The assessment of cholinesterase from the liver of Puntius javanicus as detection of metal ions

Exposure to different cobalt chloride levels produces oxidative stress and lipidomic changes and affects the liver structure of Cyprinus carpio juveniles

The present investigation was undertaken to evaluate the toxic effects of CoCl2-induced hepatotoxicity and fatty acid changes in juvenile Cyprinus carpio. Fish were divided into six experimental groups in duplicate. The first group served as controls. The second group received the lowest exposure dose at 2.5 µg/L. In the third group, fish were exposed to 25 µg/L of CoCl2. The fourth group was exposed to 50 µg/L of CoCl2. The last two groups were exposed to the highest doses, 100 and 500 µg/L of CoCl2. Total antioxidant activities were estimated using a colorimetric method. Liver fatty acid compositions were analyzed by high-performance gas chromatography (GC). Hepatopathy was identified through microscopic analysis. Exposure of C. carpio to CoCl2 resulted in hepatotoxicity, indicated by increased levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), protein carbonyls (PCO), and alterations in the ferric reducing antioxidant power system (FRAP). Superoxide dismutase (SOD), glutathione-S-transferase (GST), glutathione peroxidase (GPx), reduced glutathione (GSH), metallothioneins (MTs), and low thiol levels (L-SH) significantly increased, particularly under exposure to the highest CoCl2 doses (100 and 500 µg/L). Acetylcholinesterase activity decreased significantly in C. carpio exposed to graded CoCl2 doses. Additionally, there was a decrease in polyunsaturated fatty acids (PUFA), primarily n-3 PUFA, docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA), while an increase in monounsaturated (MUFA) and saturated fatty acids (SFA), including palmitic (C16:0), stearic (C18:0), palmitoleic (C16:1), and oleic (C18:1) acids, was observed. Histopathological examination of the liver confirmed hepatopathy revealing characteristic tissue changes such as leucocyte infiltration, hepatic cell membrane degradation, vacuolization, and lipid inclusions. The study provided ethnophysiology insights into the responses of C. carpio to CoCl2-induced oxidative stress and lipidomic alteration, underscoring its potential as a bioindicator for assessing environmental impacts and metal contamination.

Characterisation of ChE in Solea solea and exposure of isoflavones in juveniles of commercial flatfish (Solea solea and Solea senegalensis)

The isoflavones genistein and daidzein are flavonoid compounds mainly found in legumes, especially in soybeans and their derived products. These flavonoids can be present in agricultural, domestic and industrial wastewater effluents as a result of anthropogenic activities and may be discharged in the environment. Due to the large growth of the aquaculture sector in recent decades, new and cost-effective fish feeds are being sought, but there is also a particular need to determine the effects of exposed flavonoids on fish in the aquatic environment, as this is the main route of exposure of organisms to endocrine disruptors. This study evaluated the possible effects of these isoflavones on juveniles of Solea senegalensis and Solea solea. After 48-96 h of exposure, the acetylcholinesterase activity in the sole head tissues was measured, and the cholinesterase activity in juveniles of common sole (S. solea) was determined. Experiments were carried out to determine the optimal pH, investigate the specificity of three substrates (acetylthiocholine, butyrylthiocholine, propionylthiocholine) on cholinesterase activity and determine the kinetic parameters (Vmax and Km ). The results obtained showed that neither genistein nor daidzein exposure to S. senegalensis and S. solea inhibited the activity of acetylcholinesterase at the tested concentrations (genistein: 1.25, 2.5, 5, 10 and 20 mg/L; daidzein: 0.625, 1.25, 2.5, 5 and 10 mg/L).

Multi-biomarker approach to assess chromium, pH and temperature toxicity in fish

Chromium (Cr) is considered as the most common ubiquitous pollutant for aquatic animals including fish. An experiment was conducted to determine the acute and chronic toxicity of Cr, pH and high temperature in Anabas testudineus. Lethal concentration (LC₅₀) of Cr alone was determined as 55.02 mg L^-1, Cr and low pH 48.19 mg L^-1 and Cr, low pH and high temperature 47.16 mg L^-1. The chronic toxicity of low dose of Cr, pH and high temperature (1/10th and 1/20th of LC₅₀) was designed to execute the experiment for 72 days. The stress enzymes and biomarkers were determined viz. superoxide dismutase, catalase, glutathione peroxidase, glutathione-s-transferase, lipid peroxide, acetylcholine esterase, cortisol, HSP-70, blood glucose, aspartate amino transferase, alanine amino transferase and malate dehydrogenase, lactate dehydrogenase, ATPase and genotoxicity in this study. We had also studied the integrated biomarker response (IBR), which revealed that Cr toxicity enhanced with concurrent exposure to pH and high temperature. All the biochemical attributes were significantly altered with exposure to Cr alone and with low pH and high temperature except gill SOD. Further, thermal tolerance was also determined, and results revealed that thermal tolerance was significantly reduced with exposure to Cr alone and Cr and low pH exposure in A. testudineus. The present study concluded that, the chronic toxicity of Cr is enhanced with low pH and high temperature and it has led to understanding the multi-approach of Cr toxicity which affect, stress biomarkers, cellular metabolic stress and thermal tolerance of A. testudineus.

