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

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.

Semen Ziziphi Spinosae attenuates blood–brain barrier dysfunction induced by lipopolysaccharide by targeting the FAK-DOCK180-Rac1-WAVE2-Arp3 signaling pathway

“…Based on our proteomic results regarding AJ and TJ protein determination and F-actin immunofluorescence, it is possible that SZS maintains BBB integrity by regulating cell junctions and the actin cytoskeleton. It has been reported that cytoskeletal reorganization may be regulated by several signaling pathways, including the Ras-related C3 botulinum toxin substrate 1 (Rac1)- Wiskott-Aldrich syndrome protein family member 2 (WAVE2)- actin related protein 2/3 (Arp2/3) pathway 17 . F-actin assembly and small actin driven protrusions, controlled by the Arp2/3 complex, contribute to the regulation of the paracellular permeability of the BBB 18 .…”

“…The Arp2/3 complex controls actin polymerization by assembling actin monomers (G-actin) into branched actin filament (F-actin) networks and plays an important role in cadherin/catenin complex-mediated endothelial cell–cell adhesion and the formation and maintenance of barrier integrity 31 . The Arp2/3 complex is activated by the WAVE regulatory complex downstream of Rac1 GTPase 17 . The FAK-DOCK180 signaling cascade plays an important role in the activation of Rac1 GTPase 19 .…”

PINK1-Dependent Mitophagy Reduced Endothelial Hyperpermeability and Cell Migration Capacity Under Simulated Microgravity

“…Many stimuli can act on endothelial permeability such as a high-fat diet and LPS. The permeability of the blood–brain barrier increases in rats exposed to simulated microgravity by tail suspending, and 3-D clinorotation downregulates the protein levels of ZO-1 and occludin in human brain microvascular endothelial cells ( Yan et al, 2021 ). It has been well-established that the activation of the NLRP3 inflammasome is an important initiating mechanism leading to endothelial dysfunction.…”

The Blood-Brain Barrier in Space: Implications for Space Travelers and for Human Health on Earth

“…AQP4 levels, which are elevated when the BBB is compromised, are critically involved in the formation and dissolution of cerebral edema (Amiry-Moghaddam et al, 2003;Frydenlund et al, 2006), suggesting a role for BBB dysfunction in the observed behavioral changes. In another rat study, 21 days of tail suspension resulted in inflammatory cellular infiltration and nuclear pyknosis in the cortex (Yan et al, 2021). Transmission electron microscopy demonstrated a widened intercellular space of endothelial cells, swollen pericytes, and unclear mitochondria cristae.…”