Pyrethroids and piperonyl-butoxide affect human T-lymphocytes in vitro

Pyrethroid pesticide exposure and hematological cancer: epidemiological, biological and molecular evidence

Pyrethroid insecticides are commonly used worldwide. The chronic effects of these compounds are of concern given that epidemiological studies have suggested an association with hematological cancer, particularly in children. However, the biological evidence at molecular and cellular levels is limited. A review on the molecular and cellular effects of pyrethroids is helpful to guide the study of the biological plausibility of the association of pyrethroids with hematological cancer. We reviewed studies suggesting that pyrethroids are genotoxic, induce genetic rearrangements, alter gene expression and modify DNA. All of these biological modifications could potentially contribute to the carcinogenic process in hematopoietic cells.

An examination of the effect of aerosolized Permanone insecticide on zebra finch susceptibility to West Nile virus

West Nile virus (WNV) is maintained cryptically primarily in avian (passerine) populations, where it is transmitted by Culex spp. mosquitoes. Mosquito-control measures currently include physical activities to reduce mosquito-breeding sites and the application of mosquito larvicides or aerosolized insecticides to kill adults (adulticides) when arboviral diseases such as WNV or Zika virus are detected in mosquito populations. Organochlorine, organophosphorus, carbamate, and pyrethroid insecticides are often used. Previous work suggests an effect of pyrethroids on the immune system in a variety of vertebrates. We examined the effects of exposure to aerosolized Permanone® 30:30 insecticide (permethrin and piperonyl butoxide in soy oil vehicle) at approximately 10³ to 10⁶ times potential environmental concentrations on the response of captive zebra finches (Taeniopygia guttata) to experimental challenge with WNV. Compared to vehicle control birds, WNV outcome was unchanged (65% of birds produced a viremia) in the "low" exposure (9.52 ± 3.13 mg/m³ standard deviation [SD] permethrin) group but reduced in the "high" exposure (mean 376.5 ± 27.9 mg/m³ SD permethrin) group (30% were viremic; p < 0.05). After clearing WNV infection, birds treated with Permanone regained less body mass than vehicle-treated birds (p < 0.001). The present study suggests that exposure to aerosolized Permanone insecticide at levels exceeding typical application rates has the potential to not change or to mildly enhance a bird's resistance to WNV. Environ Toxicol Chem 2017;36:3376-3386. Published 2017 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Urinary concentrations of pyrethroid metabolites and its association with lung function in a Canadian general population

OBJECTIVES

While there is increasing concern about the health impact of pyrethroid insecticides, little is known about their effect on lung function. In this cross-sectional study, urinary concentrations of pyrethroid (PYR) metabolites and their associations with lung function were examined among a Canadian general population using data from the Canadian Health Measures Survey (CHMS).

METHODS

Urinary concentrations of 5 pyrethroid metabolites (3-PBA, 4-F-3-PBA, cis-DCCA, trans-DCCA and cis-DBCA) were available for 5436 CHMS participants aged 6-79 years. Lung function parameters considered were forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), FEV1/FVC ratio and forced expiratory flow between 25% and 75% of FVC. Multiple linear regression analyses were used to examine associations between PYR concentrations and lung function in children (6-11 years), adolescents (12-19 years) and adults (20-79 years), respectively.

RESULTS

Almost all CHMS participants (99.8%) had PYR metabolites detectable in urine. In multiple linear regression analyses, 1 unit increase in log transformed urinary concentration (nmol/g creatinine) of total pyrethorid metabolites (ΣPYR) was associated with a 17.4 mL reduction in FEV1 (p=0.045) in children, a 37.1 mL reduction in FVC (p=0.05) in adolescents and a 0.3% (p=0.01) increase in FEV1/FVC ratio in adults.

CONCLUSIONS

These results show evidence of widespread exposures to pyrethroid insecticides among the Canadian general population. Pyrethroid exposures were associated with lower FEV1 in children, lower FVC in adolescents and relatively higher FEV1/FVC ratio in adults. Further research is necessary to confirm the potential effect of pyrethroid insecticides on lung function reported in this study.

