Protective effects of inhibiting pericyte ferroptosis on pulmonary vascular barrier function in septic rats

To investigate the role of pericyte ferroptosis in the injury of pulmonary vascular barrier in septic rats and identify the protective effect of ferrostatin-1 (Fer-1), a ferroptosis inhibitor, on pulmonary vascular barrier function.

①Animal experiment: The septic model of rats was established by cecal ligation and puncture (CLP), and 156 SD rats were randomly divided into sham group, CLP group and Fer-1 group (10 mg/kg Fer-1 intraperitoneally in 1 h before CLP). Single cell suspension of rat lung from the sham-operation group was obtained by flow cytometry as an unstained blank control. The abundance of pericytes in pulmonary venules, changes in pulmonary vascular permeability, lung wet to dry weight ratio and lung histopathology of rats in each group were observed. Meanwhile, the contents of lipid peroxidation (LPO) in pulmonary pericytes and venules, as well as the expression of ferroptosis marker proteins including glutathione peroxidase 4 (GPX4) and cyclooxygenase-2 (COX2) were also measured in each group. ②Cell experiment: Primary pericytes were isolated and divided into normal control group, lipopolysaccharide (LPS) group (treated with 10 μg/mL LPS for 12 h), and Fer-1 group (pretreated with 2 μmol/L Fer-1 for 12 h before LPS stimulation). The contents of ROS, Lipid ROS and Fe²⁺ and the expression levels of GPX4 and COX2 in the pericytes of each group were investigated.

In vivo, massive detachment of pericytes from pulmonary veins, serious leakage of pulmonary vessels, large quantities of Evans blue extravasation, severe damage of lung pathological structure were observed in the CLP group, accompanied with infiltration of massive inflammatory cells, increase in lung wet-dry weight ratio, and accumulation of LPO in pulmonary vascular pericytes, which indicated severe ferroptosis. However, Fer-1 pretreatment reduced the ferroptosis of pulmonary pericytes, decreased the loss of pericytes, alleviated pulmonary vascular leakage, improved lung structure, and greatly lowered the contents of LPO in the pericytes (P<0.01). In vitro, LPS significantly impaired pericytes viability and induced accumulations of ROS, Lipid ROS and Fe²⁺ in the pericytes. Meanwhile, LPS down-regulated the expression of GPX4 while up-regulated that of COX2. Administration of Fer-1 restored the pericytes viability and the expression of GPX4, and decreased the levels of intracellular ROS, Lipid ROS, Fe²⁺ and COX2 expression.

Sepsis may induce the ferroptosis and detachment of pulmonary pericytes, and then impair pulmonary vascular barrier function. The ferroptosis inhibitor Fer-1 can antagonize pulmonary pericytes ferroptosis and play a vital role in protecting pulmonary vascular barrier function.