Abstract
Tris (2-chloroethyl) phosphate (TCEP) is a crucial organophosphorus flame retardant widely used in many industrial and commercial products. Available reports reported that TCEP could cause various toxicological effects on organisms, including humans. Unfortunately, toxicity data for TCEP (particularly on neurotoxicity) on aquatic organisms are lacking. In the present study, Danio rerio were exposed to different concentrations of TCEP for 42 days (chronic exposure), and oxidative stress, neurotoxicity, sodium, potassium-adenosine triphosphatase (Na+, K+-ATPase) activity, and histopathological changes were evaluated in the brain. The results showed that TCEP (100 and 1500 µg L−1) induced oxidative stress and significantly decreased the activities of antioxidant enzymes (SOD, CAT and GR) in the brain tissue of zebrafish. In contrast, the lipid peroxidation (LPO) level was increased compared to the control group. Exposure to TCEP inhibited the acetylcholinesterase (AChE) and Na+,K+-ATPase activities in the brain tissue. Brain histopathology after 42 days of exposure to TCEP showed cytoplasmic vacuolation, inflammatory cell infiltration, degenerated neurons, degenerated purkinje cells and binucleate. Furthermore, TCEP exposure leads to significant changes in dopamine and 5-HT levels in the brain of zebrafish. The data in the present study suggest that high concentrations of TCEP might affect the fish by altering oxidative balance and inducing marked pathological changes in the brain of zebrafish. These findings indicate that chronic exposure to TCEP may cause a neurotoxic effect in zebrafish.
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.Avoid common mistakes on your manuscript.
Introduction
Chlorinated organophosphate flame retardants (Cl-OPFRs) are extensively used in plastics, furniture, floor polishes, daily chemicals, etc. (Lee et al. 2016; Yang et al. 2021) due to their plasticiser and additive properties (Yang et al. 2019). Cl-OPFRs such as tris (2-cholroisopropyl) phosphate (TCPP), tris (1,3-dichloro-2-propyl) phosphate (TDCPP) and tris (2-chloroethyl) phosphate (TCEP) were widely used as alternatives for several toxic brominated flame retardants (Mihajlović and Fries 2012; Li et al. 2019a,b). As a result, these Cl-OPFRs have been detected at high levels in the aquatic environment (He et al. 2017; Yang et al. 2021) and are considered new emerging contaminants (Tang et al. 2018). In aquatic environments, the concentration of Cl-OPFRs has been detected up to 26,000 ng L-1 (Qi et al. 2019; Xu et al. 2019).
TCEP, one of the dominant Cl-OPFRs (Chokwe et al. 2020), is a ubiquitous environmental contaminant due to its overuse and has a high solubility (25 ºC, 7.93 g L-1) in water (Veen and Boer 2012; O'Brien et al. 2015; Arukwe et al. 2016; Lee et al. 2018; Hou et al. 2019; Hao et al. 2020; Yao et al. 2021; Wang et al. 2022). For example, the concentration of TCEP has been detected at 318 ng L-1 in groundwater (Marklund et al. 2005), in the range of 259–2406 ng L-1 in lakes (Yan et al. 2012), 85±10 ng L-1 in rivers (García-López et al. 2010), and 99 ng L-1 in drinking water (Stackelberg et al. 2004). TCEP is detected in higher concentrations in WWTP effluents due to their resistance to biotransformation and formation from the precursors (Kim et al. 2019; Yang et al. 2021, 2022a, b). Furthermore, TCEP has also been detected in aquatic organisms such as fish and perch (Sundkvist et al. 2010; Ma et al. 2013) and human tissues (Zhao et al. 2021).
TCEP can persist for a long time in the environment (Zhu et al. 2015; Sun et al. 2016a, b; Kim et al. 2017) and may cause adverse effects in aquatic organisms. For example, TCEP reduced the survival and growth rate of catfish (Zhao et al. 2021), thyroxine (T4) levels in zebrafish (Hu et al. 2021), growth and reproduction of protozoans (Hao et al. 2020), developmental phenotypes in zebrafish (Wu et al. 2017), changes in the AChE activity in earthworms (Yang et al. 2018), and behavioural effects in zebrafish (Jarema et al. 2015). In contrast, Li et al. (2020) have reported that TCEP at environmental concentrations promoted the growth rate of D. magna. Furthermore, Arukwe et al. (2016) have reported that TCEP exposure did not alter the 11-ketotestosterone (11-KT) levels in juvenile salmon. However, a few authors have reported the neurotoxicity of TCEP on aquatic organisms, especially fish (Behl et al. 2015; Sun et al. 2016a, b; Xu et al. 2017; Li et al. 2019a, b; Hu et al. 2021).
Vertebrate brain tissue is most sensitive to oxidative stress (Li and Li 2020). Most organelles and neurons in brain tissues are delicate and easily damaged by reactive oxygen species (ROS) formation due to antioxidant defence (Sachett et al. 2018; Barros et al. 2020; Leão-Buchir et al. 2021). Antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) play a vital role in oxidative stress in aquatic organisms. Similarly, glutathione reductase (GR) protects proteins, lipids and nucleic acids against oxidative damage (Carvalho et al. 2020). In addition, antioxidant enzymes maintain the redox status of the cell. However, high production of ROS may damage the DNA and proteins and cause lipid peroxidation (LPO). In our previous study (Sutha et al. 2020), the activities of SOD, CAT, GST, GSH and GPx and LPO levels were found to be altered in gill, liver, and kidney tissues of Cirrhinus mrigala exposed to TCEP (0.04, 0.2, and 1 mg L-1), which indicates that TCEP may induce oxidative stress in fish. Changes in the antioxidant parameters are widely used as potential biomarkers to assess the toxicity of aquatic pollutants.
Quantification of the enzyme activity can give valuable information on the affected organs/tissues. In vertebrates, the enzyme acetylcholinesterase (AChE) is essential for the normal functioning of the neuromuscular system (Mayer et al. 1992). The alteration of acetylcholinesterase (AChE) activity is commonly used as a biomarker to assess the toxicity of organophosphorus compounds (Shi et al. 2021). Due to their organophosphorus backbone, flame retardants may induce neurotoxicity (Jarema et al. 2015). TCEP also inhibits the acetylcholinesterase (AChE) activity in aquatic organisms (World Health Organization 1998; Li et al. 2019a, b). Likewise, sodium and potassium adenosine triphosphatase (Na+,K+-ATPase) play a vital role in the transport of the ions across cell membranes. Changes in the Na+,K+-ATPase activities can be used to assess the physiological integrity of aquatic organisms exposed to aquatic toxicants (Agrahari and Gopal 2008; Ajima et al. 2021). Furthermore, during stress conditions, neurotransmitters such as dopamine (DA) and serotonin (5-HT) are released from the brain and play a vital role in mediating stress in fish (Backström and Winberg 2017). Assessment of these neurotransmitter levels indicates the toxicity of aquatic pollutants in the central nervous system (Da Rochaa et al. 2019). Similarly, histopathological anomalies can be used to assess the impact of waterborne chemicals on major organs (Ramesh et al. 2018). TCEP-induced biochemical changes and their consequences are well addressed in several organ-specific studies, including liver, gill, brain, and kidney at 0.04, 0.2, or 1 mg L-1(Arukwe et al. 2016; Sutha et al. 2020), but its pathological manifestation in the brain remains elusive.
This work was intended to assess the chronic effects of TCEP on oxidative stress, acetylcholinesterase activity, and histological biomarkers in the brain tissue of zebrafish (Danio rerio).
Materials and methods
Ethical statement
The present study was conducted per the OECD guidelines for maintaining and handling fish (OECD/OCDE 2013) and the Committee for the Control and Supervision of Experiments on Animals (CPCSEA).
Chemicals
Tris (2-chloroethyl) phosphate (TCEP) was purchased from Sigma-Aldrich (degree of purity, 97%) (CAS number: 115-96-8) and the stock solution was prepared by dissolving 1 g L-1 of tris (2-chloroethyl) phosphate in Milli-Q water. All other chemicals and reagents were procured from S.D Fine Chemicals, Chennai, India.
