Abstract 30: Inhibited CaMKII Activity Decreases Hippocampal Neuronal Damage in Both Normothermic and Mild Therapeutic Hypothermic CA/CPR Mouse Model
Introduction: Glutamate excitotoxicity is an important mechanism of ischemic neuronal damage, however inhibition of glutamate receptors has proven an unsuccessful strategy. Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a major downstream target of glutamate signaling. The aim of this study is to examine the neuroprotective potential of inhibition of autonomous CaMKII activity using novel peptide inhibitors (tatCN21,19o) and transgenic mice.
Methods: C57BL/6 male wild-type (WT) and T286A mutant mice were subjected to 6 min of cardiac arrest and CPR. Mice were randomized to tatCN21 (1 mg/kg), tatCN19o (0.01,0.1,1 mg/kg) or control (tatSCR; 1 mg/kg), administered 30 min after CPR (iv). Separate experiments were performed to assess mild post-arrest hypothermia (rectal T = 34 ±0.2 °C for 1 hr after CPR). Hippocampal neuronal damage was analyzed 3 days after CA/CPR by H&E staining. Total CaMKII and Thr-286 phosphorylation levels were measured by western blot. Statistical analyses were performed using ANOVA and t tests, with P<0.05 considered significant.
Results: Analysis of histological damage 72 hrs after CA/CPR showed that tatCN21 significantly reduced neuronal injury; 28.9±5.6% (n=11) compared to 55.4±4.0% (n=8, P<0.05) in tatSCR-treated mice. Mild hypothermia decreased damage from 55.4±4.0% (n=8) to 31.9±10.5% (n=6, P<0.05), which could be further reduced by tatCN21, reducing to 7.2±4.0% (n=4, P<0.05). Interestingly, the more potent tatCN19o decreased neuronal damage at all doses tested, reducing damage to 23.6±10.8% (n=7, P<0.05) for 1 mg/kg, 25.8±8.8% (n=8, P<0.05) for 0.1 mg/kg and 10.9±3.7% (n=8, P<0.05) for 0.01 mg/kg. Western blot analysis showed that CA/CPR significantly increases p-T286 CaMKII 3 (4.5±0.31, n=4,) compared to sham controls (0.91±0.14, n=4, P<0.05). Finally, T286A mutant mice had less neuronal damage after CA/CPR (4.0 ± 0.9%, n=8) compared to WT mice (28.9 ± 10.9%, n=8; P<0.05), indicating a role for autonomous CaMKII activity in CA/CPR-induced neuronal injury.
Conclusions: The novel CaMKII inhibitors decrease neuronal damage under both normothermic and hypothermic condition following CA/CPR, indicating that inhibition of autonomous CaMKII activity is a promising new therapeutic approach.
Author Disclosures: G. Deng: None. K.U. Bayer: None. R.J. Traystman: None. P.S. Herson: None.
This research has received full or partial funding support from the American Heart Association, SouthWest - Arkansas, Colorado, New Mexico, Oklahoma, Texas, Wyoming.
- © 2015 by American Heart Association, Inc.