ABSTRACT
Objective To investigate the role of B cell lymphoma/leukemia-2 and adenovirus E1B 19 000 interacting protein 3 (BNIP3) in oligodendrocyte cell apoptosis induced by carbon monoxide poisoning (CO poisoning) and the potential signal pathways.Methods Twenty-five male C57BL/6 mice were randomly divided into control group and CO poisoning group.Mice were left to breathe room air (control group) or subjected to 40-minute exposure to 2 500-3 000 ppm CO (CO poisoning group).The mice were sacrificed at 1,3,7 d and 14 d following CO poisoning.We examined the damage of myelin sheath and oligodendrocytes by observing the expression of myelin basic protein (MBP) and oligodendrocyte transcription factor 2 (Olig2) in corpus callosum.Furthermore,we explored the role of BNIP3 and potential signal pathways in the oligodendrocyte cell death following CO poisoning by observing the expression of BNIP3,Bcl-2 associated X protein (Bax) and cysteinyl aspartate specific proteinase 9 (caspase 9).Results Immunohistochemistry showed that the expression of MBP decreased significantly in the corpus callosum from 1 d (0.12±0.02,t=3.357,P＜0.05) to7 d (0.05±0.02,t=9.730,P＜0.01) and increased from 7 d to 14 d (0.13 ± 0.02,t =2.897,P ＜ 0.05) to some degree after CO poisoning compared with the control group (0.16 ± 0.02) and that Olig2 expression increased markedly in 3 d CO poisoning group (72.2 ± 5.45,t =12.211,P ＜ 0.01) compared with the control group (36.6 ± 3.58).The results of MBP and Olig2 in Western blotting revealed that MBP began to decrease from 1 d (0.39 ± 0.02,t =10.391,P＜0.01)to 7 d(0.09 ±0.01,t =34.767,P＜0.01)and increased in 14 d (0.45 ±0.03,t =6.146,P ＜ 0.01) compared with the control group (0.55 ± 0.03),and that O1ig2 increased obviously in 3 d (0.52 ± 0.02,t =16.651,P ＜ 0.01) compared with the control group (0.31 ± 0.02).Western blotting analysis showed that the levels of BNIP3 were increased in 1 d (2.49 ±0.40,t =15.342,P ＜0.01),started to decrease in 3 d (1.90 ± 0.24,t =12.417,P ＜ 0.01) and finally recovered in 14 d (0.24 ± 0.02,t =0.798,P ＞0.05),as compared with the control group(0.25 ±0.03).Moreover,compared with the control group(0.44 ±0.03),Bax was also upregulated in the corpus callosum from 1 d (1.09 ± 0.15,t =9.427,P ＜ 0.01) to 7 d (0.64 ± 0.09,t =4.540,P ＜ 0.05) after CO poisoning.The expression of caspase 9 showed the similar tendency that increased in 1 d (1.10 ± 0.17,t =7.137,P ＜ 0.01),decreased in 3 d (0.79 ± 0.10,t =5.051,P ＜ 0.01)and recovered in 7 d (0.55 ± 0.05,t =0.910,P ＞ 0.05) compared with the control group (0.51 ± 0.08).BNIP3 expression was positively correlated with Bax (r =0.995,P ＜0.01) and caspase 9 (r =0.950,P ＜ 0.01).Conclusion BNIP3 may play an important role in the apoptosis of oligodendrocytes induced by CO poisoning via the pathway of caspase dependent mitochondrial apoptosis.