of freshly isolated rat liver mitochondria. The threshold concentration for detection of PEI-mediated impairment of rat liver mitochondrial functions is 3 μg/mL, however, lower PEI levels still exert some effects on mitochondrial morphology and respiration, and these may be related to the inherent membrane perturbing properties of this polycation. The PEI-mediated mitochondrial swelling phase is biphasic, with a fast decaying initial period (most prominent from 4 μg/mL PEI) followed by a slower, linear swelling response. The slow phase is presumably the result of a time-dependent transition permeability opening in mitochondria initially resistant to swelling/depolarization, but may further be related to PEI-induced nanoscale structural defects and/or formation of pores in the outer membrane. Respiration assessments further suggested that PEI in the presence of exogenous ADP behaves in a similar fashion to a slow-acting inhibitory compound. PEI further shows an uncoupling property that is detectable at low respiration rates. The relevance of these findings to PEI-mediated initiation of intrinsic apoptotic pathway is discussed.
authors.affiliation: Centre for Pharmaceutical Nanotechnology and Nanotoxicology, Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark. akl@farma.ku.dk
authors.forename: Anna K
authors.initials: AK
authors.lastname: Larsen
authors.forename: Dominika
authors.initials: D
authors.lastname: Malinska
authors.forename: Izabela
authors.initials: I
authors.lastname: Koszela-Piotrowska
authors.forename: Ladan
authors.initials: L
authors.lastname: Parhamifar
authors.forename: A Christy
authors.initials: AC
authors.lastname: Hunter
authors.forename: S Moein
authors.initials: SM
authors.lastname: Moghimi
mesh_terms: D000818:Animals; D019069:Cell Respiration / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D015316:Genetic Therapy; D022781:Hepatocytes / Q000187:drug effects / Q000648:ultrastructure; D008099:Liver / Q000187:drug effects; D008297:Male; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects*; D008928:Mitochondria / Q000187:drug effects / Q000648:ultrastructure; D051336:Mitochondrial Membranes / Q000187:drug effects* / Q000502:physiology; D009696:Nucleic Acids / Q000235:genetics / Q000378:metabolism; D011094:Polyethyleneimine / Q000633:toxicity*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D009696:Nucleic Acids; D011094:Polyethyleneimine