DEHP toxicity on vision, neuromuscular junction, and courtship behaviors of Drosophila

Extralong hot-spots sensor for SERS sensitive detection of phthalate plasticizers in biological tear and serum fluids

Phthalate plasticizers (PAEs) illegally used in food pose a great threat to human health. A new and efficient sensing platform for the sensitive detection of the PAE residues in biological fluids needs to be designed and developed. Here, we report a simple and reliable surface-enhanced Raman spectroscopy (SERS) active platform with extralong hot spots of Au nanobipyramids@Ag nanorods (Au NBPs@Ag NRs) for the rapid and sensitive detection of PAEs in biological fluids. To achieve high activity, Au NBPs@Ag NRs with different shell lengths were fabricated by controlling the synthesis conditions, and the corresponding SERS properties were investigated by using crystal violet (CryV) and butyl benzyl phthalate (BBP). The experimental results showed that a longer shell length correlated to greater Raman activity, which was confirmed by finite-difference time-domain (FDTD) electromagnetic simulation. More importantly, the extralong hot spots of the Au NBPs@Ag NR SERS-active substrate showed excellent homogeneity and reproducibility for the CryV probe molecules (6.21%), and the detection limit was 10-9 M for both BBP and diethylhexyl phthalate (DEHP). Furthermore, through the standard addition method, an extralong hot spots SERS substrate could achieve highly sensitive detection of BBP and DEHP in serum and tears fluids, and the detection limit was as low as 3.52 × 10-8 M and 2.82 × 10-8 M. Therefore, the Au NBPs@Ag NR substrate with an extraordinarily long surface is efficient and versatile, and can potentially be used for high-efficiency sensing analysis in complex biological fluids.

DEHP and DINP accelerate aging effects in male and female of Drosophila melanogaster depend on AKT/FOXO pathway

Phthalates are commonly used as plasticizers. Numerous studies have focused on endocrine, reproductive, and developmental toxicity of phthalates exposure to male organisms. In recent years, some studies looking into the aging effects of phthalates exposure in D. melanogaster showed discrepant results. In this study, we compared the different concentrations of Di(2-ethylhexyl) phthalate (DEHP) and di-isononyl phthalate (DINP) for acute and chronic treatment for different gender D. melanogaster and explored the potential mechanism of DEHP and DINP exposure. The results showed that acute exposure to DEHP or DINP at a high dose significantly decreased the lifespan of female and male D. melanogaster under HFD stress. Chronic exposure significantly decreased the lifespan of flies in all exposure groups except for the low-dose DINP exposure female group. Among them, in the normal feeding group, we found that female flies seemed to be more resistant to DEHP or DINP exposure. Meanwhile, the locomotion ability and fertility of flies exhibited a dose-dependent decline. Furthermore, phthalates did not significantly reduce the lifespan or health status of akt and foxo mutant flies in the mutant fly assays, and real-time quantitative-PCR (q-PCR) data revealed akt and foxo significant change with 10 μM DEHP or DINP treatment. This suggests that akt and foxo played a role in the process by which DEHP and DINP caused age-related declines in D. melanogaster.

Integrated Studies on Male Reproductive Toxicity of Bis(2-ethylhexyl)-tetrabromophthalate: in Silico, in Vitro, ex Vivo, and in Vivo

Bis(2-ethylhexyl)tetrabromophthalate (TBPH) has been widely detected in the environment and organisms; thus, its toxic effects on male reproduction were systematically studied. First, we found that TBPH can stably bind to the androgen receptor (AR) based on in silico molecular docking results and observed an antagonistic activity, but not agonistic activity, on the AR signaling pathway using a constructed AR-GRIP1 yeast assay. Subsequently, we validated the adverse effects on male germ cells by observing inhibited androgen production and proliferation in Leydig cells upon in vitro exposure and affected general motility and motive tracks of zebrafish sperm upon ex vivo exposure. Finally, the in vivo reproductive toxicity was demonstrated in male zebrafish by reduced mating behavior in F0 generation when paired with unexposed females and abnormal development of their offspring. In addition, reduced sperm motility and impaired germ cells in male zebrafish were also observed, which may be related to the disturbed homeostasis of sex hormones. Notably, the specifically suppressed AR in the brain provides further evidence for the antagonistic effects as above-mentioned. These results confirmed that TBPH affected male reproduction through a classical nuclear receptor-mediated pathway, which would be helpful for assessing the ecological and health risks of TBPH.

