Pesticides exposure and compromised fitness in wild birds: Focusing on the reproductive endocrine disruption.

Exposure of pesticides to wildlife species, especially on the aspect of endocrine disruption is of great concern. Wildlife species are more at risk to harmful exposures to the pesticides in their natural habitat through diet and several other means. Species at a higher tropic level in the food chain are more susceptible to the deleterious effects due to sequential biomagnifications of the pesticides/metabolites. Pesticides directly affect fitness of the species in the wild causing reproductive endocrine disruption impairing the hormones of the gonads and thyroid glands as reproduction is under the influence of cross regulations of these hormones. This review presents a comprehensive compilation of important literatures on the impact of the current use pesticides in disruption of both the hypothalamic-pituitary-gonadal and hypothalamic-pituitary-thyroid axes particularly in birds addressing impacts on the reproductive impairments and overall fitness. In addition to the epidemiological studies, laboratory investigations those provide supportive evidences of the probable mechanisms of disruption in the wild also have been incorporated in this review. To accurately predict the endocrine-disruption of the pesticides as well as to delineate the risk associated with potential cumulative effects, studies are to be more focused on the environmentally realistic exposure dose, mixture pesticide exposures and transgenerational effects. In addition, strategic screening/appropriate methodologies have to be developed to reveal the endocrine disruption potential of the contemporary use pesticides. Demand for adequate quantitative structure-activity relationships and insilico molecular docking studies for timely validation have been highlighted.

Seasonality of reproduction in a subtropical free living finch Amandava amandava: Plasticity of adenohypophyseal gonadotropes, lactotropes and thyrotropes.

Introduction This study sought to decipher the mechanism of transitions between life-history stages in a seasonally reproducing subtropical finch, Amandava amandava delineating the plasticity of the gonadotropes (LH cells), lactotropes (PRL cells) and thyrotropes (TSH cells) in the pituitary gland including the pars tuberalis (PT), with regard to the in-situ expression, morphological characteristics, and alteration in the plasma levels of hormones. Methods Immunohistochemistry of LH, PRL, TSH cells, morphometry and densitometry of expressed hormones (Imge J software analysis), and ELISA for plasma hormonal levels were performed. Results LH, PRL and TSH cells showed remarkable plasticity during the annual seasonal reproductive cycle. In the PT, all the three cell types were detected during the breeding phase, with additional detection of the TSH immunoreactivity during the pre breeding and the PRL immunoreactivity during post breeding phases. Pars distalis (PD) expressions and the plasma levels of the LH and TSH were at the peak during the breeding phase, but the PRL peak was during the post-breeding phase. In addition to PRL in the neurohypophysis and in the median eminence, hypothalamic PRL and TSH were also elucidated. Conclusions This study suggests activation of the gonadal axis by the PT TSH which might transduces seasonal cues, but not specifically photoperiod, in the birds of the tropics/subtropics. Post breeding phase sustained high plasma TSH and peak plasma PRL might coordinate the transition to the non-breeding phase including the trigger of parental care as the later hormone assigned with. Hypothalamic TSH and PRL might influence events of seasonality through central modulation.

Neurotensin receptor-1 antagonist SR48692 modulation of high-fat diet induced reproductive impairment in male mice.

Neurotensin (NTS), a tridecapeptide of the gastrointestinal tract, has been implicated in the facilitation of lipid absorption on ingestion of a high-fat diet (HFD) especially via NTS receptors, NTSR1, NTSR2, and NTSR3, to cause lipid metabolic dysregulation and imbalance of the oxidant-antioxidant system. Oxidative stress induced a negative impact on reproductive function, affecting the reproductive organ and related reproductive hormones. The present study elucidated the efficacy of NTSR1 antagonist SR48692 in the modulation of HFD-induced reproductive impairment in male mice. Swiss albino mice (male, 23 ± 2 g) were maintained (6/group) for eight weeks; Group-I chow diet (CD), Group-II HFD, Group-III (HFD+SR48692L), Group-IV (HFD+SR48692H), Group-V (CD+SR48692L) and Group-VI (CD+SR48692H). SR48692 low (100 µg/kg b.w./SR48692L) and high-dose (400 µg/kg b.w./SR48692H) were given intraperitoneally for the last four weeks. Treatment with low-dose (SR48692L) to HFD-fed mice showed some efficacy in mitigating lipid dysregulation, oxidative stress, and reproductive impairment as evidenced by decreased triglycerides, total cholesterol, low-density lipoprotein cholesterol, leptin, and increased high-density lipoprotein cholesterol, increased antioxidant defense enzymes, reduction of histopathological scores in testis and increase in plasma level of LH, FSH and testosterone compared to that of HFD, but not up to CD. With the high-dose of antagonist (SR48692H) showed more adverse effects even from that of HFD. Treatment of both doses of SR48692 to CD-fed mice these effects become more extended. Less effectiveness of NTSR1 antagonist with the doses tried (low and high) in normalizing the lipid dysregulation and reproductive impairments might be due to the persistence of NTSR2/NTSR3-mediated lipid absorption.

