Abstract WP112: The TLR9 Ligand, CpG-ODN, Induces Protection Against Cerebral Ischemia/reperfusion Injury Via A PI3K/Akt Dependent Mechanism
Background: Toll-like receptors (TLRs) are involved in the pathophysiology of cerebral ischemia/reperfusion injury. TLR9 is an intracellular TLR which is located in the endosome and recognizes CpG-DNA. The role of TLR9 in ischemic stroke has not been investigated. We hypothesized that TLR9 activation would induce protection against cerebral I/R injury.
Methods: To evaluate our hypothesis, we treated C57BL/6 mice with CpG-ODN (10 μg/mouse, n=8), by i.p. injection one hr before the mice were subjected to cerebral ischemia (60 min) followed by reperfusion (24 hrs). Scrambled-ODN served as control-ODN (10 μg/mouse, n=8). Untreated mice, subjected to cerebral I/R, served as I/R control (n=8). We also examined the effect of inhibitory CpG-ODN (iCpG-ODN), a TLR9 antagonist, on cerebral I/R injury (n=8). In addition, the therapeutic effect of CpG-ODN on cerebral I/R injury was investigated by i.v. injection of CpG-OND 15 min after cerebral ischemia.
Results: CpG-ODN administration significantly attenuated cerebral I/R induced infarct volume (↓ 75.8%, p<0.05) improved neurological scores and increased survival rate when compared with the untreated I/R group. Of greater significance, therapeutic administration of CpG-ODN also significantly reduced infarct volume by 52.6% (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 preservation of neuronal morphology in the ischemic hippocampus in CpG-ODN treated mice. Immunoblot showed that CpG-ODN administration increased Bcl-2 levels and attenuated Bax, Fas-L, TNF-α, and caspase-3 activity in ischemic brain tissues. CpG-ODN treatment also significantly increased the levels of p-Akt and p-GSK-3β. PI3K inhibition with LY29004 abolished CpG-ODN-induced protection against cerebral I/R injury.
Conclusion: The data suggest that the TLR9 ligand, CpG-ODN, significantly reduces focal cerebral I/R injury via a PI3K/Akt-dependent mechanism. The data also indicates that therapeutic administration of CpG-ODN during cerebral ischemia is effective in reducing cerebral I/R injury.
- © 2012 by American Heart Association, Inc.