Effects of environmentally relevant concentrations of florfenicol on the glucose metabolism system, intestinal microbiome, and liver metabolome of zebrafish.

Florfenicol, a widely used veterinary antibiotic, has now been frequently detected in various water environments and human urines, with high concentrations. Accordingly, the ecological risks and health hazards of florfenicol are attracting increasing attention. In recent years, antibiotic exposure has been implicated in the disruption of animal glucose metabolism. However, the specific effects of florfenicol on the glucose metabolism system and the underlying mechanisms are largely unknown. Herein, zebrafish as an animal model were exposed to environmentally relevant concentrations of florfenicol for 28 days. Using biochemical and molecular analyses, we found that exposure to florfenicol disturbed glucose homeostasis, as evidenced by the abnormal levels of blood glucose and hepatic/muscular glycogen, and the altered expression of genes involved in glycogenolysis, gluconeogenesis, glycogenesis, and glycolysis. Considering the efficient antibacterial activity of florfenicol and the crucial role of intestinal flora in host glucose metabolism, we then analyzed changes in the gut microbiome and its key metabolite short-chain fatty acids (SCFAs). Results indicated that exposure to florfenicol caused gut microbiota dysbiosis, inhibited the production of intestinal SCFAs, and ultimately affected the downstream signaling pathways of SCFA involved in glucose metabolism. Moreover, non-targeted metabolomics revealed that arachidonic acid and linoleic acid metabolic pathways may be associated with insulin sensitivity changes in florfenicol-exposed livers. Overall, this study highlighted a crucial aspect of the environmental risks of florfenicol to both non-target organisms and humans, and presented novel insights into the mechanistic elucidation of metabolic toxicity of antibiotics.

Understanding the toxicity risk of antibiotic emissions of aquaculture from the perspective of fluctuations concentration.

Organisms are generally exposed to target contaminant with stable concentrations in traditional ecotoxicological studies. However, it is difficult to truly represent the dynamics and complexity of actual aquatic pollution for risk management. Contaminants may enter nearby aquatic systems in pulsed exposure, thus resulting in that aquatic organisms will be exposed to contaminants at fluctuating concentrations. Especially during the season of summer, due to the changes in displacement or periodic emissions of veterinary antibiotics in aquaculture, algal blooms occur frequently in surrounding waters, thus leading to eutrophication of the water. Florfenicol (FFC) is currently widely used as a veterinary antibiotic, but the aquatic ecological risks of FFC under concentration fluctuations are still unknown. Therefore, the acute exposure, chronic exposure and pulsed exposure effects of FFC on Microcystis aeruginosa were investigated to comprehensively evaluate the ecological risk of FFC and raise awareness of the pulsed exposure mode. Results indicated that the toxic effects of FFC on M. aeruginosa were dominated by exposure mode, exposure duration, exposure frequency, and exposure concentration. The maximum growth inhibition rate of the 10 µg/L FFC treatment amounted to 4.07% during chronic exposure of 18 days. However, the growth inhibition rate decreased from 55.1% to 19.31% when algae was exposure to 10 µg/L FFC during the first pulsed exposure (8 h). Therefore, when the concentration of FFC was equal under chronic and pulsed exposure, FFC exhibited greater toxicity on M. aeruginosa in short pulsed exposure than in continuous exposure. In addition, repetitive pulsed exposure strengthened the resistance of M. aeruginosa on FFC. The adaptive regulation of algae was related to the duration and frequency of exposure. Above results suggested that traditional toxicity assessments lacked consideration for fluctuating concentrations during pollutant emissions, thus underestimating the environmental risk of contaminant. This investigation aims to facilitate the standardization of pulsed exposure.

Intestinal Histopathological Aberrations in Oreochromis niloticus Juveniles upon Dietary Florfenicol Administration.

