EMT induced by loss of LKB1 promotes migration and invasion of liver cancer cells through ZEB1-induced YAP signaling.

Liver cancer cells often exhibit mesenchymal phenotypes, a critical phenotypic alteration of cancer cells termed the epithelial-mesenchymal transition (EMT). To examine whether liver kinase B1 (LKB1) serves a potential role in EMT in liver carcinogenesis, in the present study, it was determined that the expression of LKB1 decreased in the hepatocellular carcinoma (HCC) cell line, compared with a normal liver cell line. LKB1 overexpression decreased cell motility and invasiveness. Furthermore, the loss of LKB1 induced the expression of several EMT marker proteins, including that of Zinc Finger E-Box Binding Homeobox 1 (ZEB1). Notably, the expression of Yes-associated protein (YAP) was positively associated with that of ZEB1 in LKB1-knockdown cells with a mesenchymal phenotype. Here, we describe the direct regulation of the Hippo pathway effector YAP by ZEB1. The findings of the present study demonstrate that ZEB1 regulates the expression of YAP and regulates the expression of downstream target genes to promote malignant progression.

Residue and risk assessment of pyridaben in cabbage.

The dissipation and residue of pyridaben in cabbage under field conditions were investigated. A sensitive, simple, and fast method for determining pyridaben in cabbage was established by high-performance liquid chromatography tandem mass spectrometry. The average recoveries were in the range of 90.29-95.00% with relative standard deviations ranging from 1.72% to 6.39%. The field results showed that pyridaben dissipated rapidly in cabbage and had a half-life of 2.8-3.5 d. During harvest, the terminal residues of pyridaben were 0.01-0.80 mg/kg. Given that no maximum residue limit (MRL) has been set for pyridaben in cabbage, risk assessment was evaluated by using the risk quotient (RQ). Results indicated that the RQ value was significantly lower than RQ = 1. Thus, the effect of pyridaben in cabbage at the recommended dosage was negligible to humans. This study could provide guidance for the safe and reasonable use of pyridaben as a broad-spectrum acaricide and serve as a reference for the establishment of an MRL in China.

Pyrimethanil residue and dissipation in tomatoes and soil under field conditions.

A residue analytical method to detect pyrimethanil in tomatoes and soil was developed by using high-performance liquid chromatography with a diode array detector. The dissipation and residue level of pyrimethanil in tomatoes and soil were also investigated. Results showed that the average recoveries are in the range of 87.2 to 90.0 % with a relative standard difference of 2.22 to 7.61 % in tomatoes and soil. In Guangdong, Shandong, and Yunnan, the half-lives of pyrimethanil in tomatoes were 1.8, 3.6, and 4.2 days and those in soil were 4.0, 3.3, and 3.9 days, respectively. The dissipation rate of pyrimethanil in tomatoes and soil was affected by temperature, precipitation, and soil type. The terminal residue results showed that when pesticide pyrimethanil was used under the experiment design, all the results were far below the available maximum residue limits. Low residues in tomatoes and soil suggest that this pesticide is safe to use under the recommended dosage.

Enantioselective toxic effects of hexaconazole enantiomers against Scenedesmus obliquus.

Enantioselectivity in ecotoxicity of chiral pesticides in the aquatic environment has been a subject of growing interest. In this study, the toxicological impacts of hexaconazole enantiomers were investigated with freshwater algae Scenedesmus obliquus. After 96 h of exposure, the EC(50) values for rac-hexaconazole, (+)-hexaconazole, and (-)-hexaconazole were 0.178, 0.355, and 0.065 mg l(-1) , respectively. Therefore, the acute toxicities of hexaconazole enantiomers were enantioselective. In addition, the different toxic effects were evaluated when S. obliquus were exposed to 0.2, 0.5, and 1.0 mg l(-1) of rac-hexaconazole, (+)-hexaconazole, and (-)-hexaconazole during 96 h, respectively. The chlorophyll a and chlorophyll b contents of S. obliquus treated by (-)-hexaconazole were lower than those exposed to (+)-hexaconazole, whereas the malondialdehyde contents of S. obliquus treated by (-)-form were higher than those exposed to (+)-form at higher concentrations. In general, catalase activities were significantly upregulated by exposure to (-)-enantiomer than (+)-enantiomer at all three concentrations. However, superoxide dismutase activities exposed to (-)-hexaconazole were lower than that exposed to (+)-hexaconazole at 0.2 mg l(-1) and 0.5 mg l(-1) . On the basis of these data, the acute toxicity and toxic effects of hexaconazole against S. obliquus were enantioselective, and such enantiomeric differences must be taken into consideration in pesticide risk assessment.

