Toll-like receptor 4/nuclear factor-kappa B signaling detected in brain after early subarachnoid hemorrhage.
BACKGROUND
Inflammation and immunity play a vital role in the pathogenesis of early brain injury after subarachnoid hemorrhage (SAH). Nuclear factor-kappa B (NF-kappaB) regulates many genes essential for inflammation and immunity and is activated by toll-like receptor (TLR). This study aimed to detect the expression of the toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-kappaB) signaling in the rat brain after early SAH.


METHODS
The rats were decapitated and their brains were removed at 0, 2, 4, 6, 12, 24 and 48 hours after a single injection of blood into the prechiasmatic cistern. mRNA expression of TLR4 was measured by Taqman real-time RT-PCR, and protein expression by immunohistochemistry and Western blotting. NF-kappaB activity and concentrations of tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) were measured by enzyme-linked immunosorbent assay (ELISA).


RESULTS
TaqMan real-time RT-PCR and Western blotting identified a biphasic change in TLR4 expression in both mRNA and protein: an initial peak (2 - 6 hours) and a sustained elevation (12 - 48 hours). Immunohistochemical staining showed the inducible expression of TLR4-like immunoreactions predominantly in glial cells and vascular endothelium. A similar biphasic change in the activation of NF-kappaB subunit p65 as well as the production of NF-kappaB-regulated proinflammatory cytokines (TNF-alpha, IL-1beta and IL-6) were detected by ELISA.


CONCLUSIONS
These data suggest that experimental SAH induces significant up-regulation of TLR4 expression and the NF-kappaB signaling in early brain injury. Activation of the TLR4/NF-kappaB signaling may regulate the inflammatory responses after SAH.
Ma
Chun-xiao
CX
Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, China.
Yin
Wei-ning
WN
Cai
Bo-wen
BW
Wu
Jian
J
Wang
Jun-yi
JY
He
Min
M
Sun
Hong
H
Ding
Jun-li
JL
You
Chao
C
D000818:Animals; D001921:Brain / Q000378:metabolism*; D016207:Cytokines / Q000032:analysis; D008297:Male; D016328:NF-kappa B / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology*; D013345:Subarachnoid Hemorrhage / Q000276:immunology* / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000032:analysis / Q000235:genetics / Q000502:physiology*
D016207:Cytokines; D016328:NF-kappa B; D012333:RNA, Messenger; C495347:Tlr4 protein, rat; D051197:Toll-Like Receptor 4