Ischemia-reperfusion injury up-regulates Pim-3 gene expression in myocardial tissue

PIM3 regulates myocardial ischemia/reperfusion injury via ferroptosis

BACKGROUND

Myocardial ischemia/reperfusion (I/R) injury is closely related with cardiovascular diseases; however, the underlying pathogenic mechanisms remain not fully understood. This study sought to investigate the effect and mechanisms of PIM3 implicated in myocardial I/R injury using a rat model of myocardial I/R injury and a cell model of oxygen-glucose deprivation/reoxygenation (OGD/R) induction.

METHODS

The morphology changes were detected by HE staining while cell viability was accessed by the CCK-8 method. The characteristics of ferroptosis were evaluated by ROS production, MDA content, SOD level, iron content, TfR1, FTH1, and GPX4 expression.

RESULTS

Myocardial I/R operation increased myocardial tissue damage in rats, while OGD/R treatment reduced the viability of H9c2 cells. Both myocardial I/R operation and OGD/R stimulation increased ferroptosis, as demonstrated by elevated ROS, MDA, iron content, decreased SOD level, upregulation of TfR1, and downregulation of FTH1 and GPX4. Additionally, myocardial I/R modeling or OGD/R treatment enhanced the expression of PIM3. Silencing of PIM3 inhibited ferroptosis, which resulted in alleviated myocardial I/R-induced damage and improved H9c2 cell survival.

CONCLUSIONS

Our findings highlight a vital role of PIM3 in myocardial I/R injury, indicating that PIM3-targeting ferroptosis may be a promising target for the development of novel therapies of myocardial I/R injury-associated diseases.

Effect of limb ischemic preconditioning on myocardial apoptosis-related proteins in ischemia-reperfusion injury

The aim of this study was to investigate the effect of limb ischemic preconditioning (LIPC) on myocardial apoptosis in myocardial ischemia-reperfusion injury (MIRI), as well as the regulation of caspase-3 and the B cell lymphoma 2 (Bcl-2) gene in LIPC. A total of 50 rats were divided randomly into 5 groups (n=10). Four rats in each group were drawn out for detection of apoptosis. The sham, MIRI and LIPC groups underwent surgery without additional treatment. In the LY294002 group, LY294002 preconditioning was administered 15 min before reperfusion. In the LY294002+LIPC group, following LIPC, LY294002 was administered 15 min before reperfusion. The relative expression of myocardial Bcl-2 and caspase-3 mRNA and the apoptotic index for each group were determined by reverse transcription-polymerase chain reaction (RT-PCR) and terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL), respectively. The ultrastructure of the cardiac muscle tissues was observed by election microscopy. Compared with the sham group, the expression of caspase-3 mRNA in the MIRI group significantly increased (P<0.05) and the expression of Bcl-2 mRNA clearly decreased. Compared with the MIRI group, LIPC reduced the expression of caspase-3 and increased the expression of Bcl-2 mRNA (P<0.05). There were no significant differences between the LY294002+LIPC group and the MIRI group. Compared with the sham group, the apoptotic index of myocardial cells in the MIRI group significantly increased (P<0.05). Compared with the MIRI group, LIPC significantly decreased the apoptotic index of myocardial cells (P<0.05) and LY294002 increased the apoptotic index of myocardial cells. Compared with the LIPC group, LY294002+LIPC significantly increased the apoptotic index of myocardial cells (P<0.05). There were no significant differences between the LY294002+LIPC and MIRI groups. In conclusion, LIPC increased the expression of Bcl-2 and decreased caspase-3 mRNA and apoptosis in myocardial tissue following MIRI. Therefore, LIPC plays a protective role in myocardial tissue.

PI3K-like kinases restrain Pim gene expression in endothelial cells

Pim kinases contribute to tumor formation and development of lymphoma, which shows enhanced DNA replication, DNA recombination and repair. Endothelial cells^(ECs) express all the three members of Pim kinase gene family. We hypothesized that DNA repair gene would regulate Pim expression in ECs. Human umbilical vein endothelial cells (HUVECs) were isolated and maintained in M199 culture medium. The cellular distribution of Pim-3 in ECs was determined by immunofluorescent staining. The siRNA fragments were synthesized and transfected by using Lipofectamine LTX. The total cellular RNA was extracted from the cells by using Trizol reagent. cDNAs were quantified by semi-quantity PCR. The effects of LY294002 and wortmannin on RNA stability in ECs were also examined. Our data showed that LY294002 and wortmannin, phosphatidylinositol 3-kinase (PI3K) and PI3K-like kinase inhibitors, increased Pim mRNA expression in ECs without altering the mRNA stability. RNA interference (RNAi) targeting DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and ataxia telangiectasia mutated (ATM) increased mRNA expression of Pim-3 and Pim-1, respectively. Silencing of Akt decreased Pim-1 instead of Pm-2 and Pim-3 gene expression in ECs. But etoposide, a nucleoside analogue, which could activate DNA-PKcs and ATM, increased Pim expression in ECs. Our study indicates that the expression of Pim kinases is physiologically related to DNA-PKcs and ATM in ECs.