Abstract
Apoptosis has been widely reported to be involved in the pathogenesis associated with spinal cord injury (SCI). Recently, autophagy has also been implicated in various neuronal damage models. However, the role of autophagy in SCI is still controversial and its interrelationship with apoptosis remains unclear. Here, we used an in vitro SCI model to observe a time-dependent induction of autophagy and apoptosis. Mechanical injury induced autophagy markers such as LC3 lipidation, LC3II/LC3I conversion, and Beclin-1expression. Injured neurons showed decreased cell viability and increased apoptosis. To elucidate the effect of autophagy on apoptosis, the mechanically-injured neurons were treated with the mTOR inhibitor rapamycin and 3-methyl adenine (3-MA), which are known to regulate autophagy positively and negatively, respectively. Rapamycin-treated neurons showed the highest level of cell viability and lowest level of apoptosis among the injured neurons and those treated with 3-MA showed the reciprocal effect. Notably, rapamycin-treated neurons exhibited slightly reduced Bax expression and significantly increasedBcl-2 expression. Furthermore, by plasmid transfection, we showed that Beclin-1-overexpressing neuronal cells responded to mechanical injury with greater LC3II/LC3I conversion and cell viability, lower levels of apoptosis, higher Bcl-2 expression, and unaltered Bax expression as compared to vector control cells. Beclin-1-knockdown neurons showed almost the opposite effects. Taken together, our results suggest that autophagy may serve as a protection against apoptosis in mechanically-injured spinal cord neurons. Targeting mTOR and/or enhancing Beclin-1 expression might be alternative therapeutic strategies for SCI.
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Abbreviations
- 3-MA:
-
3-Methyl adenine
- Ab:
-
Antibody
- DMEM:
-
Dulbecco’s modified eagle medium
- DMSO:
-
Dimethyl sulfoxide
- FBS:
-
Fetal bovine serum
- H&E:
-
Hematoxylin and eosin
- MDC:
-
Monodansylcadaverine
- MTT:
-
3-[4,5-Dimethylthiazol-2-yl-]-2,5-diphenyltetrazolium bromide
- NSE:
-
Neuron specific enolase
- PI:
-
Propidium iodide
- PI3K:
-
Phosphatidylinositol-3-kinase
- PVDF:
-
Polyvinylidinedifluoride
- SCI:
-
Spinal cord injury
- SD:
-
Standard deviation
- SDS-PAGE:
-
Sodium dodecyl sulfate polyacrylamide gel electrophoresis
- TEM:
-
Transmission electron microscopy
- TNF:
-
Tumor necrosis factor
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Acknowledgments
This work was supported by the National Natural Science Foundation of China (General Program, Grant No. 81371343), the Medical Innovation Project Foundation of Fujian Health Bureau (2012—CXB—020), the Scientific Research Foundation for Youth of Fujian Health Bureau (2011-2-7).
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Wang, ZY., Lin, JH., Muharram, A. et al. Beclin-1-mediated autophagy protects spinal cord neurons against mechanical injury-induced apoptosis. Apoptosis 19, 933–945 (2014). https://doi.org/10.1007/s10495-014-0976-1
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DOI: https://doi.org/10.1007/s10495-014-0976-1