Characterizing And Manipulating Neuronal Plasma Membrane Mechanoporation In Traumatic Brain Injury

Carolyn Elizabeth Keating, University of Pennsylvania


Traumatic brain injury (TBI) results from a mechanical insult such as a blow to the head that applies extreme forces to the brain. While it is a major cause of death and disability worldwide, there are no effective therapeutics. Lack of clinical effectiveness of potential treatments could be due in part to an underappreciation of the necessity to accurately model biomechanical loading parameters to recapitulate mechanisms of immediate physical damage and ensuing injury processes. To expand our knowledge of acute cell-level physical damage, as well as investigate potential avenues for preventing this aspect of injury, this dissertation focuses on damage to one structure: the neuronal plasma membrane. The plasma membrane can experience small disruptions due to TBI, known as mechanoporation. Here I characterize neuronal mechanoporation in subcortical oculomotor brain regions after single and repetitive injuries using a swine model of head rotational acceleration that replicates the biomechanics seen in the most common human injuries. Repetitive injuries separated by 15 minutes or 3 days, but not single injuries or repetitive injuries separated by 7 days, increased neuronal permeability. Permeabilized neurons lost NeuN antigenicity, despite no overt cell death. In repetitively injured animals, particularly those with injuries separated by 3 days, microglia appeared to rapidly phagocytose permeabilized neurons. Because oculomotor areas control eye movements, which exhibit deficits after TBI in humans, we created a magnetic, wireless, implantable eye tracking system to determine if this damage results in functional changes. Benchtop and cadaver tests suggest that it will be sufficient to detect large saccades in swine. Along with characterizing mechanoporation, I examined whether neuronal permeability could be modulated by varying plasma membrane lipid composition. Diet altered brain fatty acid composition in rats. Unexpectedly, a diet high in saturated fat, as opposed to a diet high in polyunsaturated fatty acids, beneficially modulated acute plasma membrane permeability and resulted in a smaller lesion size at 7 days post-fluid percussion injury. Together, this characterization and manipulation of neuronal plasma membrane mechanoporation increases our understanding of the immediate physical damage that occurs in response to TBI, and has important implications for the development of therapeutics for neuroprotection.