Alteration of the expression of pesticide-metabolizing enzymes in pregnant mice: potential role in the increased vulnerability of the developing brain

Examination of urinary pesticide concentrations, protective behaviors, and risk perceptions among Latino and Latina farmworkers in Southwestern Idaho

INTRODUCTION

Studies have documented high levels of pesticide exposure among men farmworkers; however, few have examined exposures or the experiences of women farmworkers. Data gaps also exist regarding farmworkers' perceived risk and control related to pesticides, information that is critical to develop protective interventions.

OBJECTIVE

We aimed to compare urinary pesticide biomarker concentrations between Latino and Latina farmworkers and examine associations with occupational characteristics, risk perceptions, perceived control, and protective behaviors.

METHODS

We enrolled a convenience sample of 62 farmworkers (30 men and 32 women) during the pesticide spray season from April-July 2022 in southwestern Idaho. Participants were asked to complete two visits within a seven-day period; at each visit, we collected a urine sample and administered a questionnaire assessing demographic and occupational information. Urine samples were composited and analyzed for 17 biomarkers of herbicides and of organophosphate (OP) and pyrethroid insecticides.

RESULTS

Ten pesticide biomarkers (TCPy, MDA, PNP, 3-PBA, 4-F-3-PBA, cis- and trans-DCCA, 2,4-D, Glyphosate, AMPA) were detected in >80% of samples. Men and women had similar urinary biomarker concentrations (p = 0.19-0.94); however, women worked significantly fewer hours than men (p = 0.01), wore similar or greater levels of Personal Protective Equipment (PPE), and were slightly more likely to report having experienced an Acute Pesticide Poisoning (26% of women vs. 14% of men; p = 0.25). We observed inconsistencies in risk perceptions, perceived control, and protective behaviors among men.

DISCUSSION

Our study is one the first to examine pesticide exposure and risk perceptions among a cohort of farmworkers balanced on gender. Taken with previous findings, our results suggest that factors such as job tasks, biological susceptibility, or access to trainings and protective equipment might uniquely impact women farmworkers' exposure and/or vulnerability to pesticides. Women represent an increasing proportion of the agricultural workforce, and larger studies are needed to disentangle these findings.

Impact of pregnancy related hormones on drug metabolizing enzyme and transport protein concentrations in human hepatocytes

Pregnancy alters the disposition and exposure to multiple drugs indicated for pregnancy-related complications. Previous in vitro studies have shown that pregnancy-related hormones (PRHs) alter the expression and function of certain cytochrome P450s (CYPs) in human hepatocytes. However, the impact of PRHs on hepatic concentrations of non-CYP drug-metabolizing enzymes (DMEs) and transport proteins remain largely unknown. In this study, sandwich-cultured human hepatocytes (SCHH) from five female donors were exposed to vehicle or PRHs (estrone, estradiol, estriol, progesterone, cortisol, and placental growth hormone), administered individually or in combination, across a range of physiologically relevant PRH concentrations for 72 h. Absolute concentrations of 33 hepatic non-CYP DMEs and transport proteins were quantified in SCHH membrane fractions using a quantitative targeted absolute proteomics (QTAP) isotope dilution nanoLC-MS/MS method. The data revealed that PRHs altered the absolute protein concentration of various DMEs and transporters in a concentration-, isoform-, and hepatocyte donor-dependent manner. Overall, eight of 33 (24%) proteins exhibited a significant PRH-evoked net change in absolute protein concentration relative to vehicle control (ANOVA p < 0.05) across hepatocyte donors: 1/11 UGTs (9%; UGT1A4), 4/6 other DMEs (67%; CES1, CES2, FMO5, POR), and 3/16 transport proteins (19%; OAT2, OCT3, P-GP). An additional 8 (24%) proteins (UGT1A1, UGT2B4, UGT2B10, FMO3, OCT1, MRP2, MRP3, ENT1) exhibited significant PRH alterations in absolute protein concentration within at least two individual hepatocyte donors. In contrast, 17 (52%) proteins exhibited no discernable impact by PRHs either within or across hepatocyte donors. Collectively, these results provide the first comprehensive quantitative proteomic evaluation of PRH effects on non-CYP DMEs and transport proteins in SCHH and offer mechanistic insight into the altered disposition of drug substrates cleared by these pathways during pregnancy.

