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Interaction of Poly(ethylenimine)-DNA Polyplexes with Mitochondria: Implications for a Mechanism of Cytotoxicity

Department of Chemistry & Macromolecules & Interfaces Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, United States.
Molecular Pharmaceutics (Impact Factor: 4.38). 06/2011; 8(5):1709-19. DOI: 10.1021/mp200078n
Source: PubMed

ABSTRACT

Poly(ethylenimine) (PEI) and PEI-based systems have been widely studied for use as nucleic acid delivery vehicles. However, many of these vehicles display high cytotoxicity, rendering them unfit for therapeutic use. By exploring the mechanisms that cause cytotoxicity, and through understanding structure-function relationships between polymers and intracellular interactions, nucleic acid delivery vehicles with precise intracellular properties can be tailored for specific function. Previous research has shown that PEI is able to depolarize mitochondria, but the exact mechanism as to how depolarization is induced remains elusive and therefore is the focus of the current study. Potential mechanisms for mitochondrial depolarization include direct mitochondrial membrane permeabilization by PEI or PEI polyplexes, activation of the mitochondrial permeability transition pore, and interference with mitochondrial membrane proton pumps, specifically Complex I of the electron transport chain and F(0)F(1)-ATPase. Herein, confocal microscopy and live cell imaging showed that PEI polyplexes do colocalize to some degree with mitochondria early in transfection, and the degree of colocalization increases over time. Cyclosporin a was used to prevent activation of the mitochondrial membrane permeability transition pore, and it was found that early in transfection cyclosporin a was unable to prevent the loss of mitochondrial membrane potential. Further studies done using rotenone and oligomycin to inhibit Complex I of the electron transport chain and F(0)F(1)-ATPase, respectively, indicate that both of these mitochondrial proton pumps are functioning during PEI transfection. Overall, we conclude that direct interaction between polyplexes and mitochondria may be the reason why mitochondrial function is impaired during PEI transfection.

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Available from: Giovanna Grandinetti, Apr 30, 2015
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    • "The most commonly used is polyethylenimine. However, as explained in the introduction, a number of reports have indicated that PEI can induce cytotoxicity and could cause mitochondrial damages293031. Recently, it was shown, using several polycations (poly-arginine, poly-lysine, poly-histidine and chitosan), that poly-arginine (PolyR) appears to be a good candidate for the formation of a ternary complex with Li28 and a short peptide called OVA made up of eight amino acids (SIINFEKL)[34]. "
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    • "The release of these proteins, such as cytochrome c, from the mitochondrial intermembrane space leads to caspase activation and the biochemical execution of cells, characterized by morphological changes and nuclear condensation (Moldoveanu et al., 2013;Parsons & Green, 2010;Tait & Green, 2012). Recent studies have shown that PEI-mediated cytotoxicity is generally characterized by cell death through a mixture of apoptotic and necrotic pathways, interconnected with autophagy responses and mitochondrial dysfunction (Gao et al., 2011;Grandinetti, Ingle, & Reineke, 2011;Hall et al., 2013;Larsen et al., 2012;Lin et al., 2012;Moghimi et al., 2005;Symonds et al., 2005). Polycationic vectors, such as PEI, have previously been shown to induce the release of cytochrome c from mitochondria (Moghimi et al., 2005). "
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    • "This is well illustrated by the finding that DNA polyplexes formed with branched PEI are more stable than linear PEI polyplexes, but linear PEI polyplexes were found to be more effective in gene transfer; apparently intracellular release (Itaka et al., 2004) and also nuclear entry of DNA (Brunner, Furtbauer, Sauer, Kursa, & Wagner, 2002) can be better managed by the lessstable linear PEI polyplexes. Despite many favorable properties, PEI displays also drawbacks: it is nondegradable and significantly toxic (Grandinetti, Ingle, & Reineke, 2011;Moghimi et al., 2005) in a molecular weight-dependent manner. Cytotoxicity includes cell surface and organelle membrane (mitochondria , nucleus) defects, triggering apoptosis, necrosis, and also block of ATP synthesis (Hall et al., 2013). "
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