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.

This study examined the effect of ischemia-reperfusion injury on the expression of Pim-3 gene in myocardial tissues and their underlying mechanism. Rat models of myocardial ischemia-reperfusion injury were established by ligating the left anterior descending coronary artery of the rats. A total of 30 SD male adult rats were randomly divided into 5 groups: group A (sham operation, n=6); group B (in which the rats were subjected to 15 min of ischemia by ligation of the left anterior descending coronary artery, n=6); group C (in which the rats received 30 min of ischemia, n=6), group D and group E (in which the left anterior descending coronary artery of the rats were ligated for 30 min and then reperfused for 30 min or 120 min, n=6 in each). The left ventricular tissues were removed immediately after the ischemia-reperfusion injury. Neonatal cardiomyocytes were cultured and treated with different concentrations of H(2)O(2) (0, 5, 10, 20 μmol/L) or tumor necrosis factor-α (TNF-α, 0, 1, 5, 10 ng/mL). The mRNA and protein expression of Pim-3 gene was determined by using RT-PCR, western blotting and immunohistochemistry. Additionally, neonatal cardiomyocytes were transfected with Pim-3 siRNA, and induced to develop apoptosis by using H(2)O(2). The results showed that normal myocardial tissues expressed a quantity of Pim-3 gene mRNA and protein. Ischemia-reperfusion injury could up-regulate the mRNA and protein expression of Pim-3 gene in myocardial tissues. Furthermore, H(2)O(2) but not TNF-α up-regulated the Pim-3 gene expression in cultured cardiomyocytes. And Pim-3 silencing failed to strengthen the H(2)O(2)-inducing apoptosis in cardiomyocytes. It was concluded that ischemia-reperfusion injury up-regulated the Pim-3 gene expression through oxidative stress signaling pathway in myocardial tissues.