Eleftheria Letsiou, PhD

Acute Respiratory Distress Syndrome (ARDS) is a life-threatening condition where the lungs fill with fluid and fail to provide enough oxygen to the body. One major cause is infection by methicillin-resistant Staphylococcus aureus (MRSA), a dangerous antibiotic-resistant bacterium. Our research focuses on how MRSA injures the lung’s protective blood vessel lining—the barrier that keeps fluid and inflammation out of the air spaces—and how this damage might be prevented. We are studying a key cellular “cleanup and recycling” system called the autophagy–lysosome pathway, which normally removes unwanted or harmful materials from cells. We believe that when this system malfunctions, it weakens the lung’s endothelial barrier and worsens injury. Our work has found that certain FDA-approved drugs, called phosphodiesterase inhibitors, may help restore this protective process and reduce lung barrier damage. By revealing how MRSA disrupts lung function and responds to these treatments, we hope to find new ways to effectively treat this devastating condition.

Update; Our studies generated compelling evidence demonstrating that methicillin-resistant Staphylococcus aureus (MRSA), a common cause of serious infections, is a potent inducer of lysosomal dysfunction and autophagy inhibition in lung endothelial cells. When this occurs, endothelial cells, which line the blood vessels, can no longer properly remove or recycle cellular waste, which may contribute to disease progression. We also identified key lysosome-associated proteins that are differentially regulated by MRSA and play a critical role in mediating lung endothelial dysfunction during acute lung injury (ALI). Using both laboratory and animal studies, we found that FDA-approved drugs that block specific phosphodiesterases, enzymes involved in cell signaling, helped protect the lung endothelium from damage during ALI. These drugs work, in part, by preventing changes in lysosomal and autophagy signaling in lung endothelial cells. Overall, our findings suggest that problems with this cellular cleanup and recycling system play an important role in lung endothelial damage caused by MRSA and support targeting lysosomal pathways as a promising therapeutic strategy for acute respiratory distress syndrome (ARDS).