β-Elemene Enhances GAP-43 Expression and Neurite Outgrowth by Inhibiting RhoA Kinase Activation in Rats with Spinal Cord Injury

Abstract

RhoA signaling pathway inhibitors such as Y27632 (a ROCK inhibitor) have recently been applied as treatments for spinal cord injury (SCI) because they promote neurite outgrowth and axonal regeneration in neurons. β-Elemene, a compound that is extracted from a natural plant (Curcuma zedoary), influences the expression level of RhoA protein. Whether it can promote neurite outgrowth in motor neurons or enhance locomotor recovery in SCI remains unclear. Here, we initially demonstrated that β-elemene promotes neurite outgrowth of ventral spinal cord 4.1 (VSC4.1) motoneuronal cells and primary cortical neurons. Pull-down assays showed that β-elemene significantly inhibits the activation of RhoA kinase. Western blotting assays suggested β-elemene markedly inhibits the phosphorylation of limk and confilin and significantly increases the expression level of GAP-43. Then, in a rat model of SCI, hematoxylin-eosin and myelin staining showed that β-elemene reduces the area of lesion cavity and spares the white matter. BBB scores showed β-elemene significantly promotes locomotor behavioral recovery. In addition, western blotting assays and immunofluorescence staining demonstrated that the expression level of GAP-43 is upregulated by β-elemene treatment in vivo. Thus, our study provided an encouraging novel strategy for the potential treatment of SCI patients with β-elemene.

Keywords: GAP-43; RhoA; neurite outgrowth; spinal cord injury; β-elemene.