Toxicologic and carcinogenic evaluation of Fenvalerate in the B6C3F1 mouse

A Novel Strategy to Predict Carcinogenicity of Antiparasitics Based on a Combination of DNA Lesions and Bacterial Mutagenicity Tests

Genotoxicity and carcinogenicity testing of pharmaceuticals prior to commercialization is requested by regulatory agencies. The bacterial mutagenicity test was considered having the highest accuracy of carcinogenic prediction. However, some evidences suggest that it always results in false-positive responses when the bacterial mutagenicity test is used to predict carcinogenicity. Along with major changes made to the International Committee on Harmonization guidance on genotoxicity testing [S2 (R1)], the old data (especially the cytotgenetic data) may not meet current guidelines. This review provides a compendium of retrievable results of genotoxicity and animal carcinogenicity of 136 antiparasitics. Neither genotoxicity nor carcinogenicity data is available for 84 (61.8%), while 52 (38.2%) have been evaluated in at least one genotoxicity or carcinogenicity study, and only 20 (14.7%) in both genotoxicity and carcinogenicity studies. Among 33 antiparasitics with at least one old result in in vitro genotoxicity, 15 (45.5%) are in agreement with the current ICH S2 (R1) guidance for data acceptance. Compared with other genotoxicity assays, the DNA lesions can significantly increase the accuracy of prediction of carcinogenicity. Together, a combination of DNA lesion and bacterial tests is a more accurate way to predict carcinogenicity.

Toxicological characteristics of endocrine-disrupting chemicals: developmental toxicity, carcinogenicity, and mutagenicity

It is generally accepted that endocrine-disrupting chemicals (EDCs) play a role in a variety of adverse health effects in an intact organism or its progeny as a consequence of changes in the endocrine system. Primary toxic effects of EDCs were reported to be related to infertility, reduction in sperm count, and teratogenicity, but other important toxic effects of EDCs such as carcinogenicity and mutagenicity have also been demonstrated. The aim of the present study was to systematically analyze the toxicological characteristics of EDCs in pesticides, industrial chemicals, and metals. A comprehensive literature survey on the 48 EDCs classified by the Centers for Disease Control and Prevention (CDC) was conducted using a number of databases which included Medline, Toxline, and Toxnet. The survey results revealed that toxicological characteristics of EDCs were shown to produce developmental toxicity (81%), carcinogenicity (79%, when positive in at least one animal species; 48%, when classified based on IARC evaluation), mutagenicity (79%), immunotoxicity (52%), and neurotoxicity (50%). Regarding the hormone-modulating effects of the 48 EDCs, estrogenic effects were the most predominant in pesticides, while effects on thyroid hormone were found for heavy metals. EDCs showing estrogen-modulating effects were closely related to carcinogenicity or mutagenicity with a high degree of sensitivity. Systematic information on the toxicological characteristics of the EDCs will be useful for future research directions on EDCs, the development of new screening methods, legal regulation, and for investigations of their mechanism of action.

Chronic diazinon exposure: pathologies of spleen, thymus, blood cells, and lymph nodes are modulated by dietary protein or lipid in the mouse

Little is known about the immunotoxicity of the organophosphate pesticide, diazinon. This study aims at detailing the pathologies in the thymus, spleen, blood cells, and lymph nodes (brachial, mesenteric, and hind quarter gluteal nodes) during chronic oral exposure (300 mg diazinonkg-1 food for 45 days), and explore the combined toxicity with excess dietary protein (40%) or lipid (20% corn oil). Animals were allowed to recover on normal food for 2 weeks. All experimental treatments caused organ pathologies, including necrotic degeneration of the trabeculae (spleen and thymus), hyperplasia of the cortex and medulla (thymus and lymph nodes), hyperplasia of white and red pulp (spleen), and sometimes haemorrhage (all tissues). Blood smears often showed crenated/hypochromic red cells and vacuolated white cells with abnormal nuclei. The severity of lesions during exposure was generally in the following order: lipid<protein<diazinon alone<protein plus diazinon<lipid plus diazinon. Post-exposure recovery was limited, especially in the thymus and for lipid treatments. Quantitative image analysis revealed treatment and organ-specific changes in the proportions of fixed lymphocytes, PAS-positive carbohydrates, DNA, and protein staining. Histochemical changes were greatest after exposure. We conclude that the immunotoxicity of diazinon is exacerbated by excess dietary protein or lipid. The limited recovery and post-exposure histochemical changes imply deleterious effects on metabolism with oxidative stress after exposure.

