Objective:To investigate the mechanism of microRNA-4298 (miR-4298) targeting inhibition of peptidylarginine deiminase 4 (PADI4) expression in U251 cells apoptosis induced by histone deacetylase inhibitor trichostatin A (TSA).Methods:The experiment was divided into TSA group (0.2 μmol/L TSA) and contral group. CCK8 method was used to detect the effect of TSA on the proliferation of U251 cells. Flow cytometry was used to detect the apoptosis level of U251 cells after drug action. Reverse transcription PCR and Western blotting experiments were used to determine the changes of PADI4 gene and protein expression after miR-4298 interference. Luciferase assay was used to determine the effects of miR-4298 on targeted binding and luciferase activity in the 3′UTR region of PADI4. U251 cells were transfected with PADI4 to observe the rescue effect of miR-4298 on apoptosis. Each experiment was divided into 3 groups, NC group, miR-4298 mimic group, TSA+ miR-4298 mimic group and NC group, miR-4298 inhibitor group, TSA+ miR-4298 inhibitor group.Results:U251 cells were treated with 0.2 μmol/L TSA for 4 days, the Absorbancy ( A) values of the control group was 1.168±0.148, which was higher than those of the TSA group (0.737±0.007), with statistically significant difference ( t=4.948, P=0.008). Compared with the control group, after treatment with 0.2 μmol/L TSA for 48 h, U251 cells showed obvious apoptosis (27.62%±3.49% vs. 4.99%±0.13%, t=11.190, P<0.001). Compared with those before the drug treatment, the PADI4 gene expression (0.386±0.020 vs. 0.903±0.021) and protein expression (0.276±0.041 vs. 0.777±0.031) after TSA treatment for 48 h both were decreased, with statistically significant differences ( t=30.400, P<0.001; t=16.770, P<0.001). The expression of miR-4298 during the process of TSA-induced U251 cell apoptosis increased (2.573±0.289 vs. 1.003±0.136; t=8.487, P=0.001). There was a negative correlation between the miR-4298 expression and PADI4 expression ( r=-0.877, P=0.002). Luciferase experiment confirmed that miR-4298 has targeted binding and luciferase inhibitory effects on the 3′UTR region of wild-type PADI4. Compared with NC group (0.920±0.026), the relative expression levels of PADI4 gene of miR-4298 mimic group (0.413±0.049) and TSA+ miR-4298 mimic group (0.213±0.035) were decreased, with statistically significant differences (all P<0.001). The PADI4 protein expression level change was consistent with the gene change trend. Compared with NC group (3.78%±0.68%), the apoptosis levels of miR-4298 mimic group (7.96%±1.10%) and TSA+ miR-4298 mimic group (13.74%±1.26%) were increased, with statistically significant differences ( P=0.005; P<0.001). Compared with NC group (0.183±0.025), the PADI4 gene expression of miR-4298 inhibitor group (0.483±0.032) and TSA+ miR-4298 inhibitor group (0.386±0.025) were increased, with statistically significant differences ( P<0.001; P=0.015). The PADI4 protein expression level change was consistent with the gene change trend. Compared with NC group (4.96%±0.59%), the apoptosis levels of miR-4298 inhibitor group (23.83%±2.20%) and TSA+ miR-4298 inhibitor group (9.55%±1.49%) were increased, with statistically significant differences (all P<0.001). In the rescue experiment, the expression level of PADI4 in miR-4298 mimic group was significantly increased ( P<0.001), while the expression level of PADI4 in miR-4298 mimic+ PADI4 group was relatively reversed ( P=0.002). Conclusion:miR-4298 can participate in the process of U251 cell apoptosis by targeting the expression of PADI4 gene, and miR-4298 may be the target of targeted intervention therapy for glioma.

Objective:To investigate the role of miRNA-4298/PADI4/p53 signal axis in mediating 4f-induced apoptosis of leukemia cells.Methods:The cell growth density was observed under inverted microscope and the proliferation of leukemia cells was detected by CCK-8 counting assay. The expression of PADI4 and P53 at mRNA level was detected by qRT-PCR. Cell cycle and apoptosis were measured with flow cytometry. The expression of PADI4, P53, Bcl-2, Bax, caspase-3 and caspase-9 at protein level was detected by Western blot. Differential miRNA and mRNA expression profiles was detected by next generation sequencing. Databases such as TargetScan were used to predict the potential upstream and downstream genes of PADI4. A luciferase reporter assay was used to detect the 3′UTR of PADI4 targeted by miRNA-4298. Cell transfection assay was used to detect the effect siRNA, PADI4 vector, miRNA mimics and miRNA inhibitor in interference and rescue.Results:Nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor 4f could inhibit the proliferation of THP-1, K562 and U937 cells, and induce the apoptosis of these leukemia cells. It downregulated the expression of PADI4 mainly through the binding activity of miRNA-4298 to miRNA sponges, which resulted in the proliferation inhibition and apoptosis of leukemia cells. The inhibited proliferation and apoptosis of leukemia cells by 4f were associated with the increase of P53 expression after the decrease of PADI4 expression. The PADI4-dependent upregulation of P53 led to the ratio inversion of downstream Bcl-2/Bax, which activated caspase-3 or caspase-9 to induce the apoptosis of leukemia cells.Conclusions:The apoptosis of leukemia cells induced by Nrf2 inhibitor 4f was mainly associated with the miRNA-4298/PADI4/p53 axis, suggesting that it might be a novel signaling pathway for targeted therapy.