Exposure to dibutyl phthalate adsorbed to multi-walled carbon nanotubes causes neurotoxicity in mice by inducing the release of BDNF

Neurotoxicity of dibutyl phthalate in zebrafish larvae: Decreased energy acquisition by neurons

This work was designed to investigate the neurotoxic effects of the typical plasticizer dibutyl phthalate (DBP) using zebrafish larvae as a model. The results of exhibited that zebrafish larvae exposed to DBP at concentrations of 5 μg/L and 10 μg/L exhibited brain malformations (24 h) and behavioral abnormalities (72 h). After 72 h of exposure to DBP, microglia in the brain were over-activated, reactive oxygen species (ROS) formation was increased, and apoptosis was observed. Meanwhile, it was found that neurons exhibited impaired mitochondrial structure, absent mitochondrial membrane potential and up-regulated autophagy. Further comprehensive biochemical analyses and RNA-Seq, validated by RT-qPCR, glutamate metabolism and PPAR signaling pathway were significantly enriched in the DBP stress group, this may be the main reason for the disruption of glycolysis/gluconeogenesis processes and the reduction of energy substrates for the astrocyte-neuron lactate shuttle (ANLS). In addition, the DBP-exposed group showed aberrant activation of endoplasmic reticulum (ER) stress signaling pathway, which may be related to ROS as well as neuronal apoptosis and autophagy. In conclusion, DBP-induced neurotoxicity may be the combined result of insufficient neuronal energy acquisition, damage to mitochondrial structure, apoptosis and autophagy. These results provide a theoretical basis for understanding the neurotoxic effects of DBP.

miR-145a-5p/SIK1/cAMP-dependent alteration of synaptic structural plasticity drives cognitive impairment induced by coke oven emissions

Exposure to fine particulate matter (PM) is associated with the neurodegenerative diseases. Coke oven emissions (COEs) in occupational environment are important sources of PM. However, its neurotoxicity is still unclear. Therefore, evaluating the toxicological effects of COE on the nervous system is necessary. In the present study, we constructed mouse models of COE exposure by tracheal instillation. Mice exposed to COE showed signs of cognitive impairment. This was accompanied by a decrease in miR-145a-5p and an increase in SIK1 expression in the hippocampus, along with synaptic structural damage. Our results demonstrated that COE-induced miR-145a-5p downregulation could increase the expression of SIK1 and phosphorylated SIK1, inhibiting the cAMP/PKA/CREB pathway by activating PDE4D, which was associated with reduced synaptic structural plasticity. Furthermore, restoring of miR-145a-5p expression based on COE exposure in HT22 cells could partially reversed the negative effects of COE exposure through the SIK1/PDE4D/cAMP axis. Collectively, our findings link epigenetic regulation with COE-induced neurotoxicity and imply that miR-145a-5p could be an early diagnostic marker for neurological diseases in patients with COE occupational exposure.

Dibutyl phthalate adsorbed on multi-walled carbon nanotubes can aggravate liver injury in mice via the Jak2/STAT3 pathway

Phthalic acid esters (PAEs) and carbon nanotubes (CNTs) are common environmental pollutants and may degrade differently with different resulting biotoxicity, when present together. This study investigated the toxicological effects of singular or combined exposure to dibutyl phthalate (DBP) and multi-walled carbon nanotubes (MWCNTs) in KM mice. Results indicated that combined exposure led to slower weight gain and an increased leukocyte count in the blood, as well as liver tissue lesions and downregulation of organ coefficients. Additionally, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were elevated in the liver, and glucose, pyruvate, triglyceride (TG), and total cholesterol (T-CHO) were significantly reduced, suggesting compromised liver function. Furthermore, mRNA levels of genes related to hepatic glucose and lipid metabolism were significantly altered. These findings suggest that combined exposure to DBP and MWCNTs can have severe impacts on liver function in mice, highlighting the importance of considering interactions between multiple contaminants in environmental risk assessments.

Effects of butyl benzyl phthalate on zebrafish (Danio rerio) brain and the underlying molecular mechanisms revealed by transcriptome analysis

Butyl benzyl phthalate (BBP), a widely used class of plasticizers, has caused considerable concerns due to its widespread detection in various environmental media. However, the potential impact of BBP on the brain and its underlying molecular mechanisms remain poorly understood. In this study, adult zebrafish (Danio rerio) were exposed to 0, 5, 50, and 500 μg/L BBP for 28 days. Elevated levels of both reactive oxygen species and 8-hydroxydeoxyguanosine were observed, indicating the occurrence of oxidative stress and DNA damage. Furthermore, exposure to BBP resulted in neurotoxicity, apoptosis, and histopathological damage within the zebrafish brain. Transcriptome analysis further revealed that Gene Ontology terms associated with muscle contraction were specifically expressed in the brain after BBP exposure. In addition, BBP altered the transcriptome profile of the brain, with 293 genes induced and 511 genes repressed. Kyoto Encyclopedia of Genes and Genomes analysis highlighted the adverse effects of BBP on the complement and coagulation cascades and two cardiomyopathy-related pathways. Taken together, our results revealed that BBP resulted in brain oxidative stress, histological damage, and transcriptome alterations. These findings have the potential to offer novel insights into the adverse outcome pathways of key events in the brain.

