Background
Aluminum can cause synaptic plasticity damage in the hippocampus, probably due to blocked interneuronal signal transmission. MicroRNA-29a (miR-29a) can target phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression and participate in the generation of neuronal networks, and may be involved in the effect of aluminum on the electrical activity of neuronal networks.
Objective
To study the role and mechanism of miR-29a-targeted PTEN in aluminum-induced neuronal network injury in primary hippocampal neurons of ICR mice treated with maltol aluminum Al(mal)3 in vitro.
Methods
Primary hippocampal neurons of ICR mice born within 24 h were cultured in vitro. The purity of neurons was determined by labeling neuron-specific microtubule-associated protein 2 (MAP2) by immunofluorescence staining on day six of the culture; neurons were treated with different concentrations of Al(mal)3, and divided into a control group, and 10, 20, and 40 μmol·L−1 Al(mal)3 groups, and neuronal cell viability was detected by CCK-8 method. Al(mal)3 at 20 μmol·L−1 was selected for subsequent experiments to establish a neuronal network injury model for intervention. The lentivirus infection method was used to transfect miR-29a into neurons, which were divided into mNG, mNG+20 μmol·L−1 Al(mal)3, miR-29a, and miR-29a+20 μmol·L−1 Al(mal)3 groups, and micro-electrode array (MEA) was used to analyze the firing of neuronal network. The expressions of miR-29a and PTEN mRNA in each group were detected by real-time PCR (RT-PCR), and the expression of PTEN protein in each group was detected by Western blotting.
Results
The purity of primary mouse hippocampal neurons was greater than 90%, and the viability of the neurons was above 80% in all groups. At 48 h of the designed Al(mal)3 treatments, the changes in spike frequency, burst frequency, network burst frequency, and synchrony index of neurons cultivated on MEA plates in the control group were 207.56%±38.70%, 73.19%±46.43%, 75.42%±33.04%, and 117.13%±15.54%, respectively; the Al(mal)3 groups’ neuronal network electrical activity showed a decreasing trend. Compared with the control group, the spike frequency, burst frequency, network burst frequency, and synchrony index of the 20 and 40 μmol·L−1 Al(mal)3 groups significantly decreased (The changes were 171.70%±28.08%, 49.20%±23.23%, 50.20%±18.18%, and 85.45%±20.30%; 150.68%±26.15%, 43.43%±15.54%, 52.05%±26.31%, and 26.80%±8.29%, respectively, P < 0.05). Compared with the control group (1.00), the miR-29a relative expression levels were significantly decreased in the 20 μmol·L −1 Al(mal)3 group (0.74±0.09) and the 40 μmol·L−1 Al(mal)3 group (0.62±0.12) (P < 0.05); the relative expression levels of PTEN mRNA were significantly increased in the 20 μmol·L−1 Al(mal)3 group (1.32±0.12) and the 40 μmol·L−1 Al(mal)3 group (1.48±0.11) (P < 0.05); the PTEN protein relative expression levels (1.29±0.12 and 1.82±0.10, respectively) were also significantly increased ( P < 0.05). By overexpressing miR-29a in mouse primary hippocampal neurons, the spike frequency, burst frequency, and network burst frequency were significantly higher in the miR-29a group compared with the mNG group (The changes were 252.80%±62.03%, 171.65%±56.30%, and 197.75%±27.12%, respectively, P<0.05). The mNG+20 μmol·L−1 Al(mal)3 group showed a significant decrease in all indicators of neuronal network electrical activity (The changes were 123.28%±47.31%, 66.62%±31.53%, 70.60%±12.48%, and 52.86%±20.26%, respectively, P < 0.05). Compared with the mNG+20 μmol·L −1 Al(mal)3 group, the electrical activity indicators of neuronal network were significantly higher in the miR-29a+20 μmol·L−1 Al(mal)3 group (The changes were 161.41%±42.13%, 101.16%±30.63%, 127.02%±29.58%, and 109.73%±15.61%, respectively, P < 0.05). Compared with the mNG group (1.00), the neuronal PTEN mRNA relative expression (0.67±0.11) and the PTEN protein expression (0.75±0.08) were decreased in the miR-29a group (P < 0.05); the PTEN mRNA relative expression (1.32±0.12) and the PTEN protein relative expression (1.46±0.15) in the mNG+20 μmol·L−1 Al(mal)3 group were increased (P < 0.05). Compared with the mNG+20 μmol·L −1 Al(mal)3 group, the PTEN mRNA relative expression (0.93±0.06) and the PTEN protein relative expression (0.92±0.09) were decreased in the miR-29a+20 μmol·L−1 Al(mal)3 group (P < 0.05).
Conclusion
Aluminum significantly inhibits the electrical activity of hippocampal neuronal networks, and miRNA-29a may be involved in the aluminum-induced impairment of hippocampal neuronal network electrical activity by regulating PTEN expression.
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