The in vitro exposure to cypermethrin does not inhibit the proliferative response of peripheral blood mononuclear cells

This study evaluated the effect of in vitro exposure to cypermethrin on peripheral blood mononuclear cells proliferative response, considering reduced peripheral blood mononuclear cells proliferative response observed in individuals occupationally exposed to pyrethroids. Peripheral blood mononuclear cells were obtained from 21 healthy subjects (28.0 ± 9.0 years old). The effect of cypermethrin (at 0.5, 1.0 and 5.0 mg/ml) on cell viability was evaluated by flow cytometry using an apoptosis detection kit. Cell proliferation (PI) was evaluated by 5-(and 6)-carboxyfluorescein diacetate succinimidyl ester (CFSE) fluorescence decay using flow cytometry. Cells labeled with CFSE were exposed, in vitro, to cypermethrin (0.5, 1.0, 2.0, 2.5 and 4 μg/ml) and stimulated with phytohemagglutinin (PHA 1.0 or 5.0 μg/ml) for 5 d (37 °C, 5% CO2). The in vitro treatment of peripheral blood mononuclear cells with cypermethrin did not induce apoptosis or necrosis after 5 d in culture. Stimulation by PHA induced cell proliferation (PI = 1.29 ± 1.09 and 2.01 ± 0.62, PHA at 1.0 and 5.0 μg/ml, respectively, mean ± SD) and in vitro exposure to cypermethrin did not alter cellular proliferative response to PHA (PI = 1.80 ± 0.50, 2.60 ± 0.05 and 2.10 ± 1.20 for cypermethrin at 1.0, 2.0 and 4.0 μg/ml, respectively, and PHA at 5.0 μg/ml). In vitro treatment of peripheral blood mononuclear cells with cypermethrin, at the doses tested, does not affect cell viability or proliferation. These findings suggest that the reduction of proliferation observed on lymphocytes derived from individuals occupationally exposed to pesticides may be related to other mechanisms than direct action of cypermethrin on lymphocytes.

Effects of prior oral exposure to combinations of environmental immunosuppressive agents on ovalbumin allergen-induced allergic airway inflammation in Balb/c mice

Abstract Humans are exposed daily to multiple environmental chemicals in the atmosphere, in food, and in commercial products. Therefore, hazard identification and risk management must account for exposure to chemical mixtures. The objective of the study reported here was to investigate the effects of combinations of three well-known environmental immunotoxic chemicals - methoxychlor (MXC), an organochlorine compound; parathion (PARA), an organophosphate compound; and piperonyl butoxide (PBO), an agricultural insecticide synergist - by using a mouse model of ovalbumin (OVA)-induced allergic airway inflammation. Four-week-old Balb/c mice were exposed orally to either one or two of the environmental immunotoxic chemicals for five consecutive days, prior to intraperitoneal sensitization with OVA and an inhalation challenge. We assessed IgE levels in serum, B-cell counts, and cytokine production in hilar lymph nodes, and differential cell counts and levels of related chemokines in bronchoalveolar lavage fluid (BALF). Mice treated with MXC + PARA or PBO + MXC showed marked increases in serum IgE, IgE-positive B-cells and cytokines in lymph nodes, and differential cell counts and related chemokines in BALF compared with mice that received the vehicle control or the corresponding individual test substances. These results suggest that simultaneous exposure to multiple environmental chemicals aggravates allergic airway inflammation more than exposure to individual chemicals. It is expected that the results of this study will help others in their evaluation of immunotoxic combinational effects when conducting assessments of the safety of environmental/occupational chemicals.