Neurotensin agonist PD149163 modulates lipopolysaccharide induced inflammation and oxidative stress in the female reproductive system of mice.

Inflammation-mediated reproductive health problems in females have become an emerging concern. The present investigation was aimed to elucidate the efficacy of the PD149163, agonist of the type I neurotensin receptor, in preventing/ameliorating the lipopolysaccharide (LPS) induced inflammation of the female reproductive system of the mice. Female Swiss Albino Mice (8 weeks old) were maintained in three groups (6/group): Group I as Control, Group II and Group III were exposed to intraperitoneal (i.p) LPS (1 mg/kg bw) for 5 days followed by treatment with PD149163 (100 µg/kg BW i.p.) to Group III (LPS + PD) for 28 days. After termination of the experiment on 29th day, plasma levels of inflammatory cytokines, LH, FSH, estradiol, corticosterone, oxidative stress effects in the ovary and histopathological study of the ovary and uterine horn were done. LPS-induced inflammation of the ovary and uterine horn was ameliorated/prevented by PD149163 as reflected in the reduced histopathological scores, significant elevation of the plasma anti-inflammatory cytokine IL-10 and decrease of the pro inflammatory cytokines TNF-α and IL-6. Significant decrease of lipid peroxide, increase of antioxidant defense enzymes, Superoxide dismutase and Catalase in the ovary indicated reduction of oxidative stress. The plasma levels of the reproduction related hormones and corticosterone were restored. PD149163 acts as an anti-inflammatory and anti-oxidative agent in modulation of inflammation in the female reproductive system (ovary & uterine horn). These findings suggest that the therapeutic potential of the analogs of neurotensin including PD149163 should be explored for the treatment of the female reproductive health issues.

Role of the testicular capsule in seasonal modulation of the testis.

While the seasonal testicular cycle has been well studied regarding internal components, no attention has been given to the testicular capsule (tunica albuginea and tunica serosa). This study elucidated the structure-function modulations of intra-testicular functions by its capsule in the finch red munia (Amandava amandava) during the annual testicular cycle. The birds were studied during breeding (preparatory and breeding) and nonbreeding (regressive and quiescent) reproductive phases using hematoxylin-eosin and acridine orange-ethidium bromide capsule staining, hormonal ELISA (LH and testosterone) and immunohistochemical expression of neuropeptides (GnRH, GnIH) and androgen receptor (AR). The thickness of the tunica albuginea was significantly increased with multiple myoid layers during the nonbreeding phases (p < 0.05). The thickness of the tunica serosa was not altered, although characteristics and distribution of squamous cells showed significant seasonal alterations. Immunoreactive (-ir) AR and GnIH cells were differentially localized on both layers of the capsule. Strong AR-ir cells on tunica serosa during breeding phases showed increased expression of the receptor; a significant increase in plasma LH and testosterone was also observed during the breeding cycle (p < 0.01). Contrarily, intense GnIH-ir cells on both the capsular layers peaked during testicular regression. Differential structural alterations of the testicular capsule provide mechanical support and help maintain internal homeostasis in tune with changing seasons. The seasonal expressions and alterations of reproduction-related receptors, hormones, and neuropeptides provide evidence for the potential regulatory roles of the capsule in the peripheral modulation of intratesticular functions.

Neurotensin modulation of lipopolysaccharide induced inflammation of gut-liver axis: Evaluation using neurotensin receptor agonist and antagonist.