Deltamethrin-Evoked ER Stress Promotes Neuroinflammation in the Adult Mouse Hippocampus

Endoplasmic reticulum (ER) stress and neuroinflammation are involved in the pathogenesis of many neurodegenerative disorders. Previously, we reported that exposure to pyrethroid insecticide deltamethrin causes hippocampal ER stress apoptosis, a reduction in neurogenesis, and learning deficits in adult male mice. Recently, we found that deltamethrin exposure also increases the markers of neuroinflammation in BV2 cells. Here, we investigated the potential mechanistic link between ER stress and neuroinflammation following exposure to deltamethrin. We found that repeated oral exposure to deltamethrin (3 mg/kg) for 30 days caused microglial activation and increased gene expressions and protein levels of TNF-α, IL-1β, IL-6, gp91phox, 4HNE, and iNOS in the hippocampus. These changes were preceded by the induction of ER stress as the protein levels of CHOP, ATF-4, and GRP78 were significantly increased in the hippocampus. To determine whether induction of ER stress triggers the inflammatory response, we performed an additional experiment with mouse microglial cell (MMC) line. MMCs were treated with 0-5 µM deltamethrin for 24-48 h in the presence or absence of salubrinal, a pharmacological inhibitor of the ER stress factor eIF2α. We found that salubrinal (50 µM) prevented deltamethrin-induced ER stress, as indicated by decreased levels of CHOP and ATF-4, and attenuated the levels of GSH, 4-HNE, gp91phox, iNOS, ROS, TNF-α, IL-1β, and IL-6 in MMCs. Together, these results demonstrate that exposure to deltamethrin leads to ER stress-mediated neuroinflammation, which may subsequently contribute to neurodegeneration and cognitive impairment in mice.

Nerve Growth Factor Protects Against Pyrethroid-Induced Endoplasmic Reticulum (ER) Stress in Primary Hippocampal Neurons

Neurotrophins are a family of growth factors crucial for growth and survival of neurons in the developing and adult brain. Reduction in neurotrophin levels is associated with reduced neurogenesis and cognitive deficits in rodents. Recently, we demonstrated that long-term exposure to low levels of the pyrethroid pesticide deltamethrin causes hippocampal endoplasmic reticulum (ER) stress and learning deficits in mice. Here, we found that nerve growth factor (NGF) mRNA and protein were selectively reduced in the hippocampus of deltamethrin-treated mice. To explore potential mechanisms responsible for this observation, we employed mouse primary hippocampal neurons. Exposure of neurons to deltamethrin (1-5 μM) caused ER stress as indicated by increased levels of C/EBP-homologous protein (CHOP) and glucose-regulated protein 78 (GRP78). These changes were accompanied by increased levels of caspase-12, activated caspase-3, and decreased levels of NGF. Inhibition of ER stress with the eukaryotic initiation factor 2 alpha (eIF2α) inhibitor salubrinal abolished deltamethrin-induced activation of caspase-12 and caspase-3, and restored NGF levels. Furthermore, deltamethrin decreased Akt (protein kinase B) phosphorylation, which was significantly prevented by co-treatment with NGF or SC-79 in cells. Collectively, these results demonstrate that the loss of NGF following ER stress may contribute to deltamethrin-induced apoptosis in the hippocampus through the Akt signaling pathway, and that this may provide a plausible mechanism for impaired learning and memory observed following exposure of mice to deltamethrin.

Pharmacokinetics of tenofovir alafenamide with and without cobicistat in pregnant and postpartum women living with HIV

OBJECTIVE

To evaluate the pharmacokinetics of tenofovir alafenamide (TAF) 10 mg with cobicistat and 25 mg without boosting in pregnant and postpartum women with HIV and to characterize TAF placental transfer and infant washout pharmacokinetics.

DESIGN

Open-label, multicenter phase IV prospective study of TAF pharmacokinetics during pregnancy, postpartum, delivery, and infant washout.

METHODS

Pregnant women receiving TAF 10 mg with cobicistat or TAF 25 mg without boosting as part of clinical care had intensive pharmacokinetic assessments performed during the second and third trimesters, and 6-12 weeks postpartum. Maternal and cord blood samples were collected at delivery, and washout pharmacokinetic samples were collected in infants. TAF concentrations were quantified using liquid chromatography/mass spectrometry. Comparisons between pregnancy and postpartum were made using geometric mean ratios (90% confidence intervals) and Wilcoxon signed-rank tests.

