Immunotoxicological investigation of subacute combined exposure by permethrin and the heavy metals arsenic(III) and mercury(II) in rats

Counteracting arsenic toxicity: Curcumin to the rescue?

Arsenicosis leads to various irreversible damages in several organs and is considered to be a carcinogen. The effects of chronic arsenic poisoning are a result of an imbalance between pro- and antioxidant homeostasis, oxidative stress, as well as DNA and protein damage. Curcumin, the polyphenolic pigment extracted from the rhizome of Curcuma longa, is well-known for its pleiotropic medicinal effects. Curcumin has been shown to have ameliorative effects in arsenic-induced genotoxicity, nephrotoxicity, hepatotoxicity, angiogenesis, skin diseases, reproductive toxicity, neurotoxicity, and immunotoxicity. This review aims to summarize the scientific evidence on arsenic toxicity in various organs and the ameliorative effects of curcumin on the arsenic toxicity.

Synergistic Effects of Heavy Metals and Pesticides in Living Systems

There is a widespread repeated exposure of the population to the pesticides and heavy metals of occupational and environmental origin. Such population is forced to undergo continuous stress imposed by combined exposure of the heavy metals and different classes of the pesticides used in agricultural as well as health practices. The existing reports from several workers have indicated that heavy metals and pesticides in combination may lead more severe impact on the human health when compared to their individual effects. Such a combination of pesticides and heavy metals may also change or influence the detection of exposure. Several studies in past have shown the synergistic toxic effects of heavy metals and pesticides. Such evaluations have revealed the synergistic interactions of various heavy metals and pesticides in animals as well as humans. The aim of the present article is to provide a synthesis of existing knowledge on the synergistic effects of heavy metal and pesticides in living systems. The information included in this article may be useful for different environment protection agencies and policy makers to consider the combined effects of heavy metals and pesticides on humans while designing strategies toward environmental protection and safety regulations about human health.

Arsenic and dichlorvos: Possible interaction between two environmental contaminants

Metals are ubiquitously present in the environment and pesticides are widely used throughout the world. Environmental and occupational exposure to metal along with pesticide is an area of great concern to both the public and regulatory authorities. Our major concern is that combination of these toxicant present in environment may elicit toxicity either due to additive or synergistic interactions or 'joint toxic actions' among these toxicants. It poses a rising threat to human health. Water contamination particularly ground water contamination with arsenic is a serious problem in today's scenario since arsenic is associated with several kinds of health problems, such arsenic associated health anomalies are commonly called as 'Arsenism'. Uncontrolled use and spillage of pesticides into the environment has resulted in alarming situation. Moreover serious concerns are being addressed due to their persistence in the environmental matrices such as air, soil and surface water runoff resulting in continuous exposure of these harmful chemicals to human beings and animals. Bio-availability of these environmental toxicants has been enhanced much due to anthropological activities. Dreadfully very few studies are available on combined exposures to these toxicants on the animal or human system. Studies on the acute and chronic exposure to arsenic and DDVP are well reported and well defined. Arsenic is a common global ground water contaminant while dichlorvos is one of the most commonly and widely employed organophosphate based insecticide used in agriculture, horticulture etc. There is thus a real situation where a human may get exposed to these toxicants while working in a field. This review highlights the individual and combined exposure to arsenic and dichlorvos on health.

Immunotoxicological investigation of subacute combined exposure with low doses of Pb, Hg and Cd in rats

Detectable interactions between NOEL (No Observed Effect Level) doses of Pb, Hg and Cd in general toxicological, hematological, and immune function parameters were investigated. The metals (Pb-acetate, 20 mg/kg; HgCl2, 0.40 mg/kg; CdCl2, 1.61 mg/kg) were combined. First, the rats received the combination Pb + Hg + Cd for 4 weeks per os. Significant difference vs. control was found only in the weight of lung and popliteal lymph node (PLN). The Pb + Hg and Pb + Cd combinations significantly decreased the PLN to 100 g body weight and PLN to brain weight ratio, and Pb+Hg also decreased the relative adrenal weight. After 12 weeks treatment with the same doses, effects on the thymus, kidney, and adrenal weights in the Pb + Hg, and thymus weight in the Pb + Cd, combination were seen. Pb + Cd also affected the white and red blood cell count and hematocrit. Combined with Hg or Cd, NOEL dose Pb showed toxicity, indicating that exposure limits may be inefficient in combined exposure situations.

