In the last century, industrial activities increased and caused multiple health problems for humans and animals. At this moment, heavy metals are considered the most harmful substances for their effects on organisms and humans. The impact of these toxic metals, which have no biological role, poses a considerable threat and is associated with several health problems. Heavy metals can interfere with metabolic processes and can sometimes act as pseudo-elements. The zebrafish is an animal model progressively used to expose the toxic effects of diverse compounds and to find treatments for different devastating diseases that human beings are currently facing. This review aims to analyse and discuss the value of zebrafish as animal models used in neurological conditions, such as Alzheimer’s disease (AD), and Parkinson’s disease (PD), particularly in terms of the benefits of animal models and the limitations that exist.

Environmental contamination from toxic metals and pesticides is an issue of great concern due to their harmful effects to human health and the ecosystems. In this framework, we assessed the adverse effects when aquatic organisms are exposed to toxicants such as deltamethrin (DM) and lead (Pb), alone or in combination, using zebrafish as a model. Moreover, we likewise evaluated the possible protective effect of vitamin C (VC) supplementation against the combined acute toxic effects of the two toxicants. Juvenile zebrafish were exposed to DM (2 μg L⁻¹) and Pb (60 μg L⁻¹) alone and in combination with VC (100 μg L⁻¹) and responses were assessed by quantifying acetylcholinesterase (AChE) activity, lipid peroxidation (MDA), some antioxidant enzyme activities (SOD and GPx), three-dimension locomotion responses and changes of elements concentrations in the zebrafish body. Our results show that VC has mitigative effects against behavioral and biochemical alterations induced by a mixture of contaminants, demonstrating that it can be used as an effective antioxidant. Moreover, the observations in the study demonstrate zebrafish as a promising in vivo model for assessing the neuroprotective actions of bioactive compounds.

Even though the toxic effects of antibiotics and heavy metals have been extensively studied in the last decades, their combined adverse impact on aquatic organisms is poorly understood. Therefore, the objective of this study was to assess the acute effects of a ciprofloxacin (Cipro) and lead (Pb) mixture on the 3D swimming behavior, acetylcholinesterase (AChE) activity, lipid peroxidation level (MDA—malondialdehyde), activity of some oxidative stress markers (SOD—superoxide dismutase and GPx—glutathione peroxidase), and the essential elements content (Cu—copper, Zn—zinc, Fe—iron, Ca—calcium, Mg—magnesium, Na—sodium and K—potassium) in the body of zebrafish (Danio rerio). For this purpose, zebrafish were exposed to environmentally relevant concentrations of Cipro, Pb, and a mixture for 96 h. The results revealed that acute exposure to Pb alone and in mixture with Cipro impaired zebrafish exploratory behavior by decreasing swimming activity and elevating freezing duration. Moreover, significant deficiencies of Ca, K, Mg, and Na contents, as well as an excess of Zn level, were observed in fish tissues after exposure to the binary mixture. Likewise, the combined treatment with Pb and Cipro inhibited the activity of AChE and increased the GPx activity and MDA level. The mixture produced more damage in all studied endpoints, while Cipro had no significant effect. The findings highlight that the simultaneous presence of antibiotics and heavy metals in the environment can pose a threat to the health of living organisms.