The suitability of the micronucleus assay in human lymphocytes as a new biomarker of excision repair

The cytokinesis blocked micronucleus assay is relatively insensitive to detect agents that predominantly induce excision repairable DNA lesions. However, it has been recently proposed that excision-repairable DNA lesions induced in G0/G1 phase can be converted to micronuclei by using inhibitors of the gap filling step of excision repair so that unfilled gaps are converted to double stranded breaks after S phase and micronuclei (MN) at completion of mitosis. As it has been recently demonstrated this process could be improved by combining cytosine arabinoside (ARA-C) and hydroxyurea (HU). In the present work, we have investigated the suitability of this new approach by studying its ability to detect excision repairable DNA lesions induced by 10 pesticides (alachlor, atrazine, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, maleic hydrazide, paraquat, permethrin and trifluralin) and 3 well-known mutagenic agents (ethyl methane sulphonate, EMS; methylnitrosourea, MNU; and mytomicin C, MMC). Our results showed that the combination of ARA-C and HU substantially increased the level of MN in whole blood lymphocyte cultures, but it provided an excess of toxicity when further treatments, such as MNU, were performed. When ARA-C alone was used, the ARA/CBMN assay appeared to be highly sensitive and specific in detecting agents known to induce excision repairable DNA lesions. Thus, EMS and MNU but not MMC greatly induced DNA excision repair. On the other hand, alachlor, permethrin and, to a lesser extent, trifluralin and fenpropathrin also increased the ratio of excision repairable DNA lesions converted to MN. On the contrary, atrazine, cypermethrin, deltamethrin, fenvalerate, maleic hydrazide and paraquat did not induce excision repair.

Induction of micronuclei by five pyrethroid insecticides in whole-blood and isolated human lymphocyte cultures

Five pyrethroid insecticides: cypermethrin, deltamethrin, fenpropathrin, fenvalerate and permethrin, were tested for their ability to induce micronuclei in both whole-blood (WB; three donors) and isolated human lymphocyte (IL, 2 donors) cultures, by using the cytokinesis-block method with 6 micrograms/ml cytochalasin B (Cyt-B). Fenvalerate and permethrin were tested with two different concentrations of Cyt-B (3 and 6 micrograms/ml). At the concentration ranges tested, all the five pyrethroids induced clear dose dependent cytotoxic effects, fenpropathrin being the most toxic. Nuclear division index (NDI) and the newly introduced index of cytotoxicity, the cytokinesis block proliferation index (CBPI), reflected the dose dependency more accurately than the percentage of binucleated cells did. CBPI is similar to NDI except that it estimates the average number of cell divisions that the cell population has gone through, and, therefore, classifies both trinucleate and tetranucleate cells into the same category. Cypermethrin and fenpropathrin slightly increased the number of MN and micronucleated cells in WB lymphocyte cultures from two out of the three donors. Deltamethrin produced a positive response only in WB cultures of one donor and in IL cultures of another donor. Permethrin gave mostly negative results, although it increased the MN frequency in WB cultures of one donor when 6 micrograms/ml Cyt-B was used. Fenvalerate did not significantly induce MN. With certain reservations to the purity and isomer composition of each pesticide, the existing information appears to support the idea that pyrethroid insecticides have a weak (cypermethrin, deltamethrin and fenpropathrin) or nule (fenvalerate and permethrin) genotoxic activity in vitro.