The aquaculture use of antibiotics can cause detrimental effects on fish organs and gut microbial dysbiosis. The impact of florfenicol (FFC) on fish intestinal histology, an approved antibiotic, remains unclear. This study aimed to investigate the effects of FFC on Oreochromis niloticus juveniles by administering FFC at 10 mg and 30 mg/kg biomass/day for 30 consecutive days to mimic long-term use. A dose-dependent reduction in feed intake, survival and biomass, with an upsurge in mortalities was observed. Even the therapeutic dose instigated mortalities on day 30 of FFC dosing (FD). Histopathological analysis revealed mild to moderate alterations, including loss of absorptive regions, epithelial degeneration, necrotized areas, intercellular enterocytic space and swollen laminar propria. Post-dosing, the observation of the detachment of lamina propria from the epithelium indicated imminent irritability. Goblet cells reduced drastically on day 30 FD, accompanied by an increase in intraepithelial lymphocytes. However, cessation of dosing for 13 days resulted in the reclamation of goblet cells and absorptive regions, indicating that the intestinal tissues underwent considerable repair after lifting antibiotic pressure. These findings suggested that O. niloticus can tolerate dietary FFC but emphasize the need for responsible use of antibiotics in aquaculture.

Assessing the ecotoxicity of florfenicol exposure at environmental levels: A case study of histology, apoptosis and microbiota in hepatopancreas of Eriocheir sinensis.

The intensification of production practices in the aquaculture industry has led to the indiscriminate use of antibiotics to combat diseases and reduce costs, which has resulted in environmental pollution, posing serious threats to aquaculture sustainability and food safety. However, the toxic effect of florfenicol (FF) exposure on the hepatopancreas of crustaceans remains unclear. Herein, by employing Chinese mitten crab (Eriocheir sinensis) as subjects to investigate the toxic effects on histopathology, oxidative stress, apoptosis and microbiota of hepatopancreas under environment-relevant (0.5 and 5 µg/L), and extreme concentrations (50 µg/L) of FF. Our results revealed that the damage of hepatopancreas tissue structure caused by FF exposure in a dose-and time-dependent manner. Combined with the increased expression of apoptosis-related genes (Caspase 3, Caspase 8, p53, Bax and Bcl-2) at mRNA and protein levels, activation of catalase (CAT) and superoxide dismutase (SOD), and malondialdehyde (MDA) accumulation, FF exposure also induced oxidative stress, and apoptosis in hepatopancreas. Interestingly, 7 days exposure triggered more pronounced toxic effect in crabs than 14 days under environment-relevant FF concentration. Integrated biomarker response version 2 (IBRv2) index indicated that 14 days FF exposure under extreme concentration has serious toxicity effect on crabs. Furthermore, 14 days exposure to FF changed the diversity and composition of hepatopancreas microbiota leading remarkable increase of pathogenic microorganism Spirochaetes following exposure to 50 µg/L of FF. Taken together, our study explained potential mechanism of FF toxicity on hepatopancreas of crustaceans, and provided a reference for the concentration of FF to be used in culture of Chinese mitten crab.

A review on the antibiotic florfenicol: Occurrence, environmental fate, effects, and health risks.

