Increased T-lymphocyte dependent antibody production in female SJL/J mice following exposure to commercial grade malathion

Organophosphate toxicity: updates of malathion potential toxic effects in mammals and potential treatments

Organophosphorus insecticides toxicity is still considered a major global health problem. Malathion is one of the most commonly used organophosphates nowadays, as being considered to possess relatively low toxicity compared with other organophosphates. However, widespread use may lead to excessive exposure from multiple sources. Mechanisms of MAL toxicity include inhibition of acetylcholinesterase enzyme, change of oxidants/antioxidants balance, DNA damage, and facilitation of apoptotic cell damage. Exposure to malathion has been associated with different toxicities that nearly affect every single organ in our bodies, with CNS toxicity being the most well documented. Malathion toxic effects on liver, kidney, testis, ovaries, lung, pancreas, and blood were also reported. Moreover, malathion was considered as a genotoxic and carcinogenic chemical compound. Evidence exists for adverse effects associated with prenatal and postnatal exposure in both animals and humans. This review summarizes the toxic data available about malathion in mammals and discusses new potential therapeutic modalities, with the aim to highlight the importance of increasing awareness about its potential risk and reevaluation of the allowed daily exposure level.

Lifetime Pesticide Use and Antinuclear Antibodies in Male Farmers From the Agricultural Health Study

Farming and pesticide use have been associated with systemic autoimmune diseases, and while certain organochlorine insecticides and other pesticides are suspected to influence risk, the role of specific pesticides in the development of systemic autoimmunity is not known. We measured serum antinuclear autoantibodies (ANA) by immunofluorescence on Hep-2 cells in 668 male farmers in the study of Biomarkers of Exposure and Effect in Agriculture (BEEA; 2010-2013), an Agricultural Health Study (AHS) subcohort. We examined ANA in relation to lifetime use of 46 pesticides first reported at AHS enrollment (1993-1997) and updated at intervals through BEEA enrollment. Odds ratios (OR) and 95% confidence intervals (CI) were estimated after adjusting for age, state, education, season of blood draw, current pesticide use, and correlated pesticides. Having ANA antibodies (3 or 4+ intensity at a 1:80 dilution, 21% of study participants) was associated with a reported history of seeking medical care due to exposure to pesticides (OR 2.15; 95%CI 1.17, 3.95), use of the fumigant methyl bromide (OR 3.16; 95%CI 1.05, 9.5), and use of petroleum oil/distillates (OR 1.50; 95%CI 1.00, 2.25). Using a higher threshold (3 or 4+ at a 1:160 dilution, 9%) ANA positivity was associated with the carbamate insecticide aldicarb (OR 4.82; 95%CI 1.33, 17.5) and greater combined use of four cyclodiene organochlorine insecticides (top tertile of intensity-weighted lifetime days vs. no use; OR T3 3.20; 95%CI 1.10, 9.27). By contrast, greater use of non-cyclodiene organochlorine insecticides was inversely associated with ANA (1:80 dilution 3 or 4+, OR T3 0.24; 95%CI 0.08, 0.72). Specific autoantibodies (to extractable nuclear antigens and anti-dsDNA), measured on those with ANA detected at the 1:80 dilution 3 or 4+, were seen in 15 individuals (2%), and were associated with use of two or more cyclodiene organochlorine insecticides and several other pesticides (e.g., carbofuran, ethylene dibromide). These findings suggest that specific pesticide exposures may have long-term effects on ANA prevalence and support the hypothesis that certain organochlorine insecticides may increase the risk of developing systemic autoimmunity.

Differential proteome analysis of rat plasma after diisopropyl fluorophosphate (DFP) intoxication, a surrogate of nerve agent sarin

Diisopropyl fluorophosphate (DFP), a surrogate of nerve agent sarin, is an organophosphorus (OP) compound which inhibits neuronal enzyme acetylcholinesterase (AChE). Exposure of this compound leads to a wide range of toxic symptoms and survivors may exhibit long term neurotoxicity related to cognitive and memory defects. Due to ease of availability and similar mechanism of action to other highly toxic nerve agent, DFP is widely used as model compound to trace changes associated with nerve agent exposures. Proximal fluids are widely used for the elucidation of biomarkers for exposure to toxic substances and to study the mechanism of toxicity. Using a rat model of OP intoxication, the present study was carried out to elucidate proteomic changes in plasma associated with DFP intoxication. Rats were exposed to a single dose (0.5 LD₅₀) of DFP and their plasma proteome was studied, one day post exposure by two dimensional gel electrophoresis - mass spectrometry (2DE-MS). Some of the milestone changes were validated by Western blot analysis. A total 15 proteins showed significant fold changes in expression with respect to control after 1 day of DFP intoxication. Most of the proteins showing changes in expression at initial stages were related to immunogenic function, acute phase response, blood coagulation, and stress response. Experiments reported here demonstrate that 0.5 LD₅₀ DFP intoxication leads to AChE inhibition, modulation of immunogenic function, and generation of stress at an early stage. Although, some proteins and their putative functional ramifications indicated similarity with those observed in our previous plasma proteome study, neurodegenerative changes were not observed in plasma of 0.5 LD₅₀ DFP treated animals.

