Iron overload disrupts alveolar-capillary tight junctions via oxidative stress in a murine model Free

Introduction：Iron overload is a common complication in hematologic diseases. While its toxic effects on the heart, liver, and pancreas are well-established, its impact on the lung remains underexplored. Our previous clinical data identified iron overload as an independent risk factor for pulmonary dysfunction in Thalassemia. The alveolar-capillary barrier is essential for gas exchange, and its integrity is maintained by tight junctions between alveolar epithelial and pulmonary endothelial cells. This study investigates whether iron overload impairs alveolar-capillary barrier function via disruption of tight junctions in a murine model.

Methods：C57BL/6J mice were randomly assigned to control or iron-overload groups (low-, medium-, high-dose), induced by intraperitoneal dextran iron. Lung tissue was analyzed using transmission electron microscopy (TEM) to evaluate tight junction ultrastructure. Expression levels of tight junction–related genes (Claudin-5, Claudin-18, Claudin-4, Occludin, ZO-1) were assessed by RT-qPCR, Western blot, and immunofluorescence. Oxidative stress was evaluated via ROS staining, malondialdehyde (MDA) levels, and activities of superoxide dismutase (SOD) and catalase (CAT).

Results：TEM analysis revealed intact and closely aligned tight junctions in control group. In contrast, iron-overloaded mice exhibited disrupted tight junctions. Compared with control group, the iron-overload groups showed significantly reduced mRNA and protein levels of Claudin-5, Claudin-18, Occludin, and ZO-1, whereas Claudin-4 expression was upregulated. Moreover, iron overload led to marked ROS accumulation, increased MDA levels, and decreased activity of SOD and CAT in lung tissues. Both tight junctions' disruption and oxidative stress exhibited a dose-dependent pattern, becoming more severe with increasing iron levels.

Conclusion: Iron overload disrupts tight junctions in the alveolar-capillary barrier, likely through oxidative stress–mediated mechanisms. These findings provide novel experimental evidence linking systemic iron overload to pulmonary injury and may inform future preventive strategies in transfusion-dependent conditions such as Thalassemia.