Florfenicol, as a replacement for chloramphenicol, can tightly bind to the A site of the 23S rRNA in the 50S subunit of the 70S ribosome, thereby inhibiting protein synthesis and bacterial proliferation. Due to the widespread use in aquaculture and veterinary medicine, florfenicol has been detected in the aquatic environment worldwide. Concerns over the effects and health risks of florfenicol on target and non-target organisms have been raised in recent years. Although the ecotoxicity of florfenicol has been widely reported in different species, no attempt has been made to review the current research progress of florfenicol toxicity, hormesis, and its health risks posed to biota. In this study, a comprehensive literature review was conducted to summarize the effects of florfenicol on various organisms including bacteria, algae, invertebrates, fishes, birds, and mammals. The generation of antibiotic resistant bacteria and spread antibiotic resistant genes, closely associated with hormesis, are pressing environmental health issues stemming from overuse or misuse of antibiotics including florfenicol. Exposure to florfenicol at µg/L-mg/L induced hormetic effects in several algal species, and chromoplasts might serve as a target for florfenicol-induced effects; however, the underlying molecular mechanisms are completely lacking. Exposure to high levels (mg/L) of florfenicol modified the xenobiotic metabolism, antioxidant systems, and energy metabolism, resulting in hepatotoxicity, renal toxicity, immunotoxicity, developmental toxicity, reproductive toxicity, obesogenic effects, and hormesis in different animal species. Mitochondria and the associated energy metabolism are suggested to be the primary targets for florfenicol toxicity in animals, albeit further in-depth investigations are warranted for revealing the long-term effects (e.g., whole-life-cycle impacts, multigenerational effects) of florfenicol, especially at environmental levels, and the underlying mechanisms. This will facilitate the evaluation of potential hormetic effects and construction of adverse outcome pathways for environmental risk assessment and regulation of florfenicol.

Maternal transfer of florfenicol impacts development and disrupts metabolic pathways in F1 offspring zebrafish by destroying mitochondria.

Maternal exposure to antibiotics existing in the environment is a predisposing factor for developmental malformation with metabolic disorders in offspring. In this study, female zebrafish (3 months) were exposed to 0.05 mg/L and 0.5 mg/L florfenicol (FF) for 28 days. After pairing and spawning with healthy male fish, F1 embryos were collected and developed to 5 d post-fertilization (dpf) in clear water. And the adverse effects on the F1 generation were examined thoroughly. The fecundity of F0 female fish and the hatchability, mortality, and body length of F1 larvae significantly decreased in the treatment group. Meanwhile, multi-malformation types were found in the exposure group, including delayed yolk sac absorption, lack of swim bladder, and spinal curvature. Metabolomic and transcriptomic results revealed alterations in metabolism with dysregulation in tricarboxylase acid cycle, amino acid metabolism, and disordered lipid metabolism with elevated levels of glycerophospholipid and sphingolipid. Accompanying these metabolic derangements, decreased levels of ATP and disordered oxidative-redox state were observed. These results were consistent with the damaged mitochondrial membrane potential and respiratory chain function, suggesting that the developmental toxicity and perturbed metabolic signaling in the F1 generation were related to the mitochondrial injury after exposing F0 female zebrafish to FF. Our findings highlighted the potential toxicity of FF to offspring generations even though they were not directly exposed to environmental contaminants.

Effects of natural nanoparticles on the acute toxicity, chronic effect, and oxidative stress response of phenicol antibiotics in Daphnia magna.

Natural nanoparticles (NNP) are ubiquitous in natural water and can interact with other contaminants, causing ecotoxic effects on aquatic nontarget organisms. However, the impact of NNPs on the ecotoxicity of antibiotics remains largely unknown. This work investigated the acute toxicity, chronic effect, and oxidative response and damage in Daphnia magna co-exposed to phenicol antibiotics (chloramphenicol, thiamphenicol) and different concentrations of NNPs (10 mg/L: environmentally relevant concentration; 100 mg/L: a high concentration that caused no apparent immobilization in D. magna). The results showed that the acute toxicity of chloramphenicol was increased by 10 mg/L NNPs but decreased by 100 mg/L NNPs; both concentrations of NNPs increased and decreased acute toxicities of thiamphenicol and chloramphenicol + thiamphenicol treatments, respectively. After long-term exposure, phenicol antibiotics (1 µg/L) and NNP (10 mg/L) mixtures in environmentally relevant concentrations significantly affected the reproduction of D. magna but did not influence their growth. The catalase activity, reduced glutathione level, and malonaldehyde content in D. magna also varied with the NNPs concentrations. Notably, the lowest concentration of thiamphenicol and chloramphenicol + thiamphenicol combined with NNPs significantly increased the malondialdehyde content in D. magna compared with the control, indicating membrane lipid peroxidation occurred in daphnids. This study suggests that the toxic effects of contaminants and NNPs on aquatic organisms should be considered thoroughly to avoid underestimating the hazard of these pollutants in the actual aquatic environment.

