Immunotoxicity of aminocarb. III. Exposure route-dependent immunomodulation by aminocarb in mice

From immunotoxicity to carcinogenicity: the effects of carbamate pesticides on the immune system

The immune system can be the target of many chemicals, with potentially severe adverse effects on the host's health. In the literature, carbamate (CM) pesticides have been implicated in the increasing prevalence of diseases associated with alterations of the immune response, such as hypersensitivity reactions, some autoimmune diseases and cancers. CMs may initiate, facilitate, or exacerbate pathological immune processes, resulting in immunotoxicity by induction of mutations in genes coding for immunoregulatory factors and modifying immune tolerance. In the present study, direct immunotoxicity, endocrine disruption and inhibition of esterases activities have been introduced as the main mechanisms of CMs-induced immune dysregulation. Moreover, the evidence on the relationship between CM pesticide exposure, dysregulation of the immune system and predisposition to different types of cancers, allergies, autoimmune and infectious diseases is criticized. In addition, in this review, we will discuss the relationship between immunotoxicity and cancer, and the advances made toward understanding the basis of cancer immune evasion.

Characterization of the toxicological effects of aminocarb on rats: hematological, biochemical, and histological analyses

Aminocarb is a widely applied carbamate insecticide with action of controlling pests such as Lepidoptera and Coleoptera. In this study, subchronic effects on Wistar rats were investigated using hematological, biochemical, and histological techniques. Rats were exposed orally at sublethal levels of 10, 20, or 40 mg/kg body weight (groups A, B, and C, respectively) for 14 d. Hematological results revealed no statistical differences after 1 d of exposure but significant reduction in white blood cells detected after 7 d of exposure in group C, as well as, in all treated groups after 14 d of exposure. Biochemical data showed a decrease of acetylcholinesterase activity in all groups after 1 d of exposure with a return to normal after 7 and 14 d. Significant increase in alkaline phosphatase activity of rats exposed to aminocarb was noted after 7 d of treatment. The levels of triglycerides were also significantly decreased. The present investigation also showed a significant increase in content of serum urea and creatinine in animals from group A (14 d), and from groups B and C (7 and 14 d). Histological results demonstrated hemorrhagic focus on hepatic and renal parenchyma in all exposed groups. Taken together, the attained results were dose dependent and indicated adverse effects of aminocarb on hepatic and renal functions, as well as on immune responsiveness at sublethal tested doses.

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.

Age-specific immunocompetence of the earthworm Eisenia andrei: exposure to methylmercury chloride

Little information with regard to the sensitivity of the immune system of earthworms to toxicants is currently available. To that effect, we evaluated the yield of coelomocyte immune cells and their phagocytosis potential for four different stages of development of the earthworm Eisenia andrei both for in vitro and in vivo exposure. Cell viability was similar among size classes; extruded cell yield increased from 0.7 x 10(6) cells/worm in the smallest size class to 2.9 x 10(6) cells/worm in the largest size class. The proportion of phagocytically active cells was lower in the smallest groups but not different among the other three groups. Phagocytosis increased incrementally for the first three age/weight groups. The absolute phagocytosis level of the hatchling worms is significantly lower than that of the adult worms. The in vivo filter paper exposure of the mature worms showed a hormetic stimulation of 200-300% of phagocytosis and no significant effects on the phagocytosis potential of the hatchlings. The absolute response of coelomocytes from younger worms was significantly lower and the estimates of lethal mercury concentrations showed the hatchling worms to be roughly three times more sensitive than mature worms.

Evaluation of immunotoxicity induced by propoxure in C57Bl/6 mice

Insecticides are important candidates for immunotoxicology tests in order to assess the 'No Observable Adverse Effect Level' (NOAEL). Propoxure (PPX), as a carbamate household insecticide, has been used for several decades around the world in agriculture. However, there has been no clear investigation on its immunotoxic potentials. In this study, as Tier I of immunotoxicological screening tests, we examined the effects of subacute exposure to intraperitoneally (i.p.) administered PPX, at doses of 10, 2, and 0.2 mg/kg, on C57Bl/6 female mice. After 28 days administration of PPX, the treated animals were sacrificed and peripheral blood samples were collected. Then spleen (SP), thymus (TM), and bone marrow were collected and weighed. Functional tests including SRBC-hemagglutination (HA), plaque-forming colony assay (PFC), and delayed type hypersensitivity (DTH) response to SRBCs were performed. Furthermore, spleen T-cell phenotype (CD4/CD8) was also determined. Results showed that high doses of PPX could not only produce histopathological changes in TM and SP but also suppress humoral response to antigen (SRBCs). PPX at medium doses (2 mg/kg) did not show histopathological changes in TM or SP but increased the humoral response to SRBCs, as identified by HA and PFC tests. PPX at low doses (0.2 mg/kg) did not produce any significant changes in humoral (PFC and HA) or cellular responses (DTH) of the immune system. It seems that PPX has no adverse effects on mice immune system at low doses of 0.2 mg/kg/day, which is 10 times the PPX allowed daily intake (ADI) limit.

