Tetracycline uptake by pak choi grown on contaminated soils and its toxicity in human liver cell line HL-7702

Tetracycline and sulfadiazine toxicity in human liver cells Huh-7

As typical antibiotics, tetracycline (TC) and sulfadiazine (SDZ) enter the human body through the food chain. Therefore, it is necessary to understand their individual and combined toxicity. In this study, the effects of TC, SDZ, and their mixture on cell viability, cell membrane damage, liver cell damage, and oxidative damage were evaluated in in vitro assays with human liver cells Huh-7. The results showed cytotoxicity of TC, SDZ, and their mixture, which induced oxidative stress and caused membrane and cell damage. The effect of antibiotics on Huh-7 cells increased with increasing concentration, except for lactate dehydrogenase (LDH) activity that commonly showed a threshold concentration response and cell viability, which commonly showed a biphasic trend, suggesting the possibility of hormetic responses where proper doses are included. The toxicity of TC was commonly higher than that of SDZ when applied at the same concentration. These findings shed light on the individual and joint effects of these major antibiotics on liver cells, providing a scientific basis for the evaluation of antibiotic toxicity and associated risks.

Directed evolution of TetR for constructing sensitive and broad-spectrum tetracycline antibiotics whole-cell biosensor

Antibiotic abuse is the main reason for the drug resistance of pathogenic bacteria, posing a potential health risk. Antibiotic surveillance is critical for preventing antibiotic contamination. This study aimed to develop a sensitive and broad-spectrum whole-cell biosensor for tetracycline antibiotics (TCs) detection. Wild-type TCs-responsive biosensor was constructed by introducing a tetracycline operon into a sfGFP reporter plasmid. Using error-prone PCR, mutation libraries containing approximately 107 variants of the tetracycline repressor (TetR) gene were generated. The tigecycline-senstive mutants were isolated using high-throughput flow cytometric sorting. After 2 rounds of directed evolution, a mutant epS2-22 of TerR was isolated and assembled as a TCs biosensor. The epS2-22 biosensor was more sensitive and broad-spectrum than the wild-type biosensors. The detection limits of the epS2-22 biosensor for seven TCs were 4- to 62-fold lower than the wild-type biosensor (no response to tigecycline). Meanwhile, the epS2-22 biosensor had a shorter detection time and a stronger signal output than the wild type. In addition, the evolved epS2-22 biosensor showed excellent performance in detecting low traces of TCs in environmental water. These results suggest that directed evolution is a powerful tool for developing high-performance whole-cell biosensors, and the evolved epS2-22 biosensors have the potential for wider applications in real-world TCs detection.

Screening of low-Cd accumulating early rice cultivars coupled with phytoremediation and agro-production: Bioavailability and bioaccessibility tests

Previous studies have focused on total cadmium (Cd) accumulation in rice or its transformation in soil, but only a few have examined the entire soil-rice-human system. This study investigated the Cd bioaccessibility and bioavailability for humans from grains of early rice cultivars grown in a Cd-polluted field and further combined with multi-traits to discover and evaluate the optimum safe production and phytoremediation potential cultivars. The results revealed that Cd concentration in polished rice was <0.20 mg kg^-1 in 79 % of early rice cultivars, implying that Cd levels in rice might be reduced by cultivar selection. Furthermore, the higher values of root to straw translocation factor indicates the maximal accumulation of Cd in straw and with highest soil to straw accumulation factor (>1.0) in 66.67 % of cultivars. However, bioaccessibility and bioavailability varied greatly among cultivars with corresponding values ranging from 5.68 to 7.67 % and 1.87 to 5.71 ng g^-1, respectively. Despite the fact that polynomial fitting revealed a statistically significant relationship between Cd content in polished rice and bioavailable Cd in humans (R² = 0.718, P = 0.025), poor goodness of fit for bioaccessibility, bioavailability, and toxicity varied even within low-Cd accumulating cultivars. As a result of multi trait analysis and bioavailability, Zhuliangyou4024 (ER-9), Lingliangyou211 (ER-3), and Yonxian15 (ER-28) were found to be the three best early rice cultivars with higher essential nutrients, less total and bioavailable Cd, and relative high phytoremediation potential and are suitable for healthy rice production and soil remediation.