Effects of short-term oral combined exposure to environmental immunotoxic chemicals in mice

People are constantly exposed to environmental chemicals through contact with the atmosphere or by ingestion of food. Therefore, when conducting safety assessments, the immunotoxic effects of combinations of chemicals in addition to toxicities produced by each chemical alone should be considered. The objective of the studies reported here were to demonstrate the combined effects of three well-known environmental immunotoxic chemicals -- methoxychlor (MXC), an organochlorine compound; parathion (PARA), an organophosphate compound; and piperonyl butoxide (PBO), an agricultural insecticide synergist -- by using a short-term oral exposure method. Seven-week-old Balb/cAnN mice received daily oral exposure to either one or two of the environmental immunotoxic chemicals for 5 consecutive days. On Day 2, all mice in each group were immunized with sheep red blood cells (SRBC), and their SRBC-specific IgM responses were analyzed by using an enzyme-linked immunosorbent assay and plaque-forming cell assay. T- and B-cell counts in the mouse spleens were also assessed via surface antigen expression. Mice that received MXC + PARA and PBO + MXC treatment showed marked decreases in SRBC-specific IgM production and T- and B-cell counts compared with those in mice that received vehicle control or the corresponding individual test substance. This suggests that simultaneous exposure to multiple environmental chemicals increases the immunotoxic effects of the chemicals compared to individual exposure.

Prior oral exposure to environmental immunosuppressive chemicals methoxychlor, parathion, or piperonyl butoxide aggravates allergic airway inflammation in NC/Nga mice

BACKGROUND

Immunosuppressive environmental chemicals may increase the potency of allergens and thereby play a role in the development of respiratory tract allergies, such as allergic rhinitis and asthma.

OBJECTIVES

We investigated the association between environmental immunosuppressive chemicals and the allergic airway inflammation development.

METHODS

We used a mouse model of ovalbumin (OVA)-induced allergic airway inflammation. NC/Nga mice were exposed orally to pesticides parathion (an organophosphate compound) or methoxychlor (an organochlorine compound), or to an insecticide synergist piperonyl butoxide, prior to OVA intraperitoneal sensitization and inhalation challenge. We assessed serum IgE levels, B-cell counts, cytokine production, IgE production in hilar lymph nodes, eosinophil counts, chemokine levels in bronchoalveolar lavage fluid, and cytokine gene expression in the lung.

RESULTS

Exposure to environmental immunosuppressive chemicals markedly increased serum IgE - IgE-positive B-cells, IgE and cytokines in lymph nodes - eosinophils and chemokines in BALF - IL-10a and IL-17 in the lung.

CONCLUSIONS

Allergic airway inflammation can be aggravated by prior exposure to immunosuppressive environmental chemicals.

Subacute oral toxicity of combinations of selected synthetic pyrethroids, piperonyl butoxide, and tetramethrin in rats

In this study, 70 Wistar rats were randomly divided into seven equal groups (six experimental and one control), which consisted of animals belonging to both sexes. Different combinations of insecticides were administered daily to the experimental groups (group 1: cypermethrin + piperonyl butoxide (PBO); group 2: alphacypermethrin + PBO; group 3: deltamethrin + PBO; group 4: cypermethrin + PBO + tetramethrin; group 5: alphacypermethrin + PBO + tetramethrin; and group 6: deltamethrin + PBO + tetramethrin) for 28 days. During the study period, mortality and serious clinical findings were not observed in any animal. However, feed consumptions decreased in groups 1 and 3 ( p < 0.05). Red blood cells, white blood cells, and hemoglobin levels, especially in cypermethrin and alphacypermethrin groups (groups 1, 2, and 4), were found to be higher than the control group ( p < 0.05). Furthermore, biochemical changes related to liver, kidney functions, and protein metabolism occurred in males of almost all the groups. Relative liver and kidney weights of the male animals increased in the cypermethrin and alphacypermethrin groups ( p < 0.05). The most common finding observed during the histopathological examination of all the experimental groups was centrilobular degeneration in the liver. It was concluded that although clinical symptoms were not observed, synthetic pyrethroid, synergist, and knockdown agent combinations might cause serious abnormalities when administered in certain doses in mammalians.