Combined exposure to multiwalled carbon nanotubes and dibutyl phthalates aggravated airway inflammation in rats

Previous work has shown that mice exposed to dibutyl phthalate (DBP) adsorbed onto multi-walled carbon nanotubes (MWCNTs), via tail vein injection, displayed black lesions in their lungs. To investigate the mechanism causing this toxicity in the lung tissue, we performed an experiment with rats, exposing them to DBP adsorbed onto MWCNTs via a tail vein injection for 14 days. The results revealed pulmonary edema and greyish-black lung tissue in the MWCNTs and the MWCNTs + DBP combined exposure groups. In the combined exposure group there was evident alveolar fragmentation and adhesion, and lung tissue sections showed significant levels of black particles. Sections of the non-cartilaginous region of the trachea had significant folding of the pseudostratified ciliated columnar epithelium and marked thickening of the submucosa. In broncho alveolar lavage fluid, the number of leukocytes (WBC), lymphocytes (Lym), neutrophils (Neu), and eosinophils (Eos), as well as levels of immunoglobulin E (IgE), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and interleukin 1β (IL-1β) were all significantly higher. TNF-α, IL-6, signal transducer and activator of transcription 3 (STAT3), and α-smooth muscle actin (α-SMA) mRNA expression were all elevated in the lung tissue. The combined exposure group, which had considerable airway remodeling, had a greater degree of tracheal constriction and luminal narrowing, according to the results of the α-SMA immunofluorescence assay. According to these experimental findings, the exposure to both MWCNTs and DBP seemed to have a synergistic effect and exacerbated rats' impaired respiratory function that resulted from exposure to MWCNTs alone.

Multi-walled carbon nanotubes enhance the toxicity effects of dibutyl phthalate on early life stages of zebrafish (Danio rerio): Research in physiological, biochemical and molecular aspects

Phthalate esters (PAEs) are widely used as plasticizers. PAEs are ubiquitous in natural water bodies, with dibutyl phthalate (DBP) being one of the most common PAEs. DBP is prone to leaching or migration into the environment, posing serious health and environmental risks. Carbon nanotubes (CNTs) have been widely used in various fields with the rapid development of nanotechnology. CNTs could alter the environmental behavior and toxicity of co-existing pollutants. CNTs have been shown to rapidly adsorb PEAs. However, current knowledge about the effects of CNTs on DBP toxicity is limited. Here we show that the toxic effects of single and combined exposure to DBP (0.1, 0.5, 1.0 mg/L) and different CNTs (MWCNTs/MWCNTs-COOH, 0.5 mg/L) on the early growth stage of zebrafish. The results suggested that a significant increase in heart rate and heart malformation rate was observed after co-exposure of DBP and MWCNTs/MWCNTs-COOH (p < 0.05). Furthermore, combined exposure increased antioxidant enzyme activity during early developmental stages in zebrafish (p < 0.05). The qRT-PCR results revealed that DBP and MWCNTs/MWCNTs-COOH co-exposure significantly interfered with the expression of genes related to oxidative stress, energy metabolism, development of cardiac function, and apoptosis (p < 0.05). In addition, for oxidative stress and cardiotoxicity, MWCNTs/MWCNTs-COOH aggravated the toxic effects of 0.5 mg/L DBP on embryos/larvae. The metabolomics results showed that co-exposure mitigated the disturbance of amino acid metabolism mediated by single DBP exposure. In general, MWCNTs/MWCNTs-COOH increased the impact of DBP in the early developmental stages of zebrafish. This study provides new insights into the toxicology of early developmental stages of aquatic organisms exposed to co-exist pollutants of DBP and CNTs.

Enrofloxacin hydrochloride toxicological effects on crucian carp reflected by serological changes and neurotoxicity

Due to its water solubility and wide applicability, enrofloxacin hydrochloride (EH) may enter aquatic ecosystems and cause negative effects on aquatic organisms. This study aimed to explore toxicological effects via serological changes and neurotoxicity, which were induced by EH exposure in crucian carp (Carassius auratus var. Pengze). The drug residues in brain tissue and protein content in serum were determined to analyze serological changes. Alterations in brain tissue structure and function, cerebral microvessels permeability, and the expressions of gene and protein regarding blood-brain barrier (BBB) were studied to reflect the neurotoxicity. Employing a validated high-performance liquid chromatography (HPLC) method, EH residues could be detected at various time-points throughout the experiment. Enzyme-linked immunosorbent assay (ELISA) showed that EH increased the levels of S100B, NSE and GFAP proteins in serum. Additionally, there was a significant positive correlation between serum S100B, NSE protein contents and EH residues (P < 0.05). Hematoxylin and eosin (H&E) staining revealed brain damage from EH exposure by the formation of vacuoles in brain glial cells, pyknosis of the nucleus, and a decrease in cell population density. Transmission electron microscope (TEM) revealed morphological changes in microvessels and condensation of astrocyte nucleus. Evans blue (EB) permeability test visualized an obvious increase in cerebral microvessels leakage. The real-time quantitative PCR (qPCR) results indicated that EH up-regulated the mRNA expression levels of S100B, NSE and GFAP, down-regulated the mRNA expression levels of P-gp, ZO-1, Occludin and Claudin-5. The Western blot (WB) results demonstrated increased NSE and GFAP protein expressions, decreased P-gp and Occludin protein expressions following EH exposure in brain, in consistent with the gene expressions, respectively. In conclusion, these findings indicated that EH brought about marked rise in serum biomarker levels and disrupted the central nervous system (CNS) of crucian carp. These data would help elucidate the mechanism underlying EH-induced neurotoxicological effects.

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.