Polybrominated diphenyl ethers (PBDEs) are synthetic halogen compounds, industrially used as flame retardants in many flammable products. PBDEs are environmentally persistent and bioaccumulative substances that were used from the 1970s and discontinued in the 1990s. PBDEs are present in air, soil, water, and food, where they remain stable for a long time. Chronic exposure to PBDEs is associated with adverse human health effects, including cancer, immunotoxicity, hepatotoxicity, reproductive and metabolic disorders, motor and hormonal impairments, and neurotoxicity, especially in children. It has been demonstrated that PBDE exposure can cause mitochondrial and DNA damage, apoptosis, oxidative stress, epigenetic modifications, and changes in calcium and neurotransmitter levels. Here, we conduct a comprehensive review of the molecular mechanisms of the neurotoxicity of PBDEs using different approaches. We discuss the main neurotransmitter pathways affected by exposure to PBDEs in vitro and in vivo in different mammalian models. Excitatory and inhibitory signaling pathways are the putative target where PBDEs carry out their neurotoxicity. Based on this evidence, environmental PBDEs are considered a risk to human public health and a hazard to biota, underscoring the need for environmental monitoring to mitigate exposure to PBDEs.

Soil contamination linked to anthropogenic activities has become a serious environmental problem on a global scale. It is caused by heavy metals, such as lead (Pb). Dopamine (DOP) is a biogenic amine that acts as a neurotransmitter. It is found in plant organs and induces tolerance against abiotic stresses, including contamination. 24-epibrassinolide (EBR) stimulates metabolism, positively impacting flowering and production. This research aimed to evaluate whether EBR and DOP, applied alone or combined, can mitigate the impacts caused by Pb on roots and leaves by measuring root and leaf structures and stomatal behavior. For roots, both plant growth regulators maximized the epidermis, with increases in treatments Pb2+ - DOP + EBR (45%), Pb2+ + DOP - EBR (24%), and Pb2+ + DOP + EBR (36%), when compared with equal treatment without Pb2+. To leaves, the tested molecules improved the leaf structures, significantly increasing palisade parenchyma and spongy parenchyma. Parallelly, stomatal performance was boosted after treatments with EBR and DOP, confirmed by increments in stomatal density. Our study proved that EBR and DOP, alone or combined, mitigated the damages to leaves and roots exposed to Pb stress, but better results were found when EBR was applied alone.