Pseudomonas aeruginosa-mediated cardiac dysfunction is driven by extracellular vesicles released during infection

TL;DR

This study shows that Pseudomonas aeruginosa causes heart problems through tiny vesicles released during infection, even without direct bacterial spread to the heart.

Contribution

The study identifies bacterial outer membrane vesicles and host-derived exosomes as key mediators of cardiac dysfunction during P. aeruginosa infection.

Findings

Exosomes from infected cells and bacterial outer membrane vesicles cause heart dysfunction in human and mouse models.

Toxins and immunogenic molecules in these vesicles trigger systemic inflammation and tissue injury.

Systemic administration of bacterial OMVs in mice leads to severe cardiac dysfunction.

Abstract

Pseudomonas aeruginosa is a gram-negative, opportunistic pathogen and a major cause of severe pneumonia. Healthcare-associated pneumonia accounts for up to 22% of all healthcare-acquired infections, with P. aeruginosa contributing to approximately 10–20% of these cases. Infections caused by P. aeruginosa carry a high mortality rate, ranging from 32% to 42.8%. Notably, the risk of pneumonia is strongly associated with cardiovascular diseases (CVD), particularly heart failure, independent of age, sex, comorbidities, or antibiotic usage. Individuals with CVD are at increased risk of developing both hospital-acquired pneumonia (HAP) and community-acquired pneumonia (CAP). Despite this association, the mechanisms underlying infection-induced cardiac dysfunction remain poorly understood. In our previous studies, we demonstrated that P. aeruginosa lung infection leads to severe cardiac electrical disturbances, including arrhythmias and left ventricular (LV) dysfunction, despite minimal bacterial dissemination to the heart. To further elucidate the mechanisms of P. aeruginosa-induced cardiac dysfunction, we employed both in vitro and in vivo infection models. Exposure of human-induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) to conditioned media from P. aeruginosa-infected human macrophages (hMDMs) resulted in profound contractile dysfunction in the hiPSC-CMs. We identified vesicles released from infected hMDMs along with bacterial outer membrane vesicles (OMVs) as key mediators of this dysfunction. Using liquid chromatography-tandem mass spectrometry (LC-MS/MS), we identified bacterial proteins, including toxins, packaged within both exosomes and OMVs that were responsible for the cardiotoxic effects. Moreover, systemic administration of bacterial OMVs in mice led to severe cardiac dysfunction. In summary, our findings indicate that during P. aeruginosa infection, bacterial OMVs are released into circulation and play a central role in mediating cardiac dysfunction.

Bacterial pneumonia can lead to severe cardiovascular complications and is a major contributor to increased mortality among hospitalized patients, either directly or indirectly. Pseudomonas aeruginosa, an opportunistic pathogen frequently encountered in hospital settings, accounts for nearly 20% of all infections in intensive care units (ICUs). Our previous studies demonstrated that P. aeruginosa lung infection induces profound cardiac electrical abnormalities and left ventricular (LV) dysfunction, despite minimal bacterial dissemination to the heart. In the present study, we identify exosomes released from infected host cells and outer membrane vesicles (OMVs) secreted by P. aeruginosa as critical mediators of this cardiac dysfunction. We show that host-derived exosomes are enriched with bacterial OMVs containing toxins and other immunogenic molecules, which promote systemic inflammation and tissue injury, ultimately contributing to cardiac impairment.

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