Effects of pyrethroid insecticides on gap junctional intercellular communications in Balb/c3T3 cells by dye-transfer assay

The effects of fenvalerate, esfenvalerate, permethrin, cypermethrin, deltamethrin, p-chlorophenylisovaleric acid (CPIA, major metabolite of fenvalerate) and DDT, a liver tumor promoter, on gap junctional intercellular communication (GJIC) were examined in Balb/c3T3 cells by dye-transfer assay. Separate groups of Balb/c3T3 cells were exposed to the chemicals for 1 day. On the following day, GJIC was measured by counting the number of dye-transferring cells per injection of Lucifer Yellow under a fluorescent microscope. Fenvalerate, esfenvalerate, permethrin, cypermethrin, deltamethrin and DDT inhibited GJIC at noncytotoxic concentrations, while CPIA did not inhibit GJIC even at a cytotoxic concentration. It is concluded that the examined pyrethyroid insecticides, but not a metabolite, have inhibitory effects on GJIC in Balb/c3T3 cells.

Effects of fenvalerate and esfenvalerate on hepatic gap junctional intercellular communication in rats

Effects of in vivo exposure with fenvalerate, esfenvalerate and DDT on hepatic gap junctional intercellular communication (GJIC) in Sprague-Dawley (SD) rats were examined by in vivo/in vitro dye-transfer assay and by immunohistochemical staining of connexin 32 (Cx32, major liver gap junction protein). Fenvalerate (75 mg/kg/day), esfenvalerate (25 mg/kg/day), DDT (50 mg/kg/day) and corn oil (vehicle control, 5 ml/kg/day) were administered orally once a day. Animals were killed at weeks 1, 2, 4 and 6 after starting the experiment. In the fenvalerate- and esfenvalerate-groups, no compound-related changes in GJIC and Cx32 expression were observed. On the contrary, in the DDT-group, average sizes of the dye spread after injection of Lucifer Yellow decreased at weeks 1, 2 and 4, and the area per GJ spot shown by Cx32-immunohistochemical staining decreased at weeks 4 and 6. It is concluded that neither fenvalerate nor esfenvalerate inhibits hepatic GJIC with in vivo exposure.

Lack of enhancing effects of fenvalerate and esfenvalerate on induction of preneoplastic glutathione S-transferase placental form positive liver cell foci in rats

The modifying effects of fenvalerate and esfenvalerate administration on liver carcinogenesis were investigated in male F344/DuCrj rats initially treated with N-nitrosodiethylamine (DEN). Two weeks after a single dose of DEN (200 mg/kg, intraperitoneally), rats were given fenvalerate at dietary levels of 1500, 500, 150, 50 and 15 parts per million (ppm), esfenvalerate at 500 ppm, or 2-acetylamino-fluorene (2-AAF) at 200 ppm and sodium phenobarbital (PB) at 500 ppm as positive controls for 6 weeks. At week 3 following DEN administration, all animals were subjected to partial hepatectomy. Prominent neurologic signs and moderate retardation of body weight were observed in the groups given 1500 ppm fenvalerate and 500 ppm esfenvalerate, although no adverse effects on survival were evident. While statistically significant increases in relative liver weights were noted in rats given fenvalerate at doses of 1500 or 500 ppm, no toxic hepatocyte lesions were found. Neither fenvalerate nor esfenvalerate significantly increased the numbers or areas of glutathione S-transferase placental form (GST-P) positive liver cell foci observed after DEN initiation, in clear contrast to the positive controls, 2-AAF and PB. The results thus demonstrated that fenvalerate and esfenvalerate are non-toxic for rat hepatocytes and lack modifying potential for liver carcinogenesis in our medium-term bioassay system.