Down regulation of humoral immunity in chickens due to carbendazim

This study was planned to investigate the effect of very low dose of carbendazim on the humoral immune response in the chicken. Sixteen adult chickens, earlier vaccinated against New Castle Disease were divided in two experimental groups. Chickens of group I served as control, while group II birds were given a feed containing 200 ppm of carbendazim, which is considered no observable effect level (NOEL) dose, for a period of 6 months. The Humoral immune response was measured by the B-lymphocyte blastogenesis assay using lipopolysaccharide as mitogen and the quantitation of IgG, IgA, IgM levels by using respective antichicken conjugates, through an ELISA method. Total serum proteins, serum gamma-globulins and globulins were measured using commercially available kits. Carbendazim significantly (P< or =0.05) reduced both the B-lymphocyte proliferation and serum IgG, IgM and IgA levels, leading to decreased immunocompetence. At the end of experiment percent decrease in B-lymphocyte proliferation was 20.5% and that in serum IgG, IgM and IgA were 11.2, 22.9 and 28.8%, respectively. The percent decrease in total serum protein, serum gamma-globulins and serum globulins were 14.6, 18.5 and 9.7%, respectively. Results clearly indicated down regulation of humoral immunity by carbendazim at NOEL dose.

Autoimmunity by pesticides: a critical review of the state of the science

The goals of this paper will be to present a critical review of the state of the science of pesticides and autoimmunity, and to discuss research that addresses the potential links between environmental chemicals and autoimmune disease. To date, the science of immunotoxicology has primarily focused on immunosuppression and hypersensitivity/allergy, and test methods are available to address these outcomes. So much progress has been made to address immunosuppression and contact sensitization that there are regulatory guidelines in the U.S. included in the registration of pesticides. In contrast, there are no validated approaches to assess autoimmunity. The overall objective of this paper will be to use pesticides as an important class of environmental chemicals to critically evaluate the state of the science for addressing chemical-induced autoimmunity. Specific examples of studies with pesticides will be discussed in the context of the following types of approaches: animal studies using standard immunotoxicological parameters; animal studies using specialized models of autoimmunity; human studies after environmental or occupational exposure; and human studies after accidental poisoning.

[Effects of organonitrogen, carbamate pesticides and others on beta-hexosaminidase release from rat basophilic leukemia cells (RBL-2H3)]

There have been very few reports of the effect of pesticides on immediate allergy. In the previous report, the effect of pyrethroid pesticides and organophosphorus pesticides on immediate allergic reaction was investigated. Subsequently, 12 organonitrogen pesticides, 14 carbamate pesticides and 4 other pesticides were investigated for their effects on the enzyme activity of beta-hexosaminidase as an index of chemical mediator release from rat basophilic leukemia cells (RBL-2H3). Two organonitrogen pesticides, bitertanol and pyridaben, and two organotin pesticides, cyhexatin and fenbutatin oxide, were found to promote beta-hexosaminidase release. Bitertanol non-specifically caused the promotion of chemical mediator release, while the release-promotive action of pyridaben was related to IgE antibody and those of cyhexatin and fenbutatin oxide to cell injury. On the other hand, two organonitrogen pesticides, propiconazole and triadimenol, and imazalil showed release-inhibitory action. These data suggested that some pesticides can affect immediate allergy.

Immunotoxicity of cupravit and previcur fungicides in mice

Female mice received either cupravit or previcur at dose levels of 300 ppm and 1000 ppm, respectively, for 8 weeks. Humoral immune response was evaluated by measuring the plaque-forming cell (PFC) response and hemolysing antibody titers against sheep red blood cells (SRBCs), a T lymphocyte-dependent antigen. In addition, the hemagglutinating antibody titers against Escherichia coli lipopolysaccharide (LPS), a T cell-independent antigen, were determined. Both cupravit and previcur suppressed the PFC response by 74% and 78% of control values, respectively. The primary hemolysin antibody titers were reduced to 62% and 76% of control values, respectively. The hemagglutinating antibody titers were decreased to 66% and 77% of control values, respectively. Memory function was reduced as evidenced by inhibition of secondary hemolysin titers to SRBCs. Cell-mediated immunity was inhibited by both cupravit and previcur as evidenced by reduced delayed-type hypersensitivity (DTH) reaction to tuberculin to 77% and 76% of control values, respectively. Decreases in total leukocytic and lymphocytic counts were recorded together with histopathological changes in spleen and thymus gland of intoxicated animals.

Immunotoxicity of pesticides: a review

The intricate balance that is the hallmark of the immune system shows vulnerability to any chemical, including pesticides, that can cause structural and functional alterations to the system. The immunotoxic effects of xenobiotics include: histopathologic effects in immune tissues and organs; cellular pathology; altered maturation of immunocompetent cells; changes in B and T cell subpopulations; and functional alterations of immunocompetent cells. Pesticides, including fungicides, herbicides, and insecticides, are the only class of chemicals deliberately released into the environment because of their toxicity. Around the world, millions of people are exposed to pesticides at work and/or in their home. This article reviews evidence, from animal and human studies, on the effects of pesticides on the immune system.