Reactive oxygen species-mediated p38 MAPK regulates carbon nanotube-induced fibrogenic and angiogenic responses

Department of Pharmaceutical Sciences, Hampton University , Hampton, VA , USA.
Nanotoxicology (Impact Factor: 6.41). 01/2012; 7(2). DOI: 10.3109/17435390.2011.647929
Source: PubMed

ABSTRACT Abstract Single-walled carbon nanotubes (SWCNTs) are fibrous nanoparticles that are being used widely for various applications including drug delivery. SWCNTs are currently under special attention for possible cytotoxicity. Recent reports suggest that exposure to nanoparticles leads to pulmonary fibrosis. We report that SWCNT-mediated interplay of fibrogenic and angiogenic regulators leads to increased angiogenesis, which is a novel finding that furthers the understanding of SWCNT-induced cytotoxicity. SWCNTs induce fibrogenesis through reactive oxygen species-regulated phosphorylation of p38 mitogen-activated protein kinase (MAPK). Activation of p38 MAPK by SWCNTs led to the induction of transforming growth factor (TGF)-β1 as well as vascular endothelial growth factor (VEGF). Both TGF-β1 and VEGF contributed significantly to the fibroproliferative and collagen-inducing effects of SWCNTs. Interestingly, a positive feedback loop was observed between TGF-β1 and VEGF. This interplay of fibrogenic and angiogenic mediators led to increased angiogenesis in response to SWCNTs. Overall this study reveals key signalling molecules involved in SWCNT-induced fibrogenesis and angiogenesis.

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    • "It has been reported that nanomaterials cause these damages [37–39]. It was reported that reactive oxygen species generated by titanium expressed Fas, Bcl-2-associated X protein (Bax), IL-1 beta, and induced apoptosis [40, 41]; those generated by silica induced DNA damage and autophagy [42, 43], those generated by polyvinylpyrrolidone (PVP)-coated silver nanoparticles and silver ions induce apoptosis and necrosis in THP-1 monocytes [44], and those generated by carbon nanotube activated p38 MAPK and NF-κB signaling and induced fibrogenic and angiogenic responses [45–47]. "
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    ABSTRACT: Pulmonary inflammation, especially persistent inflammation, has been found to play a key role in respiratory disorders induced by nanoparticles in animal models. In inhalation studies and instillation studies of nanomaterials, persistent inflammation is composed of neutrophils and alveolar macrophages, and its pathogenesis is related to chemokines such as the cytokine-induced neutrophil chemoattractant (CINC) family and macrophage inflammatory protein-1 α and oxidant stress-related genes such as heme oxygenase-1 (HO-1). DNA damages occur chemically or physically by nanomaterials. Chemical and physical damage are associated with point mutation by free radicals and double strand brake, respectively. The failure of DNA repair and accumulation of mutations might occur when inflammation is prolonged, and finally normal cells could become malignant. These free radicals can not only damage cells but also induce signaling molecules containing immunoreaction. Nanoparticles and asbestos also induce the production of free radicals. In allergic responses, nanoparticles act as Th2 adjuvants to activate Th2 immune responses such as activation of eosinophil and induction of IgE. Taken together, the presence of persistent inflammation may contribute to the pathogenesis of a variety of diseases induced by nanomaterials.
    Research Journal of Immunology 07/2014; 2014(2):962871. DOI:10.1155/2014/962871
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    • "The doses used in the present study both in vitro (7.5 - 30 μg/cm2) and in vivo (12.5 - 100 μg) are also higher than those used by other investigators. For example, Wang et al. [12] and Azad et al. [38] used SWCNT with doses of 0.02 - 0.2 μg/cm2 in vitro and 10 μg/mouse in vivo, and 5-25 μg/ml in vitro, respectively. However, the mass of an individual CNT differs according to structure (SW vs MW). "
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    ABSTRACT: Carbon nanotubes (CNT) can induce lung inflammation and fibrosis in rodents. Several studies have identified the capacity of CNT to stimulate the proliferation of fibroblasts. We developed and validated experimentally here a simple and rapid in vitro assay to evaluate the capacity of a nanomaterial to exert a direct pro-fibrotic effect on fibroblasts. The activity of several multi-wall (MW)CNT samples (NM400, the crushed form of NM400 named NM400c, NM402 and MWCNTg 2400) and asbestos (crocidolite) was investigated in vitro and in vivo. The proliferative response to MWCNT was assessed on mouse primary lung fibroblasts, human fetal lung fibroblasts (HFL-1), mouse embryonic fibroblasts (BALB-3T3) and mouse lung fibroblasts (MLg) by using different assays (cell counting, WST-1 assay and propidium iodide PI staining) and dispersion media (fetal bovine serum, FBS and bovine serum albumin, BSA). C57BL/6 mice were pharyngeally aspirated with the same materials and lung fibrosis was assessed after 2 months by histopathology, quantification of total collagen lung content and pro-fibrotic cytokines in broncho-alveolar lavage fluid (BALF). MWCNT (NM400 and NM402) directly stimulated fibroblast proliferation in vitro in a dose-dependent manner and induced lung fibrosis in vivo. NM400 stimulated the proliferation of all tested fibroblast types, independently of FBS- or BSA- dispersion. Results obtained by WST1 cell activity were confirmed with cell counting and cell cycle (PI staining) assays. Crocidolite also stimulated fibroblast proliferation and induced pulmonary fibrosis, although to a lesser extent than NM400 and NM402. In contrast, shorter CNT (NM400c and MWCNTg 2400) did not induce any fibroblast proliferation or collagen accumulation in vivo, supporting the idea that CNT structure is an important parameter for inducing lung fibrosis. In this study, an optimized proliferation assay using BSA as a dispersant, MLg cells as targets and an adaptation of WST-1 as readout was developed. The activity of MWCNT in this test strongly reflects their fibrotic activity in vivo, supporting the predictive value of this in vitro assay in terms of lung fibrosis potential.
    Particle and Fibre Toxicology 10/2013; 10(1):52. DOI:10.1186/1743-8977-10-52 · 7.11 Impact Factor
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    Journal of Nanomedicine & Nanotechnology 01/2012; 03(05). DOI:10.4172/2157-7439.1000140 · 5.72 Impact Factor
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Anand Iyer