The TLR9 ligand,CpG-ODN,induces protection against cerebral ischemia/reperfusion injury via activation of PI3K/Akt signaling.

Toll-like receptors (tlrs) have been shown to be involved in cerebral ischemia/reperfusion (i/r) injury. tlr9 is located in intracellular compartments and recognizes cpg-dna. this study examined the effect of cpg-odn on cerebral i/r injury. c57bl/6 mice were treated with cpg-odn by i.p. injection 1 hour before the mice were subjected to cerebral ischemia (60 minutes) followed by reperfusion (24 hours). scrambled-odn served as control-odn. untreated mice,subjected to cerebral i/r,served as i/r control. the effect of inhibitory cpg-odn (icpg-odn) on cerebral i/r injury was also examined. in addition,we examined the therapeutic effect of cpg-odn on cerebral i/r injury by administration of cpg-odn 15 minutes after cerebral ischemia. cpg-odn administration significantly decreased cerebral i/r-induced infarct volume by 69.7% (6.4±1.80% vs 21.0±2.85%,p<0.05),improved neurological scores,and increased survival rate,when compared with the untreated i/r group. therapeutic administration of cpg-odn also significantly reduced infarct volume by 44.7% (12.6±2.03% vs 22.8±2.54%,p<0.05) compared with untreated i/r mice. neither control-odn,nor icpg-odn altered i/r-induced cerebral injury or neurological deficits. nissl staining showed that cpg-odn treatment preserved neuronal morphology in the ischemic hippocampus. immunoblot showed that cpg-odn administration increased bcl-2 levels by 41% and attenuated i/r-increased levels of bax and caspase-3 activity in ischemic brain tissues. importantly,cpg-odn treatment induced akt and gsk-3β phosphorylation in brain tissue and cultured microglial cells. pi3k inhibition with ly294002 abolished cpg-odn-induced protection. cpg-odn significantly reduces cerebral i/r injury via a pi3k/akt-dependent mechanism. our data also indicate that cpg-odn may be useful in the therapy of cerebral i/r injury.