Allethrin and prallethrin stimulates MUC5AC expression through oxidative stress in human airway epithelial cells.

Pyrethroids, including allethrin and prallethrin, have been widely used as major components of the common commercial insecticides. The toxicity of allethrin and prallethrin were well established that it interfered with the way that the nerves and brain function. However, limited information was available regarding respiratory effects in humans following inhalation exposure to allethrin and prallethrin. Therefore, we demonstrated effect of allethrin and prallethrin, and the mechanism involved, on the mucin expressions in human airway epithelial cells. In human airway NCI-H292 epithelial cells, the effects of allethrin and prallethrin and its signaling pathway for airway mucin, especially MUC5AC, were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR, and enzyme-linked immunosorbent assay (ELISA). The mechanism of allethrin and prallethrin-induced MUC5AC expression in airway epithelial cells was studied in terms of reactive oxygen species (ROS) by flow cytometry analysis. Allethrin and prallethrin significant increased MUC5AC expression in human airway NCI-H292 epithelial cells. We also demonstrated allethrin and prallethrin induced a marked rise of ROS production. In addition, NAC (ROS scavenger) and DPI (NADPH oxidase inhibitor) inhibited allethrin and prallethrin-induced MUC5AC expression. These results are first to describe that allethrin and prallethrin-induced MUC5AC expression through ROS in human airway epithelial cells.

Exposure to allethrin-based mosquito coil smoke during gestation and postnatal development affects reproductive function in male offspring of rat.

The threat of zika virus looms throughout the world and the use of allethrin-based mosquito coils to prevent mosquito bites during and postpregnancy is on the rise. The aim of this study was to analyze the toxic effects of exposure to allethrin-based mosquito coil smoke in rats under conditions that reflect human settings. Pregnant female rats were exposed to mosquito coil smoke and same was continued to the male pups up to 111 days postparturition (21-day weaning plus up to 90 days postweaning). Increased oxidative stress, distorted antioxidant enzyme status, downregulation of genes involved in spermatogenesis, sperm maturation and steroidogenesis was observed. Daily sperm production, total sperm count and acrosome reaction was compromised. Results of our study indicate the toxic effects of exposure to allethrin-based mosquito coil smoke in male offspring and calls for preventing mosquito coil use during pregnancy and postnatal development. Community-based programs that will encourage general population to use classical methods such as use of mosquito nets, keeping the surroundings clean and use of natural mosquito repellents should be conducted.

A capillary micellar electrokinetic chromatography method for the stereoselective quantitation of bioallethrin in biotic and abiotic samples.

A capillary micellar electrokinetic chromatography (MEKC) method was developed enabling the stereoselective separation of the insecticide bioallethrin. The use of sodium deoxycholate bile salt and acetyl-ß-cyclodextrin (acetyl-ß-CD) made possible the separation of bioallethrin stereoisomers with a high enantioresolution (7.4) in a short analysis time (6.5min). The analytical characteristics of the developed method were evaluated in terms of linearity, accuracy, precision, and limits of detection (LOD) and quantitation (LOQ) showing a good performance for the quantitation of bioallethrin stereoisomers with LODs of 0.2 and 0.3mg/L. The developed method was applied to the stereoselective analysis of a commercial bioallethrin pediculicide formulation and to evaluate the toxicity of bioallethrin stereoisomers on the growth of the unicellular freshwater green alga Pseudokirchneriella subcapitata and on the germination of the higher plant Sorghum bicolor (non-target organisms). The analysis of the commercial pediculicide showed a good agreement between the contents determined for the two stereoisomers and those labelled in the commercial samples. Different toxic responses and biodegradation profiles were found for each stereoisomer in ecotoxicity assays. The mixture of S/R stereoisomers of bioallethrin resulted more toxic than S-bioallethrin for green algae, with EC50 values of 1.10±0.06 for the mixture and of 1.73±0.05mg/L for the pure S-biallethrin (esbiol). Germination of plants seeds was also affected.

Allethrin toxicity causes reproductive dysfunction in male rats.