Lipopolysaccharide (LPS), a toxic component of the cell wall of Gram-negative bacteria, is a potent immune stressor. LPS-induced inflammation of the gut-liver axis is well demonstrated. Neurotensin (NTS), a tri-decapeptide present in the gastrointestinal tract, has anti-inflammatory, anti-oxidative, and growth-promoting properties. This study elucidated the efficacy of PD149163, the type I NTS receptor agonist (NTS1) in the modulation of LPS-induced inflammation of the gut-liver axis of mice. Young-adult female mice (Age: 8 weeks; BW: 25 ± 2.5 g) were maintained in six groups (6/group); Group I as control and Group II, III & IV were exposed to LPS (1 mg/kg BW/Day; i.p.) for five days. LPS pre-exposed Group III and Group IV mice were treated with NTS1 agonist PD149163 (100 µg/kg BW i.p.) and antagonist SR48692 (0.5 mg/kg BW i.p.) respectively for 28 days. Group V and Group VI mice were exposed to only PD149163 and only SR48692 respectively with the doses as mentioned above for 28 days. Group I and LPS-exposed Group II mice were also maintained four weeks without further treatment. Histopathology revealed LPS-induced inflammation of the gut and liver. Significant elevation of plasma TNF-α and IL-6 and serum ALT and AST reflected as biomarkers of inflammation. Oxidative stress on both organs was distinct from decreased glutathione reductase and increased lipid peroxidation. PD149163 but not SR48692 ameliorated LPS-induced inflammation in both gut and liver counteracting inflammatory responses and oxidative stress. The use of NTS agonists including PD149163 could be exploited for therapeutic intervention of inflammatory diseases including that of the gut-liver axis.

Thyroid disrupting pesticides mancozeb and fipronil in mixture caused oxidative damage and genotoxicity in lymphoid organs of mice.

The interference in endocrine signaling in particular of hypothyroid-pituitary-thyroid axis during embryonic/neonatal development increases the risk of long-lasting immune dysfunctioning. Anticipating that, environmentally realistic exposure of established thyroid disrupting pesticides of dithiocarbamate group mancozeb and phenylpyrazole fipronil was given to mice as individual and as mixtures (MIX-I/MIX-II) during the critical initiation phase of the immune response from postnatal day (PND) 31 till PND 60 (maturation phase). The direct exposure effect was assessed at PND 61 and the persistent effect was assessed at PND 91. Pronounced oxidative stress/genotoxicity in lymphoid organs at even low dose mixture exposure of pesticides (MIX-I/ MIX-II) continued to suppress the immune system till adulthood; might be due to the synergistic/additive action. The oxidative stress/genotoxicity effect was prevented on T4 supplementation to inhibit immunotoxicity as T4 is an immune enhancer and antioxidants. Oxidative stress/genotoxicity is suggested as a mechanism of thyroid disruption mediated immune suppression.

Atypical antipsychotic drug modulates early life infection induced impairment of hypothalamic-pituitary-adrenal axis: An age related study in mice.

Evidences from human and animal studies indicate that exposure to infection during early life act as a stressor to impair the hypothalamic-pituitary-adrenal (HPA) axis and may be one of the contributing factors of mental illness of later life. Several atypical antipsychotic drugs (AAPDs) proved to be effective in alleviating psychiatric illness through normalization of HPA axis. However, AAPD are least tried to evaluate their efficacy in modulation of HPA axis impaired under infection. The present study elucidated that the treatment with AAPD paliperidone (PAL: 0.025 mg/kg/bw and 0.05 mg/kg/bw) during periadolescence period (postnatal day 35- postnatal day 56) dose-dependently normalized the HPA axis of the female mice who were gestationally (gestational day 15 and 17) exposed to bacterial endotoxin lipopolysaccharide (LPS: 800 µg/kg/bw; intraperitoneally). The effectiveness of PAL treatment in counteracting the LPS induced hyperactivity of HPA axis was age-related, better observed at postnatal day 120 than at postnatal day 200. The PAL modulation of HPA axis reflected at different levels: inhibition of hypothalamic CRF expression and reduction in plasma levels of adrenocorticotropin and corticosterone. Histopathological alterations such as hypertrophy and/or hyperplasia in cortical zona fasciculata as well as medullary chromaffin cells of adrenal also normalized on PAL treatment. The comparatively long wash out period after drug treatment (postnatal day 57- postnatal day 200) along with age related hormonal imbalance could be correlated to less effectiveness of PAL on HPA axis at postnatal day 200. PAL modulation of HPA axis might be through maintenance of cytokines and reproductive axis homeostasis.