Maintenance of zebrafish
AB strain zebrafish (Danio rerio) weighing 0.6 ± 0.2 g and an average length of 2.7 ± 0.4 cm were obtained from Siraco Fish Farm in Salem, Tamil Nadu. Fish were maintained in a tank of 1000 L capacity with dechlorinated water (temperature 28 ± 1 ºC, pH 7.5 ± 0.5, dissolved oxygen 6.4 ± 0.4, total alkalinity 18.2 ± 1.5, total hardness 18. ± 1.5 with a 14:10 h (light: dark photo-cycle) and fed with commercial fish feed.
Chronic exposure
After fifteen days of acclimation, the fish were divided into three groups and maintained in a glass aquarium containing 20 L of water. Each group consisted of 20 fish. Two different concentrations of TCEP (100 and 1500 µg L-1) were selected and introduced into the respective aquariums. The lowest concentration of TCEP (100 µg L-1) was selected based on the reported environmental concentrations (Kawagoshi et al. 1999). In ecotoxicological studies, the LC50 value is commonly used to test the toxicity of chemicals rather than environmentally relevant levels. In this practice, animals are exposed to higher concentrations than the ecologically relevant concentrations. Hence, in the present study, a high concentration of TCEP (1500 µg L-1) was selected based on the LC50 value (Sutha et al. 2022). For each concentration and control group, three replicates were maintained. After 14, 28 and 42 days of exposure, the brain tissue was dissected, washed in saline solution, and stored at -80º C for biochemical analysis.
Tissue preparation
The stored brain tissue from control and TCEP (100 and 1500 µg L-1) exposed fish was homogenised with PBS buffer (pH 7.0), using a mechanical tissue homogeniser coated with Teflon. The homogenate samples were centrifuged at 15,000 rpm for 15 min, and the supernatant was used for the enzymological assay. For pathological observations, additional brain tissues were fixed in 10% neutral buffered formalin.
Antioxidant enzyme analysis
SOD activity in the brain tissue was determined following the method of Marklund and Marklund (1974). To 50 μl enzyme source, Tris-HCl buffer (50 mM, pH 8.4), EDTA (1 mM) and pyrogallol (2.64 mM) were added, and the absorbance was measured at 420 nm for 5 min in a Spectrophotometer. The enzyme activity was expressed as Units/mg protein. Catalase (CAT) activity was determined following the Aebi method (1984). The decomposition of H2O2 was measured at 240 nm, and the enzyme activity was expressed as micromoles of H2O2 utilised per minute per milligram of protein. The activity of glutathione reductase (GR) was estimated using David and Richard’s (1983) method. The assay mixture consisted of phosphate buffer (1.0 ml), EDTA (0.1 mL), sodium azide (0.1 mL), oxidised glutathione (0.1 mL) and tissue homogenate (0.1 mL). The absorbance was read at 340 nm in a Spectrophotometer, and the enzyme activity was expressed as μM of NADPH/oxidised/min/mg protein.
To determine LPO level, thiobarbituric acid (TBA) reacting species for malondialdehyde (MDA) concentrations were measured using the method of Devasagayam and Terachand (1987). The assay consisted of Tris HCL buffer (0.5 mL), KH2 PO4 (10 mM) (0.15 mL), distilled water (0.25 mL) and tissue homogenate (0.1 µL). After incubation (37 °C for 20 mins), TCA (1.0 µL) and TBA (0.75 µL) were added, and the formation of a pink-coloured complex was read at 532 nm. The LPO level was expressed as nmol of MDA formed /mg protein. Protein concentration in the brain tissue was assayed using bovine serum albumin as a standard described by Lowry et al. (1951).
Acetylcholinesterase activity quantification
AChE activity in the brain tissue was estimated using the method of Ellman et al. (1961). 0.1 mL of 0.015 M acetylthiocholine iodide and 0.1 mL of 0.01 M DTNB (5,5-dithiobis-2-dinitrobenzoic acid) were used as a substrate along with 2.55 mL of buffer (0.1 M Phosphate buffer) and 0.2 mL of tissue homogenate. The AChE activity was expressed as μ moles/min/mg protein.
Na+/K+-ATPase activity
Na+, K+-ATPase activity was estimated as described by Shiosaka et al. (1971). Tissue extract and the assay mixture (0.3 mL of Tri-HCl buffer (pH 7.5), 0.1 mL of 0.02 M ATP, 0.1 mL of 100 mM NaCl and 0.1 mL of KCl solution) were incubated at 37 °C for 15 min and 2.00 mL of 5% TCA was added and kept at 4 °C for 30 min. After centrifugation, 1 mL of ammonium molybdate and 0.4 mL of ANSA (8-Anilino-1-naphthalenesulfonic acid) reagent were added, and the absorbance was read at 680 nm. The enzyme activity was expressed as μg/h/g.
Neurotransmitters levels
The concentrations of dopamine (DA) and serotonin (5HT) were measured using enzyme-linked immunosorbent assay (ELISA) kits (Kings Lab, India). The thawing process of the brain samples was carried out on the ice to ensure that the ambient temperature was not higher than 4 °C. Samples were weighed, homogenised in hydrochloric acid buffer, centrifuged at 4000 g for 10 min at 4 °C and the supernatant was retained and stored at -80 °C. The supernatant was used for assays according to the manufacturer's instructions.
Histological examination
The formalin-fixed brain tissue was dehydrated in ascending grades of alcohol, cleared with xylene, embedded in paraffin wax, and sectioned at a thickness of 5 µm. Sections were stained with haematoxylin and eosin stains and observed under a light microscope (Aksm et al. 2020).
Statistical Analysis
The obtained values were expressed as mean ± S.E and analysed statistically by SPSS 19.0 software. The significant differences between the control and TCEP-treated groups were tested using one-way-ANOVA (analysis of variance) followed by Duncan’s multiple range test (DMRT). The significant difference was analysed statistically at p < 0.05.
Results
We observed general stress-related behavioural changes (rapid swimming, movement around the wall of the tank, and spending time at the bottom) in the highest (1500 µg L-1) TCEP-exposed group. The observed changes can be due to the direct neurotoxicity of TCEP or alterations in AChE activity.
Antioxidant activity induced by TCEP
SOD and CAT activity was significantly (p < 0.05) decreased in the brain tissue of fish exposed to high concentration (1500 µg L-1) of TCEP (Fig. 1A, B). However, a significant statistical decrease (p < 0.05) was found in SOD and CAT activity only after 42 days of exposure to low concentration (100 µg L-1) of TCEP (Fig. 1A, B). We found that TCEP caused a significant (p < 0.05) decrease in GR activity in brain tissue (Fig. 1C) in both treatments (except on the 14th day at 100 µg L-1 of TCEP-treated groups) (Fig. 1C). In the present study, a dose-dependent decrease was observed in both concentrations.
Oxidative damage induced by TCEP
The MDA content in the brain of fish at both concentrations was significantly increased when compared with the control group (p < 0.05) (Fig. 1D). On the 14th day, there was no significant difference in MDA content between the 100 µg L-1 of the TCEP-treated group and the control group.
Neurotoxicity induced by TCEP
Exposure of fish to TCEP (100 and 1500 µg L-1) resulted in an inhibition of AChE activity compared to that of the control group (Fig. 2A). The AChE activity was inhibited significantly (p < 0.05) in treated groups, except for the 100 µg L-1 dose of TCEP on the 14th day. A concentration-related inhibition of AChE activity was observed in both experimental groups.
Na+, K+-ATPase activity induced by TCEP
In the TCEP-exposed groups, no significant difference in Na+,K+-ATPase activity was found after 42 days of exposure at both concentrations (100 and 1500 µg L-1) (Fig. 2B).
Neurotransmitter concentration induced by TCEP
The concentrations of DA and 5-HT (except on 14 and 28th day) levels were significantly increased in the brain of zebrafish treated with 100 and 1500 µg L−1 of TCEP, compared with control groups (Fig. 3A and B).
