Neutrophil extracellular traps in ischemia-reperfusion injury-induced myocardial no-reflow: therapeutic potential of DNase-based reperfusion strategy

Emerging evidence suggests a potential role of neutrophil extracellular traps (NETs) in linking sterile inflammation and thrombosis. We hypothesized that NETs would be induced during myocardial ischemia-reperfusion (I/R), and NET-mediated microthrombosis may contribute to myocardial "no-reflow". Male Wistar rats were randomly divided into I/R control, DNase (DNase I, 20 μg/rat), recombinant tissue-type plasminogen activator (rt-PA, 420 μg/rat), DNase + rt-PA, and sham control groups after 45-min myocardial ischemia. In situ NET formation, the anatomic "no re-flow" area, and infarct size were evaluated immediately after 3 h of reperfusion. Long-term left ventricular (LV) functional and histological analyses were performed 45 days after operation. Compared with the I/R controls, the DNase + rt-PA group exhibited reduced NET density 8.38 ± 1.98 vs. 26.86 ± 3.07 (per 200 × field), P < 0.001 and "no-flow" area (15.22 ± 0.06 vs. 34.6 ± 0.05%, P < 0.05) in the ischemic region, as well as reduced infarct size (38.39 ± 0.05 vs. 71.00 ± 0.03%, P < 0.001). Additionally, compared with the I/R controls, DNase + rt-PA treatment significantly ameliorated I/R injury-induced LV remodeling (LV ejection fraction: 64.22 ± 3.37 vs. 33.81 ± 2.98%, P < 0.05; LV maximal slope of the LV systolic pressure increment: 3,785 ± 216 vs. 2,596 ± 299 mmHg/s, P < 0.05). The beneficial effect was not observed in rats treated with DNase I or rt-PA alone. Our study provides evidence for the existence of NETs in I/R-challenged myocardium and confirms the long-term benefit of a novel DNase-based reperfusion strategy (DNase I + rt-PA), which might be a promising option for the treatment of myocardial I/R injury and coronary no-reflow.