Melatonin attenuates BDE-209-caused spatial memory deficits in juvenile rats through NMDAR-CaMKⅡγ-mediated synapse-to-nucleus signaling

Flame retardant polybrominated diphenyl ethers (PBDEs) accumulate in human bodies through food and dust ingestion, and cause neurobehavioral deficits with obscure mechanism. We aimed to investigate NMDAR-CaMKⅡγ-mediated synapse-to-nuclear communication involved in BDE-209-induced cognitive impairment, and alleviation from exogenous melatonin. Decreased NMDAR subunits GluN2A and 2B, autophosphorylation of CaMKⅡα, and postsynaptic GluA1 trafficking were observed in the hippocampus of juvenile rats after maternal BDE-209 exposure. Moreover, nuclear shuttling of CaMKⅡγ with CaM, as well as downstream nuclear p-CaMKIV and p-CREB-dependent genes (Bdnf, c-Fos, Arc) expression were all causally down-regulated. These resulted in less dendritic spines in CA1 area and poor spatial learning and memory. Importantly, elevated miR-219a-5p in transcriptome sequencing was identified together with its targets Grin2b and Camk2g mRNA, further elucidated the reduction in GluN2B and CaMKⅡγ protein. These changes on synaptic plasticity caused by BDE-209 were reversed correspondingly under pretreatment of melatonin, partially via miR-219a inhibition. Collectively, our findings suggest that synaptonuclear signaling alterations potentially mediated neurobehavioral deficits induced by early-life BDE-209 exposure and the neuroprotection from melatonin, therefore provided a novel perspective for prevention.