Neurotoxicity and the potential molecular mechanisms of mono-2-ethylhexyl phthalic acid (MEHP) in zebrafish

Mono-2-ethylhexyl phthalic acid (MEHP) is the most toxic metabolite of plasticizer di-2-ethylhexyl phthalic acid (DEHP), and there is limited information available on the effects of MEHP on neurotoxicity. This study aims to examine the neurotoxicity of MEHP and preliminarily explore its potential molecular mechanisms. We found that MEHP impeded the growth of zebrafish embryos and the neurodevelopmental-related gene expression at environmentally relevant concentrations. MEHP exposure also induces oxidative stress response and brain cell apoptosis accompanied by a decrease in acetylcholinesterase (AChE) activity in zebrafish larvae. RNA-Seq and bioinformatics analysis showed that MEHP treatment altered the nervous system, neurogenic diseases, and visual perception pathways. The locomotor activity in dark-to-light cycles and phototaxis test confirmed the abnormal neural behavior of zebrafish larvae. Besides, the immune system has produced a large number of differentially expressed genes related to neural regulation. Inflammatory factor IL1β and IL-17 signaling pathways highly respond to MEHP, indicating that inflammation caused by immune system imbalance is a potential mechanism of MEHP-induced neurotoxicity. This study expands the understanding of the toxicity and molecular mechanisms of MEHP, providing a new perspective for in-depth neurotoxicity exploration of similar compounds.

Improving the activity and expression level of a phthalate-degrading enzyme by a combination of mutagenesis strategies and strong promoter replacement

Phthalic acid esters (PAEs) are widely used plasticizers found in consumer products, which enter the environment and pose severe threats to human health. Here, a new PAE-degrading enzyme EstJ6 was modified by combining mutagenesis strategies and a strong promoter replacement to improve its catalytic activity and expression level. Four mutants with enhanced activity were obtained by random mutation, among which EstJ6M1.1 exhibited the highest catalytic activity with an increase in catalytic activity by 2.9-fold toward dibutyl phthalate (DBP) than that of the wild-type (WT) enzyme. With these mutants as a template, a variant EstJ6M2 with 3.1-fold higher catalytic activity and 4.61 times higher catalytic efficiency (Kcat/Km) was identified by staggered extension PCR. Targeting four mutation sites of EstJ6M2, a variant EstJ6M3.1 was gained by site-directed saturation mutagenesis and displayed 4.3-fold higher activity and 5.97 times higher Kcat/Km than WT. The expression level of three mutants EstJ6M1.1, EstJ6M2, and EstJ6M3.1, as well as the WT, increased nearly threefold after a strong promoter replacement. These results provide a proof-theoretical basis and practicable pipeline for applying PAE-degrading enzymes.

An insight into sex-specific neurotoxicity and molecular mechanisms of DEHP: A critical review

Di-2-Ethylhexyl Phthalate (DEHP) is often used as an additive in polyvinyl chloride (PVC) to give plastics flexibility, which makes DEHP widely used in food packaging, daily necessities, medical equipment, and other products. However, due to the unstable combination of DEHP and polymer, it will migrate to the environment in the materials and eventually contact the human body. It has been recorded that low-dose DEHP will increase neurotoxicity in the nervous system, and the human health effects of DEHP have been paid attention to because of the extensive exposure to DEHP and its high absorption during brain development. In this study, we review the evidence that DEHP exposure is associated with neurodevelopmental abnormalities and neurological diseases based on human epidemiological and animal behavioral studies. Besides, we also summarized the oxidative damage, apoptosis, and signal transduction disorder related to neurobehavioral abnormalities and nerve injury, and described the potential mechanisms of neurotoxicity caused by DEHP. Overall, we found exposure to DEHP during the critical developmental period will increase the risk of neurobehavioral abnormalities, depression, and autism spectrum disorders. This effect is sex-specific and will continue to adulthood and even have an intergenerational effect. However, the research results on the sex-dependence of DEHP neurotoxicity are inconsistent, and there is a lack of systematic mechanisms research as theoretical support. Future investigations need to be carried out in a large-scale population and model organisms to produce more consistent and convincing results. And we emphasize the importance of mechanism research, which can enhance the understanding of the environmental and human health risks of DEHP exposure.

