Objective: To study the protective effect of erythropoietin (EPO) on brain tissue with cardiac arrest-cardiopulmonary resuscitation (CA-CPR) and its mechanism.
Methods: 120 male Sprague-Dawley (SD) rats were randomly divided into three groups (each n = 40), namely: sham group, routine chest compression group, and conventional chest compression + EPO group (EPO group). The rats in each group were subdivided into CA and 6, 12, 24, 48 hours after restoration of spontaneous circulation (ROSC) five subgroups (each n = 8). The model of CA was reproduced according to the Hendrickx classical asphyxia method followed by routine chest compression, and the rats in sham group only underwent anesthesia, tracheostomy intubation and venous-puncture without asphyxia and CPR. The rats in EPO group were given the routine chest compression + EPO 5 kU/kg (2 mL/kg) after CA. Blood sample was collected at different time points of intervention for the determination the content of serum S100 β protein by enzyme linked immunosorbent assay (ELISA). All the rats were sacrificed at the corresponding time points, and the hippocampus was harvested for the calculation of the number of S100 β protein positive cells, and to examine the pathological changes and their scores at 24 hours after ROSC by light microscopy.
Results: With prolongation of ROSC time, the serum levels of S100 β protein (µg/L) in the routine chose compression group and the EPO group were significantly elevated, peaking at 24 hours (compared with CA: 305.7 ± 29.2 vs. 44.4 ± 6.2 in routine chest compression group, and 276.7 ± 28.9 vs. 44.7 ± 5.6 in the EPO group, both P < 0.05), followed by a fall. The levels of S100 β protein at each time point after ROSC in EPO group were significanthy lower than those of the routine chest compression group (83.2 ± 7.5 vs. 114.3 ± 15.3 at 6 hours, 123.9 ± 20.2 vs. 184.9 ± 22.2 at 12 hours, 276.7 ± 28.9 vs. 305.7 ± 29.2 at 24 hours, 256.3 ± 26.6 vs. 283.2 ± 23.6 at 48 hours, all P < 0.05). With the prolongation of ROSC time, the S100 β protein positive cell number in brain (cells/HP) in the routine chest compression group and the EPO group was significantly increased, peaking at 24 hours (compared with CA: 14.3 ± 2.2 vs. 6.7 ± 0.7 in the routine chest compression group, 11.3 ± 1.3 vs. 6.8 ± 0.9 in the EPO group, both P < 0.05), then it began to fall. The S100 β protein positive cell number in brain at each time point after ROSC in the EPO group was significantly lower than that of the routine chest compression group (7.0 ± 0.9 vs. 7.9 ± 1.9 at 6 hours, 8.4 ± 1.1 vs. 10.2 ± 2.2 at 12 hours, 11.3 ± 1.3 vs. 14.3 ± 2.2 at 24 hours, 8.3 ± 0.8 vs. 10.8 ± 2.0 at 48 hours, all P < 0.05). Under the light microscope, a serious brain cortex injury was found after reproduction of the model, and the degree of injury was reduced after EPO intervention. The pathological score at 24 hours after ROSC in EPO group was lower than that of routine chest compression group (3.83 ± 0.73 vs. 4.17 ± 0.75, P < 0.05).
Conclusions: The S100 β protein level in serum and brain tissue was increased early in asphyxia CA-CPR rats. EPO intervention can reduce the expression of S100 protein and reduce the degree of brain injury.