Allethrin Promotes Apoptosis and Autophagy Associated with the Oxidative Stress-Related PI3K/AKT/mTOR Signaling Pathway in Developing Rat Ovaries.

The increased concern regarding the reduction in female fertility and the impressive numbers of women undergoing fertility treatment support the existence of environmental factors beyond inappropriate programming of developing ovaries. Among these factors are pyrethroids, which are currently some of the most commonly used pesticides worldwide. The present study was performed to investigate the developmental effects of the pyrethroid-based insecticide allethrin on ovarian function in rat offspring in adulthood. We mainly focused on the roles of oxidative stress, apoptosis, autophagy and the related pathways in ovarian injury. Thirty-day-old Wistar albino female rats were intragastrically administered 0 (control), 34.2 or 68.5 mg/kg body weight allethrin after breeding from Day 6 of pregnancy until delivery. We found that allethrin-induced ovarian histopathological damage was accompanied by elevations in oxidative stress and apoptosis. Interestingly, the number of autophagosomes in allethrin-treated ovaries was higher, and this increase was correlated with the upregulated expression of genes and proteins related to the autophagic marker LC-3. Furthermore, allethrin downregulated the expression of PI3K, AKT and mTOR in allethrin-treated ovaries compared with control ovaries. Taken together, the findings of this study suggest that exposure to the pyrethroid-based insecticide allethrin adversely affects both the follicle structure and function in rat offspring during adulthood. Specifically, allethrin can induce excessive oxidative stress and defective autophagy-related apoptosis, probably through inactivation of the PI3K/AKT/mTOR signaling pathway, and these effects may contribute to ovarian dysfunction and impaired fertility in female offspring.

Biodegradation of allethrin, a pyrethroid insecticide, by an acidomonas sp.

Allethrin is a major mosquito repellent agent. To degrade allethrin present in used mats and the environment, a bacterium capable of utilizing allethrin was isolated. This isolate, an Acidomonas sp., grew in minimal medium with 16 mM: allethrin as sole source of carbon and degraded >70% of it in 72 h, with negligible residual metabolites in the medium. Culture filtrates collected after 48 h and 72 h showed presence of (i) cyclopropanecarboxylic acid, 2,2-dimethyl-3-(2-methyl-1-propenyl), (ii) 2-ethyl-1,3-dimethyl-cyclopent-2-ene-carboxylic acid (iii) chrysanthemic acid and (iv) allethrolone [2-cyclopenten-l-one, 4-hydroxy-3-methyl-2(-2-propenyl)] as the major metabolites with 2 minor metabolites. Allethrin is thus metabolized by a hydrolytic pathway followed by oxidation and dehydrogenation.

Metabolism of (S)-bioallethrin and related compounds in humans.

Chrysanthemate insecticides like (S)-bioallethrin, natural pyrethins, and related pyrethroids are subjected to extensive hydrolytic and oxidative degeneration by the mammalian metabolism, leading to a complex series of metabolites partially conjugated and finally eliminated in the urine. The major oxidation products of chrysanthemic acid, cis-(E)- and trans-(E)-chrysanthemumdicarboxcylic acid (cis-(E) and trans-(E)-CDCA), were synthesized and their structures were established by nuclear magnetic resonance spectrometry (H1-NMR) and mass spectrometry (MS). Diastereoselective separation was by high performance liquid chromatography (HPLC) and capillary gas chromatography (GC). An analytical method for extraction and identification of CDCA from human urine was developed. Quantitation was by gas chromatography and electron-impact mass spectrometry (GC/MS). The limit of detection was 20 microg/l for cis-(E)-CDCA and 10 microg/l for trans-(E)-CDCA. To test the applicability of the presented method, urine samples of humans exposed to (S)-bioallethrin were investigated. Urinary peak excretion of trans-(E)-CDCA occurred within 24 h after exposure.

Interactions of pyrethroids with phosphatidylcholine liposomal membranes.

Interactions of several pyrethroids with membrane lipids in the form of dipalmitoylphosphatidylcholine (DPPC) liposomes have been studied using fluorescent membrane probes. Fluorescence anisotropy values and lifetimes (determined by phase-shift and demodulation techniques) of the fluorescent probe, 1,6-diphenyl-1,3,5-hexatriene, were decreased in gel phase liposomes by pyrethroids at concentrations on the order of 10 microM. The pyrethroids containing a cyano substituent were also observed to cause collisional quenching of diphenylhexatriene fluorescence. Pyrethroids differed in their effectiveness at lowering the phase transition temperature of DPPC, and in their ability to broaden the temperature range of this transition. The fluorescence intensity of DPPC-incorporated chlorophyll a was used to monitor the pretransition of DPPC and the lateral diffusion of a membrane component located in the polar headgroup region. Permethrin did not affect chlorophyll a fluorescence intensity at any temperature. It may be concluded from these results that pyrethroids are preferentially located in the interior hydrophobic regions of the lipid bilayer, and that these compounds can disorder hydrocarbon packing in the bilayer core. However, polar headgroups were not disordered, and diffusion of membrane components in the polar headgroup region was not altered.

Allethrin interactions with the nicotinic acetylcholine receptor channel.

Interactions of the synthetic pyrethroid allethrin with the nicotinic acetylcholine (ACh) receptor/channel were studied in membranes from Torpedo electric organ. Allethrin did not inhibit binding of [3H]ACh to the receptor sites, but inhibited noncompetitively binding of [3H]perhydrohistrionicotoxin ([3H]H12-HTX) to the ionic channel sites in a dose-dependent manner. The inhibition constant (Ki) of [3H]H12-HTX binding in absence of receptor agonist was 30 micro M, while in presence of 100 micro M carbamylcholine it was 4 micro M. This inhibitory effect of allethrin had a negative temperature coefficient. The high affinity binding of allethrin to the channel sites of the nicotinic ACh-receptor may be indicative of a postsynaptic site of action for pyrethroids, in addition to their known action on the sodium channel.