Thyroxine modulation of immune toxicity induced by mixture pesticides mancozeb and fipronil in mice.

AIM: The cross regulation between neuroendocrine system, particularly Hypothalamus-Pituitary-Thyroid (HPT) axis and immune system during embryonic/early neonatal developmental stages shapes the functional attribute of immune response throughout the life. Thus, disruption of immune system was anticipated on exposure to thyroid disrupting pesticides (TDPs) mancozeb (MCZ) and fipronil (FPN) during critical windows of early postnatal days (PND) development. MAIN METHODS: Mice were exposed to MCZ and FPN as individual (0.5% LD 50 each) and as mixtures (0.25% and 0.5% LD 50 each) from PND 31 (initiation phase of immune response) till PND 60 (Maturation phase). Thyroxine (T4) supplementation was given from PND 51 to PND 60. Assessment was done at PND 61 as well as at PND 91 (adults). KEY FINDINGS: Plasma level of thyroid hormones (T3 and T4) was reduced but pituitary hormone (TSH) increased till adulthood on exposure to mixture pesticides but not on individual exposure. Mixture pesticides also increased body weight gain and reduced survival rate in adults. Exposure of individual pesticides exert immunotoxicity but more pronounced immune suppression was observed in mixture pesticides exposed group as reflected in reduced relative weight and cellularity in spleen and thymus, reduced in vitro mitogenic (Con A/LPS) response of splenocytes and thymocytes (reduced proliferative index and increased apoptotic/necrotic death). T4 supplementation ameliorated thyroid disruptive and immunotoxic effect of pesticides. SIGNIFICANCE: The additive/synergistic toxicity as well as hypothyroidism induced by mixture pesticides has produced pronounced immune suppression that reflected till adulthood. Supplementation of T4 prevented thyroid axis disruption mediated immunosuppression.

Thyroid disrupting pesticides impair the hypothalamic-pituitary-testicular axis of a wildlife bird, Amandava amandava.

The effect of two thyroid disrupting pesticides (TDPs) mancozeb (MCZ) and imidacloprid (IMI) on the hypothalamic-pituitary-gonadal/testicular (HPG) axis of a seasonally breeding bird, Amandava amandava has been evaluated. Male birds (n=8/group) were exposed to each of the pesticide (0.25% LD50 of respective pesticide) as well as to their two equimixture doses (0.25% of LD50 of each and 0.5% LD50 of each) through food for 30d during pre-breeding stage of the reproductive cycle. Reduction in weight, volume and other histopathological features revealed testicular regression. Suppression of gonadotropin releasing hormone, increased expression of gonadotropin inhibitory hormone in the hypothalamus of exposed groups as well as impairment of plasma levels of the reproduction related hormones indicated the disruption of the HPG axis. The pesticides interference of the thyroid function during the critical phase of reproductive development impaired the HPG axis; more significantly in co-exposed groups suggesting the cumulative toxicity.

Neonatal Exposure to Endocrine Disrupting Chemicals Impairs Learning Behaviour by Disrupting Hippocampal Organization in Male Swiss Albino Mice.

Hippocampus is highly susceptible to endocrine disrupting chemicals exposure particularly during the critical phase of brain development. In this study, mice offspring were exposed to endocrine disruptors mancozeb (MCZ) and imidacloprid (IMI) individually (40 mg MCZ and 0.65 mg IMI/kg/day) as well as to their equimixture (40 mg MCZ + 0.65 mg IMI/kg/day) through the diet of lactating mothers from post-natal day (PND) 1 to PND 28. Half of the randomly selected male offspring were killed at PND 29, and the rest half were left unexposed and killed at PND 63. Brain weight, histology, plasma hormone profile and working memory performance were the various end-points studied. Brain weight was significantly decreased in the mixture-exposed group at PND 29, which persisted to PND 63. Total thickness of pyramidal cell layers decreased significantly along with misalignment, shrinkage and degeneration of pyramidal neurons in CA1 and CA3 regions of the IMI and mixture-exposed groups. The length and branch points of dendrites of pyramidal neurons were decreased significantly in mixture-exposed group at both PND 29 and PND 63. Dendritic spine density was also reduced in mixture-exposed group offspring. Testosterone level was significantly decreased only at PND 29, but corticosterone level was increased at both PND 29 and PND 63 in mixture-exposed offspring. T-maze task performance revealed significantly increased time duration and reduced path efficiency in mixture-exposed group offspring. The results thus indicate that pesticide mixture exposure could lead to changes in learning behaviour even at doses that individually did not induce any adverse effect on hippocampal organization.