The relation between dietary habits and urinary levels of 3-phenoxybenzoic acid, a pyrethroid metabolite

Concerns about pesticide exposure through food consumption have increased during the past several years. Pyrethroids are applied as insecticides throughout the world. Human metabolism of pyrethroids results in urinary metabolites that are suitable for biological monitoring. The objective of our study was to investigate the relation between food consumption and urinary levels of 3-phenoxybenzoic acid (3-PBA), a general metabolite of pyrethroids, in a non-occupational exposed adult population from the IDI-IRCCS, Rome, Italy. Information on socio-demographic characteristics, smoking, diet and self-reported household pesticide exposure was collected. Urinary 3-PBA level of each subject was measured and adjusted by urinary creatinine. We found that people consuming both raw and cooked vegetables five times weekly or more had higher mean levels of 3-PBA in urine (1.03 μg/g creatinine versus 0.52 μg/g creatinine; p=0.009 and 0.99 μg/g creatinine versus 0.58 μg/g creatinine; p=0.01, respectively) than subjects consuming less than five times weekly. In a multivariate model, after adjusting for age, sex, BMI, smoking and household insecticide exposure, high intake of raw vegetables (OR: 5.31; 95%CI: 1.32-21.3) and high intake of cooked vegetables, in particular cruciferous (OR: 4.67; 95%CI: 1.07-20.5) and leafy vegetables (OR: 6.88; 95%CI: 1.50-31.7), were associated with high urine 3-PBA levels (≥0.70 μg/g creatinine). The results of this study suggest that part of the variation in pyrethrois intake is explained by vegetable intake.

Prenatal exposure to pesticide ingredient piperonyl butoxide and childhood cough in an urban cohort

RATIONALE

Previously we reported that airborne concentrations of cis-permethrin, but not trans-permethrin, measured during pregnancy in an inner city pediatric cohort was associated with cough by age 5. However, the effect of subsequent exposures to both permethrins during early childhood, and to piperonyl butoxide (PBO, a synergist for residential pyrethroid insecticides) remains to be elucidated. We hypothesized that prenatal and age 5-6 year measures of PBO and permethrins would be associated with cough at age 5-6 years in this cohort. Further, we explored the associations between these pesticide measures and wheeze, asthma, seroatopy, and fractional exhaled nitric oxide (FeNO).

METHODS

PBO and permethrins were measured in personal air during the third trimester of pregnancy and indoor residential air at age 5-6 years (n=224). Health outcome questionnaires were administered to the mothers of 5-6 year old children. Indoor allergen specific and total immunoglobulin (Ig) E production was measured from sera collected at age 5, and FeNO was measured at 5-6 years. The hypotheses were tested using regression models adjusting for common confounders.

RESULTS

Noninfectious cough was reported among 14% of children at age 5-6 years. Measures of prenatal PBO, but not age 5-6 year PBO or permethrins, increased the odds of cough [OR (95% CI): 1.27 (1.09-1.48), p<0.01; n=217]. No significant associations were found for other measured health outcomes.

CONCLUSIONS

Prenatal PBO exposure was associated with childhood cough. It is unclear whether the observed effect is due mainly to PBO itself or residential pyrethroids of which PBO is an indicator.

Lupus erythematosus. Are residential insecticides exposure the missing link?

Although the etiology of systemic lupus erythematosus (SLE) remains to be fully elucidated, it is now apparent that multiple genetic and environmental factors are at play. Because lupus has a strong female preponderance, several studies have examined the role of female hormones in disease etiology. Yet this knowledge has not helped to explain lupus etiology or to prevent it. Estrogens exist not only as natural or drug compounds, but also as environmental chemical contaminant and women are highly exposed to all of them. Estrogenic activity has been found in a number of pesticides including pyrethroids that are largely used in the household. Although there is only a small amount of published data examining a possible causal relationship between lupus and pesticides it can be hypothesized that pesticides, in particular insecticides, through their estrogenic activity and capacity to induce oxidative stress provoke autoimmune reaction influencing lupus development.

