title: Activation of Rac1 GTPase by nanoparticulate structures in human macrophages.
abstract: Inflammatory activation of alveolar macrophages by ambient particles can be facilitated via Toll-like receptors (TLR). The action of TLR agonists and antagonists has been reported to depend on the formation of nanoparticulate structures. Aim of the present study was to identify the signaling pathways induced by nanoparticulate structures in human macrophages, which might be critical for inflammatory cell activation.
  
  
  METHODS
  Studies were performed in primary human alveolar macrophages or in differentiated THP-1 macrophages. Silica nanoparticles were prepared by Stöber synthesis and characterized by dynamic light scattering and scanning electron microscopy. Mycobacterial DNA was isolated from Mycobacterium bovis BCG, and nanoparticle formation was assessed by atomic force microscopy and dynamic light scattering. Actin polymerization was measured by phalloidin-TRITC staining, and cell activation was determined by reverse transcription quantitative PCR analysis, L929 cytotoxicity assay (cytokine induction), and pull-down assays (Rho GTPases).
  
  
  RESULTS
  In contrast to immune stimulatory sequence ISS 1018, BCG DNA spontaneously formed nanoparticulate structures and induced actin polymerization as did synthetic silica nanoparticles. Co-incubation with silica nanoparticles amplified the responsiveness of macrophages toward the TLR9 ligand ISS 1018. The activation of Rac1 was induced by silica nanoparticles as well as BCG DNA and is suggested as the critical signaling event inducing both cytoskeleton changes as well as inflammatory cell activation.
  
  
  CONCLUSIONS
  Nanoparticles can induce signaling pathways, which amplify an inflammatory response in macrophages.
authors: Department of Pharmacy, Saarland University, Pharmaceutical Biology, Saarbruecken, Germany.
authors: Britta
authors: B
authors: Diesel
authors: Jessica
authors: J
authors: Hoppstädter
authors: Nina
authors: N
authors: Hachenthal
authors: Robert
authors: R
authors: Zarbock
authors: Christian
authors: C
authors: Cavelius
authors: Birgit
authors: B
authors: Wahl
authors: Nicolas
authors: N
authors: Thewes
authors: Karin
authors: K
authors: Jacobs
authors: Annette
authors: A
authors: Kraegeloh
authors: Alexandra K
authors: AK
authors: Kiemer
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D016207:Cytokines / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004269:DNA, Bacterial / Q000032:analysis; D004789:Enzyme Activation; D006801:Humans; D007249:Inflammation; D008027:Light; D016676:Macrophages, Alveolar / Q000187:drug effects* / Q000201:enzymology; D051379:Mice; D018625:Microscopy, Atomic Force; D018613:Microscopy, Confocal; D008855:Microscopy, Electron, Scanning; D009163:Mycobacterium bovis / Q000378:metabolism; D053758:Nanoparticles / Q000737:chemistry*; D012542:Scattering, Radiation; D015398:Signal Transduction; D012822:Silicon Dioxide / Q000737:chemistry; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D016207:Cytokines; D004269:DNA, Bacterial; D012822:Silicon Dioxide; D020830:rac1 GTP-Binding Protein