Gene Expression Analysis on the Early Development of Pig Embryos Exposed to Malathion

Malathion is a widely used pesticide and there is evidence that it could alter mammal’s germ and somatic cells, as well as cell lines. There are not enough studies showing how the nonacute malathion doses affect gene expression. This study analyzes gene expression alterations in pig morular embryos exposed in vitro , for 96 h, to several malathion concentrations after in vitro fertilization. cDNA libraries of isolated morular embryos were created and differential screenings performed to identify target genes. Seven clones were certainly identified. Genes related to mitochondrial metabolism as cytochrome c subunits I and III, nuclear genes such as major histocompatibility complex I (MHC I), and a hypothetical protein related with a splicing factor were the target of malathion’s deregulation effect. The widespread use of malathion as a pesticide should be regarded with reproductive implications and more detailed analysis would yield more about molecular mechanisms of malathion injury on embryo cells.

Evaluating the protective effects of vitamin C on serum and erythrocyte cholinesterase activity of male rats exposed to malathion

Introduction

Malathion is one of organophosphate poisons (OPPs) that inhibit cholinesterase activity and induce oxidative stress in target organs, such as the reproductive system. The aim of this study was to assess the effects of Malathion on serum and erythrocyte cholinesterase activity in male rats and also to assess the protective effects of vitamin C in this regard.

Methods

This experimental study was performed in the Pharmacology Laboratory of the Pharmacy Faculty and in the Advanced Histology Techniques Laboratory of the Medical Faculty of Mashhad University of Medical Sciences (MUMS) in January 2014. Thirty male wistar rats, weighting 200–250 g, were divided into five groups of six. The different groups were exposed as follows: group 1: Malathion 50 mg/kg; group 2: Vitamin C; group 3: Malathion plus Vitamin C with the specified doses; sham group: normal saline; and control group: no exposure. After six weeks, 3 ml blood samples were taken from the rats, and titrimetric and Ellman methods were used to assess serum and erythrocyte cholinesterase activity, respectively. The data was analyzed by SPSS 16, and p < 0.05 was considered significant.

Results

The activities of serum and erythrocyte cholinesterase were inhibited significantly in the Malathion exposed group compared to the control group (p < 0.001). The administration of Vitamin C alone significantly increased the activities of serum and erythrocyte cholinesterase. The serum and erythrocyte cholinesterase inhibition showed improvement in the group that received both Malathion and Vitamin C.

Conclusion

Malathion reduced the activities of serum and erythrocyte cholinesterase in exposed animals. It probably has the same intoxication effects on people who are exposed. Improvement of cholinesterase activity by antioxidant effects of Vitamin C suggests that Vitamin C supplementation can be used to decrease side effects of OPP exposure.

Malathion-induced hepatotoxicity in male Wistar rats: biochemical and histopathological studies

The increasing use of organophosphorus pesticides in the environment constitutes an ecotoxicological hazard especially for humans and non-target animals. Hereby, we analyzed the toxic effects of malathion on the histological structure of liver and biochemical parameters in male rats. Three groups received daily different amounts of malathion: 1/1000, 1/100, and 1/10 LD50 for 30 days. The weights of treated rat's liver have increased. Analyzed tissues showed centrilobular and sinusoidal congestion, hepatocyte hypertrophy, cellular vacuolization, anucleated hepatocytes, depletion of organelles affecting the majority of cells, and presence of necrotic foci into the hepatic parenchyma. Histological sections of the liver showed important hepatocyte glycogen storage. We conclude that malathion stimulates the filing of glycogen in a dose-dependent manner. Biochemical parameters showed that alanine transaminase (ALT), aspartate transaminase (AST), gamma glutamyl transpeptidase (GGT), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) levels increased in the treated groups when the level of total protein decreased in intoxicated groups.

Investigations of immunotoxicity and allergic potential induced by topical application of triclosan in mice

Triclosan is an antimicrobial chemical commonly used occupationally and by the general public. Using select immune function assays, the purpose of these studies was to evaluate the immunotoxicity of triclosan following dermal exposure using a murine model. Triclosan was not identified to be a sensitizer in the murine local lymph node assay (LLNA) when tested at concentrations ranging from 0.75-3.0%. Following a 28-day exposure, triclosan produced a significant increase in liver weight at concentrations of ≥ 1.5%. Exposure to the high dose (3.0%) also produced a significant increase in spleen weights and number of platelets. The absolute number of B-cells, T-cells, dendritic cells and NK cells were significantly increased in the skin draining lymph node, but not the spleen. An increase in the frequency of dendritic cells was also observed in the lymph node following exposure to 3.0% triclosan. The IgM antibody response to sheep red blood cells (SRBC) was significantly increased at 0.75% - but not at the higher concentrations - in the spleen and serum. These results demonstrate that dermal exposure to triclosan induces stimulation of the immune system in a murine model and raise concerns about potential human exposure.

