Impact of Toll-Like Receptor 2 Deficiency on Survival and Neurological Function after Cardiac Arrest: A Murine Model of Cardiopulmonary Resuscitation

<div><p>Background</p><p>Cardiac arrest (CA) followed by cardiopulmonary resuscitation (CPR) is associated with poor survival rate and neurofunctional outcome. Toll-like receptor 2 (TLR2) plays an important role in conditions of sterile inflammation such as reperfusion injury. Recent data demonstrated beneficial effects of the administration of TLR2-blocking antibodies in ischemia/reperfusion injury. In this study we investigated the role of TLR2 for survival and neurofunctional outcome after CA/CPR in mice.</p> <p>Methods</p><p>Female TLR2-deficient (TLR2^-/-) and wild type (WT) mice were subjected to CA for eight min induced by intravenous injection of potassium chloride and CPR by external chest compression. Upon the beginning of CPR, n = 15 WT mice received 5 µg/g T2.5 TLR2 inhibiting antibody intravenously while n = 30 TLR2^-/- and n = 31 WT controls were subjected to injection of normal saline. Survival and neurological outcome were evaluated during a 28-day follow up period. Basic neurological function, balance, coordination and overall motor function as well as spatial learning and memory were investigated, respectively. In a separate set of experiments, six mice per group were analysed for cytokine and corticosterone serum levels eight hours after CA/CPR.</p> <p>Results</p><p>TLR2 deficiency and treatment with a TLR2 blocking antibody were associated with increased survival (77% and 80% vs. 51% of WT control; both <i>P < 0.05</i>). Neurofunctional performance was less compromised in TLR2^-/- and antibody treated mice. Compared to WT and antibody treated mice, TLR2^-/- mice exhibited reduced IL-6 (both <i>P < 0.05</i>) but not IL-1β levels and increased corticosterone plasma concentrations (both <i>P < 0.05</i>).</p> <p>Conclusion</p><p>Deficiency or functional blockade of TLR2 is associated with increased survival and improved neurofunctional outcome in a mouse model of CA/CPR. Thus, TLR2 inhibition could provide a novel therapeutic approach for reducing mortality and morbidity after cardiac arrest and cardiopulmonary resuscitation.</p> </div

Survival after successful resuscitation in an observation period of 28 days.

<p>Survival of mice following eight min of cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) within the 28-day observation period. Black line (1): wildtype (WT) controls (n = 31), gray line (2): TLR2-deficient (TLR2^-/-, n = 30), dotted line (3): antibody (T2.5)-treated WT mice (n = 15). Data was analysed by Kaplan-Meier log-rank survival analysis and pairwise multiple comparison procedures (Holm-Sidak method). *<i>P < 0.05</i> WT vs. TLR2^-/-; #<i>P < 0.05</i> WT vs. WT+T2.5.</p

Graphical analysis of representative results from NeuroScore.

<p>Representative results from evaluation of mice on day 1 (A) and day 3 (B) after CA/CPR employing the NeuroScore. Data are presented as median and interquartile range and was analysed employing ANOVA/Bonferroni. *<i>P < 0.05</i> WT vs. TLR2^-/-; #<i>P < 0.05</i> WT vs. WT+T2.5.</p