Impact of Environmental Risk Factors on Mitochondrial Dysfunction, Neuroinflammation, Protein Misfolding, and Oxidative Stress in the Etiopathogenesis of Parkinson's Disease.

As a prevalent progressive neurodegenerative disorder, Parkinson's disease (PD) is characterized by the neuropathological hallmark of the loss of nigrostriatal dopaminergic (DAergic) innervation and the appearance of Lewy bodies with aggregated α-synuclein. Although several familial forms of PD have been reported to be associated with several gene variants, most cases in nature are sporadic, triggered by a complex interplay of genetic and environmental risk factors. Numerous epidemiological studies during the past two decades have shown positive associations between PD and several environmental factors, including exposure to neurotoxic pesticides/herbicides and heavy metals as well as traumatic brain injury. Other environmental factors that have been implicated as potential risk factors for PD include industrial chemicals, wood pulp mills, farming, well-water consumption, and rural residence. In this review, we summarize the environmental toxicology of PD with the focus on the elaboration of chemical toxicity and the underlying pathogenic mechanisms associated with exposure to several neurotoxic chemicals, specifically 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), rotenone, paraquat (PQ), dichloro-diphenyl-trichloroethane (DDT), dieldrin, manganese (Mn), and vanadium (V). Our overview of the current findings from cellular, animal, and human studies of PD provides information for possible intervention strategies aimed at halting the initiation and exacerbation of environmentally linked PD.

Biotransformation Mechanism of Pesticides by Cytochrome P450: A DFT Study on Dieldrin.

Pesticide biotransformation, especially by cytochrome P450 enzymes (CYPs), may produce metabolites with substantially altered toxicological and physicochemical profiles, which has drawn great attention as a basis for environmental risk assessment. CYPs are active in the metabolism of various reactions of pesticides, and there are potentially different short-lived oxidant species in CYPs (Compound I vs Compound 0), which make elucidating their biotransformation mechanism challenging. To facilitate this task, we performed density functional theory (DFT) calculations to explore the puzzling bifurcation pathways of dieldrin by CYPs. The results show that the two-oxidant mechanism does not work, while the bifurcation pathways are within the mechanistic framework of a two-state reactivity of Compound I. Specifically, 9-hydroxy-dieldrin as a hydroxylation product is formed via H-abstraction and essentially barrierless C-9 alkyl radical rebound in the doublet state; while 3-ketone-dieldrin as a dechlorination product is formed via H-abstraction, C-9 alkyl radical cyclization, and C-3 cyclized radical rebound in the quartet state followed by HCl elimination, originating from a significant barrier for C-9 alkyl radical rebound in the quartet state to provide this radical sufficient lifetime for cyclization. Thus, the ratio [dechlorination]/[hydroxylation] can be estimated as 1:35, consistent with the experimental findings. We envision that application of computational chemistry has a great potential in revealing the complex biotransformation mechanisms of pesticides.

Plasma Cholinesterase Activity in Female Green Turtles Chelonia mydas Nesting in Laguna de Terminos, Mexico Related to Organochlorine Pesticides in Their Eggs.

The inhibition of cholinesterase (ChE) activity has been used as a biomarker of exposure to organophosphate and carbamate insecticides. ChE of nesting female green turtles (Chelonia mydas) were biochemically characterized using two substrates, acetylthiocholine iodide and butyrylthiocholine iodide, and three ChE inhibitors (eserine sulfate, BW284C51 and iso-OMPA). The results indicated that BChE is the predominant plasma ChE in female C. mydas, but with atypical properties that differ from those found in human BChE. Eggs from green turtles nesting at two sites in Laguna de Terminos contained µg g-1 (wet weight) quantities of organochlorine (OC) pesticides. Drins (aldrin, dieldrin, endrin, endrin ketone, endrin aldehyde) were found at the highest concentrations with no significant differences in the concentrations in eggs collected at the two sampling sites. A negative relationship was found between levels of OC pesticides in eggs and BChE activity in the plasma of female turtles laying the eggs. Since OC pesticides are not cholinesterase inhibitors, we hypothesized that this inverse relationship may be related to an antagonistic effect between OCs and organophosphate pesticides and mobilization of OCs from the fatty tissues of the female turtles into their eggs. However, further study is required to verify the hypothesis. It is also possible that other contaminants, such as petroleum hydrocarbons are responsible for the modulation of cholinesterase activity in female turtles.

