Single-walled carbon nanotubes disturbed the immune and metabolic regulation function 13-weeks after a single intratracheal instillation

Toxicity of Single-Walled Carbon Nanotubes (SWCNTs): Effect of Lengths, Functional Groups and Electronic Structures Revealed by a Quantitative Toxicogenomics Assay

Single-walled carbon nanotubes (SWCNTs) are a group of widely used carbon-based nanomaterials (CNMs) with various applications, which raise increasing public concerns associated with their potential toxicological effect and risks on human and ecosystems. In this report, we comprehensively evaluated the nanotoxicity of SWCNTs with their relationship to varying lengths, functional groups and electronic structures, by employing both newly established quantitative toxicogenomics test, as well as conventional phenotypic bioassays. The objective is to reveal potential cellular toxicity and mechanisms of SWCNTs at the molecular level, and to probe their potential relationships with their morphological, surface, and electronic properties. The results indicated that DNA damage and oxidative stress were the dominant mechanisms of action for all SWCNTs and, the toxicity level and characteristics varied with length, surface functionalization and electronic structure. Distinguishable molecular toxicity fingerprints were revealed for the two SWCNTs with varying length, with short SWCNT exhibiting higher toxicity level than the long one. In terms of surface properties, SWCNT functionalization, namely carboxylation and hydroxylation, led to elevated overall toxicity, especially genotoxicity, as compared to unmodified SWCNT. Carboxylated SWCNT induced a greater toxicity than the hydroxylated SWCNT. The nucleus is likely the primary target site for long, short, and carboxylated SWCNTs and mechanical perturbation is likely responsible for the DNA damage, specifically related to degradation of the DNA double helix structure. Finally, dramatically different electronic structure-dependent toxicity was observed with metallic SWCNT exerting much higher toxicity than the semiconducting one that exhibited minimal toxicity among all SWCNTs.

Nanomaterial Effects on Viral Infection

The potential for environmental and occupational exposures of populations to nanomaterials (NMs) has fostered concerns of associated adverse health effects, with a particular emphasis on pulmonary injury and disease. Many studies have revealed that several types of NMs can evoke a variety of biological responses, such as pulmonary inflammation and oxidative stress, which contribute to allergy, fibrosis, and granuloma formation. Less attention has been paid to health effects that may result from exposure to NMs and additional stressors such as pathogens, with a particular focus on susceptibility to viral infection. This chapter will summarize the current body of literature related to NMs and viral exposures with a primary focus on immune modulation. A summary of the studies performed and major findings to date will be discussed, highlighting proposed molecular mechanisms behind NM-driven host susceptibility, challenges, limitations, and future research needs. Specific mechanisms discussed include direct interaction between NMs and biological molecules, activation of pattern recognition receptors (PRRs) and related signaling pathways, production of oxidative stress and mitochondrial dysfunction, inflammasome activation, and modulation of lipid signaling networks.

Single-walled carbon nanotubes repress viral-induced defense pathways through oxidative stress

Exposure of lung cells in vitro or mice to single-walled carbon nanotubes (SWCNTs) directly to the respiratory tract leads to a reduced host anti-viral immune response to infection with influenza A virus H1N1 (IAV), resulting in significant increases in viral titers. This suggests that unintended exposure to nanotubes via inhalation may increase susceptibility to notorious respiratory viruses that carry a high social and economic burden globally. However, the molecular mechanisms that contribute to viral susceptibility have not been elucidated. In the present study, we identified the retinoic acid-induced gene I (RIG-I) like receptors (RLRs)/mitochondrial antiviral signaling (MAVS) pathway as a target of SWCNT-induced oxidative stress in small airway epithelial cells (SAEC) that contribute to significantly enhanced influenza viral titers. Exposure of SAEC to SWCNTs increases viral titers while repressing several aspects of the RLR pathway, including mRNA expression of key genes (e.g. IFITs, RIG-I, MDA5, IFNβ1, CCL5). SWCNTs also reduce mitochondrial membrane potential without altering oxygen consumption rates. Our findings also indicate that SWCNTs can impair formation of MAVS prion-like aggregates, which is known to impede downstream activation of the RLR pathway and hence the transcriptional production of interferon-regulated anti-viral genes and cytokines. Furthermore, application of the antioxidant NAC alleviates inhibition of gene expression levels by SWCNTs, as well as MAVS signalosome formation, and increased viral titers. These data provide evidence of targeted impairment of anti-viral signaling networks that are vital to immune defense mechanisms in lung cells, contributing to increased susceptibility to IAV infections by SWCNTs.

