Tea polyphenols down-regulate JNK phosphorylation to inhibit neuron apoptosis in rats with cardiac arrest

Abstract

To study the effect of tea polyphenols (TP) on c-Jun N-terminal kinase 1/2 (JNK1/2) phosphorylation and cell apoptosis in brain tissues in rats with cardiac arrest (CA) following cardiopulmonary resuscitation (CPR). Healthy male Sprague-Dawley (SD) rats were randomly divided into sham group (n = 6), CA group (n = 12), and TP group (n = 12). The rats in CA and TP groups were induced ventricular fibrillation (VF) via esophagus stimulation with alternating current. Five minutes after CA, CPR was performed. Once restoration of spontaneous circulation (ROSC) was gained, normal saline (NS) and TP were injected intravenously in CA and TP groups with 10 mg/kg, respectively. Cortex of 6 rats in each group was harvested at 12 hours and 72 hours after ROSC. Cortex of sham group was harvested at 72 hours after operation without VF induction. The expressions of phosphorylated JNK1/2 (p-JNK1/2), JNK1/2, caspase-3, Bax and Bcl-2 were measured by Western Blot. Cell apoptosis was detected by TdT-mediated dUTP nick end labeling (TUNEL), and p-JNK/TUNEL double positive cells were detected by fluorescence double staining. Compared with sham group, the expressions of p-JNK, caspase-3 and Bax were increased, the expression of Bcl-2 was declined, and the apoptotic cells were significantly increased at 72 hours after ROSC in CA group. Compared with CA group, the phosphorylation of JNK was significantly declined at 12 hours and 72 hours after ROSC in TP group (the ratio of p-JNK1/2 and JNK1/2: 3.200±0.060 vs. 5.700±0.210, 1.400±0.060 vs. 5.400±0.090, both P < 0.05), the expressions of caspase-3 and Bax were decreased [caspase-3 (gray value): 42.00±5.23 vs. 54.00±7.84, 38.74±4.60 vs. 58.68±7.19; Bax (gray value): 38.04±6.21 vs. 68.76±6.08, 58.84±7.99 vs. 70.03±7.36, all P < 0.05], the expression of Bcl-2 was increased (gray value: 37.36±3.11 vs. 28.47±7.46, 48.78±6.55 vs. 29.54±3.13, both P < 0.05); the cell apoptosis rate was reduced at 72 hours [(31.14±4.51)% vs. (45.87±3.95)%, P < 0.01], and p-JNK/TUNEL double positive cells/TUNEL cells ratio was significantly decreased (10.00±0.85 vs. 52.70±3.05, P < 0.01). The inhibition of neuron apoptosis caused by TP after CPR in rats with CA is related to the inhibition of JNK1/2 phosphorylation.