Macrophage TNF-α mediates parathion-induced airway hyperreactivity in guinea pigs

Organophosphorus pesticides (OPs) are implicated in human asthma. We previously demonstrated that, at concentrations that do not inhibit acetylcholinesterase activity, the OP parathion causes airway hyperreactivity in guinea pigs as a result of functional loss of inhibitory M2 muscarinic receptors on parasympathetic nerves. Because macrophages are associated with asthma, we investigated whether macrophages mediate parathion-induced M2 receptor dysfunction and airway hyperreactivity. Airway physiology was measured in guinea pigs 24 h after a subcutaneous injection of parathion. Pretreatment with liposome-encapsulated clodronate induced alveolar macrophage apoptosis and prevented parathion-induced airway hyperreactivity in response to electrical stimulation of the vagus nerves. As determined by qPCR, TNF-α and IL-1β mRNA levels were increased in alveolar macrophages isolated from parathion-treated guinea pigs. Parathion treatment of alveolar macrophages ex vivo did not significantly increase IL-1β and TNF-α mRNA but did significantly increase TNF-α protein release. Consistent with these data, pretreatment with the TNF-α inhibitor etanercept but not the IL-1β receptor inhibitor anakinra prevented parathion-induced airway hyperreactivity and protected M2 receptor function. These data suggest a novel mechanism of OP-induced airway hyperreactivity in which low-level parathion activates macrophages to release TNF-α-causing M2 receptor dysfunction and airway hyperreactivity. These observations have important implications regarding therapeutic approaches for treating respiratory disease associated with OP exposures.

Toxicopathological evaluation in Wistar rats (Rattus norvegicus) following repeated oral exposure to acephate

The present study was carried out to evaluate the effects of exposure at different doses of acephate on hematology, blood biochemistry, oxidative stress and immune system of Wistar rats. The experiment was carried out on 40 Wistar rats, which were divided in four groups. Animals of the three treatment groups were given with different sublethal doses (1/40th, 1/20th, 1/10th of lethal dose 50 value) of acephate by oral gavage. The hematology, blood biochemistry, oxidative stress marker, humoral immune response and cell-mediated immunity were evaluated following acephate exposure. Significant alteration in hematological parameters was not observed following different doses of acephate; however, significant alteration in alkaline phosphatase, gamma glutamyl transferase, acetyl cholinesterase, lipid peroxidase and superoxide dismutase was observed in medium- and high-dose group animals. Nonsignificant decrease in antibody titer in animals exposed to high dose has been observed compared with animals of control group. However, significant alteration in cell-mediated immunity was not observed in animals treated with acephate at different doses.

Protective effects of vitamins C and E against hepatotoxicity induced by methyl parathion in rats

Male rats were given vitamins C+E, methyl parathion, or both daily via gavage for seven weeks. Body weight was decreased while liver weight increased significantly at the end of fourth and seventh weeks in the methyl parathion- and methyl parathion plus vitamin-treated groups. Serum total protein, albumin, triglyceride, low density lipoprotein-cholesterol (VLDL-cholesterol) levels decreased, and serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl-transferase (GGT), lactate dehydrogenase (LDH), and total cholesterol levels increased significantly in the methyl parathion- and the methyl parathion plus vitamin-treated rats. There was a statistically significant difference for all biochemical parameters when the methyl parathion plus vitamin-treated group was compared with methyl parathion-treated group. In electron microscopic investigation, cytopathological alterations were observed in hepatocytes of the methyl parathion- and the methyl parathion plus vitamin-treated rats. As a result, methyl parathion-induced hepatotoxicity is reduced by vitamins C+E, but vitamins C+E did not provide complete protection.

Multi residue analysis of pesticides in wheat and khat collected from different regions of Ethiopia

The present study investigated the presence and level of pesticide residues in wheat and khat samples collected from various localities of Ethiopia. The khat samples from Galemso and Aseno had p,p'-DDT concentrations ranged from 141.2 to 973.0 μg/Kg and 194.3-999.0 μg/Kg, respectively. Diazinon was detected in all the khat samples from BadaBuna (173.9-686.9 μg/Kg) but not in any of the samples from Galemso and Aseno. Diazinon was detected in all the wheat samples obtained from both Arsi and Bale (125.8 and 125.6 μg/Kg, respectively) and aldrin levels in these samples were below the quantification limit. Khat may be a contributing factor in the pathological diseases found among khat users.

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.

