Investigation of the subchronic effects of low-dose pesticide mixture on rat testes

The noxious effects of low or effective dose exposure to single or mixed pesticides on macrophage activity and the lymphohematopoietic organs were investigated. Male Wistar rats were orally exposed to dichlorvos, dicofol, endosulfan, dieldrin and permethrin, either as single or combined mixtures during a 28-day study containing eight groups: one group received a semipurified diet (non-treated); two groups received a semipurified diet containing low dose mixture (dieldrin 0.025 mg/kg, endosulfan, 0.6 mg/kg, dicofol 0.22 mg/kg, dichlorvos 0.23 mg/kg, permethrin 5 mg/kg) or an effective dose mixture (dichlorvos 2.3 mg/kg, dicofol 2.5 mg/kg, endosulfan 2.9 mg/kg, dieldrin 0.05 mg/kg and permethrin 25.0 mg/kg), respectively; the other five groups received a semipurified diet containing each single pesticide in effective doses. At sacrifice, the thymus, spleen, mesenteric lymph nodes, Payer's patches and bone marrow were removed for histological analysis. Peritoneal macrophages were obtained to determine the phagocytosis and spreading indexes and tumoral necrosis factor alpha (TNF-α), nitric oxide (NO) and H2O2 production. Exposure to pesticide mixtures did not alter the percentage of macrophage phagocytosis and spreading, TNF-α production or the NO and H2O2 release when compared to the non-treated group. Neither was there any apparent evidence that a pesticide mixture at low or effective doses altered the histological structure of the lymphohematopoietic organs. The findings indicate that short-term treatment with pesticide mixtures did not induce an apparent immunotoxic effect in male Wistar rats.

Gender-linked haematopoietic and metabolic disturbances induced by a pesticide mixture administered at low dose to mice

In vitro investigation of endocrine disrupting effects of pesticides on Ca2+-signaling in human sperm cells through actions on the sperm-specific and steroid-activated CatSper Ca2+-channel.

Further morphological and histochemical studies on organosilicone induced effects in rat testis

Neurological effects of long-term exposure to low doses of pesticides mixtures in male rats: Biochemical, histological, and neurobehavioral evaluations

Humans are chronically exposed to multiple environmental pollutants such as pesticides with no significant evidence about the safety of such poly-exposures. We exposed mesenchymal stem cells (MSC) to very low doses of mixture of seven pesticides frequently detected in food samples for 21 days in vitro. We observed a permanent phenotype modification with a specific induction of an oxidative stress-related senescence. Pesticide mixture also induced a shift in MSC differentiation towards adipogenesis but did not initiate a tumorigenic transformation. In modified MSC in which a premalignant phenotype was induced, the exposure to pesticide mixture promoted tumorigenic phenotype both in vitro and in vivo after cell implantation, in all nude mice. Our results suggest that a common combination of pesticides can induce a premature ageing of adult MSC, and as such could accelerate age-related diseases. Exposure to pesticide mixture may also promote the tumorigenic transformation in a predisposed stromal environment. Abstract Video Link: https://youtu.be/mfSVPTol-Gk Stem Cells 2017;35:800-811.