Pyrethroids are widely used for domestic and agricultural purposes and their use is increasing, especially in developing countries. Uncontrolled use of these insecticides resulted in their entry into the food chain thereby causing toxicity to different organ systems. Allethrin is one of the widely used pyrethroids, but its toxicological effects are underreported when compared to other pyrethroids. Further, its effects on the male reproductive tract remain uncharacterized. In this study, its toxicity on the male reproductive tract was evaluated by administering 25-150 mg/kg body weight allethrin to adult rats for 60 days. The mRNA expression of factors that are important in spermatogenesis (Scf, c-Kit, Hsf2, Ovol1, Brdt, Kdm3A, Ybx-2, and Grth) and steroidogenesis (StAR, 3ß-HSD, 17ß-HSD) was significantly downregulated. Decreased levels of testosterone, reduced sperm count and daily sperm production was also observed due to allethrin toxicity. However, sperm quality parameters assessed by computer-assisted sperm analyzer were not affected. Spermatozoa obtained from allethrin-treated rats failed to undergo acrosome reaction. Results of this study indicate that allethrin affects spermatogenesis and sperm function, thus lending further support to the growing evidence of its toxicity.

Inhibition of Human Drug Transporter Activities by the Pyrethroid Pesticides Allethrin and Tetramethrin.

Pyrethroids are widely-used chemical insecticides, to which humans are commonly exposed, and known to alter functional expression of drug metabolizing enzymes. Limited data have additionally suggested that drug transporters, that constitute key-actors of the drug detoxification system, may also be targeted by pyrethroids. The present study was therefore designed to analyze the potential regulatory effects of these pesticides towards activities of main ATP-binding cassette (ABC) and solute carrier (SLC) drug transporters, using transporter-overexpressing cells. The pyrethroids allethrin and tetramethrin were found to inhibit various ABC and SLC drug transporters, including multidrug resistance-associated protein (MRP) 2, breast cancer resistance protein (BCRP), organic anion transporter polypeptide (OATP) 1B1, organic anion transporter (OAT) 3, multidrug and toxin extrusion transporter (MATE) 1, organic cation transporter (OCT) 1 and OCT2, with IC50 values however ranging from 2.6 µM (OCT1 inhibition by allethrin) to 77.6 µM (OAT3 inhibition by tetramethrin) and thus much higher than pyrethroid concentrations (in the nM range) reached in environmentally pyrethroid-exposed humans. By contrast, allethrin and tetramethrin cis-stimulated OATP2B1 activity and failed to alter activities of OATP1B3, OAT1 and MATE2-K, whereas P-glycoprotein activity was additionally moderately inhibited. Twelve other pyrethoids used at 100 µM did not block activities of the various investigated transporters, or only moderately inhibited some of them (inhibition by less than 50%). In silico analysis of structure-activity relationships next revealed that molecular parameters, including molecular weight and lipophilicity, are associated with transporter inhibition by allethrin/tetramethrin and successfully predicted transporter inhibition by the pyrethroids imiprothrin and prallethrin. Taken together, these data fully demonstrated that two pyrethoids, i.e., allethrin and tetramethrin, can act as regulators of the activity of various ABC and SLC drug transporters, but only when used at high and non-relevant concentrations, making unlikely any contribution of these transporter activity alterations to pyrethroid toxicity in environmentally exposed humans.

A permethrin/allethrin mixture induces genotoxicity and cytotoxicity in human peripheral blood lymphocytes.

Two pyrethroids, permethrin and allethrin, are often combined for large-scale use in public health programs to control vector-borne diseases. In this study, the genotoxic potential of a commercial formulation of permethrin and allethrin was examined using cultured human peripheral blood lymphocytes (PBL). Genotoxicity was evaluated using the cytokinesis-block micronucleus cytome (CBMN cyt) assay by measuring the frequency of micronuclei (MN), nuclear division index (NDI), formation of nucleoplasmic bridges (NPB) and nuclear buds (NBUD), as well as apoptotic and necrotic cells. Human PBL were treated with different concentrations of a permethrin/allethrin mixture (1/0.01, 5/0.07, and 10/0.14 µg/ml) for 24 or 36 h. The highest concentration (10/0.14 µg/ml) of permethrin/allethrin mixture significantly increased MN frequency and percent apoptotic cells after incubations for 24 or 36 h. The NDI was markedly decreased in response to treatment with 5/0.07 or 10/0.14 µg/ml permethrin/allethrin for both 24 and 36 h. Exposure to the permethrin/allethrin mixture did not significantly alter formation of NBUD, NPB, or percent necrotic cells. The MN frequency was significantly correlated with the number of apoptotic and necrotic cells but inversely correlated with NDI. Data demonstrated that a mixture of permethrin and allethrin induced concentration- and time-dependent cytotoxic and genotoxic damage to human PBL in vitro.

