A monoclonal antibody against Lates calcarifer vitellogenin and a competitive ELISA to evaluate vitellogenin induction after exposure to xenoestrogen

Development of colloidal gold test strip based on the BsVg819 gene fragment of vitellogenin of Bostrichthys sinensis for the detection of vitellogenin in multiple fish species

As an environmental estrogen biomarker, the yolk precursor, vitellogenin (Vtg) is widely used in the assessment of estrogen pollution in aquatic environment. Currently, the detection of Vtg in plasma is mainly achieved by enzyme-linked immunosorbent assay (ELISA) method based on Vtg antibodies. However, due to differences in the immunological epitopes of Vtg from various species, Vtg antibodies have low universality. Therefore, identifying a universal antigenic epitopes of Vtg from multiple fish species and designing a tools that can be applied in the field can promote the use of Vtg in monitoring estrogenic contamination in aquatic environments. Bioinformatics analysis of the Vtg of Bostrichthys sinensis revealed that the protein is highly conserved in structure. The results of PCR showed that the amino acid sequence encoded by the BsVg819 gene fragment from the Vtg gene of Bostrichthys sinensis could have more than 97% similarity with the amino acid sequences of the PCR products of ten fish species. Development of a colloidal gold immunochromatographic test strip using recombinant proteins was expressed in BsVg819 gene fragments. The test strip was able to detect Vtg in the plasma of untreated female Bostrichthys sinensis and ten different female fish species. Vtg in the plasma of juvenile Bostrichthys sinensis treated with estrogen is elevated and can be detected by test strips. The results show that the test strips have good usability. Compared to ELISA, the strip is prospective for field applications. It provides a portable tool for future rapid detection of estrogenic contamination in the field.

Adverse effects of glyphosate-based herbicide on hatching rate, morphological alterations, and acetylcholinesterase (AChE) expression in golden apple snail eggs

This research investigated the effects of glyphosate herbicide on golden apple snail (Pomacea canaliculata) eggs, focusing on hatching rates, morphological changes, and acetylcholinesterase (AChE) expression to explore its potential as a biomarker of exposure. Additionally, key bioactive components in golden apple snail eggs were characterized. The study demonstrated that glyphosate toxicity increased with both exposure time and concentration. Optical coherence tomography (OCT) analysis revealed adverse morphological effects on eggs and embryos, including changes in shell structure and organ development. SDS-PAGE analysis identified four main protein bands, including Perivitellin 2 in three isoforms (98, 67, and 31 kDa) and Ovorubin (28 kDa). Lipids, phosphorus, and carbohydrates were identified as key components through Sudan Black B, Methyl Green, and Alcian Blue staining. AChE, with a molecular weight of 71 kDa, was further analyzed by Western blot, showing decreased expression with prolonged and higher concentrations of glyphosate exposure. GC-MS analysis identified major bioactive compounds in untreated eggs, including 3-Fluoro-β, 5-dihydroxy-N-methylbenzeneethanamine, 2-Aziridinylethylamine, and dextroamphetamine, which have pharmaceutical properties such as anti-hypertensive, diuretic, anti-diabetic, and anti-inflammatory effects, as well as potential applications in treating attention deficit hyperactivity disorder and narcolepsy. These compounds were present at lower levels in glyphosate-exposed groups, suggesting glyphosate's impact on the eggs' biochemical defense mechanisms. This study highlights the potential effects of glyphosate on golden apple snail eggs, which may have implications for future snail populations and aquatic ecosystems.

