Role of mitochondrial DNA in oxidative damage induced by sodium arsenite in human bronchial epithelial cells.

Long-term exposure to sodium arsenite was found to induce malignant transformation in human bronchial epithelial (HBE) cell line as evidenced by elevated ROS levels. Although chronic sodium arsenite-induced HBE cell line transformation was associated with elevated ROS generation, it was of interest to determine whether acute sodium arsenite exposure also initiated pulmonary damage. Thus, the aim of this study was to investigate oxidative-stress-related pulmonary damage using a human bronchial epithelial (HBE) cell line. Incubation of ρ+-HBE (in the presence of mitochondrial DNA) cells with various concentrations of sodium arsenite, significantly increased ROS and MDA levels accompanied by decreased SOD activity in a concentration-dependent manner. In contrast, treatment of ρ-HBE (without mitochondrial DNA) cells various concentrations of sodium arsenite a reduction in ROS and MDA levels were noted. However, the SOD activity remained decreased in ρ-HBE cells. This was accompanied by a significant rise in HO-1 protein expressions levels in both cell types with greater changes ρ-HBE cells at the lower sodium arsenite concentrations. Data indicate that acute sodium arsenite exposure exerted a greater effect ρ-HBE cells suggesting that absence of mitochondrial DNA appears to enhance sensitivity to the oxidant actions of inorganic As.

Possible differences in the mechanism of malignant transformation of HaCaT cells by arsenite and its dimethyl metabolites, particularly dimethylthioarsenics.

BACKGROUND: As a confirmed human carcinogen, arsenic can cause skin cancer, lung cancer, etc. However, its carcinogenic mechanism is still unclear. In recent years, the oxidative stress hypothesis has become widely accepted. In mammals it has been found that arsenic can be converted to dimethylarsinous acid (DMAIII) and dimethylmonothioarsinic acid (DMMTAV) through a series of methylation and redox reactions. DMAIII and DMMTAV are highly toxic. METHODS: Human keratinocytes (HaCaT) were exposed to different concentrations of NaAsO2 (IAsIII), DMMTAV and DMAIII for 24 h. Reactive oxygen species (hydrogen peroxide and superoxide), oxidative damage markers (8-hydroxydeoxyguanosine and malondialdehyde), and antioxidant markers (glutathione and superoxide dismutase) were measured. In addition, sulfane sulfurs were measured in HaCaT cells and a cell-free system. RESULTS: In the DMMTAV and DMAIII treatment groups, the levels of hydrogen peroxide and superoxide in HaCaT cells were higher than in the IAsIII treatment groups at the same dose. Levels of 8-OHdG and MDA in the DMMTAV and DMAIII treatment groups were also higher than those in the IAsIII treatment groups at the same dose. However, in the DMMTAV and DMAIII treatment groups, the levels of GSH and SOD activity were lower than that in the IAsIII treatment groups. In DMMTAV-treated HaCaT cells, sulfane sulfurs were produced. Further, it was found that DMMTAV could react with DMDTAV to form persulfide in the cell-free system, which may explain the mechanism of the formation of sulfane sulfurs in DMMTAV-treated HaCaT cells. CONCLUSIONS: DMMTAV and DMAIII more readily induce reactive oxygen species (ROS) and cause oxidative damage in HaCaT cells than inorganic arsenic. Further, the persulfide formed by the reaction of DMMTAV and DMDTAV produced from the metabolism of DMMTAV may induce a stronger reductive defense mechanism than GSH against the intracellular oxidative stress of DMMTAV. However, the cells exposed to arsenite are transformed by the continuous nuclear translocation of Nrf2 due to oxidative stress, and the persulfide from dimethylthioarsenics may promote Nrf2 by the combination with thiol groups, especially redox control key protein, Keap1, eventually cause nuclear translocation of sustained Nrf2.

High NF-E2-related factor 2 expression predicts poor prognosis in patients with lung cancer: a meta-analysis of cohort studies.

NF-E2-related factor 2 (Nrf2) plays an important role in tumour proliferation and chemoresistance. Nrf2 expression levels may be associated with prognosis of lung cancer, but previous results have been inconsistent. Pooled hazard ratios (HRs) and odds ratios were calculated to assess the prognostic value of the Nrf2 expression in this meta-analysis. Nine studies with 940 patients were included. A high Nrf2 expression level was significantly related to decreased overall survival (OS) (HR = 1.948, 95% CI = 1.564-2.427), lower response rate (HR = 2.675, 95% CI = 1.553-4.610), and poor progression-free survival (HR = 3.078, 95% CI = 1.791-5.293). Subgroup analysis demonstrated that high-Nrf2-expression was significantly correlated with worse OS of patients possessing epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) or undergoing chemotherapeutic treatments (HR = 2.500, 95% CI = 1.556-4.018). Conversely, this high expression was not significantly related to the OS of patients with surgical resection (HR = 1.750, 95% CI = 0.995-3.080, and p=.052). High Nrf2 expression was significantly correlated with worse OS of patients in advanced stage (HR = 2.500, 95% CI = 1.556-4.018), compared with early cancer stage (HR = 1.609, 95% CI = 0.675-3.835, and p=.283). This meta-analysis suggests that high Nrf2 expression may be a predictive factor of poor outcomes in lung cancer. Therefore, Nrf2 likely plays an important role in prognostic evaluation and may be a therapeutic target for EGFR-TKIs therapy and chemotherapy.

Long-term arsenite exposure decreases autophagy by increased release of Nrf2 in transformed human keratinocytes.

