Investigation of the effect of 4-T-butyl benzoic acid on zebrafish nervous system development

Environmental pollution is an increasing problem nowadays. Many pollutants enter the environment due to human activities, including industry, agriculture, urbanization, transportation, and tourism. Contaminants show toxic properties in the soil, air, and water ecosystems and harm living creatures. Among the harmful substances that show these effects, endocrine disruptor compounds (EDC) that are averse to a hormone system are among the important ones. Recent studies have determined that EDCs can also function as metabolic disruptors with fetal and pre-adolescent exposure. There are numerous studies on the association of persistent organic pollutants, BPA, and phthalates with adiposity and obesity. Reports also indicate that dioxins and phthalates may be associated with hypertension. Among the endocrine disruptors, 4-tert butyl benzoic acid (PTBBA) is one of the plastic additives. It is used in industry as a polymerization inhibitor and PVC heat stabilizer. In previous studies, PTBBA has been shown to harm the male reproductive system. Additionally, it has been found to harm the reproductive organs of rats, causing a decrease in sperm count, mobility, and morphological abnormalities. However, the survey of the damage to the aquatic ecosystem is minimal. Zebrafish are a widely used model organism for marine ecosystems. It is used because of its rapid development, the transparency of the embryos, the low maintenance and a transparent and large number of embryos, and its genetic similarity to humans. Zebrafish is a model organism studied extensively in the embryonic and nervous system development literature. The physiology and neuroanatomy of the zebrafish are parallel to that of humans. The zebrafish nervous system becomes functional within days, and all the main components of the brain are present at five dpf. Like other vertebrates, the central nervous system of the zebrafish is formed from the neural plate, an ectoderm epithelial layer on the embryo's dorsal surface. By the end of gastrulation, the neural plate forms a tube. Brain ventricles form 48 hours after fertilization, and the embryo begins to respond to touch stimuli. In some areas of the zebrafish's central nervous system, such as the hypothalamus, optic pathways, olfactory system, spinal cord, and cranial nerves, an apparent structural homology can be found in the corresponding areas of the human brain. The effects of PTBBA on zebrafish nervous system development are unknown. In addition, there are not enough studies showing that it may have teratological effects. To investigate the effects of PTBBA on the nervous system of zebrafish, fish were obtained from Istanbul University Aquatic Vertebrate Live Experiment Unit. The lethal concentration of PTBBA in zebrafish is not known. To determine the LC50 was performed at logarithmic doses of 100-0.01 mg/l for three repeated trials. The 24-hour LC50 was 3.900±2.692 mg/l, and the 120-hour LC50 was 1.775±0.321 mg/l. To investigate its teratological effects, mortality, hatching, and anomaly rates were recorded for 120 hours with three repetitions of 50%, 20%, and 10% of the 120-hour LC50 dose (0.89, 0,356, and 0,178 mg/l, respectively). Samples were taken for histological analysis for 15 days. Embryo and larvae samples were fixated with Bouine's solution after that, routinely treated with 70-100% alcohol series than xylene. Samples stained with hematoxylin-eosin and toluidine blue and photographed with Leica DM1000 and MC170 HD CCD camera. Among the adverse effects of PTBBA on zebrafish development, teratological effects such as growth retardation, decreased pigmentation, spinal disorders, craniofacial anomalies, pericardial edema, and organ deficiencies were observed. The control and solvent control groups had no anomalies whatsoever. Lower and middle dose groups had increased anomalies, respectively. In the 0.890 mg/l dose group, anomaly numbers were decreased, but the seriousness of anomalies increased. The primary anomaly was unhatched embryos due to a slower development rate. Histology analysis showed increasing vacuolization, swollen cell bodies, pycnotic cells, and regional atrophies. In high doses, neuronal atrophies were detected in the medulla oblongata area. The harmful effects of PTBBA on the male reproductive system in living things were known in the literature. However, this study revealed the teratological properties of PTBBA in zebrafish. In addition, the neurotoxic effects of PTBBA were observed at the 15 dpf stage. PTBBA in plastics harms living things due to its presence in water and other environments. In addition, different chemicals are metabolized in the body, increasing PTBBA exposure. Regulation of these substances and PTBBA will benefit the environment and human health. PTBBA in plastics harms living things due to its presence in water and other environments. In addition, different chemicals are metabolized in the body, increasing PTBBA exposure. Regulation of these substances and PTBBA will benefit the environment and human health.