Establishment and application of multiple immunoassays for environmental estrogens based on recombinant Japanese flounder (Paralichthys olivaceus) choriogenin protein

Environmental estrogens have generated great concern because of their potential threat to aquatic organisms; however, the commonly used vitellogenin (Vtg) biomarker detection methods are not capable of detecting estrogenic activity below 10 ng/L 17β-estradiol. In this study, we developed multiple immunoassays based on Japanese flounder (Paralichthys olivaceus) choriogenin (Chg), a highly sensitive biomarker of environmental estrogens. Chg genes (ChgL and ChgH) of Japanese flounder were cloned for the first time, and a recombinant ChgL protein with a molecular weight of approximately 52 kDa was prepared using a prokaryotic expression system and purified using Ni-affinity column chromatography. Subsequently, specific monoclonal antibodies against ChgL were prepared and used to develop sandwich enzyme-linked immunosorbent assays (ELISAs), which had a detection range of 3.9-250 ng/mL and detection limit of 1.9 ng/mL. An immunofluorescence method was also established and used to visually detect ChgL induction in the tissues. In addition, a lateral flow immunoassay for ChgL that could detect estrogen activity within 10 min was developed. Finally, the reliability of the immunoassays was examined by measuring ChgL induction in the plasma and tissues of Japanese flounder exposed to 0, 2, 10, and 50 ng/L 17α-ethinylestradiol (EE₂). The results showed that 2 ng/L EE₂ notably increased ChgL levels in the plasma, demonstrating that ChgL is more sensitive than Vtg to environmental estrogens; 50 ng/L EE₂ induced obvious Chg induction in the sinusoidal vessels of the liver. Conclusions taken together, this study provides reliable methods for sensitive and rapid detection of estrogenic activity in aquatic environments.

A stable and sensitive enzyme-linked immunosorbent assay (ELISA) for the determination of metsulfuron-methyl residues in foods

A hapten of metsulfuron-methyl was successfully designed and synthesized from 2-methylester-phenylsulfonamide and succinic anhydride, and the polyclonal antibody against metsulfuron-methyl was prepared by immunization procedure with the hapten-bovine serum albumin conjugate. A stable and sensitive direct competitive enzyme-linked immunosorbent assay (dcELISA) method had been developed under the optimal conditions. The sensitivity (IC₅₀ ) was 37.03 ± 1.87 µg/L, and the detection line (IC₁₅ ) was 1.57 ± 0.11 µg/L. Rice, wheat, oat, flaxseed, milk, and water were chosen to study the recovery test and the recovery rates were 83.11%-117.44% . The matrix effect was eliminated by a simple dilution of the sample extracts. The results from dcELISA were well agreement with the results from HPLC-MS. It was indicated that the developed method had good accuracy and stability. It could be applied for the detection of metsulfuron-methyl residues. It was worth mentioning that the antibody could recognize metsulfuron-methyl and tribenuron-methyl with cross-reactivities of 100% and 49.72%, respectively. In order to understand the cross-reactivity, molecular modeling including molecular alignment and electrostatic potential surfaces were introduced. It was found that the special group of metsulfuron-methyl played an important role, especially on C3 position of the phenyl group. PRACTICAL APPLICATION: A stable, sensitive, and low-cost dc ELISA method had been developed with good accuracy and applied in the determination of metsulfuron-methyl in foods. Molecular simulation was introduced to understand the specificity between the antibody and the analyst. It was a good method to study the cross-reactivity between the antibody and the analyst or analogue.

Acetylcholinesterase (AChE) monoclonal antibody generation and validation for use as a biomarker of glyphosate-based herbicide exposure in commercial freshwater fish

