Piye Niu

Silica nanoparticles induce oxidative stress, inflammation, and endothelial dysfunction in vitro via activation of the MAPK/Nrf2 pathway and nuclear factor-κB signaling

Despite the widespread application of silica nanoparticles (SiNPs) in industrial, commercial, and biomedical fields, their response to human cells has not been fully elucidated. Overall, little is known about the toxicological effects of SiNPs on the cardiovascular system. In this study, SiNPs with a 58 nm diameter were used to study their interaction with human umbilical vein endothelial cells (HUVECs). Dose- and time-dependent decrease in cell viability and damage on cell plasma-membrane integrity showed the cytotoxic potential of the SiNPs. SiNPs were found to induce oxidative stress, as evidenced by the significant elevation of reactive oxygen species generation and malondialdehyde production and downregulated activity in glutathione peroxidase. SiNPs also stimulated release of cytoprotective nitric oxide (NO) and upregulated inducible nitric oxide synthase (NOS) messenger ribonucleic acid, while downregulating endothelial NOS and ET-1 messenger ribonucleic acid, suggesting that SiNPs disturbed the NO/NOS system. SiNP-induced oxidative stress and NO/NOS imbalance resulted in endothelial dysfunction. SiNPs induced inflammation characterized by the upregulation of key inflammatory mediators, including IL-1β, IL-6, IL-8, TNFα, ICAM-1, VCAM-1, and MCP-1. In addition, SiNPs triggered the activation of the Nrf2-mediated antioxidant system, as evidenced by the induction of nuclear factor-κB and MAPK pathway activation. Our findings demonstrated that SiNPs could induce oxidative stress, inflammation, and NO/NOS system imbalance, and eventually lead to endothelial dysfunction via activation of the MAPK/Nrf2 pathway and nuclear factor-κB signaling. This study indicated a potential deleterious effect of SiNPs on the vascular endothelium, which warrants more careful assessment of SiNPs before their application.

Bone morphogenetic protein-7 inhibits silica-induced pulmonary fibrosis in rats.

Bone morphogenetic protein-7 (BMP-7) has been shown to inhibit liver and renal fibrosis in in vivo and vitro studies. There is no study to investigate BMP-7s role in the development of pulmonary fibrosis induced by silica. In the current study, we used the rat model to explore the potential antifibrotic role of BMP-7 and its underlying mechanism in silica-induced pulmonary fibrosis. Sixty Wistar rats were randomly assigned into three groups. Control group received saline, silica group received silica and BMP-7 treated group received silica and BMP-7. BMP-7 was administered to silica-treated rats intraperitoneally at a dose of 300μg/kg/injection from day 8 to day 30 every other day. After the animals were sacrificed on day 15 and 30, hydroxyproline levels, the protein expressions of BMP/Smad and TGF-β/Smad signaling, and histopathology in lung tissues were analyzed. The hydroxyproline contents in BMP-7 treated groups were significantly lower than the silica groups (P<0.05). Histopathological results showed BMP-7 could reduce the progression of silica induced fibrosis. Furthermore, the expression of p-Smad1/5/8, a marker of BMP/Smad signaling, was significantly up-regulated in BMP-7 treated groups (P<0.05) compared with the silica groups. On the contrary, the expression of p-Smad2/3, a marker for TGF-β/Smad signaling, reduced significantly in BMP-7-treated groups compared with silica groups (P<0.05). In conclusion, the pulmonary fibrosis induced by silica in rats was significantly reduced with the therapeutic treatment of BMP-7. The antifibrotic effect of BMP-7 could be related to the activation of BMP/Smad signaling and inhibition of TGF-β/Smad pathways.

Aberrant miRNA profiles associated with chronic benzene poisoning.

Chronic occupational benzene exposure is associated with an increased risk of hematological malignancies. To gain an insight into the new biomarkers and molecular mechanisms of chronic benzene poisoning, miRNA profiles and mRNA expression pattern from the peripheral blood mononuclear cells of chronic benzene poisoning patients and health controls matched age and gender without benzene exposure were performed using the Exiqon miRNA PCR ARRAY and Gene Chip Human Gene 2.0ST Arrays, respectively. Totally, 6 up-regulated miRNAs (miR-34a, miR-205, miR-10b, let-7d, miR-185 and miR-423-5p-2) and 7 down-regulated miRNAs (miR-133a, miR-543, hsa-miR-130a, miR-27b,miR-223, miR-142-5p and miR-320b) were found in chronic benzene poisoning group compared to health controls (P ≤ 0.05). By integrating miRNA and mRNA expression data, these differential miRNAs were mainly involved in regulation of transcription from RNA polymerase II promoter, axon guidance, regulation of transcription, DNA-dependent, nervous system development, and regulation of actin cytoskeleton organization. Further, pathway analysis indicated that SMAD4, PLCB1, NFAT5, GNAI2, PTEN, VEGFA, BCL2, CTNNB1 and CCND1 were key target genes of differential miRNAs which were implicated in Adherens junction, TGF-beta signaling pathway, Wnt signaling pathway, tight junction and Pathways in cancer. In conclusion, the aberrant miRNAs might be a potential biomarker of chronic benzene poisoning.

