Multi-Walled Carbon Nanotubes (MWCNTs) Cause Cellular Senescence in TGF-β Stimulated Lung Epithelial Cells

Effects of nanomaterial exposure on telomere dysfunction, hallmarks of mammalian and zebrafish cell senescence, and zebrafish mortality

Environmental and occupational exposure to hazardous substances accelerates biological aging. However, the toxic effects of nanomaterials on telomere and cellular senescence (major hallmarks of the biological aging) remained controversial. This study was to synthesize all published evidence to explore the effects of nanomaterial exposure on the telomere change, cellular senescence and mortality of model animals. Thirty-five studies were included by searching electronic databases (PubMed, Embase and Web of Science). The pooled analysis by Stata 15.0 software showed that compared with the control, nanomaterial exposure could significantly shorten the telomere length [measured as kbp: standardized mean difference (SMD) = -1.88; 95% confidence interval (CI) = -3.13 - - 0.64; % of control: SMD = -1.26; 95%CI = -2.11- - 0.42; < 3 kbp %: SMD = 5.76; 95%CI = 2.92 - 8.60), increase the telomerase activity (SMD = -1.00; 95%CI = -1.74 to -0.26), senescence-associated β-galactosidase levels in cells (SMD = 8.20; 95%CI = 6.05 - 10.34) and zebrafish embryos (SMD = 7.32; 95%CI = 4.70 - 9.94) as well as the mortality of zebrafish (SMD = 3.83; 95%CI = 2.94 - 4.72)]. The expression levels of telomerase TERT, shelterin components (TRF1, TRF2 and POT1) and senescence biomarkers (p21, p16) were respectively identified to be decreased or increased in subgroup analyses. In conclusion, this meta-analysis demonstrates that nanomaterial exposure is associated with telomere attrition, cell senescence and organismal death.

Impaired autophagy-accelerated senescence of alveolar type II epithelial cells drives pulmonary fibrosis induced by single-walled carbon nanotubes

BACKGROUND

The rapid increase in production and application of carbon nanotubes (CNTs) has led to wide public concerns in their potential risks to human health. Single-walled CNTs (SWCNTs), as an extensively applied type of CNTs, have shown strong capacity to induce pulmonary fibrosis in animal models, however, the intrinsic mechanisms remain uncertain.

RESULTS

In vivo experiments, we showed that accelerated senescence of alveolar type II epithelial cells (AECIIs) was associated with pulmonary fibrosis in SWCNTs-exposed mice, as well as SWCNTs-induced fibrotic lungs exhibited impaired autophagic flux in AECIIs in a time dependent manner. In vitro, SWCNTs exposure resulted in profound dysfunctions of MLE-12 cells, characterized by impaired autophagic flux and accelerated cellular senescence. Furthermore, the conditioned medium from SWCNTs-exposed MLE-12 cells promoted fibroblast-myofibroblast transdifferentiation (FMT). Additionally, restoration of autophagy flux with rapamycin significantly alleviated SWCNTs-triggered senescence and subsequent FMT whereas inhibiting autophagy using 3-MA aggravated SWCNTs-triggered senescence in MLE-12 cells and FMT.

CONCLUSION

SWCNTs trigger senescence of AECIIs by impairing autophagic flux mediated pulmonary fibrosis. The findings raise the possibility of senescence-related cytokines as potential biomarkers for the hazard of CNTs exposure and regulating autophagy as an appealing target to halt CNTs-induced development of pulmonary fibrosis.

Inflammatory Genes Associated with Pristine Multi-Walled Carbon Nanotubes-Induced Toxicity in Ocular Cells

Background

The wide application of multi-walled carbon nanotubes (MWCNTs) in various fields has raised enormous concerns regarding their safety for humans. However, studies on the toxicity of MWCNTs to the eye are rare and potential molecular mechanisms are completely lacking. This study was to evaluate the adverse effects and toxic mechanisms of MWCNTs on human ocular cells.