Allethrin induces oxidative stress, apoptosis and calcium release in rat testicular carcinoma cells (LC540).

Over the years, pyrethroids, including D-allethrin, are widely used for domestic and agricultural purposes and are found to be toxic to many organ systems including the male reproductive system. However, the molecular mechanisms of allethrin toxicity are not well understood. In this study, we demonstrate that allethrin exhibited a dose-dependent cytotoxicity on Leydig cell carcinoma cells (LC540) and isolated primary Leydig cells with an IC50 of 125 µM and 59 µM respectively. Cytotoxicity was associated with generation of reactive oxygen species, increased lipid peroxidation and alterations in antioxidant enzyme status. Morphological analyses of LC540 cells treated with allethrin revealed the presence of apoptotic bodies. Using flow cytometry, we observed that the number of cells that displayed early apoptotic features and entering into G0 phase of cell cycle increased significantly with loss of mitochondrial membrane potential. The levels of p53 mRNA and cleaved PARP-1 protein were increased, whereas BCL-2, pro-Caspase-3 and PARP-1 were decreased. Allethrin induced apoptosis was associated with voltage gated calcium channel mediated intracellular calcium release. Results of our study demonstrate that allethrin toxicity in the male reproductive tract may involve Leydig cell apoptotic death.

[Effect of rich-D-transallethrin on amino acid neurotransmitters in rat brain].

OBJECTIVE: To discuss the effect of rich-D-transallethrin on amino acid neurotransmitters in rats central nerves system and pathological examination of brain tissues, hypophysis and sciatic nerve. METHODS: Ninety-six male and female Wistar rats were randomly divided into four groups according to body weight, which were exposed to rich-d-transallthrin aerosol at different dose (0, 9.6, 45.8, 166 mg/m3) for 6 h/d, 7 d/week for 28 consecutive days. Neurobehavior were observed, gait and grip strength were measured during exposure. At the end of treatment the rats in all groups were sacrificed. The content of glutamate (Glu) and glycine (Gly) in brain tissues were determined and the pathological examination of brain tissues, hypophysis and sciatic nerve were conducted. RESULTS: The grip strength in 166.0 mg/m3 exposure group was significantly decreased (P < 0.05) compared with control group. The level of glutamate and glycine in female rats brain tissues was also significantly reduced (P < 0.05) after treatment with rich-d-transallethrin aerosol for 4 weeks. The result of pathological examination showed that cerebral cortex, hippocampus and cerebellum appeared neuron degeneration and slight axon swelling and myelin sheath destruction in sciatic nerve induced by 166.0 mg/m3 rich-d-transallethrin aerosol. CONCLUSION: The changes of Glu, Gly and pathological examination could be related to treatment with rich-d-transallethrin, in the meanwhile the major effect on nervous system appeared to be the cerebral cortex, hippocampal neuron and peripheral motor nerve.

Allethrin induced toxicity in the male reproductive tract of rats contributes to disruption in the transcription of genes involved in germ cell production.

Pyrethroids are known to be neurotoxic. However, their toxic effects including that of allethrin on the male reproductive tract are not elucidated. Adult male rats were treated orally with 25, 50, 100, and 150 mg/kg body weight allethrin every day for 60 days. Lipid peroxidation was increased (p < 0.001) in the caput, cauda, and testes. Nitric oxide production was increased (p < 0.001) in the caput, but unaltered in the cauda and testes. The activities of catalase, glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase were decreased in the caput and cauda where as a decrease was observed in the testis obtained from allethrin treated rats. In the epididymides and testes, damage to tubular architecture, congestion, degeneration of epithelial cell lining, intestinal edema, and presence of dead or degenerating spermatids were observed in a dose dependent manner. The expression profile of genes involved in spermatogenesis (Tgf-beta1), sperm maturation (Spag11e), and sperm function (Defb22) were reduced (p < 0.001) in allethrin rats. The expression of p53 gene was decreased and increased phosphorylation of MAPK (p42/p44) expression was observed the male reproductive tract tissues of allethrin treated rats. Although earlier studies have reported the effects of allethrin inhalation because of the use of mosquito coils and vaporizers, our results for the first time prove that oral exposure to allethrin could affect fertility and may contribute to deregulation of cell cycle in the male reproductive tract.