Dichlorvos-induced hepatotoxicity in rats and the protective effects of vitamins C and E

Dichlorvos is an organophosphate insecticide that is widely used in pest control. Vitamin C (200mg/kg)+vitamin E (200mg/kg), dichlorvos (1.6mg/kg), or a combination of vitamin C (200mg/kg)+vitamin E (200mg/kg)+dichlorvos (1.6mg/kg) was given to rats via oral gavage for 7 weeks. When rats of the dichlorvos-treated group and the vitamins+dichlorvos-treated group were compared with the control group, body weights were decreased and liver weights were increased significantly at the end of the 4th and 7th week. Serum total protein, albumin, triglyceride, low density lipoprotein-cholesterol (VLDL-cholesterol) levels were decreased, and serum alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl-transferase (GGT), lactate dehydrogenase (LDH), and total cholesterol levels were increased significantly at the end of the 4th and 7th week in the dichlorvos- and vitamins+dichlorvos-treated rats. There was a statistically significant difference for all biochemical parameters when the vitamins+dichlorvos-treated group was compared with the dichlorvos-treated group at the end of the 4th and 7th week. In an electron microscopic investigation, swelling of mitochondria and dilatation of endoplasmic reticulum were observed in liver cells of the dichlorvos- and vitamins+dichlorvos-treated rats at the end of the 4th and 7th week. As a result, vitamins C and E reduced dichlorvos hepatotoxicity, but vitamins C and E did not confer complete protection.

The Alteration of Immune Reactions in Inbred BALB/cMice Following Low-Level Sarin Inhalation Exposure

To study the influence of low-level sarin inhalation exposure on immune functions, inbred BALB/c mice were exposed to low concentrations of sarin for 60 min in the inhalation chamber. The evaluation of immune functions was carried out using phenotyping of CD3 (T lymphocytes), CD4 (helper T lymphocytes), CD8 (cytotoxic T lymphocytes), and CD19 cells (B lymphocytes) in the lungs, blood, and spleen, lymphoproliferation of spleen cells stimulated in vitro by various mitogens (concanavalin A, lipopolysaccharides), phagocyte activity of peritoneal and alveolar macrophages, production of N-oxides by peritoneal macrophages, and the measurement of the natural killer cell activity at 1 wk following sarin exposure. The results were compared to the values obtained from control mice exposed to pure air instead of sarin. The results indicate that low doses of sarin are able to alter the reaction of immune system at one week following exposure to sarin. While the numbers of CD3 cells in the lungs, blood, and spleen were slightly decreased, an increase in CD19 cells was observed, especially in the lungs and blood. The reduced proportion of T lymphocytes is caused by decay of CD4-positive T cells. Lymphoproliferation was significantly decreased regardless of the mitogen and sarin concentration used. The production of N-oxides by peritoneal macrophages was stimulated after exposure to the highest dose of sarin, whereas their ability to phagocytize the microbes was increased after exposure to the lowest dose of sarin. The natural killer cell activity was significantly higher in the case of inhalation exposure of mice to the highest level of sarin. Thus, not only organophosphorus insecticides but also nerve agents such as sarin are able to alter immune functions even at a dose that does not cause clinically manifested disruption of cholinergic nervous system in the case of inhalation exposure. Nevertheless, the alteration of immune functions following the inhalation exposure to a symptomatic concentration of sarin seems to be more pronounced.

Effects of the insecticides malathion and diazinon on the early oogenesis in mice in vitro

Malathion and diazinon are two of the most commonly used organophosphorous (OP) agrochemicals. Several studies show that these pesticides exert several effects on mammalian spermatogenesis. Nevertheless, there are no studies concerning their effects on oogenesis. The objective of this study was to evaluate the effects of these insecticides on the viability of in vitro cultured mouse oocytes during the early oogenesis and to get a further understanding of the molecular mechanisms by which OP insecticides act and affect germinal cells. Oocytes were cultured from fetal ovaries for 10 days, when most oocytes had reached the diplotene stage (germinal vesicle stage). Cultures were exposed to different concentrations of malathion or diazinon for 24 h, and the effect on oocyte viability was assessed. Gene expression in oocytes exposed to the insecticides was analyzed by generating cDNA libraries and performing differential screenings. Results show a significant decrease in oocytes survival after 24-h exposure to 250 microM malathion or 900 nM diazinon, and the effect of these insecticides on the regulation of genes encoding proteins involved in transcription (BP75), translation (ribosomal protein S5), and mitochondrial function (cytochrome oxidase subunits I and III), providing evidence for OP insecticides as toxicants for mammals oocytes during the early oogenesis.