Testing independent and interactive effects of corticosterone and synergized resmethrin on the immune response to West Nile virus in chickens

Public health agencies utilize aerial insecticides to interrupt an active West Nile virus (WNV) transmission cycle, which may expose WNV-infected birds to these agents. Although resmethrin has been considered benign to birds, no studies have evaluated whether the environmentally employed form of resmethrin with PBO synergist (synergized resmethrin (SR)) can suppress avian immunity to WNV infection and enhance a bird's host competence. Recognizing that wild birds confront toxicological stressors in the context of various physiological states, we exposed four groups (n=9-11) of 9-week-old chickens (Gallus domesticus) to drinking water with either SR (three alternate days at 50 microg/l resmethrin+150 microg/l piperonyl butoxide), CORT (10 days at 20mg/l to induce subacute stress), the combination of SR and CORT, or 0.10% ethanol vehicle coincident with WNV infection. Compared to controls, SR treatment did not magnify but extended viremia by 1 day, and depressed IgG; CORT treatment elevated (mean, 4.26 log(10)PFU/ml) and extended viremia by 2 days, enhanced IgM and IgG, and increased oral virus. The combination of SR and CORT increased the number of chickens that shed oral virus compared to those treated with CORT alone. None of the chickens developed a readily infectious viremia to mosquitoes (none >or=5 log(10)PFU/ml), but viremia in a CORT-exposed chicken was up to 4.95 log(10)PFU/ml. Given that SR is utilized during WNV outbreaks, continued work toward a complete risk assessment of the potential immunotoxic effects of SR is warranted. This would include parameterization of SR exposures with immunological consequences in wild birds using both replicating (in the laboratory) and non-replicating (in the field) antigens. As a start, this study indicates that SR can alter some immunological parameters, but with limited consequences to primary WNV infection outcome, and that elevated CORT mildly enhances SRs immunotoxicity in chickens.

Malathion, Lindane, and Piperonyl Butoxide, Individually or in Combined Mixtures, Induce Immunotoxicity via Apoptosis in Murine Splenocytes In Vitro

Lindane, malathion, and piperonyl butoxide were cultured singly or as mixtures with murine splenocytes to evaluate changes in cell death and caused cytotoxicity in a concentration- and time-dependent manner. Pesticide mixture studies were then performed based on minimum cytotoxicity concentrations (<LC25). Cytologic analysis and the alamarBlue assay revealed that individual pesticides and mixtures of malathion/lindane and malathion/piperonyl butoxide prompted cytotoxicity, which was supported by DNA ladder analysis. Using 7-aminoactinomycin D, apoptosis was quantified at 6.5%, 12.0%, 13.2%, 19.3%, and 23.4% for malathion, lindane, piperonyl butoxide, malathion-lindane, and malathion-piperonyl butoxide, respectively. Staining with 7-aminoactinomycin D and B- or T-cell–specific fluorescent-labeled monoclonal antibodies showed B cells to be more susceptible to malathion and piperonyl butoxide treatments than T cells. Treatment of murine splenocytes in vitro with minimum cytotoxic concentrations of lindane, malathion, and piperonyl butoxide and their mixtures induced apoptosis, the effect elicited by the mixtures being additive compared with the individual pesticide effect.

The association between residential pesticide use and cutaneous melanoma

Occupational pesticide exposure has been linked to cutaneous melanoma in epidemiological studies. We studied the association between cutaneous melanoma and the residential use of pesticides. This is a case-control study of cutaneous melanoma (287 incident cases; 299 controls). Data on pesticide use was obtained with a standardised interview. An increased risk of melanoma was found for high use (4 times annually) of indoor pesticides (odds ratio (OR)=2.18; 95% confidence intervals (CI) 1.07-4.43) compared to low use (1 times annually), after adjustment for sex, age, education, sun exposure and pigmentary characteristics. Subjects exposed for 10 years or more had two and a half times the risk (OR=2.46; 95% CI 1.23-4.94) of those exposed for less than 10 years. A dose response was observed for the intensity of pesticides use (p(trend)=0.027). The results indicate that residential pesticide exposure may be an independent risk factor for cutaneous melanoma.