Toxicological effects of prolonged and intense use of mosquito coil emission in rats and its implications on malaria control.

Mosquito coil is a vector control option used to prevent malaria in low income counties, while some studies have addressed this issue, additional reseach is required to increase knowledge on the adverse health effects caused by the prolonged use of coils. In this study we investigated the toxicological effects of fumes from two locally manufactured mosquito coil insecticides (with pyrethroids: transfluthrin and d-allethrin as active ingredients) on male albino rats. For this, we recorded the haematological and biochemical indices, and made histopathology and mutagenicity evaluations in rats exposed to mosquito fumes during 2, 4, 8, 12 and 16 week periods. Haematological determination was performed using automated hematology analyzer to determine White Blood Cell (WBC), Packed Cell Volume (PCV), Red Blood Cell (RBC) and Platelet (PLT) counts, while biochemical evaluations were determined using available commercial kits. Gross histopathological changes were studied for the kidney, liver and lungs in sacrificed rats. The rat sperm head abnormalities assessment was used to evaluate mutagenicity. Mosquito coil fumes produced significant increase (P < 0.05) in the levels of total protein, total albumin and bilirubin, when animals were exposed from two weeks to 16 weeks with transfluthrin. Similarly, elevation in the activities of aspartate amino transferase, alanine amino transferase and alanine phosphatase, increased significantly in both insecticides. Increase in WBC, RBC and PCV were recorded for all the exposure periods, however PLT count showed no significant increase (P > 0.05). Mutagenicity assessment revealed sperm abnormality was statistically significant (P < 0.05) compared with the control at 8, 12 and 16 weeks post exposure to transfluthrin. Histological studies revealed severe lung damage evidenced by interstitial accumulations, pulmonary oedema and emphysema in exposed rats. Intracellular accumulations and severe sinusoidal congestion of liver cells were observed from 12 weeks exposure, indicating liver damage. Our studies indicate that mosquito coil fumes do initiate gradual damage to the host. These pathological effects must be taken into consideration by the malaria control program, particularly when regulating their long term and indoor usage.

Allethrin toxicity on human corneal epithelial cells involves mitochondrial pathway mediated apoptosis.

Pyrethroids including allethrin are the most common commercial household insecticides. The detrimental effects caused by pyrethroids on humans are gaining considerable attention. The present study was aimed to elucidate the effects of allethrin on the human corneal epithelial (HCE) cells. Allethrin inhibited the proliferation of HCE cells in a dose-dependent manner. In the presence of allethrin, cells showed membrane blebbing and nuclear fragmentation along with significant decrease in mitochondrial membrane potential resulting in increased cytochrome c (Cyt c) release into the cytosol. Further, flow cytometry analysis demonstrated a marked increase in sub G0-G1 cells, characteristic of apoptosis. Increased expression of pro-apoptotic protein, Bax, a simultaneous decrease of anti-apoptotic protein, Bcl-2, and activation of Caspase 3 was evident in the treated cells. In addition, extracellular matrix digesting metalloproteinase 9 (MMP-9) was also stimulated. Furthermore, significant increase in the gene expression of inflammatory cytokines, TNF-α and IL-1ß was observed. Taken together, these findings suggest that allethrin (IC50≈85µM) is toxic to HCE cells causing death through mitochondrial pathway.

Toxicological effects of prolonged and intense use of mosquito coil emission in rats and its implications on malaria control / Efectos toxicológicos del uso prolongado e intenso de emisiones de espirales contra mosquitos en ratas y sus implicaciones sobre el control de la malaria

