Changes of autophagy in brain tissue after asphyxial cardiac arrest and cardiopuimonary resuscitation

Abstract

Objective To establish a simple rat model of asphyxia cardiac arrest (CA) by clamping endotracheal tube and observe the changes of autophagy after cardiopuimonary resuscitation (CPR). Methods A total of 30 clean male Sprague Dawley rats, weighing 200-300 g, were randomly divided into sham operation group (n=6) and CA/CPR group (n=24), then the CA/CPR group was subdivided into 4 subgroups: 3 h group, 6 h group, 24 h group and 72 h group after resuscation of spontaneous circulation (ROSC), with 6 rats in each group. Neurological deficit scores (NDS) were evaluated at different time points after ROSC. Morphological changes of rat brain were observed by hematoxylin and eosin (HE) staining. The expression of tubulin light chain 3 (LC3), Beclin-1 and Parkin in the hippocampus was detected by Western blotting. The immunofluorescence was used to observe the expression of LC3. Results Compared with the sham operation group, the NDS scores in the CA/CPR group were significantly reduced at each time point, and the brain tissue damage was significantly aggravated. The ratio of LC3Ⅱ/Ⅰ in the 6, 24 and 72 hsubgroups after ROSC was (0.443±0.058), (0.588±0.073), and (0.286±0.036), respectively. Compared with the sham operation group (0.127±0.386), the differences were statistically significant (P<0.01). The expression levels of Beclin-1 in the 6, 24 and72 hsubgroups after ROSC were (0.531±0.033), (0.640±0.039), and (0.435±0.036), respectively. Compared with the sham operation group (0.216±0.028), the expression levels were significantly higher (P<0.01). The expression levels of Parkin in the 6, 24 and 72 h subgroups after ROSC were (0.621±0.021), (0.706±0.020), and (0.588±0.014), respectively. Compared with the sham operation group (0.329±0.032), the expression levels were significantly higher. The difference was statistically significant (P<0.01). The average absorbance of the immunofluorescence in the CA/CPR group was (8.66±0.99)%, which was significantly higher than that in the sham operation group (3.87±0.62)% (P<0.01), suggesting that the proportion of LC3 particles in the CA/CPR group increased. Conclusion Five min of CA in rats causes significant damage to brain tissue. Autophagy (including mitophagy) was activated at 6 h after ROSC, which was the highest at 24 h, decreased at 72 h but was still activated by autophagy. Key words: Cardiac arrest; Cardiopulmonary resuscitation; Autophagy; Mitophagy; Rat