RESULTS

Thirty-one pregnant women receiving TAF 10 mg with cobicistat-boosting and 27 women receiving TAF 25 mg without boosting were enrolled. TAF exposures did not significantly differ between pregnancy and postpartum when administered as 10 mg with cobicistat. Antepartum TAF exposures with the 25 mg dose were 33-43% lower in comparison with postpartum, but comparable with those measured in nonpregnant adults. TAF was below the lower limit of quantitation in 43 of 44 cord blood, 41 of 45 maternal blood at delivery, and all infant washout samples.

CONCLUSION

TAF exposures were comparable or higher than those measured in nonpregnant adults during pregnancy and postpartum. These findings provide reassurance on adequate TAF exposures during pregnancy, and support efforts to expand the use of TAF in pregnant women with HIV.

Maternal and cord serum levels of polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) among Lebanese pregnant women and predictors of exposure

In this study, the six indicator non-dioxin-like polychlorinated biphenyls NDL-PCBs (PCB28, PCB52, PCB101, PCB138, PCB153, PCB180), as well as four organochlorine pesticides (OCPs), hexachlorobenzene (HCB), β-hexachlorocyclohexane (β-HCH), dichlorodiphenyltrichloroethane (DDT), and dichlorodiphenyldichlorethylene (DDE) were measured in 98 maternal and 49 cord sera samples of a group of Lebanese women who gave birth in three hospitals in Greater Beirut, between March and July 2018. Results showed that the levels of these persistent organic pollutants (POPs) in maternal serum were below critical limits as well as those in other countries (Tunisia, France, Portugal, Spain, Poland, Greenland, Canada, Brazil, and China). The ratios of cord serum concentrations to maternal serum concentrations of analyzed POPs were higher than 1. PCB maternal serum concentrations were found to be linked to illegal incineration (OR = 5.78; p = 0.004) as well as eggs (OR = 4.68; p = 0.027) and fruits and vegetables consumption (OR = 3.92; p = 0.016). OCP concentrations were linked to red meat and cold cuts intake (OR = 3.67-4.59; p = 0.001-0.004). While PCB levels were not correlated to newborns anthropometric measurements, OCP levels in cord serum were found to be positively linked to the birth length of newborns (p = 0.014-0.027).

Molecular mechanisms of developmental toxicities of azoxystrobin and pyraclostrobin toward zebrafish (Danio rerio) embryos: Visualization of abnormal development using two transgenic lines

Azoxystrobin (AZ) and pyraclostrobin (PY) are strobilurin fungicides that inhibit fungal mitochondrial respiration. In this study, a representative model, zebrafish (Danio rerio), was used as a test species for acute and developmental toxicity. Survival and malformation rates were observed only PY-treated embryos, with an LC₅₀ value of 77.75 ppb accompanied by a dramatic decrease in hatching rate, while AZ did not show great mortality. Morphological changes were observed in PY-treated embryos with the occurrence of pericadial edema at 25 ppb. A delay in growth was observed after treatment with pyraclostrobin at 50 ppb. Use of genetically engineered Tg(cmlc:EGFP) allowed fluorescence observation during heart development. PY interfered with normal heart development via upregulation of the nppa gene responsible for the expression of natriuretic peptides. Heart function was dramatically reduced as indicated by reduced heart rates. Increased expression of the nppa gene was also seen in AZ-treated embryos. The expression level of cyp24a1 was also up-regulated, while ugt1a1 and sult1st6 were down-regulated after treatment of zebrafish embryos with AZ or PY. Overall, strobilurin fungicides might inhibit normal heart formation and function within the range of concentrations tested.