Microplastics alone or co-exposed with copper induce neurotoxicity and behavioral alterations on zebrafish larvae after a subchronic exposure

Microplastics (MPs, <5 mm) have been frequently detected in aquatic ecosystems, representing both health and ecological concerns. However data about the combined effects of MPs and other contaminants is still limited. This study aimed to evaluate the impact of MPs and the heavy metal copper (Cu) on zebrafish (Danio rerio) larvae development and behavior. Zebrafish embryos were subchronically exposed to MPs (2 mg/L), two sub-lethal concentrations of Cu (60 and 125 µg/L) and binary mixtures of MPs and Cu using the same concentrations, from 2-h post fertilization until 14 days post fertilization. Lethal and sub-lethal responses (mortality, hatching, body length) were evaluated during the embryogenesis period, and locomotor, avoidance, anxiety and shoaling behaviors, and acetylcholinesterase (AChE) activity were measured at 14 dpf. The results showed that survival of larvae was reduced in groups exposed to MPs, Cu and Cu+MPs. Regarding the behavioral patterns, the higher Cu concentration and mixtures decreased significantly the mean speed, the total distance traveled and the absolute turn angle, demonstrating an adverse effect on swimming competence of zebrafish larvae. Exposure to MPs and Cu, alone or combined, also affected avoidance behavior of zebrafish, with larvae not reacting to the aversive stimulus. There was a significant inhibition of AChE activity in larvae exposed to all experimental groups, compared to the control group. Moreover, a higher inhibition of AChE was noticed in larvae exposed to MPs and both Cu+MPs groups, comparatively to the Cu alone groups. Our findings demonstrate the adverse effects of MPs, alone or co-exposed with Cu, on fish early life stages behavior. This study highlights that MPs and heavy metals may have significant impacts on fish population fitness by disrupting locomotor and avoidance behaviors.

Acetylcholine Receptor-based Biosensor Derived from Asian Swamp Eel, Monopterus Albus for Heavy Metals Biomonitoring

Cholinesterase-based biosensor well known as a sensitive method to detect the existence of harmful dissolved compounds in any type of water source, especially the river. This alternative biosensor can be used to determine the level of pollution of the water in a short period of time as well as to evaluate the low cost and simple service. The aim of this study was to exceed the effectiveness of acetylcholinesterase source extracted from the brain tissue of Asian swamp eel; Monopterus albus as a potential environmental biosensor. Purified acetylcholinesterase exposed to a different type of metal ions and mercury showed the highest percentage of inhibition at 62.9% followed by chromium at 59.22% while silver, arsenic, cadmium, cobalt, copper, nickel, zinc a¬¬nd lead at not more than 50% (approximately 37-50%). Metal ions such as mercury, zinc, chromium and copper showed exponential decay type inhibition curves with calculated half maximal inhibitory concentration; IC50 in the ascending sensitivity order 0.005, 0.595, 0.687 and 1.329 mgL-1, respectively. Field trial works exhibited that the acetylcholinesterase was applicable in sensing heavy metals pollution from the river which closed to the industrial and agricultural sites at near real-time and verified using ICP-OES. This study proves the potential use of acetylcholinesterase sourced from M. albus as a biomonitoring tool to assess the contamination level of the river.

Biochemical profile and gene expression of Clarias gariepinus as a signature of heavy metal stress

Heavy metals have been found in increasing concentrations in the aquatic environment. Fishes exposed to such metals have altered gene expression, serum profiles, tissue histology and bioindices that serve as overall health biomarkers. The heavy metals (Ni, Cd, and Cr) accumulated in water and fish tissues, were beyond the permissible limits defined by the Central Pollution Control Board/World Health Organization. Metallothionein (MT) and glutathione peroxidase (GPX) genes expression patterns highlighted the metal-specific exposure of fish. An increased fold change of genes against beta-actin serves as a potential feature for toxicity. Metal toxicity is also reflected by an increased level of digestive enzymes (amylase and lipase) in the serum and alterations in values of reproductive hormones (11-Ketotestosterone and progesterone). Total serum bilirubin attribute to the liver and biliary tract disease in fishes. Histopathological studies show cellular degeneration, breakage, vacuolization signifying the chronic stress.