Disruption of the hypothalamic-pituitary-thyroid axis on co-exposures to dithiocarbamate and neonicotinoid pesticides: Study in a wildlife bird, Amandava amandava.

Non-target organisms, including human and wildlife, are susceptible to deleterious effects of pesticide mixtures in their environment. Present study demonstrated the disruption of the hypothalamic-pituitary-thyroid (HPT) axis in a seasonally breeding wildlife bird Amandava amandava on co-exposure to dithiocarbamate mancozeb/MCZ and neonicotinoid imidacloprid/IMI, at concentrations even lower than respective environmentally realistic exposure level of each of the pesticide. Adult male birds (n=8/group) were exposed individually to 0.25% LD50 of each of MCZ (0.14mg) and IMI (2.75µl) followed by co-exposure to their equimixture as MIX-I (0.25% LD50 of each) and MIX-II (0.5% LD50 of each) through food for 30d in preparatory phase of reproductive cycle. Disruptions of thyroid gland and pituitary-thyroid axis were evident. Altered thyroid weight and volume, follicles with inactive colloids and lesions, decrease of height and nucleus-to-cytoplasm ratio of follicular epithelial cells were noted. Plasma levels of T4 and T3 were decreased, more significant in mixture groups than in individually exposed groups. Within co-exposed groups, comparatively high plasma T4 and T3 levels in MIX-II than MIX-I indicated dose non-responsiveness of the pesticides in mixtures; a characteristic displayed by endocrine disrupters. Plasma TSH level was increased in MCZ- and IMI- but decreased in MIX-I and MIX-II suggesting the disruption of the negative feedback and impairment of the HPT axis in co-exposed groups. Effects were more prominent in co-exposed groups due to combinatorial action and cumulative toxicity of pesticides. Considering the role of thyroid hormones in reproductive development, pesticides even in low dose could affect the thyroid homeostasis and reproductive axis.

Endocrine disrupting pesticides impair the neuroendocrine regulation of reproductive behaviors and secondary sexual characters of red munia (Amandava amandava).

The exposure effects of two endocrine disrupting pesticides (EDPs), mancozeb/MCZ and imidacloprid/IMI of the group dithiocarbamate and neonicotinoid respectively, on reproductive behaviors and secondary sexual characters have been studied in a seasonally breeding wildlife bird, red munia (Amandava amandava). Adult male birds were exposed to both the pesticides individually (0.25% LD50 of each) as well as co-exposed (MIX-I: 0.25% LD50 of each and MIX-II: 0.5% LD50 of each) through food for 30d in preparatory (July-August) and breeding (September-October) phase of reproductive cycle. Singing and pairing patterns started decreasing from 2nd week to complete disappearance during 4th week of pesticides exposures at both the phases of reproductive cycles. Similar trend was observed in the disappearance of spots on the plumage as well as color of both plumage and beak which turned black/gray from red. Pesticides caused impairment of the lactotropic as well as hypothalamic-pituitary-testicular (HPT) axes as there was increased plasma PRL and decreased LH, FSH and testosterone levels. Testicular expressions of GnRH and androgen receptor/AR were significantly decreased but that of GnIH significantly increased as compared to control. Significant differences among individually- and co-exposed groups were also present. Abnormalities in sexual behaviors and secondary sexual characteristics could be linked to inhibition of HPT axis and/or direct toxicity at the level of hypothalamus, pituitary and testis. In addition, pesticide-induced hyperprolactinemia as well as impaired thyroid hormones might have also affected maintenance of reproductive behaviors. On co-exposures, the more distinct impairments might be due to cumulative toxicity of pesticides.

Vitamin E pretreatment prevents the immunotoxicity of dithiocarbamate pesticide mancozeb in vitro: A comparative age-related assessment in mice and chick.