Toxicity of sumicidin (fenvalerate) to Nubian goats

Deaths in Nubian goats poisoned with oral doses of sumicidin ranging from 112.5 to 1350 mg per kg were preceded by clinical illness in which a variety of signs suggesting central nervous system dysfunction consistently occurred. Hepato-renal changes were present at necropsy in all goats that showed clinical signs. Alterations in serum urea, calcium, inorganic phosphate and cholesterol concentrations and GOT activity were recorded in sumicidin-poisoned goats.

Carcinogenicity study of the pesticide fenvalerate in mice

Fenvalerate is a widely used pesticide, which has been shown recently to be nonmutagenic. We studied its carcinogenicity in a long-term experiment in inbred C57Bl/6 mice given 0, 40 and 80 mg/kg body weight fenvalerate (99% pure) by gavage on 5 days/week for 104 weeks. Survival was decreased especially among females receiving the high dose. Exposure to fenvalerate resulted in a slight increase in the incidence of liver-cell tumours over that in controls only in male mice receiving the high dose. No significant difference in the incidence of other types of tumours was observed in treated groups when compared with controls. Fenvalerate-induced microgranulomas occurred concomitantly in the liver, spleen and lymph nodes of male and female mice, but their overall incidence did not increase with dose. In a separate experiment, groups of SJL/ola female mice were administered two different samples of fenvalerate (92% and 99% pure) once per week for 12 weeks. In animals that received 92% pure compound, the latent period for induction of lymphomas was shortened and their incidence increased, when compared with the group receiving 99% pure fenvalerate and with controls.

Neurotoxicological effects and the mode of action of pyrethroid insecticides

Neuroexcitatory symptoms of acute poisoning of vertebrates by pyrethroids are related to the ability of these insecticides to modify electrical activity in various parts of the nervous system. Repetitive nerve activity, particularly in the sensory nervous system, membrane depolarization, and enhanced neurotransmitter release, eventually followed by block of excitation, result from a prolongation of the sodium current during membrane excitation. This effect is caused by a stereoselective and structure-related interaction with voltage-dependent sodium channels, the primary target site of the pyrethroids. Near-lethal doses of pyrethroids cause sparse axonal damage that is reversed in surviving animals. After prolonged exposure to lower doses of pyrethroids axonal damage is not observed. Occupational exposure to pyrethroids frequently leads to paresthesia and respiratory irritation, which are probably due to repetitive firing of sensory nerve endings. Massive exposure may lead to severe human poisoning symptoms, which are generally treated well by symptomatic and supportive measures.

Inhibition of metabolic cooperation in vitro and enhancement of enzyme altered foci incidence in rat liver by the pyrethroid insecticide fenvalerate

The synthetic pyrethroids cypermethrin, delta-methrin, fenvalerate, permethrin, and the fenvalerate metabolite p-chlorophenylisovaleric acid were investigated for inhibition of gap-junctional intercellular communication in vitro in the Chinese hamster lung fibroblast (V79) metabolic cooperation assay. Fenvalerate was furthermore studied for enhancement of gamma-glutamyl transpeptidase-positive enzyme altered foci incidence in partially hepatectomized, nitrosodiethylamine-initiated male Sprague Dawley rats. The in vitro studies showed that fenvalerate and p-chlorophenylisovaleric acid were inhibitors of intercellular communication at non-cytotoxic concentrations while cypermethrin, deltamethrin, and permethrin were inactive. In the in vivo study in rat liver, fenvalerate administered p.o. (75 mg/kg/day) 5 days a week for 10 weeks induced significantly more foci per cm3 and a larger percentage of liver tissue occupied by foci tissue compared to a vehicle control group. Analysis of size distributions of foci in fenvalerate- and vehicle-treated rats showed elevated foci incidences in fenvalerate-treated rats at all foci sizes. Fenvalerate induced no hepatotoxic effects as judged by plasma transaminase activities and histopathology. The results of this study suggest fenvalerate to be a potential tumour promoter.