New mechanism of organophosphorus pesticide-induced immunotoxicity

Organophosphorus pesticides (OPs) are widely used throughout the world as insecticides in agriculture and as eradicating agents for termites around homes. The main toxicity of OPs is neurotoxicity, which is caused by the inhibition of acetylcholinesterase. OPs also affect the immune response, including effects on antibody production, interleukin-2 production, T cell proliferation, decrease of CD5 cells, and increases of CD26 cells and autoantibodies, Th1/Th2 cytokine profiles, and the inhibition of natural killer (NK) cell, lymphokine-activated killer (LAK) cell, and cytotoxic T lymphocyte (CTL) activities. However, there have been few studies of the mechanism of OP-induced immunotoxicity, especially the mechanism of OP-induced inhibition of cytolytic activity of killer cells. This study reviews new mechanisms of OP-induced inhibition of the activities of NK cells, LAK cells, and CTLs. It has been reported that NK cells, LAK cells, and CTLs induce cell death in tumors or virus-infected target cells by two main mechanisms. The first mechanism is direct release of cytolytic granules that contain the pore-forming protein perforin, several serine proteases termed granzymes, and granulysin by exocytosis to kill target cells, which is called the granule exocytosis pathway. The second mechanism is mediated by the Fas ligand (Fas-L)/Fas pathway, in which FasL (CD95 L), a surface membrane ligand of the killer cell cross links with the target cell's surface death receptor Fas (CD95) to induce apoptosis of the target cells. To date, it has been reported that OPs inhibit NK cell, LAK cell, and CTL activities by at least the following three mechanisms: 1) OPs impair the granule exocytosis pathway of NK cells, LAK cells, and CTLs by inhibiting the activity of granzymes, and by decreasing the intracellular levels of perforin, granzyme A, and granulysin, which were mediated by inducing degranulation of NK cells and by inhibiting the transcription of the mRNAs of perforin, granzyme A, and granulysin. 2) OPs impair the FasL/Fas pathway of NK cells, LAK cells, and CTLs, as investigated by using perforin-knockout mice, in which the granule exocytosis pathway of NK cells does not function and only the FasL/Fas pathway remains functional. 3) OPs induce apoptosis of immune cells.

Antinuclear antibodies and bromoxynil exposure in a rural sample

Previous research suggests that farmers may have an increased risk of developing autoimmunity and that exposure to certain pesticides may alter immune function. Little is known, however, about the immunologic effects of farming and pesticide exposures. As part of the Prairie Ecosystem Study, associations between detection of antinuclear antibodies (ANA), an autoimmunity indicator, and exposure to the herbicide bromoxynil (3,5-dibromo-4-hydroxybenzonitrile) were investigated in a cross-sectional study of 208 residents (94 women, 114 men) of a cereal-producing region in Saskatchewan, Canada, during spring herbicide application, 1996. The ANA were assayed in serum by indirect immunofluorescence on HEp-2 cells. Bromoxynil was measured in plasma by gas chromatography/mass spectrometry analysis. Associations were explored between ANA detection and detection of bromoxynil in plasma, self-reported use of bromoxynil and other pesticides, farming exposures, gender, age, body mass index (BMI), and residency. The mean age (SD) of the participants was 50.8 (13.6) yr [women: 49.7 (13.5) yr, men: 51.6 (13.6) yr]. ANA prevalence was 37.5% (women: 39.4%, men: 36%,) at 1:40 serum dilution, 17.3% (women: 20.2%, men: 14.9%) at 1:80, and 10.1% (women: 13.8%, men: 7%) at 1:160. In the multiple-variable Generalized Estimating Equation (GEE) logistic regression analyses, female gender was a positive predictor of ANA detection and gender differences were observed in the relative importance of other study factors. None of the variables examined in the multiple-variable GEE analysis were statistically significant predictors of ANA detection for women. For many of these variables, however, the point estimates for women are similar to those seen in men. For men, with adjustment for age, ANA presence was inversely associated with detection of concentrations of bromoxynil in winter or spring samples and recent occupational use of 2,4-dichlorophenoxyacetic acid, and the positive ANA predictors included having a BMI in the obese (BMI > 30.04 kg/m2) category, recent occupational use of trifluralin or fungicides, and current exposure to oilseed, poultry, or dairy production. The inverse association between ANA detection and bromoxynil exposure observed in farmers in this study is consistent with earlier empirical observations that certain pesticides may suppress immune function. Further research is needed to examine whether these findings are confirmed in other populations and to elucidate the biological mechanisms involved.

Effects of subchronic malathion exposure on the pharmacokinetic disposition of pefloxacin

Malathion is one of the most extensively used organophosphorus pesticides applied in agriculture, mosquito eradication and in the control of animal ectoparasites and human body lice. The widespread use of malathion has raised concern over its potential to cause untoward health effects in humans, animals and birds. Malathion inhibits cytochrome P450 monooxygenases and has the potential to alter pharmacokinetic profiles of therapeutic agents that are metabolized in the liver. The present study was undertaken to evaluate the impact of subchronic exposure of malathion on the pharmacokinetic disposition of pefloxacin. Chickens were given either normal diet or malathion through food at a concentration of 1000ppm for 28 days. Subsequently, pefloxacin was administered either intravenously or orally (control) to birds fed normal diet and orally to malathion-exposed chickens at a dosage of 10mgkg(-1) body weight. Blood samples were drawn from the brachial vein at predetermined time intervals after drug administration. Plasma was separated and analyzed for pefloxacin by reverse-phase high performance liquid chromatography. The plasma concentration-time data were analyzed by non-compartmental techniques. Following intravenous administration of pefloxacin, elimination half-life (t(1/2β)), area under the plasma concentration-time curve (AUC) and mean residence time (MRT) were 8.2±0.7h, 66±9μghml(-1) and 10.5±1.1h, respectively, and when the drug was administered orally, the respective values of pharmacokinetic parameters were 8.2±0.4h, 31±3.1μghml(-1) and 11.7±0.6h. Malathion exposure significantly increased maximum plasma drug concentration, t(1/2β), AUC and MRT of pefloxacin to 54, 22, 117 and 37% of control, respectively. These findings provide evidence that subchronic malathion exposure markedly influences the elimination kinetics of pefloxacin which may be due to malathion-mediated inhibition of metabolism of pefloxacin.