Autophagy dysfunction in arsenite toxicity plays critical roles in cancer development and progression. However, the precise mechanisms of arsenite-induced skin cancer by blocking autophagy remain uncertain. Herein, this study investigated molecular mechanisms of arsenite-induced autophagy dysfunction mediated by nuclear factor erythroid-2 related factor 2 (Nrf2) in human keratinocyte (HaCaT) cells. The effects of long-term arsenite exposure on Nrf2 activation and autophagy were established using a siRNA interference assay and western blots. A specific siRNA of Nrf2 was used to verify that autophagy induced by arsenite can be influenced by Nrf2. Specific inhibitors of PI3K (LY294002) and mTOR (Rapamycin) and siRNA of Nrf2 were employed to verify that upregulation of Nrf2 correlated with activating the PI3K/Akt pathway. Downstream mTOR and Bcl2 were upregulated by Nrf2 signaling, inhibiting autophagy initiation in arsenite-exposed HaCaT cells. In conclusion, our data suggest that long-term exposure to arsenite promotes Nrf2 upregulation via the PI3K/Akt pathway and, along with upregulation of downstream mTOR and Bcl2, contributes to autophagy dysfunction in transformed HaCaT cells. This work provides new insights into the mechanisms underlying arsenite-induced autophagy dysfunction in cancer promotion and malignancy progression.

Bootstrapping Knowledge Graphs From Images and Text.

The problem of generating structured Knowledge Graphs (KGs) is difficult and open but relevant to a range of tasks related to decision making and information augmentation. A promising approach is to study generating KGs as a relational representation of inputs (e.g., textual paragraphs or natural images), where nodes represent the entities and edges represent the relations. This procedure is naturally a mixture of two phases: extracting primary relations from input, and completing the KG with reasoning. In this paper, we propose a hybrid KG builder that combines these two phases in a unified framework and generates KGs from scratch. Specifically, we employ a neural relation extractor resolving primary relations from input and a differentiable inductive logic programming (ILP) model that iteratively completes the KG. We evaluate our framework in both textual and visual domains and achieve comparable performance on relation extraction datasets based on Wikidata and the Visual Genome. The framework surpasses neural baselines by a noticeable gap in reasoning out dense KGs and overall performs particularly well for rare relations.

The protective effect of silk fibroin on high glucose induced insulin resistance in HepG2 cells.

The therapeutic use of silk-derived materials such as fibroin in biomedicine is well-established in Southeast Asian countries. Studies indicated that silk fibroin (SF) peptide enhances insulin sensitivity and glucose metabolism phenomena associated with type 2 diabetes mellitus (T2DM) suggesting this peptide may be beneficial to treat this disease. However, the mechanisms underlying protective effect of SF in insulin-mediated hepatic metabolic dysfunction remains unclear. The aim of this study was to investigate the influence of SF on insulin resistant HepG2 cells which were used a model of T2DM. Treatment of cells with 30 mmol/L of glucose and 10-6 mol/L insulin for 48 h significantly reduced glucose consumptions and intracellular glycogen levels but increased triglyceride (TG) levels. SF or metformin alone elevated glucose consumptions and glycogen accumulation accompanied by lower TG content. Greater effects in these metabolic parameters were found when SF and metformin were combined. Treatment of insulin resistant cells with SF or metformin alone decreased levels of reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF-α) and interleukin-6 (IL-6); whereas antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) activity, as well as total antioxidant capacity (T-AOC) ability increased. The combination of SF and metformin produced greater changes in these parameters compared to metformin alone. Data indicated that the protective effect of SF or metformin in insulin resistant HepG2 cells involves inhibition of oxidant processes and that the combination of agents may prove more effective therapeutically.

[Identification and application of Mycobacterium tuberculosis esxN-specific cell epitopes in the diagnosis of pulmonary tuberculosis].

Objective To identify Mycobacterium tuberculosis ESAT-6 protein esxN-specific HLA-A*0201-restricted CTL epitopes and assess the diagnostic potential of the identified epitopes in pulmonary tuberculosis. Methods The esxN-specific HLA-A*0201-restricted CTL epitopes were predicted by the T epitope prediction software SYFPEITHI and further synthesized. The binding affinity of the candidate epitopes for HLA-A*0201 was detected using MHC-peptide complex stabilization assay. The immunogenicity of candidate epitopes were assessed using ELISPOT in HLA-A*0201 transgenic mice. Based on identified CTL epitopes, ESAT-6 and culture filtrate protein-10 (CFP-10), the ELISPOT was performed to detect the frequency of epitope/protein-specific CTL. Results In six CTL epitope candidates we tested, two epitopes, esxN15-24 (AMIRAQAASL) and esxN48-57 (VACQEFITQL), were found to have a high affinity for HLA-A*0201. In the HLA-A*0201 transgenic mice immunized with the epitope candidates, esxN48-57 induced T-cell response with a significantly high IFN-γ secretion. The IFN-γ-producing T cells directed to esxN15-24 and esxN48-57 were found to be correlated with the presence of ESAT-6 and CFP-10 in positive pulmonary tuberculosis patients. The sensitivity of these tests for the esxN15-24 and esxN48-57 epitopes was similar to that of ESAT-6 and CFP-10. Conclusion Two novel Mycobacterium tuberculosis protein esxN-derived HLA-A*0201-restricted CTL epitopes have potential for the diagnosis of tuberculosis.

Facile synthesis of polymer/Au heteronanoparticles.

Oligomeric particles with thiol groups perpendicular to their surface were successfully fabricated in toluene. Uniform oligomer-gold nanocomposites were formed via coupling with gold nanoparticles through anisotropic Au-S interactions. Monodispersed nanoparticles consisting of one Au nanoparticle and one oligomer particle were created after dissociation in THF. Because of the simplicity of the synthetic process, our method should allow for the production of large quantities of these asymmetric nanocolloids.