Pharmacological blockers of CCR5 and CXCR4 improve recovery after traumatic brain injury

CCR5 and CXCR4 are structurally related chemokine receptors that belong to the superfamily of G-protein coupled receptors through which the HIV virus enters and infects cells. Both receptors are also related to HIV-associated neurocognitive disorders that include difficulties in concentration and memory, impaired executive functions, psychomotor slowing, depression and irritability, which are also hallmarks of the long-term sequelae of TBI. Moreover, A growing body of evidence attributes negative influences to CCR5 activation on cognition, particularly after stroke and traumatic brain injury (TBI). Here we investigated the effect of their blockage on motor and cognitive functions, on brain tissue loss and preservation and on some of the biochemical pathways involved. We examined the effect of maraviroc, a CCR5 antagonist used in HIV patients as a viral entry inhibitor, and of plerixafor (AMD3100), a CXCR4 antagonist used in cancer patients as an immune-modulator, on mice subjected to closed head injury (CHI). Mice were treated with maraviroc or plerixafor after CHI for the following 4 or 5 days, respectively. Neurobehavior was assessed according to the Neurological Severity Score; cognitive tests were performed by using the Y-maze, Barnes maze and the novel object recognition test; anxiety was evaluated with the open field test. The mice were sacrificed and brain tissues were collected for Western blot, pathological and immunohistochemical analyses. Both drugs enhanced tissue preservation in the cortex, hippocampus, periventricular areas, corpus callosum and striatum, and reduced astrogliosis)GFAP expression). They also increased the levels of synaptic cognition-related signaling molecules such as phosphorylated NR1 and CREB, and the synaptic plasticity protein PSD95. Both treatments also enhanced the expression of CCR5 and CXCR4 on different brain cell types. In summary, the beneficial effects of blocking CCR5 and CXCR4 after CHI suggest that the drugs used in this study, both FDA approved and in clinical use, should be considered for translational research in TBI patients.