Pesticides induced oxidative stress in thymocytes

The role of oxidative stress in immune cell toxicity caused by the pesticides lindane, malathion and permethrin was investigated in thymic cells from C57BL/6 mice. Thymocytes treated with any of these pesticides (concentrations ranging between 50-150 microM) were found to generate both superoxide ((*)O(2) (-)) and H(2)O(2). The production of (*)O(2) (-) was detected with hydroethidine-ethidium bromide assay. H(2)O(2) production was monitored with a flow cytometric fluorescent (DCFH-DA) assay. All three pesticides stimulated (*)O(2) (-) release after 5 min exposure. Lindane and permethrin, but not malathion, continued to have significant (p < or = 0.05) effects on (*)O(2) (-) generation following 15 min of exposure. The lindane + malathion mixture was found to cause more-than-additive increase in (*)O(2) (-) production compared to individual pesticide treatments (at both 5 and 15 min). However, the effect of the lindane + permethrin mixture was not significantly different than individual components of this mixture. The effects of these pesticides on levels of antioxidant enzymes were also investigated, and only mixtures were found to have significant (p < or = 0.05) effects. Thus, lindane + malathion and lindane + permethrin mixtures increased total superoxide dismutase (SOD) specific activity, had no effect on catalase levels and inhibited GSH-peroxidase and GSH-reductase specific activities. Although the results of these studies do not explain the mechanism of action of these pesticides on the generation of (*)O(2) (-) and H(2)O(2), it is worthy of note that mixtures of these chemicals have oxidative responses greater than those of single chemicals.

Lipid peroxidative damage on malathion exposure in rats

Lipid peroxidation is one of the major outcomes of free radical-mediated injury to tissue in vivo, including the central nervous system (CNS). The aim of this study was to examine whether malathion, a commonly used organophosphorus (OP), might induce oxidative stress in cerebrospinal fluid, blood serum and brain structures in male Wistar rats. Malathion was administered intraperitoneally in the doses of 25, 50, 100 and 150 mg/kg for 28 days. Oxidative damage was determined by measuring the thiobarbituric acid reactive species (TBARS) content, as an index of lipid peroxidation. TBARS concentration in the cerebrospinal fluid (CSF) and brain structures were increased, but a decrease in TBARS concentration in serum was observed. The results of the present study suggest the usefulness of TBARS measurement as a good biomarker in the estimation of malathion-induced oxidative stress affecting CSF and brain structures.

Involvement of apoptosis in malathion-induced cytotoxicity in a grass carp (Ctenopharyngodon idellus) cell line

We investigated the role of apoptosis in malathion-induced cytotoxicity in the grass carp (Ctenopharyngodon idellus) cell line ZC-7901. Fish cells were treated with different concentrations of malathion (0.62-95 mg/L), and the IC(50) ranged from 37.94+/-1.93 mg/L for 12 h to 3.04+/-0.27 mg/L for 72 h by the MTT assay. Apoptosis was detected by confocal laser scanning microscopy, transmission electron microscopy, TUNEL reaction, DNA laddering and a flow cytometric PI staining assay. The results demonstrated that apoptosis was involved in the cytotoxic effect of malathion, and that malathion-induced apoptosis occurred in a dose- and time-dependent manner. In addition, the induction of apoptosis by malathion was accompanied by mitochondrial membrane potential (DeltaPsi(m)) disruption, intracellular Ca(2+) elevation, generation of reactive oxygen species (ROS) and ATP depletion. Our investigation suggested that malathion exerts its cytotoxic effects by the induction of apoptosis via a direct effect on the mitochondria.

Lipopolysaccharide (LPS) induced activation of the immune system in control rats and rats chronically exposed to a low level of the organothiophosphate insecticide, acephate