Histopathological alteration induced by TCEP
Brain tissues from the control group showed typical normal histological structures (Fig. 4A). Compared to the control group, TCEP-treated groups showed significant histopathological lesions such as cytoplasmic vacuolation, inflammatory cell infiltration, degenerated neurons, degenerated Purkinje and binucleate after 42 days (Fig. 4B, C). The severity of the histopathological changes was higher in fish exposed to the highest concentrations (1500 µg L-1) of TCEP.
Discussion
TCEP, a well-known endocrine disruptor in the aquatic environment causes adverse health issues, and ecological and biological risks (Yang et al. 2022a, b; Macedo et al. 2023). The brain has high oxygen consumption, moderate antioxidant defence, and lipid-rich properties and is also susceptible to oxidative stress (Halliwell 2006; Wu et al. 2019). Therefore, oxidative stress is the primary reason for brain injury (Liu et al. 2017; Sugiyama et al. 2018). The formation of reactive oxygen species (ROS) in fish species exposed to aquatic pollutants can be prevented by antioxidant enzymes such as SOD, CAT and GR. Alterations of these enzyme activities can be used to determine the oxidative stress caused by the toxicants (Paravani et al. 2019; Qiao et al. 2019). SOD plays a vital role in maintaining the level of active electron transfer chain and free radical chain reaction processes (Capolupo et al. 2016). The cellular antioxidant mechanism used for removing and degrading H2O2 into H2O and O2 in vivo is one of the most crucial enzyme systems, CAT (Espín et al. 2014). In the antioxidant defence system, GR is an auxiliary enzyme used to reduce oxidised glutathione (GSSG) to its active form, reduced glutathione (GSH) (Lushchak 2014). The lower values of SOD and CAT in the brain tissue of fish exposed to TCEP (1500 µg L-1) might be due to oxidative stress and the depletion of antioxidant enzymes in brain tissue (Issac et al. 2021; Ran et al. 2021). Similar to our study, a decrease in CAT and SOD activities has been reported in clams exposed to tributyl phosphate (TBP) and tris (2-butoxyethyl) phosphate (TBEP) (Yan et al. 2017). Furthermore, TCEP exposure also causes inhibition of the transcription of antioxidant defence genes in adult zebrafish (Hu et al. 2021).
In the present study, a significant decrease in SOD, CAT and GR activity in the brain of fish exposed to TCEP (100 and 1500 µg L-1) indicated that TCEP induced oxidative stress through the generation of ROS and damaged the antioxidant defence system of fish. The significant decrease in SOD and CAT activity may be a protection mechanism against the stress caused by the TCEP (Issac et al. 2021; Ran et al. 2021). Alterations of SOD, CAT, and GR activity in the brain tissue of D. rerio exposed to TCEP may be due to the failure of these enzymes to protect against the damaging action of hydrogen peroxide and hydroxyl radical (Sutha et al. 2022). The level of ROS generally increased in organisms exposed to OPFRs (Wang et al. 2019a, b). The present study observed a dose-dependent decrease in both experimental groups. The significant reduction of SOD activity in higher concentrations may be due to excess production of ROS due to TCEP toxicity. Likewise, the significant decrease in CAT activity might have resulted from its inactivation by the superoxide radical triggered by TCEP exposure. Furthermore, the observed decrease in SOD and CAT activity in low concentrations indicates prolonged exposure to TCEP might have damaged the antioxidant defence system of fish.
It has been reported that the extreme production of ROS in organisms will increase LPO levels (Wu et al. 2015). The assessment of end-product malondialdehyde (MDA) is commonly used to evaluate lipid peroxidation (Lushchak 2011). The elevation of MDA levels indicates oxidative damage to cell membranes. The significant increase in MDA content in the TCEP-exposed group indicates excessive production of ROS facilitated by TCEP. An increase in LPO levels suggests the potential of toxicants to induce a redox imbalance, which results in cellular damage (Leão-Buchir et al. 2021). In this study, liver tissue necrosis was noticed in the TCEP-exposed groups, indicating the oxidative stress caused by TCEP. Higher levels of MDA have been reported in fish species treated with organophosphate compounds (Arukwe et al. 2016; Sutha et al. 2020), and this reveals that TCEP can generate free radicals and act on the lipid profile. An increase in lipid peroxidation in TCEP-exposed salmon fish may be due to the high expression of antioxidant enzyme genes (Arukwe et al. 2016). Peng et al. (2023) reported that the mRNA expression of antioxidant-related genes in TCEP-treated zebrafish may be due to activation of the Nrf2-Keap1 pathway to protect the oxidative stress caused by TCEP. These findings suggest that chronic exposure to TCEP could cause physiological effects by disturbing the gene expression levels of the antioxidant enzyme.
AChE is a key nervous system enzyme responsible for hydrolysing acetylcholine into choline and acetic acid (O’Brien 1967). Inhibition of AChE activity is widely used to indicate exposure and effects. Inhibition of AChE activity has been reported in medaka larvae exposed to TPHP (Sun et al. 2016a, b) and in the brain tissue of Chinese rare minnows exposed to TDCPP (Yuan et al. 2016). Similarly, Shi et al. (2018) reported inhibition of AChE activity in zebrafish exposed to OPFRs. Inhibition of AChE activity in the brain tissue of fish exposed to TCEP might have resulted from the accumulation of acetylcholine in the brain due to TCEP toxicity. Accumulation of TCEP has been reported in the brain tissue of zebrafish (Wang et al. 2017). Generally, OPFRs may cause tissue damage and inhibit neurotransmitter transmission, which results in neurotoxicity (Yao et al. 2021). The potential neurotoxicity of TCEP has also been reported in many organisms (Sun et al. 2016b; Yang et al. 2018). Furthermore, the inhibition of AChE may also be due to the down-regulation of the AChE coding genes, induced by TCEP (Yang et al. 2018).
Accumulating acetylcholine at the cholinergic synapses may cause adverse effects such as behavioural and physiological abnormalities (Tilton et al. 2011). A high accumulation of OPFRs has been detected in the brain tissue of aquatic organisms (Wang et al. 2016) and in Cyprinus carpio exposed to organophosphorus flame retardants (OPFRs) (Tang et al. 2019). Triphenyl phosphate-induced oxidative stress and neurotoxicity in Labeo rohita (Umamaheswari et al. 2021). Likewise, hexabromobenzene and pentabromobenzene induced oxidative stress and neurotoxicity in zebrafish (Chen et al. 2021). ROS could inhibit AChE effects on neurotransmission in cholinergic synapses (Chen et al. 2021). Consequently, in this study, chronic exposure to TCEP can induce oxidative stress responses in fish. Oxidative stress negatively affects the nervous system and physiological development (Kim et al. 2021).
Ion-dependent ATPases are essential in intracellular functions and are widely used as biomarkers in toxicological studies (Agrahari and Gopal 2008; Ajima et al. 2021). In aquatic organisms, the transport of Na+ and K+ ions across the cell membrane is usually mediated by Na+,K+-ATPase enzymes (Li et al. 2010; Ajima et al. 2021). Na+,K+-ATPase are critical transmembrane enzymes that regulate the central nervous system’s intracellular pH, cell volume, and calcium ion concentration (Adefegha et al. 2016). Na+,K+-ATPase are potential biomarkers of oxidative stress (lipid peroxidation or protein carbonylation) in organisms (zebrafish and rats) under chemical affront (Cassol et al. 2022; Gupta et al. 2023). In this study, Na+,K+-ATPase activity in fish brains was inhibited upon exposure to TCEP. The inhibition of Na+,K+-ATPase activity may be due to the direct toxicity of TCEP on the enzyme. Inhibition of Na+,K+-ATPase indicates neuronal damage in the brain tissue of zebrafish under TCEP insult. Excessive production of ROS due to toxicant stress may also cause inhibition of Na+,K+-ATPase activity (Adefegha et al. 2016; Baldissera et al. 2019). Furthermore, toxicants-induced excessive LPO levels may alter the integrity of the plasma membrane, leading to inhibition of Na+,K+-ATPase (Oruc et al. 2002). According to the above study, perturbations in the ATPase system and disturbances in the movement of Na+, K+ ions due to TCEP toxicity may cause the inhibition of Na+,K+-ATPase activity. It was reported that inhibition of Na+,K+-ATPase and elevation of lipid oxidation levels in the brain resulted in traumatic brain injury in the mammalian model (Silva et al. 2011). We also noticed a reduction in Na+,K+-ATPase and increased LPO levels in zebrafish treated with TCEP. Notably, the AChE activity was also inhibited. The responses of these biomarkers indicate that TCEP could affect the CNS and cause neurotoxicity. Further, Na+,K+-ATPase activities are potential biomarkers for oxidative stress (LPO), ion-homeostasis, and neurotoxicity in aquatic models exposed to emerging chemicals.