Neurotoxicity of pesticides

Pesticides are unique environmental contaminants that are specifically introduced into the environment to control pests, often by killing them. Although pesticide application serves many important purposes, including protection against crop loss and against vector-borne diseases, there are significant concerns over the potential toxic effects of pesticides to non-target organisms, including humans. In many cases, the molecular target of a pesticide is shared by non-target species, leading to the potential for untoward effects. Here, we review the history of pesticide usage and the neurotoxicity of selected classes of pesticides, including insecticides, herbicides, and fungicides, to humans and experimental animals. Specific emphasis is given to linkages between exposure to pesticides and risk of neurological disease and dysfunction in humans coupled with mechanistic findings in humans and animal models. Finally, we discuss emerging techniques and strategies to improve translation from animal models to humans.

The anti-parkinsonian drug zonisamide reduces neuroinflammation: Role of microglial Nav 1.6

Parkinson's disease (PD), the second most common age-related progressive neurodegenerative disorder, is characterized by dopamine depletion and the loss of dopaminergic (DA) neurons with accompanying neuroinflammation. Zonisamide is an-anti-convulsant drug that has recently been shown to improve clinical symptoms of PD through its inhibition of monoamine oxidase B (MAO-B). However, zonisamide has additional targets, including voltage-gated sodium channels (Na_v), which may contribute to its reported neuroprotective role in preclinical models of PD. Here, we report that Na_v1.6 is highly expressed in microglia of post-mortem PD brain and of mice treated with the parkinsonism-inducing neurotoxin MPTP. Administration of zonisamide (20 mg/kg, i.p. every 4 h × 3) following a single injection of MPTP (12.5 mg/kg, s.c.) reduced microglial Na_v 1.6 and microglial activation in the striatum, as indicated by Iba-1 staining and mRNA expression of F4/80. MPTP increased the levels of the pro-inflammatory cytokine TNF-α and gp91^phox, and this was significantly reduced by zonisamide. Together, these findings suggest that zonisamide may reduce neuroinflammation through the down-regulation of microglial Na_v 1.6. Thus, in addition to its effects on parkinsonian symptoms through inhibition of MAO-B, zonisamide may have disease modifying potential through the inhibition of Na_v 1.6 and neuroinflammation.

Alternative microglial activation is associated with cessation of progressive dopamine neuron loss in mice systemically administered lipopolysaccharide

Inflammation arising from central and/or peripheral sources contributes to the pathogenesis of multiple neurodegenerative diseases including Parkinson's disease (PD). Emerging data suggest that differential activation of glia could lead to the pathogenesis and progression of PD. Here, we sought to determine the relationship between lipopolysaccharide (LPS) treatment, loss of dopaminergic neurons and differential activation of glia. Using a model of repeated injections with LPS (1mg/kg, i.p. for 4days), we found that LPS induced a 34% loss of dopamine neurons in the substantia nigra 19days after initiation of treatment, but no further cell loss was observed at 36days. LPS induced a strong pro-inflammatory response with increased mRNA expression of pro-inflammatory markers, including tumor necrosis factor-α (4.8-fold), inducible nitric oxide synthase (2.0-fold), interleukin-1 beta (8.9-fold), interleukin-6 (10.7-fold), and robust glial activation were observed at 1day after final dose of LPS. These pro-inflammatory genes were then reduced at 19days after treatment, when there was a rise in the anti-inflammatory genes Ym1 (1.8-fold) and arginase-1 (2.6-fold). Additionally, 36days after the last LPS injection there was a significant increase in interleukin-10 (2.1-fold) expression. The qPCR data results were supported by protein data, including cytokine measurements, western blotting, and immunofluorescence in brain microglia. Taken together, these data demonstrate that progressive neurodegeneration in the substantia nigra following LPS is likely arrested by microglia shifting to an anti-inflammatory phenotype. Thus, strategies to promote resolution of neuroinflammation may be a promising avenue to slow the progressive loss of dopamine neurons in PD.

Regulation of drug metabolism and toxicity by multiple factors of genetics, epigenetics, lncRNAs, gut microbiota, and diseases: a meeting report of the 21st International Symposium on Microsomes and Drug Oxidations (MDO)

Variations in drug metabolism may alter drug efficacy and cause toxicity; better understanding of the mechanisms and risks shall help to practice precision medicine. At the 21^st International Symposium on Microsomes and Drug Oxidations held in Davis, California, USA, in October 2-6, 2016, a number of speakers reported some new findings and ongoing studies on the regulation mechanisms behind variable drug metabolism and toxicity, and discussed potential implications to personalized medications. A considerably insightful overview was provided on genetic and epigenetic regulation of gene expression involved in drug absorption, distribution, metabolism, and excretion (ADME) and drug response. Altered drug metabolism and disposition as well as molecular mechanisms among diseased and special populations were presented. In addition, the roles of gut microbiota in drug metabolism and toxicology as well as long non-coding RNAs in liver functions and diseases were discussed. These findings may offer new insights into improved understanding of ADME regulatory mechanisms and advance drug metabolism research.

