Nix Plays a Neuroprotective Role in Early Brain Injury After Experimental Subarachnoid Hemorrhage in Rats.

Zhong Wang,Pengjie Pan,Haiying Li,Guiqiang Yuan,Haitao Shen,Juyi Zhang,Gang Chen,Tianyu Liang,Xiang Li

doi:10.3389/fnins.2020.00245

Abstract

Nix is located in the outer membrane of mitochondria, mediates mitochondrial fission and implicated in many neurological diseases. However, the association between Nix and subarachnoid hemorrhage (SAH) has not previously been reported. Therefore, the present study was designed to evaluate the expression of Nix and its role in early brain injury (EBI) after SAH. Adult male Sprague-Dawley (SD) rats were randomly assigned to various time points for investigation after SAH. A rat model of SAH was induced by injecting 0.3 ml of autologous non-heparinized arterial blood into the prechiasmatic cistern. The expression of Nix was investigated by Western blot and immunohistochemistry. Next, Nix-specific overexpression plasmids and small interfering RNAs (siRNAs) were separately administered. Western blot, neurological scoring, Morris water maze, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining and fluoro-jade B (FJB) staining were performed to evaluate the role of Nix in EBI following SAH. We found that Nix was expressed in neurons and its expression level in the SAH groups was higher than that in the Sham group, which peaked at 24 h after SAH. Overexpression of Nix following SAH significantly decreased the expression of translocase of outer mitochondrial membrane 20 (TOMM20, a marker of mitochondria), ameliorated neurological/cognitive deficits induced by SAH, and reduced the total number of apoptotic/neurodegenerative cells, whereas siRNA knockdown of Nix yielded opposite effects. Taken together, our findings demonstrated that the expression of Nix is increased in neurons after experimental SAH in rats, and may play a neuroprotective role in EBI following SAH.

Highlights

Spontaneous subarachnoid hemorrhage (SAH) is a cerebrovascular disease with high disability and mortality rates
early brain injury (EBI) is an important factor leading to the deterioration of SAH patients and refers to a series of pathophysiological processes within 72 h after SAH, including endoplasmic reticulum (ER) stress, organelle injury, cell death, destruction of the bloodbrain barrier (BBB), cerebral vasospasms, edema, and oxidative stress (Dou et al, 2017)
In order to further observe the expression of Nix at the later stages of SAH, we extended our observed time points to 7 days after SAH

Summary

INTRODUCTION

Spontaneous subarachnoid hemorrhage (SAH) is a cerebrovascular disease with high disability and mortality rates. Studies have shown that mitochondrial dysfunction affects a series of intracellular biological processes that are involved in the process of EBI after SAH, including oxidative damage, calcium homeostasis disorder, and the collapse of ATP synthesis (Li et al, 2018). Recent studies have suggested that autophagy is activated after SAH and can ameliorate EBI, the specific mechanism underlying this process remains unknown (Li et al, 2014). As mitochondria are the most important organelles for sources of intracellular energy, mitochondrial dysfunction plays a significant role in EBI after SAH (Wang et al, 2017; Zhou et al, 2017). Discovery of the key factors that regulate the occurrence of mitophagy after SAH may reverse brain injury caused by mitochondrial dysfunction (Chen et al, 2014). Our findings elucidating the role of Nix in EBI after SAH may provide a novel approach of thought for the treatment of SAH patients

MATERIALS AND METHODS

RESULTS

DISCUSSION

ETHICS STATEMENT