The role of Pre-B-cell colony-enhancing factor in neuronal death after ischemia and motor dysfunction

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Pre-B-cell colony-enhancing factor (PBEF) is the rate-limiting enzyme in the salvage pathway of mammalian nicotinamide adenine dinucleotide (NAD+) biosynthesis via converting nicotinamide (NAM) to nicotinamide mononucleotide (NMN). NAD+ is a molecule playing a pivotal role in the cellular metabolisms and energy production. Moreover, increasingly important roles of PBEF-NAD+ cascade have been reported in diverse neurodegenerative diseases including ischemic stroke, axon degeneration and motor neuron disorders. However, currently, the mechanisms downstream of PBEF are not completely understood. In Chapter one, I reviewed the biological functions of PBEF, the pathology of cerebral ischemia, the potential molecular mechanisms of PBEF mediated neuronal protection during ischemic stroke and motor dysfunctions. Then, in Chapter two and Chapter three, I investigated the role and molecular mechanisms by which PBEF-NAD+ cascade exerts brain protection following ischemia in primary cortical neuronal cultures. Using different approaches including confocal imaging, immunocytochemistry, molecular biology and Western blotting, I found that enhancing PBEF mediated NAD+ biosynthesis effectively reduced glutamate excitotoxicity and oxygen glucose deprivation (OGD) induced neuronal death, AIF translation, caspase-3 activation, mitochondrial fragmentation and impairments of mitochondrial function and biogenesis. Finally, in Chapter four, I investigated the effect of neuronal PBEF on the regulation of the motor system using a novel projection neuron-specific and inducible conditional PBEF knockout mice, i.e., Thy1-YFPCreERT2: Pbeff/f mice, in which deletion of PBEF can be achieved by tamoxifen administration. I observed that ablation of PBEF in the projection neuron resulted in muscle atrophy, progressive motor dysfunctions, impairments of synaptic connection at neuromuscular junctions, motor neuron loss and widespread astrogliosis and microgliosis. These results provide novel insights into the development of potential therapeutic strategies for cerebral ischemia and motor disorders based on PBEF-NAD+ cascade.