Rac1/Wave2/Arp3 Pathway Mediates Rat Blood-Brain Barrier Dysfunction under Simulated Microgravity Based on Proteomics Strategy.

Ranran Yan,Huayan Liu,Fang Lv,Yujuan Li,Yulin Deng

doi:10.3390/ijms22105165

Abstract

The blood-brain barrier (BBB) is critical to maintaining central nervous system (CNS) homeostasis. However, the effects of microgravity (MG) on the BBB remain unclear. This study aimed to investigate the influence of simulated MG (SMG) on the BBB and explore its potential mechanism using a proteomic approach. Rats were tail-suspended to simulate MG for 21 days. SMG could disrupt the BBB, including increased oxidative stress levels, proinflammatory cytokine levels, and permeability, damaged BBB ultrastructure, and downregulated tight junctions (TJs) and adherens junctions (AJs) protein expression in the rat brain. A total of 554 differentially expressed proteins (DEPs) induced by SMG were determined based on the label-free quantitative proteomic strategy. The bioinformatics analysis suggested that DEPs were mainly enriched in regulating the cell–cell junction and cell–extracellular matrix biological pathways. The inhibited Ras-related C3 botulinum toxin substrate 1 (Rac1)/Wiskott–Aldrich syndrome protein family verprolin-homologous protein 2 (Wave2)/actin-related protein 3 (Arp3) pathway and the decreased ratio of filamentous actin (F-actin) to globular actin contributed to BBB dysfunction induced by SMG. In the human brain microvascular endothelial cell (HBMECs), SMG increased the oxidative stress levels and proinflammatory cytokine levels, promoted apoptosis, and arrested the cell cycle phase. Expression of TJs and AJs proteins were downregulated and the distribution of F-actin was altered in SMG-treated HBMECs. The key role of the Rac1/Wave2/Arp3 pathway in BBB dysfunction was confirmed in HBMECs with a specific Rac1 agonist. This study demonstrated that SMG induced BBB dysfunction and revealed that Rac1/Wave2/Arp3 could be a potential signaling pathway responsible for BBB disruption under SMG. These results might shed a novel light on maintaining astronaut CNS homeostasis during space travel.

Highlights

During spaceflight, astronauts are exposed to environmental stress, such as microgravity (MG), radiation, and noise
The results suggested that downregulated related C3 botulinum toxin substrate 1 (Rac1), Wiskott–Aldrich syndrome protein family verprolin-homologous protein 2 (Wave2), and actin-related protein 3 (Arp3) expression and decreased ratio of filamentous actin (F-actin) to G-actin in simulated MG (SMG)-treated human brain microvascular endothelial cells (HBMECs) were largely diminished by the agonist (Figure 8C; Supplementary Figure S3)
This study suggested that SMG could disturb the integrity of blood-brain barrier (BBB) via induced inflammatory injury, damaged BBB ultrastructure, increased oxidative stress levels, increased permeability, and downregulated tight junctions (TJs) and adherens junctions (AJs) protein expression in the rat brain

Summary

Introduction

Astronauts are exposed to environmental stress, such as microgravity (MG), radiation, and noise. MG or simulated MG (SMG) might affect many aspects of human physiology, including cephalad shift of body fluids, loss of fluids and electrolytes [2], bone loss and muscle atrophy [3], and immunological deficiency [4]. Studies have shown that MG could induce a number of neurological disorders, such as learning and memory ability decline [5], cognitive deficits, visual disturbances, movement/orientation control alteration, sleep disorders [6], nausea, and headaches [7]. It is worth noting that cognitive deficits and sleep disorders are associated with blood-brain barrier (BBB) dysfunction, including increased permeability, and downregulated tight junctions (TJs) and adherens junctions (AJs) protein expression [8,9,10]. The BBB consists of the capillary basement membranes, brain microvascular endothelial cell (BMEC), astrocytic end-feet, and pericytes

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