Visible-Light-Driven Photocatalytic Degradation of Tetracycline Using Heterostructured Cu2O-TiO2 Nanotubes, Kinetics, and Toxicity Evaluation of Degraded Products on Cell Lines

This study first reports on the tetracycline photodegradation with the synthesized heterostructured titanium oxide nanotubes coupled with cuprous oxide photocatalyst. The large surface area and more active sites on TiO₂ nanotubes with a reduced band gap (coupling of Cu₂O) provide faster photodegradation of tetracycline under visible light conditions. Cytotoxicity experiments performed on the RAW 264.7 (mouse macrophage) and THP-1 (human monocytes) cell lines of tetracycline and the photodegraded products of tetracycline as well as quenching experiments were also performed. The effects of different parameters like pH, photocatalyst loading concentration, cuprous oxide concentration, and tetracycline load on the photodegradation rate were investigated. With an enhanced surface area of nanotubes and a reduced band gap of 2.58 eV, 1.5 g/L concentration of 10% C-TAC showed the highest efficiency of visible-light-driven photodegradation (∼100% photodegradation rate in 60 min) of tetracycline at pH 5, 7, and 9. The photodegradation efficiency is not depleted up to five consecutive batch cycles. Quenching experiments confirmed that superoxide radicals and hydroxyl radicals are the most involved reactive species in the photodegradation of tetracycline, while valance band electrons are the least involved reactive species. The cytotoxicity percentage of tetracycline and its degraded products on RAW 264.7 (-0.932) as well as THP-1 (-0.931) showed a negative correlation with the degradation percentage with a p-value of 0.01. The toxicity-free effluent of photodegradation suggests the application of the synthesized photocatalyst in wastewater treatment.

Tetracycline bioremediation using the novel Serratia marcescens strain WW1 isolated from a wastewater treatment plant

Tetracycline pollution is an emerging threat in aquatic and terrestrial environments because of its widespread applications in human disease, livestock, and aquaculture. Present study, investigated the tetracycline degrading novel Serratia marcescens strain WW1, which was isolated from a wastewater treatment plant (WWTP). Toxicity analysis of tetracycline with strain WW1 indicates that its intermediate metabolites are not toxic for the indicator bacteria and algae. The degradation conditions for the tetracycline optimized using response surface methodology (RSM) were determined as: pH 6.0; temperature, 36 °C; tetracycline concentration, 20 mg L^-1; and inoculum size, 100 μL (OD∼0.5). The strain WW1 was able to utilize tetracycline during the growth phase, and it degraded 89.5% of the tetracycline within 48 h. The degradation kinetics suggested the strain perform significant tetracycline removal with half-life (t_1/2) 239.04 and 12.44 h in control and treatments. Tetracycline and its intermediates were analyzed using High Performance Liquid Chromatography (HPLC) and Liquid Chromatography-Mass Spectroscopy (LC-MS). It was observed that strain WW1 could efficiently metabolize the tetracycline within 48 h of experiment. The ability of strain WW1 to degrade tetracycline justifies its use as an environmentally-useful bacterium. Therefore, the present study demonstrated that the degradation of antibiotics is possible using indigenous microbial strains.

Phytotoxic effects on chloroplast and UHPLC-HRMS based untargeted metabolomic responses in Allium tuberosum Rottler ex Sprengel (Chinese leek) exposed to antibiotics

Introduction of antibiotics into agricultural fields poses serious health risks to humans. This study investigated the uptake of antibiotics, their effects on metabolic pathways, and chloroplast structure changes of Allium tuberosum exposed to norfloxacin (NFL), oxytetracycline (OTC), and tetracycline (TC). Among all the antibiotic treatments, the highest accumulation of antibiotics in roots (4.15 mg/kg) and leaves (0.29 mg/kg) was TC, while in bulbs it was NFL (5.94 mg/kg). OTC was with the lowest accumulation in roots: 0.19 mg/kg, bulbs: 0.18 mg/kg, and leaves: 0.11 mg/kg. The number of mitochondira and the number of plastoglobulli increased. The chloroplast structure was disturbed under the stress of NFL, OTC, and TC. Disturbance in the chloroplast ultrastructure leads to altered chlorophyll fluorescence variables. Simultaneously, metabolomic profiling of leaves demonstrated that NFL stress regulated more of metabolic pathways than OTC and TC. Differences in metabolic pathways among the antibiotic treatments showed that each antibiotic has different impact even under the same experimental conditions. TC and NFL have more toxic effects than OTC antibiotic. Metabolic variations induced by antibiotics stress highlighted pools of metabolites that affect the metabolic activities, chlorophyll fluorescence, ultrastructural adjustments, and stimulate defensive impact in A. tubersoum. These findings provide an insight of metabolic destabilization as well as metabolic changes in defensive mechanism and stress response of A. tuberosum to different antibiotics.

