Ghrelin Inhibits Oligodendrocyte Cell Death by Attenuating Microglial Activation

BACKGROUND: Recently, we reported the antiapoptotic effect of ghrelin in spinal cord injury-induced apoptotic cell death of oligodendrocytes. However, how ghrelin inhibits oligodendrocytes apoptosis, is still unknown. Therefore, in the present study, we examined whether ghrelin inhibits microglia activation and thereby inhibits oligodendrocyte apoptosis. METHODS: Using total cell extracts prepared from BV-2 cells activated by lipopolysaccharide (LPS) with or without ghrelin, the levels of p-p38 phosphor-p38 mitogen-activated protein kinase (p-p38MAPK), phospho-c-Jun N-terminal kinase (pJNK), p-c-Jun, and pro-nerve growth factor (proNGF) were examined by Western blot analysis. Reactive oxygen species (ROS) production was investigated by using dichlorodihydrofluorescein diacetate. To examine the effect of ghrelin on oligodendrocyte cell death, oligodendrocytes were cocultured in transwell chambers of 24-well plates with LPS-stimulated BV-2 cells. After 48 hours incubation, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and terminal deoxynucleotidyl transferase 2'-deoxyuridine, 5'-triphosphate nick end labeling staining were assessed. RESULTS: Ghrelin treatment significantly decreased levels of p-p38MAPK, p-JNK, p-c-Jun, and proNGF in LPS-stimulated BV-2 cells. ROS production increased in LPS-stimulated BV-2 cells was also significantly inhibited by ghrelin treatment. In addition, ghrelin significantly inhibited oligodendrocyte cell death when cocultured with LPS-stimulated BV-2 cells. CONCLUSION: Ghrelin inhibits oligodendrocyte cell death by decreasing proNGF and ROS production as well as p38MAPK and JNK activation in activated microglia as an anti-inflammatory hormone.

Ethanol Extract of Bupleurum falcatum Improves Functional Recovery by Inhibiting Matrix Metalloproteinases-2 and -9 Activation and Inflammation after Spinal Cord Injury

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that degrade the extracellular matrix and other extracellular proteins. Upregulation of MMPs activity is known to be required for the inflammatory cell infiltration after spinal cord injury (SCI) and most likely contributes to early blood spinal barrier disruption and inflammation, thereby leading to the impairment of functional recovery. Here, we examined the effect of ethanol extract of Bupleurum falcatum (BF) on functional recovery by inhibiting MMP-2 and -9 activation and inflammation after SCI. Rats received a moderate, weight-drop contusion injury to spinal cord were administered orally with BF at a dose of 100 mg/kg for 14 d and functional recovery was measured by Basso-Beattie-Bresnahan locomotor open field behavioral rating test, inclined plane test and foot print analysis. To examine the neuroprotective effect of BF, TUNEL staining and counting were also performed. In addition, the expression and/or activation of MMP-2, MMP-9 and inflammatory mediators such as TNF-alpha, IL-1beta, COX-2, and iNOS were examined by RT-PCR and gelatin zymography using spinal cord tissue from 1 d after injury. Our data showed that BF significantly inhibited the expression and activation of both MMP-2 and MMP-9 after SCI. The mRNA expressions of TNF-alpha, IL-1beta, COX-2, and iNOS were also significantly attenuated by BF. Furthermore, BF reduced apoptotic cell death at 1 d after injury, thereby significantly reduced lesion volume and improved functional recovery. Taken together, these results suggest that BF can be used as a potential therapeutic agent for treating acute spinal injury.