[Effect of PFKFB3 on inflammatory activation of polymorphonuclear myeloid-derived suppressor cell in acute myocardial...

To investigate the correlation between 6-phosphofructo-2-kinase/fructose-2, 6-biphosphatase 3 (PFKFB3) and the inflammatory activation of polymorphonuclear myeloid-derived suppressor cell (PMN-MDSC) in acute myocardial infarction (AMI), and to evaluate the effect of intervention targeting PFKFB3 on the inflammatory activation of PMN-MDSC during AMI.

(1) Clinical trial section: a observational study was conducted. The patients with acute coronary syndrome (ACS) admitted to Zhenjiang Fourth People's Hospital were enrolled, and they were divided into AMI group and non-AMI group according to clinical diagnosis. The peripheral venous blood of the two groups was collected to detect the proportion of PMN-MDSC, and the expression of PFKFB3 gene in mononuclear cells was detected by real-time quantitative polymerase chain reaction (RT-qPCR). (2) Basic experiment section: a total of 30 male C57 mice (aged 6-8 weeks) were divided into normal control group (n = 5), Sham group (n = 5), AMI model group (n = 10) and PFKFB3 inhibitor PKF-15 intervention group (n = 10) according to random number table method. The AMI model of mice was reproduced by left anterior descending coronary artery (LADCA) ligation, and the mice in the Sham group did not attach the artery after thoracotomy. The PKF-15 intervention group was intraperitoneally injected with PKF-15 (20 μg/g) at the same time of LADCA ligation. Normal control mice did not receive any treatment. Peripheral venous blood and myocardial tissue of mice were collected 24 hours after modeling. Both the circulating PMN-MDSC ratio and the infiltration of PMN-MDSC in myocardial tissue were detected. After staining with hematoxylin-eosin (HE), the degree of inflammatory damage in mouse myocardial tissue was observed under light microscopy. PMN-MDSC were isolated from mice with flow cytometry, and the gene expressions of PFKFB3 and inflammatory factors were measured by RT-qPCR.

(1) Clinical trial section: the circulating PMN-MDSC ratio of patients in the AMI group (n = 25) was significantly higher than that in the non-AMI group [n = 20; (8.53±0.96)% vs. (1.13±0.39)%, P < 0.01], and PFKFB3 gene expression in the peripheral blood mononuclear cells was also increased (2^-ΔΔCt: 1.18±0.19 vs. 0.96±0.16, P < 0.01). Pearson correlation analysis showed that circulating PMN-MDSC ratio was positively correlated with PFKFB3 gene expression in mononuclear cells in AMI patients (r = 0.608, P = 0.001). (2) Basic experimental section: the circulating PMN-MDSC ratio and the infiltration of PMN-MDSC in myocardial tissue of AMI mice were significantly higher than those in the normal control group and Sham group. PFK-15 intervention could reduce the ratio of PMN-MDSC in the peripheral blood and myocardial tissue of AMI mice [(26.33±5.27)% vs. (75.12±5.02)% in peripheral blood, (20.87±2.97)% vs. (35.28±4.36)% in myocardial tissue, both P < 0.01]. Under light microscopy, the myocardial cells in the AMI modal group were disordered and a large number of inflammatory cells infiltrated. PFK-15 intervention could maintain a normal arrangement of cardiomyocytes and reduce the infiltration of inflammatory cells. The gene expression levels of PFKFB3 in the peripheral blood and myocardial tissue as well as the inflammatory factors in the myocardial tissue of AMI mice were significantly higher than those in the normal control group and Sham group. PKF-15 intervention could effectively reduce the gene expression levels of PFKFB3 in the peripheral blood and myocardial tissue as well as the inflammatory factors in the myocardial tissue of AMI mice [PFKFB3 mRNA (2^-ΔΔCt): 1.01±0.09 vs. 1.40±0.12 in peripheral blood, 0.95±0.09 vs. 1.47±0.10 in myocardial tissue; myocardial tissue tumor necrosis factor-α (TNF-α) mRNA (2^-ΔΔCt) was 14.55±3.99 vs. 29.66±3.90, interleukin-1β (IL-1β) mRNA (2^-ΔΔCt) was 8.72±1.35 vs. 18.53±2.43, IL-6 mRNA (2^-ΔΔCt) was 11.87±2.97 vs. 19.82±4.32, all P < 0.01].

The activation of PFKFB3 is closely related to the inflammatory activation of PMN-MDSC during AMI. Inhibition of PFKFB3 activity can inhibit the inflammatory activation of PMN-MDSC and reduce myocardial inflammatory injury.