Interactive alterations of arsenic and malathion in the disposition kinetics of pefloxacin

Assessment of deleterious effects produced by concurrent exposure to commonly encountered chemicals is of great concern to find out toxicological consequences arising as a result of their interactions and for a more comprehensive management of chemical-induced untoward effects. The naturally occurring heavy metal arsenic is present in food and water. Malathion is one of the most widely used pesticides in agriculture and public health practices worldwide. Humans, animals, and birds are exposed to these chemicals through environmental processes. Since arsenic and malathion are shown to exert an inhibitory effect on cytochrome P450 activities, their continuous exposure may alter the disposition kinetics of drugs that are predominantly metabolized hepatically. The current study was undertaken to evaluate the impact of subchronic exposure of arsenic, malathion, and their combination on the disposition kinetics of widely used fluoroquinolone antimicrobial pefloxacin in chickens. Broiler chickens were exposed to either arsenic (50 ppm), malathion (500 ppm), or arsenic (50 ppm) plus malathion (500 ppm). Arsenic and malathion were given in drinking water and feed, respectively. Following 28 days of exposure, all birds received a single oral dose of pefloxacin (10 mg/kg) and the plasma concentrations and the disposition kinetic parameters of the drug were determined. In the birds not exposed to arsenic and/or malathion, the elimination half-life (t(1/2beta)), area under the plasma concentration-time curve (AUC), maximum plasma drug concentration (C(max)), mean residence time (MRT), and bioavailability of pefloxacin were 8.46 +/- 0.24 h, 39.06 +/- 1.13 microg.h.ml(-1), 2.69 +/- 0.19 microg.ml(-1), 12.29 +/- 0.48 h, and 60.52 +/- 1.74%, respectively. Exposure to arsenic was associated with a significant increase in C(max) (4.28 +/- 0.45 microg.ml(-1)) and a nonsignificant increase in the values of AUC (48.96 +/- 2.55 microg.h.ml(-1)) and bioavailability (74.55 +/- 3.8 %) of pefloxacin. The values of AUC (51.62 +/- 4.76 microg.h.ml(-1)), t(1/2beta) (12.57 +/- 1.26 h), MRT (19.94 +/- 1.99 h), and bioavailability (78.59 +/- 7.25 %) of pefloxacin were significantly increased in malathion-exposed birds. Concomitant exposure to arsenic and malathion did not affect the disposition kinetic variables of pefloxacin. The study shows that subchronic malathion exposure significantly alters the elimination kinetics of pefloxacin. Following concurrent exposure, arsenic nullifies the malathion-induced changes in disposition kinetics of pefloxacin by possibly diminishing the cytochrome P450-catalyzed bioactivation of malathion.

Combined dermal exposure to permethrin and cis-urocanic acid suppresses the contact hypersensitivity response in C57BL/6N mice in an additive manner

Cutaneous exposure to the pyrethroid insecticide permethrin significantly suppresses contact hypersensitivity (CH) response to oxazolone in C57BL/6N mice. Additionally, cis-urocanic acid (cUCA), an endogenous cutaneous chromophore isomerized to its active form following exposure to ultraviolet radiation, modulates cell-mediated cutaneous immune responses. This study describes cutaneous immune alterations following combined topical permethrin and intradermal cUCA exposure. Female C57BL/6N mice were administered 5, 50 or 100 microg cUCA daily for 5 consecutive days. CH was then evaluated by the mouse ear swelling test (MEST) response to oxazolone. Decreased responses of 52.3%, 76.3% and 76.3%, respectively, as compared to controls were observed. Then, mice were co-exposed to 5 microg cUCA daily for 5 days and 1.5, 5, 15, or 25 microL permethrin, on either day 1, 3 or 5 of the cUCA treatment to evaluate combined immunomodulatory effects of the two chemicals, or cUCA daily for 5 days followed by permethrin on day 3, 5, or 7 after the last cUCA injection to demonstrate prolonged immunosuppressive effects. Two days after final treatment, mice were sensitized with oxazolone and MEST was performed. Mice receiving five cUCA injections and permethrin topically on cUCA injection day 1 showed up to 93.3% suppression of MEST compared to vehicle control. CH was suppressed by 87.5%, 86.6% and 74.2% in mice treated with 25 muL permethrin on days 3, 5 and 7 after cUCA, respectively, compared to vehicle control. Taken together, these data indicate co-exposure to cUCA and permethrin profoundly suppresses cell-mediated cutaneous immunity.

Mercury chloride effects on the function and cellular integrity of sea bass (Dicentrarchus labrax) head kidney macrophages

The objective of this work was to study mercury chloride effects on the function and integrity of sea bass (Dicentrarchus labrax) head kidney macrophages (S-HKM), and to evaluate the response of HgCl2-exposed cells to macrophage activating factor(s) (MAF) produced by sea bass head kidney leukocytes. There was considerable variability in the effects of HgCl2 on the production of reactive oxygen species (ROS) by S-HKM. When incubated with HgCl2, cells from five out of nine fish tested showed a decrease in ROS production as compared to cells incubated with medium alone. In those cultures, MAF addition prevented the mercury chloride-induced decrease in ROS production. In other S-HKM cultures isolated from different fish, mercury chloride abrogated the up-regulating effect of MAF on the respiratory burst. MAF activation of the phagocytic activity of S-HKM was also impaired by HgCl2 addition. Mercury chloride induced apoptosis in S-HKM cultures and MAF addition prevented this effect.

