Mild hypothermia reduces polymorphonuclear leukocytes infiltration in induced brain inflammation

Abstract

Over the last 50 years deep hypothermia (23(0) C) has demonstrated to be an excellent neuroprotective agent in cerebral ischemic injury. Mild hypothermia (31-33(0) C) has proven to have the same neuroprotective properties without the detrimental effects of deep hypothermia. Mechanisms of injury that are exaggerated by moderate hyperthermia and ameliorated by hypothermia include, reduction of oxygen radical production, with peroxidase damage to lipids, proteins and DNA, microglial activation and ischemic depolarization, decrease in cerebral metabolic demand for oxygen and reduction of glycerin and excitatory amino acid (EAA) release. Studies have demonstrated that inflammation potentiates cerebral ischemic injury and that hypothermia can reduce neutrophil infiltration in ischemic regions. To further elucidate the mechanisms by which mild hypothermia produces neuroprotection in ischemia by attenuating the inflammatory response, we provoked inflammatory reaction, in brains of rats, dropping a substance that provokes a heavy inflammatory reaction. Two groups of ten animals underwent the same surgical procedure: the skull bone was partially removed, the duramater was opened and an inflammatory substance (5% carrageenin) was topically dropped. The scalp was sutured and, for the group that underwent neuroprotection, an ice bag was placed covering the entire skull surface, in order to maintain the brain temperature between 29,5-31(0) C during 120 minutes. After three days the animals were sacrificed and their brains were examined. The group protected by hypothermia demonstrated a remarkable reduction of polymorphonuclear leukocytes (PMNL) infiltration, indicating that mild hypothermia can have neuroprotective effects by reducing the inflammatory reaction.

A hipotermia como estratégia protetora de encefalopatia hipóxico-isquêmica em recém-nascidos com asfixia perinatal

“…Prandini MN. et al 9 A hipotermia local atua como neuroproteção por atenuação da resposta inflamatória. Duarte SG.…”

“…8 A hipotermia tem sido estudada como um método com alto grau de neuroproteção na EHI. 5,9 Assim, o objetivo é verificar a potencialidade terapêutica da hipotermia como tratamento da EHI em recém-nascidos.…”

Brain changes in Hypothermia: Surface-versus Core-cooling in pigs

“…Our results are in contrast to other publications [18,19], where such histopathological changes in the brains of small/newborn piglets following cooling and mild hypothermia were absent. Other investigators have focused on reduced granulocyte in iltration in induced brain in lammation following mild hypothermia [20]. In our next project we will focus on micro vascular perfusion during profound hypothermia and the following in lammatory process in the brain of pigs.…”

Selective hypothermia: an experimental study on traumatic brain injury in rats

“…The effects of hypothermia described in medical literature include its effects on excitatory amino acids, free radicals, decline in vascular permeability, nitric oxide, cerebral blood flow, (due to the decline in the regional oxygen flow and oxygen consumption), decline of the inflammatory reaction and decrease in the genic expression and apoptosis 21,22,[25][26][27][28] .…”

“…These studies demonstrated encouraging results, and so did the studies published by Prandini et al on ischemic brain lesions 21 and Prandini et al on treatment of brain inflammatory lesions 22 . The aforementioned promising results for hypo-Traumatic brain injury: selective hypothermia dvilevicius and Prandini thermia gave rise to this study.…”