Developmental exposure to nonylphenol induced rat axonal injury in vivo and in vitro

Bisphenol S impairs mitochondrial function by targeting Myo19/oxidative phosphorylation pathway contributing to axonal and dendritic injury

Exposure to bisphenol S (BPS) is known to adversely affect neuronal development. As pivotal components of neuronal polarization, axons and dendrites are indispensable structures within neurons, crucial for the maintenance of nervous system function. Here, we investigated the impact of BPS exposure on axonal and dendritic development both in vivo and in vitro. Our results revealed that exposure to BPS during pregnancy and lactation led to a reduction in the complexity, density, and length of axons and dendrites in the prefrontal cortex (PFC) of offspring. Employing RNA sequencing technology to elucidate the underlying mechanisms of axonal and dendritic damage induced by BPS, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis highlighted a significant alteration in the oxidative phosphorylation (OXPHOS) pathway, essential for mitochondrial function. Subsequent experiments demonstrate BPS-induced impairment in mitochondrial function, including damaged morphology, decreased adenosine triphosphate (ATP) and superoxide dismutase (SOD) levels, and increased reactive oxygen species and malondialdehyde (MDA). These alterations coincided with the downregulated expression of OXPHOS pathway-related genes (ATP6V1B1, ATP5K, NDUFC1, NDUFC2, NDUFA3, COX6B1) and Myosin 19 (Myo19). Notably, Myo19 overexpression restored the BPS-induced mitochondrial dysfunction by alleviating the inhibition of OXPHOS pathway. Consequently, this amelioration was associated with a reduction in BPS-induced axonal and dendritic injury observed in cultured neurons of the PFC.

Therapeutic effect of thymoquinone on brain damage caused by nonylphenol exposure in rats

Nonylphenol (NP), causes various harmful effects such as cognitive impairment and neurotoxicity. Thymoquinone (TQ), has antioxidant, anti-inflammatory, and neuroprotective properties. In this study, our aim is to investigate the effects of TQ on the brain damage caused by NP. Corn oil was applied to the control group. NP (100 mg/kg/day) was administered to the NP and NP + TQ groups for 21 days. TQ (5 mg/kg/day) was administered to the NP + TQ and TQ groups for 7 after 21 days. At the end of the experiment, the new object recognition test was applied to the rats and the rats were killed and their brain tissues were removed. Sections taken from brain tissues were stained with hematoxylin-eosin for histopathological evaluation. In addition, neuronal nuclei (NeuN), glial fibrillary acidic protein (GFAP), Cas-3, and nerve growth factor (NGF) immunoreactivities were evaluated in brain tissue sections. In addition, malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) activities were determined. Comet assay was applied to determine DNA damage in cells. The results of our study showed that NP, caused behavioral disorders and damage to the cerebral cortex in rats. This damage in the form of neuron degeneration seen in the cortex was associated with apoptosis involving Cas-3 activation, increased DNA damage, and free oxygen radicals. NP, SOD, and CAT caused a decrease in enzyme activities. In addition, the cellular protein NeuN was decreased, astrocytosis-associated GFAP was increased, and growth factor NGF was decreased. When all our evaluations are taken together, treatment with TQ showed an ameliorative effect on the behavioral impairment and brain damage caused by NP exposure.

Nonylphenol induces anxiety-like behavior in rats by regulating BDNF/TrkB/CREB signal network

This study aimed to verify whether chronic exposure to nonylphenol (NP) induces anxiety behavior in rats and explored NP's regulatory effect on the BDNF/TrkB/CREB signal network in vitro. Anxiety-like behavior was assessed by elevated plus-maze and light-dark box tests. The residence time in the closed arm increased with NP dose (4, 40 mg/kg) and exposure time (3 and 6 months) (P < 0.05). The hippocampal neurons in the medium dose (M-NP, 4 mg/kg) and high dose (H-NP, 40 mg/kg) groups showed disorderly arrangement, cell swelling, and nuclear pyknosis/necrosis. The protein/mRNA expressions of BDNF/TrkB/CREB in the H-NP group decreased, and the decrease was more significant at 6 months (P < 0.05). Both, NP exposure and BDNF knockdown, increase the number of apoptotic cells (P ＜0.001). NP downregulated the proteins/mRNA expressions of BDNF/TrkB/CREB, and the trend was consistent with the BDNF silence group. Chronic exposure to NP could induce anxiety-like behavior in rats and reduce the expression of key proteins/genes in the BDNF/TrkB/CREB signaling network.

