Hyperbaric oxygen therapy reduces apoptosis and dendritic/synaptic degeneration via the BDNF/TrkB signaling pathways in SCI rats

Spinal cord injury (SCI) is a serious neurological disease without efficacious drugs. Anti-apoptosis and suppressing dendritic/synaptic degeneration in the anterior horn are essential targets after SCI. Previous studies found that hyperbaric oxygen therapy (HBOT) significantly protected rats after SCI. However, its potential effects and mechanisms remain unknown. The BDNF/TrkB signaling pathways evidently contribute to the SCI recovery. Currently, we mainly investigate the potential effects and mechanism of HBOT on anti-apoptosis and ameliorating impaired dendrites, dendritic spines and synapses after SCI. Establish SCI model and randomly divide rats into 5 groups. After SCI, rats were subjected to HBOT. ANA-12 is the specific inhibitor of BDNF/TrkB signal pathway. Changes in neurological deficit, neuronal morphology, apoptosis, protein expression and dendrite/synapse were examined by Basso-Beattie-Bresnahan (BBB) locomotor rating scale, Hematoxylin-eosin (HE) and Nissl staining, TUNEL staining, RT-PCR, Western blot, immunofluorescence and Golgi-Cox staining. We found HBOT suppressed dendritic/synaptic degeneration and alleviated apoptosis, consistent with the increase of BDNF and TrkB expression and improved neurological recovery. In contrast to the positive effects of HBOT, inhibitor increased degeneration and apoptosis. Moreover, we observed that these HBOT-mediated protective effects were significantly inhibited by inhibitor, consistent with the lower expression of BDNF/TrkB and worse neurobehavioral state. These findings suggest that hyperbaric oxygen therapy ameliorates spinal cord injury-induced neurological impairment by anti-apoptosis and suppressing dendritic/synaptic degeneration via upregulating the BDNF/TrkB signaling pathways.