Low-dose lipopolysaccharide protects nerve cells against spinal cord injury via regulating the PI3K-AKT-Nrf2 signaling pathway.

This study explored the molecular mechanism behind the protective effects from low-dose lipopolysaccharide (LPS) on an in-vitro model of spinal cord injury (SCI). For this, PC12 cells were treated with different concentrations of LPS and the cell counting kit-8 assay was used to measure the toxicity of LPS to the cells. Next, we used immunofluorescence to measure nuclear translocation of Nrf2 in PC12 cells. PC12 cells were then treated with IGF-1 (PI3K agonist) and LY294002 (PI3K inhibitor). An in-vitro model of SCI was then established via oxygen-glucose deprivation/reoxygenation. Rates of apoptosis were measured using flow cytometry and the TUNEL assay. Low-dose LPS increased the expression levels of Nrf2, p-PI3K/PI3K, and p-AKT/AKT, and facilitated nuclear translocation of Nrf2. The activation of PI3K-AKT signaling by IGF-1 significantly increased the expression of Nrf2, whereas inhibition of PI3K-AKT signaling significantly decreased the expression of Nrf2. Low-dose LPS reduced the apoptotic ratio of PC12 cells, decreased the expression levels of caspase 3 and caspase 9, and increased the expression levels of HO-1, NQO1, and γ-GCS. Low-dose LPS also reduced the rate of apoptosis and oxidative stress by activating the PI3K-AKT-Nrf2 signaling pathway. Collectively, the results indicate that PI3K-AKT-Nrf2 signaling participates in the protective effects from low-dose LPS in an in-vitro PC12 cell model of SCI.

Effect of mesenchymal stem cells transplantation combining with hyperbaric oxygen therapy on rehabilitation of rat spinal cord injury.

OBJECTIVE: To investigate the effect of BMSCs transplantation plus hyperbaric oxygen (HBO) on repair of rat SCI. METHODS: Seventy five male rats were divided randomly into five groups: sham, vehicle, BMSCs transplantation group, combination group, 15 rats in each group. Every week after the SCI onset, all animals were evaluated for behavior outcome by Basso-Beattle-Bresnahan (BBB) score and inclined plane test. Axon recovery was examined with focal spinal cord tissue by electron microscope at 6 weeks after the SCI onset. HE staining and BrdU staining were performed to examine the BMSCs and lesion post injury. Somatosensory evoked potential (SEP) testing was performed to detect the recovery of neural conduction. RESULTS: Results from the behavior tests from combination group were significant higher than rats which received only transplantation or HBO treatment. Results from histopathology showed favorable recovery from combination group than other treatment groups. The number of BrdU(+) in combination group were measureable more than transplantation group (P < 0.05). The greatest decrease in TNF-α, IL-1ß, IL-6, IFN-α determined by Elisa assay in combination group were evident too. CONCLUSIONS: BMSCs transplantation can promote the functional recovery of rat hind limbs after SCI, and its combination with HBO has a synergistic effect.

The effects of hyperbaric oxygen on macrophage polarization after rat spinal cord injury.

The immunoreactive responses are a two-edged sword after spinal cord injury (SCI). Macrophages are the predominant inflammatory cells responsible for this response. However, the mechanism underlying the effects of HBOT on the immunomodulation following SCI is unclear now. The present study was performed to examine the effects of hyperbaric oxygen therapy (HBOT) on macrophage polarization after the rat compressive injury of the spinal cord. HBOT was associated with significant increases in IL-4 and IL-13 levels, and reductions in TNF-α and IFN-É£ levels. This was associated simultaneously with the levels of alternatively activated macrophages (M2 phenotype: arginase-1- or CD206-positive), and decreased levels of classically activated macrophages (M1 phenotype: iNOS- or CD16/32-positive). These changes were associated with functional recovery in the HBOT-transplanted group, which correlated with preserved axons and increased myelin sparing. Our results suggested that HBOT after SCI modified the inflammatory environment by shifting the macrophage phenotype from M1 to M2, which may further promote the axonal extension and functional recovery.