Cofilin-actin rod formation in neuronal processes after brain ischemia

Abstract

Functional impairment after brain ischemia results in part from loss of neuronal spines and dendrites, independent of neuronal death. Cofilin-actin rods are covalently linked aggregates of cofilin-1 and actin that form in neuronal processes (neurites) under conditions of ATP depletion and oxidative stress, and which cause neurite degeneration if not disassembled. ATP depletion and oxidative stress occur with differing severity, duration, and time course in different ischemic conditions. Here we evaluated four mouse models of brain ischemia to define the conditions that drive formation of cofilin-actin rods. Three of the models provide early reperfusion: transient middle cerebral artery occlusion (MCAo), transient bilateral common carotid artery occlusion (CCAo), and cardiac arrest / cardiopulmonary resuscitation (CA/CPR). Early reperfusion restores ATP generating capacity, but also induces oxidative stress. The fourth model, photothrombotic cortical infarction, does not provide reperfusion. Cofilin-actin rods were formed in each of these models, but with differing patterns. Where acute reperfusion occurred, rod formation was maximal within 4 hours after reperfusion. Where infarction occurred, rods continued to form for at least 24 hours after ischemic onset, and extended into the adjacent non-ischemic tissue. Interventions that limit cofilin-actin rod formation may help to preserve integrity of neuronal processes in permanent ischemia.

Cofilin-actin rod formation in experimental stroke is attenuated by therapeutic hypothermia and overexpression of the inducible 70 kD inducible heat shock protein (Hsp70)

“…Sections were permeabilized with 95% methanol and 5% 0.01 M phosphate-buffered saline for 15 minutes at -20˚C. [15]…”

“…Antibody to cofilin-1 was used to identify the formation of cofilin-actin rods, utilizing the fact that the aggregated cofilin-1 in the rods generates a signal far greater than the background cofilin-1 signal. [15] All images were prepared for confocal microscopy under identical illumination and data capture conditions. Investigators photographing and analyzing the immunostains were blinded to the experimental conditions.…”

“…[21,29] The "ischemic core" was defined as the center of the ischemic lesion, well within the boundaries of the infarct. The "ischemic borderzone" was defined as the region immediately adjacent to the ischemic lesion, [15] as visually delineated by NeuN and DAPI staining. These regions of interest (ROI) were defined as shown in Figures 1a and 3a.…”

“…The immuno-positive area was automatically measured with binary images processed by Image J software in the selected ROIs and expressed as percent of the area of ROI area, as reported previously. [15]…”

“…[10][11][12][13][14] A recent article from our group showed cofilin rod formation after both transient and permanent brain ischemia. [15] Rod formation was observed within 4 h after reperfusion, and where infarction occurred, rods persisted for at least 24 h and extended into the peri-infarct tissue. Rods were observed only in neurons, and within cell bodies as well as processes, particularly dendrites.…”