Effects of antibiotics stress on growth variables, ultrastructure, and metabolite pattern of Brassica rapa ssp. chinensis

Antibiotics frequently contaminate agricultural fields and through plant uptake enter into the food chain. This study aimed to explore the effects of antibiotics; tetracycline (TC), oxytetracycline (OTC) and norfloxacin (NF) on the growth, cell ultrastructure, and metabolite pattern of Brassica rapa ssp. chinensis. Oxytetracycline accumulated more than other antibiotics followed by TC and NF. Plant growth, chlorophyll fluorescence, and antioxidant activities were negatively affected under all antibiotic treatments. Ultrastructural investigation of mesophyll of leaves performed by transmission electron microscopy indicated that antibiotic stress caused the changes in thylakoid orientation, number of plastoglobuli, and starch grains. Identification of functional groups through Fourier transform infrared analysis indicated that carboxyl group, carbonate and ammonium ions are involved in the adsorption of antibiotics. The metabolic profiling of B. rapa leaves demonstrated that all of the antibiotics treatments distorted phenylalanine, tyrosine and tryptophan biosynthesis, d-glutamine and d-glutamate metabolism, alanine, aspartate and glutamate metabolism, phenylalanine metabolism and TCA cycle. Metabolic alterations as a result of antibiotics stress provide insights of metabolites that affect the physiological changes attributed to antibiotic stress. These results will improve the understanding of antibiotic contamination effects on plants.

Tetracyclines in the environment: An overview on the occurrence, fate, toxicity, detection, removal methods, and sludge management

Tetracyclines (TCs) are a group of broad-spectrum antibiotics having vast human, veterinary, and aquaculture applications. The continuous release of TCs residues into the environment and the inadequate removal through the conventional treatment systems result in its prevalent occurrence in soil, surface water, groundwater, and even in drinking water. As aqueous TCs contamination is the tip of the iceberg, and TCs possess good sorption capacity towards soil, sediments, sludge, and manure, it is insufficient to rely on the sorptive removal in the conventional water treatment plants. The severity of the TCs contamination is evident from the emergence of TCs resistance in a wide variety of microorganisms. This paper reviews the recent research on the TCs occurrence in the environmental matrices, fate in natural systems, toxic effects, and the removal methods. The high performance liquid chromatography (HPLC) determination of TCs in environmental samples and the associated technology developments are analyzed. The benefits and limitations of biochemical and physicochemical removal processes are also discussed. This work draws attention to the inevitability of proper TC sludge management. This paper also gives insight into the limitations of TCs related research and the future scope of research in environmental contamination by TCs residues.

Rice cultivars significantly mitigate cadmium accumulation in grains and its bioaccessibility and toxicity in human HL-7702 cells

Excessive Cd accumulation in cereals, especially in high-consumption staple crops, such as rice, is of major concern. Therefore, elucidation of cultivar-specific variation in rice grain Cd bioaccessibility and toxicity in humans would help the development of remedial strategies for Cd accumulation and toxicity. The present study combined an in vitro gastrointestinal digestion model with a human HL-7702 cell and assessed Cd bioaccessibility and toxicity to humans from the grains of 30 rice cultivars of different types harvested from Cd-contaminated paddy soil. The mean grain Cd content of cultivars within the type exceeded acceptable national standards. Cadmium bioaccessibility was high in all grains (9.08-23.6%) except the low accumulator (LA) rice cultivar (7.93%). The mean estimated daily intake of Cd via the cultivars (except LA) exceeded the FAO/WHO permissible limit based not only on the total grain Cd concentration but also on bioaccessible Cd concentration. A dose-proportional correlation between the in vitro bioaccessible and total grain Cd concentrations was observed, suggesting that Cd bioaccessibility accurately reflects the transfer of Cd from rice grain to humans. Toxicity assay results demonstrated that Cd from rice grains could commence oxidative stress and injury in HL-7702 cells, except the LA rice, which did not exhibit significant alteration in HL-7702 cells owing to its low Cd concentration. These results provide primary evidence to suggest that the cultivation of the LA rice cultivar is an effective agronomic approach to avert Cd entry into the food chain and alleviate Cd toxicity in humans.