Lipopolysaccharide (LPS), a key inflammatory component of gram-negative bacteria, induces a distinctive pattern of cytokine release that regulates inflammation. An alteration in the LPS response may play a fundamental role in the pathogenesis of a number of inflammatory diseases. Therefore, this study was conducted to determine whether chronic exposure to a low level of acephate (Ace), a commonly used organophosphate insecticide, impaired the LPS response in rats. This study showed that LPS injection in control rats caused (1) a time-dependent increase in blood lymphocyte enumeration and differentiation, and (2) a sequential increase the pro-inflammatory (interleukin-1beta (IL1beta), tumor necrosis factor-alpha (TNFalpha), interferon-gamma (INTgamma), and inducible nitric oxide synthase (iNOS)) and anti-inflammatory (interleukin-4 (IL-4), corticotropin-releasing factor (CRF), and blood corticosterone (Cort)) cytokines. The pro-inflammatory cytokines increased after 30 min, while the anti-inflammatory cytokines increased 3 h after LPS injection. An increase in proinflammatory cytokines increased lymphocyte enumeration and differentiation, while the increase in anti-inflammatory cytokines re-established homeostasis. In comparison to the control rats, the Ace-exposed rats exhibited (1) lower levels of IL1beta, TNFalpha and iNOS, (2) higher levels of CRF and Cort, and (3) lower levels of IL-4 in blood and/or brain samples. The abnormal cytokine production may be associated with abnormal phenotypic distribution of B and T cells. Blood IgMhi IgDhi, IgMlo IgDlo and CD8+ CD45RA- CCR7+ cells were elevated, while IgMlo IgDhi, IgMhi IgDlo, IgMin IgDlo, CD8+ CD45RA+ CCR7+ and CD8+ CD45RA- CCR7 cells were depressed in Ace-exposed rats. Thus, chronic low-level Ace exposure may impair the lineage commitment in lymphocytes, possibly by altering cytokine signaling in the brain.

A T-cell-dependent humoral immune response is preserved during the administration of the nerve agent pre-treatment pyridostigmine bromide in a murine model

Immune regulation, either via the autonomic nervous system or by a proposed "non-neuronal" cholinergic system, suggests that the immune system may be susceptible to perturbation by compounds affecting cholinergic function. Here, the current UK and US nerve agent pre-treatment, pyridostigmine bromide (PB) and the related anti-acetylcholinesterase (AChE) compounds physostigmine (PHY) and BW284c51 were tested for their ability to affect mouse splenocyte function in vitro. In addition, PB, at a dose equivalent to that received during pre-treatment for nerve agent poisoning, was tested for its effect on a T-cell-dependent humoral response to antigen in vivo in the mouse. None of the anti-AChEs tested affected concanavalin A (Con A)-, anti-CD3- or lipopolysaccharide LPS-driven splenocyte proliferation, in vitro, at concentrations expected to give effective nerve agent pre-treatment. However, higher concentrations (>100 microM) particularly of PHY caused some inhibition of the proliferative responses. In vivo, PB or saline was administered via 28-day mini-osmotic pumps to give a 25-40% inhibition of whole blood AChE in the PB-treated animals. During PB or saline administration, primary and secondary doses (i.p.) of sheep red blood cells (SRBC) were given and the humoral response determined by monitoring anti-SRBC IgM and IgG levels. Splenocytes isolated from the experimental animals were also examined for their proliferative and cytokine responses to stimulation. No remarkable effects of PB were seen during the period of AChE inhibition on the humoral immune response. However, a modest elevation in IL-2 and IFN(gamma) in Con A-stimulated lymphocytes was seen in PB-treated animals following pump removal. Overall these data suggest that, in vivo, the SRBC stimulated T-cell-dependent immune response is unaffected by the administration of PB at pre-treatment doses.

The influence of single or repeated low-level sarin exposure on immune functions of inbred BALB/c mice

To study the influence of single or repeated low-level sarin inhalation exposure on immune functions, inbred BALB/c mice were exposed to low clinically asymptomatic concentrations of sarin for 60 min. in the inhalation chamber. The evaluation of immune functions was carried out using phenotyping of CD3 (T-lymphocytes), CD4 (helper T-lymphocytes), CD8 (cytotoxic T-lymphocytes) and CD19 (B-lymphocytes) in the lungs, blood and spleen, lymphoproliferation of spleen cells stimulated in vitro by various mitogens (concanavalin A, lipopolysaccharides), phagocyte activity of peritoneal and alveolar macrophages, production of N-oxides by peritoneal macrophages and the measurement of the natural killer cell activity at one week after sarin exposure. The results were compared to the values obtained from control mice exposed to pure air instead of sarin. The results indicate that an asymptomatic dose of sarin is able to alter the reaction of the immune system at one week after exposure to sarin. While the number of CD3 cells in lung was significantly decreased, a slight increase in CD19 cells was observed especially in the lungs after a single sarin inhalation exposure. Lymphoproliferation was significantly decreased regardless of the mitogen and sarin concentration used and the number of low-level sarin exposures. The ability of peritoneal and alveolar macrophages to phagocyte the microbes was also decreased regardless of the number of low-level sarin exposures. The production of N-oxides by peritoneal macrophages was decreased following a single low-level sarin exposure but increased following repeated low-level sarin inhalation exposure. Nevertheless, the changes in the production of N-oxides that reflects a bactericidal activity of peritoneal macrophages was not significant. The natural killer cell activity was significantly higher in the case of inhalation exposure of mice to low concentration of sarin regardless of the number of exposures. Thus, not only organophosphorous insecticides but also nerve agents such as sarin are able to alter immune functions following a single inhalation exposure even at a dose that does not cause clinically manifested intoxication. Generally, the repeated exposure to low concentrations of sarin does not increase the alteration of immune functions compared to the single low-level sarin exposure with the exception of phagocyte activity of alveolar macrophages and natural killer cell activity.

