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

A speculated signaling pathway mediated by <i>o,p</i>’-DDT for the induction of cells apoptosis.

<p>The red arrowheads indicate the more significant upregulation of apoptosis-related molecules induced by <i>R</i>-form than that of <i>S</i>-form. Reactive oxygen species (ROS), Heat shock proteins (HSPs), Lactate dehydrogenase (LDH), Superoxide dismultase (SOD), Malondialdehyde (MDA).</p

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

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

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

Enantioselective Phytotoxicity of Dichlorprop to <i>Arabidopsis thaliana</i>: The Effect of Cytochrome P450 Enzymes and the Role of Fe

The ecotoxicology effects of chiral herbicides have long been recognized and have drawn increasing attention. The toxic mechanisms of herbicides in plants are involved in production of reactive oxygen species (ROS) and cause damage to target enzymes, but the relationship between these two factors in the enantioselectivity of chiral herbicides has rarely been investigated. Furthermore, even though cytochromes P450 enzymes (CYP450s) have been related to the phytotoxicity of herbicides, their roles in the enantioselectivity of chiral herbicides have yet to be explored. To solve this puzzle, the CYP450s suicide inhibitor 1-aminobenzotriazole (ABT) was added to an exposure system made from dichlorprop (DCPP) enantiomers in the model plant <i>Arabidopsis thaliana</i>. The results indicated that different phytotoxicities of DCPP enantiomers by causing oxidative stress and acetyl-CoA carboxylase (ACCase) damage were observed in the presence and the absence of ABT. The addition of ABT decreased the toxicity of (<i>R</i>)-DCPP but was not significantly affected that of (<i>S</i>)-DCPP, resulting in smaller differences between enantiomers. Furthermore, profound differences were also observed in Fe uptake and distribution, exhibiting different distribution patterns in <i>A. thaliana</i> leaves exposed to DCPP and ABT, which helped bridge the relationship between ROS production and target enzyme ACCase damage through the function of CYP450s. These results offer an opportunity for a more-comprehensive understanding of chiral herbicide action mechanism and provide basic evidence for risk assessments of chiral herbicides in the environment

Heatmap of 84 apoptotic genes.

<p>The hierarchical clustering was performed for microarray data. Green indicates relative low expression, and red indicates relative high expression.</p

Enantioselectivity in DDT-inducted apoptosis in PC12 cell.

<p>The percent of early apoptotic cells following treatment with individual enantiomers or racemate of DDT was measured with flow cytometry quantified by Annexin V (AV)-PI staining.</p

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

Apoptotic related proteins induced by racemate and enantiomers of o,p’-DDT.

<p>The protein expression of (A) p53, (B) caspase3 and (C) NF<i>_k</i>B after exposured to <i>rac</i>-<i>o,p</i>’-DDT, <i>R</i>-(+)-<i>o,p</i>’-DDT, and <i>S</i>-(−)-<i>o,p</i>’-DDT. The asterisk indicates <i>p</i><0.05 relative to a negative control. Different capitalized 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