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Mild hypothermia reduces ICAM-1 expression, neutrophil infiltration and microglia/monocyte accumulation following
Abstract:
Mild hypothermia is an established neuroprotectant against cerebral ischemic injury. Studies have shown that inflammation potentiates cerebral ischemic injury, particularly in the setting of reperfusion. To further elucidate the mechanism by which mild hypothermia attenuates the inflammatory response, we assessed endothelial intercellular adhesion molecule-1 (ICAM-1) expression, neutrophil and monocyte infiltration, and microglial activation following 2 h of transient focal cerebral ischemia under normothermic and mildly hypothermic conditions. Ischemia was induced using the intraluminal suture method in Sprague-Dawley rats. Immunohistochemistry was used to detect endothelial ICAM-1, infiltrating neutrophils and monocytes, and microglia at 1, 3, and 7 days post-ischemia. Immunopositive cell and vessel densities were measured in the peri-infarct region. Mild hypothermia was associated with decreased neutrophils at 1 and 3 days post-ischemia, decreased ICAM-1-positive vessels at 1, 3, and 7 days, and decreased monocytes/activated microglia at 3 and 7 days, but not at 1 day. These data demonstrate that mild hypothermia significantly reduces endothelial adhesion molecule expression, acute (neutrophil) and subacute (monocyte) leukocyte infiltration, and microglial activation up to 7 days following insult in a rodent model of transient focal cerebral ischemia.
Insights
Mild hypothermia reduces inflammation after stroke. This neuroprotective effect involves decreased endothelial adhesion molecules and reduced infiltration of neutrophils and monocytes, aiding brain recovery.
Area of Science:
- Neuroscience
- Immunology
- Cerebrovascular Medicine
Background:
- Mild hypothermia is a known neuroprotectant against cerebral ischemic injury.
- Inflammation exacerbates ischemic brain injury, especially during reperfusion.
Purpose of the Study:
- To investigate how mild hypothermia reduces the inflammatory response post-cerebral ischemia.
- To assess the impact of mild hypothermia on endothelial ICAM-1 expression, leukocyte infiltration, and microglial activation.
Main Methods:
- Transient focal cerebral ischemia was induced in rats using the intraluminal suture method.
- Rats were maintained under normothermic or mild hypothermic conditions.
- Immunohistochemistry was employed to quantify endothelial ICAM-1, neutrophils, monocytes, and microglia in the peri-infarct region at 1, 3, and 7 days post-ischemia.
Main Results:
- Mild hypothermia significantly decreased neutrophil infiltration at 1 and 3 days post-ischemia.
- Endothelial ICAM-1 expression and monocyte/activated microglia infiltration were reduced by mild hypothermia at 3 and 7 days.
- A notable reduction in ICAM-1-positive vessels was observed at 1, 3, and 7 days under hypothermic conditions.
Conclusions:
- Mild hypothermia attenuates the inflammatory cascade following transient focal cerebral ischemia in a rodent model.
- The neuroprotective mechanism involves reduced endothelial adhesion molecule expression and suppressed leukocyte infiltration.
- These findings highlight mild hypothermia's potential for mitigating post-stroke inflammation and injury.