Environmental concerns have consistently been a focal point for the scientific community. Pollution is a critical ecological issue that poses significant threats to human health and agricultural production. Contamination with heavy metals and pesticides is a considerable concern, a threat to the environment, and warrants special attention. In this study, we investigated the significant issues arising from sub-chronic exposure to imidacloprid (IMI), mercury (Hg), and cadmium (Cd), either alone or in combination, using zebrafish (Danio rerio) as an animal model. Additionally, we assessed the potential protective effects of polyfloral honey enriched with natural ingredients, also called honey formulation (HF), against the combined sub-chronic toxic effects of the three contaminants. The effects of IMI (0.5 mg·L⁻¹), Hg (15 μg·L⁻¹), and Cd (5 μg·L⁻¹), both individually and in combination with HF (500 mg·L⁻¹), on zebrafish were evaluated by quantifying acetylcholinesterase (AChE) activity, lipid peroxidation (MDA), various antioxidant enzyme activities like superoxide dismutase and glutathione peroxidase (SOD and GPx), 2D locomotor activity, social behavior, histological and immunohistochemical factors, and changes in body element concentrations. Our findings revealed that all concentrations of pollutants may disrupt social behavior, diminish swimming performances (measured by total distance traveled, inactivity, and swimming speed), and elevate oxidative stress (OS) biomarkers of SOD, GPx, and MDA in zebrafish over the 21-day administration period. Fish exposed to IMI and Hg + Cd + IMI displayed severe lesions and increased GFAP (Glial fibrillary acidic protein) and S100B (S100 calcium-binding protein B) protein expression in the optic tectum and cerebellum, conclusively indicating astrocyte activation and neurotoxic effects. Furthermore, PCNA (Proliferating cell nuclear antigen) staining revealed reduced cell proliferation in the IMI-exposed group, contrasting with intensified proliferation in the Hg + Cd group. The nervous system exhibited significant damage across all studied concentrations, confirming the observed behavioral changes. Moreover, HF supplementation significantly mitigated the toxicity induced by contaminants and reduced OS. Therefore, the exposure to chemical mixtures offers a more complete picture of adverse impacts on aquatic ecosystems and the supplementation with bioactive compounds can help to reduce the toxicity induced by exposure to environmental pollutants.

Nowadays, trace metal contamination within urban atmospheres is a significant and concerning global issue. In the present study, two synanthropic bird species, namely, the feral pigeon (Columba livia f. domestica) and the rook (Corvus frugilegus), were employed as bioindicators to assess the atmospheric trace metal pollution in Iasi City, Romania. The concentrations of Ni, Pb, Cd, Co, Cr, and Cu were determined through high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF-AAS) of various tissues, including the liver, kidney, lung, heart, muscle, and bone, of feral pigeons and rooks collected in Iasi City. The order of trace metal concentrations in the tissues of feral pigeons and rooks in Iasi City was similar: Cu > Pb > Ni > Cd > Cr > Co. However, trace element values in most tissues were higher in the rook samples than in feral pigeon ones, except for Co, which had elevated levels in feral pigeon renal and cardiac tissues, and Cu, which registered the highest concentrations in feral pigeon liver and kidney tissues. While not statistically significant, Pb concentration values in the PM₁₀ fraction of atmospheric particles positively correlated with Pb concentrations in rook kidney samples (p = 0.05). The concentration levels of Cd, Pb, and Ni in the PM₁₀ fraction of air particles showed a positive correlation with Cd levels in the samples of pigeon heart and rook liver, kidney, and heart, Pb levels in the samples of pigeon kidney, heart, and muscle and rook liver and bone, and Ni levels in the samples of pigeon liver, kidney, and bone and rook liver, muscle, and bone, respectively.

The purpose of this research was to establish the baseline concentrations of thirteen trace elements (Cd, Co, Cr, Cu, Ni, Pb, Fe, Mg, Na, K, Sr, Ca, and Zn) in feathers of the common blackbird Turdus merula (n=9) at the Natura 2000 site “Marine Dunes from Agigea” (ROSCI0073). Both remiges and rectrices were pooled, and the quantification of trace elements was accomplished using two spectrometry analysis methods: high-resolution continuum source atomic absorption spectrometer with a graphite furnace (HR-CS GF-AAS) and flame atomic absorption spectrometer (FL-AAS). The concentration of Ca was the highest of the thirteen trace elements, registering at 209.9146±192.4098 µg·g-1 w.w., while Cd had the lowest concentration levels in feathers, 0.0243±0.0158 µg·g-1 w.w., respectively. However, the results obtained were significantly lower than those in the relevant literature. These findings suggest that the bioavailability of the analysed trace elements is minimal in our study area. Thus, it is imperative to conduct further research on the impact of these trace elements' accumulation and effects on avifauna in the Natura 2000 site “Marine Dunes from Agigea”.