Acute effects of pyrethroids on serotonin release in the striatum of awake rats: an in vivo microdialysis study

Acetylcholinesterase biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine neurotransmitter: A literature review

Neurotoxic pesticides are a group of chemicals that pose a severe threat to both human health and the environment. These molecules are also known to accumulate in the food chain and persist in the environment, which can lead to long-term exposure and adverse effects on non-target organisms. The detrimental effects of these pesticides on neurotransmitter levels and function can lead to a range of neurological and behavioral symptoms, which are closely associated with neurodegenerative diseases. Hence, the accurate and reliable detection of these neurotoxic pesticides and associated neurotransmitters is essential for clinical applications, such as diagnosis and treatment. Over the past few decades, acetylcholinesterase (AchE) biosensors have emerged as a sensitive and reliable tool for the electrochemical detection of neurotoxic pesticides and acetylcholine. These biosensors can be tailored to utilize the high specificity and sensitivity of AchE, enabling the detection of these chemicals. Additionally, enzyme immobilization and the incorporation of nanoparticles have further improved the detection capabilities of these biosensors. AchE biosensors have shown tremendous potential in various fields, including environmental monitoring, clinical diagnosis, and pesticide residue analysis. This review summarizes the advancements in AchE biosensors for electrochemical detection of neurotoxic pesticides and acetylcholine over the past two decades.

Prenatal pyrethroid exposure and lung function among school-aged children

BACKGROUND

Previous epidemiological evidence mainly focused on the adverse effects of prenatal exposure to pyrethroid insecticides (PYRs) on respiratory health during childhood. It remains unclear whether the PYR exposures can also impact on children's lung function.

OBJECTIVES

To explore the potential effects of prenatal PYR exposures on lung function in a population of Chinese children.

METHODS

This study included 233 mother-child dyads from the Laizhou Wan Birth Cohort (LWBC), Shandong province, northern China, between September 2010 and December 2013. Three metabolites of PYRs [3-phenoxybenzoic acid (3-PBA), and cis- and trans-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (cis-DCCA and trans-DCCA)] were measured using gas chromatography-mass spectrometry (GC-MS) in maternal urine samples collected at recruitment. Lung function was assessed with spirometry in children aged 6-8 years. Multivariable linear regression and generalized linear models (GLMs) assessed the associations of prenatal PYR exposures with lung function in children.

RESULTS

Among the PYR metabolites, 3-PBA (81.5%) were most frequently detected, followed by trans-DCCA (55.4%) and cis-DCCA (21.9%). The 3-PBA concentration was associated with a 1% decrease in FEV₁/FVC in the highest quartiles of exposure compared to the lowest quartile, with a potential dose response association (p-trend = 0.085). Our findings provide a suggestive effect modification by sex, with girls being more susceptible than the boys (p-trend = 0.011). However, there were no associations between the trans-DCCA concentration and lung function parameters.

CONCLUSION

Prenatal 3-PBA concentrations were associated with a modest decrease in FEV₁/FVC among school-aged children, and the association was slightly more pronounced for the girls than for the boys.

Effects of pyrethroids on brain development and behavior: Deltamethrin

Deltamethrin (DLM) is a Type II pyrethroid pesticide widely used in agriculture, homes, public spaces, and medicine. Epidemiological studies report that increased pyrethroid exposure during development is associated with neurobehavioral disorders. This raises concern about the safety of these chemicals for children. Few animal studies have explored the long-term effects of developmental exposure to DLM on the brain. Here we review the CNS effects of pyrethroids, with emphasis on DLM. Current data on behavioral and cognitive effects after developmental exposure are emphasized. Although, the acute mechanisms of action of DLM are known, how these translate to long-term effects is only beginning to be understood. But existing data clearly show there are lasting effects on locomotor activity, acoustic startle, learning and memory, apoptosis, and dopamine in mice and rats after early exposure. The most consistent neurochemical findings are reductions in the dopamine transporter and the dopamine D1 receptor. The data show that DLM is developmentally neurotoxic but more research on its mechanisms of long-term effects is needed.