STAT1 phosphorylation and cleavage is regulated by the histamine (H4) receptor in human atopic and non-atopic lymphocytes

Histamine can modulate the balance between T helper lymphocytes 1 and 2 (Th1 and Th2), and there is evidence that allergic reactions can be associated with excessive histamine production causing shifts toward Th2 responses. As signal transduction in Th-cells is specifically correlated to signal transducer and activator of transcription (STAT) activation and expression, the question arises whether histamine acting through histamine receptors (HR) induces modulation of the Janus kinase (JAK)-STAT pathway. Peripheral blood mononuclear cells (PBMC) from atopic and non-atopic donors were stimulated with phytohemagglutinin (PHA). Initial interleukin-4 (IL-4) levels were higher in the atopic group compared to the non-atopics and interferon-gamma (IFN-gamma) levels were lower. This was correlated to lower levels of STAT1 expression and phosphorylation. Furthermore, Western blots showed a 118-kDa STAT1 band at the start of the PHA stimulation that was apparently cleaved to STAT1alpha (91 kDa) and a 28 kDa-fragment with further stimulation. Histamine or the H4R agonist, clobenpropit, led to a significant suppression of the formation and phosphorylation of STAT1alpha in the non-atopic group after 48 h of PHA stimulation, but had no effect in the atopic group where STAT1alpha levels were already reduced. The STAT1alpha levels in the non-atopic group were enhanced by the H4R antagonist JNJ7777120. The phosphorylation of STAT1 could also be potentiated by the H4R antagonist, mimicking the precursor responses of STAT1alpha. JNJ7777120 also increased the binding of STAT1 to DNA and this effect could be reversed by histamine. As for histamine, the effects of the H4R antagonist were only seen in the non-atopic group. These results suggest that, in non-atopic individuals, histamine acting via the H4R can influence STAT1 regulation, but that this pathway is not present in atopics perhaps due to constitutive suppression of STAT1 activity.

Use of point-of-sale data to track usage patterns of residential pesticides: methodology development

BACKGROUND

Residential-use pesticides have been shown to be a major source of pesticide exposure to people in the United States. However, little is understood about the exposures to household pesticides and the resultant health effects. One reason that little is known about home-use pesticide exposure is the lack of comprehensive data on exposures to pesticides in the home. One method to help ascertain the amount of pesticides present in the home is use of point-of-sale data collected from marketing companies that track product sales to obtain the volume of pesticides sold for home-use. This provides a measure of volume of home-use pesticide.

METHODS

We have constructed a searchable database containing sales data for home-use permethrin-containing pesticides sold by retail stores in the United States from January 1997 through December 2002 in an attempt to develop a tracking method for pesticide. This pilot project was conducted to determine if point-of-sale data would be effective in helping track the purchase of home-use permethrin containing pesticides and if it would stand as a good model for tracking sales of other home-use pesticides.

RESULTS

There are several limitations associated with this tracking method, including the availability of sales data, market coverage, and geographic resolution. As a result, a fraction of sales data potentially available for reporting is represented in this database. However, the database is sensitive to the number and type of merchants reporting permethrin sales. Further, analysis of the sale of individual products included in the database indicates that year to year variability has a greater impact on reported permethrin sales than the amount sold by each type of merchant.

CONCLUSION

We conclude that, while nothing could completely replace a detailed exposure assessment to estimate exposures to home-use pesticides, a point-of-sale database is a useful tool in tracking the purchase of these types of pesticides to 1) detect anomalous trends in regional and seasonal pesticide sales warranting further investigation into the potential causes of the trends; 2) determine the most commonly purchased application types; and 3) compare relative trends in sales between indoor and outdoor use products as well as compare trends in sales between different active ingredients.