Pesticides used for crop protection cause life-threatening diseases affecting the immune system of non-target organisms including birds and mammals. Functionality of immune system is age-dependent; early- as well as old-life stages are more susceptible to toxic exposures because of less competent immune system. Vitamins are so far known to reduce toxic effect of several pesticides and/or xenobiotics. The present in vitro study elucidated immunotoxicity of fungicide mancozeb through comparable stages of immune system maturation in mice (1, 3, and 12months) and chicks (4, 8, and 11weeks). In vitro splenocytes viability on exposure to mancozeb was quantitatively assessed by MTT assay and qualitatively by acridine orange and ethidium bromide (AO/EB) double fluorescence staining. Mancozeb exposure dose dependently (250, 500, 1000, 2500, 5000 and 10,000ng/ml) decreased the splenocytes viability. The in vitro preventive effect of Vitamin E has also been explored on toxicity induced by mancozeb. The increased susceptibility observed both in early and aged groups was due to less/decline competence of the immune system.

Effect of acute hexavalent chromium exposure on pituitary-thyroid axis of a freshwater fish, Channa punctatus (Bloch).

Acute exposure to hexavalent chromium (10 mg L(-1) , 20 mg L(-1) , and 40 mg L(-1) potassium dichromate for 96 h) dose-dependently affected the pituitary-thyroid axis of teleost, Channa punctatus. Significant hypertrophy of the thyroid follicle was observed in 20 mg L(-1) and 40 mg L(-1) groups; the follicular epithelium was however hypertrophied only in 40 mg L(-1) group. The colloid depletion in the lumen of thyroid follicle was evident in 20 mg L(-1) and 40 mg L(-1) groups. Serum thyroid hormones (thyroxine/T4 and triiodothyronine/T3) level increased significantly at both the higher doses. Increased immunointensity and significant hypertrophy of the pituitary thyrotrophs (anti TSHß-immunoreactive cells) was observed in both 20 mg L(-1) and 40 mg L(-1) chromium-exposed fish. The increased thyroid hormones secretion observed in this study might be an adaptive response of the pituitary-thyroid axis under acute chromium-induced stress condition to maintain homeostasis. The long-term Cr(VI) exposures, however, may lead to attenuation/exhaustion of the pituitary-thyroid axis and pose serious threat to fish health and affect their population.

Atypical antipsychotic paliperidone prevents behavioral deficits in mice prenatally challenged with bacterial endotoxin lipopolysaccharide.

Studies on animal models provide enough evidences that old age appearance of psychosis on exposures to various insults during critical period of brain development could be prevented by antipsychotic drug treatment. Presently, gestational intervention of the atypical antipsychotic paliperidone (PAL) is done along with the exposure of bacterial endotoxin lipopolysaccharide/LPS hypothesizing that the drug would counteract and/or prevent the immune activation-induced behavioral deficits in mice. Effect of the PAL (0.05 mg/kg; GD 15-PND 28) in preventing reflex, sensorimotor and anxiety deficits in prenatally LPS-challenged (800 µg/kg; GD 15 and GD 17) mice was assessed at three different life stages: neonatal (PND 4-PND 14), adolescence (PND 35) and at adulthood (PND 85). LPS-induced behavioral deficits were recognizable even at neonatal and adolescence stages, though more pronounced at adulthood. In only PAL-treated group few behavioral deficits though observed both at neonatal and adult stages but less prominent than LPS group were found. PAL co-treatment prevented the abnormalities in nest-seeking behavior in neonates, anxiety abnormalities at adolescence and adulthood but not the sensorimotor impairment. The drug might have maintained the stress homeostasis to counteract the behavioral abnormalities as LPS-induced hypercorticosteronemia was prevented on PAL co-treatment. In view of the in utero exposure, comparatively low drug dose was selected. Though efficacy has been predicted, the dose was not effective to prevent all psychopathological impairments. Considering the wider objectives, it was not possible to conduct multi dose study simultaneously. Our ongoing study with higher dose may predict the effective PAL dose in prevention of psychiatric illness.

The neonicotinoid pesticide imidacloprid and the dithiocarbamate fungicide mancozeb disrupt the pituitary-thyroid axis of a wildlife bird.