4-[1-Ethyl-1-methylhexy]-phenol induces apoptosis and interrupts Ca2+ homeostasis via ROS pathway in Sertoli TM4 cells

Biological effect of an individual nonylphenol (NP) isomer extremely relies upon the side chain structure. This research was designed to evaluate the impact of NP isomer, 4-[1-ethyl-1-methylhexy]-phenol (NP₆₅), on Sertoli cells in vitro. Sertoli TM4 cells were exposed to various concentration (0, 0.1, 1, 10, or 20 μM) of NP₆₅ for 24 h, and the outcomes indicated that treatment of NP₆₅ induced reactive oxygen species (ROS) generation, oxidative stress, and apoptosis for Sertoli TM4 cells. In addition, it was found that NP₆₅ exposure affected homeostasis of Ca²⁺ in Sertoli TM4 cells by increasing cytoplasm [Ca²⁺]i, inhibiting Ca²⁺-ATPase activity and decreasing cyclic adenosine monophosphate (cAMP) concentration. Pretreatment with ROS scavenger, N-acetylcysteine (NAC), attenuated NP₆₅-induced oxidative stress as well as apoptosis for TM4 cells. Furthermore, NAC blocked NP₆₅-induced disorders of Ca²⁺ homeostasis by attenuating the growth of intracellular [Ca²⁺]i and the inhibition of Ca²⁺-ATPase and cAMP activities. Thus, we have demonstrated that NP₆₅ induced apoptosis as well as acted as a potent inhibitor of Ca²⁺-ATPase activity and resulted in disorder of Ca²⁺ homeostasis in Sertoli TM4 cells; ROS participated in the process. Our results supported the view that oxidative stress acted an essential role within the development of apoptosis and Ca²⁺ overload in TM4 cells as a consequence of NP₆₅ stimulation.

Thymoquinone Improved Nonylphenol-Induced Memory Deficit and Neurotoxicity Through Its Antioxidant and Neuroprotective Effects

Nonylphenol (NP), a well-known endocrine-disrupter chemical, has several harmful effects on the central nervous system including neuroendocrine disruption, cognitive impairment, and neurotoxicity. Thymoquinone (TQ) is a main bioactive compound in the black seeds of Nigella sativa that has antioxidant, anti-inflammatory, and neuroprotective properties. Here, we investigated the neuroprotective effect of TQ against NP-induced memory deficit and neurotoxicity in rats. To induce memory impairment, NP (25 mg/kg) was used as gavage in male Wistar rats for 21 days. TQ (2.5, 5, and 10 mg/kg) was intraperitoneally administered in NP-treated animals. The morris water maze test was performed to assess spatial learning and memory. The hippocampal tissues were isolated from the brain for histopathological evaluation. Biochemical, molecular, and cellular tests were performed to quantify oxidant (malondialdehyde; MDA)/antioxidant (superoxide dismutase (SOD), total antioxidant capacity (TAC), and reduced glutathione (GSH) parameters) as well as markers for astrocytic activation (glial fibrillary acidic protein; GFAP) and neuronal death (alpha-synuclein; α-syn). Results showed TQ (5 mg/kg) significantly improved NP-induced memory impairment. Histological data revealed a significant increase in the number of necrotic cells in hippocampus, and TQ treatment markedly decreased this effect. The GSH and TAC levels were significantly increased in TQ-treated groups compared to NP group. The molecular analysis indicated that NP increased GFAP and decreased α-syn expression and TQ treatment did the reverse. In vitro study in astrocytes isolated from mice brain showed that TQ significantly increased cell viability in NP-induced cytotoxicity. This study strongly indicates that TQ has neuroprotective effects on NP-induced neurotoxicity through reducing oxidative damages and neuroinflammation. This study investigates the behavioral neurotoxicity induced by Nonylphenol (NP) and the protective effects of Thymoquinone (TQ) as a potent antioxidant compound using molecular, cell culture, histopathological and biochemical techniques.