A literature review covering the last 14 yr has been performed in the field of combination toxicology and human risk assessment from exposure to chemical mixtures, with special emphasis on mixtures of pesticides at low doses, that is, at levels likely to occur in human diet and environment. Despite a large body of knowledge in the field of risk assessment methodologies for exposure to chemical and pesticide mixtures, there is no single methodological approach in "combination toxicology" and health risk assessment of chemical mixtures, and therefore professional judgment is still required. Generally, the dose or response additivity approach that may be applied to evaluate potential risk for chemical mixtures in human toxicology overestimates the risk of a combination of chemicals. The recent endocrine disrupter issue demonstrated the difficulty of reproducibility of data when testing environmental toxicants at very low levels, and the need for more basic work in this field. The use of integrated methodological approaches may provide more reliable predictive data in the risk assessment of chemical mixtures in future. Yet data have demonstrated that exposure to a combination of compounds does not cause effects stronger than the ones of their most active component, provided components are present at low concentration levels, like acceptable daily intake (ADI) or reference dose (RfD) levels, well below their respective no-observed-adverse-effect levels (NOAELs). Although it has been demonstrated that a combination of compounds with the same target organ and the same or very similar mechanisms of action may cause additive or synergistic effects, the chance of such effects will most likely diminish with decreasing exposure levels to such combinations. Synergism and antagonism may both occur at the same time at different organs or targets in the same organism. However, and despite some exceptions, it has been demonstrated that interaction between components is not a common event at low levels of human exposure such as those that may occur through pesticides residues in food or drinking water. The introduction of a special safety factor as a standard for mixtures in addition to those normally used for deriving ADIs, RfDs, or minimal risk levels is not supported by data. It can be concluded from our review that, as a general rule, exposure to mixtures of pesticides at low doses of the individual constituents does not represent a potential source of concern to human health.

Environmental effects of realistic pesticide mixtures on natural biofilm communities with different exposure histories

Alterations in small RNA profiles in liver following a subchronic exposure to a low-dose pesticide mixture in Sprague-Dawley rats

The aim of the current study was to investigate subchronic effect of dimethoate on the testes of rats. The animals of exposed groups were fed with laboratory chow combined with 2, 8 and 20 mg/kg dimethoate for 90 days. When compared to control, there was a statistically significant decrease in relative testis weights of rats treated with 20 mg/kg dimethoate. In light microscopic examinations, histopathological observation of the treated rats revealed that dimethoate caused dose-related testicular damage characterized by moderate to severe seminiferous tubule degeneration as sloughing, atrophy, germ cell degeneration and by partial arrest of spermatogenesis.

Glyceryl trinitrate (GTN) and isosorbide mononitrate (IM) are organic nitrates which release nitric oxide upon metabolism with potential to adversely affect male reproductive function. Therefore, this study was designed to evaluate the sub-chronic effect of these organic nitrates on reproductive system in male rats. Wistar rats were separately treated with GTN and IM at 2.5, 5 and 7.5mg/kg/day by oral gavage for 45 days. At the end of treatment, serum blood samples were taken from anaesthetized rats for assessment of hormonal profile. Epididymis was removed to analyse sperm parameters. Rat testes were dissected to perform histopathological evaluation and oxidative stress biomarkers. The GTN and IM treated groups showed a significant decrease in sperm parameters (count, motility and viability) and serum testosterone in comparison to normal control group. The GTN and IM treatment also altered sperm morphology such as bent tail and head deformities as compared to control. A significant decrease in catalase activity and, increase in nitric oxide and malondialdehyde were observed in high dose drug treated groups. Moreover, a significant increase in follicle stimulating hormone and decrease in testosterone levels were evident in all drug treated groups. The level of luteinizing hormone was raised in rats treated with medium doses of drugs while it decreased at the highest dose of both drugs. Histological study showed vacuolization and degeneration of seminiferous tubules. It is concluded that GTN and IM treatment adversely affected the male reproductive function by altering sperm parameters and disrupting the reproductive hormone profile which may be attributed to the increased level of nitric oxide and oxidative stress.

Testicular effects of sub-chronic administration of Hibiscus sabdariffa calyx aqueous extract in rats

