[Effects of brain necroptosis and cytokines expression array on brain injury in rats with cardiac arrest]

To investigate the underlying molecular mechanisms of brain injury in rats after cardiac arrest and cardiopulmonary resuscitation (CPR) by observing necroptosis of brain cells and changes of 90 cytokines in brain tissue.

Sprague-Dawley (SD) rats were divided into Sham group (n = 10) and cardiac arrest group (n = 10) according to random number table method. The model of asphyxia cardiac arrest for 6 minutes followed by CPR model was established. Tracheal intubation in Sham rats were routinely performed without inducing cardiac arrest. Neurological deficit score (NDS) was evaluated, blood samples were collected and rats were sacrificed, then serum S100B level was measured by enzyme linked immunosorbent assay (ELISA) on the third day after CPR. Necroptotic cells in brain were detected by immunofluorescence staining. The levels of 90 cytokines expression in brain were measured by antibody array. The relative ratio of the two groups of protein expression ≥ 1.5 or ≤ 0.5 and P < 0.05 represented the differential expression protein.

There were 8 rats successfully resuscitated and 2 died in cardiac arrest group. There were 8 rats selected in Sham group to match the sample size. Compared with Sham group, the NDS score of cardiac arrest group was significantly lower [63.0 (62.5, 64.3) vs. 80.0 (80.0, 80.0), P < 0.01], and the level of serum S100B was significantly higher (ng/L: 47.96±10.16 vs. 16.56±5.60, P < 0.01). More necroptotic cells in cerebral cortex and hippocampus were found in cardiac arrest group [proportion of cells positive for TdT-mediated nick end labeling (TUNEL) and negative for caspase-3: (15.70±0.32)% vs. (8.00±0.28)% in cortex, (20.80±1.35)% vs. (9.00±4.00)% in hippocampus, both P < 0.05]. The levels of inflammatory cytokines [cytokine-induced neutrophil chemoattractant (CINC-2α/β, CINC-3), interferon-γ (IFN-γ)] and signal protein c-Src kinase (CSK) in brain significantly increased after cardiac arrest as compared to Sham group levels (ratio of cardiac arrest group to Sham group: CINC-2 α/β was 2.503±0.428, P = 0.024; CINC-3 was 2.369±0.142, P = 0.005; IFN-γ was 3.149±1.362, P = 0.044; CSK was 1.887±0.105, P = 0.001). However, the levels of neuroprotective cytokines ciliary neurotrophic factor (CNTF), glial cell-derived neurotrophic factor receptor (GFR α-1, GFR α-2), growth hormone (GH), growth hormone receptor (GHR), granulocyte-macrophage colony-stimulating factor (GM-CSF) and anti-inflammatory protein interleukin-10 (IL-10) significantly decreased after cardiac arrest (ratio of cardiac arrest group to Sham group: CNTF was 0.341±0.137, P = 0.036; GFRα-1 was 0.461±0.164, P = 0.044; GFRα-2 was 0.447±0.017, P = 0.033; GH was 0.450±0.136, P = 0.024; GHR was 0.508±0.128, P = 0.022; GM-CSF was 0.446±0.130, P = 0.035; IL-10 was 0.502±0.211, P = 0.017).

Necroptosis is involved in brain injury after cardiac arrest. The molecular mechanisms of brain injury may be related to inflammatory response, neurogenesis disorder and impaired survival of nerve cells.