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Effect of polyethylene microplastics and antibiotic ermetoxin on oxidative and stress indices of tilapia fish (Oreochromis sp.)
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Mohammad Bahrami   , Reza Salighizadeh * , Mohsen Pournia2 , Mohammad Hossein Khanjani3 , Gholamreza Ghaedi4 |
1-Department of Veterinary, Sho.C., Islamic Azad University, Shoushtar, Iran , rezasalighehzadeh@yahoo.com
2- Department of Microbiology, MaS.C., Islamic Azad University, Masjed Soleiman, Iran
3- Department of Fisheries Sciences and Engineering, Faculty of Natural Resources, University of Jiroft, Jiroft, Kerman, Iran
4- Department of Fisheries Sciences and Engineering, Khorramshahr University of Marine Sciences and Technology, Khorramshahr, Iran |
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Abstract: (76 Views) |
Introduction: Microplastics are an emerging pollutant, defined as synthetic plastic particles with a diameter of less than 5 mm and greater than 1 μm. Microplastics have specific physical and chemical properties, including small size, high density, and color, which both allow them to absorb other pollutants and increase the accessibility of these types of pollutants to living organisms. Antibiotics are used to treat diseases and improve production in aquaculture, while many antibiotics cannot be completely metabolized after consumption and eventually enter the natural environment. Antibiotics are considered emerging pollutants due to their continuous and quasi-persistent input. Tilapia (Oreochromis sp.) was chosen as the study species because it is an important aquaculture species and the third most farmed fish species globally, and also because juvenile tilapia are sensitive to exposure to such microplastics. The aim of this study is to evaluate the separate and simultaneous effects of polyethylene microplastics and the antibiotic ermetoxin on oxidative and biochemical stress indices in tilapia fish.
Materials and Methods: A total of 360 tilapia (Oreochromis sp.) fish with an average weight of 240.5 ± 10.5 g were purchased from a private warm-water fish breeding center in the north of Karun County and transferred to the aquatic hall of the Southern Waters Aquaculture Research Institute located in Sheiban-Ahvaz, and released at a density of 10 fish in experimental units (300-liter fiberglass tanks). The fish were exposed to different doses of microplastics (100 and 200 mg/kg feed) and the antibiotic ermetoxin (15 and 30 mg/kg live weight) and their combinations (100 mg microplastic with 15 and 30 mg ermetoxin, 200 mg microplastic with 15 and 30 mg ermetoxin per kg live weight) for 21 days. At the end of the period, malondialdehyde (MDA) levels, catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) enzyme activities were measured as indicators of oxidative stress and antioxidant response. The effect of two independent variables, polyethylene microplastics and the antibiotic ermetoxin, on blood biochemical analytes and oxidative biomarkers was investigated through two-way analysis of variance.
Results and Discussion: The results showed that there was a significant difference between the experimental groups in the levels of total protein, glucose and lactate parameters in the blood of fish (p<0.05). Simultaneous exposure to polyethylene microplastics and the antibiotic ermetoxin caused a significant increase in MDA levels and a decrease in the activities of CAT, SOD, and GPx enzymes compared to control groups. The highest activity of antioxidant enzymes including GPx (42.45 μmol/L), SOD (1.309 IU/L) and catalase (2.34 IU/L) was observed in the group receiving the highest doses of antibiotics and microplastics in the diet. The findings indicate increased oxidative stress and decreased antioxidant defense capacity in fish exposed to these pollutants. Microplastics have a synergistic effect on the health of organisms when combined with other pollutants. The interaction of microplastics with chemical pollutants has shown contradictory findings. For example, in the study by Karbalaei et al. (2021), it was reported that the presence of microplastics increased the toxicity of chlorpyrifos to rainbow trout (O. mykiss). In the study by Guven et al. (2018), the presence of microplastics did not increase the acute toxicity of pyrene on the hunting performance of Asian sea bass (Lates calcarifer). Microplastics cause toxicity through the formation of free radicals that cause damage to cellular macromolecules and subsequently lead to physiological and biochemical changes in animals (Kim et al., 2021). Some studies showed increased superoxide dismutase activity in zebrafish (D. rerio) (Qiao et al., 2019) and Mozambique tilapia (Oreochromis mossambicus) (Jeyavani et al., 2023) exposed to microplastics, while Xiao et al. (2023) reported decreased superoxide dismutase activity in the freshwater fish Nothobranchius guentheri exposed to microplastics. A significant increase in catalase enzyme activity indicates a high rate of hydrogen peroxide production in liver cells of fish exposed to microplastics. In addition, the increase in hydrogen peroxide rate may be related to increased superoxide dismutase activity and accelerated dismutase of superoxide anions. A significant increase in catalase activity has been reported in zebrafish (D. rerio) (Félix et al., 2022), discus fish (Symphysodon aequifasciatus) (Wen et al., 2018), and mosquito fish (Gambusia holbrooki) (Banaee and Mohammadzadeh., 2022) exposed to microplastics. In the present study, the activity of the antioxidant enzyme glutathione peroxidase was increased under the influence of microplastics. Increased glutathione peroxidase activity in Mediterranean black mussel (M. galloprovincialis) (Capó et al., 2021), Nile tilapia (O. niloticus) (Dong et al., 2022), mosquito fish (G. holbrooki) (Banaee and Mohammadzadeh., 2022) and Mozambique tilapia (O. mossambicus) (Jeyavani et al., 2023) has been reported to be affected by microplastics. In the present study, the MDA level was high in the control group and reached the lowest value in the combined treatments, especially the highest concentration of microplastics and ermetoxin. In the study by Lin et al. (2014), the effect of sulfonamide toxin was examined on zebrafish after 72 hours and MDA was examined as a time-sensitive biomarker.
Conclusion: In general, the present results showed that the simultaneous consumption of microplastics and antibiotics in tilapia fish causes a significant increase in biochemical stress indices (such as glucose and lactate) and antioxidant enzyme activities (SOD, CAT, GPX). These synergistic effects indicate an increased level of oxidative stress and the possibility of tissue damage in fish, which can lead to significant changes in their general health and immune system efficiency.
Conflict of Interest: There are no conflicts of interest among the authors.
Acknowledgment: We would like to thank our colleagues who helped us in providing the equipment needed to conduct the experiment. |
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| Keywords: Microplastic pollution, antibiotics, oxidative stress, tilapia, microplastics |
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Full-Text [DOC 618 kb]
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Type of Study: Research |
Subject:
Special
Received: 2025/05/11 | Accepted: 2025/06/5 | Published: 2025/09/23
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Bahrami M, Salighizadeh R, Pournia M, Khanjani M H, Ghaedi G. Effect of polyethylene microplastics and antibiotic ermetoxin on oxidative and stress indices of tilapia fish (Oreochromis sp.). JAD 2025; 19 (3) :116-134 URL: http://aqudev.liau.ac.ir/article-1-895-en.html
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