Biodegradation of Aldrin and Dieldrin by the White-Rot Fungus Pleurotus ostreatus.

Aldrin and its metabolite dieldrin are persistent organic pollutants that contaminate soil in many parts of the world. Given the potential hazards associated with these pollutants, an efficient degradation method is required. In this study, we investigated the ability of Pleurotus ostreatus to transform aldrin as well as dieldrin in pure liquid cultures. This fungus completely eliminated aldrin in potato dextrose broth (PDB) medium during a 14-day incubation period. Dieldrin was detected as the main metabolite, and 9-hydroxylaldrin and 9-hydroxyldieldrin were less abundant metabolites. The proposed route of aldrin biotransformation is initial metabolism by epoxidation, followed by hydroxylation. The fungus was also capable of degrading dieldrin, a recalcitrant metabolite of aldrin. Approximately 3, 9, and 18% of dieldrin were eliminated by P. ostreatus in low-nitrogen, high-nitrogen, and PDB media, respectively, during a 14-day incubation period. 9-Dihydroxydieldrin was detected as a metabolite in the PDB culture, suggesting that the hydroxylation reaction occurred in the epoxide ring. These results indicate that P. ostreatus has potential applications in the transformation of aldrin as well as dieldrin.

Levels of persistent organic pollutants in breast milk of Maya women in Yucatan, Mexico.

In this study, 24 breast milk samples, obtained from rural Maya women, from municipalities of Yucatan, Mexico, were analyzed for organochlorine pesticide (OCP) residues by gas chromatography. Recent studies have shown that Maya communities have a poor perception about the proper usage and handling of OCP. The karstic soil in this area has a high vulnerability to groundwater pollution by the use of OCP in agriculture and livestock activities. The impact of the ecosystem on human health is much more critical due to the prevailing poverty and a very low educational level of these communities. About 30% of the Maya population consumes water directly from contaminated wells and sinkholes, resulting in a chronic exposure to OCP. The samples served to identify and quantify high levels of OCP residues (18.43 mg/kg of heptachlor epoxide and 1.92 mg/kg of endrin in the metropolitan zone; 2.10 mg/kg of dieldrin, 0.117 mg/kg of endosulfan II, 0.103 mg/kg of heptachlor, 0.178 mg/kg of endrin, and 0.127 mg/kg of endrin aldehyde in the main agricultural zone and on the west coast). The detected levels of OCP residues are a major concern and represent a potential risk to women and children in the region. This could be associated with the high rates of cervical uterine and breast cancer mortality in Yucatan. Thus, regulations on the usage of OCP and their enforcement are necessary, and it is important to establish a yearly monitoring program for OCP residues in breast milk and groundwater, as well as to implement health promotion programs for women in particular and the general population in general.

Organochlorine Pesticides Residues in Human Breast Milk from the Middle Governorates in Jordan in 2013/2014.

One hundred samples of mother breast milk were gathered from six middle governorates and districts in Jordan in 2013/2014 to monitor Organochlorine pesticides pollutants. The results showed clearly that banned organochlorine pesticides are still detected in the monitored samples in low concentration despite banning of these persistent pollutants in Jordan since 36 years ago. However, the results indicated that 1% of the contaminated samples contained ß-HCH, 5% γ-HCH, 3% p,p'-DDD, 2% heptachlor, 45% p,p'-DDE and 3% p,p'-DDT. In addition, these monitored samples had no residues of aldrin, dieldrin, α-endosulfan, ß-endosulfan, HCB, o,p'-DD, o,p'-DDT and o,p'-DDE. In conclusion, there was a decline in the residues of Organochlorine pesticides, particularly DDT group members.

Dieldrin accumulation, distribution in plant parts and phytoextraction potential for several plant species and Cucurbita pepo varieties.

