RhoA-inhibiting NSAIDs promote axonal myelination after spinal cord injury

Nonsteroidal anti-inflammatory drugs (NSAIDs) are extensively used to relieve pain and inflammation in humans via cyclooxygenase inhibition. Our recent research suggests that certain NSAIDs including ibuprofen suppress intracellular RhoA signal and improve significant axonal growth and functional recovery following axonal injury in the CNS. Several NSAIDs have been shown to reduce generation of amyloid-beta42 peptide via inactivation of RhoA signal, supporting potent RhoA-repressing function of selected NSAIDs. In this report, we demonstrate that RhoA-inhibiting NSAIDs ibuprofen and indomethacin dramatically reduce cell death of oligodendrocytes in cultures or along the white matter tracts in rats with a spinal cord injury. More importantly, we demonstrate that treatments with the RhoA-inhibiting NSAIDs significantly increase axonal myelination along the white matter tracts following a traumatic contusion spinal cord injury. In contrast, non-RhoA-inhibiting NSAID naproxen does not have such an effect. Thus, our results suggest that RhoA inactivation with certain NSAIDs benefits recovery of injured CNS axons not only by promoting axonal elongation, but by enhancing glial survival and axonal myelination along the disrupted axonal tracts. This study, together with previous reports, supports that RhoA signal is an important therapeutic target for promoting recovery of injured CNS and that RhoA-inhibiting NSAIDs provide great therapeutic potential for CNS axonal injuries in adult mammals.