The toxicity of pyrethroid compounds in neural cell cultures studied with total ATP, mitochondrial enzyme activity and microscopic photographing

Pyrethroids are important insecticides used largely because of their high activity as an insecticide and their low mammalian toxicity. Some studies have demonstrated that these products, especially compounds with an α-cyano group, show neurotoxic effects on the mammalian central nervous system (CNS). In this study, we investigate with different methods the cell toxic effects of commercial, chemically different pyrethroid compounds on neuronal cell line SH-SY5Y. Natural pyrethrin and permethrin (both with no α-cyano group) and cypermethrin (with an α-cyano group), were studied. For toxicity determinations, SH-SY5Y neuroblastoma cells were exposed to pyrethroids at 0.1-100μM concentrations for 1 day. The cell toxicity was evaluated by determining the total ATP with a luminescence method, the mitochondrial metabolic activity (WST-test) with a photometric method, and the morphological changes of the cell cultures with microscopic digital photographing at different dose levels of compounds. The results obtained with WST-1 method and with the measurement of total ATP were different. ATP measurement seemed to show cytotoxicity at lower concentrations than WST-1 method. There was induction of enzyme activities with WST-1 test with all pyrethroid compounds studied at low concentrations. With the ATP assay, exposure to 0.1-100μM of natural pyrethrin, as well as of permethrin and cypermethrin showed dose-dependent cytotoxicity. The most toxic pyrethroid was cypermethrin followed by permethrin and natural pyrethrin. Our study confirms that the cell toxicity was dependent on the chemical structure of pyrethroids and pyrethroids without an α-cyano group show the weakest physiological effect. Microscopic photographs of exposed cell cultures correlated to the toxic effects revealed by the metabolic tests.

The synaptosomal membrane bound ATPase as a target for the neurotoxic effects of pyrethroids, permethrin and cypermethrin

Pyrethroids are used widely as insecticides both in agriculture and in households. A cellular target of pyrethroids is the sodium channel in the membrane. In the present study, the activity of the membrane bound integral protein ATPase was studied as a biomarker for the membrane effect of the pyrethroids permethrin and cypermethrin. Male Sprague-Dawley rats were used for cerebral synaptosome preparation. The isolation of synaptosomes was performed with the Percoll gradient method. Both total ATPase and Mg(2+) activated ATPase were studied by determining inorganic phosphate liberated from the substrate ATP. One hour exposure to permethrin (Biokill) and cypermethrin (Ripcord) insecticide products affected ATPase activities. The activity of Na(+), K(+) ATPase decreased dose-dependently in 10-50 microM concentrations of permethrin, and Mg(2+) activated ATPase increased over twofold in the same concentrations of the active components. The effect of the cypermethrin compound Ripcord was not clearly dose-dependent. The activity of total ATPase was almost entirely lost in the concentrations of 100 microM of permethrin and cypermethrin. The results support the idea that membrane ATPases are one target of the neurotoxic effect of pyrethroid compounds.

Pyrethroids used indoors--immune status of humans exposed to pyrethroids following a pest control operation--a one year follow-up study

A multiparametric analysis of immune components was performed in blood and serum of 61 voluntary persons before and after (1 day, 3 days, 4-6 months, 10-12 months) a professional pest control operation (PCO) using pyrethroids. Following parameters were included in the study (1) immunological parameters of the humoral defence, i.e. immunoglobulins of the classes A, G, M and E, complement components C3c and C4, acute phase proteins such as acid alpha 1-glycoprotein, haptoglobin, C-reactive protein; (2) mediators and receptors of immunity, i.e. neopterin, soluble interleukin-2 receptor (sIL-2R), soluble interleukin-6 receptor (sIL-6R), soluble tumor necrosis factor receptor (sTNF RII); (3) immunological markers of the cellular defence, i.e. white blood cell counts and lymphocyte (sub)populations such as total lymphocytes (CD2), mature lymphocytes (CD3), T-helper/inducer cells (CD4), T-suppressor/cytotoxic cells (CD8), B-cells (CD20), natural killer cells (CD56), as well as the ratio of CD4/CD8. The medians of all investigated immune components found before and for all time intervals after pyrethroid application were within the reference interval with respect to the total collective. Within this physiological range the investigated parameters showed a trend to lower values predominantly during the early phase (1 and 3 days) after PCO, partially being significant. Significant decreases were no more present in the late phase (6 to 12 month) after PCO indicating reversibility. Atopics did not differ in the immune response after PCO as compared to non-atopics. Obtained results suggest a modulation of immune components after a correct performed PCO within the physiological range towards lower values during the first days. However these immune changes are considered to be subtle and underlying compensatory mechanisms of immunoregulation.

