Leukemia-associated gene MLAA-34 reduces arsenic trioxide-induced apoptosis in HeLa cells via activation of the Wnt/β-catenin signaling pathway

Assessing the double-edged of extracellular signal-regulated kinase/CCAAT-enhancer-binding protein beta signaling pathway in arsenic-induced skin damage and its potential foodborne interventions

Arsenic exposure is a major environmental public health challenge worldwide. As typical manifestations for arsenic exposure, the pathogenesis of arsenic-induced skin lesions has not been fully elucidated, as well as the lack of effective control measures. In this study, we first determined the short-term and high-dose arsenic exposure can increase the apoptosis rates, while long-term low-dose arsenic exposure decrease the apoptosis rates. Then, the HaCaT cells with knockdown and overexpression of CCAAT-enhancer-binding protein β (CEBPB) and extracellular signal-regulated kinase (ERK) were constructed. The results demonstrate that knockdown of CEBPB and ERK can reduce NaAsO2 -induced cell apoptosis by inhibiting ERK/CEBPB signaling pathway and vice versa. Further cells were treated with Kaji-Ichigoside F1 (KF1). The results clearly show that KF1 can decrease the arsenic-induced cell apoptosis rates and the expression of ERK/CEBPB signaling pathway-related genes. These results provide evidence that ERK/CEBPB signaling pathway acts as a double-edged sword in arsenic-induced skin damage. Another interesting finding was that KF1 can alleviate arsenic-induced skin cell apoptosis by inhibiting the ERK/CEBPB signaling pathway. This study will contribute to a deeper understanding of the mechanisms of arsenic-induced skin cell apoptosis, and our findings will help to identify a potential food-borne intervention in arsenic detoxification.

Parkin, as a Regulator, Participates in Arsenic Trioxide-Triggered Mitophagy in HeLa Cells

Parkin is a well-established synergistic mediator of mitophagy in dysfunctional mitochondria. Mitochondria are the main target of arsenic trioxide (ATO) cytotoxicity, and the effect of mitophagy on ATO action remains unclear. In this study, we used stable Parkin-expressing (YFP-Parkin) and Parkin loss-of-function mutant (Parkin C431S) HeLa cell models to ascertain whether Parkin-mediated mitophagy participates in ATO-induced apoptosis/cell death. Our data showed that the overexpression of Parkin significantly sensitized HeLa cells to ATO-initiated proliferation inhibition and apoptosis; however, the mutation of Parkin C431S significantly weakened this Parkin-mediated responsiveness. Our further investigation found that ATO significantly downregulated two fusion proteins (Mfn1/2) and upregulated fission-related protein (Drp1). Autophagy was also activated as evidenced by the formation of autophagic vacuoles and mitophagosomes, increased expression of PINK1, and recruitment of Parkin to impaired mitochondria followed by their degradation, accompanied by the increased transformation of LC3-I to LC3-II, increased expression of Beclin1 and decreased expression of P62 in YFP-Parkin HeLa cells. Enhanced mitochondrial fragmentation and autophagy indicated that mitophagy was activated. Furthermore, during the process of mitophagy, the overproduction of ROS implied that ROS might represent a key factor that initiates mitophagy following Parkin recruitment to mitochondria. In conclusion, our findings indicate that Parkin is critically involved in ATO-triggered mitophagy and functions as a potential antiproliferative target in cancer cells.

Inorganic arsenic promotes apoptosis of human immortal keratinocytes through the TGF-β1/ERK signaling pathway

Chronic exposure to high-dose inorganic arsenic through groundwater, air, or food remains a major environmental public health issue worldwide. Apoptosis, a method of cell death, has recently become a hot topic of research in biology and medicine. Previous studies have demonstrated that extracellular signal-regulated kinase (ERK) is related to arsenic-induced apoptosis. However, the reports are contradictory, and the knowledge of the above-mentioned mechanisms and their mutual regulation remains limited. In this study, the associations between the TGF-β1/ERK signaling pathway and arsenic-induced cell apoptosis were confirmed using the HaCaT cell model. The relative expressions of the indicators of the TGF-β1/ERK signaling pathway, apoptosis-related genes (cytochrome C, caspase-3, caspase-9, cleaved caspase-3, cleaved caspase-9, and Bax), the mitochondrial membrane potential, and the total apoptosis rate were significantly increased (P < .05), while the expression of the antiapoptosis gene Bcl-2 was significantly decreased (P < .05) in cells of the group exposed to arsenic. Moreover, the results demonstrated that the ERK inhibitor (PD98059) and TGF-β1 inhibitor (LY364947) could inhibit the activation of the ERK signaling pathway, thereby reducing the mitochondrial membrane potential, the total apoptosis rate, and the expression of pro-apoptosis-related genes in the cells, while the expression of the antiapoptosis gene Bcl-2 was significantly increased (P < .05). By contrast, the recombinant human TGF-β1 could promote apoptosis of the HaCaT cells by increasing the activation of the ERK signaling pathway (P < .05). These results indicate that inorganic arsenic promotes the apoptosis of human immortal keratinocytes through the TGF-β1/ERK signaling pathway.

