Bacterial lipopolysaccharide enhances PDGF signaling and pulmonary fibrosis in rats exposed to carbon nanotubes.

Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, 27695-7633, USA.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 4.11). 10/2009; 43(2):142-51. DOI: 10.1165/rcmb.2009-0113OC
Source: PubMed

ABSTRACT Engineered multi-walled carbon nanotubes (MWCNT) represent a possible health risk for pulmonary fibrosis due to their fiber-like shape and potential for persistence in the lung. We postulated that bacterial lipopolysaccharide (LPS), a ubiquitous agent in the environment that causes lung inflammation, would enhance fibrosis caused by MWCNT. Rats were exposed to LPS and then intratracheally instilled with MWCNT or carbon black (CB) nanoparticles 24 hours later. Pulmonary fibrosis was observed 21 days after MWCNT exposure, but not with CB. LPS alone caused no fibrosis but enhanced MWCNT-induced fibrosis. LPS plus CB did not significantly increase fibrosis. MWCNT increased platelet-derived growth factor-AA (PDGF-AA), a major mediator of fibrosis. PDGF-AA production in response to MWCNT, but not CB, was synergistically enhanced by LPS. Immunostaining showed PDGF-AA in bronchiolar epithelial cells and macrophages. Since macrophages engulfed MWCNT, were positive for PDGF-AA, and mediate fibroblast responses, experiments were performed with rat lung macrophages (NR8383 cells) and rat lung fibroblasts in vitro. LPS exposure increased PDGF-A mRNA levels in NR8383 cells and enhanced MWCNT-induced PDGF-A mRNA levels. Moreover, LPS increased MWCNT- or CB-induced PDGF receptor-alpha (PDGF-Ralpha) mRNA in fibroblasts. Our data suggest that LPS exacerbates MWCNT-induced lung fibrosis by amplifying production of PDGF-AA in macrophages and epithelial cells, and by increasing PDGF-Ralpha on pulmonary fibroblasts. Our findings also suggest that individuals with pre-existing pulmonary inflammation are at greater risk for the potential adverse effects of MWCNT.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Background Airborne exposure to nanomaterials from unintended occupational or environmental exposures or as a consequence of product use may lead to adverse health effects. Numerous studies have focused on single-walled carbon nanotubes (SWCNTs) and their ability to cause pulmonary injury related to fibrosis, and cancer; however few studies have addressed their impact on infectious agents, particularly viruses that are known for causing severe disease. Here we have demonstrated the ability of pristine SWCNTs of diverse electronic structure to increase the susceptibility of small airway epithelial cells (SAEC) to pandemic influenza A H1N1 infection and discerned potential mechanisms of action driving this response.Methods Small airway epithelial cells (SAEC) were exposed to three types of SWCNTs with varying electronic structure (SG65, SG76, CG200) followed by infection with A/Mexico/4108/2009 (pH1N1). Cells were then assayed for viral infectivity by immunofluorescence and viral titers. We quantified mRNA and protein levels of targets involved in inflammation and anti-viral activity (INFB1, IL-8, RANTES/CCL5, IFIT2, IFIT3, ST3GAL4, ST6GAL1, IL-10), localized sialic acid receptors, and assessed mitochondrial function. Hyperspectral imaging analysis was performed to map the SWCNTs and virus particles in fixed SAEC preparations. We additionally performed characterization analysis to monitor SWCNT aggregate size and structure under biological conditions using dynamic light scattering (DLS), static light scattering (SLS).ResultsBased on data from viral titer and immunofluorescence assays, we report that pre-treatment of SAEC with SWCNTs significantly enhances viral infectivity that is not dependent on SWCNT electronic structure and aggregate size within the range of 106 nm ¿ 243 nm. We further provide evidence to support that this noted effect on infectivity is not likely due to direct interaction of the virus and nanoparticles, but rather a combination of suppression of pro-inflammatory (RANTES) and anti-viral (IFIT2, IFIT3) gene/protein expression, impaired mitochondrial function and modulation of viral receptors by SWCNTs.Conclusions Results of this work reveal the potential for SWCNTs to increase susceptibility to viral infections as a mechanism of adverse effect. These data highlight the importance of investigating the ability of carbon-nanomaterials to modulate the immune system, including impacts on anti-viral mechanisms in lung cells, thereby increasing susceptibility to infectious agents.
    Particle and Fibre Toxicology 12/2014; 11(1). DOI:10.1186/s12989-014-0066-0 · 6.99 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Multi-walled carbon nanotubes (MWCNTs) pose a possible human health risk for lung disease as a result of inhalation exposure. Mice exposed to MWCNTs develop pulmonary fibrosis. Lung macrophages engulf MWCNTs and produce pro-fibrogenic cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and osteopontin (OPN). Atomic layer deposition (ALD) is a novel process used to enhance functional properties of MWCNTs, yet the consequence of ALD-modified MWCNTs on macrophage biology and fibrosis is unknown.
    PLoS ONE 09/2014; 9(9):e106870. DOI:10.1371/journal.pone.0106870 · 3.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: This experimental study evaluated the influence of the presence of lipopolysaccharide (LPS), a common bacterial endotoxin, on the nitric acid oxidised multiwalled carbon nanotubes (Ox-MWCNT) during the assessment of in vitro toxicity to splenocytes, an immune system cell isolated from BALB/c mice. The concentration of LPS was determined by Limulus Amebocyte assay and this endotoxin was removed from Ox-MWCNT by using three cycles of autoclave. Splenocytes were cultured in RPMI 1640 media with 1.0, 5.0 or 10 ng/mL of Ox-MWCNT. The results showed that the presence of LPS on Ox-MWCNT did not affect the growth of splenocytes in vitro. However, the absence of LPS decreased the splenocytes viability significantly.
    Journal of Experimental Nanoscience 12/2014; 10(9):1-9. DOI:10.1080/17458080.2014.888788 · 1.04 Impact Factor

Full-text (3 Sources)

Available from
May 21, 2014