Poly-arginine peptide R18d reduces neuroinflammation and functional deficits following traumatic brain injury in the Long-Evans rat

We have previously demonstrated that the poly-arginine peptide R18 can improve histological and functional outcomes following traumatic brain injury (TBI) in the Sprague–Dawley rat. Since D-enantiomer peptides are often exploited in pharmacology for their increased stability and potency, the present study compared the effects of R18 and its D-enantiomer, R18D, following TBI in the Long-Evans rat. Following a closed-head impact delivered via a weight-drop apparatus, peptide was administered at a dose of 1000 nmol/kg at 30 min after TBI. Treatment with R18D, but not R18 resulted in significant reductions in sensorimotor (p = 0.026) and vestibulomotor (p = 0.049) deficits as measured by the adhesive tape removal and rotarod tests. Furthermore, treatment with R18 and R18D resulted in a significant reduction in brain protein levels of the astrocytic marker, glial fibrillary acidic protein (p = 0.019 and 0.048, respectively). These results further highlight the beneficial effects of poly-arginine peptides in TBI, however additional studies are required to confirm these positive effects.