Sub-chronic exposure to antibiotics doxycycline, oxytetracycline or florfenicol impacts gut barrier and induces gut microbiota dysbiosis in adult zebrafish (Daino rerio).

Antibiotics are widely used in the treatment of bacterial infections and as food additives in the livestock industry. The wide usage of antibiotics causes residues in animal products, like milk, eggs and meat. A number of studies have reported that antibiotic residues exist at high concentrations in watercourses around the world. Doxycycline (DH), oxytetracycline (OTCC) and florfenicol (FF) are the three most commonly used veterinary antibiotics in China. However, studies of the toxic effects of DH, OTCC and FF are limited. In this study, six-moth-old healthy male adult zebrafish were exposed to 0, 10, 30, 100 µg/L DH, OTCC or FF for 21 days. After exposure, some biochemical parameters changed significantly, including total cholesterol (TC), triglyceride (TG), pyruvate and acid phosphatase (ACP). In addition, mucus secretion in the gut decreased and the transcription of related genes also decreased significantly. Moreover, the composition of microbiota in the gut changed significantly. DH, OTCC and FF exposure caused the decrease of diversity of gut microbiota. The relative abundance of Proteobacteria increased significantly after OTCC and FF exposure and Fusobacteria decreased in all antibiotic-treated groups. Further functional prediction analysis also suggested changes in gut microbiota in the OTCC and FF-treated groups, especially those linked to metabolism. To support this idea, we confirmed that some glycolipid related genes also increased significantly in the liver of adult zebrafish after antibiotic exposure. According to these results, DH, OTCC or FF exposure could cause the gut microbiota dysbiosis and dysfunction, and hepatic metabolic disorder in adult male zebrafish.

Response characteristics of nirS-type denitrifier Paracoccus denitrificans under florfenicol stress.

Florfenicol (FF) is widely used in aquaculture and can interfere with denitrification when released into natural ecosystems. The aim of this study was to analyze the response characteristics of nirS-type denitrifier Paracoccus denitrificans under FF stress and further mine antibiotic-responsive factors in aquatic environment. Phenotypic analysis revealed that FF delayed the nitrate removal with a maximum inhibition value of 82.4% at exponential growth phase, leading to nitrite accumulation reached to 21.9-fold and biofilm biomass decreased by ~38.6%, which were due to the lower bacterial population count (P < 0.01). RNA-seq transcriptome analyses indicated that FF treatment decreased the expression of nirS, norB, nosD and nosZ genes that encoded enzymes required for NO2- to N2 conversion from 1.02- to 2.21-fold (P < 0.001). Furthermore, gene associated with the flagellar system FlgL was also down-regulated by 1.03-fold (P < 0.001). Moreover, 10 confirmed sRNAs were significantly induced, which regulated a wide range of metabolic pathways and protein expression. Interestingly, different bacteria contained the same sRNAs means that sRNAs can spread between them. Overall, this study suggests that the denitrification of nirS-type denitrifiers can be hampered widely by FF and the key sRNAs have great potential to be antibiotic-responsive factors.

Effects of copper and florfenicol on nirS- and nirK-type denitrifier communities and related antibiotic resistance in vegetable soils.