Neurotransmitters such as dopamine (DA) and serotonin (5HT) play an important role in the regulation and action of neurons (Tort 2011). Dopamine is a monoamine neurotransmitter primarily involved in neurochemical and hormonal actions in vertebrates (Soares 2017). Similarly, serotonin (5-hydroxytryptamine; 5-HT) is also involved in physiological and behavioural functions (Abreu et al. 2018). Aquatic pollutants may interfere with the central nervous system and disturb brain neurotransmitters (Gaworecki and Klaine 2008; Yu et al. 2021; Huang et al. 2022). In the present study, the significant increase in dopamine levels in the brain of zebrafish exposed to TCEP indicates the neurotoxicity of TCEP. Previous authors have reported that dopamine may modulate the neurotoxic effects of aquatic pollutants (Sousa and Nunes 2020). Furthermore, TCEP may affect the synthesis of dopamine through oxidative damage to dopamine neurons (Wang et al. 2019a, b). Serotonin (5-HT) generally acts as a neurotransmitter and neuromodulator, maintaining homeostasis under stressful conditions (Thilagam et al. 2014). The serotonin system in fish is also regulated by chemical substances (Prasad et al. 2015). In the present study, the observed increase in serotonin (5-HT) levels in the brains of zebrafish treated with TCEP indicates protection against TCEP toxicity or direct action of the TCEP on the brain. The observed decrease in serotonin (5-HT) level indicates neuronal dysfunction due to TCEP toxicity. Many neurotransmitters may be released from the brain during stressful conditions to avoid or cope with the stressful conditions (Sousa and Nunes 2020). We concluded that TCEP at 100 and 1500 µg L−1 induced neurotoxicity in fish.
In the present study, TCEP induced cytoplasmic vacuolation, inflammatory cell infiltration, degenerated neurons, degenerated Purkinje and binucleate in the brain of zebrafish. Similarly, pyknosis of the nucleolus and cavitation of cytoplasm have been reported in the brain and spinal cord of zebrafish exposed to TCPP (Xia et al. 2021). The pathological changes in the brain tissue caused by toxicants may alter the behavioural and physiological functions of the fish (Yuan et al. 2015). These changes could further affect the individual’s health and, ultimately, the population and ecosystem. Histopathological anomalies have also been reported in the gill, liver, and kidney tissues of fish Cirrhinus mrigala exposed to TCEP (Sutha et al. 2020) and in the gill of catfish Pelteobagrus fulvidraco (Zhao et al. 2021).
Conclusion
Findings reported in the present study revealed that chronic exposure to high concentrations (1500 μg L-1) of TCEP caused oxidative stress, neurotoxicity, and damage to the brain tissue of zebrafish. The altered acetylcholinesterase, and Na+,K+-ATPase activities were strongly correlated with the increased oxidative stress in zebrafish brain. These results indicate that TCEP is neurotoxic to fish, and the other parameters may provide valuable information for assessing TCEP toxicity in aquatic organisms. Neurotoxicity could affect the organism’s normal physiological, behavioural (swimming, mating, eating), and biochemical activities leading to an ecological imbalance in the ecosystem or the aquatic community. Hence, strict regulations are warranted on discharging Cl-OPFRs (TCEP) in the water systems. The biomarkers studied in this study could help evaluate the potential toxicity of Cl-OPFRs on non-target organisms.
Data availability
All data generated or analysed during this study are included in this article.
References
Abreu MS, Messias JP, Thörnqvist PO, Winberg S Soares MC (2018) Monoaminergic levels at the forebrain and diencephalon signal for the occurrence of mutualistic and conspecific engagement in client reef fish. Sci Rep 8(1): 1-9. https://doi.org/10.1038/s41598-018-25513-6
Adefegha SA, Oboh G, Omojokun OS, Adefegha OM (2016) Alterations of Na+/ K+-ATPase, cholinergic and antioxidant enzymes activity by protocatechuic acid in cadmium-induced neurotoxicity and oxidative stress in Wistar rats. Biomed Pharmacother 83:559–568. https://doi.org/10.1016/j.biopha.2016.07.017
Aebi H (1984) Catalase in vitro. Methods Enzymol 105:121–126. https://doi.org/10.1016/S0076-6879(84)05016-3
Agrahari S, Gopal K (2008) Inhibition of Na+-K+-ATPase in different tissues of freshwater fish Channa punctatus (Bloch) exposed to monocrotophos. Pestic Biochem Physiol 92:57–60. https://doi.org/10.1016/j.pestbp.2008.06.003
Ajima MNO, Kumar K, Poojary N, Pandey PK (2021) Oxidative stress biomarkers, biochemical responses and Na+-K+-ATPase activities in Nile tilapia, Oreochromis niloticus exposed to diclofenac. Comp Biochem Physiol C Toxicol 240:108934. https://doi.org/10.1016/j.cbpc.2020.108934
Aksm A, Kpeds A, Lsbb D (2020) Histological and molecular changes in gill and liver of fish (Astyanax lacustris Lütken, 1875) exposed to water from the Doce basin after the rupture of a mining tailings dam in Mariana, MG Brazil. Sci Total Environ 735:139505. https://doi.org/10.1016/j.scitotenv.2020.139505
Arukwe A, Carteny CC, Eggen T (2016) Lipid peroxidation and oxidative stress responses in juvenile salmon exposed to waterborne levels of the organophosphate compounds tris (2-butoxyethyl)-and tris (2-chloroethyl) phosphates. J Toxicol Environ Health Part A 79(13–15):515–525. https://doi.org/10.1080/15287394.2016.1171978
Backström T, Winberg S (2017) Serotonin coordinates responses to social stress -What we can learn from fish. Front Neurosci 11:595. https://doi.org/10.3389/fnins.2017.00595
Baldissera MD, Souza CF, Descovi SN, Zanella R, Prestes OD, Da Silva AS, Baldisserotto B (2019) Organophosphate pesticide trichlorfon induced neurotoxic effects in freshwater silver catfish Rhamdia quelen via disruption of blood brain barrier: implications on oxidative status, cell viability and brain neurotransmitters. Comp Biochem Physiol Part C 218:8–13. https://doi.org/10.1016/j.cbpc.2018.12.006
