Temperature- and time-dependent changes in TLR2-activated microglial NF-κB activity and concentrations of inflammatory and anti-inflammatory factors.
OBJECTIVE
Therapeutic hypothermia protects neurons following injury to the central nervous system (CNS). Microglia express toll-like receptors (TLRs) that play significant roles in pathological processes in sterile CNS injury. We have examined the effects of culture temperature on the TLR2-activated microglial production of cytokines and nitric oxide (NO), which are known to be associated with CNS damage, and the possible involvement of nuclear factor-κB (NF-κB) activation underlying such effects.


METHODS
Rat microglia were cultured with a selective TLR2 agonist, Pam(3)CSK(4), under hypothermic, normothermic, and hyperthermic conditions, and with Pam(3)CSK(4) in the presence of a NF-κB activation inhibitor at 37 °C. Cytokine and NO levels and NF-κB p65 activation were measured.


RESULTS
The production of tumor necrosis factor-alpha (TNF-α), interleukin-10 (IL-10), and NO and the activation of NF-κB p65 were reduced by hypothermia, but augmented by hyperthermia at 3-6, 24-48, 48, and 0.5 h, post-treatment initiation, respectively. Pharmacological inhibition of NF-κB activation impaired the Pam(3)CSK(4)-induced TNF-α, IL-10, and NO production.


CONCLUSIONS
In TLR2-activated microglia, hypothermia reduced, while hyperthermia increased, the early activation of NF-κB and the subsequent NF-κB-mediated production of TNF-α, IL-10, and NO in a time-dependent manner, suggesting that attenuation of these factors via suppression of NF-κB in microglia is one possible neuroprotective mechanism of therapeutic hypothermia. Moreover, temperature-dependent changes in microglial TNF-α production during the early phase and IL-10 and NO production during the late phase indicate that these factors might be useful as clinical markers to monitor hypothermia-related neuronal protection and hyperthermia-related neuronal injury.
Department of Laboratory Sciences, Yamaguchi University Graduate School of Medicine, 1-1-1 Minami-kogushi, Ube, Yamaguchi 755-8505, Japan. giants@yamaguchi-u.ac.jp
Tomohiro
T
Matsui
Moe
M
Tasaki
Takahiro
T
Yoshioka
Yukari
Y
Motoki
Hidehiro
H
Tsuneoka
Junzo
J
Nojima
D000818:Animals; D018929:Cell Culture Techniques; D016753:Interleukin-10 / Q000378:metabolism; D055666:Lipopeptides / Q000494:pharmacology; D017628:Microglia / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013696:Temperature; D051195:Toll-Like Receptor 2 / Q000819:agonists / Q000502:physiology; D051996:Transcription Factor RelA / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D055666:Lipopeptides; C508075:Pam(3)CSK(4) peptide; D051195:Toll-Like Receptor 2; D051996:Transcription Factor RelA; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10; D009569:Nitric Oxide