Effects of low-dose ionizing radiation on the molecular pathways linking neurogenesis and autism spectrum disorders in zebrafish embryos

Prenatal exposure to environmental factors may play an important role in the aetiopathogenesis of autism spectrum disorder (ASD). We aim to investigate the potential effects of low-dose x-rays from dental diagnostic x-rays on neurodevelopment and molecular mechanisms associated with ASD in developing zebrafish embryos. Zebrafish embryos were divided into four groups and exposed using a dental x-ray unit: control, 0.08, 0.15 and 0.30 seconds, which are exemplary exposure settings for periapical imaging. These exposure times were measured as 7.17, 23.17 and 63.83 mSv using optical stimulated luminescence dosimeters. At the end of 72 hours post-fertilization, locomotor activity, oxidant-antioxidant status, and acetylcholine esterase (AChE) activity were analyzed. Expression of genes related to apoptosis (bax, bcl2a, p53), neurogenesis (α1-tubulin, syn2a, neurog1, elavl3) and ASD (eif4eb, adsl2a, shank3) was determined by RT-PCR. Even at reduced doses, developmental toxicity was observed in three groups as evidenced by pericardial edema, yolk sac edema and scoliosis. Deleterious effects of dental x-rays on neurogenesis through impaired locomotor activity, oxidative stress, apoptosis and alterations in genes associated with neurogenesis and ASD progression were more pronounced in the 0.30s exposure group. Based on these results we suggest that the associations between ASD and low-dose ionizing radiation need a closer look.