<i>p,p</i>′‑DDE Induces Apoptosis through the Modulation of Tumor Necrosis Factor α in PC12 Cells

<i>p,p</i>′-DDE, the main metabolite of DDT, is notorious for its persistent and bioaccumulation. It has detrimental effects on the nervous system, while the mechanism is unclear. We sought to investigate the mechanism of <i>p,p</i>′-DDE-induced neurocytic apoptosis in PC12 cells by cytoflow and screen the potential target gene by microarray and ELISA. Co-incubation with antagonist and SiRNA were applied to confirm the effect of the selected molecular. Results were also confirmed in zebrafish embryo. Results showed that <i>p,p</i>′-DDE induced apoptosis in PC12 cells at a concentration of ≥2 × 10^–5 mol/L. Microarray results indicate that the TNF family plays a key role in <i>p,p</i>′-DDE-induced apoptosis among 84-apoptotic genes. In particular, the protein level of TNFα increased 4-fold. When incubated with TNFα antibody (infliximab), the number of apoptotic cells attenuated by 50%, and both activities of caspases 8 and 9 decreased. SiRNA silencing of TNFα showed similar trends. Furthermore, <i>p,p</i>′-DDE induced neuronal apoptosis in zebrafish embryos in a dose-dependent manner.This effect was partially reversed by infliximab, too. Overall, the present study herein indicated that the TNFα signaling pathway is involved in <i>p,p</i>′-DDE-induced neurocyte apoptosis. These data could be expanded to other cases of OCP-induced apoptosis and would support the need for scientific intervention to address the neurotoxicity of these chemicals

Light-Driven Self-Cascade Peroxidase-like Nanozymes without Exogenous H₂O₂

The peroxidase (POD)-like nanozyme typically requires the addition of exogenous H2O2. To address the limitation, previous work mainly adopted a cascade strategy for H2O2 production. Herein, we propose a new light-driven self-cascade strategy to construct POD-like nanozymes without exogenous H2O2. The model nanozyme resorcinol–formaldehyde resin-Fe3+ (RF-Fe3+) is synthesized with the hydroxyl-rich photocatalytic material RF as the carrier to in situ chelate metal oxides, which can simultaneously achieve the functions of in situ H2O2 generation under irradiation and substrate oxidation via POD-like behavior. Notably, RF-Fe3+ exhibits high affinity to H2O2, attributed to the excellent adsorption ability and hydroxyl-rich feature of RF. Furthermore, the dual photoelectrode-assisted photofuel cell was further constructed with a high-power density of 120 ± 5 μW cm–2 based on the RF-Fe3+ photocathode. This work not only demonstrates the new self-cascade strategy of in situ generation of catalysis substrates but also provides an opportunity to extend the catalytical field

Enantioselective Cytotoxicity Profile of <em>o,p</em>’-DDT in PC 12 Cells

<div><h3>Background</h3><p>The continued uses of dichlordiphenyltrichloroethane (DDT) for indoor vector control in some developing countries have recently fueled intensive debates toward the global ban of this persistent legacy contaminant. Current approaches for ecological and health risk assessment has ignored the chiral nature of DDT. In this study by employing an array of cytotoxicity related endpoints, we investigated the enantioselective cytotoxicity of <em>o,p</em>’-DDT.</p> <h3>Principal Findings</h3><p>we demonstrated for the first time that <em>R</em>-(−)-<em>o,p</em>’-DDT caused more neuron cell death by inducing more severe oxidative stress, which selectively imbalanced the transcription of stress-related genes (SOD1, SOD2, HSP70) and enzyme (superoxide dismutase and lactate dehydrogenase) activities, and greater cellular apoptosis compared to its enantiomer <em>S</em>-(+)-<em>o,p</em>’-DDT at the level comparable to malaria area exposure (parts per million). We further elucidated enantioselective modes of action using microarray combined with enzyme-linked immunosorbent assay. The enantioselective apoptosis might involve three signaling pathways via caspase 3, tumor protein 53 (p53) and NF_kB.</p> <h3>Conclusions</h3><p>Based on DDT stereochemistry and results reported for other chiral pesticides, our results pointed to the same directional enantioselectivity of chiral DDT toward mammalian cells. We proposed that risk assessment on DDT should consider the enantiomer ratio and enantioselectivities.</p> </div

Primers used in Semi-RT-PCR and qPCR.