Methods

Human retinal pigment epithelial cells (ARPE-19) were treated with pristine MWCNTs (7-11 nm) (0, 25, 50, 100 or 200 μg/mL) for 24 hours. MWCNTs uptake into ARPE-19 cells was examined using transmission electron microscopy (TEM). The cytotoxicity was evaluated by CCK-8 assay. The death cells were detected by Annexin V-FITC/PI assay. RNA profiles in MWCNT-exposed and non-exposed cells (n = 3) were analyzed using RNA-sequencing. The differentially expressed genes (DEGs) were identified through the DESeq2 method and hub of which were filtered by weighted gene co-expression, protein-protein interaction (PPI) and lncRNA-mRNA co-expression network analyses. The mRNA and protein expression levels of crucial genes were verified using quantitative polymerase chain reaction (qPCR), colorimetric analysis, ELISA and Western blotting. The toxicity and mechanisms of MWCNTs were also validated in human corneal epithelial cells (HCE-T).

Results

TEM analysis indicated the internalization of MWCNTs into ARPE-19 cells to cause cell damage. Compared with untreated ARPE-19 cells, those exposed to MWCNTs exhibited significantly decreased cell viabilities in a dose-dependent manner. The percentages of apoptotic (early, Annexin V positive; late, Annexin V and PI positive) and necrotic (PI positive) cells were significantly increased after exposure to IC50 concentration (100 μg/mL). A total of 703 genes were identified as DEGs; 254 and 56 of them were, respectively, included in darkorange2 and brown1 modules that were significantly associated with MWCNT exposure. Inflammation-related genes (including CXCL8, MMP1, CASP3, FOS, CXCL2 and IL11) were screened as hub genes by calculating the topological characteristics of genes in the PPI network. Two dysregulated long non-coding RNAs (LUCAT1 and SCAT8) were shown to regulate these inflammation-related genes in the co-expression network. The mRNA levels of all eight genes were confirmed to be upregulated, while caspase-3 activity and the release of CXCL8, MMP1, CXCL2, IL11 and FOS proteins were demonstrated to be increased in MWCNT-treated ARPE-19 cells. MWCNTs exposure also can induce cytotoxicity and increase the caspase-3 activity and the expression of LUCAT1, MMP1, CXCL2, and IL11 mRNA and protein in HCE-T cells.

Conclusion

Our study provides promising biomarkers for monitoring MWCNT-induced eye disorders and targets for developing preventive and therapeutic strategies.

Advanced nanomaterials for modulating Alzheimer's related amyloid aggregation

Alzheimer's disease (AD) is a common neurodegenerative disease that brings about enormous economic pressure to families and society. Inhibiting abnormal aggregation of Aβ and accelerating the dissociation of aggregates is treated as an effective method to prevent and treat AD. Recently, nanomaterials have been applied in AD treatment due to their excellent physicochemical properties and drug activity. As a drug delivery platform or inhibitor, various excellent nanomaterials have exhibited potential in inhibiting Aβ fibrillation, disaggregating, and clearing mature amyloid plaques by enhancing the performance of drugs. This review comprehensively summarizes the advantages and disadvantages of nanomaterials in modulating amyloid aggregation and AD treatment. The design of various functional nanomaterials is discussed, and the strategies for improved properties toward AD treatment are analyzed. Finally, the challenges faced by nanomaterials with different dimensions in AD-related amyloid aggregate modulation are expounded, and the prospects of nanomaterials are proposed.

Multiwalled Carbon Nanotubes Induce Fibrosis and Telomere Length Alterations

Telomere shortening can result in cellular senescence and in increased level of genome instability, which are key events in numerous of cancer types. Despite this, few studies have focused on the effect of nanomaterial exposure on telomere length as a possible mechanism involved in nanomaterial-induced carcinogenesis. In this study, effects of exposure to multiwalled carbon nanotubes (MWCNT) on telomere length were investigated in mice exposed by intrapleural injection, as well as in human lung epithelial and mesothelial cell lines. In addition, cell cycle, apoptosis, and regulation of genes involved in DNA damage repair were assessed. Exposure to MWCNT led to severe fibrosis, infiltration of inflammatory cells in pleura, and mesothelial cell hyperplasia. These histological alterations were accompanied by deregulation of genes involved in fibrosis and immune cell recruitment, as well as a significant shortening of telomeres in the pleura and the lung. Assessment of key carcinogenic mechanisms in vitro confirmed that long-term exposure to the long MWCNT led to a prominent telomere shortening in epithelial cells, which coincided with G1-phase arrest and enhanced apoptosis. Altogether, our data show that telomere shortening resulting in cell cycle arrest and apoptosis may be an important mechanism in long MWCNT-induced inflammation and fibrosis.