Pyrethroid Insecticides Directly Activate Microglia Through Interaction With Voltage-Gated Sodium Channels

Microglia are considered to be the resident immune cells of the central nervous system and contribute significantly to ongoing neuroinflammation in a variety of neurodegenerative diseases. Recently, we and others identified that voltage-gated sodium channels (VGSC) are present on microglia cells and contribute to excessive accumulation of intracellular Na⁺and release of major pro-inflammatory cytokine tumor necrosis factor alpha (TNF-α). Based on this finding and the fact that pyrethroid pesticides act on VGSC, we hypothesized that exposure of microglia to the pyrethroid pesticides, permethrin and deltamethrin, would activate microglia and increase the release of TNF-α. BV2 cells or primary microglia were treated with 0-5 µM deltamethrin or permethrin in the presence or absence of tetrodotoxin (TTX), a VGSC blocker for 24-48 h. Both pyrethroids caused a rapid Na⁺influx and increased accumulation of intracellular sodium [(Na⁺)i] in the microglia in a dose- and time-dependent manner, which was significantly reduced by TTX. Furthermore, deltamethrin and permethrin increased the release of TNF-α in a dose- and time-dependent manner, which was significantly reduced by pre-treatment of cells with TTX. These results demonstrate that pyrethroid pesticides may directly activate microglial cells through their interaction with microglial VGSC. Because neuroinflammation plays a key role in many neurodegenerative diseases, these data provide an additional mechanism by which exposure to pyrethroid insecticides may contribute to neurodegeneration.

Pathophysiological implications of neurovascular P450 in brain disorders

Over the past decades, the significance of cytochrome P450 (CYP) enzymes has expanded beyond their role as peripheral drug metabolizers in the liver and gut. CYP enzymes are also functionally active at the neurovascular interface. CYP expression is modulated by disease states, impacting cellular functions, detoxification, and reactivity to toxic stimuli and brain drug biotransformation. Unveiling the physiological and molecular complexity of brain P450 enzymes will improve our understanding of the mechanisms underlying brain drug availability, pharmacological efficacy, and neurotoxic adverse effects from pharmacotherapy targeting brain disorders.

Isoform-Specific Regulation of Mouse Carboxylesterase Expression and Activity by Prototypical Transcriptional Activators

Nuclear receptors and transcription factors regulate the mRNA expression of many drug metabolizing enzymes, including the carboxylesterases (Ces). However, there are few data regarding whether these changes in mRNA expression result in alteration of protein levels or activity. In the present study, we sought to determine the isoform-specific regulation of hepatic Ces mRNA expression and activity following the administration of pharmacological activators of the constitutive androstane receptor (CAR), pregnane X receptor (PXR), and nuclear factor E2-related protein (Nrf2) to mice. The CAR activator 1,4-bis-[2-(3,5-dichloropyridyloxy)] benzene (TCPOBOP) and PXR ligand pregnenolone-16a-carbonitrile (PCN) increased Ces mRNA expression of various Ces2 isoforms, whereas the Nrf2 activator butylated hydroxyanisole primarily reduced Ces3a mRNA expression and induced Ces1g mRNA. TCPOBOP and PCN increased Ces2 hydrolytic activity in an isoform-specific manner. Taken together, these data demonstrate that activation of CAR, PXR, and Nrf2 regulates not only Ces mRNA expression, but also isoform-specific activity.

Reduction in urinary organophosphate pesticide metabolites in adults after a week-long organic diet

BACKGROUND

Conventional food production commonly uses organophosphate (OP) pesticides, which can have negative health effects, while organic food is deemed healthier because it is produced without these pesticides. Studies suggest that organic food consumption may significantly reduce OP pesticide exposure in children who have relatively higher pesticide exposure than adults due to their different diets, body weight, behaviour and less efficient metabolism.

