Remote ischemic perconditioning is effective alone and in combination with intravenous tissue-type plasminogen activator in murine model of embolic stroke

Abstract

Background and purpose: Remote ischemic conditioning is cardioprotective in myocardial infarction and neuroprotective in mechanical occlusion models of stroke. However, there is no report on its therapeutic potential in a physiologically relevant embolic stroke model (embolic middle cerebral artery occlusion) in combination with intravenous tissue-type plasminogen activator (tPA).

Methods: We tested remote ischemic perconditioning therapy (RIPerC) at 2 hours after embolic middle cerebral artery occlusion in the mouse with and without intravenous tPA at 4 hours. We assessed cerebral blood flow up to 6 hours, neurological deficits, injury size, and phosphorylation of Akt (Serine(473)) as a prosurvival signal in the ischemic hemisphere at 48 hours poststroke.

Results: RIPerC therapy alone improved the cerebral blood flow and neurological outcomes. tPA alone at 4 hours did not significantly improve the neurological outcome even after successful thrombolysis. Individual treatments with RIPerC and intravenous tPA reduced the infarct size (25.7% and 23.8%, respectively). Combination therapy of RIPerC and tPA resulted in additive effects in further improving the neurological outcome and reducing the infarct size (50%). All the therapeutic treatments upregulated phosphorylation of Akt in the ischemic hemisphere.

Conclusions: RIPerC is effective alone after embolic middle cerebral artery occlusion and has additive effects in combination with intravenous tPA. RIPerC may be a simple, safe, and inexpensive combination therapy with intravenous tPA.

Figure 1

A. CBF measured with LDF and presented as percent of pre-ischemic value (N=10). Comparisons between the groups were done “within the time point”. B. Representative images of cerebral perfusion detected with LDIS at 5 hours post eMCAO. The CBF values in the panels are as compared to the contralateral sides. C. Neurologic score as evaluated on Bederson scale at 48 hours post eMCAO in Experiment I. eMCAO+Veh (N=7 survived out of 10; 7/10), eMCAO+RIPerC (N=8/10), eMCAO+tPA (N=8/10) and eMCAO+RIPerC+tPA (N=10/10). Data presented as Mean ±SD. Pairs of Means with different letters are significantly different, p < 0.05.

Figure 2

A. Representative TTC stained coronal sections, and B. Means of the corrected infarct volumes calculated as percent of their corresponding contralateral sides. Data are presented as Mean ±SD (N = as above in Figure 1C). Pairs of Means with different letters are significantly different, p < 0.05.

Figure 3

p-Akt (Ser⁴⁷³) level as detected by immunoblot analysis in the ischemic hemispheres at 48 hours post eMCAO in Experiment II. A. Representative immunoblot image, and B. Densitometric analysis of immunoreactive bands normalized to β-actin as loading control. Data are presented as Mean ±SD (N=6). Pairs of Means with different letters are significantly different, p < 0.05.