Effect of hypothermia on brain inflammation following traumatic brain injury in rats

Objective To observe the effects of hypothermia therapy in inhibiting the degree of polymorphonuclear infiltration and the expression of intercellular adhesion molecule-1 (ICAM-1) and discuss its effect on brain inflammatory response during the early stage following traumatic brain injury (TBI) in rats. Methods Modified Feeney’s rat free-falling model was used in the study. Sixty-three male Sprague-Dawley (SD) rats were randomly divided into three groups: TBI group, hypothermia therapy group and sham group that were further randomly divided into three subgroups according to different time intervals of survival after TBI. The sustained brain close to traumatic brain tissues was used for analysis of myeloperoxidase (MPO) activity by spectrophotometer, for ICAM-1 immunohistochemical staining and for calculation of the positive blood vessels under the light microscopy at different time intervals of survival. Results The ICAM-1 positive blood vessels were significantly lower in hypothermia therapy group than those in TBI group at the 1st, 3rd and 5th days after TBI (P0.01). The MPO activity was significantly lower in hypothermia therapy group than that in TBI group at days 1, 3 and 5 after TBI (P0.01). Conclusions Hypothermia can significantly decrease leukocytic infiltration and expression of ICAM-1 in the lesioned areas and may be helpful to ameliorate the secondary brain injury induced by brain inflammatory response following TBI.