Effects of plant growth retardant daminozide (Alar) on neuromuscular co-ordination behavior in Drosophila melanogaster

Daminozide (alar), a plant growth retardant, is used in different fruit orchard to make fruits attractive and reduce pre-harvest losses. Previously data demonstrated that acute daminozide exposure affected reproductive fitness and produced neurodegeneration in Drosophila melanogaster. The goal of this study was to determine whether continuous exposure to daminozide affects neuromuscular co-ordination in D. melanogaster as manifested in various behavioral responses. Fruit flies were exposed to 200 or 400 mg/L concentration of daminozide for two successive generations. Treated D. melanogaster were examined for the behaviors indicative of neuromuscular coordination and cognitive abilities, that include climbing, social interaction, adult grooming, migration, flight, male aggression, and adult courtship. Aberrant behavioral responses were noted among treated D. melanogaster of both sexes as evidenced by the following parameters: reduction in flight duration, abnormal social interaction, altered copulatory acts, and over-aggressiveness. Data suggest that daminozide produces impairment in neuromuscular coordination and cognitive ability in Drosophila, which was reflected as altered behavioral patterns. As Drosophila is considered as a reliable in vivo model utilized in toxicity testing, our findings may help us to anticipate and monitor potential daminozide-induced toxicity in animals and humans.

Imidacloprid Impairs Glutamatergic Synaptic Plasticity and Desensitizes Mechanosensitive, Nociceptive, and Photogenic Response of Drosophila melanogaster by Mediating Oxidative Stress, Which Could Be Rescued by Osthole

Background: Imidacloprid (IMD) is a widely used neonicotinoid-targeting insect nicotine acetylcholine receptors (nAChRs). However, off-target effects raise environmental concerns, including the IMD’s impairment of the memory of honeybees and rodents. Although the down-regulation of inotropic glutamate receptor (iGluR) was proposed as the cause, whether IMD directly manipulates the activation or inhibition of iGluR is unknown. Using electrophysiological recording on fruit fly neuromuscular junction (NMJ), we found that IMD of 0.125 and 12.5 mg/L did not activate glutamate receptors nor inhibit the glutamate-triggered depolarization of the glutamatergic synapse. However, chronic IMD treatment attenuated short-term facilitation (STF) of NMJ by more than 20%. Moreover, by behavioral assays, we found that IMD desensitized the fruit flies’ response to mechanosensitive, nociceptive, and photogenic stimuli. Finally, the treatment of the antioxidant osthole rescued the chronic IMD-induced phenotypes. We clarified that IMD is neither agonist nor antagonist of glutamate receptors, but chronic treatment with environmental-relevant concentrations impairs glutamatergic plasticity of the NMJ of fruit flies and interferes with the sensory response by mediating oxidative stress.

Neuromuscular, retinal, and reproductive impact of low-dose polystyrene microplastics on Drosophila

Facing the challenge of global microplastics (MPs) pollution, full characterization of MPs biohazards is urgent. Recent intensive studies revealed that the toxicity depends on the material, size, and exposure concentration of MP. To better elucidate MPs biohazards, we investigated the impact of polystyrene-MPs of size 0.1 μm at a low dose of 50 μg/L on the neuromuscular, retinal, and reproductive phenotypes of fruit fly model, by voltage-clamped electrophysiology, electroretinogram, and reproductive assay, respectively. We found that MPs decreased the frequency of spontaneous junction currents of synapse and altered the receptor potential amplitude of the retina. Furthermore, MPs lowered the rate of embryo-laying of fruit flies. The differential gene expression of ligand-receptor interaction, endocytosis, phototransduction, and Toll/Imd signaling pathways might underlie these MPs-induced phenotypes. These findings call for further investigation on the potential biohazards of low-dose MPs.