Efectos toxicológicos del uso prolongado e intenso de emisiones de espirales contra mosquitos en ratas y sus implicaciones sobre el control de la malaria. Mosquito coil is a vector control option used to prevent malaria in low income counties, while some studies have addressed this issue, additional reseach is required to increase knowledge on the adverse health effects caused by the prolonged use of coils. In this study we investigated the toxicological effects of fumes from two locally manufactured mosquito coil insecticides (with pyrethroids: transfluthrin and d-allethrin as active ingredients) on male albino rats. For this, we recorded the haematological and biochemical indices, and made histopathology and mutagenicity evaluations in rats exposed to mosquito fumes during 2, 4, 8, 12 and 16 week periods. Haematological determination was performed using automated hematology analyzer to determine White Blood Cell (WBC), Packed Cell Volume (PCV), Red Blood Cell (RBC) and Platelet (PLT) counts, while biochemical evaluations were determined using available commercial kits. Gross histopathological changes were studied for the kidney, liver and lungs in sacrificed rats. The rat sperm head abnormalities assessment was used to evaluate mutagenicity. Mosquito coil fumes produced significant increase (P<0.05) in the levels of total protein, total albumin and bilirubin, when animals were exposed from two weeks to 16 weeks with transfluthrin. Similarly, elevation in the activities of aspartate amino transferase, alanine amino transferase and alanine phosphatase, increased significantly in both insecticides. Increase in WBC, RBC and PCV were recorded for all the exposure periods, however PLT count showed no significant increase (P>0.05). Mutagenicity assessment revealed sperm abnormality was statistically significant (P<0.05) compared with the control at 8, 12 and 16 weeks post exposure to transfluthrin. Histological studies revealed severe lung damage evidenced by interstitial accumulations, pulmonary oedema and emphysema in exposed rats. Intracellular accumulations and severe sinusoidal congestion of liver cells were observed from 12 weeks exposure, indicating liver damage. Our studies indicate that mosquito coil fumes do initiate gradual damage to the host. These pathological effects must be taken into consideration by the malaria control program, particularly when regulating their long term and indoor usage.

Las espirales contra los mosquitos se utilizan en los países de bajos ingresos como una opción para prevenir la malaria controlando el vector de esta enfermedad. A pesar de que algunos estudios han abordado este tema, se requiere más investigación para incrementar el conocimiento sobre los efectos adversos en la salud, causados por el uso prolongado de las espirales. En este estudio se investigaron los efectos toxicológicos de los gases de las espirales a partir de dos insecticidas fabricados en el país (con piretroides: transflutrina y d-aletrina como ingredientes activos) en machos de ratas albinas. Para esto, se registraron los índices hematológicos y bioquímicos, y se hicieron evaluaciones histopatológicas y de mutagenicidad en ratas expuestas a los gases de las espirales durante períodos de 2, 4, 8, 12 y 16 semanas. La determinación hematológica se realizó mediante un analizador de hematología automatizado para determinar el conteo de los Glóbulos Blancos (WBC), el Hematocrito (PCV), Glóbulos Rojos (RBC) y las Plaquetas (PLT), mientras que las evaluaciones bioquímicas se determinaron utilizando kits comerciales disponibles. Los cambios histopatológicos fuertes se estudiaron en el riñón, el hígado y los pulmones de ratas sacrificadas. Las anormalidades en la cabeza de los espermatozoides de las ratas se utilizaron para evaluar la mutagenicidad. El humo de las espirales contra los mosquitos producen un aumento significativo (p<0.05) en los niveles de proteína total, albúmina total y bilirrubina, cuando los animales fueron expuestos de dos semanas a 16 semanas con transflutrina. Del mismo modo, la elevación en las actividades de aspartato amino transferasa, alanina amino transferasa y alanina fosfatasa, aumentó significativamente con ambos insecticidas. Se registro un aumento en los leucocitos, eritrocitos y el hematocrito para todos los períodos de exposición, sin embargo el recuento de las plaquetas no mostró un aumento significativo (p>0.05). Las pruebas de mutagenicidad revelaron que las anormalidades en el esperma de las ratas fue estadísticamente significativa (p>0.05) al comparar el control a las 8, 12 y 16 semanas post exposición a la transflutrina. Los estudios histológicos revelaron una serie de daños pulmonares graves en las ratas expuestas al humo de la espiral, evidenciados por la acumulación intersticial, edema pulmonar y enfisema. Las acumulaciones intracelulares y la congestión sinusoidal severa de las células del hígado se observaron a partir de las 12 semanas de exposición, lo que indica daño hepático. Nuestros estudios indican que los vapores de las espirales contra mosquitos inician el daño gradual al huésped. Estos efectos patológicos deben ser tomados en cuenta por el programa de control de la malaria, particularmente a la hora de regular su uso a largo plazo y bajo techo.

Recurrent tonic-clonic seizures and coma due to ingestion of Type I pyrethroids in a 19-month-old patient.

