Bioaccumulation Characteristics And Ecotoxicological Effects Of Antidepressant Fluoxetine And Its Photodegradation Products

As the development of civilization,the use of psychotropic drugs has become more and more common.Antidepressants are important parts of psychotropic drugs.Due to their widespread applications in the treatment of human depression with inappropriate handling and disposal,a wide range of antidepressant drugs have been detected in various aquatic environments.Although their environmental concentrations are at relatively low ng/L to ?g/L levels,as emerging organic contaminants,these drug pollutants in aqueous systems have potentials to be accumulated in aquatic organisms and may pose a great risk to non-target aquatic species(such as fishes),and even threaten human health.At present,the supporting data for ecotoxicological risk assessment of the antidepressant contamination in China are still lacking,and thus,more attention should be paid for solving these environmental issues.Fluoxetine(FLU)is an antidepressant belonging to the class of selective serotonin reuptake inhibitors(SSRIs).In the present study,applying red crucian carp and zebrafish as models,we designed long-term and short-term waterborne exposure experiments,as well as exposure/purification experiments to a series of concentrations of FLU(0.1,1,10,100 and 1000 ?g/L).The distribution,bioconcentration and clearance of FLU were characterized in different fish tissues after exposure,and also the potential adverse effects of FLU exposure on the growth and development of fish were determined.Moreover,we investigated the degradation efficiency of FLU in aqueous solution under ultraviolet(UV)irradiation and electron beam irradiation,and compared the toxicity of FLU and its photodegradation products before and after photolysis treatment.The main results were as follows:1.The concentrations of FLU in red crucian carp tissues(brain,liver,muscle,kidney and heart)were determined after 30-day exposure to 0.1,1,10,100,1000 ?g/L of FLU solutions.The results were as follows:(1)The relatively high concentrations of FLU were always found in fish tissues in higher concentrations of FLU exposure group.(2)No significant difference of FLU concentrations was observed among fish brain,liver,and muscle,and the bioconcentration factor(BCF)values were within the range of 12.8-110 in brain,11.1-137 in liver,and 12.1-166 in muscle,respectively.(3)Higher BCF values were found in the relatively low concentrations of FLU exposure groups,and the highest BCF of FLU in fish tissues was found in the 0.1 ?g/L of FLU exposure group.(4)According to the observed bioconcentration patterns of FLU in this study,FLU concentrations can reach the human therapeutic thresholds(HTPC: 91 ng/ml)in fish brain and liver when the exposure concentrations of FLU in water were at 5.75 ?g/L and 1.74 ?g/L,respectively.These FLU exposure concentrations were far lower than the predicted exposure concentration of FLU(24.3 ?g/L)that can reach the HTPC according to the fish plasma model,which highlight the risk of low levels of FLU exposure.2.Red crucian carp were exposed to FLU for 6 days at 0.1 ?g/L followed by a 6-day recovery period(in clean water).The results of the short-term exposure and purification experiment were as follows:(1)The FLU levels in different fish tissues increased as the exposure time increased,with the highest concentrations of FLU found after 6 days of exposure.During the 6-day recovery period,FLU levels declined in fish tissues and the clearance rate reached 60%-100%;(2)There were significant differences of FLU concentrations among brain,liver,and muscle(p < 0.05),and the tissue accumulation levels were in the order: liver > brain > muscle;(3)acetylcholinesterase(AChE)activity in the brain of red crucian carp significantly increased following 6-day exposure to 0.1 ?g/L of FLU,but that increase was restrained following the clearance treatment and significant enhancement of AChE activity was not observed on day 9 and 12 during the 6-day recovery period.The activities of antioxidant enzymes in the liver were also significantly induced on day 3 and day 6 following exposure to FLU,with maximum induction occurring on day 6,but no significant induction of these enzymes during the 6-day recovery period.These results suggested that the changes in brain AChE activity and in antioxidant parameters in the liver were all consistent with the FLU levels in the fish organs.Our study provides fundamental data on the