Effects of hyperbaric oxygen on glucose-regulated protein 78 and c-Jun N-terminal kinase expression after spinal cord injury in rats.

Spinal cord injury (SCI) is not only devastating but also represents a public health burden for society. Endoplasmic reticulum stress (ERS) is implicated in secondary injury following damage to the SC. Hyperbaric oxygen (HBO) treatment can improve the recovery of motor function after SCI, but the effect of HBO on the ERS response is unknown. This study tested the hypothesis that HBO treatment protects against secondary SCI by inhibiting the ERS response via regulation of glucose-regulated protein (GRP) 78 and c-Jun N-terminal kinase (JNK) expression. Rats were randomly assigned to sham, SCI, and SCI + HBO groups and the extent of neuronal damage and neurological recovery were evaluated 1, 3, 7, and 14 days after surgery. GRP78 and JNK expression was evaluated by immunohistochemical, western blot, and real-time reverse transcription-polymerase chain reaction analyses, while caspase-3 activation was evaluated by enzyme-linked immunosorbent assay. SCI resulted in an upregulation in GRP78 and JNK expression compared to sham-operated animals. HBO treatment increased GRP78 level, but decreased that of JNK and suppressed caspase-3 activation as well as neuronal damage relative to the SCI group. In addition, hind limb motor function was improved by HBO treatment. HBO treatment reduces SCI-induced neuronal death and promotes the recovery of neurological function recovery by inhibiting the ERS response via modulation of GRP78 and JNK expression levels.