Neuroprotective effect by splenic hypothermia in ischemic stroke

To investigate whether spleen-targeted remote administration of hypothermia (RAH) modulates splenic neutrophil release, attenuates neutrophil-driven cerebral inflammation, and preserves BBB integrity at early reperfusion after stroke.

Adult male Sprague-Dawley rats underwent 2-h middle cerebral artery occlusion followed by 6-, 24- and 48- h of reperfusion. RAH was applied to the splenic region via surface cooling, with 1-min cycles administered at 5-min intervals. Neurological deficits, infarct volume, neutrophil infiltration, cytokine expression, BBB integrity, and apoptosis were assessed using neurobehavioral scoring, TTC staining, Western blotting, rt-PCR, immunofluorescence, ELISA, and TUNEL, respectively.

RAH rapidly reduced splenic temperature from 37⁰ to 28 °C without altering body or brain temperatures. At 6 h reperfusion, splenic neutrophil release was suppressed and brain neutrophil infiltration decreased. RAH reduced early elevations of TNF-α, IL-1β, and IL-6. At 24 h, anti-inflammatory effects persisted and BBB integrity was preserved, restoring tight-junction and matrix proteins and suppressing BBB-damaging mediators. Compared to non-RAH stroked rats, RAH reduced apoptosis, body weight loss (9.1 ± 2.8 vs. 19.7 ± 7.2 g, p < 0.05), infarct volume (33.9 ± 4.1% vs. 53.6 ± 1.9%, p < 0.05), cerebral edema (11.2 ± 0.9% vs. 16.3 ± 1.3%, p < 0.05) and Evans blue extravasation (4.8 ± 0.2 vs. 9.8 ± 0.2 mg/g, p < 0.05), and improved neurological outcomes. RAH attenuated stroke-induced spleen weight loss and contraction, consistent with reduced splenic neutrophil mobilization.

RAH induces neuroprotection after ischemic stroke by suppressing splenic neutrophil activation and mobilization, thus attenuating peripheral-to-central inflammatory trafficking and preserving BBB integrity. These findings highlight spleen-targeted cooling may represent a promising early intervention to ischemic stroke.