JWA gene is involved in cadmium-induced growth inhibition and apoptosis in HEK-293T cells

Analysis of long non-coding RNA profiled following MC-LR-induced hepatotoxicity using high-throughput sequencing

The occurrence of microcystin-LR(MC-LR) variant a known hepatotoxin constitutes a global public health concern. However, the molecular mechanisms underlying MC-LR-induced hepatotoxicity remain to be determined. The aim of this study was to investigate whether long noncoding RNAs (lncRNA) were involved in MC-LR-mediated hepatotoxicity using human normal liver cell line HL7702 to profile lncRNAs after 24 hr treatment with MC-LR. With the use of high-throughput sequencing techniques, data showed that the expression levels of 37, 33, 34, 35 lncRNA were significantly altered following exposure to 1, 2.5, 5, or 10 μM MC-LR, respectively. In particular, the expression levels of LINC00847, MIR22HG and LNC_00027 were markedly increased in all treatment groups. It is of interest that LNC_00027 was identified as a novel lncRNA. Quantitative real-time PCR (qPCR) was employed to determine the differentially expressed lncRNA levels. Analysis using Gene Ontology (GO) enrichment identified the functions of target genes involved in systems development, metabolism, and protein binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that MC-LR exposure upregulated some important signaling pathways including pathway in cancer, PI3K-AKT signaling and MAPK pathway. In summary, data indicate that the MC-LR-induced alterations in lncRNA may be associated with hepatotoxicity and that upregulation of LINC00847, MIR22HG and LNC_00027 may play important roles in the observed MC-mediated liver damage.

Identification of ARNT-regulated BIRC3 as the target factor in cadmium renal toxicity

Cadmium (Cd) is an environmental contaminant that exhibits renal toxicity. The target transcription factors involved in Cd renal toxicity are still unknown. In this study, we demonstrated that Cd decreased the activity of the ARNT transcription factor, and knockdown of ARNT significantly decreased the viability of human proximal tubular HK-2 cells. Microarray analysis in ARNT knockdown cells revealed a decrease in the expression of a number of genes, including a known apoptosis inhibitor, BIRC3, whose gene and protein expression level was also decreased by Cd treatment. Although the BIRC family consists of 8 members, Cd suppressed only BIRC3 gene expression. BIRC3 is known to suppress apoptosis through the inhibition effect on caspase-3. Knockdown of BIRC3 by siRNA as well as Cd treatment increased the level of active caspase-3. Moreover, knockdown of BIRC3 not only triggered cell toxicity and apoptosis but also strengthened Cd toxicity in HK-2 cells. Meanwhile, the activation of caspase-3 by suppression of BIRC3 gene expression was mostly specific to Cd and to proximal tubular cells. These results suggest that Cd induces apoptosis through the inhibition of ARNT-regulated BIRC3 in human proximal tubular cells.

Cadmium interference with ERK1/2 and AhR signaling without evidence for cross-talk

The possibility that Cd may activate AhR indirectlyviaERK1/2 phosphorylation was tested as a function of enterocytic differentiation status in the human Caco-2 cells.

EGCG inhibits Cd(2+)-induced apoptosis through scavenging ROS rather than chelating Cd(2+) in HL-7702 cells

CONTEXT AND OBJECTIVE

Epigallocatechin-3-gallat (EGCG), the major catechin in green tea, shows a potential protective effect against heavy metal toxicity to humans. Apoptosis is one of the key events in cadmium (Cd(2+))-induced cytotoxicity. Nevertheless, the study of EGCG on Cd(2+)-induced apoptosis is rarely reported. The objective of this study was to clarify the effect and detailed mechanism of EGCG on Cd(2+)-induced apoptosis.

METHODS

Normal human liver cells (HL-7702) were treated with Cd(2+) for 21 h, and then co-treated with EGCG for 3 h. Cell viability, apoptosis, intracellular reactive oxygen species (ROS), malondialdehyde (MDA), mitochondrial membrane potential (MMP) and caspase-3 activity were detected. On the other hand, the chelation of Cd(2+) with EGCG was tested by UV-Vis spectroscopy analysis and Nuclear Magnetic Resonance ((1)H NMR) spectroscopy under neutral condition (pH 7.2).