Behavioral disorders caused by nonylphenol and strategies for protection

Nonylphenol (NP) is widely used in daily production and life due to its good emulsification. In this review, we discuss toxicology studies that examined behavioral disorders caused by NP, the corresponding toxicological mechanisms in the central nervous system (CNS), and strategies for protection. Available in vitro and in vivo evidence suggests that exposure to NP during adulthood or early childhood is associated with cognitive dysfunction, including depression-like behaviors, anxiety-like behaviors, and impaired learning and memory. The main mechanisms underlying NP-related cognitive disorders include inflammation, destruction of synaptic plasticity, and destruction of important signaling pathways that affect the synthesis and secretion of neurotransmitters. The effects and mechanisms of NP exposure on CNS-mediated reproductive function, including interference with the expression of hormones, proteins, and enzymes, are discussed. Other abnormal behaviors such as locomotor activity and swimming behavior are also described. Several measures to prevent NP neurotoxicity are summarized. These measures are based on the toxicological mechanisms underlying NP exposure and include external protection and internal self-regulation of the nervous system. Finally, a new treatment idea is proposed based on the gut-brain axis. Characterizing the behavioral changes and underlying toxicity mechanisms associated with NP exposure and investigating the possible methods of treatment will help to expand the understanding of these mechanisms and could lead to more effective treatments.

Dose- and time-effects responses of Nonylphenol on oxidative stress in rat through the Keap1-Nrf2 signaling pathway

Nonylphenol (NP) is a representative environmental endocrine-disrupting compound that can induce oxidative stress in organisms. The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway acts an important role in preventing oxidative stress. The aim of this study was to investigate the influence of oxidative stress caused by NP on Keap1-Nrf2 pathway in rats. Rats were treated with NP (30, 90, 270 mg/kg) for different exposure time (7, 14 and 28 days). The levels of reactive oxygen species (ROS) in serum and glutathione S-transferase (GST), UDP-Glucuronosyl Transferase (UGT) in liver were detected by ELISA kits. Western blot was used to detect Keap1, Nrf2 protein expression in liver and cerebral cortex. The results showed that 28 days of NP exposure significantly increased ROS levels in NPH group. And 14 days exposure to NP significantly enhanced the levels of GST and UGT, while 28 days of exposure showed a suppressive effect. In liver, Keap1 levels was upregulated at 7, 14 and 28 days of NP exposure, while nuclear Nrf2 levels decreased at 7 and 28 days but increased at 14 days. In cerebral cortex, Keap1 and Nrf2 expression increased at 14 days but decreased at 28 days. Besides, with the prolongation of NP exposure time, the GST and UGT levels in NPM and NPH groups were increased firstly and then decreased, while Keap1 and Nrf2 protein levels were constantly decreased in liver and cerebral cortex. In conclusion, the lower dose and shorter exposure time of NP activated the Keap1-Nrf2 pathway that may reduce the damage of oxidative stress, but when further exposed to NP at higher dose and time, the pathway could be inhibited.

