Aluminum Induces Neurotoxicity through the MicroRNA-98-5p/Insulin-like Growth Factor 2 Axis

Aluminum is a well-known and widely distributed environmental neurotoxin. This study aimed to investigate the effect of miR-98-5p targeting insulin-like growth factor 2 (IGF2) on aluminum neurotoxicity. Thirty-two Sprague–Dawley rats were randomly divided into four groups and administered 0, 10, 20, and 40 μmol/kg maltol aluminum [Al(mal)3], respectively. They were intraperitoneally injected every other day for three months. PC12 cells were divided into four dose groups: 0, 100, 200, and 400 μmol/L Al(mal)3, and four intervention groups: inhibitor NC, Al(mal)3 + inhibitor NC, miR-98-5p inhibitor, and Al(mal)3 + miR-98-5p inhibitor. The Morris water maze was used to test the learning and memory abilities of rats. Hematoxylin and eosin staining was used to observe the arrangement and quantity of neurons in the CA1 area of the rat hippocampus. Cell viability was detected using the Cell Counting Kit-8. Cell apoptosis was detected using flow cytometry and the 5-ethynyl-2′-deoxyuridine assay. Real-time polymerase chain reaction and Western blotting were used to detect the expression levels of miR-98-5p, IGF2 mRNA, IGF2/Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) pathway proteins, and apoptosis-related proteins caspase3 and cleaved caspase3. The dual-luciferase assay was used to determine the targeting relationship between miR-98-5p and IGF2 mRNA. As the dose of aluminum exposure increased, the escape latency of rats gradually prolonged, and the target quadrant residence time and the number of crossing platforms gradually decreased. The arrangement of neurons in the hippocampal CA1 area was significantly loose, and their number gradually decreased. The total and early apoptosis rates of PC12 cells gradually increased, and the cell proliferation rate slowed down. Both in vivo and in vitro experimental results showed that with the increase of aluminum exposure dose, the relative expression levels of miR-98-5p and caspase3 and cleaved caspase3 proteins gradually increased, while the relative expression levels of IGF2 mRNA and IGF2, p-JAK2 (Tyr1007/1008), and p-STAT3 (Tyr705) proteins gradually decreased. After inhibiting miR-98-5p in the aluminum exposure group, the cell apoptosis rate and expression of apoptosis-related proteins decreased, and the expression of IGF2 mRNA and IGF2/JAK2/STAT3 proteins increased. These results indicate that miR-98-5p plays a vital role in aluminum-induced neurotoxicity by targeting IGF2.