Fibrous nanocellulose, crystalline nanocellulose, carbon nanotubes, and crocidolite asbestos elicit disparate immune responses upon pharyngeal aspiration in mice

With the rapid development of synthetic alternatives to mineral fibers, their possible effects on the environment and human health have become recognized as important issues worldwide. This study investigated effects of four fibrous materials, i.e. nanofibrillar/nanocrystalline celluloses (NCF and CNC), single-walled carbon nanotubes (CNTs), and crocidolite asbestos (ASB), on pulmonary inflammation and immune responses found in the lungs, as well as the effects on spleen and peripheral blood immune cell subsets. BALB/c mice were given NCF, CNC, CNT, and ASB on Day 1 by oropharyngeal aspiration. At 14 days post-exposure, the animals were evaluated. Total cell number, mononuclear phagocytes, polymorphonuclear leukocytes, lymphocytes, and LDH levels were significantly increased in ASB and CNT-exposed mice. Expression of cytokines and chemokines in bronchoalveolar lavage (BAL) was quite different in mice exposed to four particle types, as well as expression of antigen presentation-related surface proteins on BAL cells. The results revealed that pulmonary exposure to fibrous materials led to discrete local immune cell polarization patterns with a T_H2-like response caused by ASB and T_H1-like immune reaction to NCF, while CNT and CNC caused non-classical or non-uniform responses. These alterations in immune response following pulmonary exposure should be taken into account when testing the applicability of new nanosized materials with fibrous morphology.

Ambient fine particulate matters induce cell death and inflammatory response by influencing mitochondria function in human corneal epithelial cells

Ambient fine particulate matter (AFP) is a main risk factor for the cornea as ultraviolet light. However, the mechanism of corneal damage following exposure to AFP has been poorly understood. In this study, we first confirmed that AFP can penetrate the cornea of mice, considering that two-dimensional cell culture systems are limited in reflecting the situation in vivo. Then, we investigated the toxic mechanism using human corneal epithelial (HCET) cells. At 24h after exposure, AFP located within the autophagosome-like vacuoles, and cell proliferation was clearly inhibited in all the tested concentration. Production of ROS and NO and secretion of pro-inflammatory cytokines were elevated in a dose-dependent manner. Additionally, conversion of LC3B from I-type to II-type and activation of caspase cascade which show autophagic- and apoptotic cell death, respectively, were observed in cells exposed to AFP. Furthermore, AFP decreased mitochondrial volume, inhibited ATP production, and altered the expression of metabolism-related genes. Taken together, we suggest that AFP induces cell death and inflammatory response by influencing mitochondrial function in HCET cells. In addition, we recommend that stringent air quality regulations are needed for eye health.

Pulmonary persistence of graphene nanoplatelets may disturb physiological and immunological homeostasis

Accumulated evidence suggests that chronic pulmonary accumulation of harmful particles cause adverse pulmonary and systemic health effects. In our previous study, most of the graphene nanoplatelet (GNP) remained in the lung until 28 days after a single instillation. In this study, we sought to evaluate the local and systemic health effect after a long pulmonary persistence of GNP. As expected, GNP remained in the lung on day 90 after a single intratracheal instillation (1.25, 2.5 and 5 mg kg^-1 ). In the lung exposed at the highest dose, the total number of cells and the percentage of lymphocytes significantly increased in the BAL fluid with an increase in both the number of GNP-engulfed macrophages and the percentage of apoptotic cells. A Th1-shifted immune response, the elevated chemokine secretion and the enhanced expression of cytoskeletal-related genes were observed. Additionally, the expression of natriuretic-related genes was noteworthy altered in the lungs. Moreover, the number of white blood cells (WBC) and the percentage of macrophages and neutrophils clearly increased in the blood of mice exposed to a 5-mg kg^-1 dose, whereas total protein, BUN and potassium levels significantly decreased. In conclusion, we suggest that the long persistence of GNP in the lung may cause adverse health effects by disturbing immunological- and physiological-homeostasis of our body. Copyright © 2016 John Wiley & Sons, Ltd.