11 research outputs found
SOX9 Regulates Cancer Stem-Like Properties and Metastatic Potential of Single-Walled Carbon Nanotube-Exposed Cells
Engineered nanomaterials hold great promise for the future development of innovative products but their adverse health effects are a major concern. Recent studies have indicated that certain nanomaterials, including carbon nanotubes (CNTs), may be carcinogenic. However, the underlying mechanisms behind their potential malignant properties remain unclear. In this study, we linked SOX9, a stem cell associated transcription factor, to the neoplastic-like properties of human lung epithelial cells chronically exposed to a low-dose of single-walled carbon nanotubes (SWCNTs). We found
that SOX9 is upregulated in SWCNT-exposed cells, which is consistent with their abilities to induce tumor formation and metastasis in vivo. We therefore hypothesized that SOX9 overexpression may be responsible for the neoplastic-like phenotype observed in our model. Indeed, SOX9 knockdown inhibited anchorage-independent cell growth in vitro and lung colonization in vivo in a mouse xenograft model. SOX9 depletion also suppressed the formation of cancer stem-like cells (CSCs), as determined by tumor sphere formation and aldehyde dehydrogenase (ALDH) activity (Aldefluor) assays. Furthermore, SOX9 knockdown suppressed tumor metastasis and the expression of the stem cell marker ALDH1A1. Taken together, our findings provide a mechanistic insight into SWCNT-induced carcinogenesis and the role of SOX9 in CSC regulation and metastasis
Effect of Fiber Length on Carbon Nanotube-Induced Fibrogenesis
Given their extremely small size and light weight, carbon nanotubes (CNTs) can be readily inhaled by human lungs resulting in increased rates of pulmonary disorders, particularly fibrosis. Although the fibrogenic potential of CNTs is well established, there is a lack of consensus regarding the contribution of physicochemical attributes of CNTs on the underlying fibrotic outcome. We designed an experimentally validated in vitro fibroblast culture model aimed at investigating the effect of fiber length on single-walled CNT (SWCNT)-induced pulmonary fibrosis. The fibrogenic response to short and long SWCNTs was assessed via oxidative stress generation, collagen expression and transforming growth factor-beta (TGF-β) production as potential fibrosis biomarkers. Long SWCNTs were significantly more potent than short SWCNTs in terms of reactive oxygen species (ROS) response, collagen production and TGF-β release. Furthermore, our finding on the length-dependent in vitro fibrogenic response was validated by the in vivolung fibrosis outcome, thus supporting the predictive value of the in vitro model. Our results also demonstrated the key role of ROS in SWCNT-induced collagen expression and TGF-β activation, indicating the potential mechanisms of length-dependent SWCNT-induced fibrosis. Together, our study provides new evidence for the role of fiber length in SWCNT-induced lung fibrosis and offers a rapid cell-based assay for fibrogenicity testing of nanomaterials with the ability to predict pulmonary fibrogenic response in viv
Multifunctional Role of Bcl-2 in Malignant Transformation and Tumorigenesis of Cr(VI)-Transformed Lung Cells
B-cell lymphoma-2 (Bcl-2) is an antiapoptotic protein known to be important in the regulation of apoptosis in various cell types. However, its role in malignant transformation and tumorigenesis of human lung cells is not well understood. We previously reported that chronic exposure of human lung epithelial cells to the carcinogenic hexavalent chromium Cr(VI) caused malignant transformation and Bcl-2 upregulation; however, the role of Bcl-2 in the transformation is unclear. Using a gene silencing approach, we showed that Bcl-2 plays an important role in the malignant properties of Cr(VI)-transformed cells. Downregulation of Bcl-2 inhibited the invasive and proliferative properties of the cells as well as their colony forming and angiogenic activities, which are upregulated in the transformed cells as compared to control cells. Furthermore, animal studies showed the inhibitory effect of Bcl-2 knockdown on the tumorigenesis of Cr(VI)-transformed cells. The role of Bcl-2 in malignant transformation and tumorigenesis was confirmed by gene silencing experiments using human lung carcinoma NCI-H460 cells. These cells exhibited aggressive malignant phenotypes similar to those of Cr(VI)-transformed cells. Knockdown of Bcl-2 in the H460 cells inhibited malignant and tumorigenic properties of the cells, indicating the general role of Bcl-2 in human lung tumorigenesis. Ingenuity Pathways Analysis (IPA) revealed potential effectors of Bcl-2 in tumorigenesis regulation. Additionally, using IPA together with ectopic expression of p53, we show p53 as an upstream regulator of Bcl-2 in Cr(VI)-transformed cells. Together, our results indicate the novel and multifunctional role of Bcl-2 in malignant transformation and tumorigenesis of human lung epithelial cells chronically exposed to Cr(VI)
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Potential Toxicity and Underlying Mechanisms Associated with Pulmonary Exposure to Iron Oxide Nanoparticles: Conflicting Literature and Unclear Risk
This review article will focus on known risks following iron oxide nanoparticles (IONPs) exposure supported by human, animal, and cell culture-based studies, the potential challenges intrinsic to IONPs toxicity assessment, and how these may contribute to the poorly characterized IONPs toxicity profile
