Ethyl pyruvate has anti-inflammatory and delayed myocardial protective effects after regional ischemia/reperfusion injury

Abstract

Purpose: Ethyl pyruvate has anti-inflammatory properties and protects organs from ischemia/reperfusion (I/R)-induced tissue injury. The aim of this study was to determine whether ethyl pyruvate decreases the inflammatory response after regional I/R injury and whether ethyl pyruvate protects against delayed regional I/R injury in an in vivo rat heart model after a 24 hours reperfusion.

Materials and methods: Rats were randomized to receive lactated Ringer's solution or ethyl pyruvate dissolved in Ringer's solution, which was given by intraperitoneal injection 1 hour prior to ischemia. Rats were subjected to 30 min of ischemia followed by reperfusion of the left coronary artery territory. After a 2 hours reperfusion, nuclear factor κB, myocardial myeloperoxidase activity, and inflammatory cytokine levels were determined. After the 24 hours reperfusion, the hemodynamic function and myocardial infarct size were evaluated.

Results: At 2 hours after I/R injury, ethyl pyruvate attenuated I/R-induced nuclear factor κB translocation and reduced myeloperoxidase activity in myocardium. The plasma circulating levels of inflammatory cytokines decreased significantly in the ethyl pyruvate-treated group. At 24 hours after I/R injury, ethyl pyruvate significantly improved cardiac function and reduced infarct size after regional I/R injury.

Conclusion: Ethyl pyruvate has the ability to inhibit neutrophil activation, inflammatory cytokine release, and nuclear factor κB translocation. Ethyl pyruvate is associated with a delayed myocardial protective effect after regional I/R injury in an in vivo rat heart model.

Fig. 1

Effect of EP on I/R-induced translocation of NF-κB. Representative illustration of NF-NF-κB expression in the cytosolic and nuclear fractions of rat ischemic myocardium by Western blotting. Sham + LR, sham-operated rats in which no tightening of the left coronary artery was performed; sham + EP50, sham-operated rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult; I/R + LR, rats in which 4 mL LR was administered intraperitoneally 1 hour before ischemic insult; I/R + EP50, rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult. NF-NF-κB, nucl-ear factor-NF-κB; NE, nuclear extraction; CE, cytosolic extraction; I/R, ischemia/reperfusion; EP, ethyl pyruvate; LR, lactated Ringer's solution. ^*p < 0.05 vs. sham + LR. ^†p < 0.05 vs. sham + EP50. ^‡p < 0.05 vs. I/R + LR.

Fig. 2

Cardiac production of pro-inflammatory cytokines. Plasma levels of TNF-α and IL-1β at 2 hours post-reperfusion in each group. Values are the mean ± SD (n = 6 in each group). Sham + LR, sham-operated rats in which no tightening of the left coronary artery was performed; sham + EP50, sham-operated rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult; I/R + LR, rats in which 4 mL LR was administered intraperitoneally 1 hour before ischemic insult; I/R + EP50, rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult. TNF-α, tumor necrosis factor-α; IL-1β, interleukin-1β; I/R, ischemia/reperfusion; EP, ethyl pyruvate; LR, lactated Ringer's solution. ^*p < 0.05 vs. sham + LR. ^†p < 0.05 vs. sham + EP50. ^‡p < 0.05 vs. I/R + LR.

Fig. 3

MPO activity was expressed as U/g area at risk (AAR) obtained from the sham + LR, sham + EP50, I/R + LR, and I/R + EP50 groups. Values are the mean ± SD (n = 6 in each group). Sham + LR, sham-operated rats in which no tightening of the left coronary artery was performed; sham + EP50, sham-operated rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult; I/R + LR, rats in which 4 mL LR was administered intraperitoneally 1 hour before ischemic insult; I/R + EP50, rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult. MPO activity, myeloperoxidase activity; I/R, ischemia/reperfusion.; EP, ethyl pyruvate; LR, lactated Ringer's solution. ^*p < 0.05 vs. sham + LR. ^†p < 0.05 vs. sham + EP50. ^‡p < 0.05 vs. I/R + LR.

Fig. 4

Comparison of myocardial infarct size in the I/R + LR, I/R + EP25, and I/R + EP50 groups. Values are means ± SD (n = 15 in each group). I/R + LR, rats in which 4 mL LR was administered intraperitoneally 1 hour before ischemic insult; I/R + EP25, rats in which 25 mg/kg EP was administrated intraperitoneally 1 hour before ischemic insult; I/R + EP50, rats in which 50 mg/kg EP was administered intraperitoneally 1 hour before ischemic insult. I/R, ischemia/reperfusion; LR, lactated Ringer's solution; EP, ethyl pyruvate; AAR, area at risk; LV, left ventricle; IA, infracted area. ^*p < 0.05 compared to the I/R + LR group.