Downregulation of long non-coding RNA MR4435-2HG suppresses breast cancer progression via the Wnt/β-catenin signaling pathway

Extensive research has contributed to the current understanding of the critical roles played by long non-coding RNAs in various types of cancer. The present study aimed to investigate the function and mechanism of the long non-coding RNA, MIR4435-2HG (also termed LINC00978), in breast cancer growth and metastasis. Using Gene Expression Profiling Interactive Analysis, an online web tool, it was revealed that MIR4435-2HG was upregulated in breast cancer tissue, and its high expression was associated with poor prognosis based on The Cancer Genome Atlas database. MIR4435-2HG knockdown increased cell apoptosis but decreased cell proliferation, migration and invasion. MIR4435-2HG knockdown increased pro-apoptotic protein expression but decreased anti-apoptotic protein expression. In addition, MIR4435-2HG knockdown leads to dysregulation of epithelial-to-mesenchymal transition-associated genes. Furthermore, knockdown of MIR4435-2HG results in inactivation of the Wnt/β-catenin signaling pathway. The results of the present study demonstrate the tumor-promoting role of MIR4435-2HG in breast cancer progression.

Effect of bortezomib on proliferation and apoptosis of myeloma cells by activating Wnt/β-catenin signaling pathway

Effect of bortezomib on proliferation and apoptosis of myeloma cells by activating Wnt/β-catenin signaling pathway was investigated. Myeloma cells RPMI-8226 treated with different concentrations of bortezomib were used as experimental groups, and the untreated cells were used as the control group. The proliferation and apoptosis in all groups of cells were detected, as well as the expression levels of Wnt/β-catenin signaling pathway-related proteins, β-catenin and c-Myc. The results revealed that bortezomib could inhibit the proliferation of myeloma cells. The apoptotic rates of RPMI-8226 cells in the groups treated with 20, 50 and 80 nmol/l of bortezomib were 12.08±0.61, 35.97±3.11 and 57.22±5.47%, respectively, which were significantly higher than that in the control group (8.28±0.39%) (P<0.05). The expression levels of β-catenin and c-Myc in the experimental groups were significantly lower than those in the control group (P<0.05). Bortezomib can reduce the expression level of Wnt/β-catenin signaling pathway-related proteins, β-catenin and c-Myc, and may inhibit cell proliferation and accelerate apoptosis by activating the Wnt/β-catenin signaling pathway.

Effects of Arsenic on wnt/β-catenin Signaling Pathway: A Systematic Review and Meta-analysis

We aimed to systematically evaluate the regulatory effect of arsenic on wnt/β-catenin signaling pathway and to provide theoretical basis for revealing the mechanism of the relationship between arsenic and cell proliferation. The meta-analysis was carried out using Revman5.2 and Stata13.0 to describe the differences between groups with standard mean difference. We found in normal cells that the levels of wnt3a, β-catenin, glycogen synthase kinase-3β phosphorylated at serine 9 (p-GSK-3β(Ser9)), cyclinD1, proto-oncogene c-myc, and vascular endothelial growth factor (VEGF) in the arsenic intervention group were higher than those in the control group, and the level of glycogen synthase kinase-3β (GSK-3β) was lower than that in the control group (P < 0.05, respectively). Subgroup analysis showed that for a long time period (>24 h), the level of β-catenin in the arsenic intervention group was higher than that in the control group, and the level of GSK-3β of the same long-time period (>24 h) with low-dose (≤5 μM) intervention was lower than those in the control group (P < 0.05, respectively). In cancer cells, the levels of β-catenin, cyclinD1, c-myc, and VEGF in the arsenic intervention group were lower than those in the control group, while the level of GSK-3β in the arsenic intervention group was higher than that in the control group (P < 0.05, respectively). Subgroup analysis showed that the levels of β-catenin, cyclinD1, and c-myc in the high-dose (>5 μM) arsenic intervention group were lower than those in the control group, and the levels of β-catenin and cyclinD1 in the high-dose (>5 μM) arsenic intervention group were lower than those in the low-dose (≤5 μM) arsenic intervention group (P < 0.05, respectively). In addition, the regulation of arsenic on β-catenin was dose-dependent in the range of arsenic concentration from 0 to 7.5 μM. This study revealed that arsenic could upregulate wnt/β-catenin signaling pathway in normal cells and downregulate it in cancer cells, and its effect was affected by time and dose.

Arsenic trioxide induces apoptosis and the formation of reactive oxygen species in rat glioma cells

Background

Arsenic trioxide (As₂O₃) has a dramatic therapeutic effect on acute promyelocytic leukemia (APL) patients. It can also cause apoptosis in various tumor cells. This study investigated whether As₂O₃ has an antitumor effect on glioma and explored the underlying mechanism.

Results

MTT and trypan blue assays showed that As₂O₃ remarkably inhibited growth of C6 and 9 L glioma cells. Cell viability decreased in glioma cells to a greater extent than in normal glia cells. The annexin V-FITC/PI and Hoechest/PI staining assays revealed a significant increase in apoptosis that correlated with the duration of As₂O₃ treatment and occurred in glioma cells to a greater extent than in normal glial cells. As₂O₃ treatment induced reactive oxygen species (ROS) production in C6 and 9 L cells in a time-dependent manner. Cells pretreated with the antioxidant N-acetylcysteine (NAC) showed significantly lower As₂O₃-induced ROS generation. As₂O₃ significantly inhibited the expression of the anti-apoptotic gene Bcl-2, and upregulated the proapoptotic gene Bax in both C6 and 9 L glioma cells in a time-dependent manner.

Conclusions

As₂O₃ can significantly inhibit the growth of glioma cells and it can induce cell apoptosis in a time- and concentration-dependent manner. ROS were found to be responsible for apoptosis in glioma cells induced by As₂O₃. These results suggest As₂O₃ is a promising agent for the treatment of glioma.