Toxicity Of Pyriproxyfen Research Articles

Pyriproxyfen induces intracellular calcium overload and alters antioxidant defenses in Danio rerio testis that may influence ongoing spermatogenesis.

We investigated the invitro effects of pyriproxyfen on ionic balance in the testis of the zebrafish by measuring 45Ca2+ influx. Invivo pyriproxyfen treatment was carried out to study oxidative stress, and conduct morphological analysis of the testis and liver. Whole testes were incubated invitro with/without pyriproxyfen (10-12, 10-9 or 10-6M; 30min) and 45Ca2+ influx determined. To study pyriproxyfen's mechanism of action, inhibitors/activators of ionic channels or pumps/exchangers, protein kinase inhibitors or a calcium chelator were added 15min before the addition of 45Ca2+ and pyriproxyfen. We evaluated the invivo effects of 7 day exposure to waterborne pyriproxyfen (10-9M) on reactive oxygen species (ROS) formation, lipid peroxidation, and reduced glutathione content (GSH), glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and γ-glutamyltransferase (GGT) activity. Morphological analyses of the testis and liver were carried out after invivo exposure of D.rerio to pyriproxyfen. Pyriproxyfen increased 45Ca2+ influx by opening the voltage-dependent T-type channels (T-type VDCC), inhibiting sarco/endoplasmic reticulum 45Ca2+-ATPase (SERCA) and the NCX exchanger (forward mode) and by mobilizing calcium from stores. The involvement of potassium channels and protein kinase C (PKC) was also demonstrated in pyriproxyfen-induced intracellular calcium elevation. Invivo pyriproxyfen treatment of D.rerio increased lipid peroxidation, decreased GSH content and increased GST activity in testes, in addition to increasing the number and size of spermatogonia cysts and inducing hepatocyte basophilia and dilation of blood vessels in the liver. The toxicity of pyriproxyfen is mediated by calcium overload, increased lipid peroxidation, and a diminished antioxidant capacity in the testis, due to GSH depletion, and altered spermatogenesis. The development of high basophilia in the liver suggests that pyriproxyfen may have estrogenic activity, possibly acting as an endocrine-disruptor. These findings indicate that these alterations may contribute to pyriproxyfen toxicity and spermatogenesis disruption.

Fate and ecotoxicological effects of pyriproxyfen in aquatic ecosystems.

Pyriproxyfen is an insect growth regulator acting as larvicide against a large spectrum of public health insect pests, especially dipterans. It is also widely used in agriculture and horticulture for the control of many insect species. Disrupting the endocrine system by mimicking the activity of the juvenile hormone, pyriproxyfen interferes with metamorphosis in insects and prevents them from reaching maturity and reproducing. Because the aquatic ecosystems can be directly or indirectly contaminated by pyriproxyfen, the goal of this study was to establish the aquatic ecotoxicological profile of pyriproxyfen and to identify the gaps that need to be filled. Pyriproxyfen is photodegraded quickly in water. In the absence of organic matter, its persistence in aerobic water media is also limited especially with high temperature and sunlight. Analysis of the laboratory and in situ results for more than 60 aquatic algae, plants, invertebrates, and vertebrates shows that the toxicity of pyriproxyfen is highly variable including within a same taxonomical group. Abiotic and biotic factors can highly influence the toxicity of the molecule. Pyriproxyfen disrupts the development of numerous species and adversely impacts various physiological events. It can also disturb the behavior of the organisms such as their predatory and swimming performances. Although some experimental studies focus on the environmental fate of pyriproxyfen metabolites, those dealing with their aquatic ecotoxicity assessment are scarce. In the same way, the limited number of studies dealing with the search of pyriproxyfen residues in lake, river, and other natural aquatic media does not include the identification of the metabolites.

Insecticidal and inhibitory effects of dihydrobenzofuran neolignans on Bemisia tabaci

Bemisia tabaci (Gennadius) biotype B (Hemiptera: Aleyrodidae) has developed resistance to numerous conventional insecticides, which has led us to investigate the toxicity of ten dihydrobenzofuran- (DBN) and benzofuran-type (BN) neolignans structurally related to conocarpan against second instar B. tabaci nymphs. At concentrations higher than 5 mg/L, most of the tested compounds killed 100% of B. tabaci biotype B nymphs 6 days after spraying. The contact toxicity of compounds 2 ((±)-trans-dehydrodiferulate dimethyl ester), 3 ((±)-4-O-methyl-trans-dehydrodiferulate dimethyl ester), 5 ((±)-4-O-acetyl-trans-dehydrodiferulate dimethyl ester), 6 ((±)-7′,8′-dihydro-trans-dehydrodicoumarate dimethyl ester), 8 ((±)-4-O-methyl-7′,8′-dihydro-trans-dehydrodiferulate dimethyl ester), and 10 ((±)-7′,8′-dihydro-7,8-dehydro-trans-dehydrodicoumarate dimethyl ester) was higher than the contact toxicity of pyriproxyfen at a concentration of 75 mg/L, which was used as positive control. Repellent (compounds 2 and 7 ((±)-7′,8′-dihydro-trans-dehydrodiferulate dimethyl ester) and oviposition deterrent (compounds 2, 3, and 7) effects were observed for adult whiteflies exposed to leaves sprayed with DBNs for 24 and 48 h, respectively. These results suggest that DBNs have potential application in the development of effective pest management compounds.

Soil dissipation of juvenile hormone analog insecticide pyriproxyfen and its effect on the bacterial community

This investigation was undertaken to examine the dissipation rate of pyriproxyfen as well as the change in the soil bacterial community. Residues of pyriproxyfen were measured using high performance liquid chromatography (HPLC) and the changes in bacterial community were determined by comparing the 16S rDNA bands on patterns by denaturing gradient gel electrophoresis (DGGE). The dissipation of pyriproxyfen was affected by both the concentration applied and incubation temperature. Lower concentrations (1 mg Kg−1) and higher incubation temperatures (30 and 40°C) showed more rapid dissipation rates. The population of microbial community decreased rapidly after incubation with 10 mg Kg−1 of pyriproxyfen for 91 days, indicating the toxicity of pyriproxyfen toward bacterial communities in a closed soil ecosystem. Lower concentrations of pyriproxyfen showed less toxicity toward the microbial community. From cluster analysis, the structure of the bacterial community showed roughly a 60 % similarity throughout the experiment period in the control experiment, indicating the stability within soil microbiota without chemical agitation. However, the similarity was lower than 50 % both in the one and 10 mg Kg−1 of insecticide pyriproxyfen spiked experiment, indicating the soil bacterial community changed after the insecticide pyriproxyfen was applied.