Abstract 5832: Toll-like Receptor 2 Agonist Pam3sck4 Protects Against Focal Cerebral Ischemia/Reperfusion Injury
We have previously reported that modulation of cellular signaling pathways that mediate innate immune and inflammatory responses attenuated ischemia/reperfusion (I/R)-induced brain injury. We also reported that preconditioning induced by a Toll-like receptor (TLR2) ligand, Pam3sck4 (Pam3), reduced cerebral ischemic injury. We hypothesized that activation of TLR2 will induce a protection against focal cerebral ischemic injury. To test our hypothesis, we treated mice (n=8) with Pam3 (50 μg/25g body weight) one hr before the mice were subjected to focal ischemia (60 min) followed by reperfusion (24 hrs). Pam3 was also given to the mice (n=8) 30 min after ischemia. In addition, Pam3 was administered to TLR2 deficient mice (TLR2−/−, n=6) one hr before cerebral ischemia (60 min) followed by reperfusion (60 min). Untreated group mice (n=8) were subjected to ischemia (60 min)/reperfusion (24 hrs). The brains were harvested and infarct size was determined by triphenyltetrazolium chloride (TTC) staining. Morphology of neurons in brain sections was examined by Nissl staining. The data showed that infarct size in Pam3-pretreated mice was significantly reduced by 55.8% (p<0.01) compared with untreated mice (8.0±1.53% vs.18.1±2.72%) after cerebral I/R. Pam3 posttreatment also significantly reduced infarct size by 55.0%. However, the protective effect of the Pam3 was lost in TLR2−/− mice. Morphologic examination showed that there was less neuronal damage in the hippocampus of Pam3 treated mice compared with untreated cerebral I/R mice. Western blot data showed that Pam3 treatment significantly increased the levels of phospho-Akt/Akt (2.83±0.19 vs. 1.73±0.28) and phospho-GSK3β (1.08±0.08 vs. 0.55±0.07) compared with untreated I/R mice (n=6 in each group) and prevented I/R-increased phospho-IκBβ levels. In addition, Pam3 treatment significantly increased the levels of Bcl2 and attenuated I/R-increased Bax levels in the brain tissues. These data demonstrate that TLR2 is required for the protection against focal cerebral I/R injury. Our data also suggest that activation of the PI3K/Akt signaling pathway and an increased ration of Bcl2/Bax may be the protective mechanism of activation of TLR2 in focal cerebral I/R.