Barros S, Coimbra AM, Alves N, Pinheiro M, Quintana JB, Santos MM, Neuparth T (2020) Chronic exposure to environmentally relevant levels of simvastin disrupts zebrafish brain gene signaling involved in energy metabolism. J Toxicol Environ Health Part A 83:113–125. https://doi.org/10.1080/15287394.2020.1733722
Behl M, Hsieh JH, Shafer TJ, Mundy WR, Rice JR, Boyd WA, Freedman JH, Hunter ES, Jarema KA, Padilla S, Tice RR (2015) Use of alternative assays to identify and prioritize organophosphorus flame retardants for potential developmental and neurotoxicity. Neurotoxicol Teratol 52:181–193. https://doi.org/10.1016/j.ntt.2015.09.003
Capolupo M, Valbonesi P, Kiwan A, Buratti S, Franzellitti S, Fabbri E (2016) Use of an integrated biomarker-based strategy to evaluate physiological stress responses induced by environmental concentrations of caffeine in the Mediterranean mussel Mytilus galloprovincialis. Sci Total Environ 563–564:538–548. https://doi.org/10.1016/j.scitotenv.2016.04.125
Carvalho CDS, Utsunomiya HSM, Stigliani TP, Costa MJ, Fernandes MN (2020) Biomarkers of the oxidative stress and neurotoxicity in tissues of the bullfrog, Lithobates catesbeianus to assess exposure to metals. Ecotoxicol Environ Saf 196:110560. https://doi.org/10.1016/j.ecoenv.2020.110560
Cassol G, Cipolat RP, Papalia WL, Godinho DB, Quines CB, Nogueira CW, Da Veiga M, Da Rocha MIUM, Furian AF, Oliveira MS, Fighera MR, Royes LFF (2022) A role of Na+, K+ -ATPase in spatial memory deficits and inflammatory/oxidative stress after recurrent concussion in adolescent rats. Brain Res Bull 180:1–11. https://doi.org/10.1016/j.brainresbull.2021.12.009
Chen X, Guo W, Lei L, Guo Y, Yang L, Han J, Zhou B (2021) Bioconcentration and developmental neurotoxicity of novel brominated flame retardants, hexabromobenzene and pentabromobenzene in zebrafish. Environ Pollu 268:115895. https://doi.org/10.1016/j.envpol.2020.115895
Chokwe TB, Abafe OA, Mbelu SP, Okonkwo JO, Sibali LL (2020) A review of sources, fate, levels, toxicity, exposure and transformations of organophosphorus flame-retardants and plasticizers in the environment. Emerg Contam 6:345–366. https://doi.org/10.1016/j.emcon.2020.08.004
Da Rocha AM, Kist LW, Almeida EA, Silva DGH, Bonan CD, Altenhofen S, Kaufmann CG Jr, Bogo MR, Barros DM, Oliveira S, Geraldo V (2019) Neurotoxicity in zebrafish exposed to carbon nanotubes: Effects on neurotransmitters levels and antioxidant system. Comp Biochem Physiol Part C Toxicol Pharmacol 218:30–35. https://doi.org/10.1016/j.cbpc.2018.12.008
David M, Richard JS (1983) J Mariare GB (Ed) Verlag Chemic Weinheina Dec Field Beach Florida based P, 358
Devasagayam TPA, Tarachand V (1987) Decreased lipid peroxidation in the rat kidney during gestation. Biochem Biophys Res Commun 145:134–138. https://doi.org/10.1016/0006-291X(87)91297-6
Ellman GL, Courtney KD, Andres jr V, Featherstone RM (1961) A new and rapid colorimetric determination of acetylcholinesterase activity. Biochem Pharmacol 7:88-95https://doi.org/10.1016/0006-2952(61)90145-9
Espín S, Martínez-López E, Jiménez P, María-Mojica P, García-Fernández AJ (2014) Effects of heavy metals on biomarkers for oxidative stress in Griffon Vulture (Gyps fulvus). Environ Res 129:59–68. https://doi.org/10.1016/j.envres.2013.11.008
García-López M, Rodríguez I, Cela R (2010) Mixed-mode solid-phase extraction followed by liquid chromatography–tandem mass spectrometry for the determination of tri-and di-substituted organophosphorus species in water samples. J Chromatogr A 1217(9):1476–1484. https://doi.org/10.1016/j.chroma.2009.12.067
Gaworecki KM, Klaine SJ (2008) Behavioral and biochemical responses of hybrid striped bass during and after fluoxetine exposure. Aquat Toxicol 88(4):207–213. https://doi.org/10.1016/j.aquatox.2008.04.011
Gupta P, Mahapatra A, Suman A, Singh RK (2023) In silico and in vivo assessment of developmental toxicity, oxidative stress response & Na+/K+-ATPase activity in zebrafish embryos exposed to cypermethrin. Ecotoxicol Environ Safe 251:114547. https://doi.org/10.1016/j.ecoenv.2023.114547
Halliwell B (2006) Oxidative stress and neurodegeneration: where are we now? J Neurochem 97:1634–1658. https://doi.org/10.1111/j.1471-4159.2006.03907.x
Hao H, Yuan S, Cheng S, Sun Q, Giesy JP, Liu C (2020) Effects of tris (2-chloroethyl) phosphate (TCEP) on growth, reproduction and gene transcription in the protozoan Tetrahymena thermophila. Aquat Toxicol 222:105477. https://doi.org/10.1016/j.aquatox.2020.105477
He H, Gao Z, Zhu D, Guo J, Yang S, Li S, Zhang L, Sun C (2017) Assessing bioaccessibility and bioavailability of chlorinated organophosphorus flame retardants in sediments. Chemosphere 189:239–246. https://doi.org/10.1016/j.chemosphere.2017.09.017
Hou L, Jiang J, Gan Z, Dai Y, Yang P, Yan Y, Ding S, Su S, Bao X (2019) Spatial distribution of organophosphorus and brominated flame retardants in surface water, sediment, groundwater, and wild fish in Chengdu, China. Arch Environ Contam Toxicol 77:279–290. https://doi.org/10.1007/s00244-019-00624-x
Hu F, Zhao Y, Yuan Y, Yin L, Dong F, Zhang W, Chen X (2021) Effects of environmentally relevant concentrations of tris (2-chloroethyl) phosphate (TCEP) on early life stages of zebrafish (Danio rerio). Environ Toxicol Pharmacol 83:103600. https://doi.org/10.1016/j.etap.2021.103600
Huang JN, Wen B, Xu L, Ma HC, Li XX, Gao JZ, Chen ZZ (2022) Micro/nano-plastics cause neurobehavioral toxicity in discus fish (Symphysodon aequifasciatus): Insight from brain-gut-micro biota axis. J Hazard Mater 421:126830. https://doi.org/10.1016/j.jhazmat.2021.126830
Issac PK, Guru A, Velayutham M, Pachaiappa R, Aras MV, Abdullah Al-Dhabi N, Choon Choi K, Harikrishnan R, Arockiaraj J (2021) Oxidative stress induced antioxidant and neurotoxicity demonstrated in vivo zebrafish embryo or larval model and their normalization due to morin showing therapeutic implications. Life Sci 283:119864. https://doi.org/10.1016/j.lfs.2021.119864
Jarema KA, Hunter DL, Shaffer RM, Behl M, Padilla S (2015) Acute and developmental behavioral effects of flame retardants and related chemicals in zebrafish. Neurotoxicol Teratol 52:194–209. https://doi.org/10.1016/j.ntt.2015.08.010
