The role of ambra1 in Pb-induced developmental neurotoxicity in zebrafish

Cerebral Vascular Toxicity after Developmental Exposure to Arsenic (As) and Lead (Pb) Mixtures

Arsenic (As) and lead (Pb) are environmental pollutants found in common sites linked to similar adverse health effects. This study determined driving factors of neurotoxicity on the developing cerebral vasculature with As and Pb mixture exposures. Cerebral vascular toxicity was evaluated at mixture concentrations of As and Pb representing human exposures levels (10 or 100 parts per billion; ppb; µg/L) in developing zebrafish by assessing behavior, morphology, and gene expression. In the visual motor response assay, hyperactivity was observed in all three outcomes in dark phases in larvae with exposure (1-120 h post fertilization, hpf) to 10 ppb As, 10 ppb Pb, or 10 ppb mix treatment. Time spent moving exhibited hyperactivity in dark phases for 100 ppb As and 100 ppb mix treatment groups only. A decreased brain length and ratio of brain length to total length in the 10 ppb mix group was measured with no alterations in other treatment groups or other endpoints (i.e., total larval length, head length, or head width). Alternatively, measurements of cerebral vasculature in the midbrain and cerebellum uncovered decreased total vascularization at 72 hpf in all treatment groups in the mesencephalon and in all treatment groups, except the 100 ppb Pb and 10 ppb As groups, in the cerebellum. In addition, decreased sprouting and branching occurred in the mesencephalon, while only decreased branching was measured in the cerebellum. The 10 ppb Pb group showed several cerebral vasculature modifications that were aligned with a specific gene expression alteration pattern different from other treatment groups. Additionally, the 100 ppb As group drove gene alterations, along with several other endpoints, for changes observed in the 100 ppb mix treatment group. Perturbations assessed in this study displayed non-linear concentration-responses, which are important to consider in environmental health outcomes for As and Pb neurotoxicity.

Embryonic Zebrafish as a Model for Investigating the Interaction between Environmental Pollutants and Neurodegenerative Disorders

Environmental pollutants have been linked to neurotoxicity and are proposed to contribute to neurodegenerative disorders. The zebrafish model provides a high-throughput platform for large-scale chemical screening and toxicity assessment and is widely accepted as an important animal model for the investigation of neurodegenerative disorders. Although recent studies explore the roles of environmental pollutants in neurodegenerative disorders in zebrafish models, current knowledge of the mechanisms of environmentally induced neurodegenerative disorders is relatively complex and overlapping. This review primarily discusses utilizing embryonic zebrafish as the model to investigate environmental pollutants-related neurodegenerative disease. We also review current applicable approaches and important biomarkers to unravel the underlying mechanism of environmentally related neurodegenerative disorders. We found embryonic zebrafish to be a powerful tool that provides a platform for evaluating neurotoxicity triggered by environmentally relevant concentrations of neurotoxic compounds. Additionally, using variable approaches to assess neurotoxicity in the embryonic zebrafish allows researchers to have insights into the complex interaction between environmental pollutants and neurodegenerative disorders and, ultimately, an understanding of the underlying mechanisms related to environmental toxicants.

Dynamic alterations of locomotor activity and the microbiota in zebrafish larvae with low concentrations of lead exposure

Lead (Pb) is a ubiquitous heavy metal associated with developmental and behavioral disorders. The establishment of pioneer microbiota overlaps with the development of the brain during early life, and Pb-induced developmental neurotoxicity may be partially caused by early-life microbiota dysbiosis. This study investigated the locomotor activity and the microbiota in developing zebrafish at multiple developmental time points (five days post fertilization [5 dpf], 6 dpf, and 7 dpf) under exposure to low concentrations of lead (0.05 mg/L). Time-dependent reductions in the number of activities and the average movement distance of larvae compared to the control were observed following Pb exposure. Furthermore, Pb exposure significantly altered the composition of the gut microbiota of zebrafish larvae. At the phylum level, the abundance of Proteobacteria decreased from 5 to 7 dpf, while that of Actinobacteria increased in the control groups. At the class level, the proportion of Alphaproteobacteria decreased, while that of Actinobacteria increased in the control groups. Notably, all showed the opposite trend in Pb groups. A correlation analysis between indices of locomotor activity and microbial communities revealed genus-level features that were clearly linked to the neurobehavioral performance of zebrafish. Seven genera were significantly correlated with the two performance indicators of the locomotion analysis, namely Rhodococcus, Deinococcus, Bacillus, Bosea, Bradyrhizobium, Staphylococcus, and Rhizobium. Rhizobium was dominant in zebrafish and increased in the Pb groups in a time-dependent manner. In addition, the expression levels of bdnf, trkb1, trkb2, and p75ntr changed in zebrafish from 5 to 7 dpf under Pb exposure. Collectively, these results suggest that Pb-induced neurotoxicity could potentially be treated by targeting the gut microbiota.

Temperature- and chemical-induced neurotoxicity in zebrafish

Throughout their lives, humans encounter a plethora of substances capable of inducing neurotoxic effects, including drugs, heavy metals and pesticides. Neurotoxicity manifests when exposure to these chemicals disrupts the normal functioning of the nervous system, and some neurotoxic agents have been linked to neurodegenerative pathologies such as Parkinson's and Alzheimer's disease. The growing concern surrounding the neurotoxic impacts of both naturally occurring and man-made toxic substances necessitates the identification of animal models for rapid testing across a wide spectrum of substances and concentrations, and the utilization of tools capable of detecting nervous system alterations spanning from the molecular level up to the behavioural one. Zebrafish (Danio rerio) is gaining prominence in the field of neuroscience due to its versatility. The possibility of analysing all developmental stages (embryo, larva and adult), applying the most common "omics" approaches (transcriptomics, proteomics, lipidomics, etc.) and conducting a wide range of behavioural tests makes zebrafish an excellent model for neurotoxicity studies. This review delves into the main experimental approaches adopted and the main markers analysed in neurotoxicity studies in zebrafish, showing that neurotoxic phenomena can be triggered not only by exposure to chemical substances but also by fluctuations in temperature. The findings presented here serve as a valuable resource for the study of neurotoxicity in zebrafish and define new scenarios in ecotoxicology suggesting that alterations in temperature can synergistically compound the neurotoxic effects of chemical substances, intensifying their detrimental impact on fish populations.

Qilong Capsule Alleviated MPTP-Induced Neuronal Defects by Inhibiting Apoptosis, Regulating Autophagy in Zebrafish Embryo Model

Qilong capsule (QLC) originates from the famous "Buyang Huanwu decoction" prescription. It is representative of drugs used in China during recovery from stroke, but its neuroprotective mechanism of action remains obscure. HPLC was used to evaluate the similarity of 10 batches of QLC samples. Then we used a zebrafish model to study the neuroprotective effect of QLC. At 24 hpf, embryos were treated with QLC and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), and zebrafish were observed the neuronal length and the number of apoptotic cells in the brain at 72 hpf. At 120 hpf, we conduct zebrafish behavioural tests. We then also used qPCR to detect the expression of genes related to autophagy and apoptosis. The results showed that QLC significantly reduced the damage of dopaminergic neurons, the number of apoptotic cells in the brain, and alleviated motor disturbances induced by MPTP. We found that the mechanism of QLC activity involved decreased neuron cell death by inhibiting mitochondrial apoptosis and autophagy, promoting autophagy, degradation of alpha-synuclein, and neuron cell growth, and rescuing the function of neurons damaged by MPTP. The results indicated that QLC protected against MPTP-induced neuron injury and provided pharmacological evidence for clinical use of QLC.