Synthetic azo dye amaranth disrupts neuronal plasticity causing alpha-synuclein aggregation and cognitive disability in an in vivo zebrafish model

Abstract

Amaranth (AMR) or Acid red 27 is a synthetic dye widely used in the textile, pharmaceutical, and food industries. Its high solubility contributes to its environmental persistence as a pollutant, and its widespread use in confectioneries, due to its vibrant color, raises concerns about overexposure, particularly in children. Despite its prevalence, health and ecological risks of AMR remain poorly studied. We investigated the developmental and neurobehavioral effects of AMR in-vivo zebrafish. Assessments of acute and chronic toxicity revealed a dose-dependent increase in mortality and developmental abnormalities. Oxidative stress was evident from ROS accumulation, glutathione depletion (1.14 ± 0.28 U/mg of protein; p = 0.0012), and increased lipid peroxidation (2.80 fold; p < 0.0001) at 100 mg/L. Neurobehavioral analysis revealed cognitive impairment and altered locomotor activity. Molecular analysis using key markers revealed potential disruptions in neuroplasticity. Immunohistochemical analysis revealed elevated GFAP expression (2.42 fold; p < 0.0001) and accumulation of α-synuclein (2.63 fold; p < 0.0001) at 100 mg/L, indicating astrocyte activation and gliosis, suggesting key pathological mechanisms implicated in major neurodegenerative diseases such as Parkinson's disease. These findings highlight AMR's neurotoxic potential at environmentally relevant concentrations, underscoring the urgent need to reassess its regulatory safety limits and environmental impact.

Keywords: Astrogliasis; Food dye; Locomotory dysfunction; Neurotoxicity; Synaptic disability.