OBJECTIVES

A prospective, randomised, crossover study was conducted to determine if an organic food diet reduces organophosphate exposure in adults.

METHODS

Thirteen participants were randomly allocated to consume a diet of at least 80% organic or conventional food for 7 days and then crossed over to the alternate diet. Urinary levels of six dialkylphosphate metabolites were analysed in first-morning voids collected on day 8 of each phase using GC-MS/MS with detection limits of 0.11-0.51 μg/L.

RESULTS

The mean total DAP results in the organic phase were 89% lower than in the conventional phase (M=0.032 [SD=0.038] and 0.294 [SD=0.435] respectively, p=0.013). For total dimethyl DAPs there was a 96% reduction (M=0.011 [SD=0.023] and 0.252 [SD=0.403] respectively, p=0.005). Mean total diethyl DAP levels in the organic phase were half those of the conventional phase (M=0.021 [SD=0.020] and 0.042 [SD=0.038] respectively), yet the wide variability and small sample size meant the difference was not statistically significant.

CONCLUSIONS

The consumption of an organic diet for one week significantly reduced OP pesticide exposure in adults. Larger scale studies in different populations are required to confirm these findings and investigate their clinical relevance.

Prenatal cigarette smoke exposure causes hyperactivity and aggressive behavior: role of altered catecholamines and BDNF

Smoking during pregnancy is associated with a variety of untoward effects on the offspring. However, recent epidemiological studies have brought into question whether the association between neurobehavioral deficits and maternal smoking is causal. We utilized an animal model of maternal smoking to determine the effects of prenatal cigarette smoke (CS) exposure on neurobehavioral development. Pregnant mice were exposed to either filtered air or mainstream CS from gestation day (GD) 4 to parturition for 4h/d and 5d/wk, with each exposure producing maternal plasma concentration of cotinine equivalent to smoking <1 pack of cigarettes per day (25ng/ml plasma cotinine level). Pups were weaned at postnatal day (PND) 21 and behavior was assessed at 4weeks of age and again at 4-6months of age. Male, but not female, offspring of CS-exposed dams demonstrated a significant increase in locomotor activity during adolescence and adulthood that was ameliorated by methylphenidate treatment. Additionally, male offspring exhibited increased aggression, as evidenced by decreased latency to attack and number of attacks in a resident-intruder task. These behavioral abnormalities were accompanied by a significant decrease in striatal and cortical dopamine and serotonin and a significant reduction in brain-derived neurotrophic factor (BDNF) mRNA and protein. Taken in concert, these data demonstrate that prenatal exposure to CS produces behavioral alterations in mice that are similar to those observed in epidemiological studies linking maternal smoking to neurodevelopmental disorders. Further, these data also suggest a role for monaminergic and BDNF alterations in these effects.

Drug metabolism and transport during pregnancy: how does drug disposition change during pregnancy and what are the mechanisms that cause such changes?

There is increasing evidence that pregnancy alters the function of drug-metabolizing enzymes and drug transporters in a gestational-stage and tissue-specific manner. In vivo probe studies have shown that the activity of several hepatic cytochrome P450 enzymes, such as CYP2D6 and CYP3A4, is increased during pregnancy, whereas the activity of others, such as CYP1A2, is decreased. The activity of some renal transporters, including organic cation transporter and P-glycoprotein, also appears to be increased during pregnancy. Although much has been learned, significant gaps still exist in our understanding of the spectrum of drug metabolism and transport genes affected, gestational age-dependent changes in the activity of encoded drug metabolizing and transporting processes, and the mechanisms of pregnancy-induced alterations. In this issue of Drug Metabolism and Disposition, a series of articles is presented that address the predictability, mechanisms, and magnitude of changes in drug metabolism and transport processes during pregnancy. The articles highlight state-of-the-art approaches to studying mechanisms of changes in drug disposition during pregnancy, and illustrate the use and integration of data from in vitro models, animal studies, and human clinical studies. The findings presented show the complex inter-relationships between multiple regulators of drug metabolism and transport genes, such as estrogens, progesterone, and growth hormone, and their effects on enzyme and transporter expression in different tissues. The studies provide the impetus for a mechanism- and evidence-based approach to optimally managing drug therapies during pregnancy and improving treatment outcomes.