Hypothermia is considered as a promising neuroprotective treatment for
ischemic stroke but with many limitations. To expand its clinical relevance, this study evaluated the combination of physical (
ice pad) and pharmacological [transient receptor potential vanilloid channel 1 (
TRPV1) receptor agonist,
dihydrocapsaicin (DHC)] approaches for faster cooling and stronger neuroprotection. A total of 144 male Sprague Dawley rats were randomized to 7 groups:
sham (n=16),
stroke only (n=24),
stroke with physical
hypothermia at 31ºC for 3 h after the onset of reperfusion (n=24), high-dose DHC (H-DHC)(1.5 mg/kg, n=24), low-dose DHC (L-DHC)(0.5 mg/kg, n=32) with (n=8) or without (n=24) external body temperature control at ~38 ºC (L-DHC, 38 ºC), and combination
therapy (L-DHC+
ice pad, n=24). Rats were subjected to
middle cerebral artery occlusion (MCAO) for 2 h.
Infarct volume, neurological deficits and apoptotic cell death were determined at 24 h after reperfusion. Expression of pro- and
anti-apoptotic proteins was evaluated by Western blot.
ATP and
reactive oxygen species (ROS) were detected by biochemical assays at 6 and 24 h after reperfusion. Combination
therapy of L-DHC and
ice pad significantly improved every measured outcome compared to monotherapies. Combination
therapy achieved
hypothermia faster by 28.6% than
ice pad, 350% than L-DHC and 200% than H-DHC alone. Combination
therapy reduced (p<0.05) neurological deficits by 63% vs. 26% with L-DHC. No effect was observed when using
ice pad or H-DHC alone. L-DHC and
ice pad combination improved brain oxidative metabolism by reducing (p<0.05) ROS at 6 and 24 h after reperfusion and increasing
ATP levels by 42.9% compared to 25% elevation with L-DHC alone. Finally, combination
therapy decreased apoptotic cell death by 48.5% vs. 24.9% with L-DHC, associated with increased
anti-apoptotic protein and reduced
pro-apoptotic protein levels (p<0.001). Our study has demonstrated that combining physical and pharmacological
hypothermia is a promising therapeutic approach in
ischemic stroke, and warrants further translational investigations.