Dieldrin, an organochlorine pesticide (OCP) widely used for crop protection in the second half of the 20th century till the 70's, is worldwide still present in arable soils. It can be transferred to crops, notably cucurbits, depending on plant species and cultivars. Finding strategies to decrease OCP bioavailability in soil is therefore a main concern. Phytomanagement strategies could provide (i) ready-to-use short term solution for maintaining the production of edible plant parts with dieldrin concentrations below the Maximum Residue Limits (MRL) and (ii) long-term solution for dieldrin phytoextraction reducing progressively its bioavailability in the soil. This field study aimed at determining dieldrin accumulation capacities and allocation pattern in 17 non-Cucurbitaceae species and 10 Cucurbita pepo varieties, and assessing the dieldrin phytoextraction potential of these plant species when grown to maturity in a historically dieldrin-contaminated soil. Out of the non-Cucurbitaceae species, vetiver was the only one able to accumulate significant amounts of dieldrin, which mainly remained in its roots. All C. pepo varieties were able to uptake and translocate high dieldrin amounts into the shoots, leading to the highest phytoextraction potential. Despite the intraspecific variability in dieldrin concentration in zucchini plant parts, mainly in the reproductive organs, the phytoextraction capacity for shoots and fruits was high for all tested varieties (147 to 275 µg dieldrin plant-1, corresponding to 5.6 % of the n-heptane extractable soil dieldrin), even for the one with low fruit dieldrin concentration. Both food safety and phytoextraction could be achieved by selecting productive zucchini varieties displaying low dieldrin concentration in fruits and high one in shoots.

Cellular localization of dieldrin and structure-activity relationship of dieldrin analogues in dopaminergic cells.

The incidence of Parkinson's disease (PD) correlates with environmental exposure to pesticides, such as the organochlorine insecticide, dieldrin. Previous studies found an increased concentration of the pesticide in the striatal region of the brains of PD patients and also that dieldrin adversely affects cellular processes associated with PD. These processes include mitochondrial function and reactive oxygen species production. However, the mechanism and specific cellular targets responsible for dieldrin-mediated cellular dysfunction and the structural components of dieldrin contributing to its toxicity (toxicophore) have not been fully defined. In order to identify the toxicophore of dieldrin, a structure-activity approach was used, with the toxicity profiles of numerous analogues of dieldrin (including aldrin, endrin, and cis-aldrin diol) assessed in PC6-3 cells. The MTT and lactate dehydrogenase (LDH) assays were used to monitor cell viability and membrane permeability after treatment with each compound. Cellular assays monitoring ROS production and extracellular dopamine metabolite levels were also used. Structure and stereochemistry for dieldrin were found to be very important for toxicity and other end points measured. Small changes in structure for dieldrin (e.g., comparison to the stereoisomer endrin) yielded significant differences in toxicity. Interestingly, the cis-diol metabolite of dieldrin was found to be significantly more toxic than the parent compound. Disruption of dopamine catabolism yielded elevated levels of the neurotoxin, 3,4-dihydroxyphenylacetaldehyde, for many organochlorines. Comparisons of the toxicity profiles for each dieldrin analogue indicated a structure-specific effect important for elucidating the mechanisms of dieldrin neurotoxicity.

Organochlorine pesticides in green mussel, Perna viridis, from the Cienfuegos Bay, Cuba.

The green mussel, Perna viridis, was used to measure bioaccumulated levels of organochlorine pesticides in the marine environment of Cuba. Samples were collected in the Cienfuegos Bay between January and December 2010. The organochlorine pesticides (i.e. DDT, Dieldrin, Chlordane, Endosulfan, HCB, Aldrin, Heptachlor and Lindane) were quantified by gas chromatography. The sum of all organochlorine pesticides in P. viridis was 6.31 ng g(-1). The concentration ranged from 3.53 to 4.42 ng g(-1) dry weight (dw) for DDTs (i.e. sum of pp' DDT, pp' DDD, op' DDE and pp' DDE); 1.7-1.9 ng g(-1) dw for Dieldrin; 0.17-0.20 ng g(-1) dw for Chlordanes; 0.14-0.16 ng g(-1) dw for Endosulfan; 0.11-0.17 ng g(-1) dw for HCB; 0.07-0.11 ng g(-1) dw for Aldrin; 0.046-0.054 ng g(-1) dw for Heptachlor and 0.035-0.039 ng g(-1) dw for Lindane. These levels can be considered as low when compared to reported values from similar studies conducted elsewhere in the world. The concentrations of all organochlorines residues detected in this study fell below the EU Maximum Residue Limits.