Single-dose topical exposure to the pyrethroid insecticide, permethrin in C57BL/6N mice: effects on thymus and spleen

Immunomodulatory effects of single topical exposure to permethrin were evaluated in 5-week-old female C57BL/6N mice. Mice exposed to 5-25 microl permethrin (equivalent to 220-1100 mg/kg body weight) on shaved interscapular skin were evaluated for altered body weight; splenic and thymic organ weight and cellularity; thymocyte cell surface expression, cellular apoptosis; splenic macrophage phagocytosis and hydrogen peroxide production; splenic B cell antibody production and T cell cytolytic activity; and mitogen-induced proliferation of splenocytes and thymocytes after in vivo or in vitro permethrin exposure. Topical permethrin application (25 microl) caused 32% inhibition of splenic T cell proliferation; in vitro exposure to permethrin also diminished splenocyte proliferation by 72% at 25 microM and 86% at 100 microM. permethrin did not appear to affect other leukocyte functional assays. Dose-related decreases in thymic cellularity of 52 and 80% were seen in mice exposed to 15 and 25 microl permethrin, respectively. Apoptosis was significantly increased in CD4(-)8(-) and CD4(-)8(+) thymocytes, and the CD4(+)CD8(+) thymocyte subpopulation was most severely diminished, suggesting possible chemical-induced apoptotic mechanism of thymic atrophy. Permethrin also caused splenic hypocellularity by 31% at 15 microl, and by 50% at 25 microl, an effect that may relate to inhibited proliferation or reduced seeding from the hypocellular thymus.

Cuprizone and piperonyl butoxide, proposed inhibitors of T-cell function, attenuate experimental allergic encephalomyelitis in SJL mice

Multiple sclerosis (MS) and its animal model, experimental allergic encephalomyelitis (EAE), are autoimmune demyelinating diseases with autoreactive T-cells acting as important mediators of pathogenesis. Cuprizone, a copper chelator, and piperonyl butoxide (PBO), a pesticide synergist, are implicated to inhibit T-cell activation and function. The purpose of this study was to assess whether either of these agents would suppress PLP-peptide-induced EAE in the SJL mouse. Indeed, treatment with cuprizone beginning 1 week prior to disease induction, and PBO administration from days 1 to 9 of EAE, significantly attenuated EAE clinical severity. Furthermore, both agents decreased blood CD4+/CD8+ ratios, and reduced signs of chronic graft vs. host disease (GVHD) indicating attenuation of an immune T-cell response. These results suggest that cuprizone and PBO suppress EAE and use of these agents will provide insights into the mechanisms of T-cell mediated diseases.

Balancing the risks: vector control and pesticide use in response to emerging illness

The competing public health concerns of vector-borne disease and vector control strategies, particularly pesticide use, are inherently subjective and difficult to balance. Disease response decisions must frequently be made in the absence of data or clear criteria. The factors to be weighed include the vector control measures versus those posed by the disease itself; short-term versus long-term disease management goals, specifically with regard to the issue of pesticide resistance; the need to distinguish among diseases of differing severity in making response choices; and the issue of pesticide efficacy. New York City's experience with West Nile virus has illustrated each of these issues. A framework for assessing the appropriate response to West Nile virus can serve to guide our response to likely new pathogens.