Abstract WMP74: Cofilin-Actin Rod Formation in Experimental Stroke is Attenuated by Therapeutic Hypothermia and Overexpression of the Inducible 70-kDa Heat Shock Protein (Hsp70)

Abstract

Background and Purpose: Cofilin-actin rods are covalently linked aggregates of cofilin -1 and actin. Under ischemic conditions, these rods have been observed in neuronal processes, but their significance is unknown. Here, we explored a potential role of these rods in two different models of neuroprotection from experimental stroke—therapeutic hypothermia and the 70-kDa heat shock protein (Hsp70). Methods: Male C57/BL6 mice were subjected to distal middle cerebral artery occlusion (dMCAO), and treated with hypothermia. Cooling (31°C, 2hrs) was begun at the onset of dMCAO. A neuroprotective effect of hypothermia was validated by functional assessments and infarct volume measurement. Cofilin-actin rod formation was assessed by histological analysis at 4 and 24hrs after dMCAO. Its expression was analyzed in three different regions, infarct core (the center of the infarct), penumbra (area salvaged by intervention and a fixed distance from the midline), and ischemic borderzone (border of ischemic lesion). In addition, Hsp70-overexpressing transgenic (Tg) mice and Hsp70-deficient (Ko) mice were also subjected to dMCAO, and cofilin-actin rod expression was assessed in same manner. Results: As shown previously by our lab, both hypothermia and Hsp70 Tg mice had smaller lesion sizes and improved neurological outcomes compared to normothermic and wildtype (Wt) mice. Hsp70 Ko mice had larger lesion sizes and worsened neurological outcomes. Following dMCAO, cofilin-actin rods were increased, but were reduced by hypothermia in the ischemic core (24hrs, p<0.05), penumbra (4 and 24hrs, p<0.05), and ischemic borderzone (4 and 24hrs, p<0.05). Among Hsp70 Tg mice, cofilin-actin rod formation was decreased in the ischemic borderzone (4 and 24hrs, p<0.05), while Hsp70 Ko mice showed increased rod formation in the penumbra (4 and 24hrs, p<0.05). Conclusions: Cofilin-actin rod formation was suppressed under conditions of improved neurological outcome, and increased under circumstances where outcome was worsened. This suggests that cofilin-actin rods may act to participate in or exacerbate ischemic pathology, and warrants further study as a potential therapeutic target.