LncRNA FOXD3‐AS1 aggravates myocardial ischemia/reperfusion injury by inactivating the Redd1/AKT/GSK3β/Nrf2 signaling pathway via the miR‐128/TXNIP axis

Abstract Long noncoding RNA forkhead box D3‐antisense RNA 1 (FOXD3‐AS1) is associated with cardiovascular diseases, but its roles in myocardial ischemia/reperfusion (I/R) injury and the related signaling pathway have not been fully reported. We aimed to investigate the roles and mechanism of action of FOXD3‐AS1 in myocardial I/R injury. An in vivo myocardial I/R injury mouse model and an in vitro hypoxia/reoxygenation (H/R) cardiomyocyte model was established. Quantitative reverse transcription‐polymerase chain reaction, western blotting, and immunofluorescent assays were performed to examine the expression levels of FOXD3‐AS1, microRNA (miR)‐128, thioredoxin‐interacting protein/regulation of development and DNA damage response 1/protein kinase B/glycogen synthase kinase 3β/nuclear factor erythroid 2‐related factor 2 (TXNIP/Redd1/AKT/GSK3β/Nrf2) pathway‐related proteins and apoptosis‐related proteins. The interactions between FOXD3‐AS1 and miR‐128 and miR‐128 and TXNIP were analyzed by Spearman's correlation test, predicted by ENCORI, and verified by dual‐luciferase reporter assay. In addition, the levels of cardiac injury markers and oxidative stress markers were evaluated by corresponding kits. Cell Counting Kit‐8 assays and flow cytometry were performed to assess cell viability and apoptosis. Hematoxylin and eosin staining was applied to observe the effect of FOXD3‐AS1 on the morphology of myocardial I/R injured tissues. The results showed that the FOXD3‐AS1 and TXNIP were highly expressed, whereas miR‐128 was expressed at low levels in I/R myocardial tissues and H/R‐induced H9c2 cells. FOXD3‐AS1 directly targeted miR‐128 to reduce its expression. TXNIP was confirmed as a downstream target of miR‐128. Knockdown of FOXD3‐AS1 led to the alleviation of I/R injury in vivo and in vitro. FOXD3‐AS1 enhanced the expression of TXNIP by sponging miR‐128, which inhibited the Redd1/AKT/GSK3β/Nrf2 pathway. Both inhibition of miR‐128 and overexpression of TXNIP reversed the cardioprotective effect of FOXD3‐AS1 small interfering RNA in H/R‐induced H9c2 cells.