CONTEXT: Pyrethroids are synthetic pyrethrin analogues that induce sodium-channel depolarization and hyperexcitation. Severe pyrethroid poisoning is manifested by a "Tremor Syndrome" (Type I cyano-agents) or a "Choreoathetosis/Salivation Syndrome" (Type II non cyano-agents). Very few reports of neurotoxic effects caused by Type I pyrethroids ingestion are available, and no human data concerning Type I pyrethroid blood levels in pediatric poisoning are reported in the medical literature. CASE DETAILS: A 19-month-old female patient presented with irritability and inconsolable crying that rapidly worsened to tonic-clonic seizures and coma (GCS 6). On admission vital signs including BP 110/70 mmHg, HR 110 beats/min, and SpO2 98% on room air were normal. Orotracheal intubation, oxygen administration, and midazolam infusion (4 µg/kg/min) were performed. Intravenous thiopental sodium, up to 18 mg/kg/hour, was administered to control convulsions. An inquiry revealed that 9 h before presentation the patient had ingested an unknown amount of an insecticide containing 7% piperonyl-butoxide and a mixture of the Type I pyrethroids bifenthrin (5%) and esbiothrin (3%). Consequently, gastric lavage was performed, followed by administration of activated charcoal and cathartics. On the subsequent 48 h, the patient returned progressively alert; she was extubated on day 4 and discharged asymptomatically 12 days after hospitalization. After 9, 48, and 72 h of ingestion, the plasma levels were 500, 95, and 40 ng/mL for bifenthrin and 1,640, 640, and 165 ng/mL for piperonyl-butoxide respectively. DISCUSSION: This pediatric case showed severe pyrethroid neurotoxicity associated with measurable plasma levels of bifenthrin and piperonyl-butoxide. In pediatric pyrethroid poisoning, coma and seizures may represent the main life-threatening features. First-aid therapy including airway maintenance and control of muscle fasciculation and seizures is of major importance. Benzodiazepines and high-dose thiopental sodium were effective treatments for convulsion.

Sublethal toxicity of esbiothrin relationship with total antioxidant status and in vivo genotoxicity assessment in fish (Cyprinus carpio L., 1758) using the micronucleus test and comet assay.

Esbiothrin, synthetic pyrethroid with quick activity against insects, is widely used against household pests and in public health. Despite widespread use, data on ecotoxicity and genotoxic effects are extremely scarce. The aim of the present study is to evaluate the genotoxic potential of esbiothrin on a model fish species Cyprinus carpio L., 1758 (Pisces: Cyprinidae, koi) using the micronucleus test and comet assay in peripheral blood erythrocytes. Effects of two sublethal exposure concentrations on plasma total antioxidant status (TAS mmol/L), and Hct values were examined. On the basis of the 96 h LC50 data from U.S. EPA ecotox database (32 µg/L) two sublethal exposure concentrations (5 and 10 µg/L) were used together with ethyl methanesulfonate (EMS) (5 mg/L) as positive control. Five fish were used for each dose/duration group (24, 48, and 72 h) under controlled laboratory conditions. The fish showed behavioral changes at the higher dose. Plasma TAS (mmol/L) levels decreased in 24 h; an increase was observed slightly for 48 and obviously for 72 h in both exposure doses. Similarly, hematocrit (Hct) values differed between exposure duration but no significant differences in mean values were found between groups of the same exposure time. The general trend was a rise after 48 h, which decreased afterwards. Our results revealed significant increases in the frequencies of micronuclei and levels of DNA strand breaks and thus demonstrated the genotoxic potential of this pesticide on fish, a nontarget organism of the aquatic ecosystem. To our knowledge this is the first study to report observable genotoxic effects of esbiothrin on fish.

Allethrin-induced genotoxicity and oxidative stress in Swiss albino mice.

Allethrin (C(19)H(26)O(3)) is non-cyano-containing pyrethroid insecticide that is used extensively for controlling flies and mosquitoes. Apart from its neurotoxic effects in non-target species, allethrin is reported to be mutagenic in bacterial systems. In this study, we observed oxidative damage-mediated genotoxicity caused by allethrin in Swiss albino mice. The genotoxic potential of allethrin was evaluated using chromosome aberrations (CAs) and a micronuclei (MN) induction assay as genetic end-points. The oral intubation of allethrin (25 and 50mg/kg b.wt.) significantly induces CAs and MN in mouse bone marrow cells. The DNA-damaging potential of allethrin was estimated in mouse liver using the DNA alkaline unwinding assay (DAUA) and by measuring the levels of 8-hydroxy-2'-deoxy-guanosine (8-OH-dG). Furthermore, a dose-dependent increase in reactive oxygen species (ROS) generation and lipid peroxidation (LPO), with a concurrent decrease in superoxide dismutase (SOD) and catalase, confirm its pro-oxidant potential. The DNA-damaging potential of allethrin was found to be mediated through the modulation of p53, p21, GADD45α and MDM-2. These results confirm the genotoxic and the pro-oxidant potential of allethrin in Swiss albino mice.