Denitrification play an important role in nitrogen cycle and is affected by veterinary drugs entering agricultural soils. In the present study, the effects of copper and florfenicol on denitrification, related antibiotic resistance and environmental variables were characterized using real-time quantitative PCR (qPCR) and amplicon sequencing in a short-term (30 d) soil model experiment. Drug additions significantly decreased the nirS gene abundance (P < 0.05) but maximized the abundance of gene nirK in soil containing florfenicol and moderate copper levels (150 mg kg-1). Surprisingly, copper additions decreased the fexB gene abundance, however, the abundance of gene pcoD significantly increased in soils containing florfenicol, moderate copper levels (150 mg kg-1), and florfenicol and low copper levels (30 mg kg-1), respectively (P < 0.05). Overall, the nirK-type community composition was more complex than that of nirS-type but Proteobacteria predominated (> 90%) in both communities. Correlation analysis indicated that the gene abundance of fexB was highly correlated with NH4+-N (P < 0.05) and NO3--N (P < -0.01), and floR gene abundance was positively correlated with nirK (P < 0.01). Besides, the abundance of nirS-type genera Bradyrhizobium and Pseudomonas were obviously related to total organic matter (TOM), total nitrogen (TN) or total phosphorus (TP) (P < 0.05), while the abundance of nirK-type Rhizobium, Sphingomonas and Bosea showed a significantly correlated with TOM, TN or copper contents (P < 0.05). Taken together, copper and florfenicol contamination increased the possibility of durg resistance genes spread in agricultural soils through nitrogen transformation.

Mixture toxicity effects of chloramphenicol, thiamphenicol, florfenicol in Daphnia magna under different temperatures.

Acute toxicities of chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FLO) and their mixtures on Daphnia magna under two representative temperatures of the aquatic environment (20 and 25 °C) have been examined. Their toxicities depicted with an order of 72-h EC50 values were as follows: CAP > FLO > TAP and CAP ≈ FLO > TAP under 20 and 25 °C, separately. Furthermore, the acute toxicity significantly increased with the rise of temperature from 20 to 25 °C in nearly all separate and mixture phenicol antibiotics. Meanwhile, the most toxic combination under two different temperatures was diverse. The nature of toxicological interactions of phenicol antibiotic mixtures was analyzed by Combination Index (CI) equation. In general, a dual synergism-antagonism effect was dominant in nearly all mixtures at both temperatures. The prediction suitability of Concentration Addition (CA), Independent Action (IA) models, and CI method was compared, suggesting that the CI equation seems to be more appropriate for predicting the toxicity values of phenicol drugs than CA and IA models. In brief, phenicol antibiotic mixtures with temperature variation may pose more significant hazards and risks to aquatic organisms; hence, the environment.

Florfenicol causes excessive lipid peroxidation and apoptosis induced renal injury in broilers.

In order to study the effects and mechanism of florfenicol (FFC) on the kidney function of broilers, 180 1-day-old broilers were randomly divided into 6 groups, 30 in each group. Except for the control group, different doses of FFC were added to drinking water in the other 5 groups (0.15 g/L, 0.3 g/L, 0.6 g/L, 1.2 g/L and 1.8 g/L). After continuous administration for 5 days, renal histopathological changes, serum renal function indicators, renal peroxidation products and antioxidant factors, and apoptotic factors were detected in broilers aged 21 and 42 days. The results showed that compared with the control group, the kidney tissue structure was disordered, the glomerulus was atrophic, the cystic cavity was enlarged, and the epithelial cells of renal tubules were seriously vacuolated in broilers of treatment groups. And with the growth of broilers, the kidney injury of broilers in the low-dose FFC group was relieved. FFC significantly increased the contents of uric acid (UA), blood urea nitrogen (BUN), creatinine (CRE) in serum and malondialdehyde (MDA) in kidney of broilers, but significantly reduced the levels of glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT) in kidney. FFC significantly inhibited the mRNA relative transcriptional levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and nicotinamide adenine dinucleotide phosphate: quinone oxidoreductase-1 (NQO-1), and increased the mRNA and protein expression levels of p53, Caspase-3 and Caspase-6 in kidney tissue of broilers. It is concluded that FFC has certain nephrotoxicity to broilers, and its effect on kidney is dose-dependent and reversible. FFC causes intense lipid peroxidation in broiler kidney by inhibiting the expression of related factors in the downstream signal pathway of Nrf2. FFC can also up-regulate the expression of pro-apoptotic factors and accelerate the abnormal apoptosis of renal cells, thus seriously affecting the renal function of broilers.