Variation in pentose phosphate pathway-associated metabolism dictates cytotoxicity outcomes determined by tetrazolium reduction assays
Abstract Tetrazolium reduction and resazurin assays are the mainstay of routine in vitro toxicity batteries. However, potentially erroneous characterization of cytotoxicity and cell proliferation can arise if verification of baseline interaction of test article with method employed is neglected. The current investigation aimed to demonstrate how interpretation of results from several standard cytotoxicity and proliferation assays vary in dependence on contributions from the pentose phosphate pathway (PPP). Non-tumorigenic Beas-2B cells were treated with graded concentrations of benzo[a]pyrene (B[a]P) for 24 and 48 h prior to cytotoxicity and proliferation assessment with commonly used MTT, MTS, WST1, and Alamar Blue assays. B[a]P caused enhanced metabolism of each dye assessed despite reductions in mitochondrial membrane potential and was reversed by 6-aminonicotinamide (6AN)—a glucose-6-phosphate dehydrogenase inhibitor. These results demonstrate differential sensitivity of standard cytotoxicity assessments on the PPP, thus (1) decoupling “mitochondrial activity” as an interpretation of cellular formazan and Alamar Blue metabolism, and (2) demonstrating the implicit requirement for investigators to sufficiently verify interaction of these methods in routine cytotoxicity and proliferation characterization. The nuances of method-specific extramitochondrial metabolism must be scrutinized to properly qualify specific endpoints employed, particularly under the circumstances of metabolic reprogramming
Short-Term Pulmonary Toxicity Assessment of Pre- and Post-incinerated Organomodified Nanoclay in Mice
Organomodified nanoclays
(ONCs) are increasingly used as filler
materials to improve nanocomposite strength, wettability, flammability,
and durability. However, pulmonary risks associated with exposure
along their chemical lifecycle are unknown. This study’s objective
was to compare pre- and post-incinerated forms of uncoated and organomodified
nanoclays for potential pulmonary inflammation, toxicity, and systemic
blood response. Mice were exposed <i>via</i> aspiration
to low (30 μg) and high (300 μg) doses of preincinerated
uncoated montmorillonite nanoclay (CloisNa), ONC (Clois30B), their
respective incinerated forms (I-CloisNa and I-Clois30B), and crystalline
silica (CS). Lung and blood tissues were collected at days 1, 7, and
28 to compare toxicity and inflammation indices. Well-dispersed CloisNa
caused a robust inflammatory response characterized by neutrophils,
macrophages, and particle-laden granulomas. Alternatively, Clois30B,
I-Clois30B, and CS high-dose exposures elicited a low grade, persistent
inflammatory response. High-dose Clois30B exposure exhibited moderate
increases in lung damage markers and a delayed macrophage recruitment
cytokine signature peaking at day 7 followed by a fibrotic tissue
signature at day 28, similar to CloisNa. I-CloisNa exhibited acute,
transient inflammation with quick recovery. Conversely, high-dose
I-Clois30B caused a weak initial inflammatory signal but showed comparable
pro-inflammatory signaling to CS at day 28. The data demonstrate that
ONC pulmonary toxicity and inflammatory potential relies on coating
presence and incineration status in that coated and incinerated nanoclay
exhibited less inflammation and granuloma formation than pristine
montmorillonite. High doses of both pre- and post-incinerated ONC,
with different surface morphologies, may harbor potential pulmonary
health hazards over long-term occupational exposures
Short-Term Pulmonary Toxicity Assessment of Pre- and Post-incinerated Organomodified Nanoclay in Mice
Organomodified nanoclays
(ONCs) are increasingly used as filler
materials to improve nanocomposite strength, wettability, flammability,
and durability. However, pulmonary risks associated with exposure
along their chemical lifecycle are unknown. This study’s objective
was to compare pre- and post-incinerated forms of uncoated and organomodified
nanoclays for potential pulmonary inflammation, toxicity, and systemic
blood response. Mice were exposed <i>via</i> aspiration
to low (30 μg) and high (300 μg) doses of preincinerated
uncoated montmorillonite nanoclay (CloisNa), ONC (Clois30B), their
respective incinerated forms (I-CloisNa and I-Clois30B), and crystalline
silica (CS). Lung and blood tissues were collected at days 1, 7, and
28 to compare toxicity and inflammation indices. Well-dispersed CloisNa
caused a robust inflammatory response characterized by neutrophils,
macrophages, and particle-laden granulomas. Alternatively, Clois30B,
I-Clois30B, and CS high-dose exposures elicited a low grade, persistent
inflammatory response. High-dose Clois30B exposure exhibited moderate
increases in lung damage markers and a delayed macrophage recruitment
cytokine signature peaking at day 7 followed by a fibrotic tissue
signature at day 28, similar to CloisNa. I-CloisNa exhibited acute,
transient inflammation with quick recovery. Conversely, high-dose
I-Clois30B caused a weak initial inflammatory signal but showed comparable
pro-inflammatory signaling to CS at day 28. The data demonstrate that
ONC pulmonary toxicity and inflammatory potential relies on coating
presence and incineration status in that coated and incinerated nanoclay
exhibited less inflammation and granuloma formation than pristine
montmorillonite. High doses of both pre- and post-incinerated ONC,
with different surface morphologies, may harbor potential pulmonary
health hazards over long-term occupational exposures