link between the potential effects of pharmaceuticals and their internal exposure doses in fish.FLU exposure can alter multiple parameters in fish at water concentrations as low as 0.1 ?g/L when the predicted internal plasma concentrations of FLU were below human therapeutic doses.3.Adult zebrafish were exposed to FLU for 6 days at 0.1 ?g/L,followed by a 6-day recovery period(clean water).The results of the short-term exposure and purification experiment showed that there were significant differences of FLU concentrations among brain,viscera and muscle(p < 0.05),and the tissue accumulation levels were in the order brain > viscera > muscle.Taken the results from the red crucian carp study together,we found that the capacities of accumulation and purification of FLU were different among different fish species.4.The physiological,behavioral,biochemical indices and nervous system development associated endpoints were affected in zebrafish(Danio rerio)embryos exposed to a series of FLU concentrations(0.1,1,10,100,1000 ?g/L of water)from 4 hours post-fertilization(hpf)until 120 hpf.The results were as follows:(1)FLU exposure significantly delayed the hatching time of zebrafish embryos,and accelerated the heart rate(48 and 72 hpf).There was a significant reduction in body length of zebrafish at 1000 ?g/L compared to the control group(p < 0.05)at 120 hpf;(2)The swimming distance and swimming speed of zebrafish increased significantly in the FLU exposure groups compared to the control group(p < 0.05)at 120 hpf;(3)A dynamic response involving AChE activity and antioxidant parameters was displayed in the fish,and a correlation between biochemical effects and FLU levels in fish was observed.These physiological responses in zebrafish embryos might be an attempt to adapt to the changed environment owing to the FLU exposure;(4)FLU exposure also affected the expression of neuron-related and apoptosis-related genes,therefore,the pharmaceutical compound may affect the normal development of nervous system in zebrafish embryos.5.The initial FLU concentration of 1 mg/L was used in zebrafish embryo exposure experiment.Exposure solutions were 1 mg/L of FLU solutions after 0,15,30 and 60 min UV photodegradation.Zebrafish embryos(4 hpf)were exposed to the solutions until 120 hpf.The results were as follows:(1)UV irradiation can effectively remove the FLU from water,with more than 90% of FLU being removed after 60 min UV photodegradation;(2)The hatching time of zebrafish embryos exposed to non-irradiated group(0-min)and irradiated group(60-min)were both delayed,accompanied by the increase of heart rates at 48 and 72 hpf and the decrease of body length at 120 hpf.However,there were significantly differences between non-irradiated group(0-min)and UV irradiated(15-or 30-min)groups.The results confirmed that the ongoing degradation of parent FLU throughout the UV treatment period,together with concurrent increases in degradation products.Thus,the toxicity was occurred in the exposure group,which might be due to the coexistence of parent FLU and these transformation products;(3)A dynamic response involving AChE activity and antioxidant parameters was displayed both in the non-irradiated and UV irradiated exposure groups in order to adapt the changed environment owing to the chemical exposure;(4)The toxic response of neuron-related and apoptosis-related genes increased over time(60-min)during the UV-treatment experiments in parallel with the formation of FLU degradation products.These results highlight the potential toxicity of the relevant transformation products for assessing the environmental risks posed by pharmaceutical compounds.6.The initial FLU concentration of 1 mg/L was used in zebrafish embryos exposure experiment.Exposure solutions were 1 mg/L of FLU solutions after 0,0.5 and 1 kGy electron beam irradiation.Zebrafish embryos(4 hpf)were exposed to the solutions until 120 hpf.The results were as follows:(1)Electron beam irradiation can effectively remove the FLU from water,with approximately 99% of FLU being removed after 0.5 and 1 kGy electron beam irradiation;(2)The hatching time of zebrafish embryos exposed to non-irradiated group(0 kGy)and irradiated group(0.5 and 1 kGy)was both delayed,accompanied by the increase of heart rates at 48 and 72 hpf and the decrease of body length at 120 hpf;(3)A dynamic response of antioxidant parameters was also displayed in the irradiated groups.Therefore,the toxicity of the transformation products also needs our enough attention.