Effects of Mono-2-ethylhexyl Phthalate on the Neural Transmission of PNs in Drosophila Antennal Lobe

Long-term exposure to different types of chemicals is hazardous to human health. Di(2-ethylhexyl) phthalate (DEHP) could exert pleiotropic deleterious effects on nervous systems. Mono(2-ethylhexyl) phthalate (MEHP), as one of the most toxic metabolites of DEHP, may have similar effects on nervous systems. However, no effects of MEHP on neural circuits have been reported. To uncover the regulation of MEHP on neural transmission, the functional changes of neural excitability and synaptic plasticity of projection neurons (PNs) have been assessed. In the current study, we recorded the action potentials (APs), stimulate action potentials (sti-APs), mini excitement postsynaptic current (mEPSC), calcium currents, and sodium currents from PNs of isolated whole brain of Drosophila model utilizing patch clamp recordings. We found that MEHP-300 (at the concentration of 300 μM), but not MHEP-100 (at the concentration of 100 μM), significantly decreased the frequency and amplitude of APs. Besides, the amplitude and anti-amplitude of sti-APs were reduced with the application of MEHP-300. Meanwhile, MEHP-300 reduced the frequency of mEPSC, but not the amplitude. Furthermore, MEHP-300 reduced the peak current densities of sodium and calcium channels. Therefore, our results indicated that MEHP could alter the neural excitability and synaptic plasticity of PNs by inhibiting the ion channels activities, revealing the potential modulation of MEHP on neural transmission of PNs.

Detrimental effects induced by diisononyl phthalate on development and behavior of Drosophila larva and potential mechanisms

Diisononyl phthalate (DINP) as one of the most commonly used phthalates, has been found in various environmental samples and is considered to have potential risks to ecosystem. Till now, DINP has no clear effect consensus on insects from development to behavior and even mechanisms. Here, Drosophila melanogaster was selected as model organisms and the toxic effects of DINP (0.1%, 0.2%, 0.5% and 1.0%) (v/v) on its metamorphosis, crawling behavior, intestinal cells and cellular redox balance were investigated. During metamorphosis process, lower hatching rate, longer development time, lighter body weight and malformation were observed at high concentration groups. The crawling ability of larvae was severely inhibited by DINP and the movement distance was drastically reduced. DINP could cause severe damage to the larval intestinal cells in the dose-dependent and time-dependent manners. DINP was found to induce redox imbalance with activities of two important antioxidant enzymes (catalase (CAT) and superoxide dismutase (SOD)) increasing, and reactive oxygen species (ROS) level fluctuation in larvae. Our findings provide theoretical basis and data support for scientific management of DINP to reduce ecological risk.

Exploring the multilevel effects of triclosan from development, reproduction to behavior using Drosophila melanogaster

Triclosan (TCS) is widely used as an antibacterial agent, but its residue in the environment poses a great threat. In this study, Drosophila melanogaster were treated with series concentrations of TCS and the effects on development, behavior, reproduction, and oxidative stress indicators were investigated. The results showed that high concentrations of TCS severely interfered with the metamorphosis, resulting in lower hatching rate and longer development time. The hatching rate was only 75.00% ± 4.08% in 0.80 mg/mL TCS group. TCS also showed dose-dependent damage to the fertility of flies, causing ovarian defects and decreased the number of offspring. Almost no offspring adults hatched when exposed to high concentrations of TCS (0.50 and 0.80 mg/mL), and the hatching rate was 0% in 0.80 mg/mL TCS group. Larvae crawling, adult climbing and anti-starvation ability were also affected to varying degrees and showed hormesis. TCS could damage larval intestinal cells in a dose-dependent manner, and injury was lightened with culture time prolonging to 30 h. It is noteworthy that TCS caused redox imbalance with an increase on catalase (CAT) activity and decrease on reactive oxygen species (ROS) level. Our results conclude that TCS elicits multiple impacts on Drosophila and its rational use should be strengthened.

Carbon Nanotube Fibers for Neural Recording and Stimulation

Recordings and stimulations of neuronal electrical activity are topics of great interest in neuroscience. Many recording techniques, and even treatment of neurological disorders, can benefit from a microelectrode that is flexible, chemically inert, and electrically conducting and preferentially transfers electrons via capacitive charge injection. Commercial electrodes that currently exist and other electrodes that are being tested with the purpose of facilitating and improving the electron transport between solid materials and biological tissues still have some limitations. This paper discusses carbon nanotube (CNT)-based microelectrodes to record and stimulate neurons and compares their electron transport capabilities to noble metals such as Au and Ag. The recording ability of electrodes is tested through electroretinography on Sarcophaga bullata fly eyes by using Au and Ag wires and CNT fibers as electrodes. Stimulation is demonstrated through the implantation of Au wire and CNT fibers into the antennas of the Madagascar hissing cockroach (Gromphadorhina portentosa) to control their locomotion. Our results demonstrate that a particular property of the CNT fiber is its high rate of electron transfer, leading to an order of magnitude lower impedance compared to Au and Ag and an impressive 15.09 charge injection capacity. We also established that this carbon nanomaterial assembly performs well for in vivo electrophysiology, rendering it a promising prospect for neurophysiological applications.

