Hypertonic/hyperoncotic solution attenuate blood-brain barrier breakdown and brain pathology in whole body hyperthermia rats

Abstract

This study was designed to investigate the effects of hypertonic/hyperoncotic solution on blood-brain barrier damage, brain edema and morphological changes of rats during whole body hyperthermia. 90 adult male Sprague-Dawley rats were randomized into 5 groups: Control group (a room temperature for 4 hours); Whole body hyperthermia group without solution treatment; Whole body hyperthermia group with Ringer's solution treatment; Whole body hyperthermia group with hydroxyethyl starch and Ringer's solution treatment; Whole body hyperthermia group with Hypertonic/hyperoncotic solution treatment. All rats except those of control group were housed in a heated container and maintained at 36°C for 3 hours until the rectal temperature reached 41-42°C. Corresponding solutions were administered intravenously at the beginning of whole body hyperthermia within 30 minutes as designed. Following whole body hyperthermia, rats were subsequently cooled down for 1h. Evans blue was administered intravenously when the rectal temperature was cooled down to 37°C. The leakage of Evans blue-albumin and water content of brain were calculated and morphological changes were investigated. In group with hypertonic/hyperoncotic solution treatment, brain water content and the leakage of Evans blue-albumin were the lowest among the four whole body hyperthermia groups. Compared with the other three whole body hyperthermia groups, in which profound to moderate damages to blood-brain barrier and brain tissue and cells were found, there were only slight morphological changes in the group with hypertonic/hyperoncotic solutionon treatment. Treatment with hypertonic/hyperoncotic solution appeared to attenuate the injury to blood-brain barrier and reduce brain edema and cell morphological changes in whole body hyperthermia rats.

Keywords: Whole body hyperthermia; blood-brain barrier; brain edema; brain morphological changes; hypertonic/hyperoncotic solution.

Figure 1

Rectal temperature changes of rats in five groups (n=12).

Figure 2

MAP changes of rats in five groups (n=12). *P<0.05 vs the control group; #P<0.05 vs T0.

Figure 3

Moderate to profound hippocampus tissue and cell damages were found under microscopy in WBH groups except HHS group. A showed the normal hippocampus tissue and cells under high power microscopy. Under low power (B), the light micrographs of HT group showed considerable tissue damage mostly vacuolation (marked by #). Under high power (C), the light micrographs from HT group indicated cellular edema and sponginess (@), perivascular edema ($), and darkly stained neurons (*). Compared with HT group, there were less extensive perivascular edema and vacuolation in RS group (D, E). In HRS group, vacuolation, edema and sponginess were still obvious and neurons were not arranged in order (F, G). While in HHS group, no significant tissue structural changes were found under low power micrograph and only trivial edema and sponginess as well as slightly widen perivascular gap and continuous neurons were visible under high power microscopy (H, I).

Figure 4

Ultrastructural studies further confirmed BBB and neuron damages of hippocampus in WBH groups. In HT group, there were large quantities of swollen astrocytic foot processes and perivascular edema was serious (A). While in HHS group, the structure of tight junction between endothelial cells was normal and there were much fewer swollen astrocytic foot processes and slighter perivascular edema than that in HT group (B). Swollen neurons with vacuolated cytoplasm, ruptured cloudy mitochondrion carinas and without rough endoplasmic reticulum were seen in RS group (C). But these pathologic changes were not so apparent in HHS group and clear neuron nucleoli, plenty organellae such as rough endoplasmic reticulum could be seen under electron microscopy (D). Damages to glial cells such as swollen nucleoli and vacuolated cytoplasm were found in HRS group, while not in HHS group (E), in which there were many rough endoplasmic reticulum, Golgi apparatus and mitochondria (F).Normal neuron in control group (G). Bars: A=2um; B=2um; C=2um; D=2um; E=2um; F=1um; G=2um.