Temporal profiles of aquaporin 4 expression and astrocyte response in the process of brain damage in fat embolism model in rats.
OBJECTIVE
Fat embolism syndrome is a serious complication observed after trauma, orthopedic surgery, and cardiac surgery. We investigated brain damage in relationship to temporal profiles of water channel aquaporin 4 (AQP4) and astrocyte response to fat embolism in rats.


METHODS
Triolein (2 microl) was injected into the right internal carotid artery in rats. Neurological outcome (score: range, 0-5 = no deficit-dead), brain water content, histopathology, and immunohistochemistry for AQP4 and glial fibrillary acidic protein (GFAP) were evaluated at 2 h (2 h group, n = 12), 24 h (24 h group, n = 12), and 72 h (72 h group, n = 12) after triolein injection. Saline was injected in the control (C) group (n = 12).


RESULTS
Neurological deficit score (median score of 2) and brain water content (mean value, 86.2%) increased significantly at 2 h with no progressive increase over 72 h. Damaged tissues with shrunken and triangular-shaped neurons with vacuole degeneration in cytoplasm and halo formation were distributed mainly, but not exclusively, to the ipsilateral hemisphere and were associated with increase in infiltration of inflammatory cells during the time course. Increases in immunostaining for AQP4 and GFAP were observed in the peri-affected region but not in the core. Reactive astrocytes with hypertrophy and dendrite elongation were detected at 72 h in the peri-affected region.


CONCLUSIONS
The results suggest that brain damage with edema is induced very rapidly after triolein injection in association with increase in AQP4 expression and GFAP in the peri-affected region.
Gohara
Toru
T
Department of Anesthesiology, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-Kogushi, Ube, Yamaguchi, 755-8505, Japan.
Ishida
Kazuyoshi
K
Nakakimura
Kazuhiko
K
Yoshida
Mitsuyoshi
M
Fukuda
Shiro
S
Matsumoto
Mishiya
M
Sakabe
Takefumi
T
D000818:Animals; D051401:Aquaporin 4 / Q000378:metabolism*; D001253:Astrocytes / Q000378:metabolism; D001921:Brain / Q000378:metabolism / Q000473:pathology; D004195:Disease Models, Animal; D004620:Embolism, Fat / Q000150:complications*; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism*; D008297:Male; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D014304:Triolein / Q000008:administration & dosage
C496032:Aqp4 protein, rat; D051401:Aquaporin 4; D005904:Glial Fibrillary Acidic Protein; D014304:Triolein