Objective: To investigate the effect of long non-coding ribonucleic acid nuclear paraspeckle assembly transcript 1 (lncRNA NEAT1) on lipopolysaccharide (LPS)-induced myocardial injury in mice and the underlying mechanism. This study aims to provide some references for the prevention and treatment of sepsis-induced myocardial injury.
Materials and methods: According to the random number table, 60 male C57 mice were divided into the Sham group (n=20), LPS group (n=20) and LPS + NEAT1 small interfering ribonucleic acid (siRNA) group (n=20). Sepsis-induced myocardial injury model in mice was established by intraperitoneal injection of LPS (10 mg/kg), and the NEAT1 knockout model was established by tail vein injection of NEAT1 siRNAs. After 12 h, the cardiac function of mice in each group was detected via the two-dimensional ultrasound; ejection fraction [EF (%)] and fraction shortening [FS (%)] were recorded. Hematoxylin and eosin (H&E) staining was conducted to evaluate the pathological changes in the heart tissues in each group. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was used to detect the apoptotic levels of myocardial cells and fibroblasts in each group. In addition, the expression level of the oxidative stress marker 4-hydroxynonena (4-HNE) and the positive proportions of cluster of differentiation 45 (CD45) and CD68 in the mouse heart of three groups were detected via immunohistochemical staining. Moreover, the messenger RNA (mRNA) expression levels of inflammatory indicators [interleukin-1 (IL-1), IL-6, monocyte chemotactic protein 1 (MCP-1) and tumor necrosis factor-alpha (TNF-α)] in mouse serum of the three groups were examined by enzyme-linked immunosorbent assay (ELISA). Finally, the effects of NEAT1 siRNAs on the Toll-like receptor 2 (TLR2)/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway were detected by Western blotting.
Results: ENEAT1 knockdown could significantly improve ischemia/reperfusion (I/R)-induced cardiac insufficiency in rats, and increase EF (%) and FS (%) (p<0.05). Besides, NEAT1 knockdown remarkably inhibited the LPS-induced myocardial injury. Compared with the LPS group, LPS + NEAT 1 siRNA group has more orderly arranged cardiac myofilament, a lower degree of degradation and necrosis, and significantly reduced cell edema. TUNEL staining showed that NEAT1 knockdown markedly reduced LPS-induced apoptosis of cardiac cells (p<0.05). Immunohistochemical results revealed that NEAT1 knockdown could remarkably reverse LPS-induced elevation of the myocardial 4-HNE expression and decrease the oxidative stress in the heart (p<0.05). At the same time, CD45+ and CD68+ cells were reduced after NEAT1 knockdown in myocardial tissues (p<0.05). Reverse Transcription-Polymerase Chain Reaction (RT-PCR) showed that the mRNA levels of inflammatory indicators in LPS + NEAT1 siRNA group were lower than that in the LPS group (p<0.05). According to Western blotting results, NEAT1 siRNAs could significantly downregulate the protein expressions of TLR2 and p-p65.
Conclusions: NEAT1 knockdown can improve LPS-induced myocardial injury in mice by inhibiting the TLR2/NF-κB signaling pathway. LncRNA NEAT1 is expected to be a potential target for clinical treatment of the sepsis-induced myocardial injury.