title: Ultrasound enhanced PEI-mediated gene delivery through increasing the intracellular calcium level and PKC-δ protein expression.
abstract: OBJECTIVE
  Polyethylenimine (PEI), a cationic polymer, has been shown to aggregate plasmid DNA and facilitate its internalization. It has also been shown that combining ultrasound (US) with PEI could enhance and prolong in vitro and in vivo transgene expression. However, the role US in the enhancement of PEI uptake is poorly understood. This study investigates the impact of US on PEI-mediated gene transfection.
  
  
  METHODS
  Specific endocytosis pathway siRNA, including clathrin HC siRNA, caveolin-1 siRNA and protein kinase C-delta (PKC-δ) siRNA, are used to block the corresponding endocytosis pathways prior to the transfection of luciferase DNA/PEI polyplexes to cultured cells by 1-MHz pulsed US with ultrasound contrast agent SonoVue®.
  
  
  RESULTS
  Transgene expression was found not to be enhanced by US treatment in the presence of the PKC-δ siRNA. We further demonstrated that PKC-δ protein could be enhanced at 6 h after US exposure. Moreover, intracellular calcium levels were found to be significantly increased at 3 h after US exposure, while transgene expressions were significantly reduced in the presence of calcium channel blockers both in vitro and in vivo.
  
  
  CONCLUSIONS
  Our results suggest that US enhanced PEI-mediated gene transfection specifically by increasing PKC-δ related fluid phase endocytosis, which was induced by increasing the intracellular calcium levels.
authors.affiliation: Department of Physical Medicine and Rehabilitation, National Taiwan University Hospital National Taiwan University College of Medicine, Taipei, Taiwan, Republic of China.
authors.forename: Jyun-Lin
authors.initials: JL
authors.lastname: Lee
authors.forename: Chia-Wen
authors.initials: CW
authors.lastname: Lo
authors.forename: Claude
authors.initials: C
authors.lastname: Inserra
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Béra
authors.forename: Wen-Shiang
authors.initials: WS
authors.lastname: Chen
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004247:DNA / Q000008:administration & dosage* / Q000235:genetics; D004705:Endocytosis; D048888:Fireflies / Q000201:enzymology / Q000235:genetics; D006801:Humans; D049409:Luciferases, Firefly / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D011094:Polyethyleneimine / Q000378:metabolism*; D051745:Protein Kinase C-delta / Q000235:genetics* / Q000378:metabolism; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D014162:Transfection / Q000379:methods*; D014465:Ultrasonics
chemical_list: D034741:RNA, Small Interfering; D011094:Polyethyleneimine; D004247:DNA; D049409:Luciferases, Firefly; D051745:Protein Kinase C-delta; D002118:Calcium