OBJECTIVES: To investigate the inhibitory effect of GSK484, a PAD4 inhibitor, on H3Cit expression following sepsis and its effects for improving sepsis-induced endothelial dysfunction. METHODS: Eighteen C57BL/6 mice were randomized into sham-operated group, sepsis model group and GSK484 treatment group (6), and in the latter two groups, models of sepsis were established by cecal ligation and puncture (CLP). The mice in GSK484 treatment group were given an intraperitoneal injection of GSK484 (4 mg/kg) on the second day following the surgery. Twenty-four hours after the injection, the mice were euthanized for measurement of serum levels of VEGF, ESM-1, IL-6 and IL-1β using ELISA. Lung tissue pathology was observed with HE staining, and pulmonary expressions of F-actin, VE-cadherin, ZO-1 and H3Cit proteins were detected using immunofluorescence staining and Western blotting. In primary cultured of mouse lung microvascular endothelial cells, the effect of stimulation with LPS (10 μg/mL) for 24 h on tube formation, proliferation, apoptosis and expressions of VEGF, ESM-1, IL-6 and IL-1β were assessed using CCK-8 assay, flow cytometry and ELISA. RESULTS: Compared to the sham-operated mice, the septic mice exhibited significant lung tissue pathologies characterized by vascular congestion, alveolar rupture, edema, and neutrophil infiltration. Serum levels of IL-6, IL-1β, VEGF, and ESM-1 were elevated, pulmonary expressions of F-actin, VE-cadherin, and ZO-1 were decreased, and H3Cit expression was increased significantly in the septic mice. GSK484 treatment effectively mitigated these changes in the septic mice. The LPS-stimulated endothelial cells showed increased productions of IL-6, IL-1β, VEGF and ESM-1, which were significantly reduced after treatment with 2.5 μmol/L GSK484. CONCLUSIONS: GSK484 treatment effectively suppresses H3Cit expression in septic mice to ameliorate sepsis-induced endothelial dysfunction.