Differential metabolism of fenvalerate and granuloma formation. II. Toxicological significance of a lipophilic conjugate from fenvalerate

Male mice of the ddY strain were fed a diet containing the [2S, alpha S]-, [2S, alpha RS]-, [2R, alpha S]-, and [2R, alpha R]-isomers of fenvalerate. Microgranulomatous changes were observed only in mice treated with the [2R, alpha S]-isomer at 125 and 1000 ppm for 1, 2, or 3 months. In contrast, the changes did not occur in mice treated with the [2R, alpha R]-isomer under the same conditions. Feeding of the [2S, alpha S]- and [2S, alpha RS]-isomers for 1 year did not cause the microgranulomatous changes at 500 or 1000 ppm. To clarify the causative agent of granuloma formation, cholesterol ester of 2-(4-chlorophenyl)isovaleric acid (CPIA), a lipophilic conjugate from the [2R, alpha S]-isomer of fenvalerate, was injected iv into ddY mice. Microgranulomatous changes were observed in the liver of mice treated with the [2R]-, [2S]-, or [2RS]-CPIA-cholesterol ester 1 week after a single treatment of 1, 10, or 100 mg/kg, as well as in liver of mice treated with a single dose of 10 or 30 mg/kg of the [2R]-CPIA-cholesterol ester and kept up to 26 weeks afterward. Histochemistry and microscopic autoradiography of the liver of mice demonstrated the presence of tritium derived from 3H-labeled[2R]-2-(4-chlorophenyl)isovalerate and cholesterol. Histochemistry also was positive for cholesterol ester in livers of mice treated with the [2R, alpha S]-isomer of fenvalerate. These results lend support for the hypothesis that CPIA-cholesterol ester is the causative agent of microgranulomatous changes induced by fenvalerate.

Lack of mutagenicity of synthetic pyrethroids in Salmonella typhimurium strains and in V79 Chinese hamster cells

Seven pyrethroids, i.e., cypermethrin, permethrin, deltamethrin, bioresmethrin, resmethrin, cismethrin and fenvalerate, were not found to be mutagenic in (a) Salmonella typhimurium strains TA100 or TA98 in the presence or absence of a rat liver activation system using the plate incorporation assay and fluctuation tests, or (b) V79 Chinese hamster cells in the presence or absence of hepatocytes.

Chronic toxicity and carcinogenicity evaluation of fenvalerate in rats

Groups of 93 male and 93 female Sprague-Dawley rats were fed diets containing 1, 5, 25, and 250 ppm fenvalerate for up to 2 yr. The control group consisted of 183 males and 183 females. Approximately 10 treatment and 20 control rats/sex . group were killed at intervals of 3, 6, 12, and 18 mo. When body weights, food consumption, hematology, clinical chemistry and organ weights did not reveal a treatment effect, two additional groups of 50 males and 50 female rats were placed on 0 or 1000 ppm fenvalerate diets and maintained for 2 yr. Body weight was decreased and organ/body weight ratios were increased in brain, liver, spleen, kidneys (females), heart (females), and testes (males) in the 1000 ppm group. Mammary and pituitary tumors were commonly observed, along with a variety of other tumors occurring randomly among all control and treatment groups. No statistically significant differences in the number and type of neoplasms were observed except for mammary tumors in females in the main study. These effects were judged not to be toxicologically significant, since mammary tumor incidences did not exceed expected incidences in aged female Sprague-Dawley rats, time to tumor appearance was unchanged, and no shift in percent benign versus malignant tumors occurred. Sarcomas identified in the subcutis and dermis in 5/51 1000-ppm-treated males were also identified in 2% (1/50), 2% (2/102), and 0-6% of concurrent, original, and historical controls, respectively. Microscopic examination did not reveal any treatment-related lesions. The no-observable-effect level was determined to be 250 ppm.