To investigate the targeting relationship between LncRNA Plasmacytoma Variant Translocation 1 (PVT1) and miR-145-5p, and its effects on H₂O₂-induced apoptosis and oxidative stress in H9C2 cardiomyocytes.

Serum samples were collected from patients with acute myocardial infarction (AMI) (AMI group) and healthy individuals (control group). RT-qPCR were used to detect the expression levels of PVT1 and miR-145-5p. H9C2 cardiomyocytes were cultured and divided into NC group, H₂O₂ group, H₂O₂+si-NC group, H₂O₂+si-PVT1 group, H₂O₂+si-PVT1+anti-miR-NC group, and H₂O₂+si-PVT1+anti-miR-145-5p group. RT-qPCR was used to detect the expression levels of PVT1 and miR-145-5p in H9C2 of each group. CCK-8 and immunofluorescence were used to detect the proliferation ability of H9C2 cells in each group. Flow cytometry, AO/EB staining, and Caspase-3 activity were used to assess apoptosis of H9C2 cells in each group. The DCFH-DA probe method and reagent kit were used to measure the oxidative stress of H9C2 cells in each group. In addition, dual luciferase activity and RIP assay were used to detect the targeting relationship between PVT1 and miR-145-5p in H9C2 cells. One-way analysis of variance was used for comparisons among multiple groups, and SNK-q test was used for pairwise comparisons between groups. Pearson correlation analysis was used to examine the correlations between variables.

Compared to the control group, the expression level of PVT1 was significantly up regulated (1.80 ± 0.58 vs 1.08 ± 0.34, P < 0.05) in AMI patients, while the expression level of miR-145-5p was significantly downregulated (0.52 ± 0.16 vs 1.02 ± 0.32, P < 0.05), and the expression of PVT1 and miR-145-5p were negatively correlated (r = -0.612, P < 0.05). PVT1 is primarily localized in the cytoplasm. Compared to the NC group, H₂O₂ treatment could significantly up-regulated the expression of PVT1 (2.35 ± 0.49 vs 1.01 ± 0.08, P < 0.05), cell apoptosis rate[ (32.16 ± 5.06) %vs (5.16 ± 0.45) %, P < 0.05], AO/EB apoptosis rate[ (40.24 ± 6.16) %vs (6.49 ± 0.97) %, P < 0.05], Caspase-3 activity [ (70.54 ± 9.16) vs (15.98 ± 1.69) U/mL, P < 0.05]and enhance the oxidative stress levels, including a significant increase in ROS fluorescence intensity (423.87 ± 45.16 vs 98.33 ± 11.36, P < 0.05), LDH activity[ (375.69 ± 30.16) vs (132.56 ± 18.63) U/L, P < 0.05], and MDAcontent [ (16.98 ± 2.36) vs (3.69 ± 0.51) nmol/mL, P < 0.05]. Conversely, H₂O₂ treatment significantly inhibited miR-145-5p expression (0.25 ± 0.04 vs 1.04 ± 0.06, P < 0.05) and cell proliferation capacity, specifically manifested as decreased OD value (0.34 ± 0.06 vs 0.83 ± 0.09, P < 0.05) and Ki67 positive rate [ (21.09 ± 4.03) % vs (68.96 ± 8.65) %, P < 0.05]. Knocking down PVT1 (H₂O₂+si-PVT1 group) reversed the effects induced by H₂O₂ (all P < 0.05). In contrast, inhibiting miR-145-5p (H₂O₂+si-PVT1+anti-miR-145-5p group) partially counteracted the protective effect conferred by PVT1 knockdown, thereby re-aggravating apoptosis and oxidative stress, and suppressing proliferation (all P < 0.05). Dual-luciferase and RIP assays confirmed that PVT1 can directly target and bind to miR-145-5p (P < 0.05) .

PVT1 promotes H₂O₂-induced apoptosis and oxidative stress in H9C2 cardiomyocytes by targeting and negatively regulating miR-145-5p.