Knocking down PFL can improve myocardial ischemia/reperfusion injury in rats by up-regulating heat shock protein-20

To investigate the effect and mechanism of long non-coding ribonucleic acid (lncRNA) PFL on myocardial ischemia/reperfusion (I/R) injury in rats, and to provide a reference for the prevention and treatment of myocardial infarction (MI) in clinic.

According to the random number table, 60 male Sprague-Dawley (SD) rats were randomly divided into 3 groups: Control group (n=20), I/R group (n=20), and I/R + PFL small interfering ribonucleic acid (siRNA) group (n=20). The I/R model was established by ligating the left anterior descending coronary artery (LAD) and then recanalizing it. PFL siRNAs were injected intravenously into the tail vein of rats in I/R + PFL siRNA group to construct a PFL knockout model. Triphenyl tetrazolium chloride (TTC) test was used to detect the infarction area of each group. Echocardiography was adopted to measure the ejection fraction [EF (%)] and fraction shortening [FS (%)] of rats in each group. Hematoxylin and eosin (H&E) staining was applied to detect the morphological changes in myocardial cells in each group. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was conducted to detect the apoptosis levels of myocardial cells and fibroblasts in heart tissues in each group. Meanwhile, the protein expression levels of apoptosis-related genes, Bcl-2-associated X protein (BAX), and Bcl-2, were measured via Western blotting. Also, the expression level of heat shock protein 20 (HSP-20) in the heart of three groups of rats was examined using immunohistochemical staining. Finally, the effects of PFL siRNAs on the expression level of HSP-20 were detected via Western blotting.

PFL siRNAs could significantly improve I/R-induced cardiac insufficiency in rats, thus increasing EF (%) and FS (%) (p<0.05). Besides, PFL siRNAs could remarkably inhibit cardiac infarction caused by I/R injury and reduce the infarction area from (59.54±3.45)% to (24.85±1.30)% (p<0.05). H&E staining results manifested that, compared with those in I/R group, the cardiac myofilament was better in alignment, degradation and necrosis were milder, and cell edema was notably reduced in I/R + PFL siRNA group. Immunohistochemistry and Western blotting results showed that PFL siRNAs could remarkably reverse the decrease in the HSP-20 expression caused by I/R (p<0.05).

We found that PFL knockdown can significantly improve the myocardial injury caused by I/R and improve the cardiac function in rats. The mechanism may be related to the activation of HSP-20 by PFL siRNAs. Therefore, PFL is expected to become a new target for the treatment of MI.