The Val66Met BDNF Polymorphism and Peripheral Nerve Injury: Enhanced Regeneration in Mouse Met-Carriers Is Not Further Improved With Activity-Dependent Treatment

New Frontiers in Neurodegeneration and Regeneration Associated with Brain-Derived Neurotrophic Factor and the rs6265 Single Nucleotide Polymorphism

Brain-derived neurotrophic factor is an extensively studied neurotrophin implicated in the pathology of multiple neurodegenerative and psychiatric disorders including, but not limited to, Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, traumatic brain injury, major de-pressive disorder, and schizophrenia. Here we provide a brief summary of current knowledge on the role of BDNF and the common human single nucleotide polymorphism, rs6265, in driving the pathogenesis and rehabilitation in these disorders, as well as the status of BDNF-targeted therapies. A common trend has emerged correlating low BDNF levels, either detected within the central nervous system or peripherally, to disease states, suggesting that BDNF replacement therapies may hold clinical promise. In addition, we introduce evidence for a distinct role of the BDNF pro-peptide as a biologically active ligand and the need for continuing studies on its neurological function outside of that as a molecular chaperone. Finally, we highlight the latest research describing the role of rs6265 expression in mechanisms of neurodegeneration as well as paradoxical advances in the understanding of this genetic variant in neuroregeneration. All of this is discussed in the context of personalized medicine, acknowledging there is no “one size fits all” therapy for neurodegenerative or psychiatric disorders and that continued study of the multiple BDNF isoforms and genetic variants represents an avenue for discovery ripe with therapeutic potential.

Early Intervention of Cold-Water Swimming on Functional Recovery and Spinal Pain Modulation Following Brachial Plexus Avulsion in Rats

Brachial plexus avulsion (BPA) causes peripheral nerve injury complications with motor and sensory dysfunction of the upper limb. Growing evidence has shown an active role played by cold-water swimming (CWS) in alleviating peripheral neuropathic pain and functional recovery. This study examined whether CWS could promote functional recovery and pain modulation through the reduction of neuroinflammation and microglial overactivation in dorsal horn neurons at the early-stage of BPA. After BPA surgery was performed on rats, they were assigned to CWS or sham training for 5 min twice a day for two weeks. Functional behavioral responses were tested before and after BPA surgery, and each week during training. Results after the two-week training program showed significant improvements in BPA-induced motor and sensory loss (p < 0.05), lower inflammatory cell infiltration, and vacuole formation in injured nerves among the BPA-CWS group. Moreover, BPA significantly increased the expression of SP and IBA1 in dorsal horn neurons (p < 0.05), whereas CWS prevented their overexpression in the BPA-CWS group. The present findings evidenced beneficial rehabilitative effects of CWS on functional recovery and pain modulation at early-stage BPA. The beneficial effects are partially related to inflammatory suppression and spinal modulation. The synergistic role of CWS combined with other management approaches merits further investigation.

Early regeneration of axons following peripheral nerve injury is enhanced if p75NTR is eliminated from the surrounding pathway

The common neurotrophin receptor, p75^NTR , has been proposed to be an inhibitor of axon regeneration after peripheral nerve injury, but whether this effect is on the regenerating axons, immune cells migrating into the injury site, or cells in the pathway surrounding the axons is not clear. Cut nerves in mice expressing fluorescent proteins in axons were repaired with grafts from non-fluorescent hosts to study axon elongation when p75^NTR was eliminated separately from axons and immune cells in the proximal stump of cut nerves, from cells in the regeneration pathway, or both. Two weeks later, axons from wild type mice regenerating into grafts devoid of p75^NTR had elongated more than twice as far as axons in grafts from wild type mice. No enhancement of regeneration of axons in p75^NTR knockout mice was observed, whether nerves were repaired with grafts from wild type mice or from p75^NTR knockout mice. To evaluate whether inhibition of p75^NTR could be used to improve regeneration, nerves in wild type mice repaired without grafts were exposed to a specific inhibitor of the p75^NTR receptor, LM11A-31, at the time of nerve repair. This local blockade of p75^NTR resulted in successful regeneration of axons of nearly three times as many motoneurons and reinnervation of twice as many muscle fibers by regenerating motor axons as untreated controls. Expression of p75^NTR surrounding regenerating axons contributes to poor regeneration during the first 2 weeks after peripheral nerve injury. Inhibition of p75^NTR might be a therapeutic target for treatments of peripheral nerve injuries.