Oxidative effects of lungs in Wistar rats caused by long-term exposure to four kinds of China representative chrysotile

Vitamin B complex blocks the dust fall PM2 .5 -induced acute lung injury through DNA methylation in rats

This study aimed to explore whether vitamin B complex (folic acid, B₆ , and B₁₂ ) could avert DNA methylation changes associated with inflammation induced by acute PM_2.5 exposure. Sprague-Dawley rats were administered by gavage with different concentrations of vitamin B complex once a day for 28 days, and then by intratracheal instillation with saline or PM_2.5 once every 2 days for three times. Vitamin B continued to be taken during the PM_2.5 exposure. Rats were sacrificed 24 h after the last exposure. The results showed that vitamin B complex could block the pathological changes and injury in lungs induced by PM_2.5 . Meanwhile, vitamin B complex could prevent the abnormal DNA methylation of IL-4 and IFN-γ to antagonize the imbalance of IL-4/IFN-γ associated with inflammation. It was further found that vitamin B complex could regulate DNA methyltransferases (DNMTs) and increase the S-adenosylmethionine (SAM)/S-Adenosyl-L-homocysteine (SAH) ratio to reverse the hypomethylation of genomic DNA and the abnormal DNA methylation of IL-4 and IFN-γ. In conclusion, vitamin B complex has a protective effect on acute lung injury by attenuating abnormal DNA methylation induced by PM_2.5 in rats. This study may provide a new insight into the physiological function of vitamin B to prevent the health effects induced by PM_2.5 .

Role of PARP1 on DNA damage induced by mineral silicate chrysotile in bronchial epithelial and pleural mesothelial cells

To investigate whether poly (ADP ribose) polymerase-1 (PARP1) is involved in chrysotile-induced DNA damage in pleural mesothelial cells (MeT-5A) and bronchial epithelial cells (BEAS-2B), two PARP1-deficient cell lines were established. Efficiencies of RNA interference on PARP1 were detected by western blot and qPCR. Here, normal cells and PARP1-deficient cells were exposed to chrysotile, and DNA damage and DNA repair were detected by alkaline comet assay. All cells were treated with chrysotile at the indicated concentrations (5, 10, 20, and 40 μg/cm²) for 24 h and then the DNA repair capacity was observed for 12 and 24 h, respectively. The results showed that chrysotile caused DNA damage at an obvious dose-dependent manner in MeT-5A and BEAS-2B cells. In addition, MeT-5A cells had more persistent DNA damage than BEAS-2B. Compared to normal cells, the PARP1-deficient cells were more sensitive to DNA damage caused by chrysotile. In DNA repair experiments, all cell lines recovered from the damage over time. The results of relative repair percentage (RRP) of MeT-5A and BEAS-2B were higher than those of MeT-5A shPARP1 and BEAS-2B shPARP1 cells at all experimental concentrations (except 5 μg/cm²) at 12-h repair. However, RRP of BEAS-2B and BEAS-2B shPARP1 tended to be closer, and RRP of MeT-5A shPARP1 was still lower than that of MeT-5A at 24-h repair. All results suggest that PARP1 plays an important role in early repair of DNA damage in BEAS-2B and MeT-5A cells exposed to chrysotile.

Role of microRNAs in Lung Carcinogenesis Induced by Asbestos

MicroRNAs are a class of small noncoding endogenous RNAs 19–25 nucleotides long, which play an important role in the post-transcriptional regulation of gene expression by targeting mRNA targets with subsequent repression of translation. MicroRNAs are involved in the pathogenesis of numerous diseases, including cancer. Lung cancer is the leading cause of cancer death in the world. Lung cancer is usually associated with tobacco smoking. However, about 25% of lung cancer cases occur in people who have never smoked. According to the International Agency for Research on Cancer, asbestos has been classified as one of the cancerogenic factors for lung cancer. The mechanism of malignant transformation under the influence of asbestos is associated with the genotoxic effect of reactive oxygen species, which initiate the processes of DNA damage in the cell. However, epigenetic mechanisms such as changes in the microRNA expression profile may also be implicated in the pathogenesis of asbestos-induced lung cancer. Numerous studies have shown that microRNAs can serve as a biomarker of the effects of various adverse environmental factors on the human body. This review examines the role of microRNAs, the expression profile of which changes upon exposure to asbestos, in key processes of carcinogenesis, such as proliferation, cell survival, metastasis, neo-angiogenesis, and immune response avoidance.

Long-term instillation to four natural representative chrysotile of China induce the inactivation of P53 and P16 and the activation of C-JUN and C-FOS in the lung tissues of Wistar rats

Chrysotile is the only type of asbestos still widely exploited, and all kinds of asbestos including chrysotile was classified as a group I carcinogen by the IARC. There is a wealth of evidence that chrysotile can cause a range of cancers, including cancer of the lung, larynx, ovary, and mesothelioma. As the second largest chrysotile producer, China is at great risk of occupational exposure. Moreover, our previous experiment and some other studies have shown that the toxicity of mineral fibre from various mining areas may be different. To explore the oncogenic potential of chrysotile from different mining areas of China, Wistar rats were administered 0.5 mL chrysotile asbestos suspension of 2.0 mg/mL (from Akesai, Gansu; Mangnai, Qinghai; XinKang, Sichuan; and Shannan, Shaanxi) dissolved in saline by intratracheal instillation once-monthly and were sacrificed at 1 mo, 6 mo, and 12 mo. Our results found that chrysotile caused lung inflammation and lung tissue damage. Moreover, prolonged exposure of chrysotile can induce inactivation of the tumor suppressor gene P53 and P16 and activation of the protooncogene C-JUN and C-FOS both in the messenger RNA and protein level. In addition, chrysotile from Shannan and XinKang has a stronger effect which may link to cancer than that from Akesai and Mangnai.

Anticancer Effect of Rosiglitazone, a PPAR-γ Agonist against Diethylnitrosamine-Induced Lung Carcinogenesis

Multiple effects on cancer cells are exerted by the peroxisome proliferator-activated receptor γ (PPAR-γ). Recent studies have shown that rosiglitazone, a synthetic PPAR-γ ligand, inhibits the growth of cells. This research was designed to assess the impact of rosiglitazone on diethylnitrosamine (DENA)-induced lung carcinogenesis in Wistar rats and to study the underlying molecular mechanism. A total of 40 adult male Wistar rats were separated into four groups as follows: group 1 is known as a control. Group 2 is known as the DENA group (150 mg/kg, i.p.). Group 3 and group 4 denote DENA-induced rats treated with 5 and 10 mg/kg rosiglitazone, respectively. Lipid peroxidation, various antioxidant enzymes, histological perceptions, and caspase-3, Bcl2, and Bax gene expression were measured in lung tissues. Rosiglitazone treatment reverted the DENA-induced changes in the expression of these genes, inflammatory cytokines, and oxidative stress. However, blotting analysis discovered reduced caspase-3 and BAX expressions and elevated Bcl-2 expression in DENA-induced rats. The expression of such proteins causing DENA lung cancer was restored by rosiglitazone therapy.