Pesticide mixtures potentiate the toxicity in murine thymocytes

The immunotoxic risks of multiple pesticide exposure were evaluated. C57BL/6 mouse thymocytes were exposed to lindane, malathion, and permethrin, either separately or in mixtures of two pesticides, in vitro. These pesticide exposures caused both apoptotic and necrotic cell death in thymocytes as evaluated by flow cytometric analysis in combination with 7-aminoactinomycin-D (7-AAD), Annexin-V/propidium iodide (PI) staining assays and lactate dehydrogenase release assays. When cells exposed to mixtures of two pesticides, a significantly greater than additive interaction was observed in both apoptotic and necrotic populations of cells. The gel electrophoresis of DNA of cells showed DNA ladder formation with limited genomic DNA and increased laddering in mixture exposures. Based on these findings, it is suggested that these pesticides are potent immunotoxicants, in vitro, and that the mechanism of cytotoxicity observed upon exposure to these pesticides may, at least in part, be due to induction of apoptosis. We also provided evidence that induction of drug metabolizing mixed function oxidase system with lindane may, in part, be responsible for the potentiation of cytotoxicity in the combined exposures. As more information is obtained on the potential immunotoxic effects of pesticides, further insights will be gained for the risk assessment of these environmental pollutants.

Breast cancer metastasis alters acetylcholinesterase activity and the composition of enzyme forms in axillary lymph nodes

Because of the probable involvement of cholinesterases (ChEs) in tumorigenesis, this research was addressed to ascertaining whether breast cancer metastasis alters the content of acetylcholinesterase (AChE) and/or butyrylcholinesterase (BuChE) in axillary lymph nodes (LN). ChE activity was assayed in nine normal (NLN) and seven metastasis-bearing nodes (MLN) from women. AChE and BuChE forms were characterised by sedimentation analyses, hydrophobic chromatography and western blotting. The origin of ChEs in LN was studied by lectin interaction. AChE activity dropped from 21.6 mU/mg (nmol of the substrate hydrolysed per minute and per milligram protein) in NLN to 3.8 mU/mg in MLN (p < 0.001), while BuChE activity (3.6 mU/mg) was little affected. NLN contained globular amphiphilic AChE dimers (G2A, 35%), monomers (G1A, 30%), hydrophilic tetramers (G4H, 8%), and asymmetric species (A4, 23%, and A8, 4%); MLN displayed only G2A (65%) and G1A (35%) AChE forms. NLN and MLN contained G4H (79%), G4A (7%), and G1H (14%) BuChE components. Neither the binding of ChE forms with lectins and antibodies nor the subunit size were altered by metastasis. The higher level of AChE in NLN than in brain and the specific pattern of AChE forms in NLN support its role in immunity. The different profile of AChE forms in NLN and MLN may be useful for diagnosis.

Low-level sarin-induced alteration of immune system reaction in inbred BALB/c mice

To study the influence of low-level sarin inhalation exposure on immune functions, inbred BALB/c mice were exposed to low concentrations of sarin for 60 min in the inhalation chamber. Two concentrations of sarin were chosen-asymptomatic concentration (LEVEL 1) and non-convulsive symptomatic concentration (LEVEL 2). The evaluation of immune functions was carried out using phenotyping of CD3 (T-lymphocytes), CD4 (helper T-lymphocytes), CD8 (cytotoxic T-lymphocytes) and CD19 cells (B-lymphocytes) in the lungs, blood and spleen, lymphoproliferation of spleen cells stimulated in vitro by various mitogens (concanavalin A, lipopolysaccharides), phagocyte activity of peritoneal and alveolar macrophages, production of N-oxides by peritoneal macrophages and the measurement of the natural killer cell activity at 1 week following sarin exposure. The results were compared to the values obtained from control mice exposed to pure air instead of sarin. The results indicate that not only symptomatic but also asymptomatic dose of sarin is able to alter the reaction of immune system at 1 week following exposure to sarin. While the number of CD3 cells in the lungs was slightly decreased, an increase in CD19 cells was observed especially in the lungs and blood. The reduced proportion of T-lymphocytes is caused by decay of CD4 positive T-cells. Lymphoproliferation was significantly decreased regardless of the mitogen and sarin concentration used. The production of N-oxides by peritoneal macrophages was stimulated after exposure to LEVEL 2 of sarin whereas their ability to phagocyte the microbes was increased after exposure to LEVEL 1. The natural killer cell activity was significantly higher in the case of inhalation exposure of mice to LEVEL 2 of sarin. Thus, not only organophosphorus insecticides but also nerve agents such as sarin are able to alter immune functions even at a dose that does not cause clinically manifested intoxication following the inhalation exposure. Nevertheless, the alteration of immune functions following the inhalation exposure to a symptomatic concentration of sarin seems to be more pronounced.