Differential state-dependent modification of inactivation-deficient Nav1.6 sodium channels by the pyrethroid insecticides S-bioallethrin, tefluthrin and deltamethrin.

Pyrethroid insecticides disrupt nerve function by modifying the gating kinetics of transitions between the conducting and nonconducting states of voltage-gated sodium channels. Pyrethroids modify rat Na(v)1.6+ß1+ß2 channels expressed in Xenopus oocytes in both the resting state and in one or more states that require channel activation by repeated depolarization. The state dependence of modification depends on the pyrethroid examined: deltamethrin modification requires repeated channel activation, tefluthrin modification is significantly enhanced by repeated channel activation, and S-bioallethrin modification is unaffected by repeated activation. Use-dependent modification by deltamethrin and tefluthrin implies that these compounds bind preferentially to open channels. We constructed the rat Na(v)1.6Q3 cDNA, which contained the IFM/QQQ mutation in the inactivation gate domain that prevents fast inactivation and results in a persistently open channel. We expressed Na(v)1.6Q3+ß1+ß2 sodium channels in Xenopus oocytes and assessed the modification of open channels by pyrethroids by determining the effect of depolarizing pulse length on the normalized conductance of the pyrethroid-induced sodium tail current. Deltamethrin caused little modification of Na(v)1.6Q3 following short (10ms) depolarizations, but prolonged depolarizations (up to 150ms) caused a progressive increase in channel modification measured as an increase in the conductance of the pyrethroid-induced sodium tail current. Modification by tefluthrin was clearly detectable following short depolarizations and was increased by long depolarizations. By contrast modification by S-bioallethrin following short depolarizations was not altered by prolonged depolarization. These studies provide direct evidence for the preferential binding of deltamethrin and tefluthrin (but not S-bioallethrin) to Na(v)1.6Q3 channels in the open state and imply that the pyrethroid receptor of resting and open channels occupies different conformations that exhibit distinct structure-activity relationships.

Effect of continuous inhalation of allethrin-based mosquito coil smoke in the male reproductive tract of rats.

OBJECTIVES: Continuous inhalation of allethrin-based mosquito coil smoke may affect fertility, an aspect that has not received much attention. In this study, we attempt to understand the harmful effects on the male reproductive system caused by continuous exposure to allethrin-based mosquito coil smoke. METHODS: Adult Wistar rats were allowed to inhale mosquito coil smoke for 15-180 days, and male reproductive tract tissues (caput, cauda, and testes) were collected. Using standard biochemical techniques, changes in oxidative stress (lipid peroxidation) and antioxidant status was measured. Histopathological analyses were carried out to assess pathomorphological damage in the caput, cauda, and testis. Real-time polymerase chain reaction was carried out to determine the expression pattern of the stress-response gene, p53, and the spermatogenic factors c-Kit, Scf, and Tgf-ß1. RESULTS: In rats exposed to allethrin-based mosquito coil smoke for 15-180 days, compared to the unexposed controls, lipid peroxidation was increased in the cauda and testes. The activity of antioxidant enzymes remained largely unchanged in the all the tissues analyzed. Histopathological analyses revealed loss of tubule architecture, epithelial cell disruption, increase in lumen size, interstitial edema, and presence of dead spermatozoa. p53 gene expression was differentially altered in the epididymis and testes. The expression of spermatogenic factors, namely, stem cell factor and its ligand c-Kit was unaltered though decreased levels of Tgf-ß1 were observed. CONCLUSION: Results of this study demonstrate that prolonged exposure to allethrin-based mosquito coil smoke could lead to oxidative stress and compromise germ cell production.

Effect of mosquito mats (pyrethroid-based) vapor inhalation on rat brain cytochrome P450s.