Kawagoshi Y, Fukunaga I, Itoh H (1999) Distribution of organophosphoric acid trimesters between water and sediment at a sea-based solid waste disposal site. J Mater Cycles Waste Manag 1:53–61. https://doi.org/10.1007/s10163-999-0005-6
Kim JH, Yu YB, Choi JH (2021) Toxic effects on bioaccumulation, hematological parameters, oxidative stress, immune responses and neurotoxicity in fish exposed to microplastics: A review. J Hazard Mater 413:125423. https://doi.org/10.1016/j.jhazmat.2021.125423
Kim UJ, Oh JK, Kannan K (2017) Occurrence, removal, and environmental emission of organophosphate flame retardants/plasticizers in a wastewater treatment plant in New York State. Environ Sci Technol 51:872–7880. https://doi.org/10.1021/acs.est.7b02035
Kim UJ, Wang Y, Li W, Kannan K (2019) Occurrence and human exposure to organophosphate flame retardants/plasticizers in indoor air and dust from various microenvironments in the United States. Environ Int 125:342–349. https://doi.org/10.1016/j.envint.2019.01.065
Krivoshiev BV, Beemster GT, Sprangers K, Blust R, Husson SJ (2018) A toxicogenomics approach to screen chlorinated flame retardants tris (2-chloroethyl) phosphate and tris (2-chloroisopropyl) phosphate for potential health effects. J Appl Toxicol 38(4):459–470. https://doi.org/10.1002/jat.3553
Leão-Buchir J, Folle NMT, de Souza TL, Brito PM, Oliveira EC, de Almeida Roque A, Ramsdorf WA, Fávaro LF, Garcia JRE, Esquivel L, Neto FF (2021) Effects of trophic 2, 2′, 4, 4′-tetrabromodiphenyl ether (BDE-47) exposure in Oreochromis niloticus: a multiple biomarkers analysis. Environ Toxicol Pharmacol 103693. https://doi.org/10.1016/j.etap.2021.103693
Lee S, Cho H, Choi W, Moon H (2018) Organophosphate flame retardants (OPFRs) in water and sediment: occurrence, distribution, and hotspots of contamination of Lake Shihwa, Korea. Mar Pollut Bull 130:105–112. https://doi.org/10.1016/j.marpolbul.2018.03.009
Lee S, Jeong W, Kannan K, Moon HB (2016) Occurrence and exposure assessment of organophosphate flame retardants (OPFRs) through the consumption of drinking water in Korea. Water Res 103:182–188. https://doi.org/10.1016/j.watres.2016.07.034
Li W, Yuan S, Sun Q, Liu C (2020) Toxicity of tris (2-chloroethyl) phosphate in Daphnia magna after lifetime exposure: Changes in growth, reproduction, survival and gene transcription. Ecotoxicol Environ Saf 200:110769. https://doi.org/10.1016/j.ecoenv.2020.110769
Li ZH, Zlabek V, Grabic R, Li P, Machova J, Velisek J, Randak T (2010) Effects of exposure to sublethal propiconazole on the antioxidant defense system and Na+–K+-ATPase activity in brain of rainbow trout Oncorhynchus mykiss. Aquat Toxicol 98(3):297–303. https://doi.org/10.1016/j.aquatox.2010.02.017
Li P, Li ZH (2020) Neurotoxicity and physiological stress in brain of zebrafish chronically exposed to tributyltin. J Toxicol Environ Health Part A 84(1):20–30. https://doi.org/10.1080/15287394.2020.1828209
Li R, Wang H, Mi C, Feng C, Zhang L, Yang L, Zhou B (2019a) The adverse effect of TCIPP and TCEP on neurodevelopment of zebrafish embryos/larvae. Chemosphere 220:811–817. https://doi.org/10.1016/j.chemosphere.2018.12.198
Li T, Bao L, Wu C, Liu L, Wong CS, Zeng EY (2019b) Organophosphate flame retardants emitted from thermal treatment and open burning of e-waste. J Hazard Mater 367:390–396. https://doi.org/10.1016/j.jhazmat.2018.12.041
Liu X, Sui B, Sun J (2017) Blood-brain barrier dysfunction induced by silica NPs in vitro and in vivo: Involvement of oxidative stress and Rho-kinase/JNK signaling pathways. Biomaterials 121:64–82. https://doi.org/10.1016/j.biomaterials.2017.01.006
Lowry OH, Rosebrough NJ, Farr AL, Randall RJ (1951) Protein measurement with the folin phenol reagent. J Biol Chem 193:265–275. https://doi.org/10.1016/S0021-9258(19)52451-6
Lushchak VI (2011) Environmentally induced oxidative stress in aquatic animals. Aquat Toxicol 101(1):13–30. https://doi.org/10.1016/j.aquatox.2010.10.006
Lushchak VI (2014) Free radicals, reactive oxygen species, oxidative stress and its classification. Chem Biol Interact 224:164–175. https://doi.org/10.1016/j.cbi.2014.10.016
Ma Y, Cui K, Zeng F, Wen J, Liu H, Zhu F, Ouyang G, Luan T, Zeng Z (2013) Microwave-assisted extraction combined with gel permeation chromatography and silica gel cleanup followed by gas chromatography–mass spectrometry for the determination of organophosphorus flame retardants and plasticizers in biological samples. Anal Chim Acta 786:47–53. https://doi.org/10.1016/j.aca.2013.04.062
Macedo S, Teixeira E, Gaspar TB, Boaventura P, Soares MA, Miranda-Alves L, Soares P (2023) Endocrine-disrupting chemicals and endocrine neoplasia: A forty-year systematic review. Environ Res 218:114869. https://doi.org/10.1016/j.envres.2022.114869
Marklund A, Andersson B, Haglund P (2005) Organophosphorus flame retardants and plasticizers in Swedish sewage treatment plants. Environ Sci Technol 39:7423–7429. https://doi.org/10.1021/es051013l
Marklund S, Marklund G (1974) Involvement of the superoxide anion radical in the autoxidation of pyrogallol and a convenient assay for superoxide dismutase. Eur J Biochem 47:469–474. https://doi.org/10.1111/j.1432-1033.1974.tb03714.x
Mayer FL, Versteeg DJ, McKee MJ, Folmar LC, Graney RL, McCume DC, Rattner BA (1992) Physiological and nonspecific biomarkers. In: Huggett RJ, Kimerle RA, Mehrle PM, Bergman HL (eds) Biomarkers—biochemical, physiological, and histological markers of anthropogenic stress. Lewis Publ, Boca Raton, FL, pp 5–85
Mihajlović I, Fries E (2012) Atmospheric deposition of chlorinated organophosphate flame retardants (OFR) onto soils. Atmos Environ 56:177–183. https://doi.org/10.1016/j.atmosenv.2012.03.054
O’Brien JS (1967) Cell membranes—composition: structure: function. J Theo Biol 15(3):307–324. https://doi.org/10.1016/0022-5193(67)90140-3
O’Brien JW, Thai PK, Brandsma SH, Leonards PE, Ort C, Mueller JF (2015) Wastewater analysis of Census day samples to investigate per capita input of organophosphorus flame retardants and plasticizers into wastewater. Chemosphere 138:328–334. https://doi.org/10.1016/j.chemosphere.2015.06.014
OECD/OCDE (2013) Fish Embryo Acute Toxicity (FET) Test, OECD Guidelines for the testing of chemicals.