Muscarinic acetylcholine receptor activation synergizes the knockdown and toxicity of GABA-gated chloride channel insecticides.

BACKGROUND: Pest management requires continual identification of new physiological targets and strategies to control pests affecting agriculture and public/animal health. We propose the muscarinic system as a target for agrochemicals because of its physiological importance. Unlike the muscarinic system, gamma-amino butyric acid (GABA) receptors are an established insecticide target. Here, we investigated target-site synergism using small molecule probes (agonist and antagonist) against the muscarinic system and their ability to enhance the toxicity of GABAergic insecticides in Drosophila melanogaster (Meigen). RESULTS: Oral delivery of pilocarpine (muscarinic agonist) enhanced the toxicity of dieldrin, fipronil, and lindane, resulting in synergist ratios (SRs) between 4-32-fold (orally delivered) or between 2-67-fold when insecticides were topically applied. The synergism between pilocarpine and the GABA-insecticides was greater than the synergism observed with atropine (muscarinic antagonist), and was greater, or comparable, to the synergism observed with the metabolic inhibitor piperonyl butoxide. In addition to lethality, pilocarpine increased the knockdown of lindane. The mechanism of synergism was also investigated in the central nervous system using extracellular electrophysiology, where pilocarpine (3 µmo/L) lowered the half-maximal inhibitory concentration (IC50 ) of lindane from 1.3 (0.86-1.98) µmol/L to 0.17 (0.14-0.21) µmol/L and fipronil's IC50 from 2.2 (1.54-3.29) µmol/L to 0.56 (0.40-0.77) µmol/L. CONCLUSION: Convergence of the cellular function between the muscarinic and GABAergic systems enhanced the insecticidal activity of GABA receptor blocking insecticides through the modulation of the central nervous system (CNS). The future impact of the findings could be the reduction of the active ingredient needed in a formulation with the development of muscarinic synergists. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Isolation and identification of dieldrin-degrading Pseudonocardia sp. strain KSF27 using a soil-charcoal perfusion method with aldrin trans-diol as a structural analog of dieldrin.

We isolated a novel aerobic dieldrin-degrading bacterium from an enrichment culture in a soil-charcoal perfusion system. Enrichment culture using a soil-charcoal perfusion system was an effective way to obtain microorganisms that degrade recalcitrant compounds. The soil-charcoal perfusion was performed using aldrin trans-diol, which was a metabolite of dieldrin. Aldrin trans-diol had higher bioavailability (2.5 mg/l) than dieldrin (0.1-0.25 mg/l), therefore it is possible for microorganisms to utilize it as a substrate in soil. After 100 days of circulation and three exchanges of the medium, the enriched charcoal was harvested and a bacterium isolated. The isolate was designated as strain KSF27 and was found to be closely related to Pseudonocardia spp. as determined by 16S rRNA sequencing analysis. Strain KSF27 degraded aldrin trans-diol by 0.05 µmol/l from an initial concentration of 25.5 µmol/l. The metabolite of aldrin trans-diol was detected by HPLC/MS and determined to be aldrindicarboxylic acid based on retention time and the MS fragment. Moreover, strain KSF27 degraded dieldrin from 14.06 µmol/l to 2.01 µmol/l over a 10-day incubation at 30°C. This strain degraded dieldrin and other persistent organochlorine pesticides, such as α-endosulfan, ß-endosulfan, endosulfan sulfate, heptachlor, heptachlor epoxide and chlordecone.

Bottlenose dolphins as indicators of persistent organic pollutants in the western North Atlantic Ocean and northern Gulf of Mexico.