The effect of transfluthrin (TF) or D-allethrin (DA) pyrethroid (PYR) vapors, often contained as main ingredients in two commercially available mosquito repellent mats, on cytochrome P450 (CYP) enzymes of rat brain and liver was assessed. Immunodetection of CYP2E1 and CYP3A2 proteins revealed their induction in cerebrum and cerebellum, but not in liver microsomes of rats exposed by inhalation to TF or DA. This overexpression of proteins correlated with an increase of their catalytic activities. The specifically increased expression of CYP isoenzymes, due to PYR exposure in the rat brain, could perturb the normal metabolism of endogenous and xenobiotic compounds and leads to increased risks of neurotoxicity by bioactivation, lipid peroxidation and DNA damage.

Multimodal pyrethroid resistance in malaria vectors, Anopheles gambiae s.s., Anopheles arabiensis, and Anopheles funestus s.s. in western Kenya.

Anopheles gambiae s.s., Anopheles arabiensis, and Anopheles funestus s.s. are the most important species for malaria transmission. Pyrethroid resistance of these vector mosquitoes is one of the main obstacles against effective vector control. The objective of the present study was to monitor the pyrethroid susceptibility in the 3 major malaria vectors in a highly malaria endemic area in western Kenya and to elucidate the mechanisms of pyrethroid resistance in these species. Gembe East and West, Mbita Division, and 4 main western islands in the Suba district of the Nyanza province in western Kenya were used as the study area. Larval and adult collection and bioassay were conducted, as well as the detection of point mutation in the voltage-gated sodium channel (1014L) by using direct DNA sequencing. A high level of pyrethroid resistance caused by the high frequency of point mutations (L1014S) was detected in An. gambiae s.s. In contrast, P450-related pyrethroid resistance seemed to be widespread in both An. arabiensis and An. funestus s.s. Not a single L1014S mutation was detected in these 2 species. A lack of cross-resistance between DDT and permethrin was also found in An. arabiensis and An. funestus s.s., while An. gambiae s.s. was resistant to both insecticides. It is noteworthy that the above species in the same area are found to be resistant to pyrethroids by their unique resistance mechanisms. Furthermore, it is interesting that 2 different resistance mechanisms have developed in the 2 sibling species in the same area individually. The cross resistance between permethrin and DDT in An. gambiae s.s. may be attributed to the high frequency of kdr mutation, which might be selected by the frequent exposure to ITNs. Similarly, the metabolic pyrethroid resistance in An. arabiensis and An. funestus s.s. is thought to develop without strong selection by DDT.

Divergent actions of the pyrethroid insecticides S-bioallethrin, tefluthrin, and deltamethrin on rat Na(v)1.6 sodium channels.

We expressed rat Na(v)1.6 sodium channels in combination with the rat beta(1) and beta(2) auxiliary subunits in Xenopus laevis oocytes and evaluated the effects of the pyrethroid insecticides S-bioallethrin, deltamethrin, and tefluthrin on expressed sodium currents using the two-electrode voltage clamp technique. S-Bioallethrin, a type I structure, produced transient modification evident in the induction of rapidly decaying sodium tail currents, weak resting modification (5.7% modification at 100 microM), and no further enhancement of modification upon repetitive activation by high-frequency trains of depolarizing pulses. By contrast deltamethrin, a type II structure, produced sodium tail currents that were ~9-fold more persistent than those caused by S-bioallethrin, barely detectable resting modification (2.5% modification at 100 microM), and 3.7-fold enhancement of modification upon repetitive activation. Tefluthrin, a type I structure with high mammalian toxicity, exhibited properties intermediate between S-bioallethrin and deltamethrin: intermediate tail current decay kinetics, much greater resting modification (14.1% at 100 microM), and 2.8-fold enhancement of resting modification upon repetitive activation. Comparison of concentration-effect data showed that repetitive depolarization increased the potency of tefluthrin approximately 15-fold and that tefluthrin was approximately 10-fold more potent than deltamethrin as a use-dependent modifier of Na(v)1.6 sodium channels. Concentration-effect data from parallel experiments with the rat Na(v)1.2 sodium channel coexpressed with the rat beta(1) and beta(2) subunits in oocytes showed that the Na(v)1.6 isoform was at least 15-fold more sensitive to tefluthrin and deltamethrin than the Na(v)1.2 isoform. These results implicate sodium channels containing the Na(v)1.6 isoform as potential targets for the central neurotoxic effects of pyrethroids.