Aberrant hypomethylated STAT3 was identified as a biomarker of chronic benzene poisoning through integrating DNA methylation and mRNA expression data

Chronic occupational benzene exposure is associated with an increased risk of hematological malignancies such as aplastic anemia and leukemia. The new biomarker and action mechanisms of chronic benzene poisoning are still required to be explored. Aberrant DNA methylation, which may lead to genomic instability and the altered gene expression, is frequently observed in hematological cancers. To gain an insight into the new biomarkers and molecular mechanisms of chronic benzene poisoning, DNA methylation profiles and mRNA expression pattern from the peripheral blood mononuclear cells of four chronic benzene poisoning patients and four health controls that matched age and gender without benzene exposure were performed using the high resolution Infinium 450K methylation array and Gene Chip Human Gene 2.0ST Arrays, respectively. By integrating DNA methylation and mRNA expression data, we identified 3 hypermethylated genes showing concurrent down-regulation (PRKG1, PARD3, EPHA8) and 2 hypomethylated genes showing increased expression (STAT3, IFNGR1). Signal net analysis of differential methylation genes associated with chronic benzene poisoning showed that two key hypomethylated STAT3 and hypermethylated GNAI1 were identified. Further GO analysis and pathway analysis indicated that hypomethylated STAT3 played central roles through regulation of transcription, DNA-dependent, positive regulation of transcription from RNA polymerase II promoter, JAK-STAT cascade and adipocytokine signaling pathway, Acute myeloid leukemia, and JAK-STAT signaling pathway. In conclusion, the aberrant hypomethylated STAT3 might be a potential biomarker of chronic benzene poisoning.

Long non-coding RNA NR_045623 and NR_028291 involved in benzene hematotoxicity in occupationally benzene-exposed workers

Benzene is an established human hematotoxicant and leukemogen. New insights into the pathogenesis of benzene hematotoxicity are urgently needed. Long non-coding RNA (lncRNA) widely participate in various physiological and pathological processes. It has been shown that lncRNA plays an important role in hematologic malignancy tumorigenesis. However, the expression and biological function of lncRNA during benzene hematotoxicity progress remain largely unknown. An integrated analysis of differentially expressed lncRNA and mRNA was performed to identify genes which were likely to be critical for benzene hematotoxicity through Microarray analysis. Dynamic gene network analysis of the differentially expressed lncRNA and mRNA was constructed and two main lncRNA (NR_045623 and NR_028291) were discovered and two key lncRNA subnets were involved in immune responses, hematopoiesis, B cell receptor signaling pathway and chronic myeloid leukemia. These findings suggested that NR_045623 and NR_028291 might be the key genes associated with benzene hematotoxicity.

Suppression of thioredoxin system contributes to silica-induced oxidative stress and pulmonary fibrogenesis in rats.

Silicosis is one of the most prevalent occupational lung diseases worldwide. This study aimed to investigate the possible mechanism that silica affected thioredoxin (Trx) system during the development of silicosis in vivo. Male Wistar rats were randomly divided into saline group and silica group in which rats were intratracheally instilled with a single dose of silica suspension (50mg in 1ml saline/rat). After 7, 15 or 30 days instillation, rats were sacrificed. Biochemical parameters and histopathology were assessed. Our results demonstrated that silica could significantly cause the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) as well as activate antioxidative protein Nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream protein Trx in the early exposure to silica. The inhibition of Trx activity and the down-regulated expression of thioredoxin reductase (TrxR), suggesting that the function of Trx system may be suppressive induced by silica. Content of lung hydroxyproline and histopathological results showed significant fibrosis development with time. In conclusion, our study demonstrated that silica could suppress the Trx system to perturb the redox balance, elicit oxidative stress, and eventually induce pulmonary fibrosis.