Single or combined exposure to chlorpyrifos and cypermethrin provoke oxidative stress and downregulation in monoamine oxidase and acetylcholinesterase gene expression of the rat's brain

The extensive uses of organophosphates and pyrethroids have made it necessary to investigate the neurotoxicity of their combination as they may implicate in the neurodegenerative syndromes. Monoamine oxidase-A (MAO-A) and acetylcholinesterase (AChE) gene expression in the rat brain were evaluated after independent and combined intoxications with chlorpyrifos and cypermethrin. Twenty-four mature male rats were equally distributed into four groups. The first one was kept as a control group, whereas the second, third and fourth were orally gavage with chlorpyrifos (16.324 mg/kg), cypermethrin (25.089 mg/kg) and their combination (9.254 mg/kg), respectively, for 4 weeks. As compared to the control group, intoxications with chlorpyrifos and/or cypermethrin revealed significant (P < 0.05) declines in the levels of brain neurotransmitters (dopamine and serotonin) plus the enzymatic activities of MAO-A, AChE and sodium-potassium adenosine triphosphatase. The mRNA genes expression of MAO-A and AChE have also confirmed the enzymatic actions. Moreover, the oxidative injury recorded as the levels of malondialdehyde and nitric oxide markedly increased (P < 0.01), while the total thiol content reduced and the histopathological outcomes have confirmed these impacts. In conclusion, chlorpyrifos and cypermethrin revealed antagonistic inhibitions on the brain MAO-A and AChE gene regulation through neurotransmission deteriorations and oxidative damage, which could describe their contributions in the neuropathological progressions.

Deltamethrin Exposure Daily From Postnatal Day 3-20 in Sprague-Dawley Rats Causes Long-term Cognitive and Behavioral Deficits

Pyrethroids are synthetic insecticides that act acutely on voltage gated sodium channels to prolong channel opening and depolarization. Epidemiological studies find that exposure to pyrethroids are associated with neurological and developmental abnormalities in children. The long-term effects of type II pyrethroids, such as deltamethrin (DLM), on development have received little attention. We exposed Sprague-Dawley rats to DLM by gavage at doses of 0, 0.25, 0.5, and 1.0 mg/kg/day from postnatal day (P) 3-20 in a split-litter design. Following behavioral testing as adults, monoamine levels, release, and mRNA were assessed via high performance liquid chromatography, microdialysis, and qPCR, respectively. Long-term potentiation (LTP) was assessed at P25-35. Developmental DLM exposure resulted in deficits in allocentric and egocentric learning and memory, increased startle reactivity, reduced conditioned contextual freezing, and attenuated MK-801 induced hyperactivity compared with controls. Startle and egocentric learning were preferentially affected in males. Deltamethrin-treated rats exhibited increased CA1 hippocampal LTP, decreased extracellular dopamine release by microdialysis, reduced dopamine D1 receptor mRNA expression in neostriatum, and decreased norepinephrine levels in the hippocampus. The data indicate that neonatal DLM exposure has adverse long-term effects on learning, memory, startle, glutamatergic function, LTP, and norepinephrine.

Bifenthrin-induced neurotoxicity in rats: involvement of oxidative stress

Extensive use of synthetic pyrethroids has resulted in serious human health issues. Induction of oxidative stress is an important mechanism of action of most pesticides including pyrethroids. In the present study, we have elucidated the possible role of oxidative stress in bifenthrin-induced neurotoxicity. Adult male Wistar rats were administered bifenthrin (3.5 and 7 mg per kg body weight p.o.) for 30 days. Behavioral studies were conducted on a set of randomly selected rats from each treatment group after completion of treatment. Neurochemical parameters were assessed 24 h after the last dose was administered. The selected behavioral and neurochemical endpoints were also assessed 15 days after cessation of exposure to reveal whether the neurobehavioral changes produced by bifenthrin were temporary or permanent. Deficits in motor activity, motor incoordination, and cognitive impairment were observed after exposure to bifenthrin. Levels of biogenic amines viz. dopamine (DA) and its metabolites, i.e. 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), epinephrine (EPN), norepinephrine (NE), and serotonin (5-HT) altered in the frontal cortex, corpus striatum, and hippocampus of bifenthrin-treated rats. A decrease in the activity of acetylcholinesterase (AChE) occurred in all regions of the brain. Both doses of bifenthrin significantly induced lipid peroxidation (LPO) and increased protein carbonyl levels in the frontal cortex, corpus striatum, and hippocampus of rats. The activities of antioxidant enzymes, i.e. catalase, superoxide dismutase, and glutathione peroxidase, were also suppressed in all selected regions of the brain. A trend of recovery was, however, observed in all the behavioral and neurochemical endpoints 15 days after withdrawal of exposure. Oxidative stress seems to play an important role in bifenthrin-induced neurotoxicity. Our study suggests that long-term exposure to these compounds can produce detrimental effects.