Enantioselective toxicological response of the green alga Scenedesmus obliquus to isocarbophos.

Chiral compounds usually behave enantioselectively in phyto-biochemical processes. Isocarbophos (ICP) is a chiral pesticide that is widely used. To evaluate the toxicological response of ICP and its enantiomers to Scenedesmus obliquus, algal growth, total chlorophyll, total soluble protein, and the superoxide anion radicals (O(2)(•-)) were investigated. The microalgae were treated with ICP and its enantiomers at 0.01-10 mg/l for 96 h. The growth of S. obliquus was stimulated at low levels of ICP and its enantiomers (0.01-1 mg/l), but all were inhibited at high concentrations (10 mg/l). The total soluble protein content and total chlorophyll content of the tested green alga S. obliquus gradually increased, depending on the growth of algal cells in the medium. Meanwhile, the content of O(2)(•-) was decreased. Interestingly, the cell number and content of the chlorophylls and protein decreased with increasing levels of concentration, whereas O(2)(•-) increased. Our results indicated that enantioselectivity was observed in the dose-response of ICP and its enantiomers in S. obliquus. The high O(2)(•-) level might lead to the death of S. obliquus. The stimulation of growth suggests a regulatory mechanism that is related to the capability of the algae to adapt to the O(2)(•-).

Enantioselective toxic effects and biodegradation of benalaxyl in Scenedesmus obliquus.

Enantioselectivity in ecotoxicity and biodegradation of chiral pesticide benalaxyl to freshwater algae Scenedesmus obliquus was studied. The 96 h-EC(50) values of rac-, R-(-)-, S-(+)-benalaxyl were 2.893, 3.867, and 8.441 mg L(-1), respectively. Therefore, the acute toxicities of benalaxyl enantiomers were enantioselective. In addition, the pigments chlorophyll a and chlorophyll b, antioxidant enzyme activities catalase (CAT) and superoxide dismutase (SOD) as well as lipid peroxide malondialdehyde (MDA) were determined to evaluate the different toxic effects. Chlorophyll a was induced by S-(+)-benalaxyl but inhibited by R-(-)-benalaxyl at 1 mg L(-1). Chlorophyll b were both induced at 1 mg L(-1), but S-(+)-form was fourfold higher than R-(-)-form. S-(+)-benalaxyl inhibited more CAT activities at 3 mg L(-1) and 5 mg L(-1), induced less SOD activity and MDA content at 5 mg L(-1) than R-(-)-benalaxyl. Based on these data, enantioselectivity occurred in anti-oxidative stress when S. obliquus response to benalaxyl. In the biodegradation experiment, the half-lives of S-(+)-benalaxyl and R-(-)-benalaxyl were 4.07 d and 5.04 d, respectively, resulting in relative enrichment of the R-(-)-form. These results showed that toxic effects and biodegradation of benalaxyl in S. obliquus were enantioselective, and such enantiomeric differences must be taken into consideration in pesticide risk.

Environmental behavior of the chiral aryloxyphenoxypropionate herbicide diclofop-methyl and diclofop: enantiomerization and enantioselective degradation in soil.

