Mild Hypothermia Inhibits Inflammation After Experimental Stroke and Brain Inflammation

Abstract

Background and Purpose— We previously showed that mild hypothermia protects against experimental stroke, even when cooling was delayed by 2 hours. Protection may be due in part to inhibiting inflammation. To clarify, we examined leukocyte infiltration, microglial activation, and adhesion molecule expression in models of stroke and pure brain inflammation. Methods— Rats underwent 2-hour middle cerebral artery occlusion (MCAO; n=36) or intravenous injection with 5 mg/kg lipopolysaccharide (LPS; n=22). Temperature was lowered to 33°C for 2 hours or kept at 37°C. In MCAO, cooling was applied intraischemically or on reperfusion (delayed). In the LPS model, cooling began after injection. One and 3 days later, brains were assessed for neutrophils, monocytes/microglia, major histocompatibility complex class II antigen, and intercellular adhesion molecule-1 (ICAM-1). Results— One day after MCAO, both intraischemic and delayed hypothermia decreased ICAM-1 (51% and 60%, respectively, versus normothermia; P<0.001), m...