The PTP4A3 Inhibitor KVX-053 Disrupts STAT3 and NF-κB Signaling to Preserve Endothelial Barrier Integrity in Lipopolysaccharide-Induced Acute Lung Injury

Abstract Acute Respiratory Distress Syndrome (ARDS) remains a devastating clinical condition with limited pharmacologic interventions capable of modifying disease progression. We have recently demonstrated that Protein Tyrosine Phosphatase Type IVA (PTP4A3 aka PRL3) is a key mediator of the inflammatory cascade that drives ALI following SARS-CoV-2 infection. Here, we investigated whether pharmacological inhibition of PTP4A3 with the small molecule inhibitor KVX-053 could attenuate Lipopolysaccharide (LPS)-induced acute lung injury (ALI) in C57BL/6J mice and LPS-induced endothelial barrier dysfunction in human lung microvascular endothelial cells (HLMVEC). C57BL/6J mice were intratracheally instilled with LPS (1 mg/kg) and treated with KVX-053 (10 mg/kg, intraperitoneally) beginning 1-hour post-instillation and every 24 hours thereafter for 72 hours. LPS-challenged mice exhibited significant weight loss, increased bronchoalveolar lavage fluid (BALF) white blood cell and protein concentrations, elevated lung injury scores, and impaired pulmonary mechanics. Treatment with KVX-053 attenuated weight loss, reduced BALF cytosis and proteinosis, diminished histological evidence of lung injury, and reduced the activation of key inflammatory signaling mediators, including phosphorylated STAT3 (p-STAT3), NLRP3 inflammasome, HSP70, and MMP8 in lung tissue. In HLMVEC, KVX-053 pre-treatment abolished LPS-induced phosphorylation of STAT3 and IκBα, restored VE-Cadherin expression and phospho-Cofilin levels and preserved endothelial monolayer integrity as assessed by immunofluorescence microscopy. Genetic silencing of PTP4A3 by RNA interference protected HLMVEC barrier function against LPS, and the combination of silencing and KVX-053 was not additive, confirming that the compound acts specifically through PTP4A3. Collectively, these findings define a PTP4A3 dependent signaling axis, converging on STAT3, NF-κB, NLRP3, and Cofilin, that governs endothelial barrier integrity in LPS induced acute lung injury, and demonstrate that its pharmacological interruption by KVX-053 attenuates pulmonary inflammation and barrier disruption, supporting the broader therapeutic potential of PTP4A3 inhibitors in ARDS and ALI.