RESULTS AND CONCLUSION

Cd(2+) significantly decreased the cell viability and induced apoptosis in HL-7702 cells. Conversely, EGCG co-treatment resulted in significant inhibition of Cd(2+)-induced reduction of cell viability and apoptosis, implying a rescue effect of EGCG against Cd(2+) poisoning. The protective effect most likely arises from scavenging ROS and maintaining redox homeostasis, as the generation of intracellular ROS and MDA is significantly reduced by EGCG, which further prevents MMP collapse and suppresses caspase-3 activity. However, no evidence is observed for the chelation of EGCG with Cd(2+) under neutral condition. Therefore, a clear conclusion from this work can be made that EGCG could inhibit Cd(2+)-induced apoptosis by acting as a ROS scavenger rather than a metal chelating agent.

Cadmium-Induced Pathologies: Where Is the Oxidative Balance Lost (or Not)?

Over the years, anthropogenic factors have led to cadmium (Cd) accumulation in the environment causing various health problems in humans. Although Cd is not a Fenton-like metal, it induces oxidative stress in various animal models via indirect mechanisms. The degree of Cd-induced oxidative stress depends on the dose, duration and frequency of Cd exposure. Also the presence or absence of serum in experimental conditions, type of cells and their antioxidant capacity, as well as the speciation of Cd are important determinants. At the cellular level, the Cd-induced oxidative stress either leads to oxidative damage or activates signal transduction pathways to initiate defence responses. This balance is important on how different organ systems respond to Cd stress and ultimately define the pathological outcome. In this review, we highlight the Cd-induced oxidant/antioxidant status as well as the damage versus signalling scenario in relation to Cd toxicity. Emphasis is addressed to Cd-induced pathologies of major target organs, including a section on cell proliferation and carcinogenesis. Furthermore, attention is paid to Cd-induced oxidative stress in undifferentiated stem cells, which can provide information for future therapies in preventing Cd-induced pathologies.

Global DNA hypomethylation, rather than reactive oxygen species (ROS), a potential facilitator of cadmium-stimulated K562 cell proliferation

Cell proliferation plays a critical role in the process of cadmium (Cd) carcinogenesis. Although both induction of reactive oxygen species (ROS) and alteration of DNA methylation are involved in Cd-stimulated cell proliferation, the detailed mechanism of Cd-stimulated cell proliferation remains poorly understood. In this study, K562 cells pre-treated with N-acetylcysteine (NAC) or methionine (Meth) were exposed to Cd to investigate the potential contribution of ROS and global DNA methylation pathways in Cd-induced cell proliferation. The results showed that Cd-stimulated cell proliferation, increased ROS and DNA damage levels, and induced global DNA hypomethylation. The increases of ROS and DNA damage levels were attenuated by pre-treatment with NAC. Cd-stimulated cell proliferation did not appear to be suppressed through eliminating ROS by NAC. However, methionine was shown to prevent Cd-induced global DNA hypomethylation and Cd-stimulated cell proliferation. Our results suggest that global DNA hypomethylation, rather than ROS, is a potential facilitator of Cd-stimulated K562 cell proliferation.

JWA is required for arsenic trioxide induced apoptosis in HeLa and MCF-7 cells via reactive oxygen species and mitochondria linked signal pathway

Arsenic trioxide, emerging as a standard therapy for refractory acute promyelocytic leukemia, induces apoptosis in a variety of malignant cell lines. JWA, a novel retinoic acid-inducible gene, is known to be involved in apoptosis induced by various agents, for example, 12-O-tetradecanoylphorbol 13-acetate, N-4-hydroxy-phenyl-retinamide and arsenic trioxide. However, the molecular mechanisms underlying how JWA gene is functionally involved in apoptosis remain largely unknown. Herein, our studies demonstrated that treatment of arsenic trioxide produced apoptosis in HeLa and MCF-7 cells in a dose-dependent manner and paralleled with increased JWA expression. JWA expression was dependent upon generation of intracellular reactive oxygen species induced by arsenic trioxide. Knockdown of JWA attenuated arsenic trioxide induced apoptosis, and was accompanied by significantly reduced activity of caspase-9, enhanced Bad phosphorylation and inhibited MEK1/2, ERK1/2 and JNK phosphorylations. Arsenic trioxide induced loss of mitochondrial transmembrane potential was JWA-dependent. These findings suggest that JWA may serve as a pro-apoptotic molecule to mediate arsenic trioxide triggered apoptosis via a reactive oxygen species and mitochondria-associated signal pathway.