The Effects Of VDAC2 In The Mitochondrial Apoptosis Pathway Following High-level Spinal Cord Injury In Rats Cardiomyocytes

Objective To observe the expression of voltage-dependent anion channel 2 in the mitochondrial apoptosis pathway following high-level spinal cord injury in rats cardiomyocytes and preliminary explore it’s role of apoptosis in the myocardium after spinal cord injuryMethods A total of 48 healthy adult male SD rats, weighing 200-250 g,were randomly divided into eight groups(each group n = 6):The sham-operation control group(TC):6h(TC1), 12h(TC2), 24h(TC3) and 48h(TC4), respectively, after the sham surgery; spinal cord injury group(TS): 6h(TS1), 12h(TS2), 24h(TS3) and 48h(TS4) after spinal cord injury respectively. The model of spinal cord injury in rats were established by using a modified Allen’s combat method, only exposed spinal cord without combating in TC group. Cardiac tissue of the same site were harversted in 6h,12 h,24h and 48 h both TC group and TS group. Myocardical injury were assessed with the change of ultrastructure in the myocardium by transmission electron microscopy. Apoptotic rate of myocardial cells was detected by Terminal-deoxynucleoitidyl Transferase Mediated Nick End Labeling(Tunel method). Mitochondrial apoptotic activity was estimated by factors of Bax,Bcl-2 and Bax/Bcl-2 ratio. And the expression quantity of Bax,Bcl-2 and VDAC2 m RNA and protein were respectively determined by RT-PCR and Western Blot.Results ①The result of transmission electron microscopy shows that: the majority of cardiomyocytes at each time point in TC group present that cytomembrane integrity,myofibrils and muscle filaments neat arrangement and clear, mitochondrial structure is normal without swelling and vacuolar degeneration, intercalated disc structure is regular, glycogen granules abundant; the myocardial damage in TC group is significantly less than TS group at the same time point.②The result of TUNEL display that: TS group shows significant apoptosis compared with TC group(p<0.01). ③Western blot and PCR results are the same, it shows that Bax, Bcl-2 and VDAC 2 were expressed in TC group and there are no significant differences each time point between each other. The level of Bax in TS group increased, which is prominent in TS3.Bax m RNA and protein level in TS group increased significantly compared with TC group at the corresponding point(p<0.05);The level of Bcl-2 in TS group decreased after SCI in hour 6,12 and 24,the expression come to recovery after SCI in 48 h, Bcl-2 m RNA and protein level in TS group decreased significantly compared with TC group at the corresponding point(p<0.05);At the same time, The level of Bax/Bcl-2 in TS group increased, and it is significant difference between TC group and TS group at each time point(p<0.05). After SCI 12 h, 24 h, 48 h, expression of VDAC2 in TC group increased, and decreased in TS group,there were significant differences between them(P <0.05). There is no difference in 6h between TC group and TC group and it is barely detected in 48 h after SCI, although it start to rise in 48 h,it still lower than TC group.Conclusion ① It can cause the change of ultrastructure in the myocardium and apoptosis after SCI in rats. ② VDAC2 and Bcl-2 may promote myocardial apoptosis and Bax may inhibit apoptosis in rats after SCI.