Compromised endothelial Wnt/β-catenin signaling mediates the blood-brain barrier disruption and leads to neuroinflammation in endotoxemia

The blood-brain barrier (BBB) is a critical interface that maintains the central nervous system homeostasis by controlling the exchange of substances between the blood and the brain. Disruption of the BBB plays a vital role in the development of neuroinflammation and neurological dysfunction in sepsis, but the mechanisms by which the BBB becomes disrupted during sepsis are not well understood. Here, we induced endotoxemia, a major type of sepsis, in mice by intraperitoneal injection of lipopolysaccharide (LPS). LPS acutely increased BBB permeability, activated microglia, and heightened inflammatory responses in brain endothelium and parenchyma. Concurrently, LPS or proinflammatory cytokines activated the NF-kappa B pathway, inhibiting Wnt/beta-catenin signaling in brain endothelial cells in vitro and in vivo. Cell culture study revealed that NF-kappa B p65 directly interacted with beta-catenin to suppress Wnt/beta-catenin signaling. Pharmacological NF-kappa B pathway inhibition restored brain endothelial Wnt/beta-catenin signaling activity and mitigated BBB disruption and neuroinflammation in septic mice. Furthermore, genetic or pharmacological activation of brain endothelial Wnt/beta-catenin signaling substantially alleviated LPS-induced BBB leakage and neuroinflammation, while endothelial conditional ablation of the Wnt7a/7b co-receptor Gpr124 exacerbated the BBB leakage caused by LPS. Mechanistically, Wnt/beta-catenin signaling activation rectified the reduced expression levels of tight junction protein ZO-1 and transcytosis suppressor Mfsd2a in brain endothelial cells of mice with endotoxemia, inhibiting both paracellular and transcellular permeability of the BBB. Our findings demonstrate that endotoxemia-associated systemic inflammation decreases endothelial Wnt/beta-catenin signaling through activating NF-kappa B pathway, resulting in acute BBB disruption and neuroinflammation. Targeting the endothelial Wnt/beta-catenin signaling may offer a promising therapeutic strategy for preserving BBB integrity and treating neurological dysfunction in sepsis.