Sequential Exposure to Carbon Nanotubes and Bacteria Enhances Pulmonary Inflammation and Infectivity

Pathology/Physiology Research Branch, HELD, National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA.
American Journal of Respiratory Cell and Molecular Biology (Impact Factor: 3.99). 06/2008; 38(5):579-90. DOI: 10.1165/rcmb.2007-0255OC
Source: PubMed


Carbon nanotubes (CNT), with their applications in industry and medicine, may lead to new risks to human health. CNT induce a robust pulmonary inflammation and oxidative stress in rodents. Realistic exposures to CNT may occur in conjunction with other pathogenic impacts (microbial infections) and trigger enhanced responses. We evaluated interactions between pharyngeal aspiration of single-walled CNT (SWCNT) and bacterial pulmonary infection of C57BL/6 mice with Listeria monocytogenes (LM). Mice were given SWCNT (0, 10, and 40 mug/mouse) and 3 days later were exposed to LM (10(3) bacteria/mouse). Sequential exposure to SWCNT/LM amplified lung inflammation and collagen formation. Despite this robust inflammatory response, SWCNT pre-exposure significantly decreased the pulmonary clearance of LM-exposed mice measured 3 to 7 days after microbial infection versus PBS/LM-treated mice. Decreased bacterial clearance in SWCNT-pre-exposed mice was associated with decreased phagocytosis of bacteria by macrophages and a decrease in nitric oxide production by these phagocytes. Pre-incubation of naïve alveolar macrophages with SWCNT in vitro also resulted in decreased nitric oxide generation and suppressed phagocytizing activity toward LM. Failure of SWCNT-exposed mice to clear LM led to a continued elevation in nearly all major chemokines and acute phase cytokines into the later course of infection. In SWCNT/LM-exposed mice, bronchoalveolar lavage neutrophils, alveolar macrophages, and lymphocytes, as well as lactate dehydrogenase level, were increased compared with mice exposed to SWCNT or LM alone. In conclusion, enhanced acute inflammation and pulmonary injury with delayed bacterial clearance after SWCNT exposure may lead to increased susceptibility to lung infection in exposed populations.