Perinatal exposure to nonylphenol promotes proliferation of granule cell precursors in offspring cerebellum: Involvement of the activation of Notch2 signaling

Nonylphenol (NP), a widely diffused persistent organic pollutant (POP), has been shown to impair cerebellar development and cause cerebellum-dependent behavioral and motor deficits. The precise proliferation of granule cell precursors (GCPs), the source of granular cells (GCs), is required for normal development of cerebellum. Thus, we established an animal model of perinatal exposure to NP, investigated the effect of NP exposure on the cerebellar GCPs proliferation, and explored the potential mechanism involved. Our results showed that perinatal exposure to NP increased cerebellar weight, area, and internal granular cell layer (IGL) thickness in offspring rats. Perinatal exposure to NP also resulted in the GCPs hyperproliferation in the external granular layer (EGL) of the developing cerebellum, which may underlie the above-mentioned cerebellar alterations. However, our results suggested that perinatal exposure to NP had no effects on the length of GCPs proliferation. Meanwhile, perinatal exposure to NP also increased the activation of Notch2 signaling, the regulator of GCPs proliferation. In conclusion, our results supported the idea that exposure to NP caused the hyperproliferation of GCPs in the developing cerebellum. Furthermore, our study also provided the evidence that the activation of Notch2 signaling may be involved in the GCPs hyperproliferation.

Intergenerational toxicity of nonylphenol ethoxylate (NP-9) in Caenorhabditis elegans

The ethoxylated isomers of nonylphenol (NPEs, NP-9) are one of the main active ingredients present in nonionic surfactants employed as herbicides, cosmetics, paints, plastics, disinfectants and detergents. These chemicals and their metabolites are commonly found in environmental matrices. The aim of this work was to evaluate the intergenerational toxicity of NP-9 in Caenorhabditis elegans. The lethality, length, width, locomotion and lifespan were investigated in the larval stage L4 of the wild strain N2. Transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. RT-qPCR was utilized to measure mRNA expression for neurotoxicity-related genes (unc-30, unc-25, dop-3, dat-1, mgl-1, and eat-4). Data were obtained from parent worms (P0) and the first generation (F1). Lethality of the nematode was concentration-dependent, with 48 h-LC₅₀ values of 3215 and 1983 μM in P0 and F1, respectively. Non-lethal concentrations of NP-9 reduced locomotion. Lifespan was also decreased by the xenobiotic, but the negative effect was greater in P0 than in F1. Non-monotonic concentration-response curves were observed for body length and width in both generations. The gene expression profile in P0 was different from that registered in F1, although the expression of sod-4, hsp-70, gpx-6 and mtl-2 increased with the surfactant concentration in both generations. None of the tested genes followed a classical concentration-neurotoxicity relationship. In P0, dopamine presented an inverted-U curve, while GABA and glutamate displayed a bimodal type. However, in F1, inverted U-shaped curves were revealed for these genes. In summary, NP-9 induced intergenerational responses in C. elegans through mechanisms involving ROS, and alterations of the GABA, glutamate, and dopamine pathways.

Exposure to nonylphenol in early life increases pro-inflammatory cytokines in the prefrontal cortex: Involvement of gut-brain communication

A growing body of evidence indicates that exposure to nonylphenol (NP), a typical persistent organic pollutant (POP), in early life results in the impairment of the central nervous system (CNS), but the underlying mechanism still remains to be elucidated. High levels of pro-inflammatory cytokines in the brain have been implicated in the CNS damages. The animal model of exposure to NP in early life was established by maternal gavage during the pregnancy and lactation in the present study. We found that exposure to NP in early life increased the levels of pro-inflammatory cytokines in the rat prefrontal cortex. Interestingly, the levels of pro-inflammatory cytokines in the intestine as well as in the serum were also increased by NP exposure. Furthermore, the increased permeability of intestinal barrier and blood-brain barrier (BBB), two critical barriers in the gut to brain communication, was observed in the rats exposed to NP in early lives. The decreased expression of zonula occludens-1 (ZO-1) and claudin-1 (CLDN-1), tight junction proteins (TJs) that responsible for maintaining the permeability of intestinal barrier and BBB, was found, which may underlie these increases in permeability. Taken together, these results suggested that the disturbed gut-brain communication may contribute to the increased levels of pro-inflammatory cytokines in the prefrontal cortex caused by NP exposure in early life.