The Improvement of Sepsis-Associated Encephalopathy by P2X7R Inhibitor through Inhibiting the Omi/HtrA2 Apoptotic Signaling Pathway

Abstract

The pathogenesis of sepsis-associated encephalopathy (SAE) involves many aspects, including intracellular peroxidative stress damage, mitochondrial dysfunction, and cell apoptosis. In this study, we mainly explored the influence of P2X7R on the cognitive function of SAE and its molecular mechanism. We established a sepsis model using lipopolysaccharide (LPS) stimulation, followed by an assessment of cognitive function using Morris water maze, and then Western Blot was used to analyze the expression of tight junction proteins ZO-1 and Occludin in the hippocampus of mice. TUNEL assay was used to analyze the apoptosis of brain cells in frozen brain slices of mice during sepsis. Human brain microvascular endothelial cells (HBMECs) were used to research the molecular mechanism of brain cell damage induced by P2X7R. The results showed that P2X7R inhibitors dramatically improved the survival rate of mice, relieved the cognitive dysfunction caused by LPS stimulation, and significantly reduced the brain cell apoptosis caused by LPS. In addition, the inhibition of P2X7R can also reduce the production and accumulation of reactive oxygen species (ROS) in HBMECs in vitro and inhibit the apoptosis signaling pathway associated with mitochondrial serine protease Omi/HtrA2 in HBMECs in vitro. These results suggest that P2X7R has strong value as a potential target for the treatment of SAE.

Purinergic signaling: A gatekeeper of blood-brain barrier permeation

“…In addition, P2X6 receptors were expressed mainly in rat paraventricular nucleus microvascular endothelial cells and perivascular astrocytes end-foot ( Loesch, 2021 ). Human brain microvascular endothelial cells (HBMECs) express P2X7 receptors ( Wang et al, 2022 ). After stimulation by LPS, intracellular mitochondria produced a large amount of ATP and activated P2X7R, which further mediated the activation of the intracellular Omi/HtrA2 apoptosis signaling pathway and promoted cell apoptosis ( Wang et al, 2022 ).…”

“…Human brain microvascular endothelial cells (HBMECs) express P2X7 receptors ( Wang et al, 2022 ). After stimulation by LPS, intracellular mitochondria produced a large amount of ATP and activated P2X7R, which further mediated the activation of the intracellular Omi/HtrA2 apoptosis signaling pathway and promoted cell apoptosis ( Wang et al, 2022 ). Although the expression of these receptors in neurovascular units is partially understood, how P2X receptors regulate BBB permeability is less well studied, and the regulation of BBB by receptors other than P2X4 and P2X7 is unclear.…”

“…In addition, P2X7R plays a key role in LPS-induced BBB injury in mice. LPS significantly upregulated hippocampus P2X7R expression, whereas treatment with the P2X7R inhibitor A-438079 prevented the LPS-induced decrease in hippocampal Occludin and ZO-1 expression in mice ( Wang et al, 2022 ).…”

Sepsis-Induced Brain Dysfunction: Pathogenesis, Diagnosis, and Treatment

“…Although sepsis cause BBB damage is not entirely elucidated, several mechanisms have been postulated. The BBB is primarily comprised of microvascular endothelial cells (ECs), tight junction (TJ) proteins, astrocyte endfeet, pericytes, and capillary basement membrane, which are adversely affected by sepsis [27][28][29][30]. In normal physiologic conditions, the BBB serves as a physical barrier because TJ between adjacent ECs restrict molecules from diffusing through ECs, ensuring that most molecular trafficking takes a controlled transcellular route across the BBB.…”

“…Inhibiting endothelial nitric oxide synthase (eNOS) and Guanosine triphosphate cyclohydrolase 1 (GTPCH1) and increasing the activation of caspase-3/7 at last promote EC apoptosis during sepsis [ 29 ]. Furthermore, DAPMs that are released during sepsis such as ATP could induce apoptosis by purinergic receptor (P2X7R) in brain ECs [ 28 ]. Microglia, astrocytes, pericytes, and neutrophils participate in damaging the BBB in sepsis through inflammatory cascade amplification.…”