Foliar application of zinc and selenium alleviates cadmium and lead toxicity of water spinach - Bioavailability/cytotoxicity study with human cell lines

The present study investigated the effects of foliar application of zinc (Zn) and selenium (Se) on bioavailability of Zn and Se and toxicity of cadmium (Cd) and lead (Pb) to different water spinach ecotypes (LA and HA) grown in slightly (XZ) or moderately (LJY) contaminated fields via in vitro digestion combined with Caco-2/HL-7702 cell model. The obtained results revealed that foliar application of Zn and Se promoted yield, increased total, bioaccessible and bioavailable fractions of Zn and Se in plants, indicating that foliar application is a feasible way of biofortification. Although there was no significant effect on liver cell proliferation (MTT), membrane stability (LDH) and hepatocyte enzyme (ALT and AST) activities, the obvious ecotype and soil dependent fluctuations of lipid peroxidation (MDA) and antioxidant enzyme (SOD, POD and CAT) activities in serum highly suggest that the low accumulator and clean field should be used in agricultural production rather than the high accumulator and contaminated farmland. Moreover, foliar application of Zn and Se improved nutritional quality of all water spinach genotypes in both fields, including increased Fe, vitamin C, cellulose and chlorophyll, maintained concentrations of potassium (K), manganese (Mn), copper (Cu), protein, and nitrate. These results demonstrate that this agricultural management practice may prove to be an effective approach for minimizing health risk and alleviating "hidden hunger" in the developing countries.

Potential of Myriophyllum aquaticum for phytoremediation of water contaminated with tetracycline antibiotics and copper

Water pollution caused by antibiotics and heavy metals has attracted considerable concern, and efficient approaches are urgently needed for their removal. The objective of this study was to investigate the potential of Myriophyllum aquaticum for long-term phytoremediation of wastewater containing tetracycline (TC) antibiotics and copper. Seven hydroponic microcosms were constructed, spiked with tetracycline, oxytetracycline (OTC) and chlortetracycline (CTC) (300-30,000 μg/L), alone or simultaneously with Cu (II), and operated for 12 weeks. The TC removal efficiencies using the hydroponic microcosms here were commensurate or higher than those in previous studies. However, the Cu/TC ratio greatly affected the removal, accumulation of TCs by M. aquaticum, and plant growth. Low levels of Cu (II) (<1000 μg/L) promoted TC removal, but excessive Cu (II) (>10,000 μg/L) impeded it. Mass balance analysis showed that most TCs (45%-64% on average) accumulated in the roots of M. aquaticum. Plant biomass was correlated with the removal of COD, TN, TP, and NH₄⁺-N (p ≤ 0.05) but not with removal of the TCs. Proteobacteria, Bacteroidetes, and Fusobacteria were dominant in the microbial communities, but they showed little correlation with the TC removal. M. aquaticum can be employed as an effective means of TC removal from water. The co-existence of heavy metals should be considered when evaluating the removal potential of TCs in phytoremediation.

Responses of seeds of typical Brassica crops to tetracycline stress: Sensitivity difference and source analysis

Antibiotics can induce adverse effects on plants. Brassica crop seeds, for their advantages, are used widely in seed germination test to investigate phytotoxicity of substances. However, their performances on evaluating antibiotics remain to be studied to select sensitive species for control of potential risks. In this work, common species of Chinese cabbage (Brassica rapa L.), edible rape (Brassica napus L.), and cabbage (Brassica oleracea L.) with three cultivars each were selected to compare and analyze the sensitivity difference of their seeds to tetracycline (TC) stress. Results showed that the ratio of axis to cotyledon (RAC) by fresh weight was an alternative endpoint besides radicle length (RL) in the test. The species sensitivity distribution (SSD) based on the effective concentrations causing x% inhibition (EC_x) in RL of seeds exposed to TC was applied to compare the sensitivity of seeds and estimate the hazardous concentration for x% species (HC_x). From the species-dependent sensitivity and the sensitivity difference of cultivars in the same species of seeds to TC, the performance of Chinese cabbage was the best in the study. The sensitivity of seeds to TC could be evaluated by EC₂₀ related to seed physical traits and germination indices, while the extent of seeds affected by TC could be evaluated by EC₅₀ related to the composition of seed storage reserves. We recommended that it was a new idea to analyze responses of different seeds to TC at large scale according to seed innate characteristics.