Acute Toxicity and Risk Assessment of Florfenicol for Nile Tilapia Larvae.

The aim of this study was to determine the median lethal concentration (LC50-96h), effective concentration (EC50-96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L-1 plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC50-96h of FF for Nile tilapia larvae was 349.94 mg L-1. The EC50-96h of FF was 500 mg L-1 for weight reduction and was 1040 mg L-1 for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

Growth and cardiovascular development are repressed by florfenicol exposure in early chicken embryos.

Florfenicol (FLO) is one of the most popular antibacterial drugs used in veterinary clinics and aquaculture. The drug was found to decrease the hatchability of eggs laid by treated hens in veterinary clinics and research work. However, the pathological changes in developing embryos and their cardiovascular system and the mechanism underlying FLO-induced embryonic death remain unclear. In the present study, fertilized eggs laid by hens treated with a therapeutic dose of FLO were collected and incubated. Results showed that FLO exposure repressed embryonic development and induced early embryonic death. As a result, FLO decreased the hatchability and increased the proportion of weak chicks. Moreover, FLO exposure led to embryonic lethality and inhibited the development of chick embryos as characterized by decreased weights, lagging distribution of Hamburger-Hamilton stages, and dysplastic eyes. Pathological examination indicated that FLO exposure affected the normal development of the heart in 4.5-day-old chick embryos, as characterized by shorter transverse cardiac diameter, disordered arrangement of trabecular muscles in ventricles, and reduced thickness of ventricular walls. Furthermore, FLO decreased blood vascular densities and downregulated the expression levels of key angiogenesis-related genes, including the vascular endothelial growth factor and fibroblast growth factor, in the yolk sac membrane. These findings indicated that FLO exposure restricted vascular development during early embryonic development. In summary, our data suggest that the restricted growth and abnormal cardiovascular development may be responsible for FLO-induced early embryonic death. Thus, these findings can be useful for guiding the proper use of FLO and in laying a foundation for further studies on the mechanism of FLO-induced embryonic toxicity.

Effects of florfenicol on growth, photosynthesis and antioxidant system of the non-target organism Isochrysis galbana.

Florfenicol (FFC) is one of the most universally used antibiotics in aquaculture, which is substitute for chloramphenicol extensively, while the massive residues in aquatic environment were assumed to threaten the non-target organisms. Present research investigated the effects of florfenicol on growth, chlorophyll content, photosynthesis, and antioxidant ability of Isochrysis galbana. The results showed that FFC at 0.001-1 mg/L stimulated the growth of I. galbana and increased the content of chlorophyll. In addition, photosynthesis of I. galbana was inhibited and the photosynthetic parameters were uplifted with the increased exposure duration and FFC concentration. Furthermore, superoxide dismutase (SOD), catalase (CAT) activity significantly dropped at 0.01-20 mg/L FFC, while the contents of malondialdehyde (MDA), glutathione (GSH) and reactive oxygen species (ROS) increased after 72 h exposure, indicating that FFC at high concentrations caused a serious oxidative stress on algae. The simultaneous increase of ROS disrupted the equilibration between oxidants and antioxidant systems. Under the high concentration of FFC, the excessive of ROS was generated in algae which affected the membrane permeability and further decreased the cell biomass. Present study showed that acute exposure (72 h) at the environmental relevant concentration (0.01 mg/L) cannot induce the physiological dysfunction of the microalgae I. galbana, but the feeding concentration (20 mg/L) can. Additionally, this study hinted the possible negative impacts on ecosystems with the chronic exposure even at low FFC concentration or with the uncontrolled use of FFC.

Florfenicol induces oxidative stress and hepatocyte apoptosis in broilers via Nrf2 pathway.

