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.

Inflammation in the pleural cavity following injection of multi-walled carbon nanotubes is dependent on their characteristics and the presence of IL-1 genes.

Upon inhalation, multi-walled carbon nanotubes (MWCNTs) may reach the subpleura and pleural spaces, and induce pleural inflammation and/or mesothelioma in humans. However, the mechanisms of MWCNT-induced pathology after direct intrapleural injections are still only partly elucidated. In particular, a role of the proinflammatory interleukin-1 (IL-1) cytokines in pleural inflammation has so far not been published. We examined the MWCNT-induced pleural inflammation, gene expression abnormalities, and the modifying role of IL-1α and ß cytokines following intrapleural injection of two types of MWCNTs (CNT-1 and CNT-2) compared with crocidolite asbestos in IL-1 wild-type (WT) and IL-1α/ß KO (IL1-KO) mice. Histopathological examination of the pleura 28 days post-exposure revealed mesothelial cell hyperplasia, leukocyte infiltration, and fibrosis occurring in the CNT-1 (Mitsui-7)-exposed group. The pleura of these mice also showed the greatest changes in mRNA and miRNA expression levels, closely followed by CNT-2. In addition, the CNT-1-exposed group also presented the greatest infiltrations of leukocytes and proliferation of fibrous tissue. WT mice were more prone to development of sustained inflammation and fibrosis than IL1-KO mice. Prominent differences in genetic and epigenetic changes were also observed between the two genotypes. In conclusion, the fibrotic response to MWCNTs in the pleura depends on the particles' physico-chemical properties and on the presence or absence of the IL-1 genes. Furthermore, we found that CNT-1 was the most potent inducer of inflammatory responses, followed by CNT-2 and crocidolite asbestos.

Effects of carbon nanotubes on intercellular communication and involvement of IL-1 genes.

An increasing amount of products containing engineered nanoparticles is emerging. Among these particles are carbon nanotubes (CNTs) which are of interest for a wide range of industrial and biomedical applications. There have been raised concerns over the effects of CNTs on human health. Some types of CNTs are classified as group 2B carcinogens by the International Agency for Research on Cancer. CNTs may also induce pulmonary inflammatory and fibrotic effects. By utilizing CNTs of different lengths, we investigated the role of the proinflammatory cytokine, interleukin-1 (IL-1) on gap junctional intercellular communication (GJIC) by using IL-1 wild-type (IL1-WT) and IL-1 knock-out (IL1-KO) cells. GJIC decreased equally in both cell types after CNT exposure. Immunofluorescence staining showed Gja1 and Gjb2 in gap junctions and hemichannels for both cell types. Gjb1 and Gjb2 expression was low in IL1-KO cells, which was confirmed by protein analysis. Gja1 was upregulated with both CNTs, whereas Gjb1 was down-regulated by CNT-2 in IL1-WT cells. Connexin mRNA expression was regulated differently by the CNTs. CNT-1 affected Gja1 and Gjb2, whereas CNT-2 had an effect on Gjb1. CNTs negatively affect GJIC through gap junctions independently of the length of CNT and IL-1 status. Furthermore, connexin gene expression was affected by IL-1 at transcriptional and translational levels. As both CNTs used in this study are cytotoxic to the cells and reduce cell survival, we suggest that CNT-induced reduction in GJIC may be important for inhibiting transfer of cell survival signals between cells.

Analysis of polymorphisms in the circadian-related genes and breast cancer risk in Norwegian nurses working night shifts.

INTRODUCTION: Some studies have suggested that night work may be associated with an increased risk of breast cancer in nurses. We aimed to explore the role of circadian gene polymorphisms in the susceptibility to night work-related breast cancer risk. METHODS: We conducted a nested case-control study of Norwegian nurses comprising 563 breast cancer cases and 619 controls within a cohort of 49,402 Norwegian nurses ages 35 to 74 years. We studied 60 single-nucleotide polymorphisms (SNPs) in 17 genes involved in the regulation of the circadian rhythm in cases and controls. The data were analyzed in relation to the two exposure variables "maximum number of consecutive night shifts ever worked" and "maximum number of consecutive night shifts worked for at least 5 years." The odds of breast cancer associated with each SNP was calculated in the main effects analysis and in relation to night shift work. The statistically significant odds ratios were tested for noteworthiness using two Bayesian tests: false positive report probability (FPRP) and Bayesian false discovery probability (BFDP). RESULTS: In the main effects analysis, CC carriers of rs4238989 and GG carriers of rs3760138 in the AANAT gene had increased risk of breast cancer, whereas TT carriers of BMAL1 rs2278749 and TT carriers of CLOCK rs3749474 had reduced risk. The associations were found to be noteworthy using both the FPRP and BFDP tests. With regard to the effect of polymorphisms and night work, several significant associations were observed. After applying FPRP and BFDP in women with at least four night shifts, an increased risk of breast cancer was associated with variant alleles of SNPs in the genes AANAT (rs3760138, rs4238989), BMAL1 (rs2290035, rs2278749, rs969485) and ROR-b (rs3750420). In women with three consecutive night shifts, a reduced risk of breast cancer was associated with carriage of variant alleles of SNPs in CLOCK (rs3749474), BMAL1 (rs2278749), BMAL2 (rs2306074), CSNK1E (rs5757037), NPAS2 (rs17024926), ROR-b (rs3903529, rs3750420), MTNR1A (rs131113549) and PER3 (rs1012477). CONCLUSIONS: Significant and noteworthy associations between several polymorphisms in circadian genes, night work and breast cancer risk were found among nurses who had worked at least three consecutive night shifts.