The human natural killer-1 (HNK-1) glycan mimetic ursolic acid promotes functional recovery after spinal cord injury in mouse.

Human natural killer-1 (HNK-1) cell antigen is a glycan epitope involved in several neural events, such as neuritogenesis, myelination, synaptic plasticity and regeneration of the nervous system after injury. We have recently identified the small organic compound ursolic acid (UA) as a HNK-1 mimetic with the aim to test its therapeutic potential in the central nervous system. UA, a plant-derived pentacyclic triterpenoid, is well known for its multiple biological functions, including neuroprotective, antioxidant and anti-inflammatory activities. In the present study, we evaluated its functions in a mouse model of spinal cord injury (SCI) and explored the molecular mechanisms underlying its positive effects. Oral administration of UA to mice 1 h after SCI and thereafter once daily for 6 weeks enhanced the regaining of motor functions and axonal regrowth, and decreased astrogliosis. UA administration decreased levels of proinflammatory markers, including interleukin-6 and tumor necrosis factor-α, in the injured spinal cord at the acute phase of inflammation and activated the mitogen-activated protein kinase and phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin pathways in the injured spinal cord. Taken together, these results suggest that UA may be a candidate for treatment of nervous system injuries.