Ischemia-induced injury to neuronal processes: role of cofilin-actin rod formation

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Disability caused by ischemic stroke results not only from neuronal death, but also from injury to axons and dendrites of surviving neurons. The mechanisms by which ischemia causes injury to these neuronal processes are not well understood, and have not been well-explored as a therapeutic target. Cofilin-actin rods are 1:1 linear aggregates of cofilin-1 and actin that form in neuronal processes under conditions of ATP depletion or oxidant stress. These rods cause degeneration of the neuronal processes in which they persist. Recent studies demonstrate that cofilin-actin rods form in neurons during and after brain ischemia, and that their formation can be suppressed genetically and pharmacologically. Here we will determine the extent to which suppression of rod formation (or accelerated rod dissolution) can promote neurite survival and improve motor function after stroke. We will use transient and permanent models of stroke in the mouse to evaluate effects of rod suppression on survival of neuronal processes at specified intervals after ischemia. We will evaluate the effects of rod suppression on motor impairment and recovery using a skilled reaching task and other measures of forelimb dexterity. We also aim to better elucidate the role of inflammation and subcellular mechanisms that drive rod formation and link rod formation to subsequent neurite degeneration. We will employ subcellular fluorescent probes and real- time imaging in cell culture preparations to determine why rods form and persist in specific locations of neurons, and do so even after the ischemic stimuli are removed; whether the persistence of cofilin-actin rods represent stable aggregates; and whether rod formation influences bioenergetic failure in the affected neurites.