Background Research has found that aluminum exposure can cause nerve damage and affect neuronal function through epigenetic mechanism. The role of N6-methyladenosine (m6A) in neurodegeneration has attracted much attention in recent years, and the modification of fat mass and obesity-associated protein (FTO), a m6A demethylase, may regulate the expression of p16 gene (p16^INK4a), thus aggravating neuronal aging. It is speculated that this mechanism may be a key pathway of aluminum-induced neuronal damage.

Objective To investigate the role of FTO-regulated m6A methylation of the p16 gene in aluminum-induced learning and memory impairment using a mouse model of aluminum exposure.

Methods Morris water maze was used to assess the learning and memory abilities of mice, including escape latency, time spent in target quadrant, and number of platform crossings. Golgi staining was used to analyze density and complexity of dendritic spines in the hippocampal CA1 region, and transmission electron microscopy was used to observe synaptic structures. m6A RNA methylation quantitative kit was used to assess the level of m6A modification, Western blot was used to detect the expression of FTO protein in the hippocampus, and real-time fluorescent quantitative PCR (qPCR) was used to determine the mRNA levels of FTO and p16. Methylated RNA immunoprecipitation (MeRIP)-qPCR was used to detect the m6A methylation level of the p16 gene to verify its correlation with gene expression.

Results The results of the water maze experiment showed that as the dose of aluminum increased, the escape latency of mice was significantly prolonged, and the time spent in target quadrant and number of platform crossings decreased, indicating a significant decline in learning and memory ability (P<0.05). The aluminum exposure resulted in a significant decrease in the density of dendritic spines in the CA1 region of the hippocampal neurons with increasing aluminum dose (F=5.191, P=0.004). Compared with the control group, postsynaptic density (PSD) decreased with increasing dose of aluminum exposure (F=25.29, P<0.05). At the same time, aluminum exposure significantly increased the m6A methylation level in the hippocampus of mice (F=16.264, P=0.001). The mRNA and protein expression levels of FTO significantly decreased with increasing aluminum dose (P<0.05), while the mRNA expression level and m6A methylation level of the p16 gene significantly increased (P<0.05). The MeRIP-qPCR results showed that the m6A modification levels of the p16 gene in the aluminum exposure groups were significantly increased (F=889.041, P<0.05).

Conclusion Aluminum exposure leads to a down-regulation of FTO expression, resulting in an increase in m6A methylation levels in the hippocampus and an abnormal up-regulation of p16 expression, which damages synaptic structure and function and ultimately leads to a decline in learning and memory ability.