Thyroid is an important homeostatic regulator of metabolic activities as well as endocrine mechanisms including those of reproduction. Present investigation elucidated the thyroid disrupting potential of a neonicotinoid imidacloprid and a dithiocarbamate mancozeb in a seasonally breeding wildlife bird, Red Munia (Amandava amandava) who is vulnerable to these two pesticides through diet (seed grains and small insects). Adult male birds were exposed to 0.5% LD50 mgkg(-1)bwd(-1) of both the pesticides through food for 30days during the preparatory and breeding phases. Weight, volume and histopathology of thyroid gland were distinctly altered. Disruption of thyroid follicles reflected in nucleus-to-cytoplasm ratio (N/C) in epithelial and stromal cells, epithelial cell hypertrophy and altered colloid volume. Impairment of thyroid axis was pesticide and phase specific as evident from the plasma levels of thyroid (T4 and T3) and pituitary (TSH) hormones. In preparatory phase, plasma TSH was increased in response to decrease of T4 on mancozeb exposure showing responsiveness of the hypothalamic-pituitary-thyroid (HPT) axis to feedback regulation. On imidacloprid exposure, however, plasma levels of both T4 and TSH were decreased indicating non-functioning of negative feedback mechanism. Increased plasma T3 in response to both the pesticides exposure might be due to synthesis from non-thyroidal source(s) in a compensatory response to decrease level of T4. In breeding phase, impairment of HPT axis was more pronounced as plasma T4, T3 and TSH were significantly decreased in response to both mancozeb and imidacloprid. Thus, low dose pesticide exposure could affect the thyroid homeostasis and reproduction.

Pesticides in mixture disrupt metabolic regulation: in silico and in vivo analysis of cumulative toxicity of mancozeb and imidacloprid on body weight of mice.

Pesticides acting as endocrine disrupting chemicals disrupt the homeostasis of body metabolism. The present study elucidated that the low dose coexposure of thyroid disrupting dithiocarbamate fungicide mancozeb (MCZ) and neonicotinoid insecticide imidacloprid (IMI) during lactation increased the risk of body weight gain in mice later in life. Body weight gain has been linked to pesticide-induced hypothyroidism and hyperprolactinemia and alteration of lipid profiles. In vivo results were substantiated with in silico molecular docking (MD) analysis that predicted the binding affinity of pesticides with thyroid hormone receptors (TRα and TRß) and peroxisome proliferator activated receptor gamma (PPARγ), the major nuclear receptors of peripheral fat metabolism. Binding potency of MCZ and IMI was compared with that of T3, and its antagonist ethylene thiourea (ETU) as well as PPARγ agonist (rosiglitazone) and antagonist (HL005). MD simulation predicted that both MCZ and IMI may compete with T3 for binding with TRs. Imidazole group of IMI formed hydrogen bonds with TRs like that of ETU. MCZ may compete with rosiglitazone and HL005 for PPARγ, but IMI showed no affinity. Thus while both MCZ and IMI could disrupt the TRs functioning, MCZ alone may affect PPARγ. Coexposure of pesticides decreased the plasma thyroid hormones and increased the cholesterol and triglyceride. Individual pesticide exposure in low dose might not exert the threshold response to affect the receptors signaling further to cause hormonal/metabolic impairment. Thus, cumulative response of the mixture of thyroid disrupting pesticides can disrupt metabolic regulation through several pathways and contribute to gain in body weight.

Acute spill-mimicking exposure effect of hexavalent chromium on the pituitary-ovarian axis of a teleost, Channa punctatus (Bloch).

Acute exposure to hexavalent chromium (as 10, 20, and 40 mg/L potassium dichromate for 96 h) adversely affected the pituitary-ovarian axis of a teleost Channa punctatus. The toxic impact of metal exposure on fish ovary was revealed in the form of increased percentage of atretic follicles, significantly in 20 mg/L and 40 mg/L exposure groups. The follicular atresia mostly occurred in vitellogenic (stage II and stage III) oocytes. Reduction of serum level of 17ß-estradiol was also significant in 20 mg/L and 40 mg/L exposure groups. The increase of LH-immunointensity of pituitary gonadotrophs (LHß-immunoreactive cells) and their hypertrophy was evident, significantly in fish of 40 mg/L exposed group. Thus, the present acute metal spill-mimicking laboratory study clearly demonstrated that short-term exposures to high doses of hexavalent chromium may disrupt reproduction of the fish and affect their population.