title: Uptake and intracellular traffic of siRNA dendriplexes in glioblastoma cells and macrophages.
abstract: BACKGROUND
  Gene silencing using small interfering RNA (siRNA) is a promising new therapeutic approach for glioblastoma. The endocytic uptake and delivery of siRNA to intracellular compartments could be enhanced by complexation with polyamidoamine dendrimers. In the present work, the uptake mechanisms and intracellular traffic of siRNA/generation 7 dendrimer complexes (siRNA dendriplexes) were screened in T98G glioblastoma and J774 macrophages.
  
  
  METHODS
  The effect of a set of chemical inhibitors of endocytosis on the uptake and silencing capacity of dendriplexes was determined by flow cytometry. Colocalization of fluorescent dendriplexes with endocytic markers and occurrence of intracellular dissociation were assessed by confocal laser scanning microscopy.
  
  
  RESULTS
  Uptake of siRNA dendriplexes by T98G cells was reduced by methyl-β-cyclodextrin, and genistein, and cytochalasine D, silencing activity was reduced by genistein; dendriplexes colocalized with cholera toxin subunit B. Therefore, caveolin-dependent endocytosis was involved both in the uptake and silencing activity of siRNA dendriplexes. On the other hand, uptake of siRNA dendriplexes by J774 cells was reduced by methyl-β-cyclodextrin, genistein, chlorpromazine, chloroquine, cytochalasine D, and nocodazole, the silencing activity was not affected by chlorpromazine, genistein or chloroquine, and dendriplexes colocalized with transferrin and cholera toxin subunit B. Thus, both clathrin-dependent and caveolin-dependent endocytosis mediated the uptake and silencing activity of the siRNA dendriplexes. SiRNA dendriplexes were internalized at higher rates by T98G but induced lower silencing than in J774 cells. SiRNA dendriplexes showed relatively slow dissociation kinetics, and their escape towards the cytosol was not mediated by acidification independently of the uptake pathway.
  
  
  CONCLUSIONS
  The extent of cellular uptake of siRNA dendriplexes was inversely related to their silencing activity. The higher silencing activity of siRNA dendriplexes in J774 cells could be ascribed to the contribution of clathrin-dependent and caveolin-dependent endocytosis vs only caveolin-dependent endocytosis in T98G cells.
authors: Programa de Nanomedicinas, Departamento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal, Buenos Aires, Argentina.
authors: Ana Paula
authors: AP
authors: Perez
authors: Maria Luz
authors: ML
authors: Cosaka
authors: Eder Lilia
authors: EL
authors: Romero
authors: Maria Jose
authors: MJ
authors: Morilla
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D022461:Caveolins / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002966:Clathrin / Q000378:metabolism; D050091:Dendrimers / Q000008:administration & dosage / Q000493:pharmacokinetics*; D004705:Endocytosis / Q000187:drug effects*; D011992:Endosomes / Q000378:metabolism; D020868:Gene Silencing; D005909:Glioblastoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D034741:RNA, Small Interfering / Q000008:administration & dosage / Q000493:pharmacokinetics*
chemical_list: D015415:Biomarkers; D022461:Caveolins; D002966:Clathrin; D050091:Dendrimers; C104700:PAMAM Starburst; D034741:RNA, Small Interfering