Impairment of mitochondrial integrity and redox status in brain regions during a low-dose long-term exposition of rats to pyrethrinoïds: the preventive effect of quercetin

Pyrethrinoïds are synthetic pesticides widely used in agriculture and farms to protect crops from weeds, insects, fungi, and molds. Increased and uncontrolled use of these pollutants can have harmful effects on human health via consumption of contaminated food products. In the present study, deltamethrin (DLT = 3.72 mg/kg) and Bifenthrin (BF = 2.6 mg/kg) were used during a long-term exposition in the rats to assess their effect on mitochondrial integrity and function in different brain areas (hippocampus, striatum, cortex, and cerebellum). The results of this study have shown that chronic treatment of rats by both DLT and BF, on their own or in a mixture, has induced a significant increase in mitochondrial MDA, but when quercetin (Que) was co-administered with pesticides, this enhancement has been prevented in the almost of treated rats compared to solvent and control groups. In hippocampus area, GSH has significantly increased in all treated rats, except for BF and DLT-Que.-treated groups. In striatum, GSH has been depleted in the BF and DLT-treated groups compared to control and solvent groups; in contrast, when Que. was associated with pesticides, the rate of this tripeptide has been maintained at normal levels. In the cortex and cerebellum, GSH has been depleted significantly in all treated animals but has increased in DLT-Que. and mixture-Que.-treated groups in the cerebral cortex, at the same time; it has been maintained at normal levels in BF-Que.-treated groups in the cerebellum compared to control and solvent rats. On the other side, the results of this study have shown a loss of catalase (CAT) and glutathione S-transferase (GST) activities in all brain regions of pesticide-treated rats, but such a fall in enzymatic activities has been prevented by Que. when it was co-administered to rats with pesticides at the dose of 5 mg/kg, except in the cerebellum. In addition, this study has shown mitochondria's swelling in almost all the brain areas with exception of the cerebellum, providing information about a loss of mitochondrial membrane integrity in brain neurons of rats exposed to pyrethrinoïds. Furthermore, preventive administration of Que., in association with pesticides (5 mg/kg) or their mixture (10 mg/kg), has prevented mitochondria swelling in almost all of the analyzed brain tissues.

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.

Transcriptomic changes underlie altered egg protein production and reduced fecundity in an estuarine model fish exposed to bifenthrin

Pyrethroid pesticides are a class of insecticides found to have endocrine disrupting properties in vertebrates such as fishes and in human cell lines. Endocrine disrupting chemicals (EDCs) are environmental contaminants that mimic or alter the process of hormone signaling. In particular, EDCs that alter estrogen and androgen signaling pathways are of major concern for fishes because these EDCs may alter reproductive physiology, behavior, and ultimately sex ratio. Bifenthrin, a pyrethroid with escalating usage, is confirmed to disrupt estrogen signaling in several species of fish, including Menidia beryllina (inland silverside), an Atherinid recently established as a euryhaline model. Our main objective was to broadly assess the molecular and physiological responses of M. beryllina to the ng/L concentrations of bifenthrin typically found in the environment, with a focus on endocrine-related effects, and to discern links between different tiers of the biological hierarchy. As such, we evaluated the response of juvenile Menidia to bifenthrin using a Menidia-specific microarray, quantitative real-time polymerase chain reaction (qPCR) on specific endocrine-related genes of interest, and a Menidia-specific ELISA to the egg-coat protein choriogenin, to evaluate a multitude of molecular-level responses that would inform mechanisms of toxicity and any underlying causes of change at higher biological levels of organization. The sublethal nominal concentrations tested (0.5, 5 and 50ng/L) were chosen to represent the range of concentrations observed in the environment and to provide coverage of a variety of potential responses. We then employed a 21-day reproductive assay to evaluate reproductive responses to bifenthrin (at 0.5ng/L) in a separate group of adult M. beryllina. The microarray analysis indicated that bifenthrin influences a diverse suite of molecular pathways, from baseline metabolic processes to carcinogenesis. A more targeted examination of gene expression via qPCR demonstrated that bifenthrin downregulates a number of estrogen-related transcripts, particularly at the lowest exposure level. Choriogenin protein also decreased with exposure to increasing concentrations of bifenthrin, and adult M. beryllina exposed to 0.5ng/L had significantly reduced reproductive output (fertilized eggs per female). This reduction in fecundity is consistent with observed changes in endocrine-related gene expression and choriogenin production. Taken together, our results demonstrate that environmental concentrations of bifenthrin have potential to interfere with metabolic processes, endocrine signaling, and to decrease reproductive output.

Evaluation of changes in monoamine levels and apoptosis induced by cyfluthrin in rats

The aim of this study was to evaluate monoamine and mitochondrial cytochrome c levels and lipid peroxidation in adult male rats treated with cyfluthrin (14 mg kg⁻¹dose; approximately 1/10 of the LD₅₀value) for 14 days. This study also examined cyfluthrin induced-apoptosisviathe signaling proteins Bcl-2, caspase-9 and caspase-3, and possible anti-apoptotic effects of Alfa-basic crystallin.