Immuno- and neurotoxicological investigation of combined subacute exposure with the carbamate pesticide propoxur and cadmium in rats

In the present study, the effects of subchronic per os exposures to cadmium chloride (CdCl(2)), and a carbamate insecticide, propoxur (Pr), were investigated in male Wistar rats on general toxicological (body weight gain, relative organ weights) haematological (RBC, WBC, Ht, MCV, cell content of the femoral bone marrow) immune function (plaque forming cell (PFC) assay, delayed type hypersensitivity (DTH) reaction) and neurotoxicological (spontaneous and stimulus-evoked cortical activity, nerve conduction velocity) parameters. The animals were treated for 4, 8 and 12 weeks with 6.43 mg/kg CdCl(2), 8.51 mg/kg Pr, or with a combination of 6.43 mg/kg CdCl(2)+0.851 mg/kg Pr or 8.51 mg/kg Pr+1.61 mg/kg CdCl(2). Cadmium exposure affected the relative thymus, liver, and adrenal weight, RBC count, haematocrit and MCV, and there was an increase in nerve conduction velocity and a decrease in the cortical evoked potential latency. Pr induced a decrease in thymus weight, had some effect on the liver weight but none on the electrophysiological parameters. A significant interaction between Cd and Pr was detected by the following parameters: RBC, Ht, PFC, and nerve conduction velocity. The results indicate that combined exposures in humans may result in a shift in the apparent detection limits and/or in the LOEL of the single substances. The latter raises the necessity to reconsider exposure limits in situations where the risk of combined exposure is high.

Immunotoxicological investigation in rats dosed repeatedly with combinations of cypermethrin, As(III), and Hg(II)

The effects of the combined exposure of cypermethrin (CY), NaAsO2 (As), and HgCl2 (Hg) were investigated in male Wistar rats following 4 weeks of oral exposure. Standard toxicological (body weight gain, organ weights of brain, thymus, heart, lung, liver, kidneys, adrenals, testes, and popliteal lymph node), haematological (white blood cell, red blood cell, haematocrit, MCV-mean volume of red blood cells, and cell content of the femoral bone marrow), and immune function (IgM-PFC response, delayed type hypersensitivity (DTH) reaction) parameters were measured. The two doses selected for the combination were: a high (H) dose equal to lowest observed effect level determined in preliminary experiments (CY(H)=55.4 mg/kg, As(H)=13.3 mg/kg, Hg(H)=3.20 mg/kg), and a low (L) dose which was ineffective (non-observed effect level); CY(L)=11.1 mg/kg, As(L)=3.33 mg/kg, Hg(L)=0.40 mg/kg). CY(H) was combined with As(L) or Hg(L), and the H doses of the heavy metals were combined with CY(L). Beside vehicle control, the H dose components of the combinations were also used as internal controls. The main finding of this study was that certain combinations, when compared to H dose internal control, significantly altered the body weight gain (As(H)+CY(L)), the relative weight of adrenals and popliteal lymph node (CY(H)+As(L) and CY(H)+Hg(L)), the cell content of the femoral bone marrow (CY(H)+Hg(L)), and the time course of DTH reaction (CY(H)+As(L)). According to the present results, combined exposure with CY and the heavy metals investigated can modify the toxicity and/or the functional detection limit of the single substances.

Immunotoxicological investigations on rats treated subacutely with dimethoate, As3+ and Hg2+ in combination

Effects of combined exposure with dimethoate (DM), HgCl2 (Hg), and NaAsO2 (As) were investigated following a 28 - day oral exposure in male Wistar rats. In preliminary experiments, the LOEL (Lowest Observed Effect Level) and NOEL (Non Observed Effect Level) doses of the substances were determined using the same experimental system [determination of body weight gain, organ weights of brain, thymus, heart, lung, kidneys, adrenals, spleen, testicles, popliteal lymph node, white blood cell (WBC) and red blood cell (RBC) count, haematocrit (Ht), mean cell volume (MCV) of RBCs, cell content of the femoral bone marrow, IgM-plaque forming cell (PFC) content of the spleen, delayed type hypersensitivity (DTH) reaction] and animal strain. In the combination studies, LOEL dose of DM (28.2 mg/kg) was combined with NOEL doses of the heavy metals ( HgCl2 = 0.40 mg/kg, NaAsO2 = 3.33 mg/kg), and vice versa (DM = 7.04 mg/kg, HgCl2 = 3.20 mg/kg, NaAsO2 = 13.3 mg/kg). In the DM-Hg combinations, significant alterations were found versus the corresponding high- dose internal control in the body weight gain, relative liver and kidney weights, and in the PFC response. When DM was combined with As, interactions were indicated by changes of relative liver weight, MCV value, and the PFC content of the spleen. These results support the theory that the interactions between pesticides and heavy metals may modify the toxic effects of the single substances, and may also change the functional detection limits of the exposure. The changes in the functional detection limits, if they occur, can lead to false-positive and false-negative results in human epidemiological studies.