A PTPRO inhibitor Pi mitigates endotoxemia‐induced encephalopathy‐mediated blood–brain barrier disruption through cytoskeletal regulation

BACKGROUND AND PURPOSE: Septic encephalopathy (SE) is closely associated with disruption of blood-brain barrier (BBB), resulting in neurological deficits and poor clinical outcomes. Protein tyrosine phosphatase receptor type O (PTPRO) regulates disease states by dephosphorylating membrane-associated proteins and modulating intracellular signalling. Here we have examined the role of PTPRO in regulating BBB permeability and have assessed a PTPRO inhibitor (Pi) in mitigating BBB disruption during endotoxemia-associated encephalopathy. EXPERIMENTAL APPROACH: Genetic and pharmacological approaches, including PTPRO overexpression, knockdown or deficiency and Pi treatment, were used to evaluate endothelial dysfunction in bEND.3 cells, primary mouse brain microvascular endothelial cells and an LPS-induced murine model of endotoxemia-associated encephalopathy. Barrier dysfunction, cytoskeletal remodelling and signalling events were assessed using permeability assays, immunoblotting, immunofluorescence and in vivo BBB leakage analyses. KEY RESULTS: LPS increased PTPRO expression in brain tissue from endotoxemic mice and cerebral endothelial cells. Elevated PTPRO promoted F-actin reorganization, stress fibre formation and intercellular gap formation, whereas Pi treatment or PTPRO silencing attenuated these changes. PTPRO overexpression worsened endothelial barrier dysfunction, while Pi reduced thrombin-induced permeability in bEND.3 cells and wild-type primary endothelial cells. Primary endothelial cells from PTPRO-deficient mice were protected. Mechanistically, PTPRO regulated cytoskeletal dynamics through the ErbB2-Rho-MLC2 pathway. In vivo, Pi treatment and PTPRO deficiency reduced BBB leakage, with limited effects on inflammatory cytokines. CONCLUSION AND IMPLICATIONS: These findings identify PTPRO as an important regulator of BBB disruption in endotoxemia-associated encephalopathy and support pharmacological targeting of PTPRO as a potential strategy for preserving sepsis-associated BBB injury.