Assessment of Monopterus albus liver as a source of Cholinesterase for the detection of heavy metals

Heavy metals pollution has now become a serious environmental problem worldwide especially in Malaysia River. As a precaution, continuous environmental monitoring is needed to minimize heavy metal to the ecosystem. Inhibitive enzyme assay based on enzyme including cholinesterase has been introduced as a rapid, cheap and reliable method to assess the level of contamination in the river. In this study, the Asian swamp eel,Monopterus albus, was selected and determined of the sensitivity level towards heavy metals. The liver of M. albus was extracted and purified using ion exchange chromatography of which DEAE sepharose as the matrix of the column. Based on the Ellman assay, cholinesterase was obtained at 4.86 purification fold with the percentage recovery of 30.32 %. The enzyme works optimally at pH 9 (0.1 M Tris-HCl buffer) and 25 °C, while BTC; 369×103U.mg−1was selected as the preferable substrate which shows highest catalytic efficiencies compared to ATC and BTC at 1457 × 103, 1220 × 103and 488 × 103Vmax.Km−1, respectively, Cholinesterase was tested with eight metal ions at the concentration of 5 ppm and the ascending order of inhibition is as followed; arsenic = chromium ⩽ plumbum ⩽ copper ⩽ argentum = nickel < mercury. From this study, the ability of cholinesterase partially purified from the liver tissue ofM. albushas the potential to be an assay for heavy metals.

Characterization and kinetic study of the brain and muscle acetylcholinesterase from Danio rerio

Acetylcholinesterase (AChE) plays an important role in the therapy of Alzheimer's disease and in the detection of pesticides such as organophosphates which are also widely used in chemical warfare. The aim of this study is the physicochemical and kinetic characterization of brain and muscle ChE from Danio rerio (Zebrafish). Optimal activity was found for brain ChE at alkaline pH 9.0 at 30 °C, and for muscle ChE at alkaline pH 8.5 at temperatures between 20 °C and 35 °C. The apparent kinetic constants, K_m^app and V_max^app, for brain ChE were determined as 0.191 ± 0.024 mM and 0.566 ± 0.028 U/mg protein, and for muscle ChE as 0.230 ± 0.030 mM and 0.677 ± 0.039 U/mg protein. Both brain and muscle ChE showed inhibition at high substrate concentrations. Brain and muscle ChE showed IC50 values for physostigmine of 0.61 μM and 0.37 μM, respectively. The ChE activity in brain was significantly inhibited by BW254c51 in all concentrations tested, but not by Iso-OMPA, while muscle ChE presented a moderate decrease (13 to 29%) in the activity values, indicating that BuChE is present.

In vivo and in vitro effects on cholinesterase of blood of Oreochromis mossambicus by copper

The present study is aimed to evaluate the effects of sub-acute toxicity testing of copper sulphate (CuSO₄), on behavioural, histological and biochemical changes of the Oreochromis mossambicus (black tilapia) blood tissues. The effects were assessed according to the previous results on sub-acute toxicity test after exposing fish to several concentrations (0.0, 2.5, 5.0, and 10.0 mg/L). The observations of scanning electron microscope, and transmission electron microscope studies revealed severe histopathological changes on the surface and the cellular changes in blood tissues, respectively. The morphological alterations in blood involved irregular structure of red blood cell and blood clot formation. CuSO₄ affected the biochemical alteration of the blood cholinesterase also known as serum cholinesterase (ChE). Blood ChE inhibited up to 80% of activity when exposed to 10.0 mg/L CuSO₄. The findings from this study can further improve the quality standards of aquaculture industry and the fundamental basis in selecting suitable strains among freshwater fish species to be used as bioindicator.

Toxic effects of copper on liver and cholinesterase of Clarias gariepinus

The release of pollutants, especially heavy metals, into the aquatic environment is known to have detrimental effects on such an environment and on living organisms including humans when those pollutants are allowed to enter the food chain. The aim of this study is to analyse the damage to Clarias gariepinus' liver caused by exposure to different concentrations of copper. In the present study, samples of C. gariepinus were exposed to sub-lethal copper sulphate (CuSO₄) concentrations (from 0.2 to 20.0 mg/L) for 96 h. Physiological and behavioural alterations were observed with respect to their swimming pattern, mucus secretion and skin colour. Mortality was also observed at high concentrations of copper. Histopathological alterations of the liver were analysed under light, transmission and scanning electron microscopies. The liver of the untreated group showed normal tissue structures, while histopathological abnormalities were observed in the treated fish under light and electron microscopes with increased copper concentrations. Histopathological abnormalities include necrosis, melanomacrophage, hepatic fibrosis and congested blood vessels. In addition, the enzyme activity of liver cholinesterase (ChE) was also found to be affected by copper sulphate, as 100% of cholinesterase activity was inhibited at 20.0 mg/L. Thus, liver enzyme activity and histopathological changes are proven to be alternative sources for biomarkers of metal toxicity.