Oruc EO, Uner N, Tamer L (2002) Comparison of Na+ K+-ATPase activities and malondialdehyde contents in liver tissue for three fish species exposed to azinphosmethyl. Bull Environ Contam Toxicol 69(2):271–277. https://doi.org/10.1007/s00128-002-0057-y
Paravani E, Simoniello MF, Poletta GL, Casco VH (2019) Cypermethrin induction of DNA damage and oxidative stress in zebrafsh gill cells. Ecotoxicol Environ Saf 30:1–7. https://doi.org/10.1016/j.ecoenv.2019.02.004
Peng H, Wang H, Li W, Jing C, Zhang W, Zhao H, Hu F (2023) Life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in antioxidative status, ion regulation and histology of zebrafish gills. Comp Biochem Physiol Part C Toxicol Pharmacol 274:109746. https://doi.org/10.1016/j.cbpc.2023.109746
Prasad P, Ogawa S, Parhar IS (2015) Role of serotonin in fish reproduction. Front Neurosci 9:195. https://doi.org/10.3389/fnins.2015.00195
Qi C, Yu G, Zhong M, Peng G, Huang J, Wang B (2019) Organophosphate flame retardants in leachates from six municipal landfills across China. Chemosphere 218:836–844. https://doi.org/10.1016/j.chemosphere.2018.11.150
Qiao R, Sheng C, Lu Y, Zhang Y, Ren H, Lemos B (2019) Microplastics induce intestinal inflammation, oxidative stress, and disorders of metabolome and microbiome in zebrafish. Sci Total Environ 662:246–253. https://doi.org/10.1016/j.scitotenv.2019.01.245
Ramesh M, Anitha S, Poopal RK, Shobana C (2018) Evaluation of acute and sublethal effects of chloroquine (C18H26CIN3) on certain enzymological and histopathological biomarker responses of a freshwater fish Cyprinus carpio. Toxicol Rep 5:18–27. https://doi.org/10.1016/j.toxrep.2017.11.006
Ran L, Yang Y, Zhou X, Jiang X, Hu D, Lu P (2021) The enantioselective toxicity and oxidative stress of dinotefuran on zebrafish (Danio rerio). Ecotoxicol Environ Saf 226:112809. https://doi.org/10.1016/j.ecoenv.2021.112809
Sachett A, Bevilaqua F, Chitolina R, Garbinato C, Gasparetto H, Dal Magro J, Conterato GM, Siebel AM (2018) Ractopamine hydrochloride induces behavioral alterations and oxidative stress in zebrafish. J Toxicol Environ Health Part A 81:194–201. https://doi.org/10.1080/15287394.2018.1434848
Shi Q, Guo W, Shen Q, Han J, Lei L, Chen L, Yang L, Feng C, Zhou B (2021) In vitro biolayer interferometry analysis of acetylcholinesterase as a potential target of aryl-organophosphorus flame-retardants. J Hazard Mater 409:124999. https://doi.org/10.1016/j.jhazmat.2020.124999
Shi QP, Wang M, Shi FQ, Yang LH, Guo YY, Feng CL, Liu JF, Zhou BS (2018) Developmental neurotoxicity of triphenyl phosphate in zebrafish larvae. Aquat Toxicol 203:80–87. https://doi.org/10.1016/j.aquatox.2018.08.001
Shiosaka T, Okuda H, Fujii S (1971) Mechanism of the phosphorylation of thymidine by the culture filtrates of Clostridium perfringens and rat liver extract. Biochim Et Biophys Acta 246(2):171–183. https://doi.org/10.1016/0005-2787(71)90125-0
Silva LFA, Hoffmann MS, Rambo LM, Ribeiro LR, Lima FD, Furian AF, Oliveira MS, Fighera MR, Royes LFF (2011) The involvement of Na+, K+-ATPase activity and free radical generation in the susceptibility to pentylenetetrazol-induced seizures after experimental traumatic brain injury. J Neurol Sci 308:35–40. https://doi.org/10.1016/j.jns.2011.06.030
Soares MC (2017) The neurobiology of mutualistic behavior: the cleaner fish swims into the spotlight. Front Behav Neurosci 11:1–12. https://doi.org/10.3389/fnbeh.2017.00191
Sousa B, Nunes B (2020) Reliability of behavioral test with fish: How neurotransmitters may exert neuromodulatory effects and alter the biological responses to neuroactive agents. Sci Total Environ 734:139372. https://doi.org/10.1016/j.scitotenv.2020.139372
Stackelberg PE, Furlong ET, Meyer MT, Zaugg SD, Henderson AK, Reissman DB (2004) Persistence of pharmaceutical compounds and other organic wastewater contaminants in a conventional drinking-water-treatment plant. Sci Total Environ 329(1–3):99–113. https://doi.org/10.1016/j.scitotenv.2004.03.015
Sugiyama T, Imai T, Nakamura S, Yamauchi K, Sawada S, Shimazawa M, Hara H (2018) A novel Nrf2 activator, RS9, attenuates secondary brain injury after intracerebral hemorrhage in sub-acute phase. Brain Res 1701:137–145. https://doi.org/10.1016/j.brainres.2018.08.021
Sutha J, Anila PA, Umamaheswari S, Ramesh M, Arul N, Poopal RK, Ren Z (2020) Biochemical responses of a freshwater fish Cirrhinus mrigala exposed to tris (2-chloroethyl) phosphate (TCEP). Environ Sci Pollu Res 27(27):34369–34387. https://doi.org/10.1007/s11356-020-09527-0
Sutha J, Anila PA, Gayathri M, Ramesh M (2022) Long term exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in reproductive hormones, vitellogenin, antioxidant enzymes, and histology of gonads in zebrafish (Danio rerio): In vivo and computational analysis. Comp Biochem Physiol Part C Toxicol Pharmacol 254:109263. https://doi.org/10.1016/j.cbpc.2021.109263
Sun L, Tan H, Peng T, Wang S, Xu W, Qian H, Jin Y, Fu Z (2016a) Developmental neurotoxicity of organophosphate flame retardants in early life stages of Japanese medaka (Oryzias latipes). Environ Toxicol Chem 35(12):2931–2940. https://doi.org/10.1002/etc.3477
Sun L, Xu W, Peng T, Chen H, Ren L, Tan H, Xiao D, Qian H, Fu Z (2016b) Developmental exposure of zebrafish larvae to organophosphate flame retardants causes neurotoxicity. Neurotoxicol Teratol 55:16–22. https://doi.org/10.1016/j.ntt.2016.03.003
Sundkvist AM, Olofsson U, Haglund P (2010) Organophosphorus flame retardants and plasticizers in marine and fresh water biota and in human milk. J Environ Monitor 12:943. https://doi.org/10.1039/b921910b
Tang T, Lu G, Wang W, Wang R, Huang K, Qiu Z, Tao X, Dang Z (2018) Photocatalytic removal of organic phosphate esters by TiO2: Effect of inorganic ions and humic acid. Chemosphere 206:26–32. https://doi.org/10.1016/j.chemosphere.2018.04.161
Tang B, Poma G, Bastiaensen M, Yin SS, Luo XJ, Mai BX, Covaci A (2019) Bioconcentration and biotransformation of organophosphorus flame retardants (PFRs) in common carp (Cyprinus carpio). Environ Internat 126:512–522. https://doi.org/10.1016/j.envint.2019.02.063
Thilagam H, Gopalakrishnan S, Bo J, Wang KJ (2014) Comparative study of 17 β-estradiol on endocrine disruption and biotransformation in fingerlings and juveniles of Japanese sea bass Lateolabrax japonicus. Mar Pollut Bull 85(2):332–337. https://doi.org/10.1016/j.marpolbul.2014.05.024
Tilton FA, Bammler TK, Gallagher EP (2011) Swimming impairment and acetylcholinesterase inhibition in zebrafish exposed to copper or chlorpyrifos separately, or as mixtures. Comp Biochem Physiol Part C Toxicol Pharmacol 153(1):9–16. https://doi.org/10.1016/j.cbpc.2010.07.008
Tort L (2011) Stress and immune modulation in fish. Develop Comp Immunol 35(12):1366–1375. https://doi.org/10.1016/j.dci.2011.07.002
Umamaheswari S, Karthika P, Suvenitha K, Kadirvelu K, Ramesh M (2021) Dose-dependent molecular responses of Labeo rohita to triphenyl phosphate. Chem Res Toxicol 20:2500–2511. https://doi.org/10.1021/acs.chemrestox.1c00281
Veen IVD, Boer JD (2012) Phosphorus flame retardants: Properties, production, environmental occurrence, toxicity and analysis. Chemosphere 2:1119–1153. https://doi.org/10.1016/j.chemosphere.2012.03.067
Wang H, Jing C, Peng H, Liu S, Zhao H, Zhang W, Chen X, Hu F (2022) Parental whole life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) disrupts embryonic development and thyroid system in zebrafish offspring. Ecotoxicol Environ Safe 248:114313. https://doi.org/10.1016/j.ecoenv.2022.114313
Wang C, An J, Bai Y, Li H, Chen H, Ou D, Liu Y (2019a) Tris (1, 3-dichloro-2- propyl) phosphate accelerated the aging process induced by the 4-hydroxynon-2- enal response to reactive oxidative species in Caenorhabditis elegans. Environ Pollut 246:904–913. https://doi.org/10.1016/j.envpol.2018.12.082
Wang G, Du Z, Chen H, Su Y, Gao S, Mao L (2016) Tissue-specific accumulation, depuration, and transformation of triphenyl phosphate (TPHP) in adult zebrafish (Danio rerio). Environ Sci Technol 24:13555–13564. https://doi.org/10.1021/acs.est.6b04697
Wang G, Shi H, Du Z, Chen H, Peng J, Gao S (2017) Bioaccumulation mechanism of organophosphate esters in adult zebrafish (Danio rerio). Environ Pollu 229:177–187. https://doi.org/10.1016/j.envpol.2017.05.075
Wang Q, Lin F, He Q, Liu X, Xiao S, Zheng L, Yang H, Zhao H (2019b) Assessment of the effects of bisphenol A on dopamine synthesis and blood vessels in the goldfish brain. Int J Mol Sci 20(24):6206. https://doi.org/10.3390/ijms20246206
World Health Organization (1998) Flame Retardants: Tris (Chloropropyl) Phosphate and Tris (2-Chloroethyl) Phosphate.