In order to explore the mechanism of liver injury induced by florfenicol (FFC) in broilers, one hundred and twenty broilers were randomly divided into six groups, twenty broilers in each group. Except for control group, the other five groups were given different doses of FFC (0.15 g/L, 0.3 g/L, 0.6 g/L, 1.2 g/L and 1.8 g/L) in drinking water. After five days of continuous use, blood was collected from the subpterional vein and the chickens' liver were obtained. Chicken weight gain and liver indices were calculated; blood routine analysis was performed; the oxidative stress and apoptosis of hepatocytes was detected. The results showed that compared with the control group, except for 0.15 g/L FFC, the other doses of FFC significantly decreased the weight gain, white blood cell (WBC) and platelet (PLT) contents in blood, 0.3 g/mL FFC and 1.8 g/L FFC significantly reduced the content of hemoglobin (RGB) (P < 0.05); all doses of FFC significant decreased red blood cell (RBC) increased Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST) contents in serum of chickens (P < 0.05), and significantly decreased the contents of albumin (ALB) and total protein (TP) in serum (P < 0.05), but had no significant effect on alkaline phosphatase (ALP) contents(P > 0.05). FFC significantly increased malondialdehyde (MDA) content in serum and liver tissues, but decreased glutathione (GSH), Superoxide dismutase (SOD) and catalase (CAT) content (P < 0.05), and significantly inhibited the mRNA transcription and protein expression of antioxidant proteins nuclear factor-erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and NAD(P)H dehydrogenase quinone-1 (NQO-1)(P < 0.05). FFC also inhibited the content and the transcription level of cytochrome P4501A1(CYP1A1) and CYP2H1 in liver (P < 0.05). At the same time, FFC significantly promoted the apoptotic rate of hepatocytes and the mRNA transcription and protein expression of caspase-3 and caspase-6 (P < 0.05). With the increase of FFC concentration, liver injury became more and more serious, which affected liver function in chickens by inhibiting enzyme activity in Nrf2-ARE pathway to increase oxidative stress and promoting apoptotic protein expression to accelerate hepatocyte apoptosis.

Compound ammonium glycyrrhizin protects hepatocytes from injury induced by lipopolysaccharide/florfenicol through oxidative stress and a MAPK pathway.

Compound ammonium glycyrrhizin (CAG) protects hepatocytes from injury induced by lipopolysaccharide (LPS)/florfenicol (FFC) through a mitochondrial pathway. On this basis, the research was aimed to investigate whether CAG protects hepatocytes from injury induced by LPS/FFC through oxidative stress and the MAPK pathway. For liver injury induced by LPS/FFC, not only CAG can protect hepatocytes and prevent membrane permeability from being increased, but also the activities of ALT and AST were decreased significantly by CAG. Flow cytometry analysis indicated that the apoptosis rate (35.65 ±â€¯2.48%) of LPS/FFC group was significantly higher than that of the control group (8.60 ±â€¯0.32%). CAG (concentration of 0.01 µg/mL, 0.1 µg/mL, 1 µg/mL) significantly decreased the apoptosis rate (23.69 ±â€¯0.54%, 14.92 ±â€¯2.45% and 9.47 ±â€¯1.28%) for the liver injury induced by LPS/FFC. The activities of SOD and GSH were increased with the increased concentration of CAG, and the activity of MDA was decreased with the increased concentration of CAG. All the mRNA and proteins expression levels were increased by LPS/FFC-induced liver injury which associated with the MAPK pathway, and those of the CAG group were decreased with the increased concentration of CAG. And the change of caspase-3 activity was consistent with that of proteins and mRNA. It is suggested that LPS/FFC can induce liver injury through apoptosis and the CAG can protect hepatocytes from injury through the MAPK pathway and oxidative stress.

Response of Freshwater Biofilms to Antibiotic Florfenicol and Ofloxacin Stress: Role of Extracellular Polymeric Substances.