In this study, the degradation of diclofop-methyl (DM) and its main metabolite, diclofop (DC), in two soils under aerobic and anaerobic conditions were investigated using enantioselective HPLC. Under aerobic or anaerobic conditions, rapid hydrolysis to the corresponding acid diclofop (DC)was observed. The results from this study revealed that the degradation of DM in the two soils is not enantioselective, and the calculated half-lives (t(1/2)) for the two soils were both less than 1 day. However, the degradation of DC in the two soils is enantioselective both under aerobic and anaerobic conditions, and the S-(-)-DC was preferentially degraded, resulting in relative enrichment of the R-(+)-form. The calculated t(1/2) values of the enantiomers of DC ranged between 8.7 and 43.3 days for aerobic incubation experiments and between 14.7 and 77.0 days for anaerobic incubation experiments, respectively. The enantiopure S-(-)- and R-(+)-DC were incubated under aerobic conditions, and it revealed significant enantiomerization with inversion of the S-(-)-enantiomer into R-(+)-enantiomer, and vice versa, and the S-(-)-DC showed a significantly higher inversion tendency than the R-(+)-DC.

Enantioselective degradation in sediment and aquatic toxicity to Daphnia magna of the herbicide lactofen enantiomers.

Many pesticides in use are chiral compounds containing stereoisomers. However, the environmental behavior and fate of such compounds with respect to enantioselectivity so far has received little attention. In this study, the degradation of lactofen and its main metabolites (acifluorfen, an achiral compound; desethyl lactofen, a chiral compound) in sediment were investigated under laboratory conditions using enantioselective HPLC, and the enantioselectivities of individual enantiomers of lactofen and desethyl lactofen in acute toxicity to Daphnia magna were studied. The calculated LC(50) values of S-(+)-, rac-, and R-(-)-lactofen were 17.689, 4.308, and 0.378 microg/mL, respectively, and the calculated LC(50) values of S-(+)-, rac-, and R-(-)-desethyl lactofen were 21.327, 13.684, and 2.568 mug/mL, respectively. Therefore, the acute toxicities of lactofen and desethyl lactofen enantiomers were enantioselective. In sediments, S-(+)-lactofen or S-(+)-desethyl lactofen was preferentially degraded, resulting in relative enrichment of the R-(-)-form. Lactofen and desethyl lactofen were both configurationally stable in sediment, showing no interconversion of S- to R-enantiomers or vice versa. Furthermore, the conversion of lactofen to desethyl lactofen proceeded with retention of configuration. These results for major differences in acute toxicity and degradation of the enantiomers may have some implications for better environmental and ecological risk assessment for chiral pesticides.

Enantioselective acute toxicity and bioaccumulation of benalaxyl in earthworm (Eisenia fedtia).

The enantioselectivities of individual enantiomers of benalaxyl in acute toxicity and bioaccumulation in earthworm ( Eisenia fedtia ) were studied. The acute toxicity was tested by paper contact test. After 48 h of exposure, the calculated LC(50) values of the R-(-)-form, rac-form, and S-(+)-form were 4.99, 5.08, and 6.66 microg/cm(2), respectively. After 72 h of exposure, the calculated LC(50) values were 1.23, 1.73, and 2.45 microg/cm(2), respectively. Therefore, the acute toxicity of benalaxyl enantiomers was enantioselective. A method for determining residues of the two enantiomers of benalaxyl in earthworm tissue by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase was developed. During the bioaccumulation experiment, the enantiomer fraction in earthworm tissue was maintained approximately at 0.6, whereas enantiomer fraction in spiked soil was maintained at 0.5; in other words, the bioaccumulation of benalaxyl was enantioselective in earthworm tissue. Peak-shaped accumulation curves were observed for both enantiomers, and the calculated biota to soil accumulations (kg dry kg(-1) wet weight) at steady state were below 1 for both enantiomers. During the elimination experiment, 79.0% of R-(-)-enantiomer and 89.6% of S-(+)-enantiomer in earthworm tissue were eliminated within 2 days.