Bone morphogenetic protein 7 attenuates epithelial–mesenchymal transition induced by silica

The epithelial–mesenchymal transition (EMT) is a critical process in the pulmonary fibrosis. It has been reported that bone morphogenetic protein 7 (BMP-7) was able to reverse EMT in proximal tubular cells. Therefore, we test the hypothesis that EMT contributes to silica-induced pulmonary fibrosis and BMP-7 inhibits EMT in silica-induced pulmonary fibrosis. Progressive silica-induced pulmonary fibrosis in the rat was used as a model of silicosis. Epithelial and mesenchymal markers were measured from rat fibrotic lungs. Then the effects of BMP-7 on the EMT were further confirmed in A549 cells. There are increases of vimentin as a mesenchymal marker and decreases of E-cadherin as an epithelial marker in the silica-exposed rat lungs, which is in agreement with the A549 cells data. However, BMP-7 treatment significantly reduced expression of vimentin in the rat pulmonary fibrosis model and in A549 cells. In conclusion, EMT contributes to silica-induced pulmonary fibrosis. Meanwhile, the treatment of BMP-7 can inhibit silica-induced EMT in vitro and in vivo.

Effect of bone morphogenic protein-7 on the expression of epithelial-mesenchymal transition markers in silicosis model

This study presented the effect of bone morphogenic protein-7 (BMP-7) inhibiting epithelial-mesenchymal transition (EMT) in silicosis model. In vivo, Wistar rats were exposed to silica by intratracheal instillation. Seven days later rats were treated with BMP-7. Rats were sacrificed at 15 and 30days after exposure of silica. The results demonstrated vimentin expression was down-regulated; and E-cadherin was up-regulated after intervention with BMP-7. The TGF-β expression and phosphorylation-p38 were lower in BMP-7 treated group than in silica group. In vitro, p38 MAPK/Snail signaling pathway was involved in the occurrence of EMT in A549 cells treated by silica. EMT was inhibited by BMP-7. The data showed BMP-7 inhibited EMT induced by silica associated with inhibition of p38 MAPK/Snail pathway.

Differential gene expression profiling analysis in workers occupationally exposed to benzene

UNLABELLED Benzene is an important industrial chemical and an environmental contaminant, but the pathogenesis of hematotoxicity induced by chronic occupational benzene exposure remains to be elucidated. To gain an insight into the molecular mechanisms and new biomarkers, microarray analysis was used to identify the differentially expressed mRNA critical for benzene hematotoxicity. RNA was extracted from four chronic benzene poisoning patients occupationally exposed to benzene, three benzene-exposed workers without clinical symptoms and three health controls without benzene exposure and mRNA expression profiling was performed using Gene Chip Human Gene 2.0ST Arrays. Analysis of mRNA expression profiles were conducted to identify key genes, biological processes and pathways by the series test of cluster (STC), STC-Gene Ontology analysis (STC-GO), pathway analysis and Signal-net. PRINCIPAL FINDINGS 1) 1661 differentially expressed mRNAs were identified and assigned to sixteen model profiles. 2) Profiles 14, 10, 11, 1 and 15 are the predominant expression profiles which were involved in immune response, inflammatory response, chemotaxis, defense response, anti-apoptosis and signal transduction. 3) The importance of immune response at benzene hematotoxicity is highlighted by several immune-related signaling pathways such as B/T cell receptor signaling pathway, acute myeloid leukemia, hematopoietic cell lineage and natural killer cell mediated cytotoxicity. 4) Signet analysis showed that PIK3R1, PIK3CG, PIK3R2, GNAI3, KRAS, NRAS, NFKB1, HLA-DMA, and HLA-DMB were key genes involved in benzene hematotoxicity. These genes might be new biomarkers for the prevention and early diagnosis of benzene poisoning. This is a preliminary study that paves the way to further functional study to understand the underlying regulatory mechanisms.

PTEN methylation involved in benzene-induced hematotoxicity.

It is well known that benzene is a hematotoxic carcinogen. PTEN promoter methylation is a representative example of transcriptional silencing of tumor suppressor genes. However, the effect of PTEN methylation on benzene-induced hematotoxicity has not yet been elucidated. In this study, the animal model of benzene hematotoxicity was successfully established. WBC significantly decreased in experimental groups (P < 0.01). Compared with the control group, the weight of rats increased slowly and even declined with increasing doses of benzene in the benzene-treated groups. An increase in the level of PTEN methylation was observed in the low dose group, and PTEN methylation level increased significantly in a dose-dependent manner. However, it was interesting that PTEN mRNA expression increased in the low dose group, but declined with increasing doses of benzene. The decrease of tumor suppressor function caused by PTEN methylation may be an important mechanism of benzene hematotoxicity. Furthermore, lymphoblast cell line F32 was incubated by benzene and then treated with 5-aza and TSA, alone or in combination. A dramatic decrease in the PTEN mRNA expression and a significant increase of PTEN methylation level in benzene-treated cells were also shown. PTEN mRNA expression was up regulated and PTEN methylation level was reduced by the epigenetic inhibitors, 5-aza and TSA. In conclusion, PTEN methylation is involved in benzene-induced hematotoxicity through suppressing PTEN mRNA expression.