Wu Q, Yan W, Liu C, Hung TC, Li G (2019) Co-exposure with titanium dioxide nanoparticles exacerbates. MCLR-induced brain injury in zebrafish. Sci Total Environ 693:133540. https://doi.org/10.1016/j.scitotenv.2019.07.346
Wu Y, Su G, Tang S, Liu W, Ma Z, ZhengnX LH, Yu H (2017) The combination of in silico and in vivo approaches for the investigation of disrupting effects of tris (2-chloroethyl) phosphate (TCEP) toward core receptors of zebrafish. Chemosphere 168:122–130. https://doi.org/10.1016/j.chemosphere.2016.10.038
Wu SM, Liu JH, Shu LH, Chen CH (2015) Anti-oxidative responses of zebrafish (Danio rerio) gill, liver and brain tissue upon acute cold shock. Comp Biochem Physiol A Mol Integr Physiol 187:202–213. https://doi.org/10.1016/j.cbpa.2015.05.016
Xia M, Wang X, Xu J, Qian Q, Gao M, Wang H (2021) Tris (1-chloro-2-propyl) phosphate exposure to zebrafish causes neurodevelopmental toxicity and abnormal locomotor behavior. Sci Total Environ 758:143694. https://doi.org/10.1016/j.scitotenv.2020.143694
Xu L, Hu Q, Liu J, Liu S, Liu C, Deng Q, Zeng X, Yu ZJEP (2019) Occurrence of organophosphate esters and their diesters degradation products in industrial wastewater treatment plants in China: Implication for the usage and potential degradation during production processing. Environ Pollut 250:559–566. https://doi.org/10.1016/j.envpol.2019.04.058
Xu Q, Wu D, Dang Y, Yu L, Liu C, Wang J (2017) Reproduction impairment and endocrine disruption in adult zebrafish (Danio rerio) after waterborne exposure to TBOEP. Aquat Toxicol 182:163–171. https://doi.org/10.1016/j.aquatox.2016.11.019
Yan S, Wu H, Qin J, Zha J, Wang Z (2017) Halogen-free organophosphorus flame retardants caused oxidative stress and multixenobiotic resistance in Asian freshwater clams (Corbicula fluminea). Environ Pollut 225:559–568. https://doi.org/10.1016/j.envpol.2017.02.071
Yan X, He H, Peng Y, Wang X, Gao Z, Yang S, Sun C (2012) Determination of organophosphorus flame retardants in surface water by solid phase extraction coupled with gas chromatography-mass spectrometry. Chinese J Anal Chem 40:1693–1697. https://doi.org/10.1016/S1872-2040(11)60586-0
Yang D, We X, Zhang Z, Chen X, Zhu R, Oh Y, Gu N (2022a) Tris (2-chloroethyl) phosphate (TCEP) induces obesity and hepatic steatosis via FXR-mediated lipid accumulation in mice: Long-term exposure as a potential risk for metabolic diseases. Chemico-Biol Interact 363:110027. https://doi.org/10.1016/j.cbi.2022.110027
Yang L, Huang C, Yin Z, Meng J, Guo M, Feng L, Liu Y, Zhang L, Du Z (2021) Rapid electrochemical reduction of a typical chlorinated organophosphorus flame retardant on copper foam: degradation kinetics and mechanisms. Chemosphere 264(2):128515. https://doi.org/10.1016/j.chemosphere.2020.128515
Yang L, Yin Z, Tian Y, Liu Y, Feng L, Ge H, Du Z Zhang L (2022). A new and systematic review on the efficiency and mechanism of different techniques for OPFRs removal from aqueous environments. J Hazard Mater 431: p.128517. https://doi.org/10.1016/j.jhazmat.2022.128517
Yang J, Zhao Y, Li M, Du M, Li X, Li Y (2019) A review of a class of emerging contaminants: the classification, distribution, intensity of consumption, synthesis routes, environmental effects and expectation of pollution abatement to organophosphate flame retardants (OPFRs). Int J Mol Sci 20(12):2874. https://doi.org/10.3390/ijms20122874
Yang Y, Xiao Y, Chang Y, Cui Y, Klobučar G, Li M (2018) Intestinal damage, neurotoxicity and biochemical responses caused by tris (2-chloroethyl) phosphate and tricresyl phosphate on earthworm. Ecotoxicol Environ Saf 158:78–86. https://doi.org/10.1016/j.ecoenv.2018.04.012
Yao C, Yang H, Li Y (2021) A review on organophosphate flame retardants in the environment: Occurrence, accumulation, metabolism and toxicity. Sci Total Environ 795:148837. https://doi.org/10.1016/j.scitotenv.2021.148837
Yuan L, Li J, Zha J, Wang Z (2016) Targeting neurotrophic factors and their receptors, but not cholinesterase or neurotransmitter, in the neurotoxicity of TDCPP in Chinese rare minnow adults (Gobiocypris rarus). Environ Pollut 208:670–677. https://doi.org/10.1016/j.envpol.2015.10.045
Yuan H, Myers SJ, Wells G, Nicholson KL, Swanger SA, Lyuboslavsky P, Tahirovic YA, Menaldino DS, Ganesh T, Wilson LJ, Liotta DC (2015) Context-dependent GluN2B-selective inhibitors of NMDA receptor function are neuroprotective with minimal side effects. Neuron 85(6):1305–1318. https://doi.org/10.1016/j.neuron.2015.02.008
Yu Y, Hou Y, Dang Y, Zhu X, Li Z, Chen H, Xiang M, Li Z, Hu G (2021) Exposure of adult zebrafish (Danio rerio) to Tetrabromobisphenol A causes neurotoxicity in larval offspring, an adverse transgenerational effect. J Hazard Mater 414:125408. https://doi.org/10.1016/j.jhazmat.2021.125408
Zhao Y, Yin L, Dong F, Zhang W, Hu F (2021) Effects of tris (2-chloroethyl) phosphate (TCEP) on survival, growth, histological changes and gene expressions in juvenile yellow catfish Pelteobagrus fulvidraco. Environ Toxicol Pharmacol 87:103699. https://doi.org/10.1016/j.etap.2021.103699
Zhu Y, Ma X, Su G, Yu L, Letcher RJ, Hou J, Yu H, Giesy JP, Liu C (2015) Environmentally relevant concentrations of the flame retardant tris (1, 3-dichloro-2- propyl) phosphate inhibit growth of female zebrafish and decrease fecundity. Environ Sci Technol 49:14579–14587. https://doi.org/10.1021/acs.est.5b03849
Funding
The author (Jesudass Sutha) wish to thank Rashtriya Uchchattar Shiksha Abhiyan (RUSA) 2.0 – BCTRC Bharathiar Cancer Theranostics Research Centre for providing fellowship.
Author information
Authors and Affiliations
Contributions
Jesudass Sutha: Conceptual framework, Experiments, Investigation, Data curation, Original manuscript writing.
Murugesh Gayathri: Resources, Experiments, Investigation, Formal data analysis.
Mathan Ramesh: Conceptual framework, Supervision, Resources, Writing—review and editing.
Corresponding author
Ethics declarations
Ethical approval
The present study was conducted as per the guidelines of the OECD for maintaining and handling fish (OECD/OCDE 2013) and the Committee for the Control and Supervision of Experiments on Animals (CPCSEA).
Consent to participate
Not applicable.
Consent for publication
Not applicable.
Competing interests
The authors declare that they have no competing interests.
Additional information
Responsible Editor: Bruno Nunes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary Information
Below is the link to the electronic supplementary material.
Rights and permissions
Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
About this article
Cite this article
Sutha, J., Gayathri, M. & Ramesh, M. Chronic exposure to tris (2-chloroethyl) phosphate (TCEP) induces brain structural and functional changes in zebrafish (Danio rerio): A comparative study on the environmental and LC50 concentrations of TCEP. Environ Sci Pollut Res 31, 16770–16781 (2024). https://doi.org/10.1007/s11356-024-32154-y
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11356-024-32154-y