Persistent organic pollutants (POPs) including legacy POPs (PCBs, chlordanes, mirex, DDTs, HCB, and dieldrin) and polybrominated diphenyl ether (PBDE) flame retardants were determined in 300 blubber biopsy samples from coastal and near shore/estuarine male bottlenose dolphins (Tursiops truncatus) sampled along the U.S. East and Gulf of Mexico coasts and Bermuda. Samples were from 14 locations including urban and rural estuaries and near a Superfund site (Brunswick, Georgia) contaminated with the PCB formulation Aroclor 1268. All classes of legacy POPs in estuarine stocks varied significantly (p < 0.05) among sampling locations. POP profiles in blubber varied by location with the most characteristic profile observed in bottlenose dolphins sampled near the Brunswick and Sapelo estuaries along the Georgia coast which differed significantly (p < 0.001) from other sites. Here and in Sapelo, PCB congeners from Aroclor 1268 dominated indicating widespread food web contamination by this PCB mixture. PCB 153, which is associated with non-Aroclor 1268 PCB formulations, correlated significantly to human population indicating contamination from a general urban PCB source. Factors influencing regional differences of other POPs were less clear and warrant further study. This work puts into geographical context POP contamination in dolphins to help prioritize efforts examining health effects from POP exposure in bottlenose dolphins.

Alterations in thyroid hormone status in Greenland sledge dogs exposed to whale blubber contaminated with organohalogen compounds.

As a model of high trophic level carnivores, sledge dogs were fed from 2 to 18 months of age with minke whale blubber containing organohalogen compounds (OHC) corresponding to 128 µg PCB/day. Controls were fed uncontaminated porcine fat. Thyroid hormone levels were assessed in 7 exposed and 7 control sister bitches (sampled at age 6-18 months) and 4 exposed and 4 control pups, fed the same diet as their mothers (sampled age 3-12 months). Lower free and total T3 and T4 were seen in exposed vs. control bitches beyond 10 months of age, and total T3 was lower through 3-12 months of age in exposed pups. A negative correlation with thyroid gland weight was significant for ΣDDT, as was a positive association with total T3 for dieldrin. This study therefore supports observational data that OHCs may adversely affect thyroid functions, and it suggests that OHC exposure duration of 10 months or more may be required for current OHC contamination levels to result in detectable adverse effects on thyroid hormone dynamics.

Biodegradation of dieldrin by a soil fungus isolated from a soil with annual endosulfan applications.

An aerobic dieldrin-degrading fungus, Mucor racemosus strain DDF, was isolated from a soil to which endosulfan had been annually applied for more than 10 years until 2008. Strain DDF degraded dieldrin to 1.01 microM from 14.3 microM during a 10-day incubation at 25 degrees C. Approximately 0.15 microM (9%) of aldrin trans-diol was generated from the dieldrin degradation after a 1-day incubation. The degradation of dieldrin by strain DDF was detected over a broad range of pH and concentrations of glucose and nitrogen sources. Extracellular fluid without mycelia also degraded dieldrin. Strain DDF degraded not only dieldrin but also heptachlor, heptachlor epoxide, endosulfan, endosulfan sulfate, DDT, and DDE. Endosulfan sulfate and heptachlor were degraded by 0.64 microM (95%) and 0.75 microM (94%), respectively, whereas endosulfan and DDE were degraded by 2.42 microM (80%) and 3.29 microM (79%), respectively, and DDT and heptachlor epoxide were degraded by 6.95 microM (49.3%) and 5.36 microM (67.5%), respectively, compared with the control, which had a concentration of approximately 14 microM. These results suggest that strain DDF could be a candidate for the bioremediation of sites contaminated with various persistent organochlorine pesticides including POPs.

Preliminary note on potential use of forage crops for soil phytoremediation of dieldrin.

The aim of this trial was to evaluate the feasibility of using tall fescue (Festuca arundinacea) and alfalfa (Medicago sativa) for phytoremediation of dieldrin. Experimental trial was carried out in greenhouse with temperature and light control. Each tested crop were seeded in individual pots (10 plants/pot) filled with contaminated soil (47 microg/kg dieldrin) and uncontaminated soil collected in sites located in the province of Latina (Italy). Samples of soil, root, and aerial part of plants were analysed at 3 and 6 months after seeding. The analytical determinations in soil and plant samples were carried out by GLC-ECD and confirmed by GLC-MS. After 6 months in the greenhouse, recoveries of dieldrin from soil planted with tall fescue and alfalfa were significantly lower than recoveries in unplanted control soil. Dieldrin residue values in root did not differ between the two different sampling times for each forage crop tested, but they were always higher in fescue than in alfalfa. Residue levels in aerial part were low (< 10 microg/kg) in the two forage crops. Preliminary results seem to confirm the ability of tested plants to enhance dissipation of dieldrin in soil at low level of contamination.