Simple SummaryPesticide exposure is a public health concern. Two recent studies reported that exposure of normal primary bone marrow mesenchymal stem/stromal cells (BM-MSCs) to low-dose pesticide mixture induces deleterious consequences, such as oxidative stress, senescence, accelerated aging and increased sensitivity to oncogenic hits. Here, we show that exposure to this mixture decreases aldehyde dehydrogenase-2 (ALDH2) activity, with a concomitant increase in acetaldehyde level and DNA damage and alters the MSC capacity to support primitive hematopoiesis. Similar abnormalities were observed in bone marrow-MSCs from patients suffering from myelodysplastic syndrome (MDS), suggesting a role of pesticide-induced ALDH2 inhibition in the pathophysiology of this pre-leukemic disease.(1) Background: The impact of occupational exposure to high doses of pesticides on hematologic disorders is widely studied. Yet, lifelong exposure to low doses of pesticides, and more particularly their cocktail effect, although poorly known, could also participate to the development of such hematological diseases as myelodysplastic syndrome (MDS) in elderly patients. (2) Methods: In this study, a cocktail of seven pesticides frequently present in water and food (maneb, mancozeb, iprodione, imazalil, chlorpyrifos ethyl, diazinon and dimethoate), as determined by the European Food Safety Authority, were selected. Their in vitro effects at low-doses on primary BM-MSCs from healthy volunteers were examined. (3) Results: Exposure of normal BM-MSCs to pesticides for 21 days inhibited cell proliferation and promoted DNA damage and senescence. Concomitantly, these cells presented a decrease in aldehyde dehydrogenase 2 (ALDH2: mRNA, protein and enzymatic activity) and an increase in acetaldehyde levels. Pharmacological inhibition of ALDH2 with disulfiram recapitulated the alterations induced by exposure to low doses of pesticides. Moreover, BM-MSCs capacity to support primitive hematopoiesis was significantly altered. Similar biological abnormalities were found in primary BM-MSCs derived from MDS patients. (4) Conclusions: these results suggest that ALDH2 could participate in the pathophysiology of MDS in elderly people long exposed to low doses of pesticides.

Health effects of pesticides are not always accurately detected using the current battery of regulatory toxicity tests. We compared standard histopathology and serum biochemistry measures and multi-omics analyses in a subchronic toxicity test of a mixture of six pesticides frequently detected in foodstuffs (azoxystrobin, boscalid, chlorpyrifos, glyphosate, imidacloprid and thiabendazole) in Sprague-Dawley rats. Analysis of water and feed consumption, body weight, histopathology and serum biochemistry showed little effect. Contrastingly, serum and caecum metabolomics revealed that nicotinamide and tryptophan metabolism were affected, which suggested activation of an oxidative stress response. This was not reflected by gut microbial community composition changes evaluated by shotgun metagenomics. Transcriptomics of the liver showed that 257 genes had their expression changed. Gene functions affected included the regulation of response to steroid hormones and the activation of stress response pathways. Genome-wide DNA methylation analysis of the same liver samples showed that 4,255 CpG sites were differentially methylated. Overall, we demonstrated that in-depth molecular profiling in laboratory animals exposed to low concentrations of pesticides allows the detection of metabolic perturbations that would remain undetected by standard regulatory biochemical measures and which could thus improve the predictability of health risks from exposure to chemical pollutants.

We describe a comprehensive repository describing a collection of data from a range of studies investigating the molecular mechanisms of toxicity of glyphosate, the glyphosate-based herbicide commercial formulation Roundup, and a mixture of glyphosate and 5 other most frequently used pesticides (azoxystrobin, boscalid, chlorpyrifos, imidacloprid and thiabendazole) present as residues in food products in Europe. The data were obtained by analysing tissues from rats exposed to the pesticides for 90 days via drinking water. The administration of the mixture of six pesticides was chosen to mimic a possible human exposure scenario. We compared conventional methods used in regulatory toxicity studies to evaluate the safety of pesticide exposure (gross pathology, serum biochemistry) to new molecular profiling methods encompassing the analysis of the caecum and blood metabolome, liver transcriptome, liver DNA methylation, liver small RNA profiles, and caecum metagenome of the exposed animals. Altogether, these investigations provided in-depth molecular profiling in laboratory animals exposed to pesticides revealing metabolic perturbations that would remain undetected by standard regulatory biochemical measures. Our results highlight how multi-omics phenotyping can be used to improve the predictability of health risk assessment from exposure to toxic chemicals to better protect public health.