Monoclonal antibody specific to acetylcholinesterase (AChE) was extracted from the brain of hybrid catfish after exposure to glyphosate-based herbicide for 24 h. AChE was partially purified using hydroxyapatite and chromatography columns. The specific characteristics of AChE were studied by western blot using commercial polyclonal antibody (Rabbit anti-Fish AChE). It was found that the protein band had a molecular weight of 71 kDa. After mice were injected with AChE 4 times, the spleen showed a response to the induction. Polyclonal B cells from the mouse's spleen were taken and fused with myeloma cells to produce hybrid cells. After two fusions were performed, the clones specific to AChE were selected by dot blot, ELISA, immunohistochemistry and western blot techniques. Two clones, ACHE 33 and ACHE 99, which had the isotype of IgM were found. These two produced monoclonal antibodies specific to AChE in both denatured and native forms. The ACHE 33 monoclonal antibody clone from hybrid catfish could be cross-react with two commercial freshwater fishes, Nile tilapia and climbing perch, based on dot blot, immunohistochemistry, and western blot techniques. Moreover, AChE in Nile tilapia and climbing perch with glyphosate- based herbicide exposure gave a positive result with ACHE 33 as protein with molecular weight of 66 kDa. Based on our results, the produced monoclonal antibody showed specificity and could be applied to test AChE expression to assess glyphosate-based herbicide contamination in hybrid catfish, Nile tilapia and climbing perch. It could be also be a useful tool in indicating the quality of water resources.

Distribution of vitellogenin in Japanese flounder (Paralichthys olivaceus) for biomarker analysis of marine environmental estrogens

Estrogen pollution in marine environments has become a research hotspot due to its adverse effects on the reproduction of wild organisms. To early detection of estrogen pollution, this study developed two methods for detecting Japanese flounder vitellogenin (Vtg), a sensitive biomarker for environmental estrogens. Firstly, monoclonal antibodies (mAb) specific to Vtg were prepared using purified lipovitellin (Lv), a main Vtg-derived yolk protein. Anti-Lv mAb (C1F1) had the highest titer (1:256,000) and was labeled with fluorescein isothiocyanate to establish a direct immunofluorescence (DIF) method for histological detection of Vtg in tissues. Additionally, using the purified Lv and mAb, an enzyme-linked immunosorbent assay (ELISA) was developed and this assay had a detection limit of 0.75 ng/mL and a working range of 1.95-250 ng/mL. Furthermore, Vtg induction in the plasma of Japanese flounder exposed to 17β-estradiol (E₂), 17α-ethinylestradiol (EE₂), and bisphenol A (BPA) were quantified by ELISA, and Vtg induction in the liver of EE₂-exposed Japanese flounder were measured by DIF. Finally, the distribution of Vtg in Japanese flounder was detected using these two methods. The results revealed that Vtg mainly appeared in the terminal tail fin, liver, kidney, intestine, and spleen. Considering the high concentration of Vtg and easy sample collection, the terminal tail fin could be a new alternative to plasma for Vtg quantification, while kidney and liver are suitable for histological detection of Vtg.

New methods for purification of Paralichthys olivaceus lipovitellin and immunoassay-based detection of vitellogenin

Increasing levels of estrogenic pollution in marine environments has made the development of reliable biological detection techniques urgently needed. In this study, Japanese flounder (Paralichthys olivaceus) lipovitellin (Lv) was purified and used to establish three immunological methods for the detection of vitellogenin (Vtg), a biomarker for environmental estrogens. Firstly, five different methods were employed to purify Lv, among which water-precipitation was the fastest and easiest way to purify Lv. Japanese flounder Lv was characterized as a phospholipoglycoprotein with a molecular weight of ∼369 kDa. Using purified Lv and its specific polyclonal antibody, a sandwich enzyme-linked immunosorbent assay (ELISA) was developed. This assay had a working range from 7.8 to 250 ng/mL and a detection limit of 3.1 ng/mL. Furthermore, we developed an immunohistochemistry (IHC) and an immunofluorescence (IF) assay, both of which allowed visual detection of liver Vtg. Finally, Vtg induction in plasma and liver of juvenile Japanese flounders exposed to 17β-ethinylestradiol (EE₂) was measured using these three methods. Exposure to 10 and 50 ng/L EE₂ significantly increased plasma Vtg levels, and obvious positive fluorescence signals were observed near the liver sinusoidal vessels. These results confirmed that the methods developed effectively detected estrogenic activity of exogenous chemicals. Therefore, this study provides reliable methodologies for biomonitoring of estrogenic pollution in marine environments.