Peripheral nerve damage and diseases are common health problems that often result in long-term functional deficits. Peripheral axons can regenerate and reinnervate target tissue following nerve injury or disease in young rodent animals. However, human axonal regeneration is very slow and both denervated Schwann cells, which provide a permissive micro-environment for regeneration, and target tissues are at risk for undergoing atrophy and death, precluding functional recover. This situation underscores the critical need for agents that can speed up axonal regeneration to restore function. A prime candidate for enhancing axonal regeneration is inhibition of Beta -Amyloid Cleaving Enzyme (BACE1). Recently, we show that genetic deletion and pharmacological inhibition of BACE1 markedly accelerate axonal regeneration in the injured peripheral nerves of mice. However, it is unclear how inhibition of BACE1 improves nerve regeneration. We postulate that accelerated nerve regeneration is due to blockade of BACE1 cleavage of two different BACE1 substrates. The two proposed substrates are the amyloid precursor protein (APP) in axons and tumor necrosis factor receptor 1 (TNFR1) on macrophages, which infiltrate injured nerves and clear the inhibitory myelin debris. We will systematically explore genetic manipulations of these two substrates in regard to accelerated axonal regeneration and rapid myelin debris removal seen in BACE1 KO mice. Equally importantly, we propose critical evaluations of a new and very attractive therapeutic approach (e.g. pharmacological inhibition of BACE1) to accelerate nerve regeneration in preclinical rodent models. As experimental models, we will employ peripheral nerve injury and chemotherapy-induced peripheral neuropathy in mice. To evaluate BACE1 inhibitors as a therapy for nerve damage and chemotherapy-induced peripheral neuropathy, we plan to take combined approaches of morphological, electrophysiological and behavioral studies. The proposed studies are highly relevant because faster rate of outgrowth associated with BACE1 inhibition could be useful in speeding nerve regeneration in human conditions.

Public Health Relevance

Peripheral neuropathies and nerve injuries are major unmet health problems. Drugs originally developed for Alzheimer's disease, e.g. BACE1 inhibitors, could be a therapy for diseases of the peripheral nerve. These drugs can easily be applied as a therapy for nerve damage and diseases if the proposed studies in preclinical animal models show beneficial effects.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
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Clinical Neuroplasticity and Neurotransmitters Study Section (CNNT)
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Jakeman, Lyn B
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Johns Hopkins University
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