Antibiotic residues have been detected in aquatic environments worldwide. Biofilms are one of the most successful life forms, and as a result are ubiquitous in natural waters. However, the response mechanism of freshwater biofilms to the stress of various antibiotic residues is still unclear. Here, the stress of veterinary antibiotic florfenicol (FF) and fluoroquinolone antibiotic ofloxacin (OFL) on freshwater biofilms were investigated by determining the changes in the key physicochemical and biological properties of the biofilms. The results showed that the chlorophyll a content in biofilms firstly decreased to 46⁻71% and then recovered to original content under the stress of FF and OFL with high, mid, and low concentrations. Meanwhile, the activities of antioxidant enzymes, including superoxide dismutase and catalase, increased between 1.3⁻6.7 times their initial values. FF was more toxic to the biofilms than OFL. The distribution coefficients of FF and OFL binding in extracellular polymeric substances (EPS)-free biofilms were 3.2 and 6.5 times higher than those in intact biofilms, respectively. It indicated that EPS could inhibit the FF and OFL accumulation in biofilm cells. The present study shows that the EPS matrix, as the house of freshwater biofilms, is the primary barrier that resists the stress from antibiotic residues.

Evaluation of the subtle effects and oxidative stress response of chloramphenicol, thiamphenicol, and florfenicol in Daphnia magna.

Phenicol antibiotics, such as chloramphenicol, thiamphenicol, and florfenicol, are commonly used in the veterinary and aquaculture fields to treat diseases and have frequently been detected in aquatic environments. Nevertheless, there is limited information regarding the effects of phenicol antibiotics on aquatic nontarget species. Thus, the present study aims to investigate the long-term (21-d) influence on the reproduction and growth of and the acute (24-h) oxidative response and tissue damage in the crustacean Daphnia magna after exposure to phenicol drugs, including their environmental concentrations. The results indicate that D. magna exposed to florfenicol are likely to cause more adverse effects than those exposed to chloramphenicol and thiamphenicol over long-term (21-d) exposures. Furthermore, changes in biochemical biomarkers such as malondialdehyde (MDA), catalase (CAT), and reduced glutathione (GSH) induced by individual and mixtures of phenicol antibiotics were also observed. Low concentrations of chloramphenicol, thiamphenicol + florfenicol, and chloramphenicol + thiamphenicol significantly increased the MDA levels of D. magna after 24-h exposures, causing cellular oxidative damage in the animals. In addition, discrepancies between CAT activities and GSH levels were observed, underscoring the need to evaluate multiple indicators of oxidative stress in toxicological studies using D. magna as a model. Environ Toxicol Chem 2019;38:575-584. © 2018 SETAC.

Effects of florfenicol and oxytetracycline on the tropical cladoceran Ceriodaphnia silvestrii: A mixture toxicity approach to predict the potential risks of antimicrobials for zooplankton.

Antimicrobials are commonly used in aquaculture to treat infectious diseases in fish. The overuse of these chemicals, however, has made them a contamination source for the aquatic environments. In this study, single and combined effects of florfenicol (FLO) and oxytetracycline (OTC), two antimicrobials widely used in the fish farming, were evaluated in acute and chronic toxicity tests using the tropical cladoceran Ceriodaphnia silvestrii as a model species. Also, a preliminary risk characterization of FLO and OTC for zooplankton was carried out, taking into account different exposure scenarios. The results obtained revealed that FLO and OTC have adverse effects on the mobility, reproduction and population growth rate of C. silvestrii in single exposures. In addition, mixture effects on the C. silvestrii were more severe than predicted effects based on the Concentration Addition model, showing a synergistic deviation for the mobility and a dose-level dependent deviation for the reproduction (synergism at higher levels than EC60). In relation to the risk characterization, risk quotients (RQs) exceeded 1 for chronic toxicity data obtained in both OTC and mixture exposures, indicating that the concentrations of these chemicals in Brazilian freshwater bodies could potentially present risks for the reproduction of zooplankton species in tropical regions. The RQs obtained for the mixtures were higher than those obtained for each chemical separately. Therefore, it is highly recommended that RQs are derived from single and mixture exposure data in order to obtain a more accurate risk characterization.