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    • "In vitro assays have reported that SWCNTs inhibit phagocytosis greater than MWCNTs at low concentrations [54] and that inhibition of phagocytosis by MWCNTs is both diameter and concentration dependent [55]. Shvedova et al. showed a concentration dependent inhibition of the phagocytosis of L.monocytogenes by alveolar macrophages in vitro [12]. However, in vivo phagocytosis was inhibited to a similar extent in both the low and high dose groups, suggesting that inhibition of phagocytosis and clearance of pulmonary pathogens by CNTs may involve additional mechanisms. "
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    ABSTRACT: Aerosolized or aspirated manufactured carbon nanotubes have been shown to be cytotoxic, cause pulmonary lesions, and demonstrate immunomodulatory properties. CD-1 mice were used to assess pulmonary toxicity of helical carbon nanotubes (HCNTs) and alterations of the immune response to subsequent infection by Pseudomonas aeruginosa in mice. HCNTs provoked a mild inflammatory response following either a single exposure or 2X/week for three weeks (multiple exposures) but were not significantly toxic. Administering HCNTs 2X/week for three weeks resulted in pulmonary lesions including granulomas and goblet cell hyperplasia. Mice exposed to HCNTs and subsequently infected by P. aeruginosa demonstrated an enhanced inflammatory response to P. aeruginosa and phagocytosis by alveolar macrophages was inhibited. However, clearance of P. aeruginosa was not affected. HCNT exposed mice depleted of neutrophils were more effective in clearing P. aeruginosa compared to neutrophil-depleted control mice, accompanied by an influx of macrophages. Depletion of systemic macrophages resulted in slightly inhibited bacterial clearance by HCNT treated mice. Our data indicate that pulmonary exposure to HCNTs results in lesions similar to those caused by other nanotubes and pre-exposure to HCNTs inhibit alveolar macrophage phagocytosis of P. aeruginosa. However, clearance was not affected as exposure to HCNTs primed the immune system for an enhanced inflammatory response to pulmonary infection consisting of an influx of neutrophils and macrophages.
    PLoS ONE 11/2013; 8(11):e80283. DOI:10.1371/journal.pone.0080283 · 3.23 Impact Factor
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    • "Human welders are more prone to develop bronchitis and pneumonia, and animal studies have shown the inability to clear L. monocytogenes after welding inhalation exposure [1,2,13]. Since GMA-SS, GMA-MS or CNT exposure induce localized immunosuppression [2,13,45], but only GMA-SS induced type I interferon signaling, a general compensatory upregulation in response to a dampened immune system seems unlikely. In fact, the exact opposite may be true. "
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    ABSTRACT: Background Welding, a process that generates an aerosol containing gases and metal-rich particulates, induces adverse physiological effects including inflammation, immunosuppression and cardiovascular dysfunction. This study utilized microarray technology and subsequent pathway analysis as an exploratory search for markers/mechanisms of in vivo systemic effects following inhalation. Mice were exposed by inhalation to gas metal arc – stainless steel (GMA-SS) welding fume at 40 mg/m3 for 3 hr/d for 10 d and sacrificed 4 hr, 14 d and 28 d post-exposure. Whole blood cells, aorta and lung were harvested for global gene expression analysis with subsequent Ingenuity Pathway Analysis and confirmatory qRT-PCR. Serum was collected for protein profiling. Results The novel finding was a dominant type I interferon signaling network with the transcription factor Irf7 as a central component maintained through 28 d. Remarkably, these effects showed consistency across all tissues indicating a systemic type I interferon response that was complemented by changes in serum proteins (decreased MMP-9, CRP and increased VCAM1, oncostatin M, IP-10). In addition, pulmonary expression of interferon α and β and Irf7 specific pattern recognition receptors (PRR) and signaling molecules (Ddx58, Ifih1, Dhx58, ISGF3) were induced, an effect that showed specificity when compared to other inflammatory exposures. Also, a canonical pathway indicated a coordinated response of multiple PRR and associated signaling molecules (Tlr7, Tlr2, Clec7a, Nlrp3, Myd88) to inhalation of GMA-SS. Conclusion This methodological approach has the potential to identify consistent, prominent and/or novel pathways and provides insight into mechanisms that contribute to pulmonary and systemic effects following toxicant exposure.
    Particle and Fibre Toxicology 07/2012; 9(1):25. DOI:10.1186/1743-8977-9-25 · 7.11 Impact Factor
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    • "Witasp et al. (2009) reported that SWCNTs could impair the phagocytic function of human macrophages at non-cytotoxic concentration, leading to inhibited elimination of apoptotic cell corpses. Decreased phagocytosis might also result in decreased bacterial clearance and enhanced pulmonary inflammation and infectivity, in vivo (Shvedova et al. 2008). Similar to this study, AF-SWCNTs and SWCNTs, at non-cytotoxic concentrations , affected the phagocytic ability of mouse primary peritoneal macrophages (Figure 5). "
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    ABSTRACT: Abstract It is increasingly important to understand the single-walled carbon nanotubes' (SWCNTs) immune response as their increasingly biomedical researches and applications. Macrophages and T cells play important roles in scavenging foreign materials and pathogens and regulating immune response. In this work, primarily cultured murine peritoneal macrophages and purified splenic T cells were utilised to determine the toxic effects of SWCNTs and acid-functionalised SWCNTs (AF-SWCNTs) on the immune system, especially on macrophage functions. Macrophages were exposed to 0-50 μg/ml of CNTs for 24 h and no significant cytotoxicity was found by live/dead and annexin-V-FITC/PI analyses. The TEM images revealed that AF-SWCNTs were engulfed mostly through phagocytosis and located in lysosomes of macrophages. Measurement of mitochondrial membrane potential and proteasome subunit gene expression demonstrated that 10 and 50 μg/ml AF-SWCNTs could damage mitochondrial function and proteasome formation in a concentration-dependent manner. Functional analyses revealed that the percentage of phagocytic cells were affected significantly by 20 μg/ml CNTs, and 5 μg/ml AF-SWCNTs inhibited the phagocytic efficiency of latex beads in macrophages. The accessory cell function was affected by both AF-SWCNTs and SWCNTs at concentrations of 10 and 50 μg/ml, respectively. Furthermore, AF-SWCNT biased naïve T-cell differentiation to Th1 type by inducing the production of IFN-γ and TNF, implying the potential risk of Th1-associated diseases (e.g. autoimmune diseases and inflammation) on AF-SWCNT exposure.
    Nanotoxicology 05/2012; 7(5). DOI:10.3109/17435390.2012.694487 · 6.41 Impact Factor
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