<p>Note: AT = Annealing temperature.</p

The expression of <i>Tyrp1</i>, <i>Tyr</i>, <i>c-Kit</i> and <i>Mitf</i> genes in retina samples from black plumage and white plumage ducks.

<p>The expression of <i>Tyrp1</i>, <i>Tyr</i>, <i>c-Kit</i> and <i>Mitf</i> genes in retina samples from black plumage and white plumage ducks.</p

RNA-Seq data summary and annotation results.

<p>Note: DCT- distinct clean tag; TDCT- Total distinct clean tag; Chicken- <i>Gallus gallus</i>; Duck<i>- Anas platyrhynchos</i>.</p

Oxidative stress induced by racemate and enantiomers of <i>o,p’</i>-DDT.

<p>Effect of the racemate of <i>o,p’</i>-DDT and individual stereoisomers on extracellular lactate dehydrogenase (LDH) release, intracellular superoxide dismutase (SOD) and malondialdehyde (MDA) production at concentration of 3.5×10⁻⁵ mol/L. Data are presented as the relative value of control. PC12 cells were exposed to different compounds for 24 h. The asterisk above each bar indicates a significant difference compared to a negative control (<i>p</i><0.05, n = 3). Different letters above adjacent bars indicate a significant difference (<i>p</i><0.05) between the two enantiomers, whereas the same letter indicates no significant difference.</p

Enantioselective Induction of Cytotoxicity by <i>o</i>,<i>p</i>′‑DDD in PC12 Cells: Implications of Chirality in Risk Assessment of POPs Metabolites

The increased release of chiral persistent organic pollutants (POPs) into the environment has resulted in more attention to the role of enantioselectivity in the fate and ecotoxicological effects of these compounds. Although the enantioselectivity of chiral POPs has been considered in previous studies, little effort has been expended to discern the enantiospecific effects of chiral POPs metabolites, which may impede comprehensive risk assessments of these chemicals. In the present study, <i>o</i>,<i>p</i>′-DDD, the chiral metabolite of <i>o</i>,<i>p</i>′-DDT, was used as a model chiral metabolite. First, a preferential chiral separation at 100% ethanol was employed to obtain a pure enantiomer. The enantioselective cytotoxicity of <i>o</i>,<i>p</i>′-DDD in rat cells (PC12) was evaluated by detecting activation of the cellular apoptosis and oxidative stress systems and microarray analysis. We have documented for the first time that <i>R</i>-(+)-<i>o</i>,<i>p</i>′-DDD increases apoptosis by selectively disturbing the oxidative system (enzymes and molecules) and regulating the transcription of Aven, Bid, Cideb and Tp53. By comparing the data from the present study to data derived from the parent compound, we concluded that the <i>R</i>-enantiomer is the more detrimental stereostructure for both <i>o</i>,<i>p</i>′-DDT and <i>o</i>,<i>p</i>′-DDD. This observed stereostructural effect is in line with the structure–activity relationship formulated at other structural levels. Biological activities of the chiral metabolites are likely to occur in the same absolute configuration between chiral POPs and their metabolites provided that they have the similar stereostructures

Results of RT-PCR verification of microarray on <i>rac-o,p</i>’-DDT.

<p>Results of RT-PCR verification of microarray on <i>rac-o,p</i>’-DDT.</p

Oxidative stress related gene induction by racemate and enantiomers of <i>o,p’</i>-DDT.

<p>The relative expression of anti-oxidative related genes encoding superoxide dismutase (SOD1 and SOD2) and heat shock protein (HSP) genes in response to racemate and enantiomers of <i>o,p</i>’-DDT. The asterisk denoted <i>p</i><0.05 relative to the negative control. Different letters above adjacent bars indicate a significant difference (<i>p</i><0.05) between individual enantiomers or between an enantiomer and racemate, while the same letter indicates no significant difference.</p