Effects of DEHP on the ecdysteroid pathway, sexual behavior and offspring of the moth Spodoptera littoralis

Bis(2-ethylhexyl) phthalate (DEHP) is a widely produced plasticizer that is considered to act as an endocrine-disrupting chemical in vertebrates and invertebrates. Indeed, many studies have shown that DEHP alters hormonal levels, reproduction and behavior in vertebrates. Few studies have focused on the effects of DEHP on insects, although DEHP is found almost everywhere in their natural habitats, particularly in soils and plants. Here, we investigated the effects of DEHP on the sexual behavior and physiology of a pest insect, the noctuid moth Spodoptera littoralis. In this nocturnal species, olfaction is crucial for sexual behavior, and ecdysteroids at the antennal level have been shown to modulate sex pheromone detection by males. In the present study, larvae were fed food containing different DEHP concentrations, and DEHP concentrations were then measured in the adults (males and females). Hemolymphatic ecdysteroid concentrations, the antennal expression of genes involved in the ecdysteroid pathway (nuclear receptors EcR, USP, E75, and E78 and calmodulin) and sexual behavior were then investigated in adult males. The success and latency of mating as well as the hatching success were also studied in pairs consisting of one DEHP male and one uncontaminated female or one DEHP female and one uncontaminated male. We also studied the offspring produced from pairs involving contaminated females to test the transgenerational effect of DEHP. Our results showed the general downregulation of nuclear receptors and calmodulin gene expression associated with the higher concentrations of DEHP, suggesting peripheral olfactory disruption. We found some effects on male behavior but without an alteration of the mating rate. Effects on offspring mortality and developmental rates in the N + 1 generation were also found at the higher doses of DEHP. Taken together, the results of the study show for the first time that larval exposure to DEHP can induce delayed endocrine-disruptive effects in the adults of a terrestrial insect as well as effects on the next generation. To date, our study is also the first description of an impact of endocrine disrupter on olfaction in insects.

Toxicological effects of ciprofloxacin exposure to Drosophila melanogaster

The abuse of ciprofloxacin (CIP) may cause serious side effects and the mechanisms underlying these effects remain unclear. Here, we determinate the 48 h, 72 h and 96 h LC₅₀ values of CIP to Drosophila melanogaster and demonstrate a series of adverse effects after D. melanogaster was exposed to CIP at a sublethal concentration (3.2 mg mL^-1). Treated individuals showed shorter lifespan, delayed development and many of the treated larvae failed to pupate or hatch. Smaller body size was observed at every life stage when exposed to CIP and the size of pupae, the weight of third-instar larvae exhibited a perfectly dose-response relationship that the larger concentration exposed to, the smaller body size or lighter weight is. Moreover, reduction in fat body cell viability, elevated oxidative stress markers (SOD and CAT) and down-regulation of diap1, ex, two target genes of Yorkie (Yki), was observed in response to CIP exposure. Most importantly, we found two types of black spot in Drosophila and the proportion of larvae with a black spot was positively related to the treatment dose, which is new in the field. This study provides a scientific basis for the potential harm caused by abuse of quinolones with the goal of urging cautious use of antibiotics.

Transgenerational impact of DEHP on body weight of Drosophila

Bis(2-ethylhexyl) phthalate (DEHP) is the most typical plasticizer and an environmental endocrine disruptor (EDC). DEHP is known to influence offspring fertility, growth, and obesity. However, the role of the DEHP as a transgenerational obesogen is still controversial. In this study, we used fruit flies (Drosophila melanogaster) to investigate where the exposure period, doses, and exposed parental sex are critical to change the body weight of the offspring. We found long-term but not short-term, and high-dose but low-dose exposure resulted in significant change. Moreover, we found DEHP treatment on the father or mother Drosophila resulted in increased or decreased body weight of the offspring respectively. Our results demonstrated the heterogeneity of transgenerational impact of DEHP and highlighted the involvement of parental endocrine system in its role as an obesogen.