Endoplasmic reticulum stress induces liver cells apoptosis after brain death by suppressing the phosphorylation of protein phosphatase 2A.

Abstract

The present study aimed to investigate whether brain death (BD) induces the activation of endoplasmic reticulum stress (ERS) and protein phosphatase 2A (PP2A), and reveal the possible association with BD-induced liver cell apoptosis. A total of 30 healthy adult male Sprague-Dawley rats were randomized into three groups: Sham-operated group (S), BD group and 4-phenylbutyric acid group (BD + 4-PBA), with 10 rats in each group. All rats were anesthetized. The model of BD was established by inflating a balloon catheter that was placed into the extradural space after anesthesia. 4-PBA was administered via an intraperitoneal injection when the BD model was established. Anesthesia of the S group of rats was maintained for 6 h. Liver tissues were harvested after 6 h of BD. HE staining was used to evaluate the damage of liver. Terminal deoxynucleotidyl transferase-mediated 2′-deoxyuridine 5′-triphosphate nick-end labeling staining was used to observe the apoptosis of liver cells. Activation of ERS and PP2A was examined by western blotting and immunohistochemical staining. We reported that the apoptosis of liver cells after BD was significantly promoted than in the S group. Activation of ERS and PP2A was induced in the BD group when compared with S group. Phosphorylation of PP2A was suppressed in BD group. Application of 4-PBA decreased the activation of ERS and apoptosis rate compared with the BD group. In addition, activation of PP2A in the BD + 4-PBA group was decreased due to the reduction of PP2A phosphorylation compared with the BD group, but the levels were higher than in the S group. (P<0.05). In summary, our results indicated that BD induced ERS, then activated PP2A by suppressing the phosphorylation of PP2A, resulting in the apoptosis of liver cells.