Strong Adsorption of Dieldrin by Parent and Processed Montmorillonite Clays.

Widespread use of pesticides has resulted in the accumulation of pesticide residues in the environment due to their persistence and stability. To reduce potential exposures, we have developed broad-acting clay-based sorbents that can be included in the diet as enterosorbents to reduce the bioavailability and toxicity of chemicals. In the present study, parent and acid-processed calcium montmorillonite clays (CM and APM, respectively) were used to determine their potential as sorbents of the organochlorine insecticide dieldrin. We used adsorption isotherms, thermodynamics, and dosimetry studies to determine the capacities and affinities of the clays, the enthalpies of the binding reactions, and potential doses of sorbent that could protect against high exposures. Adsorption isotherms for APM fit a Langmuir model with high enthalpy (suggesting chemisorption) and high capacity (Qmax value = 0.45 mol kg-1 ), indicating tight binding of dieldrin. Cultures of Hydra vulgaris were used to determine the ability of sorbents to protect a living organism from dieldrin toxicity. The inclusion of acid-processed clays resulted in the highest reduction of dieldrin toxicity (70%) in the hydra. Further work indicated that both CM and APM can significantly reduce the bioavailability of dieldrin from soil (p ≤ 0.01). These results suggest that APM (and similar clays) can be effective sorbents of dieldrin and may be included in the diet and/or soil to protect against environmental exposures. Environ Toxicol Chem 2020;39:517-525. © 2019 SETAC.

Anti-RDL and Anti-mGlutR1 Receptors Antibody Testing in Honeybee Brain Sections using CRISPR-Cas9.

Cluster Regularly Interspaced Short Palindromic Repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) is a gene editing technique widely used in studies of gene function. We use this method in this study to check for the specificity of antibodies developed against the insect GABAA receptor subunit Resistance to Dieldrin (RDL) and a metabotropic glutamate receptor mGlutR1 (mGluRA). The antibodies were generated in rabbits against the conjugated peptides specific to fruit flies (Drosophila melanogaster) as well to honeybees (Apis mellifera). We used these antibodies in honeybee brain sections to study the distribution of the receptors in honeybee brains. The antibodies were affinity purified against the peptide and tested with immunoblotting and the classical method of preadsorption with peptide conjugates to show that the antibodies are specific to the corresponding peptide conjugates against which they were raised. Here we developed the CRISPR-Cas9 technique to test for the reduction of protein targets in the brain 48 h after CRISPR-Cas9 injection with guide RNAs designed for the corresponding receptor. The CRISPR-Cas9 method can also be used in behavioral analyses in the adult bees when one or multiple genes need to be modified.

Formation of "photodieldrin" by microorganisms.

Photodieldrin, previously reported as the major conversion product of dieldrin by sunlight, was found among the metabolic products of dieldrin among microorganisms isolated from various environments including soil, water (Lake Michigan), rat intestines, and rumen stomach contents of a cow.

Dieldrin: degradation by soil microorganism.

An attempt was made to discover microorganisms that degrade dieldrin, an extremely stable chlorinated hydrocarbon insecticide. Examination of more than 500 isolates from soil that had been heavily contaminated with various insecticides revealed the existence of a few microbes that are very active in degrading this compound to various metabolites.

Chlorinated hydrocarbon insecticides: root uptake versus vapor contamination of soybean foliage.

The major environmental source of DDT (dichlorodiphenyltrichlo-roethane) residues in soybean plants arises from vapor movement from contaminated soil surfaces. In contrast, the presence of dieldrin, endrin, and heptachlor results primarily from root uptake and translocation through stems to leaves and seeds.