Metformin alleviates lung-endothelial hyperpermeability by regulating cofilin-1/PP2AC pathway

Area of Science:

• Cell Biology
• Molecular Biology
• Pharmacology

Background:

• Microvascular endothelial hyperpermeability is a key early sign of Acute Lung Injury (ALI), potentially leading to Acute Respiratory Distress Syndrome (ARDS).
• Metformin demonstrates vascular protective and anti-inflammatory effects independent of glycemic control, but its mechanism in lung endothelial cells remains unclear.
• Endothelial barrier dysfunction is linked to actin cytoskeleton reorganization and stress fiber formation, which compromise adherens junctions.

Purpose of the Study:

• To investigate the molecular mechanisms by which metformin protects lung endothelial cells (ECs) from hyperpermeability.
• To determine if metformin inhibits stress fiber formation via the cofilin-1-PP2AC pathway.
• To explore metformin's effects on EC barrier integrity, stress fibers, and inflammatory cytokine expression.

Main Methods:

• Human lung microvascular ECs were pretreated with metformin and challenged with thrombin.
• Barrier function was assessed using electric cell-substrate impedance sensing.
• Levels of actin stress fibers, IL-1β, IL-6, and cofilin-1 phosphorylation were analyzed.
• PP2AC subunit depletion and ectopic expression were used to elucidate the signaling pathway.

Main Results:

• Metformin attenuated thrombin-induced hyperpermeability, stress fiber formation, and IL-6/IL-1β expression in lung ECs.
• Metformin reduced Ser3-phosphorylation of cofilin-1, preserving its activity.
• Genetic depletion of PP2AC impaired metformin's protective effects, while PP2AC upregulation enhanced barrier function.
• Metformin increased PP2AC activity via enhanced methylation.

Conclusions:

• Metformin protects against lung vascular endothelial injury and inflammation through the cofilin-1/PP2AC signaling pathway.
• This study reveals a novel endothelial cofilin-1/PP2AC axis as a target for metformin's protective effects.
• Enhancing endothelial PP2AC activity presents a potential therapeutic strategy for ALI.