Progesterone alters Nogo-A, GFAP and GAP-43 expression in a rat model of traumatic brain injury

Previous studies have demonstrated that progesterone has neuroprotective effects in the central nervous system (CNS) following traumatic brain injury (TBI). Numerous cellular mechanisms have been reported to be important in the neuroprotective effects of progesterone, including the reduction of edema, inflammation and apoptosis, and the inhibition of oxidative stress. However, the effect of progesterone on neuronal protection following TBI remains unclear. The present study aimed to investigate the effects of progesterone on the expression of Nogo-A, an inhibitor of axonal growth, glial fibrillary acidic protein (GFAP), a main component of the glial scar and growth-associated protein-43 (GAP-43), a signaling molecule in neuronal growth in TBI rats. The TBI model was produced by the weight drop method. In total, 75 rats were assigned to three groups: the sham group, TBI group with vehicle treatment and TBI group with progesterone treatment. The protein expression of Nogo-A, GFAP and GAP-43 in the cortex and the hippocampus was examined by immunocytochemistry. TBI rats significantly increased the expression of Nogo-A, GFAP, and GAP-43 at 1, 3, 7 and 14 days post-injury. Progesterone significantly decreased the expression of Nogo-A and GFAP, and upregulated the GAP-43 protein. Our findings suggested that progesterone promotes neuroprotection following TBI by inhibiting the expression of Nogo-A and GFAP, and increasing GAP-43 expression.